Synthesis of MTBE in zeolite membrane reactors

A zeolite membrane was employed to selectively remove water from the reaction atmosphere during the gas-phase synthesis of methyl-tert-butyl ether (MTBE) from tert-butanol and methanol. This reaction was carried out over a bed of Amberlyst™ 15 catalyst packed on the inside of a zeolite tubular membrane. The results obtained with different hydrophilic membranes (mordenite or NaA zeolite) are presented. Prior to reaction, the zeolite membranes were characterized by measuring their performance in the separation of the equilibrium mixture containing water, methanol, tert-butanol, MTBE and isobutene. The results obtained with zeolite membrane reactors (ZMR) were compared with those of a fixed bed reactor (FBR) under the same operating conditions. MTBE yields obtained with the ZMR at 334 K reached 67.6%, under conditions where the equilibrium value without product removal (FBR) would be 60.9%.     

A photocatalytic membrane reactor for gas-phase reactions using porous titanium oxide membranes

Photocatalytic membrane reactors using porous titanium oxide membranes having pore sizes of several nanometers were utilized for a gas-phase reaction of methanol. Air mixed with methanol (MeOH) vapor, the concentration of which was controlled in the range of 500–6000 ppm, was fed to the photocatalytic membrane reactor in the range of 50–500 cm³/min using several types of flow patterns. Photocatalysis with membrane permeation resulted in a large decomposition rate, compared to photocatalysis without membrane permeation. The characteristics of the reaction such as decomposition ratio of MeOH, the conversion of the decomposed MeOH to CO₂ and H₂O were found to be a function of the residence time in the reactor. The photocatalytic reaction was analyzed based on pseudo-first-order kinetics to ascertain its simplicity, and the fitted curves were found to be in a relatively good agreement with the experimental data. Apparent rate constants with and without membrane permeation were 2.5 and 1.5×10⁻⁶ m s⁻¹, respectively, indicating that the performance of the photocatalytic reaction system with membrane permeation was enhanced.     

用于脱除C5及MTBE中甲醇的渗透汽化膜研究

Several pervaporation membranes, cellulose acetate (CA), polyvinylbutyral (PVB), poly(MMA-co-AA),MMA-AA-BA, CA/PVB blend and CA/poly(MMA-co-AA) blend, were prepared, and their pervaporation properties were evaluated by separation of methanol/C5 or methanol/MTBE (methyl tert-butyl ether). The results shows that the CA composite membrane has a high separation performance (flux Jmethanol = 350 g.m-2.h-1 and separation factor α＞400) for methanol/C5 mixtures, and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer. For CA/poly(MMA-co-AA) blend membrane, the pervaporation performance is improved in comparison with CA or poly(MMA-co-AA) membrane. From the experiment of CA/PVB blend membranes for methanol/MTBE mixture, it is found that the compatibility of blends may affect the separation features of blend membrane.     

Methyl tert-butyl ether decomposition over heteropoly acid catalyst in a cellulose acetate membrane reactor

In this study the methyl tert-butyl ether (MTBE) decomposition over H₃PW₁₂O₄₀ was carried out in a cellulose acetate membrane reactor. The permeability of methanol through the cellulose acetate membrane was about 30 and 300 times higher than that of either isobutene or MTBE, respectively. The isobutene selectivity in the fixed bed reactor was only slightly higher than the methanol selectivity due to the side reaction. In the cellulose acetate membrane reactor, however, the isobutene selectivity in the rejected stream was 68% and the methanol selectivity in the permeated stream was up to 97%. The MTBE conversion in the membrane reactor was about 7% higher than that in the membrane-free fixed bed reactor under the same reaction conditions. The enhanced performance of the membrane reactor in this reversible reaction was mainly due to the selective permeation of methanol which resulted in a methanol-deficient condition suppressing MTBE synthesis reaction.     

用于脱除C5及MTBE中甲醇的渗透汽化膜研究

Several pervaporation membranes, cellulose acetate (CA), polyvinylbutyral (PVB), poly(MMA-co-AA), MMA-AA-BA, CA/PVB blend and CA/poly(MMA-co-AA) blend, were prepared, and their pervaporation properties were evaluated by separation of methanol/C5 or methanol/MTBE (methyl tert-butyl ether). The results shows that the CA composite membrane has a high separation performance (flux Jmenthanol =350g.m-2.h-1 and separation factor a > 400) for methanol/C5 mixtures, and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer. For CA/poly(MMA-co-AA) blend membrane, the pervaporation performance is improved in comparison with CA or poly(MMA-co-AA) membrane. From the experiment of CA/PVB blend membranes for methanol/MTBE mixture, it is found that the compatibility of blends may affect the separation features of blend membrane.     

分离有机/有机混合物的PVA、CA系列膜及其渗透汽化性能研究(Ⅰ)膜材料与成膜工艺

依据溶度参数原则和分离甲基叔丁基醚(MTBE)/甲醇(MeOH)混合物的选择渗透性,选择了聚乙烯醇(PVA)为复合膜的分离层材料,聚丙烯腈(PAN)、醋酸纤维素(CA)系列为支撑层的膜材料.初步讨论了膜材料和复合膜结构对分离性能的影响,给出了用不同成膜工艺制备的膜性能,获得了可用于有机/有机体系分离的性能优良的PVA/PAN和PVA/CA复合膜,以及CTA中空纤维渗透汽化膜.     

Pervaporation separation of methyl tert-butyl ether/methanol mixtures using a high-performance blended membrane

For the separation of methyl tert-butyl ether (MTBE) and methanol mixtures, we investigated the pervaporation performance of a blend membrane made from cellulose acetate and cellulose acetate hydrogen phthalate. At first the influence of the blend composition was studied with a certain feed mixture. We found that all the tested membranes permeate methanol preferentially. The selectivity increases and the permeation rate decreases with increasing cellulose acetate content in the blend. Therefore, an optimal blend composition of 30 wt % in cellulose acetate was chosen to evaluate the influence of the feed composition and the experimental temperature on the pervaporation performance. When the feed temperature or the methanol content in the feed increases, the permeation rates are greatly enhanced and the selectivity decreases. However, the temperature effect is more significant at low methanol content in the feed and becomes negligible at high methanol content in the feed where plasticity effects prevail. A comparison, carried out with all the membranes until now used for the separation of MTBE/methanol mixtures, showed that the blended membrane studied in this present work presents good permselective properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 875–882, 1997     

Experimental study and modeling of organic solvent reverse osmosis separations through organosilica membranes

Exceptionally stable, mechanically robust, and highly methanol-selective organosilica membranes, including Bis(triethoxysiyl)acetylene (BTESA), fluorine-doped bis(triethoxysiyl) methane (F-BTESM), and Cetyltrimethylammonium chloride-etched bis(trimethoxysiyl)hexane (CTAC-BTMSH), were prepared and utilized for organic solvent reverse osmosis (OSRO) separations. The BTESA membrane showed optimal separation performance regarding methanol/toluene and possessed the highest levels of both permeation flux and rejection. Continuous measurements were performed to highlight the molecule size/shape discrimination of BTESA membranes using compounds such as methanol/methyl acetate, methanol/dimethyl carbonate (DMC) and methanol/methyl tert-butyl ether (MTBE). Also, a generalized solution-diffusion model was successful in predicting the permeation behaviors through organosilica membranes when used in an OSRO modality, and proved to be capable of accurate predictions on pressure-dependent permeation flux and rejection for a wide range of feed concentrations (0–55 wt%) and pressures (2–14 MPa). This study lends important insight for the development of organosilica membranes and process design for the energy-efficient OSRO separation of organic liquids.     

用于分布式制氢的甲烷蒸汽重整膜反应器的数值模拟

采用反应-分离集成的膜反应器进行分布式制氢,对简化工艺、降低能耗、提升技术经济性至关重要。本文采用数学模型对甲烷蒸汽重整制氢过程膜反应器进行模拟,系统分析了渗透侧操作策略、反应压力、反应温度、钯基膜性能、催化剂性能对反应器行为的影响;并以1m³/h甲烷最大程度转化为目标进行分布式制氢案例分析,详细比较膜反应器技术与“常规反应器+膜分离”工艺技术。结果表明,膜反应器在反应压力30atm（1atm=101325Pa）、反应温度500℃下操作可实现紧凑设计,比“常规反应器+膜分离”工艺技术具有明显优势,但是亟需研发更佳活性（10倍）的钯基膜和催化剂以实现显著的过程强化。模拟结果可为不同规模分布式制氢膜反应器的操作与设计及进一步的性能强化提供指导。     

Economic feasibility of silica and palladium composite membranes for industrial dehydrogenation reactions

This article addresses the economic feasibility of silica and palladium composite membranes for gaseous dehydrogenation reaction schemes. Unlike other methodologies addressed so far, this work presents the economic assessment of dehydrogenation reaction schemes using a conceptual design based simulation methodology for the comparative economic assessment of membrane reactors with conventional reactors. The suggested methodology is applied to two industrially prominent reaction schemes namely styrene (from ethylbenzene) and propylene (from propane) production using silica and palladium composite membrane reactors. Various sub-cases studied in this work include the influence of membrane area per reaction zone volume, reaction zone temperature, reaction and permeation zone pressure, membrane thickness and sweep gas flow rate on process economics. Based on this work, the propylene production scheme is evaluated to provide 60–70% excess profits using membrane reactors when compared with the conventional reactor based technology. However, the gross profit profiles for both conventional reactor and membrane reactor configurations have been found to be similar for styrene production case. For all cases, the cost contribution of membranes and other auxiliary equipment is estimated not to exceed 20% of the total costs. In addition, similar economic performance has been observed for both silica and palladium membranes. Based on these studies, it has been concluded that the industrial applicability of membrane reactors is economically suitable for those dehydrogenation reactions that enable significant conversion enhancement with respect to the conventional reactor technologies.     

Oxyfuel combustion using a catalytic ceramic membrane reactor

Membrane catalytic combustion (MCC) is an environmentally friendly technique for heat and power generation from methane. This work demonstrates the performances of a MCC perovskite hollow fibre membrane reactor for the catalytic combustion of methane. The ionic–electronic La_0.6Sr_0.4Co_0.2Fe_0.8O₃₋ (LSCF6428) mixed conductor, in the form of an oxygen-permeable hollow fibre membrane, has been prepared successfully by means of a phase-inversion spinning/sintering technique. For this process polyethersulfone (PESf) was used as a binder, N-methyl-2-pyrrollidone (NMP) as solvent and polyvinylpyrrolidone (PVP, K16-18) as an additive. With the prepared LSCF6428 hollow fibre membranes packed with catalyst, hollow fibre membrane reactors (HFMRs) have been assembled to perform the catalytic combustion of methane. A simple mathematical model that combines the local oxygen permeation rate with approximate catalytic reaction kinetics has been developed and can be used to predict the performance of the HFMRs for methane combustion. The effects of operating temperature and methane and air feed flow rates on the performance of the HFMR have been investigated both experimentally and theoretically. Both the methane conversion and oxygen permeation rate can be improved by means of coating platinum on the air side of the hollow fibre membranes.     

沸石膜反应器苯脱氢反应性能

采用管式沸石膜反应器,研究了乙苯脱氢反应生成苯乙烯的性能。考察了不同渗透分离性能的沸石膜对乙苯脱氢反应的影响和不同沸石膜反应器上乙苯脱氢反应的规律。结果表明,与固定床操作条件下相比,沸石膜反应器乙苯转化率可提高近10％－16％,苯乙烯选择性可提高3％－5％。渗透分离性能是决定沸石膜提高脱氢反应性能的最重要因素,H2渗透量越大、H2／C3H8分离系数越高,对反应越有利。渗透分离性能相近但类型不同的沸石膜对乙苯脱氢反应性能有差异,其中Fe-ZSM-5沸石膜反应性能较好,这是杂原子Fe进入沸石骨架后引起的。反应后膜的渗透分离性能略有变化。     

Preparation and characterization of methanol selective membranes based on polyheteroarylene − Cu(I) complexes for purification of methyl tertiary butyl ether

A comparative study of metal ? polymer complexes of Cu(I) with polybenzoxazinoneimide (PBOI) and its prepolymer imide‐containing polyamic acid (PAA) as novel membrane materials for methyl tertiary butyl ether (MTBE) purification was undertaken. The structure, physical parameters and transport properties were characterized in detail to analyse the separation performance of the membranes and obtain new knowledge on the interdependence of the chemical structure and physical data with transport parameters. Thermally initiated conversion of PAA ? Cu(I) to PBOI ? Cu(I) was studied by TGA and DSC. The thermal conversion increases the polymer glass transition temperature and membrane density. Both polymers were applied to pervaporation separation of MTBE from methanol impurities. Membranes based on PAA are highly effective in MTBE purification and preferably permeate methanol. The transport properties of PAA ? Cu(I) membrane are compared with those of known membranes. © 2017 Society of Chemical Industry     

Vapor permeation separation of MeOH/MTBE through polyimide/sulfonated poly(ether-sulfone) hollow-fiber membranes

Mixtures ofmethanol/MTBE were separatedwithpolyimide/sulfonatedpoly(ether-sulfone) hollow-fiber membranes. The separation was attempted by vapor permeation instead of pervaporation, which had been used by most researchers. The separation properties of the hollow-fiber membranes and operating conditions are discussed. The results showed that separation factors ofthe blended polyimide/sulfonated poly(ether-sulfone) hollow-fiber membranes were extremely high for the methanol/MTBE mixtures.     

Preparation and properties of hollow fibre nanofiltration membrane with continuous coffee-ring structure

Polyamide(PA)hollow fibre composite nanofiltration(NF)membranes with a coffee-ring structure and beneficial properties were prepared by adding graphene oxide(GO)into the interfacial polymerization process.The presentation of the coffee-ring structure was attributed to the heterogeneous,finely dispersed multiphase reaction system and the“coffee-stain”effect of the GO solution.When the piperazine concentration was 0.4 wt-%,the trimesoyl chloride concentration was 0.3 wt-%,and the GO concentration was 0.025 wt-%,the prepared NF membranes showed the best separation properties.The permeate flux was 76 L·m^?2·h^?1,and the rejection rate for MgSO4 was 98.6%at 0.4 MPa.Scanning electron microscopy,atomic force microscopy,and attenuated total reflectance-Fourier transform infrared spectroscopy were used to characterize the chemical structure and morphology of the PA/GO NF membrane.The results showed that GO was successfully entrapped into the PA functional layer.Under neutral operating conditions,the PA/GO membrane showed typical negatively charged NF membrane separation characteristics,and the rejection rate decreased in the order of Na2SO₄>MgSO₄>MgCl₂>NaCl.The PA/GO NF membrane showed better antifouling performance than the PA membrane.     

Non-Fluorinated Membranes Thickness Effect on the DMFC Performance

Abstract

In order to study the influence of the proton exchange membrane thickness on the direct methanol fuel cell (DMFC) performance, sulfonated poly (ether ether ketone) (sPEEK) membranes with a sulfonation degree (SD) of 42% and thicknesses of 25, 40, and 55 µm were prepared, characterized, and tested in a DMFC. These polymeric membranes were tested in a DMFC at several temperatures by evaluating the current-voltage polarization curve, the open circuit voltage (OCV) and the constant voltage current (CV, 35 mV). The CO₂ concentration at the cathode outlet was also measured. The thinnest sPEEK membrane proved to have the best DMFC performance, although having lower Faraday efficiency (lower ohmic losses but higher methanol permeation). In contrast, the thickest membrane presented improved properties in terms of methanol permeation (lower methanol crossover). DMFC tests results for this membrane showed 30% global efficiency, obtained with pure oxygen at the cathode feed.     

基于聚异丁烯胺改性的耐甲醇溶胀新型薄膜复合膜

聚合物膜可以在甲醇/染料废液处理中发挥重要作用。为了保证膜在甲醇处理过程中的高性能,提高膜的耐甲醇溶胀性是必要的。然而,关于耐甲醇溶胀膜的研究相对较少。在此,提出将活性聚合物(聚异丁烯胺,PIBA)引入分离层,制备新型耐甲醇溶胀聚酰胺(PA)薄膜复合(TFC)膜。PIBA的掺入增加了膜的表面粗糙度、活性层厚度和活性层背面的致密性。PIBA提高了膜的耐甲醇溶胀性能:当PIBA的添加量从0增加到1g/L时,溶胀率从46.81%下降到15.00%。因此,PA/PIBA膜表现出比PA膜更高的染料(藏红T)截留率(99.53%与94.62%)。此外,在20bar (1bar=0.1MPa)的操作压力下,PA/PIBA膜保持了高通量[84.62L/(m²·h)]和良好的长期运行稳定性。最后,由于聚异丁烯(PIB)在先前的工作中同样用于提高膜的耐甲醇溶胀性,本工作将PIBA与PIB进行了比较,得出PIBA优于PIB。这项工作为开发一种用于甲醇流出物处理的分离膜提供了新途径。     

多孔膜反应器中丙烷催化脱氢制丙烯的模拟研究

针对丙烷高效脱氢制丙烯的多孔膜反应器构建了无量纲数学模型并进行了模拟研究,考察了催化剂活性、透氢膜性能、操作条件对多孔膜反应器中丙烷脱氢的转化率、丙烯收率、氢气收率和纯度的影响。结果表明,移走产物氢气可以有效提升膜反应器的性能,其性能的提升程度由不同温压条件下催化剂和透氢膜性能共同决定。高活性催化剂是丙烷高效转化的基础,催化剂活性越高,膜反应器内的产氢速率越快;其次,膜的选择性和渗透通量越高,氢气的移除效率越高,可在最大程度上打破热力学平衡的限制,使反应向生成丙烯的方向移动。当多孔透氢膜的氢气渗透率在10^-7~10^-6 mol·m^-2·s^-1·Pa^-1,H₂/C₃H₈选择性达到100时,其丙烷转化率可以与Pd膜反应器内的转化率相当,但分离的氢气纯度低于Pd膜反应器。与传统的固定床反应器相比,膜反应器由于促进了化学平衡的移动,可以在较低的反应温度下获得相当高的丙烷转化率,且丙烷转化率随着反应压力的增加呈现出一个最大值。该模拟研究可为实际生产过程中膜反应器用于PDH反应的高效强化提供有益的技术指导。     

Promotion of hydrogen permeation on metal-dispersed alumina membranes and its application to a membrane reactor for methane steam reforming

A mesoporous membrane for selective separation of hydrogen was prepared usingthe sol-gel method. Some metal salts such as RuCl₃, Pd(NH₃)₄Cl₂, RhCl₃,, and H ₂PtCl₆, were added to the boehmite sol and coated on a porous alumina substrate before firing at 500°C. It was foundthat the permeability of hydrogen and the separation factor for a hydrogen-nitrogen gaseous mixture of these metaldispersed membranes exceeded the limitations of the Knudsen diffusion mechanism. Although the gas permeation through a neat alumina membrane is governed by the Knudsen diffusion, the metals dispersed in alumina membranes were effective in promoting hydrogen permeation. These metaldispersed alumina membranes were also used in a membrane reactor for methane steam reforming at low temperature. In the temperature range of 300 to 500°C, the membrane reactor attained a methane conversion twice as high as the equilibrium value of the packed bed catalytic reactor system as a result of the selective removal of hydrogen from the reaction system.     

Influence of oxygen supply rates on performances of catalytic membrane reactors: Application to the oxidative coupling of methane

The impact of oxygen permeability using an ionic oxygen conducting membrane reactor with surface catalyst was investigated for the oxidative coupling of methane to higher hydrocarbons. Dense Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCFO), Ba_0.5Sr_0.5Mn_0.8Fe_0.2O_3−δ (BSMFO) and BaBi_0.4Fe_0.6O₃ (BBFO) membrane disks with Pt/MgO catalysts were prepared by sol–gel deposition or wash-coating. It is demonstrated that the oxygen supply by permeation needs to fit to the consumption during the coupling reaction. In case of insufficient oxygen supply comparably poor conversions are observed while higher oxygen fluxes lead to increased methane conversions, especially in the presence of an efficient catalyst. Generally, increasing catalytic activity leads to lower C₂ selectivity, especially for low oxygen permeation fluxes. The concept of a reactor employing dense catalytic membranes is viable, but the present study identifies further potential when the activity of the catalyst for the oxidative coupling is improved, leading to an overall enhanced performance of the membrane reactor.