Beveridge J. Mair

Sulfur: Role in Genesis of Petroleum

Sulfur reacts readily with cholesterol at 150�C, and the product of the reaction contains aromatic hydrocarbons, some with a benzene, some a naphthalene, and some a phenanthrene ring system as part of the molecule. The reaction of farnesol with sulfur takes place at 135�C. Cadalene (1,6-dimethyl-4-isopropylnaphthalene) is one of the products of the reaction. These reactions at relatively low temperatures support the proposition that a thermal reaction of sulfur with terpenoids and steroids plays a part in the genesis of petroleum.

Terpenoids, fatty acids and alcohols as source materials for petroleum hydrocarbons

Abstract The evidence that terpenoids and the related steroids are important progenitors of petroleum hydrocarbons is very extensive. Probably well over 95 per cent of the hydrocarbons in petroleum have carbon numbers below 40. Terpenoids in this range are abundantly available among plants and animals, land and marine. By hydrogenation or dehydrogenation, with, in most cases, partial fragmentation of the terpenoid molecules, it is possible to account for most of the structures found in those petroleum hydrocarbons which contain aromatic or cyclohexane rings. Indeed, no other source material can explain in as satisfactory a manner the presence of large amounts of short-chain, principally methyl, substituents on the rings of the “average” 6-membered cyclic hydrocarbon molecule in the gasoline fraction of petroleum. The terpenoids also appear to be the most probable source for the cyclopentanes; these also are rich in methyl substituents. However, the proportion of cyclopentane rings in the terpenoids is not sufficient to account for the relatively large amounts of cyclopentanes found in many petroleums. Thus, it is necessary to assume either that cyclopentane rings are preferentially preserved in some degradation process or that cyclohexane rings are isomerised to give cyclopentane rings. The evidence appears excellent that some of the highly branched alkane hydrocarbons are derived from the acyclic terpenoids. It also appears that the normal paraffins are derived for the most part from the straight chain fatty acids and alcohols. The situation with respect to the slightly branched alkanes is less clear. In most petroleums the monomethylalkanes are nearly as abundant as the normal paraffins. The branched chain constituents of the fatty acids cannot be regarded as a suitable source since the amounts are extremely small. Several alternatives may be suggested: 1. (1) The fatty acids from ancient plant and animal life contained a higher proportion of branched-chain constituents than those of modern times. If this were true, the slightly branchedchain hydrocarbons could be produced in a manner analogous to that of the normal alkanes from the straight-chain acids. 2. (2) The slightly branched-chain alkanes are produced from the acyclic terpenoids by a degradation process which removes most of the methyl branches. 3. (3) The slightly branched-chain alkanes are produced from the straight-chain fatty acids by isomerisation to give chains with methyl branches.

Terpenoid precursors of hydrocarbons from the gasoline range of petroleum.

2,6-Dimethyloctane and 2-methyl-3-ethylheptane were isolated from petroleum. These hydrocarbons which are present in relatively large amounts appear to be derived from the monoterpenoids.