Patent GB-520159-A (GB)
Title: Improvements in or relating to the treatment or production of gasoline hydrocarbons
IPC: C07C2/62
Filed: 1938-10-13
Abstract: 520,159. Alkylating isoparaffins. TEXACO DEVELOPMENT CORPORATION. Oct. 13, 1938, No. 29682. Convention date, Oct. 15, 1937. [Class 2 (iii)] Isoparaffins are alkylated by treatment with olefins in the presence of an alkylation catalyst characterized in that the ratio of isoparaffins to olefines in a hydrocarbon mixture of gasoline boiling range or below is adjusted to at least 1:1 without the addition of extraneous hydrocarbons: Any suitable alkylation catalyst may be used, the preferred one being sulphuric acid. Others mentioned include aluminium chloride, boron trifluoride and sodium aluminium chloride. Parent charging stocks which may be used for the process of the present invention include commercial fractions of hydrocarbons, oils or gases or mixtures thereof commonly obtained in refinery practice such as stabilizer reflux, accumulator drum gases from cracking stills, unstabilized gasoline fractions, cracked gasoline or fractions thereof, gases from refinery recovery systems, and residual gases from polymerization operations. The adjustment of the ratio of isoparaffins to olefins is preferably carried out by decreasing the proportion of olefins since the are normally in excess of requirements. Such reduction may be effected in several known ways such as fractional absorption in suitable solvents like sulphuric acid, or reaction with materials which result in readily separable compounds such as addition products with hydrochloric acid or relatively concentrated sulphuric acid. Alternatively, the olefine concentration may be decreased by partial polymerization by means of heat and pressure, or by means of active polymerization catalysts. Suitable catalysts mentioned for this purpose include phosphoric acid, aluminium chloride, and sulphuric acid. Instead of decreasing the olefins, the isoparaffins may be increased. This is preferably done by isomerizing some of the normal chain paraffins to branch chain paraffins by treatment with an isomerization catalyst such as aluminium chloride or bromide operating under relatively low temperatures for a relatively long period. In a few cases stocks used as parent materials for the present invention may contain an excessive amount of isoparaffin. To increase the olefin content in this case the stock may be subjected to a mild selective cracking in which the olefins resulting from the cracking of the paraffins and isoparaffins increases faster than the disappearance of the isoparaffin. This condition is difficult to attain and it is preferred to use either a cracking or a dehydrogenating catalyst such as aluminium chloride or bromide or absorptive catalytic materials of the clay type on the one hand or a chromic oxide gel at about 600‹-1,000‹F. on the other hand. The preferred ratio of isoparaffins to olefins is about 1:1 or 1.5:1. In a oncethrough operation a ratio between about 1:1 and 3:1 is satisfactory. In an example, a charging stock comprising 19 per cent butene-1, 10.5 per cent. butene-2, 10 per cent. isobutene, 17 per cent. isobutane, and 43 per cent. normal butane is treated with a polymerization catalyst to polymerize about 75 per cent. of the olefins to give a product in which the ratio of isobutane to olefins in the unpolymerized gases is about 2:1. This product was then treated with about 50 per cent. by volume of 94 per cent. sulphuric acid at 85‹F., and the resulting product fractionally distilled. Specifications 479,345, 479,827, 486,355 and 496,273 are referred to.