DD156175A1 - METHOD FOR HYDROGENATING GLUCOSE TO SORBIT - Google Patents

Abstract

The invention relates to an improved process for the hydrogenation of glucose, wherein sorbitol with high purity is obtained with low catalyst consumption and high Durchsetzen the hydrogenation plant. The task of carrying out the glucose hydrogenation under conditions such that a high selectivity for the formation of sorbitol, a high space-time yield and a low deactivation of the catalyst is achieved by hydrogenating at 373 to 423 K, 5 to 30 MPa hydrogen pressure, catalyst loadings with 35 to more than 50% aqueous glucose solution from 1.1 to 1.5 t / th, catalyst loading with hydrogen from 4000 to 8000 Nm high 3 / th and a pH value of the glucose solution from 3.5 to 7 is carried out with a fixed, stabilized nickel-silica Faellkatalysator. The catalyst, which is desorbed after reduction of the hydrogen at temperatures above 673 K with an inert gas stream, is activated before it is used in the hydrogenation reactor. During the hydrogenation, a selectivity of at least 95% and a glucose conversion of at least 99.8% is achieved.

Description

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Title of the invention

Process for the hydrogenation of glucose to sorbitol

Field of application of the invention

The invention "relates to a process for the continuous catalytic Hoohdruckhydrierung ron glucose in aqueous solution to sorbitol at stationarily arranged catalysts. The sorbitol produced by the inventive process /? Ird in particular as a sweetener for dietary products, for the production of ascorbic acid as a component of solutions for infusion, as Conditioner used to adjust the moisture content and as a polyol for synthesizing many substances.

Characterization of the known technical solutions

The catalytic high-pressure hydrogenation of glucose to sorbitol is a known reaction and is carried out industrially in many countries. Ni-skeleton and, in addition, Ni support and Ni / Cu / Mn catalysts are used most frequently β> 2, 57.

The continuous glucose hydrogenation is carried out predominantly with suspended Ni skeleton catalysts. Hydrogenation is carried out in vertically arranged tubular reactors, through which the glucose solution and a large excess of hydrogen are passed from bottom to top at pressures between 5 and 30 MPa and temperatures between 370 K and 455 K. With this method, a high space / time yield at high sorbitol

Achieved in hexitol * However, the always exforderliohej labor-consuming catalyst metering and separation is still a disadvantage. In addition, the catalyst particles in the suspension on the thus applied machine and Appaxateteilen cause a high, abrasive wear of costly special technical solutions and frequent renewal made to achieve economic Catalyst consumption (kg catalyst / t product) is a catalyst reuse required For this purpose, a technically complex catalyst cycle can be built * These Na.chteile be avoided in the continuous GluGosehydrierung with Pest bed catalysts Here, the hydrogenation in both the trickle phase reactor _s in the glucose solution and Hydrogen can be passed from top to bottom over the catalyst ", as in the fixed-bed bottom reactor, where the glucose solution and hydrogen are passed from bottom to top over the catalyst.» For this procedure Ifi / SiO 2, Ni / Cu / Mn and Ni / Cu / SiG ₂ catalysts have been proposed. The reaction temperatures and pressures in the fixed bed processes are equal to or lower than in the case of continuous catalyst suspension suspended phase dehydrogenation. The disadvantage compared to the process with suspended catalyst is the relatively low space / time yield, which can only be improved by particularly highly active _s long-term stable catalysts. «

Object of the invention

The aim of the invention is a continuous process for the hydrogenation of gluoose _? in which ongoing catalyst dosing and separation is not required and which allows a higher Rauna / Zei c yield than that of the prior art.

Explanation of the essence of the invention

The invention has for its object to carry out the hydrogenation of glucose in aqueous solution of stationary catalysts arranged with high tree / time yields.

The object is achieved by the present invention, the hydrogenation at temperatures of 373 K to 423 K and hydrogen pressures of 5 MPa to 30 MPa in the bottom phase with conducting an aqueous glucose solution in cocurrent with hydrogen from bottom to top through a fixed catalyst bed or in the trickle with Guiding the aqueous glucose solution in cocurrent with hydrogen from top to bottom through a fixed Ka ta Iy sat or oration is carried out "This nickel-silica precipitation catalyst is used, which after the reduction in Y / a current at temperatures of 673 K to 723 K is then loaded above 673 K with an inert gas Strora of 300 to 1GQO Y / Yh until the hydrogen is completely desorbed from the catalyst. On cooling to 433 Κ to 333 K, the catalyst is treated with an inert gas stream, into which air has been metered until 1 to 5 volts of oxygen are measured in the exhaust gas. The air supply is maintained until the temperature has dropped to 323 K. Dex catalyst has a nickel content of 60 to 75 tf ° . It is activated in the hydrogen txome before hydrogenation starts. It is important that the activation of the nickel-silica catalyst in the hydrogenation reactor with a hydrogen loading of 4000 to 8000 Nm ³ Zt h at a pressure of 2 MPa to 10 L ¹ IPa according to the following temperature-time program:

Heat up within 3 hours to 353 K Heat up within 2 hours to 373 K Heat up within 12 hours to 443 K Hold temperature for 5 hours at 443 K.

The erfindunssgemäße process is at a catalyst loading with aqueous glucose solution from 0.5 to 1.5 tZth

and with hydrogen from 1000 to 12000 NrP / th, whereby the hydrogen is recycled ". The glucose solution has a concentration of 35 % to more than 50 $ glucose and the pH of the solution is in the range of 3.5 to 7 "It is also necessary that the tablet-promoting catalyst ia.it dimensions of 4 to 6 ram diameter and 4 to 6 mm in height inside the reactor in superimposed baskets is housed. The inventive method allows for high reactor throughputs and high Gluoosekonzentrationen. long service life »As a result, a widespread use of the catalyst achieved in addition to reducing the EatalysatGrverbrauch.es thus a significant reduction in downtime is possible, resulting from the frequently required Kontaktwchsels in the known methods with fixed-bed catalysts. Under the terms of the method, sorbitol high Oneness is won, "It is necessary for the method ^ that a G-lucoseurasatz of at least 99j8% and a selectivity of at least 95 $> _s, preferably at least $ 97? complied with

embodiment

Example 1 (Comparative Example)

A nickel catalyst prepared by co-precipitation of nickel and silica from nickel salt solution and sodium silicate solution is reduced at 698 K in the mains stream after heating at 623 K and after forming into tablets of 5 mm diameter and 5 mm height for 8 hours. Ström in hydrogen cooled to 253 K and then rinsed at this temperature for one hour in an inert gas stream (nitrogen ) . Thereafter, the catalyst is stabilized with an inert gas-air mixture containing 1 vol- $ oxygen in the inlet until there is no appreciable oxygen uptake by the catalyst, i. h _e the oxygen concentrations in the inlet and outlet of the stabilization tank are the same «The load

in all cases amounts to 500 Y / Yh. Dex catalyst has a nickel content of 63 & «

200 g of this catalyst are installed in a high-pressure test reactor and heated in a hydrogen stream of 600 l / h within 10 hours at 443 K and kept for 5 hours at this temperature »Nacia cooling to 398 K and rinsing the reactor with water under 25 MPa Hydrogen pressure, an aqueous glucose solution was hydrogenated under the following conditions:

Pressure 25 MPa, temperature 398 K, 1000 Nm ⁵ hydrogen passage / hour, pH of the glucose solution 4.3. Table 1 summarizes the measured values.

Table 1

Glucose concentration ($ 0 250 50 150 250 30 150 Load with glucose solution (ml / h) 99.3 99.82 99, 9 y, 94 Sales of glucose (.%) 91.8 90.0 94 87 93.2 Sorbitol selectivity <J>) 1

In a further experiment, starting at 398 E, the reaction temperature is increased by 99.8 % by 5 degrees each time the glucose is 99.8 %, giving a reaction temperature of 418 K. From the glucose hydrogenated up to this time and the one used The amount of catalyst used determines the catalyst consumption and the following consumption values were determined for the above conditions:

catalyst consumption

Cg Cat./kg 505 & ige GIu 9.5 6.7 3.6 3.3

Goselosungy

Example 2 (Inventive Example)

A nickel catalyst prepared by co-precipitation of coil and silica from nickel salt solution and sodium silicate solution is reduced after heating to 623 K and after "forming tablets of 5 m diameter and 5 ram height for 8 hours" at 723 K in hydrogen flow, 1 hour purged with nitrogen at 723 K and then cooled in the inert gas stream to 353 K. At this temperature, the catalyst is stabilized with an inert gas-air mixture containing Yol ~ # oxygen in the inlet 1 until there is no appreciable oxygen uptake by the catalyst, i. the oxygen concentrations at the inlet and outlet of the stabilization tank are the same »The load is in all cases 500 Y / Vh. The catalyst has a nickel content of 65% «

200 β of this catalyst are installed in a high-pressure test reactor and heated in a hydrogen stream of 1,000 Nra / h according to the following temperature-time programra;

Heating up within 3 hours to 353 E Heating up within 2 hours to 373 E Heating up to 443 K within 12 hours

Keep the temperature at 443 K for 5 hours

NaOH cooling to 398 K and rinsing the reactor with water under 25 MPa V / asserstoffdruck an aqueous glucose solution was hydrogenated under the same conditions as in Example 1. In Table 2, the measured values are collected.

Table 2

(KL concentration (.%) 50 40

Load with glucose solution (ral / h) 250 150 250 150 Sales of glucose ($>) 99.84 99.92 99.93 100 Sorbitol selectivity O) 97.3 96.2 98.2 97.2

74 4 5

Bex catalyst consumption is determined in the same manner as in Example 1. The following consumption values were determined for the abovementioned conditions:

catalyst consumption

(g Cat./kg 5OftLg glucose -2.7 2.5 2.1 2.0

solution)

A comparison of the results of the two examples makes it clear that under the conditions of the process according to the invention a higher selectivity, a higher space / time yield and a significantly better utilization of the catalyst is achieved than in the known processes *

Claims (4)

invention claim 1β Process for the hydrogenation τοπ glucose to sorbitol, characterized in that the hydrogenation "at temperatures of 373 K to 423 Κ, preferably at 383 * K to 403 K, at hydrogen pressures of 5 MPa to 30 MPa, preferably at 15 IvIPa to 25 MPa at catalyst loadings of from 35 to more than 5% glutathione solution of 1.1 to 1.5 t / th, hydrogen loading of the catalyst from 4000 to 8000 mm / t and pH of the glucosene solution of 3j5 to 7 in the bottom phase with leadership of the aqueous glucose solution in cocurrent with the hydrogen from bottom to top, by a fixed catalyst or in the trickle stream with Guiding the aqueous GluGoselösung in cocurrent with the hydrogen from top to bottom through a fixed Katalysatorschüttang is performed, wherein a nickel -Silisiumdioxid precipitated catalyst is used, which then after the reduction in a stream of hydrogen at temperatures of 673 K to 723 K above is loaded with an inert gas stream of 300 to 1000 V / Yh, preferably 500 to 800 Y / Yhj until the hydrogen is completely desorbed from the catalyst and then treated after cooling to 433 K to 333 K with an inert gas stream is metered into the air until the exhaust gas measures 1 to 5 vol. % oxygen and the air supply is maintained until the temperature has dropped to 323K, after which the catalyst has a content of 60 to 75 % and above Start of the hydrogenation is activated in the hydrogen stream iso 2 «method according to item 1, characterized in that the activation of the nickel-siliceous catalyst before the hydrogenation in the hydrogenation reactor with a hydrogen load of 4000 to 8000 Nm ⁵ / th at a pressure of 2 IvEPa to 10 MPa according to the following Teraperatur- Time Programra done? Germination within 3 hours to 353 K Heating up to 373 K within 2 hours Heat up to 443 K within 12 hours Keep the temperature at 443 K for 5 hours. 3 * method naoh point 1 and 2, characterized in that selecting the hydrogenation, a glucose conversion of at least 99.8 ¹ Io and a hydrogenation selectivity to sorbitol of at least 95 % _{y are} preferably maintained at least. Method according to items 1 to 3, characterized in that the catalyst has tablet shape with a diameter of 4 to 6 ram and a height of 4 to 6 mm and is housed inside the hydrogenation reactor in 8 to 12 baskets arranged one above the other.