CN111659405A - Method for preparing copper-based catalyst by spray drying - Google Patents

Abstract

The invention discloses a method for preparing a copper-based catalyst by a spray drying method, which comprises the steps of preparing a suspended substance containing water and a copper-containing substance, an auxiliary agent substance and a carrier substance, then grinding the suspended substance into water-based slurry by a colloid mill, and adjusting the pH value of the water-based slurry to be alkaline. Filtering the slurry to remove mother liquor, adding a binder, adjusting the solid content of the slurry, spray-drying the slurry to obtain a catalyst precursor, and roasting to obtain the copper-based catalyst. The catalyst prepared by the method has the characteristics of uniform dispersion of active components, high activity, high selectivity, high stability and the like in high-space-velocity hydrogenation reaction.

Description

A kind of method for preparing copper-based catalyst by spray drying

technical field

The invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of a copper-based catalyst and application of the catalyst to catalytic reactions such as hydrogenation, dehydrogenation, hydrogenolysis and the like in the chemical field.

Background technique

Catalytic hydrogenation technology is not only widely used in petrochemical and petroleum refining, but also has been continuously developed and applied in fine chemical industry. Designing a hydrogenation catalyst with excellent performance is one of the key technologies in catalytic hydrogenation.

In the fields of petrochemical and fine chemicals, copper-based catalysts have been widely used in many gas-solid phase reactions such as hydrogenation, dehydrogenation and reforming to hydrogen production, such as methanol dehydrogenation to methyl formate, medium and low pressure synthesis gas to methanol, Reactions such as methanol steam reforming for hydrogen production and carbon monoxide low temperature shift. The main components of traditional copper-based catalyst products are generally CuO, ZnO and Al ₂ O ₃ , which are mainly synthesized by the co-precipitation reaction of the nitrates of the three metal components of Cu, Zn and Al and alkali liquor. For example, patent CN102755897A discloses a copper-based catalyst prepared by distributed precipitation-spray drying, the catalyst adopts the nitrate and sodium carbonate solutions of Cu, Zn, Al to carry out co-current co-precipitation reaction under certain temperature and pH value conditions, It is prepared by washing, drying, roasting and other steps.

After studying the microstructure of traditional copper-based catalysts, it is found that the crystal form of copper-based catalysts prepared by co-precipitation method is in an irregular state, the particle size distribution and pore size distribution of CuO crystallites are very uneven, and the specific surface area of the catalyst is small. As a result, the catalytic activity of the copper-based catalyst, especially the target product selectivity and thermal stability, is relatively low, and the service life of the catalyst is relatively short.

Therefore, it is necessary to provide a hydrogenation catalyst with short preparation process, high hydrogenation conversion rate, high hydrogenation selectivity and low cost.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a preparation method for preparing a copper-based catalyst using spray drying. Compared with the catalyst prepared by the traditional method, the catalyst prepared by the method of the present invention has more uniform distribution of CuO active components and higher activity under the condition of high space velocity. And the catalyst produced by the method of the present invention greatly shortens the technological process, thereby reducing the production cost.

To achieve the above objects, the present invention adopts the following technical solutions.

A method for preparing a copper-based catalyst by spray drying, specifically, the method comprises the following steps:

(a) Preparation of water-based slurries comprising water, copper-containing substances, adjuvant-containing substances, carrier substances and binders;

(b) adjusting the pH of the slurry to obtain an insoluble compound slurry;

(c) after the above-mentioned slurry is filtered to remove most of the mother liquor, deionized water and a binder are added for stirring and beating;

(d) spray drying the slurry to obtain a catalyst precursor;

(e) calcining the catalyst precursor to obtain a copper-based catalyst.

In the method of the present invention, the copper-containing substances described in step 1 include copper nitrate, basic copper carbonate, copper chloride, copper ammonia solution, copper hydroxide, copper oxide or cuprous oxide, preferably copper nitrate or chlorine copper. Auxiliary substances include zinc chloride, zinc acetate, manganese nitrate, manganese acetate, zirconium hydroxide or zirconium acetate, preferably one or more of zinc acetate, manganese nitrate, and zirconium acetate; carrier substances include kaolin, diatomaceous earth , clay, alumina, silica, calcium silicate, magnesium silicate or silica-alumina molecular sieve, preferably one or more of diatomaceous earth, silica, alumina or magnesium silicate.

In the method of the present invention, step 1 involves the preparation process of the slurry. First, the copper-containing substance, the auxiliary-containing substance and water are formed into a suspension. This suspension may be milled until the desired particle size is formed in the slurry. Additionally, the copper-containing material, adjuvant-containing material, and carrier may be milled separately, or together, prior to forming the suspension until the desired particle size is formed.

In the method of the present invention, the average particle size formed in the slurry in step 1 is 0.1 to 20 microns, preferably 0.2 to 10 microns, more preferably 0.5 to 5 microns. Depending on the particle size and particle size distribution requirements to be achieved, the milling time may be longer or shorter, possibly about 10 to 30 minutes, or 1 to 5 hours.

In the method of the present invention, the alkaline solution for adjusting pH in step 2 is an aqueous solution of ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate, preferably an aqueous sodium carbonate solution.

In the method of the present invention, the adjustment range of the pH of the slurry in step 2 is preferably 6.5-9.0, more preferably 7.0-8.5.

In the method of the present invention, in step 3, the formed insoluble compound slurry is filtered to remove most of the mother liquor, and deionized water and a binder are added to the filter cake to be slurried again.

In the method of the present invention, the binder in step 3 includes silica gel, aluminum glue, water glass, aluminum chloride, methyl cellulose, polyvinyl alcohol, succulent powder or starch, preferably aluminum glue, water glass, One or more of aluminum chloride. The amount of the added binder is 1.0 wt % to 30.0 wt %, and the specific addition amount is determined according to the solid content in the suspension.

In the method of the present invention, step 3 will use a centrifugal spray dryer or a pressure spray dryer to spray dry the slurry prepared in step 1. The resulting powder has an average particle diameter of 10 to 90 microns, preferably 40 to 70 microns.

In the method of the present invention, step 4 is to calcinate the powder obtained in step 3 at a temperature of 250°C to 600°C, preferably 360°C to 580°C, to form a powdered copper-based catalyst.

Figure 1 is a transmission electron microscope (HRTEM) image of the copper-based catalyst, in which A is the catalyst prepared in Comparative Example 1, and B is the catalyst prepared in Example 3. It can be seen that the CuO particles with a particle size of 15-20 nm are relatively distributed. In the matrix of the carrier, the dispersed state of CuO of the catalyst prepared by the present invention is more uniform, and the particle size of the CuO particles is smaller.

The copper-based catalyst according to the present invention may be suitable for hydrogenation, hydrogenolysis or dehydrogenation reactions. Possible reactions include: hydrogenolysis of lipids, hydrogenation of nitriles such as 3-hydroxypropionitrile, dehydrogenation of primary alcohols to aldehydes, dehydrogenation of secondary alcohols to ketones, dehydrogenation of diols such as butanediol, Hydrogenation of aldehydes, hydrogenation of nitroaromatics, hydrogenation of ketones or hydrogenation of furfural.

In a preferred embodiment, the copper-based catalyst prepared by the process according to the invention is used for the hydrogenation of carbonyl compounds, in particular for the hydrogenation of aldehydes, ketones, carboxylic acids and their esters or their diesters. In particular, 1,4-cyclohexanedimethanol (CHDM) is preferably prepared by hydrogenation of dimethyl 1,4-cyclohexanedicarboxylate (DMCD) using the above catalyst.

Description of drawings

Figure 1 is the HRTEM of the medium copper-based catalyst (A is Comparative Example 1 and B is Example 3).

Detailed ways

The present invention will be further described below through examples and comparative examples. However, these specific examples do not in any way limit the scope of the invention.

Example 1

Accurately weigh CuCl ₂ ·2H ₂ O, add deionized water, stir to dissolve, and configure into solution A, where the Cu ²⁺ ion concentration is 0.5mol/L. Accurately weigh C ₄ H ₆ O ₄ Zn·2H ₂ O, add deionized water, stir to dissolve, and configure solution B to make the Zn ^{2 +} ion concentration 0.5mol/L. Prepare 0.45 mol/L potassium hydroxide solution. The required solution A and solution B were weighed according to the mass percentages of Cu and Zn in the final catalyst, added to the reaction kettle, then diatomaceous earth carrier was added to the reaction kettle, potassium hydroxide solution was added dropwise and vigorously stirred to control the reaction temperature 30 ^o C, the pH is 7.8~8.0, and the slurry containing insoluble compounds is obtained after treatment with a colloid mill. The above-mentioned insoluble slurry was centrifuged to remove most of the mother liquor, and then 3wt% of aluminum glue and deionized water were added to the filter cake and fully stirred to adjust the solid content of the slurry to 25%. Pass the slurry through a centrifugal spray dryer, control the temperature of the inlet to 380 ^° C and the temperature of the outlet to 150 ^° C to obtain the catalyst precursor, and then calcinate at 450 ^° C for 9 hours to obtain the finished catalyst. The mass percentage of Cu in the catalyst is 45.63%, the mass percentage of Zn is 5.17%, the specific surface area of the catalyst is 150.5 m ² /g, and the metal surface area of Cu in the catalyst is 18.5 m ² /g. The physical properties are detailed. in Table 1.

Example 2

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O, add deionized water, stir to dissolve, and configure solution A, so that the Cu ²⁺ ion concentration is 0.8mol/L. Accurately weigh C ₄ H ₆ O ₄ Zn·2H ₂ O, add deionized water, stir and dissolve, and configure solution B, so that the Zn ²⁺ ion concentration is 0.5mol/L. Prepare 0.45 mol/L sodium carbonate solution. The required solution A and solution B were weighed according to the mass percentages of Cu and Zn in the final catalyst, added to the reaction kettle, then the diatomite carrier was added to the reaction kettle, the sodium carbonate solution was added dropwise and vigorously stirred, and the reaction temperature was controlled to 30 ℃ ^o C, pH is 7.8~8.0, and a slurry containing insoluble compounds is obtained after treatment with a colloid mill. The above-mentioned insoluble slurry was centrifuged and most of the mother liquor was filtered off, and then 3wt% of silica gel and deionized water were added to the filter cake and fully stirred to adjust the solid content of the slurry to 25%. Pass the slurry through a centrifugal spray dryer, control the temperature of the inlet to 380 ^° C and the temperature of the outlet to 150 ^° C to obtain the catalyst precursor, and then calcinate at 450 ^° C for 9 hours to obtain the finished catalyst. The mass percentage of Cu in the catalyst is 44.89%, the mass percentage of Zn is 5.05%, the specific surface area of the catalyst is 108.7 m ² /g, and the metal surface area of Cu in the catalyst is 18.3 m ² /g. The physical properties are listed in detail. in Table 1.

Example 3

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O, add deionized water, stir to dissolve, and configure solution A, so that the Cu ²⁺ ion concentration is 0.8mol/L. Accurately weigh (CH ₃ COO) ₃ Mn·2H ₂ O, add deionized water, stir to dissolve, and configure solution B, so that the Mn ²⁺ ion concentration is 0.8mol/L. Prepare 0.45 mol/L sodium carbonate solution. The required solution A and solution B were weighed according to the mass percentages of Cu and Mn in the final catalyst, added to the reaction kettle, then the silicon oxide carrier was added to the reaction kettle, the sodium carbonate solution was added dropwise and vigorously stirred, and the reaction temperature was controlled to 30 ^° C. C, pH is 8.0~8.2, and a slurry containing insoluble compounds is obtained after treatment with a colloid mill. The above-mentioned insoluble slurry was centrifuged and most of the mother liquor was filtered off, and then 3wt% of water glass and deionized water were added to the filter cake and fully stirred to adjust the solid content of the slurry to 25%. Pass the slurry through a centrifugal spray dryer, control the temperature of the inlet to 380 ^° C and the temperature of the outlet to 150 ^° C to obtain the catalyst precursor, and then calcinate at 450 ^° C for 9 hours to obtain the finished catalyst. The mass percentage of Cu in the catalyst is 43.25%, the mass percentage of Mn is 4.98%, the specific surface area of the catalyst is 207.5 m ² /g, and the metal surface area of Cu in the catalyst is 17.6 m ² /g. The physical properties are listed in detail. in Table 1.

Example 4

Accurately weigh (CH ₃ COO) ₃ Mn·2H ₂ O, add deionized water, stir to dissolve, and configure solution A to make the Mn ²⁺ ion concentration 0.5mol/L. Prepare 0.45 mol/L potassium hydroxide solution. The required solid Cu(OH) solution _A was weighed according to the mass percentage of Cu and Mn in the final catalyst, added to the reactor, then the magnesium silicate carrier was added to the reactor, the potassium hydroxide solution was added dropwise and vigorously stirred, The reaction temperature was controlled at 30 ^o C, and the pH was 8.0~8.2, and a slurry containing insoluble compounds was obtained after treatment with a colloid mill. The above-mentioned insoluble slurry was centrifuged and most of the mother liquor was filtered off, and then 3wt% of aluminum chloride and deionized water were added to the filter cake and fully stirred to adjust the solid content of the slurry to 25%. The slurry treated by the colloid mill was passed through a centrifugal spray dryer, and the temperature of the inlet was controlled to 380 ^o C and the temperature of the outlet was 150 ^o C to obtain the catalyst precursor, and then calcined at 450 ^o C for 9 hours to obtain the finished catalyst. The mass percentage of Cu in the catalyst is 46.02%, the mass percentage of Mn is 5.21%, the specific surface area of the catalyst is 187.7 m ² /g, and the metal surface area of Cu in the catalyst is 15.8 m ² /g. The physical properties are detailed. in Table 1.

Example 5

Accurately weigh CuCl ₂ ·2H ₂ O, add deionized water, stir to dissolve, and configure solution A, so that the Cu ²⁺ ion concentration is 0.8mol/L. Accurately weigh C ₈ H ₁₂ O ₈ Zr, add deionized water, stir and dissolve, and configure solution B, in which the Zr ⁴⁺ ion concentration is 0.8 mol/L. Prepare 0.45 mol/L potassium hydroxide solution. The required solution A and solution B were weighed according to the mass percentages of Cu and Zr in the final catalyst, added to the reaction kettle, then the silicon oxide carrier was added to the reaction kettle, potassium hydroxide solution was added dropwise and vigorously stirred, and the reaction temperature was controlled to 30 ℃ ^o C, pH is 8.0~8.2, and a slurry containing insoluble compounds is obtained after treatment with a colloid mill. The above-mentioned insoluble slurry was centrifuged and most of the mother liquor was filtered off, and then 3wt% of silica gel and deionized water were added to the filter cake and fully stirred to adjust the solid content of the slurry to 25%. Pass the slurry through a centrifugal spray dryer, control the temperature of the inlet to 380 ^° C and the temperature of the outlet to 150 ^° C to obtain the catalyst precursor, and then calcinate at 450 ^° C for 9 hours to obtain the finished catalyst. The mass percentage of Cu in the catalyst is 50.81%, the mass percentage of Zr is 5.16%, the specific surface area of the catalyst is 305.5 m ² /g, and the metal surface area of Cu in the catalyst is 19.8 m ² /g. The physical properties are detailed. in Table 1.

Example 6

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O, add deionized water, stir to dissolve, and configure into solution A, where the Cu ²⁺ ion concentration is 0.7mol/L. Accurately weigh C ₈ H ₁₂ O ₈ Zr, add deionized water, stir to dissolve, and configure solution B, so that the Zr ⁴⁺ ion concentration is 0.7 mol/L. Prepare 0.45 mol/L sodium bicarbonate solution. The required solution A and solution B were weighed according to the mass percentages of Cu and Zr in the final catalyst, added to the reaction kettle, then the alumina carrier was added to the reaction kettle, the sodium bicarbonate solution was added dropwise and vigorously stirred, and the reaction temperature was controlled to 30 ℃ ^o C, pH is 8.5~8.7, and a slurry containing insoluble compounds is obtained after treatment with a colloid mill. The above-mentioned insoluble slurry was centrifuged and most of the mother liquor was filtered out, and then 3wt% of aluminum glue and deionized water were added to the filter cake and fully stirred to adjust the solid content of the slurry to 25%. Pass the slurry through a centrifugal spray dryer, control the temperature of the inlet to 380 ^° C and the temperature of the outlet to 150 ^° C to obtain the catalyst precursor, and then calcinate at 450 ^° C for 9 hours to obtain the finished catalyst. The mass percentage of Cu in the catalyst is 45.27%, the mass percentage of Zr is 5.01%, the specific surface area of the catalyst is 380.7 m ² /g, and the metal surface area of Cu in the catalyst is 20.8 m ² /g. The physical properties are listed in detail. in Table 1.

Comparative Example 1

Accurately weigh Cu(NO ₃ ) ₂ ·3H ₂ O, add deionized water, stir to dissolve, and configure solution A, so that the Cu ²⁺ ion concentration is 0.7mol/L. Prepare 0.45 mol/L sodium bicarbonate solution. The required solution A was weighed according to the mass percentage of Cu in the final catalyst, added to the reaction kettle, then the alumina carrier was added to the reaction kettle, the sodium bicarbonate solution was added dropwise and vigorously stirred, and the reaction temperature was controlled to 30 ^° C, and the pH was 7.8~8.0, after treatment with a colloid mill, a slurry containing insoluble compounds is obtained. The above-mentioned insoluble slurry was centrifuged and filtered to remove most of the mother liquor, and then deionized water was added to the filter cake to fully stir to adjust the solid content of the slurry to 25%. Pass the slurry through a centrifugal spray dryer, control the temperature of the inlet to 380 ^° C and the temperature of the outlet to 150 ^° C to obtain the catalyst precursor, and then calcinate at 450 ^° C for 9 hours to obtain the finished catalyst. The mass percentage of Cu in the catalyst is 44.82%, the specific surface area of the catalyst is 80.9 m ² /g, and the metal surface area of Cu in the catalyst is 6.5 m ² /g. The physical properties are listed in Table 1.

Determination of Cu metal surface area

The Cu metal area of the catalyst was determined by the _N2O decomposition principle ( _N2O pulse chemisorption):

2Cu+N ₂ O→Cu ₂ O+N ₂

To this end, after reduction with mixed hydrogen ( ₅ % H in Ar synthesis gas) for 8 h in a chemisorber (Micromeritics AutoChem II 2920) at 230 ^o C, the chemisorption was purged with Ar and _N2O pulsed chemisorption was started . _The Cu metal surface area was measured and calculated by N formed in Ar as determined by a TCD detector.

Table 1 Catalyst components and related physical properties.

Activity test of 1,4-cyclohexanedimethanol (CHDM) by hydrogenation of dimethyl 1,4-cyclohexanedicarboxylate (DMCD).

The hydrogenation reaction was carried out on a high-pressure micro-reaction catalyst evaluation device. In order to prevent the thermal effect from affecting the performance of the catalyst, 3.0 g (crushed into 20-40 mesh after tableting) catalyst and quartz sand (40-60 mesh) were mass ratio 1. :1 phase was mixed and charged into the reactor. In the atmosphere of 10% H ₂ /N ₂ , the temperature was raised to 250 ^oC at a rate of 5 ^oC /min, and the temperature was maintained for 2 hours to fully reduce and activate the catalyst. The bed temperature was lowered to 240 ^o C, the hydrogen pressure was raised to 8 MPa, the H ₂ /DMCD ratio was kept at 406, and the liquid phase space velocity was 0.5 to 2.0 h ^-1 . The content of the reaction product was analyzed by Agilent GC7890A gas chromatography, the chromatography column was HP-5, the detector was a hydrogen flame ionization detector, and the injection volume was 0.2 μl. According to the chromatographic analysis results, the DMCD conversion rate and the target product CHDM selectivity were calculated.

Table 2. Performance comparison of catalysts in DMCD gas-phase hydrogenation.

It can be seen from the results in Table 2 that, relative to the comparative example, the conversion rate and selectivity of the catalysts of each group of examples can reach about 99%. Therefore, the liquid phase space velocity also directly reflects the catalytic activity. Specifically, the activity of the catalyst=liquid phase space velocity*conversion rate*selectivity. According to the settlement results, the catalyst prepared by the present invention can still maintain high activity under high space velocity, which can reach more than 2.8g/gcat.h.

In addition, the catalyst prepared by the comparative example has a slightly poorer activity in the gas phase hydrogenation of DMCD, about 2.4 g/gcat.h.

It can be seen from the above data that the above-mentioned embodiments of the present invention achieve the technical effects of high hydrogenation conversion rate and high selectivity under the condition of high space velocity. Meanwhile, the copper-based catalyst provided by the present invention also has higher dehydrogenation efficiency in the catalytic dehydrogenation reaction.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, various modifications and changes may be made to the methods described in the present invention. Any modifications, equivalent replacements, and modifications made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (7)

1. a method for preparing copper-based catalyst by spray drying, the method comprises the following steps: (a) prepare a water-based slurry containing water, copper-containing substances, auxiliary substances, and carrier substances; (b) adjusting the pH of the slurry to obtain an insoluble compound slurry; (c) after the above-mentioned slurry is filtered to remove most of the mother liquor, deionized water and binder are added for stirring and beating; (d) spray drying the slurry to obtain a catalyst precursor; (e) calcining the catalyst precursor to obtain a copper-based catalyst. 2. The method of claim 1, wherein the copper-containing substance comprises one or more of copper nitrate, basic copper carbonate, copper chloride, cupric ammonia solution, copper hydroxide, copper oxide or cuprous oxide. 3. The method of claim 1, wherein the auxiliary substances comprise one or more of zinc chloride, zinc acetate, manganese nitrate, manganese acetate, zirconium hydroxide or zirconium acetate. 4. The method of claim 1, wherein the carrier material comprises one or more of kaolin, diatomaceous earth, clay, alumina, silica, calcium silicate, magnesium silicate or silico-alumina molecular sieve. 5. The method of claim 1, wherein the binder comprises one or more of silica gel, aluminum glue, water glass, aluminum chloride, methyl cellulose, polyvinyl alcohol, succulent powder or starch . 6. The method of claim 1, wherein the adjustment range of the slurry pH is preferably 6.5~9.0, more preferably 7.0~8.5. 7. The method of claim 1, wherein the catalyst is a hydrogenation, hydrogenolysis or dehydrogenation catalyst.

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