浆态床中合成气制二甲醚宏观动力学的研究(英文)

以液体石蜡为介质,在合成甲醇催化剂与甲醇脱水催化剂比例为5、催化剂浓度为10 g/300 mL液体石蜡,温度为250℃~280℃,压力为3 MPa~5 MPa,气体空速为4 000 mL/(g(h)~7 000 mL/(g(h)的条件下,建立了浆态床合成气制二甲醚宏观动力学模型。甲醇合成反应和甲醇脱水反应的活化能分别为14.06 kJ/mol和23.53 kJ/mol。甲醇当量生成速率和二甲醚生成速率的计算值与实验值的相对误差在10%和20%以内。     

EFFECT OF CATALYST CONCENTRATION ON CATALYTIC PERFORMANCE IN LIQUID PHASE DIMETHYL ETHER SYNTHESIS FROM SYNGAS

利用ＺＳＭ－５型沸石可将轻烃选择性地转化为苯，甲苯和二甲苯。ＨＺＳＭ－５催化剂上丙烷转化率和芳烃选择性都很低，但在ＨＺＳＭ－５上添加Ｇａ或Ｐｔ－Ｇａ（双金属改性）后丙烷转化率和芳烃选择性都有很大提高。实验结果表明，Ｇａ／ＨＺＳＭ－５催化剂经氢气高温预处理后，其上的Ｂｒｏ．．ｎｓｔｅｄ酸中心数目减少。铂的加入促进了镓物种的还原，而还原的镓物种可以中和相当一部分催化剂表面Ｂｒ．ｎｓｔｅｄ酸中心，然后形成高度不饱和的催化活性中心。这些中心可以作为Ｌｅｗｉｓ中心，从丙烷和反应中间产物中拔除Ｈ－，使丙烷高选择性地生成芳烃     

含有多级孔复合分子筛的复合催化剂上合成气一步制二甲醚

以Beta分子筛为核、Y型分子筛为壳层的多级孔复合分子筛(BFZ)作为甲醇脱水催化剂用于固定床中合成气一步法制备二甲醚,并与纯Y型分子筛进行了比较,研究了二甲醚合成催化反应活性与甲醇脱水催化剂孔道结构和酸性之间的关系.结果表明,复合分子筛HBFZ具有中等强度的酸性和中孔孔道结构,有利于提高合成气制备二甲醚的催化反应活性.二甲醚直接合成催化剂由工业CuO/ZnO/Al₂O₃催化剂(CZA)与分子筛(HBFZ、HY)采用机械混合方法制备;催化评价结果显示,CZA/HBFZ比CZA/HY具有更优的催化活性和稳定性.在250 ℃, 5.0 MPa 和 1 500 h^-1的反应条件下,CZA/HBFZ催化剂上CO的转化率和DME的选择性分别达到94.2%和67.9%.     

Synthesis of Dimethyl Ether from CO Hydrogenation： a Thermodynamic Analysis of the Influence of Water Gas Shift Reaction

Three reactions involved in dimethyl ether (DME) synthesis from CO hydrogenation: methanol synthesis reaction (MSR), methanol dehydration reaction (MDR) and water gas shift reaction (WGSR) are studied by thermodynamic calculation. For demonstrating this process in detail, three models, MSR,MSR MDR, MSR MDR WGSR, are used. Their basic characteristics can be obtained by varying widely the ratios of H2 to CO in the feed (no CO2). Through thermodynamic analysis a chemical synergic effect obviously exists in the second and third models. By comparison between two models it is found that WGSR plays a special role in dimethyl ether synthesis. It is possible for the two models to shift one to the other by regulating CO2 concentration in feed. For Model 2, the selectivity for DME in oxygenates (DME methanol) does not change with the ratio of H2 to CO.     

含氮合成气直接制二甲醚的Cu基催化剂研究

研究了CuO-ZnO-Al2O3／HZSM－5系列双功能催化剂催化含N2合成气直接制二甲醚的性能，考察了助剂和催化剂制备方法对反应性能的影响，结果表明，在CuO-ZnO-Al2O3／HZSM－5催化剂中加入ZrO2，有利于提高催化活性；用胶体沉积法制备的CuO-ZnO-Al2O3／HZSM－5双功能催化剂，其CuO晶粒小，分散好、易于还原，同时增强了各组分间的协同作用，表现出良好的催化性能。     

Cu/ZnO@H-β-P催化剂在合成气制备液化石油气反应中的性能研究

采用共沉淀法制备Cu/ZnO催化剂、水热合成法制备H-β分子筛、通过物理包膜法制备了具有核壳结构的Cu/ZnO@H-β-P催化剂,并用于合成气制备液化石油气(LPG)反应。通过XRD、NH3-TPD、BET和SEM-EDS等手段对催化剂进行了表征,利用固定床连续反应装置对催化剂进行了活性评价。结果表明,Cu/ZnO@H-β-P催化剂是具有中孔的核壳结构材料,其协同作用打破了原有的热力学平衡,促进了甲醇→DME→LPG串联反应的连续进行。与物理混合的Mix-Cu/ZnO-H-β催化剂相比,Cu/ZnO@H-β-P催化剂的CO转化率和LPG选择性更高,空速和反应温度对催化剂活性影响明显,最佳空速和反应温度分别为2 400 h~(-1)和350℃。使用Cu/ZnO@H-β-P催化剂在最佳条件下进行合成气制备LPG反应,CO转化率达到了57.22%,LPG选择性达到了60.52%。     

Mechanism and Kinetics of Reactions of C1 Molecules on Cu-Based Catalysts

The mechanism and kinetics of reactions occurring in the course of natural gas processing into motor fuels and other chemical products are considered with emphasis on copper-based catalysts. The following reactions are considered: methanol and methyl formate syntheses, dimethyl ether synthesis from syngas and by methanol dehydration, water-gas shift reaction, steam reforming of methanol and its decomposition to produce syngas, and others. It is shown that a key role in the mechanisms of the above reactions belong to transformations of stable, strongly (irreversibly) chemisorbed species, and this fact determines the specific features of the schemes of their mechanisms and kinetic models. The use of the specific features of reaction mechanisms makes it possible to increase the process efficiency (methanol and dimethyl ether syntheses) and provide a high selectivity (methyl formate synthesis).     

完全液相法中Cu源对Cu-Zn-Al催化剂结构及性能的影响

采用完全液相法,分别以柠檬酸铜、硝酸铜、乙酸铜为Cu源制备了三种Cu-Zn-Al浆状催化剂,考察了不同铜源对催化剂催化合成气制二甲醚性能的影响,利用XRD、H2-TPR、NH3-TPD、BET、XPS和TEM等技术对催化剂进行了表征。结果表明,铜源对催化剂织构形貌及性能影响显著,用柠檬酸铜为铜源制备的催化剂铜物种分散性最好,铜物种与其他组分间相互作用强,可还原物质的量多,同时催化剂表面弱酸量与强酸量的比较高,催化剂的甲醇脱水能力提升,三种催化剂中柠檬酸铜催化剂性能最好,CO转化率为63.4%,二甲醚选择性为66.0%。     

添加聚乙二醇对CuZnAl浆状催化剂结构和性能的影响

首先利用共沉淀沉积法制备CuZnAl催化剂前驱体,并且通过添加聚乙二醇(PEG600)对其进行改性,最后采用完全液相法对前驱体进行热处理制得浆状催化剂,考察了其在浆态床合成气一步法制二甲醚反应中的催化性能,采用X射线粉末衍射、程序升温还原、氨程序升温脱附和X射线光电子能谱对其进行了表征.结果表明,PEG600的添加促进了催化剂中铜组分在热处理过程中被还原成低价铜,提高了催化剂中Cu2O的分散性,改变了催化剂表面酸量和酸强度的分布,同时PEG600的添加方式对催化剂的甲醇合成和甲醇脱水能力有显著影响.在硝酸铜和硝酸锌水溶液中添加0.5 wt%的PEG600时,在热处理过程中形成的Cu2O最稳定,不易被还原,其晶粒度小,进而使CO转化率大幅度提高.     

分子筛硅／铝比对Cu-ZnO-Al2O3／HMCM-22催化合成二甲醚反应性能的影响

以六亚甲基亚胺为模板剂,采用动态水热晶化法合成了不同硅/铝比的HMCM-22分子筛,并以其为甲醇脱水活性组分与铜基甲醇合成活性组分(Cu-ZnO-Al2O3)组成双功能催化剂,在连续流动加压固定床微型反应器上考察了其对合成气直接制二甲醚反应的催化性能. 结果表明,随着HMCM-22分子筛硅/铝比的增大, CO转化率变化不大,但CO2和烃类副产物的生成量逐渐减少,从而导致目的产物二甲醚的选择性和收率均逐渐升高. 氨程序升温脱附和吡啶吸附红外光谱表征结果表明,随着分子筛硅/铝比的增大, HMCM-22分子筛的酸中心的数量逐渐减少.     

复合催化剂上合成气一步法制备液化石油气的研究

合成气一步法制备液化石油气(LPG)可在甲醇合成催化剂和分子筛组成的复合催化剂上实现.本实验选用与Y分子筛孔径相近的SAPO-5分子筛(0.73 nm × 0.73 nm)作为研究对象,在335 ℃、3.0 MPa、空速1 500 h^-1、Cu-Zn-Al/Pd-SAPO-5质量比为1/2的条件下获得了73.9%的CO转化率和73.0%的LPG选择性,该结果进一步证实了较大孔径的分子筛有利于LPG的合成.此外,研究结果还表明,合成气一步法制备LPG过程中甲醇/二甲醚向烃类的转化遵循烃池机理.     

生物质气化重整合成二甲醚

以松木粉为原料，采用空气 水蒸气气化制备了富氢气化气，通过添加甲烷重整富氢气化气，调整了合成气化学当量比，在260 ℃、4 MPa、12 000 h－1条件下，对生物质合成气一步法合成二甲醚进行了实验研究。结果表明：引入甲烷重整，活化了富氢气化气中过量的CO2，甲烷的最佳加入量为CH4/CO2=1，生物质碳转化率达到70%以上，尾气中二甲醚选择性达到69.6%。     

浆态床反应器中生物质合成气合成二甲醚的研究

进行了浆态床反应器中,甲醇合成催化剂与分子筛混合制复合催化剂上,生物质制取的合成气(简称生物质合成气)一步法合成二甲醚的研究,重点考察了不同脱水组分和工艺条件对催化剂反应性能的影响,同时,结合NH₃-TPD等手段对催化剂进行了表征。结果表明,含有较弱酸性SAPO-11分子筛的复合催化剂更适合生物质合成气原料气杂质多、氢碳比低的特点,在合成二甲醚反应中具有更高的选择性和稳定性。250℃、5 MPa、500 h^-1时,在甲醇催化剂与SAPO-11分子筛比例为3:1的复合催化剂上,合成气合成二甲醚反应35 h内,CO转化率稳定在40%以上,二甲醚在有机产品中的选择性保持在97%左右。     

Direct and Highly Selective Conversion of Synthesis Gas into Lower Olefins: Design of a Bifunctional Catalyst Combining Methanol Synthesis and Carbon–Carbon Coupling

The direct synthesis of lower (C₂ to C₄) olefins, key building‐block chemicals, from syngas (H₂ /CO), which can be derived from various nonpetroleum carbon resources, is highly attractive, but the selectivity for lower olefins is low because of the limitation of the Anderson–Schulz–Flory distribution. We report that the coupling of methanol‐synthesis and methanol‐to‐olefins reactions with a bifunctional catalyst can realize the direct conversion of syngas to lower olefins with exceptionally high selectivity. We demonstrate that the choice of two active components and the integration manner of the components are crucial to lower olefin selectivity. The combination of a Zr–Zn binary oxide, which alone shows higher selectivity for methanol and dimethyl ether even at 673 K, and SAPO‐34 with decreased acidity offers around 70 % selectivity for C₂–C₄ olefins at about 10 % CO conversion. The micro‐ to nanoscale proximity of the components favors the lower olefin selectivity.     

Kinetic modeling for the conversion of synthesis gas to dimethyl ether on a mixed Cu-ZnO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst with γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

A model is proposed for the kinetics of the direct conversion of synthesis gas to dimethyl ether (DME) on a bifunctional catalyst in a flow reactor. Calculations for the yield of methanol and DME were carried out using literature data for the kinetics of methanol synthesis and methanol dehydration.     

Problems of producing motor fuels from alternative raw materials

The mechanism and kinetics of reactions occurring in different processes of natural gas processing to motor fuels are considered. Among them are the syntheses of methanol, dimethyl ether, and gasoline from synthesis gas (syngas) and production of pure hydrogen from methanol. The general scheme of carbon-containing raw materials processing to produce motor fuels is considered using natural gas as example. The advantages of the direct synthesis of dimethyl ether (DME) from syngas (instead of methanol synthesis) over all processes producing motor fuels were shown. The synthesis of DME uses the syngas of almost any composition and, hence, the process scheme of carbon-containing feedstock syngas DME gasoline becomes universal and appropriate for processing various raw materials. Prospects of using methanol as an easily transportable source of pure hydrogen were considered. The steam reforming of methanol is a reaction inverse to its synthesis. The oxidation of residual CO in order to purify hydrogen is favored in the mode of catalyst surface ignition. Modern catalysts and methods for removal of CO traces can provide production of pure hydrogen by methanol processing with an efficiency appropriate, in principle, for using the corresponding devices aboard a vehicle.The materials of the report at the III International School Engineering Chemical Science for Advanced Technologies¹ and recent publication² were used in part.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2352–2363, November, 2004.     

Study on Highly Active Catalysts and a Once—Through Process for Methanol Synthesis from Syngas

Highly active CNT-promoted co-precipitated Cu-ZnO-Al2O3 catalysts, symbolized as CuiZnj;Alfc-a;%CNTs, were prepared, and their catalytic activity for once-through methanol synthesis from syngas was investigated. The results illustrated that, under the reaction conditions (at 493 K, 5.0 MPa, the volume ratio of H2/CO/CO2/N2= 62/30/5/3, GHSV= 4000 h-1), the observed single-pass CO-conversion and methanol-STY over a Cu6Zn3Al1-12.5%CNTs catalyst reached 64% and 1210 mg/(h-g), which was about 68% and 66% higher than those (38% and 730 mg/(h-g)) over the corresponding CNT-free catalyst, Cu6Zn3Al1, respectively. The characteristic studies of the catalysts revealed that appropriate incorporation of a minor amount of the CNTs into the CuiZnjAlk brought about little change in the apparent activation energy of the methanol synthesis reaction, however, led to a considerable increase in the catalyst's active Cu surface area and pronouncedly enhanced the stationary-state concentration of active hydrogen-adspecies on     

Green process of fuel production under porous γ-Al2O3 catalyst: Study of activation and deactivation kinetic for MTD process

One of the methods of industrial dimethyl ether production is the catalytic dehydration of methanol. In this research work, methanol dehydration reactor has been modeled using continuous model and its results have been compared with experimental works and Voronoi pore network model. A 1D heterogeneous dispersed plug flow model was utilized to model an adiabatic fixed-bed reactor for the catalytic dehydration of methanol to dimethyl ether. The mass and heat transfer equations are numerically solved for the reactor. The concentration of the reactant and products and also the temperature varies along the reactor, therefore the effectiveness factor would also change in the reactor. We used the the effectiveness factor that was simulated according to the diffusion and reaction in the catalyst pellet as a Voronoi pore network model. Sensitivity analysis was performed to determine the influence of T, P and weight hourly space velocity on performance of the chemical reactor. Acceptable agreement was reached between the measured and the model data. The results showed that the maximum reaction conversion was obtained about 90 % at WHSV = 10 h^?1 and T = 560 K, while the inlet temperature (T_inlet) had a greater effect on methanol conversion. In addition, the effect of water in the feed on methanol conversion was quantitatively studied. Also, the deactivation kinetics of γ-Al₂O₃ heterogeneous-acidic catalyst in methanol to dimethyl ether dehydration process was studied using integral analysis method. Based on independent deactivation kinetics, a second order was found that accurately fitted the experimental conversion time data. The main reaction activation energies and catalyst deactivation energies were 143.1 and ?102.1 kJ/mol, respectively.     

Simulation and model design of pipe-shell reactor for the direct synthesis of dimethyl ether from syngas

The simulation was made based on the model of pipe-shell reactor that was established by the model of global kinetics of synthesis of dimethyl ether from syngas over a bifunctional catalyst. The results of simulation showed that the selectivity for dimethyl ether （DME） and the conversion of CO were higher but the hot spot was kept below the temperature limit of the pipe-shell reactor. The suitable diameter of the pipe was φ38×2 mm, and the length of the pipe was 5.8 m. The optimal process conditions of the reactor were that the pressure was 5 MPa, the temperature of the cooling water was 240 ℃, and the temperature of the raw gas at inlet of the reactor was 220 ℃. The production of this reactor was 102800 t/y （ton per year） under these conditions.     

Synthesis of ethylidene diacetate from dimethyl ether, CO and H2

Ethylidene diacetate was prepared by reacting dimethyl ether, acetic acid and syngas in the presence of a catalytic system comprising RhI3, PPh3 and CH3I. The effects of reaction temperature, pressure, time and the CO/H2 molar ratio on the conversion of dimethyl ether and the product selectivity were investigated under the same catalyst formulation. Results showed that a maximum conversion of dimethyl ether was obtained when a mixture consisting of 0.3 mol dimethyl ether and 120 ml acetic acid was reacted at 180 ℃ and 3.0 MPa for 10 h at a stirring speed of 600 rpm under a syngas flow with a CO/H2 molar ratio of 2.5, which was catalyzed by a catalyst mixture comprising 0.3 g RhI3, 6 g PPh3 and 1.3 g CH3I. The selectivity of ethylidene diacetate increased with temperature, decreased with the CO/H2 molar ratio and exhibited a maximum with pressure.