Copper-cobalt-iron composite catalyst for highly selective preparation of perfluoroalkyl alcohol, preparation method and application

Abstract

A copper-cobalt-iron composite catalyst, preparation method and application for highly selective production of perfluoroalkyl alcohols, belonging to the field of nano catalysis. The copper-cobalt-iron composite catalyst is prepared by an impregnation method and is a heterogeneous catalyst with a composition of Cu x Co y Fe z / TiO2(x = 1, y = 0.5 - 2, z = 0.5 - 2), wherein the active components are spherical Cu particles, Co particles, and Fe particles, and the content of each of the Cu particles, Co particles, and Fe particles is 4 - 18 wt%. The steps are as follows: First, copper nitrate trihydrate, cobalt nitrate hexahydrate, and iron nitrate nonahydrate are dissolved in water, and then titanium dioxide is added and stirred and mixed. Secondly, after the mixed solution is centrifuged and separated, the solid phase is dried and ground into a powder, and then calcined. Finally, after cooling to room temperature, a mixed gas of H2 and N2 is introduced to reduce the high-valence metals in the sample, obtaining the Cu x Co y Fe z / TiO2 catalyst. This catalyst has high activity, selectivity and stability for catalyzing the hydrogenation of methyl perfluoroalkylate to the corresponding alcohol.

Description

Technical Field

[0001] The present invention belongs to the field of nano-catalysis, and relates to a three-metal composite catalyst, a preparation method and an application thereof. Specifically, it relates to a catalyst composed of three metals, namely copper, cobalt and iron, and a preparation method thereof, and provides a method for highly selectively preparing perfluoroalkyl alcohol from methyl perfluoroalkylate at low temperature. Background Art

[0002] An alcohol in which all hydrogen atoms in the carbon chain are replaced by fluorine is called a perfluoroalkyl alcohol. Due to the presence of a perfluoro carbon chain, perfluoroalkyl alcohols have unique chemical stability, corrosion resistance, flame retardancy, etc., and are widely used in fields such as surfactants, fabric finishing agents, and pharmaceutical intermediates. At the same time, they are also the main components of foam fire extinguishers. Since the demand for perfluoroalkyl alcohols increases year by year and the market demand is broad, while the domestic production capacity is insufficient and the production technology is monopolized by foreign companies such as DuPont in the United States, Daikin in Japan, and Clariant in Germany, it is crucial to carry out research on the production of perfluoroalkyl alcohols.

[0003] Currently, the research on perfluoroalkyl alcohols mainly focuses on the hydrogenation of perfluoroalkyl esters to produce perfluoroalkyl alcohols. In 1967, Case et al. used a copper oxide catalyst to catalyze the hydrogenation of methyl trifluoroacetate to produce trifluoroethanol (U.S. Pat. Nos. 3,314,987). In the same year, Anello et al. used ruthenium and palladium catalysts to catalyze the hydrogenation of fluorinated esters to produce fluorinated alcohols (U.S. Pat. No. 3,356,746).

[0004] Due to the great difficulty in hydrogenating methyl perfluoroalkylate, the catalysts currently used for the catalytic hydrogenation of methyl perfluoroalkylate to produce perfluoroalkyl alcohol are mainly noble metal catalysts, which are expensive and difficult to be widely used in industrialization; the reaction conditions required for non-noble metal catalysts are harsh and the activity still needs to be improved.

[0005] Based on the above, the present invention aims to utilize a three-metal composite catalyst with high hydrogenation activity, and with the synergistic effect of the three, improve the catalytic hydrogenation ability of the catalyst and realize the conversion of methyl perfluoroalkylate at low temperature. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the present invention provides a three-metal composite catalyst, a preparation method and an application thereof for highly active and highly selective hydrogenation of methyl perfluoroalkylate to produce perfluoroalkyl alcohol. This catalyst has high activity, selectivity and stability for catalyzing the hydrogenation of methyl perfluoroalkylate to produce the corresponding alcohol.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A copper-cobalt-iron composite catalyst for the highly selective production of perfluoroalkyl alcohols from methyl perfluoroalkyl acids. The copper-cobalt-iron composite catalyst prepared by the impregnation method is a heterogeneous catalyst, and its specific composition is Cu x Co y Fe z / TiO2(x = 1, y = 0.5 - 2, z = 0.5 - 2). Among them, the active components are spherical Cu particles, Co particles, and Fe particles, and the content of each of the Cu particles, Co particles, and Fe particles is 4 - 18 wt%.

[0009] The particle sizes of the active components are specifically: Cu particles of 15 - 25 nm, Co particles of 10 - 20 nm, and Fe particles of 10 - 20 nm. The three are loaded on the surface of the carrier TiO2 with a size of about 25 nm (standard TiO2 for commercial use).

[0010] A preparation method of a copper-cobalt-iron composite catalyst for the highly selective production of perfluoroalkyl alcohols from methyl perfluoroalkyl acids, comprising the following steps:

[0011] (1) Dissolve copper nitrate trihydrate, cobalt nitrate hexahydrate, and iron nitrate nonahydrate in water according to a molar ratio of 1:0.5 - 2:0.5 - 2, and stir at 30 - 70 °C for 10 - 30 min to dissolve. Among them, 1.14 g of copper nitrate trihydrate is added to every 3 - 10 mL of water, that is, the concentration of copper nitrate is 1.7 mol / L - 0.51 mol / L.

[0012] (2) At 30 - 50 °C, add titanium dioxide to the mixed solution obtained in step (1), and stir and mix for 2 - 6 h. Among them, 0.2 - 0.7 g of titanium dioxide is added to every 3 - 10 mL of water in step (1). In this step, copper nitrate trihydrate, cobalt nitrate hexahydrate, and iron nitrate nonahydrate will be uniformly loaded onto the titanium dioxide.

[0013] (3) Transfer the mixed solution obtained in step (2) to a centrifuge tube, centrifuge at a speed of 8000 - 10000 rpm for 10 - 20 min, pour out and remove the liquid phase after centrifugation, and dry the obtained solid phase at 70 - 150 °C for 6 - 15 h.

[0014] (4) After the dried sample obtained in step (3) is cooled to room temperature, grind it into a powder. Calcinate it in a tube furnace, and the calcination temperature is 200 - 400 °C, and keep it for 2 - 6 h.

[0015] (5) After the sample obtained in step (4) is cooled to room temperature, introduce a mixed gas of 5% H2 and 95% N2 into the tube furnace to reduce the high-valent metals in the sample. After heating to 200 - 400 °C, keep it for 1 - 4 h. The sample obtained after reduction is the corresponding Cu xCo y Fe z / TiO₂ catalyst.

[0016] Furthermore, the heating rate in step (4) and step (5) is 1 - 6 °C / min;

[0017] Furthermore, the rate of introducing the mixed gas in step (5) is 20 - 100 mL / min.

[0018] An application of a three-metal composite catalyst, which is applied to the selective preparation of perfluoroalkyl alcohols from methyl perfluoroalkylates. The specific implementation process of the catalytic reaction is as follows: Using a high-pressure reaction kettle as the reaction vessel, add Cu x Co y Fe z / TiO₂ catalyst, reaction substrate, and solvent into the reaction kettle in sequence. After sealing the reaction kettle, use 99.99% hydrogen as the reducing agent. First, displace the air in the reaction kettle with 1 MPa hydrogen, and then fill the reaction kettle with hydrogen to 1 - 5 MPa. React at 140 - 200 °C for 5 - 20 h. The yield can reach over 73%, and the highest can reach 97%.

[0019] For every 100 mg of Cu x Co y Fe z / TiO₂ catalyst, add 1 - 5 mmol of reaction substrate (such as methyl heptafluorobutyrate, methyl nonafluorovalerate, methyl pentadecafluorooctanoate, etc., but not limited to these several kinds) and 5 - 25 mL of anhydrous ethanol as the solvent.

[0020] The innovation point of the present invention is that the three metals used have good synergistic effects and can obtain high performance at a relatively low temperature.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) In the process of catalytic reduction of methyl perfluoroalkylates to perfluoroalkyl alcohols by the Cu x Co y Fe z / TiO₂ catalyst of the present invention, the catalytic activity is high, the hydrogenation conversion rate of methyl perfluoroalkylates > 90%, and the selectivity > 90%.

[0023] (2) The Cu x Co y Fe z / TiO₂ as the catalyst for the hydrogenation reduction of methyl perfluoroalkylates to perfluoroalkyl alcohols has a simple preparation process, mild conditions, and the raw materials used are cheap and easily available, which is beneficial to large-scale industrial production. The synthesized catalyst has high stability and can be stored in the environment for a long time. Description of the Drawings

[0024] Figure 1 The trimetallic composite catalyst Cu x Co y Fe z / TiO2 prepared for Example 4, TEM image. Detailed implementation manners

[0025] The present invention will be further described in detail below in conjunction with the examples. Of course, the present invention is not limited to the following specific examples.

[0026] Example 1

[0027] 1.14 g of copper nitrate trihydrate, 0.74 g of cobalt nitrate hexahydrate, and 4.234 g of iron nitrate nonahydrate were added to 7 mL of deionized water and stirred at 70 °C for 10 min to dissolve. Subsequently, 0.4 g of titanium dioxide was added to the above solution, and the mixture was continuously stirred for 6 h. Then, the obtained mixture was transferred to a centrifuge tube and centrifuged at 8000 rpm for 15 min. The liquid phase after centrifugation was poured off, and the obtained solid phase was dried at 150 °C for 6 h. After the dried sample was cooled to room temperature, it was ground into a powder. Calcination was carried out in a tube furnace at a calcination temperature of 300 °C for 6 h with a heating rate of 1 °C / min. After the obtained sample was cooled to room temperature, a mixed gas of 5% H2 and 95% N2 by volume was introduced into the tube furnace to reduce the high-valent metals in the sample. The heating rate was 3 °C / min, the rate of introducing the mixed gas was 100 mL / min, and after heating to 200 °C, it was maintained for 3 h. The sample obtained after reduction is the corresponding Cu x Co y Fe z / TiO2 catalyst.

[0028] In the Cu x Co y Fe z / TiO2 catalyst obtained in this example, the content of the active component Cu is 4%, the content of Co is 4.5%, the content of Fe is 17%, and the structure is spherical. The specific structure is that Cu with a particle size of 25 nm, Co with a particle size of 10 nm, and Fe with a particle size of 20 nm are supported on the surface of the carrier TiO2 with a size of about 25 nm.

[0029] Application of the catalyst in this example: 100 mg of the prepared Cu x Co y Fe z / TiO2, 5 mmol of methyl perfluorooctanoate and 5 mL of absolute ethanol were placed in an autoclave. Using 99.99% hydrogen as the reducing agent, the air in the reaction kettle was first replaced with 1 MPa of hydrogen, and then hydrogen was filled into the reaction kettle to 3 MPa. The reaction was carried out at 200 °C for 5 h. The conversion rate of methyl perfluorooctanoate detected by GC was 100%, the selectivity of perfluorooctanol was 73%, and the yield was 73%.

[0030] Example 2

[0031] 1.14 g of copper nitrate trihydrate, 1.48 g of cobalt nitrate hexahydrate, and 1.0585 g of iron nitrate nonahydrate were added to 10 mL of deionized water and stirred at 30 °C for 20 min to dissolve. Subsequently, 0.7 g of titanium dioxide was added to the above solution, and the mixture was continuously stirred for 2 h. Then, the obtained mixture was transferred to a centrifuge tube and centrifuged at 9000 rpm for 20 min. The liquid phase after centrifugation was poured off, and the obtained solid phase was dried at 70 °C for 12 h. After the obtained dried sample was cooled to room temperature, it was ground into a powder. Calcination was carried out in a tube furnace at a calcination temperature of 400 °C for 2 h with a heating rate of 3 °C / min. After the obtained sample was cooled to room temperature, a mixed gas of 5% H2 and 95% N2 was introduced into the tube furnace to reduce the high-valent metals in the sample. The heating rate was 6 °C / min, the rate of introducing the mixed gas was 20 mL / min, and after heating to 300 °C, it was maintained for 4 h. The sample obtained after reduction was the corresponding Cu x Co y Fe z / TiO2 catalyst.

[0032] The Cu x Co y Fe z / TiO2 catalyst obtained in this example had an active component Cu content of 4%, a Co content of 9%, and an Fe content of 4%. Its structure was spherical. Specifically, Cu with a particle size of 20 nm, Co with a particle size of 15 nm, and Fe with a particle size of 10 nm were loaded on the surface of the carrier TiO2 with a size of about 25 nm.

[0033] Application of the catalyst in this example: 100 mg of the prepared Cu x Co y Fe z / TiO2, 1 mmol of methyl heptafluorobutyrate and 5 mL of absolute ethanol were placed in an autoclave. Using 99.99% hydrogen as the reducing agent, the air in the reaction kettle was first replaced with 1 MPa of hydrogen, and then hydrogen was filled into the reaction kettle to 5 MPa. The reaction was carried out at 140 °C for 13 h. The conversion rate of methyl heptafluorobutyrate detected by GC was 92%, the selectivity of heptafluorobutanol was 85%, and the yield was 78.2%.

[0034] Example 3

[0035] 1.14 g of copper nitrate trihydrate, 2.96 g of cobalt nitrate hexahydrate, and 2.117 g of iron nitrate nonahydrate were added to 3 mL of deionized water and stirred at 50 °C for 30 min to dissolve. Subsequently, 0.2 g of titanium dioxide was added to the above solution, and after continuing to stir and mix for 4 h, the resulting mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 min. The liquid phase after centrifugation was poured off, and the resulting solid phase was dried at 120 °C for 15 h. After the dried sample was cooled to room temperature, it was ground into a powder. Calcination was carried out in a tubular furnace at a calcination temperature of 200 °C for 4 h and a heating rate of 6 °C / min. After the obtained sample was cooled to room temperature, a mixed gas of 5% H2 and 95% N2 was introduced into the tubular furnace to reduce the high-valent metals in the sample. The heating rate was 1 °C / min, the rate of introducing the mixed gas was 60 mL / min, and after heating to 400 °C, it was maintained for 1 h. The sample obtained after reduction was the corresponding Cu x Co y Fe z / TiO2 catalyst.

[0036] The Cu x Co y Fe z / TiO2 catalyst obtained in this example has an active component Cu content of 4%, a Co content of 18%, and an Fe content of 8.5%. The structure is spherical, specifically, Cu with a particle size of 15 nm, Co with a particle size of 20 nm, and Fe with a particle size of 15 nm are loaded on the surface of the carrier TiO2 with a size of about 25 nm.

[0037] Application of the catalyst in this example: Add 100 mg of the prepared Cu x Co y Fe zFor Cu / TiO₂, 3 mmol of methyl nonafluorovalerate and 25 mL of absolute ethanol were placed in an autoclave. Using 99.99% hydrogen as the reducing agent, the air in the reaction kettle was first replaced with 1 MPa of hydrogen, and then hydrogen was filled into the reaction kettle to 1 MPa. The reaction was carried out at 170 °C for 20 h. The conversion rate of methyl nonafluorovalerate detected by GC was 82%, the selectivity of nonafluoropentanol was 89%, and the yield was 73.0%.

[0038] Example 4

[0039] 1.14 g of copper nitrate trihydrate, 1.48 g of cobalt nitrate hexahydrate, and 2.117 g of iron nitrate nonahydrate were added to 3 mL of deionized water and stirred at 35 °C for 10 min to dissolve. Subsequently, 0.4 g of titanium dioxide was added to the above solution, and after continuing to stir and mix for 4 h, the obtained mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 min. The liquid phase after centrifugation was poured off, and the obtained solid phase was dried at 100 °C for 12 h. After the dried sample was cooled to room temperature, it was ground into a powder. Calcination was carried out in a tubular furnace at a calcination temperature of 250 °C for 4 h with a heating rate of 2 °C / min. After the obtained sample was cooled to room temperature, a mixed gas of 5% H₂ and 95% N₂ was introduced into the tubular furnace to reduce the high-valent metals in the sample. The heating rate was 2 °C / min, the rate of introducing the mixed gas was 60 mL / min, and after heating to 300 °C, it was maintained for 2 h. The sample obtained after reduction was the corresponding Cu x Co y Fe z / TiO₂ catalyst.

[0040] In the Cu x Co y Fe z / TiO₂ catalyst obtained in this example, the content of the active component Cu was 4%, the content of Co was 9%, the content of Fe was 8.5%, and the structure was spherical. The specific structure was that Cu with a particle size of 20 nm, Co with a particle size of 15 nm, and Fe with a particle size of 15 nm were supported on the surface of the carrier TiO₂ with a size of about 25 nm.

[0041] Application of the catalyst in this example: Add 100 mg of the prepared Cu x Co y Fe z / TiO2, 1 mmol of methyl heptafluorobutyrate and 10 mL of absolute ethanol were placed in an autoclave. Using 99.99% hydrogen as the reducing agent, the air in the reaction kettle was first replaced with 1 MPa of hydrogen, and then hydrogen was charged into the reaction kettle to 3 MPa. The reaction was carried out at 150 °C for 6 h. The conversion rate of methyl heptafluorobutyrate detected by GC was 97%, the selectivity of heptafluorobutanol was 100%, and the yield was 97%.

[0042] Example 5

[0043] 1.14 g of copper nitrate trihydrate, 2.96 g of cobalt nitrate hexahydrate, and 4.234 g of iron nitrate nonahydrate were added to 10 mL of deionized water and stirred at 50 °C for 20 min to dissolve. Subsequently, 0.7 g of titanium dioxide was added to the above solution, and after continuous stirring and mixing for 2 h, the resulting mixture was transferred to a centrifuge tube and centrifuged at 9000 rpm for 15 min. The liquid phase after centrifugation was poured off, and the resulting solid phase was dried at 150 °C for 6 h. After the dried sample was cooled to room temperature, it was ground into a powder. Calcination was carried out in a tubular furnace at a calcination temperature of 330 °C for 4 h, and the heating rate was 5 °C / min. After the obtained sample was cooled to room temperature, a mixed gas of 5% H2 and 95% N2 was introduced into the tubular furnace to reduce the high-valent metals in the sample. The heating rate was 2 °C / min, the rate of introducing the mixed gas was 20 mL / min, and after heating to 270 °C, it was maintained for 4 h. The sample obtained after reduction was the corresponding Cu x Co y Fe z / TiO2 catalyst.

[0044] In the Cu x Co y Fe z / TiO2 catalyst obtained in this example, the content of the active component Cu was 4%, the content of Co was 18%, the content of Fe was 17%, and the structure was spherical. The specific structure was that Cu with a particle size of 15 nm, Co with a particle size of 20 nm, and Fe with a particle size of 20 nm were supported on the surface of the carrier TiO2 with a size of about 25 nm.

[0045] Application of the catalyst in this example: 100 mg of the prepared Cu x Co y Fe z / TiO2 was added to the reaction kettle. 2 mmol of methyl heptafluorobutyrate and 5 mL of absolute ethanol were placed in the autoclave. Using 99.99% hydrogen as the reducing agent, the air in the reaction kettle was first replaced with 1 MPa of hydrogen, and then hydrogen was charged into the reaction kettle to 2 MPa. The reaction was carried out at 160 °C for 8 h. The conversion rate of methyl heptafluorobutyrate detected by GC was 98%, the selectivity of heptafluorobutanol was 90%, and the yield was 88.2%.

[0046] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as stipulated, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. Application of a copper-cobalt-iron composite catalyst for highly selective preparation of perfluoroalkyl alcohol, characterized in that, The copper-cobalt-iron composite catalyst described is prepared by an impregnation method and is a heterogeneous catalyst with a composition of Cu x Co y Fe z / TiO2, where x = 1, y = 0.5 - 2, z = 0.5 - 2. Among them, the active components are spherical Cu particles, Co particles, and Fe particles, and the content of each of the Cu particles, Co particles, and Fe particles is 4 - 18 wt%. The copper-cobalt-iron composite catalyst is applied to the selective production of perfluoroalkyl alcohols from methyl perfluoroalkyl acids; The particle sizes of the active components are as follows: Cu particles with a size of 15 - 25 nm, Co particles with a size of 10 - 20 nm, and Fe particles with a size of 10 - 20 nm, and the three are loaded on the surface of the carrier TiO2.

2. Use of a copper-cobalt-iron composite catalyst for highly selectively preparing perfluoroalkyl alcohol according to claim 1, characterized in that, The implementation process of the catalytic reaction is as follows: Using a high-pressure reactor as the reaction vessel, Cu x Co y Fe z / TiO2 catalyst, reaction substrate, and solvent are successively added into the reaction kettle. After sealing the reaction kettle, high-purity hydrogen is used as the reducing agent, and the reaction is carried out at 140-200 °C for 5-20 h.

3. Use of a copper-cobalt-iron composite catalyst for highly selectively preparing perfluoroalkyl alcohol according to claim 1, characterized in that, Per 100 mg Cu x Co y Fe z / TiO2 catalyst, 1 - 5 mmol of reaction substrate and 5 - 25 mL of anhydrous ethanol as solvent are added correspondingly.

4. A preparation method of the copper-cobalt-iron composite catalyst for highly selectively preparing perfluoroalkyl alcohol from methyl perfluoroalkylate as claimed in claim 1, characterized in that, It includes the following steps: (1) Dissolve cupric nitrate trihydrate, cobalt nitrate hexahydrate, and ferric nitrate nonahydrate in water according to a molar ratio of 1:0.5 - 2:0.5 - 2, and stir for 10 - 30 min at 30 - 70 °C for dissolution. Among them, 1.14 g of cupric nitrate trihydrate is added per 3 - 10 mL of water, that is, the concentration of cupric nitrate is 1.7 mol / L - 0.51 mol / L; (2) At 30 - 50 °C, add titanium dioxide to the mixed solution obtained in step (1), and stir and mix for 2 - 6 h; among them, 0.2 - 0.7 g of titanium dioxide is added per 3 - 10 mL of water in step (1); (3) Transfer the mixed solution obtained in step (2) into a centrifuge tube, remove the liquid phase after centrifugal separation, and dry the obtained solid phase; (4) After the dried sample obtained in step (3) is cooled to room temperature, grind it into a powder; carry out calcination in a tubular furnace, the calcination temperature is 200 - 400 °C, and keep it for 2 - 6 h; After the sample obtained in step (4) is cooled to room temperature, a mixed gas of 5% H2 and 95% N2 is introduced into the tubular furnace to reduce the high-valence metals in the sample; after heating to 200-400 °C, it is maintained for 1-4 h; the sample obtained after reduction is the corresponding Cu x Co y Fe z / TiO2 catalyst.

5. The preparation method of a copper-cobalt-iron composite catalyst for highly selectively preparing perfluoroalkyl alcohol from methyl perfluoroalkylate according to claim 4, characterized in that, In the step (3) described above, the centrifugal speed is 8000 - 10000 rpm, and the time is 10 - 20 min.

6. The preparation method of a copper-cobalt-iron composite catalyst for highly selectively preparing perfluoroalkyl alcohol from methyl perfluoroalkylate according to claim 4, characterized in that, In the step (3) described above, the drying temperature is 70 - 150 °C, and the drying time is 6 - 15 h.

7. The preparation method of a copper-cobalt-iron composite catalyst for highly selectively preparing perfluoroalkyl alcohol from methyl perfluoroalkylate according to claim 4, characterized in that, The heating rate in step (4) and step (5) described above is 1 - 6 °C / min.

8. The preparation method of a copper-cobalt-iron composite catalyst for highly selectively preparing perfluoroalkyl alcohol from methyl perfluoroalkylate according to claim 4, characterized in that, In the step (5) described above, the rate of introducing the mixed gas is 20 - 100 mL / min.

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