Glycerol‐Reforming Kinetics Using a Pt/C Catalyst

Catalytic steam reforming of glycerol, a by‐product in biodiesel production, represents an attractive route to hydrogen. For the first time, the kinetics of the glycerol steam reforming reaction over a Pt/C catalyst was considered. Kinetic data, i.e., glycerol conversion vs. space time, were obtained experimentally by using a fixed‐bed reactor and were analyzed by the integral method of analysis. It was found that in the studied ranges of temperature from 623 to 673 K and space time from 0.39 to 1.56 g h/mol the investigated reaction is of the first‐order with respect to glycerol. The specific reaction rate constant at 673 K was determined to be 1.1·10⁵ cm³/g_cat h. The values of glycerol conversion predicted by the first‐order kinetic model were in good agreement with those obtained experimentally. The increase in temperature, space time, and initial water/glycerol ratio caused the expected increase in hydrogen yield.     

一氧化碳等温变换技术进展

对现代合成氨CO变换技术中发展起来的不同种类的固定床等温反应器进行了比较 ,从转化率、操作稳定性、结构复杂程度及发展前景等方面进行了论述。特别分析了另一类等温反应器———流化床反应器的特点 ,并结合其在传热、传质、处理量及操作等方面的优势和流态化技术的发展。流化床反应器在CO变换过程中的工业化应用很有前景     

Co-Fe/硅藻土催化剂上肉桂醛的选择加氢——反应性能的研究

在固定床反应器中对肉桂醛选择加氢制肉桂醇的反应性能进行了研究。考察了Co-Fe催化剂的活性和选择性;Co负载量、助剂Fe对催化剂选择加氢性能的影响;考察了反应温度、压力、H2的空速等对肉桂醛在催化剂上加氢性能的影响。结果表明,钴/硅藻土催化剂的最佳钴负载量为12%,助催化剂和主催化剂的最佳比为Fe/Co=0.20(mol/mol)。最佳反应温度为423 K,反应的压力越高越有利于催化反应,但压力大于4 MPa后,肉桂醛的转化率和肉桂醇的选择性提高幅度不大,宜控制在4 MPa左右。空速对肉桂醇的选择性影响不大,但空速越高肉桂醛的转化率越低,催化反应中宜控制较低的氢气空速为佳。     

纳米CuO/SiO_2催化甘油氢解制备1,2-丙二醇反应研究

采用共沉淀法制备了纳米CuO/SiO2催化剂,在固定床反应器上考察了纳米催化剂对甘油催化加氢制1,2-丙二醇（1,2-PDO）的催化活性。结果表明,在反应温度200℃,反应压力1.0 MPa,n（H2）∶n（甘油）=30∶1,液空速0.30 h-1的条件下,甘油转化率100%,1,2-PDO选择性98.71%。     

Influence of Reactor Configuration on the Selective Oxidation of Glycerol over Au/TiO2

The oxidation of glycerol by molecular oxygen in the aqueous phase over Au/TiO₂ was investigated in both a batch reactor and a continuous upflow fixed bed reactor. The effects of catalyst particle size, gas flow rate, liquid flow rate, reaction temperature, dioxygen pressure, and solution pH were examined in the fixed bed system. The unique hydrodynamics of the fixed bed system allowed for secondary oxidation products such as tartronic acid and oxalic acid to form in substantial amounts, which contrasts the product distribution observed in a batch system. These results suggest that reactor configuration can play an important role in the observed product selectivity from oxidation reactions over highly active gold catalysts.     

CFD study on partial oxidation of methane in fixed-bed reactor

Partial oxidation of methane (POM) is a preferred method for synthesis gas, which usually occurs in fixed bed reactors. In this paper, the discrete element method (DEM) is used to reconstruct the structure of a reactor bed via simulating the process of filling the reactor with catalyst. The particle resolved CFD physical model with the detailed micro-kinetcis of the POM reaction was established to study the interaction among reactant flow, heat and mass transfer, and reaction in the fixed bed. The gas composition and temperature distribution in the reactor were obtained based on the simulation results. The effects of the space velocity and the reaction temperature on the CH₄ conversion, catalyst selectivity, and catalyst surface coke formation were analyzed. The simulation results show that the temperature hot spots of the catalyst in the bed occur at the inlet and the temperature increases further near the wall. With the increase in space velocity, the conversion rate of CH₄ decreases gradually, and the selectivity does not change significantly. As the temperature increases, the conversion rate of CH₄ gradually increases and the selectivity decreases. The risk of coke formation on the catalyst surface rises axially and the C species concentration is relatively higher near the outlet. Appropriately increasing the gas velocity and increasing the temperature helps to reduce the surface coke accumulation of the catalyst.     

Liquid phase hydrogenation of aniline in a trickle bed reactor

A rate equation is developed for the liquid phase hydrogenation of aniline over cylindrical catalyst pellets of 30% nickel deposited on clay in a trickle bed reactor. The equation takes into account external and internal diffusional limitations, and describes the experimental data adequately. The hydrogenation reaction is first order with respect to hydrogen and zero order with respect to aniline. Effectiveness factors are in the range 0.003–0.03. Apparent activation energy of the reaction is 12.7 kcal/mol and true activation energy is 39.6 kcal/mol.     

Hydrogen production via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system

Hydrogen production was prepared via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system. Low-cost catalyst dolomite was chosen for the primary steam reforming of bio-oil in consideration of the unavoidable deactivation caused by direct contact of metal catalyst and bio-oil itself. Nickel-based catalyst Ni/MgO was used in the second stage to increase the purity and the yield of desirable gas product further. Influential parameters such as temperature, steam to carbon ratio (S/C, S/CH₄), and material space velocity (W_BHSV, GHSV) both for the first and the second reaction stages on gas product yield, carbon selectivity of gas product, CH₄ conversion as well as purity of desirable gas product were investigated. High temperature (> 850 °C) and high S/C (> 12) are necessary for efficient conversion of bio-oil to desirable gas product in the first steam reforming stage. Low W_BHSV favors the increase of any gas product yield at any selected temperature and the overall conversion of bio-oil to gas product increases accordingly. Nickel-based catalyst Ni/MgO is effective in purification stage and 100% conversion of CH₄ can be obtained under the conditions of S/CH₄ no less than 2 and temperature no less than 800 °C. Low GHSV favors the CH₄ conversion and the maximum CH₄ conversion 100%, desirable gas product purity 100%, and potential hydrogen yield 81.1% can be obtained at 800 °C provided that GHSV is no more than 3600 h^− 1. Carbon deposition behaviors in one-stage reactor prove that the steam reforming of crude bio-oil in a two-stage fixed bed reaction system is necessary and significant.     

Renewable hydrogen production by steam reforming of glycerol over Ni/CeO<Subscript>2</Subscript> catalyst prepared by precipitation deposition method

Catalytic steam reforming of glycerol for renewable hydrogen generation has been investigated over Ni/CeO₂ catalyst prepared by precipitation-deposition method. The fresh and used catalysts were characterized by surface area and pore size analysis, X-ray diffraction patterns and scanning electron micrographs. Reforming experiments were carried out in a fixed bed tubular reactor at different temperatures (400–700 °C), glycerol concentrations (5–15 wt%) and contact times. (W/F _Ao =2−80 g-cat·h/mol of glycerol). The investigation revealed that the Ni/CeO₂ catalyst prepared by the above method is effective to produce high yield of hydrogen up to 5.6 (moles of H₂/moles of glycerol fed). The formation of methane and carbon monoxide was greatly reduced over this catalyst. Significantly low amount of coke deposition was observed on the CeO₂ supported catalyst. From the kinetic analysis, the activation energy for the steam reforming of glycerol was found to be 36.5 kJ/mol.     

液相反应物起限制性作用的滴流床反应器模型评价

在实验滴流床反应器内用含２３％Ｃｕ，１７％Ｃｒ的氧化铝催化剂进行过氧化氢的等温分解，以测试不同操作条件下液相色反应物围化率空时的依赖关系。实验证实对氧化氢分解是一个液相反应物起限制性作用的１级反应，模型预测与实验数据的比较表明：除催化剂效率因子以外，必须考虑外部质量传递和催化剂不完全润湿的影响，Ｄｕｄｋｏｖｉｃ提出考虑催化剂总效率因子的近似模型完全能够模拟上述２种影响。     

Modelling of the reversed flow fixed bed reactor for catalytic decontamination of waste gases

Catalytic decontamination of waste gases in a fixed bed reactor, operating at non-steady state conditions achieved by periodic gas flow reversal, is simulated on the basis of a mathematical model. The opportunity to utilize a significant part of the reaction heat is discussed and the effect of catalyst inactivation upon reactor performance is analyzed. Stable temperature regime and conversion exceeding 99.5% could be ensured by a more than eightfold reduction of catalyst activity.     

流化床二氧化碳吸附强化甘油重整的数值模拟

生物甘油催化重整技术为制氢工业的发展提供了广阔的前景,而二氧化碳吸附强化重整因能降低能耗和促进氢气产量被广泛关注。基于欧拉-欧拉双流体模型,结合化学反应动力学,对流化床反应器中二氧化碳吸附强化甘油重整过程开展了数值模拟,评估了催化剂和吸附剂颗粒在反应器中的流动行为,分析了操作压力对气体产物分布的影响。结果表明,催化剂和吸附剂在床中形成了典型的内循环流动结构,压力的增加会促进吸附反应,但在一定程度上减少了氢气的纯度。     

Reaction Kinetics and Coking Behavior for Furan Deoxygenation via Catalytic Pyrolysis Using Methane

The effective deoxygenation of oxygenates remains a major challenge that needs to be overcome for industrial‐scale conversion of biomass to fuels. Present technology uses expensive gaseous hydrogen for deoxygenation. This work looks at the possibility of using methane or natural gas as an alternative for the deoxygenation process. Catalytic pyrolysis studies were carried out using furan as the model oxygenate in the presence of methane in a fixed‐bed reactor over 5 % Ni/HZSM‐5 as catalyst. The effects of temperature and space velocity on the catalyst activity, reaction kinetics, and deactivation behavior were studied. It was found that the deoxygenation of furan was first and second order with respect to furan and methane concentration, respectively. Deactivation studies suggested that catalyst deactivation takes place through poisoning, fouling, and sintering.     

Experimental, kinetic and 2-D reactor modeling for simulation of the production of hydrogen by the catalytic reforming of concentrated crude ethanol (CRCCE) over a Ni-based commercial catalyst in a packed-bed tubular reactor

Mechanistic kinetic models were formulated based on Langmuir-Hinshelwood-Hougen-Watson and Eley-Rideal approaches to describe the kinetics of hydrogen production by the catalytic reforming of concentrated crude ethanol over a Ni-based commercial catalyst at atmospheric pressure, temperature range of 673-863 K, ratio of weight of catalyst to the molar rate of crude ethanol 3472-34722 kg cat s/kmol crude in a stainless steel packed bed tubular microreactor. One of the models yielded an excellent degree of correlation, and was selected for the simulation of the reforming process which used a pseudo-homogeneous numerical model consisting of coupled material and energy balance equations with reaction. The model was solved using finite elements method without neglecting the axial dispersion term. The crude ethanol conversion predicted by the model was in good agreement with the experimental data (AAD%=4.28). Also, the predicted concentration and temperature profiles for the process in the radial direction indicate that the assumption of plug flow isothermal behavior is justified within certain reactor configurations. However, the axial dispersion term still contributed to the results, and thus, cannot be neglected.     

Autothermal CO2 reforming of methane over NiO–MgO solid solution catalysts under pressurized condition: Effect of fluidized bed reactor and its promoting mechanism

The effect of fluidized bed reactor in autothermal CO₂ reforming of methane over NiO–MgO solid solution catalysts was investigated by comparing with fixed bed reactor. Methane conversion to syngas was drastically enhanced by using a fluidized bed reactor. The catalyst was reduced and oxidized repeatedly in fluidized bed reactor during the reaction. The enhancement of methane conversion is related to the catalyst reducibility.     

Upgrading Siberian (Russia) crude oil by hydrodesulfurization: Kinetic parameter estimation in a trickle-bed reactor

Hydrodesulfurization(HDS) of sour crude oil is an effective way to address the corrosion problems in refineries and is an economic way to process sour crude oil in an existing refinery built for sweet oil.Siberian crude oil transported through the Russia-China pipeline could be greatly sweetened and could be refined directly in local refinery designed for Daqing crude oil after the effective HDS treatment.In this study,the HDS of Siberian crude oil was carried out in a continuous flow isothermal trickle-bed reactor over Ni-Mo/γ-Al_2 O_3.The effects of temperature,pressure and LHSV were investigated in the ranges of 320-360℃,3-5 MPa and 0.5-2 h~(-1),keeping constant hydrogen to oil ratio at 600 L·L~(-1).The HDS conversion could be up to 92.89% at the temperature of 360℃, pressure of 5 MPa,and LHSV of 0.5 h~(-1), which is sufficient for local refineries(84%).A three phase heterogeneous model was established to analyze the performance of the trickle-bed reactor based on the two-film theory using Langmuir-Hinshelwood mechanism.The order of sulfur component is estimated as 1.28,and the order of hydrogen is 0.39.By simulating the reactor using the established model,the concentration of H_2, H_2 S and sulfur along the catalyst bed is discussed.The model is significantly useful for industrial application with respect to reactor analysis,optimization and reactor design,and can provide further insight of the HDS of Siberian crude oil.     

Activation studies with an iron fischer-tropsch catalyst in fixed bed and stirred tank slurry reactors

A precipitated iron catalyst (100 Fe/5 Cu/4.2 K/25 SiO₂ on a mass basis) was tested in a fixed bed reactor and a stirred tank slurry reactor under the same process conditions (250°C, 1.48 MPa, 2 L (STP)/gcat · h, H₂ : CO = 2:3). Two different pretreatment procedures were employed (hydrogen reduction at 220°C and carbon monoxide activation at 280°C) in each of the two reactor types. In the stirred tank slurry reactor tests the activity (based on an apparent first order reaction rate constant) of the carbon monoxide pretreated catalyst was about 25% higher than that of hydrogen reduced catalyst, due to incomplete reduction of the latter. In all tests the catalyst selectivity changed slowly with time on stream. Hydrocarbon distribution shifted toward lower molar mass products, and secondary reactions (l-olefin hydrogenation, isomerization and readsorption) increased with time. The secondary reactions were the most pronounced on the hydrogen reduced catalyst in the fixed bed reactor.     

Hydrogen production from fluidized bed steam reforming of hydrocarbons

Steam reforming of methane, kerosene and heavy oil over a nickel/alumina commercial catalyst and other materials such as limestone, dolomite and iron ore, was studied using a 5 cm i.d. fluidized bed reactor. The effects of operating parameters on conversion, hydrogen yield, product gas composition and elutriation of fine catalysts were investigated. It was found that a fluidized bed is flexible enough to handle various feedstocks, including hydrocarbons heavier than naphtha, because it permits the addition of catalyst to, or withdrawals of, coked catalyst from the bed. The yield of hydrogen obtained from fluidized bed steam reforming of heavy oil at 800‡C over limestone was similar to that obtained over commercial nickel-based catalyst. This indicates that limestone could be a promising catalyst for the production of hydrogen from heavy oil. However, hydrogen yield decreased with reaction time in the experiments using the limestone catalyst. The main cause of the decrease in hydrogen yield was elutriation of fine catalysts from the bed during the reaction.     

钯复合膜反应器中异丁烷催化脱氢反应

引　言异丁烷脱氢反应是一个受热力学平衡限制的反应 ,平衡转化率很低 ,若将膜反应器用于该反应 ,则可以通过膜不断地从反应区选择性分离出氢气 ,克服了反应受热力学平衡制约的缺点 ,这样就可降低反应温度和减压程度的要求 ,改善反应的工艺条件 ,从而达到高效和节能的目的 .文献中已分别对钯 /陶瓷复合膜[1,2 ]和钯 -钌 (钌的质量分数为 2 % )合金膜[3]反应器中的异丁烷脱氢反应进行了初步研究 .前文[4 ]已对用改进的化学镀新工艺制备的钯和钯 -银 /陶瓷复合膜进行了表征 ,本文将用钯-银 /陶瓷复合膜反应器进行异丁烷脱氢反应的研究 .本工作…     

负载型CuO/γ-Al2O3催化剂结构与催化甘油氢解性能

采用浸渍法制备了CuO/γ-Al2O3催化剂,通过BET、XRD、XPS和TPR方法表征催化剂上CuO的分布与化学形态,结合固定床催化甘油氢解制备1,2-丙二醇试验.结果表明,催化剂表面高度分散缺电子状态的Cu物种是甘油氢解制备1,2-丙二醇的活性中心.采用浸渍法制备的铜基催化剂具有较好的甘油氢解制备1,2-丙二醇性能...