Solid-Acid Catalysis

Zeolites are widely applied in the processing of oil Acid-catalyzed reactions of hydrocarbons proceed through carbenium ion intermediates. Bifunctional catalysis combines the catalytic properties of metal particles and of zeolites. 

Transforming cmde oil to gasoline is the most important process catalyzed by solid acids, such as chlorine-treated clays and zeolites. The reaction is performed at high temperatures (500°C) but is unfortunately accompanied by significant coke formation, causing a short lifetime for the catalyst. In a riser-downer reactor the catalyst is exposed for a short time to the feed, and in a second step, carbon is removed by oxidative combustion. 

Application of zeolites has significantly improved gasoline yield. The protons form carbenium or carbonium ions with reactant hydrocarbon molecules that 

In catalytic dewaxing, linear alkanes are separated from branched hydrocarbons by cracking the molecules over zeolites with micropores that access linear alkanes only, but not branched molecules. Branched alkanes are desired as high octane gasoline components. A low reaction temperature (200° C) is preferred for the isomerization reaction because isomerization is an exothermic reaction. In this reaction linear paraffins are isomerized and more branched molecules are produced. 

Conventional cracking catalysts operate at a temperature of - 500-600°C. The difficult step is the generating carbenium ions from alkanes. This occurs through a reaction sequence that initially proceeds with formation of carbonium ions  

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J. P. DeYoung, B. E. Kipp, and J. M. DiSimone, Solid acid catalysis using Nafion in supercritical... 

There has been an enormous technological interest in tertfa/j-butanol (tBA) dehydration during the past thirty years, first as a primary route to methyl te/f-butyl ether (MTBE) (1) and more recently for the production of isooctane and polyisobutylene (2). A number of commercializable processes have been developed for isobutylene manufacture (eq 1) in both the USA and Japan (3,4). These processes typically involve either vapor-phase tBA dehydration over a silica-alumina catalyst at 260-370°C, or liquid-phase processing utilizing either homogenous (sulfonic acid), or solid acid catalysis (e.g. acidic cationic resins). More recently, tBA dehydration has been examined using silica-supported heteropoly acids (5), montmorillonite clays (6), titanosilicates (7), as well as the use of compressed liquid water (8). 

In this research Initiative, we have examined the potential of reactive distillation (9) for terb a/j-butanol dehydration to isobutylene using solid acid catalysis. Advantages to employing reactive distillation for reaction (1) include a) the mild operating conditions required (<120°C), b) quantitative tBA conversions per pass, and c) the option to use lower purity/lower cost, tBA feedstocks. 

Selective lertiarj-Butanol Dehydration to Isobutylene via Reactive Distillation and Solid Acid Catalysis... 

There has been a phenomenal growth of interest in theoretical simulations over the past decade. The concomitant advances made in computing power and software development have changed the way that computational chemistry research is undertaken. No longer is it the exclusive realm of specialized theoreticians and supercomputers rather, computational chemistry is now accessible via user-friendly programs on moderately priced workstations. State-of-the-art calculations on the fastest, massively parallel machines are continually enlarging the scope of what is possible with these methods. These reasons, coupled with the continuing importance of solid acid catalysis within the world s petrochemical and petroleum industries, make it timely to review recent work on the theoretical study of zeolite catalysis. 

Harmer, M.A. and Sun, Q. (2001) Solid acid catalysis using ion-exchange resins. Appl. Catal. A Gen., 221, 45. 

Yoneda, Y., Linear Free Energy Relationships in Heterogeneous Catalysis IV Regional Analysis for Solid Acid Catalysis., J. of Catal., 9,51-56,1967. 

Corma A., Garcia H. Organic reactions catalyzed over solid acids. Catalysis Today, 1997, 38(3), 257-308. 

Various trisubstituted imidazoles (xix) have been synthesized in good yields by Shaabani et al. [19] via the condensation of 1,2-diketone or a-hydroxyketone or a-ketoxime with various aromatic aldehydes and ammonium acetate using a solid acid catalysis. 

Lassila, K. R., Ford, M. E. Solid acid catalysis of the Fries rearrangement thermodynamic limitations based on solvent polarity. Chem. Ind. 1992,47, 169-180. 

Single electron transfer (SET), as antioxidant mechanism 844, 896, 897 Size exclusion chromatography 953 Slash pine bark, phenolic compounds in 944 Smiles rearrangement 466-470, 759 S Ar reactions 673 Soil samples, phenolic compounds in, analysis of 932, 965, 972, 985 field screening of 938 Sol-gel technique 1082 Solid acid catalysis 612-621 Solid-phase extraction (SPE) 930-933, 936, 942, 944-950, 955, 958, 960, 962-964, 969, 972, 985, 986, 995, 1354 Solvation energy 500, 992 Solvation free energy 5 Solvatochromic comparison method, for solvent hydrogen-bond basicity 591 Solvent effects,... 

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