Catalytic hydrogenolysis of alditols to product glycerol and polyols

A process for catalytically converting sorbitol solution to produce mainly glycerol product, comprising the steps of:

• (a) providing a feedstream containing 20-60 W % sorbitol in aqueous solution;
• (b) adding calcium hydroxide promoter to the feedstream sufficient to provide a pH within the range of 7-14;
• (c) preheating the feed solution together with hydrogen gas to at least about 200.degree. F., and introducing the heated feedstream mixture into a fixed-bed reaction zone containing a particulate high activity stabilized nickel catalyst containing 50-65 W % porous nickel on silica support and having 4-20 mesh (0.187-0.33 inch) particle size (U.S. Sieve Series), said catalyst being regenerated after 20-60 hours use by washing it with a water-methanol solution and then contacting said catalyst with flowing hydrogen at 550.degree.-600.degree. F. temperature and at reduced pressure for 2-8 hours to provide improved selectivity for a glycerol product;
• (d) maintaining the reaction zone conditions within the range of 430.degree.-480.degree. F. temperature, 1400-1900 psig hydrogen partial pressure, 1.8-2.8 liquid hourly space velocity (LHSV) and catalyst age of 10-200 hours for achieving 30-70 W % conversion of the sorbitol to yield mainly glycerol with the remainder being alcohols and glycols;
• (e) withdrawing from the reaction zone a stream containing glycerol and glycol products and phase separating said stream into a gaseous portion and a liquid portion;
• (f) reducing pressure of said liquid portion and passing it to a vacuum distillation step maintained at 10-80 mm Hg pressure to remove water vapor and produce 40-90 W % purity glycerol product and a heavy bottoms liquid stream containing unconverted sorbitol and other alditols;
• and
• (g) recycling at least a portion of said bottoms stream to the reaction zone for further catalytic conversion of sorbitol to mainly glycerol product.

A process for catalytic hydrogenolysis of an alditol solution to produce glycerol, comprising the steps of:

• (a) providing a feedstream containing at least about 10 W % alditol in water solution and adding an alkaline promotor material to the feedstream to provide a pH within a range sufficient to prevent leaching of the catalyst metal;
• (b) preheating the feed solution together with hydrogen gas to at least about 200.degree. F. temperature, and introducing the heated feedstream mixture into a reaction zone with a particulate high activity stabilized nickel catalyst containing 50-65 W % porous nickel on silica support and having 4-20 mesh (0.187-0.033 inch) particle size (U.S. Sieve Series), said catalyst being regenerated after 20-60 hours use by washing it with a water-methanol solution and then contacting said catalyst with flowing hydrogen at 550.degree.-600.degree. F. temperature and at reduced pressure for 2-8 hours to provide improved selectivity for a glycerol product;
• (c) maintaining the reaction zone conditions within the range of 430.degree.-490.degree. F. temperature, 1200-2000 psig hydrogen partial pressure, 1.5-3.0 liquid hourly space velocity (LHSV), for achieving at least about 30 W % conversion of the alditol to glycerol and glycol products;
• (d) withdrawing from the reaction zone a stream containing glycerol and glycols and phase separating said stream into a gaseous portion and a liquid portion;
• (e) distilling said liquid portion to remove alcohols, water and glycols to produce high purity glycerol stream at 1-100 mm Hg pressure using thin film evaporation at temperature not exceeding about 400.degree. F. to produce glycerol product and a heavy bottoms liquid stream containing alditols;
• and
• (f) recycling at least a portion of said vacuum distillation bottoms stream to the reaction zone for further catalytic conversion of alditols to mainly glycerol product.