Louis Hegedus

Reaction engineering for catalyst design

Abstract The development of new or improved catalysts is an interdisciplinary effort. Reaction engineering, via mathematical models, can identify key catalyst design variables and quantify their optimum values. By providing this type of qualitative and quantitative guidance, reaction engineering has vastly accelerated the development of new catalysts in many instances. This paper identifies frontier areas of investigation and suggests opportunities for the future.

Computer-aided design of catalytic monoliths for automobile emission control

Abstract Automotive exhaust emission control catalysts are now in widespread commercial use in the U.S. and Japan, with rapid growth in Europe. The majority of these catalysts is of the monolith type. There is an ongoing interest in improving the durability performance of these catalysts in the presence of poisons. This paper describes the use of mathematical modeling as a tool for the design and optimization of monolith-type catalysts. The model has been used together with an optimization procedure to maximize the steady-state diffusion-controlled catalytic performance of a monolith-type catalyst after 1000 h of operation in the presence of poisons. The algorithm predicts optimum values of several important catalyst design variables (including washcoat thickness and pore structure) and monolith physical properties (such as channel size, wall thickness, and overall aspect ratio). Experimental data are presented for three-way monolith catalysts prepared with washcoats of differing pore structure and aged in the presence of typical exhaust poisons. The model properly ranks the observed differences in poison resistance for these washcoats and demonstrates its utility as a tool in the development of improved catalysts.

A Novel Catalyst Geometry for Automobile Emission Control

Abstract The catalytic control of automobile exhaust pollutants (hydrocarbons, carbon monoxide, nitrogen oxides) is now a common practice in the United States and Japan, and there are strong indications that the technology may be introduced in other parts of the world in the coming years. The simultaneous conversion of all three of the above pollutants is achieved by the near-stoichiometric operation of noble metal catalysts which are supported either on alumina particles or on alumina-washcoated cordierite monoliths, A summary of the developments which lead to this technology can be found, e. g., in Hegedus and Gumbleton [1] and references therein.

12 Catalyst Design

Publisher Summary Chemical reaction engineering is a way of integrating chemical and physical phenomena into systematic models of catalyst performance. These models have to contain parameters with physical and chemical meaning; their optimum combination would then yield the optimum design for a catalyst. There are strong economic forces that demand rational methods for the development of new catalysts. Driving forces that demand more efficient methodologies for catalyst development include new business opportunities, the high cost of empirical developments, and the increasing competitiveness in the catalyst industry, which demands speedier routes toward commercialization. Several advances promise to replace certain types of catalytic experimentation by mathematical modeling. Ideally, optimum design requires the identification of the pertinent design variables, the identification of the objective function or functions to be maximized or minimized, and the identification of bounds on the design variables to satisfy a set of constraints, implicit and explicit. This chapter illustrates an example of the catalytic control of NO x emissions from fossil fuel-fired electric power generating facilities that use selective catalytic reduction (SCR) process.