阅读说明：本技术 一种甘油催化氢解制备丙二醇的方法 (Method for preparing propylene glycol by catalytic hydrogenolysis of glycerol ) 是由 丁国强 朱玉雷 李显清 魏星 杨勇 李永旺 于 2021-05-24 设计创作，主要内容包括：本发明公开了一种甘油催化氢解制备丙二醇的方法。它包括如下步骤：1)将粉末状金属氢解催化剂和甘油水溶液加入到浆态床反应器内；2)向步骤1)中所述浆态床反应器内持续通入氢气,进行氢解反应,生成丙二醇,并且通入的所述氢气使生成的所述丙二醇携带出所述浆态床反应器；3)向步骤2)中进行氢解反应的所述浆态床反应器内泵入所述甘油水溶液,维持所述浆态床反应器内液面高度,以持续进行步骤2),得到所述丙二醇。本发明在浆态床反应器进行反应能有效克服内外传质对1,2-丙二醇和1,3-丙二醇选择性影响,而且生成的丙二醇及时被氢气携带出反应体系,从而有效避免了二次氢解反应的发生,显著提高了1,2-丙二醇和1,3-丙二醇总选择性。(The invention discloses a method for preparing propylene glycol by catalytic hydrogenolysis of glycerol. It comprises the following steps: 1) adding a powdered metal hydrogenolysis catalyst and a glycerol aqueous solution into a slurry bed reactor; 2) continuously introducing hydrogen into the slurry bed reactor in the step 1), carrying out hydrogenolysis reaction to generate propylene glycol, and carrying the generated propylene glycol out of the slurry bed reactor by the introduced hydrogen; 3) pumping the glycerol aqueous solution into the slurry bed reactor for carrying out hydrogenolysis reaction in the step 2), and maintaining the liquid level height in the slurry bed reactor to continuously carry out the step 2) to obtain the propylene glycol. The invention can effectively overcome the influence of internal and external transmission on the selectivity of the 1, 2-propylene glycol and the 1, 3-propylene glycol when the reaction is carried out in the slurry bed reactor, and the generated propylene glycol is carried out of a reaction system by hydrogen in time, thereby effectively avoiding the occurrence of secondary hydrogenolysis reaction and obviously improving the total selectivity of the 1, 2-propylene glycol and the 1, 3-propylene glycol.)

1. A method for preparing propylene glycol by the catalytic hydrogenolysis of glycerol comprises the following steps: 1) adding a powdered metal hydrogenolysis catalyst and glycerol into a slurry bed reactor;

2) continuously introducing hydrogen into the slurry bed reactor in the step 1), carrying out hydrogenolysis reaction to generate propylene glycol, and carrying the generated propylene glycol out of the slurry bed reactor by the introduced hydrogen;

3) pumping the glycerol aqueous solution into the slurry bed reactor for carrying out hydrogenolysis reaction in the step 2), and maintaining the liquid level height in the slurry bed reactor to continuously carry out the step 2) to obtain the propylene glycol.

2. The method of claim 1, wherein: the metal hydrogenolysis catalyst is selected from at least one of a copper-based catalyst, a platinum-based catalyst, and an iridium-rhenium catalyst.

3. The method according to claim 1 or 2, characterized in that: the particle size of the metal hydrogenolysis catalyst is 100-400 meshes.

4. The method according to any one of claims 1-3, wherein: the mass ratio of the glycerol to the metal hydrogenolysis catalyst in the step 1) is 5-50: 1.

5. the method of claim 4, wherein: the mass ratio of the glycerol to the metal hydrogenolysis catalyst in the step 1) is 10-40: 1.

6. the method according to any one of claims 1-5, wherein: in step 2), the hydrogenolysis reaction conditions are as follows: introducing the hydrogen with the flow rate of 50-800 mL/min;

the pressure is 0.5-8.0 MPa; the temperature is 110-200 ℃.

7. The method of claim 6, wherein: the pressure is 1.0-6 MPa; the temperature is 120-180 ℃.

8. The method according to claim 6 or 7, characterized in that: in the step 2), the hydrogen flow is 100-600 mL/min.

9. The method according to any one of claims 1-8, wherein: in the steps 1) and 3), the mass concentration of the glycerol aqueous solution is 50-90%;

the pumping flow rate of the glycerol aqueous solution is 0.005-5 mL/min.

10. The method according to any one of claims 1-9, wherein: the liquid level height in the slurry bed reactor is maintained at 2/3-4/5 of the height of the slurry bed reactor.

Technical Field

The invention relates to a method for preparing propylene glycol by catalytic hydrogenolysis of glycerol, belonging to the field of glycerol processing.

Background

With the rapid development of the biomass diesel in recent years, the byproduct glycerol is abundant, and the global annual yield exceeds 400 million tons. Therefore, there is a need to develop new ways for efficient conversion and utilization of glycerol. Under the hydrogen condition, the glycerol can be efficiently converted into high value-added chemicals such as 1, 2-propylene glycol, 1, 3-propylene glycol and the like. Wherein, the 1, 2-propylene glycol is an important raw material of unsaturated polyester, epoxy resin, polyurethane resin and surfactant, and can be widely used as a moisture absorbent, an antifreeze and a lubricant in the industries of food, medicine and cosmetics; the 1, 3-propylene glycol is widely applied as an important chemical intermediate, is mainly used as a monomer for synthesizing polyester fiber PTT (poly (1, 3-propylene glycol terephthalate)), and the PTT fiber has the characteristics of terylene, chinlon and acrylon, has good antifouling property, is easy to dye, has soft hand feeling and high elasticity, and is very suitable for high-grade clothing fabrics. The reaction scheme for the hydrogenolysis of glycerol to propylene glycol is shown in figure 1.

Although the production of 1, 2-propanediol and 1, 3-propanediol by using glycerol, which is a byproduct of biodiesel, as a raw material has a high economic prospect, the production of 1, 2-propanediol and 1, 3-propanediol is very challenging in the aspects of catalyst and process development. The glycerol molecule contains three adjacent hydroxyl groups, wherein 1, 2-propylene glycol can be obtained by selective hydrogenolysis of a primary hydroxyl group, and 1, 3-propylene glycol can be obtained by hydrogenolysis of a secondary hydroxyl group. However, the 1, 2-propanediol and 1, 3-propanediol produced may undergo secondary hydrogenolysis reactions to produce by-products such as n-propanol and isopropanol.

At present, the preparation of propylene glycol by glycerol hydrogenolysis mostly adopts a batch autoclave process or a continuous trickle bed process. Patent CN201410284148.2 discloses a method for preparing propylene glycol by catalytic hydrogenolysis of biodiesel-based crude glycerol, which comprises the steps of putting the crude glycerol with the adjusted pH value or an aqueous solution thereof into a high-pressure reaction kettle, adding a catalyst, and reacting under proper conditions to obtain the propylene glycol. The kettle type intermittent hydrogenolysis process has the advantages that the powder catalyst with small particles can be adopted, the stirring is strong, and the influence of the internal diffusion of the catalyst on the secondary hydrogenolysis reaction can be inhibited to the maximum extent. The method has the disadvantages of difficult realization of continuous operation, low gas-liquid contact surface, large liquid film thickness, difficult hydrogen mass transfer and low glycerol conversion efficiency. In addition, the generated 1, 2-propylene glycol and 1, 3-propylene glycol cannot leave the reaction system in time, so that secondary hydrogenolysis reaction is difficult to avoid, and the side product propanol is more.

Patent CN200710020031.3 discloses a method for continuously preparing 1, 2-propanediol by hydrogenation of glycerol catalyst, which uses a catalyst containing copper and zinc and manganese and/or aluminum, glycerol and hydrogen are simultaneously and continuously introduced from the upper end of a reactor, catalytic hydrogenation reaction is carried out under certain conditions, and reaction products are continuously output and collected from the lower end of the reactor. The continuous trickle bed process is favorable to hydrogen mass transfer and can obtain high glycerin converting rate. However, in order to prevent the bed pressure difference from being too large, the trickle bed process generally adopts a catalyst with a larger particle size, and the trickle bed process has no disturbance and small turbidity, so that the mass transfer of the glycerol and the products in the catalyst is slow, and the 1, 2-propylene glycol and the 1, 3-propylene glycol are easy to generate secondary hydrogenolysis reaction to generate the n-propanol and the isopropanol.

Therefore, the batch kettle type process and the continuous trickle bed reaction process developed at present are difficult to avoid the occurrence of secondary hydrogenolysis reaction of propylene glycol and a plurality of byproducts. To improve the selectivity of 1, 2-propanediol and 1, 3-propanediol, the conversion of glycerol is generally strictly controlled to be kept at a low level (< 40%) to suppress the occurrence of side reactions, while a large amount of unconverted glycerol needs to be separated and then converted, which increases the separation cost.

Disclosure of Invention

The invention aims to provide a method for preparing propylene glycol by the catalytic hydrogenolysis of glycerol.

The method can effectively overcome the influence of internal and external transmission on the selectivity of the 1, 2-propylene glycol and the 1, 3-propylene glycol, and the generated 1, 2-propylene glycol and the 1, 3-propylene glycol can be carried out of a reaction system by hydrogen in time, so that the occurrence of secondary hydrogenolysis reaction is effectively avoided, the total selectivity of the 1, 2-propylene glycol and the 1, 3-propylene glycol is obviously improved, and the total selectivity of the 1, 2-propylene glycol and the 1, 3-propylene glycol can be up to 83.5 percent.

The invention provides a method for preparing propylene glycol by catalytic hydrogenolysis of glycerol, which comprises the following steps: 1) adding a powdered metal hydrogenolysis catalyst and a glycerol aqueous solution into a slurry bed reactor;

2) continuously introducing hydrogen into the slurry bed reactor in the step 1), carrying out hydrogenolysis reaction to generate propylene glycol, and carrying the generated propylene glycol out of the slurry bed reactor by the introduced hydrogen;

3) pumping the glycerol aqueous solution into the slurry bed reactor for carrying out hydrogenolysis reaction in the step 2), and maintaining the liquid level height in the slurry bed reactor to continuously carry out the step 2) to obtain the propylene glycol.

In the invention, the powdered metal hydrogenolysis catalyst and the glycerol aqueous solution are mixed or directly added into a slurry bed reactor for reaction.

In the invention, the slurry bed reactor is a conventional reactor known in the field, and specifically comprises key components such as a gas feeding hole, a gas distributor, a gas-liquid separator, a liquid feeding hole and the like.

In the above method, the metal hydrogenolysis catalyst is at least one selected from the group consisting of a copper-based catalyst, a platinum-based catalyst, and an iridium-rhenium catalyst.

In the present invention, the metal hydrogenolysis catalyst is a conventional catalyst well known in the art, and is prepared according to a method well known in the art.

The composition of the platinum-based catalyst is given below by way of example:

the platinum-based catalyst is prepared by adopting a conventional impregnation method, and mainly comprises three components of hydrogenation component platinum, metal oxidation auxiliary agent and carrier. In the case of the platinum-based catalyst,the metal oxidation auxiliary agent can be selected from one or more of oxides of Ca, Mo, W and Zn, for example, the auxiliary agent can be CaO and Mo₃O₄、WO₃And/or ZnO; in the platinum-based catalyst, the support may be selected from one or more of oxides of Ti, Zr, Al, Si. For example, the support may be ZrO₂、Al₂O₃And TiO₂Or SiO₂One or more of (a).

In some further preferred embodiments, the platinum loading in the platinum-based catalyst is from 0.5 wt% to 5.0 wt% (relative to the support oxide), preferably from 1 wt% to 5 wt%, for example, 1 wt%, 2 wt%, 2.5 wt%, 3 wt%, 4 wt%, 5 wt%, or any value therebetween. The platinum-based catalyst has an oxide promoter loading of 5 wt% to 15.0 wt% (relative to the support oxide), preferably 6 wt% to 11 wt%, for example 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt% or any value therebetween.

In some further preferred embodiments, the platinum-based catalyst is prepared using methods conventional in the art (e.g., impregnation methods) comprising: a solution of a water-soluble salt of the metal is prepared and then impregnated on an oxide support, followed by drying and calcination.

For example, with Pt-WO₃/Al₂O₃Catalyst is exemplified by Pt-WO₃/Al₂O₃Typical impregnation procedures for the catalyst may include (but are not limited to): preparing a mixed aqueous solution of water-soluble platinum salt and tungsten salt with a certain concentration, wetting a powdery oxide carrier with deionized water, pouring the prepared mixed aqueous solution of platinum salt and tungsten salt onto the wetted oxide carrier, stirring, soaking at room temperature for 20-40 h, drying in an oven at 60-120 ℃ for 8-24 h after soaking, and roasting in a muffle furnace at 350-500 ℃ for 4-8 h.

In the above method, the particle size of the metal hydrogenolysis catalyst may be 100 to 400 mesh, and preferably 200 to 300 mesh.

The mass ratio of the glycerol to the metal hydrogenolysis catalyst in the step 1) of the method can be 5-50: 1.

the mass ratio of the glycerol to the metal hydrogenolysis catalyst in the step 1) of the method can be specifically 10-40: 1, more specifically 10 to 20: 1. 20-30: 1 or 10-30: 1, and in specific embodiments, can be 12:1, 10.5: 1. 10: 1 or 8: 1.

In step 2) of the above method, the hydrogenolysis reaction conditions are as follows: introducing the hydrogen with the flow rate of 50-800 mL/min;

the pressure can be 0.5-8.0 MPa; the temperature can be 110-200 ℃.

In the above method, the pressure may be 1.0 to 6MPa, more specifically 2MPa, 4MPa, 5MPa, 6MPa or 2.0 to 6 MPa; the temperature may be in the range of 120 to 180 deg.C, more specifically 120 deg.C, 140 deg.C, 150 deg.C, 180 deg.C.

In the step 2), the hydrogen flow rate may be specifically 100 to 600mL/min, and more specifically 100mL/min, 200mL/min, 300mL/min, 400mL/min, 500mL/min, or 600 mL/min.

In the steps 1) and 3) of the method, the mass concentration of the glycerol aqueous solution can be 50-90%, specifically 50%, 60%, 70%, 80% or 50-80%;

the pumping flow rate of the glycerol aqueous solution can be 0.005-5 mL/min, specifically 0.005mL/min, 0.01mL/min, 0.015mL/min, 0.02mL/min, 0.025mL/min, 0.03mL/min or 0.005-3 mL/min.

In the method, the liquid level in the slurry bed reactor is maintained at 2/3-4/5 of the height of the slurry bed reactor, and the liquid level can be 2/3, 7/10 and 4/5.

The invention has the following advantages:

(1) the slurry bed reactor provided by the invention is provided with the gas distributor, hydrogen enters the reactor through the gas distributor to form bubbles with extremely small particle size, the gas-liquid contact area is high, the hydrogen mass transfer resistance is low, and the glycerol conversion efficiency can be obviously improved;

(2) the internal disturbance of the slurry bed reactor developed by the invention can reduce the influence of external diffusion on product distribution to the maximum extent, and is beneficial to improving the glycerol conversion efficiency;

(3) the invention adopts the powdery catalyst, eliminates the influence of internal diffusion of the catalyst to the maximum extent and is beneficial to improving the yield of the propylene glycol;

(4) the hydrogen circulation amount of the glycerin hydrogenolysis process of the slurry bed developed by the invention is large, and the 1, 2-propylene glycol (188 ℃) and the 1, 3-propylene glycol (210 ℃) with relatively low boiling points generated in the reaction process can be timely taken away from the reactor, so that the occurrence of secondary hydrogenolysis reaction is inhibited;

(5) in the slurry-bed glycerin hydrogenolysis process developed by the invention, as the boiling point of the reaction raw material glycerin is higher (290 ℃), only a small amount of glycerin is carried out of the reactor by hydrogen, and most of glycerin is continuously left in the reactor for continuous reaction, so that higher propylene glycol total selectivity is obtained under high glycerin conversion rate, and the glycerin recycling amount is reduced.

(6) The glycerin hydrogenolysis process of the slurry bed developed by the invention can bring the generated heat out of the reaction system in time, and is beneficial to avoiding the local overheating of the reactor.

Drawings

FIG. 1 is a reaction scheme for the hydrogenolysis of glycerol to propylene glycol.

Detailed Description

The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Glycerol, ammonium metatungstate, tetraammineplatinum dichloride, alumina and the like used in the following examples are all commercially available, and quartz sand of 20 to 40 mesh is all commercially available. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

In the following procedure, comparative example 1 was carried out in a conventional 50ml autoclave, comparative example 2 in a conventional trickle bed and examples 1-6 in a 1L slurry bed reactor. The reaction liquid product was detected and analyzed by Agilent 6890 using AB-InoWax (30 m. times.0.32 mm. times.0.5 μm) as a test column, and each substance to be detected was quantified by an external standard method.

The following embodimentsIn the examples, Pt-WO₃/Al₂O₃The general impregnation procedure for the catalyst is specified below: preparing a mixed aqueous solution of water-soluble platinum salt and tungsten salt with a certain concentration, and simultaneously adding a powdery oxide carrier (Al)₂O₃) Wetting with deionized water, pouring the prepared mixed aqueous solution of platinum salt and tungsten salt onto the wetted oxide carrier, stirring, soaking at room temperature for 20-40 h, drying in an oven at 60-120 ℃ for 8-24 h after soaking, and roasting in a muffle furnace at 350-500 ℃ for 4-8 h;

Pt/Al₂O₃preparation method of catalyst and Pt-WO₃/Al₂O₃The catalyst preparation is basically the same, and the difference is that no tungsten salt is added during the preparation;

Cu-WO₃/Al₂O₃preparation method of catalyst and Pt-WO₃/Al₂O₃The preparation of the catalyst is basically the same, and the difference is that the platinum salt is replaced by copper salt during the preparation;

Cu-ZnO/Al₂O₃preparation method of catalyst and Pt-WO₃/Al₂O₃The catalyst is prepared basically in the same way, and the difference is that the platinum salt is replaced by copper salt and the tungsten salt is replaced by zinc salt during preparation.

Examples 1,

Weighing Pt-WO₃/Al₂O₃Catalyst 25g (200-300 mesh), 500 g of 60 wt% aqueous glycerol solution were fed into a 1L slurry bed reactor. The reaction temperature is set to be 140 ℃, the reaction pressure is 5MPa, pure hydrogen is adopted in the hydrogen atmosphere, and the flow rate is 100 mL/min. After the hydrogenolysis reaction, 60 wt% of glycerol aqueous solution is input into the slurry bed reactor at the flow rate of 0.005ml/min, and the liquid level in the slurry bed reactor is maintained to be 2/3 which accounts for the total height of the slurry bed reactor, so that the hydrogenolysis reaction is continuously carried out, and the propylene glycol is obtained. After 24h of reaction, a sample was taken from the gas-liquid separator for analysis. The reaction results are shown in Table 1.

Pt-WO₃/Al₂O₃The catalyst has Pt content of 2% and is prepared through conventional soaking process.

Examples 2,

Weighing Cu-WO₃/Al₂O₃35g (100-400 mesh) of a catalyst, 350 g of an 80 wt% aqueous glycerol solution were fed into a 1L slurry bed reactor. The reaction temperature is set to be 140 ℃, the reaction pressure is 6MPa, pure hydrogen is adopted in the hydrogen atmosphere, and the flow rate is 200 mL/min. After the initiation of the hydrogenolysis reaction, an aqueous solution of glycerin of 80 wt% was fed into the reactor at a flow rate of 0.01ml/min to maintain 4/5, which is the height of the liquid level in the reactor to the total height, to continue the hydrogenolysis reaction to obtain propylene glycol. After 24h of reaction, a sample was taken from the gas-liquid separator for analysis. The reaction results are shown in Table 1.

Cu-WO₃/Al₂O₃The Cu content of the catalyst is 5 percent, and the catalyst is prepared by a conventional impregnation method.

Examples 3,

Weighing Cu-ZnO/Al₂O₃Catalyst 40g (100-400 mesh), 600 g of 70 wt% aqueous glycerol solution were fed into a 1L slurry bed reactor. The reaction temperature is set to be 150 ℃, the reaction pressure is set to be 4MPa, pure hydrogen is adopted in the hydrogen atmosphere, and the flow rate is 300 mL/min. After the hydrogenolysis reaction was started, a 70 wt% aqueous solution of glycerin was fed into the reactor at a flow rate of 0.015ml/min, and 7/10, which was the height of the liquid level in the reactor to the total height, was maintained to continue the hydrogenolysis reaction to obtain propylene glycol. After 24h of reaction, a sample was taken from the gas-liquid separator for analysis. The reaction results are shown in Table 1.

Cu-ZnO/Al₂O₃The Cu content of the catalyst is 4 percent, and the catalyst is prepared by a conventional impregnation method.

Examples 4,

Weighing Pt/Al₂O₃20g (100-400 mesh) of a catalyst, 400 g of a 60 wt% aqueous glycerol solution were fed into a 1L slurry bed reactor. The reaction temperature is set to be 180 ℃, the reaction pressure is 1MPa, pure hydrogen is adopted in the hydrogen atmosphere, and the flow rate is 400 mL/min. After the initiation of the hydrogenolysis reaction, a 60 wt% aqueous glycerol solution was fed into the reactor at a flow rate of 0.02ml/min, and 2/3, which was the height of the liquid surface in the reactor based on the total height, was maintained to continue the hydrogenolysis reaction to obtain propylene glycol. After 24h of reaction, a sample was taken from the gas-liquid separator for analysis. The reaction results are shown in Table 1.

Pt/Al₂O₃The catalyst has Pt content of 2% and is prepared through conventional soaking process.

Examples 5,

Weighing Pt-WO₃/Al₂O₃30g (100-400 mesh) of a catalyst, 600 g of a 50 wt% aqueous glycerol solution were fed into a 1L slurry bed reactor. Setting the reaction temperature at 120 ℃, the reaction pressure at 2MPa, and adopting pure hydrogen in the hydrogen atmosphere at the flow rate of 500 mL/min. After the initiation of the hydrogenolysis reaction, a 50 wt% aqueous glycerol solution was fed into the reactor at a flow rate of 0.025ml/min to maintain 4/5, which is the height of the liquid level in the reactor to the total height, to continue the hydrogenolysis reaction to obtain propylene glycol. After 24h of reaction, a sample was taken from the gas-liquid separator for analysis. The reaction results are shown in Table 1.

Pt-WO₃/Al₂O₃The catalyst has Pt content of 2% and is prepared through conventional soaking process.

Examples 6,

Weighing Pt-WO₃/Al₂O₃Catalyst 25g (200-300 mesh), 500 g of 60 wt% aqueous glycerol solution were fed into a 1L slurry bed reactor. The reaction temperature is set to be 140 ℃, the reaction pressure is 5MPa, pure hydrogen is adopted in the hydrogen atmosphere, and the flow rate is 600 mL/min. After the initiation of the hydrogenolysis reaction, a 60 wt% aqueous glycerol solution was fed into the reactor at a flow rate of 0.03ml/min, and 2/3, which was the height of the liquid surface in the reactor as the total height, was maintained to continue the hydrogenolysis reaction to obtain propylene glycol. After 24h of reaction, a sample was taken from the gas-liquid separator for analysis. The reaction results are shown in Table 1.

Pt-WO₃/Al₂O₃The catalyst has Pt content of 2% and is prepared through conventional soaking process.

TABLE 1 catalytic conversion of glycerol to propylene glycol results

Reaction conversion (%) × 100% (number of moles of reactant converted/number of moles of reactant in raw material).

Product selectivity (%) × (moles of certain product produced/moles of reactant converted) × 100%.

Wherein the others comprise acetone and ethylene glycol.

According to the reaction results of the above examples 1 to 6, the hydrogenolysis efficiency of glycerin in the slurry bed reactor was high, and the conversion rate of glycerin was higher than 76%. The main products of the hydrogen flow rate was lower (example 1) and were secondary hydrogenolysis products such as n-propanol (6.5%) and isopropanol (55.5%). But the generated 1, 2-propylene glycol and 1, 3-propylene glycol can be brought out of the reaction system in time by gradually increasing the hydrogen flow rate, the secondary hydrogenolysis reaction is obviously inhibited, and the total selectivity of the 1, 2-propylene glycol and the 1, 3-propylene glycol can reach 83.5 percent.

In contrast, the reaction of comparative example 1 showed a low hydrogenolysis efficiency of glycerol in the reactor, a glycerol conversion of only 20.5% at 24 hours, and a low total selectivity (27%) for the main products n-propanol (65%), 1, 2-propanediol and 1, 3-propanediol. According to the reaction results in comparative example 2, the hydrogenolysis efficiency of glycerol in the trickle bed reactor was slightly improved, the glycerol conversion rate was 34.4%, and the selectivity for 1, 3-propanediol was also significantly improved to 45.5%, but the selectivity for 1, 2-propanediol was still only 5.1% lower.

Comparative examples 1,

Weighing Pt-WO₃/Al₂O₃Catalyst 1.5g (200 meshes 300 meshes), 30g of 60 wt% glycerol aqueous solution were put into a 50mL autoclave. Setting the reaction temperature at 140 ℃ and the reaction pressure at 5.0MPa, stopping the reaction after reacting for 24 hours, and sampling and analyzing after cooling. The reaction results are shown in Table 1.

Pt-WO₃/Al₂O₃The catalyst is prepared by a conventional impregnation method with the Pt content of 2%.

Comparative examples 2,

Weighing Pt-WO₃/Al₂O₃10.0g (20-40 mesh) of catalyst, and the weighed catalyst was charged in the constant temperature section of the trickle bed reactor. The upper and lower parts of the catalyst bed layer in the reactor are respectively filled with a certain amount of quartz sand with the same mesh number as the catalyst.

The reaction temperature is set to be 140 ℃, the reaction pressure is 5.0MPa, and the liquid space velocity is 0.1h-¹Wherein, the hydrogen atmosphere adopts pure hydrogen, and the flow rate is 300 mL/min. Feeding 60 wt% glycerol water solution into reaction tube at flow rate of 0.028ml/min, reacting for 24 hr, sampling, and dividingAnd (6) analyzing. The reaction results are shown in Table 1.

Pt-WO₃/Al₂O₃The Pt content of the catalyst is 3 percent, and the catalyst is prepared by adopting a conventional impregnation method.