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CN-121974778-A - Method for preparing xylitol by one-step hydrolysis and hydrogenation of xylan or biomass

CN121974778ACN 121974778 ACN121974778 ACN 121974778ACN-121974778-A

Abstract

The invention discloses a method for preparing xylitol by one-step hydrolysis and hydrogenation of xylan or biomass, which comprises the following steps of placing raw materials, water, a metal chloride additive and a ruthenium-based catalyst in a high-pressure reaction kettle, replacing air in the kettle with hydrogen, filling initial hydrogen with the pressure of 0.5-4.0 MPa, reacting for 1-6 hours at the temperature of 140-180 ℃, and completing hydrolysis and hydrogenation reaction of the raw materials to obtain the xylitol in one step, wherein the raw materials are xylan or real biomass, and the introduction of the metal halide additive (or self-contained in seawater) can promote hemicellulose depolymerization, xylose hydrogenation and xylitol isomerization inhibition, so that the overall efficiency is improved.

Inventors

  • CUI YANBIN
  • Ou Jiayi
  • WANG CHENGUANG
  • DU XIAORUI

Assignees

  • 中国科学院广州能源研究所

Dates

Publication Date
20260505
Application Date
20260115

Claims (10)

  1. 1. A method for preparing xylitol by one-step hydrolysis and hydrogenation of xylan or biomass is characterized by comprising the following steps of placing raw materials, water, a metal chloride additive and a ruthenium-based catalyst into a high-pressure reaction kettle, replacing air in the kettle with hydrogen, filling initial hydrogen with the pressure of 0.5-4.0 MPa, reacting for 1-6 hours at the temperature of 140-180 ℃, and completing hydrolysis and hydrogenation reaction of the raw materials to obtain xylitol in one step, wherein the raw materials are xylan or real biomass.
  2. 2. The method of claim 1, wherein the initial hydrogen pressure is 1.0-4.0 MPa and the reaction is carried out at a temperature in the range of 150-170 ℃ for 2-5 hours.
  3. 3. The method according to claim 1, wherein when the raw material is xylan, the hydrogen pressure is 1.0MPa-2.0 MPa and the reaction is carried out at 160 ℃ for 4 hours.
  4. 4. The method of claim 1, wherein when the feedstock is real biomass, the hydrogen pressure is 2.0 MPa-4.0 MPa and the reaction is carried out at 160 ℃ for 4 hours.
  5. 5. The method of claim 1, wherein the metal chloride is selected from one of NaCl, KCl, mgCl 2 、CaCl 2 .
  6. 6. The method according to claim 1, wherein the metal chloride is added at a concentration of 0.5-20 wt% and the raw material is added at a concentration of 1.0-10.0 wt%.
  7. 7. The method of claim 1, wherein the metal chloride is added at a concentration of 1.5-5.0 wt%.
  8. 8. The method of claim 1, wherein the metal chloride is added at a concentration of 3.5 wt%.
  9. 9. The method of claim 1, wherein the metal chloride is not additionally added when the water is selected to be seawater or concentrated seawater.
  10. 10. The method of claim 1, wherein the ruthenium-based bifunctional catalyst is one of Ru/C、Ru/Nb 2 O 5 、Ru/Al 2 O 3 、Ru/ZrO 2 、Ru/SiO 2 、Ru/TiO 2 、Ru/USY、Ru/ZSM-5, ru is used as the catalyst, ru loading is 2.5 wt% -10 wt%, the biomass is one of corncob, corn stalk, bagasse, reed and pine, the biomass is crushed before use, and stirring speed is 400-1000 rpm.

Description

Method for preparing xylitol by one-step hydrolysis and hydrogenation of xylan or biomass Technical Field The invention relates to the technical field of xylitol preparation, in particular to a method for preparing xylitol by one-step hydrolysis and hydrogenation of xylan or biomass. Background Xylitol is a five-carbon sugar alcohol with important economic value and is widely applied to the fields of food, medicine and chemical industry. The traditional xylitol production process is generally divided into two steps, namely, firstly extracting xylose from hemicellulose-rich biomass such as corncobs, bagasse and the like through acid hydrolysis, and then carrying out catalytic hydrogenation on the purified xylose. The process has the advantages of long route, high energy consumption, large amount of waste acid and wastewater production, and complicated steps of separating and purifying the intermediate product xylose, so that the production cost is high. To simplify the process, researchers have proposed a "one-pot" strategy, i.e., hydrolysis of the feedstock and hydrogenation reduction of xylose are carried out continuously in the same reactor. However, the existing one-pot process still faces the challenges that (1) inorganic acid is generally required to be added to hydrolyze a substrate, equipment corrosion and subsequent waste liquid treatment are easy to cause, the preparation cost of the catalyst is increased by adopting a solid acid catalyst, the hydrolysis performance of the catalyst is obviously reduced along with the increase of the reaction times, and (2) the existing method is to purify hemicellulose or polysaccharide, and the conversion efficiency of the system to biomass raw materials with complex components and intractable structures is not ideal. For example, prior art such as CN105777485A, CN109879723B and CN109879721B discloses a method for directly preparing xylitol from hemicellulose, which adopts hemicellulose (such as corncob hemicellulose, bagasse hemicellulose, etc.) separated by pretreatment as raw materials, and performs one-pot catalytic hydrogenation reaction in an aqueous phase system under the action of a metal catalyst. Therefore, development of a novel one-pot conversion process for efficiently converting xylan and real biomass raw materials to prepare xylitol has important application value. Disclosure of Invention The invention aims to provide a method for preparing xylitol by one-step hydrolysis and hydrogenation of xylan or biomass, which solves the problems of complex pretreatment of raw materials and low product selectivity in the existing biomass-based xylitol preparation process. The invention is realized by the following technical scheme: A method for preparing xylitol by one-step hydrolysis and hydrogenation of xylan or biomass comprises the steps of placing raw materials, water, a metal chloride additive and a ruthenium-based catalyst in a high-pressure reaction kettle, replacing air in the kettle with hydrogen, and then charging the raw materials into the kettle, wherein the initial hydrogen pressure is 0.5-4.0 MPa, preferably 1.0-4.0 MPa, and the raw materials are reacted for 1-6 hours, preferably 2-5 hours, most preferably 4 hours at a temperature range of 140-180 ℃, preferably 150-170 ℃, most preferably 160 ℃, and the hydrolysis and hydrogenation reaction of the raw materials are completed in one step to obtain xylitol, and the raw materials are xylan or real biomass. When the feedstock is xylan, the initial hydrogen pressure is preferably 1.0-4.0 MPa, and in combination with the standpoint of saving the cost of the feedstock, the hydrogen pressure is preferably 1.0-2.0 MPa, and when the feedstock is real biomass, the hydrogen pressure is preferably 2.0 MPa-4.0 MPa, and most preferably 4.0 MPa. The metal chloride is selected from NaCl, KCl, mgCl 2、CaCl2 or the like, preferably NaCl and KCl, and most preferably NaCl. The metal chloride is added at a concentration of 0.5-20 wt%, including 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 5.0 wt%, 10.0 wt%, 15.0 wt%, 20.0 wt%, preferably 1.5-5.0 wt%, and most preferably 3.5 wt%. When water is selected as seawater or concentrated seawater, the metal chloride is not additionally added. The ruthenium-based bifunctional catalyst is selected from one of Ru/C、Ru/Nb2O5、Ru/Al2O3、Ru/ZrO2、Ru/SiO2、Ru/TiO2、Ru/USY、Ru/ZSM-5, and the like, and is preferably Ru/C, ru/TiO 2、Ru/Al2O3、Ru/ZrO2、Ru/SiO2 and Ru/USY. When the catalyst is Ru/C, the Ru loading is 2.5 wt-10 wt%, preferably 5 wt-7.5-wt%. The biomass is one of corncob, corn stalk, bagasse, reed and pine, preferably corncob or reed, and most preferably corncob. When the raw material is biomass, the biomass is crushed before use, and the particle size of the biomass is 20 meshes. The raw material concentration is 1.0-10.0 wt%, including 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 10.0 and wt%. The stirring speed of the reaction is preferably 400-1000 rpm, including 400, 500, 600,