Expanded clays catalyst preparation

The two clay samples were expanded using a SiOj-TiOj sol solution prepared by a procedure described by Yamanaka and coworkers (4). Tetraethylorthosilicate is first hydrofyzed with an excess of an HQ (IN) and ethanol mixture, and then reacted with titanium tetraisopropoxide (hydrolyzed with IN HQ). to form a sol with composition TiOj-lOSiO. The sol is then added to a slurry containing 1% clay. The resulting mixture is stirred for 90 minutes at 60 C. After filtration and washing, part of the clay is allowed to diy in air at 60 C. The remaining clay was washed with ethanol (to displace interlamellar water) and then dried with supercritical COj at 120 atm and 40°C A schematic of the clay catalyst s preparation is shown in Figure 5-1. 

Thus, these expanded clays have the thermal stability required of materials used in the preparation of catalysts for certain hydrocarbon conversion reactions, such as hydrodesulfurization, hydrodenitrogenation, hydrodemetallation, and the hydrocracking of oil fractions. 

On September 25-30, 1988 in Los Angeles, California the first ACS Symposium on zeolite synthesis emphasized the importance that gel chemistiy, zeolite nucleation, crystal growth, crystallization kinetics, and structure-directing phenomena have in understanding zeolite (and molecular sieve) synthesis. The objectives of a similar ACS Symposium held in New York on August 25-30, 1990 where expanded to include papers on pillared clay synthesis and on the synthesis of other microporous materials that could be used in catalyst preparation. About 90% of all the chemical processes in the U.S. are based on catalysis and today catalysts have become indispensable to petroleum refining, an industry that in 1990 had sales of 140 billion (U.S. Dept, of Commerce U.S. Industrial Outlook, 1991). 

Porphyrins were first introduced into clays in 1977 by the physical absorption of porphyrin molecules into montmor-illonite in aqueous solutions." The most common examples are the binding of tetracationic M(TMPyP) porphyrins, M = Co(II), Mn(III), Fe(III), into montmor-illonite clays. Co(TMPyP) was the first porphyrin to be intercalated into montmorillonite by ion exchange in acid solution. The interlayer distance expanded from 27 to 37 A upon intercalation. UV-visible studies revealed the retention of cobalt ions in the porphyrin molecules. Mansuy and coworkers have extended this approach and prepared the Mn-porphyrin intercalated materials. These solids are efficient alkene epoxidation and alkane hydroxylation catalysts." Additionally, the catalyst exhibited a marked shape selectivity in favor of small linear alkanes when compared to more bulky substrates. It was also shown that... 

---