Continuous gas-liquid countercurrent method for preparing sugar alcohol

Abstract

Disclosed in the present invention is a continuous gas-liquid countercurrent method for preparing a sugar alcohol. The continuous countercurrent method comprises the following steps: in a gas-liquid countercurrent trickle bed reactor, enabling a biomass sugar solution to flow into the reactor from top to bottom from a liquid phase inlet and hydrogen to pass through the reactor from bottom to top from a gas phase inlet; and enabling the biomass sugar solution and the hydrogen to pass through a catalyst bed layer in a gas-liquid countercurrent form for hydrogenation reduction to obtain a biomass sugar alcohol solution. The continuous gas-liquid countercurrent method for preparing a sugar alcohol provided by the present invention implements continuous hydrogenation of the biomass sugar solution by efficiently strengthening the gas-liquid-solid three-phase mass transfer and shortening the retention time; in addition, the conversion rate of the biomass sugar and the yield of the corresponding sugar alcohol are greatly improved.

Description

A gas-liquid countercurrent continuous method for preparing sugar alcohols Technical Field

[0001] The invention belongs to the technical field of hydrogenation production of sugar alcohols, and particularly relates to a gas-liquid countercurrent continuous method for preparing sugar alcohols. Background Art

[0002] Sugar alcohols generally refer to a class of functional polyols produced by hydrogenation and reduction of biomass sugars. These include xylitol, sorbitol, mannitol, maltitol, and lactitol. They are important raw materials and products in the food, fine chemical, and pharmaceutical industries. Compared to more common aldoses and ketoses, biomass sugar alcohols offer advantages such as low calories, low blood sugar content, and a reduced risk of tooth decay. They are recognized globally as safe and healthy foods.

[0003] Currently, the main production process for biomass sugar alcohols is batch hydrogenation in an intermittent reactor. The catalyst is easily lost due to mechanical stirring, and the catalyst recovery is difficult. In addition, in order to ensure the thorough hydrogenation of biomass sugars during industrial production, hydrogen is usually continuously replenished to maintain the hydrogen supersaturation state in the sugar solution. To address the above problems, continuous hydrogenation processes have been gradually developed and applied in this field. U.S. Patent US8816068B2 discloses a continuous catalytic hydrogenation process for preparing high-purity sugar alcohols. It uses two sets of fixed-bed reactors in series to achieve continuous hydrogenation of glucose. This process has excellent glucose conversion rate and sorbitol selectivity. However, the catalysts loaded in the reactors are ruthenium-based and platinum-based catalysts, which are relatively expensive. In addition, the patent prefers a material flow rate of 1-1.5 kg / L / h, a hydrogen flow rate of 15 kg / h, and a hydrogen pressure of 8-15 MPa. Problems such as high cost, high hydrogen consumption, and high hydrogen pressure limit its industrial application. Patent WO2018118854A1 discloses a method for continuously hydrogenating maltose to produce maltitol. Using a fixed-bed reactor, the method achieves a high yield (>90%). However, this technology faces stringent operating conditions, such as the hydrogen-to-maltose molar ratio (>40:1) and the reaction hydrogen pressure (12.4-17.2 MPa). Chinese patent CN208949158U discloses an apparatus for continuously hydrogenating glucose to produce sorbitol. This method sequentially connects a slurry-bed reactor with a fixed-bed reactor, but the total material residence time is long and production efficiency is low. Furthermore, the reaction hydrogen pressure used is >10.5 MPa, which raises cost and safety issues.

[0004] In summary, the existing technology still has problems such as a large molar ratio of hydrogen to substrate, high hydrogen consumption, and low production efficiency, and is in urgent need of improvement. Technical issues

[0005] The technical purpose of the present invention is to provide a gas-liquid countercurrent continuous method for preparing sugar alcohols, which realizes continuous hydrogenation of biomass sugar solution by efficiently enhancing gas-liquid-solid three-phase mass transfer and shortening residence time, and greatly improves the conversion rate of biomass sugar and the yield of corresponding sugar alcohols. Technical Solutions

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A gas-liquid countercurrent continuous method for preparing sugar alcohols, comprising the following steps: in a gas-liquid countercurrent trickle bed reactor, a biomass sugar solution flows into the reactor from top to bottom from a liquid phase inlet, while hydrogen passes through the reactor from bottom to top from a gas phase inlet; the biomass sugar solution and hydrogen are hydrogenated and reduced through a catalyst bed in a gas-liquid countercurrent form to obtain a biomass sugar alcohol solution.

[0008] The catalyst is selected from Raney nickel, Raney copper, ruthenium carbon or platinum carbon.

[0009] Preferably, the catalyst is Raney nickel or Raney copper, which are relatively inexpensive and have high catalytic efficiency.

[0010] The average particle size of the catalyst is 1-6 mm, which can effectively avoid the pressure drop problem caused by too small catalyst particles and also avoid the uneven liquid dispersion caused by too large particles.

[0011] The biomass sugar solution includes but is not limited to maltose, glucose, mannose, xylose or lactose. The corresponding sugar alcohol includes but is not limited to maltitol, sorbitol, mannitol, xylitol or lactitol.

[0012] The molar concentration of the biomass sugar solution is 0.6 to 2.2 mol / L. The concentration of the biomass sugar solution can effectively increase the product concentration and reduce the subsequent crystallization separation cost while ensuring the conversion efficiency.

[0013] The biomass sugar solution is continuously fed using a liquid phase pump at a flow rate of 0.5-5 mL / min. This flow rate helps prolong the residence time of the liquid on the catalyst surface, increases sugar alcohol yield, and effectively prevents hydrolysis side reactions caused by local overheating.

[0014] The hydrogen pressure is 5-10 MPa, which can ensure excellent biomass sugar conversion rate and sugar alcohol yield while taking into account safety and economic considerations.

[0015] The hydrogen gas is controlled by a mass flow meter, and the hydrogen gas flow rate is 10-100 sccm.

[0016] The temperature of the gas-liquid countercurrent trickle bed reactor is 100-140° C. The reactor temperature can achieve both high conversion rate and high selectivity, thereby maximizing the production of target sugar alcohol.

[0017] Preferably, the catalyst has an average particle size of 1 to 4 mm, the molar concentration of the biomass sugar solution is 0.6 to 1.8 mol / L, the feed flow rate of the biomass sugar solution is 1 to 2 mL / min, the hydrogen pressure is 6 to 9 MPa, the hydrogen flow rate is 20 to 80 sccm, and the trickle bed reactor temperature is 120 to 140°C. These process conditions can achieve a biomass sugar conversion rate of at least 87% and a sugar alcohol yield of at least 83%.

[0018] More preferably, the catalyst has an average particle size of 1 to 3.5 mm, the molar concentration of the biomass sugar solution is 0.6 to 1.6 mol / L, the feed rate of the biomass sugar solution is 1 to 1.5 mL / min, the hydrogen pressure is 6 to 9 MPa, the hydrogen flow rate is 20 to 70 sccm, and the trickle bed reactor temperature is 120 to 140°C. These process conditions can achieve a biomass sugar conversion rate of at least 92% and a sugar alcohol yield of at least 90%.

[0019] More preferably, the catalyst has an average particle size of 1 to 3.5 mm, the molar concentration of the biomass sugar solution is 1 to 1.6 mol / L, the feed rate of the biomass sugar solution is 1 to 1.5 mL / min, the hydrogen pressure is 6 to 9 MPa, the hydrogen flow rate is 20 to 50 sccm, and the trickle bed reactor temperature is 120 to 140°C. These process conditions can achieve a biomass sugar conversion rate of at least 97.5% and a sugar alcohol yield of at least 94.5%.

[0020] More preferably, the catalyst has an average particle size of 2-3 mm, the molar concentration of the biomass sugar solution is 1.4-1.6 mol / L, the feed rate of the biomass sugar solution is 1 mL / min, the hydrogen pressure is 6-8 MPa, the hydrogen flow rate is 20-50 sccm, and the trickle bed reactor temperature is 120-130°C. These process conditions can achieve a biomass sugar conversion rate of at least 99% and a sugar alcohol yield of at least 98%. Beneficial effects

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Compared to existing continuous hydrogenation processes for biomass sugars, the present invention utilizes a gas-liquid countercurrent trickle bed apparatus to produce the corresponding sugar alcohols, effectively ensuring sufficient contact between hydrogen, sugar solution, and catalyst. By enhancing three-phase mass transfer, the material residence time is shortened, and the sugar alcohol production efficiency is improved.

[0023] (2) The hydrogen flow rate and pressure of the present invention are lower, and the amount of hydrogen used is smaller, which greatly reduces the production cost and effectively avoids the safety hazards caused by high-pressure hydrogen.

[0024] (3) The present invention is suitable for the continuous hydrogenation of various biomass sugars and can maintain a good biomass sugar conversion rate and sugar alcohol yield (including time-space yield) under high material concentration conditions (e.g., 1.2-1.8 mol / L), and has excellent potential for industrial scale-up.

[0025] (4) The present invention can be widely used in the industrial preparation of functional sugar alcohols such as sorbitol, mannitol, xylitol, maltitol, and lactitol. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic structural diagram of a gas-liquid countercurrent trickle bed reactor according to the present invention.

[0027] Among them: 11, liquid phase inlet; 12, gas phase outlet; 13, gas phase inlet; 14, liquid phase outlet; 15, upper quartz sand filler; 16, catalyst bed; 17, lower quartz sand filler; 18, support frame.

[0028] FIG2 is a schematic structural diagram of a gas-liquid co-current trickle bed reactor in Comparative Example 1 of the present invention.

[0029] Among them: 21, liquid phase inlet; 22, gas phase inlet; 23, gas-liquid outlet; 24, upper quartz sand filler; 25, catalyst bed; 26, lower quartz sand filler; 27, support frame. Best Mode for Carrying Out the Invention

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0033] As shown in Figure 1, the present invention provides a continuous gas-liquid countercurrent method for preparing sugar alcohols. In a gas-liquid countercurrent trickle bed reactor, a catalyst bed is placed above a support frame 18. A biomass sugar solution flows downward from the liquid inlet 11 into the reactor, while hydrogen gas flows upward from the gas inlet 13 through the reactor. The two gases flow in a gas-liquid countercurrent pattern through an upper quartz sand packing 15, a catalyst bed 16, and a lower quartz sand packing 17, undergoing hydrogenation reduction to produce a biomass sugar alcohol solution. Modes for Carrying Out the Invention

[0034] Example 1:

[0035] A gas-liquid countercurrent trickle bed reactor was filled with 90g of Raney nickel catalyst (average particle size of 1mm). The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 30mL / min of hydrogen was introduced into the reactor from the lower gas phase inlet 13 and out from the upper gas phase outlet 12. The pressure in the reactor was controlled at 8MPa using a backpressure valve. Simultaneously, a 1.4mol / L maltose solution was added to the reactor from the upper liquid phase inlet 11 using a liquid phase metering pump at a flow rate of 1mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0036] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 97.5%, and the maltitol yield was 94.8%. Example 2

[0037] A gas-liquid countercurrent trickle bed reactor was filled with 90g of Raney nickel catalyst (average particle size 3mm). The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 30mL / min of hydrogen was introduced into the reactor from the lower gas phase inlet 13 and out from the upper gas phase outlet 12. The pressure in the reactor was controlled at 8MPa using a backpressure valve. Simultaneously, a 1.4mol / L maltose solution was added to the reactor from the upper liquid phase inlet 11 using a liquid phase metering pump at a flow rate of 3mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0038] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 70.4%, and the maltitol yield was 67.9%. Example 3

[0039] A gas-liquid countercurrent trickle bed reactor was filled with 90g of Raney nickel catalyst (average particle size 4mm). The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Hydrogen was then introduced into the reactor at a rate of 30mL / min from the lower gas phase inlet 13 and out of the upper gas phase outlet 12. The pressure in the reactor was controlled at 8MPa using a backpressure valve. Simultaneously, a 1.4mol / L maltose solution was added to the reactor from the upper liquid phase inlet 11 at a flow rate of 5mL / min using a liquid phase metering pump. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent pattern, resulting in a continuous hydrogenation reaction. Maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0040] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 55.1%, and the maltitol yield was 53.5%. Example 4

[0041] A gas-liquid countercurrent trickle bed reactor was filled with 80 g of Raney nickel catalyst (average particle size 3 mm). The reactor was heated to 110°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 50 mL / min of hydrogen was introduced into the reactor from the gas phase inlet 13 at the lower end and discharged from the gas phase outlet 12 at the upper end. The pressure in the reactor was controlled at 7.5 MPa using a backpressure valve. Simultaneously, a 1.4 mol / L maltose solution was added to the reactor from the liquid phase inlet 11 at the upper end of the reactor using a liquid phase metering pump at a flow rate of 1.5 mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0042] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 75.5%, and the maltitol yield was 69.3%. Example 5

[0043] A gas-liquid countercurrent trickle bed reactor was filled with 80 g of Raney nickel catalyst (average particle size 3 mm). The reactor was heated to 120°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 50 mL / min of hydrogen was introduced into the reactor from the gas phase inlet 13 at the lower end and discharged from the gas phase outlet 12 at the upper end. The pressure in the reactor was controlled at 7.5 MPa using a backpressure valve. Simultaneously, a 1.4 mol / L maltose solution was added to the reactor from the liquid phase inlet 11 at the upper end of the reactor using a liquid phase metering pump at a flow rate of 1.5 mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0044] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 87.2%, and the maltitol yield was 83.3%. Example 6

[0045] A gas-liquid countercurrent trickle bed reactor was filled with 80 g of Raney nickel catalyst (average particle size 3 mm). The reactor was heated to 140°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 50 mL / min of hydrogen was introduced into the reactor from the gas phase inlet 13 at the lower end and discharged from the gas phase outlet 12 at the upper end. The pressure in the reactor was controlled at 7.5 MPa using a backpressure valve. Simultaneously, a 1.4 mol / L maltose solution was added to the reactor from the liquid phase inlet 11 at the upper end of the reactor using a liquid phase metering pump at a flow rate of 1.5 mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0046] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 98.3%, and the maltitol yield was 94.5%. Example 7

[0047] A gas-liquid countercurrent trickle bed reactor was filled with 100 g of Raney nickel catalyst (average particle size 3 mm). The reactor was heated to 125°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 70 mL / min of hydrogen was introduced into the reactor from the lower gas phase inlet 13 and out from the upper gas phase outlet 12. The pressure in the reactor was controlled at 6 MPa using a backpressure valve. Simultaneously, a 1.4 mol / L maltose solution was added to the reactor from the upper liquid phase inlet 11 using a liquid phase metering pump at a flow rate of 1 mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0048] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 87.6%, and the maltitol yield was 84.4%. Example 8

[0049] A gas-liquid countercurrent trickle bed reactor was filled with 100 g of Raney nickel catalyst (average particle size 3 mm). The reactor was heated to 125°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 70 mL / min of hydrogen was introduced into the reactor from the lower gas phase inlet 13 and out from the upper gas phase outlet 12. The pressure in the reactor was controlled at 7 MPa using a backpressure valve. Simultaneously, a 1.4 mol / L maltose solution was added to the reactor from the upper liquid phase inlet 11 using a liquid phase metering pump at a flow rate of 1 mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0050] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 92.3%, and the maltitol yield was 90.0%. Example 9

[0051] A gas-liquid countercurrent trickle bed reactor was filled with 100 g of Raney nickel catalyst (average particle size 2.5 mm). The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 30 mL / min of hydrogen was introduced into the reactor from the gas phase inlet 13 at the lower end and discharged from the gas phase outlet 12 at the upper end. The pressure in the reactor was controlled at 9 MPa using a backpressure valve. Simultaneously, a 0.6 mol / L maltose solution was added to the reactor from the liquid phase inlet 11 at the upper end of the reactor using a liquid phase metering pump at a flow rate of 1 mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0052] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 99.4%, and the maltitol yield was 96.9%.

[0053] Example 10:

[0054] A gas-liquid countercurrent trickle bed reactor was filled with 100 g of Raney nickel catalyst (average particle size 2.5 mm). The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 30 mL / min of hydrogen was introduced into the reactor from the gas phase inlet 13 at the lower end and discharged from the gas phase outlet 12 at the upper end. The pressure in the reactor was controlled at 9 MPa using a backpressure valve. Simultaneously, a 1.0 mol / L maltose solution was added to the reactor from the liquid phase inlet 11 at the upper end of the reactor using a liquid phase metering pump at a flow rate of 1 mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0055] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 98.7%, and the maltitol yield was 95.3%.

[0056] Example 11:

[0057] A gas-liquid countercurrent trickle bed reactor was filled with 100g of Raney nickel catalyst (average particle size 2.5mm). The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 30mL / min of hydrogen was introduced into the reactor from the lower gas phase inlet 13 and out from the upper gas phase outlet 12. The pressure in the reactor was controlled at 9MPa using a backpressure valve. Simultaneously, a 2mol / L maltose solution was added to the reactor from the upper liquid phase inlet 11 using a liquid phase metering pump at a flow rate of 1mL / min. The hydrogen and maltose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent manner, thereby undergoing a continuous hydrogenation reaction. A maltose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0058] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 88.2%, and the maltitol yield was 86.1%.

[0059] Example 12:

[0060] A gas-liquid countercurrent trickle bed reactor was filled with 100g of Raney nickel catalyst (average particle size 3mm). The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 50mL / min of hydrogen was introduced into the reactor from the lower gas phase inlet 13 and out from the upper gas phase outlet 12. The pressure in the reactor was controlled at 7MPa using a backpressure valve. Simultaneously, a 1.6mol / L glucose solution was added to the reactor from the upper liquid phase inlet 11 at a flow rate of 1mL / min using a liquid phase metering pump. The hydrogen and glucose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent pattern, resulting in a continuous hydrogenation reaction. A glucose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0061] The glucose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the glucose conversion rate was 99.1%, and the sorbitol yield was 98.0%.

[0062] Example 13:

[0063] A gas-liquid countercurrent trickle bed reactor was filled with 90g of Raney nickel catalyst (average particle size 2mm). The reactor was heated to 125°C, and the air in the reactor was replaced and evacuated with high-purity nitrogen. Subsequently, 20mL / min of hydrogen was introduced into the reactor from the lower gas phase inlet 13 and out from the upper gas phase outlet 12. The pressure in the reactor was controlled at 8MPa using a backpressure valve. Simultaneously, a 1.4mol / L mannose solution was added to the reactor from the upper liquid phase inlet 11 at a flow rate of 1mL / min using a liquid phase metering pump. The hydrogen and mannose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent pattern, resulting in a continuous hydrogenation reaction. A mannose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0064] The mannose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the mannose conversion rate was 99.7%, and the mannitol yield was 98.5%.

[0065] Example 14:

[0066] A gas-liquid countercurrent trickle bed reactor was filled with 80g of Raney nickel catalyst (average particle size 2.5mm). The reactor was heated to 120°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Hydrogen was then introduced into the reactor at a rate of 30mL / min from the lower gas phase inlet 13 and out of the upper gas phase outlet 12. The pressure in the reactor was controlled at 6MPa using a backpressure valve. Simultaneously, a 1.4mol / L xylose solution was added to the reactor from the upper liquid phase inlet 11 using a liquid phase metering pump at a flow rate of 1mL / min. The hydrogen and xylose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent pattern, thereby undergoing a continuous hydrogenation reaction. A xylose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0067] The xylose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the xylose conversion rate was 99.9%, and the xylitol yield was 98.7%.

[0068] Example 15:

[0069] A gas-liquid countercurrent trickle bed reactor was filled with 80g of Raney nickel catalyst (average particle size 3.5mm). The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Hydrogen was then introduced into the reactor at a rate of 40mL / min through the lower gas phase inlet 13 and out through the upper gas phase outlet 12. The pressure in the reactor was controlled at 8MPa using a backpressure valve. Simultaneously, a 1.2mol / L lactose solution was added to the reactor from the upper liquid phase inlet 11 using a liquid phase metering pump at a flow rate of 1mL / min. The hydrogen and lactose solution flowed through the catalyst bed 16 in a gas-liquid countercurrent pattern, resulting in a continuous hydrogenation reaction. Lactose hydrogenated liquid was obtained from the bottom liquid phase outlet 14.

[0070] The lactose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the lactose conversion rate was 97.3%, and the lactitol yield was 95.5%.

[0071] Comparative Example 1:

[0072] 80 g of Raney nickel catalyst (average particle size 3 mm) was placed above support frame 27 in a gas-liquid co-current trickle bed reactor b. The reactor was heated to 130°C, and the air in the reactor was replaced and exhausted with high-purity nitrogen. Subsequently, 30 mL / min of hydrogen was introduced into the reactor from the gas phase inlet 22 at the lower end of the reactor, and the pressure in the reactor was controlled at 8 MPa via a back-pressure valve. Simultaneously, a 1.4 mol / L maltose solution was added to the reactor from the liquid phase inlet 21 at the upper end of the reactor using a liquid phase metering pump at a flow rate of 1 mL / min. The hydrogen and maltose solution were mixed through a T-shaped tube and flowed sequentially into the quartz sand layer 24, catalyst bed 25, and quartz sand layer 26 for continuous hydrogenation reaction. Maltose hydrogenated liquid was obtained after gas-liquid separation at the bottom gas-liquid outlet 23.

[0073] The maltose hydrogenation liquid sample was analyzed by high performance liquid chromatography, and the following results were obtained: the maltose conversion rate was 73.1%, and the maltitol yield was 69.7%.

[0074] The specific implementation methods described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A gas-liquid countercurrent continuous method for preparing sugar alcohols, characterized in that: The countercurrent continuous method comprises the following steps: in a gas-liquid countercurrent trickle bed reactor, a biomass sugar solution flows into the reactor from top to bottom from a liquid phase inlet, while hydrogen passes through the reactor from bottom to top from a gas phase inlet; the biomass sugar solution and hydrogen are hydrogenated and reduced through a catalyst bed in a gas-liquid countercurrent form to obtain a biomass sugar alcohol solution.

2. The gas-liquid countercurrent continuous method for preparing sugar alcohols according to claim 1, characterized in that The catalyst is selected from Raney nickel, Raney copper, ruthenium carbon or platinum carbon.

3. The gas-liquid countercurrent continuous method for preparing sugar alcohols according to claim 1 or 2, characterized in that The average particle size of the catalyst is 1-6 mm.

4. The gas-liquid countercurrent continuous method for preparing sugar alcohols according to claim 1, characterized in that The biomass sugar solution is selected from maltose, glucose, mannose, xylose or lactose, and the corresponding sugar alcohol is selected from maltitol, sorbitol, mannitol, xylitol or lactitol.

5. The gas-liquid countercurrent continuous method for preparing sugar alcohols according to claim 1, characterized in that The molar concentration of the biomass sugar solution is 0.6-2.2 mol / L, and the feed flow rate of the biomass sugar solution is 0.5-5 mL / min.

6. The countercurrent continuous method for preparing sugar alcohols according to claim 1, wherein The hydrogen pressure is 5-10 MPa, and the hydrogen flow rate is 10-100 sccm.

7. The gas-liquid countercurrent continuous method for preparing sugar alcohols according to claim 1, characterized in that The temperature of the trickle bed reactor is 100-140°C.

8. The gas-liquid countercurrent continuous method for preparing sugar alcohols according to claim 1, wherein The feed flow rate of the biomass sugar solution is 1-2 mL / min, the hydrogen pressure is 6-8 MPa, the hydrogen flow rate is 20-80 sccm, and the temperature of the trickle bed reactor is 120-135°C.

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