CN112570015B - Molecular sieve catalyst for packaging Pd-based alloy and preparation method and application thereof - Google Patents
Molecular sieve catalyst for packaging Pd-based alloy and preparation method and application thereof Download PDFInfo
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- B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
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- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
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- C07C5/02—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation
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- C07C5/08—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation of carbon-to-carbon triple bonds
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Abstract
The invention belongs to the technical field of molecular sieve catalysts, and discloses a molecular sieve catalyst for packaging Pd-based alloy, a preparation method and application thereof, wherein the molecular sieve catalyst comprises a sodalite molecular sieve, and PdM nano alloy particles are packaged in the sodalite molecular sieve; firstly, preparing a sodalite molecular sieve, then impregnating a Pd-loaded metal and an M metal precursor, and roasting and reducing to form a molecular sieve catalyst impregnated with nano alloy particles; then uniformly mixing the catalyst with a silicon-aluminum sol solution, stirring and uniformly mixing the mixture, evaporating the mixture to dryness, then adding ethylene glycol, grinding the mixture to be uniform paste, carrying out hydrothermal reaction, cooling, washing, drying, roasting and reducing to obtain the catalyst; the molecular sieve catalyst is applied to the selective hydrogenation reaction of acetylene, can avoid an excessive hydrogenation process, and has high acetylene conversion rate and ethylene selectivity.
Description
Technical Field
The invention belongs to the technical field of supported catalysts, and particularly relates to a molecular sieve catalyst for packaging Pd-based alloy, and a preparation method and application thereof.
Background
Ethylene is a national important industrial base material and is currently prepared mainly by pyrolysis of naphtha. However, the industrial ethylene product usually contains 0.5-2% mole fraction of acetylene, and the acetylene can cause the service life of the downstream catalyst for synthesizing polyethylene to be reduced, and the existence of acetylene can seriously reduce the purity of the polyethylene product, and the quality of the polyethylene product is influenced. Therefore, it is necessary to reduce the trace amount of acetylene impurity in the ethylene feed to 5ppm or less by an effective means. The process of generating ethylene by selectively hydrogenating acetylene with a fixed bed catalyst can remove acetylene and increase the yield of ethylene, and is simple and economical, so that the process becomes a common method for removing acetylene in the industry at present. In the selective hydrogenation of acetylene, the catalyst plays a decisive role. Therefore, the preparation of the acetylene selective hydrogenation catalyst with high activity and high selectivity is the target of cumin in the industry and scientific research.
The reaction formula for preparing ethylene by selective hydrogenation of acetylene is C 2 H 2 +H 2 →C 2 H 4 △H 298 The reaction is a strong exothermic reaction, so that excessive hydrogenation is easily caused to generate ethane or byproducts such as green oil are easily generated by polymerization between ethylene molecules, and the yield of the target product ethylene is influenced. Currently, the carbon dioxide hydrogenation catalysts are mainly divided into two major components, namely palladium catalysts and non-palladium catalysts, in terms of active components. Because of the unique properties of palladium metal, the palladium metal has very good capability of activating hydrogen and can absorb acetylene preferentially over ethylene. Therefore, the industry still uses the supported catalyst which uses palladium base as active component. The industrial catalyst composition is subjected to the reaction from Pd/alpha-Al 2 O 3 To PdAg/alpha-Al 2 O 3 The upgrading of (2) is mainly that the adsorption capacity of the single metal palladium catalyst to ethylene is still strong, so that the acetylene is difficult to desorb after being hydrogenated to generate ethylene, and thus the acetylene is easy to excessively hydrogenate to generate ethylene.
In 1960s, acetylene selective hydrogenation reaction has been industrialized, and the currently industrially applied catalysts mainly include G-58 series of Clariant catalyst company in Germany (original Germany, southern chemical company), KL7741-B series of Netherlands royal Shell CRI Kataleuna (original Germany catalyst company purchased), C31-1 series of American CCI company, LT series of catalysts of French Petroleum Institute (IFP), BC-1-037 series of Beijing chemical institute, and LY-C2 series of petrochemical institute LY-C in Petroleum Lanzhou. At present, the industrial catalyst can achieve 100% of acetylene conversion rate, but the ethylene selectivity is about 80%, so that the catalyst has a very large promotion space, and the ethylene selectivity index can greatly influence the economic benefit of the process production and has a very large promotion space. Based on the current industrialized catalyst composition (palladium and palladium-silver alloy), it is very necessary to design the catalyst structure to further improve the selectivity of ethylene.
Disclosure of Invention
The invention aims to solve the related technical problems of preparing an ethylene catalyst by selective hydrogenation of acetylene, and provides a molecular sieve catalyst for packaging Pd-based alloy, a preparation method and application thereof, wherein PdM nano-alloy particles are packaged inside sodalite molecular Sieve (SOD) pore channels, and a molecular sieve nano-reactor for site separation and concerted catalysis is constructed; the catalyst is used in the process of acetylene selective hydrogenation reaction, and has higher ethylene selectivity.
In order to solve the technical problems, the invention is realized by the following technical scheme:
according to one aspect of the invention, a molecular sieve catalyst for packaging Pd-based alloy is provided, and comprises a sodalite molecular sieve, wherein PdM nano-alloy particles are packaged In the sodalite molecular sieve, and M In the PdM nano-alloy particles is at least one of Cu, Ag, Au, Zn, Sn, In, Ga, Pb and Bi; the mass percentage of Pd in the molecular sieve catalyst is 0.01-1%, and the molar ratio of Pd to M in the PdM nano-alloy particles is 1:5-5: 1.
Further, the size of the sodalite molecular sieve encapsulated with PdM nano alloy particles is 100 +/-30 nm.
Further, the PdM nano-alloy particles are PdAg nano-alloy particles, the mass percentage of Pd in the molecular sieve catalyst is 0.1-0.4wt%, and the molar ratio of Pd to Ag in the PdM nano-alloy particles is 1: 1.
According to another aspect of the present invention, there is provided a method for preparing the above Pd-based alloy-encapsulated molecular sieve catalyst, the method comprising the steps of:
(1) preparing a sodalite molecular sieve;
(2) saturating and dipping the sodalite molecular sieve obtained in the step (1) with loaded Pd metal and M metal precursor;
(3) drying the sample obtained in the step (2), roasting at 300-350 ℃ for 2-4h, and then fully reducing in 300-350 ℃ hydrogen atmosphere to obtain the PdM/SOD catalyst impregnated with the PdM-loaded nano alloy particles;
(4) dispersing the PdM/SOD catalyst obtained in the step (3) in a silicon-aluminum sol solution, stirring at room temperature until the solution is uniform, and slowly stirring and evaporating to dryness;
(5) adding ethylene glycol into the sample obtained in the step (4), grinding the mixture to be uniform paste, and performing hydrothermal reaction at the temperature of 180-200 ℃ for 24-48 h;
(6) and (4) washing the sample obtained in the step (5) to be neutral, drying, roasting at the temperature of 300-350 ℃ for 2-4h, and then fully reducing in the hydrogen atmosphere at the temperature of 300-350 ℃ to obtain the PdM @ SOD catalyst for packaging the PdM nano alloy particles.
Further, the preparation process of the sodalite molecular sieve of the step (1) is as follows: dissolving an aluminum source, a silicon source and sodium hydroxide in water, fully stirring to form a silicon-aluminum sol solution which is uniformly mixed, carrying out hydrothermal reaction on the solution at 100 ℃ for 12 hours, cooling, washing, drying and roasting to obtain the sodalite molecular sieve; the aluminum source is one of boehmite, sodium metaaluminate, amorphous aluminum hydroxide powder and aluminum isopropoxide, and the silicon source is fumed silica, water glass, silica sol, silica gel and amorphous SiO 2 One of the powders.
Further, the silicon-aluminum sol solution in the step (4) is a precursor gel solution of the sodalite molecular sieve, and the silicon-aluminum ratio of the silicon-aluminum sol solution is 1: 1.
According to another aspect of the invention, the application of the molecular sieve catalyst for packaging the Pd-based alloy in the selective hydrogenation reaction of acetylene is provided.
Further, the reaction temperature is 50-150 ℃, and the reaction space velocity is 6000- -1 *h -1 The molar ratio of acetylene to hydrogen is 1:5-1:20, and the volume fraction of the flow rate of acetylene gas in the total gas flow rate is 0.6%.
According to another aspect of the invention, the invention provides an application of the molecular sieve catalyst for packaging the Pd-based alloy in preparation of carbon-carbon double-bond olefin products by selective hydrogenation of carbon-carbon triple-bond alkynes such as propyne.
According to another aspect of the invention, the invention provides an application of the molecular sieve catalyst for encapsulating Pd-based alloy in preparing mono-olefin by selective hydrogenation of diolefin such as 1, 3-butadiene and the like.
The invention has the beneficial effects that:
the molecular sieve catalyst for packaging Pd-based alloy encapsulates PdM nano-alloy particles inside SOD sodalite molecular sieve pore channels, and constructs a molecular sieve nano-reactor with site separation and concerted catalysis. Because acetylene hydrogenation is a strong exothermic reaction, the design of the molecular sieve encapsulated catalyst can effectively avoid temperature runaway, so that the hydrogenation reaction process is safer. By utilizing the sieving effect of the SOD sodalite molecular sieve pore canal (the pore canal is six-membered ring about 0.28nm), hydrogen molecules (the molecular dynamics diameter is about 0.28nm) are selectively led to enter the molecular sieve, acetylene molecules (the molecular dynamics diameter is about 0.33nm) are effectively prevented from entering the molecular sieve, and the acetylene molecules can only be adsorbed on the outer surface of the zeolite molecular sieve. Hydrogen enters the molecular sieve, is activated by the PdM component and overflows to the surface of the molecular sieve to perform hydrogenation reaction with acetylene molecules adsorbed on the surface to generate ethylene. After the surface of the molecular sieve is hydrogenated, because the adsorption of ethylene is very weak, further hydrogenation is not available, the adsorbed ethylene can be rapidly desorbed and changed into gaseous ethylene, and thus, the ethylene selectivity is very high.
The Pd-based alloy molecular sieve catalyst is packaged, the whole sodalite molecular sieve is 100 +/-30 nm particles, and compared with the sodalite molecular sieve synthesized by the traditional method, the particle size is greatly reduced, the specific surface area is effectively increased, and the number of reaction sites on the surface of the sodalite molecular sieve is increased; meanwhile, the reduction of the size of the molecular sieve shortens the hydrogen diffusion distance, accelerates the mass transfer rate and further improves the reaction performance of the catalyst.
In conclusion, the Pd-based alloy encapsulated molecular sieve catalyst disclosed by the invention can utilize the excellent capability of dissociating and activating hydrogen by using the palladium-based metal component, and can effectively avoid excessive hydrogenation caused by direct contact of PdM nano alloy particles and acetylene, so that the Pd-based alloy encapsulated molecular sieve catalyst is excellent in activity and selectivity when used as an acetylene selective hydrogenation catalyst. The second metal is added to form a PdM nano alloy structure, so that the dispersion degree of Pd is improved, the adsorption strength of adsorbed hydrogen is reduced, the hydrogen overflow process is accelerated, more hydroxyl hydrogenation sites are generated on the surface of the molecular sieve, and the performance of the catalyst is improved.
According to the preparation method of the molecular sieve catalyst, the molecular sieve catalyst for encapsulating metal is synthesized by using a crystal seed guiding method, so that a large amount of organic template agent is not added in the synthesis process, and the synthesis process is more green and environment-friendly; the loading capacity of the metal can be adjusted in a large range, and the type and the addition proportion of the metal can be adjusted; by utilizing a crystal seed guiding method and a two-step synthesis process, the participation of a water solvent in a hydrothermal process is avoided, and the process of mutual adhesion growth among molecular sieve crystal species can be greatly reduced, so that the size of the catalyst can be effectively reduced to 100 +/-30 nm; the synthesis process is simple and controllable, the repeatability is high, the batch synthesis yield is high, and the method is favorable for further expanding production and applying to an industrial process.
The application of the molecular sieve catalyst in the selective hydrogenation reaction of acetylene avoids the direct contact reaction of acetylene and palladium, and can greatly avoid the excessive hydrogenation process. In laboratory tests, at larger temperature intervals (50-150 ℃), various molar ratios of acetylene to hydrogen (1:5-1:20) and reaction space velocities (6000- -1 *h -1 ) The catalyst has very high acetylene conversion rate and ethylene selectivity and great industrial application potential.
Drawings
FIG. 1 is an XRD representation of the PdM @ SOD sample prepared in example 1;
FIG. 2 is a scanning electron microscope characterization of the PdM @ SOD sample prepared in example 1;
FIG. 3 is a transmission electron microscopy characterization of the PdM @ SOD sample prepared in example 1;
FIG. 4 is a CO infrared characterization plot of the PdM @ SOD sample prepared in example 1;
FIG. 5 is a CO oxidation probe reaction test chart of the PdM @ SOD sample prepared in example 1;
FIG. 6 is a graph showing the measurement of the PdM @ SOD sample obtained in example 1.
Detailed Description
The method comprises the steps of selecting a proper silicon source, a proper aluminum source and deionized water in a proper proportion by utilizing a molecular sieve in-situ synthesis technology, uniformly stirring, aging, transferring to a hydrothermal kettle for hydrothermal treatment, washing, drying and roasting to obtain the sodalite molecular Sieve (SOD) carrier. Then loading PdM alloy components, drying, roasting and reducing. Then the crystal is used as a seed crystal of the molecular sieve, placed in a silicon-aluminum sol solution, stirred and evaporated, added with a template agent, fully ground and transferred to a hydrothermal kettle for hydrothermal treatment; in the process, the PdM nano alloy particles can be coated in channels of a sodalite molecular Sieve (SOD) in the crystallization process of the molecular sieve by utilizing the guiding effect of the seed crystal, and then the target catalyst is obtained by washing, drying, roasting and reducing.
The present invention is further described in detail below by way of specific examples, which will enable one skilled in the art to more fully understand the present invention, but which are not intended to limit the invention in any way.
The various materials used in the examples below:
the aluminum source is sodium metaaluminate as a precursor and is from Guangdong chemical industry Co., Ltd; besides sodium metaaluminate, the aluminum source can also select pseudo-boehmite, amorphous aluminum hydroxide powder and aluminum isopropoxide as precursors;
the silicon source adopts gas-phase silicon dioxide produced by Alfa-Elsa chemical company Limited as a precursor; the silicon source can be selected from water glass, silica sol, silica gel, amorphous SiO besides fumed silica 2 Powder is used as a precursor;
sodium hydroxide was obtained from chemical reagents ltd of miuiou, tianjin;
the palladium source adopts palladium nitrate as a precursor, the silver source adopts silver nitrate as a precursor, and the palladium source and the silver source are from Shanghai Saen chemical technology Limited company;
copper nitrate is selected as a precursor of the copper source, chloroauric acid is selected as a precursor of the gold source, and the copper source and the chloroauric acid are both from Shanghai Aladdin chemical technology Limited;
zinc nitrate, gallium nitrate, indium nitrate, lead nitrate, bismuth nitrate, and ethylene glycol were all from Tianjin Kalmatt chemical reagent GmbH, and ultrapure water was self-made.
Example 1:
(1) adding 0.0181mol of aluminum source into 8g of water, uniformly mixing to form a solution A, adding 0.0181mol of silicon source into 8g of water, and uniformly mixing to form a solution B; quickly adding 0.0816mol of sodium hydroxide into the solution A, uniformly stirring, and stirring for thirty minutes at room temperature to form a mixed solution C; dropwise adding the solution B into the mixed solution C, and stirring for thirty minutes at room temperature to form a uniform mixed solution D; transferring the solution D to a 100mL hydrothermal kettle, placing the hydrothermal kettle in a 100 ℃ oven, and statically crystallizing for 12 hours; centrifugally washing the product with deionized water until the pH value is neutral, drying at 100 ℃ for 12h, and roasting at 300 ℃ in a muffle furnace for 4h (the heating rate is 2 ℃/min) to obtain sodalite molecular Sieve (SOD) powder;
(2) dissolving palladium nitrate powder and silver nitrate powder in deionized water added with a small amount of dilute nitric acid to prepare a solution; soaking the sodalite molecular Sieve (SOD) powder obtained in the step (1) in the solution, wherein the volume of the solution is equal to the pore volume (1.0mL/g) of the sodalite molecular Sieve (SOD) as a carrier, and a saturated soaking state is formed; the loading amount of the metal palladium is 0.2 wt%, and the molar ratio of Pd to Ag is 1: 1;
(3) naturally drying the obtained sample at the room temperature of 20-25 ℃ for 12h, drying the sample at the temperature of 70-100 ℃ for 12h by using an oven, roasting the sample at the temperature of 350 ℃ for 2-4h by using a tubular furnace, and reducing the sample at the temperature of 350 ℃ for 2h in the atmosphere of 10% hydrogen/nitrogen mixed gas to obtain the PdM/SOD catalyst impregnated with the PdM nano alloy particle active component;
(4) dispersing the PdM/SOD catalyst obtained in the step (3) in a silicon-aluminum sol solution, stirring at room temperature for 1-5h until the solution is uniform, transferring the solution to a water bath kettle at 50-90 ℃, and slowly stirring and evaporating to dryness; wherein the silicon-aluminum sol solution in the step is a precursor gel solution of the sodalite molecular Sieve (SOD) prepared in the step (1), and has the same component as the mixed solution D in the step (1);
(5) adding a proper amount of ethylene glycol into the sample obtained in the step (4), grinding the mixture for 0.5 to 1 hour by using a mortar to obtain uniform paste, transferring the paste into a 100mL hydrothermal kettle, placing the kettle in a 180 ℃ oven, and statically crystallizing the mixture for 48 hours;
(6) and (3) washing the sample obtained in the step (5) with deionized water until the pH value is neutral, drying in an oven at 100 ℃ for 12h, roasting in a muffle furnace at 350 ℃ for 2-4h (the heating rate is 2 ℃/min), and then fully reducing in a hydrogen atmosphere at 350 ℃ at 300 ℃ to obtain the PdM @ SOD catalyst for encapsulating the PdM nano-alloy particles.
The catalyst is used for testing the selective hydrogenation reaction performance of acetylene and is carried out according to the following steps:
(7) tabletting the prepared catalyst to obtain a 20-40 mesh granular catalyst for later use;
(8) weighing a proper amount of the prepared catalyst and a proper amount of quartz sand, uniformly mixing, filling into a fixed bed reactor, introducing a nitrogen-hydrogen mixed gas, and carrying out in-situ reduction on the catalyst at the temperature of 300-350 ℃ for 1h, wherein the volume ratio of hydrogen in the nitrogen-hydrogen mixed gas is 5-10%;
(9) after the reduction is finished, the bed temperature of the fixed bed reactor is controlled to be 100 ℃, the pressure is controlled to be 1bar, and the space velocity is 60000mL x g -1 *h -1 Wherein the molar ratio of acetylene to hydrogen is 1:10, the balance gas is nitrogen, the volume fraction of the acetylene gas flow rate in the total gas flow rate is 0.6%, and the total gas flow rate is 50 mL/min -1 。
The acetylene conversion, ethylene selectivity and ethylene yield were calculated according to the following formulas:
conversion rate:
and (3) selectivity:
yield:
the reaction product was analyzed on-line by gas chromatography, and the relationship between acetylene conversion, ethylene selectivity and ethylene yield and time is shown in table 1.
TABLE 1 acetylene conversion, ethylene selectivity and ethylene yield for different reaction times
| Reaction time (h) | Acetylene conversion (%) | Ethylene selectivity (%) | Ethylene yield (%) |
| 1 | 99.9 | 94.1 | 94.0 |
| 5 | 99.4 | 94.2 | 93.6 |
| 10 | 98.6 | 94.2 | 92.9 |
| 15 | 97.7 | 94.5 | 92.3 |
As can be seen from Table 1, the catalyst has higher activity and ethylene selectivity, and shows better stability.
FIG. 1 is an XRD representation of the PdM @ SOD sample prepared in example 1; the XRD shows that the diffraction peak position of the encapsulated catalyst is completely consistent with that of the sodalite SOD molecular sieve and is a typical SOD molecular sieve structure; the strongest diffraction peak is a peak near 24.5 degrees and is assigned as the crystal face diffraction peak of the SOD zeolite molecular sieve (211); there is no obvious PdM alloy diffraction peak, because the loading is low, and the particle size is small, there is very high dispersion.
FIG. 2 is a scanning electron microscope characterization of the PdM @ SOD sample prepared in example 1; the surface appearance of the PdM @ SOD encapsulated molecular sieve catalyst is formed by stacking small spherical particles with the size of about 100nm, the particles are uniform in size, small in particle size and large in specific surface area, and reaction sites and mass transfer rate are increased.
FIG. 3 is a transmission electron microscopy characterization of the PdM @ SOD sample prepared in example 1; as can be seen from the characterization result of the transmission electron microscope,PdM nano alloy particles in PdM @ SOD encapsulated molecular sieve catalystIs well encapsulated inside the molecular sieve,the particle size is 2-2.5The particles in the nm interval are uniform in size and are uniformly distributed in space.
FIG. 4 is a CO infrared characterization of PdM @ SOD samples prepared in example 1; the result shows that the PdM @ SOD encapsulated molecular sieve catalyst does not have an obvious CO adsorption signal, and the PdM/SOD catalyst impregnated on the outer surface of the SOD molecular sieve has a very strong CO adsorption signal; the reason is that CO gas molecules have larger diameter than SOD molecular sieve pore canals, so the CO gas molecules can not enter the molecular sieve to contact PdM nano alloy particle particles,further proves that the PdM nano alloy particles are all coatedIs well encapsulated in the SOD molecular sieve.
FIG. 5 is a test chart of the CO oxidation probe reaction of the PdM @ SOD sample prepared in example 1; further proves that PdM nano alloy particles in the PdM @ SOD encapsulated molecular sieve catalyst are encapsulated inside the SOD molecular sieve, and CO molecules are directly larger than SOD pore channels and cannot enter the SOD molecular sieve, so that the PdM nano alloy particles cannot catalyze CO conversion; the chip is mutually corresponding to CO adsorption infrared, and the existence of a packaging structure is further verified; compared with the PdM/SOD catalyst, the PdM nano alloy particles are exposed outside the molecular sieve, so that the CO conversion rate is very high.
FIG. 6 is a graph showing the performance test of the PdM @ SOD sample prepared in example 1; under the test conditions of example 1, the impregnated catalyst and the encapsulated catalyst both have very high acetylene conversion rates, but the ethylene and ethane selectivities are very different, the ethylene yield of the PdM @ SOD encapsulated catalyst is very high, the ethylene selectivity is about 94%, and the ethane selectivity is about 6%, which is relatively ideal catalyst performance; in contrast, although the PdM/SOD impregnated catalyst has a very high acetylene conversion rate, the ethylene selectivity is only about 20%, most of acetylene is excessively hydrogenated to generate ethane, and the ethylene selectivity of the catalyst is very poor; the performance comparison is obvious, and the necessity and the importance of the packaging structure for improving the selectivity of the olefin in the hydrogenation of the acetylene are fully illustrated. In a test of 20 hours, the encapsulated catalyst finds that the selectivity of ethylene is always kept between 92 and 94 percent, a small amount of byproduct ethane is generated, and the conversion rate of acetylene is not obviously reduced; overall, the stability is very good.
Example 2
The preparation and reaction were carried out by the method of example 1, except that the loading amount of metallic palladium in step (2) was 0.4 wt%.
Example 3
The preparation and reaction were carried out by the method of example 1, except that the loading amount of metallic palladium in step (2) was 0.1 wt%.
Example 4
The preparation and reaction were carried out by the method of example 1 except that the loading of metallic palladium in step (2) was 0.01 wt% and the molar ratio of Pd to Ag was 1: 5.
Example 5
The preparation and reaction were carried out by the method of example 1 except that the loading of metallic palladium in step (2) was 1 wt% and the molar ratio of Pd to Ag was 5: 1.
Example 6
The preparation and reaction were carried out by the method of example 1, differing only in that step (2) was: dissolving palladium nitrate, silver nitrate powder and copper nitrate in deionized water added with a small amount of dilute nitric acid to prepare a solution; soaking the sodalite molecular Sieve (SOD) powder obtained in the step (1) into the solution, wherein the volume of the solution is equal to the pore volume (1.0mL/g) of the sodalite molecular Sieve (SOD) as a carrier, and a saturated soaking state is formed; the loading amount of the metal palladium is 0.2 wt%, and the molar ratio of Pd, Ag and Cu is 1:0.5: 0.5.
Example 7
The preparation and reaction were carried out as in example 1, with the only difference that step (2) was: dissolving palladium nitrate, silver nitrate, copper nitrate and zinc nitrate in deionized water added with a small amount of dilute nitric acid to prepare a solution; soaking the sodalite molecular Sieve (SOD) powder obtained in the step (1) into the solution, wherein the volume of the solution is equal to the pore volume (1.0mL/g) of the sodalite molecular Sieve (SOD) as a carrier, and a saturated soaking state is formed; the supported amount of metallic palladium was 0.2 wt%, and the molar ratio of Pd, Ag, Cu, and Zn was 1:0.33:0.33: 0.33.
Example 8
The preparation and reaction were carried out by the method of example 1, differing only in that step (2) was: dissolving palladium nitrate, silver nitrate, copper nitrate, zinc nitrate and lead nitrate in deionized water added with a small amount of dilute nitric acid to prepare a solution; soaking the sodalite molecular Sieve (SOD) powder obtained in the step (1) into the solution, wherein the volume of the solution is equal to the pore volume (1.0mL/g) of the sodalite molecular Sieve (SOD) as a carrier, and a saturated soaking state is formed; the loading amount of the metal palladium is 0.2 wt%, and the molar ratio of Pd, Ag, Cu, Zn and Pb is 1:0.25:0.25:0.25: 0.25.
Example 9
The preparation and reaction were carried out by the method of example 1, except that the hydrothermal temperature in step (5) was 200 ℃ and the hydrothermal time was 24 hours.
Example 10
The preparation and reaction were carried out as in example 1, except that the space velocity in step (9) was 120000mL × g -1 *h -1 。
Example 11
The preparation and reaction were carried out by the method of example 1, except that the reaction temperature (fixed bed reactor bed temperature) in step (9) was 50 ℃.
Example 12
The preparation and reaction were carried out by the method of example 1, except that the reaction temperature (fixed bed reactor bed temperature) in step (9) was 150 ℃.
Example 13
The preparation and reaction were carried out as in example 1, except that the molar ratio of acetylene to hydrogen in step (9) was 1: 20.
Example 14
The preparation and reaction were carried out by the method of example 1, except that the molar ratio of acetylene to hydrogen in step (9) was 1: 5.
Example 15
The preparation and reaction were carried out by the method of example 1, except that the acetylene feed gas was replaced with either a propyne feed gas or a 1, 3-butadiene feed gas in step (9).
For the results of the above examples, the activity data of 10h after the reaction were compared to examine the influence of different parameters on the catalyst reaction performance.
(ii) effect of different space velocities on catalytic activity, see table 2; the reaction conditions were the same as in examples 10 and 11.
TABLE 2 acetylene conversion, ethylene selectivity and ethylene yield at different space velocities
From the above results, it can be seen that as the space velocity of the reaction increases, the conversion gradually decreases while the selectivity remains the same, and that a large space velocity indicates a large amount of reactants treated per unit time, which is of practical significance, and taken together, it can be found that the space velocity is 60000mL g -1 *h -1 Is optimal.
(ii) the effect of different reaction temperatures on catalytic activity, see table 3; the reaction conditions were the same as in examples 1, 11 and 12.
TABLE 3 acetylene conversion, ethylene selectivity and ethylene yield at different reaction temperatures
| Reaction temperature (. degree.C.) | Acetylene conversion (%) | Ethylene Selectivity (%) | Ethylene yield (%) |
| 50 | 27.5 | 95.2 | 31.9 |
| 100 | 62.4 | 94.4 | 58.9 |
| 150 | 87.8 | 94.2 | 82.7 |
From the above results, it can be seen that the conversion rate gradually increases and the selectivity is maintained substantially constant as the reaction temperature increases, probably because as the temperature increases, hydrogen enters the molecular sieve pore channels to contact the PdAg nano alloy particles, the overflow speed to the surface after activation is increased, the activated hydrogen species on the surface can be replenished more quickly, and therefore the conversion rate is gradually increased.
(III) Effect of different palladium contents (Pd: Ag molar ratio 1:1 unchanged) on catalytic activity, see Table 4; the reaction conditions were the same as in examples 1, 2 and 3.
TABLE 4 acetylene conversion, ethylene selectivity and ethylene yield for different palladium contents
| Palladium content (wt%) | Acetylene conversion (%) | Ethylene selectivity (%) | Ethylene yield (%) |
| 0.1 | 39.5 | 94.8 | 37.4 |
| 0.2 | 66.4 | 94.2 | 62.5 |
| 0.4 | 92.1 | 93.8 | 86.4 |
From the above results, it can be seen that the acetylene conversion rate is gradually increased and the selectivity is maintained at a constant level as the palladium loading is increased, which indicates that as the palladium content is increased, the sites for dissociating and activating hydrogen are increased, and thus, the conversion rate is greatly increased.
(V) Effect of different alloy compositions on catalytic activity, see Table 6; the reaction conditions were the same as in examples 1, 4, 5, 6, 7 and 8.
TABLE 6 acetylene conversion, ethylene selectivity and ethylene yield for different acetylene to hydrogen ratios
From the above results, it can be seen that the acetylene conversion varied with the palladium loading. The palladium content is increased, the acetylene conversion is increased, the palladium content is reduced, the acetylene conversion is reduced, and the ethylene selectivity is maintained at a constant level. Illustrating that palladium is critical to catalyst performance. The palladium can also be dispersed by adding various metals.
(vi) the effect of different hydrothermal conditions on catalytic performance, see table 7; the reaction conditions were the same as in examples 1 and 9.
TABLE 7 acetylene conversion, ethylene selectivity and ethylene yield for the synthesis of catalysts under different hydrothermal conditions
| Hydrothermal conditions | Acetylene conversion (%) | Ethylene selectivity (%) | Ethylene yield (%) |
| 180℃48h | 98.6 | 94.2 | 92.9 |
| 200℃24h | 99.1 | 94.1 | 93.2 |
From the above results, it can be seen that the performance of the catalyst is not affected basically by adjusting the hydrothermal conditions, and can be adjusted within a large temperature range, and the catalyst has high performance repeatability.
(VII) the performance data of the catalyst used for selective hydrogenation of propyne and selective hydrogenation of 1, 3-butadiene are shown in Table 7, and the reaction conditions are the same as in example 15.
Table 8, conversion, selectivity and yield data for propyne and 1, 3-butadiene for PdAg @ SOD catalyst;
therefore, the molecular sieve catalyst for packaging the Pd-based alloy can also be applied to the preparation of carbon-carbon double-bond olefin products by selective hydrogenation of carbon-carbon triple-bond alkynes such as propyne and the like and the preparation of mono-olefin by selective hydrogenation of diolefins such as 1, 3-butadiene and the like, has very high butene selectivity, and can be suitable for a catalytic system for preparing mono-olefin by selective hydrogenation of diolefins.
Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make various changes and modifications within the spirit and scope of the present invention without departing from the spirit and scope of the appended claims.
Claims (7)
1. A molecular sieve catalyst for packaging Pd-based alloy is characterized by comprising a sodalite molecular sieve, wherein PdM nano alloy particles are packaged In the sodalite molecular sieve, and M In the PdM nano alloy particles is at least one of Cu, Ag, Au, Zn, Sn, In, Ga, Pb and Bi; the mass percentage of Pd in the molecular sieve catalyst is 0.01-1%, and the molar ratio of Pd to M in the PdM nano-alloy particles is 1:5-5: 1; the sodalite molecular sieve is packaged with PdM nano alloy particles, and the size of the sodalite molecular sieve is 100 +/-30 nm;
the preparation method of the molecular sieve catalyst for packaging the Pd-based alloy comprises the following steps:
(1) preparing sodalite molecular sieve SOD;
(2) saturating and dipping the sodalite molecular sieve obtained in the step (1) with loaded Pd metal and M metal precursor;
(3) drying the sample obtained in the step (2), roasting at the temperature of 300-;
(4) dispersing the PdM/SOD catalyst obtained in the step (3) in a silicon-aluminum sol solution, stirring at room temperature until the solution is uniform, and slowly stirring and evaporating to dryness; the silicon-aluminum sol solution in the step (4) is the silicon-aluminum sol solution of the sodalite molecular sieve prepared in the step (1), and the silicon-aluminum ratio is 1: 1;
(5) adding ethylene glycol into the sample obtained in the step (4), grinding the mixture to be uniform paste, and carrying out hydrothermal reaction at the temperature of 180-;
(6) and (3) washing the sample obtained in the step (5) to be neutral, drying, roasting at the temperature of 300-350 ℃ for 2-4h, and fully reducing in the hydrogen atmosphere at the temperature of 300-350 ℃ to obtain the PdM @ SOD catalyst for encapsulating the PdM nano-alloy particles.
2. The Pd-based alloy encapsulated molecular sieve catalyst as claimed in claim 1, wherein the PdM nano-alloy particles are PdAg nano-alloy particles, the mass percentage of Pd in the molecular sieve catalyst is 0.1-0.4wt%, and the molar ratio of Pd to Ag in the PdM nano-alloy particles is 1: 1.
3. The encapsulated Pd-based alloy molecular sieve catalyst of claim 1, wherein said sodalite molecular sieve of step (1) is prepared as follows: dissolving an aluminum source, a silicon source and sodium hydroxide in water, fully stirring to form a silicon-aluminum sol solution which is uniformly mixed, carrying out hydrothermal reaction on the solution at 100 ℃ for 12 hours, cooling, washing, drying and roasting to obtain the sodalite molecular sieve; the aluminum source takes one of boehmite, sodium metaaluminate, amorphous aluminum hydroxide powder and aluminum isopropoxide as a precursor, and the silicon source takes gas-phase silicon dioxide, water glass, silica sol, silica gel and amorphous SiO 2 One of the powders is a precursor.
4. Use of a molecular sieve catalyst encapsulating a Pd-based alloy according to any one of claims 1-3 in selective hydrogenation of acetylene.
5. The application of the Pd-based alloy encapsulated molecular sieve catalyst in the selective hydrogenation reaction of acetylene as claimed in claim 4, wherein the reaction temperature is 50-150 ℃, and the reaction space velocity is 6000-120000 mL-g -1 ·h -1 The molar ratio of acetylene to hydrogen is 1:5-1:20, and the volume fraction of the flow rate of acetylene gas in the total gas flow rate is 0.6%.
6. Use of a molecular sieve catalyst encapsulating a Pd-based alloy according to any one of claims 1 to 3 in selective hydrogenation of propyne.
7. Use of a molecular sieve catalyst encapsulating a Pd-based alloy according to any one of claims 1-3 in the selective hydrogenation of 1, 3-butadiene.
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