The literature treating mechanisms of catalyst deactivation is reviewed. Intrinsic mechanisms of catalyst deactivation are many; nevertheless, they can be classified into six distinct types: (i) poisoning, (ii) fouling, (iii) thermal degradation, (iv) vapor compound formation accompanied by transport, (v) vapor-solid and/or solid-solid reactions, and (vi) attrition/crushing. As (i), (iv), and (v) are chemical in nature and (ii) and (v) are mechanical, the causes of deactivation are basically three-fold: chemical, mechanical and thermal. Each of these six mechanisms is defined and its features are illustrated by data and examples from the literature. The status of knowledge and needs for further work are also summarized for each type of deactivation mechanism. The development during the past two decades of more sophisticated surface spectroscopies and powerful computer technologies provides opportunities for obtaining substantially better understanding of deactivation mechanisms and building this understanding into comprehensive mathematical models that will enable more effective design and optimization of processes involving deactivating catalysts. © 2001 Elsevier Science B.V. All rights reserved.

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Mechanisms of catalyst deactivation

In this review, the progress made in the last ten years concerning the synthesis of porous carbon materials is summarized. Porous carbon materials with various pore sizes and pore structures have been synthesized using several different routes. Microporous activated carbons have been synthesized through the activation process. Ordered microporous carbon materials have been synthesized using zeolites as templates. Mesoporous carbons with a disordered pore structure have been synthesized using various methods, including catalytic activation using metal species, carbonization of polymer/polymer blends, carbonization of organic aerogels, and template synthesis using silica nanoparticles. Ordered mesoporous carbons with various pore structures have been synthesized using mesoporous silica materials such as MCM-48, HMS, SBA-15, MCF, and MSU-X as templates. Ordered mesoporous carbons with graphitic pore walls have been synthesized using soft-carbon sources that can be converted to highly ordered graphite at high temperature. Hierarchically ordered mesoporous carbon materials have been synthesized using various designed silica templates. Some of these mesoporous carbon materials have successfully been used as adsorbents for bulky pollutants, as electrodes for supercapacitors and fuel cells, and as hosts for enzyme immobilization. Ordered macroporous carbon materials have been synthesized using colloidal crystals as templates. One-dimensional carbon nanostructured materials have been fabricated using anodic aluminum oxide (AAO) as a template.

Recent Progress in the Synthesis of Porous Carbon Materials

In the last years membrane processes for gas separation are gaining a larger acceptance in industry and in the market are competing with consolidated operations such as pressure swing absorption and cryogenic distillation. The key for new applications of membranes in challenging and harsh environments (e.g., petrochemistry) is the development of new tough, high performance materials. The modular nature of membrane operations is intrinsically fit for process intensification, and this versatility might be a decisive factor to impose membrane processes in most gas separation fields, in a similar way as today membranes represent the main technology for water treatment. This review highlights the most promising areas of research in gas separation, by considering the materials for membranes, the industrial applications of membrane gas separations, and finally the opportunities for the integration of membrane gas separation units in hybrid systems for the intensification of processes.

Membrane Gas Separation: A Review/State of the Art

http://bioprocesos.unq.edu.ar/Biopro%20II/Paper%20escalado.pdf

Bioreactor scale-up and oxygen transfer rate in microbial processes: An overview

Deactivation of heterogeneous catalysts is a ubiquitous problem that causes loss of catalytic rate with time. This review on deactivation and regeneration of heterogeneous catalysts classifies deactivation by type (chemical, thermal, and mechanical) and by mechanism (poisoning, fouling, thermal degradation, vapor formation, vapor-solid and solid-solid reactions, and attrition/crushing). The key features and considerations for each of these deactivation types is reviewed in detail with reference to the latest literature reports in these areas. Two case studies on the deactivation mechanisms of catalysts used for cobalt Fischer-Tropsch and selective catalytic reduction are considered to provide additional depth in the topics of sintering, coking, poisoning, and fouling. Regeneration considerations and options are also briefly discussed for each deactivation mechanism.

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Heterogeneous Catalyst Deactivation and Regeneration: A Review

Factors affecting the reactivity of coal chars during gasification, and indices representing reactivity

Heat Transfer in Aerated Tower Filled with Non-Newtonian Liquid

A process for producing a higher-fructose syrup containing more than 50% fructose was developed that involves a new system combining selective adsorption of fructose and an immobilized glucose isomerase reaction. Continuous countercurrent contact of the liquid stream with the solid adsorbent is simulated by advancing adsorption columns against the fixed inlets and outlet of liquid streams without actual movement of the solid adsorbent, while the immobilized enzyme reactors are stationary. Two mathematical models, an intermittent moving-bed and a continuous moving-bed model, are presented for calculation the concentration profiles of glucose and fructose in the system. The validity of the models is experimentally confirmed, and a criterion for good production in the system is presented. This system requires less desorbent than a process using a fixed-bed adsorber and a simulated moving-bed process to produce the syrup with 45-65% fructose content, the level desired in food manufacture.

A new process combining adsorption and enzyme reaction for producing higher-fructose syrup.

The continuous separation of a glucose/fructose mixture was experimentally performed using a simulated moving-bed adsorber packed with the Ca2+ ion form of Y zeolite. In the adsorber, the continuous and countercurrent contact of the liquid stream with the solid adsorbent is simulated by advancing adsorption columns against the fixed inlets and outlets of liquid streams, without actual movement of the solid adsorbent. Two mathematical models, i.e., an intermittent moving-bed and a continuous moving-bed type, are presented for calculating the concentration profiles of glucose and fructose in the simulated moving-bed adsorber. The validity of the models is experimentally confirmed, and a criterion for good separation in the simulated moving-bed adsorber is presented.

Models for the separation of glucose/fructose mixture using a simulated moving-bed adsorber

The reduction of copper oxide thin films by a hydrogen plasma generated by an atmospheric-pressure glow (APG) discharge was investigated. The copper oxide films were prepared by heating the sputtered copper films to C in the air (heat-formed copper oxide) or by sputtering (sputtered copper oxide). Both films were composed of . The reduction occurs first on the surface, then the interface gradually shifts from the surface into the inner region and finally the whole layer is reduced to metallic copper. This process is approximately explained by assuming that the diffusion of the atomic hydrogen in the reduced layer is the rate-deyermining step. By transmission electron microscopic (TEM) observation, a layer of 3 - 5 nm thickness composed of many microcrystals was observed along the surface of the heat-formed copper oxide. After the APG hydrogen plasma treatment, the crystal layer disappeared and the crystalline lattice was re-arranged to form large crystal Cu grains.

https://iopscience.iop.org/article/10.1088/0022-3727/29/10/003/pdf

Kenji Hashimoto

Papers

Factors affecting the reactivity of coal chars during gasification, and indices representing reactivity

Heat Transfer in Aerated Tower Filled with Non-Newtonian Liquid

A new process combining adsorption and enzyme reaction for producing higher-fructose syrup.

Models for the separation of glucose/fructose mixture using a simulated moving-bed adsorber

The reduction of copper oxide thin films with hydrogen plasma generated by an atmospheric-pressure glow discharge