0.4nm分子筛负载Cu-Ni双金属催化剂用于CO2和CH3OH直接合成碳酸二甲酯（英文）

The 0.4 nm molecular sieve supported Cu-Ni bimetal catalysts for direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH were prepared and investigated. The synthesized catalysts were fully characterized by BET, XRD (X-ray diffraction), TPR (temperature programmed reduction), IR (infra-red adsorption), NH 3-TPD (temperature programmed desorption) and CO 2-TPD (temperature programmed desorption) techniques. The results showed that the surface area of catalysts decreased with increasing metal content, and the metals as well as Cu-Ni alloy co-existed on the reduced catalyst surface. There existed interaction between metal and carrier, and moreover, metal particles affected obviously the acidity and basicity of carrier. The large amount of basic sites facilitated the activation of methanol to methoxyl species and their subsequent reaction with activated carbon dioxide. The catalysts were evaluated in a continuous tubular fixed-bed micro-gaseous reactor and the catalyst with bimetal loading of 20% (by mass) had best catalytic activities. Under the conditions of 393 K, 1.1 MPa, 5 h and gas space velocity of 510 h 1 , the selectivity and yield of DMC were higher than 86.0 % and 5.0 %, respectively.     

Evaluation of an improved epichlorohydrin synthesis from dichloropropanol using a microchemical system

Synthesizing epichlorohydrin (ECH) from dichloropropanol (DCP) is a complicated reaction due to the partial decomposition of ECH under harsh conditions. A microchemical system can provide a feasible platform for improving this process by conducting a separation once full conversion has been achieved. In this work, referring to a common DCP feed used in industry, the reaction performance of mixed DCP isomers with NaOH in the microchemical system on various time scales was investigated. The operating window for achieving high conver-sion and selectivity was on a time scale of seconds, while the side reactions normal y occurred on a time scale of minutes. Plenty of Cl?ions together with a high temperature were proved to be critical factors for ECH hydrolysis. A kinetic study of alkaline mediated ECH hydrolysis was performed and the requirements for an improved ECH synthesis were proposed by combining quantitative analysis using a simplified reaction model with experimen-tal results on the time scale of minutes. Compared with the conventional distillation process, this new strategy for ECH synthesis exploited microchemical system and decoupled the reaction and separation with potentials of higher productivity and better reliability in scaling up.     

用自热式高温好氧消化工艺预处理肺炎杆菌生物降解动力学研究(英文)

Biodegradation parameters and kinetic characteristics for pre-treating waste strains of Klebsiella pneu-moniae were studied in laboratory scale with an insulated reactor by an innovative technique,autothermal thermo-philic aerobic digestion(ATAD) . Based on an Arrhenius-type equation,an empirical model was developed to corre-late the removal of total suspended solid(TSS) with the initial TSS concentration,influent reaction temperature,aeration rate and stirring rate. The reaction temperatures of the ATAD system could be raised from the ambient temperatures of 25 °C to a maximum temperature of 65 °C. The exponentials for the initial TSS concentration,aeration rate and stirring rate were 1.579,-0.8175 and-0.6549,respectively,and the apparent activation energy was 6.8774 kJ·mol-1. The correlation coefficient for the pre-exponential factor was 0.9223. The TSS removal effi-ciency predicted by the model was validated with an actual test,showing a maximum relative deviation of 10.79%. The new model has a good practicability.     

Reaction kinetics and internal diffusion of Zhundong char gasification with CO2

Mass transfer usually affects the rate of chemical reactions in coal.The effect of internal diffusion on char gasification with CO₂ in the temperature range from 1123 K to 1273 K was investigated via thermo-gravimetric analysis and assessment of char morphology features.The results revealed that the effect of internal diffusion on the initial reaction rate was more significant with an increase of particle size,due to the concentration gradient of the gasification agent within the solid particles.In the early stage of gasification,the generation of new micropores and the opening of closed pores led to an increase in specific surface area.As the reaction proceeded,the openings were gradually expanded and the specific surface area continued to increase.However,with further reaction,disappearance of edge pores,melting and collapse of the pore structure led to a decrease in specific surface area.The intrinsic activation energy and reaction order based on the nth-order model were 157.67 kJ?mol^?1 and 0.36,respectively.Thus,temperature zones corresponding to chemical reaction and diffusion control were identified.Moreover,the calculated effectiveness factor provided a quantitative estimation of internal diffusion in the initial stage.     

乙酸与甲醇的催化酯化

Esterification of methyl alcohol with acetic acid catalysed by Amberlyst-15 (cation-exchange resin) was carried out in a batch reactor in the temperature ranging between 318-338 K, at atmospheric pressure. The reaction rate increased with increase in catalyst concentration and reaction temperature, but decreased with an increase in water concentration. Stirrer speed had virtually no effect on the rate under the experimental conditions. The rate data were correlated with a second-order kinetic model based on homogeneous reaction. The apparent activation energy was found to be 22.9kJmol-1 for the formation of methyl acetate. The methyl acetate production was carried out as batch and continuous in a packed bed reactive distillation column with high purity methyl acetate produced.     

甲基二乙醇胺水溶液在改进的湿壁塔上吸收二氧化碳的动力学模型

To get more accurate kinetic data of the absorption of CO2 into aqueous solution of N-methyldiethanolamine, a wetted wall column was modified to more uniformly distribute the liquid on the column surface and gas in the absorbing chamber and change the length of the column. The average liquid film thickness and the liquid-phase mass transfer coefficient were measured, and a correlation for the Sherwood number, Reynolds number and Schmidt number was obtained for the modified wetted wall column. The equilibrium concentrations in chemical reactions were calculated with a minor absolute error for calculating the rate constant more accurately. A mathematical model for the CO2 absorption was established based on the diffusional mass transfer accompanied with parallel reversible reactions, and the partial differential equation was solved by Laplace transform. An analytical expression for the concentration of carbon dioxide as a function of time and penetration depth in liquid film and the average interphase mass transfer rate was obtained. This model was also used to calculate the rate constant for a second-order reaction, which was in good agreement with reported data.     

Tuning the crystallite size of monoclinic ZrO_2 to reveal critical roles of surface defects on m–ZrO_2 catalyst for direct synthesis of isobutene from syngas

The effects of crystallite size on the physicochemical properties and surface defects of pure monoclinic ZrO_2 catalysts for isobutene synthesis were studied. We prepared a series of monoclinic ZrO_2 catalysts with different crystallite size by changing calcination temperature and evaluated their catalytic performance for isobutene synthesis from syngas. ZrO_2 with small crystalline size showed higher CO conversion and isobutene selectivity, while samples with large crystalline size preferred to form dimethyl ether(DME) instead of hydrocarbons, much less to isobutene. Oxygen defects(ODefects) analyzed by X-ray photoelectron spectroscopy(XPS) provided evidence that more ODefectsoccupied on the surface of ZrO_2 catalysts with smaller crystalline size. Electron paramagnetic resonance(EPR) and ultraviolet–visible diffuse reflectance(UV–vis DRS) confirmed the presence of high concentration of surface defects and Zr~(3+) on mZrO_2-5.9 sample, respectively. In situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS) analysis indicated that the adsorption strength of formed formate species on catalyst reduced as the crystalline size decreased. These results suggested that surface defects were responsible for CO activation and further influenced the adsorption strength of surface species, and thus the products distribution changed. This study provides an in-depth insight for active sites regulation of ZrO_2 catalyst in CO hydrogenation reaction.     

Kinetics of water-isocyanate reaction in N,N-dimethylformamide

The uncatalyzed reaction of p-tolyl isocyanate (p-TI) with water in N,N-dimethylformamide (DMF) was investigated by high performance liquid chromatography (HPLC).The reactions were carried out at different temperatures from 293 K to 323 K,using various molar ratios of water to p-TI.DMF,as a special amide,was proved to be an efficient catalyst for water-isocyanate reaction.Under the reaction conditions in this study,substituted urea was the only final product observed.An appreciable amount of intermediate p-toluidine was detected.Concentrations of the isocyanate group as well as the amine and urea were determined as a function of time.New kinetic equations were deduced for each of the substance on the basis of a multistep mechanism,instead of a simple second order reaction as usual.Kinetic constants were calculated using the software MATLAB.Furthermore,the effects of temperature and concentrations of reactants on the reaction rate and amine content were discussed.The activation energy of each step was also determined.     

微通道内乙醇胺吸收CO2的过程特征（英文）

Process characteristics of CO2 absorption using aqueous monoethanolamine(MEA) in a microchannel reactor were investigated experimentally in this work.A T-type rectangular microchannel with a hydraulic diameter of 408 μm was used.Operating parameters,i.e.temperature,pressure and molar ratio of MEA to CO2 were studied.Under 3 MPa pressure,the mole fraction of CO2 in gas phase could decrease from 32.3% to 300×10?6 at least when gas hourly space velocity ranged from 14400 to 68600 h?1 and molar ratio of MEA to CO2 was kept at 2.2.In particular,the effects of temperature on CO2 absorption flux,mass transfer driving force,gas-liquid contact time and en-hancement factor were analyzed in detail and found that mass transfer enhancement by chemical reaction was a crucial factor for the process of CO2 absorption.     

碳酸钙在化学镀表面上的结垢与脱除

The scaling process of calcium carbonate on a low-energy heat transfer surface clectroless plating surface was investigated in a simulated cooling water system. Owing to the very low surface energy, the electroless plating surface exhibited less scaling susceptibility. A longer induction period and a lower scaling rate were obtained on the low-energy surface compared to copper surface under identical conditions. The calcite particles obtained on the electroless plating surface during the induction period were larger in size than those on copper surface because fewer cryst~s formed and grew at the same time on the |ow-energy surface. With increasing surface temperature, the induction period reduced and the scaling rate increased for the low-energy surface. When initial surface temperature was fixed, an increase in fluid velocity would reduce the induction period and increase the scaling rate due to the diffusion effect. However, when the heat flux was fixed, an increase in fluid velocity would decrease the surface temperature, and lead to a longer induction period and a lower scaling rate. The removal experiments of calcium carbonate scale indicated that during post induction period, the detachment was not obvious, while during the induction period, apparent removal of crystal particles was obtained on the electroless plating surface owing to the weak adhesion force. The more frequently the transient high hydrodynamic force acted, the more the detached crystal particles were.     

Surface and bulk changes of a Pt 1%/Ce0.6Zr0.4O2 catalyst during CO oxidation in the absence of O2

Topics in Catalysis - The reduction of a Pt 1%/Ce0.6Zr0.4O2 catalyst by CO in the absence of gaseous oxygen was studied by transient reactivity tests, temperature programmed surface reaction with...     

Gold modified cobalt-based Fischer-Tropsch catalysts for conversion of synthesis gas to liquid fuels

The addition of Au as a promoter/modifier for alumina supported Co catalyst has been studied by combined in-situ high temperature, high pressure Fourier transform infrared (FTIR) and on-line gas chromatography. The combination of these tools permitted the state of the active catalyst surface to be monitored while following the elution of reaction products during the first 5–7 h on stream of the catalyst. The catalysts under study were a 10%Co/Al₂O₃ and a 2.5%Au/10%Co/Al₂O_3. Samples were characterised before use using Raman and temperature programmed reduction (TPR). During the initial stages of reaction, hydrocarbons were built up on the surface of the catalyst as monitored by FTIR and the nature and amount of these species were assessed in terms of CH₂/CH₃ ratio and the density of these alkyl fragments by employing absorption coefficients for the individual components. The nature and reducibility of the Co particles were modified by the presence of Au while the later also shifted the CO/H₂ balance by acting as an effective water-gas shift catalyst during the early stages of reaction. This characteristic was lost during reaction as a consequence of redistribution of the two metallic phases.     

Reaction and characterization studies of an industrial Cr-free iron-based catalyst for high-temperature water gas shift reaction

Activity and stability of an industrial Cr-free iron-based catalyst (NBC-1) for high-temperature water gas shift (WGS) reaction were studied in a fixed-bed reactor under 350 °C, 1 atm, H₂O:gas = 1:1 and 3000 h⁻¹ (dry-gas basis). Physical properties of the NBC-1 catalyst before and after the WGS reaction, the desorption behavior of H₂O, CO, CO₂ and H₂, and surface reaction over the catalyst were characterized by BET, X-ray diffraction (XRD), Mössbauer emission spectroscopy (MES), temperature programmed desorption (TPD) and temperature programmed surface reaction (TPSR). The NBC-1 catalyst is active and has excellent thermo-stability even after pretreatment at a high temperature of 530 °C. Its activity and thermo-stability are comparable to those of an UCI commercial Fe-Cr catalyst, C12-4. XRD and MES studies show that iron in the fresh NBC-1 catalyst is present as γ-Fe₂O₃, most of which is converted to Fe₃O₄ during reduction and reaction. Results of TPD demonstrate that adsorbed CO₂ and CO cannot exist on the NBC-1 surface beyond the temperature of 300 °C while higher temperatures (>400 °C) are required to completely desorb H₂O. A redox mechanism of WGS on the NBC-1 surface is proposed based on the TPD and TPSR observations.     

溶胶凝胶法制备Cu-ZnO-ZrO2催化剂：pH对其性能的影响

采用溶胶-凝胶法以硝酸盐、柠檬酸为原料，加入氨水调节溶液pH，制备出一系列Cu-ZnO-ZrO2催化剂。并通过粉末XRD、热重-差示扫描量热分析(TG-DSC)、N2吸附-脱附(BET)、氢气程序升温还原(H2-TPR)、CO2程序升温脱附(CO2-TPD)、SEM、TEM及傅里叶变换红外光谱(FTIR)对干凝胶及催化剂进行了理化性能测试，并在高温高压固定床反应器上进行催化剂活性评价。讨论了溶液pH对干凝胶结构及催化剂性能的影响。结果表明：pH为0.5制备得到的干凝胶中存在未配位的游离羧酸，同时又有部分羧酸通过羧基与金属离子进行了配位，而pH为4、6、8、10制备得到的干凝胶中不存在游离羧酸，羧酸均通过羧基与金属离子进行了配位。pH的改变调控着Cu2+、Zn2+、Zr4+与柠檬酸之间的配位能力，使得pH为6时制备得到的催化剂具有较大的比表面积以及铜分散度，比表面积为92.5 m2/g，铜分散度为18.63%，并表现出较好的CO2加氢合成甲醇催化性能 ，CO2转化率为24.7%，甲醇选择选择性为42.3%。     

Effects of ZrO2/Al2O3 properties on the catalytic activity of Pd catalysts for methane combustion and CO oxidation

Zirconia supported on alumina was prepared and characterized by BET surface area, X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), temperature programmed desorption (TPD), and pulse reaction. 0.2% Pd/ZrO₂/Al₂O₃ catalyst were prepared by incipient wetness impregnation of supports with aqueous solution of Pd(NO₃)₂. The effects of support properties on catalytic activity for methane combustion and CO oxidation were investigated. The results show that ZrO₂ is highly dispersed on the surface of Al₂O₃ up to 10 wt.% ZrO₂, beyond this value tetragonal ZrO₂ is formed. The presence of a small amount of ZrO₂ can increase the surface area, pore volume and acidity of support. CO–TPD results show that the increase of CO adsorption capacity and the activation of CO bond after the presence of ZrO₂ lead to the increase of catalytic activity of Pd catalyst for CO oxidation. CO pulse reaction results indicate that the lattice oxygen of support can be activated at lower temperature following the presence of ZrO₂, but it does not accelerate the activity of 0.2% Pd/ZrO₂/Al₂O₃ for methane combustion. 0.2% Pd/ZrO₂/Al₂O₃ dried at 120 °C shows highest activity for CH₄ combustion, and the activity can be further enhanced following the repeat run. The increase of treatment temperature and pre-reduction can decrease the activity of catalyst for CH₄ combustion.     

On the mechanism of CO adsorption on a silica‐supported ruthenium catalyst

The adsorption of CO at room temperature on a Ru/SiO₂ catalyst has been studied by means of FTIR spectroscopy. Spectral evidence for formation of water molecules and a quantity of very dispersed ruthenium on the catalyst surface during CO adsorption was found. On the basis of these experimental results a new reaction scheme for the interaction of CO with a silica‐supported ruthenium catalyst is proposed. This revised version was published online in July 2006 with corrections to the Cover Date.     

固体碱催化黄连木籽油制备生物柴油

制备了K2CO3/Mg(A l)O固体碱催化剂,适宜制备条件为:K2CO3负载量30%、在700℃下焙烧4 h。用比表面积测定仪、X射线衍射仪、红外光谱仪对其进行了表征。以黄连木籽油为原料,开展了酯交换法制备生物柴油的研究,考察了主要影响因素:醇油摩尔比、催化剂用量、反应时间和反应温度对酯交换反应的影响,得到的酯交换反应适宜条件为:以黄连木籽油0.01 mol计,醇油摩尔比12∶1、催化剂用量为黄连木籽油质量的4.0%、反应时间2.5 h、反应温度68℃。在该条件下生物柴油的收率可达99%以上。催化剂经4次循环使用,生物柴油收率仍可保持在96%以上。用FTIR1、HNMR对所制备的产品进行了表征,证明产品中含有饱和脂肪酸甲酯和不饱和脂肪酸甲酯。     

Development of a transient kinetic model for the CO oxidation by O2 over a Pt/Rh/CeO2/γ-Al2O3 three-way catalyst

A transient kinetic model was developed for the CO oxidation by O₂ over a Pt/Rh/CeO₂/γ-Al₂O₃ three-way catalyst. The experiments which were modelled consisted of periodically switching between a feed stream containing 0.5 mol% CO in helium and a feed stream containing 0.5 mol% O₂ in helium, with a frequency from 0.1 to 0.25 Hz, in the temperature range 393–433 K. These temperatures are representative for cold start conditions. The transient experiments yield information about the reaction mechanism. A transient kinetic model based on elementary reaction steps was developed which describes the experimental data in the above mentioned range of experimental conditions adequately. The kinetic model consists of two monofunctional and one bifunctional contribution. The first monofunctional reaction path comprises competitive adsorption of CO and O₂ on the noble metal surface followed by a surface reaction. The second monofunctional reaction path consists of CO adsorption on an oxygen atom adsorbed on the noble metal surface, followed by a reaction to CO₂. The bifunctional reaction path involves a reaction between CO adsorbed on the noble metal surface and oxygen from ceria at the noble metal/ceria interface. Also, reversible adsorption of carbon dioxide on the support is taken into account. The kinetic parameters, i.e. preexponential factors and activation energies for the different elementary reaction steps, and the oxygen storage capacity were estimated using multi-response non-linear regression analysis of the oxygen, carbon monoxide and carbon dioxide outlet concentrations.     

密闭空间CO消除的Pd/Al_2O_3催化剂合成及其催化性能研究

采用浸渍法制备不同PdCl_2含量的贵金属催化剂,并对反应前后催化剂进行傅里叶红外和物理结构表征。结果表明,PdCl_2质量分数为3%的催化剂活性最高,可在70℃实现低浓度CO的完全转化。反应后,催化剂表面没有明显变化,催化剂比表面积增大,孔容及平均孔径呈减小趋势。研究进口CO浓度和空速对CO转化率的影响,结果表明,在一定浓度范围,提高进口CO浓度对CO转化率没有影响,浓度超过1 000×10~(-6)时,CO转化率下降;空速升高,CO转化率下降,温度越低,空速对CO转化率影响越大。     

Preparation of Ni2P/Al-SBA-15 catalyst and its performance for benzofuran hydrodeoxygenation

The Al-doped Ni2P/Al-SBA-15 catalyst with high hydrodeoxygenation(HDO)activity was synthesized by tem-perature programmed reduction at a relatively low reduction temperature of 400°C.The as-prepared catalyst was characterized by X-ray diffraction(XRD),H2temperature-programmed reduction(H2-TPR),X-ray photo-electron spectroscopy(XPS),transmission electron microscope(TEM),NH3temperature programmed desorp-tion (NH3-TPD), N2adsorption-desorption and CO uptake. The effect of Al on benzofuran (BF) HDO performance was investigated.The result indicates that the incorporation of Al into the SBA-15 support can pro-mote the formation of much uniform,smaller,highly dispersed Ni2P particles on the catalyst.The Al also contrib-utes to suppress the enrichment of P and promote more exposed Ni sites on the surface. In addition,the incorporation of Al can enhance the acid strength.The total deoxygenated product yield over Ni2P/Al-SBA-15 reached 90.3%,which is an increase of 19.4%,when compared with that found for Ni2P/SBA-15(70.9%).