Patent GB-736422-A (GB)
Title: Alkylation of carbocyclic hydrocarbons
IPC: C07C2/72
Filed: 1952-11-06
Abstract: Carbocyclic hydrocarbons containing a saturated hydrogen-bearing carbon atom adjacent to an unsaturated nuclear carbon atom are alkylated by reacting with a non-conjugated olefin at elevated temperature in the presence of an alkali metal hydride as catalyst. The carbon atom to be alkylated can be either cyclic or acyclic in its bonding.  Typical compounds in which the carbon atom alkylated is cyclic include cyclohexene, 1-cyclohexylcyclohexene, cyclopentene, tetralin and hydrindene. Aromatic compounds such as toluene, diphenylmethane and n-butylbenzene alkylate on an acyclic carbon atom alpha to the nucleus.  Compounds such as 1-methylcyclohexene-1 and 5 - methyl - 1,2,3,4 - tetrahydronaphthalene can alkylate on either an acyclic or cyclic carbon atom or both.  Other starting materials specified include o-, m- and p-xylenes, trimethylbenzenes, ethylbenzene, the isomeric diethylbenzenes, n-propylbenzene, o-, m- and p-di-n-propylbenzenes, cumene, 9,10-dihydrophenanthrene, sec.-butylbenzene, 2-phenyldodecane, p-methyl - tert - butylbenzene, alphamethylnaphthalene and n-dodecylbenzene. Specified alkylating agents are non-cyclic mono-olefins of 12 or less carbon atoms, e.g. ethylene, propylene, butene - 1, butene - 2, pentene - 1 (or - 2), hexene - 1 (- 2) or (- 3), heptenes, octenes, nonenes, decenes, undecenes, dodecenes, isobutylene, 3 - methyl - heptene - 1, 2 - ethylpentene - 1, and 3 - methylhexane - 3.  Other olefinic materials mentioned are cyclic olefines, non-conjugated polyolefines, and mono-olefines of more than 12 carbon atoms, e.g. cyclohexene, cyclopentene, 1,4 cyclohexadiene, 1,5 hexadiene, 1,4 hexadiene, pentadecene-1, other pentadecenes and tetradecenes.  Specified alkali metal hydrides are those of lithium, sodium, potassium, rubidium and caesium. Mixtures of alkali metal hydrides may also be used and the catalyst may be mixed with an inert carrier such as finely divided glass, refractory oxides or "Carborundum" (Registered Trade Mark). The reaction should be carried out in a substantially oxygen-free atmosphere and the reactants should be low, preferably below 0.5 per cent, in oxygen content.  The amount of catalyst should be about 0.01 to 10 per cent by weight of the carbocyclic compound.  The process is operable at temperatures of 150-500 DEG  C. preferably 200-375 DEG C. and is preferably operated at elevated pressures of 20 to 3000 atmospheres.  The reaction may be conducted with either or both of the reactants dissolved in an inert solvent which may be a paraffin, cycloparaffin, or an aromatic compound containing no saturated hydrogen-bearing carbon atoms alpha to the aromatic nucleus. Specified solvents are n-octane, iso-octane, cyclohexane, benzene, tert-amylbenzene and tert-heptylbenzenes.  The process may be carried out batchwise or in a continuous manner and the reactants can be diluted with inert gases such as propane, ethane, methane, nitrogen, helium and neon.  In the continuous process the reactants in the liquid or vapour state or in mixed liquid-vapour state may be passed over a fixed bed of the catalyst or the liquid or liquid-vapour reaction can be carried out in the presence of a suspended catalyst which is transported through the reaction zone by the velocity of the liquid reactants and products.  In the vapour phase reaction the dense phase fluidized bed catalyst technique can be used.  Examples describe the alkylation (using sodium hydride as catalyst) of: (1) isopropylbenzene with ethylene to form tert-amylbenzene; (2) commercial xylene with ethylene to yield methyl-n-propylbenzene; (3) toluene with ethylene to yield n-propylbenzene, 3-phenylpentane and 3-phenyl-3-ethylpentane. Reference is also made in the examples to the alkylation of isopropylbenzene with propylene, butene-2, hexene-1, and dodecene-1 to yield 2,3 - dimethyl - 2 - phenylbutane, 2,3 - dimethyl - 2 - phenylpentane, 2,3 - dimethyl - 2-phenylheptane, and 2,3-dimethyl-2-phenyltridecane respectively, and to the alkylation of sec-butylbenzene, a -isopropyl naphthalene, 1-methyl - 1,2,3,4 - tetrahydronaphthalene, 1,4-dimethyl - 1,2,3,4 - tetrahydronaphthalene, and diisopropyl benzene, with ethylene, the main products being 3 - phenyl - 3 - methylpentane, alpha - (tert - amyl) - naphthalene, 1 - methyl - 4-ethyl - 1,2,3,4 - tetrahydronaphthalene, 1,4-dimethyl - 1 - ethyl - 1,2,3,4 - tetrahydronaphthalene and p-(tert-amyl)isopropylbenzene, respectively.  In the case of 1-methyl-1,2,3,4-tetrahydro naphthalene small amounts of 1-methyl - 1 - ethyl - 1,2,3,4 - tetrahydronaphthalene, 1 - methyl - 1,4 - diethyl - 1,2,3,4 - tetrahydronaphthalene and 1-methyl-1,4,4-triethyl-1,2,3,4 - tetrahydronaphthalene are obtained.  In the case of 1,4-dimethyl-1,2,3,4-tetrahydronaphthalene some 1,4 - dimethyl - 1,4 - diethyl-1,2,3,4 - tetrahydronaphthalene is also obtained and with diisopropylbenzene a small amount of diisopropyl benzene is also formed.  The products obtained by alkylation of various other cyclic hydrocarbons with ethylene are also specified.