Conceptual design and CFD simulation of a novel metal-based monolith reactor with enhanced mass transfer

This paper introduces a novel structured metallic catalyst that improves mass transfer performance of a monolith reactor for highly exothermic gas–solid reactions. The monolith channels are designed to have metallic substrates that consist of two layers with one of the layers being the metallic support and another layer being a foam metal annular that is tightly deposited onto the support surface by some means. Parametrical studies based on a 2D monolith reactor model showed that the present design yields an enhanced mass transfer between the bulk fluid and the catalyst layer due to a decrease in external film resistance, and an enhanced mass transfer within the solid phase mainly due to the viscous flow effect within the porous catalyst layer.     

Catalytic combustion of methane in the presence of organic and inorganic compounds over La0.9Ce0.1CoO3 catalyst

The catalytic combustion of the emission from coke ovens containing various volatile organic compounds (VOCs) and inorganic species over a La_0.9Ce_0.1CoO₃ catalyst is investigated in an integral fixed reactor through several steps. (1) Combustion of a mixture of VOC reveals that the kinetics of total oxidation of methane determines the total VOC conversion. (2) The conversion of methane, in the case of sulfur-free feed is inhibited by H₂O and CO₂.     

钙钛矿型催化剂去除VOC的性能研究

挥发性有机化合物（VOCs）是大气的主要污染物之一,催化燃烧法是目前研究的处理VOCs的有效方法之一。本研究基于VOCs的催化燃烧进行,用浸渍法制备了性能优良的负载型稀土钙钛矿催化剂La0.8Sr0.2MnO3,以气相色谱为检测手段,用常压气体流动评价装置研究该催化剂对低浓度（100~1000mg/m3）VOC（甲苯）催化燃烧的去除效果。     

催化燃烧技术在石化企业VOCs处理中的进展

催化燃烧技术是目前工业上最有效的处理低浓度挥发性有机物（VOCs）技术之一.文章介绍了石化企业催化燃烧技术中常用催化剂活性和载体,综述了近年来VOCs催化燃烧催化剂的国内外研究近况,指出未来可以应用到工业化中的新兴催化剂.     

MnCu Catalyst Deposited on Metallic Monoliths for Total Oxidation of Volatile Organic Compounds

Abstract  

The MnCu mixed catalyst with a Mn:Cu = 9:1 molar ratio prepared by coprecipitation method was deposited by washcoating on a FeCrAlloy monolith (FM-W). On the other hand, an anodized aluminum monolith was impregnated with an aqueous solution of manganese and copper acetates in Mn:Cu = 9:1 molar ratio (AM-2IS). The structured catalysts were evaluated in volatile organic compounds (VOCs) combustion. The effects of the deposition methods used and the nature of the structured supports on the catalytic activity were observed. The FM-W monolithic catalyst and the Mn9Cu1 powder catalyst showed the same catalytic behavior for the combustion of all VOCs tested. The influence of the nature of structured support was not observed. The AM-2IS monolithic catalyst showed a slightly higher catalytic activity in most of the tested molecules, than FM-W catalyst. The effect of the substitution of orbital stirring by recirculation during the impregnation process on the loading of the deposited phase, and its effect on the catalytic activity were observed.     

The hydrogenation of isophorone to trimethyl cyclohexanone using the downflow single capillary reactor

Despite many innovations in the intensification of catalytic multiphase reactors for the small and medium scale manufacture of chemicals, there have as yet been relatively few commercial successes. One reason for this might be that many of these developments inherently incorporate a fixed catalyst, which may not suit an industry that is based on principles of batch manufacture and multi-product plant. This study evaluates an intensified reactor that encompasses the opportunities demonstrated from structured flows and thin channels, together with a mobile, slurry catalyst, namely a capillary reactor with gas/liquid/suspended catalyst flow. A downflow single capillary reactor (SCR) was designed, built and evaluated for the selective hydrogenation of isophorone to trimethyl cyclohexanone using commercial Pd- and Rh-based catalysts. Using the single capillary arrangement, the reaction was shown to be operating under kinetic control.

Comparison of the rate of hydrogenation with autoclave showed a significant increase of the reaction rate when capillary reactor was used. The temperature of reaction is a crucial factor in tuning the reaction towards different products. The constant relative reaction rate obtained for different catalyst loading as well as the calculated value of the apparent activation energy show that the reaction of hydrogenation of isophorone is not mass transfer limited in the single capillary reactor.     

流向变换催化燃烧反应器的可操作性

在流向变换催化燃烧小型中试装置上利用国产催化剂进行了含混合芳烃模拟工业废气的净化试验,重点考察了挥发性有机物 (VOCs)能够通过调整换向周期在既不“飞温”也不“熄火”的条件下保持很高的VOCs转化率的浓度变化范围,初步观察了由于VOCs浓度过高或过低所引起的“飞温”或“熄火”过程.     

Influence of the heat exchangers’ construction material on catalytic incineration

In industrial scale catalytic volatile organic compounds (VOCs) incineration it is sometimes observed that the VOC conversions are higher than expected, based on the laboratory scale experiments at the same temperatures. One reason for this is that the construction material of the industrial scale catalytic incinerator may have an effect on the total VOC conversion. In this study, the effect of construction material on VOC removal activity is studied through laboratory experiments, by thermodynamic calculations and by flow modelling. The results showed that copper and Aluzinc decreased the light-off temperature (T₅₀) of n-butyl acetate compared to thermal experiments. Copper and Aluzinc did not, however, further decrease the T₅₀ when they were introduced into the reactor packed with the catalyst. The higher total VOC conversion observed in the industrial scale incinerator is presumably due to the higher temperatures at the outlet of the catalyst, which is maintained by the heat exchangers.     

Comparison of different reactor types for low temperature Fischer-Tropsch synthesis: A simulation study

The commercially established slurry bubble column and fixed-bed reactors for low temperature Fischer-Tropsch synthesis were compared with novel micro- and monolith-reactors by mathematical modeling. Special attention was paid to the influence of catalytic activity on the reactor efficiency and the losses by mass and heat transfer resistances. The simulation results show that a micro-structured reactor exhibits the highest productivity per unit of catalyst volume followed by slurry bubble column reactor and monolith reactor. The fixed-bed reactor that was assumed to operate in the trickle-flow regime has a particularly low catalyst specific productivity due to severe mass transfer resistances. However, caused by a very low ratio of catalyst and reactor volume the micro-reactor has only a similarly low productivity per unit of reactor volume as the fixed-bed reactor. In contrast, the reactor specific productivity of slurry bubble column reactor and monolith reactor is up to one order of magnitude higher.     

整体构件型La_(0.8)Sr_(0.2)MnO_3催化剂的制备和催化燃烧特性

为了解不同整体构件钙钛矿催化剂的VOCs催化燃烧特性,以不锈钢316L丝网和堇青石蜂窝陶瓷为基材,通过电泳沉积和浸涂技术在基材表面均匀涂覆γ-Al_2O_3粘合层,再在涂层表面负载钙钛矿型2.0%(wt)的La_(0.8)Sr_(0.2)MnO_3活性组分.SEM表征发现100 nm左右的La_(0.8)Sr_(0.2)MnO_3颗粒可以均匀、牢固地分散在不锈钢丝网和蜂窝陶瓷表面,经过550℃焙烧后无龟裂现象.超声振荡30 min后,活性组分损失率均小于5.0%(wt).甲苯催化燃烧测试表明,金属丝网型、蜂窝陶瓷型和颗粒型La_(0.8)Sr_(0.2)MnO_3催化剂表现出相似的催化性能,但金属丝网具有更好的传质效果和热响应速率,更适合处理高空速、温度和浓度波动较大的有机废气.     

Shouldn’t catalysts shape up?: Structured reactors in general and gas–liquid monolith reactors in particular

In this paper, the advantage of structuring catalytic reactors is discussed. In structured systems, the exact shape of all column internals is determined by design rather than chance. This results in two advantages for the engineer in charge of designing a reactor: (1) the structuring introduces additional characteristic length scales, leading to new degrees of freedom that allow decoupling of phenomena that otherwise would need a sub-optimal compromise and (2) full control over the entire geometry results in higher precision. Taking full control over the geometry boosts performance, especially if the catalyst is tailored to the reactor design.The monolith structure is the best-known example of a structured catalyst. We discuss the industrial benefits and practical pitfalls of this honeycomb of parallel capillaries that allows the advantages of microfluidics to be applied on an enormous scale. In this paper it is argued that the monolith is most suitable for processes that are (1) stable enough for packed-bed operation and (2) need better mass transfer than can be obtained in any conventional reactor, including the trickle bed and the stirred tank reactor. This includes several large-scale processes such as HDS. Fine chemical synthesis, where the objective of robust scale-up and predictability will never be met using stirred tanks, may equally benefit from the scalable ultra-high mass transfer that is obtained in monoliths.     

A Comparison Between Monolithic and Wire Gauze Structured Catalytic Reactors for CH4 and CO Removal from Biogas-Fuelled Engine Exhaust

The application of the wire gauzes as the catalytic supports can provide a number of advantages in biogas exhaust abatement. In this paper, a model of wire gauze structured reactor for biogas exhaust removal is proposed and model based calculations are performed to compare the wire gauze catalytic reactor with the classic monolith. The modelling bases on kinetic data experimentally obtained in a small-scale tubular reactor for cobalt and palladium (as reference) oxide catalysts doped with promoters (Ce, Pd). The heat and mass transfer characteristics of the wire gauze reactor are taken from the former studies by the authors. The simulations show that for assumed reactor parameters, a combination of the promoted cobalt oxide catalyst and the wire gauze support can give high conversion of methane and carbon monoxide.     

Performance of the monolithic stirrer reactor: applicability in multi-phase processes

The novel monolithic stirrer reactor is a promising replacement for a conventional slurry reactor in multi-phase reactions. In this reactor monolithic structures are used as stirrer blades, creating a catalytic stirrer. The most important advantage of the monolithic stirrer reactor is the easy catalyst handling. The influences of different parameters on the performance of the monolithic stirrer reactor in the selective hydrogenation of 3-methyl-1-pentyn-3-ol were investigated. The decreasing catalyst layer thickness with increasing cell density proved to be beneficial for the performance of the monolithic stirrer reactor. An increasing stirrer speed caused an increase in the activity because of the higher flow through the monolith channels and the improved gas–liquid mass transfer. If the length of the monolithic stirrer blades was smaller than 0.03 m the performance of the monolithic stirrer was enhanced.     

A catalytic combustion technology of concentrated VOCs in textile coating process

We developed a new process employing catalytic combustion for textile coating aimed at decreasing emissions of volatile organic compounds (VOCs) and saving energy at the same time. For this purpose, the VOCs are concentrated in a temperature swing adsorption (TSA) device. A fraction of the concentrated VOCs is completely oxidized on an electrically heated (EHC) system, and its combustion gas of EHC is supplied as the heating source via heat exchangers. The remaining concentrated VOC is recycled as a renewable energy source for the drying process to dual-type catalytic burners designed specially to operate with LPG and concentrated VOC at the same time. This system minimizes the problem of VOC emission and maximizes energy conservation by reusing the VOC, toluene, from textile coating.     

Removal of VOCs from gas streams via plasma and catalysis

Emission of volatile organic compounds (VOCs) has resulted in various environmental issues. Therefore, development of effective VOC removal technology is essential for reducing the adverse effects associated. This work provides a systematic review on VOC removal from gas stream via catalytic oxidation, plasma degradation, and plasma catalysis. For catalytic oxidation of VOCs, possible reaction mechanisms and how physicochemical properties of catalyst influences catalytic performance are presented and discussed, followed by plasma removal of VOCs, VOC degradation, and byproduct formation mechanisms. Next, interactions between plasma and catalyst are interpreted for comprehensive understanding. Last, perspectives are provided for further development of VOC removal technology.     

Catalytic combustion of VOCs on non-noble metal catalysts

Volatile organic compounds (VOCs) are toxic and contribute significantly to the formation of the photochemical smog, which has remarkable impact to the air quality; therefore, the research on the removal of VOCs has attracted increasing interests during the last decade. This review covers the recent developments in catalytic combustion of VOCs over non-noble metal catalysts including mixed metal oxide catalysts, perovskite catalysts and Au-containing catalysts. The effect of water vapor, coke formation and the effect of supports on the catalytic combustion process will be discussed. The concept of an adsorption/catalytic combustion dual functional system is introduced and several examples of such systems are evaluated. To develop efficient and cost effective VOC removal technologies, further research in catalytic combustion needs to develop novel non-noble metal catalysts and adsorbents, and improve the understanding of catalytic mechanisms involved.     

燃烧处理挥发性有机污染物的研究进展

随着环境问题的日益严重,治理作为PM_2.5前体的挥发性有机物（VOCs）越来越受到重视,燃烧法是目前常用的处理VOCs污染物技术之一。本文从燃烧的机理出发综述了燃烧法处理VOCs的研究进展,将燃烧法分为两大类,即非催化燃烧法和催化燃烧法。非催化燃烧法中从燃烧方式出发,总结了直接燃烧法、蓄热式热力燃烧法、多孔介质燃烧法的研究进展,并对燃烧影响因素进行了综述。在催化燃烧法中阐述了贵金属催化剂、非贵金属催化剂和复合金属氧化物催化剂的研究进展,探讨了催化剂的失活问题,分析了每种催化剂的优势与不足。贵金属催化剂活性高,但是价格昂贵、稳定性差;非贵金属催化剂价格低廉、寿命长,但是起燃温度高;复合金属氧化物催化剂活性高、抗毒性强,但是制备工艺复杂。最后基于目前的研究现状和不足,展望了未来燃烧法处理VOCs的研究方向为：结合实际应用的工艺条件和催化燃烧的机理,制备出活性高、价格低廉、抗毒性强和寿命长的催化剂用于蓄热式催化燃烧技术;将催化燃烧和多孔介质燃烧相结合,开发出高效、稳定、经济的燃烧技术处理VOCs污染物。     

Anodic Alumina Supported Pt Catalyst for Total Oxidation of Trace Toluene

Featuring an assembly of identical pores, through-pore anodic alumina (AAO) makes an ideal monolith-like cat-alyst support for volatile organic compound (VOC) combustion. This work employs the oxidatio...     

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.     

Oxygen vacancy engineering on copper-manganese spinel surface for enhancing toluene catalytic combustion: A comparative study of acid treatment and alkali treatment

Copper-manganese spinel is a low-cost VOCs catalytic combustion catalyst with good performance. Oxygen vacancy has excellent properties for oxygen activation and VOCs dehydrogenation activation, which is beneficial for the catalytic combustion of VOCs. In this study, a large number of oxygen vacancies were introduced on the copper-manganese spinel surface by selective dissolution method (acid treatment and alkali treatment) for catalytic combustion of toluene. Furthermore, the effects of acid treatment and alkali treatment on the catalytic performance, oxygen vacancy amount, physical and chemical properties, and toluene catalytic combustion mechanism of copper-manganese spinel were studied. Both acid treatment and alkali treatment can produce large quantities of oxygen vacancies on the copper-manganese spinel surface. The generation of surface oxygen vacancies can greatly improve the catalytic combustion activity of copper-manganese spinel. At 240 °C, the combustion rate of toluene increased by 8.8 times for the acid-treated catalyst and 11.2 times for the alkali-treated catalyst. The numerous surface oxygen vacancies, Mn³⁺/Mn⁴⁺ at the ratio of 1.11 and appropriate acidity result in the alkali-treated catalyst exhibiting excellent catalytic activity and stability for toluene combustion. This strategy provides a new method to further improve catalytic combustion activity of copper-manganese spinel and a reference for the development of the surface oxygen vacancy engineering of transition metal oxides.