CN114632545A - A kind of ultra-stable acetylene selective hydrogenation catalyst and its preparation method and application - Google Patents

Abstract

The invention discloses an ultra-stable acetylene selective hydrogenation catalyst and a preparation method and application thereof, wherein the ultra-stable acetylene selective hydrogenation catalyst consists of a carrier and an active component loaded on the carrier, wherein the active component is noble metal palladium, the carrier is a zeolite imidazole framework ZIF-8, and the noble metal palladium is dispersed on the surface of the zeolite imidazole framework ZIF-8 in a stable monoatomic form by cooperating with the domain-limiting action of the zeolite imidazole framework material and the strong interaction of palladium zinc metal and metal. The invention adopts an ultra-stable catalyst as a catalyst for acetylene selective hydrogenation reaction, the catalyst has excellent ethylene selectivity and stability, the activity is not reduced in a test of 300h, 100 percent of acetylene conversion rate and 90 percent of ethylene selectivity are obtained at a reaction temperature of 130 ℃, and the catalyst can be stably used for 155 h.

Description

A kind of ultra-stable acetylene selective hydrogenation catalyst and its preparation method and application

technical field

The invention belongs to the technical field of preparation of industrial catalysts, in particular to an ultra-stable acetylene selective hydrogenation catalyst and a preparation method and application thereof.

Background technique

As an indispensable raw material in petrochemical industry, ethylene is mainly used to produce polyethylene, polyvinyl chloride, ethylene oxide, etc. In industry, ethylene is mainly obtained from naphtha cracking, and the process inevitably contains about 0.1wt%-2wt% of acetylene by-products. Acetylene can cause poisoning and deactivation of catalysts used in the polymerization of ethylene, so the acetylene content must be reduced to less than 5 ppm before polymerization.

Selective hydrogenation has the advantages of low energy consumption, simple process, and turning waste into treasure. Therefore, it has become a common method for removing acetylene and refining ethylene in industry. On the one hand, the palladium single-atom catalyst improves the utilization of noble metals, and on the other hand, it helps to control the ethylene adsorption behavior from strong 2σ bonds to weaker π bonds, which promotes its desorption and improves ethylene selectivity. However, as the size of metal species decreases, their surface energy increases. Therefore, the preparation of ultra-stable palladium single-atom catalysts is urgently needed and faces great challenges.

In recent years, zeolitic imidazole framework materials have become excellent catalytic materials or catalyst supports due to their high porosity, good thermal stability and chemical stability. In addition, there is a strong metal-metal interaction between palladium atoms and zinc atoms. Based on the above background, the present invention provides a palladium single-atom catalyst confined by a zeolite imidazole framework material to improve the selectivity and stability in the selective hydrogenation of acetylene.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is to provide an ultra-stable catalyst for selective hydrogenation of acetylene and a preparation method thereof. The catalyst can make palladium stable at a stable level through the confinement effect of the zeolite imidazole framework material and the strong palladium-zinc metal-metal interaction. The monoatomic form is highly dispersed on the surface of the support, which can significantly improve the ethylene selectivity and catalyst stability in the selective hydrogenation of acetylene.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical scheme, an ultra-stable acetylene selective hydrogenation catalyst, characterized in that: the catalyst is composed of a carrier and an active component supported on the carrier, wherein the active component is precious metal palladium, The carrier is the zeolite imidazole framework ZIF-8, and the precious metal palladium is dispersed on the surface of the zeolite imidazole framework ZIF-8 in the form of a stable single atom through the confinement of the zeolite imidazole framework material and the strong palladium-zinc metal-metal interaction.

Further limited, the loading amount of the precious metal palladium is 0.01wt% to 0.5wt%.

The preparation method of the ultra-stable acetylene selective hydrogenation catalyst of the present invention is characterized in that the specific steps are:

Step S1: dissolving the zinc source in methanol or water solvent to obtain solution A, dissolving the organic ligand 2-methylimidazole in methanol or water solvent to obtain solution B, pouring solution A into solution B and adding the solution at 20-50 Stir in a water bath for 6 to 24 hours to obtain a suspension;

Step S2: the suspension obtained in step S1 is centrifuged and washed for several times, then dried at 50 to 80 ° C for 8 to 12 hours, and then ground and then calcined at 100 to 350 ° C for 2 to 12 hours to obtain a zeolite imidazole framework ZIF-8 carrier;

Step S3: the palladium source solution and the zeolite imidazole framework ZIF-8 carrier obtained in step S2 are impregnated with an equal volume so that the active metal palladium is loaded on the surface of the zeolite imidazole framework ZIF-8 carrier, dried in the shade for 6 to 24 hours at 50 to 150° C. Drying for 6-24 hours, calcining at 200-400 DEG C for 2-5 hours, and reduction at 100-400 DEG C to obtain a palladium-based catalyst supported by zeolite imidazole framework ZIF-8.

Further limitation, the zinc source described in step S1 is zinc nitrate hexahydrate, zinc acetate or zinc chloride, and the palladium source described in step S3 is one or more of palladium nitrate, palladium chloride or palladium acetate.

It is further limited that the molar ratio of the zinc source to the organic ligand in step S1 is 1:5 to 1:20.

Further limited, in step S2, the centrifugation speed is 8000-10000rpm, the centrifugation time is 5min, and methanol is used for washing after centrifugation.

Further limited, in step S3, the reduction treatment process adopts a hydrogen atmosphere, the flow rate is 20-50mL/min, the hydrogen atmosphere is 50-100Vol% H ₂ /Ar, the reduction temperature is 100-400°C, and the reduction time is 0.5-3h.

The application of the ultra-stable acetylene selective hydrogenation catalyst in the acetylene selective hydrogenation reaction of the present invention is characterized in that: in the acetylene selective hydrogenation reaction process, the use temperature of the catalyst is 60-325° C., the feed gas is The composition is: 1Vol% acetylene, 5~20Vol% hydrogen, 20Vol% ethylene, argon as the equilibrium gas, and the space velocity is 36000~300000mL/(g·h).

The application of the ultra-stable acetylene selective hydrogenation catalyst of the present invention is characterized in that: in the acetylene selective hydrogenation reaction, with the increase of the number of reaction cycles, the catalyst performance is overall improved; after four cycles of performance tests with the reaction temperature, The stability test was carried out at a fixed reaction temperature of 130 °C, the acetylene conversion rate was 100%, the ethylene selectivity was 90%, and no catalyst deactivation was observed in the 155-h test; followed by stability tests at 120 °C, 110 °C, 100 °C, and 90 °C, Ethylene selectivity was maintained at around 90%, and no deactivation was still observed.

The present invention has the following advantages and beneficial effects:

1. In view of the problem of poor thermal stability of single-atom catalysts, the present invention assists the confinement of the zeolite imidazole framework structure and the strong metal-metal interaction between zinc atoms and palladium atoms in ZIF-8, so as to obtain ultra-highly stable single atoms catalyst.

2. In the four-cycle acetylene selective hydrogenation reaction evaluation test, the catalyst performance of the present invention is improved, and in the subsequent stability test, it shows ultra-high stability, and no deactivation of the catalyst is observed for 300 hours.

3. The preparation method is simple, the repeatability is good, and it is easy to be enlarged in large-scale industrialization.

Detailed ways

The technical solution created by the present invention will be further described below with reference to specific embodiments, so as to fully understand it. It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present invention, and are not used to limit the present invention.

Example 1

Weigh 3.8771g of zinc nitrate hexahydrate and dissolve it in 80mL of methanol to prepare solution A. Then weigh 8.5384g of 2-methylimidazole and dissolve it in 80mL of methanol to prepare solution B. Pour solution A into solution B and put it in solution B. Stir at 25°C for 12h, centrifuge the resulting mixed solution and wash with methanol three times, then put the sample into a 60°C oven to dry for 12h, then grind the obtained solid and put it into a muffle furnace, and heat up at 5°C/min in an air atmosphere The rate of heating was increased to 300 °C for 3 h, and the catalyst carrier ZIF-8 was obtained. Take 0.8802mL of palladium nitrate solution, the concentration is 0.001g/mL, then add 2.3295mL of deionized water, according to the loading of 0.1wt%, adopt the same volume impregnation method to the above-mentioned catalyst carrier ZIF-8 while stirring, drip the impregnation solution, Immerse at 25°C for 12h, put it in an oven to dry at 120°C for 12h, then put it in a muffle furnace, and heat it up to 300°C for 3h at a heating rate of 5°C/min in an air atmosphere to obtain a zeolite imidazole framework supported palladium monolayer. Atomic catalyst precursors. Then 20 mg of catalyst precursor was placed in a quartz tube into a fixed-bed reactor, treated with 30 mL/min of hydrogen at 300 °C for 1 h, and then cooled to room temperature under a hydrogen atmosphere to obtain a zeolite imidazole framework structure but a palladium-loaded single-atom catalyst , denoted as Pd/ZIF-8. Subsequently, the acetylene selective hydrogenation reaction test was carried out, and the feed gas was fed: 1Vol% acetylene, 10Vol% hydrogen, 20Vol% ethylene, argon was the equilibrium gas, the space velocity was 150000mL/(g h), and the operating temperature of the catalyst was 60 ~325°C, the reaction product is detected by gas chromatography, and the catalyst after the selective hydrogenation reaction of acetylene has been tested is recorded as Pd/ZIF-8-1.

Example 2

The catalyst of Example 1 was purged to room temperature with argon with a flow rate of 30 mL/min after the acetylene selective hydrogenation reaction test was completed, and the acetylene selective hydrogenation reaction test was performed again. Feeding raw material gas: 1Vol% acetylene, 10Vol% hydrogen, 20Vol% ethylene, argon is equilibrium gas, space velocity is 150000mL/(g h), the service temperature of catalyst is 60～325 ℃, and the reaction product is detected by gas chromatographic analysis , and the catalyst tested for the selective hydrogenation of acetylene is denoted as Pd/ZIF-8-2.

Example 3

The catalyst of Example 2 was purged to room temperature with argon with a flow rate of 30 mL/min after the acetylene selective hydrogenation reaction test was completed, and the acetylene selective hydrogenation reaction test was performed again. Feeding raw material gas: 1Vol% acetylene, 10Vol% hydrogen, 20Vol% ethylene, argon is equilibrium gas, space velocity is 150000mL/(g h), the service temperature of catalyst is 60～325 ℃, and the reaction product is detected by gas chromatographic analysis . The catalyst tested for the selective hydrogenation of acetylene was denoted as Pd/ZIF-8-3.

Example 4

The catalyst of Example 3 was purged to room temperature with argon with a flow rate of 30 mL/min after the acetylene selective hydrogenation reaction test was completed, and the acetylene selective hydrogenation reaction test was performed again. Feeding raw material gas: 1Vol% acetylene, 10Vol% hydrogen, 20Vol% ethylene, argon is equilibrium gas, space velocity is 150000mL/(g h), the service temperature of catalyst is 60～325 ℃, and the reaction product is detected by gas chromatographic analysis , and the catalyst tested for the selective hydrogenation of acetylene is denoted as Pd/ZIF-8-4. At this time, the obtained catalyst is an ultra-stable acetylene selective hydrogenation catalyst.

Example 5

The catalyst of Example 4 was purged to room temperature with argon with a flow rate of 30 mL/min after the acetylene selective hydrogenation reaction test, and the acetylene selective hydrogenation reaction stability test was performed again. Feed the raw material gas: 1Vol% acetylene, 10Vol% hydrogen, 20Vol% ethylene, argon is an equilibrium gas, the space velocity is 150000mL/(g h), the catalyst service temperature is 90～130 ℃, and the reaction product is detected by gas chromatographic analysis .

Example 6

Performance comparison of catalysts for selective hydrogenation of acetylene

The catalyst obtained from each embodiment is used in the selective hydrogenation of acetylene, and the performance comparison is shown in Table 1:

Reaction temperature (℃) Acetylene conversion % Ethylene selectivity % Example 1 150 27 63 Example 2 150 100 82 Example 3 150 100 91 Example 4 150 100 92 Example 5 150 100 90

Example 7

Embodiment 5 The catalyst has carried out the acetylene selective hydrogenation reaction stability test, and the performance chart is shown in Table 2:

Response time (h) Reaction temperature (℃) Acetylene conversion % Ethylene selectivity % 30 130 99 90 60 130 100 90 90 130 100 90 120 130 100 90 155 130 100 90 180 120 98 91 200 110 98 92 230 100 91 93 300 90 81 93

From the above experimental results, it can be seen that the ultra-stable zeolite imidazole framework structure-supported palladium single-atom catalyst proposed by the present invention has an overall improvement in the performance of the catalyst as the number of reaction cycles increases. After four laps of performance tests with reaction temperature, the stability test was carried out at a fixed reaction temperature of 130 °C. The acetylene conversion rate was 100%, the ethylene selectivity was 90%, and no catalyst deactivation was observed in the 155-h test. , 100 ℃, 90 ℃ stability test, the ethylene selectivity is maintained at about 90%, and no inactivation phenomenon is still observed. It shows that the catalyst has high industrial application value.

The basic principles, main features and advantages of the present invention have been shown and described above. Without departing from the spirit and scope of the present invention, the present invention has various changes and improvements, which all fall into the claimed invention. range.

Claims (9)

1. an ultra-stable acetylene selective hydrogenation catalyst is characterized in that: this catalyst is made up of carrier and the active component that is loaded on the carrier, and wherein the active component is precious metal palladium, and the carrier is zeolite imidazole framework ZIF-8, and precious metal Palladium is dispersed on the surface of zeolite imidazole framework ZIF-8 in the form of stable single atoms through the synergistic confinement effect of zeolite imidazole framework materials and strong palladium-zinc metal-metal interaction. 2 . The ultra-stable acetylene selective hydrogenation catalyst according to claim 1 , wherein the loading of the precious metal palladium is 0.01wt% to 0.5wt%. 3 . 3. a preparation method of the ultra-stable acetylene selective hydrogenation catalyst described in claim 1 or 2, is characterized in that concrete steps are: Step S1: dissolving the zinc source in methanol or water solvent to obtain solution A, dissolving the organic ligand 2-methylimidazole in methanol or water solvent to obtain solution B, pouring solution A into solution B and adding the solution at 20-50 ℃ water bath stirring for 6 ~ 24h to obtain a suspension; Step S2: the suspension obtained in step S1 is centrifuged and washed for several times, then dried at 50 to 80 ° C for 8 to 12 hours, and then ground and then calcined at 100 to 350 ° C for 2 to 12 hours to obtain a zeolite imidazole framework ZIF-8 carrier; Step S3: using the palladium source solution and the zeolite imidazole framework ZIF-8 carrier obtained in step S2 to load the active metal palladium on the surface of the zeolite imidazole framework ZIF-8 carrier by an equal volume impregnation method, drying in the shade for 6-24 hours and drying at 50-150°C 6～24h, calcination at 200～400℃ for 2～5h, and reduction at 100～400℃ to obtain a palladium-based catalyst supported by zeolite imidazole framework ZIF-8. 4. the preparation method of ultra-stable acetylene selective hydrogenation catalyst according to claim 3, is characterized in that: the zinc source described in step S1 is hexahydrate zinc nitrate, zinc acetate or zinc chloride, described in step S3 The palladium source is one or more of palladium nitrate, palladium chloride or palladium acetate. 5 . The method for preparing an ultra-stable acetylene selective hydrogenation catalyst according to claim 3 , wherein the molar ratio of the zinc source to the organic ligand described in step S1 is 1:5 to 1:20. 6 . 6. The preparation method of the ultra-stable acetylene selective hydrogenation catalyst according to claim 3, characterized in that: in step S2, the centrifugation speed is 8000～10000rpm, the centrifugation time is 5min, and methanol is used for washing after centrifugation. 7. the preparation method of ultra-stable acetylene selective hydrogenation catalyst according to claim 3, is characterized in that: in step S3, reduction treatment process adopts hydrogen atmosphere, and flow velocity is 20～50mL/min, and hydrogen atmosphere is 50～100Vol% H ₂ /Ar, the reduction temperature is 100-400°C, and the reduction time is 0.5-3h. 8. the application of the ultra-stable acetylene selective hydrogenation catalyst according to claim 1 in the acetylene selective hydrogenation reaction, it is characterized in that: in the acetylene selective hydrogenation reaction process, the use temperature of the catalyst is 60～325 ℃ , the raw gas composition is: 1Vol% acetylene, 5~20Vol% hydrogen, 20Vol% ethylene, argon is the balance gas, and the space velocity is 36000~300000mL/(g·h). 9. the application of the ultra-stable acetylene selective hydrogenation catalyst according to claim 1, it is characterized in that: in the acetylene selective hydrogenation reaction, along with the increase of the number of reaction circles, the catalyst performance is improved as a whole; the performance of the four circles with the reaction temperature After the test, the stability test was carried out at a fixed reaction temperature of 130 °C, the acetylene conversion rate was 100%, the ethylene selectivity was 90%, and no catalyst deactivation was observed in the 155-h test; then it was stable at 120 °C, 110 °C, 100 °C, and 90 °C The ethylene selectivity was maintained at about 90%, and no inactivation was observed.