Separation of Hydrogen from Carbon Monoxide Using a Hollow Fiber Polyimide Membrane: Experimental and Simulation

The separation of hydrogen from carbon monoxide (syngas ratio adjustment) with polymeric membranes was investigated in this work. A polyimide hollow fiber membrane module was used for hydrogen separation. This polymer has shown large permeability and selectivity for hydrogen separation (selectivity of ca. 30). Permeation tests were carried out at different feed conditions. Feed flow rates were varied between 150–300 mL/min, temperature was varied in the range of 20–80 °C and feed pressure was varied between 5–9 bar. Mixtures containing 0–50 % carbon monoxide were used when carrying out experiments. Measured membrane permeances for hydrogen and carbon monoxide were about 70–100 GPU (gas permeation units) and 3–5.5 GPU, respectively. In addition, a mathematical model for simulation of gas separation in hollow fiber membrane modules with all flow patterns (crossflow, countercurrent and cocurrent) was presented. This model can be used for calculation of membrane performance or its required surface area for a specific separation. Experimental results have shown good correlation with simulation results. Plasticization, competitive sorption and concentration polarization effect of carbon monoxide on membrane performance is shown with experimental results. This effect reduced hydrogen permeances in mixed gas experiments.     

一氧化碳在苯酚+乙醇中的溶解度测量和关联

The solubility of carbon monoxide in phenol＋ethanol mixed solvents at elevated pressures is reported in this article. The experimental results revealed the influence of pressure on the solubility of CO in phenol＋ethanol mixtures. These mixtures are a poorer solvent for carbon monoxide. The solubility of CO is a linear function of pressure, and the extended Henry＇s constants were presented at different concentrations of phenol. The cubic Soave-Redlich-Kwong equation of state was used to correlate the experimental gas liquid equilibrium data and to predict the solubility of CO. At the same time, the binary interaction parameters, kO, for CO-phenol, CO-ethanol and phenol-ethanol systems were estimated by fitting experimental GLE data at 303.15 K and at 2.0-9.0 MPa. Hence, a model was suggested for the solubility of CO in phenol＋ethanol mixed solvents. The agreement between experimental and calculated solubilities with the proposed model was rather satisfactory.     

Concentration oscillations of carbon monoxide,oxygen and 1-butene over a platinum supported catalyst

The effect of a wide range of experimental parameters on the sinusoidal and multiple spike oscillations observed during the oxidation of mixture of carbon monoxide and 1-butene over platinum supported on γ-alumina has been investigated in a CSTR. An elementary step model, where the rate constants are assumed independent of surface coverages, is found to be able to account largely for the observed oscillatory phenomena. The carbon monoxide and oxygen adsorption and desorption rate constant values in the model have been evaluated by fitting experimental transients, while 1-butene parameter values were obtained from stability conditions. Rate constant values and operating conditions have a profound effect on the observed and predicted oscillations. A parameter of great importance is the ratio of the number of adsorption sites to reactor volume.     

Reaction modeling on the phosphorous-treated Ru/Co/Zr/SiO2 Fischer-Tropsch catalyst with the estimation of kinetic parameters and hydrocarbon distribution

The catalytic performances and the kinetics model of the cobalt-based Fischer-Tropsch (FT) catalyst were investigated on Ru/Co/Zr/SiO₂ with different amounts of phosphorous. The preliminary analysis of the CO conversion, the hydrocarbon selectivity and the activation energy revealed that the 0.5 wt.% phosphorous-treated Ru/Co/Zr/SiO₂ catalyst was found to have the highest catalytic activity because of the good dispersion of the cobalt species and the suppressed aggregation during the FT reaction. Kinetics model was concomitantly developed on the selected catalyst. The model that was reported in the literature was modified in order to explain the characteristics that were observed in the experimental studies, and the kinetic parameters were estimated to fit the experimental data under various reaction conditions. The simulation results along with the estimated kinetic parameters satisfactorily predicted the effects of the operating conditions on both the CO conversion and the entire hydrocarbon distribution.     

Kinetic modeling of hydrocracking reaction in a trickle-bed reactor with Pt/Y-zeolite catalysts

A kinetic model is developed to predict the entire distribution of hydrocarbon products for the hydrocracking reaction with Pt/Y-zeolite catalysts in a trickle-bed reactor. Operating conditions, such as temperature, pressure, and wax and H2 flow rates were varied to evaluate their effects on conversion and distribution, and kinetic parameters were estimated using the experimental data that covers the window of operating conditions. The comparison between experimental data and simulated results corroborated the validity of the developed model, and the quantitative prediction of the reactor performance was clearly demonstrated. To make evident the usefulness of the model, an optimization method, genetic algorithm (GA), was applied, and the optimal condition for the maximum production of C₁₀-C₁₇ was successfully calculated.     

氢气和一氧化碳在混二甲苯中的溶解度

在１立升的高压机械搅拌釜中,采用气体间歇吸收技术,在８０－１６０℃,０．５－５ＭＰａ的范围内,测定了氢气和一化碳在混二甲苯中的溶解度。氢气和一氧化碳的溶解度随着温度和压力的增加而增大,且在相同的温度和压力下,一氧化碳的淀粉 度大于氢气的溶解度。与它们在间二甲苯中的溶解度相比,在混二甲苯中的溶解度是较小的。此外,使用正规溶液理论的Ｐｒａｕｓｎｉｔｚ－Ｓｈａｉｒ方法对它们的溶解度进行了估算。可以看出,一氧化碳在二甲苯中的溶解度的估算值与实验结果较相符,氢气由地临界温度较低,没有合适的估算式,故用实验回归的公式结合Ｐｒａｕｓｎｉｔｚ－Ｓｈａｉｒ方法中的其它公式进行估算,估算值与实验值大体相符。     

气液固相催化合成甲醇本征动力学

研究了以液体石蜡为液相介质在铜基催化剂上由CO、CO_2与氢气合成甲醇的本征动力学,按CO和CO_2加氢生成甲醇的反应途径,提出了反应机理,建立了6种动力学模型,经参数估值及模型筛选,得出了最终模型,该模型的计算值与实验值吻合很好,对CO及CO_2转化速率的平均偏差分别为3.69%和3.92%。     

Modeling a slurry CSTR with Co/P–Al2O3 catalyst for Fischer–Tropsch synthesis

A kinetic model of cobalt-based Fischer–Tropsch synthesis was developed based on detailed reaction mechanisms. A mathematical model of a slurry CSTR was also constructed. Kinetic parameters and physical properties were estimated by fitting experimental data under a variety of conditions. Simulated values were in good agreement with experimental data, and the suitability of the estimated parameters was discussed by comparison with reported values. The developed model was used to evaluate the effects of operating conditions on CO conversion and the distribution of hydrocarbon products. Temperature and H₂/CO ratio were found to be important variables, affecting the entire product distribution.     

A highly efficient catalyst for direct synthesis of methyl acrylate via methoxycarbonylation of acetylene

A non-petroleum approach for the catalytic synthesis of methyl acrylate via methoxycarbonylation of acetylene with carbon monoxide and methanol as nucleophilic reagent has been studied under various conditions. Pd(OAc)₂/2-PyPPh₂/p-tsa was found to be a highly efficient catalytic system. The types of phosphorus ligands and their concentration was a determinative factor for catalytic activity. Mono-dentate phosphorus ligand such as triphenylphosphine has no activity while 2-(diphenylphosphino)pyridine with a mixed N-P bidentate structure has an excellent activity. Catalytic performance of acids depends on their acidic strength and coordinative property. Among all acidic promoters, p-toluenesulfonic acid displayed an excellent performance. Other parameters such as solvent polarity and initial pressure of carbon monoxide have also important influences on the hydroesterification of acetylene. It is beneficial for the reaction that the solvents have a high polarity. At low pressure of carbon monoxide, to high active palladium catalyst, the reaction easily proceeded. However, at high pressure of carbon monoxide, acetylene will transfer from solution to gas phase, resulting in lower conversion of acetylene. In addition, due to steric hindrance of alcohols, methanol has a highest activity in hydroesterification of acetylene in low carbon alcohols. Under the optimal reaction conditions, 99.5% of acetylene conversion and 99.7% of selectivity toward methyl acrylate as well as 2,502 h^?1 TOF were achieved.     

Catalytic properties of potassium-or lanthanum-promoted Co/γ-Al2O3 catalysts in carbon monoxide hydrogenation

The effects of potassium or lanthanum additives on the catalytic properties of alumina-supported cobalt catalysts were examined through carbon monoxide hydrogenation reaction. The catalysts were characterized by hydrogen or carbon monoxide chemisorption, oxygen titration, and temperature-programmed desorption. The reactions were carried out at 270 °C and atmospheric pressure. When a small amount of potassium was added to alumina-supported cobalt catalysts, the amount of hydrogen adsorption decreased more significantly than that of carbon monoxide adsorption, and the extent of reduction also decreased. With the addition of potassium, the overall carbon monoxide conversion decreased, while the selectivity to higher hydrocarbon and olefin increased. The effect of lanthanum on activity and selectivity in carbon monoxide hydrogenation was less significant than the effect of potassium. Temperature-programmed desorption showed that the presence of additives changed the adsorbed state of CO on cobalt. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Fluidized bed char combustion kinetic models

The effect of the kinetics of the heterogeneous reaction between the char and oxygen, and the importance of the subsequent homogeneous oxidation of carbon monoxide oil the performance of an atmospheric fluidized bed combustor have been examined by a comparative analysis of three models. Numerical calculations illustrating the effect of operating variables such as bed temperature, fuel and sorbent particle feed size and excess air were performed for values of the parameters which are pertinent to the design of large scale utility boilers. It is found that the kinetic models predict existence of multiple steady states over a wide range of operating conditions and values of model parameters. The model predictions of combustion efficiency, carbon loading and CO concentrations are in qualitative agreement with experimental data reported in the literature.     

Direct conversion of methane to acetylene or syngas at room temperature using non-equilibrium pulsed discharge

Non-catalytic direct conversion of methane to valuable products was studied using non-equilibrium pulsed discharge under the conditions of ambient temperature and atmospheric pressure. Acetylene was produced with 95% selectivity and 52% methane conversion. An addition of oxygen, carbon dioxide and steam contributed significantly to suppress the carbon deposition and produced carbon monoxide as well as acetylene. Methane conversion increased with an increase in the pulse frequency while the product selectivity remained almost constant. The selectivity depended on the composition of the feed gas. The effect of the partial pressure of oxygen was examined, and it was found that the pulsed discharge would be able to produce synthesis gas by partial oxidation of methane. Carbon monoxide selectivity of 79% with methane conversion of 76% was obtained under the conditions of CH₄/O₂=25/25 cm³ min⁻¹, gap distance of 10 mm and the frequency of 45 Hz.     

Cu修饰的多孔碳材料高效电化学还原CO2为CO

将二氧化碳电化学还原为一氧化碳是一种实现碳循环和利用的有效途径。为了利用大量过剩的二氧化碳资源,本文制备了一种简单合成的电催化剂,以生物质壳聚糖为前体制备了含氮多孔碳基底,嵌入均匀分布的非贵金属铜纳米颗粒进行修饰,通过调节铜的负载量,达到充分利用铜金属的活性,从而在电化学二氧化碳还原过程中实现了优异的一氧化碳法拉第效率和选择性。在-0.6V vs. RHE时下,一氧化碳的最大法拉第效率（FE）为78%,并且没有其他有效产物的生成,从而一氧化碳的选择性达到了100%,电流密度为1.9mA/cm²。并且在0.1mol/L KHCO₃水溶液中连续电解13h以上,一氧化碳的法拉第效率和选择性基本保持不变,制备的电极材料具有优异的稳定性。     

Fischer-Tropsch-Synthese. Neuere Untersuchungen und Entwicklungen

Fischer-Tropsch synthesis – Recent studies and Developments . This article surveys some results of recent research and new lines of development in Fischer-Tropsch synthesis. Most interest is focussed on variants synthesis showing high selectivity of C₂-C₄ alkenes or C₅-C₂₀ 1-alkenes or Diesel oil. In the last decade catalysts of improved alkene selectivity have been developed. Also the dependence of selectivity on process parameters such as pressure of hydrogen and carbon monoxide and temperature has been investigated in order to find appropriate conditions of operation for a synthesis of high selectivity. Some preliminary process designs are discussed.     

Incorporation of Dynamic Flexibility in the Design of a Methanol Synthesis Loop in the Presence of Catalyst Deactivation

A typical methanol loop reactor is analyzed in this study. All basic equipment in the Lurgi‐type methanol loop is included in the proposed model. A detailed dynamic model described by a set of ordinary differential and algebraic equations is developed to predict the behavior of the overall process. The model is validated against plant data. A new deactivation model is proposed and its parameters are estimated using daily plant data. The interesting feature of this model is that it incorporates the effect of carbon dioxide and carbon monoxide on the catalyst deactivation. Using the model, the effect of various factors to compensate for the reduction of production rate due to catalyst deactivation has been examined. Some improvements can be achieved by adjusting the operating conditions. Finally, a strategy is proposed for prevention of reduced production due to catalyst deactivation.     

Studies on phase equilibria of a multicomponent model mixture in supercritical carbon dioxide and trifluoromethane

Phase equilibria were studied of a multicomponent model mixture representing the middle distillate of a coal liquefaction product in the gases carbon dioxide and trifluoromethane at temperatures (308–338 K) and pressures (6–30 MPa) above the critical points of the gases. Partition coefficients and separation factors were determined for the individual mixture components by analysing samples from the coexisting phases. The results show that selectivity due to structural properties (π-bonds, dipole moments, etc.) is superimposed by selectivity due to differences in vapor pressures. The concepts of structure selectivity and vapor pressure selectivity are introduced and changes of these parameters with pressure and temperature are reported. Enhancement factors in the carbon dioxide/model mixture system were calculated and show good agreement with the experimental results.     

Three-dimensional numerical modelling of a fast fluidized bed biomass gasifier to generate energy from wastes

The modelling of a biomass fluidized bed gasification system, one of the most effective ways to produce energy from biomass resources and wastes, has been performed in this study. The effect of the turbulence phenomena, including calculations relating to flow turbulence, chemical fuel reactions, and energy and momentum exchange between multiple solid and gas phases, has been taken into account in the current research as a novel approach. A computational fluid dynamics case study model that combines equations with comprehensive geometry has been considered. Results have been compared with published operational records of an existing power plant to validate the model. The solid particle distribution, the velocity of the mixture and gas phase, the turbulent flow viscosity ratio, and the temperature distribution in the model indicated the accuracy of the simulation performance compared with the experimental studies. The production of the molar fraction of the constituent elements of the synthesis gas has been evaluated in transient conditions. Additionally, 35 s after the process began, the system's performance was estimated, and the results indicated the average molecular weights of hydrogen, carbon monoxide, carbon dioxide, and methane are 26%, 23%, 12.5%, and 3.3%, respectively, which presented high precision with the experimental results.     

描述CO2的柔性模型

A fully flexible potential model for carbon dioxide has been developed to predict the vapor-liquid coexistence properties using the NVT-Gibbs ensemble Monte Carlo technique (GEMC). The average absolute deviation between our simulation and the literature experimental data for saturated liquid and vapor densities is 0.3% and 2.0%, respectively. Compared with the experimental data, our calculated results of critical properties (7.39 MPa, 304.04 K, and 0.4679 gcm－3) are acceptable and are better than those from the rescaling the potential parameters of elementary physical model (EPM2). The agreement of our simulated densities of supercritical carbon dioxide with the experimental data is acceptable in a wide range of pressure and temperature. The radial distribution function es-timated at the supercritical conditions suggests that the carbon dioxide is a nonlinear molecule with the C O bond length of 0.117 nm and the O C O bond angle of 176.4°, which are consistent with Car-Parrinello molecular- dynamics (CPMD), whereas the EPM2 model shows large deviation at supercritical state. The predicted self-diffusion coefficients are in agreement with the experiments.     

Cobalt Particle Size Effects in the Fischer–Tropsch Synthesis and in the Hydrogenation of CO2 Studied with Nanoparticle Model Catalysts on Silica

We have investigated the effect of cobalt nanoparticle size in Fischer–Tropsch synthesis (CO/H₂) and have compared it to data obtained for carbon dioxide hydrogenation (CO₂/H₂) using model catalysts produced by colloidal methods. Both reactions demonstrated size dependence, in which we observed an increase of the turnover frequency with increasing average particle size. In both case, a maximum activity was found for cobalt particles around 10–11 nm in size. Regarding the selectivity, no size-dependent effect has been observed for the CO₂ hydrogenation, whereas CO hydrogenation selectivity depends both on the temperature and on the size of the particles. The hydrogenation of CO₂ produces mainly methane and carbon monoxide for all sizes and temperatures. The Fischer–Tropsch reaction exhibited small changes in the selectivity at low temperature (below 250 °C) while at high temperatures we observed an increase in chain growth with the increase of the size of cobalt particles. At 250 °C, large crystallites exhibit a higher selectivity to olefin than to the paraffin equivalents, indicating a decrease in the hydrogenation activity.     

Performance and aging of catalysts for the selective hydrogenation of acetylene: a micropilot-plant study

Some catalysts for the “tail-end” selective hydrogenation of acetylene were tested in a micropilot plant. This was operated under conditions similar to those of industrial plants. The influence of temperature, carbon monoxide concentration and H₂/C₂H₂ ratio on the activity and selectivity were investigated. Three possible definitions for the calculation of the selectivity to ethylene were used and compared. Great differences in the physico-chemical properties and in catalytic performance were found among the catalysts examined. A decrease in the conversion of acetylene was found at high temperatures.In spite of the short duration of the tests (⩽350 h), aging phenomena were frequently observed, due to the formation of oligomers on the catalysts. Large amounts of carbon were measured in the unloaded catalysts. The formation of oligomers was favoured by higher acetylene concentrations and occurred only in the presence of the hydrogenation reaction. Deactivation was also correlated with 1) the concentration of carbon monoxide, 2) the hydrogen/acetylene ratio, 3) the use of constant or variable reaction conditions during the test and 4) the linear velocity. It was suggested that carbon monoxide is involved in the formation of the organic compounds that deactivate the catalysts. Aging was faster for fresh catalysts. It caused a loss of total surface area, of activity in acetylene hydrogenation and, often, of selectivity to ethylene.A set of tests, planned according to statistical criteria, was performed. Results were interpolated by second degree polynomials, yielding an empirical model which accounted for the influence of both time and reaction variables. This model was used to find conditions of high selectivity and to simulate some runs at constant conversion, maximum selectivity and minimum deactivation of the catalysts.