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Table of Content
28 August 2014, Volume 22 Issue 8
    Zhigang Lei, Biaohua Chen
    2014, 22(8):  842-842.  doi:10.1016/j.cjche.2014.08.001
    Abstract ( 1539 )   PDF (144KB) ( 28 )  
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    Simulation of a Reverse FlowReactor for the Catalytic Combustion of Lean Methane Emissions
    Jiajin Zhang, Zhigang Lei, Jianwei Li,Biaohua Chen, Jiajin Zhang, Zhigang Lei, Jianwei Li, Biaohua Chen
    2014, 22(8):  843-853.  doi:10.1016/j.cjche.2014.06.005
    Abstract ( 3230 )   PDF (1954KB) ( 46 )  
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    Thiswork is focused on the performance prediction of pilot scale catalytic reverse flow reactors used for combustion of lean methane-air mixtures. An unsteady one-dimensional heterogeneous model for the reactor was established to account for the influence of the reactor wall on the heat transfer. Results of the simulation indicate that feed concentration, switch time and compensatory temperature impose important influence on the performance of the reactor. The amount of the heat extracted from the mid-section of the reactor can be optimized via adjusting the parameters mentioned above. At the optimal operating conditions, i.e. switching time of 400 s, feed concentration of 1% (by volume), and insulation layer temperature of 343 K, the axial temperature of the reactor revealed a comparatively symmetrical "saddle" distribution, indicating a favorable operating status of the catalytic reverse flow reactor.
    Acidic Montmorillonite/Cordierite Monolithic Catalysts for Cleavage of Cumene Hydroperoxide
    Li Han, Yanjun Wang, Jie Zhang, Zhigang Lei, Chongpin Huang, Biaohua Chen
    2014, 22(8):  854-860.  doi:10.1016/j.cjche.2014.06.006
    Abstract ( 3176 )   PDF (2115KB) ( 36 )  
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    In thiswork, a series of acidicmontmorillonite/cordieritemonolithic catalystswere prepared by a coatingmethod using silica sol as the binder. The morphology and structure of the acidic montmorillonite/cordierite samples were characterized by means of X-ray diffraction (XRD), N2 adsorption/desorption isotherms, and scanning electron microscope (SEM). The cleavage of cumene hydroperoxide (CHP) in a conventional fixed-bed reactor was chosen as a model reaction to evaluate the catalytic activity of the monolithic catalysts. The influences of acidic montmorillonite loading, reaction temperature, CHP concentration, and weight hourly space velocity (WHSV) on the catalytic activity and selectivity of phenol were studied. The results indicated that the obtained acidic montmorillonite/cordierite monolithic catalysts were firm and compact, and the loading of acidic montmorillonite was found to reach 40% (by mass) after three coating operations. The surface area of acidic montmorillonite/cordierite catalysts increases greatly as acidicmontmorillonite loading increases due to higher surface area of acidic montmorillonite. Under the optimal reaction conditions (acidic montmorillonite loading of 32.5% (by mass), temperature of 80℃, a mass ratio of CHP to acetone of 1:3, and WHSV of CHP of 90 h-1), the conversion of CHP can reach 100%, and the selectivity of phenol is up to 99.8%.
    Growth of Hierarchically Structured High-Surface Area Alumina on FeCralloy® Rods
    Chandni Rallan, Arthur Garforth
    2014, 22(8):  861-868.  doi:10.1016/j.cjche.2014.06.007
    Abstract ( 2858 )   PDF (5746KB) ( 63 )  
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    The formation of metastable alumina phases due to the oxidation of commercial FeCralloy® rods (0.5 mm thickness) at various temperatures and time periods has been examined. This structured layer acts as an anchor to bind additional coatings of alumina via wash-coat techniques, thereby improving the layer thickness and increasing adhesion of the catalytic surface. Optimisation of the layer thickness and catalytic properties were conducted, using a range of analytical systems [scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD)]. The modified FeCralloy® rodswere tested in a fixed bed reactor rig to assess the impact on yield for the dehydrogenation of methylcyclohexane.
    Synthesis of ITQ-2 Zeolites and Catalytic Performance in n-Dodecane Cracking
    Jiangge Hao, Ying Wang, Guozhu Liu, Jingwen Zhang, Guozhu Li, Xuesong Ma
    2014, 22(8):  869-874.  doi:10.1016/j.cjche.2014.06.008
    Abstract ( 3243 )   PDF (1678KB) ( 67 )  
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    ITQ-2 zeolites were prepared by sequential alkali-swelling and ultrasonic-delamination of precursor MCM-22 and characterized by X-ray powder diffraction, scanning electron microscopy, nitrogen adsorption-desorption, ammonia temperature-programmed desorption and in-situ Fourier-transform infrared spectroscopy. The delamination induced a change in the morphology of ITQ-2 zeolites from aggregated thin platelets to scattered platelets, together with a significant increase in external specific surface area, which reached a plateau at the ultrasonic treatment time of 3 h. The catalytic cracking of n-dodecane over ITQ-2 zeolites was evaluated with ITQ-2 coated on the inside wall of a tubular reactor at 550℃ and 4 MPa. The sample obtained by ultrasonic treatment of 3 h (ITQ-2-3) gave the highest initial conversion of n-dodecane, whereas those of 5 h and 1 h gave the conversion even lower than MCM-22, which was in agreement with the trend of the ratio of strong Lewis acid to the total acid amount. Although the amount of cokes deposited on ITQ-2-3 was larger than that on MCM-22, the former deactivated slowly, suggesting that a large external specific surface area benefits the stability of zeolite coatings.
    Effects of Colloidal Silica Binder on Catalytic Activity and Adhesion of HZSM-5 Coatings for Structured Reactors
    Guozhu Liu, Jinhua Guo, Fanxu Meng, Xiangwen Zhang, Li Wang
    2014, 22(8):  875-881.  doi:10.1016/j.cjche.2014.06.010
    Abstract ( 2810 )   PDF (7922KB) ( 10 )  
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    HZSM-5 coating using three colloidal silica binders, acidic colloidal silica (ACS), neutral colloidal silica (NCS) and basic colloidal silica (BCS), was prepared to study the effect of binders on their adhesion and catalytic activity. Scanning electron microscopy characterization indicated that the zeolite coating using BCS shows the smoothest surface with higher homogeneity and adherence strength. The specific surface area, relative crystallization and acid site strength of zeolites are also dependent on the binder used. Catalytic cracking of supercritical n-dodecane over the series of zeolite coating with various binders indicated that HZSM-5 coating with BCS exhibits the highest and the most stable catalytic activity compared with other kinds of binders, and also exhibits a stable catalytic activity ascribed to its proper acid property and microstructure.
    Anodic Alumina Supported Pt Catalyst for Total Oxidation of Trace Toluene
    Zebao Rui, Chunyan Chen, Yubing Lu, Hongbing Ji
    2014, 22(8):  882-887.  doi:10.1016/j.cjche.2014.06.011
    Abstract ( 3401 )   PDF (2417KB) ( 48 )  
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    Featuring an assembly of identical pores, through-pore anodic alumina (AAO) makes an ideal monolith-like catalyst support for volatile organic compound (VOC) combustion. This work employs the oxidation of toluene as a model reaction to investigate the applicability of AAOsupported Pt catalysts in VOC catalytic combustion. In order tomodify themicrostructure of AAO, some AAO sampleswere exposed to hotwater treatment (HWT) firstly. Results show that the optimum HWT time is 18 h. Pt/HWT18 gives a toluene conversion of 95% at 200℃, which is comparable to the initial activity of commercial γ-Al2O3 particle supported Pt catalyst. Considering its confinement effect for the supportedmetal and its monolith-like compact unit, AAO support offers potential applications in VOC catalytic combustion.
    Intensification of Deep Hydrodesulfurization Through a Two-stage Combination of Monolith and Trickle Bed Reactors
    Min Xu, Hui Liu,Shengfu Ji, Chengyue Li
    2014, 22(8):  888-897.  doi:10.1016/j.cjche.2014.06.012
    Abstract ( 3711 )   PDF (1011KB) ( 49 )  
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    Deep hydrodesulfurization (HDS) is an important process to produce high quality liquid fuels with ultra-lowsulfur. Process intensification for deep HDS could be implemented by developing new active catalysts and/or new types of reactors. In this work, the kinetics of dibenzothiophene (DBT) hydrodesulfurization over Ni-P/SBA-15/cordierite catalyst was investigated at 340-380℃ and 3.0-5.0 MPa. The first-order reaction model with respect to both DBT and H2 was used to fit the kinetics data in a batch recycle operation system. It is found that both the activation energy and rate constant over the Ni-P monolithic catalyst under our operating conditions are close to those over conventionally used HDS catalysts. Comparative performance studies of two types of reactors, i.e., trickle bed reactor and monolithic reactor, were performed based on reactor modeling and simulation. The results indicate that the productivity of themonolithic reactor is 3 times higher than that of the trickle bed reactor on a catalyst weight basis since effective utilization of the catalyst is higher in the monolithic reactor, but the volumetric productivity of the monolithic reactor is lower for HDS of DBT. Based on simulation results, a tworeactor-in-series configuration for hydrodesulfurization is proposed, in which a monolithic reactor is followed by a tickled bed reactor so as to attain intensified performance of the system converting fuel oil of different sulfur-containing compounds. It is illustrated that the two reactor scheme outperforms the trickle bed reactor both on reactor volume and catalyst mass bases while the content of sulfur is reduced from 200 μg·g-1 to about 10 μg·g-1.
    Transalkylation of Multi-secbutylbenzenes with Benzene over Hierarchical Beta Zeolite
    Yingxia Li, Can Luo, Xuan Wang, Chongpin Huang, Biaohua Chen
    2014, 22(8):  898-902.  doi:10.1016/j.cjche.2014.06.013
    Abstract ( 3332 )   PDF (1260KB) ( 37 )  
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    A hierarchical beta zeolite synthesized by quasi-solid phase conversion method was characterized by BET, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), temperature-programmed desorption of ammonia (NH3-TPD), 27Al and 29Si magic angle spinning nuclear magnetic resonance (27Aland 29Si MAS NMR), and its catalytic performance was compared with that of conventional microporous beta zeolite for liquid phase transalkylation of multi-secbutylbenzenes (MSBBs) with benzene. The results indicate that the hierarchical beta zeolite consists of nanosized crystals with a meso/microporous structure and has stronger acid strength than the microporous beta zeolite. The higher conversion of tri-secbutylbenzene (TSBB) and selectivity of sec-butylbenzene (SBB) are achieved on hierarchical beta zeolite than microporous beta zeolite, while the conversion of di-secbutylbenzene (DSBB) is slightly higher. The improvement of catalytic performance over hierarchical beta zeolite can be ascribed to the presence of mesopores, nanosized crystals and stronger acidity.
    Preparation, Structure Characterization and Hydrodesulfurization Performance of B-Ni2P/SBA-15/Cordierite Monolithic Catalysts
    Pingyi Wu, Qingyuan Li, Ling Lan, Hongfei Liu, Yana Ju, Jiarui Piao, Shengfu Ji
    2014, 22(8):  903-908.  doi:10.1016/j.cjche.2014.06.014
    Abstract ( 2991 )   PDF (897KB) ( 24 )  
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    A series of B-Ni2P/SBA-15/cord monolithic catalysts were prepared by coating the slurry of the B-Ni2P/SBA-15 precursors on a pretreated cordierite support, and followed by temperature-programmed reduction in a H2 flow. The samples were characterized by X-ray diffraction (XRD) and N2 adsorption-desorption technique. The catalytic activities for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) were evaluated. The results showed that Ni2P phase was present in all B-Ni2P/SBA-15/cord monolithic catalysts. The specific surface areas (SBET) of the B-Ni2P/SBA-15/cord monolithic catalysts was first increased to 167 m2·g-1, and then decreased to 155 m2·g-1 with the increase of boron contents. The catalytic activity also showed the similar trend with the increase of boron contents. The 1.75% (by mass) B-Ni2P/SBA-15/cord monolithic catalysts exhibited the highest DBT conversion of 98.4% at 380℃. The cordierite-based monolithic catalysts showed better low temperature sensitivity for HDS of DBT in comparison with the particle catalysts. Moreover, two HDS routes, direct desulfurization (DDS) and hydrogenation (HYD), proceeded independently over B-Ni2P/SBA-15/cord monolithic catalysts and the main pathway was DDS.
    Enhanced Photocatalytic Properties of Silver Oxide Loaded Bismuth Vanadate
    Lianwei Shan, Jinbo Mi, Limin Dong, Zhidong Han, Bo Liu
    2014, 22(8):  909-913.  doi:10.1016/j.cjche.2014.06.015
    Abstract ( 3505 )   PDF (858KB) ( 47 )  
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    In this work, BiVO4 powders were synthesized by a sol-gel method, and the BiVO4 gels with different calcination temperaturewere investigated by X-ray diffraction (XRD). Absorption range and band gap energy,which are responsible for the observed photocatalyst behavior,were investigated by UV/vis diffuse reflectance spectroscopy (DRS) for pure and silver oxide loaded BiVO4. Photocatalytic properties of the prepared samples were examined by studying the degradation of themethyl orange. When using NaClO2 as an electron acceptor, the possible photocatalytic mechanism has been discussed by photocatalytic reactions.With the help of electron acceptor, the results show clearly that the BiVO4 loaded silver oxide exhibited superior photocatalytic activity in simulated dye wastewater treatment.
    Recovery and Recycling of Ti Supported Bimodal Mesoporous Catalysts Prepared via Ship-in-a-bottle Method in the Epoxidation of Cyclohexene
    Shiyang Bai, Xintao Hu, Jihong Sun, Bo Ren, Jinpeng Wang
    2014, 22(8):  914-920.  doi:10.1016/j.cjche.2014.06.016
    Abstract ( 2984 )   PDF (1874KB) ( 32 )  
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    Ti/BMMs (Ti supported bimodal mesoporous silica) catalysts have been prepared via self-assembly route combined with ship-in-a-bottle method. The recovery and recycling performances of Ti/BMMs were investigated in the epoxidation of cyclohexene. In order to the evaluate the regeneration methods and to examine the deactivation behaviors, the deactivated Ti/BMMs catalysts were washed in chloroform or calcinated at 450℃ for 6 h and then activity of the recovery catalysts were examined.Meanwhile, the structure features and surface properties of the regenerated catalysts were characterized by X-ray diffraction, N2-sorption analysis, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, UV visible spectroscopy and X-ray photoelectron spectroscopy. The results showed that the typical bimodal mesoporous structure of recycled Ti/BMMs catalysts was still maintained, and the phenomenon of Ti leaching during the catalytic process and recovery was negligible. In particular, spectroscopic observations indicated that the effects of the regeneration methods on the tetrahedrally-coordinated Ti species and catalytic deactivation were remarkable. The main reasons were related to the polarities of used solvents during recovery tests, the environment medium of adsorbed water inside mesopore channels and the deposition of bulky molecules of by-products on the mesoporous surface.
    Promoting Xylene Production in Benzene Methylation using Hierarchically Porous ZSM-5 Derived from a Modified Dry-gel Route
    Wei Deng, Xuan He, Chao Zhang, Yunyi Gao, Xuedong Zhu, Kake Zhu, Qisheng Huo, Zhijie Zhou
    2014, 22(8):  921-929.  doi:10.1016/j.cjche.2014.06.009
    Abstract ( 4102 )   PDF (2052KB) ( 95 )  
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    Methylation of benzene is an alternative low-cost route to produce xylenes, but selectivity to xylene remains low over conventional zeolitic catalysts. In this work, a combined dry-gel-conversion and steam-assistedcrystallization method is used to synthesize hierarchically porous zeolite ZSM-5 with varied Si/Al malar ratios. X-ray diffraction (XRD), N2 physisorption, NH3-temperature programmed desorption (TPD), scanning electronic microscopic (SEM) measurement and Fourier transforminfrared (FT-IR) are employed to characterize the structure and acidity of both hierarchically porous zeolites and their conventional counterparts. The method is found to be applicable to ZSM-5 with molar ratios of Si/Al from 20 to 180. The ZSM-5 zeolites are used as catalysts for benzene methylation at 460℃ to investigate the effect of additional porosity and Si/Al ratios. At low Si/Al ratios, the benzene conversions over conventional and hierarchical ZSM-5 are close, and selectivity to toluene is high over hierarchical ZSM-5. It is found that hierarchical porositymarkedly enhances the utility of zeolite and the selectivity towards xylenes via improved mass transport at higher Si/Al ratios. Under an optimized hierarchical ZSM-5 catalyst, xylene selectivity reaches 34.9% at a Si/Al ratio of 180.
    Performance Prediction of Structured Packing Column for Cryogenic Air Separation with Hybrid Model
    Xiaobin Zhang, Jiakai Zhu, Zhao Wu, Wei Xiong, Xuejun Zhang, Limin Qiu
    2014, 22(8):  930-936.  doi:10.1016/j.cjche.2014.06.004
    Abstract ( 3130 )   PDF (900KB) ( 55 )  
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    A detailed investigation of a thermodynamic process in a structured packing distillation column is of great importance in prediction of process efficiency. In order to keep the simplicity of an equilibrium stagemodel and the accuracy of a non-equilibrium stage model, a hybrid model is developed to predict the structured packing column in cryogenic air separation. A general solution process for the equilibrium stage model is developed to solve the set of equations of the hybrid model, in which a separation efficiency function is introduced to obtain the resulting tri-diagonal matrix and its solution by the Thomas algorithm. As an example, the algorithm is applied to analyze an upper column of a cryogenic air separation plant with the capacity of 17000 m3·h-1. Rigorous simulations are conducted using Aspen RATEFRACmodule to validate the approach. The temperature and composition distributions are in a good agreementwith the two methods. The effects of inlet/outlet position and flowrate on the temperature and composition distributions in the column are analyzed. The results demonstrate that the hybrid model and the solution algorithms are effective in analyzing the distillation process for a cryogenic structured packing column.
    The Effect of pH Control on Acetone–Butanol–Ethanol Fermentation by Clostridium acetobutylicum ATCC 824 with Xylose and D-Glucose and D-Xylose Mixture
    Wei Jiang, Zhiqiang Wen, Mianbin Wu, Hong Li, Jun Yang, Jianping Lin, Yijun Lin, Lirong Yang, Peilin Cen
    2014, 22(8):  937-942.  doi:10.1016/j.cjche.2014.06.003
    Abstract ( 3412 )   PDF (475KB) ( 37 )  
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    D-Glucose, L-arabinose, D-mannose, D-xylose, and cellobiose are saccharification products of lignocellulose and important carbon sources for industrial fermentation. The fermentation efficiency with each of the five sugars and the mixture of the two most dominant sugars, D-glucose and D-xylose, was evaluated for acetone- butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum ATCC 824. The utilization efficacy of the five reducing sugars was in the order of D-glucose, L-arabinose, D-mannose, D-xylose and cellobiose. D-Xylose, the second most abundant component in lignocellulosic hydrolysate, was used in the fermentation either as sole carbon source or mixed with glucose. The results indicated that maintaining pH at 4.8, the optimal pH value for solventogenesis, could increase D-xylose consumption when it was the sole carbon source. Different media containing D-glucose and D-xylose at different ratios (1:2, 1:5, 1.5:1, 2:1) were then attempted for the ABE fermentation. When pH was at 4.8 and xylose concentration was five times that of glucose, a 256.9% increase in xylose utilization and 263.7% increase in solvent production were obtained compared to those without pH control. These results demonstrate a possible approach combining optimized pH control and D-glucose and D-xylose ratio to increase the fermentation efficiency of lignocellulosic hydrolysate.
    Experimental and Modeling Study on de-NOx Characteristics of Selective Non-catalytic Reduction in O2/CO2 Atmosphere
    Hui Li, Kuihua Han, Hongtao Liu, Chunmei Lu
    2014, 22(8):  943-949.  doi:10.1016/j.cjche.2014.06.002
    Abstract ( 3227 )   PDF (1203KB) ( 22 )  
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    An experimental study of thermal de-NOx using NH3 as reductant in O2/CO2 atmosphere with the effect of SO2 and different additiveswas performed in a drop tube furnace. Results show that the optimum temperature window is 841-1184℃, and the optimumreaction temperature is about 900℃ with a de-NOx efficiency of 95.4%. A certain amount of SO2 has an inhibiting effect on NO reduction. The effect of additives, including Na2CO3, C2H5OH and FeCl3, on NO reduction by NH3 is also explored. The addition of Na2CO3 and FeCl3 is useful towiden the temperature window and shift the reaction to lower temperature for the efficiency is increased from 30.5% to 74.0% and 67.4% respectively at 800℃. Qualitatively, the modeling results using a detailed kinetic modeling mechanism represent well most of the process features. The effect of Na2CO3, C2H5OH and FeCl3 addition can be reproduced well by the Na2CO3, C2H5OH and Fe(CO)5 sub-mechanism respectively. The reaction mechanism analysis shows that the effects of these additives on NO reduction are achievedmainly by promoting the production of OH radicals at lower temperature.
    CO2 Removal from Biogas byWater Washing System
    Yong Xiao, Hairong Yuan, Yunzhi Pang, Shulin Chen, Baoning Zhu, Dexun Zou, Jingwei Ma, Liang Yu, Xiujin Li
    2014, 22(8):  950-953.  doi:10.1016/j.cjche.2014.06.001
    Abstract ( 2878 )   PDF (448KB) ( 196 )  
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    CO2 removal from biogas by water washing system was investigated with various parameters, including liquid/gas ratio, pressure, temperature, and CO2 content. The results indicate that CO2 removal ratio could reach 34.6%- 94.2% as liquid/gas ratio increased from0.14 to 0.50. Increasing pressure (from0.8 to 1.2MPa) could improve gas purification with a constant inflow rate of gas. Temperature played a key role in the process and lower temperature in absorption tower was beneficial for reducing CO2 content. CO2 removal ratio could reach 24.4%-83.2% when CO2 content in the simulated gas was 25%-45%. The lowest CO2 content after absorption was 2.6% at 1.2MPawith 400 L·h-1 gas flowand 200 L·h-1 water flow,whichmeets the requirement of CO2 content in natural gas for vehicle fuel.