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Table of Content
28 February 2022, Volume 42 Issue 2
    Large-scale simulations of CO2 diffusion in metal-organic frameworks with open Cu sites
    Tongan Yan, Minman Tong, Qingyuan Yang, Dahuan Liu, Yandong Guo, Chongli Zhong
    2022, 42(2):  1-9.  doi:10.1016/j.cjche.2021.08.013
    Abstract ( 89 )   PDF (2295KB) ( 304 )  
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    Understanding CO2 diffusion behavior in functional nanoporous materials is beneficial for improving the CO2 adsorption, separation, and conversion performances. However, it is a great challenge for studying the diffusion process in experiments. Herein, CO2 diffusion in 962 metal-organic frameworks (MOFs) with open Cu sites was systematically investigated by theoretical methods in the combination of molecular dynamic simulations and density functional theory (DFT) calculations. A specific force field was derived from DFT-D2 method combined with Grimme's dispersion-corrected (D2) density functional to well describe the interaction energies between Cu and CO2. It is observed that the suitable topology is conductive to CO2 diffusion, and 2D-MOFs are more flexible in tuning and balancing the CO2 adsorption and diffusion behaviors than 3D-MOFs. In addition, analysis of diffusive trajectories and the residence times on different positions indicate that CO2 diffusion is mainly along with the frameworks in these MOFs, jumping from one strong adsorption site to another. It is also influenced by the electrostatic interaction of the frameworks. Therefore, the obtained information may provide useful guidance for the rational design and synthesis of MOFs with enhanced CO2 diffusion performance for specific applications.
    A pillared-layer metal-organic framework for efficient separation of C3H8/C2H6/CH4 in natural gas
    Pengtao Guo, Miao Chang, Tongan Yan, Yuxiao Li, Dahuan Liu
    2022, 42(2):  10-16.  doi:10.1016/j.cjche.2021.08.011
    Abstract ( 52 )   PDF (1227KB) ( 327 )  
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    Metal-organic frameworks (MOFs) have great potentials as adsorbents for natural gas purification. However, the trade-off between selectivity and adsorption capacity remains a challenge. Herein, we report a pillared-layer metal-organic framework Ni(HBTC)(bipy) for efficiently separating the C3H8/C2H6/CH4 mixture. The experimental results show that the adsorption capacity of C3H8 and C2H6 on Ni(HBTC)(bipy) are as high as 6.18 and 5.85 mmol·g-1, while only 0.93 mmol·g-1 for CH4 at 298 K and 100 kPa. Especially, the adsorption capacity of C3H8 at 5 kPa can reach an unprecedented 4.52 mmol·g-1 and for C2H6 it is 1.48 mmol·g-1 at 10 kPa. The ideal adsorbed solution theory predicted C3H8/CH4 selectivity is as high as 1857.0, superior to most of the reported materials. Breakthrough experiment results indicated that material could completely separate the C3H8/C2H6/CH4 mixture. Therefore, Ni(HBTC)(bipy) is a promising material for separation of natural gas.
    Shaping of metal-organic frameworks through a calcium alginate method towards ethylene/ethane separation
    Jinlong Li, Xiaoqing Wang, Puxu Liu, Xiaohua Liu, Libo Li, Jinping Li
    2022, 42(2):  17-24.  doi:10.1016/j.cjche.2021.08.010
    Abstract ( 38 )   PDF (1783KB) ( 194 )  
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    The separation of ethylene and ethane is a crucial, challenging and cost-intensive process in chemical engineering. Metal-organic frameworks (MOFs) are a class of novel porous adsorbents used for the separation of ethylene/ethane mixtures. However, MOFs are normally crystalline powders that cause multiple problems, such as dust, abrasion and heat/mass loss, as well as significant pressure drops on the adsorption bed resulting in a sudden stop in production. To solve these issues, we have prepared four different sphere-shaped adsorbents, including Mg-gallate, Co-gallate, MUV-10(Mn) and MIL-53(Al) using a calcium alginate method to achieve excellent ethylene/ethane separation performance. The performance of the sphere-shaped adsorbents has been validated using mechanical strength measurements, powder X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, gas adsorption isotherms and dynamic breakthrough experiments. The excellent mechanical strength of these sphere-shaped adsorbents meets the criteria for industrial application in gas separation. Thus, the energy consumption and operating cost will be further reduced in the ethylene production process. We believe that this shaping method will open a prosperous route to the development of MOFs toward higher technology levels and their commercial application.
    Catalytic adsorptive desulfurization of mercaptan, sulfide and disulfide using bifunctional Ti-based adsorbent for ultra-clean oil
    Cuiting Yang, Bowen Wu, Zewei Liu, Guang Miao, Qibin Xia, Zhong Li, Michael J. Janik, Guoqing Li, Jing Xiao
    2022, 42(2):  25-34.  doi:10.1016/j.cjche.2021.08.031
    Abstract ( 44 )   PDF (2089KB) ( 206 )  
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    Ultra-deep desulfurization of transformer oil is of great demand among power industry. In this work, the effective and deep removal of various types of organosulfurs, including mercaptan, sulfide and disulfide via catalytic adsorptive desulfurization (CADS) using bifunctional Ti-based adsorbent is reported. Compared to adsorptive desulfurization (ADS), dramatically improvement of the organosulfur uptakes were achieved under CADS process. The equilibrium adsorption capacity at 5 μg·g-1 S reached up to 15.7, 33.4, 11.6 and 11.9 mg·g-1 for propyl mercaptan(n-PM), dimethyl sulfide(DMS), di-t-butyl disulfide (DTBDS) and dibenzyl disulfide (DBDS), which was 262, 477, 97 and 128 times to that of ADS process, respectively, and was the highest among the reported desulfurization adsorbents. Moreover, it achieved superior breakthrough capacity of 2050, 530 and 210 ml F·(g A)-1 at the breakthrough S concentration of 1 μg·g-1 of the commercial transformer oil S containing 10, 50 and 150 μg·g-1, respectively. The effectiveness of CADS is associated to the transformation of sulfur species to higher polar sulfonic species with the assistance of mild oxidant, which can be readily captured by silanol groups on SiO2 through H-bonding interaction. The excellent recyclability of the adsorbent can be realized through solvent washing or oxidative air treatment. This work provides an effective and economic approach for the elimination of trace amount of mercaptan, sulfide and disulfide from transformer oil.
    Stable titanium metal-organic framework with strong binding affinity for ethane removal
    Puxu Liu, Yong Wang, Yang Chen, Xiaoqing Wang, Jiangfeng Yang, Libo Li, Jinping Li
    2022, 42(2):  35-41.  doi:10.1016/j.cjche.2021.07.027
    Abstract ( 37 )   PDF (2118KB) ( 165 )  
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    Direct separation of high purity ethylene (C2H4) from an ethane (C2H6)/ethylene mixture is a critical and challenging task owing to the very similar molecular size and physical properties of the two components. While some studies have attempted this separation, there is a lack of excellent porous materials with strong binding affinity for C2H6-selective adsorption via an energy-efficient adsorptive separation process. Herein, we report a titanium metal-organic framework with strong binding affinity and excellent stability for the highly efficient removal of C2H6 from C2H6/C2H4 mixtures. Single component adsorption isotherms demonstrated a larger amount of adsorbed ethane (1.16 mmol·g-1 under 1 kPa) and high C2H6/C2H4 selectivity (2.7) for equimolar C2H6/C2H4 mixtures, especially in the low-pressure range, which is further confirmed by the results of grand canonical Monte Carlo simulations for C2H6 adsorption in this framework. The experimental breakthrough curves showed that C2H4 with a high purity was collected directly from both 1:9 and 1:15 C2H6/C2H4 (volume ratio) mixtures at 298 K and 100 kPa. Moreover, the unchanged adsorption and separation performance after cycling experiments confirmed the promising applicability of this material in future.
    Decorating MXene with tiny ZIF-8 nanoparticles: An effective approach to construct composites for water pollutant removal
    Chen Gu, Wenqiang Weng, Cong Lu, Peng Tan, Yao Jiang, Qiang Zhang, Xiaoqin Liu, Linbing Sun
    2022, 42(2):  42-48.  doi:10.1016/j.cjche.2021.06.004
    Abstract ( 34 )   PDF (1908KB) ( 206 )  
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    MXenes have attracted increasing research enthusiasm owing to their unique physical and chemical properties. Although MXenes exhibit exciting potential in cations adsorption due to their unique surface groups, the adsorption capacity is limited by the low specific surface area and undeveloped porosity. Our work aims at enhancing the adsorption performance of a well-known MXene, Ti3C2Tx, for methylene blue (MB) by decorating tiny ZIF-8 nanoparticles in the interlayer. After the incorporation of ZIF-8, suitable interspace in the layers resulting from the distribution of tiny ZIF-8 appears. When employing in MB, the adsorption capacity of composites can reach up to 107 mg·g-1 while both ZIF-8 (3 mg·g-1) and Ti3C2Tx (9 mg·g-1) show nearly no adsorption capacity. The adsorption mechanism was explored, and the good adsorption capacity is caused by the synergistic effect of ZIF-8 and Ti3C2Tx, for neither of them is of suitable interspace or surface groups for MB adsorption. Our work might pave the way for constructing functional materials based on the introduction of nanoparticles into layered materials for various adsorption applications.
    Efficient separation of C4 olefins using tantalum pentafluor oxide anion-pillared hybrid microporous material
    Bin Gao, Zhaoqiang Zhang, Jianbo Hu, Jiyu Cui, Liyuan Chen, Xili Cui, Huabin Xing
    2022, 42(2):  49-54.  doi:10.1016/j.cjche.2021.09.001
    Abstract ( 78 )   PDF (1033KB) ( 445 )  
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    With the increasing demand for synthetic rubber, the purification of 1,3-butadiene (C4H6) is of great industrial significance. Herein, the successful removal of n-butene (n-C4H8) and iso-butene (iso-C4H8) from 1,3-butadiene (C4H6) was realized by synthesizing a novel TaOF52- anion-pillared ultramicroporous material TaOFFIVE-3-Ni (also referred to as ZU-96, TaOFFIVE=TaOF52-, 3=pyrazine). Single-component adsorption isotherms show that TaOFFIVE-3-Ni can achieve the exclusion of n-C4H8 and iso-C4H8 in the low pressure region (0-30 kPa), and uptake C4H6 with a high capacity of 92.78 cm3·cm-3 (298 K and 100 kPa). The uptake ratio of C4H6/iso-C4H8 on TaOFFIVE-3-Ni was 20.83 (298 K and 100 kPa), which was the highest among the state-of-the-art adsorbents reported so far. With the rotation of anion and pyrazine ring, the pore size changes continuously, which makes smaller-size C4H6 enter the channel while larger-size n-C4H8 and iso-C4H8 are completely blocked. The excellent breakthrough performance of TaOFFIVE-3-Ni shows great potential in industrial separation of C4 olefins. The specific adsorption binding sites within ZU-96 was further revealed through the modeling calculation.
    Simultaneous degradation of RhB and reduction of Cr(VI) by MIL-53(Fe)/Polyaniline (PANI) with the mediation of organic acid
    Wanyuan Wang, Chengxin Wen, Daoyuan Zheng, Chunhu Li, Junjie Bian, Xinbo Wang
    2022, 42(2):  55-63.  doi:10.1016/j.cjche.2021.08.008
    Abstract ( 49 )   PDF (2150KB) ( 190 )  
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    MIL-53(Fe)/polyaniline (PANI) composite was prepared by in situ depositing PANI on the surface of MIL-53(Fe) and their catalytic performances on the simultaneous removal of RhB and Cr(VI) were investigated. The elimination efficiency of both RhB and Cr(VI) reached more than 98% under pH=2 where hydrochloric acid and citric acid were used to adjust the pH. The results indicated that MIL-53(Fe)/PANI revealed an obvious pH response to the degradation of RhB, while citric acid promoted the Cr(VI) photoreduction. UV-Vis spectra, EIS, and photocurrent response experiments showed that MIL-53(Fe)/PANI had a better light response and carrier migration ability than MIL-53(Fe). The transient absorption spectra also exhibited that the lifetimes of photo-generated carriers were prolonged after the conductive polymer deposition on the MIL-53(Fe) surface. Scavenger experiments demonstrated that the main active species were ·O2- and OH. Combined with activity evaluation results, and the possible photocatalytic mechanism of MIL-53(Fe)/PANI on RhB oxidation and Cr(VI) reduction was proposed. The addition of conductive polymer can effectively improve the light response of the catalyst under acidic conditions, and meanwhile citric acid also provided a new mediation for the synergistic degradation of multiple pollutants. Good activity and stability of the catalysts made the scale-up purification of acid water feasible under UV-Vis light.
    Boosting selective C2H2/CH4, C2H4/CH4 and CO2/CH4 adsorption performance via 1,2,3-triazole functionalized triazine-based porous organic polymers
    Xionghui Liu, Jianfeng Du, Yu Ye, Yuchuan Liu, Shun Wang, Xianyu Meng, Xiaowei Song, Zhiqiang Liang, Wenfu Yan
    2022, 42(2):  64-72.  doi:10.1016/j.cjche.2021.09.032
    Abstract ( 31 )   PDF (1492KB) ( 208 )  
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    Nitrogen-rich porous organic polymers have shown great potentials in gas adsorption/separation, photocatalysis, electrochemistry, sensing and so on. Herein, 1,2,3-triazole functionalized triazine-based porous organic polymers (TT-POPs) have been synthesized by the copper-catalyzed azide-alkyne cycloaddition (Cu-AAC) polymerization reactions of 1,3,5-tris(4-azidophenyl)-triazine with 1,4-diacetylene benzene and 1,3,5-triacetylenebenzene, respectively. The characterizations of N2 adsorption at 77 K show TT-POPs possess permanent porosity with BET surface areas of 666 m2·g-1 (TT-POP-1) and 406 m2·g-1 (TT-POP-2). The adsorption capacities of TT-POPs for CO2, CH4, C2H2 and C2H4, as well as the selective separation abilities of CO2/N2, CO2/CH4, C2H2/CH4 and C2H4/CH4 were evaluated. The gas selective separation ratio of TT-POPs was calculated by the ideal adsorbed solution theory (IAST) method, wherein the selective separation ratios of C2H2/CH4 and C2H4/CH4 of TT-POP-2 was 48.4 and 13.6 (298 K, 0.1 MPa), which is comparable to other adsorbents (5.6-120.6 for C2H2/CH4, 10-26 for C2H4/CH4). This work shows that the 1,2,3-triazole functionalized triazine-based porous organic polymer has a good application prospect in natural gas purification.
    Sustainable preparation of graphene-analogue boron nitride by ball-milling for adsorption of organic pollutants
    Haofeng Wu, Yanhong Chao, Yan Jin, Duanjian Tao, Xiaowei Li, Jing Luo, Guohua Xia, Linhua Zhu, Wenshuai Zhu
    2022, 42(2):  73-81.  doi:10.1016/j.cjche.2021.09.025
    Abstract ( 44 )   PDF (1284KB) ( 184 )  
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    The method of fabricating low-cost adsorbents with high activity and durability via a convenient and eco-friendly procedure is of great importance to wastewater treatment. Herein, a high-efficient mechanical exfoliation strategy was proposed to facilely prepare few-layered graphene-analogue boron nitride (BN) via a one-step non-organic solvent assisted wet ball mill procedure. Ball-milling treatment increased the specific surface area of BN 3.5-fold by reducing the thickness to ~3 layers with 45 min. The exfoliated BN exhibited strikingly improved sorption performance to organic contaminants with around 124% and 116% increased removal efficiency respectively for oxytetracycline (OTC) and Rhodamine B (RhB) as compared to the bulk BN. Batches sorption experiments showed that the sorption processes were thermodynamic endothermic, and well fitted to pseudo-second-order kinetic model and Freundlich isotherm equation. The π-π stacking interaction, hydrophobic effect and electrostatic interaction were proposed as the dominated sorption mechanism. In addition, no significant decline in adsorptive removal ability for the sorbent after 5 times recycling. The results indicate that the ball-milling exfoliation is a fast, green, sustainable and promising strategy for synthesis of highly potent BN based two-dimensional layered adsorbents.
    Additive manufacturing of sodalite monolith for continuous heavy metal removal from water sources
    Hengyu Shen, Run Zou, Yangtao Zhou, Xing Guo, Yanan Guan, Duo Na, Jinsong Zhang, Xiaolei Fan, Yilai Jiao
    2022, 42(2):  82-90.  doi:10.1016/j.cjche.2021.12.016
    Abstract ( 35 )   PDF (2248KB) ( 44 )  
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    Herein, we present a simple strategy for preparing monolithic sodalite adsorbents via sequential additive manufacturing and post-treatments. In detail, the method includes (i) 3D printing of cylindrical monoliths using clay as the base material; (ii) thermal activation of the 3D-printed clay monoliths by calcination (to produce reactive alumina and silica species and enable mechanical stabilization); (iii) conversion of the activated clay monoliths to hierarchical porous sodalite monoliths via hydrothermal alkaline treatment. Parametric studies on the effect of calcination temperature, alkaline concentration and hydrothermal treatment time on the property of the resulting materials (such as phase composition and morphology) at different stages of preparation was conducted. Under the optimal conditions (i.e., calcination temperature of 850℃, NaOH concentration of 3.3 mol·L-1, reaction temperature of 150℃, and reaction time of 6 h), a high-quality pure sodalite monolith was obtained, which possesses a relatively high BET surface area (58 m2·g-1) and hierarchically micro-meso-macroporous structure. In the proposed application of continuous removal of heavy metals (chromium ion as the model) from wastewater, the developed 3D-printed sodalite monolith showed excellent Cr3+ removal performance and fast kinetics (~98% removal efficiency within 25 cycles), which outperformed the packed bed using sodalite pellets (made by extrusion).
    Recent Advances in Adsorptive Separation Materials and Technologies
    Recent progress in porous organic polymers and their application for CO2 capture
    Jiajia Wang, Lizhi Wang, You Wang, Du Zhang, Qin Xiao, Jianhan Huang, You-Nian Liu
    2022, 42(2):  91-103.  doi:10.1016/j.cjche.2021.08.028
    Abstract ( 36 )   PDF (1534KB) ( 103 )  
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    Carbon capture, storage, and utilization (CCSU) is recognized as an effective method to reduce the excessive emission of CO2. Absorption by amine aqueous solutions is considered highly efficient for CO2 capture from the flue gas because of the large CO2 capture capacity and high selectivity. However, it is often limited by the equipment corrosion and the high desorption energy consumption, and adsorption of CO2 using solid adsorbents has been receiving more attention in recent years due to its simplicity and high efficiency. More recently, a great number of porous organic polymers (POPs) have been designed and constructed for CO2 capture, and they are proven promising solid adsorbents for CO2 capture due to their high Brunauer-Emmett-Teller (BET) surface area (SBET), adjustable pore size and easy functionalization. In particular, they usually have rigid skeleton, permanent porosity, and good physiochemical stability. In this review, we have a detailed review for the different POPs developed in recent years, not only the design strategy, but also the special structure for CO2 capture. The outlook of the opportunities and challenges of the POPs is also proposed.
    Light-responsive adsorbents with tunable adsorbent-adsorbate interactions for selective CO2 capture
    Peng Tan, Yao Jiang, Qiurong Wu, Chen Gu, Shichao Qi, Qiang Zhang, Xiaoqin Liu, Linbing Sun
    2022, 42(2):  104-111.  doi:10.1016/j.cjche.2021.07.010
    Abstract ( 69 )   PDF (1128KB) ( 110 )  
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    Amines in porous materials have been employed as active species for the selective CO2 adsorption from natural gas because of their target-specific interactions. Nevertheless, it is difficult to modulate such strong interactions to reach a high efficiency in the adsorption processes. Herein, we fabricated light-responsive adsorbents with tunable adsorbent-adsorbate interactions for CO2 capture. The adsorbents were synthesized by introducing primary and secondary amines into a mesoporous silica that had been grafted with azobenzene groups on the surfaces. The target-specific amine sites render the adsorbents significantly selective in the uptake of CO2 over CH4, and the azobenzene groups were used as light-responsive switches to influence the adsorbent-adsorbate interactions. The adsorbents can freely adsorb CO2 when the azobenzene groups are in the trans state. Ultraviolet-light irradiation makes the azobenzene groups transform to the cis configuration, which greatly hinders amines in the uptake of CO2. The caused difference of adsorption capacity can reach 34.9%. The alternative irradiation by ultraviolet- and visible-light can lead to a recyclable regulation on adsorption performance. The changes of the electrostatic potentials of amines are responsible for the light-induced regulation on adsorption.
    Comparative study on pressure swing adsorption system for industrial hydrogen and fuel cell hydrogen
    Jian Chen, Lingbing Bu, Yingqi Luo
    2022, 42(2):  112-119.  doi:10.1016/j.cjche.2021.09.029
    Abstract ( 20 )   PDF (1185KB) ( 137 )  
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    In order to improve the design of PSA system for fuel cell hydrogen production, a non-isothermal model of eight-bed PSA hydrogen process with five-component (H2/N2/CH4/CO/CO2=74.59%/0.01%/4.2%/2.5%/18.7% (vol)) four-stage pressure equalization was developed in this article. The model adopts a composite adsorption bed of activated carbon and zeolite 5A. In this article, pressure variation, temperature field and separation performance are stimulated, and also effect of providing purge (PP) differential pressure and the ratio of activated carbon to zeolite 5A on separation performance in the process of producing industrial hydrogen (CO content in hydrogen is 10 μl·L-1) and fuel cell hydrogen (CO content is 0.2 μl·L-1) are compared. The results show that Run 3, when the CO content in hydrogen is 10 μl·L-1, the hydrogen recovery is 89.8%, and the average flow rate of feed gas is 0.529 mol·s-1; When the CO content in hydrogen is 0.2 μl·L-1, the hydrogen recovery is 85.2%, and the average flow rate of feed gas is 0.43 mol·s-1. With the increase of PP differential pressure, hydrogen recovery first increases and then decreases, reaching the maximum when PP differential pressure is 0.263 MPa; With the decrease of the ratio of activated carbon to zeolite 5A, the hydrogen recovery increases gradually. When the CO content in hydrogen is 0.2 μl·L-1 the hydrogen recovery increases more obviously, from 83.96% to 86.37%, until the ratio of activated carbon to zeolite 5A decreases to 1. At the end of PP step, no large amount of CO2 in gas or solid phase enters the zeolite 5A adsorption bed, while when the CO content in hydrogen is 10 μl·L-1, and the ratio of carbon to zeolite 5A is less than 1.4, more CO2 will enter the zeolite 5A bed.
    Nitrogen rejection from low quality natural gas by pressure swing adsorption experiments and simulation using dynamic adsorption isotherms
    Xinran Zhang, Hua Shang, Jiangfeng Yang, Libo Li, Jinping Li
    2022, 42(2):  120-129.  doi:10.1016/j.cjche.2021.06.028
    Abstract ( 79 )   PDF (1517KB) ( 81 )  
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    In order to remove N2 from low quality natural gas, a mathematical model has been established by Aspen adsorption, using the CH4-selective sorbent silicalite-1 pellets. The dynamic adsorption isotherm was first simulated by breakthrough simulation of a CH4/N2 mixture at different adsorption pressures and feed flow rates based on breakthrough experiments. The resulting simulated CH4 dynamic adsorption amounts were very close to the experimental data at three different adsorption pressures (100, 200, and 300 kPa). Moreover, a single-bed, three-step pressure swing adsorption (PSA) experiment was performed, and the results were in good agreement with the simulated data, further corroborating the accuracy of the gas dynamic adsorption isotherm obtained by the simulation method. Finally, based on the simulated dynamic adsorption isotherm of CH4 and N2, a four-bed, eight-step PSA process has been designed, which enriched 75% (vol) CH4 and 80% (vol) CH4 to 95% (vol) and 99% (vol), and provided 99% (vol) recovery.
    Designed synthesis of porous carbons for the separation of light hydrocarbons
    Shuang Xu, Ru-Shuai Liu, Meng-Yao Zhang, An-Hui Lu
    2022, 42(2):  130-150.  doi:10.1016/j.cjche.2021.11.005
    Abstract ( 45 )   PDF (3564KB) ( 75 )  
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    The separation of light hydrocarbon mixtures (C1-C3) generated from petrochemical industry is vital and challenging process for obtaining valuable pure chemical feedstocks. In comparison to the energy intensive conventional separation technologies (cryogenic distillation, absorption and hydrogenation), the adsorptive separation is considered as a low energy cost and high efficiency process. Porous carbons have been demonstrated as excellent adsorbents for the separation of light hydrocarbons, owing to their designable structure and tailorable properties. This review summarizes the recent advances of using porous carbons as adsorbents for the separation of light hydrocarbons, including methane/nitrogen, methane/alkane, methane/carbon dioxide, ethylene/ethane and propylene/propane. We discuss the separation mechanisms and highlight the material features including pore structure, surface chemistry and target molecular properties that determine the separation performance. Furthermore, the challenges and development direction associated with carbonaceous adsorbents for light hydrocarbon separation are discussed, meanwhile the guidelines for the design of porous carbons are proposed.
    Adsorption desalination: Advances in porous adsorbents
    Boya Qiu, Patricia Gorgojo, Xiaolei Fan
    2022, 42(2):  151-169.  doi:10.1016/j.cjche.2021.08.032
    Abstract ( 109 )   PDF (2859KB) ( 109 )  
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    With the continuous growth of the world population, the demand for fresh water is ever increasing. Water desalination is a means of producing fresh water from saline water, and one of the proposed solutions in the scientific community for solving the current global freshwater shortage. Adsorption is foreseen as a promising technology for desalination due to its relatively low energy requirements, low environmental impact, low cost and high salt removal efficiency. More importantly, chemicals are not required in adsorption processes. Active carbons, zeolites, carbon nanostructures, graphene and coordination framework materials are amongst the most investigated adsorbents for adsorption desalination, which show different performances regarding adsorption rate, adsorption capacity, stability and recyclability. In this review, the latest adsorbent materials with their features are assessed (using metrics) and commented critically, and the current trend for their development is discussed. The adsorption mode is also reviewed, which can provide guidance for the design of adsorbents from the engineering application point of view.
    Screening and design of COF-based mixed-matrix membrane for CH4/N2 separation
    Tongan Yan, Dahuan Liu, Qingyuan Yang, Chongli Zhong
    2022, 42(2):  170-177.  doi:10.1016/j.cjche.2021.09.003
    Abstract ( 72 )   PDF (1097KB) ( 49 )  
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    Membrane separation is a high-efficiency, energy-saving, and environment-friendly separation technology. Covalent organic framework (COF)-based mixed-matrix membranes (MMMs) have broad application prospects in gas separation and are expected to provide new solutions for coal-bed methane purification. Herein, a high-throughput screening method is used to calculate and evaluate COF-based MMMs for CH4/N2 separation. General design rules are proposed from thermodynamic and kinetic points of view using the computation-ready, experimental COFs. From our database containing 471,671 generated COFs, 5 COF membrane materials were screened with excellent membrane selectivities, which were then used as the filler of MMMs for separation performance evaluation. Among them, BAR-NAP-Benzene_CF3 combined with polydimethylsiloxane and styrene-b-butadiene-b-styrene show high CH4 permeability of 4.43×10-13 mol·m·s-1·Pa-1·m-2 and high CH4/N2 selectivity of 9.54, respectively. The obtained results may provide reasonable information for the design of COF-based membranes for the efficient separation of CH4/N2.
    The concave-wall jet characteristics in vertical cylinder separator with inlet baffle component
    Jing Zhang, Zhongyi Ge, Wei Wang, Bin Gong, Yaxia Li, Jianhua Wu
    2022, 42(2):  178-189.  doi:10.1016/j.cjche.2021.05.023
    Abstract ( 45 )   PDF (3244KB) ( 40 )  
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    The concave-wall jet was formed in the vertical cylinder separator with inlet baffle component. The effect of curvature of radial baffle on the jet flow in the separator was investigated by the experiment of concentration and the numerical simulation of species transport. The results show that the concave-wall jet was confined within the narrow region near the concave-wall and the flow disturbance in the center of separator was weakened. The distribution of concentration and the flow region of wall jet depended on the curvature of radial baffle (K). Compared with the turbulent intensity of the plate baffle (K=0), that of concave baffle (K=2) reduced by 6.1% and the turbulent intensity of convex baffle (K=-2) increased by 13.5%. The best flow stability was obtained by the concave baffle because the baffle outlet was similar to convergent nozzle. The outlet convergent angle was between 0° and 19.5° when 0 ≤ K ≤ 2. The secondary vortices were caused by the tangential velocity irregularity on the cross-section of two axial baffles in the separator with convex baffle. The baffle with K ≥ 0 was more suitable in separator inlet than that with K < 0.
    Depicting the role of gas-solid interactions on the hydrodynamics of converging pneumatic riser
    Rashmi Dhurandhar, Sumit H. Dhawane, Jyoti Prakash Sarkar, Bimal Das
    2022, 42(2):  190-195.  doi:10.1016/j.cjche.2020.11.041
    Abstract ( 44 )   PDF (854KB) ( 25 )  
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    The understanding of the flow characteristics and effect of gas-solid interactions in pneumatic risers is fundamental to investigate to ensure effective design cost-effective operation. Thus, to understand the effect of gas-solid interactions on the hydrodynamics of newly proposed conversing risers, this study mainly focused on predicting pressure drop in the dilute phase pneumatic conveying system. The experiments were conducted in a converging riser having a convergence angle of 0.2693°. Various solid particles such as sago, black mustard, and alumina have been considered to study the effect of particle sizes and density on the pressure drop. The experimental outcomes indicate that the total pressure drop increases with an increase in the solid density and gas mass flow rate. Moreover, smaller particle sizes are also increased the pressure drop. An empirical correlation is developed for the prediction of total pressure drop ΔPT in converging pneumatic riser via dimensional analysis. All dependent variables such as particle and air density, drag force, acceleration due to gravity, the mass flow rate of air and particle, the diameter of particle and converging riser, the height of converging riser were considered to develop the empirical correlation. The established relationship is tested, and experimental data have been fitted for its validation. The estimated relative error of less than 0.05 proved the significance of the developed correlation. Hence, it can be stated that the established relationship is useful in studying the effects of various parameters on the pressure drop across the length of the conversing riser.
    Improving hydrocarbons production via catalytic co-pyrolysis of torrefied-biomass with plastics and dual catalytic pyrolysis
    Peter Keliona Wani Likun, Huiyan Zhang, Yuyang Fan
    2022, 42(2):  196-209.  doi:10.1016/j.cjche.2020.09.074
    Abstract ( 28 )   PDF (2389KB) ( 201 )  
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    To increase the low yield and selectivity of aromatic hydrocarbons during the biomass pyrolysis process, we torrefied the biomass and then co-pyrolyzing with plastics such as high-density polyethylene (HDPE), polystyrene (PS), ethylene-vinyl acetate (EVA) and polypropylene (PP) and also single and dual catalyst layouts were investigated by Py-GC/MS. The results showed that non-catalytic fast pyrolysis (CFP) of raw bagasse (RBG) generated no aromatics. After torrefaction non-CFP of torrefied bagasse (TBG) generated low aromatic yield. Indicating that torrefaction would enhance the proportion of aromatics during the pyrolysis process. The CFP of TBG200℃ and TBG240℃ over ZSM-5 produced the total aromatic yield of 1.96 and 1.88 times higher, respectively, compared to non-CFP of TBG. Furthermore, the addition of plastic could increase H/Ceff ratio of the mixture, consequently, increase the yield of aromatic compounds. Among the various torrefied-bagasse/plastic mixtures, the CFP of TBG/EVA (7:3 ratio) mixture generated the highest the total aromatic yield of 7.7 times more than the CFP of TBG alone. The dual catalyst layout could enhance the yield of aromatics hydrocarbons. The dual-catalytic co-pyrolysis of TBG200℃/plastic (1:1) ratio over USY (ultra-stable Y zeolite)/ZSM-5, improved the total aromatics yield by 4.33 times more than the catalytic pyrolysis of TBG200oC alone over ZSM-5 catalyst. The above results showed that the yield and selectivities of light aromatic hydrocarbons can be improved via catalytic co-pyrolysis and dual catalytic co-pyrolysis of torrefied-biomass with plastics.
    Determination of interfacial tension and viscosity under dripping flow in a step T-junction microdevice
    Li Ma, Yongjin Cui, Lin Sheng, Chencan Du, Jian Deng, Guangsheng Luo
    2022, 42(2):  210-218.  doi:10.1016/j.cjche.2021.07.028
    Abstract ( 36 )   PDF (1477KB) ( 29 )  
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    Microfluidic approaches for the determination of interfacial tension and viscosity of liquid-liquid systems still face some challenges. One of them is liquid-liquid systems with low interfacial and high viscosity, because dripping flow in normal microdevices can't be easily realized for the systems. In this work, we designed a capillary embedded step T-junction microdevice to develop a modified microfluidic approach to determine the interfacial tension of several systems, specially, for the systems with low interfacial tension and high viscosity. This method combines a classical T-junction geometry with a step to strengthen the shear force further to form monodispersed water/oil (w/o) or aqueous two-phase (ATP) droplet under dripping flow. For systems with low interfacial tension and high viscosity, the operating range for dripping flow is relative narrow whereas a wider dripping flow operating range can be realized in this step T-junction microdevice when the capillary number of the continuous phase is in the range of 0.01 to 0.7. Additionally, the viscosity of the continuous phase was also measured in the same microdevice. Several different systems with an interfacial tension from 1.0 to 8.0 mN·m-1 and a viscosity from 0.9 to 10 mPa·s were measured accurately. The experimental results are in good agreement with the data obtained from a commercial interfacial tensiometer and a spinning digital viscometer. This work could extend the application of microfluidic flows.
    Synthesis of silica powder with high pore volume by skeleton reinforcement
    Hongwei Shan, Xiaodong Zhou, Hao Jiang, Yanjie Hu, Haibo Jiang, Chunzhong Li
    2022, 42(2):  219-226.  doi:10.1016/j.cjche.2021.07.026
    Abstract ( 25 )   PDF (1725KB) ( 25 )  
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    In this paper, a method composed of gelation of basic skeleton (first step) and skeleton reinforcement process (second step) was introduced to synthesize silica powder with high pore volume through the reaction between water glass and sulfuric acid. No organic solvents were involved in the entire preparation process and the final product was collected by spray drying. The effect of concentration of base solution, gelation point pH value and skeleton reinforcement time on the BET specific surface area and pore volume of the prepared silica powder were investigated intensively. The results show that, a basic skeleton with good dispersibility and high porosity was obtained when the concentration of base solution was 0.1 mol·L-1 and the gelation pH value reached 6.5. Then the basic skeleton grew into a more uniform porous structure after 30 min skeleton reinforcement. Under these optimum conditions, silica powder prepared by skeleton reinforcement method had a BET specific surface area of 358.0 m2·g-1, and its pore volume reached 2.18 cm3·g-1, which was much higher than that of prepared by skeleton-free method (1.62 cm3·g-1) and by direct gelation method (0.31 cm3·g-1).
    Zwitterionic monolayer grafted ceramic membrane with an antifouling performance for the efficient oil-water separation
    Tianyu Zhang, Qian Wang, Wei Luan, Xue Li, Xianfu Chen, Dong Ding, Zhichao Shen, Minghui Qiu, Zhaoliang Cui, Yiqun Fan
    2022, 42(2):  227-235.  doi:10.1016/j.cjche.2021.03.049
    Abstract ( 27 )   PDF (3150KB) ( 87 )  
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    Enormous demands on the separation of oil/water (O/W) emulsions in various industries, such as petrochemical, food and pharmaceutical industries, are looking for high performance and energy-efficient separation methods. Ceramic membranes have been used to deal with O/W emulsions, for its outstanding characteristics of easy-operation, high-flux, and long-term stability. However, membrane fouling is still a challenge in the industrial application of ceramic membranes. Herein, antifouling ceramic membranes were fabricated by grafting zwitterions on the membrane surface via an environment-friendly two-step grafting method, which improves the antifouling property and permeability. Successful grafting of such zwitterion on the ceramic surface was assessed by the combination of FTIR and XPS characterization. More importantly, the hydration can be formed by electrostatic interactions layer on the modified membrane, which was confirmed by TGA characterization. The antifouling performance of prepared zwitterionic ceramic membranes in the separation of O/W emulsions was systematically tested. The results suggested that zwitterion can significantly improve the flux of ceramic ultrafiltration membrane, and can also improve antifouling property dramatically by reducing the irreversible fouling in the separation of O/W emulsions. Therefore, zwitterionic ceramic membranes hold promising potentials as an antifouling, highly efficient and green method in the practical purification of the O/W emulsions.
    Life cycle assessment of HFC-134a production by calcium carbide acetylene route in China
    Suisui Zhang, Jingying Li, Yan Nie, Luyao Qiang, Boyang Bai, Zhiwei Peng, Xiaoxun Ma
    2022, 42(2):  236-244.  doi:10.1016/j.cjche.2021.03.023
    Abstract ( 25 )   PDF (946KB) ( 104 )  
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    HFC-134a is a widely used environment-friendly refrigerant. At present, China is the largest producer of HFC-134a in the world. The production of HFC-134a in China mainly adopts the calcium carbide acetylene route. However, the production route has high resource and energy consumption and large waste emission, and few of the studies addressed on the environmental performance of its production process. This study quantified the environmental performance of HFC-134a production by calcium carbide route via carrying out a life cycle assessment (LCA) using the CML 2001 method. And uncertainty analysis by Monte-Carlo simulation was also carried out. The results showed that electricity had the most impact on the environment, followed by steam, hydrogen fluoride and chlorine, and the impact of direct CO2 emissions in calcium carbide production stage on the global warming effect also could not be ignored. Therefore, the clean energy (e.g., wind, solar, biomass, and natural gas) was used to replace coal-based electricity and coal-fired steam in this study, showing considerable environmental benefits. At the same time, the use of advanced production technologies could also improve environmental benefits, and the environmental impact of the global warming category could be reduced by 4.1% via using CO2 capture and purification technology. The Chinese database of HFC-134a production established in this study provides convenience for the relevant study of scholars. For the production of HFC-134a, this study helps to better identify the specific environmental hotspots and proposes useful ways to improve the environmental benefits.
    Development trend and prospect of solid phase extraction technology
    Chao Zhang, Huifang Xing, Liangrong Yang, Pengfei Fei, Huizhou Liu
    2022, 42(2):  245-255.  doi:10.1016/j.cjche.2021.05.031
    Abstract ( 189 )   PDF (1690KB) ( 213 )  
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    Solid phase extraction is widely used in sample pretreatment, concentration and analysis processes due to high selectivity and suitability for low concentration sample system. In this review, we systematically summarized and discussed the development trends of solid phase extraction by bibliometrics method. By analyzing papers output scale, the research and development direction of solid phase extraction technology is prospected. We also give an overview on current strategies of novel solid phase extraction from the separation medium and separation technology. The paper aims to describe the global research profile and the development trends of solid phase extraction, to help researchers to accurately grasp the research trend and to provide support for scientific research institutions to formulate scientific policies and strategic plans. Furthermore, the prospect of the development and application of solid phase extraction is also discussed.
    Electrokinetic mixing of two fluids with equivalent conductivity
    Fang Yang, Wei Zhao, Guiren Wang
    2022, 42(2):  256-260.  doi:10.1016/j.cjche.2021.03.032
    Abstract ( 30 )   PDF (805KB) ( 53 )  
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    Electrokinetic (EK) micromixers have been widely studied in the past decade for biochemical applications, biological and chemical analysis, etc. Unfortunately, almost all EK mixers require different electrical conductivity between the two fluids to be mixed, which has greatly limited their wide applications, in cases where the two streams to be mixed have equivalent electrical conductivity. Here we show that mixing enhancement between two fluids with identical conductivity can be achieved in an EK micromixer with conductive sidewalls, where the electric field is in transverse direction of the flow. The results revealed that the mixing became stronger with increased conductivity value. This mixing method provides a novel and convenient strategy for mixing two liquids with the same or similar electrical conductivity in microfluidic systems, and could potentially serves as a powerful tool for sample preparation in applications such as liquid biopsy, and environmental monitoring, etc.
    Heterogeneous numerical modelling for the auto thermal reforming of crude glycerol in a fixed bed reactor
    Jason Williams, Hussameldin Ibrahim, Nima Karimi, Kelvin Tsun Wai Ng
    2022, 42(2):  261-268.  doi:10.1016/j.cjche.2021.03.054
    Abstract ( 32 )   PDF (862KB) ( 41 )  
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    A mathematical model for the catalytic autothermal reforming (ATR) reaction of synthetic crude glycerol to hydrogen in a fixed bed tubular reactor (FBTR) and over an in-house developed metal oxide catalyst is presented in this work. The heterogeneous model equations account for a two-phase system of solid catalyst and bulk feed gas. Also, the ATR of crude glycerol reaction scheme and intrinsic kinetic rate model over an active, selective, and stable nickel-based catalyst were integrated in the developed model. Also, the model was validated using experimental data generated in our labs for the ATR of synthetic crude glycerol. The modelling results adequately described the detailed gas product composition and distribution, temperature profiles, and conversion propagation in the axial direction of the fixed bed reactor over a wide range of reaction temperature (773-923 K) and mass-time (12.71-158.23 g cat·min·(mol C)-1). The crude glycerol conversion predicted with the model showing a close resemblance to those obtained experimentally with an average absolute deviation (AAD) of less than 8%. The maximum crude glycerol conversion and hydrogen yield were found to be 92% and 3 mol hydrogen/mol crude glycerol, respectively. Also, the gas product concentration profile in the reactor was adequately described (90%) accuracy with a hydrogen concentration of 39% (volume).
    Solvent-free partial oxidation of cyclohexane to KA oil over hydrotalcite-derived Cu-MgAlO mixed metal oxides
    Jian Jian, Dexing Yang, Peng Liu, Kuiyi You, Weijie Sun, Hu Zhou, Zhengqiu Yuan, Qiuhong Ai, Hean Luo
    2022, 42(2):  269-276.  doi:10.1016/j.cjche.2021.04.020
    Abstract ( 26 )   PDF (1754KB) ( 40 )  
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    A highly efficient and stable hydrotalcite-derived Cu-MgAlO catalyst was developed for the partial oxidation of cyclohexane with molecular oxygen. The physical-chemical properties of Cu-MgAlO catalysts were studied, and the results indicated that the copper component had been successfully introduced into the hydrotalcite unit layer structure. The catalytic reaction results showed that copper as the active species could activate C-H bond and effectively promote the decomposition of cyclohexyl hydroperoxide (CHHP) to the mixture of cyclohexanol and cyclohexanone (KA oil). 8.3% of cyclohexane conversion and 82.9% of selectivity for KA oil were obtained over 9%Cu-MgAlO catalyst at 150℃ with 0.6 MPa of oxygen pressure for 2 h. Especially, its catalytic performance was still stable after five runs.
    O3 based advanced oxidation for ibuprofen degradation
    Vitória M. Almeida, Carla A. Orge, M. Fernando R. Pereira, O. Salomé G.P. Soares
    2022, 42(2):  277-284.  doi:10.1016/j.cjche.2021.04.032
    Abstract ( 36 )   PDF (927KB) ( 25 )  
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    The degradation of the anti-inflammatory ibuprofen (IBP) was evaluated by several advanced oxidation processes. IBP was treated by single ozonation and oxidation with hydrogen peroxide (H2O2), as well as a combination of these treatments. In order to improve the efficiency, the presence of catalysts such as original carbon nanotubes, labelled as CNT, and iron oxide supported on carbon nanotubes, named as Fe/CNT sample, was considered. The evolution of IBP degradation, mineralization and toxicity of the solutions was assessed. The formation of intermediates was also monitored. In the non-catalytic processes, IBP was faster removed by single ozonation, whereas no significant total organic carbon (TOC) removal was achieved. Oxidation with H2O2 did not present satisfactory results. When ozone and H2O2 were combined, a higher mineralization was attained (70% after 180 min of reaction). On the other hand, in the catalytic processes, this combined process allowed the fastest IBP degradation. In terms of mineralization degree, the presence of Fe/CNT increases the removal rate in the first hour of reaction, achieving a TOC removal of 85%. Four compounds were detected as by-products. All treated solutions presented lower toxicity than the initial solution, suggesting that the released intermediates during applied processes are less toxic.
    Mechanistic insights into homogeneous electrocatalytic reaction for energy storage using finite element simulation
    Peng Song, Yan Li, Shuang Yin
    2022, 42(2):  285-296.  doi:10.1016/j.cjche.2021.12.001
    Abstract ( 28 )   PDF (2970KB) ( 182 )  
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    The application of homogeneous electrocatalytic reactions in energy storage and conversion has driven surging interests of researchers in exploring the reaction mechanisms of molecular catalysts. In this paper, homogeneous electrocatalytic reaction between hydroxymethylferrocene (HMF) and L-cysteine is intensively investigated by cyclic voltammetry and square wave voltammetry for which, the second-order rate constant (kec) of the chemical reaction between HMF+ and L-cysteine is determined via a 1D homogeneous electrocatalytic reaction model based on finite element simulation. The corresponding kec (1.1 (mol·m-3)-1·s-1) is further verified by linear sweep voltammograms under the same model. Square wave voltammetry parameters including potential frequency (f), increment (Estep) and amplitude (ESW) have been comprehensively investigated in terms of the voltammetric waveform transition of homogeneous electrocatalytic reaction. Specifically, the effect of potential frequency and increment is in accordance with the potential scan rate in cyclic voltammetry and the increase of pulsed potential amplitude results in a conspicuous split oxidative peaks phenomenon. Moreover, the proposed methodology of kec prediction is examined by hydroxyethylferrocene (HEF) and L-cysteine. The present work facilitates the understanding of homogeneous electrocatalytic reaction for energy storage purpose, especially in terms of electrochemical kinetics extraction and flow battery design.
    Two-dimensional graphitic carbon nitride for membrane separation
    Tao Zheng, Xiuyang Zou, Meisheng Li, Shouyong Zhou, Yijiang Zhao, Zhaoxiang Zhong
    2022, 42(2):  297-311.  doi:10.1016/j.cjche.2021.01.011
    Abstract ( 151 )   PDF (2602KB) ( 145 )  
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    Recent years, membrane separation technology has attracted significant research attention because of the efficient and environmentally friendly operation. The selection of suitable materials to improve the membrane selectivity, permeability and other properties has become a topic of vital research relevance. Two-dimensional (2D) materials, a novel family of multifunctional materials, are widely used in membrane separation due to their unique structure and properties. In this respect, as a novel 2D material, graphitic carbon nitride (g-C3N4) have found specific attention in membrane separation. This study reviews the application of carbon nitride in gas separation membranes, pervaporation membranes, nanofiltration membranes, reverse osmosis membranes, ion exchange membranes and catalytic membranes, along with describing the separation mechanisms.
    Regulatable pervaporation performance of Zn-MOFs/polydimethylsiloxane mixed matrix pervaporation membranes
    Guorong Wu, Qiangwen Fan, Wenjie Sun, Zhiwu Yu, Zhiqian Jia, Jianguo Ma
    2022, 42(2):  312-318.  doi:10.1016/j.cjche.2021.02.011
    Abstract ( 33 )   PDF (1700KB) ( 186 )  
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    Pervaporation (PV) is an emerging separation technique for liquid mixture. Mixed matrix membranes (MMMs) often demonstrate trade-off relationship between separation factor and flux. In this study, by changing the organic linkers (2-methyl imidazolate, imidazole-2-carboxaldehyde, 2-ethyl imidazolate), ZIF-8, ZIF-90 and MAF-6 were prepared and filled in polydimethylsiloxane (PDMS) membranes for dealcoholization of 5% (mass) n-butanol solution, and the membranes properties and pervaporation performances were adjusted. Compared with the pure PDMS membrane, the addition of ZIF-8 resulted in a 9% increase in flux (1136 g·m-2·h-1) and a 22.5% increase in separation factor (28.3), displaying anti-trade-off effect. For the MAF-6/PDMS MMMs (2.0% mass loading), the pervaporation separation index (PSI) and separation factor were 32347 g·m-2·h-1 and 58.6 respectively (increased by 34% and 154% in contrast with that of the pure PDMS membrane), and the corresponding permeation flux was 552 g·m-2·h-1, presenting great potential in the removal butanol from water. It was deduced that the large aperture size combined with moderate hydrophobicity of metal-organic frameworks (MOFs) favor the concurrent increase in permeability and selectivity.
    Reaction characteristics investigation of CeO2-enhanced CaSO4 oxygen carrier with lignite
    Baowen Wang, Zhongyuan Cai, Heyu Li, Yanchen Liang, Tao Jiang, Ning Ding, Haibo Zhao
    2022, 42(2):  319-328.  doi:10.1016/j.cjche.2021.02.016
    Abstract ( 24 )   PDF (1322KB) ( 16 )  
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    Calcium sulfate (CaSO4) has been verified as a promising oxygen carrier (OC) in the chemical looping combustion (CLC) for its high oxygen capacity, abundant reserve and low cost, but its low reactivity and deleterious sulfur species emission from the side reactions of CaSO4 should be well considered for its wide application in CLC. In order to promote the reactivity of CaSO4 and increase its potential to inhibit the gaseous sulfur emission, a CeO2-enhanced CaSO4 OC mixed OC of core-shell structure was prepared using the combined template synthesis method. Reaction characteristics of the prepared CaSO4-CeO2 mixed OC with a typical lignite was first conducted and systematically investigated, and an improved reactivity of the prepared CaSO4-CeO2 mixed OC was demonstrated than its single component CaSO4 or CeO2 due to the fast transfer and exchange of oxygen from the CaSO4 substrate to coal via the doped CeO2. Furthermore, the solid products formed from the mixed CaSO4-CeO2 OC with the selected coal were collected and analyzed. Especially, evolution and redistribution of the sulfur species of different forms were focused. At the latter reaction stage of YN reaction with the CaSO4-CeO2 mixed OC, the SO2 emitted from the side reactions of CaSO4 was greatly diminished and the doped CeO2 was proven effective to directionally fix the SO2 released to turn into different solid sulfur compounds, which were determined as Ce2O2S, Ce2S3 and Ce2(SO4)3·5H2O and formed through the different pathways. In addition, good regeneration of the reduced CaSO4-CeO2 mixed OC could be reached in spite of the unavoidable interaction between the included minerals in coal and the reduced mixed OC. Overall, the combined template method-made CaSO4-CeO2 mixed OC reported herein was not only endowed with enhanced reactivity for coal conversion, but also owned the potential to directionally fix the gaseous sulfur emission, which is quite applicable as OC for simultaneous decarbonatization and desulfurization in the real CLC process.
    Simulation and experiment of six-bed PSA process for air separation with rotating distribution valve
    Tao Tian, Yayan Wang, Bing Liu, Zhaoyang Ding, Xinxi Xu, Meisheng Shi, Jun Ma, Yanjun Zhang, Donghui Zhang
    2022, 42(2):  329-337.  doi:10.1016/j.cjche.2021.03.027
    Abstract ( 26 )   PDF (2349KB) ( 124 )  
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    In this work, a six-bed pressure swing adsorption (PSA) process was investigated to produce medical oxygen from air, which uses the combination of six-way rotating distribution valve and PSA and has the main advantage of effectively saving space compared to the traditional two-bed or four-bed PSA process and can obtain greater productivity. The mathematical model of adsorption beds was developed based on the separation mechanism and the interaction among different equipment. Moreover, a pilot-scale device has been constructed to verify the accuracy of mathematical model by experiment. The oxygen product conformed to the medical standard (>93% (vol)) with a recovery of over 57%. Some related parameters were also discussed in detail, such as step time, ratio of length to the diameter, flow rate of product.
    Process parameters influence on zone refining and thermodynamics analysis of 1,2-diphenylethane
    Yabing Qi, Jun Li
    2022, 42(2):  338-343.  doi:10.1016/j.cjche.2021.07.021
    Abstract ( 28 )   PDF (624KB) ( 22 )  
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    Effective distribution coefficients of 9 impurities in 1,2-diphenylethane have been calculated by directional crystallization under different ambient frozen temperature. The effect of varied zone size, temperature difference between the melt and ambient frozen environment, number of zone on purity of 1,2-diphenylethane have been also investigated during the process of zone refining. The results indicate that the product purity in the intermediate purified region with varied zone size is higher 0.04%-0.2% than that with constant zone size. The product purity increases with temperature difference between the melt and ambient frozen environment. The appropriate temperature difference is adopted 50℃. The product purity in the intermediate region of sample bar with 2 molten zones is higher 0.05%-0.43% than that with 1 molten zone. In addition, the change of enthalpy and entropy between impurities and 1,2-diphenylethane have been determined.
    Effect of copper nanoparticles on thermal behavior of two-phase argon-copper nanofluid flow in rough nanochannels with focusing on the interface properties and heat transfer using molecular dynamics simulation
    Shabnam Ghahremanian, Abbas Abbassi, Zohreh Mansoori, Davood Toghraie
    2022, 42(2):  344-350.  doi:10.1016/j.cjche.2021.03.044
    Abstract ( 33 )   PDF (1252KB) ( 20 )  
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    A comparison between the efficacy of surface boundary structure and presence of nanoparticles on the condensation two-phase flow inside rough nanochannels has been accomplished by applying molecular dynamics procedure to evaluate the thermal conductivity and flow characteristics. Simulation is performed in a computational region with two copper walls containing rectangular rough elements under different saturated temperatures. The main properties of liquid-vapor interface including density and the number of liquid atoms, are obtained. It is observed that the density profile is more affected by nanoparticles than the roughness. Also, compared to the condensation of nanofluid in a smooth nanochannel, the rough wall causes a greater drop in the temperature at the early time steps and by development of liquid films, effects of the wall roughness reduce. At the first of the condensation process, adding nanoparticle causes that transferring argon particles to the liquid phase increases with a steeper slope. Furthermore, heat current autocorrelation function (HCACF) for nanofluid condensation flow over considered correlation time is analyzed and following that the thermal conductivity for different saturated conditions is calculated. It has been represented that at lower temperatures the roughness makes more significant influence on the heat transfer of two-phase flow, while at higher temperatures the importance of nanoparticles prevails.
    Effect of impeller type and scale-up on spatial distribution of shear rate in a stirred tank
    Huina Wang, Xiaoxia Duan, Xin Feng, Zai-Sha Mao, Chao Yang
    2022, 42(2):  351-363.  doi:10.1016/j.cjche.2021.03.004
    Abstract ( 40 )   PDF (2608KB) ( 127 )  
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    The main spatial distribution features of shear rate in a stirred tank operated with five different radial and axial flow impellers were presented with particle image velocimetry (PIV) experiments. Not only the average shear rate in the whole tank but also the local value in the vicinity of impeller increases linearly with impeller speed. Furthermore, the shear coefficient (Ks,imp) at the impeller outlet is linearly related to the impeller flow number (Nq) and decreases with the increase of Nq in general at the constant power consumption per unit volume (Pv). During scale-up based on the constant Pv and geometric similarity, CFD results show that the volume-averaged shear rate (γavg) for RDT decreases faster than that of other impellers with the impeller tip velocity (Utip). The novel multi-blade combined (MBC) impeller with the increased height-to-diameter ratio of the stirred tank is able to more effectively improve the distribution uniformity of shear rate at the same Pv after scale-up. These studies provide a data basis for selecting the impeller types and improving the shear rate environment in the large-scale stirred tank.
    Flow characteristics simulation of spiral coil reactor used in the thermochemical energy storage system
    Xiaoyi Chen, Danyang Song, Dong Zhang, Xiaogang Jin, Xiang Ling, Dongren Liu
    2022, 42(2):  364-379.  doi:10.1016/j.cjche.2021.04.027
    Abstract ( 25 )   PDF (2435KB) ( 30 )  
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    According to environmental and energy issues, renewable energy has been vigorously promoted. Now solar power is widely used in many areas but it is limited by the weather conditions and cannot work continuously. Heat storage is a considerable solution for this problem and thermochemical energy storage is the most promising way because of its great energy density and stability. However, this technology is not mature enough to be applied to the industry. The reactor is an important component in the thermochemical energy storage system where the charging and discharging process happens. In this paper, a spiral coil is proposed and used as a reactor in the thermochemical energy storage system. The advantages of the spiral coil include simple structure, small volume, and so on. To investigate the flow characteristics, the simulation was carried out based on energy-minimization multi-scale model (EMMS) and Eulerian two-phase model. CaCO3 particles were chosen as the reactants. Particle distribution was shown in the results. The gas initial velocity was set to 2 m·s-1, 3 m·s-1, and 4 m·s-1. When the particles flowed in the coil, gravity, centrifugal force and drag force influenced their flow. With the Reynold numbers increasing, centrifugal and drag force got larger. Accumulation phenomenon existed in the coil and results showed with the gas velocity increasing, accumulation moved from the bottom to the outer wall of the coil. Besides, the accumulation phenomenon was stabilized when φ > 720°. Also due to the centrifugal force, a secondary flow formed, which means solid particles moved from the inside wall to the outside wall. This secondary flow could promote turbulence and mixing of particles and gas. In addition, when the particle volume fraction is reduced from 0.2 to 0.1, the accumulation at the bottom of the coil decreases, and the unevenness of the velocity distribution becomes larger.
    Metal-organic framework-derived Ni doped Co3S4 hierarchical nanosheets as a monolithic electrocatalyst for highly efficient hydrogen evolution reaction in alkaline solution
    Jiankang Wang, Yajing Wang, Zhongping Yao, Zhaohua Jiang
    2022, 42(2):  380-388.  doi:10.1016/j.cjche.2021.02.010
    Abstract ( 22 )   PDF (2192KB) ( 23 )  
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    Hierarchical nanostructure construction and electronic structure engineering are commonly employed to increase the electrocatalytic activity of HER electrocatalysts. Herein, Ni doped Co3S4 hierarchical nanosheets on Ti mesh (Ni doped Co3S4 HNS/TM) were successfully prepared by using metal organic framework (MOF) as precursor which was synthesized under ambient condition. Characterization results confirmed this structure and Ni incorporation into Co3S4 lattice as well as the modified electronic structure of Co3S4 by Ni doping. Alkaline HER performance showed that Ni doped Co3S4 HNS/TM presented outstanding HER activity with 173 mV overpotential at -10 mA·cm-2, surpassing most of metal sulfide-based electrocatalysts. The hierarchical structure, superior electrical conductivity and electronic structure modulation contributed to the accelerated water dissociation and enhanced intrinsic activity. This work provides a new avenue for synthesizing hierarchical nanostructure and simultaneously tuning the electronic structure to promote HER performance, which has potential application in designing highly efficient and cost-effective HER nanostructured electrocatalyst.
    Empirical modeling of normal/cyclo-alkanes pyrolysis to produce light olefins
    Xu Hou, Bochong Chen, Zhenzhou Ma, Jintao Zhang, Yuanhang Ning, Donghe Zhang, Liu Zhao, Enxian Yuan, Tingting Cui
    2022, 42(2):  389-398.  doi:10.1016/j.cjche.2021.03.037
    Abstract ( 27 )   PDF (2686KB) ( 30 )  
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    Due to the complexity of feedstock, it is challenging to build a general model for light olefins production. This work was intended to simulate the formation of ethylene, propene and 1,3-butadiene in alkanes pyrolysis by referring the effects of normal/cyclo-structures. First, the pyrolysis of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, cyclohexane, methylcyclohexane, n-hexane and cyclohexane mixtures, and n-heptane and methylcyclohexane mixtures were carried out at 650-800℃, and a particular attention was paid to the measurement of ethylene, propene and 1,3-butadiene. Then, pseudo-first order kinetics was taken to characterize the pyrolysis process, and the effects of feedstock composition were studied. It was found that chain length and cyclo-alkane content can be qualitatively and quantitively represented by carbon atom number and pseudo-cyclohexane content, which made a significant difference on light olefins formation. Furthermore, the inverse proportional/quadratic function, linear function and exponential function were proposed to simulate the effects of chain length, cycloalkane content and reaction temperature on light olefins formation, respectively. Although the obtained empirical model well reproduced feedstock conversion, ethylene yield and propene yield in normal/cyclo-alkanes pyrolysis, it exhibited limitations in simulating 1,3-butadiene formation. Finally, the accuracy and flexibility of the present model was validated by predicting light olefins formation in the pyrolysis of multiple hydrocarbon mixtures. The prediction data well agreed with the experiment data for feedstock conversion, ethylene yield and propene yield, and overall characterized the changing trend of 1,3-butadiene yield along with reaction temperature, indicating that the present model could basically reflect light olefins production in the pyrolysis process even for complex feedstock.
    Evaluation of phenanthrene removal from soil washing effluent by activated carbon adsorption using response surface methodology
    Zenan Wang, Xin Zheng, Yan Wang, Heng Lin, Hui Zhang
    2022, 42(2):  399-405.  doi:10.1016/j.cjche.2021.02.027
    Abstract ( 24 )   PDF (1392KB) ( 19 )  
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    Soil washing is a promising technology for the remediation of polycyclic aromatic hydrocarbons (PAH)-contaminated sites, but surfactant needs to be recovered to reduce remediation cost and avoid secondary pollution. In this study, activated carbon (AC), prepared from waste walnut shells, was applied to the adsorptive removal of phenanthrene (PHE) from synthetic soil washing effluent with Tween 80 as a model surfactant. Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM) were used to investigate the influence of AC dosage, Tween 80 concentration and adsorption time, and their potential interaction effect on PHE removal. A response surface model was established based on the BBD experimental results. The goodness of fit of the model was confirmed by determination coefficient, coefficient of variation (CV) and residuals analysis. The RSM model indicates that AC dosage or adsorption time had positive effect on PHE removal while Tween 80 concentration had negative effect. The interaction effect between AC dosage and Tween 80 concentration was significant but the other two interaction effects were not. The 3D response surface plots were developed based on the RSM equation. The RSM model was validated by an additional experiment and the obtained result of PHE removal was very close to the model prediction, indicating the RSM model can effectively predict the PHE removal from soil washing effluent with activated carbon adsorption.
    Effects of formaldehyde on fermentable sugars production in the low-cost pretreatment of corn stalk based on ionic liquids
    Kaili Zhang, Ligang Wei, Qingqin Sun, Jian Sun, Kunlan Li, Shangru Zhai, Qingda An, Junwang Zhang
    2022, 42(2):  406-414.  doi:10.1016/j.cjche.2021.01.001
    Abstract ( 18 )   PDF (1164KB) ( 20 )  
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    Low cost processing of lignocellulosic biomass is of great importance for sustainable chemistry and engineering. Herein, a low cost system composed of 1-butyl-3-methylimidazolium chloride ([C4C1im]Cl), HCl and formaldehyde (FA) was developed for the pretreatment of corn stalk at 80℃. The efficiency of this technology was compared with that in dioxane system or without FA addition. Due to FA stabilization, the extent of acid-hydrolysis of carbohydrate fraction can be significantly decreased while 70% above of lignin was removed with the pretreatment of[C4C1im]Cl/HCl/FA system at 80℃ for 2 h. A maximum reducing sugar yield of 93.7% and glucose concentration of 7.0 mg·ml-1 were subsequently obtained from enzymatic hydrolysis of the slurry. There were great differences in compositions of small molecule degraded products obtained with FA addition or not. The present[C4C1im]Cl based system exhibits great potential of substituting volatile organic solvents (i.e. dioxane) in developing low cost lignocellulosic biomass pretreatment at low temperature. Also, this work would gain insight into understanding on the roles of stabilization methods on the economic improvement of IL based biomass processing.
    Influence of coke rate on thermal treatment of waste selective catalytic reduction (SCR) catalyst during iron ore sintering
    Pengnan Ma, Jiankang Wang, Hanxiao Meng, Laiquan Lv, Hao Fang, Kefa Cen, Hao Zhou
    2022, 42(2):  415-423.  doi:10.1016/j.cjche.2021.02.029
    Abstract ( 28 )   PDF (4087KB) ( 15 )  
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    Waste selective catalytic reduction (SCR) catalyst as a hazardous waste has a significant impact on the environment and human health. In present study, a novel technology for thermal treatment of waste SCR catalyst was proposed by adding it to sinter mix for iron ore sintering. The influences of coke rate on the flame front propagation, sinter microstructure, and sinter quality during sintering co-processing the waste SCR catalyst process were studied. In situ tests results indicated the maximum sintering bed temperature increased at higher coke rate, indicating more liquid phase generated and higher airflow resistance. The sintering time was longer and the calculated flame front speed dropped at higher coke rate. Sinter microstructure results found the coalescence and reshaping of bubbles were more fully with increasing coke rate. The porosity dropped from 35.28% to 25.66%, the pore average diameter of large pores decreased from 383.76 μm to 311.43 μm. With increasing coke rate, the sinter indexes of tumbler index, productivity, and yield, increased from 33.2%, 9.2 t·m-2·d-1, 28.9% to 58.0%, 36.0 t·m-2·d-1, 68.9%, respectively. Finally, a comprehensive index was introduced to systematically assess the influence of coke rate on sinter quality, which rose from 100 to 200 when coke rate was increased from 3.5% (mass) to 5.5% (mass).
    A core-shell amidoxime electrospun nanofiber affinity membrane for rapid recovery Au (III) from water
    Yang Chen, Lanying Jiang
    2022, 42(2):  424-436.  doi:10.1016/j.cjche.2021.08.021
    Abstract ( 34 )   PDF (2338KB) ( 9 )  
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    An affinity membrane was prepared by coaxial electrospinning and amidoxime (AONFA), and it was applied to selectively recovery Au (III) from an aqueous solution. The static adsorption results showed that, when pH at 5, the maximum adsorption capacity of AONFA membrane for Au (III) was 509.3 mg·g-1. AONFA membrane exhibit much higher affinity and selectivity towards Au (III) than other metal cations. The membrane could be regenerated effectively by mixture solution of thiourea and HCl, and the desorption ratio reached almost 100% after 4 hours desorption. The dead-end filtration results showed that, the membrane utilization efficiency and adsorption capacity can be improved by increasing the flow rate, while increasing the concentration shorted the breakthrough process and had little impact to adsorption capacity. We can flexibly adjust the flow rate and concentration according to the situation to obtain the maximum utilization efficiency of the membrane in filtration process. The dynamic adsorption capacity is higher than the static adsorption capacity. The adsorption mechanism for Au (III) is electrostatic adsorption and reduction. Thus, AONFA membrane filtration was demonstrated to be a promising method for continuous recover Au (III) from wastewater.
    Chlorinated butyl rubber/two-step modified montmorillonite nanocomposites: Mechanical and damping properties
    Keya Tang, Jincheng Wang
    2022, 42(2):  437-449.  doi:10.1016/j.cjche.2021.02.001
    Abstract ( 33 )   PDF (2019KB) ( 30 )  
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    Montmorillonite (MMT) was modified by ultrasound and castor oil quaternary ammonium salt intercalation method to prepare a new type of organic montmorillonite (OMMT). The surface structure, particle morphology, interlayer distance, and thermal behavior of the samples obtained were characterized. The modified OMMT was then added to chlorinated butyl rubber (CIIR) by mechanical blending, and a composite material with excellent damping properties was obtained. The mechanical experiment results of CIIR nanocomposites showed that the addition of OMMT improved their tensile strength, hardness, and stress relaxation rate. Compared with pure CIIR, when the content of OMMT was 5 phr (part per hundred of rubber), the tensile strength of the nanocomposite was increased by 677% and the elongation at break was also increased by 105.4%. The enhancement of this performance was mainly due to the dispersion of the nanosheets in CIIR rubber and the chemical interaction between the organoclay and the polymer matrix, which was confirmed by morphology and spectral analysis. OMMT also endowed a positive effect on the damping properties of CIIR nanocomposites. After adding 5 phr of OMMT, the nanocomposite owned the best damping performance, and the damping factor, tanδmax, was 37.9% higher than that of pure CIIR. Therefore, the good damping and mechanical properties of these CIIR nanocomposites provided some novel and promising methods for preparing high-damping rubber in a wide temperature range.
    Thermal performance and entropy generation for nanofluid jet injection on a ribbed microchannel with oscillating heat flux: Investigation of the first and second laws of thermodynamics
    Yu-Liang Sun, Davood Toghraie, Omid Ali Akbari, Farzad Pourfattah, As'ad Alizadeh, Navid Ghajari, Mehran Aghajani
    2022, 42(2):  450-464.  doi:10.1016/j.cjche.2021.03.042
    Abstract ( 25 )   PDF (3123KB) ( 65 )  
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    In current numerical study, forced flow and heat transfer of water/NDG (Nitrogen-doped graphene) nanofluid in nanoparticles mass fractions (φ) of 0, 2% and 4% at Reynolds numbers (Re) of 10, 50, 100 and 150 are simulated in steady states. Studied geometry is a two-dimensional microchannel under the influence of nanofluid jet injection. Temperature of inlet fluid equals with Tc=293 K and hot source of microchannel is under the influence of oscillating heat flux. Also, in this research, the effect of the variations of attack angle of triangular rib (15°, 30°, 45° and 60°) on laminar nanofluid flow behavior inside the studied rectangular geometry with the ratio of L/H=28 and nanofluid jet injection is investigated. Obtained results indicate that the increase of Reynolds number, nanoparticles mass fraction and attack angle of rib leads to the increase of pressure drop. By increasing fluid viscosity, momentum depreciation of fluid in collusion with microchannel surfaces enhances. Also, the increase of attack angle of rib at higher Reynolds numbers has a great effect on this coefficient. At low Reynolds numbers, due to slow motion of fluid, variations of attack angle of rib, especially in angles of 30°, 45° and 60° are almost similar. By increasing fluid velocity, the effect of the variations of attack angle on pressure drop becomes significant and pressure drop figures act differently. In general, by using heat transfer enhancement methods in studied geometry, heat transfer increases almost 25%.