Method for preparing glycine from glycollic acid

Abstract

The invention discloses a method for preparing glycine from glycollic acid, and the method for preparing glycine by catalyzing glycollic acid comprises the following steps: feeding a glycollic acid raw material solution into a first reactor, introducing nitrogen, and carrying out dehydrogenation reaction; the obtained mixture enters a second reactor, ammonia gas and hydrogen are introduced, a reductive amination reaction is carried out, and glycine is obtained; the method solves the problem of low yield of a one-step method product through a two-step method, realizes continuous reaction operation, and realizes high yield and stability. The method and the use of the catalyst provide a new direction for various fields in the future.

Description

Technical Field

[0001] The present application relates to a method for preparing glycine from glycolic acid, and belongs to the technical field of chemical synthesis. Background Art

[0002] Glycine has important applications in medicine, food, cosmetics, etc., and is used to prepare antioxidants, drugs and protein synthesis. Problems and limitations of current methods for preparing glycine include low efficiency, low yield, high cost, the need for toxic or environmentally unfriendly raw materials and catalysts, as well as environmental and sustainability issues such as waste generation and energy consumption.

[0003] Glycolic acid is an important organic compound widely used in many fields. It can be obtained from renewable raw materials, meeting the demand for efficient, sustainable and green synthesis methods, reducing adverse impacts on the environment, and complying with the principle of sustainable development. In the process of preparing glycine from glycolic acid, the dehydrogenation of glycolic acid to produce glyoxylic acid is the rate-determining step in the reaction process, which requires harsh reaction conditions. In the process of reductive amination of glyoxylic acid to produce glycine, the yield of by-products is increased, resulting in a decrease in the yield of glycine. Therefore, it is urgent to develop a new method for producing glycine with high selectivity and environmental stability to meet the market demand for high-quality glycine, and to effectively reduce production costs and reduce environmental burdens. Summary of the invention

[0004] The present invention aims to develop a method for preparing glycine from glycolic acid with high efficiency, wherein glycolic acid is first dehydrogenated to generate glyoxylic acid through a two-step method, and then glycine is prepared through reductive amination.

[0005] The present application provides a method for preparing glycine from glycolic acid, which has high product yield, simple and easy operation, and is environmentally friendly. The method adopts a two-step method, and the dehydrogenation reaction and the reductive amination reaction are carried out separately, which is conducive to increasing the yield of glyoxylic acid, thereby increasing the yield of glycine. The step-by-step reaction can avoid the polymerization of intermediates, improve the yield of intermediates, and achieve efficient preparation of glycine. The catalyst activity is stable, and it has broad application prospects.

[0006] According to one aspect of the present application, a method for preparing glycine from glycolic acid is provided, the preparation method comprising the following steps:

[0007] (1) contacting glycolic acid with a copper-based catalyst to undergo a dehydrogenation reaction to obtain a mixture containing glyoxylic acid;

[0008] (2) contacting the mixture containing glyoxylic acid with a ruthenium-based catalyst to undergo a reductive amination reaction to obtain glycine.

[0009] In the present application, a two-step method for preparing glycine by catalyzing glycolic acid is provided, wherein a fixed bed reactor is connected in series, wherein the first reactor catalyzes the dehydrogenation of glycolic acid to produce glyoxylic acid, and the second reactor catalyzes the reductive amination of glyoxylic acid to produce glycine;

[0010] The first reactor catalyst comprises a carrier and a dehydrogenation metal copper supported on the carrier, wherein the carrier is a metal oxide;

[0011] The second reactor catalyst comprises a carrier and hydrogenation metal ruthenium supported on the carrier, and the carrier is a metal oxide.

[0012] Optionally, the dehydrogenation reaction is carried out in reactor I, and the reductive amination reaction is carried out in reactor II.

[0013] Optionally, the reactor I is connected in series with the reactor II.

[0014] Optionally, the copper-based catalyst includes a carrier I and an active component copper supported on the carrier I.

[0015] Optionally, the ruthenium-based catalyst includes a carrier II and an active component ruthenium supported on the carrier II.

[0016] Optionally, the carrier I and carrier II are independently selected from Al 2 O 3 、V 2 O 5 、ZrO 2 、MoO 3 ,MgO,Fe 2 O 3 At least one of .

[0017] Optionally, in the copper-based catalyst, the copper loading is 5 to 40 wt%.

[0018] The mass of the catalyst is calculated based on the mass of the carrier, and the mass of the copper is calculated based on the mass of the copper element.

[0019] Optionally, in the copper-based catalyst, the copper loading is independently selected from any value of 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt% or a range between any two of the above.

[0020] Optionally, in the copper-based catalyst, the copper loading is 10-30 wt%, wherein the mass of the catalyst is calculated as the mass of the carrier, and the mass of the copper is calculated as the mass of the copper element.

[0021] Optionally, in the copper-based catalyst, the copper loading is 10-20 wt%, wherein the mass of the catalyst is calculated based on the mass of the carrier, and the mass of the copper is calculated based on the mass of the copper element.

[0022] Optionally, in the ruthenium-based catalyst, the loading amount of ruthenium is 0.5 to 10 wt %.

[0023] The mass of the catalyst is calculated based on the mass of the carrier, and the mass of ruthenium is calculated based on the mass of the ruthenium element.

[0024] Optionally, in the ruthenium-based catalyst, the loading amount of ruthenium is independently selected from any value among 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt% or a range between any two of the above.

[0025] Optionally, in the ruthenium-based catalyst, the loading amount of ruthenium is 3 to 6 wt %, wherein the mass of the catalyst is calculated based on the mass of the carrier, and the mass of ruthenium is calculated based on the mass of the ruthenium element.

[0026] Optionally, in the ruthenium-based catalyst, the loading amount of ruthenium is 3 to 5 wt %, wherein the mass of the catalyst is calculated based on the mass of the carrier, and the mass of ruthenium is calculated based on the mass of the ruthenium element.

[0027] Optionally, the preparation method of the copper-based catalyst comprises:

[0028] The carrier I is immersed in a solution containing a copper precursor, and I is dried to obtain the copper-based catalyst.

[0029] Optionally, the copper precursor solution is selected from at least one of copper nitrate, copper acetate, copper chloride and copper sulfate.

[0030] Optionally, the preparation method of the ruthenium-based catalyst comprises:

[0031] The carrier II is immersed in a solution containing a ruthenium precursor, and II is dried to obtain the ruthenium-based catalyst.

[0032] Optionally, the ruthenium precursor solution is selected from at least one of ruthenium nitrate, ruthenium chloride, ruthenium acetate, and carbonyl ruthenium chloride.

[0033] Optionally, the temperatures of the drying I and the drying II are independently selected from 105 to 150° C., and the times of the drying I and the drying II are independently selected from 6 to 15 hours.

[0034] Optionally, the carrier is impregnated into a solution containing a metal ruthenium precursor to obtain the catalyst, and the carrier is a metal oxide.

[0035] Specifically, the support (metal oxide) is impregnated into a solution containing a metal precursor, and the catalyst is obtained through stirring, standing and drying.

[0036] Optionally, the solvent in the solution containing the metal precursor is water, and the amount of water is the saturated water absorption amount of the carrier.

[0037] Optionally, the specific conditions of the stirring include: the stirring time is 0.5 to 6 hours.

[0038] Optionally, the stirring time is independently selected from any value among 0.5h, 1h, 2h, 4h, 5h, 6h or a range between any two of the above.

[0039] Optionally, the stirring time is 1 to 4 hours.

[0040] Optionally, the standing time is 8 to 36 hours.

[0041] Optionally, the standing time is independently selected from any value among 8h, 10h, 12h, 18h, 24h, 30h, 36h or a range between any two of the above.

[0042] Optionally, the standing time is 12 to 24 hours.

[0043] Optionally, the specific conditions for drying include: a drying temperature of 105 to 150° C. and a drying time of 6 to 15 hours.

[0044] Optionally, the specific conditions for drying include: a drying temperature of 110 to 120° C. and a drying time of 8 to 12 hours.

[0045] Optionally, the drying temperature is independently selected from any value of 105°C, 110°C, 120°C, 130°C, 140°C, 150°C or a range between any two of the above values.

[0046] Optionally, the drying time is independently selected from any value among 6h, 7h, 8h, 10h, 12h, 15h, or a range between any two of the above.

[0047] Optionally, in step (1), the copper-based catalyst is reduced to I in a hydrogen atmosphere before contacting with glycolic acid.

[0048] Optionally, the temperature of the reduction I is 200 to 550° C., and the time of the reduction I is 1 to 6 hours.

[0049] Optionally, the reduction temperature I is independently selected from any value of 200°C, 250°C, 300°C, 350°C, 450°C, 500°C, 550°C or a range between any two of the above values.

[0050] Optionally, the time for reduction I is independently selected from any value among 1h, 2h, 3h, 4h, 5h, 6h or a range value between any two of the above.

[0051] Optionally, the temperature of the reduction I is 200-450° C., and the time of the reduction I is 2-4 hours.

[0052] Optionally, in the step (2), the ruthenium-based catalyst is reduced to II in a hydrogen atmosphere before contacting with glyoxylic acid.

[0053] Optionally, the temperature of the reduction II is 200-400° C., and the time of the reduction II is 1-4 hours.

[0054] Optionally, the temperature of the reduction II is independently selected from any value of 200°C, 250°C, 300°C, 350°C, 400°C or a range between any two of the above values.

[0055] Optionally, the reduction time of II is independently selected from any value of 1h, 2h, 3h, 4h or a range between any two of the above.

[0056] Optionally, the temperature of reduction II is 250-350° C., and the time of reduction II is 2-4 hours.

[0057] Optionally, the conditions for the dehydrogenation reaction are: under a nitrogen atmosphere, the temperature of the dehydrogenation reaction is 120-180°C, and the volumetric space velocity of the glycolic acid feed is 0.5h -1 ~3.0h -1 .

[0058] Optionally, the temperature of the dehydrogenation reaction is independently selected from any value of 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C or a range between any two of the above values.

[0059] Optionally, the glycolic acid feed volume space velocity is independently selected from 0.5h -1 , 1.0h -1 , 1.5h -1 , 2.0h -1 , 2.5h -1 , 3.0h -1 Any value in or a range between any two of the above.

[0060] Optionally, the conditions for the dehydrogenation reaction are: under a nitrogen atmosphere, the temperature of the dehydrogenation reaction is 130-150° C., and the volumetric space velocity of the glycolic acid feed is 0.5 h -1 ~1.5h -1 .

[0061] Optionally, the conditions for the reductive amination reaction are: under a hydrogen and ammonia atmosphere, the temperature of the reductive amination reaction is 40 to 120° C., and the volumetric space velocity of the glyoxylic acid feed is 1.0 h -1 ~6.0h -1 , the ammonia inlet flow rate is 50~100mL min -1 .

[0062] Optionally, the conditions for the reductive amination reaction are: under a hydrogen and ammonia atmosphere, the temperature of the reductive amination reaction is 50-100° C., the volumetric space velocity of the glyoxylic acid feed is 2.0 h -1 ~6.0h -1 The ammonia inlet flow rate is 60-80 mL min -1 .

[0063] Optionally, the temperature of the reductive amination reaction is independently selected from any value of 40°C, 50°C, 80°C, 90°C, 100°C, 110°C, 120°C or a range between any two of the above values.

[0064] Optionally, the glyoxylic acid feed volume space velocity is independently selected from 1.0h -1 , 2.0h -1 , 3.0h -1 , 4.0h -1 , 5.0h -1 , 6.0h -1 Any value in or a range between any two of the above.

[0065] Optionally, the inlet flow rate of ammonia is independently selected from 50 mL min -1 、60mL min -1 、70mL min -1 、80mL min -1 、90mL min -1 、100mL min -1 Any value in or a range between any two of the above.

[0066] As a specific embodiment, the glycolic acid aqueous solution is heated for 0.5 h. -1 ~3.0h -1 Enter the first reactor containing the reduced catalyst, introduce nitrogen, and react at 120-180°C; the obtained mixture is heated for 1.0 h -1 ~6.0h -1 Entering the second reactor, ammonia and hydrogen are introduced to carry out reductive amination reaction to obtain glycine.

[0067] In a specific embodiment, the present invention provides a two-step method for preparing glycine by catalyzing glycolic acid. In the method, a glycolic acid raw material liquid is fed into a first reactor by a two-step method, nitrogen is introduced, and a dehydrogenation reaction is carried out; the obtained mixture enters a second reactor, ammonia and hydrogen are introduced, and a reductive amination reaction is carried out to obtain glycine. The method adopts a two-step method, and the dehydrogenation reaction and the reductive amination reaction are carried out separately, which is conducive to increasing the yield of glyoxylic acid, and then increasing the yield of glycine. The step-by-step reaction can avoid the polymerization of intermediates, improve the yield of intermediates, and achieve efficient preparation of glycine. The catalyst activity is stable and has broad application prospects.

[0068] The method can prepare glycine by two steps of dehydrogenation and reductive amination of glycolic acid. The catalyst of the method has the characteristics of simple preparation and high catalytic activity after multiple cycles. The method has high yield of glycine product, environmental stability and environmental friendliness. The method and catalyst have broad application prospects and broad market potential.

[0069] The beneficial effects of this application include:

[0070] 1) The method for preparing glycine by reductive amination of glycolic acid provided in the present application improves the yield of intermediates and avoids the occurrence of side reactions, thereby achieving an increase in the yield of glycine because the reaction is carried out in two steps.

[0071] 2) The catalyst system used in the method provided in the present application has good stability, can maintain high catalytic activity, has a high product yield, and the preparation process is simple, easy to operate, and environmentally friendly.

[0072] 3) The preparation method provided in this application has simple operation steps, is easy to implement, and reduces adverse effects on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 This is the H NMR spectrum of the reaction solution in Example 1 of the present application.

[0074] Figure 2 This is the NMR carbon spectrum of the reaction solution in Example 1 of the present application. DETAILED DESCRIPTION

[0075] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0076] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0077] Glycolic acid conversion rate (C mol%) = (glycolic acid feed amount - glycolic acid detected amount after the reaction is completed) / glycolic acid feed amount × 100%;

[0078] Glycine yield (C mol%) = glycine detected amount / glycolic acid feed amount × 100%.

[0079] Example 1

[0080] 10g Al 2 O 3 and Al 2 O 3 20wt% copper chloride (calculated as copper element) is added to 10gAl 2 O 3 After stirring for 1 hour in water with saturated water absorption, the mixture was allowed to stand at room temperature for 24 hours and dried at 110°C for 12 hours to obtain a copper-based catalyst. 10 g Al 2 O 3 and Al 2 O 3 5 wt% ruthenium chloride (calculated as ruthenium element) is added to 10 g Al 2 O 3 After stirring for 1 hour in water with saturated water absorption, the mixture was allowed to stand at room temperature for 24 hours and dried at 110°C for 12 hours to obtain a ruthenium-based catalyst; the prepared copper-based catalyst and ruthenium-based catalyst were pressed into tablets.

[0081] 5g of copper-based catalyst was weighed and loaded into the first fixed bed reactor, and 5g of ruthenium-based catalyst was loaded into the second fixed bed reactor. The copper-based catalyst in the first reactor was reduced at 450°C for 2h under hydrogen atmosphere; the ruthenium-based catalyst in the second reactor was reduced at 250°C for 2h under hydrogen atmosphere.

[0082] 5% aqueous solution of glycolic acid was added for 0.5 h -1 The first reactor was fed with nitrogen at a volume space velocity of 1.5 mol / L and reacted at 130°C. The mixture obtained in the first reactor was heated at 6.0 h -1 The second reactor was fed with hydrogen and ammonia at a volume space velocity of 80 mL min-1. -1 After the reaction, the product was condensed, the liquid phase was sampled and analyzed, the reaction solution was evaporated to remove the solvent, internal standard trioxane and deuterated water were added and mixed evenly, and samples were taken and subjected to NMR quantitative analysis, such as Figure 1 As shown, 1 H NMR (400 MHz, D2O, 298K): δ = 3.57 (s, 1H). The methylene of glycine peaks at 3.57 ppm, trioxane as an internal standard peaks at 5.24 ppm, and water peaks at 4.82 ppm; Figure 2 As shown, 13C NMR (100 MHz, D2O, 298K): δ = 172.45 (s), 93.43 (s), 41.39 (s). The carboxyl and methylene groups of glycine peak at 172.45 ppm and 41.39 ppm, and trioxane as an internal standard peaks at 93.43 ppm; the results of NMR analysis are the yields of the corresponding products. Among them, the conversion rate of glycolic acid is 99%, and the yield of glycine is 88%.

[0083] Example 2

[0084] 10g V 2 O 5 and V 2 O 5 10 wt% copper nitrate (calculated as copper element) is added to 10 g V 2 O 5 After stirring for 4 hours in water with saturated water absorption, the mixture was allowed to stand at room temperature for 12 hours and dried at 120°C for 8 hours to obtain a copper-based catalyst. 10 g V 2 O 5 and V 2 O 5 3 wt% ruthenium nitrate (calculated as ruthenium element) was added to 10 g V 2 O 5 After stirring for 4 hours in water with saturated water absorption, the mixture was allowed to stand at room temperature for 12 hours and dried at 120°C for 8 hours to obtain a ruthenium-based catalyst; the prepared copper-based catalyst and ruthenium-based catalyst were pressed into tablets.

[0085] 5g of copper-based catalyst was weighed and loaded into the first fixed bed reactor, and 5g of ruthenium-based catalyst was loaded into the second fixed bed reactor. The copper-based catalyst in the first reactor was reduced at 200°C for 4h under hydrogen atmosphere, and the ruthenium-based catalyst in the second reactor was reduced at 350°C for 4h under hydrogen atmosphere.

[0086] 5% aqueous glycolic acid solution was added for 1.5 h -1 The first reactor was fed with nitrogen at a volume space velocity of 1.5 mol / L and reacted at 150°C. The mixture obtained in the first reactor was heated at 2.0 h -1 The second reactor was fed with hydrogen and ammonia at a volume space velocity of 60 mL min-1. -1 After the reaction, the product was condensed, the liquid phase was sampled and analyzed, the reaction liquid was evaporated to remove the solvent, internal standard trioxane and deuterated water were added and mixed evenly, and samples were taken and subjected to NMR quantitative analysis. The results of NMR analysis were the yields of the corresponding products. The conversion rate of glycolic acid was 99%, and the yield of glycine was 85%.

[0087] Example 3

[0088] 10g ZrO 2and ZrO 2 30wt% copper acetate (calculated as copper element) is added to 10g ZrO 2 After stirring for 6 hours in water with saturated water absorption, the mixture was allowed to stand at room temperature for 8 hours and dried at 150°C for 6 hours to obtain a copper-based catalyst. 2 and ZrO 2 6 wt% ruthenium acetate (calculated as ruthenium element) was added to 10 g ZrO 2 After stirring for 6 hours in water with saturated water absorption, the mixture was allowed to stand at room temperature for 8 hours and dried at 150°C for 6 hours to obtain a ruthenium-based catalyst; the prepared copper-based catalyst and ruthenium-based catalyst were pressed into tablets.

[0089] 5g of copper-based catalyst was weighed and loaded into the first fixed bed reactor, and 5g of ruthenium-based catalyst was loaded into the second fixed bed reactor. The copper-based catalyst in the first reactor was reduced at 550°C for 1h under hydrogen atmosphere, and the ruthenium-based catalyst in the second reactor was reduced at 400°C for 1h under hydrogen atmosphere.

[0090] 5% aqueous solution of glycolic acid was added for 3.0 h -1 The first reactor was fed with nitrogen at a volume space velocity of 1.0 h and reacted at 180 °C. The mixture obtained in the first reactor was heated to 1.0 h. -1 The second reactor was fed with hydrogen and ammonia at a volume space velocity of 50 mL min-1. The reaction was carried out at 40 °C, with the ammonia flow rate of 50 mL min-1. -1 After the reaction, the product was condensed, the liquid phase was sampled and analyzed, the reaction liquid was evaporated to remove the solvent, internal standard trioxane and deuterated water were added and mixed evenly, and samples were taken and subjected to NMR quantitative analysis. The results of NMR analysis were the yields of the corresponding products. The conversion rate of glycolic acid was 99%, and the yield of glycine was 84%.

[0091] Example 4

[0092] 10g MoO 3 and MoO 3 15wt% copper sulfate (calculated as copper element) is added to 10gMoO 3 After stirring for 0.5 h in saturated water, the mixture was allowed to stand at room temperature for 36 h and dried at 105 °C for 15 h to obtain a copper-based catalyst. 3 and MoO 3 4 wt% carbonyl ruthenium chloride (calculated as ruthenium element) was added to 10 g MoO 3 After stirring for 0.5 h in water with saturated water absorption, the mixture was allowed to stand at room temperature for 36 h and dried at 105°C for 15 h to obtain a ruthenium-based catalyst; the prepared copper-based catalyst and ruthenium-based catalyst were pressed into tablets.

[0093] 5g of copper-based catalyst was weighed and loaded into the first fixed bed reactor, and 5g of ruthenium-based catalyst was loaded into the second fixed bed reactor. The copper-based catalyst in the first reactor was reduced at 250°C for 6h under hydrogen atmosphere, and the ruthenium-based catalyst in the second reactor was reduced at 200°C for 3h under hydrogen atmosphere.

[0094] 5% aqueous solution of glycolic acid was added for 2.0 h -1 The first reactor was fed with nitrogen at a volume space velocity of 1.5 mol / L and reacted at 120°C. The mixture obtained in the first reactor was heated at 5.0 h -1 The second reactor was fed with hydrogen and ammonia at a volume space velocity of 100 mL / min. The reaction was carried out at 120 °C, with the ammonia flow rate of 100 mL / min. -1 After the reaction, the product was condensed, the liquid phase was sampled and analyzed, the reaction liquid was evaporated to remove the solvent, internal standard trioxane and deuterated water were added and mixed evenly, and samples were taken and subjected to NMR quantitative analysis. The results of NMR analysis were the yields of the corresponding products. The conversion rate of glycolic acid was 99%, and the yield of glycine was 82%.

[0095] Example 5

[0096] 10 g MgO and 40 wt% copper chloride (calculated as copper element) by mass of MgO are added to water with saturated water absorption of 10 g MgO, stirred for 2 h, allowed to stand at room temperature for 18 h, and dried at 130° C. for 10 h to obtain a copper-based catalyst; 10 g MgO and 0.5 wt% ruthenium nitrate (calculated as ruthenium element) by mass of MgO are added to water with saturated water absorption of 10 g MgO, stirred for 2 h, allowed to stand at room temperature for 18 h, and dried at 130° C. for 10 h to obtain a ruthenium-based catalyst; the prepared copper-based catalyst and ruthenium-based catalyst are pressed into tablets.

[0097] 5g of copper-based catalyst was weighed and loaded into the first fixed bed reactor, and 5g of ruthenium-based catalyst was loaded into the second fixed bed reactor. The copper-based catalyst in the first reactor was reduced at 300°C for 3h under hydrogen atmosphere, and the ruthenium-based catalyst in the second reactor was reduced at 300°C for 2h under hydrogen atmosphere.

[0098] 5% aqueous solution of glycolic acid was added for 1.0 h -1 The first reactor was fed with nitrogen at a volume space velocity of 1.0 h and reacted at 160 °C. The mixture obtained in the first reactor was heated at 3.0 h. -1 The second reactor was fed with hydrogen and ammonia at a volume space velocity of 70 mL min-1. -1 After the reaction, the product was condensed, the liquid phase was sampled and analyzed, the reaction liquid was evaporated to remove the solvent, internal standard trioxane and deuterated water were added and mixed evenly, and samples were taken and subjected to NMR quantitative analysis. The results of NMR analysis were the yields of the corresponding products. The conversion rate of glycolic acid was 99%, and the yield of glycine was 83%.

[0099] Example 6

[0100] 10g Fe 2 O 3 and Fe 2 O 3 5wt% copper acetate (calculated as copper element) is added to 10gFe 2 O 3 After stirring for 5 hours in water with saturated water absorption, the mixture was allowed to stand at room temperature for 30 hours and dried at 140°C for 7 hours to obtain a copper-based catalyst. 2 O 3 and Fe 2 O 3 10 wt% ruthenium chloride (calculated as ruthenium element) is added to 10 g Fe 2 O 3 After stirring for 5 hours in water with saturated water absorption, the mixture was allowed to stand at room temperature for 30 hours and dried at 140°C for 7 hours to obtain a ruthenium-based catalyst; the prepared copper-based catalyst and ruthenium-based catalyst were pressed into tablets.

[0101] 5g of copper-based catalyst was weighed and loaded into the first fixed bed reactor, and 5g of ruthenium-based catalyst was loaded into the second fixed bed reactor. The copper-based catalyst in the first reactor was reduced at 350°C for 5h under hydrogen atmosphere, and the ruthenium-based catalyst in the second reactor was reduced at 300°C for 1h under hydrogen atmosphere.

[0102] 5% aqueous solution of glycolic acid was added for 2.5 h -1 The first reactor was fed with nitrogen at a volume space velocity of 1.0 h and reacted at 140 °C. The mixture obtained in the first reactor was heated at 4.0 h. -1 The second reactor was fed with hydrogen and ammonia at a volume space velocity of 90 mL min-1. -1 After the reaction, the product was condensed, the liquid phase was sampled and analyzed, the reaction liquid was evaporated to remove the solvent, internal standard trioxane and deuterated water were added and mixed evenly, and samples were taken and subjected to NMR quantitative analysis. The results of NMR analysis were the yields of the corresponding products. The conversion rate of glycolic acid was 99%, and the yield of glycine was 81%.

[0103] Comparative Example 1

[0104] The catalyst was prepared according to the conditions of Example 1 and reduced for use in the reduction amination reaction of glycolic acid. The difference from Example 1 was that the first reactor was not used, 5 g of the copper-based catalyst was weighed and loaded into the second fixed bed reactor, and the catalyst was reduced at 450° C. for 2 h under a hydrogen atmosphere, and glycolic acid was fed from the second reactor. The conversion rate of glycolic acid was 99%, and the yield of glycine was 10%.

[0105] Comparative Example 2

[0106] The catalyst was prepared according to the conditions of Example 1 and reduced for use in the reduction amination reaction of glycolic acid. The difference from Example 1 was that the first reactor was not used, 5 g of the ruthenium-based catalyst was weighed and loaded into the second fixed bed reactor, and the catalyst was reduced at 250° C. for 2 h under a hydrogen atmosphere, and glycolic acid was fed from the second reactor. The conversion rate of glycolic acid was 99%, and the yield of glycine was 25%.

[0107] Comparative Example 3

[0108] The catalyst was prepared according to the conditions of Example 1, and the catalyst was reduced and then used for the reductive amination reaction of glycolic acid. The difference from Example 1 was that the first reactor was not used, 2.5 g of the copper-based catalyst reduced at 450° C. for 2 h in a hydrogen atmosphere and 2.5 g of the ruthenium-based catalyst reduced at 250° C. for 2 h in a hydrogen atmosphere were weighed and loaded into the second fixed bed reactor, and glycolic acid was fed from the second reactor. The conversion rate of glycolic acid was 99%, and the yield of glycine was 44%.

[0109] The method of the invention adopts a two-step method to carry out the dehydrogenation reaction and the reductive amination reaction separately, which is beneficial to improving the yield of glyoxylic acid and thus increasing the yield of glycine. The step-by-step reaction can avoid the polymerization of intermediates, improve the yield of intermediates, realize the efficient preparation of glycine, and the catalyst activity is stable, so the method has broad application prospects.

[0110] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing glycine from glycolic acid, It is characterized in that The preparation method comprises the following steps: (1) contacting glycolic acid with a copper-based catalyst to undergo a dehydrogenation reaction to obtain a mixture containing glyoxylic acid; (2) contacting the mixture containing glyoxylic acid with a ruthenium-based catalyst to undergo a reductive amination reaction to obtain glycine.

2. The preparation method according to claim 1, It is characterized in that The dehydrogenation reaction is carried out in reactor I, and the reductive amination reaction is carried out in reactor II; Preferably, the reactor I and the reactor II are connected in series.

3. The preparation method according to claim 1, It is characterized in that The copper-based catalyst comprises a carrier I and an active component copper supported on the carrier I; Preferably, the ruthenium-based catalyst comprises a carrier II and an active component ruthenium supported on the carrier II; Preferably, the carrier I and carrier II are independently selected from Al 2 O 3 、V 2 O 5 、ZrO 2 、MoO 3 ,MgO,Fe 2 O 3 At least one of .

4. The preparation method according to claim 1, It is characterized in that In the copper-based catalyst, the copper loading is 5-40wt%, Wherein, the mass of the catalyst is measured by the mass of the carrier, and the mass of the copper is measured by the mass of the copper element; Preferably, in the copper-based catalyst, the copper loading is 10-30wt%, wherein the mass of the catalyst is calculated as the mass of the carrier, and the mass of the copper is calculated as the mass of the copper element; Preferably, in the copper-based catalyst, the loading amount of copper is 10-20 wt %, wherein the mass of the catalyst is calculated as the mass of the carrier, and the mass of the copper is calculated as the mass of the copper element.

5. The preparation method according to claim 1, It is characterized in that In the ruthenium-based catalyst, the loading amount of ruthenium is 0.5-10 wt %. Wherein, the mass of the catalyst is measured by the mass of the carrier, and the mass of ruthenium is measured by the mass of the ruthenium element; Preferably, in the ruthenium-based catalyst, the loading amount of ruthenium is 3-6 wt %, wherein the mass of the catalyst is calculated based on the mass of the carrier, and the mass of ruthenium is calculated based on the mass of the ruthenium element; Preferably, in the ruthenium-based catalyst, the loading amount of ruthenium is 3 to 5 wt %, wherein the mass of the catalyst is calculated based on the mass of the carrier, and the mass of ruthenium is calculated based on the mass of the ruthenium element.

6. The preparation method according to claim 1, It is characterized in that The preparation method of the copper-based catalyst comprises: The support I is immersed in a solution containing a copper precursor, and dried I to obtain the copper-based catalyst; Preferably, the copper precursor solution is selected from at least one of copper nitrate, copper acetate, copper chloride and copper sulfate.

7. The preparation method according to claim 1, It is characterized in that The preparation method of the ruthenium-based catalyst comprises: The carrier II is immersed in a solution containing a ruthenium precursor, and II is dried to obtain the ruthenium-based catalyst; Preferably, the ruthenium precursor solution is selected from at least one of ruthenium nitrate, ruthenium chloride, ruthenium acetate, and carbonyl ruthenium chloride; Preferably, the temperatures of the drying I and the drying II are independently selected from 105 to 150° C., and the times of the drying I and the drying II are independently selected from 6 to 15 hours.

8. The preparation method according to claim 1, It is characterized in that In the step (1), the copper-based catalyst is reduced in a hydrogen atmosphere before contacting with glycolic acid; Preferably, the temperature of the reduction I is 200-550° C., and the time of the reduction I is 1-6 hours.

9. The preparation method according to claim 1, It is characterized in that In the step (2), the ruthenium-based catalyst is reduced in a hydrogen atmosphere before contacting with glyoxylic acid. Preferably, the temperature of the reduction II is 200-400° C., and the time of the reduction II is 1-4 hours.

10. The preparation method according to claim 1, It is characterized in that The conditions of the dehydrogenation reaction are: under nitrogen atmosphere, the temperature of the dehydrogenation reaction is 120-180°C, the volumetric space velocity of the glycolic acid feed is 0.5h -1 ~3.0h -1 ; Preferably, the conditions of the reductive amination reaction are: under a hydrogen and ammonia atmosphere, the temperature of the reductive amination reaction is 40-120° C., the volumetric space velocity of the glyoxylic acid feed is 1.0 h -1 ~6.0h -1 , the ammonia inlet flow rate is 50~100mL min -1 ; Preferably, the conditions of the reductive amination reaction are: under a hydrogen and ammonia atmosphere, the temperature of the reductive amination reaction is 50-100° C., the volumetric space velocity of the glyoxylic acid feed is 2.0 h -1 ~6.0h -1 The ammonia inlet flow rate is 60-80 mL min -1 .

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