Reactive distillation: Non-ideal flow behaviour of the liquid phase in structured catalytic packings

Reactive distillation, the combination of chemical reaction and multistage distillation, is one of the most important industrial applications of the multifunctional reactor concept. The most promising column internals for reactive distillation are the so-called structured catalytic packings that combine favourable characteristics of traditional structured packings and heterogeneous catalysts. The non-ideal flow behaviour of the gas and the liquid phase is a fundamental aspect in multiphase reactor design since it has a strong influence on the reactor performance. In this study, liquid phase residence time distributions for the catalytic structured packing MULTIPAK^® were measured by means of conductivity measurements under different liquid and gas flow rates and evaluated with differential models.     

Cobalt Fischer-Tropsch synthesis: Deactivation by oxidation?

Cobalt catalysts as used in the Fischer-Tropsch synthesis (FTS) are relatively expensive (as compared to iron) and need to have a high metal dispersion and long life to be able to offer a good balance between cost and performance. The oxidation of nano-sized metallic cobalt to cobalt oxide during Fischer-Tropsch synthesis has long been postulated as a major deactivation mechanism. However, to date there is no consistent picture. This paper presents an extensive overview of the literature on this topic of deactivation by means of oxidation for unsupported as well as silica-, alumina- and titania-supported cobalt catalysts. Furthermore, it presents results on the deactivation of an industrial Co/Al₂O₃ catalyst as obtained by pseudo in situ X-ray diffraction, magnetic measurements and X-ray absorption near-edge spectroscopy. These analyses were performed to study the oxidation state of spent industrial Co/Al₂O₃ catalyst samples withdrawn from a slurry reactor operating under realistic FTS conditions, and it was concluded that oxidation can be ruled out as a major deactivation mechanism. Finally, these data together with all relevant literature were used to create a common view on the oxidation behaviour of metallic cobalt during FTS. The apparent discrepancies in literature on the oxidation behaviour of cobalt are most likely due to the lack of direct characterisation of the cobalt oxidation state and due to the comparison of catalysts with varying cobalt crystallites sizes, compared at different reactor partial pressures of hydrogen and water (P_H2O/P_H2). It was shown that the oxidation of cobalt can be prevented by selecting the correct combination of the reactor partial pressures of hydrogen and water (P_H2O/P_H2) and the cobalt crystallite size.     

Conversion of hydrocarbon fuels to syngas in a short contact time catalytic reactor

Some results of the theoretical and experimental research on the oxidative production of syngas from hydrocarbon fuels in catalytic reactors which operate at high temperatures and short contact times are presented. Pilot scale tests of the partial oxidation of methane, isooctane and gasoline have been carried out in nearly adiabatic conditions on structured catalysts developed at the Boreskov Institute of Catalysis and characterized by a low (≤0.5 wt./wt.%) content of noble metals. High yield of syngas and stable performance of the catalysts were revealed in the experiments. The details of interaction between chemical and physical processes inside adiabatic monolith reactor have been elucidated by mathematical modeling of the partial oxidation reaction on the base of catalyst detailed chemistry. The problems that emerged from the short contact time reactor operating on a pilot scale are also discussed.     

Assessment of micro-structured fixed-bed reactors for highly exothermic gas-phase reactions

The application of micro-structured fixed-bed reactors for highly exothermic partial oxidation reactions and their comparison to established multi-tubular fixed-bed reactors was investigated by numerical simulation. As examples, the partial oxidations of butane to maleic anhydride and of o-xylene to phthalic anhydride were chosen. The simulation results revealed that the reactor productivity, i.e. the amount of product per unit of reactor volume, achievable in micro-structured fixed-bed reactors is between 2.5 and 7 times higher than in conventional multi-tubular fixed-bed reactors without the danger of excessive pressure drop. For the partial oxidation of butane to maleic anhydride this can be explained by the increased reactor efficiency caused by lower efficiency losses through heat and mass transfer limitations. In addition, maleic anhydride selectivities and yields are higher in micro-structured fixed-bed reactors. In the case of o-xylene oxidation to phthalic anhydride the main advantage is that egg-shell catalysts in the conventional fixed-bed reactor can be replaced by bulk catalysts in the micro-structured fixed-bed reactor. For this reaction, product selectivities are very similar for all reactor configurations. Thus the catalyst inventory and reactor productivity are strongly increased. This study underlines, that micro-structured fixed-bed reactors exhibit the potential to intensify large scale industrial processes significantly.     

Partial Oxidation of Propane Using Dense Carbon Dioxide

The present work was aimed at investigating activity and selectivity of various catalysts for the partial oxidation of propane in sc‐CO₂ atmosphere. Catalytic experiments were performed in a stirred batch reactor. This paper reports on the used reactor system and first results of a catalyst screening using different metal (oxide) catalysts as well as the variation of the reaction conditions.     

An aerosol reactor for the controlled synthesis of heterogeneous catalyst particles

Commercialized catalysts are often needed in multiton quantities for industrial deployment. Although scalable, manufacturing methods to produce catalysts at quantity often produce materials with an ensemble of physical and chemical characteristics. This work explores an aerosol reactor to synthesize homogeneous, uniform catalyst materials in order to develop correlations between key chemical and physical characteristics and their resulting catalytic performance. With these insights, we optimize reactor processing conditions to engineer particles with the desired physical and chemical characteristics to produce enhanced performance catalysts. Control over several process parameters, including reactor residence time, temperature, precursor type, and precursor composition, allows for the rational determination of key physical and chemical characteristics on the resulting catalyst materials and enables process optimization to engineer catalysts with enhanced performance. To demonstrate the methodology, the aerosol reactor was used to synthesize and optimize WO _x catalyst materials for the isomerization and metathesis of a 2-butene feed into propylene.     

XY-S型催化剂在全密度聚乙烯装置上的应用

从流化床反应器基本工艺出发,通过对反应过程中的乙烯分压,n(H2)/n(C2H4),n(C4H8)/n(C2H4),两种催化剂质量比等的调整,反应器静电、流化床上下部的线型低密度聚乙烯(LLDPE)质量比、松密度、反应压力等参数均受控。催化剂活性随着XY-S型催化剂加入比例的增大而下降,w(XY-S)为100%时,催化剂平均活性达6.572 t/kg,与w(XY-S)为50%,70%相比,催化剂活性下降了14.3%～18.7%。产品合格率达100%,国产XY-S型催化剂在全密度聚乙烯装置上成功应用,基本满足装置长周期运行,达到了降低生产成本和催化剂国产化的目的。     

Mathematical modelling of a reverse flow reactor with catalytic surface dynamics

This paper studies a system of partial differential equations modelling the behaviour of a reverse flow reactor. For the parameters appropriate for the oxidation of ammonia on a Pt/Al₂O₃ catalyst in a typical laboratory set-up, the reactor may be split into regions where approximate formulas that determine its behaviour are deduced. Numerical calculations are presented and can be used to compare with the analytical formulas. The physical insight gained from the asymptotic analysis suggests a new switching strategy which is the subject of numerical experiments. The switching strategy is found to be efficient at minimising the ammonia exiting the reactor after reversal.     

Supported nanocomposite catalysts for high-temperature partial oxidation of methane

In order to utilize the vast potential of nanoparticles for industrial catalysis, it is necessary to develop methods to stabilize these particles at realistic technical conditions and to formulate nanoparticle-based catalysts in a way that facilitates handling and reduces health and safety concerns. We have previously demonstrated that metal nanoparticles can be efficiently stabilized by embedding them into a high-temperature stable nanocomposite structure. Building onto these results, we report here on the next step towards a simple, hierarchically structured catalyst via supporting platinum barium-hexaaluminate (Pt-BHA) nanocomposites onto a range of different conventional and novel support structures (monoliths, foams, and felts). The catalysts were characterized via SEM, TEM, XRD, porosimetry, chemisorption, and reactive tests in catalytic partial oxidation of methane to synthesis gas (CPOM), and compared to conventionally prepared Pt-catalysts. In particular silica felt supported Pt-BHA showed excellent activity and selectivity combined with good stability and very low noble metal requirement at the demanding high-temperature conditions of short-contact time CPOM. Overall, we see great potential for these supported nanocomposite catalysts for use in demanding environments, such as high-temperature, high-throughput conditions in fuel processing and similar energy-related applications.     

Performance of a large scale packed recirculating reactor for homogeneous catalytic oxidation of car-3-ene

Autooxidation of car-3-ene was carried out in a large scale packed recirculating reactor, where the catalyst cobalt acetylacetonate and the liquid were recirculated and sprayed on top of an inert packing. Gas is introduced from the bottom. The mass transfer parameters and mixing characteristics of the reactor were determined. The effect of catalyst quantity, operating pressure on car-3-ene conversion, and selectivity for various products were studied. The reaction system was mathematically modelled, and the simulation compared with the observed behaviour. The rate constants of the elementary reaction steps had been determined separately in a laboratory reactor.     

Computation of nickel catalyst activity in the hydrogenation of triacylglycerol oils

The development of a new method for a faster and more accurate computation of the nickel catalyst activity was studied. This catalyst is used in partial catalytic hydrogenation of vegetable oils for production of edible fats. In order to index the activity, a computer program, CATACT, was developed using FORTRAN language. This program uses 3 easily determined experimental values as input data (refractive index at 60 C, catalyst concentration and hydrogenation time). Output data are catalyst activity indexes either in word or numerical form. The hydrogenation data were gathered from a laboratory reactor under laboratory conditions. Using these data, we computed the activity of Ni catalysts which have been reused in oil hydrogenation under industrial conditions. The classical method of determining such activity by evaluating the melting point is, in view of the very low activity of such catalysts, inadequate to provide sufficient information for easy interpretation.     

CO2 reforming and partial oxidation of methane

CO₂ reforming and partial oxidation of CH₄ were investigated on different supported noble metal and Ni catalysts. A detailed thermodynamic analysis was performed for both reactions. The observed reaction behaviour can be predicted by thermodynamics. Product selectivity is catalyst independent, the role of the catalyst is to bring the reactants to approach equilibrium. The partial oxidation is a two-stage process, total oxidation of CH₄ is followed by CO₂ and H₂O reforming of the remaining CH₄. A staged addition of O₂ to the reactor is tested and recommended. TPSR show that the catalyst surface for CO₂ reforming was highly covered with carbonaceous species of four different types; two were identified as reactive intermediates.     

微管内环己烷氧化反应研究进展

介绍了微管反应器和微管内环己烷氧化反应的特点;详述了微管内环己烷无催化氧化的反应工艺、微管内气液流动情况、反应机理以及微管内壁负载催化剂的环己烷催化氧化反应工艺;指出无催化及内壁涂覆催化剂的微管内环己烷氧化反应在改善反应的安全性、强化气液传质效果和提高催化性能等方面具有较大优势,微管内壁负载纳米金催化剂的反应器形式在环己烷氧化反应中前景看好。     

problems of increase in the selectivity of ethylene oxychlorination processes: II. General patterns in the formation of chloroorganic byproducts in the ethylene oxychlorination Process

We continue to consider some general patterns in the formation of chloroorganic byproducts during the process of ethylene oxychlorination in a fluidized catalyst bed. Based on the literature data, some conclusions are drawn as to chloroorganic byproducts generally resulting from the secondary conversion of 1,2-dichloroethane via the reactions of its dehydrochlorination and partial oxidation. An rise in process temperature increases the yield of byproducts. It is shown that the use of catalysts containing chlorides of alkali or alkali-earth metals along with copper chloride reduces the share from side reactions. When the process is performed under industrial conditions, it is best to use catalysts with low contents of copper on the outer surfaces of the grains. The penetration of iron into a catalyst due to the erosion of industrial reactor walls results in both a slowdown in the rate of oxychlorination and an increase in the yield of chloroorganic byproducts.     

甲醇氧化重整制氢过程(Ⅱ)反应器构型对制氢过程的影响

在质子交换膜燃料电池 (PEMFC)移动氢源———甲醇氧化重整制氢自热体系中 ,研究了反应器构型对产氢能量效率和床层内“热点”温度的影响 ,得到了反应器设计准则 ,提出了实际应用中可采用的反应器型式     

光催化降解染料废水的研究现状及展望

在光催化氧化法降解染料废水的研究中，通常使用金属氧化物为催化剂，其中TiO2最为理想。催化负载方式很多，以溶胶—凝胶法更具应用前景。催化氧化过程中的催化剂的用量、废水的pH值和初始浓度、温度、光照强度和光源类型等因素对氧化效果有看不同程度的影响；在各式的反应器中，管式反应器被认为最具有发展前景。要使这项技术成功走向工业化，必须解决好催化剂的活性、负载技术和反应器设计等方面的问题。     

Problems of increase in the selectivity of ethylene oxychlorination processes: I. General patterns in the formation of carbon oxides in the ethylene oxychlorination process

General patterns in the formation of carbon oxides (byproducts of deep oxidation) in the process of ethylene oxychlorination in a fluidized catalyst bed are considered. Based on the literature data, some conclusions are drawn as to a possible reagent oxidation mechanism, allowing for the oxidation of the initial ethylene and target dichloroethane. Raising the process temperature increases the contribution from dichloroethane oxidation. It is shown that a catalyst must also be active in the oxidation of carbon monoxide to carbon dioxide in order to stabilize the process and improve the selectivity to target 1,2-dichloroethane. Under industrial conditions, a lower yield of side carbon oxides is attained at minimal excesses of ethylene and oxygen with respect to hydrogen chloride; this requires catalysts with a low content of copper on the outer surface of a grain. The presence of promoting alkali or alkali-earth chloride additives in a catalyst is important. The penetration of iron into a catalyst due to the erosion of industrial reactor walls leads to an increase in the yield of deep oxidation products and a reduction in the speed of the oxychlorination process.     

The process for catalytic incineration of waste gas on IC-12-S102 platinum glass fiber catalyst

The process for catalytic afterburning of volatile organic compounds (VOCs) in waste industrial gases was developed on the basis of a new platinum glass fiber catalyst (GFC) IC-12-S102 with low platinum content (∼0.02 wt %). The catalyst was shown to be more effective than the known industrial afterburning catalysts. The way of glass fiber catalyst loading to a reactor in the form of vertical spiral cartridges, structured with wire mesh of bulk weaving is described. The successful application of the IC-12-S102 catalyst was confirmed by its operation at OAO Nizhnekamskneftekhim in the process of waste gases afterburning in an industrial reactor with cleaned gases capacity up to 15000 m³/h. During the reactor operation in harsh conditions (low oxygen content, high content of water vapor), the degree of gas cleaning was 99.5–99.9% and the residual VOC content in the purified gases was no higher than 10–15 mg/m³. For more than 15 months of catalyst operation, the degree of gas purification was not reduced; thus, overall lifetime of the IC-12-S102 catalyst may be substantially longer than the life of well-known industrial afterburning catalysts.     

Using vanadium catalysts for the oxidation of hydrogen chloride with molecular oxygen

Regeneration of chlorine by oxidation of hydrogen chloride is an important problem in the production of chloroorganic products. The known catalysts for this reaction are insufficiently active and typically not stable enough, while data on the use of V catalysts for this process are absent. Here we report on our study of the stability and catalytic activity of the industrial sulfuric acid production sulfate-promoted vanadium catalyst IK-1-6 in the process of oxidation of hydrogen chloride with molecular oxygen. Under conditions of low conversion (less than 15%) with the reaction in the external diffusion region, the catalyst activity attained 660 g/(kg cat h) at 400°C, and the mass loss rate of the catalyst was (due to the formation of volatile vanadyl chloride) 4.6 % per hour, based on vanadium. Under high conversion conditions (over 60%), the vanadyl chloride formed in the top layer of the catalyst was hydrolyzed and precipitated on subsequent layers as the conversion of the reaction mixture increased, leading to a redistribution of vanadium over the catalyst bed height and hindering its removal form the reactor. The stable operation of the catalyst can be ensured by intermittently changing the flow direction of the reactant gas in the catalytic reactor or using an array of several reactors connected in series, intermittently changing their places in the inlet-outlet chain. Our results show that the industrial sulfate-promoted vanadium catalysts for the oxidation of sulfur dioxide are more active and stable than all known catalysts of the Deacon process (except for ruthenium catalysts) and could be used for catalytic oxidation of hydrogen chloride.