GB796085A - Hydrocarbon conversion process - Google Patents

Abstract

Hydrocarbons containing at least three carbon atoms and non-aromatic carbon-to-hydrogen bonds are converted into hydrocarbons containing a new carbon-to-carbon linkage and having a higher carbon to hydrogen ratio by heating with an hydrogen-accepting olefine and a proportion of iodine (or hydrogen iodide, alkyl iodides or other compound which liberates iodine under the reaction conditions) of at least 0.05 mol. per mol. of hydrocarbon to be converted at at least 300 DEG C. to effect carbonto-hydrogen bond cleavage in the hydrocarbon feed and convert the olefine to paraffin. Conversions which may be effected are dehydrogenation of alkanes or aralkanes, e.g. isobutane to isobutene, n-butane to butenes and butadiene, ethyl benzene to styrene, o-methyl ethyl benzene to o-methyl styrene, and n-butyl benzene to 4 - phenyl - butadiene - 1,3; dehydrocoupling, e.g. propylene to diallyl, isobutene to dimethallyl, toluene to dibenzyl and stilbene; dehydrocyclization often with aromatization, e.g. n-hexane to benzene, n-heptane to toluene, n-octane to m-xylene and ethyl benzene, 2,5-dimethyl hexane to p-xylene, hexadiene-1,3 to benzene, hexane-1 to cyclohexene, o-diethylbenzene to naphthalene, o-methyl propyl benzene to naphthalene, n-butyl benzene to naphthalene, 2,3-diethyl naphthalene to anthracene, butylcyclohexane to naphthalene, and butylcyclopentane to indene; and dehydrogenation, often with aromatization of hydroaromatic hydrocarbons, e.g. cyclohexane to cyclohexene and benzene, and methylcyclohexane to toluene. In the case of acyclic hydrocarbons containing a quaternary carbon atom, dealkylation and/or isomerization may occur, e.g. 2,2,5-trimethylhexane gives p- and m-xylenes. The olefine used should be such that the sum of the standard free energy change for the hydrogenation of the olefine to the corresponding paraffin and the standard free energy change for the conversion of the hydrocarbon, both measured at the desired reaction temperature, is a negative number. Ethylene is preferred being most suitable thermodynamically but higher olefines can be used, e.g. propylene, the butenes, pentenes and hexenes, particularly when aromatization occurs. In converting alkanes to alkenes or alkadienes, the olefine should have fewer carbon atoms and be of no greater degree of branching than the alkane. The olefine may be regenerated from the paraffin produced, e.g. by cracking and recycled to the reaction zone. It may be used mixed with other olefines and/or paraffins. The ratio of olefine to hydrocarbon feed employed expressed in theoretical equivalents (theories) may be 0.1 to 10. The total amount of iodine (or equivalent) added may be 0.1 to 0.8 theory; where an iodine compound is used some elemental iodine is also preferably added. Reaction temperatures of 400-600 DEG C., pressures of subatmospheric to 10 atmospheres and residence times of 0.01 second to 5 minutes may be used. In an example, n-butane is dehydrogenated to butenes and butadiene with varying amounts of iodine and ethylene using a small amount of helium as a diluent. Specifications 793,135, 793,214 and 793,215 are referred to.