Low-tungsten-loaded platinum-tungsten bimetallic catalyst prepared based on solid-phase grinding method as well as preparation method and application of low-tungsten-loaded platinum-tungsten bimetallic catalyst

Abstract

The invention belongs to the technical field of deoxidation and hydrogenation catalysis, and provides a low-tungsten-loaded platinum-tungsten bimetallic catalyst prepared based on a solid-phase grinding method and a preparation method and application of the low-tungsten-loaded platinum-tungsten bimetallic catalyst. The preparation method of the catalyst comprises the following steps: loading metal platinum on a silicon dioxide carrier by adopting an impregnation method, and drying to obtain a catalyst precursor; mixing and grinding the catalyst precursor and solid tungsten salt to obtain mixed powder, and drying to obtain catalyst raw powder; and finally, roasting the catalyst raw powder at high temperature in an air atmosphere to prepare the required platinum-tungsten bimetallic catalyst. And in the prepared catalyst, the mass ratio of the active metal platinum is 1.0%-5.0%, and the mass ratio of the metal tungsten is 0.4%-4.0%. When the platinum-tungsten bimetallic catalyst prepared by the method is used in a reaction for preparing 1, 3-propylene glycol through glycerol hydrogenolysis, the yield of 1, 3-propylene glycol is ensured while the tungsten loading capacity is remarkably reduced; and the preparation process is simple, convenient to operate and beneficial to industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of deoxygenation hydrogenation catalysis, and specifically relates to a platinum-tungsten bimetallic catalyst with low tungsten loading prepared by a solid phase grinding method, and a preparation method and application thereof. Background Art

[0002] With the rapid growth of the biodiesel industry, the supply of glycerol as a byproduct has increased significantly, and new and efficient conversion methods are urgently needed. In a hydrogen environment, glycerol can be converted into high-value-added 1,3-propylene glycol and 1,2-propylene glycol, of which 1,3-propylene glycol is not only an important raw material for antifreeze, plasticizers, detergents, preservatives and emulsifiers, but is also widely used in food, cosmetics and pharmaceutical industries.

[0003] Glycerol molecules contain three hydroxyl groups, of which the hydrogenolysis of the primary hydroxyl group can produce 1,2-propylene glycol, while the hydrogenolysis of the secondary hydroxyl group can produce 1,3-propylene glycol. However, since the two terminal hydroxyl groups in the glycerol molecule are close to the secondary hydroxyl groups, a steric hindrance is formed, which hinders the effective binding of the secondary hydroxyl groups to the catalytic active sites. In addition, the three C-OH bonds in the glycerol molecule are very similar in activation energy and proton affinity, which makes it very difficult to selectively break the secondary hydroxyl groups while retaining the two terminal hydroxyl groups. Therefore, although the production of 1,3-propylene glycol and 1,2-propylene glycol from biodiesel byproduct glycerol has good economic prospects, the key challenge of current technology still lies in the development of catalysts. At present, the catalytic systems for preparing 1,3-propylene glycol by hydrogenolysis of glycerol mainly include Pt-W system and Ir-Re system, while the catalyst of the Ir-Re catalytic system is very expensive, and the content of 1,2-propylene glycol and 1-propanol in the product is high, and additional acid needs to be added to maintain the life of the catalyst. In comparison, the Pt-W system catalyst has a relatively high selectivity for 1,3-propylene glycol, and the catalyst has good stability and better industrial prospects.

[0004] The researchers found that the Pt-W interface formed by the W species and the metal Pt can form a unique Brønsted (B) acid under the action of hydrogen, which can further selectively activate the secondary -OH of glycerol, resulting in the formation of 1,3-propylene glycol. It is generally believed that the strength and quantity of the B acid produced by the metal-acid (Pt-W) bifunctional synergistic site directly affect the activity of glycerol hydrogenolysis. The degree of polymerization of the tungsten species on the interface determines the strength of the B acid on the interface. The higher the degree of polymerization, the weaker the acid strength and the weaker the hydrogenolysis ability (ACS Catal., 2020, 10, 15217-15226). In the process of sequentially impregnating PtW to prepare the catalyst using the traditional impregnation method, the first loaded platinum metal is distributed on the inner surface of the carrier pores in the form of nanoparticles, and then the tungsten precursor is deposited on the carrier surface and Pt nanoparticles during the impregnation and drying process of the tungsten precursor aqueous solution. During the subsequent calcination in a high-temperature oxidizing gas atmosphere, due to the strong metal-support interaction between Pt metal and W species (Appl. Catal. B: Environ. 2022, 307, 121207-121217), the tungsten precursor near the Pt nanoparticles will gradually grow from the bottom to the top and wrap the platinum nanoparticles. At the same time, the tungsten precursor deposited on the Pt nanoparticles will also chemically bond with the Pt particles, eventually forming a WO3@Pt interface in close contact at the atomic scale, such as Figure 1 shown.

[0005] However, this process has the following problems. First, the formation of a large number of WO3@Pt interface sites requires the introduction of a higher W loading during the impregnation process to increase the probability of species deposition on Pt nanoparticles, so as to increase the number of Pt-W interface sites of the catalyst after calcination. This causes a large amount of W metal to be deposited on the carrier and is not fully utilized. Second, since the selective hydrogenolysis of glycerol requires the synergistic effect of Pt and W, a large amount of W deposited on the surface of Pt will reduce the number of exposed Pt sites, thereby reducing the ability to dissociate H2 and slowing down the reaction rate. Third, due to the extremely high degree of polymerization of tungsten in soluble tungsten precursors (such as ammonium metatungstate and ammonium paratungstate), it is necessary to degrade it to low-polymerization WO3 at extremely high temperatures (900°C) (ChemCatChem. 2021, 13, 3695-3705). This results in a high degree of polymerization of tungsten at the final tightly contacted WO3@Pt interface, insufficient B acid strength at the interface site, and a slow hydrogenolysis rate.

[0006] A large number of studies have shown that the activity of hydrogenolysis catalysts can be improved by increasing the number of B acid sites and improving the strength of B acid. The current existing technology uses relatively complex means to prepare composite oxide carriers (mainly modified alumina), strengthen the anchoring effect between the carrier and Pt to improve the dispersion of Pt, increase the interface sites of Pt-W to improve the reaction activity, or introduce a third metal to the Pt and WOx The interface is electronically and structurally modified, and the B acid strength of the Pt-W interface is regulated to improve the reaction activity. For example, in patent document CN106883098B, the active components Pt and La are impregnated step by step on a tungsten oxide-alumina composite carrier, with the mass fractions of Pt and WO3 being 5% and 20% respectively. Under the optimal conditions, the glycerol conversion rate is 70% and the 1,3-propylene glycol selectivity is 55%. In patent document CN105688906 B, platinum nanoparticles are assembled in the pores of mesoporous alumina by ethylene glycol reduction combined with solvent evaporation induced self-assembly strategy, and finally the catalyst is prepared by impregnation method to load silicotungstic acid. Under the optimal conditions, the glycerol conversion rate is 67.4% and the 1,3-propylene glycol selectivity is 30.0%. In patent document CN106944050B, a composite carrier WO3-Al2O3-SiO2 is prepared by precipitation method, and Pt particles are loaded on the carrier by impregnation method. The mass fractions of Pt and WO3 are 4% and 15%, respectively. Under the optimal conditions, the glycerol conversion rate is 36.2% and the selectivity of 1, 3-propylene glycol is 45.4%. In patent document CN 112570039 B, a sodium borohydride aqueous solution is used as a reducing agent to pretreat the PtW bimetallic catalyst. The mass fractions of Pt and WO3 are 2% and 98%, respectively. Under the optimal conditions, the glycerol conversion rate is 72.0% and the selectivity of 1, 3-propylene glycol is 50.3%. In patent document CN111389397B, Re-Pt-WOx-ZrO2 / Al2O3 was prepared by introducing metal additive Re to regulate PtW bimetallic catalyst. The mass fractions of Pt and WO3 were 1% and 10%, respectively. Under the optimal conditions, the glycerol conversion rate was 38.6% and the selectivity of 1,3-propylene glycol was 31.6%. In patent document CN116764632A, Pt-Au / WOx / Al2O3 catalyst was synthesized by microwave irradiation enhanced impregnation method. Under the optimal conditions, the glycerol conversion rate was 40.9% and the selectivity of 1,3-propylene glycol was 46.12%. In patent application document CN114762825A, a new WO3-Al2O3 composite carrier was synthesized by the sol-gel method-dynamic crystallization method, and the active components were loaded on the carrier to prepare Pt-Au / WO3-Al2O3 catalyst. The mass fractions of Pt and WO3 were 2% and 7.5%, respectively. Under the optimal conditions, the glycerol conversion rate was 81.0% and the 1, 3-propylene glycol selectivity was 54.8%.

[0007] Although the use of the above-mentioned composite oxide carrier and the introduction of the third metal can improve the performance of the catalyst, this also makes the catalyst preparation process very complicated, significantly increases the production cost, and thus limits the industrial application prospects of this technology. In addition, a large number of patent inventions use high W loading to fully dilute the Pt metal to build as many Pt-W interfaces as possible. Therefore, the use of a simpler and more effective catalyst preparation method to develop a more efficient catalyst, while significantly reducing the loading of metal W and reducing production costs, will help promote the high-value utilization of glycerol by-products, thereby enhancing the economic and environmental benefits of the entire bioenergy industry chain. Summary of the invention

[0008] In view of the above problems, the present invention provides a platinum-tungsten bimetallic catalyst with low tungsten loading prepared by solid phase grinding method, and its preparation method and application. The platinum-tungsten bimetallic catalyst prepared by the preparation method of the present invention can greatly reduce the loading amount of metal W, and at the same time obtain excellent 1,3-propylene glycol yield; and simplify the preparation steps of the catalyst.

[0009] To achieve the above object, the technical solution of the present invention is as follows:

[0010] A method for preparing a platinum-tungsten bimetallic catalyst with low tungsten loading based on a solid phase grinding method comprises the following steps:

[0011] S1. Using an impregnation method, metal platinum is loaded onto a silica carrier, and after drying, a catalyst precursor is obtained;

[0012] S2, mixing the catalyst precursor obtained in step S1 with a solid tungsten source, and grinding the mixture to a particle size of 50 mesh or less to obtain a mixed powder, which is the catalyst raw powder;

[0013] S3, calcining the catalyst powder obtained in step S2 at a high temperature in an air atmosphere with a relative humidity of ≤40%RH, wherein the calcination conditions are: 350-550°C for 0.5-4h in an air atmosphere to obtain a platinum-tungsten bimetallic catalyst for producing 1,3-propylene glycol by hydrogenolysis of glycerol;

[0014] Among them, in the platinum-tungsten bimetallic catalyst, the mass proportion of metal platinum is 1.0%~5.0%, and the mass proportion of metal tungsten is 0.4%~4.0%.

[0015] The technical solution of the present invention is based on the "self-limiting saturation" reconstruction phenomenon of soluble tungsten species generated during the glycerol hydrogenolysis reaction at the Pt-support interface, and aims to construct a Pt-low-polymerization degree tungsten interface with better hydrogenolysis performance.

[0016] like Figure 2As shown, in the technical solution of the present invention, the metal Pt precursor solution is first loaded onto the SiO2 carrier by an impregnation method, and after drying, a Pt / SiO2 catalyst precursor with highly dispersed Pt particles is obtained. Subsequently, it is physically mixed with a small amount of solid tungsten source powder. It is worth noting that even if the catalyst precursor and the tungsten source powder are fully mixed, the Pt / SiO2 catalyst precursor and the tungsten source are still two separate phases. Therefore, Figure 2 As shown in (a), Pt and W are isolated at the atomic scale. The present invention controls the formation of the Pt-W interface by further calcination. Figure 2 As shown in (b), during the high-temperature calcination process, the Pt particles move and collide under the "lubrication" of the hydroxyl groups on the surface of the inert SiO2 carrier, and some Pt ​​atoms migrate to the surface of the WO3 particles to form a primary Pt@WO3 interface. Figure 2 As shown in (c), the calcined catalyst is directly used for glycerol hydrogenolysis reaction. H2 dissociates into active H species on the Pt atoms at the primary Pt@WO3 interface and overflows to the WO3 interface, promoting the reduction of WO3 to soluble HWO with oxygen vacancies. x Species. Then, Figure 2 As shown in (d), these HWOx species with oxygen vacancies are dissolved in water in the form of ions and captured by unsaturated Pt sites (such as Pt / SiO2 interface), undergoing "self-limiting saturation" reconstruction to form a unique secondary Pt-low-polymerization WOx interface, which significantly enhances the B acid strength and thus improves the hydrogenolysis efficiency of the catalyst.

[0017] Therefore, through the approach of "isolation-migration-dissolution-capture-reconstruction", the technical solution of the present invention can construct an efficient secondary Pt-low-polymerization degree WOx interface, which can not only significantly reduce the loading amount of metal W and improve the utilization efficiency of metal W, but also reduce the polymerization degree of WOx and increase the B acid strength of the Pt-W interface site, thereby improving the hydrogenolysis efficiency. In addition, since the soluble HWOx species with oxygen vacancies are only captured by the unsaturated Pt sites (such as the Pt / SiO2 interface), a large number of Pt sites are not covered by W species, the utilization rate of Pt metal is improved, the rate of dissociation of H2 is enhanced, and the hydrogenolysis process is further enhanced.

[0018] Based on the above principle and the catalyst preparation and application principle in the prior art, there are significant differences. In the catalyst preparation process of the present invention, the selection of the carrier, the powder particle size during the preparation process, and the process conditions and other parameters are strictly controlled, so as to achieve an unexpectedly good catalytic effect while simplifying the preparation process. Under the parameter conditions defined by the present invention, the prepared catalyst can achieve a significant reduction in the amount of W used and has a high 1,3-propylene glycol yield.

[0019] The present invention is further configured such that, in the platinum-tungsten bimetallic catalyst, the mass proportion of metal platinum is 1.5% to 4.0%, and the mass proportion of metal tungsten is 0.6% to 2.0%.

[0020] The present invention is further configured such that in step S1, the platinum salt solution is added dropwise to the silica carrier and immersed for 1 to 12 hours, and then placed at 50 to 120° C. and dried for 6 to 16 hours to obtain the catalyst precursor.

[0021] The present invention is further configured such that the platinum salt is selected from one or more of chloroplatinic acid, tetraammine platinum nitrate, and platinum nitrate.

[0022] The present invention is further configured such that, in step S2, the tungsten source powder is selected from one or more of tungsten oxide, ammonium metatungstate or ammonium paratungstate.

[0023] The present invention is further configured such that, in step S2, the particle size of the mixed powder is 50-500 mesh. The grinding in step S2 can be performed by a physical mixing method commonly used in the art, such as mortar grinding, dry ball milling, high-speed stirring, etc.

[0024] The present invention is further configured such that, in step S3, before the catalyst raw powder is roasted by the roasting equipment, dry air is used to replace the air in the roasting equipment to reduce the relative humidity in the roasting equipment.

[0025] The present invention is further configured such that, in step S3, the relative humidity of the air atmosphere in the roasting equipment is 5-35%RH.

[0026] The present invention is further configured such that in step S3, the calcination conditions are: 350-550° C. in air atmosphere, calcination for 0.5-4.0 h. Preferably, the calcination temperature is 400-500° C., calcination for 0.5-2.0 h.

[0027] The present invention also provides a platinum-tungsten bimetallic catalyst prepared according to the above preparation method.

[0028] The present invention also provides an application of the above-mentioned platinum-tungsten bimetallic catalyst for catalyzing the reaction of selective hydrogenolysis of glycerol to produce 1,3-propylene glycol.

[0029] The present invention is further configured such that the conditions for the reaction of catalyzing the selective hydrogenolysis of glycerol to produce 1,3-propylene glycol are: the mass ratio of the catalyst to glycerol is 1% to 10%, the reaction temperature is 100 to 160°C, and the hydrogen pressure ranges from 4 to 9 MPa.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The technical solution of the present invention creatively physically mixes the catalyst precursor powder and the tungsten source powder directly, and obtains a platinum-tungsten bimetallic catalyst by regulating the particle size of the mixed powder and controlling the subsequent process conditions; it achieves a significant reduction in the loading amount of the catalyst W. When the mass proportion of metal platinum is 1.0% to 4.0% and the mass proportion of metal tungsten is 0.4% to 4.0%, and when there is no need to add a third metal additive, the catalyst exhibits an unexpected catalytic effect and obtains a high 1,3-propylene glycol yield.

[0032] (2) The technical solution of the present invention constructs a platinum-tungsten bimetallic catalyst with a Pt-rich and low-polymerization degree tungsten interface through the "self-limiting saturation" reconstruction phenomenon of soluble tungsten species at the Pt-carrier interface. The catalyst has an extremely high hydrogenolysis rate while retaining a high selectivity for 1,3-propylene glycol. At the same time, the catalyst does not require pre-reduction treatment and can be directly used in the hydrogenolysis reaction, which can significantly improve the economic efficiency of the process of producing 1,3-propylene glycol by glycerol hydrogenolysis.

[0033] (3) The technical solution of the present invention simplifies the preparation process of the platinum-tungsten bimetallic catalyst, making the operation simpler and the processing conditions milder, which is more conducive to promotion in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the platinum-high-polymer tungsten interface of the PtW catalyst prepared by the traditional sequential impregnation method.

[0035] Figure 2 The schematic diagram of the interface formation of platinum-low-polymerization-degree tungsten of the PtW catalyst prepared by the preparation method of the present invention is shown. DETAILED DESCRIPTION

[0036] The present invention is further described below by way of examples. The following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0037] The present invention provides a method for preparing a low-tungsten-loaded platinum-tungsten bimetallic catalyst based on a solid phase grinding method, comprising the following steps:

[0038] S1. Using an impregnation method, metal platinum is loaded onto a silica carrier, and after drying, a catalyst precursor is obtained;

[0039] S2, physically mixing the catalyst precursor obtained in step S1 with a solid tungsten source, and grinding the mixture to a particle size of ≤50 mesh to obtain a mixed powder, which is the catalyst raw powder;

[0040] S3, calcining the catalyst powder obtained in step S2 at a high temperature in an air atmosphere with a relative humidity of ≤40%RH, wherein the calcination conditions are: 350-550°C for 0.5-4h in an air atmosphere to obtain a platinum-tungsten bimetallic catalyst for producing 1,3-propylene glycol by hydrogenolysis of glycerol;

[0041] Among them, in the platinum-tungsten bimetallic catalyst, the mass proportion of active metal platinum is 1.0%~5.0%, and the mass proportion of metal tungsten is 0.4%~4.0%.

[0042] In an embodiment of the present invention, in the platinum-tungsten bimetallic catalyst, the mass proportion of the active metal platinum is 1.5% to 4.0%, for example, the mass proportion of the active metal platinum can be 1.5%, 2.0%, 3.0%, or 4.0%.

[0043] In an embodiment of the present invention, in the platinum-tungsten bimetallic catalyst, the mass proportion of metal tungsten is 0.6%~2.0%. For example, the mass proportion of metal tungsten can be 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, and 2.0%.

[0044] In the embodiments of the present invention, the silica carrier can be homemade or directly purchased.

[0045] In an embodiment of the present invention, in step S1, a platinum salt solution is added dropwise into a silica carrier and impregnated for 1 to 12 hours, and then dried at 50 to 120° C. for 6 to 16 hours to obtain the catalyst precursor.

[0046] In an embodiment of the present invention, the platinum salt is selected from one or more of chloroplatinic acid, tetraammine platinum nitrate, and platinum nitrate.

[0047] In an embodiment of the present invention, in step S2, the tungsten source is selected from one or more of tungsten oxide, ammonium metatungstate or ammonium paratungstate.

[0048] In an embodiment of the present invention, in step S2, the particle size of the mixed powder is 50-500 mesh, preferably 50-200 mesh. The physical mixing process in step S2 can be carried out by a method commonly used in the art, such as mortar grinding, dry ball milling, high-speed stirring, etc.

[0049] In an embodiment of the present invention, in step S3, before the catalyst raw powder is roasted by the roasting equipment, air with lower relative humidity is used to replace the air in the roasting equipment to reduce the relative humidity in the roasting equipment.

[0050] In an embodiment of the present invention, in step S3, the relative humidity of the air atmosphere in the roasting equipment is 5-35%RH.

[0051] In an embodiment of the present invention, in step S3, the calcination conditions are: in air atmosphere, 350-550° C., calcination for 0.5-4.0 h. Preferably, the calcination temperature is 400-500° C., calcination for 0.5-2.0 h, and the calcination time is, for example, 0.5 h, 1 h, 1.5 h or 2 h.

[0052] The present invention also provides a platinum-tungsten bimetallic catalyst prepared according to the above preparation method.

[0053] The present invention also provides an application of the above-mentioned platinum-tungsten bimetallic catalyst for catalyzing the reaction of selective hydrogenolysis of glycerol to produce 1,3-propylene glycol.

[0054] In an embodiment of the present invention, the conditions for the reaction of catalyzing the selective hydrogenolysis of glycerol to produce 1,3-propylene glycol are: the mass ratio of catalyst to glycerol is 1% to 10%, the reaction temperature is 100 to 160° C., and the hydrogen pressure ranges from 4 to 9 MPa. Preferably, the stirring rate is 300 to 800 rpm, the reaction temperature is 120 to 140° C., and the hydrogen pressure ranges from 4 to 8 MPa.

[0055] The technical solution of the present invention is further described in detail below using specific embodiments.

[0056] Example 1

[0057] The preparation method of the platinum-tungsten bimetallic catalyst comprises the following steps: 0.5333g of hexahydrated chloroplatinic acid is dissolved in 9.6000g of deionized water, the obtained solution is added dropwise to 4.8000g of silica carrier, aged for 12h, and dried in an oven at 120°C for 6h to obtain a catalyst precursor. The catalyst precursor is physically mixed with 0.0588g of WO3 powder, ground with a mortar until the powder is fully mixed, and sieved with a 50-mesh sieve to obtain a catalyst raw powder. Then the obtained catalyst raw powder is placed in a muffle furnace, and the air in the muffle furnace is replaced by pure air, the relative humidity of the pure air is 30%RH, and then calcined at 400°C in an air atmosphere for 1h to obtain the target catalyst platinum-tungsten bimetallic catalyst. After testing, the platinum mass fraction in the platinum-tungsten bimetallic catalyst is: 4.0 wt%, and the tungsten mass fraction is: 1.0 wt%.

[0058] Example 2

[0059] The preparation method of the platinum-tungsten bimetallic catalyst is the same as that of Example 1, except that the amount of WO3 powder used is different, and other conditions are the same. In this embodiment, 0.0235 g of WO3 powder is mixed with the catalyst precursor. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4.0 wt%, and the mass fraction of tungsten is 0.4 wt%.

[0060] Example 3

[0061] The preparation method of the platinum-tungsten bimetallic catalyst is the same as that of Example 1, except that the amount of WO3 powder used is different, and other conditions are the same. In this embodiment, 0.0353 g of WO3 powder is mixed with the catalyst precursor. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4.0 wt%, and the mass fraction of tungsten is 0.6 wt%.

[0062] Example 4

[0063] The preparation method of the platinum-tungsten bimetallic catalyst is the same as that of Example 1, except that the amount of WO3 powder used is different, and other conditions are the same. In this embodiment, 0.0470 g of WO3 powder is mixed with the catalyst precursor. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4.0 wt%, and the mass fraction of tungsten is 0.8 wt%.

[0064] Example 5

[0065] The preparation method of the platinum-tungsten bimetallic catalyst is the same as that of Example 1, except that the amount of WO3 powder used is different, and other conditions are the same. In this embodiment, 0.0706 g of WO3 powder is mixed with the catalyst precursor. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4.0 wt%, and the mass fraction of tungsten is 1.2 wt%.

[0066] Example 6

[0067] The preparation method of the platinum-tungsten bimetallic catalyst is the same as that of Example 1, except that the amount of WO3 powder used is different, and other conditions are the same. In this embodiment, 0.0823 g of WO3 powder is mixed with the catalyst precursor. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4.0 wt%, and the mass fraction of tungsten is 1.4 wt%.

[0068] Example 7

[0069] The preparation method of the platinum-tungsten bimetallic catalyst is the same as that of Example 1, except that the amount of WO3 powder used is different, and other conditions are the same. In this embodiment, 0.1176 g of WO3 powder is mixed with the catalyst precursor. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4.0 wt%, and the mass fraction of tungsten is 2.0 wt%.

[0070] Example 8

[0071] The preparation method of the platinum-tungsten bimetallic catalyst is the same as that of Example 1, except that the amount of WO3 powder used is different, and other conditions are the same. In this embodiment, 0.2352 g of WO3 powder is mixed with the catalyst precursor. After testing, the mass fraction of platinum and the mass fraction of tungsten in the prepared platinum-tungsten bimetallic catalyst are 4.0 wt% and 4.0 wt%.

[0072] Example 9

[0073] The difference from Example 1 is that in this example, 0.0714 g of ammonium paratungstate powder is used as the tungsten salt, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4% and the mass fraction of tungsten is 1%.

[0074] Example 10

[0075] The difference from Example 1 is that in this example, 0.0673 g of ammonium metatungstate powder is used as the tungsten salt, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4% and the mass fraction of tungsten is 1%.

[0076] Embodiment 11

[0077] The difference from Example 1 is that in this example, 0.4000 g of tetraammine platinum nitrate is used as the platinum salt, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4% and the mass fraction of tungsten is 1%.

[0078] Example 12

[0079] The difference compared with Example 1 is that in this embodiment, a 200-mesh screen is used to screen the mixed powder after the catalyst precursor and the tungsten salt are mixed and ground, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4% and the mass fraction of tungsten is 1%.

[0080] Example 13

[0081] Compared with Example 1, the difference is that the calcination temperature is different. In this embodiment, the calcination temperature is 500°C, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4%, and the mass fraction of tungsten is 1%.

[0082] Embodiment 14

[0083] Compared with Example 1, the difference is that the calcination temperature is different. In this embodiment, the calcination temperature is 600°C, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 4%, and the mass fraction of tungsten is 1%.

[0084] Embodiment 15

[0085] Compared with Example 1, the difference is that the amount of platinum salt used is different. In this embodiment, 0.1333g of chloroplatinic acid hexahydrate is used, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is: 1%, and the mass fraction of tungsten is: 1%. The reaction product is tested and analyzed, and the catalytic reaction results are shown in Table 1.

[0086] Example 16

[0087] Compared with Example 1, the difference is that the amount of platinum salt used is different. In this embodiment, 0.2000g of hexahydrate chloroplatinic acid is used, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 1.5%, and the mass fraction of tungsten is 1%. The reaction product is tested and analyzed, and the catalytic reaction results are shown in Table 1.

[0088] Embodiment 17

[0089] Compared with Example 1, the difference is that the amount of platinum salt used is different. In this example, 1.0667 g of chloroplatinic acid hexahydrate is used, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the prepared platinum-tungsten bimetallic catalyst is 8%, and the mass fraction of tungsten is 1%.

[0090] Comparative Example 1

[0091] This comparative example adopts a conventional sequential impregnation method to prepare a platinum-tungsten bimetallic catalyst, and the specific process is as follows: 0.5333g of hexahydrate chloroplatinic acid is dissolved in 9.6000g of deionized water, and the resulting solution is added dropwise to 4.8000g of silica carrier, left to stand for 12h, and dried in an oven at 120°C for 6h. 0.0673g of ammonium metatungstate is dissolved in 9.6000g of deionized water, and the resulting solution is added dropwise to the carrier after the above treatment, left to stand for 12h, and dried in an oven at 120°C for 6h. The resulting powder is placed in a muffle furnace, and the air in the muffle furnace is replaced by pure air purge, and the relative humidity of the pure air is 30%RH, and the resulting powder is roasted at 400°C in an air atmosphere for 1h. After testing, the platinum mass fraction of the finally obtained platinum-tungsten bimetallic catalyst is 4.0%, and the tungsten mass fraction is 1.0%.

[0092] Comparative Example 2

[0093] Compared with Comparative Example 1, the difference is that the impregnation order of the platinum precursor and the tungsten precursor is changed. The specific process is: 0.0673g of ammonium metatungstate is dissolved in 9.6000g of deionized water, and the resulting solution is added dropwise to 4.8000g of silica carrier, left to stand for 12h, and dried in a 120°C oven for 6h. 0.5333g of hexahydrated chloroplatinic acid is dissolved in 9.6000g of deionized water, and the resulting solution is added dropwise to the carrier after the above treatment, left to stand for 12h, and dried in a 120°C oven for 6h. The obtained powder is placed in a muffle furnace, and the air in the muffle furnace is replaced by pure air purge, the relative humidity of the pure air is 30%RH, and the obtained powder is roasted at 400°C in an air atmosphere for 1h. After testing, the platinum mass fraction of the finally obtained platinum-tungsten bimetallic catalyst is 4.0%, and the tungsten mass fraction is 1.0%.

[0094] Comparative Example 3

[0095] Ir commonly used in the art is selected as the catalyst active metal, and the preparation method includes the following steps: 0.5333g of chloroiridic acid is dissolved in 9.5000g of deionized water, and the resulting solution is added dropwise to 4.8000g of silica carrier, left to stand for 12h, and dried in an oven at 120°C for 6h. The above powder is mixed with 0.0588g of WO3 powder, ground with a mortar until the powder is fully mixed, left to stand for 12h, and dried in an oven at 120°C for 6h. The resulting powder is placed in a muffle furnace, and the air in the muffle furnace is replaced by pure air purge, the relative humidity of the pure air is 30%RH, and the resulting powder is roasted at 400°C in an air atmosphere for 1h. After testing, the iridium mass fraction of the finally obtained tungsten bimetallic catalyst is 4.0% and the tungsten mass fraction is 1.0%.

[0096] Comparative Example 4

[0097] Compared with Example 1, the difference is that after the catalyst precursor and WO3 powder are physically mixed, no grinding treatment is performed, and the particle size of the obtained mixed powder is about 20 meshes, and the other conditions remain unchanged. After testing, the target catalyst finally obtained has a platinum mass fraction of 4% and a tungsten mass fraction of 1%. The reaction product is tested and analyzed, and the catalytic reaction results are shown in Table 1.

[0098] Comparative Example 5

[0099] Compared with Example 1, the difference is that the calcination atmosphere of the catalyst raw powder is different, the obtained catalyst raw powder is directly placed in the muffle furnace, there is no need to replace the air in the calcination device, the relative humidity of the air is detected to be 50%RH, and the catalyst is calcined at 400°C for 1h in the air atmosphere, and the other conditions remain unchanged. The target catalyst finally obtained by detection has a platinum mass fraction of 4% and a tungsten mass fraction of 1%.

[0100] Comparative Example 6

[0101] Compared with Example 1, the difference is that the calcination atmosphere in the muffle furnace is different. In this comparative example, the calcination is carried out in a nitrogen atmosphere, and the other conditions remain unchanged. After testing, the mass fraction of platinum in the target catalyst finally obtained is: 4%, and the mass fraction of tungsten is: 1%.

[0102] Comparative Example 7

[0103] Compared with Example 1, the difference is that the catalyst carrier is different. In this comparative example, commonly used Al2O3 is selected as the catalyst carrier to prepare a platinum-tungsten bimetallic catalyst with a platinum mass fraction of 4% and a tungsten mass fraction of 1%.

[0104] Catalyst performance evaluation

[0105] The performance of the platinum-tungsten bimetallic catalysts prepared in Examples 1 to 17 and Comparative Examples 1 to 7 was evaluated by the following method:

[0106] 0.10 g of the platinum-tungsten bimetallic catalyst prepared in each embodiment and comparative example was taken to convert glycerol in a 50 mL batch reactor. The mass concentration of the glycerol aqueous solution was 5%, and the weight of the glycerol aqueous solution was 10 g. The reaction temperature was 140° C., the hydrogen pressure was 8 MPa, and the reaction time was 8 h. The reaction products were detected and analyzed. The catalytic reaction results are shown in Table 1.

[0107] Table 1 Glycerol conversion and product selectivity under different catalyst preparation processes

[0108]

[0109] According to the reaction results of the above examples and comparative examples, it can be found that the PtW catalyst prepared by the technical solution of the present invention can significantly improve the activity of the glycerol hydrogenolysis catalyst by using a small amount of tungsten, and at the same time obtain a high 1,3-propylene glycol yield; while the catalyst prepared by the conventional impregnation method has a glycerol conversion rate far lower than that of the physical mixing method under the same evaluation conditions, that is, the PtW catalyst prepared by the physical mixing method has significant advantages over the traditional impregnation method. And according to the results in Table 1, it is found that the preparation method of the present invention exhibits poor catalytic performance when other commonly used metals are used as active components, such as Ir, which shows that the technical solution of the present invention has more outstanding applicability to the Pt-W catalyst system, which was not expected before the study.

[0110] Although the technical solution of the present invention simplifies the preparation process of the catalyst, and the preparation conditions are mild and easy to operate, in order to achieve excellent catalytic performance, it is necessary to impose more stringent requirements on the particle size of the mixed powder, the calcination atmosphere and humidity, and the selection of the carrier during the preparation process. After a lot of research, the technical solution of the present invention has realized the preparation of a platinum-tungsten bimetallic catalyst with a more simplified preparation method, and the platinum-tungsten bimetallic catalyst is applied to the reaction of glycerol hydrogenolysis to produce 1,3-propylene glycol, which can achieve an excellent catalytic effect with a significantly reduced tungsten loading compared to the prior art. In addition, the catalyst preparation process provided by the present invention is simple, the operation is simple, and the processing conditions are mild, which is more conducive to industrial application and promotion.

[0111] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a low tungsten-loaded platinum-tungsten bimetallic catalyst based on a solid phase grinding method, characterized in that: The steps include: S1. Using an impregnation method, metal platinum is loaded onto a silica carrier, and after drying, a catalyst precursor is obtained; S2, mixing the catalyst precursor obtained in step S1 with a solid tungsten source, and grinding them to a particle size of 50 mesh or less to obtain a mixed powder, which is the catalyst raw powder; S3, calcining the catalyst powder obtained in step S2 at a high temperature in an air atmosphere with a relative humidity of ≤40%RH, wherein the calcination conditions are: 350-550°C for 0.5-4h in an air atmosphere, to obtain a platinum-tungsten bimetallic catalyst with low tungsten loading for producing 1,3-propylene glycol by hydrogenolysis of glycerol; In the platinum-tungsten bimetallic catalyst, the mass proportion of metal platinum is 1.0% to 5.0%, and the mass proportion of metal tungsten is 0.4% to 4.0%.

2. The method for preparing a platinum-tungsten bimetallic catalyst with low tungsten loading based on a solid phase grinding method according to claim 1, characterized in that: In the platinum-tungsten bimetallic catalyst, the mass proportion of metal platinum is 1.5% to 4.0%, and the mass proportion of metal tungsten is 0.6% to 2.0%.

3. The method for preparing a platinum-tungsten bimetallic catalyst with low tungsten loading based on a solid phase grinding method according to claim 1, characterized in that: In step S1, a platinum salt solution is added dropwise into a silica carrier and impregnated for 1 to 12 hours, and then dried at 50 to 120° C. for 6 to 16 hours to obtain the catalyst precursor.

4. The method for preparing a low tungsten-loaded platinum-tungsten bimetallic catalyst based on a solid phase grinding method according to claim 3, characterized in that: The platinum salt is selected from one or more of chloroplatinic acid, tetraammine platinum nitrate, and platinum nitrate.

5. The method for preparing a platinum-tungsten bimetallic catalyst with low tungsten loading based on a solid phase grinding method according to claim 1, characterized in that: In step S2, the solid tungsten source is selected from one or more of tungsten oxide, ammonium metatungstate or ammonium paratungstate.

6. The method for preparing a platinum-tungsten bimetallic catalyst with low tungsten loading based on a solid phase grinding method according to claim 1, characterized in that: In step S2, the particle size of the mixed powder is 50-500 mesh.

7. The method for preparing a platinum-tungsten bimetallic catalyst with low tungsten loading based on a solid phase grinding method according to claim 1, characterized in that: In step S3, before using the calcination equipment to calcine the catalyst raw powder, dry air is used to replace the air in the calcination equipment to reduce the relative humidity in the calcination equipment.

8. A platinum-tungsten bimetallic catalyst with low tungsten loading obtained according to the method described in any one of claims 1 to 7.

9. Use of the platinum-tungsten bimetallic catalyst as claimed in claim 8, characterized in that: Used to catalyze the selective hydrogenolysis of glycerol to produce 1,3-propylene glycol.

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