加氢脱氮催化剂载体的研究

介绍了加氢脱氮催化剂载体的特点和性能,总结了加氢脱氮催化剂载体的发展趋势,提出了高活性加氢脱氮催化剂载体的研究思路和途径。     

A new approach to fluid separation modelling in the columns equipped with structured packings

An analogy between the flow patterns in real separation columns equipped with structured packing and film flow is used to develop a new modelling approach. The packing is represented as a bundle of channels with identical triangular cross section. The dimensions of the channels as well as their number are derived from the packing geometry. The channel inner surface is wetted by a liquid flowing downwards, whereas the rest of the volume is occupied by a countercurrent vapour flow. Both phases are assumed to be totally mixed at regular intervals, determined by the corrugation geometry of the packing. The mathematical model is based on a set of partial differential equations describing hydrodynamics and mass and heat transport phenomena. These equations are complemented by the conjugate boundary conditions at the phase interface. A numerical solution of the model yields velocity profiles as well as concentration and temperature fields throughout the column. The model is verified using experimental data for a binary distillation in a column equipped with Montz-Pak A3-500.     

Multiscale modelling strategy for structured catalytic reactors

Structured reactors, and especially arranged reactors, are multiscale systems, in which the design on the small scale essentially determines the macroscopic reactor behaviour. In the present contribution, we propose a modelling strategy for the design and optimisation of an arranged flat-bed reforming reactor. It consists of three model levels, each describing the structure of the reactor on a different scale and detail level. The elements of this hierarchy are consistent and compatible, which means that results obtained with one model can be transferred to the other models. The possible applications of this model hierarchy range from estimation of pressure drop coefficients up to the integration of the structured reactor into a process plant.     

Optimization of structured catalyst carriers for VOC combustion

Typical catalytic afterburners do not offer sufficient mass transport properties for volatile organic compounds (VOC) combustion. Therefore, displaying highly increased transport properties, short-channel microstructures of various geometries and wire gauze structures have been designed and evaluated as an alternative to monoliths. The structures have been deposited with Pd promoted cobalt oxide catalyst using Langmuir–Blodgett technique. The catalyst has proved to meet the specific requirements of VOC combustions and also not to change the microstructure geometry. According to the models of mass transfer proposed in this study, short-channel and gauze structures have up to 15 times higher mass transfer coefficients, and up to 90 times higher volumetric coefficients than standard monoliths. The results of experiments performed using the stacked wire gauze structure were in accordance with the results derived from modelling giving high convergence for higher Reynolds number values (>15). According to the evaluation criteria proposed by us, the majority of short-channel microstructures have shown very high mass transfer efficiency both in diffusional regime (40 times higher than monoliths) and in levelled diffusional and kinetic regime (over 20 times higher).     

交错型开窗导流填料的流体力学性能

为了提高规整填料通量,对传统开窗导流填料结构进行改善,提出一种新型交错式开窗导流填料。在不同喷淋密度下,采用空气-水系统对3种不同交错高度的开窗导流填料进行冷模实验,研究分析了其流体力学性能,并与传统开窗导流填料进行对比。实验结果表明:新型交错规整填料的压降随着喷淋密度的增加而增大,填料盘的交错式结构有效降低塔压降,提高通量,改善气液分布。与传统开窗导流填料相比,3种新型填料盘的干塔压降、湿塔压降显著降低,液泛气速显著提高。其中180-20型填料的压降降低最为显著,220-20型填料的液泛气速最低。同时,在LEVA模型和Bain-Hougen模型的基础上,获得了实验条件下干塔压降、湿塔压降和液泛气速的关联式,其计算结果与实验数据吻合较好。     

高通量催化精馏规整填料的流体力学性能

介绍了一种可应用于催化精馏工艺的高通量催化精馏规整填料(HCCP),并对其流体力学性能进行了研究与讨论。以空气-水物系为介质在内径为400 mm的冷模精馏塔内进行实验,测量了该填料的干湿塔压降、持液量等流体力学性能。高通量催化精馏规整填料在结构方面进行了改进,使催化剂装填量可控,实验结果表明:填料在降低塔内压降、增加通量方面具有明显优势。最后对实验数据进行回归,获得经验关联式;实验测量值与公式计算结果吻合较好,这表明,数据回归获得的关联式可用于预测一定操作条件下填料的流体力学性能,用于工业实践及设备放大。     

Carbon catalyst supports for oxidative decomposition of hydrogen sulfide

Carbon supports having various porous structures and compositions of the mineral matter were obtained. On the basis of the carbon supports, a number of catalyst samples were prepared via the decomposition of an iron complex adsorbed in support pores. The effect of the treatment mode during catalyst preparation on the formation of iron clusters in the porous volume of the support has been studied by means of Mössbauer spectroscopy. The catalysts deposited on carbon supports were tested in the decomposition of hydrogen sulfide.     

Preparation and characterisation of carbon-coated monoliths for catalyst supports

Carbon coated monoliths have been prepared by dipcoating cordierite monoliths in a polymer mixture and subsequent carbonisation and activation. Preparation parameters that were varied were viscosity of the dipcoating mixture, carbon precursor and carbonisation temperature. Two different polymers have been used as carbon precursors, Novolac and Furan resins. Also monoliths have been coated with slurry of these resins and a commercial activated carbon, CP-97. The features of the final carbon that have been optimised are carbon loading, carbon layer thickness, coverage and mesoporosity. Coverage has been tested by leaching tests in acid media and SEM analysis. Both coverage and mesoporosity are considerably enhanced when the dipcoating mixture was a slurry of Furan resin and activated carbon. Leaching of the cordierite was considerably reduced but not completely eliminated. The morphology of the activated carbon could be transferred to the coating layer.     

Hydrothermal stability of aluminophosphate catalyst supports

Alumina and aluminophosphate (AP) with Al/P ratio of 6 were subjected to hydrothermal treatment at 750 ° C for up to 48 h. The results indicate that AP had a higher hydrothermal stability than the -alumina. The pore size distribution and surface area of AP did not change much under hydrothermal conditions. The pore size distribution of alumina, on the other hand, shifted toward larger pore diameter accompaning with decreasing surface area upon deactivation.     

Role of catalyst supports in biocatalysis

Biocatalysis utilizes enzymes and microbial cells as catalysts for a wide range of applications in biotechnology. Immobilization of biocatalysts on various materials has several advantages, including the capacity for reuse, quick reaction termination, easy biocatalyst recovery and operational stability. The present article focuses on the use of material supports for developing immobilized biocatalysts in applications related to energy, environment and chemical synthesis. The work provides a comprehensive overview of a broad class of materials, including organic, inorganic and composites, that have been shown to be prosperous candidates to support the immobilization of enzymes and microbial cells. It also highlights the properties of nanomaterial support such as large surface area and comfort compartment for immobilization. The availability of different types of materials as catalyst support provides an opportunity to understand and develop efficient biocatalytic systems. The choice of selecting a catalyst support will mostly depend on the interaction of the material with the enzyme or microbial cell. Finally, potential challenges, future approaches in developing immobilized biocatalytic systems for various applications and novel material supports are suggested. © 2022 Society of Chemical Industry (SCI).     

Modelling of reactive stripping in monolith reactors

In this work, (reactive) stripping carried out in film flow monolith reactors developed for counter-current operation is investigated. Usually mass transfer in reactive separation has to be determined experimentally due to the complex flow patterns. However, monoliths have a simple geometry; only laminar flow is present throughout the column. This allows the calculation of the thickness of the liquid layer directly using Navier–Stokes equations. With this thickness known, the mass transfer can be calculated based on the convection in axial direction, diffusion in radial direction and vapour–liquid equilibrium. A model has been developed and implemented in Fortran^® based on the concept of a direct solution of convective diffusion equations, using the Thomas algorithm for solving the counter-current operation mode. Experimental data from literature have been used to validate the model for a binary and a multi-component system. The stripping of oxygen from saturated water by nitrogen was modelled assuming Fickian diffusion and vapour–liquid transfer based on the Henry constants. In a second step, multi-component diffusion and complex mass transfer at the interface were taken into account to describe the stripping of water by nitrogen from a mixture of hexyl-octanoate and cumene (solvent) under reactive stripping conditions.     

Novel methanol electro-oxidation catalyst assisting with functional phthalocyanine supports

Novel electro-catalyst based on phthalocyanine stabilized Pt colloids has been developed for methanol electro-oxidation. Water soluble Cu²⁺ phthalocyanine functioned with sulfonic groups were selected as catalyst supports because of the relatively high catalytic activity of Pt catalyst and nearly the same catalytic selectivity complex with Cu-phthalocyanine, compared to others that chelated with Fe, Co and Ni ions. The as-resulting Pt-CuTsPc catalysts have average particle size of 2 nm and narrow size distribution. With the assistance of CuTsPc supports, the methanol electro-oxidation activity and poison tolerance of Pt catalyst have a significant increase. I_f/I_b ratio (anodic peak current density, forward to backward) of the Pt-CuTsPc/C catalysts also has obvious increase to 2.5, from value of 0.8 for pure Pt/C catalyst. The reaction Tafel slope of Pt-CuTsPc/C catalysts is 56.6 mV dec⁻¹, much smaller than that of the Pt/C catalyst. The transient current density on Pt-CuTsPc/C at 0.60 V is enhanced to 650% of that on the Pt/C catalyst while the enhancement factor R for comparison of steady-state current obtained on Pt-CuTsPc/C and Pt/C catalyst varies between 111% and 534% in the potential region of 0.3-0.75 V.     

Alumina foam catalyst supports for industrial steam reforming processes

The manufacture and the characterisation of alumina foams as alternative catalysts supports for industrial steam reforming processes are presented here. The possibility of use of alumina foams as catalysts supports in such processes is evaluated by studying their resistance toward mechanical and chemical stresses. The alumina foams produced are characterised owing to their processing parameters (slurry infiltration, sintering temperature, template pore size). Their ability to work in hydrothermal atmosphere is assessed by characterising the evolution of microstructures and mechanical strengths upon aging. Thermodynamic studies of the stability of alumina in industrial steam reforming working conditions are performed and correlated to the experiments to demonstrate the stability of such a system.     

Additive manufacturing of periodic ceramic substrates for automotive catalyst supports

Additive manufacturing (AM) has the potential to revolutionize engineering because of its advantages in the product development phase. The revolution consists in the new approach of components’ design by function and no longer by manufacturability. This is the motivation driving authors to design and realize by additive manufacturing a new catalyst support for automotive exhausts which is no longer constrained by the industrial manufacturing methods and thus allows an optimized flow of the exhaust gasses. This work presents a new class of periodic cellular ceramic substrates. To authors’ knowledge this is the first time such kind of structures are employed in the automotive field. After a review the different ceramic AM techniques which are currently utilized in the production of highly complex ceramic architectures, the most suited one was selected and several samples were produced by AM. They were finally characterized via microscopic analysis (SEM, CT) compression tests revealing the best printing configuration for their mechanical behavior.     

抗水合氧化铝载体研究进展

氧化铝系载体用于含水或有水生成的催化过程时，均会发生再水合现象，从而造成催化剂强度的下降，并导致其比表面积大幅下降，使催化剂不可逆失活。镁铝尖晶石的抗水合性远高于氧化铝系载体，是一种很好的催化剂载体。综述了氧化铝系载体的再水合现象、改进载体抗水合性能的方法以及镁铝尖晶石粉体和载体的制备方法及改进措施。     

Claus尾气加氢催化剂载体研究进展

阐述了近年来Claus尾气加氢脱硫催化剂载体的研究现状。主要介绍了Al₂O₃和TiO₂单组分载体及Al₂O₃-TiO₂复合载体。Al₂O₃载体具有比表面积大、机械性能好和容易成型的特点,应用较广,但低温加氢活性较差;TiO₂载体具有较高的低温加氢和有机硫水解活性,但比表面积较小,一般以复合载体形式使用;复合载体具有较好的低温加氢活性和抗水性能,但制备工艺复杂。介孔结构不仅可以增大载体的比表面积,同时有利于分子的扩散,具有更加优异的活性。活性组分在复合载体表面呈现不同的活性状态,从而改变反应条件。如何调控Al₂O₃载体的孔道结构,研究复合载体各组分之间的作用及对活性组分的影响是今后的发展方向。     

Nanocasting of novel,designer-structured catalyst supports

Highly structured catalyst support pellets have been produced that possess multiple, but regiospecific and well-defined, pore geometries. Mesoporous silica pellets with controlled pore sizes have been synthesised using one type of pore template for the pellet core zone, whilst using a different type of template for the surrounding shell region. These materials offer the potential of adding precisely engineered diffusion barriers to the outside of structured catalyst supports, or providing different environments for pore structure-sensitive reactions in different parts of a catalyst pellet. The pore structures of the newly synthesised materials have been characterised using the recently introduced, integrated nitrogen sorption and mercury porosimetry technique. The data arising from the latter type of experiments on materials with cylindrical channels has been analysed using both the conventional BJH pore diameter technique, and also a new analysis method that can determine both the pore length distribution and interconnectivity. The transport properties of the new materials have also been assessed.     

A network theory for the structured modelling of chemical processes

A structuring methodology for dynamic models of chemical engineering processes is presented. The main ideas of the methodology were outlined in a previous publication for the class of well-mixed systems. In this contribution, the methodology is extended to spatially distributed systems and to particulate processes. Furthermore, the structuring principle is used to make a conceptual link between the macroscopic world of process simulation and the microscopic world of molecular simulation. It is shown that a uniform structuring principle can be applied to the modularisation of most classes of chemical engineering models. The structuring principle can be used as a theoretical framework for the implementation of modular families of chemical engineering models in modern computer aided modelling tools.