Abstract
M.Sc. (Chemistry)
The isomerization of short chain olefins on a catalyst containing a H-X zeolite (HZ-1) produces mainly branched olefins at 400°C. At SASOL the catalyst is also used to reduce organic acids present in the feed. Amarked increase in the acid concentration over a period of time has been reported. Other impurities in the reactor feed include
short chain alcohols, aldehydes and ketones. This study consisted of kinetic experiments which concentrated on the formation of acids from ketones and aldehydes during the isomerization of 1-hexene on 60/80 mesh HZ-1. The formation of acetic and
propionic acid from methyl ethyl ketone was observed. It was also shown that n-butyrealdehyde forms formic acet ic, propionic and n-butyric acid at 400°C. The presence of n-buthanol during the reaction of methyl ethyl ketone enhanced the formation of acid. A supplementary study showed the formation of only acetic acid from
acetone. The study of the formation of acids from a 5% methyl ethyl ketone/5% n-buthanol at 400, 300, 250, 200 and 150°C showed an overall decrease in the acid concentration with a lowering in temperature. These results showed the development of a definite maximum in the acid production. The formation of formic acid was also observed at 200 and 150°C. Amechanism for the formation of acids from ketones is proposed and discussed. Other than existing mechanisms this explains the formation
of formic, acetic and propionic acid from methyl ethyl ketone. The mechanism includes Bronsted and Lewis acid sites. During this study a method was developed for the analysis of trace quantities of organic acids present in the reaction product. Ion
exclusion chromatography was used for the quantitative determination of the different types of acids. Surface studies with nitrogen adsorptics showed a drastic decrease in the surface area during the reactions. Pore volume studies showed remarkably the loss of macropores' with a pore diameter bigger than 3,6 nm. Pikinometry showed the existance of micropores which were unaffected by the reactions. Aneutron activation analysis of HZ-l showed the presence of a great variety of transition elements mainly Scandium, Cobalt and Iron.