Simulation of municipal solid waste gasification for syngas production in fixed bed reactors

This study proposes a model of syngas production from municipal solid waste （MSW） gasification with air in fixed bed reactors. The model （using Aspen plus simulator） is used to predict the results of MSW gasification and to provide some process fundamentals concerning syngas production from MSW gasification. The effects of gasification temperature, air equiva- lence ratio and moisture concentration on the composition of syngas, lower heating value （LHV） of syngas, heat conversion efficiency, and carbon conversion are discussed. The results indicate that higher temperature improves gasification, and higher air equivalence ratio increases the carbon conversion while decreasing syngas LHV. Heat conversion efficiency increases and reaches the maximum and then decreases with the increase of air equivalence ratio. Higher moisture concentration increases the carbon conversion and increases the heat conversion efficiency at lower ratios. Higher temperature and a lower equivalence ratio are favorable for obtaining a higher LHV of syngas at the same moisture concentration.     

Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor

Fluidized-bed reactor is a candidate for dimethyl ether （DME） synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller （BET）, X-ray powder diffraction （XRD） and temperature programmed reduction （TPR）.     

Tunable Syngas Synthesis from Photocatalytic CO_2 Reduction Under Visible-Light Irradiation by Interfacial Engineering

Visible-light-driven CO_2 photoreduction to achieve renewable materials,such as syngas,hydrocarbons,and alcohols,is a key process that could relieve environmental problems and the energy crisis simultaneously.Reduction of syngas products with different H_2:CO proportions is highly expected to produce high value-added chemicals in the industry.However,the development of technologies employing long-wavelength irradiation to achieve CO_2 photoreduction and simultaneous tuning of the resultant H_2:CO proportion remains a challenging endeavor.In this work,we carried out interfacial engineering by designing a series of heterostructured layered double-hydroxide/MoS_2 nanocomposites via electrostatic self-assembly.The syngas proportion(H_2:CO) obtained from CO_2 photoreduction could be modulated from 1:1 to 9:1 by visible-light irradiation(λ 400 nm) under the control of the interface-rich heterostructures.This work provides a cost-effective strategy for solar-tofuel conversion in an artificial photosynthetic system and describes a novel route to produce syngas with targeted proportions.     

Ni/ZrO_2 Catalysts Synthesized via Urea Combustion Method for CO_2 Methanation

A series of Ni/ZrO_2 catalysts were synthesized by urea combustion method for CO_2 methanation.The effects of zirconium precursors and urea dosage on the structure and catalytic performance of the catalysts were tested.Results showed that the Ni/ZrO_2–O catalyst derived from zirconium oxynitrate hydrate exhibited better catalytic activity than the Ni/ZrO_2 catalyst because of its higher Ni dispersion and smaller Ni particle size.In addition,the urea dosage significantly influenced the low-temperature activity of the catalysts by affecting the metal–support interaction,Ni dispersion,and Ni particle size.The Ni/ZrO_2–O-0.4 catalyst with a urea-to-nitrate molar ratio of 0.4 exhibited the best catalytic activity owing to its moderate metal–support interaction,highest Ni dispersion,and smallest Ni particle size,achieving 69.2% CO_2 conversion and 100% CH_4 selectivity at 300℃,0.1 MPa,and a weight hour space velocity(WHSV)of 50,000 mL/(g·h).Moreover,the urea combustion method can lead to the entire phase transformation from monoclinic ZrO_2 to tetragonal ZrO_2 accompanied by the incorporation of oxygen vacancies in the ZrO_2 lattice.This phenomenon can also be related to the high catalytic activity of the as-prepared catalysts.     

In-situ investigation of melting characteristics of waste selective catalytic reduction catalysts during harmless melting treatment

Selective catalytic reduction(SCR) catalyst waste is a hazardous solid waste that seriously threatens the environment and public health.In this study,a thermal melting technology is proposed for the treatment of waste SCR catalysts.The melting characteristics and mineral phase transformation of waste SCR catalysts blended with three different groups of additives were explored by heating stage microscopy,thermogravimetric analysis/differential scanning calorimetry(TG/DSC) analysis,thermodynamic simulation,and X-ray diffraction(XRD) analysis;heavy metal leaching toxicity was tested by inductively coupled plasma-atomic emission spectrometry(I CP-AES) analysis.The results indicated that the melting point of waste SCR catalysts can be effectively reduced with proper additives.The additive formula of 39.00% Fe_2 O_3(in weight),6.50% CaO,3.30% SiO_2,and 1.20% Al_2 O_3 achieves the optimal fluxing behavior,significantly decreasing the initial melting temperature from 1223℃ to1169℃.Furthermore,the whole heating process of waste SCR catalysts can be divided into three stages:the solid reaction stage,the sintering stage,and the primary melting stage.The leaching concentrations of V,As,Pb,and Se are significantly reduced,from 10.64,1.054,0.195,and 0.347 mg/L to 0.178,0.025,0.048,and 0.003 mg/L,respectively,much lower than the standard limits after melting treatment,showing the strong immobilization capacity of optimal additives for heavy metals in waste SCR catalysts.The results demonstrate the feasibility of harmless melting treatments for waste SCR catalysts with relatively low energy consumption,providing theoretical support for a novel method of disposing of hazardous waste SCR catalysts.     

Promoting Positive Backwash on Practical English Test for Colleges

Practical English Test for Colleges (PRETCO) is a large-scale national standardized EFL test for the students of higher vocational colleges,postsecondary specialized colleges,and colleges for adults.This thesis is for a preliminary research of PRETCO backwash based on previous studies from home and abroad,making use of their research methods and models.It attempts to explore the aspects of practical English learning of students from higher vocational colleges (HVC) influenced by PRETCO,and the nature of the backwash.Based on the results reported in the study,the writer analyzes the factors inducing negative backwash and puts forward some suggestions for promoting positive one.     

SiO2和聚乙烯醇双负载纳米ZnS对CO2的光催化还原反应

Nanosized photocatalyst ZnS particles supported on silica and polyvinyl alcohol was successfully prepared by complex transformation method. The photocatalytic reduction of CO2 was carried out in the presence of nanosized ZnS catalyst irradiated by a high-pressure mercury-vapor lamp to give the main products of formaldehyde and ethanol. The catalytic ability of ZnS characterized by the uptaken rate of CO2P volume in the reaction system depended upon the preparing conditions of nanosized ZnS catalysts. Decreasing the concentration of Na2S and increasing the molar ratio of oxygen in the PVA to Zn2 could result in the decreasing of the size of ZnS parti-     

Hydrogenation of commercial polystyrene over Pd/BaSO4 catalysts: Effect of carrier structure

A variety of barium sulfate （BaSO4） carriers with or without mesopore structure were synthesized via precipitation reaction in aqueous solution of barium hydroxide and sulfuric acid with ethylene glycol as a modifying agent, and then calcined at various temperatures. The obtained BaSO4 was used as catalyst carriers for polystyrene （PS） hydrogenation, and BaSO4 supported palladium （Pd） catalysts with Pd content of 5wt% were prepared by using impregnation method. N2 physisorption, transmission electron microscopy, X-ray diffraction and kinetics studies were used to investigate the effect of carrier structure on the dispersion and geometric location of active metal and their catalytic activities in PS hydrogenation. It was found that the pore structure of carrier played an important role in the dispersion and location of Pd grains. The activation energy values for all the Pd/BaSO4 catalysts were around 49.1 kJ/mol, while the pre-exponential factor for Pd/BSC-6H was much higher than others. The Pd/BSC-6H without mesopores had Pd grains deposited on the external surface of the carrier, and exhibited better activity than the mesoporous catalysts. It is indicated that the utilization of Pd/BSC-6H can reduce the pore diffusion of PS coils and enabled more active sites to participate in the PS hydrogenation.     

Investigation on influencing factors of 5-HMF content in <Emphasis Type="Italic">Schisandra</Emphasis>

In order to investigate the influencing factors of 5-hydroxymethyl-2-furaldehyde （5-HMF） content in Schisandra, confirm the theory of 5-HMF deriving mainly from Schisandra processing course, and give some suggestions about the Schisandra processing method, the 5-HMF contents in decoctions of Schisandra under different heating temperature, decocting time, soaking time, processing methods and treatment with different solvents before decocting the Schisandra were measured by RP-HPLC method. The results showed that there is great difference of 5-HMF level in decoctions from differently processed Schisandra and unprocessed Schisandra; decocting time of 60 rain has some effects on 5-HMF level in decoctions and there is certain quantity 5-HMF in processed Schisandra itself and very little 5-HMF in unprocessed Schisandra. Heating time, heating temperature and treating solvents all have effect on 5-HMF level in decoction of Schisandra. 5-HMF in Schisandra was mainly from processing course. Both long heating time and high heating temperature can increase 5-HMF level in Schisandra. The production of 5-HMF in Schisandra may have some relationships with some polar components, which can dissolve in water, ethanol and acetone, especially in ethanol. To control processing temperature, processing time and treatment with some solvent is very important for controlling 5-HMF level in Schisandra.     

Fluidized-bed pyrolysis of waste bamboo

Bamboo was a popular material substituting for wood,especially for one-off commodity in China. In order to recover energy and materials from waste bamboo,the basic characteristics of bamboo pyrolysis were studied by a thermogravimetric analyzer. It implied that the reaction began at 190～210 °C,and the percentage of solid product deceased from about 25% to 17% when temperature ranged from 400 °C to 700 °C. A lab-scale fluidized-bed furnace was setup to research the detailed properties of gaseous,liquid and solid products respectively. When temperature increased from 400 °C to 700 °C,the mass percent of solid product decreased from 27% to 17% approximately,while that of syngas rose up from 19% to 35%. When temperature was about 500°C,the percentage of tar reached the top,about 31%. The mass balance of these experiments was about 93%～95%. It indicated that three reactions involved in the process: pyrolysis of exterior bamboo,pyrolysis of interior bamboo and secondary pyrolysis of heavy tar.     

助剂对负载型镍催化剂重整活性和抗积炭性能的影响

应用XRD和催化活性评价手段,考察了助剂对CH_4与CO_2重整制合成气的负载型Ni催化剂的重整活性和其抗积炭性能的影响。实验结果表明,NiO在Υ-Al_2O_3表面上最大分散量随MgO、La_2O_3助剂的添加不同程度地增大,助剂能影响负载型Ni催化剂的催化性能,MgO、La_2O_3的添加对改善Ni催化剂的重整活性和抗积炭性能有明显效果,并与助剂的种类、添加次序有关。La_2O_3助剂的突出作用表现在维持Ni为低价还原态和促进CO_2转化等方面。     

NiO/γ—Al_2O_3催化剂的阈值效应

应用XRD、TPR和催化活性评价手段,考察了CH_4与CO_2重整制合成气的负载型Ni催化剂的阈值效应。实验结果表明,在反应温度为750℃和空速为2500h~(-1)下,NiO载量为14.0％NiO/γ—Al_2O_3(相当于0.163gNiO/gγ—Al_2O_3或0.077gNiO/100m~2γ7—Al_2O_3)催化剂具有最佳的催化性能,NiO在γ—Al_2O_3表面上分散阀值为0.238gNiO/gγ—Al_2O_3(相当于0.112gNiO/100m~2γ—Al_2O_3),能明显体现负载型Ni催化剂在重整反应中的阈值效应。     

制备方法对镍催化剂重整活性影响研究

利用XRD,TPR和活性评价等手段,研究了NiO/γ-Al2O3催化剂的制备方法对CH4与CO2转化制合成气催化活性的影响.在本实验条件下,采用浸渍法和焙烧温度为400℃制备的NiO/γAl2O3(ω=0.113)催化剂,在反应温度为750℃和空速为2500h-1下,对CH4和CO2重整反应会显示良好的催化活性.本文还对催化剂抗积炭性能作初步讨论.     

SiO_2气凝胶钼尾矿金属催化剂的应用研究

利用商洛钼尾矿与亲水型Si O2气凝胶结合制成的气凝胶钼尾矿催化剂对甲醇与乙醇一步合成异丁醛、仲丁醇的氧化反应的催化活性进行考察。通过改变催化剂的用量和反应时间考察催化剂的催化活性。用傅立叶变换红外光谱仪对产物进行分析。结果表明:甲醇与乙醇一步合成异丁醛的反应在2 h时有醛基吸收峰;仲丁醇氧化反应在2 h时有羰基吸收峰;说明此催化剂对这两个反应均有一定活性。     

一种微型天然气氧化重整制氢反应器的研发及性能测试

基于质子交换膜燃料电池的天然气微型热电联产系统的核心单元是重整制氢反应器．设计研发了一种集蒸汽发生和天然气水蒸汽氧化重整于一体的制氢反应器,实验测试了典型工况下反应器的性能,以及操作条件（水碳比、空碳比、空速）对反应器性能的影响．在典型操作条件下,反应器平均床层温度为630℃,反应器出口合成气的物质的量组成为H。40．61％、N。37．63％、CO5．56％、CH43．62％、C0212．58％,甲烷的转化率为92．56％,反应器能量利用效率88．3％．实验表明这种制氢反应器可用干微型天蚨气执由群声桑缔     

部分气化联合循环发电系统热力性能分析

针对增压部分气化2种增压流化床(PFB)锅炉半焦燃烧和2种常压流化床(CFB)半焦燃烧的先进增压流化床燃烧联合循环(APFBC-CC)方案,进行了系统热力性能计算, 分析比较了主要参数对系统性能的影响. 结果表明,将PFB锅炉高温烟气引入部分气化炉的方案一避开了高温烟气过滤式除尘器, 但降低了煤气热值和系统效率; 方案二则可获得较高的系统效率, 然而高温过滤式除尘器目前技术上有一定困难, 需降温运行; 方案三、四采用CFB锅炉半焦燃烧系统, 其中方案四采用气化空气/蒸汽预热方法, 不仅可获得较高的煤气热值, 而且可提高系统效率.     

Hydrogenation of ortho-nitrochlorobenzene on activated carbon supported platinum catalysts

INTRODUCTION 2,2′-dichlorohydrazobenzene (DHB) is a com-mercially important intermediate, and is convention-ally manufactured by zinc reduction of or-tho-nitrochlorobenzene (Xu, 1996). The major dis-advantage of this process is the generation of largeamounts of sludge in reduction. A single step catalytichydrogenation of ortho-nitrochlorobenzene to DHBusing supported noble metal catalyst in the presenceof aqueous sodium hydroxide medium becomes moreimportant, because it is enviro…