GB783469A - Improvements in or relating to the preparation of higher alkenes by thermal crackingof heavy hydrocarbon oils and to the preparation of certain derivatives thereof - Google Patents

Abstract

Alkenes containing at least 5 carbon atoms per molecule are obtained by submitting to thermal cracking, in the vapour phase, heavy cycle oil boiling above 300 DEG C. which has been separated by fractional distillation from the products of the catalytic cracking of hydrocarbon oils, and has been substantially wholly freed from aromatics by solvent extraction. The heavy cycle oil may be used in admixture with the residual oil drawn off as bottoms in the fractional distillation. Suitable solvents are: furfural, liquidsulphur dioxide and mixtures of phenol and water. The cracking is effected by heating the vapours of the raffinate, together with an inert diluent such as steam, at a temperature between 500 DEG and about 700 DEG C. for a short period, e.g. a few seconds. In an example, the starting material was a mixture of heavy cycle oil of B.R. 300-500 DEG C., obtained by fractionation of the product obtained by cat. cracking a mineral oil distillate of B.R. 300-500 DEG C., and of the oil withdrawn as bottoms in this fractionation; this mixture contained 55 per cent of aromatics. The mixture was extracted with furfural at between 60 DEG and 70 DEG C. in a rotating disc extraction column, the volume ratio of solvent to oil being about 3 : 1. The raffinate, which contained only 1.5 per cent aromatics, was vaporized rapidly at a maximum temperature of about 470 DEG C., together with a fraction of the resulting cracked product boiling above 300 DEG C., which was recycled in a weight-ratio of 2.9:1 with reference to the raffinate. The vapours, after separation of unvaporized material still present, were passed through a furnace at a maximum temperature of about 550 DEG C. for a period of 3.6 seconds, together with 6.5 per cent by weight of steam. The portion of the cracked product boiling above 300 DEG C. was recycled to the supply of fresh raffinate, while the portion boiling below 300 DEG C. was separated by fractional distillation into a fraction containing gaseous alkenes, a C5-alkene fraction, a C6-C8 alkene fraction, a C9-C13 alkene fraction, and a C14-C18 alkene fraction. The alkene content of these fractions was 85 to 90 per cent by weight. Specification 659,241 is referred to.ALSO:Alkenes containing at least 5 carbon atoms per molecule are obtained by submitting to thermal cracking, in the vapour phase, heavy cycle oil boiling above 300 DEG C. which has been separated by fractional distillation from the products of the catalytic cracking of hydrocarbon oils, and has been substantially wholly freed from aromatics by solvent extraction. In an example, a C12-C16 fraction having an alkene content of 88 per cent was separated from the thermally cracked products, and was used to alkylate benzene at 30 DEG C. employing liquid HF as catalyst. The crude alkylate was separated from the non-acid phase, and then distilled under reduced pressure to yield purified alkylate having an average M.W. of 271. This alkylate was converted with oleum and caustic soda into an alkylaryl sulphonate, which had good detergent properties. In another example, a C6-C8 alkene fraction was treated with sulphuric acid to remove dienes, and was then converted into aldehydes by treatment with water gas in the presence of cobalt-on-kieselguhr as catalyst, the maximum temperature and pressure being 140 DEG C. and 250 atm. respectively. The product was freed from cobalt carbonyl compounds by cooling, releasing the pressure, introducing hydrogen up to a pressure of 50 atm., heating for 2 hours at 160 DEG C., and then, after cooling, releasing the gas and adding further hydrogen under pressure. The resulting aldehydes were then converted into alcohols by heating with hydrogen at 185 DEG C. under 140 atm. in the presence of nickel-on-kieselguhr catalyst. After filtering off the catalyst the resulting alcohols were distilled to separate the fraction boiling between 161 DEG and 221 DEG C. which comprised the C7-C9 alcohols. In order to remove formates, the C7-C9 alcohols were subjected to treatment with hydrogen at 250 DEG C. and 140 atm. in the presence of copper chromite catalyst. After filtering off the catalyst, the alcohols were re-distilled, and recovered as a colourless fraction boiling between 161 DEG and 199 DEG C. In a further example, the C7-C9 alcohols were converted into the corresponding phthalates; and the crude esters were purified by heating with 1 per cent lime and 0.02 per cent potassium permanganate (as a 1 per cent aqueous solution) with strong agitation for 45 minutes at about 110 DEG C., and subsequently heating with activated carbon for some hours at 80 DEG C. Esters of adipic, methyladipic, and sebacic acids are also referred to; these may be used as synthetic lubricating oils. A further example, describes the preparation of sodium alkyl sulphates from a C8-C18 alkene fraction. Calcium alkyl salicylates, and the calcium salts of alkyl aromatic sulphonic acids, are also referred to. Specification 659,241, [Group III], is referred to.