Acid Catalysis

Solid acids have been extensively studied and used as catalysts or catalyst carriers in chemical industry, particularly in the petroleum field, for many years. They are active areas of research for isomerization, cracking, hydrocraking, dehydration, alkylation, acylation, etc. Low-temperature reactions require strong acidity to overcome kinetic barriers, but the acidity of strongest solid acids is lower than that of the halide systems. Liquid superacids present exceptional high activity and are still employed in hydrocarbon chemistry. Conventional technologies for chemical synthesis also use homogeneous processes and Friedel-Crafts (AlCl3, TiCl4, FeCl3) catalysts which cause problems of high toxicity, corrosion, and spent acid disposal. Thus, considerable research work has been lately performed to find suitable, recyclable and environmentally benign solid acids for replacing homogeneous catalysts.
In this field, we study the employ of solid acids for efficiently promoting acylation, alkylation, dehydration, and cyclization reactions. We use different solid acids such as zeolites HY, Beta, and ZSM-5, SiO2-Al2O3, Al-MCM-41, HPA, and resins for selectively promoting the formation of valuable compounds in fine chemistry and petrochemistry.

Synthesis of aromatic ketones:
Aromatic ketones are valuable intermediate compounds for the synthesis of pharmaceuticals and fragrances. In particular, ortho- (o-HAP) and para-hydroxyacetophenone are widely used for producing aspirin and paracetamol, respectively. We study the development of solid acids for selectively obtaining o-HAP via the gas-phase acylation of phenol with acetic acid. Our goal is to relate the surface acid site density and strength of the solids with their ability for the efficient catalysis of the phenol acylation reaction to yield o-HAP.

Synthesis of ionones
The b-ionone isomer is used for the synthesis of vitamin A, whereas a- and g-ionones are very appreciated in the fragrance industry. Ionones are commercially produced via the liquid-phase cyclization of pseudoionone using mineral acids. We study the cyclization of pseudoionone to ionones on solid acids containing essentially strong Brønsted acid sites. The goal is to select the best catalyst and reaction conditions to improve the catalyst activity and selectively for obtaining ionone yields comparable to those of the homogeneous process using liquid acids.

Synthesis of cresols
p-Cresol is employed for the production of pharmaceuticals, herbicides, agrochemicals and dyes, but its current commercial synthesis via toluene dehydration using sulphuric acid entails serious environmental concerns. We investigate the gas-phase methylation of phenol on acid zeolites with the goal of significantly improving the selective synthesis of p-cresol. The goal is to ascertain the effect that the pore microstructure and the nature, density, and strength of surface acid sites have on the catalyst para-selectivity.

Liquid-phase dehydration reactions
Commercial processes for liquid-phase dehydration of alcohols use strong mineral acid catalysts. In particular, 15 % of the worldwide production of styrene is obtained via the intramolecular dehydration of 1-phenylethanol (PhE). However, 1-PhE is simultaneously converted to alpha-methylbenzene ether via an intermolecular dehydration/condensation reaction. We investigate the acid site density and strength requirements for selectively promoting on solid acids the liquid-phase PhE dehydration to styrene.

Recent Publications

Acid site requirements for the synthesis of o-hydroxyacetophenone by acylation of phenol with acetic acid, C.L. Padró, M.E. Sad, C.R. Apesteguía,
Synthesis of cresols by alkylation of phenol with methanol on solid acids, M.E. Sad, C.L. Padró, C.R. Apesteguía, Catal. Today, 133–135, 720-728, (2008).
Selective synthesis of p-cresol by methylation of phenol, M.E. Sad, C.L. Padró, C.R. Apesteguía, Appl. Catal. A: General, 342, 40-48 (2008).
Synthesis of ionones by cyclization of pseudoione on solid acid catalysts, V.K. Díez, C.R. Apesteguía, J.I. Di Cosimo, Catal. Lett., 123 (3-4), 213-219 (2008).
Liquid-phase dehydration of 1-phenyletanol over mordenite-like zeolites: Influence of Si/Al ratio, N.M. Bertero, C.R. Apesteguía, A.J. Marchi, Catal. Comm. 10, 261-265 (2008).
Ionone synthesis by cyclization of pseudoionone on silica-supported heteropolyacid catalysts, V.K. Díez, B.J. Marcos, C.R. Apesteguía, J.I. Di Cosimo, Appl. Catal. A: General , (2009)
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