Titanium silicon molecular sieve solid gold catalyst and its preparation method and application

Abstract

The invention provides a titanium silicon molecular sieve immobilized gold catalyst and a preparation method and application thereof. The invention adopts an improved deposition-precipitation method, uses a volatile amine solution or ammonia water as a precipitant, and places the precipitant and a slurry containing a gold precursor solution and the titanium silicon molecular sieve separately. The amine solution or ammonia water slowly volatilizes into the slurry containing the gold precursor solution and the titanium silicon molecular sieve to realize the deposition of gold on the titanium silicon molecular sieve, thereby obtaining a catalyst precursor. The catalyst precursor is dried and activated to obtain a supported Au-Ti bifunctional catalyst. The preparation method improves the dispersion of gold particles and promotes the formation of defective Ti(OSi)3OH active sites in the titanium silicon molecular sieve, significantly improves the loading efficiency of gold, improves the generation rate of propylene oxide in a propylene hydrogenation reaction and the generation rate of acetone in a propane hydrogenation reaction, and simultaneously improves the selectivity of the target product and the hydrogen utilization efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and specifically relates to a titanium silicon molecular sieve solid-supported gold catalyst and a preparation method and application thereof. Background Art

[0002] Propylene oxide (PO) is the second largest propylene derivative after polypropylene, and is mainly used to produce chemical products such as polyether polyols, propylene glycol, and propylene carbonate. Among the many PO production processes, the direct epoxidation of propylene with H2 and O2 to synthesize PO has long been regarded as an ideal process for PO production because of its advantages such as cheap and readily available raw materials and green and environmentally friendly processes.

[0003] Acetone is one of the important chemical raw materials, mainly used as a solvent and for the production of methyl methacrylate (MMA), isopropanol, polycarbonate intermediate bisphenol A and other chemical products. In recent years, with the rapid development of the polycarbonate industry and the epoxy resin industry, the consumption of products such as bisphenol A and MMA has increased significantly, driving the continuous growth of the domestic acetone market demand. Compared with the current mainstream isopropylbenzene method, the new process of direct oxidation of propane to acetone in a hydrogen / oxygen atmosphere shows unique advantages: i) The production raw materials are propane, hydrogen and oxygen, which are cheap and easy to obtain; ii) The acetone selectivity is high and the atom economy is good; iii) The process is simple, the reaction is carried out in the gas phase, and no organic solvent is required.

[0004] At present, the catalyst used for the catalytic oxidation of propylene to produce PO and the catalytic oxidation of propane to produce acetone is a nano-gold catalyst immobilized on a titanium silicalite molecular sieve. Studies have found that this gold catalyst supported on a titanium silicalite molecular sieve is an Au-Ti bifunctional catalyst: the Au site catalyzes H2 and O2 to produce hydroperoxide species, which then diffuses to the Ti site to produce a Ti-OOH active intermediate, which catalyzes the oxidation of propylene or propane to produce PO and acetone, respectively.

[0005] Numerous studies have found that 4+ The type of site is an important factor affecting the catalytic performance of Au-Ti bifunctional catalysts. Studies have shown that the defective Ti in TS-1 4+ (e.g. Ti(OSi)3OH) is more effective than non-defective Ti in propylene epoxidation. 4+ (e.g. Ti(OSi)4) is more active. This suggests that the non-defective Ti 4+ Transfer to defect site Ti 4+It may be beneficial to the uniform deposition of gold and increase the Ti active sites, thereby improving the catalytic performance. In addition, the size of gold nanoparticles also has an important influence on the catalytic performance of Au-Ti bifunctional catalysts. Generally speaking, small-sized gold nanoparticles show higher activity in catalyzing the propylene hydrogen-oxygen reaction.

[0006] Studies have shown that the catalyst preparation method has a significant effect on the size of gold nanoparticles. Among the reported catalyst preparation methods, the deposition-precipitation method (DP method) is the most widely used method to uniformly disperse and fix gold nanoparticles on Ti-containing materials because it can 4- The species gradually hydrolyzes to [AuCl x (OH) 4-x ] - To effectively eliminate chlorine, thereby preventing the agglomeration of gold particles caused by chloride ions. However, the performance of Au-Ti bifunctional catalysts prepared by the traditional DP method is very sensitive to preparation parameters, and these preparation parameters include gold precursor concentration, pH, precipitant type, preparation temperature, preparation time, etc., involving many complicated factors, which brings great challenges to the controllable preparation and engineering scale-up of Au-Ti bifunctional catalysts. In addition, the gold loading efficiency of the traditional DP method is low, and the performance of the catalyst prepared by the traditional DP method is still a certain distance from industrial application. Although current studies have found that the DP Urea method (i.e., DPU method) using urea as a precipitant to prepare uncalcined titanium silicon molecular sieve TS-1 and TS-2 solid gold catalysts can achieve a very high gold loading efficiency (about 90%), the performance of the catalyst prepared by the DPU method is very sensitive to preparation parameters such as preparation time, urea / gold molar ratio, preparation temperature, especially preparation temperature, which also brings challenges to the engineering scale-up of the catalyst. In addition, the performance of the catalyst prepared by the DPU method is also a certain distance from industrial application. Therefore, further development and research are needed to prepare efficient titanium silicalite immobilized gold catalysts. Summary of the invention

[0007] The present invention aims at the shortcomings of the existing catalyst preparation methods and performance of the reaction of propylene hydrogenation to produce PO and the reaction of propane hydrogenation to produce acetone, and provides an improved DP method for the preparation of catalysts for the reaction of propylene hydrogenation to produce PO and the reaction of propane hydrogenation to produce acetone. The improved DP method can improve the dispersibility of gold particles and promote the formation of defective Ti(OSi)3OH active sites in titanium silicon molecular sieves. Compared with the Au-Ti bifunctional catalyst prepared by the traditional DP method and the DPU method using urea as a precipitant, the improved DP method has a gold loading efficiency close to 100%, and the prepared catalyst has a significant promoting effect on improving the reaction rate of propylene hydrogenation to produce PO and the reaction rate of propane hydrogenation to produce acetone, and can also significantly improve the selectivity and hydrogen efficiency of the target product (PO and acetone). The present invention not only clarifies a new preparation method of an efficient Au-Ti bifunctional catalyst for propylene / propane hydrogenation reaction, but also provides an effective solution for improving the catalytic activity of zeolite-supported gold nanocatalysts for other reactions.

[0008] The first aspect of the present invention provides a method for preparing a titanium silicalite-supported gold catalyst, which improves the existing DP method. The preparation method uses a volatile amine solution or ammonia water as a precipitant. The preparation process is not to add the precipitant directly to the slurry formed by mixing the gold precursor solution and the titanium silicalite according to the traditional deposition-precipitation method, but to place the precipitant and the slurry containing the gold precursor solution and the titanium silicalite separately in a closed container, and the amine solution or ammonia water slowly evaporates into the slurry containing the gold precursor solution and the titanium silicalite to achieve the deposition of gold on the titanium silicalite to obtain a catalyst precursor; the catalyst precursor is dried and activated to obtain a supported Au-Ti bifunctional catalyst.

[0009] The present invention is further configured such that the amine solution or ammonia water and the slurry containing the gold precursor solution and the titanium silicon molecular sieve can be placed in the same closed container, or the amine solution or ammonia water and the slurry containing the gold precursor solution and the titanium silicon molecular sieve can be placed in two different closed containers, and the two closed containers are connected by a pipeline. Specifically, the improved DP method preparation method comprises the following steps:

[0010] (1) adding a gold precursor solution and titanium silicon molecular sieve into a first open container, stirring to obtain a mixed slurry, and transferring the first open container into a first sealable container;

[0011] Alternatively, the gold precursor solution and the titanium silicon molecular sieve are directly added into the first sealable container, and stirred evenly to obtain a mixed slurry;

[0012] (2) adding the amine solution or aqueous ammonia into a second open container, placing the second open container into the first sealable container, and sealing the first sealable container;

[0013] Alternatively, the amine solution or aqueous ammonia is added to a second open container, the second open container is placed in a second sealable container, and the first sealable container is connected to the second sealable container through a pipeline, and the first sealable container is sealed with the second sealable container;

[0014] Alternatively, the amine solution or ammonia water is added into a second sealable container, the first sealable container is connected to the second sealable container through a pipeline, and the first sealable container is sealed with the second sealable container;

[0015] (3) The mixed slurry is placed under the sealed conditions of step (2) for a period of time, and the amine solution or ammonia water slowly evaporates into the mixed slurry to achieve the deposition of gold on the titanium silicon molecular sieve, thereby obtaining a catalyst precursor; the catalyst precursor is dried and activated to obtain a supported Au-Ti bifunctional catalyst.

[0016] The present invention is further configured such that water is added as a diluting solvent in step (1); preferably, the order of adding the materials is to add water, gold precursor solution, and titanium silicon molecular sieve in sequence.

[0017] The present invention is further configured that the titanium silicon molecular sieve described in step (1) is a titanium silicon molecular sieve conventionally used in the field of propylene hydroxide epoxidation to produce propylene oxide or propane hydroxide to produce acetone, including but not limited to Ti-SBA-15, Ti-MCM-41, Ti-MCM-48, Ti-MCM-36, Ti-MWW, Ti-MOR, Ti-Beta, Ti-TUD-1, TS-1, multi-stage pore TS-1, TS-2 and one or more titanium silicon molecular sieves of multi-stage pore TS-2; the titanium silicon molecular sieve can be a titanium silicon molecular sieve calcined at 150-1000°C, or a titanium silicon molecular sieve that has not been calcined and whose pores are blocked by a template.

[0018] The present invention is further configured such that the gold precursor used in the gold precursor solution described in step (1) has a general formula of MAuCl4, wherein M is H, Na, K, Cs, Li or NH4, and the gold precursor solution contains at least one gold precursor as described in the general formula; the solvent used in the gold precursor solution is one or a mixture of two or more of water, ethanol, and acetone.

[0019] The present invention is further configured that the amine solution described in step (2) is a volatile amine solution with an organic amine having a carbon number less than 7 as a solute component; the ammonia water and the amine solution use water as a solvent, or add some alcohol having a carbon number less than 5 as a solvent to water, or use all alcohol having a carbon number less than 5 as a solvent; the concentration of the ammonia water and the amine solution is not higher than 5wt%.

[0020] The present invention is further configured as follows: the mixed slurry described in step (3) can be stirred or not; the pH of the mixed slurry is 10-12; the gold in the mixed slurry is deposited on the titanium silicon molecular sieve, and the temperature for preparing the catalyst precursor is 5-50°C, preferably room temperature; the preparation time is 0.15-6h, preferably 3-6h; the catalyst precursor obtained after reaching the preparation time can be washed and filtered, or it can be not washed and filtered.

[0021] The present invention is further configured such that the drying method in step (3) is a drying method conventionally used in the field of catalyst preparation, preferably vacuum drying.

[0022] The present invention is further configured such that the activation method described in step (3) is that the catalyst precursor is treated at a certain temperature and in a certain atmosphere, the certain temperature range is 50-800°C, preferably 200-350°C, and more preferably 300-320°C; the atmosphere is a reducing atmosphere, an oxidizing atmosphere, or an inert atmosphere, and more than one atmosphere can be used for treatment, and the composition and sequence of the atmospheres are not limited.

[0023] The second aspect of the present invention provides a titanium silicalite immobilized gold catalyst prepared by the improved DP method as described above, which is a supported Au-Ti bifunctional catalyst.

[0024] The present invention is further configured such that the particle size of the nano-gold particles on the titanium silicon molecular sieve solid-supported gold catalyst obtained by the method is less than 10 nm, preferably less than 5 nm, and more preferably less than 2.5 nm.

[0025] The third aspect of the present invention provides an application of the above titanium silicon molecular sieve immobilized gold catalyst for the propylene hydroxoepoxidation reaction to produce PO and the propane hydrogenation reaction to produce acetone.

[0026] The present invention has the following beneficial effects:

[0027] (1) Compared with the conventional DPU method, the improved DP method for preparing supported Au-Ti bifunctional catalysts developed in the present invention can significantly enhance the dispersion of gold through the strong interaction between N and Au in the nitrogen-containing groups grafted on the surface of the molecular sieve, thereby obtaining a smaller and narrower Au particle size distribution, which is beneficial to increasing the generation rate of hydroperoxide species on the nanogold particles, thereby improving the activity of the catalyst.

[0028] (2) Compared with the traditional DP method and DPU method, the improved DP method developed in the present invention for preparing the supported Au-Ti bifunctional catalyst adopts a strong alkaline environment that is conducive to the hydrolysis of Ti-O-Si bonds to form more active defective Ti(OSi)3OH active sites, thereby improving the performance of the catalyst.

[0029] (3) The improved DP method developed by the present invention for preparing supported Au-Ti bifunctional catalysts introduces ammonia water or a volatile amine solution as a precipitant. During the deposition process, a positively charged gold-ammine complex is formed. When preparing the supported Au-Ti bifunctional catalyst, the surface of the titanium silicate molecular sieve is negatively charged. The strong interaction between the positively charged gold-ammine complex and the negatively charged surface of the titanium silicate molecular sieve makes the catalyst prepared by the improved DP method show a gold loading efficiency close to 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a scanning transmission electron microscopy image (HAADF-STEM) of the catalyst prepared in Example 1;

[0031] Figure 2 This is a scanning transmission electron microscopy image (HAADF-STEM) of the catalyst prepared in Comparative Example 1;

[0032] Figure 3 The catalyst precursor prepared in Example 1 and Comparative Example 1 29 Si NMR spectrum ( 29 Si NMR);

[0033] Figure 4 The ultraviolet spectrum (UV-Vis) of the catalyst precursor prepared in Example 1;

[0034] Figure 5 The ultraviolet spectrum (UV-Vis) of the catalyst precursor prepared in Comparative Example 1;

[0035] Figure 6 Comparison of the generation rate of PO by catalytic hydrogenation of propylene by the catalyst prepared in Example 1 and Comparative Example 1;

[0036] Figure 7 The production rates of acetone produced by catalyzing propane hydrogenation by the catalysts prepared in Example 1 and Comparative Example 1 were compared. DETAILED DESCRIPTION

[0037] The technical scheme of the present invention is described clearly and completely below in conjunction with specific embodiments. It should be understood that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention. The experimental methods in the following embodiments that do not specify specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight, and room temperature refers to a temperature of 20-30°C.

[0038] Example 1

[0039] Au-Ti bifunctional catalyst was prepared using chloroauric acid as a precursor, uncalcined TS-1 (i.e., TS-1-B) as a carrier, and ammonia water as a precipitant. The steps are as follows:

[0040] (1) Mix 1 g TS-1-B, 40 mL water, 1.00 mL chloroauric acid solution (1.10 mg Au / ml) were sequentially added into a quartz beaker (100ml) and mixed and stirred for 5min to obtain a suspension; the suspension was transferred into a sealed glass desiccator with a diameter of 18cm; a small beaker (10mL) containing 8mL of ammonia water (2wt%) was fixed on the side wall of the sealed glass desiccator; the suspension was vigorously stirred for 6h at room temperature, and the pH value of the suspension was measured to be 10.6; the solid and the liquid were separated and washed by centrifugation, and the obtained solid was vacuum dried at room temperature.

[0041] (2) The dried solid was placed in a fixed bed reactor, and the temperature was increased from room temperature to 300°C at a rate of 1.5°C / min for 2 h in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.11 wt%.

[0042] Example 2

[0043] Au-Ti bifunctional catalyst was prepared using chloroauric acid as precursor, TS-1-B as carrier and ammonia water as precipitant. The steps are as follows:

[0044] (1) Mix 1 g TS-1-B, 40 mL water, 1.00 mL chloroauric acid solution (1.10 mg Au / ml) were sequentially added into a quartz beaker (100ml) and mixed and stirred for 5min to obtain a suspension; the suspension was transferred into a sealed glass desiccator with a diameter of 18cm, and a small beaker (10mL) containing 8mL of ammonia water (2wt%) was fixed on the side wall of the sealed glass desiccator; the suspension was vigorously stirred at room temperature for 6h, and the pH value of the suspension was measured to be 10.6; the solid and the liquid were separated and washed by centrifugation, and the obtained solid was vacuum dried at room temperature.

[0045] (2) The dried solid was placed in a fixed bed reactor and reduced for 2 h at a rate of 1.5°C / min from room temperature in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to 320°C to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.11 wt%.

[0046] Example 3

[0047] Au-Ti bifunctional catalyst was prepared using chloroauric acid as precursor, TS-1-B as carrier, and ammonia / ethanol solution as precipitant. The steps are as follows:

[0048] (1) Mix 1 g TS-1-B, 40 mL water, 0.83 mL chloroauric acid solution (1.10 mg Au / ml) are sequentially added into a quartz beaker (100ml) and mixed and stirred for 5min to obtain a suspension; the suspension is transferred into a sealed glass desiccator with a diameter of 18cm, and a small beaker (10ml) containing 6ml ammonia water / ethanol solution (3 wt%) is fixed on the side wall of the sealed glass desiccator, that is, the precipitant uses NH3 as solute and part of ethanol is added to water as solvent; the suspension is vigorously stirred at room temperature for 6h, and the pH value of the suspension is measured to be 10.7; the solid and the liquid are separated and washed by centrifugation, and the obtained solid is vacuum dried at room temperature.

[0049] (2) The dried solid was placed in a fixed bed reactor, and the temperature was increased from room temperature to 300°C at a rate of 1.5°C / min for 2 h in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.09 wt%.

[0050] Example 4

[0051] Au-Ti bifunctional catalyst was prepared using chloroauric acid as precursor, TS-1-B as carrier, and ethylamine aqueous solution as precipitant, and the steps are as follows:

[0052] (1) Mix 1 g TS-1-B, 40 mL water, 1.00 mL chloroauric acid solution (1.10 mg Au / ml) were sequentially added into a quartz beaker (100ml) and mixed and stirred for 5min to obtain a suspension; the suspension was transferred into a sealed glass desiccator with a diameter of 18cm, and a small beaker (10ml) containing 8ml of ethylamine aqueous solution (3wt%) was fixed on the side wall of the sealed glass desiccator; the suspension was vigorously stirred at room temperature for 6h, and the pH value of the suspension was measured to be 10.9; the solid and the liquid were separated and washed by centrifugation, and the obtained solid was vacuum dried at room temperature.

[0053] (2) The dried solid was placed in a fixed bed reactor, and the temperature was increased from room temperature to 300°C at a rate of 1.5°C / min for 2 h in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.11 wt%.

[0054] Example 5

[0055] Au-Ti bifunctional catalyst was prepared using chloroauric acid as precursor, TS-1-B as carrier, and ethylenediamine aqueous solution as precipitant, and the steps are as follows:

[0056] (1) Mix 1 g TS-1-B, 40 mL water, 1.00 mL chloroauric acid solution (1.10 mg Au / ml) were sequentially added into a quartz beaker (100ml) and mixed and stirred for 5min to obtain a suspension; the suspension was transferred into a sealed glass desiccator with a diameter of 18cm, and a small beaker (10ml) containing 8ml of ethylenediamine aqueous solution (3wt%) was fixed on the side wall of the sealed glass desiccator; the suspension was vigorously stirred at room temperature for 6h, and the pH value of the suspension was measured to be 10.4; the solid and the liquid were separated and washed by centrifugation, and the obtained solid was vacuum dried at room temperature.

[0057] (2) The dried solid was placed in a fixed bed reactor, and the temperature was increased from room temperature to 300°C at a rate of 1.5°C / min for 2 h in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.11 wt%.

[0058] Example 6

[0059] The Au-Ti bifunctional catalyst was prepared using sodium chloroaurate as a precursor, uncalcined TS-2 (i.e., TS-2-B) as a carrier, and ammonia water as a precipitant. The steps are as follows:

[0060] (1) Mix 1 g TS-2-B, 40 mL water, 1.00 mL sodium chloroaurate solution (1.10 mg Au / ml) were sequentially added into a quartz beaker (100ml) and mixed and stirred for 5min to obtain a suspension; the suspension was transferred into a sealed glass desiccator with a diameter of 18cm, and a small beaker (10ml) containing 8ml ammonia water (2wt%) was fixed on the side wall of the sealed glass desiccator; the suspension was vigorously stirred at room temperature for 6h, and the pH value of the suspension was measured to be 11.3; the solid and the liquid were separated and washed by centrifugation, and the obtained solid was vacuum dried at room temperature.

[0061] (2) The dried solid was placed in a fixed bed reactor, and the temperature was increased from room temperature to 300°C at a rate of 1.5°C / min for 2 h in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.11 wt%.

[0062] Example 7

[0063] Au-Ti bifunctional catalyst was prepared using chloroauric acid as precursor, TS-1 as carrier and ammonia water as precipitant. The steps are as follows:

[0064] (1) Mix 1 g TS-1, 20 mL water, and 1.55 mL chloroauric acid solution (1.10 mg Au / ml) and 1ml potassium nitrate solution (0.4M) are sequentially added into a quartz beaker (100ml), mixed and stirred for 5min to obtain a suspension; the suspension is transferred into a sealed glass desiccator with a diameter of 18cm, and a small beaker (10mL) containing 8mL ammonia water (5wt%) is fixed on the side wall of the sealed glass desiccator; the suspension is vigorously stirred at room temperature for 3h, and the pH value of the suspension is measured to be 11.2; the solid and the liquid are separated and washed by centrifugation, and the obtained solid is vacuum dried at room temperature.

[0065] (2) The dried solid was placed in a fixed bed reactor, and the temperature was raised from room temperature to 200° C. at a rate of 0.5° C. / min at a flow rate of 35 mL / min in a reaction atmosphere of oxygen: hydrogen: propylene: nitrogen = 1:1:1:7 (volume ratio) to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.17 wt %.

[0066] Example 8

[0067] Au-Ti bifunctional catalyst was prepared using chloroauric acid as precursor, Ti-SBA-15 as carrier and ammonia water as precipitant. The steps are as follows:

[0068] (1) Mix 1g Ti-SAB-15, 38mL water, and 1.65mL chloroauric acid solution (1.10mg Au / ml) and 1 ml of sodium nitrate solution (0.4M) are sequentially added into a quartz beaker (100ml), mixed and stirred for 5 minutes to obtain a suspension; the suspension is transferred to a sealed glass desiccator with a diameter of 18cm, and a small beaker (10ml) containing 8ml of ammonia water (4wt%) is fixed on the side wall of the sealed glass desiccator; the suspension is vigorously stirred at room temperature for 4 hours, and the pH value of the suspension is measured to be 11.0; the solid and the liquid are separated and washed by centrifugation, and the obtained solid is vacuum dried at room temperature.

[0069] (2) The dried solid was placed in a fixed bed reactor and reduced for 2 h at a rate of 1.5°C / min from room temperature to 300°C in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.18 wt%.

[0070] Example 9

[0071] Au-Ti bifunctional catalyst was prepared using chloroauric acid as precursor, TS-1-B as carrier and ammonia water as precipitant. The steps are as follows:

[0072] (1) Mix 1 g TS-1-B, 40 mL water, and 0.65 mL chloroauric acid solution (1.10 mg Au / ml) were sequentially added into a quartz beaker (100ml) and mixed and stirred for 5min to obtain a suspension; the suspension was transferred into a sealed glass desiccator with a diameter of 18cm, and a small beaker (10ml) containing 8ml ammonia water (2wt%) was fixed on the side wall of the sealed glass desiccator; the suspension was vigorously stirred at room temperature for 6h, and the pH value of the suspension was measured to be 10.8; the solid and the liquid were separated and washed by centrifugation, and the obtained solid was vacuum dried at room temperature.

[0073] (2) The dried solid was placed in a fixed bed reactor and reduced for 2 h at a rate of 1.5°C / min from room temperature in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to 320°C to obtain a supported Au-Ti bifunctional catalyst. The gold loading was determined to be 0.07 wt%.

[0074] Comparative Example 1

[0075] Au-Ti bifunctional catalyst was prepared by DPU method using chloroauric acid as precursor and TS-1-B as carrier. The steps are as follows:

[0076] (1) 1 g TS-1-B, 40 mL water, and 1.14 mL chloroauric acid solution (1.10 mg Au / ml) were sequentially added to a beaker, mixed and stirred to obtain a suspension, and 0.09 g urea was added to the suspension; the suspension was heated to 90° C. in a water bath and maintained for 6 h; the solid and liquid were separated and washed by centrifugation, and the obtained solid was vacuum dried at room temperature.

[0077] (2) The dried solid was placed in a fixed bed reactor, and the temperature was increased from room temperature to 300°C at a rate of 1.5°C / min for 2 h in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.11 wt%.

[0078] Comparative Example 2

[0079] Using sodium chloroaurate as a precursor and TS-2-B as a carrier, the Au-Ti bifunctional catalyst was prepared by the DPU method. The steps are as follows:

[0080] (1) 1 g TS-2-B, 40 mL water, and 1.2 mL sodium chloroaurate solution (1.10 mg Au / ml) were sequentially added to a beaker, mixed and stirred to obtain a suspension, and 0.09 g urea was added to the suspension; the suspension was heated to 90° C. in a water bath and maintained for 6 h; the solid and liquid were separated and washed by centrifugation, and the obtained solid was vacuum dried at room temperature.

[0081] (2) The dried solid was placed in a fixed bed reactor, and the temperature was increased from room temperature to 300°C at a rate of 1.5°C / min for 2 h in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.11 wt%.

[0082] Comparative Example 3

[0083] Au-Ti bifunctional catalyst was prepared by DP method using sodium chloroaurate as precursor, TS-1 as carrier and potassium hydroxide as precipitant. The steps are as follows:

[0084] (1) 1 g TS-1, 20 mL water, and 10 mL sodium chloroaurate solution (9.000 mg Au / ml) were added to a beaker in sequence, mixed and stirred to obtain a suspension, which was stirred at room temperature for 8 h. 0.1 M KOH solution was added dropwise to the suspension to maintain the pH of the suspension between 7 and 7.5. The solid and liquid were separated and washed by centrifugation, and the obtained solid was dried under vacuum at room temperature.

[0085] (2) The dried solid was placed in a fixed bed reactor, and the temperature was raised from room temperature to 200° C. at a rate of 0.5° C. / min at a flow rate of 35 mL / min in a reaction atmosphere of oxygen: hydrogen: propylene: nitrogen = 1:1:1:7 (volume ratio) to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.15 wt %.

[0086] Comparative Example 4

[0087] Au-Ti bifunctional catalyst was prepared by DP method using sodium chloroaurate as precursor, Ti-SBA-15 as carrier and sodium hydroxide as precipitant. The steps are as follows:

[0088] (1) 1 g Ti-SBA-15, 20 mL water, and 10 mL sodium chloroaurate solution (9.000 mg Au / ml) were added to a beaker in sequence, mixed and stirred to obtain a suspension, which was stirred at room temperature for 8 h. 0.1 M NaOH solution was added dropwise to the suspension to maintain the pH of the suspension between 7 and 7.5. The solid and liquid were separated and washed by centrifugation, and the obtained solid was dried under vacuum at room temperature.

[0089] (2) The dried solid was placed in a fixed bed reactor and reduced for 2 h at a rate of 1.5°C / min from room temperature to 300°C in a reaction atmosphere of hydrogen:nitrogen = 0.36:0.64 (volume ratio) at a flow rate of 50 mL / min to obtain a supported Au-Ti bifunctional catalyst. The gold loading was measured to be 0.16 wt%.

[0090] Example 10

[0091] The catalysts prepared in Examples 1-9 and Comparative Examples 1-4 were used to evaluate their catalytic performance in the reaction of propylene hydro-epoxidation to prepare propylene oxide. The propylene gas phase epoxidation reaction was carried out in a fixed bed reactor at atmospheric pressure. The reaction atmosphere was composed of propylene: hydrogen: oxygen: nitrogen = 1:1:1:7 (volume ratio) and the space velocity was 14000 mL·h -1 ·g cat -1 The outlet product was analyzed by gas chromatography. The catalytic results are shown in Table 1.

[0092] Table 1

[0093]

[0094] Combination Figure 1-6 As shown, the relevant physicochemical properties and catalytic performance of Example 1 and Comparative Example 1 are compared. As shown in Figures 1-2, the HAADF-STEM images of the catalysts prepared in Example 1 and Comparative Example 1 show that the average particle size of the nano-gold particles in the catalyst of Example 1 is 1.6±0.3nm, which has the advantages of narrow particle size distribution of nano-gold particles, small particles, and uniform distribution. The present invention can significantly improve the dispersibility of gold particles through the improved DP method. Figure 3-5 The nuclear magnetic resonance and ultraviolet spectra show that the present invention promotes the formation of defective Ti(OSi)3OH sites in the titanium-containing carrier by an improved DP method. Compared with the catalyst prepared by the traditional DPU method, the catalyst obtained by the improved DP method significantly improves the PO generation rate in the propylene hydrogen oxidation reaction, while maintaining a high PO selectivity and hydrogen efficiency. The catalyst preparation method proposed in the present invention has a simple process, high gold loading efficiency, a wide range of applicability to the carrier, and is easy to industrially scale up. The present invention not only illustrates a new method for synthesizing an efficient Au-Ti bifunctional catalyst in the propylene hydrogen oxidation reaction, but also provides a new idea for improving the catalytic activity of zeolite-loaded gold nanocatalysts for other reactions.

[0095] Embodiment 11

[0096] The catalytic performance of the catalysts prepared in Examples 1, 9 and Comparative Example 1 was evaluated in the reaction of hydrogenation of propane to produce acetone. The propane hydrogenation reaction was carried out in a fixed bed reactor at atmospheric pressure. The reaction atmosphere was propane: hydrogen: oxygen: nitrogen = 1:1:1:7 (volume ratio), and the space velocity was 14000 mL·h -1 ·g cat -1 The reaction temperature was 200°C, and the outlet product was analyzed by gas chromatography. The catalytic results are shown in Table 2.

[0097] Table 2

[0098]

[0099] Combination Figure 1-5 and Figure 7As shown, the relevant physicochemical properties and catalytic performance comparison of Example 1 and Comparative Example 1, the present invention can significantly improve the dispersibility of gold particles and promote the formation of defective Ti(OSi)3OH sites in the titanium-containing carrier through the improved DP method. Compared with the Au-Ti bifunctional catalyst prepared by the traditional DPU method, the Au-Ti catalyst obtained by the improved DP method significantly improves the formation rate of acetone in the propane hydrogenation reaction, and also has high acetone selectivity and hydrogen efficiency. The present invention not only illustrates a new method for synthesizing a highly efficient Au-Ti bifunctional catalyst in the propane hydrogenation reaction to produce acetone, but also provides a reference for improving the catalytic activity of zeolite-supported gold nanocatalysts for other reactions.

Claims

1. A method for preparing a titanium silicon molecular sieve immobilized gold catalyst, characterized in that: The preparation method adopts a volatile amine solution or ammonia water as a precipitant, and the precipitant and a slurry containing a gold precursor solution and a titanium silicon molecular sieve are placed separately, and the amine solution or ammonia water volatilizes into the slurry containing the gold precursor solution and the titanium silicon molecular sieve to achieve the deposition of gold on the titanium silicon molecular sieve, thereby obtaining a catalyst precursor; the catalyst precursor is dried and activated to obtain a supported Au-Ti bifunctional catalyst; The pH of the slurry containing the gold precursor solution and the titanium silicon molecular sieve is 10-12; The gold precursor used in the gold precursor solution has a general formula of MAuCl4, wherein M=H, Na, K, Cs, Li or NH4, and the gold precursor solution contains at least one gold precursor as described in the general formula; The amine solution is a volatile amine solution with an organic amine having a carbon number less than 7 as a solute; the concentration of the precipitant is not higher than 5 wt%.

2. The preparation method according to claim 1, characterized in that: The amine solution or ammonia water and the slurry containing the gold precursor solution and the titanium silicon molecular sieve are placed in the same closed container, or placed in two different closed containers, and the two closed containers are connected through a pipeline.

3. The preparation method according to claim 1, characterized in that: The titanium silicon molecular sieve is selected from one or more of Ti-SBA-15, Ti-MCM-41, Ti-MCM-48, Ti-MCM-36, Ti-MWW, Ti-MOR, Ti-Beta, Ti-TUD-1, TS-1, multi-level pore TS-1, TS-2 and multi-level pore TS-2; the titanium silicon molecular sieve is 150-1000 o C calcined titanium silicon molecular sieve, or titanium silicon molecular sieve that is not calcined and whose pores are blocked by a template agent.

4. The preparation method according to claim 1, characterized in that: The precipitant uses water as solvent, or adds some alcohol with carbon number less than 5 as solvent to water, or uses alcohol with carbon number less than 5 as solvent.

5. The preparation method according to claim 1, characterized in that: The temperature for preparing the catalyst precursor is 5-50 o C; the time for preparing the catalyst precursor is 0.15-6 h; the drying method is vacuum drying.

6. The preparation method according to claim 1, characterized in that: The temperature for preparing the catalyst precursor is room temperature; the time for preparing the catalyst precursor is 3-6 h; and the drying method is vacuum drying.

7. The preparation method according to claim 1, characterized in that: The activation method is that the catalyst precursor is heated to 50-800 o C is treated in one or more of a reducing atmosphere, an oxidizing atmosphere and an inert atmosphere.

8. The preparation method according to claim 1, characterized in that: The activation method is that the catalyst precursor is heated at 200-350 o C is treated in one or more of a reducing atmosphere, an oxidizing atmosphere and an inert atmosphere.

9. The preparation method according to claim 1, characterized in that: The activation method is that the catalyst precursor is heated at 300-320 o C is treated in one or more of a reducing atmosphere, an oxidizing atmosphere and an inert atmosphere.

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