Catalyst, preparation method and application thereof, and method for producing lactic acid

Abstract

The invention relates to the technical field of molecular sieve catalysts, and discloses a catalyst, a preparation method and application thereof, and a method for producing lactic acid. The preparation method of the catalyst comprises the following steps: mixing the modified beta molecular sieve, metal salt and deionized water, dipping, drying, roasting and cooling to obtain the catalyst, the metal salt is bimetallic salt of yttrium salt and tin salt, and the preparation method of the modified beta molecular sieve comprises the following steps: mixing acid and the beta molecular sieve, and heating to obtain the catalyst. The catalyst has the advantages of being high in catalytic activity, capable of directionally catalyzing cellulose into lactic acid, simple in preparation method, environmentally friendly and the like, has relatively high cycling stability, and has a wide prospect for improving the yield of lactic acid and industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular sieve catalysts, in particular to a catalyst, a preparation method and application thereof. In addition, the present application also includes a method for producing lactic acid. BACKGROUND

[0002] Cellulose is a biomass carbon resource macromolecule, which is very rich in China and has low price. The research on the depolymerization of cellulose into lactic acid by chemical catalytic method is a promising way and attracts much attention. Lactic acid, as an important organic acid, can be used in various organic synthesis fields, such as medicine, daily chemical and renewable degradable materials, and has a very broad application prospect.

[0003] At present, most of the lactic acid in industry is synthesized by biological fermentation method, which is limited to glucose raw material and is difficult to convert cellulose. In the chemical production process, lactic acid can be obtained by strong acid degradation of lactate. Considering that the cellulose macromolecule contains more hydroxyl bonds, some liquid acid catalysts are used to catalyze the degradation of cellulose to prepare lactic acid. However, due to the miscibility of these liquid acids and products, the separation process is difficult and cumbersome, the equipment is easy to be corroded, and there are serious environmental pollution and low lactic acid yield. Therefore, some solid acid catalysts are tried to replace liquid acid catalysts to catalyze the degradation of cellulose. How to find a green catalytic conversion method to direct the conversion of cellulose to lactic acid, improve the yield of lactic acid, and be economic and safe to the environment has become the focus of many forward-looking researchers in the field SUMMARY The purpose of the present application is to overcome the problems of low lactic acid yield, complicated production process and serious environmental pollution in the prior art, and to provide a catalyst, a preparation method and application thereof. The catalyst has high catalytic activity, is friendly to the environment, is easy to separate and recycle, and has good industrial prospect.

[0004] In order to achieve the above purpose, the first aspect of the present application provides a catalyst, which contains β molecular sieve and yttrium oxide and tin oxide supported on the β molecular sieve.

[0005] Preferably, in the catalyst, the mass ratio of the yttrium oxide to the tin oxide is 1:3-10.

[0006] Preferably, in the catalyst, the loading amount of the yttrium oxide is 10-15wt%, and the loading amount of the tin oxide is 30-45wt%.

[0007] The second aspect of the present application provides a preparation method of the catalyst, which comprises the following steps: S1, mixing the β molecular sieve, yttrium salt and tin salt to obtain a catalyst precursor; S2, calcining the catalyst precursor.

[0008] Preferably, in the step S1, the beta molecular sieve is subjected to acid treatment before mixing with the yttrium salt and the tin salt. Preferably, the acid is nitric acid. Preferably, the acid is nitric acid. Preferably, the concentration of the acid in the reaction system of the step S1 is 10-30 mol / L. Preferably, the amount of the acid is 0.1-0.3 mol relative to 1 g of the beta molecular sieve.

[0009] Preferably, the conditions of the contact reaction I include at least: temperature of 60-100℃, time of 1-12 h.

[0010] Preferably, in the step S2, the mass ratio of the beta molecular sieve, the yttrium salt and the tin salt is 1:0.1-0.5:0.1-1.

[0011] Preferably, the yttrium salt is yttrium nitrate, and the tin salt is tin tetrachloride.

[0012] Preferably, in the step S2, the mixing time is 6-12 h.

[0013] Preferably, the step S2 further comprises: standing the mixture obtained by mixing for 10-12 h.

[0014] Preferably, in the step S3, the conditions of the calcination treatment include: temperature of 400-650℃, time of 2-6 h.

[0015] The third aspect of the present application provides a catalyst prepared by the method as described above.

[0016] The fourth aspect of the present application provides at least one of the catalyst as described above, the catalyst prepared by the preparation method as described above, for use in catalyzing the production of lactic acid from biomass.

[0017] Preferably, the biomass is cellulose.

[0018] The fifth aspect of the present application provides a method for producing lactic acid, which comprises: contacting a catalyst as described above, a catalyst prepared by the preparation method as described above, with biomass and water in a contact reaction II.

[0019] Preferably, the mass ratio of the catalyst, the biomass and the water is 1:0.7-10.

[0020] Preferably, the contact reaction II is carried out under oxygen-free conditions, and the conditions of the contact reaction II include: a pressure of 0.1-1.0 MPa, a temperature of 180-260 DEG C, and a time of 3-10 h. By the technical scheme, the catalyst contains the beta molecular sieve and the yttrium oxide and the tin oxide supported on the beta molecular sieve, the activity of the catalyst in catalyzing the biomass to prepare lactic acid is improved through the interaction of the yttrium oxide and the tin oxide in the beta molecular sieve, the conversion rate of the biomass and the yield of the lactic acid are effectively improved, and the catalyst has a wide industrial application prospect.

[0021] In addition, the catalyst preparation method is simple, does not need high-temperature hydrogen reduction treatment, is easy to operate, has high cycle stability, is friendly to the environment and has no pollution. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the purposes of the application. The endpoints of the ranges and any values are provided as approximations only, and are understood to encompass values approximately the same as the endpoints. Any numerical range is intended to include all combinations and subcombinations of the numbers in the range. Any reference to the term "about" includes all absolute values and all values approximately the same as the absolute values.

[0023] The first aspect of the application provides a catalyst, which contains a beta molecular sieve and yttrium oxide and tin oxide supported on the beta molecular sieve.

[0024] In the catalyst of the application, the tin and the yttrium replace the removed aluminum, so that the catalytic activity of the catalyst of the application is higher.

[0025] According to the application, preferably, in the catalyst, the mass ratio of the yttrium oxide to the tin oxide is 1:3-10, which can be 1:3, 1:4, 1:7, 1:10, or any value in the range formed by any two of the above ratios. The inventors have found that the preferred mode can make the catalytic conversion effect of the catalyst better.

[0026] Preferably, in the catalyst, the loading amount of the yttrium oxide is 10-15 wt%, and the loading amount of the tin oxide is 30-45 wt%. The inventors have found that the preferred mode can further improve the catalytic activity of the catalyst.

[0027] The second aspect of the application provides a catalyst preparation method, which comprises the following steps: S1, mixing the beta molecular sieve, a yttrium salt and a tin salt to obtain a catalyst precursor; S2, performing a calcination treatment on the catalyst precursor.

[0028] The inventors have found that the preparation method of the catalyst can better control the surface structure and active center of the catalyst, and has better catalytic conversion effect of the catalyst.

[0029] According to the present application, the beta molecular sieve is subjected to acid treatment before being mixed with the yttrium salt and the tin salt in the reaction system of step S1. The acid is at least one selected from nitric acid, hydrochloric acid, sulfuric acid, boric acid, oxalic acid, citric acid, phosphoric acid and acetic acid. The present application does not have a particular limitation on the specific selection of the acid, and any acid known to those skilled in the art can be used for modification. Those skilled in the art can select and adjust the acid according to the production situation, product requirements and quality requirements. The acid used in the present application preferably includes at least one or more of nitric acid, hydrochloric acid, sulfuric acid, boric acid, oxalic acid, citric acid, phosphoric acid and acetic acid, and is further preferably nitric acid. The inventors have found that the preferred embodiment can make the catalyst have higher catalytic activity. The concentration of the acid used in the present application is preferably 10-30 mol / L, and can be 10 mol / L, 15 mol / L, 20 mol / L, 30 mol / L, or any value between the above two values. The inventors have found that the preferred method can make the dealumination effect of the beta molecular sieve better, and further improve the catalytic performance of the catalyst in combination with tin and yttrium.

[0030] According to the present application, the amount of the acid used is 0.1-0.3 mol with respect to 1 g of the beta molecular sieve. The inventors have found that the preferred method for preparing the modified beta molecular sieve can better improve the pore structure characteristics of the molecular sieve.

[0031] According to the present application, preferably, the conditions of the contact reaction I include at least a temperature of 60-100℃, specifically 60℃, 70℃, 80℃, 100℃, or any value between the above two values; and a time of 1-12 h, specifically 1 h, 6 h, 8 h, 12 h, or any value between the above two values. The present application does not have a particular limitation on the selection of the tin salt and the yttrium salt, and any soluble yttrium salt and tin salt known to those skilled in the art can be used. The yttrium salt is at least one selected from yttrium nitrate, yttrium acetate and yttrium carbonate, and the tin salt is at least one selected from dibutyltin dilaurate, tin tetrachloride and stannous benzenesulfonate. Yttrium nitrate and tin tetrachloride can improve the selectivity of the catalytic reaction, improve the cycle stability and enhance the activity of the catalyst when they are calcined with the modified beta molecular sieve to form a beta molecular sieve loaded with yttrium oxide and tin oxide. According to the present application, preferably, the yttrium salt is yttrium nitrate and the tin salt is tin tetrachloride.

[0032] In the step S2, the mass ratio of the beta zeolite, the yttrium salt and the tin salt is 1:0.1-0.5:0.1-1; the yttrium salt is yttrium nitrate, and the tin salt is tin tetrachloride; the step S2 further comprises standing the mixed mixture for 10-12 h. The standing condition is not particularly limited, and the acid-modified beta zeolite, the yttrium salt and the tin salt can be fully contacted and uniformly reacted to obtain the catalyst precursor.

[0033] According to the present application, the mixing condition is not particularly limited, and can be any one of stirring mixing and oscillation mixing, and the acid-modified beta zeolite, the yttrium salt and the tin salt can be fully contacted and uniformly reacted. Preferably, the mixing condition in the step S2 comprises that the mixing time is 6-12 h, and can be 6 h, 8 h, 10 h, 12 h or any value between the above two values. In the step S3, the preferred condition of the calcination treatment comprises that the temperature is 400-650℃, and can be 400℃, 500℃, 550℃, 650℃ or any value between the above two values. The calcination mode can fully heat the yttrium salt and the tin salt in the catalyst precursor to form yttrium oxide and tin oxide loaded on the modified beta zeolite to obtain the supported Y2O3-SnO2 / β catalyst. The calcination equipment can be at least one of a crucible furnace, a muffle furnace and a high-temperature tube furnace, and the muffle furnace is used in the present application to calcine the catalyst precursor. The preferred calcination time is 2-6 h, and can be 2 h, 3 h, 4 h, 6 h or any value between the above two values.

[0034] The inventors have found that the catalyst prepared by the above preferred reaction conditions has better catalytic performance.

[0035] For example, the preparation method of the modified beta zeolite is as follows: 100 mL of a nitric acid solution (10-30 mol / L) is weighed, and then 10-15 g of beta zeolite is added thereto, mixed for 30-40 min, and continuously mixed at 60-100℃ for 1-12 h. After that, the mixture is washed with water for 3-4 times, dried at 100-110℃, and then the modified beta zeolite is obtained and used.

[0036] According to the present application, the mixing can be stirring mixing, and the stirring condition is not particularly limited, as long as the beta zeolite and the acid can be fully mixed and uniformly contacted. The obtained mixture can be washed with water, preferably deionized water, for 3-4 times, and dried at 60-100℃ for standby. The deionized water used in the present application is directly taken from a deionized water machine.

[0037] The third aspect of the present application provides a catalyst prepared by the method as described above.

[0038] The fourth aspect of the present application provides an application of at least one of the catalyst as described above, the catalyst prepared by the method as described above in catalyzing the biomass to produce lactic acid.

[0039] The biomass raw material is not particularly limited in the present application, and can be any conventional biomass raw material known to those skilled in the art. Those skilled in the art can select and adjust the biomass raw material according to the production situation, product requirements and quality requirements. The biomass raw material in the present application can be selected from any one of cellulose, starch, glucose and fructose, and is preferably cellulose. The cellulose (microcrystal, powder, 20 μm) used in the present application is purchased from Shanghai Aldrin Biochemical Technology Co., Ltd. It is found that the yield of lactic acid can be further improved when the biomass is cellulose.

[0040] The fifth aspect of the present application provides a method for producing lactic acid, which comprises contacting the catalyst as described above, the catalyst prepared by the method as described above with biomass and water for reaction II.

[0041] The water used in the present application is preferably deionized water, which is directly taken from a deionized water machine.

[0042] In order to further improve the efficiency of catalytic conversion of biomass into lactic acid, preferably, the mass ratio of the catalyst, biomass and water is 1:0.7-10.

[0043] Preferably, the reaction is carried out under anaerobic conditions, and the mixing conditions include: the pressure is 0.1-1.0 MPa, and can be specifically 0.1 MPa, 0.3 MPa, 0.5 MPa, 1.0 MPa or any value between the above two values; the temperature is 180-260℃, and can be specifically 180℃, 200℃, 220℃, 260℃ or any value between the above two values; the time is 3-10 h, and can be specifically 3 h, 4 h, 6 h, 10 h or any value between the above two values. Under the above conditions, the catalyst and biomass can be fully reacted, and the yield of lactic acid can be improved.

[0044] For example, the step of converting the catalyst into lactic acid by reacting with cellulose is as follows: The catalyst, cellulose and deionized water are weighed and put into a high-pressure reactor, the mass ratio of the catalyst and the vitamin is 1:0.7-10, the air in the reactor is replaced by nitrogen, and the pressure is maintained at 0.1-1.0 MPa, the reaction temperature is controlled at 180-260 DEG C, heating and stirring for 3-10 hours, cooling to room temperature to collect the filtrate, and the cellulose conversion rate and lactic acid yield of the product are analyzed by high performance liquid chromatography.

[0045] In the following examples, the beta molecular sieve is purchased from Tianjin Nanhua Catalyst Co., Ltd.; the ZSM-5 molecular sieve is purchased from Tianjin Nanhua Catalyst Co., Ltd.; the cellulose is purchased from Shanghai Aladdin Biochem Technology Co., Ltd.; the tin tetrachloride and yttrium nitrate are purchased from Shanghai Aladdin Biochem Technology Co., Ltd.; the rest of the reagents and raw materials are conventional commercial products.

[0046] The concentration analysis of the substrate and product is analyzed and detected by high performance liquid chromatography (HPLC), and the chromatographic column model of HPLC is Aminex HPX-87X, which is ordered from Biorad Company. The mobile phase is 0.005 M H2SO 4； The flow rate is 0.55 mL / min, the injection amount is 20 μL, the column oven temperature is 45 DEG C, and the differential detector temperature is 50 DEG C.

[0047] Example 1-1 S1, weigh 100 mL of nitric acid solution (13 mol / L), then add 10 g of beta molecular sieve, stir for 30 min, and continue to stir at 80 DEG C for 6 h, then wash with deionized water for 3 times, dry at 110 DEG C, and get modified beta molecular sieve, ready for use; S2, weigh 1.7 g of yttrium nitrate and 2.52 g of tin tetrachloride, dissolve in 30 mL of deionized water, then add 5 g of modified beta molecular sieve prepared in step S1, stir for 8 h, then stand for 11 h, and dry in an oven at 110 DEG C for 12 h, to get catalyst precursor; S3, place the catalyst precursor in step S2 in a muffle furnace, calcine at 550 DEG C for 3 h, cool down, and get the supported 10 wt% Y2O3-40 wt% SnO2 / β catalyst, marked as Cat 1.

[0048] Example 1-2 S1, weigh 100 mL of nitric acid solution (30 mol / L), then add 5 g of beta molecular sieve, stir for 30 min, and continue to stir at 60 DEG C for 1 h, then wash with deionized water for 3 times, dry at 110 DEG C, and get modified beta molecular sieve, ready for use; S2, 1.7 g of yttrium nitrate and 1.9 g of tin tetrachloride were weighed and dissolved in 30 mL of deionized water, then 5 g of the modified β molecular sieve prepared in step S1 was added, stirred for 6 h, then stood for 10 h, and dried in an oven at 110 °C for 12 h to obtain a catalyst precursor; S3, the catalyst precursor in step S2 was placed in a muffle furnace and calcined at 650 °C for 2 h, then cooled to obtain a supported 10wt%Y2O3-30wt%SnO2 / β catalyst, denoted as Cat 2.

[0049] Example 1-3 S1, 100 mL of nitric acid solution (13 mol / L) was weighed, then 5 g of β molecular sieve was added, stirred for 30 min, and then stirred at 80 °C for 6 h, then washed with deionized water for 3 times, dried at 110 °C to obtain a modified β molecular sieve, which was used for standby; S2, 1.7 g of yttrium nitrate and 3.15 g of tin tetrachloride were weighed and dissolved in 30 mL of deionized water, then 5 g of the modified β molecular sieve prepared in step S1 was added, stirred for 6 h, then stood for 12 h, and dried in an oven at 110 °C for 12 h to obtain a catalyst precursor; S3, the catalyst precursor in step S2 was placed in a muffle furnace and calcined at 550 °C for 3 h, then cooled to obtain a supported 10wt%Y2O3-50wt%SnO2 / β catalyst, denoted as Cat 3.

[0050] Example 1-4 The catalyst was prepared according to the method described in Example 1-1, except that the calcination temperature was adjusted to 650 °C, to obtain a supported 10wt%Y2O3-40wt%SnO2 / β-650 catalyst, denoted as Cat 4.

[0051] Example 1-5 The catalyst was prepared according to the method described in Example 1-1, except that the amount of yttrium nitrate was 2.54 g, to obtain a supported 15wt%Y2O3-40wt%SnO2 / β catalyst, denoted as Cat 5.

[0052] Example 1-6 The catalyst was prepared according to the method described in Example 1-1, except that the amount of tin tetrachloride was 1.88 g, to obtain a supported 10wt%Y2O3-30wt%SnO2 / β catalyst, denoted as Cat 6.

[0053] Example 1-7 The catalyst was prepared according to the method described in Example 1-1, except that the β molecular sieve was not treated with nitric acid, and 3.0 g of tin chloride was added instead of tin tetrachloride, to obtain a supported 10 wt% Y2O3-40 wt% SnO2 / β catalyst, which was denoted as Cat 8.

[0054] Example 1-8 The catalyst was prepared according to the method described in Example 1-1, except that the β molecular sieve was not treated with nitric acid, and 3.0 g of tin chloride was added instead of tin tetrachloride, to obtain a supported 10 wt% Y2O3-40 wt% SnO2 / β catalyst, which was denoted as Cat 8.

[0055] Comparative Example 1-1 The catalyst was prepared according to the method described in Example 1-1, except that the β molecular sieve was not treated with nitric acid, and no tin tetrachloride was added, to obtain a supported 10 wt% Y2O3 / β catalyst, which was denoted as Cat A.

[0056] Comparative Example 1-2 The catalyst was prepared according to the method described in Example 1-1, except that the β molecular sieve was not treated with nitric acid, and no yttrium nitrate was added, to obtain a supported 40 wt% SnO2 / β catalyst, which was denoted as Cat B.

[0057] Comparative Example 1-3 The catalyst was prepared according to the method described in Example 1-1, except that the β molecular sieve was replaced by ZSM-5 molecular sieve, to obtain a supported 10 wt% Y2O3-40 wt% SnO2 / ZSM-5 molecular sieve catalyst, which was denoted as Cat C.

[0058] Example 2-1 The catalyst Cat 1 obtained by the preparation method described in Example 1-1 was taken 0.15 g, and cellulose 0.1 g and deionized water 20 g were put into a high-pressure reaction kettle, the pressure was set to 1 MPa, the temperature was set to 240°C, and the catalytic reaction was carried out for 3 h, and then the reaction liquid was cooled.

[0059] Example 2-2 The catalyst Cat 2 obtained by the preparation method described in Example 1-2 was taken 0.15 g, and cellulose 1.5 g and deionized water 20 g were put into a high-pressure reaction kettle, the pressure was set to 0.1 MPa, the temperature was set to 180°C, and the catalytic reaction was carried out for 10 h, and then the reaction liquid was cooled.

[0060] Example 2-3 The catalytic reaction was carried out according to the method of Example 2-1, except that the catalyst Cat 1 obtained by the preparation method of Example 1-1 was replaced by the catalyst Cat 3 obtained by the preparation method of Example 1-3.

[0061] Example 2-4 The catalytic reaction was performed according to the method of Example 2-2, except that the catalyst Cat 1 obtained from the preparation method of Example 1-1 was replaced with the catalyst Cat 4 obtained from the preparation method of Example 1-4.

[0062] Example 2-5 The catalytic reaction was performed according to the method of Example 2-2, except that the catalyst Cat 1 obtained from the preparation method of Example 1-1 was replaced with the catalyst Cat 5 obtained from the preparation method of Example 1-5.

[0063] Example 2-6 The catalytic reaction was performed according to the method of Example 2-2, except that the catalyst Cat 1 obtained from the preparation method of Example 1-1 was replaced with the catalyst Cat 6 obtained from the preparation method of Example 1-6.

[0064] Example 2-7 The catalytic reaction was performed according to the method of Example 2-1, except that the catalyst Cat 1 obtained from the preparation method of Example 1-1 was replaced with the catalyst Cat 7 obtained from the preparation method of Example 1-7.

[0065] Example 2-8 The catalytic reaction was performed according to the method of Example 2-2, except that the catalyst Cat 1 obtained from the preparation method of Example 1-1 was replaced with the catalyst Cat 8 obtained from the preparation method of Example 1-8.

[0066] Comparative Example 2-1 The catalytic reaction was performed according to the method of Example 2-1, except that the catalyst Cat 1 obtained from the preparation method of Example 1-1 was replaced with the catalyst Cat A obtained from the preparation method of Comparative Example 1-1.

[0067] Comparative Example 2-2 The catalytic reaction was performed according to the method of Example 2-2, except that the catalyst Cat 1 obtained from the preparation method of Example 1-1 was replaced with the catalyst Cat B obtained from the preparation method of Comparative Example 1-2.

[0068] Comparative Example 2-3 The catalytic reaction was performed according to the method of Example 2-1, except that the catalyst Cat 1 obtained from the preparation method of Example 1-1 was replaced with the catalyst Cat C obtained from the preparation method of Comparative Example 1-3.

[0069] Test Example 1 The cooling liquid obtained in the above-mentioned examples 2-1 to 2-6 and comparative examples 2-1 to 2-6 was analyzed by high performance liquid chromatography, and the analysis results are shown in Table 1. Table 1

[0070] As shown in Table 2, the conversion rate and yield of lactic acid prepared in the examples are obviously higher than those of lactic acid prepared in the comparative examples, and the conversion rate and yield of lactic acid prepared in examples 2-1 to 2-3 are obviously higher than those of other examples, therefore, the catalytic conversion effect of lactic acid prepared by the method provided by the present application is more optimal.

[0071] Test example 2 The catalytic reaction was carried out according to the method of example 2-1, after the reaction was completed, 0.1 g of cellulose was continuously added for catalytic reaction, and the cycle was repeated five times, and the cooling liquid of each reaction was measured, and the obtained data is shown in Table 2.

[0072] Table 2

[0073] As shown in Table 2, the yield of lactic acid is slightly reduced after each catalytic reaction, and the reduction amount of each time is within 0.2%, therefore, the catalyst prepared by the present application has high cycle stability, and has great industrial development prospect.

[0074] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed content of the present application, and all belong to the protection scope of the present application.

Claims

1. A catalyst, characterized in that The catalyst contains beta molecular sieve and yttrium oxide and tin oxide supported on the beta molecular sieve.

2. The catalyst according to claim 1, characterized in that In the catalyst, the mass ratio of the yttrium oxide to the tin oxide is 1:3-10; Preferably, in the catalyst, the loading amount of the yttrium oxide is 10-15 wt %, and the loading amount of the tin oxide is 30-45 wt %.

3. A method for preparing a catalyst, characterized in that: The method comprises the following steps: S1, mixing the beta molecular sieve, yttrium salt and tin salt to obtain a catalyst precursor; S2. calcining the catalyst precursor.

4. The preparation method according to claim 3, characterized in that In the step S1, the beta molecular sieve is further treated with acid before being mixed with the yttrium salt and the tin salt; wherein the acid is selected from at least one of nitric acid, hydrochloric acid, sulfuric acid, boric acid, oxalic acid, citric acid, phosphoric acid and acetic acid; Preferably, the acid is nitric acid; Preferably, in the reaction system of step S1, the concentration of the acid is 10-30 mol / L; Preferably, the amount of the acid used is 0.1-0.3 mol relative to 1 g of the β molecular sieve.

5. The preparation method according to claim 3, characterized in that In the step S1, the conditions of the contact reaction I include at least: a temperature of 60-100° C. and a time of 1-12 h.

6. The preparation method according to any one of claims 3 to 5, characterized in that In the step S2, the mass ratio of the modified beta molecular sieve, the yttrium salt and the tin salt is 1:0.1-0.5:0.1-1; Preferably, the yttrium salt is yttrium nitrate, and the tin salt is tin tetrachloride; Preferably, in step S2, the mixing time is 6-12 h; Preferably, the step S2 further comprises allowing the mixture to stand for 10-12 hours.

7. The preparation method according to claim 3, characterized in that In step S3, the calcination treatment conditions include: a temperature of 400-650° C. and a time of 2-6 h.

8. A catalyst prepared by the preparation method according to any one of claims 3 to 8.

9. Use of the catalyst according to any one of claims 1, 2 and 8 in catalyzing the production of lactic acid from biomass; Preferably, the biomass is cellulose.

10. A method for producing lactic acid, characterized in that: The method comprises contacting the catalyst according to any one of claims 1, 2 and 9 with biomass and water to carry out reaction II; Preferably, the mass ratio of the catalyst to the biomass is 1:0.7-10; Preferably, the contact reaction II is carried out under anaerobic conditions, and the conditions of the contact reaction II include: pressure of 0.1-1.0 MPa, temperature of 180-260° C., and time of 3-10 h.

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