Catalytic cracking, octane enhancement

Until the recent discovery of UTD-1 and CIT-5, the largest pore zeolites known were composed of pore structures having 12-MRs or less. Many of these materials such as zeolite Y have enjoyed immense commercial success as catalysts (2). There is some evidence from catalytic cracking data that suggests the inverse selectivity found with the 12-MR pore ( 7.5 A) structure such as for SSZ-24 (Chevron) might be used to enhance octane values of fuel (3). However, small increases in pore size as well as variations in pore shape and dimensionality could further improve the catalysts. Pores with greater than a 12-MR structure might allow the conversion of... 

Strategies for Catalytic Octane Enhancement in a Fluid Catalytic Cracking Unit... 

There are three different kinds of octane catalysts in current use. Some are based in part on an active non-zeolite matrix composed of a porous silica/alumina component. Others are based on low cell size (2.425-2.428 nm) ultra stable faujasite (USY), a catalyst composition developed in 1975 (2) for the purpose of octane enhancement. A third catalyst system makes use of a small amount (1-2%) of ZSM-5 as an additive. While the net effect in all cases is an increase in the measured octane number, each of the three catalytic systems have different characteristic effects on the composition and yield of the gasoline. The effects of the ZSM-5 component on cracking is described in other papers of this symposium and will not be discussed here. 

Octane Enhancement in Catalytic Cracking by Using High-Silica Zeolites... 

Krishna, Ashok S. Gasoline octane enhancement in fluid catalytic cracking with split feed injection to a riser reactor, PCT International, WO 8702695 (1987). 

The analysis of dialkyl ethers used as octane enhancers in automobile fuel (oxygenates) was carried out by catalytic cracking to CO followed by reduction to methane (Verga et al. 1988). 

Conditions of a step for template molecule removal affected strongly the concentration of very strong acid site in HZSM-5. Treatment with ammonia water at ca 373 K was also studied as a procedure to affect the solid acidity, and a similarity of acid sites created by both methods was identified. From the quantitative measurements of acid sites, it was found that the very strong acid site consisted of two A1 cations. Catalytic activity for octane cracking was enhanced by the presence of very strong acid site. 

Biswas, J. and Maxwell, I.E., "Octane enhancement in fluid catalytic cracking. I. Role of ZSM-5 addition and reactor temperature". Applied Catalysis, 58, 1-18 (1990). 

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