Chemical Engineering Science 59 (2004) 5663 – 5669 www.elsevier.com/locate/ces Adsorption and catalytic reaction in FCC catalysts using a novel fluidized CREC riser simulator Jesus A. Atias, Hugo de Lasa ∗ Department of Chemical & Biochemical Faculty of Engineering, Chemical Reactor Engineering Centre, University of Western Ontario, Richmond street, London, Ont., Canada N6A 5B9 Received 1 March 2004; received in revised form 22 June 2004; accepted 11 July 2004 Available online 25 September 2004 Abstract The present manuscript offers new insights into the fundamental mechanisms of catalytic cracking. Adsorption and diffusion are studied under reaction conditions similar to those of fluid catalytic cracking (FCC); an approach advancing the study of adsorption and diffusion of reactants on zeolitic catalysts. This method surpasses traditional studies done at low temperatures under low or no reactivity conditions. Experiments are performed in a novel fluidized CREC riser simulator using FCC catalysts of various crystallite sizes. Different catalyst operating regimes are observed under simultaneous chemical species adsorption, reaction, and diffusion.  2004 Elsevier Ltd. All rights reserved. Keywords: Adsorption; Diffusion; Kinetics; Modelling; Reaction engineering; Zeolites 1. Introduction Fluid catalytic cracking (FCC) of hydrocarbons is still among the most important technologies in the refining in- dustry. FCC is the most important and profitable process in petroleum refining industry, converting low-value heavy oils into more valuable products like gasoline, light cycle oil, and lighter products (Marcilly, 2003). Central to a successful catalytic process is the develop- ment of an effective catalyst, which is often a complex sys- tem in terms of both composition and functionality ( Ying, 2000). A wide range of catalysts is available from catalyst manufacturing companies. FCC catalysts are in the form of fine powders with an average particle size in the range of 75 m. A modern catalytic cracking catalysts has four major components: zeolite, matrix, binder, and filler (Sadeghbeigi, 2000). Zeolites employed in the manufacture of the FCC cata- lysts are synthetic versions of naturally occurring zeolites called faujasites. The structure of these zeolites consists in ∗ Corresponding author. Tel.: +1-519-661-2144; fax: +1-519-661-3498. E-mail address: hdelasa@eng.uwo.ca (H. de Lasa). 0009-2509/$ - see front matter  2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.ces.2004.07.100 supercages (sorption cavity) that are sufficiently large for an inscribed sphere with a diameter of 12 ˚ A. The opening into these large cavities is 12-membered oxygen ring with a 7.4 ˚ A free diameter (Bhatia, 1990). Each cavity is connected to four other cavities, which are themselves connected to three- dimensional cavities to form a highly porous framework structure. In catalysts with inactive matrices, only the zeolite determines the activity and selectivity of the catalyst. A considerable amount of research has been done and progress has been made with respect to FCC. Yet, the need still remains for an in-depth understanding of the simulta- neous effects of adsorption, reaction, and diffusion. Toward that end, current research targets a deeper understanding of the fundamental mechanisms of catalytic cracking reactions. It also fills a relevant void in the technical literature regard- ing the adsorption and diffusion of hydrocarbons in zeolite catalysts under relevant conditions of industrial fluid cat- alytic cracking units. 2. Experimental apparatus Catalytic cracking reactions of 1,3,5-triisopropylbenzene were performed in a CREC riser simulator using FCC