US 4,380,678 AGranted

Multi-stage aldoses to polyols process

AssigneeHydrocarbon Research, Inc.

InventorAmalesh K. Sirkar

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Abstract

Aldoses such as glucose solution are catalytically hydrogenated in a multiple-stage fixed-bed reaction process to produce glycerol and other polyol products. The feedstream pH to each reactor is controlled to between about 7 and 14 by adding an alkaline promotor material such as calcium hydroxide. First-stage reaction zone conditions are 130.degree.-180.degree. C. temperature, 500-2000 psig hydrogen partial pressure, and feedstream liquid space velocity is within range of 0.5-3.5 V.sub.f /Hr/V.sub.c. The first reactor uses a high activity nickel catalyst to produce at least about 98 W % conversion to alditol such as sorbitol solution. The resulting alditols such as 15-40 W % sorbitol solution in water is catalytically hydrocracked in a second-stage fixed-bed reaction zone preferably using a high-activity nickel catalyst to produce at least about 30 W % conversion to glycerol and glycols products. Second-stage reaction zone conditions are 420.degree.-520.degree. F. temperature, 1200-2000 psig hydrogen partial pressure, and liquid hourly space velocity of 1.5 to 3.0. The reaction products are separated in a recovery step, and unconverted heavy alditol feed can be diluted and recycled to the second-stage reaction zone for further hydrogenolysis to produce 40-90 W % glycerol product. Sorbitol conversion is maintained preferably at between about 30-70 W % and a purge stream containing unconverted sugars is passed to a third-stage catalytic reaction zone for further conversion to alditols and polyols.

A process for catalytic conversion of monosaccharides to produce polyols, comprising the steps of:

(a) providing a feedstream containing at least about 20 W % monosaccharide solution and having pH of 7 to 14;
(b) preheating the feed and hydrogen gas to at least about 100.degree. C., and passing the heated feedstream mixture through a first stage fixed bed catalytic reaction zone containing a stabilized high activity nickel on silica-alumina support containing 50-60 W % porous nickel and having 0.060-0.250 inch diameter particle size and surface area of 140-180 M.sup.2 /gm;
(c) maintaining said first reaction zone at conditions of 130.degree.-180.degree. C. temperature, 500-2000 psig partial pressure of hydrogen, and 0.5-3.5 V.Hr/V space velocity, for achieving at least about 90 W % conversion of the feed to alditols;
(d) withdrawing product containing alditol solution and passing it with a promotor material and hydrogen gas to a second-stage fixed-bed reaction zone containing a particulate high activity stabilized metal catalyst which catalyst comprises 50-65 W % porous nickel on an inert support, has 4-12 mesh (0.187-0.66 inch) particle size (U.S. Sieve Series), and a catalyst age of 8-200 hours before regeneration to maintan its activity;
(e) maintaining said second reaction zone conditions within the range of 430.degree.-490.degree. F. temperature, 1200-2000 psig hydrogen partial pressure, and 1.5-3.0 liquid hourly space velocity (LHSV) for achieving at least about 30 W % conversion of the alditol to products;
(f) withdrawing from the second reaction zone a product stream in which the alditol is converted between about 30 to 80 W % to yield glycerol and glycol products, and passing the polyol-containing stream to a recovery step from which mainly glycerol product is withdrawn;
(g) recycling a heavy purge stream containing aldose and alditols diluted with alcohol and/or water to the first stage reaction zone for further conversion to alditols and glycerols, respectively.

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Abstract

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