Method for preparing 1,3-propanediol with high space-time yield and high concentration

Abstract

A method for preparing 1,3-propanediol with a high space-time yield, in which A methyl 3-hydroxypropionate solution is pumped into a tubular fixed-bed reactor loaded with a surface modifier-coated nano-Cu-based catalyst for continuous hydrogenation to obtain a reaction mixture, where the catalyst includes Cu as active component, a metal oxide XO.sub.n/2 as additive and a SiO.sub.2SnO.sub.2 composite carrier. The reaction mixture is subjected to rectification to separate light components from heavy components, where the light components include methanol, n-propanol, methyl propionate, methyl 3-hydroxypropionate and 1,3-propanediol, and the heavy components include 1,3-propanediol mono-propionate and 1,3-propanediol mono-3-hydroxypropionate. The heavy components are fed back to the tubular fixed-bed reactor for secondary hydrogenation, and the light components are separated to obtain 1,3-propanediol.

Claims

1. A method for preparing 1,3-propanediol, comprising: pumping, by a feed pump, a methyl 3-hydroxypropionate solution into a tubular fixed-bed reactor for hydrogenation to obtain a reaction mixture, wherein the tubular fixed-bed reactor is loaded with a surface modifier-coated nano-Cu-based catalyst; a concentration of methyl 3-hydroxypropionate in the methyl 3-hydroxypropionate solution is 90-99 wt. %; and the nano-Cu-based catalyst comprises an active component, an additive component, and a carrier, wherein the active component is Cu, and the additive component is a metal oxide of XO.sub.n/2, wherein a metal in the metal oxide is represented by X; subjecting the reaction mixture to rectification to separate light components from heavy components, wherein the light components comprise methanol, n-propanol, methyl propionate, methyl 3-hydroxypropionate and 1,3-propanediol; and the heavy components comprise 1,3-propanediol mono-propionate and 1,3-propanediol mono-3-hydroxypropionate; and feeding the heavy components back to the tubular fixed-bed reactor for secondary hydrogenation; and subjecting the light components to separation to collect 1,3-propanediol; wherein the surface modifier-coated nano-Cu-based catalyst is prepared through steps of: (1) mixing a copper precursor and an X.sup.n+ precursor in a preset weight ratio to form a mixed aqueous solution with a molar concentration of 0.1-1 mol/L; (2) preparing a base solution with a molar concentration of 0.5-5 mol/L as precipitant; (3) adding a sol or nano-powder of SiO.sub.2 and SnO.sub.2 to a cooled aqueous solution containing an organic polyol to form a carrier mixture solution; (4) simultaneously adding the mixed aqueous solution and the base solution to the carrier mixture solution under stirring for co-precipitation to form a slurry, wherein a pH of the slurry is kept at 10-12 during the co-precipitation; (5) after the co-precipitation is completed, heating the slurry to 80-100 C. for aging for 2-24 h, followed by filtration, washing, atmospheric-pressure drying, and calcination to obtain a nano-Cu-based catalyst precursor; (6) subjecting the nano-Cu-based catalyst precursor to impregnation with a surface modifier, drying and calcination to obtain a catalyst powder; and (7) subjecting the catalyst powder obtained from step (6) to pressing-sieving or extrusion, and reduction activation to obtain the surface modifier-coated nano-Cu-based catalyst; wherein the surface modifier is selected from the group consisting of an organic aluminum salt, an organic zirconium salt and a combination thereof; the base solution is one or two of sodium hydroxide, sodium bicarbonate, sodium carbonate, ammonium carbonate, ammonium bicarbonate and ammonia; the carrier is a SiO.sub.2SnO.sub.2 composite; and X is selected from the group consisting of Zn, Ga, Ge, In, Y, Ce, Ho and a combination thereof.

2. The method of claim 1, wherein the surface modifier is aluminum isopropoxide, aluminum sec-butoxide, zirconium n-propoxide, zirconium n-butoxide, or a combination of one of aluminum isopropoxide and aluminum sec-butoxide and one of zirconium n-propoxide and zirconium n-butoxide.

3. The method of claim 1, wherein the surface modifier-coated nano-Cu-based catalyst comprises 30-70 wt. % of the active component, 1-15 wt. % of the additive component, 15-60 wt. % of SiO.sub.2, 1-5 wt. % of SnO.sub.2, and 0.3-9 wt. % of the surface modifier.

4. The method of claim 1, wherein the co-precipitation in step (4) is performed at a temperature ranging from 10 C. to 10 C.

5. The method of claim 1, wherein operation parameters of the tubular fixed-bed reactor are as follows: a temperature at a constant-temperature section is 160-200 C., pressure is 8-12 MPa, the concentration of the methyl 3-hydroxypropionate solution is 90-99 wt. %, a hydrogen-to-methyl 3-hydroxypropionate molar ratio is 30-200:1, and a weight hourly space velocity is 0.2-0.6 h.sup.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a high-resolution transmission electron microscope (TEM) image of a catalyst provided in Example 1 of the present disclosure;

(2) FIG. 2 is a flow chart of a method for preparing 1,3-propanediol with a high space-time yield according to an embodiment of the present disclosure; and

(3) FIG. 3 shows evaluation results of hydrogenation stability using a fixed-bed reactor loaded with the catalyst provided in Example 1 of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

(4) To make the objects, technical solutions and advantages of the present disclosure clearer and more understandable, the present disclosure will be described in further detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the present disclosure and are not intended to limit the present disclosure.

(5) The application principle of the present disclosure will be further described below with reference to the accompanying drawings and specific embodiments.

(6) In the following description, 3-HPM refers to methyl 3-hydroxypropionate, and 1,3-PDO refers to 1,3-propanediol.

Example 1

(7) 1. Preparation of a Surface Modifier-Coated Nano-Cu-Based Catalyst

(8) 48.32 g of copper nitrate, 4.39 g of zinc nitrate, 2.1 g of holmium nitrate and 1.95 g of indium nitrate were dissolved in 441 mL of deionized water to form a mixed nitrate solution. 32 g of silica sol, 1.5 g of SnO.sub.2 nano-powder, 16 mL of ionized water and 2.34 g of ethylene glycol were added to a reactor, cooled to 5 C. and kept at 5 C. to form a carrier mixture solution. The mixed nitrate solution and a 5 mol/L sodium hydroxide solution were simultaneously dropwise added into the carrier mixture solution under stirring for precipitation, during which the reaction solution was kept at pH 12. After the precipitation was completed, the reaction solution was heated to 90 C. for aging for 6 h, and filtrated to collect a filter cake, which was rinsed with deionized water to neutral, dried at 110 C. for 24 h and calcinated at 500 C. for 4 h to obtain a nano-Cu-based catalyst precursor 53CuO4ZnO3Ho.sub.2O.sub.33In.sub.2O.sub.3/32SiO.sub.25SnO.sub.2. 0.41 g of aluminum sec-butoxide was dissolved in sec-butanol with calculated amount, to which 10 g of the above catalyst precursor was added, impregnated at room temperature for 2 h, dried at 110 C. for 12 h, and calcinated at 600 C. for 4 h to obtain the surface modifier-coated nano-Cu-based catalyst (53CuO4ZnO3Ho.sub.2O.sub.33In.sub.2O.sub.3/32SiO.sub.25SnO.sub.2@1% Al.sub.2O.sub.3).

(9) The transmission electron microscope (TEM) image of the prepared catalyst was shown in FIG. 1, which showed that the catalyst had an obvious core-shell structure after the reductive activation, and the active component copper was coated by the surface modifier.

(10) 2. Preparation of 1,3-Propanediol (as Shown in FIG. 2)

(11) (1) 8 g of the surface modifier-coated nano-Cu-based catalyst was pressed, ground, and sieved to obtain 20-40 mesh particles, which were loaded into a constant-temperature section of a tubular fixed-bed reactor. The rest part of the tubular fixed-bed reactor was filled with inert SiC. The catalyst was subjected to reductive activation in a mixed atmosphere of 20% H.sub.2 and 80% N.sub.2 at an atmospheric pressure and 250 C. for 8 h. After cooled down to 170 C., the tubular fixed-bed reactor was pressurized to 9 MPa with high-purity H.sub.2.

(12) (2) A methyl 3-hydroxypropionate solution with a concentration of 99 wt. % was pumped into the tubular fixed-bed reactor via a feed pump and hydrogenated at 170 C. under hydrogen gas pressure (9 MPa H.sub.2) to obtain a hydrogenated product, where a mole ratio of hydrogen to methyl 3-hydroxypropionate was 120:1, and a weight hourly space velocity was 0.25 h.sup.1.

(13) (3) The hydrogenated product was cooled by a condenser, and then entered a gas-liquid separator, where the separated liquid was collected into a liquid collection tank, and the gas was collected into a H.sub.2 collection tank to be pressurized by the gas pressurization system for reuse.

(14) (4) The liquid in the liquid collection tank was fed into a rectification column to separate light components from heavy components, where the light components included methanol, n-propanol, methyl propionate, methyl 3-hydroxypropionate and the target product 1,3-propanediol, and the heavy components included 1,3-propanediol mono-propionate and 1,3-propanediol mono-3-hydroxypropionate. The heavy components were mixed with the next batch of raw material in a concentration of 5 wt. % for secondary hydrogenation.

(15) 3. Evaluation of Catalyst Performance

(16) After the hydrogenation reaction was performed for 60 h, the hydrogenated product obtained from step (2) was analyzed qualitatively and quantitatively by gas chromatography.

(17) FIG. 3 showed that the conversion rate of methyl 3-hydroxypropionate was 99.5%, the 1,3-propanediol selectivity was 85.0%, and the catalyst performance remained stable in 1000 h. These results demonstrated that the preparation method of the present disclosure had a high space-time yield of 1,3-propanediol (up to 0.154 g/(g.Math.h)), and the catalyst provided by the present disclosure has an excellent long-term stability. High-purity of 1,3-propanediol (99.9%) could be obtained by distillation of the light components.

Example 2

(18) 1. Preparation of a Surface Modifier-Coated Cu-Based Nano-Catalyst

(19) 27.35 g of copper nitrate, 1.4 g of holmium nitrate and 4.09 g of gallium nitrate were dissolved in 1228 mL of deionized water to form a mixed nitrate solution. 18 g of SiO.sub.2 nano-powder, 0.9 g of SnO.sub.2 nano-powder, 50 mL of ionized water and 8.5 g of sucrose were added to a reactor, cooled to 5 C. and kept at 5 C. to form a carrier mixture solution. The mixed nitrate solution and a 0.5 mol/L sodium hydroxide solution were simultaneously dropwise added into the carrier mixture solution under stirring for precipitation, during which the reaction solution was kept at pH 12. After the precipitation was completed, the reaction solution was heated to 100 C. for aging for 2 h, and filtrated to collect a filter cake, which was rinsed with deionized water to neutral, dried at 100 C. for 24 h and calcinated at 500 C. for 4 h to obtain a nano-Cu-based catalyst precursor 30CuO2Ho.sub.2O.sub.35Ga.sub.2O.sub.3/60SiO.sub.23SnO.sub.2. 0.78 g of zirconium tetra-n-propanol and 0.42 g of aluminum sec-butoxide were dissolved in sec-butanol with calculated amount, to which 10 g of the above catalyst precursor powder was added, impregnated at room temperature for 2 h, dried at 110 C. for 12 h, and calcinated at 600 C. for 4 h to obtain the surface modifier-coated nano-Cu-based catalyst (30CuO2Ho.sub.2O.sub.35Ga.sub.2O.sub.3/60SiO.sub.23SnO.sub.2@2% Al.sub.2O.sub.3@1% ZrO.sub.2).

(20) 2. Preparation of 1,3-Propanediol

(21) The preparation of 1,3-propanediol in Example 2 was basically the same as that in Example 1, except that in Example 2, the hydrogenation was performed at 180 C., and the ratio of hydrogen to methyl 3-hydroxypropionate was 200:1.

(22) 3. Evaluation of Catalyst

(23) After the hydrogenation reaction was performed for 60 h, the hydrogenated product was analyzed qualitatively and quantitatively by gas chromatography, and results were as follows: the conversion rate of methyl 3-hydroxypropionate was 98.6%, the 1,3-propanediol selectivity was 81.2%, and a space-time yield of 1,3-propanediol was 0.146 g/(g.Math.h)).

Example 3

(24) 1. Preparation of a Surface Modifier-Coated Cu-Based Nano-Catalyst

(25) 63.28 g of copper nitrate, 7.68 g of zinc nitrate, 1.95 g of indium nitrate, 0.76 g of cerium nitrate and 2.46 g of gallium nitrate were dissolved in 600 mL of deionized water to form a mixed nitrate solution. 15 g of silica sol, 0.3 g of SnO.sub.2 nano-powder, 7.5 ml of ionized water and 15 g of ethylene glycol were added to a reactor, cooled to 5 C. and kept at 5 C. to form a carrier mixture solution. The mixed nitrate solution and a 3 mol/L sodium hydroxide solution were simultaneously dropwise added into the carrier mixture solution under stirring for precipitation, during which the reaction solution was kept at pH 10. After the precipitation was completed, the reaction solution was heated to 80 C. for aging for 24 h, filtrated to collect a filter cake, which was rinsed with deionized water to neutral, dried at 90 C. for 24 h and calcinated at 400 C. for 4 h to obtain a nano-Cu-based catalyst precursor 70CuO7ZnO1Ce.sub.2O.sub.33In.sub.2O.sub.33GeO.sub.2/15SiO.sub.21SnO.sub.2. 3.69 g of aluminum sec-butoxide was dissolved in sec-butanol with calculated amount, to which 10 g of the above catalyst precursor powder was added, impregnated at room temperature for 3 h, dried at 110 C. for 12 h, and calcinated at 600 C. for 4 h to obtain the surface modifier-coated nano-Cu-based catalyst (70CuO7ZnO1Ce.sub.2O.sub.33In.sub.2O.sub.33GeO.sub.2/15SiO.sub.21SnO.sub.2@9% Al.sub.2O.sub.3).

(26) 2. Preparation of 1,3-propanediol

(27) The preparation of 1,3-propanediol in Example 3 was basically the same as that in Example 1, except that in Example 3, the hydrogenation was performed at 165 C., and a concentration of methyl 3-hydroxypropionate raw material was 90%.

(28) 3. Evaluation of Catalyst

(29) After the hydrogenation reaction was performed for 60 h, the hydrogenated product was analyzed qualitatively and quantitatively by gas chromatography, and results were as follows: the conversion rate of methyl 3-hydroxypropionate was 99.8%, the selectivity to 1,3-propanediol was 85.6%, and a space-time yield of 1,3-propanediol was 0.156 g/(g.Math.h)).

Example 4

(30) 1. Preparation of a Surface Modifier-Coated Cu-Based Nano-Catalyst

(31) 51.82 g of copper sulfate, 6.36 g of zinc sulfate and 7.37 g of gallium nitrate were dissolved in 488 mL of deionized water to form a mixed sulfate solution. 26 g of silica sol, 1.2 g of SnO.sub.2 nano-powder, 13 mL of ionized water and 2.0 g of ethylene glycol were added to a reactor, cooled to 10 C. and kept at 10 C. to form a carrier mixture solution. The mixed sulfate solution and a 4 mol/L mixture solution of sodium carbonate and sodium bicarbonate were simultaneously dropwise added into the carrier mixture solution under stirring for precipitation, during which the reaction solution was kept at pH 10. After the precipitation was completed, the reaction solution was heated to 90 C. for aging for 4 h, and filtrated to collect a filter cake, which was rinsed with deionized water to neutral, dried at 110 C. for 24 h and calcinated at 500 C. for 4 h to obtain a nano-Cu-based catalyst precursor 55CuO6ZnO9Ga.sub.2O.sub.3/26SiO.sub.24SnO.sub.2. 0.21 g of aluminum sec-butoxide was dissolved in sec-butanol with calculated amount, to which 10 g of the above catalyst precursor powder was added, impregnated at room temperature for 3 h, dried at 110 C. for 12 h, and calcinated at 700 C. for 4 h to obtain the surface modifier-coated nano-Cu-based catalyst (55CuO6ZnO9Ga.sub.2O.sub.3/26SiO.sub.24SnO.sub.2@0.3% Al.sub.2O.sub.3).

(32) 2. Preparation of 1,3-Propanediol

(33) The preparation of 1,3-propanediol in Example 4 was basically the same as that in Example 1, except that in Example 4, the hydrogenation was performed at 200 C., and a weight hourly space velocity was 0.6 h.sup.1.

(34) 3. Evaluation of Catalyst Performance

(35) After the hydrogenation reaction was performed for 60 h, the hydrogenated product was analyzed qualitatively and quantitatively by gas chromatography, and results were as follows: the conversion rate of methyl 3-hydroxypropionate was 99.0%, the 1,3-propanediol selectivity was 80.3%, and a space-time yield of 1,3-propanediol was 0.157 g/(g.Math.h)).

Example 5

(36) 1. Preparation of a Surface Modifier-Coated Cu-Based Nano-Catalyst

(37) 41.03 g of copper nitrate, 3.29 g of zinc nitrate, 2.8 g of holmium nitrate and 1.02 g of yttrium nitrate were dissolved in 185 mL of deionized water to form a mixed nitrate solution. 42 g of silica sol, 1.5 g of SnO.sub.2 nano-powder, 21 mL of ionized water and 2.5 g of ethylene glycol were added to a reactor, cooled to 5 C. and kept at 5 C. to form a carrier mixture solution. The mixed nitrate solution and a 3 mol/L sodium hydroxide solution were simultaneously dropwise added into the carrier mixture solution under stirring for precipitation, during which the reaction solution was kept at pH 12. After the precipitation was completed, the reaction solution was heated to 100 C. for aging for 6 h, and filtrated to collect a filter cake, which was rinsed with deionized water to neutral, dried at 110 C. for 24 h and calcinated at 500 C. for 4 h to obtain a nano-Cu-based catalyst precursor 45CuO3ZnO4Ho.sub.2O.sub.31Y.sub.2O.sub.3/42SiO.sub.25SnO.sub.2. 1.56 g of zirconium tetra-n-propanol was dissolved in n-propanol with calculated amount, to which 10 g of the above catalyst precursor powder was added, impregnated at room temperature for 3 h, dried at 110 C. for 12 h, and calcinated at 600 C. for 4 h to obtain the surface modifier-coated nano-Cu-based catalyst (45CuO3ZnO4Ho.sub.2O.sub.31Y.sub.2O.sub.3/42SiO.sub.25SnO.sub.2@2% ZrO.sub.2).

(38) 2. Preparation of 1,3-Propanediol

(39) The preparation of 1,3-propanediol in Example 5 was basically the same as that in Example 1, except that in Example 5, the hydrogenation was performed at a pressure of 12 MPa, and a concentration of the methyl 3-hydroxypropionate raw material was 95%.

(40) 3. Evaluation of Catalyst

(41) After the hydrogenation reaction was performed for 60 h, the hydrogenated product was analyzed qualitatively and quantitatively by gas chromatography, and results were as follows: the conversion rate of methyl 3-hydroxypropionate was 99.8%, the 1,3-propanediol selectivity was 90.1%, and a space-time yield of 1,3-propanediol was 0.164 g/(g.Math.h)).

Example 6

(42) 1. Preparation of a Surface Modifier-Coated Cu-Based Nano-Catalyst

(43) 54.70 g of copper nitrate, 10.96 g of zinc nitrate and 1.95 g of indium nitrate were dissolved in 533 mL of deionized water to form a mixed nitrate solution. 25 g of silica sol, 0.6 g of SnO.sub.2 nano-powder, 12.5 mL of ionized water and 8.5 g of glucose were added to a reactor, cooled to 10 C. and kept at 10 C. to form a carrier mixture solution. The mixed nitrate solution and a 4 mol/L sodium hydroxide solution were simultaneously dropwise added into the carrier mixture solution under stirring for precipitation, during which the reaction solution was kept at pH 11. After the precipitation was completed, the reaction solution was heated to 90 C. for aging for 4 h. After the aging was completed, the reaction solution was filtrated to collect a filter cake, which was rinsed with deionized water to neutral, dried at 120 C. for 24 h and calcinated at 400 C. for 4 h to obtain a nano-Cu-based catalyst precursor 60CuO10ZnO3In.sub.2O.sub.3/25SiO.sub.22SnO.sub.2. 1.23 g of aluminum sec-butoxide was dissolved in sec-butanol with calculated amount, to which 10 g of the above catalyst precursor powder was added, impregnated at room temperature for 3 h, dried at 110 C. for 12 h, and calcinated at 600 C. for 4 h to obtain the surface modifier-coated nano-Cu-based catalyst (60CuO10ZnO3In.sub.2O.sub.3/25SiO.sub.22SnO.sub.2@3% Al.sub.2O.sub.3).

(44) 2. Preparation of 1,3-Propanediol

(45) The preparation of 1,3-propanediol in Example 6 was basically the same as that in Example 1, except that in Example 6, the hydrogenation was performed at 160 C. and a pressure of 8.0 MPa.

(46) 3. Evaluation of Catalyst

(47) After the hydrogenation reaction was performed for 60 h, the hydrogenated product was analyzed qualitatively and quantitatively by gas chromatography, and the results were as follows: the conversion rate of methyl 3-hydroxypropionate was 99.2%, the 1,3-propanediol selectivity was 86.5%, and a space-time yield of 1,3-propanediol was 0.157 g/(g.Math.h)).

Example 7

(48) 1. Preparation of a Surface Modifier-Coated Cu-Based Nano-Catalyst

(49) 59.26 g of copper nitrate, 1.95 g of indium nitrate and 1.2 g of germanium dioxide nanoparticles were dissolved in 497 mL of deionized water to form a mixed nitrate solution. 26 g of silica sol, 0.6 g of SnO.sub.2 nano-powder, 12.5 mL of ionized water and 8.5 g of glucose were added to a reactor, cooled to 0 C. and kept at 0 C. to form a carrier mixture solution. The mixed nitrate solution and a 4 mol/L sodium hydroxide solution were simultaneously dropwise added into the carrier mixture solution under stirring for precipitation, during which the reaction solution was kept at pH 11. After the precipitation was completed, the reaction solution was heated to 90 C. for aging for 4 h, and filtrated to collect a filter cake, which was rinsed with deionized water to neutral, dried at 110 C. for 24 h and calcinated at 500 C. for 4 h to obtain a nano-Cu-based catalyst precursor 65CuO3In.sub.2O.sub.34GeO.sub.2/26SiO.sub.22SnO.sub.2. 0.82 g of aluminum sec-butoxide was dissolved in sec-butanol with calculated amount, to which 10 g of the above catalyst precursor was added, impregnated at room temperature for 3 h, dried at 90 C. for 12 h, and calcinated at 600 C. for 4 h to obtain the surface modifier-coated nano-Cu-based catalyst (65CuO3In.sub.2O.sub.34GeO.sub.2/26SiO.sub.22SnO.sub.2@2% Al.sub.2O.sub.3).

(50) 2. Preparation of 1,3-propanediol

(51) The preparation of 1,3-propanediol in Example 7 was basically the same as that in Example 1, except that in Example 6, the hydrogenation was performed at a pressure of 10.0 MPa, and the ratio of hydrogen to methyl 3-hydroxypropionate was 30:1.

(52) 3. Evaluation of Catalyst

(53) After the hydrogenation reaction was performed for 60 h, the hydrogenated product was analyzed qualitatively and quantitatively by gas chromatography, and results were as follows: the conversion rate of methyl 3-hydroxypropionate was 99.1%, the 1,3-propanediol selectivity was 80.5%, and a space-time yield of 1,3-propanediol was 0.146 g/(g.Math.h)).

Comparative Example 1

(54) The preparation of the Cu-based nano-catalyst (53CuO4ZnO3Ho.sub.2O.sub.33In.sub.2O.sub.3/32SiO.sub.25SnO.sub.2) in Comparative Example 1 was basically the same as that in Example 1, except that the catalyst was not subjected to surface modification. The preparation of 1,3-propanediol and the evaluation of catalyst in Comparative Example 1 were the same as that in Example 1, and the results were as follows. An initial conversion of methyl 3-hydroxypropionate and an initial 1,3-propanediol selectivity were 98.7% and 82.4%, respectively. After reaction for 200 h, the conversion of methyl 3-hydroxypropionate and the 1,3-propanediol selectivity decreased to 91.2% and 74.8%, respectively.

(55) Comparing the evaluation results of the catalyst of Example 1 and Comparative Example 1, it revealed that the catalyst with surface modification exhibited more excellent hydrogenation activity, selectivity and stability on methyl 3-hydroxypropionate. The main reason was that the coating of surface modifier on the surface of the catalyst formed more oxygen vacancies on the surface of the catalyst, which enhanced the adsorption and activation ability of the catalyst to the ester carbonyl, and the coating effectively inhibited the sintering of the active copper species and the loss of the silica carrier, which significantly enhanced the long-life stability of the catalyst.

Comparative Example 2

(56) The surface modifier-coated Cu-based nano-catalyst (53CuO.sub.4ZnO3Ho.sub.2O.sub.33In.sub.2O.sub.3/32SiO.sub.25SnO.sub.2@1% Al.sub.2O.sub.3) prepared in Example 1 was adopted herein. The preparation of 1,3-propanediol was basically the same as that in Example 1, except that the raw material in Comparative Example 2 was a 20 wt. % methyl 3-hydroxypropionate methanol solution. The catalyst evaluation conditions were the same as that of Example 1, and the experimental results were as follows. The conversion of methyl 3-hydroxypropionate was 98.4%, and the 1,3-propanediol selectivity was 85.4%. After reaction for 500 h, the conversion of methyl 3-hydroxypropionate and the 1,3-propanediol selectivity decreased to 90.8% and 80.1%, respectively.

(57) Comparing the evaluation results of the catalyst of Example 1 and Comparative Example 2, it revealed that the use of a high-concentration methyl 3-hydroxypropionate could significantly prolong the service life of the catalyst, mainly due to the fact that the high-concentration raw material could mitigate structural damage to the catalyst caused by the flushing with a large amount of solvent.

Comparative Example 3

(58) The preparation of the surface modifier-coated Cu-based nano-catalyst (53CuO.sub.4ZnO3Ho.sub.2O.sub.33In.sub.2O.sub.3/32SiO.sub.25SnO.sub.2@1% Al.sub.2O.sub.3) in Comparative Example 3 was basically the same as that in Example 1, except for that the carrier mixture solution in Comparative Example 3 was formed and kept at 50 C. for precipitation. The preparation of 1,3-propanediol and catalyst evaluation conditions were the same as that in Example 1, and the experimental results were as follows. The conversion of methyl 3-hydroxypropionate was 85.4%, and the 1,3-propanediol selectivity was 78.6%.

(59) Comparing the evaluation results of the catalyst of Example 1 and Comparative Example 3, it revealed that the catalyst prepared by low-temperature precipitation had a higher dispersion of active component particles and additive components particles, resulting in higher hydrogenation activity and selectivity.

Comparative Example 4

(60) The preparation of the surface modifier-coated Cu-based nano-catalyst in Comparative Example 4 was basically the same as that in Example 1, except that the surface modifier used in Comparative Example 4 was different from that in Example 1, and the results were shown in Table 1.

(61) TABLE-US-00001 TABLE 1 Hydrogenation performance of Cu-based nano-catalysts coated with different surface modifiers Conversion of 1,3-PDO Surface modifier 3-HPM (%) selectivity (%) Aluminum nitrate 77.9 92.6 Zirconium nitrate 66.2 85.4 Zinc nitrate 66.2 85.4 Manganese nitrate 69.3 84.5 Sucrose 82.5 86.5 Propyltrimethoxysilane 91.3 87.9

(62) As could be seen from Table 1, when preparing 1,3-propanediol via hydrogenation of methyl 3-hydroxypropionate using Cu-based nano-catalysts coated with different surface modifiers, these catalysts showed poorer performance in terms of the hydrogenation conversion and the selectivity of the target product than the Cu-based nano-catalyst coated with the surface modifier in Example 1.

(63) The foregoing are only preferred embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.