High throughput discovery of CO oxidation/VOC combustion and water–gas shift catalysts for industrial multi-component streams

High-throughput and combinatorial approaches have been applied to the discovery of catalysts for selective low temperature CO oxidation/VOC removal using mixed CO/propylene feeds, and for the water–gas shift (WGS) reaction using real post-reformer feeds containing CO, CO₂, H₂O and H₂. The screening approach was based on a hierarchy of qualitative and semi-quantitative primary screens for the discovery of hits, and quantitative secondary screens for hit confirmation, lead optimization and scale-up. For WGS, primary screening was carried out using scanning mass spectrometry. For CO oxidation and VOC removal, parallel IR thermography was the primary screen. Multi-channel fixed bed reactors equipped with imaging reflection FTIR spectroscopy or GC were used for secondary screening. Novel RuCoCe compositions were discovered and optimized for CO oxidation/VOC removal and the effect of doping was investigated for supported and bulk mixed oxide catalysts. For WGS, noble metal-free and Pt-doped CoFeRu mixed oxides as well as Pt on CeO₂ and Pt on CeO₂/ZrO₂ were investigated and a new synergistic PtFeCe ternary composition was discovered. In these cases oxygen vacancies in the ceria lattice are believed to play a key role in the strong and synergistic Pt–Ce interaction. Alkaline metal doping was found to enhance the selectivity towards WGS by suppressing the unselective methanation side reaction and to increase the low temperature catalytic activity.     

Design and Parallel Synthesis of Novel Selective Hydrogen Oxidation Catalysts and their Application in Alkane Dehydrogenation

A library of 19 supported metal oxides of group IIIA, IVA, and VA metals is prepared using a simple gram‐scale reactor for parallel pore impregnation. The activity, stability, and selectivity of these potential hydrogen combustion catalysts in the dehydrogenation of ethane to ethylene at 600 °C is examined over several redox cycles using gas mixtures that simulate real process conditions. Lead, indium, and thallium oxides are highly selective (>99.9%) to hydrogen combustion. Low‐loading catalysts are found to exhibit higher oxygen exchange activity. Differences between co‐fed and redox oxidative dehydrogenation are discussed.     

Corrosion‐Resistant Parallel Fixed‐Bed Reactors for High‐Throughput Screening of New Deacon Reaction Catalysts

Two ten‐channel fixed‐bed reactor systems were developed for high‐throughput screening of new Deacon catalysts. The sequential ten‐channel reactor allows the determination of the activity of up to ten catalysts per day. With a ten‐channel ageing reactor the long‐time stability of catalytic activity can be tested in parallel. Both systems are robust, quite resistant against corrosion, and use the identical reaction tubes which enable the direct transfer of a catalyst from one to the other system. A mass‐spectrometric pulse method has been developed and applied successfully for the analysis of the corrosive product gas mixture of the Deacon reaction.     

Parallel synthesis and fast screening of heterogeneous catalysts

We are presenting an effective method to prepare and test heterogeneous catalysts much faster than by the conventional way. A catalyst array was prepared via an incipient wetness method by combination of different amounts of Pt, Zr, and V on Al₂O₃ by means of an automatic liquid handler. For catalytic testing for methane oxidation a ceramic monolith reactor module, the channels of which contain the different catalyst compositions, was developed in which up to 250 catalyst compositions can be prepared and tested in parallel. Gas samples from each channel of the monolith were analysed sequentially by a mass spectrometer by moving the QMS inlet capillary into the channels using a three-dimensional positioning system which works at high temperatures. By comparison of the testing results with experiments carried out in flow reactors it is shown that the monolithic reactor is an efficient tool for fast screening of heterogeneous catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Rapid evaluation of oxidation catalysis by gas sensor system: total oxidation, oxidative dehydrogenation, and selective oxidation over metal oxide catalysts

The rapid evaluation of catalysis is an indispensable technology for the success of combinatorial chemistry. A small-sized, less expensive, easily operating screening is desirable for parallel settings which dramatically shortens the evaluation time. Recent advances in gas sensors have enabled us to use them for the rapid evaluation of oxidation catalysis. Three typical catalytic oxidations over metal oxide catalysts were evaluated by gas sensor systems optimized for each catalytic system. The first one is the total oxidation of carbon monoxide in air. Five catalytic combustion-type gas sensors were used in a parallel reactor system to shorten the evaluation time. The second one is the oxidative dehydrogenation (ODH) of ethane over the mixed oxide of nickel and iron. The evaluation of the ODH catalysis was performed by a selective olefin sensor which determines the concentration of C₂H₄ in C₂H₆. The third one is the selective oxidation catalysis of propane over alkali modified Fe/SiO₂. The effluents including CO, CO₂, aldehydes and ketones in propane were analyzed by the CO, CO₂ and semiconductor-type gas sensors selective toward aldehydes and ketones. These evaluation results indicated that gas sensors have a good potential for the rapid evaluation of oxidation catalysts.     

Influence of Reactor Configuration on the Selective Oxidation of Glycerol over Au/TiO2

The oxidation of glycerol by molecular oxygen in the aqueous phase over Au/TiO₂ was investigated in both a batch reactor and a continuous upflow fixed bed reactor. The effects of catalyst particle size, gas flow rate, liquid flow rate, reaction temperature, dioxygen pressure, and solution pH were examined in the fixed bed system. The unique hydrodynamics of the fixed bed system allowed for secondary oxidation products such as tartronic acid and oxalic acid to form in substantial amounts, which contrasts the product distribution observed in a batch system. These results suggest that reactor configuration can play an important role in the observed product selectivity from oxidation reactions over highly active gold catalysts.     

On the link between intrinsic catalytic reactions kinetics and the development of catalytic processes: Catalytic dehydrogenation of ethylbenzene to styrene

A procedure linking kinetic modeling of catalytic reactions to reactor modeling for different configurations is developed and applied to the catalytic dehydrogenation of ethylbenzene to styrene. The procedure is applied to four configurations, namely fixed bed with/without hydrogen selective membranes and bubbling fluidized beds with/without selective membranes. The kinetic data for the industrial catalyst are extracted from industrial fixed bed data using a rigorous heterogeneous model. The kinetic data for the three in-house prepared catalysts are obtained from the laboratory scale experiments using pseudo-homogeneous models.     

Selective oxidation of alcohols by combinatorial catalysis

High-throughput synthesis and screening of polyoxometalate (POM) and supported-metal libraries have been developed for the selective aerobic oxidation of alcohols to the corresponding aldehydes/ketones in the liquid phase. Libraries consisting of 96 catalysts were prepared in multi-well reactors and screened for catalytic activity using TLC, GC and NMR detection methods. Promising hits identified in the high-throughput primary screens were successfully scaled up and optimized in conventional laboratory test units. Isolated yields confirm high selectivities of more than 90% with quantitative conversions. Substrates tested include primary and secondary alcohols. Specific results will be presented for hydroxymethyl-substituted heterocycles and bicyclo-octanols.     

A Microfluidic Approach to the Rapid Screening of Palladium‐Catalysed Aminocarbonylation Reactions

The evaluation and selection of the most appropriate catalyst for a chemical transformation is an important process in many areas of synthetic chemistry. Conventional catalyst screening involving batch reactor systems can be both time‐consuming and expensive, resulting in a large number of individual chemical reactions. Continuous flow microfluidic reactors are increasingly viewed as a powerful alternative format for reacting and processing larger numbers of small‐scale reactions in a rapid, more controlled and safer fashion. In this study we demonstrate the use of a planar glass microfluidic reactor for performing the three‐component palladium‐catalysed aminocarbonylation reaction of iodobenzene, benzylamine and carbon monoxide to form N‐benzylbenzamide, and screen a series of palladium catalysts over a range of temperatures. N‐Benzylbenzamide product yields for this reaction were found to be highly dependent on the nature of the catalyst and reaction temperature. The majority of catalysts gave good to high yields under typical flow conditions at high temperatures (150 °C), however the palladium(II) chloride‐Xantphos complex [PdCl₂(Xantphos)] proved to be far superior as a catalyst at lower temperatures (75–120 °C). The utilised method was found to be an efficent and reliable way for screening a large number of palladium‐catalysed carbonylation reactions and may prove useful in screening other gas/liquid phase reactions.     

Ethane oxidehydrogenation selectivity and reductibility of mixed NiVSb oxides

Alumina-supported NiV, SbV and NiVSb oxides were characterized and tested as catalysts for the oxidehydrogenation of ethane. The results of their surface and bulk reduction by hydrogen revealed that the most easily reduced NiVSb catalyst was the most selective. The relationship between catalyst reducibility and selectivity was interpreted on the assumption that the reaction occurred through a redox mechanism.     

铜系催化剂选择性催化还原脱除NOx研究

以硅胶改性堇青石蜂窝陶瓷为载体,分别制备了以Cu-O、Cu-Ce-O和Cu-Ce-Mn-O为活性组分的催化剂。以CO(NH₂)₂为还原剂,在固定床反应器中进行选择性催化还原NO的研究。采用XRD、SEM和BET等测试方法对催化剂进行表征。结果表明,在温度(300～500) ℃,催化剂Cu-Ce-Mn-O/SiO₂/堇青石的活性优于催化剂Cu-O/SiO₂/堇青石和Cu-Ce-O/SiO₂/堇青石,反应温度为450 ℃、空速为8 000 h^-1时,Cu-Ce-Mn-O/SiO₂/堇青石催化剂催化还原NO的转化率可达到88%。     

Highly Selective Supported Alkali Chloride Catalysts for the Oxidative Dehydrogenation of Ethane

Binary, ternary and quaternary molten eutectic alkali chloride catalysts, supported on mildly redox active oxides, were investigated for the oxidative dehydrogenation of ethane. The influence of different support oxides, on the catalytic performance, as well as that of different anions (bromide vs. chloride) and cations in a chloride eutectic system were studied. Metal oxides which react with chlorides are not suitable and lead to substantial deactivation. Especially supports forming volatile chlorides induce irreversible chloride depletion. Bromides catalyze oxidative dehydrogenation of ethane with higher rates, but lower olefin selectivities, highlighting the similarities and differences of Cl^? and Br^? in the redox cycle. Two catalysts were identified having olefin selectivities up to 98 % at 70 % ethane conversion, which ranges among the highest selectivities reported for ethane ODH.     

Ethane to Aromatic Hydrocarbons: Past, Present, Future

Ranking high in the current challenges of catalysis, direct transformations of lower saturated hydrocarbons (alkanes) have been investigated for a long time. However, unsaturated hydrocarbons (e.g., aromatics and olefins) have always been the more important feedstocks to produce basic and intermediate chemicals because of their wide variety of possible reaction pathways. This article focuses on the conversion of one representative of lower alkanes—ethane, which is an important constituent of natural gas, accompanying gases and waste effluents of petrochemical processes—to aromatic compounds.

Following general considerations on the aromatization of ethane, efficient modification methods of MFI-type zeolites to obtain active and selective catalysts will be presented. The nature of active sites, including the promoting effects of zinc, gallium, or noble metals, will be discussed. Single pathways in the reaction network from ethane toward aromatic hydrocarbons are explored based on experiments under steady-state and transient-state conditions. Finally, an outlook for possible transformations of the fundamental knowledge to full-scale industrial application will be given.

A meandering ethane river flows beneath a line of bluffs on Titan. Methane fog blankets the lowlands beyond to the horizon. Attempts to glimpse Titan's surface from Earth-bound observatories and interplanetary probes have been thwarted by the thick hydrocarbon haze that covers the moon at all times. [1]     

铈改性丝光沸石用于合成甲胺

铈改性丝光沸石用于合成甲胺邱祖民李凤仪章磊吴晓聪罗来涛（南昌大学现代应用化学研究所，南昌３３００４７）关键词二甲胺丝光沸石胺化反应铈改性１前言甲胺有三种，即一甲胺（ＭＭＡ）、二甲胺（ＤＭＡ）、三甲胺（ＴＭＡ），它们都是重要的有机化工原料。三种甲胺中...     

Hydrotalcite-like compounds as precursors for mixed oxides catalysts in the oxydehydrogenation of ethylbenzene

The dehydrogenation of ethylbenzene to styrene is a very important industrial reaction due to the multiple applications of styrene as a monomer for synthetic polymers. Reported catalysts that are active and selective in the oxidative dehydrogenation of alkylaromatics include supported metals through both main group and transition metal oxides to polymers and activated carbons. However, most of these catalysts are acid oxides, inducing the formation of an active coke layer that is the actual catalyst. We report in this work the use of various hydrotalcite-like compounds as precursors for the preparation of mixed oxides which are then used as basic catalysts in the oxydehydrogenation reaction. A series of materials has been synthesised by coprecipitation at constant pH and fully characterised by usual analytical techniques. The catalytic screening tests were carried out in a fixed bed quartz reactor at a temperature of 450°C and the liquid products were analysed off-line by gas chromatography. Some particularities of these materials are brought forward, like the absence of coking which however, does not seem to affect the activity, thus suggesting a different mechanism; the results show high selectivity in styrene, while the activity of the catalysts needs some improvements. For example, with vanadium containing oxides a selectivity of 98% in styrene is achieved with a conversion of 38% in ethylbenzene.     

组合催化在石油化工催化开发中的应用

概述了组合催化的基本原理及实验装置,主要介绍了组合催化在丙烯环氧化制环氧丙烷、甲醇与甲苯侧链烷基化制苯乙烯、丁二烯制四氢呋喃、乙烷/丙烷氧化脱氢制乙烯/丙烯等石油化工过程催化剂研发中的应用,指出组合催化将是未来发现新催化材料及新催化过程的有效手段。     

Selective Conversion of Ethane to Ethene via Oxidative Dehydrogenation Over Ca-doped ThO2 Using CO2 as Oxidant

Ca-doped ThO₂, synthesized by solution combustion method was tested for dehydrogenation of ethane with CO₂. Doping ThO₂ with Ca resulted in the creation of oxide ion vacancies and an increased conversion of ethane compared to pure ThO₂. On Th_0.75Ca_0.25O₂ selectivity to ethene was 97 at 46% ethane conversion at 725 °C. Well-known reference catalysts like 5%Cr/TS-1 or OMS-2 showed significantly lower selectivity, but the former was more active under the same conditions.     

Screening of bifunctional water-gas shift catalysts

A large number of different formulations have been recently proposed in the literature as new catalysts for the water-gas shift (WGS) reaction. These formulations typically consist of a metal deposited on a reducible support. As these catalysts have been synthesized and tested by different groups in different operating conditions, a true comparison of their activities is not really possible. The aim of this study is to screen these samples under identical conditions using a model reformate as reaction mixture. A commercial parallel reactor has been used for this task. Comparison of the data obtained for the Pt catalysts from the parallel reactor with those obtained from a single fixed bed reactor showed deviations of 20–30% in the kinetic parameters. Rh and Ru based catalysts produced significant amounts of methane. Pt/CeO₂/Al₂O₃ and Pt/TiO₂ were found to be the most active catalysts for the high temperature water-gas shift while gold and copper catalysts showed promising results for low temperature applications, but they require testing at lower CO partial pressures.     

Is True Ethane Oxydehydrogenation Feasible?

Oxydehydrogenation of ethane as a route to ethylene has the attractive feature of removing the thermodynamic equilibrium conversion limitation of the simple dehydrogenation. For example, in the dehydrogenation of ethane to ethylene, the maximum conversion possible at 1000 °C is 51%, while essentially complete (100%) conversion is possible even at ambient conditions. The best catalysts discovered to date are those from Union Carbide's work (in the late 1970s and early 1980s), which operate at 300-400 °C. These reducible Mo–V–Nb oxide catalysts are thought to react via a surface ethoxide intermediate on a Mo or V site that can then undergo a β-elimination process to form ethylene. On the other hand, the surface ethoxide can be oxidized further to form surface acetate, which leads to acetic acid on hydrolysis with water. Aside from these low-temperature reducible catalysts, many catalysts containing reducible metal oxides and non-reducible metals are known to convert ethane to ethylene at 500-800 °C. It is proposed that these catalysts are essentially dehydrogenation catalysts where the H₂ formed from straight dehydrogenation or during a surface intermediate stage after H-abstraction is converted to H₂O, thereby shifting the dehydrogenation equilibrium. Therefore, the big question, the challenge, and the opportunity remains as to whether true oxydehydrogenation is possible at relative low-to-moderate temperatures? This challenge/opportunity will be discussed in the backdrop of some of the recent advances in alkane activation.     

Selective Oxidation of Methanol to Formaldehyde Using Modified Iron-Molybdate Catalysts

Methanol selective oxidation to formaldehyde over a modified Fe-Mo catalyst with two different stoichiometric (Mo/Fe atomic ratio = 1.5 and 3.0) was studied experimentally in a fixed bed reactor over a wide range of reaction conditions. The physicochemical characterization of the prepared catalysts provides evidence that Fe₂(MoO₄)₃ is in fact the active phase of the catalyst. The experimental results of conversion of methanol and selectivity towards formaldehyde for various residence times were studied. The results showed that as the residence time increases the yield of formaldehyde decreases. Selectivity of formaldehyde decreases with increase in residence time. This result is attributable to subsequent oxidation of formaldehyde to carbon monoxide due to longer residence time.