Catalyst for producing lactic acid from ethylene glycol by dehydrogenation, preparation method and application thereof

Abstract

The present invention provides a catalyst for ethylene glycol dehydrogenation to lactic acid, the general formula being M / S@C; wherein M is an active component selected from a combination of any one or more of Ru, Ir, Sn, Rh, Pd, Ag, Cd, In, and Sb; S@C is a solid base carrier, and C is a carrier selected from a combination of any one or more of Al2O3, SiO2, and ZrO2; S is a basic oxide shell coated on the surface of C, selected from a combination of any one or more of BeO, MgO, CaO, SrO, BaO, and RaO; based on the mass of C, the mass of M is 0.75-30wt% and the mass of S is 2-15wt%. Also provided are a preparation method of the catalyst and its application and method in ethylene glycol dehydrogenation to lactic acid. The catalyst can be used in ethylene glycol dehydrogenation to lactic acid, has high activity, and is suitable for use in a fixed-bed reactor.

Description

Technical Field

[0001] The invention belongs to the field of preparing lactic acid by dehydrogenating alcohol, and particularly relates to a catalyst used in preparing lactic acid by dehydrogenating ethylene glycol, and a preparation method and application thereof. Background Art

[0002] Currently, the production of lactic acid from polyols is carried out in stirred tanks. However, stirred tanks have the following three disadvantages: (1) no matter how much stirring is done, there is always a "dead corner" at the bottom of the reactor, and solid particles inevitably precipitate, resulting in low catalyst utilization; (2) liquid alkali is required during the process, which seriously corrodes the equipment; and (3) the solid-liquid separation of the reactor discharge mixture is difficult. When other reaction devices are used, suitable catalysts are not available. Summary of the Invention

[0003] The first object of the present invention is to provide a catalyst for use in the dehydrogenation of ethylene glycol to produce lactic acid, which catalyst can be used in the dehydrogenation of ethylene glycol to produce lactic acid, has high activity, and is suitable for use in a fixed bed reactor;

[0004] The second object of the present invention is to provide a method for preparing the aforementioned catalyst;

[0005] The third object of the present invention is to provide an application of the aforementioned catalyst in the dehydrogenation of ethylene glycol to produce lactic acid;

[0006] A fourth object of the present invention is to provide a method for preparing lactic acid by dehydrogenating ethylene glycol.

[0007] In order to achieve the first object of the present invention, the following technical solutions are adopted:

[0008] A catalyst for dehydrogenating ethylene glycol to produce lactic acid, having the general formula M / S@C; wherein:

[0009] M is an active component selected from any one or more combinations of Ru, Ir, Sn, Rh, Pd, Ag, Cd, In and Sb;

[0010] S@C is a solid base carrier, C is a carrier selected from any one or more combinations of Al2O3, SiO2 and ZrO2; S is a basic oxide shell coated on the surface of C, selected from any one or more combinations of BeO, MgO, CaO, SrO, BaO and RaO;

[0011] Based on the mass of C, the mass of M is 0.75-30wt%, such as 1wt%, 1.5wt%, 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt% and 28wt%, as well as any value within this range; the mass of S is 2-15wt%, such as 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt% and 14wt%, as well as any value within this range.

[0012] The catalyst of the present invention can be used in the dehydrogenation of ethylene glycol to produce lactic acid, and due to its high activity, is suitable for use in a fixed bed reactor.

[0013] To improve the catalytic performance of the catalyst, in one embodiment, M includes Ru and Sn.

[0014] In one embodiment, the mass of Ru in M ​​is 0.5-10 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt% and 9 wt%, based on the mass of C, and any value within this range.

[0015] In one embodiment, in M, the mass ratio of Ru to Sn is 1:(0.4-3), such as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.2, 1:2.4, 1:2.6 and 1:2.8, and any ratio within this range.

[0016] In order to improve the catalytic performance of the catalyst, in one embodiment, C is a granular carrier with a bipore distribution.

[0017] In one embodiment, the pore sizes of the double pores are 5-50 nm (such as 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm and 45 nm) and 100-300 nm (such as 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm and 280 nm).

[0018] In one embodiment, the average pore diameters of the dual pores are 20±4 nm and 200±10 nm, respectively.

[0019] The catalyst of the invention has high activity and good catalytic performance, can be used in preparing lactic acid by dehydrogenating ethylene glycol, and is suitable for use in a fixed-bed reactor.

[0020] To achieve the second object of the present invention, a method for preparing the above-mentioned catalyst is provided.

[0021] In one embodiment, the steps include:

[0022] (1) dissolving the salt corresponding to the oxide shell S in deionized water to obtain a shell impregnation solution;

[0023] (2) impregnating the carrier C in the shell impregnation solution obtained in step (1), and then filtering, drying and calcining the solution in sequence to obtain a solid base carrier S@C;

[0024] (3) dissolving the salt corresponding to the active component M in deionized water to obtain an active component impregnation solution;

[0025] (4) The solid base carrier S@C obtained in step (2) is placed in the active component impregnation solution obtained in step (3) for immersion, and then a formaldehyde aqueous solution is added thereto to cause a reduction reaction, and then the process is filtered, washed and dried in sequence to obtain the catalyst M / S@C.

[0026] Those skilled in the art will appreciate that the filtration in step (2) and step (4) can be performed by any filtration method commonly used in the art, such as suction filtration, plate and frame filtration, sedimentation separation, etc. In one embodiment, suction filtration is used.

[0027] In order to improve the catalytic performance of the prepared catalyst, in one embodiment, in step (1), the salt corresponding to the oxide shell S is selected from any one or a combination of nitrates, chlorides and sulfates of Be, Mg, Ca, Sr, Ba and Ra, such as Ba(NO3)2, BaCl2, CaCl2, MgSO4, Sr(NO3)2, etc.

[0028] Those skilled in the art will appreciate that in step (1), the salt may be a salt containing crystalline water or a salt not containing crystalline water.

[0029] In order to improve the catalytic performance of the prepared catalyst, in one embodiment, in step (1), the concentration of the shell impregnation solution is 0.05-0.5 mmol / ml, such as 0.07 mmol / ml, 0.1 mmol / ml, 0.15 mmol / ml, 0.2 mmol / ml, 0.25 mmol / ml, 0.3 mmol / ml, 0.35 mmol / ml, 0.4 mmol / ml and 0.45 mmol / ml, as well as any value within this range.

[0030] To improve the impregnation effect of the shell layer, in one embodiment, in step (2), the impregnation temperature is 20-50°C, such as 25°C, 30°C, 35°C, 40°C and 45°C, and any temperature within this range; the impregnation time is 24-72h, such as 30h, 36h, 42h, 48h, 54h, 60h and 66h, and any value within this range.

[0031] In order to improve the coating effect of the shell layer, in one embodiment, in step (2), the drying temperature is 60-100°C, such as 65°C, 70°C, 75°C, 80°C, 85°C, 90°C and 95°C, and any temperature within this range; the drying time is 12-36h, such as 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h and 34h, and any value within this range.

[0032] To improve the coating effect of the shell layer, in one embodiment, in step (2), the calcination temperature is 400-600°C, such as 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C and 580°C, and any temperature within this range; the calcination time is 2-6h, such as 2.5h, 3h, 3.5h, 4h, 4.5h, 5h and 5.5h, and any value within this range.

[0033] In order to improve the impregnation effect of the active component, in one embodiment, in step (3), the concentration of the active component impregnation solution is 0.05-0.5 mmol / ml, such as 0.07 mmol / ml, 0.1 mmol / ml, 0.15 mmol / ml, 0.2 mmol / ml, 0.25 mmol / ml, 0.3 mmol / ml, 0.35 mmol / ml, 0.4 mmol / ml and 0.45 mmol / ml, as well as any value within this range.

[0034] In one embodiment, in step (3), the salt corresponding to the active component M is selected from any one or more combinations of nitrates, chlorides and sulfates of Ru, Sn, Rh, Ir, Pd, Ag, Cd, In and Sb, such as RuCl3·3H2O, H2IrCl6·6H2O, SnCl2·2H2O, In(NO3)2, PdSO4 and SbCl2.

[0035] Those skilled in the art will appreciate that in step (3), the salt may be a salt containing crystalline water or a salt not containing crystalline water.

[0036] In order to improve the impregnation effect of the active component, in one embodiment, in step (4), the impregnation temperature is 20-50°C, such as 25°C, 30°C, 35°C, 40°C and 45°C, and any temperature within this range; the impregnation time is 6-18h, such as 8h, 10h, 12h, 14h and 16h, and any value within this range.

[0037] In order to reduce the salt corresponding to the active component M to the active component M, in one embodiment, in step (4), the reduction temperature is 40-60°C, such as 45°C, 50°C and 55°C, and any temperature within this range; the reduction time is 0.5-1.5h, such as 1h, and any value within this range.

[0038] In order to improve the reduction effect, in one embodiment, in step (4), the concentration of the formaldehyde aqueous solution is 5-15wt%, such as 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt% and 14wt%, and any value within this range.

[0039] In order to improve the loading effect of the active component, in one embodiment, in step (4), the drying temperature is 60-100°C, such as 65°C, 70°C, 75°C, 80°C, 85°C, 90°C and 95°C, and any temperature within this range; the drying time is 2-5h, such as 2.5h, 3h, 3.5h, 4h and 4.5h, and any value within this range.

[0040] In order to improve the catalytic performance of the prepared catalyst, in one embodiment, the amounts of the active component M, the salt corresponding to the oxide shell S and the carrier C meet the following conditions: based on the mass of C, the mass of M is 0.75-30wt%, such as 1wt%, 1.5wt%, 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt% and 28wt%, and any value within this range; the mass of S is 2-15wt%, such as 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt% and 14wt%, and any value within this range.

[0041] To achieve the third object of the present invention, the present invention provides the above-mentioned catalyst and the use of the catalyst prepared according to the above-mentioned preparation method in the dehydrogenation of ethylene glycol to produce lactic acid.

[0042] To achieve the fourth object of the present invention, a method for preparing lactic acid by dehydrogenating ethylene glycol is provided, comprising:

[0043] Ethylene glycol and methanol are mixed and passed through a fixed bed reactor from bottom to top, and a catalytic dehydrogenation reaction is carried out on the catalyst bed therein to produce lactic acid; wherein,

[0044] The catalyst used is the aforementioned catalyst or a catalyst prepared according to the aforementioned preparation method.

[0045] Those skilled in the art will understand that when a fixed bed reactor is used to carry out the reaction of ethylene glycol dehydrogenation to produce lactic acid, the raw materials are fed from the lower part of the fixed bed reactor and the products are discharged from the upper part of the fixed bed reactor.

[0046] The present invention uses the aforementioned catalyst and a fixed-bed reactor to carry out a reaction of producing lactic acid from ethylene glycol by dehydrogenation, thereby realizing the production of lactic acid from ethylene glycol by dehydrogenation. On the one hand, the use of the fixed-bed reactor to carry out the reaction of producing lactic acid from ethylene glycol by dehydrogenation can avoid the "dead corner" problem existing when a stirred tank is used to carry out the reaction, thereby improving the utilization rate of the catalyst. Furthermore, no solid-liquid separation is required for the discharge, resulting in a simple process and high production efficiency. On the other hand, during the reaction process of producing lactic acid from ethylene glycol by dehydrogenation, the aforementioned catalyst of the present invention is used to catalyze the dehydrogenation of ethylene glycol. The catalyst has high activity and is applicable to the fixed-bed reactor. Moreover, the catalyst carrier is a solid alkali carrier, thereby avoiding the use of liquid alkali, thereby avoiding corrosion of the equipment by alkali solution.

[0047] In one embodiment, the molar ratio of methanol to ethylene glycol is (1-4):1, such as 1.5:12:1, 2.5:1, 3:1 and 3.5:1, and any ratio within this range.

[0048] In one embodiment, the feed volume space velocity of ethylene glycol is 0.1-2h -1 , for example 0.2h -1 , 0.4h -1 , 0.6h -1 , 0.8h -1 , 1h -1 , 1.2h -1 , 1.4h -1 , 1.6h -1 and 1.8h -1 , and any value within this range.

[0049] In one embodiment, the reaction temperature is 100-200°C, such as 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C and 190°C, and any temperature within this range; the reaction pressure is 0.1-3MPa, such as 0.2MPa, 0.4MPa, 0.6MPa, 0.8MPa, 1MPa, 1.2MPa, 1.4MPa, 1.6MPa, 1.8MPa, 2MPa, 2.2MPa, 2.4MPa, 2.6MPa and 2.8MPa, and any value within this range.

[0050] The beneficial effects of the present invention are:

[0051] The catalyst for preparing lactic acid by dehydrogenating ethylene glycol has high activity, good catalytic performance, and alkalinity. It can be used in preparing lactic acid by dehydrogenating ethylene glycol and is suitable for use in a fixed-bed reactor without adding liquid alkali, thereby preventing corrosion of the equipment by the liquid alkali.

[0052] The method for preparing the catalyst of the present invention is simple and can easily produce a catalyst with high activity and good catalytic performance;

[0053] The catalyst of the present invention can be applied to the production of lactic acid by dehydrogenating ethylene glycol, and the method for producing lactic acid by dehydrogenating ethylene glycol comprises using the catalyst and a fixed-bed reactor to carry out the reaction of producing lactic acid by dehydrogenating ethylene glycol, thereby realizing the production of lactic acid by dehydrogenating ethylene glycol. On the one hand, the use of the fixed-bed reactor to carry out the reaction of producing lactic acid by dehydrogenating ethylene glycol can avoid the "dead corner" problem existing when using a stirred tank to carry out the reaction, thereby improving the utilization rate of the catalyst, and no solid-liquid separation is required for the discharge, resulting in a simple process and high production efficiency. On the other hand, during the reaction process of producing lactic acid by dehydrogenating ethylene glycol, the catalyst of the present invention is used to catalyze the dehydrogenation of ethylene glycol, the catalyst has high activity and can be applied to the fixed-bed reactor, and the catalyst carrier is a solid alkali carrier, thereby avoiding the use of liquid alkali, thereby avoiding the corrosion of the equipment by alkali solution. DETAILED DESCRIPTION

[0054] The following further describes the technical solutions and effects of the present invention in conjunction with specific embodiments and examples. The following embodiments and examples are intended only to illustrate the present invention and are not intended to be limited to the following embodiments and examples. Simple modifications to the present invention that utilize the concepts of the present invention fall within the scope of protection claimed herein.

[0055] The main raw materials used in the following examples and comparative examples are shown in Table 1:

[0056] Table 1 Main raw materials used in the examples of the present invention and comparative examples

[0057]

[0058] The catalyst performance test method is as follows:

[0059] 1. The content of active components in the catalyst is tested using X-ray fluorescence spectrometer (XRF);

[0060] 2. Ethylene glycol conversion and lactic acid selectivity:

[0061] Assume that the original molar amount of ethylene glycol in the system before the reaction is n1, the molar amount of ethylene glycol in the system after the reaction is n2, and the molar amount of lactic acid in the system after the reaction is n3, then

[0062] The molar amount of ethylene glycol converted = n1-n2;

[0063] Ethylene glycol conversion = (n1-n2) / n1×100%;

[0064] Lactic acid selectivity = n3 / (n1-n2) x 100%.

[0065] Example 1 (S1)

[0066] Catalyst A1 for use in dehydrogenation of ethylene glycol to produce lactic acid was prepared according to the following preparation method:

[0067] (1) Dissolve 2.6 g of Ba(NO3)2 (the salt corresponding to the oxide shell S) in 50 ml of deionized water to obtain a shell impregnation solution with a concentration of 0.199 mmol / ml;

[0068] (2) placing the bi-porous granular alumina carrier K1 (carrier C) in the shell impregnation solution obtained in step (1) at room temperature (25°C) for 48 hours, and then successively performing suction filtration (filtration), drying at 85°C for 24 hours, and calcining at 500°C for 4 hours to obtain a solid alkali carrier S@C;

[0069] (3) Dissolve 2.05 g of RuCl3·3H2O and 1.9 g of SnCl2·2H2O (the salt corresponding to the active component M) in 50 ml of deionized water to obtain a Ru solution with a concentration of 0.155 mmol / ml. 3+ and 0.168mmol / ml Sn 2+ Active ingredient impregnation solution;

[0070] (4) 25 g of the solid base carrier S@C obtained in step (2) was placed in the active component impregnation solution obtained in step (3) and immersed at room temperature (25°C) for 12 h. Then 100 ml of a 10 wt% formaldehyde aqueous solution was added thereto and a reduction reaction was carried out at 50°C for 1 h to reduce Ru 3+ and Sn 2+The catalyst was reduced to elemental Ru and Sn, and then filtered, washed with deionized water, and dried at 90 °C for 3 h to obtain the catalyst Ru(3.4)-Sn(4.2) / BaO(6.5)@Al2O3 (catalyst M / S@C), which was designated as catalyst A1.

[0071] The obtained catalyst A1, namely Ru(3.4)-Sn(4.2) / BaO(6.5)@Al2O3, is calculated based on the mass of the carrier C.

[0072] In the active component M, the content of Ru is 3.4 wt% and the content of Sn is 4.2 wt%;

[0073] The content of BaO in the oxide shell layer S is 6.5 wt%.

[0074] Catalyst A2-7 was prepared according to the preparation method of Example 1; the reaction raw materials and reaction conditions of each step are shown in Table 2.

[0075] Catalyst A2 is Ru(0.8)-Sn(1.1) / BaO(2)@Al2O3;

[0076] Catalyst A3 is Ru(2)-Sn(2.5) / BaO(3)@Al2O3;

[0077] Catalyst A4 is Ru(0.5)-Sn(1) / BaO(2)@Al2O3;

[0078] Catalyst A5 is Ru(10)-Sn(5) / BaO(15)@Al2O3;

[0079] Catalyst A6 is In(10)-Sb(20) / MgO(10)@ZrO2;

[0080] Catalyst A7 is Sb(18) / SrO(8)@SiO2;

[0081] Table 2 Reaction materials and reaction conditions of each step of Example 1-7 (S1-7)

[0082]

[0083] Application Example 1-7 (Y1-7)

[0084] The catalyst A1-7 obtained in Example 1-7 was applied to the dehydrogenation of ethylene glycol to produce lactic acid, as follows:

[0085] Ethylene glycol and methanol were mixed and passed from bottom to top through a fixed-bed reactor, where they underwent a catalytic dehydrogenation reaction on the catalyst bed to produce lactic acid. The reaction conditions and results are shown in Table 3.

[0086] Table 3 Reaction conditions and reaction results of application examples 1-7 (Y1-7)

[0087] Application Examples Y1 Y2 Y3 Y4 Y5 Y6 Y7 catalyst A1 A2 A3 A4 A5 A6 A7 Molar ratio of methanol to ethylene glycol 2:1 1:1 4:1 3:1 1.5:1 2:1 2:1 <![CDATA[The feed volume hourly space velocity of ethylene glycol (h -1 )]]> 1 0.1 2 1.5 0.5 1 1 Reaction temperature (℃) 150 100 200 120 180 150 150 Reaction pressure (MPa) 1.5 0.1 3 1 2 1.5 1.5 Ethylene glycol conversion rate (%) 99 96 97 96 97 95 94 Lactic acid selectivity (%) 99 96 98 96 97 94 94

[0088] According to Application Examples 1-7 and Table 3, the catalyst A1-7 prepared in Examples 1-7 of the present invention exhibits high catalyst activity in the dehydrogenation of ethylene glycol to lactic acid in a fixed-bed reactor, with ethylene glycol conversion reaching 94-99% and lactic acid selectivity reaching 94-99%. This avoids the problems associated with the use of a stirred tank reactor.

Claims

1. A catalyst for producing lactic acid from ethylene glycol by dehydrogenation, characterized in that: The general formula of the catalyst is M / S@C; wherein, M is an active component selected from any one or more combinations of Ru, Ir, Rh, Pd and Sb, or a combination of Ru and Sn, or a combination of In and Sb; S@C is a solid base carrier, C is a carrier selected from any one or more combinations of Al2O3, SiO2 and ZrO2; S is a basic oxide shell coated on the surface of C, selected from any one or more combinations of MgO, SrO and BaO; Based on the mass of C, the mass of M is 0.75-30 wt%, and the mass of S is 2-15 wt%; C is a granular carrier with double pore distribution; The pore sizes of the double pores are 5-50 nm and 100-300 nm respectively.

2. The catalyst according to claim 1, characterized in that M is Ru and Sn.

3. The catalyst according to claim 2, characterized in that The mass of Ru in M ​​is 0.5-10 wt% based on the mass of C; and / or In M, the mass ratio of Ru to Sn is 1:(0.4-2).

4. The catalyst according to any one of claims 1 to 3, characterized in that The average pore diameters of the double pores are 20±4 nm and 200±10 nm, respectively.

5. A method for preparing the catalyst according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) dissolving the salt corresponding to the oxide shell S in deionized water to obtain a shell impregnation solution; (2) impregnating the carrier C in the shell impregnation solution obtained in step (1), and then filtering, drying and calcining the solution in sequence to obtain a solid base carrier S@C; (3) Dissolving the salt corresponding to the active component M in deionized water to obtain an active component impregnation solution; (4) The solid base carrier S@C obtained in step (2) is placed in the active component impregnation solution obtained in step (3) and then an aqueous formaldehyde solution is added thereto to cause a reduction reaction, followed by filtering, washing and drying in sequence to obtain the catalyst M / S@C.

6. The preparation method according to claim 5, characterized in that In step (1), the salt corresponding to the oxide shell S is selected from any one or a combination of nitrates, chlorides and sulfates of Mg, Sr and Ba; and / or In step (2), the calcination temperature is 400-600 ° C and the calcination time is 2-6 h; and / or In step (4), the reduction temperature is 40-60°C and the reduction time is 0.5-1.5 h; and / or In step (4), the concentration of the formaldehyde aqueous solution is 5-15 wt%.

7. Use of the catalyst according to any one of claims 1 to 4 and the catalyst prepared according to the preparation method according to claim 5 or 6 in the dehydrogenation of ethylene glycol to produce lactic acid.

8. A method for preparing lactic acid by dehydrogenating ethylene glycol, characterized in that: The method comprises: Ethylene glycol and methanol are mixed and passed through a fixed bed reactor from bottom to top, and a catalytic dehydrogenation reaction is carried out on the catalyst bed therein to produce lactic acid; wherein, The catalyst used is the catalyst according to any one of claims 1 to 4 or the catalyst prepared according to the preparation method according to claim 5 or 6.

9. The method according to claim 8, characterized in that The molar ratio of methanol to ethylene glycol is (1-4):1; and / or The reaction temperature is 100-200 °C and the reaction pressure is 0.1-3 MPa.

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