| 摘要 |
Methyl bromide is removed from aliphatic hydrocarbons, at least one of which contains four carbon atoms, by distillation in the presence of a solvent which either (a) has a dielectric constant at 25 DEG C. of at least 9, a boiling-point of at least 25 DEG C. and a molecular weight of at least 35 or (b) has a dielectric constant at 25 DEG C. of below 9 and has the formula <FORM:1043511/C4-C5/1> in which each X is the same or different and is H, CH3, Cl, Br or NH2 or mixtures of any such compounds, and recovering purified hydrocarbons overhead. Solvents under heading (a) may be amides, ketones, aldehydes, alcohols, polyols, acids, acid chlorides or anhydrides, esters, ethers, nitrates, nitriles, amines, ether alcohols, halogenated alcohols, alkanolamines, halogenated hydrocarbons, alkyl thiocyanates, nitro-compounds, halogenated aliphatic acids, sulphates, sulphoxides, phenols, cyanamides, and nitrogen- or oxygen-containing heterocyclic compounds. The solvent may contain water. An amount of 5-35% mol. of solvent based on total hydrocarbons may be used. Particularly preferred is methyl ethyl ketone especially when purifying the product of dehydrogenating a C4 hydrocarbon mixture in the presence of bromine or a bromine-containing compound to form butadiene. Separated methyl bromide is recycled to the dehydrogenation and any methyl ethyl ketone therein forms butadiene. Alpha values between methyl bromide and C4 hydrocarbons are given for dimethyl sulphoxide, methyl ethyl ketone, 1-butanol, dimethylformamide, furfural, acetonitrile, nitrobenzene, benzene and chlorobenzene. |
