NL8105092A - TWO STAGE PROCESS FOR THE CONVERSION OF ALDOSES IN POLYOLS. - Google Patents

Description

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Tweet rapping method for the conversion of aldoses into polyols.

The invention relates to the catalytic hydrogenation of aldoses, such as glucose, for the preparation of polyols. The. More particularly, the invention relates to a two-stage work. manner, wherein a portion of the hydrodesulfin or alditol (sorbitol); sugars formed by genolysis for further conversion to the first or 1; aldose (glucose) hydrogenation step is recycled.

1 It has been noted that in the catalytic hydrogenolysis of alditols, such as sorbitol, in a fixed bed reactor using nickel catalyst (¾ an inert carrier for the preparation of polyols, such as glycerol and glycols, also some polyglycerols, aldoses and glucose from the feed of alditols and sorbitol are formed: Dehydrogenation of alcohols to sugars and dehydration of glycerol to polyglycerols causes the problem of accumulation of such materials in the recovery stage due to the usual recirculation flow to the sorbitol cracking reaction zone. unreacted sorbitol and alditols, as well as the sugars and polyglycerols, which are not removed in the distillation step or extracted in a solvent extraction step, if used, in order to avoid such build-up of strikers and related materials, which is detrimental to the process steps is too good a blowdown stream is removed from the distillation separation stage. However, with such a blowdown, valuable products and reactants are lost from the process along with sugars, thereby reducing yields and increasing product costs.

. It is thus desirable to recover these sugars through some suitable reprocessing steps.

A description regarding the hydrogenolysis of sorbitol can be found in Clark, Industrial and Engineering Chemistry, Vol. 50, No. 8 (August 1958), p. 1125. An aqueous solution containing kQ% -30 99% D-sorbitol was used with 1 # calcium hydroxide promoter and 30% nickel-on-silica catalyst catalyzed in suspension with the feed in a stirred reactor. The conditions used to prepare glycerol, ethylene glycol, propylene glycol and other minor products were a hydrogen partial pressure of 100 - 392 kg / cm @ 8105092. . 1 ”“? ï i «i - i J 2 t I / I» q! a temperature of 215 - 2U5 C and a reaction period up to UOO minutes j j (6.7 hours).

! Set U.S. Pat. reactor type The reaction conditions are a temperature of 200-300 ° C, a pressure of 500-1000 atmospheres, and a pH of 8-10, followed by filtration to remove catalyst and separation. of the products.

•>! 101 Ih Journal of Applied Chemistry, Vol. 19, pp. -3 - i! b-5, Tan Ling et al. describe hydrogenation experiments using i4 i; of a suspended catalyst in an autoclave reactor of feedstocks i »| 1 of sucrose, glucose and fructose in methanol-what solution, to prepare glycerol. The catalyst used was CuO-CeOp-SiOp, Id d.

15: adding 0-5% Ca (OH) to the feed. The reaction conditions used were a temperature of 200-250 ° C, a pressure of 100-300 atmospheres and a reaction period of 1.0. 120 minutes, U.S. Pat. No. 3,171,55θ discloses that by using a one-stage or multi-stage catalytic boiling 20-bed upflow reactor at a temperature of 93 ~ 287 ° C and a hydrogen partial pressure of 9-2l + 5 kg / cm, can be formed from saccharides glycerol and glycols Examples of the conditions used for the conversion of a sorbitol type feed into glycerol in a one-stage reaction were a temperature of about 191 ° C, a hydrogen partial pressure of 119 kg / cm, a liquid space velocity (LHST) of 1.2, using a nickel-on-alumina catalyst, globally containing 50% by weight glycerol and 20% by volume of ethyl and glycerol and propylene glycol were formed with the residue being methanol, ethanol, isopropanol and other products (column 5, lines 1 * 0 - 53) · 30 None of these are assumed. Known methods are currently commercially used to continuously prepare glycerol and related products. Thus, further process improvements for the conversion of aldoses and alditols are desirable, not only to achieve continuous embodiments, moderate reaction conditions, and increased glycerol product yields, in in particular using improved catalysts in solid catalysts, but also to 8105092 .........

I * \ \ "3; I ·: Prevent the loss of unreacted sugars, which are usually removed by blowdown.

The invention describes an improved catalytic two-stage process for the hydrogenation of monosaccharides and aldoses, such as glucose, to prepare glycerol and polyol products. The aldoses,; such as a glucose solution, are catalytically hydrogenated in a first stage, fixed bed reaction zone, to prepare alditols, such as! sorbitol, which are further hydrocracked in a two-stage reaction zone. to form glycerol and other polyol products. The pH of the feed stream to each reactor is maintained between about T-tU by addition of an alkaline promoter material, such as calcium hydro-; system to prevent acidic leaching of metal from the catalyst.

The first stage reaction zone conditions are maintained at a temperature of 130 DEG-180 DEG C., a hydrogen partial pressure of 35-100 kg / cm and a hydrogen gas / liquid feed ratio of 1000-5000. The liquid space velocity of the feed stream is maintained at 0.5-3.5 Yf / hr / Yc. In the first stage reaction, a high active catalyst, preferably containing nickel, is used. used to achieve at least a conversion of about 90 gav.% of aldoses into alditols, such as sorbitol-20 solution.

The resulting alditol, such as a 15 wt.% Solution of sorbitol in water, is catalytically hydrocracked in a second stage solid bed reaction, usually using a high-activity acetic catalyst to achieve at least a conversion of about 30 wt. . # in 25 glycerol and glycol products. The conditions of the two-stage reaction zone are maintained at a temperature of 200 - 270 ° C, a hydrogen partial pressure of 8U - 1 ^ 0 kg / cm 2 and an hourly liquid space velocity of 1.5 - 3.0. To maintain the desired catalytic activity and glycerol yield, the catalyst is regenerated to have a life of 8-200 hours. The reaction products are separated in a recovery step and any unconverted alditol feed can be recycled to the two stage reaction zone for further hydrogenolysis to prepare from 0 to 90 wt% glycerol product. Preferably, the sorbitol conversion is maintained at about b0 - 95 35 wt.% And a purge stream containing unconverted sugars is drained and recycled to the two stage reaction zone for further conversion to 1ΠΓ5ΠΓ9 2 I ï

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\ To avoid unwanted loss of. unconverted. ; ; sugars from the second or alditol hydrogenolysis stage caused by their usual discharge through a purge stream. after the product the still phase 5, it has proved advantageous to transfer part of the purge stream containing such sugars to the. the first or aldose-to-alditol hydrogenation reaction step. Here the sugars are catalytically hydrogenated! ; .nated to form alditols and alcohols in the presence of an i; catalyst, such as supported nickel. The other aldose materials present are expected to also exist in the presence of the same catalyst; will be converted to alditols. By means of such recirculation, the sugars may be reconverted into alcohols in the second or sorbitol cracking stage, so that significant process losses. of reactant and product are avoided.

. 15; It should be noted that in addition to sugar formed in the second stage sorbitol hydrogenolysis reactor, a certain amount of polyglycene. role (formed by dehydration and polymerization reactions) and other compounds similar to polyglycerol. can be produced in the sorhitol cracking reactor. The formation of these 20 compounds is expected to increase as the reaction temperature rises above about 200 ° C. Thus, the blowdown also prevents the accumulation of polyglycerols if this compound is not cracked at a rate greater than that at which it is formed in the two-stage reactor. Although it is desirable to control the concentration of undesired sugars in the polyol products by controlling the catalytic sorbitol cracking reaction conditions so that no polyglycerol is present in the system. It is usually necessary to drain a purge stream from the distillation stage to avoid the accumulation of polyglycerols and increase the yield of glycerol product.

According to the invention, part of such a blowdown stream is recycled to the first stage reaction zone for further catalytic conversion to alditols.

Figure 1 shows a two-stage catalytic process for the hydrogenation of glucose to form polyols, with recycle of by-product sugars to the first or glucose hydrogenation stage for further conversion.

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As indicated in the drawing, a glucose water supply solution "at 10 is mixed with an alkaline promoter material" at: 11 such as calcium hydroxide. The mixture is pumped at 12 with hydrogen from 13 through preheater 1¼ to the catalytic fixed bed reactor 16-15 for the hydrogenation reaction to form essentially sorbitol. The promoter material added at 11 should be sufficient to maintain the pH of the feed stream 15 in the range of J-13; port to prevent attack of the catalyst in reactor 16.

; The catalyst is preferably a reduced and stabilized nickel-1Q on silica-alumina support and usually contains 50-66% by weight of nickel. Here, a catalyst particle size in the range of 0.15 - 0.63 cm can be used. The reactor conditions that can be used are a temperature of 130 - 180 ° C, a hydrogen partial pressure of 35 - 1 ^ 0 kg / cm and a space velocity of 0.5 - 3.5 Vf / h / Vc in order to convert T5 at least 95 wt.% of the glucose feed in the sorbitol solution.

The sorbitol solution obtained is removed from reactor 16 as stream TT and passed to the phase separation stage 18, from which the overhead fraction of vapor stream 19, which contains mainly hydrogen, is discharged and passed to the hydrogen purification stage UU.

If desired, some sorbitol product can be removed from the process. The remaining liquid portion 21 is fed to the fixed bed reactor 26 using recycled hydrogen at U5 and fresh hydrogen from 23 via heater 2¼. 27 with high-active nickel catalyst, such as about 50-66 wt. % nickel supported on a silica-alumina support, for the hydrogenolysis of the sorbitol. Again, sufficient alkaline promoter material must be added at 11a to maintain the pH of the feed 25 in the range of T - 1¾.

The reaction conditions in reactor 26 are a temperature of 216 DEG-260 DEG C., a solids partial pressure of 8U-1 ^ 0 kg / cm 2 and an hourly liquid cream rate of 1.5-3.0 Vf / hr / Vc. achieving a 95% by weight conversion of the sorbitol (or other alditol) feed to polyols, mainly glycerol, and a smaller concentration of glycols and related compounds. The life of the catalyst is maintained between about 10 and 200 hours by periodically regenerating the catalyst as needed to maintain its activity. "1 '..... .....' .....

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* 1 maintain, h.v. by means of reactors 26 and 26a, Ι connected in parallel, where one reactor is in use, while in the other reactor the f 1 Ί; catalyst is regenerated. The spent catalyst is regenerated by first washing it with a solvent, such as water, and then contacting it with a reducing gas, such as hydrogen, at a temperature above the reaction temperature, eg, 260 - 3 ^ 3 C, and at reduced pressure such as atmospheric pressure for a period of 2 - 10 hours.

| The reaction products from reactor 26 (or parallel reactor 10, 26a) are discharged at 28 and passed to a recovery or separation stage 30. where hydrogen-containing gas is removed at 29 and passed to the hydrogen purification stage kb. From the residual liquid flow. 32, the pressure is reduced at 31 and is directed to the; recovery step 3, often comprising two or more distillation columns, T 5: the final column is operated at subatmospheric pressure. A vapor I: stream containing alcohols is removed at 33, water vapor at 35, glycols are removed at 36, and 50 - 90 wt. Glycerol product is removed at 37 Unreacted sorbitol is removed at 39 and passed to distillation column U0 operating at a pressure of 5-100 mm of mercury. The vapor stream k1, which contains extra glycerol, is combined with product stream 38. The heavy liquid stream k2, containing unconverted sorbitol and sugars, is partially recycled to stream 21 and fed to the hydrogenolysis reactor 26 (or 26a) for further processing. A heavy fluid stream i + 3, containing unwanted sugars, 25 is recycled to the first stage hydrogenation reactor 16 to convert such sugars into sorbitol and related products.

The remaining heavy liquid is discharged as blowdown stream 50.

The invention is further illustrated by the following examples, which have no limiting meaning.

Example I

In the catalytic hydrogenolysis of sorbitol solution to form predominantly glycerol, a liquid purge stream is usually withdrawn from the bottom of the distillation recovery stage to prevent an undesirable increase in the concentration of sugars in the glycerol product. A typical composition of this liquid blowdown stream is listed in Table A for distillation conditions of 50 mm Hg pressure and a temperature of 2k6 ° C ~ 288 ° C.

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Typical composition of bottom purge stream from the distillation stage

Aldoses and alditols (1) 0.677; ^ 1,2,2-butanetriol 0,161; 3 'glycerol. 0,155: 1,2,3, - - butanediol 0.0039 [propanol-2 ^ 0.001: butanol-2 (1) <0.001: (!) The weight percentages are: erythritol - 0.033, arabinose - 0.078, iq; arabitol - 0-, 0 ^ 2, xylose - 0.169, xylitol - 0.103, mannose - 0.022, mannitol - 0.088, glucose - 0.086, and sorbitol - 0.378.

; The benefits of recirculating a portion of this liquid purge stream containing mainly unreacted sugars (aldoses and alditols) to the first stage catalytic reaction for T5 · further hydrogenation, compared to (a) single run and "(b) recirculation of the blowdown liquid to only the second or sorbitol reaction stage are listed in Table B for typical reaction conditions. The results are based on a sorbitol feed of 1 -50 kg to the second or sorbitol reaction stage (at stream 21} and on reaction conditions of a temperature of about 260 ° C, a hydrogen part pressure of 98-136 kg. / cm, a space velocity of 2.0 hours, a catalyst particle equivalent diameter of 0.3 cm, bed height of 15 cm, and a 25 wt.% sorbitol concentration in the feed stream to the catalytic reactor 26.

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I 'Execution Life Total. Purge Glycerolop-1 form catalyst, recycle flow yield (3lp 1l hours of flow,. (39), kg / kg: - kg / h kg / h kg / feed · i 5! _37 + 38) ____ j I "I; No recirculation i; from liquid; purge stream Ί6 - · .- 25.9 0.251 i: 10! Recirculation to: sorbitol reactor 26 16 9.33 10.8 26.0 0.21 +1

Recirculation to • both reactors 16 11 ', 09 9 Λ 26, k 0.21 + 3 * ι; No recirculation j 15! vani fluid purge.

j flow 20 .- - 2l +, 9 0.21 + 6 i '

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i l Recirculation to i | sorbitol reactor 26 20 10.6 11.8 25.1 0.23l +

Recirculation to 120; both reactors · 20 12.1+ 10.3 25.1 0.236 y '! No recirculation, from liquid spray

] current T0 - - 13.3 0.1 TJ

; Recirculation to 25 'sorbitol reactor 26 70 30.1+28.1+ 13.1 0.11 + 2

Recirculation to both reactors T0 39.8 21.5 1 i +, 8 0.151

The results for the reaction conditions according to Table B except 36 wt.% Sorbitol concentration in the feed stream are reported in Table C.

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TABLE · C

Execution Life Total Re-Liquid Glycerolop: Catalyst Form, Circulation Blowdown Flow (36) Hours of Flow, (39) »kg / kg / kg kg / h kg / h Hour Feed 5 (Flow 37 _ * _ + 38 ) _: No recirculation of blowdown liquid 16 - - 1 * 0.9 0.26l • Recirculation to: 10; sorbitol reactor 26 16 6.6 9.7 1 * 0.7 0.255

Recirculation to both reactors 16 8.0 8.6 1 * 0.9 0.256 "i

The results reported in Tables B and C show that by recirculating a portion of the liquid blowdown stream to the first, or glucose hydrogenation, reaction stage, not only the amount of variable sugars usually discharged into the blowdown stream; is reduced, but the yield of glycerol product is also increased • by an amount that is significant for a process plant.

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Claims (10)

1. Process for the catalytic conversion of mono-saccharides to form polyols, characterized in that it comprises the following steps:. (a) an input flow is provided which is at least about 2 wt. % of monosaccharide solution and has a: pH of 7-14; ! ; (h) "the supply" and the. hydrogen gas are preheated to at least about 100 ° C, and "the heated feedstream mixture 1" is passed through a first-stage solid hed catalyst reaction zone which "includes a highly active inert metal catalyst; of the first stage reaction zone ii are maintained at a temperature of 130 - 180 ° C, a hydrogen partial pressure of 35 - 140 kg / cm and a space velocity of 0.5 - 5.5 V / h / V, to ensure at least one conversion of the feed into alditols of about: 90 wt.%; Is "1 15" (d) product which contains alditol solution. Is drained off and passed with a promoter material and hydrogen gas to a two-stage fixed bed reaction zone containing a finely divided stabilized high active metal catalyst; (e) the conditions of the second reaction zone are maintained at a temperature within the range of 200-270 ° C, a 2 hydrogen partial pressure of 84-100 kg / cm gauge pressure and an hourly liquid space velocity (LHSV) of 1.5-3.0 to achieve at least one conversion of the alditol in product and about 30 wt.% (f) from the second reaction zone, a product stream is discharged in which the alditol is converted to between about 30 and 80 wt.% to form glycerol and glycol products, and the polyol-containing stream is passed to a recovery stage from which substantially glycerol product is discharged, and (g) a heavy blowdown stream containing aldoses and alditols to the first and second stage reaction zones. is recycled for further conversion to alditols and glycerols. 2 * Process according to claim 1, characterized in that the catalyst in the first reaction zone consists of stabilized, high-active nik- 5 0 9 2 ....... f * i: "| j; Op count on silica-alumina support "consists of 50 - 66 d / S porous nickel,; a particle diameter of. 0.15 - 0.63 cm and a specific surface area of; 1 ^ 0 - 180 mfg. : Process according to claim 1, characterized in that 5. the catalyst is in the. second reaction zone comprises 50 - 65% by weight of porous nickel on an inert support, has a particle size of 0.168-0.75 cm, and the service life of. the. catalyst is from 8 to 200 hours "before it is regenerated to maintain its activity. Method according to claim 1, characterized in that; 10; the pE of the supply flow to. enter each reaction zone, the range of 7.5-12 "is maintained by adding sodium hydroxide in an amount of 0.1-2.0% by weight of the feed stream to prevent leaching of metal from the catalyst . 5 * Method according to claim 1, characterized in that the conditions of. the first reaction zone is maintained at a temperature of 140 - 170aC, a hydrogen partial pressure of 52.5 - 112 kg / cm, a space velocity of 0.6 - 3.3 V / h / V and a hydrogen gas / liquid -: feed ratio of 1000 - 5000 at standard conditions. 6. Process according to claim 1, characterized in that the feed to the first stage reaction zone is 30-60% by weight of glucose in water solution and the glucose therein is converted into sorbitol for 98.5-99.9% by weight. . The method of claim 1. characterized in that the feed stream to the first zone is 20-50 wt.% mannose solution and the product is mannitol solution. 8. Process according to claim 1, characterized in that the feed stream to the second reaction zone contains 20-50% by weight sorhitol, the reaction zone conditions are maintained at a temperature within the range of 226-29 ° C, a hydrogen partial pressure of 98-133 kg / -p 30 cm, a liquid space velocity / hour of 2.0-2.7, and the life of the catalyst for regeneration is 10-200 hours, and the sorbitol feed solution for ko-99 wt. % is converted into mainly glycerol product with glycols as the balance. 9. Process according to claim 1, characterized in that the feed stream to the first stage contains 3 - 60 wt.% Glucose in alcohol solution and the feed to the two-stage reaction zone. 15 - 50 wt.% Sorbitol. 0 5 0 02% r; ! ~ r * ι I -. 12 f r * i,. . ! m is alcohol solution. ! ! The method of claim 1, with. the characteristic that I, .....! The catalyst in the two-stage reaction zone is regenerated after ten years; ·; at least about 20 hours of operation by washing it, with a solvent,! 5! in. contact "with hydrogen" at a. temperature, from 2βθ - 3 ^ 3 ° C! ! for a period of at least 2 hours, and then again in j; to take it. 1:11: "Process for the preparation of glycerol by catalytic conversion of monosaccharide, characterized in that it comprises the following steps: 10. (A feed stream is already provided which contains about 20-160 wt% monosaccharide solution in water and has a pH of 7.5-12 to prevent leaching of metal from the catalyst; The feed and hydrogen gas are preheated to about 120 DEG C. - 120 DEG C., and the heated feed flow mixture is passed through a first stage fixed catalytic reaction zone. which contains a one-hour high-active nickel catalyst with 50-66 wt.% nickel on a silica-alumina support and has a particle size, in the range of 0.15T-0.635 cm; : 20 'Cell the conditions of the first reaction zone are maintained at a temperature of 140 - 1TQ ° C, a hydrogen partial pressure o of 52.5 - 112 kg / cm, a space velocity of 0.6 - 3.3 V / hour / V, and a hydrogen gas / liquid feed ratio of 120-4000 the standard conditions to achieve at least a conversion of about 90% by weight of the feed into alditols; The product containing mainly sorbitol in water solution is discharged and led with a hydrogen promoter material to a two-stage reaction zone. Maintained at a temperature within the range of 226-249 ° C, a hydrogen partial pressure of 98-133 kg / cm, 30 an hourly liquid space velocity (LHSV ") of 2.0 - 2.7, and a catalyst life before regeneration of 12 - 100 hours, to achieve at least a 30 - 70% conversion of the sorbitol to form glycerol with residual glycols; (el from the second reaction zone a stream containing glycerol and glycol products is withdrawn, and passed to a distillation section including a vacuum distillation stage maintained at a pressure of 5 DEG-1 mm Hg to remove alcohols and —ΓΤϋ5ίΓ92 .................... # ί; ~ "'rt ί E t! L 13' i \ 'water vapor, whereby a high purity glycerol product is - formed; (t) unconverted sorbitol to the second tr aps reaction: is recirculated, and a heavy blowdown liquid stream containing alditose and 5: alditol is recycled to said first and second stage reaction zones for ► • further conversion to alditols and glycerols, respectively: s: S. t * S 8 1 0 5 0 92