A process for the preparation of dl-tartaric acid

Abstract

The application discloses a preparation method of DL-tartaric acid, which uses maleic anhydride as raw material, uses WO3-SiO2-ZrO2 solid acid as a catalyst, and is prepared through catalytic oxidation reaction under the condition of an oxidant. The catalyst is prepared through the following steps: mixing and dissolving a tungsten-containing compound and a zirconium-containing compound; adding silica sol, a surfactant and a precipitant to form a gel, and then performing filtration, washing and calcination to obtain the catalyst. Since the active species and the carrier in the catalyst have strong interaction, the recycling rate of the catalyst is high, so that the residual amount of heavy metal tungsten in the prepared tartaric acid crystal is effectively reduced, the DL-tartaric acid yield is still high during recycling, the production cost of the tartaric acid is reduced, and the catalyst is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of tartaric acid, in particular to a preparation method of DL-tartaric acid. BACKGROUND

[0002] Tartaric acid (2,3-dihydroxybutanedioic acid) is a carboxylic acid, which is widely used as an additive and a resolving agent in food and medicine. The two asymmetric carbon atoms in the tartaric acid molecule cause it to have three optical isomers, and DL-tartaric acid (racemic tartaric acid) is the most widely used one among them.

[0003] The main method for preparing DL-tartaric acid is chemical synthesis: maleic anhydride is used as raw material, hydrogen peroxide is used as oxidant, tungstic acid is used as catalyst, and catalytic oxidation is carried out to generate epoxy succinic acid, which is then hydrolyzed to obtain tartaric acid, and then DL-tartaric acid product is obtained through cooling, crystallization, separation and drying. Although the tungstic acid catalyst can achieve a high yield of tartaric acid, it has the disadvantage of being difficult to separate as a homogeneous catalyst, which can easily cause the heavy metal content of the tartaric acid product to exceed the standard.

[0004] At present, the heterogeneous catalysts used for the catalytic oxidation of maleic anhydride or maleic acid to prepare tartaric acid are mainly catalysts with WO3 as the active component supported on different carriers. Patent CN1381436 discloses a hydrothermal method for synthesizing WO3-MCM-41 catalyst, which is used for preparing tartaric acid from maleic acid, and the yield of tartaric acid decreases by 13% after one cycle; Hao Jia (Fine Chemicals, 2016, 33:440-444) uses an impregnation method to load phosphotungstic acid on silica spheres to prepare PW / SiO2 catalyst, which is used for preparing tartaric acid from maleic acid, and the yield of tartaric acid decreases by 33% after one cycle. The decrease in the yield of tartaric acid is due to the relatively weak interaction between the active species and the carrier, which causes a large amount of active component WO3 and phosphorus to be dissolved and detached into the reaction solution during the reaction, ultimately resulting in a large amount of tungsten and phosphorus in the tartaric acid crystal product. In addition, the synthesis of WO3-MCM-41 catalyst by the hydrothermal method has a long synthesis period and requires high temperature and high pressure operation, which has high requirements for production equipment and is not easy to scale up production. The preparation of PW / SiO2 and WO3 / TiO2 catalysts requires the preparation of the carrier first and then the impregnation of WO3, which has a long production period and a relatively complex process.

[0005] Therefore, the existing preparation of DL-tartaric acid mainly has the following disadvantages: complex preparation process, long production period, catalyst cannot be recycled, and high catalyst use cost, which increases the production cost of tartaric acid. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of DL-tartaric acid with low heavy metal residue and high product yield.

[0007] Technical solution: The preparation method of DL-tartaric acid disclosed by the application uses maleic anhydride as raw material, uses WO3-SiO2-ZrO2 solid acid as catalyst, and is prepared through catalytic oxidation reaction under the condition of oxidant.

[0008] The WO3-SiO2-ZrO2 solid acid is prepared through a precipitation method, and is specifically prepared through the following steps:

[0009] (1) mixing and dissolving a tungsten-containing compound and a zirconium-containing compound;

[0010] (2) adding silica sol, a surfactant and a precipitant to form a gel, and then preparing the gel through filtration, washing and calcination.

[0011] The tungsten-containing compound is at least one of ammonium metatungstate, ammonium tungstate, sodium tungstate or phosphotungstic acid; and the zirconium-containing compound is at least one of zirconium oxychloride, zirconium nitrate or zirconium sulfate. The silica sol is preferably acidic silica sol.

[0012] The precipitant is one of ammonia, NaOH, KOH or urea; the concentration of the precipitant solution is 1.0-12.0 mol / L, preferably 1.0-6.0 mol / L; and the pH of the system is 7-14 after the precipitant is added.

[0013] The concentration of the zirconium-containing compound solution is 0.1-2.0 mol / L, and is preferably 0.1-0.5 mol / L.

[0014] The surfactant is at least one of polyethylene glycol, polyvinyl alcohol, Tween-80, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and fluorine-containing anionic surfactant.

[0015] The amount of the surfactant is 5-20 wt% of the mass of ZrO2 in the WO3-SiO2-ZrO2 solid acid, and is preferably 10-20 wt%.

[0016] The calcination temperature is 350-700 DEG C, and the calcination time is 1-10 h; and the calcination temperature is preferably 400-550 DEG C, and the calcination time is preferably 2-6 h.

[0017] The loading amount of WO3 in the WO3-SiO2-ZrO2 solid acid is 5.0-15.0 wt%, the loading amount of SiO2 is 2.5-20.0 wt%, and the rest is ZrO2; and the loading amount of WO3 is preferably 7.5-15.0 wt%, the loading amount of SiO2 is preferably 2.5-10.0 wt%, and the rest is ZrO2.

[0018] The preparation method of DL-tartaric acid comprises the following steps: maleic anhydride is added into deionized water, and after the maleic anhydride is fully dissolved by heating, WO3-SiO2-ZrO2 catalyst and hydrogen peroxide are added, and the reaction is carried out by heating to a reaction temperature; after the reaction, the reaction liquid and the catalyst are separated while hot, the solid catalyst is collected for regeneration and recycling, the collected liquid product is hydrolyzed by heating and concentrated, then cooled and crystallized at low temperature, filtered, washed, and dried to obtain DL-tartaric acid.

[0019] The amount of the WO3-SiO2-ZrO2 solid acid is 5.0-20.0 wt% of the mass of the raw material maleic anhydride.

[0020] The molar ratio of hydrogen peroxide to maleic anhydride is 1.5-2.5:1.0, and the concentration of maleic anhydride in deionized water is 3.0-5.0 mol / L.

[0021] The reaction temperature is 50-90 DEG C, and the reaction time is 1-12 h; preferably, the reaction temperature is 65-75 DEG C, and the reaction time is 3-6 h; the reaction liquid and the catalyst are separated by filtration.

[0022] The hydrolysis conditions of the liquid product are 80-100 DEG C for 2-10 h; preferably, 90-100 DEG C for 6-10 h; the concentration conditions are 80-100 DEG C, and the concentration is to half of the original solution volume; the cooling and crystallization conditions are 3-10 DEG C, preferably 3-9 DEG C; and the remaining mother liquor can be recycled.

[0023] The regeneration conditions of the catalyst are that the used WO3-SiO2-ZrO2 catalyst is washed with deionized water, dried, and then activated at 300-600 DEG C for 1-12 h; the used WO3-SiO2-ZrO2 catalyst has a high activation rate, and the activation rate can reach 95% after calcination; and the catalyst has a high recycling rate because the active substance and the carrier have strong binding force.

[0024] Basic principle: the present application fully uses the principle that the gel periphery has positive charges and can effectively adsorb anions, as shown in the preparation of WO3-SiO2-ZrO2 catalyst by the precipitation method. Figure 1 When the alkaline solution is added into the above salt solution, Si(OH) x and Zr(OH) x crystals are generated, and the tungsten-containing anion compound is immediately adsorbed, so that the tungsten-containing anion compound is uniformly distributed on the surface of the gel; at the same time, the adsorbed anion compound can inhibit Si(OH) xand Zr(OH) x The growth of the crystal seeds can promote the generation of W-O-Zr bonds and increase the specific surface area of the catalyst during the calcination process, thereby leading to WO x The WO

[0025] The WO x The Lewis acid sites provided by the (W-OH and W-O-Zr) species can generate a tungsten-containing peroxide compound with hydrogen peroxide, and the tungsten-containing peroxide compound combines with maleic acid to generate maleic acid-tungsten-containing peroxide, which undergoes proton transfer to generate epoxy succinic acid and water, as shown in the following formula: Figure 2 Under high temperature and acidic conditions, the oxygen in the three-membered ring ether structure in the epoxy succinic acid is first protonated, which enhances the polarity of the carbon-hydrogen bond, and water reacts with the carbon in the three-membered ring ether structure to generate DL-tartaric acid. The WO3-SiO2-ZrO2 solid acid catalyst prepared by the simple and easy precipitation method of the present application is used for preparing tartaric acid from maleic anhydride, as a heterogeneous catalyst, which is easy to separate and has a strong interaction between the active species WO3 and the SiO2-ZrO2 composite oxide, so that the catalyst can be recycled, and when recycled, it still has a high DL-tartaric acid yield and a high-purity tartaric acid crude product, thereby reducing the production cost of tartaric acid and having important application significance.

[0026] Advantages: Compared with the prior art, the present application has the following remarkable effects: 1. The heterogeneous catalyst of the present application can effectively reduce the residual amount of tungsten in the crystallization of tartaric acid, and still has a high DL-tartaric acid yield when recycled; 2. The catalyst of the present application is synthesized by a simple and easy precipitation method in one step, and the raw materials are cheap and easy to obtain; 3. The catalyst of the present application has a strong interaction between the active species and the carrier through gel adsorption, thereby improving the recycling rate of the catalyst and increasing the yield of tartaric acid; 4. The production cost of tartaric acid is reduced, and it is suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a synthesis mechanism diagram of the catalyst of the present application;

[0028] Figure 2 It is a reaction mechanism diagram of the catalyst of the present application for preparing epoxy succinic acid;

[0029] Figure 3 It is an NH3-DRTFIR spectrum of the catalyst of Example 3 of the present application;

[0030] Figure 4 It is an XRD diagram of the catalyst of Example 4 of the present application;

[0031] Figure 5 BET spectrum of the catalyst of Example 4 of the present application;

[0032] Figure 6 HPLC spectrum of the crude tartaric acid of Example 1 of the present application;

[0033] Figure 7 HPLC spectrum of the crude tartaric acid of Example 1 of the present application;

[0034] Figure 8 XRD spectrum of the catalyst of Example 6 of the present application after 5 times of activation;

[0035] Figure 9 IR spectrum of the catalyst of Example 6 of the present application after 5 times of activation. DETAILED DESCRIPTION

[0036] The present application will be further described in conjunction with the accompanying drawings of the specification.

[0037] Example 1

[0038] Firstly, the 7.5% WO3-5% SiO2-ZrO2 solid acid catalyst is prepared, including the following steps:

[0039] (1) Under the conditions of temperature of 25℃ and stirring rate of 600 r / min, 3.0 g of ammonium metatungstate and 52.2 g of zirconium oxychloride are weighed and dissolved into 630 ml of deionized water respectively, heated to 100℃ and continuously stirred for 2 h, and then cooled to room temperature;

[0040] (2) 5.7 g of acid silica sol and 2.0 g of polyethylene glycol are respectively put into it, stirred for 30 min until they are fully mixed, then 2 mol / L of ammonia water solution is added dropwise to the above liquid within 40 min until pH = 9.0, continuously stirred, and then filtered, washed with deionized water until the filtrate is not detected by 1 mol / L silver nitrate aqueous solution, the filter cake is taken out and put into 200 ml of anhydrous ethanol for 15 min, re-filtered, and then the filter cake is washed with 500 ml of anhydrous ethanol, and the filter cake is calcined at 500℃ for 4 h to obtain the 7.5% WO3-5% SiO2-ZrO2 solid acid catalyst.

[0041] The method for preparing DL-tartaric acid by using the above solid acid catalyst includes the following steps:

[0042] Example 1 Figure 5 The conversion rate of maleic anhydride in the epoxidation reaction was 59.6%, and the actual yield of DL-tartaric acid after the final reaction was 42.3%. Although this yield is lower than the conversion rate of fresh catalyst in the prior art, the higher conversion rate in the prior art is due to the homogeneous catalyst after WO3 leaching, which causes the problems of easy residual metal components and the inability to recycle the catalyst. Therefore, although the final yield of tartaric acid in this example is 42.3%, the catalyst can be recycled, and there is no problem of residual metal components.

[0043] Example 2

[0044] First, a 10% WO3-5% SiO2-ZrO2 solid acid catalyst was prepared, including the following steps:

[0045] (1) At a temperature of 25°C and a stirring rate of 600 r / min, 2.42 g of ammonium tungstate and 57.6 g of zirconium sulfate were dissolved in 330 ml of deionized water, respectively, and heated to 100°C for 2 h of continuous stirring, and then cooled to room temperature;

[0046] (2) 5.7 g of acid silica sol and 4.0 g of Tween-80 were added, respectively, and stirred for 30 min until they were fully mixed. Then, 1 mol / L aqueous sodium hydroxide solution was added dropwise to the above liquid within 40 min until the pH was 8.2, and continuous stirring was performed. Then, the filter cake was washed with deionized water as a washing agent until the conductivity of the filtrate was consistent with that of the washing agent. The filter cake was taken out and soaked in 200 ml of anhydrous ethanol for 15 min, and then re-filtered. Then, the filter cake was washed with 500 ml of anhydrous ethanol, and then calcined at 550°C for 3 h to obtain a 10% WO3-5% SiO2-ZrO2 solid acid catalyst.

[0047] The method for preparing DL-tartaric acid using the above solid acid catalyst includes the following steps:

[0048] The 20.8 g of maleic anhydride was added to 60.0 g of deionized water, and heated to 50 °C until it was completely dissolved. Then, 2.1 g of the catalyst obtained in Example 2 was added to the solution, which accounted for 10.0 wt% of the maleic anhydride. Then, 76.0 g of 30 wt% H2O2 was added to the solution in 6 min. The reaction solution was heated to 70 °C, and the epoxidation reaction was carried out for 4 h. The catalyst was separated by simple filtration, and the reaction solution was heated to 90 °C for hydrolysis for 8 h. Then, the solution was concentrated to half of the original volume at 100 °C, and cooled to 6 °C for crystallization. DL-tartaric acid was obtained by filtration, washing and drying. The conversion rate of maleic anhydride in the epoxidation reaction was 88.3%, and the actual yield of DL-tartaric acid after the reaction was 73.2%.

[0049] Example 3

[0050] First, the 7.5% WO3-2.5% SiO2-ZrO2 solid acid catalyst was prepared by the following steps:

[0051] (1) 2.31 g of sodium tungstate and 69.5 g of zirconium nitrate were weighed and dissolved in 1620 ml of deionized water at 25 °C and a stirring rate of 600 r / min. The solution was heated to 100 °C and stirred for 2 h, and then cooled to room temperature.

[0052] (2) 2.8 g of acidic silica sol and 3.0 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer were added to the solution, and stirred for 30 min until they were completely mixed. Then, 4 mol / L potassium hydroxide solution was added dropwise to the solution in 40 min until the pH was 7. The solution was continuously stirred, and then filtered. The filter cake was taken out and soaked in 200 ml of anhydrous ethanol for 15 min, and then re-filtered. The filter cake was washed with 500 ml of anhydrous ethanol, and then calcined at 400 °C for 6 h to obtain the 7.5% WO3-2.5% SiO2-ZrO2 solid acid catalyst. The NH3-DRT FIR spectrum of the catalyst is shown in Figure 3 From Figure 3 It can be seen that the catalyst not only has a large number of Bronsted acid sites, but also has a large number of Lewis acid sites, which is beneficial to the catalytic reaction.

[0053] The method for preparing DL-tartaric acid using the above solid acid catalyst includes the following steps:

[0054] Take 24.0 g of maleic anhydride and dissolve it in 60.0 g of deionized water, and heat to 50°C until it is fully dissolved. Add the catalyst obtained in Example 3, 3.6 g, which is 15.0 wt% of the mass of maleic anhydride, to the solution. Then, in 6 min, add 50.0 g of 30 wt% H2O2 to the solution. Heat the reaction solution to 72°C and carry out the epoxidation reaction for 5 h. Separate and collect the catalyst by simple filtration. Reheat the reaction solution to 95°C and hydrolyze for 6 h. Concentrate the solution to half the original volume at 90°C, and cool to crystallize at 9°C. Filter, wash, and dry to obtain DL-tartaric acid. The conversion rate of maleic anhydride in the epoxidation reaction is 65.1%, and the actual yield of DL-tartaric acid after the final reaction is 48.1%. The reason for the decrease in the conversion rate of the fresh catalyst compared to the prior art is described in Example 1.

[0055] Example 4

[0056] First, prepare a 15% WO3-10% SiO2-ZrO2 solid acid catalyst, including the following steps:

[0057] (1) At a temperature of 25°C and a stirring rate of 600 r / min, take 3.11 g of phosphotungstic acid and 37.3 1 g of zirconium oxychloride and dissolve them in 1000 ml of deionized water, respectively. Heat to 100°C and continuously stir for 2 h, and then cool to room temperature.

[0058] (2) Respectively add 11.2 g of acidic silica sol and 3.0 g of lauryl alcohol polyoxyethylene ether to the solution, stir for 30 min until they are fully mixed, then add a 6 mol / L urea solution dropwise to the above-mentioned liquid until the pH is 12, continuously stir, then suction filter, and rinse with deionized water as a washing agent until the conductivity of the filtrate is consistent with that of the washing agent. Take out the filter cake and soak it in 200 ml of anhydrous ethanol for 15 min, then re-suction filter, and then wash the filter cake with 500 ml of anhydrous ethanol. Finally, calcine the filter cake at 480°C for 2 h to obtain a 15% WO3-10% SiO2-ZrO2 solid acid catalyst.

[0059] The XRD pattern of the catalyst is shown in Figure 4 As can be seen, the catalyst only has a crystalline form of tetragonal zirconia, and no diffraction peaks corresponding to the crystalline phases of SiO2 and WO3 are observed, indicating that they are uniformly dispersed on the surface of the catalyst. The BET spectrum of the catalyst is shown in Figure 5 As can be seen, the catalyst has a large specific surface area and regular pore channels.

[0060] The method for preparing DL-tartaric acid using the above-mentioned solid acid catalyst includes the following steps:

[0061] Example 5 20.8 g of maleic anhydride was weighed into 60.0 g of deionized water, and the mixture was warmed to 50°C until the maleic anhydride was completely dissolved. 2.1 g of the catalyst obtained in Example 1 was added to the solution, and the catalyst accounted for 10.0 wt% of the maleic anhydride. Then, 53.0 g of 30 wt% H2O2 was added to the solution in 6 min. The reaction solution was warmed to 70°C and the epoxidation reaction was carried out for 4 h. The catalyst was separated and collected by simple filtration. The reaction solution was warmed to 90°C and the hydrolysis reaction was carried out for 8 h. The solution was concentrated to half of the original volume at 80°C, and then the solution was cooled to 6°C for crystallization. The DL-tartaric acid was obtained by filtration, washing and drying. The collected catalyst was washed, dried and activated at 300°C for 12 h, and then used in the next reaction. The catalyst was recycled for 5 times, and the performance of the recycled catalyst was investigated, as shown in Tables 1 and 2.

[0062] The crude tartaric acid prepared in this example is shown in the figure Figure 6 The HPLC spectrum of the crude tartaric acid is shown in the figure Figure 7 The crude tartaric acid is shown in the figure Figure 6 and Figure 7 It can be seen that the sample is a white crude DL-tartaric acid with a purity of 98%, indicating that the method can synthesize a crude tartaric acid with less impurities and high purity.

[0063] Example 5

[0064] 20.8 g of maleic anhydride was weighed into 60.0 g of deionized water, and the mixture was warmed to 50°C until the maleic anhydride was completely dissolved. 2.1 g of the catalyst obtained in Example 1 was added to the solution, and the catalyst accounted for 10.0 wt% of the maleic anhydride. Then, 53.0 g of 30 wt% H2O2 was added to the solution in 6 min. The reaction solution was warmed to 70°C and the epoxidation reaction was carried out for 4 h. The catalyst was separated and collected by simple filtration. The reaction solution was warmed to 90°C and the hydrolysis reaction was carried out for 8 h. The solution was concentrated to half of the original volume at 80°C, and then the solution was cooled to 6°C for crystallization. The DL-tartaric acid was obtained by filtration, washing and drying. The collected catalyst was washed, dried and activated at 300°C for 12 h, and then used in the next reaction. The catalyst was recycled for 5 times, and the performance of the recycled catalyst was investigated, as shown in Tables 1 and 2.

[0065] Table 1 7.5% WO3-5% SiO2-ZrO2 catalyst recycling reaction

[0066] Reaction number Maleic anhydride conversion (%) DL-tartaric acid yield (%) 1 68.2 51.2 2 66.9 49.1 3 64.9 49.8 4 65.6 46.7 5 61.8 47.1

[0067] Table 2 Element content analysis (XRF) of 7.5% WO3-5% SiO2-ZrO2 catalyst before and after reaction

[0068] Catalyst [wt% of W03] SiO2(wt%) 7.5% WO3 - 5% SiO2 - ZrO2 (before reaction) 7.72 4.96 <![CDATA[7.5%WO3-5%SiO2-ZrO2(反应后)]]> 7.56 4.77

[0069] As can be seen from Table 1 and Table 2, the conversion rate and actual yield of 7.5% WO3-5% SiO2-ZrO2 catalyst decreased by only 6.4% and 4.1% after being recycled for 5 times, and the WO x Species and SiO x The loss of species was small, indicating that the catalyst had good cyclic reaction performance for the epoxidation of maleic anhydride to DL-tartaric acid. After 5 reactions, the catalyst activity was relatively stable and still had a high DL-tartaric acid yield.

[0070] Example 6

[0071] Weigh 20.8g maleic anhydride and join 60.0g deionized water, be warming up to 50 ℃ and treat that it fully dissolves, add 2.1g catalyst obtained in embodiment 2 wherein, this catalyst accounts for 10.0wt% of maleic anhydride quality, then in 6min, by 30wt% H of 76.0g O drop into wherein, reaction solution is warming up to 70 ℃ and carries out epoxidation reaction 4h, separate and collect catalyst by the mode of simple filtration, after reaction solution is again warming up to 100 ℃ of hydrolysis 8h, be concentrated to half of original solution volume under 80 ℃ of conditions, crystallize by cooling under 6 ℃ of conditions, filter, wash and dry and obtain DL-tartaric acid.The catalyst of collection is washed, oven dry, and is used for next reaction after 600 ℃ of activation 1h, as shown in Table 3, investigates catalyst recycling performance, and circulates reaction 5 times altogether.

[0072] The XRD patterns and IR spectra of the catalyst after activation for 5 times are shown as follows: Figure 8 、 9 As shown. Figure 8 It can be seen that there is only the diffraction peak of tetragonal zirconia on the catalyst, and no diffraction peaks of SiO2 and WO3 are seen, indicating that the active species are still highly dispersed on the catalytic surface. Figure 9 It can be seen that only the infrared stretching vibration peak corresponding to ZrO2 exists on the activated catalyst, and no infrared stretching vibration peak related to maleic acid, epoxysuccinic acid or DL-tartaric acid is seen.

[0073] Table 3 10% WO3-5% SiO2-ZrO2 catalyst cycle reaction

[0074] Reaction number Maleic anhydride conversion (%) DL-tartaric acid yield (%) 1 88.1 73.4 2 85.6 70.5 3 83.4 68.1 4 82.1 67.1 5 80.3 65.3

[0075] from Figure 8 、 Figure 9As shown in Table 3, the structure and dispersion state of the active components of the 10% WO3-5% SiO2-ZrO2 catalyst after activation did not change, there was no organic matter covering the surface of the catalyst, and the conversion and actual yield only decreased by 7.8% and 8.1% after 5 cycles, indicating that the catalyst after simple high-temperature activation has good reaction performance for the epoxidation of maleic anhydride to DL-tartaric acid, and the catalyst activity is relatively stable after 5 reactions, and still has a high DL-tartaric acid yield.

Claims

1. A method for preparing DL-tartaric acid, using maleic anhydride as raw material, characterized in that: The WO3-SiO2-ZrO2 solid acid is used as a catalyst and is prepared by a catalytic oxidation reaction under oxidant conditions; the WO3-SiO2-ZrO2 solid acid is specifically prepared by the following steps: (1) Mixing and dissolving a tungsten-containing compound and a zirconium-containing compound; (2) Adding silica sol, surfactant and precipitant to form gel, which is then filtered, washed and calcined; The surfactant is at least one of polyethylene glycol, polyvinyl alcohol, Tween-80, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer; the amount of the surfactant is 5-20 wt% of the mass of ZrO2 in the WO3-SiO2-ZrO2 solid acid; The loading amount of WO3 in the WO3-SiO2-ZrO2 solid acid is 5.0~15.0 wt%, the loading amount of SiO2 is 2.5~20.0 wt%, and the balance is ZrO2.

2. The method for preparing DL-tartaric acid according to claim 1, wherein The precipitant is one of ammonia water, NaOH, KOH or urea.

3. The preparation method of DL-tartaric acid according to claim 1, characterized in that, The calcination temperature is 350-700°C, and the calcination time is 1-10 h.

4. The method for preparing DL-tartaric acid according to claim 1, wherein The amount of the WO3-SiO2-ZrO2 catalyst used is 1.0-20.0 wt% of the mass of maleic anhydride.

5. The method for preparing DL-tartaric acid according to claim 1, wherein The liquid product obtained after the raw material reacts with the WO3-SiO2-ZrO2 solid acid is hydrolyzed at 80-100°C for 2-10 hours, and then concentrated and crystallized to obtain DL-tartaric acid.

6. The method for preparing DL-tartaric acid according to claim 1, wherein The regeneration conditions of the WO3-SiO2-ZrO2 solid acid are as follows: the used WO3-SiO2-ZrO2 solid acid is washed and dried and then activated at 300-600°C for 1-12 hours.

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