Patent GB-563555-A (GB)
Title: Cyclisation of hydrocarbons
IPC: C07C5/41
Filed: 1942-08-05
Abstract: Aromatic hydrocarbons are produced by contacting a hydrocarbon having not more than 12 carbon atoms in an open chain and capable of cyclization to a six-membered ring with a relatively active cyclization catalyst comprising a cyclizing metal compound promoted with about 2.5-20 per cent of a rare earth element, and about 6-30 per cent of potassium, rubidium or caesium or a mixture of one of these with not more than 15 per cent of sodium, said percentages being based upon the metal in the cyclizing metal compound. Cyclization catalysts comprising a compound, preferably an oxide, of a heavy metal of the first transition series, viz. Ti, V, Cr, Mn, Fe, Co and Ni, give the most pronounced effect, particularly chromium oxide-alumina.  Others referred to are compounds, preferably oxides, of metals of the left-hand columns of Groups 4, 5 and 6 of the Periodic Table. These are generally used on carriers such as activated carbon, magnesia, clays, silica gel and particularly activated aluminas, prepared, for example, according to the process of U.S.A. Specification 1,868,869, the active metal amounting to 2-30 per cent of the carrier.  They can be made by impregnating the carrier with a solution of a metal compound and drying or calcining if necessary or precipitating a metal hydroxide and calcining.  The promoters are preferably incorporated, for example, in one further impregnation operation prior to the calcining or other conversion of the active metal compound. Cerium is the preferred rare earth but others, e.g. lanthanum, praseodymium, neodymium or mixtures obtained from minerals such as monazite sand may be used.  They may be added, for example, as oxygenated compounds such as nitrates, acetates or oxalates which are converted to oxides upon subsequent treatment. The alkali metal is preferably applied as a nitrate.  The catalysts may be heated for some hours at 300-600 DEG  C. in the presence of hydrogen, hydrogen sulphide or other gas prior to use.  Hydrocarbons from hexanes to decanes, octenes, and hexenes may be cyclized to benzene, toluene, xylenes or other alkyl benzenes and alkylated cyclics to polynuclear hydrocarbons.  Mixtures containing both cyclizable and non-cyclizable hydrocarbons may be treated, for example, petroleum fractions.  The hydrocarbon vapours may be contacted at about 350-700 DEG  C. for about 6 secs.-2 mins., preferably 450-550 DEG  C. and 6-80 secs., with the catalyst in a fixed bed or moving through the reaction zone as a bed or finely-divided powder.  Pressure may be above or below normal and is normally 1-10 atm.  Hydrogen may be added up to about 5 mols. per mol. of hydrocarbon, its partial pressure preferably being below 15 atm.  Examples show the average conversion over various periods of time with catalysts consisting of a -alumina or a -alumina monohydrate impregnated with chromic acid to give a chromium content ranging from 8.4-13.7 per cent and promoted with various percentages of cerium or a commercial mixture of rare earths together with potassium.  The added promoting effect of the presence of sodium with the potassium and cerium, and the superiority of potassium nitrate over potassium hydroxide is also shown.  Specifications 531,668 and 555,046 are referred to.