Synthesis of mordenite by solvent-free method and its application in the dimethyl ether carbonylation reaction

Mordenite with different Si/Al ratios were synthesized by solvent-free method and used for dimethyl ether(DME)carbonylation reaction.The influence of Si/Al ratio in the feedstock on the structure,porosity and acid sites were systematically investigated.The characterization results showed that with the increase of Si/Al ratio in the feedstock,part of silicon species fail to enter the skeleton and the specific surface area and pore volume of the samples decreased.The amount of weak acid and medium strong acid decreased alongside with the increasing Si/Al ratio,and the amount of strong acid slightly increased.The Al atoms preferentially enter the strong acid sites in the 8 member ring(MR)channel during the crystallization process.The high Si/Al ratio sample had more acid sites located in the 8 MR channel,leading to more active sites for carbonylation reaction and higher catalytic performance.Appropriately increasing the Si/Al ratio was beneficial for the improvement of carbonylation reaction activity over the mordenite(MOR)catalyst.

A1_2O_3 Effect on the Catalytic Activity of Cu-ZnO-Al_2O_3-SiO_2 Catalysts for Dimethyl Ether Synthesis from CO_2 Hydrogenation

The effect of Al2O3 on the Cu-ZnO-Al2O3-SiO2 catalysts prepared by a pseudo sol-gel method has been investigated and these catalysts were characterized by XRD, H2-TPR, XPS, NH3-TPD and CO2- TPD techniques. As revealed by XRD and H2-TPR, the added alumina produces high dispersion of CuO and makes the reduction of CuO difficult. XPS analysis detects a remarkably high Al^3＋ enrichment at the surface of calcined samples, along with a decrease of Eb of Cu 2p3/2, which confirms the Cu-Al interaction. Another important role of Al203 would be to incorporate into the SiO2 structure to form the acid-base sites for ether formation. The reaction results shows that the addition of Al2O3 exhibits a promoting effect on the CO2 conversion only when its content is below 1.4%, and an optimal DME selectivity is obtained when 4.0%Al2O3 is added, indicating a better ＇synergistic effect＇ is present between the methanol forming component and the acidic component in bifunctional catalysts. Possible relationship between the catalytic activity and the Cu-Al interaction as well as the surface acidity is discussed.

Modelling-based Optimisation of the Direct Synthesis of Dimethyl Ether from Syngas in a Commercial Slurry Reactor

In the present study, we developed a multi-component one-dimensional mathematical model for simulation and optimisation of a commercial catalytic slurry reactor for the direct synthesis of dimethyl ether （DME） from syngas and CO2, operating in a churn-turbulent regime. DME productivity and CO conversion were optimised by tuning operating conditions, such as superficial gas velocity, catalyst concentration, catalyst mass over molar gas flow rate （W/F）, syngas composition, pressure and temperature. Reactor modelling was accomplished utilising mass balance, global kinetic models and heterogeneous hydrodynamics. In the heterogeneous flow regime, gas was distributed into two bubble phases： small and large. Simulation results were validated using data obtained from a pilot plant. The developed model is also applicable for the design of large-scale slurry reactors.

Mathematical Simulation and Design of Three-Phase Bubble Column Reactor for Direct Synthesis of Dimethyl Ether from Syngas

A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.

Intrinsic Kinetics of Dimethyl Ether Synthesis from Syngas

The intrinsic kinetics of dimethyl ether (DME) synthesis from syngas over amethanol synthesis catalyst mixed with methanol dehydration catalyst has been investigated in atubular integral reactor at 3-7 MPa and 220-260℃. The three reactions including methanol synthesisfrom CO and H_2, CO_2 and H_2, and methanol dehydration were chosen as the independent reactions.The L-H kinetic model was presented for dimethyl ether synthesis and the parameters of the modelwere obtained by using simplex method combined with genetic algorithm. The model is reliableaccording to statistical analysis and residual error analysis. The synergy effect of the reactionsover the bifunctional catalyst was compared with the effect for methanol synthesis catalyst underthe same conditions based on the model. The effects of syngas containing Na on the reactions werealso simulated.

Optimization of hydrothermal synthesis of H-ZSM-5 zeolite for dehydration of methanol to dimethyl ether using full factorial design

H-ZSM-5 zeolite was synthesized by hydrothermal method. The effects of different synthesis parameters, such as hydrothermal crystallization temperature （170-190 ℃） and Si/A1 molar ratio （100-150）, on the catalytic performance of the dehydration of methanol to dimethyl ether （DME） over the synthesized H-ZSM-5 zeolite were studied. The catalysts were characterized by N2 adsorption-desorption, XRD, NH3-TPD, TGA/DTA, and SEM techniques. The full factorial design of experiments was applied to the synthesis of H-ZSM-5 zeolite and the effects of synthesis conditions and their interaction on the yield of DME as the response variable were determined. Analysis of variance showed that two variables and their interaction significantly affected the response. According to the experimental results, the optimized catalyst prepared at 170℃ with the Si/A1 molar ratio of 100 showed the best catalytic performance among the tested H-ZSM-5 zeolite.

Synthesis and Crystal Structure of 3,3'-Dimethyl-dibenzo-18-crown-6

3,3′-Dimethyl-dibenzo-18-crown-6 was synthesized and characterized by elemental analysis, FT-IR, ^1H NMR, UV, MS spectra and X-ray single-crystal diffraction. It belongs to orthorhombic, space group Pna21 with a = 8.0790（18）, b = 16.780（4）, c = 15.222（3） .A, Z= 4, V= 2063.6（8） A3 Dc = 1.250 g/cm^3,μ = 0.090 mm^-1, F（000） = 832, R = 0.0474 and wR = 0.1103. According to structural analysis, the title compound possesses a boat-like configuration.

Modifying the acidity of H-MOR and its catalytic carbonylation of dimethyl ether

Among the reactions catalyzed by zeolites there are some that exhibit high selectivity due to the spatial confinement effect of the zeolite framework.Tailoring the acidity,particularly the distribution and location of the Bronsted acid sites in the zeolite is effective for making it a better catalyst for these reactions.We prepared a series of H-mordenite（H-MOR） samples by varying the composition of the sol-gel,using different structure directing agents and post-treatment.NH3-TPD and IR characterization of adsorbed pyridine were employed to determine the amount of Bronsted acid sites in the 8-membered ring and 12-membered ring channels.It was shown that controlled synthesis was a promising approach to improve the concentration of Bronsted acid sites in MOR,even with a low Al content.Using an appropriate composition of Si and Al in the sol-gel favored a higher proportion of Bronsted acid sites in the 8-membered ring channels.HMI as a structure-direct agent gave an obvious enrichment of Bronsted acid sites in the 8-membered ring.Carbonylation of dimethyl ether was used as a probe reaction to examine the modification of the acid properties,especially the Bronsted acid sites in the 8-membered ring channels.There was a linear relationship between methyl acetate formation and the number of Bronsted acid sites in the 8-membered ring channels,demonstrating the successful modification of acid properties.Our results provide information for the rational design and modification of zeolites with spatial constraints.

A three dimensional CFD simulation and optimization of direct DME synthesis in a fixed bed reactor

In this study, a comprehensive three-dimensional dynamic model was developed for simulating the flow behavior and catalytic coupling reactions for direct synthesis of dimethyl ether （DME） from syngas including CO2 in a fixed bed reactor at commercial scale under both adiabatic and isothermal conditions. For this purpose, a computational fluid dynamic （CFD） simulation was carried out through which the standard κ-ε model with 10% turbulence tolerations was implemented. At first, an adiabatic fixed bed reactor was simulated and the obtained results were compared with those of an equivalent commercial slurry reactor. Then the concentration and temperature profiles along the reactor were predicted. Consequently, the optimum temperature, pressure, hydrogen to carbon monoxide ratio in the feedstock and the reactor height under different operation conditions were determined. Finally, the results obtained from this three-dimensional dynamic model under appropriate industrial boundary conditions were compared with those of others available in literature to verify the model. Next, through changing the boundary conditions, the simulation was performed for an isothermal fixed bed reactor. Furthermore, it was revealed that, under isothermal conditions, the performed equilibrium simulations were done for a single phase system. Considering the simultaneous effects of temperature and pressure, the optimum operation conditions for the isothermal and adiabatic fixed bed reactors were investigated. The results of the H2＋CO conversions indicated that, under isothermal condition, higher conversion could be achieved, in compared with that under adiabatic conditions. Then, the effects of various operating parameters, including the pressure and temperature, of the reactor on the DME production were examined. Ultimately, the CFD modeling results generated in the present work showed reasonable agreement with previously obtained data available in the literature.

Mathematical modeling of a slurry reactor for DME direct synthesis from syngas

In this paper,an axial dispersion mathematical model is developed to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether（DME） from syngas.This large-scale reactor is modeled using mass and energy balances,catalyst sedimentation andsingle-bubble as well as two-bubbles class flow hydrodynamics.A comparison between the two hydrodynamic models through pilot plantexperimental data from the literature shows that heterogeneous two-bubbles flow model is in better agreement with the experimental data thanhomogeneous single-bubble gas flow model.Also,by investigating the heterogeneous gas flow and axial dispersion model for small bubblesas well as the large bubbles and slurry（i.e.including paraffins and the catalyst） phase,the temperature profile along the reactor is obtained.Acomparison between isothermal and non-isothermal reactors reveals no obvious performance difference between them.The optimum values ofreactor diameter and height were obtained at 7 m and 50 m,respectively.The effects of operating variables on the axial catalyst distribution,DME productivity and CO conversion are also investigated in this research.

Mechanism and catalytic performance for direct dimethyl ether synthesis by CO2 hydrogenation over CuZnZr/ferrierite hybrid catalyst

Direct synthesis of dimethyl ether(DME)by CO2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods:co-precipitation,sol-gel,and solid grinding to produce mixed Cu,ZnO,ZrO2 catalysts that were physically mixed with a commercial ferrierite(FER)zeolite.The catalysts were characterized by N2 physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),temperature programmed desorption of CO2(CO2-TPD),temperature programmed desorption of NH3(NH3-TPD),and temperature programmed H2 reduction(H2-TPR).The results demonstrate that smaller CuO and Cu crystallite sizes resulting in better dispersion of the active phases,higher surface area,and lower reduction temperature are all favorable for catalytic activity.The reaction mechanism has been studied using in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).Methanol appears to be formed via the bidentate-formate(b-HCOO)species undergoing stepwise hydrogenation,while DME formation occurs from methanol dehydration and reaction of two surface methoxy groups.

A study on the catalytic performance of Pd/γ-Al_(2)O_(3),prepared by microwave calcination,in the direct synthesis of dimethylether

A series of Pd/γ-Al_(2)O_(3) hybrid catalysts were prepared by impregnation and subsequent calcination under microwave irradiation.The catalysts were used for direct synthesis of dimethylether(DME)from syngas.The results show that calcination under microwave irradiation improved both the activity and selectivity of the catalysts for DME synthesis.The optimum power of the microwave was determined to be 420 W.Under such optimum conditions,CO conversion,DME selectivity and time space yield of DME were 60.1%,67.0%,and 21.5 mmol$mL-1$h^(-1),respectively.Based on various characterizations such as nitrogen physisorption,X-ray diffraction,COtemperature-programmed desorption,and Fourier transform infrared spectral analysis,the promotional effect of the microwave irradiation on the catalytic property was mainly attributed to both the higher dispersion of Pd and the significant increase in the adsorption on the CO-bridge of Pd.Microwave irradiation with very high power led to the increase in CO-bridge adsorption and thereby decreased the catalytic activity,whereas the coverage by metallic Pd of the active sites on acidicγ-Al_(2)O_(3) significantly occurred under microwave irradiation with very low power,resulting in a decrease in the selectivity to DME.

Cu改性丝光沸石催化剂及其在二甲醚羰基化反应中的性能研究

以六亚甲基亚胺(HMI)为水热合成模板制备H-MOR和Cu/H-MOR系列丝光沸石催化剂,并在二甲醚羰基化反应中对其进行评价。为了研究Cu的掺入量对丝光沸石反应性能的影响,利用XRD、SEM、氮气吸附/脱附、ICP-AES、NH_(3)-TPD和CO-TPD等对催化剂进行表征。结果表明,随着Cu的掺入,催化剂的酸量和酸强度明显增加,同时促进了催化剂对CO的吸附,进而提高了催化剂的反应性能。在反应温度为200℃、反应压力为1.0 MPa和反应空速为2040 mL/(g·h)条件下的评价结果表明,当掺入Cu的质量分数达到2.36%时,催化剂的反应性能最优,二甲醚转化率为58%且乙酸甲酯(MA)选择性为95%。

合成气直接合成二甲醚与甲醇的热力学分析

确定了合成气直接合成二甲醚与甲醇的复合反应体系独立方程数 ,并进行了热力学计算与分析 ,计算了不同初始组成、温度。

甲醇、二甲醚共进料合成碳酸二甲酯

研究了以甲醇、二甲醚为原料合成碳酸二甲酯。试验表明 ,加入少量二甲醚可通过其水解作用消耗产物水的含量 ,提高碳酸二甲酯的产率。考察了二甲醚对甲醇氧化羰化的影响 ,催化剂采用二甲醚水解催化剂与甲醇氧化羰化催化剂的机械混合物。最佳反应条件 :温度 1 2 0℃、时间 4h、m(HX) /m(CuCl) =1 /6、n(甲醇 ) /n(二甲醚 ) =5/3。

聚甲氧基二甲醚研究进展

聚甲氧基二甲醚(PODME)是一种有潜力的柴油添加剂,其物化性质、合成方法和催化剂被总结和评述。

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℃、4MPa、12000h-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%。

生物质热化学转化合成二甲醚

在鼓泡流化床反应器内,采用空气-水蒸汽气化松木粉制备了富氢燃气,在下游的固定床重整反应器内,通过添加沼气重整富氢燃气,调变化学当量比,制备了含氮的生物质合成气. 在Cu-Zn-Al/HZSM-5催化剂上,对生物质合成气一步法合成二甲醚进行了实验研究. 在280℃, 4 MPa, 1000~4000 h-1的条件下,CO的单程转化率达到67%,单位质量催化剂的最大二甲醚时空收率0.358 g/(g(h) [DME/(催化剂(h)];通过添加沼气重整,90%以上的生物质碳转化为合成气,二甲醚的最大产量为0.244 kg/kg (DME/生物质).

甲烷空气催化部分氧化制合成气与含氮合成气制二甲醚的研究

采用常规浸渍法制备了经镧和镁改性的镍基催化剂 ,以铜锌铝甲醇合成催化剂和HZSM 5分子筛通过机械混合制备了二甲醚合成催化剂。采用固定床流动反应色谱装置研究了甲烷空气催化部分氧化制合成气的催化性能 ,同时开展了以含氮合成气制备二甲醚的研究。结果说明 ,镍基催化剂对甲烷空气部分氧化制合成气在常压下具有高的转化率 ,随压力升高 ,转化率明显下降 ,并且催化剂严重积炭 ,通过向反应体系添加H2 O和CO2 可以提高加压条件下的CH4转化率并抑制催化剂积炭 ,还可获得n(H2 ) /n(CO)接近 2的合成气 ,满足合成二甲醚的要求。采用含氮合成气制备二甲醚 ,在压力 7.0MPa ,空速 10 0 0h-1条件下 ,催化剂连续使用 2 0 0h性能基本稳定 ,CO转化率在 93%左右 ,DME选择性在 77%左右 ,DME收率在 72

合成气一步法制二甲醚双功能催化剂的研究进展

概述了以合成气为原料一步法合成二甲醚双功能催化剂的研究现状及最新进展,分别介绍了双功能催化剂中的甲醇合成活性组分、甲醇脱水活性组分、两种活性组分的复合方法及配比等。锫和硼等是CuO-ZnO-Al2O3甲醇合成活性组分的良好助剂,硼、硅和钨可增强脱水组分γ-Al2O3的酸性,水蒸气处理和添加助剂可增加脱水组分HZSM-5的稳定性,共沉淀沉积法是制备双功能催化剂的较好方法。