Method for preparing lactic acid by using ethylene glycol as raw material and used catalyst

Abstract

The invention discloses a method for preparing lactic acid by taking ethylene glycol as a raw material and a used catalyst, and belongs to the technical field of fine chemical engineering. The method comprises the following step: by taking ethylene glycol and CO as reaction raw materials, carrying out contact reaction with a catalyst to obtain lactic acid. When the method is used for preparing lactic acid, the conversion rate of ethylene glycol reaches 70% or above, and the selectivity of lactic acid reaches 99% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemicals, and particularly relates to a method for preparing lactic acid using ethylene glycol as a raw material and a catalyst used therein. Background Art

[0002] Lactic acid, also known as 2-hydroxypropionic acid, is a widely used organic acid in food, medicine, fermentation, leather, printing and dyeing and other fields.

[0003] Currently, the main methods for producing lactic acid are fermentation and chemical synthesis. The fermentation method primarily utilizes biomass resources such as corn starch, lignin, and cottonseed hulls. Under the action of microorganisms, a lactic acid mixture is fermented to produce lactic acid, which is then separated and purified to obtain lactic acid. However, this method suffers from complex separation and purification processes and low production efficiency. The chemical synthesis method uses acetaldehyde and hydrocyanic acid as raw materials. Lactocyanide is first prepared, and lactic acid is obtained by acidifying the lactocyanide. The lactic acid is then purified through esterification and hydrolysis steps. However, this method involves toxic raw materials, which has limited its widespread application.

[0004] In recent years, CN110357770 uses methanol and ethylene glycol as raw materials to produce lactic acid in the presence of alkali and a nitrogen heterocyclic carbene iridium catalyst. However, this catalyst is expensive and the reaction system is severely corrosive. Summary of the Invention

[0005] To solve the above problems in the prior art, the present invention provides a method for preparing lactic acid using ethylene glycol as raw material. A catalyst containing active components Zn, Ni, and Cu is used, and the conversion rate of ethylene glycol reaches above 70%, and the selectivity of lactic acid reaches above 99%.

[0006] In a first aspect, the present invention provides a method for preparing lactic acid, comprising:

[0007] Ethylene glycol and CO are used as reaction raw materials and are contacted with a catalyst to react to obtain lactic acid.

[0008] Wherein, the catalyst comprises a carrier and an active component supported on the carrier;

[0009] Wherein, the carrier is activated carbon, and the active components include Zn, Ni, and Cu; preferably, based on the total amount of the catalyst as 100%, the content of Zn is 1-5%, the content of Ni is 1-8%, and the content of Cu is 3-6%.

[0010] In some embodiments, the molar ratio of the ethylene glycol to the CO is 1:(2-10). Preferably, the ethylene glycol is vaporized ethylene glycol.

[0011] In some embodiments, the catalyst is first subjected to a reduction reaction, and the reduction comprises: treating with CO at 200° C.-600° C., preferably 400° C., for 1 h-6 h, preferably 4 h.

[0012] In some embodiments, the contact reaction temperature is 100°C-300°C, the reaction pressure is 0.1MPa-5MPa, and the ethylene glycol feed volume space velocity is 0.1h -1 -5h -1 .

[0013] In a second aspect, the present invention provides a catalyst for preparing lactic acid using ethylene glycol as a raw material, comprising a carrier and an active component supported on the carrier;

[0014] Wherein, the carrier is activated carbon, and the active components include Zn, Ni, and Cu; preferably, based on the total amount of the catalyst as 100%, the content of Zn is 1-5%, the content of Ni is 1-8%, and the content of Cu is 3-6%.

[0015] In a third aspect, the present invention provides a method for preparing the above catalyst, comprising the following steps:

[0016] S1. Modification of activated carbon: boiling the activated carbon in deionized water, performing a first drying treatment, placing the activated carbon in an acid solution for reflux boiling, and then performing a second drying treatment to obtain modified activated carbon;

[0017] S2, placing the modified activated carbon in a zinc-containing solution for a first impregnation treatment, and after a third drying and a first calcination treatment, obtaining a zinc-loaded catalyst precursor;

[0018] S3, placing the zinc-loaded catalyst precursor in a nickel-containing solution for a second impregnation treatment, and after a fourth drying and a second calcination treatment, obtaining a zinc- and nickel-loaded catalyst precursor;

[0019] S4, placing the catalyst precursor loaded with zinc and nickel in a copper-containing solution for a third impregnation treatment, and performing a fifth drying and a third calcination treatment to obtain a catalyst loaded with zinc, nickel and copper.

[0020] In some embodiments, in step S1, the bulk density of the modified activated carbon is 0.2 g / ml-1 g / ml, preferably 0.5 g / ml; the water absorption rate is 0.5 g / g-5 g / g, preferably 1.5 g / g.

[0021] In some embodiments, in step S1, the mass ratio of the activated carbon to the deionized water is 1:(1.5-10); the boiling time is 1h-6h, preferably 4h; and / or,

[0022] The temperature of the first drying treatment is 100°C-150°C, preferably 120°C; the time is 3h-16h, preferably 12h; and / or,

[0023] The mass concentration of the acid solution is 0.5%-5%, preferably 2%; the acid solution is selected from sulfuric acid solution, nitric acid solution or hydrochloric acid solution, preferably nitric acid solution; the reflux boiling time is 1h-5h, preferably 3h; the mass ratio of the activated carbon to the acid solution is 1:(2-5); and / or,

[0024] The temperature of the second drying treatment is 100°C-150°C, preferably 120°C; the time is 3h-16h, preferably 12h;

[0025] In some embodiments, in step S2, the volume ratio of the modified activated carbon to the zinc-containing solution is 1:(1-3), preferably 1:2;

[0026] Preferably, the zinc solution is selected from one or more of zinc nitrate, zinc chloride or zinc sulfate; the zinc ion concentration in the zinc-containing solution is 0.05-0.4 mmol / L;

[0027] The first immersion treatment lasts for 10 hours to 30 hours, preferably 24 hours; and / or,

[0028] The third drying comprises: first drying at 70-90°C, preferably 80°C, for 3-8 hours, preferably 6 hours; then drying at 100-150°C, preferably 120°C, for 3-8 hours, preferably 6 hours;

[0029] The temperature of the first calcination treatment is 350° C.-650° C., preferably 550° C.; the time is 1 h-6 h, preferably 3 h.

[0030] In some embodiments, in step S3, the volume ratio of the zinc-loaded catalyst precursor to the nickel-containing solution is 1:(1-4), preferably 1:2;

[0031] Preferably, the nickel solution is selected from one or more of nickel nitrate, nickel chloride or nickel sulfate; the concentration of nickel ions in the nickel-containing solution is 0.05-0.6 mmol / L;

[0032] The second immersion treatment lasts for 10 hours to 30 hours, preferably 24 hours; and / or,

[0033] The fourth drying comprises: first drying at 70-90°C, preferably 80°C, for 3-8 hours, preferably 6 hours; then drying at 100-150°C, preferably 120°C, for 3-8 hours, preferably 6 hours;

[0034] The temperature of the second calcination treatment is 350° C.-650° C., preferably 550° C.; the time is 1 h-6 h, preferably 3 h.

[0035] In some embodiments, in step S4, the volume ratio of the catalyst precursor loaded with zinc and nickel to the copper-containing solution is 1:(1-4), preferably 1:2;

[0036] Preferably, the copper solution is selected from one or more of copper nitrate, copper chloride or copper sulfate; the concentration of copper ions in the copper-containing solution is 0.05-0.6 mmol / L;

[0037] The third immersion treatment lasts for 10 hours to 30 hours, preferably 24 hours; and / or,

[0038] The fifth drying comprises: first drying at 70-90°C, preferably 80°C, for 3-8 hours, preferably 6 hours; then drying at 100-150°C, preferably 120°C, for 3-8 hours, preferably 6 hours;

[0039] The temperature of the third calcination treatment is 350° C.-650° C., preferably 550° C.; the time is 1 hour-6 hours, preferably 3 hours.

[0040] In a fourth aspect, the present invention provides use of the catalyst described above or a catalyst prepared according to any one of the preparation methods described above in the preparation of lactic acid.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] When the catalyst of the present invention uses Zn, Ni and Cu as active components and activated carbon as a carrier to prepare lactic acid, the conversion rate of ethylene glycol reaches above 70% and the selectivity of lactic acid reaches above 99%. DETAILED DESCRIPTION

[0043] The technical solutions of the present invention will be described clearly and completely below with reference to specific embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0044] For experimental methods in the examples where specific conditions are not specified, generally conventional conditions and conditions described in the manual or conditions recommended by the manufacturer were followed. The general equipment, materials, reagents, etc. used were all commercially available unless otherwise specified.

[0045] Example 1

[0046] A method for preparing a catalyst for preparing lactic acid using ethylene glycol as a raw material comprises the following steps:

[0047] Activated carbon modification treatment: Weigh 50g of commercial activated carbon (Beijing Yinuokai Technology Co., Ltd.), place it in 250ml of deionized water and boil it for 4h, dry it at 120℃ for 12h, then place it in 150g of 2% by weight nitric acid solution and reflux and boil it for 3h, and dry it at 120℃ for 12h; the volume of the activated carbon obtained is 100ml, the bulk density is 0.5g / ml, and the water absorption rate is 1.5g / g.

[0048] Zinc Impregnation: Pretreated activated carbon (AC) was placed in a 50°C waterbath and evacuated to remove adsorbed gases and reduce the metal solution's penetration time. The evacuated activated carbon was immediately immersed in 200ml of 0.1761mmol / ml zinc nitrate solution for 24 hours. Excess solution was then filtered off, and the AC was dried at 80°C for 6 hours, then at 120°C for another 6 hours. The AC was then calcined in a muffle furnace at 550°C for 3 hours to yield a ZnO / AC catalyst with a zinc loading of 3.9%.

[0049] Nickel impregnation: ZnO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.3772 mmol / ml nickel nitrate solution for 24 hours after evacuation. The excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO / AC catalyst with a zinc loading of 3.9% and a nickel loading of 7.5%.

[0050] Copper impregnation: ZnO-NiO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.1811 mmol / ml copper nitrate solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO-CuO / AC catalyst with a zinc loading of 3.9%, a nickel loading of 7.5%, and a copper loading of 3.9%.

[0051] Example 2

[0052] A method for preparing a catalyst for preparing lactic acid using ethylene glycol as a raw material comprises the following steps:

[0053] Activated carbon modification treatment: Weigh 50g of commercial activated carbon (Beijing Yinuokai Technology Co., Ltd.), place it in 250ml of deionized water and boil it for 4h, dry it at 120℃ for 12h, then place it in 150g of 2% by weight nitric acid solution and reflux and boil it for 3h, and dry it at 120℃ for 12h; the volume of the activated carbon obtained is 100ml, the bulk density is 0.5g / ml, and the water absorption rate is 1.5g / g.

[0054] Zinc Impregnation: Pretreated activated carbon (AC) was placed in a 50°C waterbath and evacuated to remove adsorbed gases and reduce the metal solution's penetration time. The evacuated activated carbon was immediately immersed in 200ml of 0.1259mmol / ml zinc chloride solution for 24 hours. Excess solution was then filtered off, and the AC was dried at 80°C for 6 hours, then at 120°C for another 6 hours. The AC was then calcined in a muffle furnace at 550°C for 3 hours to yield a ZnO / AC catalyst with a zinc loading of 3.0%.

[0055] Nickel impregnation: ZnO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.08416 mmol / ml nickel nitrate solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO / AC catalyst with a zinc loading of 3.0% and a nickel loading of 1.8%.

[0056] Copper impregnation: ZnO-NiO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.1771 mmol / ml copper chloride solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO-CuO / AC catalyst with a zinc loading of 3.0%, a nickel loading of 1.8%, and a copper loading of 4.1%.

[0057] Example 3

[0058] A method for preparing a catalyst for preparing lactic acid using ethylene glycol as a raw material comprises the following steps:

[0059] Activated carbon modification treatment: Weigh 50g of commercial activated carbon (Beijing Yinuokai Technology Co., Ltd.), place it in 250ml of deionized water and boil it for 4h, dry it at 120℃ for 12h, then place it in 150g of 2% by weight nitric acid solution and reflux and boil it for 3h, and dry it at 120℃ for 12h; the volume of the activated carbon obtained is 100ml, the bulk density is 0.5g / ml, and the water absorption rate is 1.5g / g.

[0060] Zinc Impregnation: Pretreated activated carbon (AC) was placed in a 50°C waterbath and evacuated to remove adsorbed gases and reduce the metal solution's penetration time. The evacuated activated carbon was immediately immersed in 200ml of 0.07716mmol / ml zinc chloride solution for 24 hours. Excess solution was then filtered off, and the AC was dried at 80°C for 6 hours, then at 120°C for another 6 hours. The AC was then calcined in a muffle furnace at 550°C for 3 hours to yield a ZnO / AC catalyst with a zinc loading of 1.8%.

[0061] Nickel impregnation: ZnO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.2388 mmol / ml nickel nitrate solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO / AC catalyst with a zinc loading of 1.8% and a nickel loading of 5.0%.

[0062] Copper impregnation: ZnO-NiO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.1764 mmol / ml copper chloride solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO-CuO / AC catalyst with a zinc loading of 1.8%, a nickel loading of 5.0%, and a copper loading of 4.0%.

[0063] Example 4

[0064] A method for preparing a catalyst for preparing lactic acid using ethylene glycol as a raw material comprises the following steps:

[0065] Activated carbon modification treatment: Weigh 50g of commercial activated carbon (Beijing Yinuokai Technology Co., Ltd.), place it in 250ml of deionized water and boil it for 4h, dry it at 120℃ for 12h, then place it in 150g of 2% by weight nitric acid solution and reflux and boil it for 3h, and dry it at 120℃ for 12h; the volume of the activated carbon obtained is 100ml, the bulk density is 0.5g / ml, and the water absorption rate is 1.5g / g.

[0066] Zinc Impregnation: Pretreated activated carbon (AC) was placed in a 50°C waterbath and evacuated to remove adsorbed gases and reduce the metal solution's penetration time. The evacuated activated carbon was immediately immersed in 200ml of 0.2048mmol / ml zinc chloride solution for 24 hours. The excess solution was then filtered off, and the AC was dried at 80°C for 6 hours, then at 120°C for another 6 hours. The AC was then calcined in a muffle furnace at 550°C for 3 hours to yield a ZnO / AC catalyst with a zinc loading of 4.5%.

[0067] Nickel impregnation: ZnO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of a 0.3042 mmol / ml nickel chloride solution after evacuation for 24 hours. The excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO / AC catalyst with a zinc loading of 4.5% and a nickel loading of 6.0%.

[0068] Copper impregnation: ZnO-NiO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.2576 mmol / ml copper chloride solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO-CuO / AC catalyst with a zinc loading of 4.5%, a nickel loading of 6.0%, and a copper loading of 5.5%.

[0069] Comparative Example 1

[0070] Activated carbon modification treatment: Weigh 50g of commercial activated carbon (Beijing Yinuokai Technology Co., Ltd.), place it in 250ml of deionized water and boil it for 4h, dry it at 120℃ for 12h, then place it in 150g of 2% by weight nitric acid solution and reflux and boil it for 3h, and dry it at 120℃ for 12h; the volume of the activated carbon obtained is 100ml, the bulk density is 0.5g / ml, and the water absorption rate is 1.5g / g.

[0071] Rhodium Impregnation: Pretreated activated carbon (AC) was placed in a 50°C waterbath and evacuated to remove adsorbed gases and reduce the metal solution's penetration time. The evacuated AC was immediately immersed in 200ml of 0.004918mmol / ml rhodium chloride solution for 24 hours. Excess solution was then filtered off, and the AC was dried at 80°C for 6 hours, then at 120°C for another 6 hours. The AC was then calcined in a muffle furnace at 550°C for 3 hours to yield the catalyst Rh / AC with a rhodium loading of 0.2%.

[0072] Gold impregnation: Rh / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.01285 mmol / ml chloroauric acid solution for 24 h after evacuation. The excess solution was then filtered off and the mixture was dried at 80°C for 6 h and then at 120°C for 6 h. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 h to obtain a catalyst Rh-Au / AC with a rhodium loading of 0.2% and a gold loading of 1%.

[0073] Comparative Example 2

[0074] Activated carbon modification treatment: Weigh 50g of commercial activated carbon (Beijing Yinuokai Technology Co., Ltd.), place it in 250ml of deionized water and boil it for 4h, dry it at 120℃ for 12h, then place it in 2% by weight nitric acid solution and reflux and boil it for 3h, and dry it at 120℃ for 12h; the volume of the activated carbon obtained is 100ml, the bulk density is 0.5g / ml, and the water absorption rate is 1.5g / g.

[0075] Zinc Impregnation: Pretreated activated carbon (AC) was placed in a 50°C waterbath and evacuated to remove adsorbed gases and reduce the metal solution's penetration time. The evacuated activated carbon was immediately immersed in 200ml of 0.1923mmol / ml zinc nitrate solution for 24 hours. The excess solution was then filtered off, and the AC was dried at 80°C for 6 hours, then at 120°C for another 6 hours. The AC was then calcined in a muffle furnace at 550°C for 3 hours to yield a ZnO / AC catalyst with a zinc loading of 4.5%.

[0076] Nickel impregnation: ZnO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.2855 mmol / ml nickel nitrate solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO / AC catalyst with a zinc loading of 4.5% and a nickel loading of 6.0%.

[0077] Comparative Example 3

[0078] Activated carbon modification treatment: Weigh 50g of commercial activated carbon (Beijing Yinuokai Technology Co., Ltd.), place it in 250ml of deionized water and boil it for 4h, dry it at 120℃ for 12h, then place it in 2% by weight nitric acid solution and reflux and boil it for 3h, and dry it at 120℃ for 12h; the volume of the activated carbon obtained is 100ml, the bulk density is 0.5g / ml, and the water absorption rate is 1.5g / g.

[0079] Zinc Impregnation: Pretreated activated carbon (AC) was placed in a 50°C waterbath and evacuated to remove adsorbed gases and reduce the metal solution's penetration time. The evacuated activated carbon was immediately immersed in 200ml of 0.3695mmol / ml zinc nitrate solution for 24 hours. Excess solution was then filtered off, and the AC was dried at 80°C for 6 hours, then at 120°C for another 6 hours. The AC was then calcined in a muffle furnace at 550°C for 3 hours to yield a ZnO / AC catalyst with a zinc loading of 7.2%.

[0080] Nickel impregnation: ZnO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.5717 mmol / ml nickel nitrate solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO / AC catalyst with a zinc loading of 7.2% and a nickel loading of 10.0%.

[0081] Copper impregnation: ZnO-NiO / AC was placed in a 50°C water bath and immediately immersed in 200 ml of 0.4383 mmol / ml copper nitrate solution for 24 hours after evacuation. Excess solution was then filtered off and the mixture was dried at 80°C for 6 hours and then at 120°C for 6 hours. The mixture was then placed in a muffle furnace and calcined at 550°C for 3 hours to obtain a ZnO-NiO-CuO / AC catalyst with a zinc loading of 7.2%, a nickel loading of 10.0%, and a copper loading of 8.3%.

[0082] Evaluation parameters

[0083] Ethylene glycol conversion rate = amount of ethylene glycol converted to product / amount of ethylene glycol entering the reactor * 100%

[0084] Lactic acid selectivity = amount of ethylene glycol converted to lactic acid / amount of ethylene glycol converted to product * 100%

[0085] Application comparison

[0086] The catalyst evaluation test was conducted with reference to the application examples, and the catalyst prepared in Example 1 was used for the test, except that ethylene glycol was fed directly in liquid phase without undergoing gasification treatment.

[0087] Application Example 1

[0088] 5 ml of the catalyst prepared in Example 1 was weighed and mixed evenly with an equal amount of quartz sand. The mixture was then loaded into a fixed-bed reactor. Under nitrogen protection, the temperature was raised to 200°C at a rate of 3°C / min. After maintaining the temperature, the reaction mixture was reduced in a CO atmosphere at atmospheric pressure for 4 hours. The temperature was then lowered to 250°C, and CO and ethylene glycol were introduced at a molar ratio of CO:ethylene glycol of 2:1 at atmospheric pressure. The ethylene glycol feed rate was 0.03 ml / min. The ethylene glycol was vaporized at 193°C before addition. Lactic acid was produced after the reaction, and the condensate was collected after 1 hour for HPLC analysis.

[0089] Application Example 2

[0090] 5 ml of the catalyst prepared in Example 1 was weighed and mixed evenly with an equal amount of quartz sand. The mixture was then loaded into a fixed-bed reactor. Under nitrogen protection, the temperature was raised to 300°C at a rate of 3°C / min. After maintaining the temperature, the reaction was reduced in a CO atmosphere at atmospheric pressure for 4 hours. The temperature was then lowered to 250°C, and the pressure was raised to 4.5 MPa in a CO atmosphere. CO and ethylene glycol were introduced at a molar ratio of CO:ethylene glycol of 2:1 at a rate of 0.03 ml / min. The ethylene glycol was vaporized at 193°C before addition. Lactic acid was produced after the reaction, and the condensate was collected after 1 hour for HPLC analysis.

[0091] Application Example 3

[0092] 5 ml of the catalyst prepared in Example 1 was weighed and mixed evenly with an equal amount of quartz sand. The mixture was then loaded into a fixed-bed reactor. Under nitrogen protection, the temperature was raised to 300°C at a rate of 3°C / min. After maintaining the temperature, the reaction mixture was reduced in a CO atmosphere at atmospheric pressure for 4 hours. The temperature was then lowered to 250°C, and the pressure was raised to 4.5 MPa in a CO atmosphere. CO and ethylene glycol were introduced at a molar ratio of CO:ethylene glycol of 2:1 at a rate of 0.4 ml / min. The ethylene glycol was vaporized at 193°C before addition. Lactic acid was produced after the reaction, and the condensate was collected after 1 hour for HPLC analysis.

[0093] Application Example 4

[0094] 5 ml of the catalyst prepared in Example 1 was weighed and mixed evenly with an equal amount of quartz sand. The mixture was then loaded into a fixed-bed reactor. Under nitrogen protection, the temperature was raised to 300°C at a rate of 3°C / min. After maintaining the temperature, the reaction mixture was reduced in a CO atmosphere at atmospheric pressure for 4 hours. The temperature was then lowered to 250°C, and the pressure was raised to 4.5 MPa in a CO atmosphere. CO and ethylene glycol were introduced at a molar ratio of CO:ethylene glycol of 15:1 at a rate of 0.4 ml / min. The ethylene glycol was vaporized at 193°C before addition. Lactic acid was produced after the reaction, and the condensate was collected after 1 hour for HPLC analysis.

[0095] The results of the application examples and comparative examples are shown in Table 1 below:

[0096] Table 1 Catalyst performance test results

[0097]

[0098] As can be seen from the above table, the catalyst with specific composition prepared in Examples 1-4 of the present invention has higher ethylene glycol conversion and lactic acid selectivity. Comparative Example 1 is the catalyst of the traditional load rhodium and gold prepared. It was found that the ethylene glycol conversion of the catalyst significantly reduced, and no lactic acid was generated. Comparative Example 2 is the catalyst of the load bimetallic (Zn, Ni). It was found that the ethylene glycol conversion and lactic acid selectivity of the catalyst significantly reduced. Comparative Example 3 is the catalyst whose metal loading content exceeds the scope of the present invention. It was found that the ethylene glycol conversion and lactic acid selectivity of the catalyst did not significantly increase. In the application comparative example, ethylene glycol was directly liquid-phase fed without gasification treatment. It was found that the ethylene glycol conversion and lactic acid selectivity of the catalyst significantly reduced.

[0099] It can be seen from the above table that after changing the catalyst composition, the reaction effect becomes worse; after increasing the active component content, the reaction effect does not improve; after changing the reaction feed process, the reaction effect becomes worse.

[0100] The reduction temperature was changed from 200℃ to 400℃, and the reaction pressure was changed from normal pressure to 4.5MPa, but the reaction results did not change significantly. -1 Mentioned 4.8h -1 , only the ethylene glycol conversion rate decreased, while the target product selectivity did not decrease; the CO: ethylene glycol molar ratio was increased from 2:1 to 15:1, which only led to a slight decrease in the ethylene glycol conversion rate, while the target product selectivity increased.

[0101] In summary, in the present invention, by selecting specific amounts of Zn, Ni, and Cu as active components and using activated carbon as a carrier catalyst for preparing lactic acid, the conversion rate of ethylene glycol reaches over 70% and the selectivity of lactic acid reaches over 99%.

[0102] The above embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that any technician familiar with this technical field can still modify the technical solutions recorded in the above embodiments within the technical scope disclosed by the present invention, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention.

Claims

1. A method for preparing lactic acid, characterized in that: include Ethylene glycol and CO are used as reaction raw materials and are contacted with a catalyst to react to obtain lactic acid; preferably, the catalyst includes a carrier and an active component supported on the carrier; further preferably, the carrier is activated carbon, and the active component includes Zn, Ni, and Cu; preferably, based on the total amount of the catalyst as 100%, the content of Zn is 1-5%, the content of Ni is 1-8%, and the content of Cu is 3-6%.

2. The preparation method according to claim 1, characterized in that The molar ratio of the ethylene glycol to the CO is 1:(2-10), preferably, the ethylene glycol is gasified ethylene glycol; Preferably, the catalyst is first reduced, and the reduction comprises: treating with CO at 200°C-500°C, preferably 400°C, for 1h-6h, preferably 4h under nitrogen protection; Preferably, the contact reaction temperature is 100°C-300°C, the reaction pressure is 0.1 MPa-5 MPa, and the ethylene glycol feed volume space velocity is 0.1h -1 -5h -1 .

3. A catalyst for preparing lactic acid using ethylene glycol as raw material, characterized in that: comprising a carrier and an active component loaded on the carrier; Wherein, the carrier is activated carbon, and the active components include Zn, Ni, and Cu; preferably, based on the total amount of the catalyst as 100%, the content of Zn is 1-5%, the content of Ni is 1-8%, and the content of Cu is 3-6%.

4. The method for preparing the catalyst according to claim 3, wherein The steps include: S1. Modification of activated carbon: boiling the activated carbon in deionized water, performing a first drying treatment, placing the activated carbon in an acid solution for reflux boiling, and then performing a second drying treatment to obtain modified activated carbon; S2, placing the modified activated carbon in a zinc-containing solution for a first impregnation treatment, and after a third drying and a first calcination treatment, obtaining a zinc-loaded catalyst precursor; S3, placing the zinc-loaded catalyst precursor in a nickel-containing solution for a second impregnation treatment, and after a fourth drying and a second calcination treatment, obtaining a zinc- and nickel-loaded catalyst precursor; S4, placing the catalyst precursor loaded with zinc and nickel in a copper-containing solution for a third impregnation treatment, and performing a fifth drying and a third calcination treatment to obtain a catalyst loaded with zinc, nickel and copper.

5. The method for preparing the catalyst according to claim 4, wherein: In step S1, the bulk density of the modified activated carbon is 0.2 g / ml-1 g / ml, preferably 0.5 g / ml; the water absorption rate is 0.5 g / g-5 g / g, preferably 1.5 g / g.

6. The method for preparing the catalyst according to claim 4, wherein: In step S1, the mass ratio of the activated carbon to the deionized water is 1:(1.5-10); the boiling time is 1h-6h, preferably 4h; and / or, The temperature of the first drying treatment is 100°C-150°C, preferably 120°C; the time is 3h-16h, preferably 12h; and / or, The mass concentration of the acid solution is 0.5%-5%, preferably 2%; the acid solution is selected from sulfuric acid solution, nitric acid solution or hydrochloric acid solution, preferably nitric acid solution; the reflux boiling time is 1h-5h, preferably 3h; the mass ratio of the activated carbon to the acid solution is 1:(2-5); and / or, The temperature of the second drying treatment is 100° C.-150° C., preferably 120° C.; the time is 3 h-16 h, preferably 12 h.

7. The method for preparing the catalyst according to claim 4, characterized in that: In step S2, the volume ratio of the modified activated carbon to the zinc-containing solution is 1:(1-3), preferably 1:2; Preferably, the zinc-containing solution is selected from one or more of zinc nitrate, zinc chloride or zinc sulfate; the zinc ion concentration in the zinc-containing solution is 0.05-0.4 mmol / L; The first immersion treatment lasts for 10 hours to 30 hours, preferably 24 hours; and / or, The third drying comprises: first drying at 70-90°C, preferably 80°C, for 3-8 hours, preferably 6 hours; then drying at 100-150°C, preferably 120°C, for 3-8 hours, preferably 6 hours; The temperature of the first calcination treatment is 350° C.-650° C., preferably 550° C.; the time is 1 h-6 h, preferably 3 h.

8. The method for preparing the catalyst according to claim 4, wherein: In step S3, the volume ratio of the zinc-loaded catalyst precursor to the nickel-containing solution is 1:(1-4), preferably 1:2; Preferably, the nickel-containing solution is selected from one or more of nickel nitrate, nickel chloride or nickel sulfate; the nickel ion concentration in the nickel-containing solution is 0.05-0.6 mmol / L; The second immersion treatment lasts for 10 hours to 30 hours, preferably 24 hours; and / or, The fourth drying comprises: first drying at 70-90°C, preferably 80°C, for 3-8 hours, preferably 6 hours; then drying at 100-150°C, preferably 120°C, for 3-8 hours, preferably 6 hours; The temperature of the second calcination treatment is 350° C.-650° C., preferably 550° C.; the time is 1 h-6 h, preferably 3 h.

9. The method for preparing the catalyst according to claim 4, wherein: In step S4, the volume ratio of the catalyst precursor loaded with zinc and nickel to the copper-containing solution is 1:(1-4), preferably 1:2; Preferably, the copper-containing solution is selected from one or more of copper nitrate, copper chloride or copper sulfate; the concentration of copper ions in the copper-containing solution is 0.05-0.6 mmol / L; The third immersion treatment lasts for 10 hours to 30 hours, preferably 24 hours; and / or, The fifth drying comprises: first drying at 70-90°C, preferably 80°C, for 3-8 hours, preferably 6 hours; then drying at 100-150°C, preferably 120°C, for 3-8 hours, preferably 6 hours; The temperature of the third calcination treatment is 350° C.-650° C., preferably 550° C.; the time is 1 hour-6 hours, preferably 3 hours.

10. Use of the catalyst according to claim 3 or the catalyst prepared according to the preparation method according to any one of claims 4 to 9 in the preparation of lactic acid.

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