Jens Hagen Industrial Catalysis

2021

The three-factor kinetic equation of catalyst deactivation was obtained in terms of apparent kinetic parameters. The three factors correspond to the main cycle with a linear, detailed mechanism regarding the catalytic intermediates, a cycle of reversible deactivation, and a stage of irreversible deactivation (aging), respectively. The rate of the main cycle is obtained for the fresh catalyst under a quasi-steady-state assumption. The phenomena of reversible and irreversible deactivation are presented as special separate factors (hierarchical separation). In this case, the reversible deactivation factor is a function of the kinetic apparent parameters of the reversible deactivation and of those of the main cycle. The irreversible deactivation factor is a function of the apparent kinetic parameters of the main cycle, of the reversible deactivation, and of the irreversible deactivation. The conditions of such separability are found. The obtained equation is applied successfully to desc...

AIChE Journal, 1988

A large number of studies on the effectiveness of a partially wetted catalyst particle have appeared in the literature (for example, . With the exception of work by Goto et al., all these earlier studies considered only a bimolecular reaction with pseudofirst-order kinetics; i.e., first order with respect to the limiting reactant and zero order for the excess reactant. Goto et al. used pseudo-nth-order kinetics. Recently, Beaudry et al. (1987) and Harold and Ng (1 987) demonstrated that pseudofirst-order kinetics can be misleading in that depletion of the supposedly abundant (zeroorder) reactant may occur within the pellet. Also recently, suggested that bimolecular kinetics, first order with respect to each reactant, is essential for hydrodesulfurization processes.

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.

Chemical Engineering Science, 2003

iii iv This evolution does present the drawback, however, of increasingly hiding the global and general aspects of the problems. One of the major advantages of analytical solutions is the way in which they can provide insight in these aspects, e.g., by analyzing the limiting behavior of solutions. It is therefore not surprising that we witness today a renewal of interest in analytical methods, which is further supported by the wide availability of symbolic manipulation and computer algebra.

Journal of Catalysis, 2003

The present paper deals with a "reactivity approach" to complex catalytic reactions. It utilizes data obtained with a reactor and demonstrates the very important role of both rate constants and concentrations of adsorbed species, on catalytic cycle, activity, and selectivity. It develops a link between global kinetics and closed sequence of elementary steps. It emphasizes the aspects of "assisted" catalytic reactions, kinetic "coupling" of catalytic cycles, and selectivity.

International Journal of Chemical Kinetics, 2016

Non-steady-state kinetic measurements contain a wealth of information about catalytic reactions and other gas-solid chemical interactions, which is extracted from experimental data via kinetic models. The standard mathematical framework of microkinetic models, which are typically used in computational catalysis and for advanced modeling of steady-state data, encounters multiple challenges when applied to non-steady-state data. Robust phenomenological models, such as the steady-state Langmuir-Hinshelwood-Hougen-Watson equations, are presently unavailable for non-steady-state data. Herein, a novel modeling framework is proposed to fulfill this need. The rate-reactivity model (RRM) is formulated in terms of experimentally observable quantities including the gaseous transformation rates, concentrations, and surface uptakes. The model is linear with respect to these quantities and their pairwise products, and it is also linear in terms of its parameters (reactivities). The RRM parameters have a clear physicochemical meaning and fully characterize the kinetic behavior of a specific

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

Catalysis today, 1999