Catalyst deactivation Common causes

Applied Catalysis A: General, 2001

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 threefold: 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.

Catalysts, 2019

Catalyst life-time represents one of the most crucial economic aspects in most industrial catalytic processes, due to costly shut-downs, catalyst replacements and proper disposal of spentmaterials[...]

In this article a study about catalyst regeneration is been put forward. A study of how catalyst regeneration is done, why there is a need of regeneration and also about catalyst deactivation mainly in refinery processes. Catalyst Regeneration is widely used in many industries by in-situ or ex-situ methods as an economical beneficial technique for processes. In this article I have also shared some important test done on catalyst before they are used in a specific process. Catalyst Regeneration is mainly seen where the spent catalyst is costly

Russian Journal of Physical Chemistry A, 2011

Problems of catalyst deactivation kinetics and catalyst stability testing are considered. An appar ent delay of deactivation and its interpretation is discussed. The coordinates of inflection points on the curves of conversion decay are also considered. The influence of reaction and deactivation kinetics, as well as type of laboratory reactor on inflection point is analysed. Several helpful and practical equations, as well as real examples are presented.

Catalysts, 2015

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.

ChemInform, 2011

Solving the problem of catalyst deactivation is essential in process design. To do this, various aspects of the kinetics of processes with catalyst deactivation, and their different mechanisms, are discussed. Catalyst deactivation often cannot be avoided, but more knowledge on its mechanism can help to find kinetic means to reduce its harmful consequences. When deactivation is caused by coke, the generation of coke precursors is the determining step in the deactivation kinetics. Different types of deactivation were distinguished that lead to different evolution of the process. The phenomenon of non-uniform coking can be linked to catalyst surface non-uniformity. For the class of catalysts with more than one type of active sites, an explanation was suggested for the observed trends in the deactivation modes. For catalytic processes using catalyst particles of industrial size, the influence of intraparticle diffusion resistance is important. The analysis showed that for a number of processes, the decrease of the reaction rate due to deactivation is less under diffusion control. For certain reaction mechanisms, there exist operation conditions where the rate of the process under diffusion control exceeds the rate in the kinetic control regime. A significant problem is the change of selectivity in the course of catalyst deactivation. The selectivity may either decrease or increase, and depends on the reaction mechanism during deactivation. The changes are larger when there is no diffusion resistance. The intentional poisoning of catalysts and its influence on catalyst activity and selectivity for the process of ethylene oxide production was discussed.

Kinetics and Catalysis, 2005

Problems arising in kinetic studies of catalyst deactivation and in catalyst stability tests are considered. The choice and substantiation of deactivation conditions, the primary analysis and interpretation of experimental data, and the construction of a kinetic model of deactivation are illustrated by examples. Accelerated deactivation for quick catalyst stability testing is discussed. z° b Ol 0 View publication stats View publication stats

Chemical Engineering Science, 1980

The deactlvatlon of a catalyst by coke deposItIon IS described m terms of two mechamsms site coverage and pore blockage The blockage IS caused by coke growmg from a precursor covenng a site Prewous work by the authors considered the rate of growth of the coke to be mfimte, but the present paper generalizes the theory to allow for finite rates The relation between the deactlvatlon functron and the coke content IS denved for single ended pores, for pores open at both ends and for networks of pores 1 lNTRODUCTlON

Catalysts, 2015

Catalyst deactivation, the loss over time of catalytic activity and/or selectivity, is a problem of great and continuing concern in the practice of industrial catalytic processes. Costs to industry for catalyst replacement and process shutdown total tens of billions of dollars per year. While catalyst deactivation is inevitable for most processes, some of its immediate, drastic consequences may be avoided, postponed, or even reversed through regeneration. Accordingly, there is considerable motivation to better understand catalyst decay and regeneration. Indeed, the science and technology of catalyst deactivation and regeneration have been developing rapidly as evidenced by the considerable literature addressing these topics, including about 24,000 journal articles, presentations, reports, reviews, and books; and more than 33,500 patents for the period of 1980 to 2015. About 15% of this literature appeared in the last three years, a rate of growth double that of the past 35 years. New insights into the science of catalyst deactivation and regeneration are laying the foundation for new developments in the technology, e.g., for substantial improvements in catalyst stability and catalyst deactivation models leading to better process economics, and more effective regeneration processes. Research and development activities in catalyst deactivation and regeneration range over a broad spectrum, which includes (1) fundamental and applied studies of deactivation and regeneration at the nano, micro, and reactor scales to understand mechanistic, process, and catalyst chemistries; (2) laboratory reactor studies of deactivation and regeneration rates to develop reaction kinetics and process variable-rate relationships important in scale-up; and (3) development of models of deactivation and regeneration processes at the catalyst surface, pellet, reactor, and process scales for controlling, optimizing, and scaling-up these processes.