Low temperature catalytic combustion of propane over Pt-based catalyst with inverse opal microstructure in a microchannel reactor

A novel Pt-based catalyst with highly regular, periodic inverse opal microstructure was fabricated in a microchannel reactor, and catalytic testing revealed excellent conversion and stable activity for propane combustion at low temperatures.     

Palladium Membrane‐Installed Microchannel Devices for Instantaneous Suzuki–Miyaura Cross‐Coupling

Instantaneous catalytic carbon–carbon bond‐forming reactions were achieved in catalytic membrane‐installed microchannel devices that have a polymeric palladium‐complex membrane. The catalytic membrane‐installed microchannel devices were provided inside the microchannels by means of coordinative and ionic molecular convolution at the interface between the organic and aqueous phases flowing laminarly, in which both non‐crosslinked linear polymer ligands and palladium species dissolved. The palladium‐catalyzed Suzuki–Miyaura reaction of aryl, heteroaryl, and alkenyl halides with arylboronic acids and sodium tetraarylborates was performed with the catalytic membrane‐installed microchannel devices to give quantitative yields of biaryls, heterobiaryls, and aryl alkenes within 5 s of residence time in the defined channel region. These microchannel devices were applied to the instantaneous allylic arylation reaction of allylic esters with arylboron reagents under microflow conditions to afford the corresponding coupling products within 1 s of residence time.     

Effect of internal diffusion on preferential CO oxidation in a hydrogen-rich mixture on a copper-cerium oxide catalyst in a microchannel reactor

The effect of internal diffusion on preferential CO oxidation in a hydrogen-rich mixture on a copper-cerium catalyst in a microchannel reactor was estimated. It was found that the internal effectiveness factor η_CO > 0.8 was reached at a catalytic coating thickness of ∼30 μm.     

The nature of permeability anisotropy and catalytic activity

The phenomena of permeability anisotropy and an increase in the rates of catalytic reactions in porous membranes modified with highly dispersed catalytic systems were analyzed. A model of stochastic gas motions was proposed; this model is based on the hypothesis of the specific interaction of molecules with the inner surface of pores resulting in a nonisotropic distribution of molecules over traveling directions. The effects of asymmetric gas transfer in porous and gradient-porous membranes were considered to explain differences in the rates of heterogeneous catalytic reactions in a nanoporous membrane reactor under changes in the direction of supplying a reaction mixture. From the model proposed, it follows that the transversal diffusion of gas molecules is most probable in the porous medium of a ceramic membrane with a pore-size distribution gradient from large to small pores along the flow direction. This diffusion results in an increase in the frequency of molecular collisions with the wall of a microchannel and, correspondingly, in an increase in the contact time. The model proposed explains the intensification of a number of heterogeneous catalytic reactions performed in the porous media of catalytic porous membranes.     

无机膜反应器用于正丁烷氧化制顺丁烯二酐的研究(英文)

通过浸渍法在中孔γ－Ａｌ２Ｏ３膜上制备出Ｖ－Ｐ－Ｃｏ－Ｃｅ－Ｏ多组分金属氧化物催化膜,将之应用于非燃料电池型催化膜反应器并研究其可行性及正丁烷制顺丁烯二酐的反应特性。考察了反应温度、空速和吹好气流速对催化活性的影响,对膜反应器的稳定性也进行了简单的测试。实验证明,与固定床相比,膜反应器具有更高的反应转化率和选择性。     

微通道反应器内"就地"合成沸石膜催化层及其性能

采用简单、新颖的沸石粒子引入方法,将NaX沸石晶种引入不锈钢微反应器的微通道内,并用流动法"就地"直接在微通道内通过沸石生长形成NaX沸石膜层,经铯离子交换处理成为CsNaX催化层,用苯甲醛和氰基乙酸乙酯的Knoevenagel缩合反应评价了该催化层的催化性能.结果表明,微通道内形成的沸石膜层连续,均匀,具有良好的催化功能.微反应器内缩合反应的结果明显优于传统反应器.     

Modeling of microreactor for syngas production by catalytic partial oxidation of methane

Fixed-bed reactors for the catalytic partial oxidation of methane (CPOM) to produce synthesis gas still pose hot spots problems. Microreactor is a good alternative reactor proposed to resolve these problems. In this paper, synthesis gas (hydrogen and carbon monoxide) production was investigated by a two-dimensional numerical model of single microchannel. CFD modeling with detailed chemistry was conducted to understand the CPOM on platinum (Pt) catalyst. Gas inlet velocity, microchannel pressure, and fuel to air ratio (F/A) are selected as the effective parameters on microchannel performance. Study results show that Reynolds number has considerable effect on methane conversion, hydrogen to carbon monoxide ratio (H2/CO), and product distribution. Increasing gas inlet velocity causes all the above parameters to decrease. It is noted that increasing microchannel pressure and decreasing the ratio of fuel to air cause the decrease of the H2/CO ratio.     

Zeolite containing catalytic membranes as interphase contactors

In this study, a catalytic membrane reactor was developed. A titanium silicalite (TS-1) containing polydimethylsiloxane (PDMS) catalytic composite membrane was placed at the interface between the two immiscible phases containing respectively n-hexane (organic phase) and a solution of hydrogen peroxide (aqueous phase). This allowed adequate transport of both reactants to the catalyst surface, without using a co-solvent. This concept of zeolite containing catalytic membrane as interphase contactor, which may be applicable to numerous multiphase reactions, has been tested for the oxyfunctionalization of n-hexane to a mixture of hexanols and hexanones using H₂O₂ as the oxidant. It was shown that the oxyfunctionalization products are formed in and separated by the catalytic membrane. The experimental results illustrated the technical advantages of such a catalytic membrane reactor since the observed conversion and selectivity are similar to the ones obtained with the same catalyst in a conventional reactor. The various factors (membrane thickness, catalyst loading and membrane modifications) which may affect the membrane catalytic and permeation performances were investigated.     

膜催化研究II. 多孔无要膜的制备与表征及其反应器对甲醇脱氢反应的促进作用

采用溶胶-凝胶法制备了多孔氧化铝膜, 并通过DSC、TGA、SEM、N~2吸附和气体透过率测定等手段, 对膜的性能进行了表征。结果表明, 用这种方法制备的多孔氧化铝膜是一种均匀无裂痕和具有较窄孔径分布(约4nm)的膜材料。将此多孔氧化铝膜制成膜反应器后, 用于甲醇催化脱氢制甲醛的反应, 发现甲醇转化率比常规反应器有较大幅度的提高。同时首次尝试采用溶胶-凝胶法将催化活性组分直接负载到多孔氧化铝膜上, 从而得到了一种具有催化活性的多孔膜, 并考察了它的反应活性。文中对由这两种多孔膜及钯/陶瓷复合膜制成的反应器的特点进行了比较。     

Use of a membrane reactor to improve selectivity to intermediate products in consecutive catalytic reactions

Through modeling it has been shown that a concentric-tube catalytic membrane reactor can be used to increase the selectivity for the intermediate products of a consecutive reaction scheme. The reactants are fed to the tube-side of the reactor where the catalyst is also located. The wall of the tube is permeable, allowing the intermediate products to pass through to the annular space instead of undergoing further reaction. The annular space is swept by an inert gas flow and contains no catalyst. Both permselective and non-permselective membranes have been considered in both co-current and counter-current flow regimes. In contrast to most catalytic membrane reactor applications where reactions are reversible and thermodynamically limited, in the present study the reactions considered are irreversible and are under kinetic control.     

Energy-efficient dehydrogenation of methanol in a membrane reactor: a mathematical modeling

A two-dimensional non-isothermal stationary mathematical model of the catalytic membrane reactor for the process of methanol dehydrogenation is described. Copper supported on the carbonaceous support was considered as a catalyst. The reaction of methanol dehydrogenation was thermodynamically conjugated with a reaction of hydrogen oxidation taking place in a shell side of the membrane reactor. The effects of various parameters on the methanol conversion and the methyl formate yield have been calculated with the developed model and discussed. Two different types of heating the gas flow were considered and compared. In the case of conjugated dehydrogenation process, the methyl formate yield reaches 77%, when the reactor outer wall was heated up to 150 °C. When the inlet gas flows in the tube and shell sides were heated up to 100 and 83 °C, correspondingly, the yield was 72%.     

Deactivation of a Zn/TiO<Subscript>2</Subscript> catalyst in the course of methanol steam reforming in a microchannel reactor

The service life tests of a Zn/TiO₂ catalyst deposited on the microchannel plates of copper foam, nickel foam, and corrugated brass foil in the process of methanol steam reforming demonstrated that the catalyst stability and operation time depend on microchannel plate material. The rate of catalyst deactivation correlated with the thermal conductivity of the microchannel plate material. It was found that catalyst deactivation resulted from the decomposition of zinc titanates, which are active components, and it was accompanied by the appearance of a zinc oxide phase. The best results in the service life tests were obtained with the microchannel plates of copper foam. A microchannel reactor containing 16 copper plates continuously operated at 400°C for 150 h; in this case, the conversion of methanol decreased by 8%. The subsequent microreactor operation for 500 h caused a decrease in the methanol conversion by 26%. It was found that the loss of the catalyst activity was a reversible process, and the activity can be restored by annealing in air.     

膜供氧催化氧化处理太空舱冷凝废水研究

采用膜供氧催化氧化反应器处理太空舱冷凝废水。以乙醇为目标污染物,研究了膜供氧催化氧化反应器对其的处理效果,并考察了催化反应对膜传质模型的影响。结果表明,随着停留时间的增加,乙醇的去除率增大,中间产物乙酸的生成率减少。当废水流量为0.5mL·min-1,气室压力为2kPa时,乙醇的去除率可达86.1%,其中81.4%完全氧化,4.7%转化成乙酸。基于传质模型对实验结果分析表明,催化反应有利于提高膜供氧总传质系数,当流量为0.5mL·min-1时,与无催化反应条件相比,氧总传质系数提高11.8倍。停留时间的增加也有利于提高膜供氧传质系数。结果表明,膜供氧催化氧化反应器可高效降解冷凝废水中的乙醇,在太空舱冷凝废水处理中有潜在的应用价值。     

Methanol synthesis from carbon dioxide and hydrogen using a ceramic memebrane reactor

Methanol was synthesized from CO₂ and H₂ using a silica/alumina composite membrane reactor, which improved methanol conversion to 150% of the value in conventional reactor, by in situ removal of water formed in catalytic reaction. This revised version was published online in June 2006 with corrections to the Cover Date.     

Efficiency of Zn/TiO<Subscript>2</Subscript> catalyst operation in a microchannel reactor in methanol steam reforming

The activity of a Zn/TiO₂ catalyst deposited on metal microchannel plates in methanol steam reforming was studied. The catalyst exhibited maximum activity upon deposition on microchannel plates made of copper foam. In this case, the specific hydrogen production of a microreactor at 450°C was 78.6 l (g Cat)^?1 h^?1. The catalysts deposited on a microchannel plate of nickel foam and on corrugated brass foil exhibited lower activity because of the lower efficiency of heat transfer to the reaction zone. A correlation between the thermal conductivity of the microchannel plate material and the activity of the catalyst was observed in the following order: copper, brass, and nickel. The kinetic parameters of the process of methanol steam reforming in a microreactor were calculated with the use of a plug-flow reactor model. In this case, the calculated formal activation energy of 132 kJ/mol was independent of the microchannel plate material. A comparison of the equilibrium concentrations of reaction products at the reactor outlet, which were calculated from thermodynamic data, with the experimental data demonstrated that methanol steam reforming at a temperature higher than 400°C occurred in the nonequilibrium region. The concentration of carbon monoxide at the microreactor outlet was lower than 1 mol %, which is lower than the equilibrium concentration by one order of magnitude. This effect was attributed to the suppression of the reversed water gas shift reaction on the catalyst.     

A STUDY ON MEMBRANE PROCESS WITH |?-ALUMINA MEMBRANE REACTOR FOR ETHYLBENZENE DEHYDROGENATION TO STYRENE

The membrane reaction of ethylbenzene(EB) dehydrogenation to styrene(ST) has been studied by using K2O/Fe2O3 industrial catalyst and alumina ceramic membrane developed by our institute. In comparison with the packed bed reactor (that is, plug flow reactor, abbr. PFR) in industrial practice, the yield of styrene was increased by 5%~10% in the membrane reactor. Furthermore, mathematical modeling of membrane reaction has been studied to display the principle of optimal match between the catalytic activity and the membrane permeability.     

Modeling a catalytic polymeric non-porous membrane reactor

A theoretical study on a catalytic polymeric non-porous membrane reactor is performed. The conversion enhancement over the thermodynamic equilibrium is studied when conducting an equilibrium gas-phase reaction of the type A+B⇔C+D. The model used considers perfectly mixed flow patterns and isothermal operation for the retentate and permeate. It is concluded that the conversion of a reversible reaction can be significantly enhanced when the reactants’ diffusion coefficients are lower and/or sorption coefficients are higher than the products’. This happens for Thiele modulus and contact time over certain threshold values. It was also observed that it is preferable to enhance conversion through an increase in the reactants’ sorption coefficients, since this leads to lower reactor dimensions. Since the performance of a non-porous membrane reactor depends on both the sorption and diffusion coefficients, a study of such system cannot be based exclusively on the permeabilities of the components. Favorable combinations of diffusion and sorption coefficients can provide a coupled effect over the reactor’s conversion.     

渗透汽化型酯化膜反应器研究——PVA/PSSA共混聚合物管式复合膜的膜反应性能

聚合物共混是制备具有预定性能的功能膜材料的有效方法．报道了以惰性素烧陶瓷管为支撑体的ＰＶＡ／ＰＳＳＡ共混聚合物管式复合膜的制备及其在渗透汽化型酯化膜反应器中不同实验条件下的膜催化反应性能．探讨了共混膜的组成,反应温度等对膜反应和分离性能的影响以及同步膜分离过程对反应转化率的促进作用．交联ＰＶＡ／ＰＳＳＡ管式复合膜具有良好的催化和分离性能．     

膜反应器在乙苯脱氢反应过程中的应用(英文)

以γ－Ａｌ２Ｏ３微孔陶瓷膜构成膜反应器（ＣＭＲ），使用ＧＳ－０５工业催化剂，在工业过程的操作条件下，研究了乙苯脱氢生产苯乙烯膜的反应规律。与工业上的固定康（ＰＦＲ）过程比较，有膜反应过程产率可提高５％－１０％。在本研究的条件下，股反应的优化实际上就是催化剂反应活性和膜渗透性的匹配。     

T形微反应器共沉淀法制备Mg-Al层状双金属氢氧化物及其粒径可控性

采用T形微反应器通过共沉淀法制备了Mg-Al层状双金属氢氧化物(LDHs)纳米颗粒, 考察了流速、混合盐溶液浓度和温度等对产物粒径及其分布的影响. 实验结果表明, 所制备的LDHs样品的形貌和晶体结构与传统共沉淀法结果一致, 但本方法制备的样品粒径小、分布窄. 随着流速增大, 温度升高, 所合成的LDHs样品平均粒径减小, 分布变窄; 而随着混合盐溶液浓度的增大, 所得LDHs样品粒径增大, 分布变宽.