Intrinsic kinetics study of LPDME process from syngas over bi-functional catalyst

The intrinsic kinetics of the three-phase dimethyl ether (DME) synthesis from syngas over a bi-functional catalyst has been investigated in a agitated slurry reactor at 20–50 bar, 200–240 °C and H₂/CO feed ratio from 1 to 2. The bi-functional catalyst was prepared by physical mixing of CuO/ZnO/Al₂O₃ as methanol synthesis catalyst and H-ZSM-5 as methanol dehydration catalyst. The three reactions including methanol synthesis from CO and H₂, methanol dehydration and water gas shift reaction were chosen as the independent reactions. A kinetic model for the combined methanol and DME synthesis based on a methanol synthesis model proposed by Graaf et al. [G.H. Graaf, E.J. Stamhuis, A.A.C.M. Beenackers, Kinetics of low pressure methanol synthesis, Chem. Eng. Sci. 43 (12) (1988) 3185; G.H. Graaf, E.J. Stamhuis, A.A.C.M. Beenackers, Kinetics of the three-phase methanol synthesis, Chem. Eng. Sci. 43 (8) (1988) 2161] and a methanol dehydration model by Bercic and Levec [G. Bercic, J. Levec, Intrinsic and global reaction rate of methanol dehydration over γ-Al₂O₃ pellets, Ind. Eng. Chem. Res. 31 (1992) 399–434] has been fitted our experimental data. The obtained coefficients in equations follow the Arrhenius and the Van’t Hoff relations. The calculated apparent activation energy of methanol synthesis reaction and methanol dehydration reaction are 115 kJ/mol and 82 kJ/mol, respectively. Also, the effects of different parameters on the reactor performance have been investigated based on the presented kinetic model.     

Catalytic kinetics of dimethyl ether one-step synthesis over CeO_2–CaO–Pd/HZSM-5 catalyst in sulfur-containing syngas process

CeO_2–CaO–Pd/HZSM-5 catalyst was prepared for the dimethyl ether(DME) one-step synthesis in a continuous fixed-bed micro-reactor from the sulfur-containing syngas. The catalytic stability over hybrid catalyst of CeO_2–CaO–Pd/HZSM-5 was investigated to ensure that the kinetics experimental results were not significantly influenced by induction period and catalytic deactivation. A large number of kinetic data points(40 sets) were obtained over a range of temperature(240–300 °C), pressure(3–4 MPa), gas hourly space velocity(GHSV)(2000–3000 L·kg~(-1)·h~(-1)) and H_2/CO mole ratio(2–3). Kinetic model for the methanol synthesis reaction and the dehydration of methanol were obtained separately according to reaction mechanism and Langmuir–Hinshelwood mechanism. Regression parameters were investigated by the method combining the simplex method and Runge–Kutta method. The model calculations were in appropriate accordance with the experimental data.     

一步法合成二甲醚反应器的研究进展

综述了合成气一步法合成二甲醚反应器的发展近况,着重介绍了固定床、浆态床及组合床的研究进展,并根据国内外的研究对几种反应器进行了工艺比较。     

合成气一步法制二甲醚工艺及催化剂研究进展

二甲醚在车用燃料和民用燃料方面具有良好发展前景。合成气一步法制二甲醚工艺分气相法和浆态床法。综述了合成气一步法制取二甲醚的工艺和催化剂的研究进展以及工业化前景。     

合成气一步法制二甲醚催化剂的研究

在Cu-Zn-Al甲醇催化剂制备工艺的基础上,研制出合成气一步法制二甲醚催化剂。经过实验室试验和评价,确定了催化剂使用的最佳工艺条件：压力40 MPa,温度270～310 ℃,空速1 000～2 000 ｈ^-1,合成气中H2体积分数为70%～80%,CO体积分数6%～12%,CO₂体积分数3%～4%。在该条件下,CO转化率大于85％,二甲醚选择性大于90％,二甲醚的收率达65％以上。催化剂表现出良好的活性、选择性和稳定性。     

生物质合成气一步法合成二甲醚的研究

用共沉淀沉积法制备了生物质合成气直接合成二甲醚(DME)的催化剂,考察了固定床中温度、压力、空速等工艺条件对二甲醚合成性能的影响,同时基于Gibbs自由能最小法对合成DIME反应的化学平衡进行模拟计算,并与实际测试结果相比较.结果表明,模拟结果与测试结果吻合较好.     

Intrinsic kinetics of the Fischer-Tropsch synthesis over an impregnated cobalt-potassium catalyst

The optimal amount of 15 wt%Co/10 wt%K/Al₂O₃ catalyst was prepared using the impregnation technique in order to study the kinetics of the Fischer-Tropsch synthesis. The rate of synthesis was measured in a fixed-bed micro reactor with H₂/CO feed ratio of 1–3 and space velocity in the range of 2,700–5,200 h⁻¹ under reactor pressure of 8 bar and a temperature range of 210–240 °C. The experimental data were best fitted by a Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach rate in the form of - r_CO = (k₂ K₁ P_CO P_H2 )/(1 + K₁ P_CO ) - r_{CO} = (k_2 K_1 P_{CO} P_{H_2 } )/(1 + K_1 P_{CO} ). Furthermore, the data were fitted fairly well by a power law equation in the form of - r_CO = kP_CO^1.32 P_H2 ^1.42 - r_{CO} = kP_{CO}^{1.32} P_{H_2 }^{1.42} . The activation energies for LHHW approach model and power law equation were obtained as 138.5 kJ/mol and 87.39 kJ/mol, respectively.     

合成气一步法制备二甲醚的工艺流程模拟与优化

二甲醚作为燃料的替代品,其生产开发在化学工程领域受到了广泛关注。本文对合成气一步法制备二甲醚过程进行了模拟分析,提出了用水作为吸收剂并采用多效精馏的二甲醚生产新工艺。利用Aspen Plus化工模拟软件对吸收塔进行模拟比较了甲醇和水作为吸收剂的能耗,模拟结果表明,用水吸收较甲醇吸收总热负荷降低23.54％,总冷负荷降低35.97％,更为节能。从节能降耗角度出发,根据不同的分离任务,提出了采用两塔分离甲醇-水及三塔分离甲醇-水的两项工艺改进措施。结果表明,采用两塔分离甲醇-水工艺比原工艺二甲醚产量增加了11.50%,能量消耗无明显变化。进一步采用三塔精馏工艺总冷负荷比原工艺减少45.07％,总热负荷减少19.27%,且二甲醚产量增加11.15％,节能效果显著。     

Thermodynamic equilibrium in the synthesis of dimethyl ether from synthesis gas

Chemical equilibrium in dimethyl ether synthesis from synthesis gas was studied thermodynamically over wide ranges of gas compositions and process parameters.     

Specifics of dimethyl ether synthesis from syngas over mixed catalysts

Dimethyl ether (DME) synthesis from syngas over a mixture of a methanol synthesis catalyst (ZnO, 25.10 wt %; AuO, 64.86 wt %; Al₂O₃, 10.04 wt %) and a methanol dehydration catalyst (γ-A1₂O₃) has been investigated for one-, two-, and three-layer catalyst beds. There is a common regularity for these three variants: with an increasing temperature, the total CO conversion decreases, the CO-to-methanol conversion decreases, and the CO-to-DME conversion increases. The largest values of DME selectivity and DME yield have been attained with the three-layer bed. The highest DME yield has been obtained at 250–285°C. Use of a mechanical mixture of the methanol synthesis catalyst and alumina makes it possible to efficiently obtain DME from syngas ballasted with nitrogen (20 vol %) at an H₂/CO ratio of 1, which is unfavorable for methanol synthesis. The DME yield on the syngas input basis in this case with the ballast gas (nitrogen or CO₂) taken into account can be about 10 wt %.     

Effect of H2O on Cu-based catalyst in one-step slurry phase dimethyl ether synthesis

One-step dimethyl ether (DME) synthesis in slurry phase was catalyzed by a hybrid catalyst composed of a Cu-based methanol synthesis catalyst and a γ-Al₂O₃ methanol dehydration catalyst under reaction conditions of 260 °C and 5.0 MPa. It was found that instability of the Cu-based catalyst led to rapid deactivation of the hybrid catalyst. The stability of the Cu-based catalyst under DME synthesis conditions was compared with that under methanol synthesis conditions. The results indicated that harmfulness of water, which formed in DME synthesis, caused the Cu-based catalyst to deactivate at a high rate. Surface physical analysis, elemental analysis, XRD and XPS were used to characterize the surface physical properties, components, crystal structures and surface morphologies of the Cu-based catalysts. It was found that Cu⁰ was the active component for methanol synthesis and Cu₂O might have less activity for the reaction. Compared with methanol synthesis process, crystallite size of Cu became bigger in DME synthesis process, but carbon deposition was less severe. It was also found that there was distinct metal loss of Zn and Al caused by hydrothermal leaching, impairing the stability of the catalyst. In slurry phase DME synthesis, a part of Cu transformed into Cu₂(OH)₂CO₃, causing a decrease in the number of active sites of the Cu-based catalyst. And some ZnO converted to Zn₅(OH)₆(CO₃)₂, which caused the synergistic effect between Cu and ZnO to become weaker. Crystallite size growth of Cu, carbon deposition, metal loss of Zn and Al, formation of Cu₂(OH)₂CO₃ and Zn₅(OH)₆(CO₃)₂ were important reasons for rapid deactivation of the Cu-based catalyst.     

合成气一步法制二甲醚催化剂研究进展

简述了二甲醚的物化特性及其应用前景,对现有的几种合成气一步法合成二甲醚的反应机理及动力学模型进行了概述。分别研究了双功能催化剂中的甲醇合成活性组分和甲醇脱水活性组分,CuO/ZnO/Al₂O₃ 作为甲醇合成组分,活性和稳定性较好,甲醇脱水活性组分以γ-Al₂O₃ 、分子筛及其改性后产物较为常用。探讨了双功能催化剂的制备方法及改性方法。     

串联催化剂在二甲醚与合成气制备乙醇反应中的性能研究

通过水热合成法和共沉淀法分别制备了分子筛催化剂和Cu/ZnO催化剂,将分子筛与Cu/ZnO调控成双层串联催化剂,并用于二甲醚与合成气通过两段反应制备乙醇。研究了反应温度和反应气组成等因素对反应的影响,比较了分子筛类型、助剂种类和含量等对催化剂活性的影响。结果表明,随反应温度增加,DME转化率和乙醇选择性呈现先增加后减小趋势,随着DME含量减少和CO含量增加,DME转化率和乙醇选择性增加。H-MOR分子筛与Cu/ZnO串联催化剂显示了最佳的催化活性;金属助剂能提高催化剂活性,尤其是含5%Cu的Cu/H-MOR与Cu/ZnO串联催化剂显示了最佳的催化反应活性,于最佳反应温度493 K下以Ar/DME/CO/H_2(1.6/1.0/47.4/50.0)为原料进行反应,DME转化率达到33.6%,乙醇选择性达到了44.5%。     

完全液相制备催化剂上合成二甲醚动力学研究

采用浆态床反应器,研究了用完全液相法制备的Cu-Zn-A l双功能催化剂上CO加氢直接合成二甲醚(DME)的反应动力学。按CO加氢先合成CH3OH,再由CH3OH脱水生成DME二步串联的反应机理,根据不同的中间产物及控制步骤分别建立了动力学模型,以反应物的平衡浓度代替逸度进行计算,最终选取的模型计算值和实验值吻合较好,说明采用L-H型动力学模型可以合理地描述催化剂表面的反应过程,模型参数计算结果表明,催化剂表面对CO2的弱吸附是该催化剂在浆态床中稳定性较好的主要原因之一。     

Kinetics of dimethyl ether oxidation over Pt/ZSM-5 catalyst

A kinetic study of dimethyl ether (DME) combustion over Pt/ZSM-5 was performed below 423 K. Power law model and Langmuir-Hinshelwood model were established to predict the reaction rate. Reaction orders for DME and O₂ were 0.28 and 2.30, respectively. Activation energies for the two models were 99.35 and 109.30 kJ/mol. The reaction orders and adsorption constants suggested DME was more strongly adsorbed on Pt/ZSM-5 than O₂ at low temperatures. The reliability of the models was confirmed by the comparison between the predicted and experimental conversions of DME.     

Cu-K/Al_2O_3催化剂上溴甲烷合成二甲醚的失活动力学研究

采用Cu-K/Al2O3催化剂,在固定床积分反应器上进行溴甲烷合成二甲醚的动力学实验,反应温度(463.15~523.15)K条件下,得出主反应的宏观动力学方程:r=1.1+2.8×10-3T-4.4exp(-21.5/RT)pCH3Br,主反应的活化能约为21.5 k J·mol-1。对主反应宏观动力学方程进行统计检验,结果表明,在给定99%的置信度下,方程显著、可信。失活前后的XRD表征结果表明,催化剂晶相由Cu O转变为Cu Br2是导致催化剂失活的主要原因。采用独立失活机理描述催化剂失活速率方程,通过回归得到各项参数,建立了适用于Cu-K/Al2O3催化剂上溴甲烷合成二甲醚的失活动力学方程:r=[-1.1+2.8×10-3T-4.4exp(-21.5/RT)pCH3Br]×exp(-2.1×10-3t)。     

BX 型中温变换催化剂上CO 变换反应本征动力学研究

采用常压等温直流积分反应器, 研究了在BX 型中温变换催化剂上CO 变换反应的本征动力学。应用正交实验设计方法, 模拟生产条件进行测试, 用非线性最小二乘法优化参数估值, 获得本征动力学模型, 并经F 检验、相关指数检验及运用此数学模型进行某工厂变换炉催化剂用量的计算, 证明了实验数据及数学模型的准确性。     

合成气一步法制二甲醚的一种分离流程

针对合成气一步法制备二甲醚的工艺路线,在进行了二甲醚吸收和精馏的实验基础上,提出了用水吸收一步反应冷凝后气相产物中的二甲醚的分离工艺流程:反应冷凝液相与吸收后的液体混合后进入二甲醚精馏塔,二甲醚产品从精馏塔侧线引出,塔底甲醇和水去甲醇精馏塔。在实验数据的基础上,对二甲醚分离工艺流程进行了模拟计算。     

Nanocrystalline gamma-alumina: A highly active catalyst for dimethyl ether synthesis

In this article, mesoporous nanocrystalline γ-Al₂O₃ with high surface area is synthesized by a simple sol-gel method with cationic surfactant as template. This sample is used for vapor-phase dehydration of methanol to Dimethyl ether. The synthesized catalyst showed a high surface area of 375 m² g^− 1 and a crystallite size of about 3.9 nm. NH₃-TPD analysis revealed that the sample with smaller crystallite size possesses higher concentration of medium acidic sites and consequently the catalytic activity.