GB798030A - Improvements in or relating to process for the preparation of wholly or partly deuterated hydrocarbon material - Google Patents

Abstract

A liquid or solid hydrocarbon is wholly or partly deuterated by allowing it to flow downwardly as a shallow liquid layer over the surface of a catalyst at elevated temperature and pressure and a gas, consisting wholly or mainly of deuterium and/or a deuterium compound which yields deuterium under the reaction conditions, is also passed into the reaction zone, the catalyst being such as to promote the isotope exchange. The gas is preferably passed upwards in countercurrent to the liquid, deuterium being heavier is therefore prevented from mixing with the lighter hydrogen leaving the top of the reaction zone. Flow of hydrocarbon may be high, e.g. 1 kg. of hydrocarbon per litre of reaction zone per hour, but preferably should not be so high as to cause turbulence or so low that lateral diffusion of the gas occurs. Temperatures and pressures are generally above 100 DEG C. and 10 atm. and are chosen to give sufficient catalyst activity without causing cracking while maintaining the hydrocarbon in the liquid phase. A temperature gradient lower at the bottom of the reaction zone than the top is advantageous. A series of zones may be used. The degree of deuteration depends on the relative feed rates of the hydrocarbon and gas. Generally hydrogenating/dehydrogenating catalysts are suitable including nickel, platinum, and palladium, oxides and sulphides of nickel, cobalt, tungsten, molybdenum and chromium which may be supported on kieselguhr, silica gel, pumice or active carbon and may be tablets or pellets. Alumina is also particularly effective. Any solid or liquid hydrocarbon of natural or synthetic origin may be used including branched or unbranched C6-C12 alkanes and mixtures such as mineral oil fractions, cyclohexane and its homologues and aromatics such as benzene, toluene, xylenes and naphthalene. Sulphur and nitrogen impurities are preferably removed prior to the reaction. The products may be used as moderating material or cooling media in nuclear reactors (see Group XL (a)) and for this purpose aromatic, particularly polycyclic hydrocarbons are preferred, including naphthalene, acenaphthene diphenyl, fluorene, anthracene, phenanthrene, pyrene, benzanthrene, chrysene and their homologues, preferably any short side chains being removed beforehand by dealkylation. Deuterated aromatic hydrocarbons particularly those with a D : C ratio between 1 : 1 and 1 : 5 can be used to prepare carbon containing a small amount of deuterium as described in Specification 798,029, [Group XL (a)]. The gas used in the deuteration is preferably deuterium as pure as possible, but small amounts of components non-harmful to the catalyst may be added where partial deuteration is required. Deuterium compounds which yield deuterium which may be used with or instead of deuterium include deuterated lower hydrocarbons such as methane, ethane and ethylene. In an example, anthracene is deuterated with 99.2 per cent pure deuterium over alumina at 100 atmospheres and 325 DEG C. to give 78 per cent conversion of hydrogen in the anthracene to deuterium.