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Table of Content
28 March 2022, Volume 43 Issue 3
    Editorial for special issue on Carbon-neutrality Chemical Engineering
    2022, 43(3):  1-1.  doi:10.1016/j.cjche.2022.02.007
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    Green hydrogen: A promising way to the carbon-free society
    Ying Zhou, Ruiying Li, Zexuan Lv, Jian Liu, Hongjun Zhou, Chunming Xu
    2022, 43(3):  2-13.  doi:10.1016/j.cjche.2022.02.001
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    With increasing importance attached by the international community to global climate change and the pressing energy revolution, hydrogen energy, as a clean, efficient energy carrier, can serve as an important support for the establishment of a sustainable society. The United States and countries in Europe have already formulated relevant policies and plans for the use and development of hydrogen energy. While in China, aided by the “30·60” goal, the development of the hydrogen energy, production, transmission, and storage industries is steadily advancing. This article comprehensively considers the new energy revolution and the relevant plans of various countries, focuses on the principles, development status and research hot spots, and summarizes the different green hydrogen production technologies and paths. In addition, based on its assessment of current difficulties and bottlenecks in the production of green hydrogen and the overall global hydrogen energy development status, this article discusses the development of green hydrogen technologies.
    Electrochemical CO2 mineralization for red mud treatment driven by hydrogen-cycled membrane electrolysis
    Heping Xie, Yunpeng Wang, Tao Liu, Yifan Wu, Wenchuan Jiang, Cheng Lan, Zhiyu Zhao, Liangyu Zhu, Dongsheng Yang
    2022, 43(3):  14-23.  doi:10.1016/j.cjche.2022.02.002
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    CO2 mineralization as a promising CO2 mitigation strategy can employ industrial alkaline solid wastes to achieve net emission reduction of atmospheric CO2. The red mud is a strong alkalinity waste residue produced from the aluminum industry by the Bayer process which has the potential for the industrial CO2 large scale treatment. However, limited by complex components of red mud and harsh operating conditions, it is challenging to directly mineralize CO2 using red mud to recover carbon and sodium resources and to produce mineralized products simultaneously with high economic value efficiently. Herein, we propose a novel electrochemical CO2 mineralization strategy for red mud treatment driven by hydrogen-cycled membrane electrolysis, realizing mineralization of CO2 efficiently and recovery of carbon and sodium resources with economic value. The system utilizes H2 as the redox-active proton carrier to drive the cathode and anode to generate OH- and H+ at low voltage, respectively. The H+ plays as a neutralizer for the alkalinity of red mud and the OH- is used to mineralize CO2 into generate high-purity NaHCO3 product. We verify that the system can effectively recover carbon and sodium resources in red mud treatment process, which shows that the average electrolysis efficiency is 95.3% with high-purity (99.4%) NaHCO3 product obtained. The low electrolysis voltage of 0.453 V is achieved at 10 mA·cm-2 in this system indicates a potential low energy consumption industrial process. Further, we successfully demonstrate that this process has the ability of direct efficient mineralization of flue gas CO2 (15% volume) without extra capturing, being a novel potential strategy for carbon neutralization.
    Fabrication of azobenzene-functionalized porous polymers for selective CO2 capture
    Ding-Ming Xue, Wen-Juan Zhang, Xiao-Qin Liu, Shi-Chao Qi, Lin-Bing Sun
    2022, 43(3):  24-30.  doi:10.1016/j.cjche.2021.10.029
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    Many solid adsorbents have been prepared for the CO2 capture. In particular, the photoresponsive adsorbents have attracted extensive interests because of their tunable pore structure and variable responsive behaviors provoked by the external light. However, it is challenging to fabricate the photoresponsive adsorbents featured the big CO2 capacity and high CO2 selectivity. Herein, copolymerized between 4-phenylazobenzoyl chloride, 2,4,6-trichloro-1,3,5-triazine and melamine, a series of azobenzene-functionalized porous polymers (PTM-AZOs) are successfully synthesized. The PTM-AZOs are verified in possession of proper pore structures, large surface area and photoconductive properties through a series of characterization. The PTM-AZO-2 with the trans-isomerization exhibits the best CO2 adsorption amount of 2.7 mmol·g-1 (273 K and 0.1 MPa), while the CO2/N2 selectivity can reach 2459 and 607 on the trans- and cis-isomerization, respectively. The regulatable pore structures controlled by the photoresponsive azobenzene groups affect the CO2 capture performance of the PTM-AZOs.
    Significantly enhanced charge transfer efficiency and surface reaction on NiP2/g-C3N4 heterojunction for photocatalytic hydrogen evolution
    Xiaoqing Yan, Hua An, Zihao Chen, Guidong Yang
    2022, 43(3):  31-39.  doi:10.1016/j.cjche.2021.12.019
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    In this work, a novel NiP2/g-C3N4 heterojunction via homogeneous precipitation method assisted by thermal phosphorization reaction was designed and constructed, and the optimized sample showed the excellent photocatalytic H2 evolution activity under visible-light irradiation, which was nearly 112 times higher than that of pristine g-C3N4 sample. Experimental characterizations and DFT calculations demonstrated that the NiP2 nanoparticles covered on the g-C3N4 surface can form a built-in electric field at the interface to accelerate the transfer of photoexcited electrons from g-C3N4 to NiP2, crucial for hindering the recombination of electron-hole pairs. Moreover, the energy barrier of hydrogen evolution reaction can also vastly reduce when combined NiP2 and g-C3N4 to construct NiP2/g-C3N4 heterojunction. This work represents a method through combing experimental and theoretical tools to thoroughly investigate the mechanism of photocatalytic process.
    CO2 capture by double metal modified CaO-based sorbents from pyrolysis gases
    Xiaobin Chen, Yuting Tang, Chuncheng Ke, Chaoyue Zhang, Sichun Ding, Xiaoqian Ma
    2022, 43(3):  40-49.  doi:10.1016/j.cjche.2021.09.002
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    High-temperature pyrolysis technology can effectively solve the problem of municipal solid waste pollution. However, the pyrolysis gas contains a large amount of CO2, which would adversely affect the subsequent utilization. To address this problem, a novel method of co-precipitation modification with Ca, Mg and Zr metals was proposed to improve the CO2 capture performance. X-ray diffraction (XRD) patterns and energy dispersive X-ray spectroscopy analysis showed that the two inert supports MgO and CaZrO3 were uniformly distributed in the modified calcium-based sorbents. In addition, the XRD results indicated that CaZrO3 was produced by the reaction of ZrO2 and CaO at high temperatures. The effects of doping ratios, adsorption temperature, calcination temperature, CO2 concentration and calcination atmosphere on the adsorption capacity and cycle stability of the modified calcium-based sorbent were studied. The modified calcium-based sorbent achieved the best CO2 capture performance when the doping ratio was 10:1:1 with carbonation at 700 ℃ under 20% CO2/80% N2 atmosphere and calcination at 900 ℃ under 100% N2 atmosphere. After ten cycles, the average carbonation conversion rate of Ca-10 sorbent was 72%. Finally, the modified calcium-based sorbents successfully reduced the CO2 concentration of the pyrolysis gas from 37% to 5%.
    Methane hydrate crystal growth on shell substrate
    Xin Jiang, Baojiang Sun, Zhiyuan Wang, Wantian Zhou, Jiakai Ji, Litao Chen
    2022, 43(3):  50-61.  doi:10.1016/j.cjche.2021.12.025
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    Hydrate crystals growth on the surface of methane bubble (hydrate film) in pure water was studied by using a high-pressure visible microscope under the conditions of subcooling ΔT = 5.44–13.72 K and methane concentration difference ΔC = 2.92–8.19 mol·L-1. It was found the hydrate film is porous and the hydrate crystals grow towards the liquid phase on the film substrate. The crystal morphology and growth rate are affected by ΔT and ΔC. When ΔT < 8.82 K and ΔC < 4.12 mol·L-1, the hydrate grows into scattered columnar crystals, and the axial growth rate of the crystal gradually decreases. When ΔT > 8.82 K or ΔC > 4.12 mol·L-1, the hydrate crystals grow in dendritic shape, and the axial growth rate increases first and then decreases. The perimeter and area of the growing hydrate crystals were measured, and the fractal dimension of hydrate crystal under different ΔC and ΔT was calculated. The results show that the fractal dimension of columnar hydrate crystal is greater than 3. When 3.87 mol·L-1 < ΔC < 4.20 mol·L-1 and 7.4 K < ΔT < 8.8 K, the fractal dimension of columnar hydrate crystal is greater than 4; The fractal dimension of dendritic hydrate crystal is less than 3. When ΔC > 4.77 mol·L-1, ΔT < 8.52 K, the fractal dimension of dendritic hydrate crystal is less than 2.
    Rh single atoms embedded in CeO2 nanostructure boost CO2 hydrogenation to HCOOH
    Bo Wu, Xing Yu, Min Huang, Liangshu Zhong, Yuhan Sun
    2022, 43(3):  62-69.  doi:10.1016/j.cjche.2021.11.018
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    CO2 hydrogenation to value-added chemicals is a promising pathway to solve CO2-relevant environmental problems but still remains a great challenge. Herein, we report a CeO2 nanostructure supported Rh single atoms (Rh-SAs/CeO2) catalyst and was used for the efficient CO2 hydrogenation to HCOOH. The Rh-SAs/CeO2 exhibited high catalytic activity with turnover numbers (TON) up to 221 at 200 ℃, which was 4-fold to that of CeO2 supported Rh nanoparticles (Rh-NPs/CeO2). Moreover, HCOOH selectivity for Rh-SAs/CeO2 reached 85%, much higher than that of Rh-NPs/CeO2 (46%). Mechanism studies revealed that Rh single atoms in the Rh-SAs/CeO2 with high metal atoms utilization efficiency not only provided abundant active sites to promote the catalytic activity, but also suppressed the decomposition of HCOOH to CO and benefited the formation of HCOOH.
    Molecular dynamic simulation of carbon dioxide, methane, and nitrogen adsorption on Faujasite zeolite
    Hojatollah Moradi, Hedayat Azizpour, Hossein Bahmanyar, Mohammad Emamian
    2022, 43(3):  70-76.  doi:10.1016/j.cjche.2021.05.034
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    Removing impurities such as carbon dioxide and nitrogen from natural gas is a technical challenge and one of the major concerns in natural gas treatment process. In this study, adsorption of CH4, N2, and CO2 on the Faujasite (FAU) zeolite has been studied using molecular dynamics simulation at temperatures of 293, 308, and 323 K and pressures up to 1 MPa. COMPASS force field was used to model the interactions between zeolite and guest molecules. Ewald and atom-based summation methods were used for the calculation of electrostatic and van der Waals forces, respectively. Simulated results were modeled using Langmuir, Freundlich, Toth, and Sips adsorption isotherms. Sips isotherm for CO2, and Toth isotherm for CH4 and N2 pure compounds showed the best performance. Heat of adsorption for CH4, CO2, and N2 were calculated to be -15.48, -24.1, and -13.31 kJ·mol-1, respectively. A comparative study showed that the simulation model was successful in predicting the overall trend of the adsorption with acceptable accuracy.
    Highly dispersed nickel boosts catalysis by Cu/SiO2 in the hydrogenation of CO2-derived ethylene carbonate to methanol and ethylene glycol
    Youwei Yang, Jingyu Zhang, Yueqi Gao, Busha Assaba Fayisa, Antai Li, Shouying Huang, Jing Lv, Yue Wang, Xinbin Ma
    2022, 43(3):  77-85.  doi:10.1016/j.cjche.2022.01.017
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    The efficient hydrogenation of CO2-derived ethylene carbonate (EC) to yield methanol (MeOH) and ethylene glycol (EG) is a key process for indirect conversion of CO2 to MeOH. However, a high H2/EC molar ratio during the hydrogenation process (usually as 180–300) is generally required to achieve good catalytic performance, resulting in high cost and energy consumption for H2 circulation in the promising industrial application. Here, we prepared a series of Ni-modified Cu/SiO2 catalysts and explored the effects of synthesis methods and Ni contents on catalytic performance under different H2/EC molar ratios. The Cu/SiO2 catalyst with 0.2% (mass) Ni loading prepared by co-ammonia evaporation method exhibited above 99% conversion of EC, 91% and 98% selectivity to MeOH and EG respectively at H2/EC ratio of 60. And no significant deactivation was observed within 140 h at a lower H2/EC of 40. It is demonstrated that a few of Ni addition could not only promote Cu dispersion and increase surface Cu+ species due to the strong interaction between Cu and Ni species, but also form uniformly-dispersed CuNi alloy species and thus enhance the adsorption and dissociation of H2. But the excess Ni species would aggregate and segregate to cover partial surface of Cu nanoparticles, leading to a significantly drop of catalytic performance in EC hydrogenation. These insights may provide guidance for further design of catalysts for the ester hydrogenation reactions.
    CO2 mineralization of carbide slag for the production of light calcium carbonates
    Tongyang Zhang, Guanrun Chu, Junlin Lyu, Yongda Cao, Wentao Xu, Kui Ma, Lei Song, Hairong Yue, Bin Liang
    2022, 43(3):  86-98.  doi:10.1016/j.cjche.2022.02.011
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    The production of polyvinyl chloride by calcium carbide method is a typical chemical process with high coal consumption, leading to massive flue gas and carbide slag emissions. Currently, the carbide slag with high CaO content is usually stacked in residue field, easily draining away with the rain and corroding the soil. In this work, we coupled the treatment of flue gas and carbide slag to propose a facile CO2 mineralization route to prepare light calcium carbonate. And the route feasibility was comprehensively evaluated via experiments and simulation. Through experimental investigation, the Ca2+ leaching and mineralization reaction parameters were determined. Based on the experiment, a process was built and optimized through Aspen Plus, and the energy was integrated to obtain the overall process energy and material consumption. Finally, the net CO2 emission reduction rate of the entire process through the life-cycle assessment method was analyzed. Moreover, the relationship between the parameters and the CO2 emission life-cycle assessment was established. The final optimization results showed that the mineralization process required 1154.69 kW·h·(t CO2)-1 of energy (including heat energy of 979.32 kW·h·(t CO2)-1 and electrical energy of 175.37 kW·h·(t CO2)-1), and the net CO2 emission reduction rate was 35.8%. The light CaCO3 product can be sold as a high value-added product. According to preliminary economic analysis, the profit of mineralizing can reach more than 2,100 CNY·(t CO2)-1.
    High-energy-density gelled fuels with high stability and shear thinning performance
    Yang Liu, Hongzhi Zhang, Lun Pan, Kang Xue, Xiangwen Zhang, Ji-Jun Zou
    2022, 43(3):  99-109.  doi:10.1016/j.cjche.2022.01.007
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    Gelled fuels are the very promising propellants for new-generation rocket and ramjet propulsion. Here we report a new type of low-molecular mass organic gellant (Z), and prepared four kinds of stable gelled fuels based on HD-01, HD-03, RP-3 and QC liquid fuels, with the critical gellant concentration less than 1% (mass). The characterizations show that the gellant can form 3D network structure, via hydrogen bonding, π-π stacking and van der Waals forces, to fix fuel molecules during the formation of gelled fuels. So, the gelled fuels show high stability, with the remaining gel mass of 0.25% (mass) Z/HD-01 more than 90% even at high centrifugal speed of 7500 r·min-1, but the rheological property test shows that all gelled fuels have obvious shear thinning property, which benefits its storage in gelled state while supply in liquid state. The gelation of liquid fuels by gellant Z can increase the volumetric net heat of combustion (for HD-01, it increases from 39.58 MJ·L-1 to 40.76 MJ·L-1 with 1% (mass) Z), and liquefied gelled fuels show the comparable ignition delay time with the pristine liquid fuels. So, the gelled fuels made by gellant Z have better stability, shear thinning and combustion performances, which have great potential for the practical application.
    Efficient homogenous catalysis of CO2 to generate cyclic carbonates by heterogenous and recyclable polypyrazoles
    Zhen Lu, Jie He, Bogeng Guo, Yulai Zhao, Jingyu Cai, Longqiang Xiao, Linxi Hou
    2022, 43(3):  110-115.  doi:10.1016/j.cjche.2022.01.009
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    The cycloaddition between CO2 and epoxides to produce cyclic carbonate is an attractive and efficiency pathway for the utilization of CO2 as C1 source. The development of catalyst to mediate cycloaddition between CO2 and epoxides at low temperature and pressure is still a challenge. Herein, a series of polypyrazoles with glass transition temperature (Tg) in the range of 42.3–52.5 ℃ were synthesized and served as catalyst to mediate the cycloaddition of CO2 and epoxides by the assistant of tetrabutylammonium bromide. The catalytic behaviors of polypyrazole on the model cycloaddition of CO2 to epichlorohydrin, including the reaction parameters optimization and versatility were investigated in detail, and excellent yield (99.9%) and selectivity (99%) were obtained under the optimized reaction conditions of 70 ℃ and 1.0 MPa for 6.0 h. Noteworthily, the polypyrazole acts as homogeneous catalyst during reaction (higher than Tg). And under room temperature, polypyrazoles can be easily separated and recovered, which is a promising feature of a heterogeneous catalyst. Furthermore, the reaction mechanism was proposed. The DFT calculation suggested that the formation of hydrogen bond between pyrazole and epoxide greatly reduced the energy barrier, which play an important role in promoting CO2 cycloaddition.
    Layered bismuth oxide/bismuth sulfide supported on carrageenan derived carbon for efficient carbon dioxide electroreduction to formate
    Xiangzhao Hu, Junjie Sun, Wanzhen Zheng, Sixing Zheng, Yu Xie, Xiang Gao, Bin Yang, Zhongjian Li, Lecheng Lei, Yang Hou
    2022, 43(3):  116-123.  doi:10.1016/j.cjche.2022.02.009
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    Electrochemical reduction of carbon dioxide (CO2ER) into formate plays a crucial role in CO2 conversion and utilization. However, it still faces the problems of high overpotential and poor catalytic stability. Herein, we report a hybrid CO2ER electrocatalyst composed of layered bismuth sulfide (Bi2S3) and bismuth oxide (Bi2O3) supported on carrageenan derived carbon (Bi-CDC) prepared by a combined pyrolysis with hydrothermal treatment. In such 3D hybrid, layered Bi2O3 and Bi2S3 are uniformly grown on nanocarbon supports. Benefiting from strong synergistic effect between Bi2O3/Bi2S3 and nanocarbon, Bi-CDC-1:2 displays a high Faradic efficiency (FE) of >80% for formate production in the range of -0.9 V to -1.1 V with the maximum formate FE of 85.6% and current density of 14.1 mA·cm-2 at -1.0 V. Further, a positive onset potential of -0.5 V, a low Tafel slope of 112.38 mV·dec-1, and a slight performance loss during long-term CO2ER tests are observed on Bi-CDC-1:2. Experimental results shows that the better CO2ER performance of Bi-CDC-1:2 than that of Bi2O3 can be attributed to the strong interfacial interactions between nanocarbons and Bi2O3/Bi2S3. In situ ATR-FTIR measurements reveal that the rate-determining step in the CO2ER is the formation of HCOO* intermediated. Compared with carbon support, Bi-CDC-1:2 can promote the production of HCOO* intermediate and thus promoting CO2ER kinetic.
    Influence of zinc state on the catalyst properties of Zn/HZSM-5 zeolite in 1-hexene aromatization and cyclohexane dehydrogenation
    Di Gao, Yibo Zhi, Liyuan Cao, Liang Zhao, Jinsen Gao, Chunming Xu, Mingzhi Ma, Pengfei Hao
    2022, 43(3):  124-134.  doi:10.1016/j.cjche.2022.01.005
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    Rational design of Zn-containing HZSM-5 zeolite (Zn/HZSM-5) with high reactivity and excellent aromatization performance for olefin aromatization is crucially desired. We develop a new and uncomplicated method to synthesize Zn/HZSM-5 (IMX/Z5) with superior aromatization performance in the paper. Compared to incipient wetness impregnation (IMP/Z5) and mechanical mixing (MIX/Z5), the as-prepared IMX/Z5 presents a higher amount of surface ZnOH+ species (2.87%) while keeping identical bulk zinc content. As a result, more surface ZnOH+ favor both the aromatization of 1-hexene and cyclohexane dehydrogenation. For the two olefin aromatization pathways (hydrogen transfer and dehydrogenation), it is the first time found both the hydrogen transfer ability and the dehydrogenation ability increase linearly with the amount of surface ZnOH+ species while keeping identical bulk zinc content. We believe that the linear relationships are essential to design next generation olefin aromatization catalysts.
    Experimental study of the mass transfer behavior of carbon dioxide absorption into ternary phase change solution in a packed tower
    Yihan Yin, Aoqian Qiu, Hongxia Gao, Yanqing Na, Zhiwu Liang
    2022, 43(3):  135-142.  doi:10.1016/j.cjche.2022.01.025
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    Phase change absorbents for CO2 are of great interest because they are expected to greatly reduce the heat energy consumption during the regeneration process. Compared with other phase change absorbents, monoethanolamine (MEA)-sulfolane-water is inexpensive and has a fast absorption rate. It is one of the most promising solvents for large-scale industrial applications. Therefore, this study investigates the mass transfer performance of this phase change system in the process of CO2 absorption in a packed tower. By comparing the phase change absorbent and the ordinary absorbent, it is concluded that the use of MEA/sulfolane phase change absorbent has significantly improved mass transfer efficiency compared to a single MEA absorbent at the same concentration. In the 4 mol·L-1 MEA/5 mol·L-1 sulfolane system, the CO2 loading of the upper liquid phase after phase separation is almost zero, while the volume of the lower liquid phase sent to the desorption operation is about half of the total volume of the absorbent, which greatly reduces the energy consumption. This study also investigates the influence of operating parameters such as lean CO2 loading, gas and liquid flow rates, CO2 partial pressure, and temperature on the volumetric mass transfer coefficient (KGaV). The research shows that KGaV increases with increasing liquid flow rate and decreases with the increase of lean CO2 loading and CO2 partial pressure, while the inert gas flow rate and temperature have little effect on KGaV. In addition, based on the principle of phase change absorption, a predictive equation for the KGaV of MEA-sulfolane in the packed tower was established. The KGaV obtained from the experiment is consistent with the model prediction, and the absolute average deviation (AAD) is 7.8%.
    Cadmium-based metal-organic frameworks for high-performance electrochemical CO2 reduction to CO over wide potential range
    Xin Li, Song Hong, Leiduan Hao, Zhenyu Sun
    2022, 43(3):  143-151.  doi:10.1016/j.cjche.2021.10.013
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    Electrochemical CO2 reduction (ECR) powered by renewable energy sources provides a sustainable avenue to producing carbon–neutral fuels and chemicals. The design and development of high performance, cost-effective, and stable catalysts for ECR remain a focus of intense research. Here, we report a novel electrocatalyst, two-dimensional cadmium-based 1,4-benzenedicarboxylate metal–organic frameworks (Cd-BDC MOFs) which can effectively convert CO2 to CO with a faradaic efficiency (FE) of more than 80.0% over the voltage range between -0.9 and -1.1 V (versus reversible hydrogen electrode, vs. RHE) in 0.1 mol·L-1 CO2-saturated KHCO3 solution with an H-type cell, reaching up to 88.9% at -1.0 V (vs. RHE). The performance outperforms commercial CdO and many other MOF-based materials demonstrated in prior literature. The catalytic property can be readily tuned by manipulating synthesis conditions as well as electrolyte type. Especially, high CO FEs exceeding 90.0% can be attained on the Cd-BDC electrode at potentials ranging from -0.16 to -1.06 V (vs. RHE) in 0.5 mol·L-1 KHCO3 solution by using a gas diffusion electrode cell system. The maximum CO FE approaches ~97.6% at -0.26 V (vs. RHE) and the CO partial geometric current density is as high as about 108.1 mA cm-2 at -1.1 V (vs. RHE). This work offers an efficient, low cost, and alternative electrocatalyst for CO2 transformation.
    Covalent organic frameworks-incorporated thin film composite membranes prepared by interfacial polymerization for efficient CO2 separation
    Haoqing Xu, Wenyan Feng, Menglong Sheng, Ye Yuan, Bo Wang, Jixiao Wang, Zhi Wang
    2022, 43(3):  152-160.  doi:10.1016/j.cjche.2022.02.014
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    Thin film composite (TFC) membranes with nanofillers additives for CO2 separation show promising applications in energy and environment-related fields. However, the poor compatibility between nanofillers and polymers in TFC membranes is the main problem. In this work, covalent organic frameworks (COFs, TpPa-1) with rich —NH— groups were incorporated into polyamide (PA) segment via in situ interfacial polymerization to prepare defect-free TFC membranes for CO2/N2 separation. The formed covalent bonds between TpPa-1 and PA strengthen the interaction between nanofillers and polymers, thereby enhancing compatibility. Besides, the incorporated COFs disturb the rigid structure of the PA layer, and provide fast CO2 transfer channels. The incorporated COFs also increase the content of effective carriers, which enhances the CO2 facilitated transport. Consequently, in CO2/N2 mixed gas separation test, the optimal TFC (TpPa0.025-PIP-TMC/mPSf) membrane exhibits high CO2 permeance of 854 GPU and high CO2/N2 selectivity of 148 at 0.15 MPa, CO2 permeance of 456 GPU (gas permeation unit) and CO2/N2 selectivity of 92 at 0.5 MPa. In addition, the TpPa0.025-PIP-TMC/mPSf membrane also achieves high permselectivty in CO2/CH4 mixed gas separation test. Finally, the optimal TFC membrane showes good stability in the simulated flue gas test, revealing the application potential for CO2 capture from flue gas.
    A dual metal-organic framework strategy for synthesis of FeCo@NC bifunctional oxygen catalysts for clean energy application
    Jun Chen, Liandong Li, Liu Yang, Chang Chen, Shitao Wang, Yan Huang, Dapeng Cao
    2022, 43(3):  161-168.  doi:10.1016/j.cjche.2022.02.017
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    Developing high efficient bifunctional oxygen electrocatalysts for clean energy applications like Zin-air battery (ZAB) is highly desired, because it would reduce the cost and speed up the practical application of ZAB. Here we use a dual metal–organic framework (MOF) synthesis strategy to prepare the N-doped carbon supported bimetallic FeCo nanoparticle catalysts (marked as FeCo@NC) by pyrolysis of ZnCo-ZIF/MIL-101(Fe) composite. The FeCo@NC exhibits remarkable electrocatalytic activity for ORR with half-wave potential of 0.89 V vs. the reversible hydrogen electrode (RHE) and robust durability for both ORR and OER (oxygen reduction reaction and oxygen evolution reaction), which is attributed to the generation of Fe0.26Co0.74 crystalline phase and mesopores due to the dual-MOF synthesis strategy. The rechargeable ZAB based on FeCo@NC air electrode shows a maximum energy density of 139.6mW·cm-2 and excellent cyclic stability over 130 h, significantly surpassing the Pt and Ir-based ZAB. The present work provides a useful dual-MOF synthesis strategy for preparing high-performance multifunctional catalysts for ORR, OER and hydrogen evolution reaction (HER).
    The effect of protic ionic liquids incorporation on CO2 separation performance of Pebax-based membranes
    Haiyan Jiang, Lu Bai, Bingbing Yang, Shaojuan Zeng, Haifeng Dong, Xiangping Zhang
    2022, 43(3):  169-176.  doi:10.1016/j.cjche.2022.02.006
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    The separation of carbon dioxide (CO2) is of great importance for environment protection and gas resource purification. The ionic liquids (ILs)-based gas separation membrane provides a new chance for efficient CO2 separation, while high permeability and selectivity of membranes is a great challenge. In this study, the influence of two protic ILs with different anion ([TMGH][Im] and [TMGH][PhO]) on the CO2 separation performance of the prepared ILs/Pebax blended membranes were systematically investigated at different temperature. The results showed the CO2 permeability exhibits the rising trend for ILs/Pebax blended membranes with the increment of IL content. Especially, the [TMGH][Im] with low viscosity and high CO2 absorption capacity leads to the blended membranes showing better CO2 permeability and ideal CO2 selectivity than that of membranes with [TMGH][PhO] at high IL content. Besides, with operating temperature increasing, the gas permeability of 20% (mass) [TMGH][Im]/Pebax blended membrane increases due to the decreasing viscosity of IL and the rising chain mobility of polymer. Inversely, the gas selectivity shows decreasing trend because CO2 absorption capacity obviously decreased at higher temperature.
    Highly efficient subnanometer Ru-based catalyst for ammonia synthesis via an associative mechanism
    Yanliang Zhou, Qianjin Sai, Zhenni Tan, Congying Wang, Xiuyun Wang, Bingyu Lin, Jun Ni, Jianxin Lin, Lilong Jiang
    2022, 43(3):  177-184.  doi:10.1016/j.cjche.2022.01.015
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    The industrial manufacture of ammonia (NH3) using Fe-based catalyst works under rigorous conditions. For the goal of carbon-neutrality, it is highly desired to develop advanced catalyst for NH3 synthesis at mild conditions to reduce energy consumption and CO2 emissions. However, the main challenge of NH3 synthesis at mild conditions lies in the dissociation of steady NN triple bond. In this work, we report the design of subnanometer Ru clusters (0.8 nm) anchored on the hollow N-doped carbon spheres catalyst (Ru-SNCs), which effectively promotes the NH3 synthesis at mild conditions via an associative route. The NH3 synthesis rate over Ru-SNCs (0.49% (mass) Ru) reaches up to 11.7 mmol NH3·(g cat)-1·h-1 at 400 ℃ and 3 MPa, which is superior to that of 8.3 mmol NH3·(g cat)-1·h-1 over Ru nanoparticle catalyst (1.20% (mass) Ru). Various characterizations show that the N2H4 species are the main intermediates for NH3 synthesis on Ru-SNCs catalyst. It demonstrates that Ru-SNCs catalyst can follow an associative route for N2 activation, which circumvents the direct dissociation of N2 and results in highly efficient NH3 synthesis at mild conditions.
    Hydrate formation from liquid CO2 in a glass beads bed
    Nan Li, Jing-Yu Kan, Chang-Yu Sun, Guang-Jin Chen
    2022, 43(3):  185-191.  doi:10.1016/j.cjche.2022.01.008
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    CO2 sequestration in marine sediments as solid hydrates is a potential way to capture and store anthropogenic CO2. In this study, hydrate formation from liquid CO2 in marine sediments was simulated in a glass beads bed, and the factors affecting the kinetics of hydrate formation were investigated. The results indicated that the rapid initial hydrate formation with a high driving force always increases the mass transfer resistance, which slows down hydrate growth. The final ratio of water conversion is higher under conditions of low temperature and higher pressure. A smaller particle size is conductive to initial CO2 hydrate growth, but the water conversion ratio in a bed with larger particles is slightly higher. Compared with other factors, the change in water saturation has an obvious effect on the final water conversion. To inhibit the initial hydrate formation during the injection process, in this paper, a kinetic inhibitor is proposed for pre-injection into marine sediments. This work shows that at a low pressure, a low-concentration inhibitor has an obvious inhibition effect on hydrate growth. However, at a high pressure, it is necessary to increase the concentration of inhibitor to produce an obvious inhibition effect.
    Pyrolyzing soft template-containing poly(ionic liquid) into hierarchical N-doped porous carbon for electroreduction of carbon dioxide
    Mingdong Sun, Zhengyun Bian, Weiwei Cui, Xiaolong Zhao, Shu Dong, Xuebin Ke, Yu Zhou, Jun Wang
    2022, 43(3):  192-201.  doi:10.1016/j.cjche.2021.07.020
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    Heteroatom-doped carbon materials have demonstrated great potential in the electrochemical reduction reaction of CO2 (CO2RR) due to their versatile structure and function. However, rational structure control remains one challenge. In this work, we reported a unique carbon precursor of soft template-containing porous poly(ionic liquid) (PIL) that was directly synthesized via free-radical self-polymerization of ionic liquid monomer in a soft template route. Variation of the carbonization temperature in a direct pyrolysis process without any additive yielded a series of carbon materials with facile adjustable textural properties and N species. Significantly, the integration of soft-template in the PIL precursor led to the formation of hierarchical porous carbon material with a higher surface area and larger pore size than that from the template-free precursor. In CO2RR to CO, the champion catalyst gave a Faraday efficiency of 83.0% and a current density of 1.79 mA·cm-2 at -0.9 V vs. reversible hydrogen electrode (vs. RHE). The abundant graphite N species and hierarchical pore structure, especially the unique hierarchical small-/ultra-micropores were revealed to enable better CO2RR performance.
    Improving ionic conductivity of polymer-based solid electrolytes for lithium metal batteries
    Q. Yang, A. Wang, J. Luo, W. Tang
    2022, 43(3):  202-215.  doi:10.1016/j.cjche.2021.07.008
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    Because of its superior safety and excellent processability, solid polymer electrolytes (SPEs) have attracted widespread attention. In lithium based batteries, SPEs have great prospects in replacing leaky and flammable liquid electrolytes. However, the low ionic conductivity of SPEs cannot meet the requirements of high energy density systems, which is also an important obstacle to its practical application. In this respect, escalating charge carriers (i.e. Li+) and Li+ transport paths are two major aspects of improving the ionic conductivity of SPEs. This article reviews recent advances from the two perspectives, and the underlying mechanism of these proposed strategies is discussed, including increasing the Li+ number and optimizing the Li+ transport paths through increasing the types and shortening the distance of Li+ transport path. It is hoped that this article can enlighten profound thinking and open up new ways to improve the ionic conductivity of SPEs.
    Auto-thermal reforming of acetic acid for hydrogen production by ZnxNiyCrOm±δ catalysts: Effect of Cr promoted Ni-Zn intermetallic compound
    Xuanyi Jia, Xiaomin Hu, Qiao Wang, Baiquan Chen, Xingyue Xie, Lihong Huang
    2022, 43(3):  216-221.  doi:10.1016/j.cjche.2021.04.017
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    A series of ZnxNiyCrOm±δ catalysts were synthesized via a typical co-precipitation method, in which Zn-Cr layered double hydroxides (LDHs) were found and Ni-Zn intermetallic compound (IMC) was formed after reduction in hydrogen. During auto-thermal reforming (ATR) of acetic acid (HAc), the Ni-Zn IMC was transformed into Ni/(amorphous-ZnO)-ZnCr2O4 species with uniformed distribution and appropriate interaction within these Ni-Zn-Cr-O species; besides, the adsorbed oxygen promoted the activation and transfer of oxygen species; therefore, deactivation by oxidation, sintering and coking was inhibited. And the optimized Zn2.37Ni0.63CrO4.5±δ catalyst presented high activity and stability in a 45-h ATR test with HAc conversion near 100% and hydrogen yield at 2.7 mol-H2/mol-HAc, showing potential for hydrogen production via ATR of HAc.
    Defective NH2-UiO-66 (Zr) effectively converting CO2 into cyclic carbonate under ambient pressure, solvent-free and co-catalyst-free conditions
    Xueting Liu, Chunhui Hu, Jingjing Wu, Peng Cui, Fengyu Wei
    2022, 43(3):  222-229.  doi:10.1016/j.cjche.2022.02.016
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    In this study, a series of metal–organic frameworks (MOFs) NH2-UiO-66-xHAc catalysts were synthesized by solvothermal method using acetic acid (HAc) as a modulator, and were applied to the cycloaddition of CO2 and epichlorohydrin (EPIC) under ambient pressure. Influences of the modulation by HAc on morphologies and structures of the MOFs are demonstrated via PXRD, FESEM, FTIR, N2 adsorption–desorption, XPS and 1H NMR characterizations. The results show that the MOFs containing mesoporous pores can be prepared by adjusting the concentration of HAc. By optimizing the amount of HAc added, the specific surface area of NH2-UiO-66-8HAc is as high as 879.17 m2·g-1, which is 28.3% higher than that of the original MOFs. And the evaluation of catalytic performance showed that HAc modulation enhanced the activity of NH2-UiO-66-xHAc under mild conditions. The exposure of Lewis acid sites, increased specific surface area and porosity via the modulation of HAc defective ligand can be supposed the key factors to determine the enhanced catalytic activities. In addition, considering the influence of gas concentration on the reaction, the concept of TOP (Turnover of Pressure, defined as the mass of conversions of a unit mass catalyst under unit pressure and unit time) was first proposed in this article.
    Fabricating amide functional group modified hyper-cross-linked adsorption resin with enhanced adsorption and recognition performance for 5-hydroxymethylfurfural adsorption via simple one-step
    Lei Hu, Shunhui Tao, Junting Xian, Xiaodong Zhang, Yao Liu, Xiaojie Zheng, Xiaoqing Lin
    2022, 43(3):  230-239.  doi:10.1016/j.cjche.2021.11.006
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    In this study, three kinds of amide functional group modified hyper-cross-linked adsorption resin were synthesized by alternating radical copolymerization in simple one-step and applied for 5-hydroxymethylfurfural (5-HMF) adsorption. The successful synthesis and properties of adsorbents were evaluated with Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption–desorption isotherms, thermogravimetric analysis, and elemental analysis. Poly (N, N'-4,4'-diphenylmethane-bismaleimide-alt-divinylbenzene) (poly (BDM-alt-DVB)) resin exhibited highest adsorption capacity for 5-HMF (64.0 mg·g-1 wet resin) and excellent adsorption selectivity (α5-HMF/LA = 2.71 ±0.12, α5-HMF/FA = 13.88 ±0.15, α5-HMF/Glucose = 11.91 ±1.11) in the multi-component solution at 25 ℃. Langmuir isotherm model well fitted the equilibrium adsorption data within the initial 5-HMF concentration range of 0.5–10.0 g·L-1 with highest correlation coefficient. Furthermore, the thermodynamic parameters demonstrated that the adsorption of 5-HMF onto poly (BDM-alt-DVB) resin was spontaneous and exothermic. Kinetic study revealed that the adsorption process was fast, reaching equilibrium within 12 min. Importantly, the poly (BDM-alt-DVB) resin also demonstrated excellent reusability. In summary, the poly (BDM-alt-DVB) resin will be useful in 5-HMF hydrolysate separation applications.
    Role of Ni species in ZnO supported on Silicalite-1 for efficient propane dehydrogenation
    Bofeng Zhang, Mingxia Song, Hongwang Liu, Guozhu Li, Sibao Liu, Li Wang, Xiangwen Zhang, Guozhu Liu
    2022, 43(3):  240-247.  doi:10.1016/j.cjche.2022.02.015
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    Propane dehydrogenation (PDH) is one of the most effective technologies to produce propene. Non-noble zinc-based catalysts have paid increasing attention because of low cost and nontoxic, compared with industrial Pt and Cr-based catalysts. However, they often suffer from limited catalytic activity and poor stability. Here, we introduced moderate Ni into ZnO supported Silicalite-1 zeolite to increase catalytic activity and stability simultaneously. Zn2+ was the definite active site and NiZn alloy facilitated the sluggish H recombination into H2 via reverse spillover. Furthermore, the introduction of Ni increased Lewis acid strength caused by electron transfer from ZnO to NiZn alloy, contributing to improved stability. For resulted 0.5NiZn/S-1, propene formation rate was 0.18 mol C3H6·(g Zn)-1·h-1 at 550 ℃, which was above 1.5 times higher than that over Zn/S-1 without Ni. Under stability test, the deactivation of 0.5NiZn/S-1 was 0.019 h-1, which was only 1/10 of that over Zn/S-1.
    The highly selective catalytic hydrogenation of CO2 to CO over transition metal nitrides
    Yichao Wu, Zhiwei Xie, Xiaofeng Gao, Xian Zhou, Yangzhi Xu, Shurui Fan, Siyu Yao, Xiaonian Li, Lili Lin
    2022, 43(3):  248-254.  doi:10.1016/j.cjche.2021.12.022
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    Three transition metal-like facet centered cubic structured transition metal nitrides, γ-Mo2N, β-W2N and δ-NbN, are synthesized and applied in the reaction of CO2 hydrogenation to CO. Among the three nitride catalysts, the γ-Mo2N exhibits superior activity to target product CO, which is 4.6 and 76 times higher than the other two counterparts of β-W2N and δ-NbN at 600 ℃, respectively. Additionally, γ-Mo2N exhibits excellent stability on both cyclic heating–cooling and high space velocity steady state operation. The deactivation degree of cyclic heating–cooling evaluation after 5 cycles and long-term stability performance at 773 and 873 K in 50 h are all less than 10%. In-situ XRD and kinetic studies suggest that the γ-Mo2N itself is able to activate both of the reactants CO2 and H2. Below 400 ℃, the reaction mainly occurs at the surface of γ-Mo2N catalyst. CO2 and H2 competitively adsorbe on the surface of catalyst and CO2 is the relatively stronger surface adsorbate. At a higher temperature, the interstitial vacancies of the γ-Mo2N can be reversibly filled with the oxygen from CO2 dissociation. Both of the surface and bulk phase sites of γ-Mo2N participate in the high temperature CO2 hydrogenation pathway.
    Highly dispersible cerium-oxide modified Ni/SBA-15 for steam reforming of bio-mass based JP10
    Haocui Zhang, Zhourong Xiao, Mei Yang, Jijun Zou, Guozhu Liu, Xiangwen Zhang
    2022, 43(3):  255-265.  doi:10.1016/j.cjche.2022.01.016
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    Ni/SBA-15 modified by highly dispersed cerium-oxide was prepared with the aid of sucrose for steam reforming of JP10 (C10H16). Their characterization showed that addition of appropriate amount ceria led to the formation of highly dispersed CeO2 and Ni, and the CeO2 covered smaller nickel particles like strawberry seeds to form much more interface between them. Their catalytic activity exhibited higher stability over time on stream of 6.5 h with conversion higher than 95% and higher carbon resistance (mass loss less than 4.5% by TG), which may derive from good properties below: (1) much more interface enhanced cooperation effect and increased turnover frequency at the interface; (2) the stronger interaction between Ni and ceria to suppress sintering by formation of Ni-O-Ce solid solution; (3) the large amount of oxygen vacancies from the formation of Ni-O-Ce solid solution and highly dispersed CeO2 to facilitate the water–gas–shift reaction and carbon removal.
    CdS nanoparticles decorated hexagonal Fe2O3 nanosheets with a Z-scheme photogenerated electron transfer path for improved visible-light photocatalytic hydrogen production
    Feng Guo, Haoran Sun, Yuxing Shi, Fengyu Zhou, Weilong Shi
    2022, 43(3):  266-274.  doi:10.1016/j.cjche.2021.03.055
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    Photocatalytic water splitting for hydrogen production (H2) is one of the main potential applications of photocatalytic technology, which can use solar energy as the energy required for chemical reactions to alleviate the energy crisis. In this work, zero-dimensional/two-dimensional (0D/2D) contact surface CdS/α-Fe2O3 (CF) heterojunction photocatalyst was synthesized via a simple solvothermal method. Photocatalytic hydrogen production experiments revealed that the CF-15 sample shows the optimal photocatalytic H2 rate (1806 (μmol·h-1·g-1)) and apparent quantum efficiency (AQE = 13.7% at λ = 420 nm). The enhancement of photocatalytic performance is mainly attributed to the contact of 0D/2D interface and the synergistic effect of Z-scheme electron transfer mechanism. This work provides an effective way for modified composite semiconductor photocatalyst by constructing special interface heterojunction to achieve highly efficiently catalysis.
    The role of diffusion in the nucleation of calcium carbonate
    Xiangyu Dou, Haoyang Huang, Yongsheng Han
    2022, 43(3):  275-281.  doi:10.1016/j.cjche.2021.03.039
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    Nucleation widely exists in nature, from cloud formation to haze generation. The classical nucleation theory (CNT) was created to describe the nucleation process, but it fails to predict many experimental phenomena due to the short consideration of nanoscale phenomena and macroscale dynamics. Although the attachment and detachment of monomers are considered in the developed model of nucleation, the diffusion of chemicals in the bulk is not valued as supersaturation in the nucleation process so far. Here we employ simulation and experimental approaches to investigate how the diffusion of ions affects the nucleation of calcium carbonate. The diffusion of ions is regulated by the viscosity of solvents and the sonication imposed on the solution. It is found that the nucleation rates increased exponentially with the diffusion coefficient of ions, which is beyond the prediction of CNT. This abnormal finding might be ascribed to the involvement of cluster aggregation in the nucleation of calcium carbonate. This study highlights the significance of chemical diffusion in the nucleation process, which may help to revise the nucleation theory and develop solutions for the rational synthesis of materials, as well as for the control of air pollution.
    Perspective of hydrogen energy and recent progress in electrocatalytic water splitting
    Yixuan Gong, Jiasai Yao, Ping Wang, Zhenxing Li, Hongjun Zhou, Chunming Xu
    2022, 43(3):  282-296.  doi:10.1016/j.cjche.2022.02.010
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    As a secondary energy with great commercialization potential, hydrogen energy has been widely studied due to the high calorific value, clean combustion products and various reduction methods. At present, the blueprint of hydrogen energy economy in the world is gradually taking shape. Compared with the traditional high-energy consuming methane steam reforming hydrogen production method, the electrocatalytic water splitting hydrogen production stands out among other process of hydrogen production owning to the mild reaction conditions, high-purity hydrogen generation and sustainable production process. Basing on current technical economy situation, the highly electric power cost limits the further promotion of electrocatalytic water splitting hydrogen production process. Consequently, the rational design and development of low overpotential and high stability electrocatalytic water splitting catalysts are critical toward the realization of low-cost hydrogen production technology. In this review, we summarize the existing hydrogen production methods, elaborate the reaction mechanism of the electrocatalytic water splitting reaction under acidic and alkaline conditions and the recent progress of the respective catalysts for the two half-reactions. The structure–activity relationship of the catalyst was deep-going discussed, together with the prospects of electrocatalytic water splitting and the current challenges, aiming at provide insights for electrocatalytic water splitting catalyst development and its industrial applications.
    Progress of vanadium phosphorous oxide catalyst for n-butane selective oxidation
    Muhammad Faizan, Yingwei Li, Ruirui Zhang, Xingsheng Wang, Piao Song, Ruixia Liu
    2022, 43(3):  297-315.  doi:10.1016/j.cjche.2021.10.026
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    The utilization of lighter alkanes into useful chemical products is essential for modern chemistry and reducing the CO2 emission. Particularly, n-butane has gained special attention across the globe due to the abundant production of maleic anhydride (MA). Vanadium phosphorous oxide (VPO) is the most effective catalyst for selective oxidation of n-butane to MA so far. Interestingly, the VPO complex exists in more or less fifteen different structures, each one having distinct phase composition and exclusive surface morphology and physiochemical properties such as valence state, lattice oxygen, acidity etc., which relies on precursor preparation method and the activation conditions of catalysts. The catalytic performance of VPO catalyst is improved by adding different promoters or co-catalyst such as various metals dopants, or either introducing template or structural-directing agents. Meanwhile, new preparation strategies such as electrospinning, ball milling, hydrothermal, barothermal, ultrasound, microwave irradiation, calcination, sol–gel method and solvothermal synthesis are also employed for introducing improvement in catalytic performance. Research in above-mentioned different aspects will be ascribed in current review in addition to summarizing overall catalysis activity and final yield. To analyze the performance of the catalytic precursor, the reaction mechanism and reaction kinetics both are discussed in this review to help clarify the key issues such as strong exothermic reaction, phosphorus supplement, water supplement, deactivation, and air/n-butane pretreatment etc. related to the various industrial applications of VPO.
    The quasi-activity coefficients of non-electrolytes in aqueous solution with organic ions and its application on the phase splitting behaviors prediction for CO2 absorption
    Xiaomeng Zhao, Xingyu Li, Changjun Liu, Shan Zhong, Houfang Lu, Hairong Yue, Kui Ma, Lei Song, Siyang Tang, Bin Liang
    2022, 43(3):  316-323.  doi:10.1016/j.cjche.2022.02.003
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    CO2 capture with a low energy consumption is of important application significance for reducing CO2 emission. The phase-change absorbent developed in recent years shows its potential for low-energy CO2 capture. The unclear phase-splitting rule hinders the efficient development of CO2 phase-change absorbents. To predict phase-splitting behaviors of mono/poly-amine-organic solvent–water system with various concentrations, a quasi-activity coefficient was developed based on Debye & McAulay equation and some Density function theory descriptors. Six models based on Debye & McAulay equation were developed with different ion radius, descriptors or poly-amine-CO2 products. The phase-splitting boundary was drawn on the model with the best predictability. This quasi-activity coefficient would provide guidance for the phase-splitting systems development, especially for polyamines.
    Conformance control by a microgel in a multi-layered heterogeneous reservoir during CO2 enhanced oil recovery process
    Zheyu Liu, Jian Zhang, Xianjie Li, Chunming Xu, Xin Chen, Bo Zhang, Guang Zhao, Han Zhang, Yiqiang Li
    2022, 43(3):  324-334.  doi:10.1016/j.cjche.2022.01.011
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    Injecting CO2 into the underground for oil displacement and shortage is an important technique for carbon capture, utilization and storage (CCUS). One of the main problems during the CO2 injection is the channeling plugging. Finding an effective method for the gas channeling plugging is a critical issue in the CO2 EOR process. In this work, an acid-resistance microgel named dispersed particle gel (DPG) was characterized and its stability was tested in the CO2 environment. The microgel size selection strategies for the homogeneous and heterogeneous reservoirs were respectively investigated using the single core flooding and three parallel core flooding experiments. Moreover, the comparison of microgel alternate CO2 (MAC) injection and water alternate CO2 (WAC) injection in the dual core flooding experiments were presented for the investigation of the role of microgel on the conformance control in CO2 flooding process. The results have shown that the microgel featured with —NH and C—N groups can keep its morphology after aging 7 days in the CO2 environment. Where, the small microgel with unobstructed migration and large microgel with good plugging efficiency for the high permeability zone were respectively featured with the higher recovery factor in homogeneous and heterogeneous conditions, which indicate they are preferred used for the oil displacement and conformance control. Compared to WAC injection, MAC injection had a higher incremental recovery factor of 12.4%. It suggests the acid-resistance microgel would be a good candidate for the conformance control during CO2 flooding process.
    Amine-immobilized HY zeolite for CO2 capture from hot flue gas
    Wanqiao Liang, Jihuan Huang, Penny Xiao, Ranjeet Singh, Jining Guo, Leila Dehdari, Gang Kevin Li
    2022, 43(3):  335-342.  doi:10.1016/j.cjche.2022.02.004
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    Solid amine-based adsorbents were widely studied as an alternative to liquid amine for post-combustion CO2 capture (PCC). However, most of the amine adsorbents suffer from low thermal stability and poor cyclic regenerability at the temperature of hot flue gases. Here we present an amine loaded proton type Y zeolite (HY) where the amines namely monoethanolamine (MEA) and ethylenediamine (ED) are chemical immobilized via ionic bond to the zeolite framework to overcome the amine degradation problem. The MEA and ED of 5%, 10% and 20% (mass) concentration – immobilized zeolites were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and N2 -196 ℃ adsorption to confirm the structure integrity, amine functionalization, and surface area, respectively. The determination of the amine loading was given by C, H, N elemental analysis showing that ED has successfully grafted almost twice as many amino groups as MEA within the same solvent concentration. CO2 adsorption capacity and thermal stability of these samples were measured using thermogravimetric analyser. The adsorption performance was tested at the adsorption temperature of 30, 60 and 90 ℃, respectively using pure CO2 while the desorption was carried out with pure N2 purge at the same temperature and then followed by elevated temperature at 150 ℃. It was found that all the amine@HY have a substantial high selectivity of CO2 over N2. The sample 20% ED@HY has the highest CO2 adsorption capacity of 1.76 mmol·g-1 at 90 ℃ higher than the capacity on parent NaY zeolite (1.45 mmol·g-1 only). The amine@HY samples presented superior performance in cyclic thermal stability in the condition of the adsorption temperature of 90 ℃ and the desorption temperature of 150 ℃. These findings will foster the design of better adsorbents for CO2 capture from flue gas in post-combustion power plants.
    The effect of different Co phase structure (FCC/HCP) on the catalytic action towards the hydrogen storage performance of MgH2
    Liuting Zhang, Haijie Yu, Zhiyu Lu, Changhao Zhao, Jiaguang Zheng, Tao Wei, Fuying Wu, Beibei Xiao
    2022, 43(3):  343-352.  doi:10.1016/j.cjche.2021.10.016
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    High hydrogen desorption temperature and sluggish reaction kinetics are the major limitations for the practical application of MgH2. In this study, Co particles with a face centered cubic (FCC) structure and a hexagonal close packed (HCP) structure were prepared facilely and proved to be good catalysts for magnesium hydride. Co particles with FCC structure presented better catalytic effect on MgH2 than that with HCP structure. Both 7% (mass) Co FCC and HCP particle modified MgH2 decreased the initial dehydrogenation temperature from 301.3 ℃ to approximately 195.0 ℃, but 7% (mass) Co with FCC structure modified MgH2 has a faster desorption rate, and around 6.5% (mass) H2 was desorbed in 10 min at 325 ℃. Hydrogen uptake was detected at 70 ℃ under 3.25 MPa hydrogen pressure and 6.0% (mass) H2 was recharged in 40 min at 150 ℃. The hydrogen desorption and absorption activation energy for 7% (mass) FCC Co modified MgH2 was significantly decreased to (76.6±8.3) kJ·mol-1 and (68.3±6.0) kJ·mol-1, respectively. Thermodynamic property was also studied, the plateau pressures of MgH2 + 7% (mass) FCC Co were determined to be 0.14, 0.28, 0.53 and 0.98 MPa for 300 ℃, 325 ℃, 350 ℃ and 375℃. The decomposition enthalpy of hydrogen (ΔH) for MgH2 + 7% (mass) FCC Co was (80.6±0.1) kJ·mol-1, 5.8 kJ·mol-1 lower than that of as-prepared MgH2. Moreover, cycling performance for the first 20 cycles revealed that the reaction kinetics and capacity of MgH2-FCC Co composite remained almost unchanged. The result of density functional theory calculation demonstrated that cobalt could extract the Mg—H bond and reduced the decompose energy of magnesium hydride. Our paper can be presented as a reference for searching highly effective catalysts for hydrogen storage and other energy-related research fields.
    Structural reconstruction of Sn-based metal-organic frameworks for efficient electrochemical CO2 reduction to formate
    Yachen Deng, Shifu Wang, Yanqiang Huang, Xuning Li
    2022, 43(3):  353-359.  doi:10.1016/j.cjche.2022.03.006
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    MOF-based materials have been widely explored in electrochemical CO2 reduction reactions for the production of valuable chemicals. Understanding the reconstruction of those catalysts under working conditions is crucial for the identification of active sites and clarification of reaction mechanism. Herein, a series of six N coordinated Sn-based metal-organic frameworks (Sn-N6-MOFs) are newly developed for electrochemical CO2 reduction (CO2RR). 2% Sn-N6-MOF achieves the optimal catalytic performance with a formate Faradaic efficiency of ~85% and a current density of 23 mA·cm-2 at -1.23 V vs. RHE. In-situ Raman results combined with ex-situ 119Sn Mössbauer measurements reveal the structural reconstruction of Sn-N6-MOFs during CO2RR, generating tin nanoclusters as the real active sites for CO2 electroreduction to HCOOH.
    Top-down strategy for bamboo lignocellulose-derived carbon heterostructure with enhanced electromagnetic wave dissipation
    Shaoxiang Cai, Han Yan, Qiuyi Wang, He Han, Ru Li, Zhichao Lou
    2022, 43(3):  360-369.  doi:10.1016/j.cjche.2021.12.031
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    Biomass-derived residue carbonization has been an important issue for “carbon fixation” and “zero emission”, and the carbonized products have multiple application potentials. However, there have been no specific research to study the differences in macro- and micro-morphology, electrical properties and many other aspects of the products obtained from carbonization of pure cellulose, pure lignin or their complex, lignocellulose. In this work, lignocellulose with cellulose to lignin mass ratio of 10:1 is obtained using p-toluenesulfonic acid hydrolysis followed by homogenization process at a controlled condition. Then, carbon heterostructure with fibers and sheets (CH-10) are obtained by pyrolysis at 1500 ℃. Detailed results imply that the fiber-like carbon structure possesses high crystallinity and low defect density, coming from carbonization of the cellulose content in lignocellulose (LC) nanofibers. Correspondingly, the graphite-like carbon sheet with high defect density and low crystallinity comes from carbonization of the lignin content in LCs. Further investigation indicates CH-10 possesses enhanced polarization and moderate impedance matching which makes it an ideal candidate for electromagnetic wave (EMW) absorption. CH-10 exhibits an excellent EMW absorption performance with a minimum RL value of -50.05 dB and a broadest absorption bandwidth of 4.16 GHz at a coating thickness as thin as 1.3 mm.
    3D multiphase flow simulation of Marangoni convection on reactive absorption of CO2 by monoethanolamine in microchannel
    Shuai Chen, Jiahong Lan, Yu Zhang, Jia Guo, Zhikai Cao, Yong Sha
    2022, 43(3):  370-377.  doi:10.1016/j.cjche.2021.02.014
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    A multiphase flow 3D numerical simulation method employing the coupled volume of fluid (VOF) and level set model is established to study the reactive absorption of CO2 by the monoethanolamine (MEA) aqueous solution in a falling film microchannel. Based on the flow-reaction-mass transfer model of the MEA-CO2 system in the falling film microchannel, the enhancement effect of the Marangoni convection in this reactive absorption process is analyzed. The enhancement factor of the Marangoni convection obtained in this work is in good agreement with experimental results in the literature. With consideration of the absorption ratio as well as the enhancement effect of the Marangoni convection, the influence of different MEA concentrations on absorption of CO2 is investigated. Furthermore, the appropriate MEA concentration for absorption enhanced by the Marangoni convection is acquired.
    Design and experiment of high-productivity two-stage vacuum pressure swing adsorption process for carbon capturing from dry flue gas
    Xiuxin Yu, Bing Liu, Yuanhui Shen, Donghui Zhang
    2022, 43(3):  378-391.  doi:10.1016/j.cjche.2021.02.022
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    A two-stage vacuum pressure swing adsorption (VPSA) process that coupled kinetically controlled and equilibrium controlled separation process with reflux has been investigated for capturing carbon dioxide from dry flue gas (85% N2/15% CO2). In the first enriching stage, carbon molecular sieve (CMS), which shows kinetic selectivity for CO2/N2, is adopted as the adsorbent to remove most N2 in feed gas, thereby upgrading CO2 and significantly reducing the amount for further refinement. The second stage loads zeolite 13X as adsorbent to purify the CO2-rich flow from the first stage for meeting the requirements of National Energy Technology Laboratory. Series of experiments have been conducted for adsorption isotherms measuring and lab-scale experimental validation as well as analysis. The effect of feed composition on the separation performance of the PSA system was studied experimentally and theoretically here. The optimal results achieved 95.1% purity and 92.9% recovery with a high CO2 productivity (1.89 mol CO2·h-1·kg-1) and an appropriate energy consumption of 1.07 MJ·(kg CO2)-1. Further analysis has been carried out by simulation for explicating the temperature, pressure, and concentration distribution at cyclic steady state.