Patent ID: 8227646

Claim:
A process for the production of propylene glycol by reaction of a feed material comprising glycerol in the presence of hydrogen which comprises the steps of: (a) supplying a stream comprising the feed material to a first vaporisation zone and contacting said feed with cycle gas comprising hydrogen such that at least a portion of the feed is vaporised by and into the cycle gas; (b) supplying at least a portion of the cycle gas and the vaporised feed material to a first reaction zone comprising catalyst and operating under reaction conditions to allow hydrogenation and dehydration to occur such that a major part of the glycerol is converted; (c) recovering from the first reaction zone an intermediate product stream comprising cycle gas, minor amounts of unconverted glycerol, and propylene glycol; (d) supplying the intermediate product stream from the preceding reaction zone to a final vaporisation zone and contacting it with additional feed material such that an amount of glycerol, approximately equivalent to that vaporised in the preceding vaporisation zone, is vaporised by and into the intermediate product stream; (e) supplying the stream from step (d) to a final reaction zone comprising catalyst and operating under reaction conditions to allow hydrogenation and dehydration to occur such that a major part of the glycerol is converted; and (f) recovering from the final reaction zone a final product stream comprising cycle gas, minor amounts of unconverted feed glycerol and propylene glycol.