Transport studies of multielectrolyte solutions across a sintered disc impregnated with cellulose acetate

Experimental results for the measurement of electroosmotic pressure, electroosmotic velocity and streaming potential for different aqueous solutions of ammonium chloride—ammonium nitrate through a sintered disc impregnated with cellulose acetate at 30°C are reported. The data have been analysed in the light of non-equilibrium thermodynamics. The Onsager reciprocity relation has been found to hold good for all the systems. The efficiencies of electrokinetic energy conversion have also been determined. The maximum values of conversion efficiencies for both the modes of conversion, i.e., electroosmotic flow and streaming potential, have been found to be equal to each other and independent of the applied input forces.     

Catalytic Synthesis of Isopropyl Benzene over SO4^2-/ZrO2 -MCM-41

Introduction Owingtotheirlargeporediametersandlargesur faceareas,silicon basedmolecularsieves(M41S)have receivedmuchattention[1—5]inthefieldsofcatalytic reactions,adsorptiveseparations,andnonmetallicma terialsscience.MCM41isthemosttypicalmaterialof thisk…     

Photocatalytic degradation of toluene using a novel flow reactor with Fe-doped TiO2 catalyst on porous nickel sheets

A novel continuous-flow photocatalytic reactor was designed to decompose toluene by using porous nickel sheets that were coated with a Fe-doped TiO2 catalyst. While locating the UV lamp at the central axis, the catalyst sheets were located along the inner wall and positioned vertically with an equal space of 50 mm along the reactor. This geometry ensures better use of UV light, and a zigzag flow pattern of gas between the vertically located sheets provides for better mass transfer. The X-ray diffraction, scanning electron microscope and electric field-induced surface photovoltage spectra characterizations showed that Fe3+ ions were embedded effectively and distributed evenly throughout the TiO2 crystal lattice and an optimum molar ratio of Fe:Ti was 0.007. The reactor was used to investigate the factors that affect toluene degradation. The results showed that inlet toluene concentration, relative humidity and gas flow rate significantly affect toluene decomposition. The conversion decreases as inlet concentration increases. Degradation efficiencies of more than 95% can be achieved provided that the toluene concentration is kept below 3200 mg/m3. The conversion is affected little when oxygen content exceeds 21%. The optimal relative humidity is 25%. From the experimental data, a rate constant k of 131 mg/(m3.min) and Langmuir adsorption coefficient K of 0.0175 m3/mg were obtained.     

含氮合成气在三相淤浆床-固定床中直接合成二甲醚

在三相淤浆床－固定床反应装置中,研究含氮合成气直接合成二甲醚。使用双功能混合催化剂,粒度为0.15 mm～0.18 mm。在220 ℃～260 ℃、3.0 MPa～7.0 MPa、空速1 000 mL·g-1·h-1时考察了温度、压力及两种反应器中催化剂的装填比例对CO转化率及二甲醚选择性的影响。结果表明,一氧化碳转化率随反应压力的增加而提高,随着温度升高二甲醚的选择性变化不大,CO转化率的升高较明显,因此在催化剂活性适宜的温度范围内,该反应装置可以采用较高的反应温度。当260 ℃、7.0 MPa、三相床与固定床中催化剂比例为1∶1时,CO的转化率可达84.5％,二甲醚的选择性为78.7％。淤浆床－固定床反应装置具有操作稳定性好、CO转化率高的优点。催化剂在该装置中反应370 h活性没有明显下降。     

Polymer end group modifications and polymer conjugations via “click” chemistry employing microreactor technology

This study presents the development of microreactor protocols for the successful continuous flow end group modification of atom transfer radical polymerization precursor polymers into azide end‐capped materials and the subsequent copper‐catalyzed azide alkyne click reactions with alkyne polymers, in flow. By using a microreactor, the reaction speed of the azidation of poly(butyl acrylate), poly(methyl acrylate), and polystyrene can be accelerated from hours to seconds and full end group conversion is obtained. Subsequently, copper‐catalyzed click reactions are executed in a flow reactor at 80 °C. Good coupling efficiencies are observed and various block copolymer combinations are prepared. Furthermore, the flow reaction can be carried out in only 40 min, while a batch procedure takes several hours to reach completion. The results indicate that the use of a continuous flow reactor for end group modifications as well as click reactions has clear benefits towards the development and improvement of well‐defined polymer materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1263–1274     

在SO42-/ZrO2 上苯与丙烯的烷基化反应

Super acidic catalyst SO42-/ZrO2 was prepared and characterized by XRD,IR,and Py-IR. Selectively catalytic gas phase flow reactions of benzene and propene over the catalyst were carried out in a made-to-measure high pressure flow reactor with a thermometer and a condenser. The benzene and propene were kept in pressure tanks at 8 : 1 ratio with N2 gas at 4. 0 MPa. The reactants were pumped into the quantifier where the pressure was maintained by N2 gas at 8. 0 MPa. They were then pumped into the reaction reactor using catalytic synthesis of isopropyl benzene. The collected liquid phase products were analyzed using GC-MS. Product analyses were carried out on SE-54. The effect of the preparative condition on the catalytic synthesis of isopropyl benzene over the catalysts has been tested. The result shows that the SO42-/ZrO2 can be used as a catalyst for the title reaction,and shows higher conversion（99.2%）for the propene and higher selectivity（93.3%）for the isopropyl benzene when the catalyst is preparated in some condition.     

Non-Oxidative Reforming of Methane in a Mini-Gliding Arc Discharge Reactor: Effects of Feed Methane Concentration, Feed Flow Rate, Electrode Gap Distance, Residence Time, and Catalyst Distance

In this work, a mini-gliding arc discharge reactor was employed for the reforming of methane under ambient temperature and pressure operation. Acetylene and hydrogen were produced dominantly with high selectivities of ~70?C90 and ~75%, respectively. The results showed that both methane conversion and product selectivities depended strongly on various operating parameters, including feed methane concentration, feed flow rate, electrode gap distance, residence time, and the presence of a reforming catalyst (as a function of catalyst distance). The Ni catalyst-loaded porous alumina-silica plate was used to study the catalytic effect on the process performance at various residence times. A considerable enhancement of methane conversion and product yields was achieved in the combined plasma-catalytic system, particularly at a longer residence time. The catalyst distance, or packing position of catalyst plate, was also found to be an important factor affecting the process performance of the combined plasma-catalytic methane reforming. The closer catalyst distance led to the greater methane conversion because of the greater possibility of adsorption?Cdesorption interactions of excited gaseous species on the catalyst surface to enhance subsequent reactions.     

Direct Non‐Oxidative Methane Conversion in a Millisecond Catalytic Wall Reactor

Direct non‐oxidative methane conversion (DNMC) has been recognized as a single‐step technology that directly converts methane into olefins and higher hydrocarbons. High reaction temperature and low catalyst durability, resulting from the endothermic reaction and coke deposition, are two main challenges. We show that a millisecond catalytic wall reactor enables stable methane conversion, C₂₊ selectivity, coke yield, and long‐term durability. These effects originate from initiation of the DNMC on a reactor wall and maintenance of the reaction by gas‐phase chemistry within the reactor compartment. The results obtained under various temperatures and gas flow rates form a basis for optimizing the process towards lighter C₂ or heavier aromatic products. A process simulation was done by Aspen Plus to understand the practical implications of this reactor in DNMC. High carbon and thermal efficiencies and low cost of the reactor materials are realized, indicating the technoeconomic viability of this DNMC technology.     

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.     

Graphene supported NiMo catalyst: A promising novel hydrocracking catalyst

The graphene nanosheet (GNS) is used as a catalyst support for various catalytic reactions. A comprehensive study of functionalized GNS (FGNS)-supported catalyst for the purpose of hydrocracking (HDC) process provides a guide to exploring the potential applications and discovering their superior properties. In this research, to study the effect of the support on the conversion and selectivity of n-hexadecane HDC process, experiments are carried out over a synthesized NiMo/FGNS (NMFG) and a commercial NiMo/Al₂O₃-SiO₂ (NMAS) catalysts in a fixed-bed reactor. The functional groups on the NMFG surface anchor and disperse active metals on the catalyst surface, and they enhance the HDC conversion and stability of NMFG catalyst. Moreover, results prove that, in comparison with the commercial catalyst, NMFG increases the HDC conversion of n-hexadecane about 48%, and decreases the coke deposition on its surface.     

Selective Oxidation of Propane by Lattice Oxygen of Vanadium-Phosphorous Oxide in a Pulse Reactor

Selective oxidation of propane by lattice oxygen of vanadium-phosphorus oxide (VPO) catalysts was investigated with a pulse reactor in which the oxidation of propane and the re-oxidation of catalyst were implemented alternately in the presence of water vapor. The principal products are acrylic acid (AA),acetic acid (HAc), and carbon oxides. In addition, small amounts of C1 and C2 hydrocarbons were also found, molar ratio of AA to HAc is 1.4-2.2. The active oxygen species are those adsorbed on catalyst surface firmly and/or bound to catalyst lattice, i.e. lattice oxygen; the selective oxidation of propane on VPO catalysts can be carried out in a circulating fluidized bed (CFB) riser reactor. For propane oxidation over VPO catalysts, the effects of reaction temperature in a pulse reactor were found almost the same as in a steady-state flow reactor. That is, as the reaction temperature increases, propane conversion and the amount of C1 C2 hydrocarbons in the product increase steadily, while selectivity to acrylic acid and to acetic acid increase prior to 350℃ then begin to drop at temperatures higher than 350℃, and yields of acrylic acid and of acetic acid attained maximum at about 400℃. The maximum yields of acrylic acid and of acetic acid for a single-pass are 7.50% and 4.59% respectively, with 38.2% propane conversion. When theamount of propane pulsed decreases or the amount of catalyst loaded increases, the conversion increases but the selectivity decreases. Increasing the flow rate of carrier gases causes the conversion pass through a minimum but selectivity and yields pass through a maximum. In a fixed bed reactor, it is hard to obtainhigh selectivity at a high reaction conversion due to the further degradation of acrylic acid and acetic acid even though propane was oxidized by the lattice oxygen. The catalytic performance can be improved inthe presence of excess propane. Propylene can be oxidized by lattice oxygen of VPO catalyst at 250℃, nevertheless, selectivity to AA and to HAc are even lower, much more acetic acid was produced (molar ratio of AA to HAc is 0.19:1-0.83:1) though the oxidation products are the same as from propane.     

Transesterification of rapeseed oil in supercritical methanol in a flow reactor

Transesterification reactions of rapeseed oil in supercritical methanol in a flow reactor over a wide range of variation of the methanol/oil ratio, pressure, and contact time are studied. Conditions ensuring selectivity and a high degree of rapeseed oil conversion are found. Experiments to study this reaction in the presence of zeolite heterogeneous catalyst are performed.     

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%。     

Heterogeneous Versus Homogeneous Palladium Catalysts for Ligandless Mizoroki–Heck Reactions: A Comparison of Batch/Microwave and Continuous‐Flow Processing

Mizoroki–Heck couplings of aryl iodides and bromides with butyl acrylate were investigated as model systems to perform transition‐metal‐catalyzed transformations in continuous‐flow mode. As a suitable ligandless catalyst system for the Mizoroki–Heck couplings both heterogeneous and homogeneous Pd catalysts (Pd/C and Pd acetate) were considered. In batch mode, full conversion with excellent selectivity for coupling was achieved applying high‐temperature microwave conditions with Pd levels as low as 10^?3 mol %. In continuous‐flow mode with Pd/C as a catalyst, significant Pd leaching from the heterogeneous catalyst was observed as these Mizoroki–Heck couplings proceed by a homogeneous mechanism involving soluble Pd colloids/nanoparticles. By applying low levels of Pd acetate as homogeneous Pd precatalyst, successful continuous‐flow Mizoroki–Heck transformations were performed in a high‐temperature/pressure flow reactor. For both aryl iodides and bromides, high isolated product yields of the cinnamic esters were obtained. Mechanistic issues involving the Pd‐catalyzed Mizoroki–Heck reactions are discussed.     

高温Shilov甲烷转化反应的机理和反应动力学研究

传统的Shilov反应是以PtCl2作为催化剂在水溶液中实现甲烷转化的,该反应的条件温和,在低至80°C时即可将甲烷中非常稳定的C–H键活化.然而,如果将反应温度提高达100°C以上,催化剂Pt(II)则非常容易发生歧化反应转化为Pt(0)或者Pt(IV),其中Pt(0)将会以沉淀的形式存在于反应溶液中.所以该反应只能在较低的温度进行, Shilov体系也只能得到较低的甲烷转化率,因此如何避免高温时催化剂因沉淀失活成为了提高反应转化率的研究重点.本文重点考察了高温条件下Shilov体系的反应机理和反应动力学,从而寻求提高催化体系活性和稳定性的途径.我们在特殊设计的金管反应器中进行了一系列的H/D置换实验,通过GC根据产物不同的分子量来分析检测.实验中,利用特殊设计的金管反应器可将反应压力增加到25.5 MPa,此时甲烷的溶解度与常温条件下(~60°C)相比可被提高1000倍以上,因此甲烷的转化率大大提高.在高温(~200°C)条件下的Shilov体系的水溶液中添加了CD3COOD, F3COOD, D2SO4, DCl和一系列阳离子为[1mim]+的离子液体来考察它们对催化剂沉淀的抑制作用,结果发现,在140°C时添加30%CD3COOD可在少量催化剂存在的条件下就能够明显促进H/D交换,与Shilov的结论吻合.这可能是由于CD3COO基团的螯合作用造成的,但将反应温度升到150°C时则不可避免的生成了Pt(0)沉淀.而F3COOD却在较多催化剂的条件下仍未表现出明显作用,可能是因为F较强的亲电子性使得F3COO基团的螯合作用变弱所致.在140°C时, D2SO4和DCl均能有效抑制Pt(0)沉淀的生成,尤其是DCl,在185°C反应24 h后仍能够稳定水溶液中的Pt基催化剂,但是在该条件下D2SO4却并没有作用.我们还发现, Cl–的浓度与沉淀的抑制直接相关,浓度越高对Pt基催化剂的稳定作用越强,但质子浓度的增加则对沉淀现象没有太大影响,我们推断原因是大量的Cl-能够在[PtCl6]2–的共同作用下将Pt(0)重新转化为了[PtCl6]2–.在140°C进行反应时,各类离子液体的添加能够使Pt(0)沉淀得到抑制,但是对H/D交换率却没有影响,可能是因为离子液体与Pt基催化剂螯合形成了Pt-离子液复合物而削弱了催化活性.在此基础上,我们特别考察了Cl–浓度对催化剂沉淀的影响,发现在200°C时将Cl-浓度提高到一定程度,就能够完全抑制Pt(0)的生成,但Pt基催化剂的活性也会被同时削弱.由于高压金管反应器的应用和高浓度Cl–的添加,使得甲烷的转化率达到90%以上,因此,我们设计了H/D同位素交换实验来考察反应的活性和选择性,从而针对高温Shilov体系的反应动力学进行研究.反应在200°C时进行,催化剂为K2PtCl4,反应介质为30% CD3COOD和DCl的水溶液,实验产物中检测到了CH3D, CH2D2, CHD3和CD4四种甲烷的多重氘代同位素体,说明了交换反应中有多个C–H键被活化.在此基础上,为了对甲烷活化过程进行全面描述,我们建立了涵盖所有连锁反应在内的综合反应网络,其中包含了H/D交换过程中涉及到的一系列平行的一级反应,基于实验数据通过阿伦尼乌斯方程计算得到了全部反应的频率因子、活化能和化学计量系数等反应动力学参数.结果证明,由于甲烷中所有的C–H键均相同,因此多重氘代产物的生成在甲烷转化过程中是不可避免的.其中,甲烷的单一氘代反应活化能为29.9 kcal/mol,双重氘代反应活化能为29.8 kcal/mol,两者十分相近,因此甲烷活化后的单一氘代产物的选择性最高不会超过50%.     

Cycloaliphatic epoxy resin coating for capillary electrophoresis

Coating the interior surface of a fused-silica capillary with a polymeric material has long been used in capillary electrophoresis (CE) to reduce or eliminate electroosmotic flow and suppress adsorption. A cycloaliphatic epoxide-based resin was bonded to silane treated capillaries and crosslinked with a curing agent. The epoxy resin coating significantly reduced electroosmotic flow over a pH range of 3-10. This coating was sufficiently hydrophilic to suppress protein adsorption. The epoxy resin coated capillary was used to separate several acidic and basic proteins and peptides. Separation efficiencies greater than 400,000 theoretical plates were achieved. The relative standard deviations in migration times for proteins were <0.8%. Speed and simplicity are important advantages of the coating procedure compared to other published coating methods.     

Microreactor for the Catalytic Partial Oxidation of Methane

Fixed-bed reactors for the partial oxidation of methane to produce synthetic gas still pose hot-spot problems. An alternative reactor, which is known as the shell-and-tube-typed microreactor, has been developed to resolve these problems. The microreactor consists of a 1 cm outside-diameter, 0.8 cm inside-diameter and 11 cm length tube, and a 1.8 cm inside-diameter shell. The tube is made of dense alumina and the shell is made of quartz. Two different methods dip and spray coating were performed to line the tube side with the LaNixOy catalyst. Combustion and reforming reactions take place simultaneously in this reactor. Methane is oxidized in the tube side to produce flue gases (CO2 and H2O) which flow counter-currently and react with the remaining methane in the shell side to yield synthesis gas. The methane conversion using the higher-loading catalyst spray-coated tube reaches 97% at 700℃, whereas that using the lower-loading catalyst dip-coated tube reaches only 7.78% because of poor adhesion between the catalyst film and the alumina support. The turnover frequencies (TOFs) using the catalyst spray-and dip-coated tubes are 5.75×10-5 and 2.24×10-5 mol/gcat·s, respectively. The catalyst spray-coated at 900℃provides better performance than that at 1250℃because sintering reduces the surface-area. The hydrogen to carbon monoxide ratio produced by the spray-coated catalyst is greater than the stoichiometric ratio, which is caused by carbon deposition through methane cracking or the Boudouard reaction.     

The investigation of an equilibrium dependent reaction for the formation of enamines in a microchemical system

The paper describes the equilibrium dependant reaction for the formation of enamines in a microchemical system utilising electroosmotic flow (EOF) for fluid mobilisation. The authors have shown that the reaction can be carried out without the presence of a Lewis acid catalyst, in addition the enamine intermediate was synthesised at room temperature using mild solvent conditions. A 42% conversion of cyclohexanone into the enamine has been achieved to date.     

Oligomerization of endo-dicyclopentadiene using a mesoporous catalyst in a fixed-bed reactor

The oligomerization of endo-dicyclopentadiene (endo-DCPD) over a mesoporous catalyst in a continuous-flow reactor at elevated pressure was studied to produce tricyclopentadiene (TCPD) and tetracyclopentadiene (TeCPD). The mesoporous material prepared from zeolite beta (MMZ_Hβ) was utilized as a catalyst. In addition, this study focused on the catalytic performance of the regenerated catalyst in comparison with the fresh catalyst. The TCPD and TeCPD were continuously produced through DCPD oligomerization over the MMZ_Hβ catalyst in a fixed bed reactor. At early time-on-stream, the conversion of endo-DCPD, the yield of TCPD and TeCPD, and the isomerization selectivity of TCPD in the fixed bed reactor were comparable to those in the batch-type reactor. The yield of oligomer containing TCPD and TeCPD decreased drastically from 28.5 % at 3 h time-on-stream to 21.5 % at 12 h time-on-stream, indicating that the catalyst was significantly deactivated. The in situ calcination in air flow at 500 °C was found to be effective for the regeneration of the used MMZ_Hβ catalyst.     

Polymer-Supported Poly(Ethylene Glycol) as a Phase-Transfer Catalyst for Cross-Aldol Condensation of Isobutyroaldehyde and Formaldehyde

Immobilized poly(ethylene glycol) (PEG 600-PS) was used as an effective phase-transfer catalyst for the synthesis of hydroxypivaldehyde from isobutyraldehyde (IBA) and formaldehyde in the presence of an inorganic base. Studies on the influence of the parameters on the course of the reaction in a batch reactor showed that the use of the PEG 600-PS catalyst allowed one to obtain HPA with high efficiency (IBA conversion >96%, selectivity >98%) in a relatively short time and under mild conditions (2 h, 40 °C). The developed method enables easy separation of the post-reaction mixture by simple phase separation, and the immobilized catalyst can be separated by filtration and then used five times without a loss in its activity. The high activity and stability of the catalyst was also confirmed in a test carried out in a flow reactor.