Method for preparing esterification reaction catalyst by using waste vanadium-titanium-based SCR (Selective Catalytic Reduction) catalyst, esterification reaction catalyst and application of esterification reaction catalyst

Abstract

The invention discloses a method for preparing an esterification reaction catalyst by using a waste vanadium-titanium-based SCR (Selective Catalytic Reduction) catalyst, the esterification reaction catalyst and application of the esterification reaction catalyst. According to the method, the waste vanadium-titanium-based SCR catalyst reacts with thionyl chloride and alcohol substances to synthesize the catalyst product capable of efficiently catalyzing esterification reaction, and the catalyst product is efficient in catalytic performance which is equivalent to that of commercially available tetrabutyl titanate. The method for recycling the waste vanadium-titanium-based SCR catalyst is simple in process and short in flow, does not need to use substances such as strong acid and strong alkali, not only reduces the treatment cost of the waste vanadium-titanium-based SCR catalyst, but also improves the additional value of the waste vanadium-titanium-based SCR catalyst, and has better environmental protection and economic significance.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste catalyst recycling, and specifically relates to a method for preparing an esterification reaction catalyst by utilizing waste vanadium-titanium-based SCR catalysts, and the catalyst obtained by the method and its application. Background Art

[0002] Nitrogen oxides produced by coal combustion can cause serious air pollution, so denitrification catalysts are needed to treat the exhaust gas before it can be discharged. At present, high-temperature selective catalytic reduction (SCR) denitrification technology is mature and widely used. SCR denitrification catalysts have the advantages of high denitrification efficiency in the range of 300-400°C, good dust resistance, and low manufacturing cost. Among them, vanadium-titanium-based catalysts are the most widely used. However, denitrification catalysts will gradually lose their activity during use. In the early stage of reduced activity, regeneration can be used to increase the activity. However, as the use cycle increases, such as after 3-4 years, the catalyst strength and activity cannot meet the application requirements even after regeneration. At this time, the catalyst can only be scrapped. Scrap disposal methods include direct landfill, which not only pollutes the environment, but also wastes the rare metal components.

[0003] To address this issue, the industry has conducted extensive research. For example, CN201210023122.3 and CN201310467454.5 generally utilize multiple processes, including alkaline leaching, acid leaching, and precipitation, to extract the oxides. These processes present long and costly preparation processes, require extensive use of strong acids and bases, and result in difficult wastewater treatment, as well as insufficient economic and environmental value. Therefore, the industry is continuously researching how to achieve the comprehensive utilization of discarded vanadium-titanium-based SCR catalysts through shorter production processes, lower costs, and higher added value. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, the present invention provides a method for preparing an esterification catalyst using discarded vanadium-titanium SCR catalysts, as well as the catalyst prepared by this method and its application. Specifically, the present invention utilizes discarded vanadium-titanium SCR catalysts to react with thionyl chloride and alcohols to synthesize a catalyst product that can be used to efficiently catalyze esterification reactions.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing an esterification reaction catalyst using a waste vanadium-titanium SCR catalyst, comprising the following steps:

[0007] S1: A waste vanadium-titanium-based SCR catalyst that has been deashed and crushed to 100-120 mesh is reacted with thionyl chloride in the presence of coke at 160-180°C. After the reaction is complete, excess thionyl chloride is removed to obtain a chlorinated product;

[0008] S2: The chlorinated product obtained in step S1 is subjected to an esterification reaction with an alcohol at 110-115° C. After the reaction is completed, the target catalyst product is obtained after separation and purification.

[0009] In this invention, the waste vanadium-titanium-based SCR catalyst refers to the mainstream commercially used high-temperature denitration catalyst, V2O5·WO3 / TiO2, which has been discarded after long-term use due to a decrease in catalyst strength and / or activity. The waste vanadium-titanium-based SCR catalyst consists of TiO2 as a carrier component, accounting for 85-90wt%; V2O5 as a catalyst active component, accounting for 1.5-2.5wt%; and WO3 as a catalyst additive, accounting for 7-12wt%. The remainder is impurities such as dust.

[0010] In some embodiments, the alcohol substance includes n-propanol, n-butanol, and n-pentanol, preferably n-butanol.

[0011] In some embodiments, in the method of preparing an esterification reaction catalyst using a waste vanadium-titanium SCR catalyst of the present invention, the ratio of the waste vanadium-titanium-based SCR catalyst, dichloride and alcohol substances is: (30-35): (250-280): (150-170) by mass, and the amount of coke used is 1.5-2wt% of the waste vanadium-titanium-based SCR catalyst.

[0012] In some embodiments, in step S1, in order to make the chlorination reaction as complete as possible and control higher reaction energy efficiency, a secondary chlorination method can be adopted, including the following steps:

[0013] S1-1: A primary chlorination reaction is carried out in a sealed autoclave at 160-165°C in the presence of coke, using a discarded vanadium-titanium-based SCR catalyst that has been ash-removed and crushed to 100-120 mesh. The reaction is then cooled to 60-65°C and the by-product sulfur dioxide gas generated in the autoclave is vented.

[0014] S1-2: Seal the autoclave again and heat it to 175-180°C for secondary chlorination reaction; when the titanium dioxide content in the reaction system is lower than 0.5wt%, cool it down to 60-65°C again and vent the by-product sulfur dioxide gas generated in the autoclave.

[0015] In a specific embodiment, in step S1, the chlorination product includes titanium tetrachloride (TiCl4), vanadium trichloride (VCl3) and tungsten chloride (WCl).

[0016] In a specific embodiment, in step S1, the sulfur dioxide gas generated as a by-product of the chlorination reaction is recovered and processed, for example, the discharged sulfur dioxide gas is absorbed by ammonia water containing 10-20 wt% concentration to obtain ammonium sulfate as a by-product.

[0017] In some embodiments, in step S1, the method of removing excess thionyl chloride can be performed by distilling the reactants, and the distillation temperature is 90-95°C.

[0018] In some embodiments, in step S2, to maximize the esterification reaction, an inert gas (e.g., nitrogen) may be introduced into the reaction system to expel the generated hydrogen chloride gas. In some embodiments, the generated hydrogen chloride gas is recovered, for example, by absorption in a 10% sodium carbonate solution.

[0019] In some embodiments, in step S2, when the content of titanium tetrachloride in the reaction system is less than 0.5 wt%, the reaction is determined to be complete, and the chlorinated product is esterified to obtain a mixture of tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten.

[0020] In some embodiments, the reactions in steps S1 and S2 are performed while stirring to ensure that the reaction system is uniformly mixed.

[0021] In some embodiments, in step S2, the separation and purification can be performed by the following steps:

[0022] (1) Cooling the reaction product to 50-55°C, adding a decolorizing agent and performing decolorization treatment for 20-30 minutes;

[0023] (2) filtering and removing insoluble matter in the reaction system to obtain a filtrate containing a mixture of butanol, tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten;

[0024] (3) removing excess n-butanol from the filtrate to obtain the final catalyst product.

[0025] Preferably, in step (1), activated clay containing 0.3-0.5% of the mass of n-butanol is used as the decolorizing agent.

[0026] Preferably, in step (3), the excess n-butanol in the filtrate can be removed by vacuum distillation, and the conditions of the vacuum distillation are: vacuum degree: -0.095 MPa to -0.098 MPa, and distillation temperature is 100-105°C.

[0027] In a second aspect, the present invention provides an esterification reaction catalyst prepared by the method described in the first aspect.

[0028] In a third aspect, the present invention provides use of the esterification reaction catalyst described in the second aspect in a catalytic esterification reaction.

[0029] Beneficial effects

[0030] The present invention utilizes waste vanadium-titanium-based SCR catalysts to react with thionyl chloride and alcohols to synthesize a catalyst product that can be used in highly efficient catalytic esterification reactions. This method not only reduces the disposal cost of waste vanadium-titanium-based SCR catalysts but also increases their added value, offering excellent environmental and economic benefits.

[0031] The process for recycling the waste vanadium-titanium-based SCR catalyst of the present invention is simple and has a short process, and does not require the use of substances such as strong acid and strong base.

[0032] The esterification reaction catalyst obtained by the invention has high catalytic performance and is comparable to that of commercially available tetrabutyl titanate. DETAILED DESCRIPTION

[0033] In order to better understand the technical solution provided by the present invention, the present invention is described in detail below through specific implementation methods, but the claims of the present invention are not limited to these embodiments. The embodiments only provide some experimental conditions for achieving the purpose of this technical invention.

[0034] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, and methods in the art.

[0035] Reagents and sources:

[0036] Waste vanadium-titanium SCR catalyst V2O5·WO3 / TiO2: from Huangshan Huizhou District Juneng Heating Co., Ltd., of which TiO2 accounts for 87wt%, V2O5 accounts for 2.1wt%, WO3 accounts for 8.5wt%, and the remainder is dust and other impurities.

[0037] Coke was purchased from Lingshou County Henglin Mineral Products Co., Ltd.

[0038] Tetrabutyl titanate: industrial grade, purchased from Tianchang Tianchen Chemical Additive Oil Factory.

[0039] The present invention will be further described below with reference to the embodiments, but the present invention is not limited thereto.

[0040] Example 1 Preparation of esterification catalyst using discarded vanadium-titanium SCR catalyst

[0041] A: Use a blower to remove the dust on the surface of the discarded vanadium-titanium SCR catalyst, then crush it into 100-120 mesh and set aside;

[0042] B: 30 parts by weight of the waste vanadium-titanium SCR catalyst powder crushed in step A, 1.9% by weight of the coke catalyst of the waste vanadium-titanium SCR catalyst, and 255 parts by weight of thionyl chloride were added to the autoclave 1 in sequence. Stirring was started, the autoclave was sealed, and the temperature was raised to 163° C. to carry out a primary chlorination reaction.

[0043] C: Sampling and testing the titanium dioxide content in the autoclave 1. When the titanium dioxide content reaches 9 wt%, the temperature is lowered to 62°C. The vent valve of the autoclave 1 is slowly opened to vent the gas to discharge sulfur dioxide gas, a byproduct of the chlorination reaction in the autoclave, to promote the chlorination reaction. The discharged sulfur dioxide gas is absorbed by a tank filled with 17 wt% ammonia water to obtain ammonium sulfate as a byproduct.

[0044] D: When there is almost no gas discharged from the vent valve of the high-pressure reactor 1 and the pressure in the reactor returns to normal pressure, it means that the sulfur dioxide is basically discharged. At this time, the high-pressure reactor 1 is sealed again and the temperature is raised to 176°C for secondary chlorination reaction;

[0045] E: Sampling and testing the titanium dioxide content in the autoclave 1. When the titanium dioxide content is less than 0.5 wt %, indicating that the secondary chlorination reaction has been completed, the temperature is lowered to 62° C. again and the sulfur dioxide gas is evacuated for the second time. The discharged sulfur dioxide gas is still absorbed by a tank filled with 12 wt % ammonia water to obtain ammonium sulfate by-product;

[0046] F: After the evacuation is completed, the contents of the autoclave 1 are placed in a reactor 2 equipped with a distillation apparatus, the stirring of the reactor 2 is started, and the temperature is gradually raised to 95° C. to distill and remove excess thionyl chloride, and the recovered thionyl chloride is used in the next batch; after no obvious thionyl chloride is distilled out (less than 1 drop in 20 seconds), indicating that the excess thionyl chloride in the reactor has been completely removed, 153 parts by weight of n-butanol is added, and the temperature is raised to 113° C. to carry out an esterification reaction, while continuously blowing nitrogen into the reactor to discharge hydrogen chloride gas generated by the reaction; the discharged hydrogen chloride gas is absorbed and treated with a 10% sodium carbonate solution;

[0047] G: Sampling and testing the contents of reactor 2. When the titanium tetrachloride content is less than 0.5 wt %, the esterification reaction of the chloride in the reactor is essentially complete, resulting in a mixture of tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten. The reaction mixture is then cooled to 52° C., and decolorized for 25 min by adding activated clay (0.35% by weight of n-butanol). The mixture is then filtered to remove insoluble matter from the reaction system, yielding a filtrate containing a mixture of butanol, tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten. The filtrate is then pumped to a distillation kettle for vacuum distillation to remove excess n-butanol (the vacuum degree of the vacuum distillation is controlled at -0.096 MPa, and the distillation temperature is 102° C.), yielding the final catalyst product 1, which is a light yellow, transparent, viscous liquid.

[0048] Example 2 Preparation of esterification catalyst using discarded vanadium-titanium SCR catalyst

[0049] A: Use a blower to remove the dust on the surface of the discarded vanadium-titanium SCR catalyst, then crush it into 100-120 mesh and set aside;

[0050] B: 33 parts by weight of the waste vanadium-titanium SCR catalyst powder crushed in step A, 1.5% by weight of the coke catalyst of the waste vanadium-titanium SCR catalyst, and 269 parts by weight of thionyl chloride were added to the autoclave 1 in sequence. Stirring was started, the autoclave was sealed, and the temperature was raised to 161° C. to carry out a primary chlorination reaction.

[0051] C: Sampling and testing the titanium dioxide content in the autoclave 1. When the titanium dioxide content reaches 11 wt %, the temperature is lowered to 64° C. The vent valve of the autoclave 1 is slowly opened to vent the gas to discharge sulfur dioxide gas, a byproduct of the chlorination reaction in the autoclave, to promote the chlorination reaction. The discharged sulfur dioxide gas is absorbed in a tank filled with 15 wt % ammonia water to obtain ammonium sulfate as a byproduct;

[0052] D: When there is almost no gas discharged from the vent valve of the high-pressure reactor 1 and the pressure in the reactor returns to normal pressure, it means that the sulfur dioxide is basically discharged. At this time, the high-pressure reactor 1 is sealed again and the temperature is raised to 175°C for secondary chlorination reaction;

[0053] E: Sampling and testing the titanium dioxide content in the autoclave 1. When the titanium dioxide content is less than 0.5 wt %, indicating that the secondary chlorination reaction has been completed, the temperature is lowered to 60° C. again and the sulfur dioxide gas is evacuated for the second time. The discharged sulfur dioxide gas is still absorbed by a tank filled with 10 wt % ammonia water to obtain ammonium sulfate by-product;

[0054] F: After the evacuation is completed, the contents of the autoclave 1 are placed in a reactor 2 equipped with a distillation apparatus, the stirring of the reactor 2 is started, and the temperature is gradually raised to 91° C. to distill and remove excess thionyl chloride, and the recovered thionyl chloride is used in the next batch; after no obvious thionyl chloride is distilled out (less than 1 drop in 20 seconds), indicating that the excess thionyl chloride in the reactor has been completely removed, 165 parts by weight of n-butanol is added, and the temperature is raised to 114° C. to carry out an esterification reaction, while continuously blowing nitrogen into the reactor to discharge hydrogen chloride gas generated by the reaction; the discharged hydrogen chloride gas is absorbed and treated with a 10% sodium carbonate solution;

[0055] G: Sampling and testing the contents of reactor 2. When the titanium tetrachloride content is less than 0.5 wt %, the esterification reaction of the chloride in the reactor is basically complete, resulting in a mixture of tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten. The temperature is then lowered to 55° C., and activated clay (0.5% by weight of n-butanol) is added for decolorization for 20 min. The mixture is then filtered to remove insoluble matter from the reaction system, yielding a filtrate containing a mixture of butanol, tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten. The filtrate is then pumped to a distillation kettle for vacuum distillation to remove excess n-butanol (the vacuum degree of the vacuum distillation is controlled at -0.097 MPa, and the distillation temperature is 105° C.), yielding the final catalyst product 2, which is a light yellow, transparent, viscous liquid.

[0056] Example 3 Preparation of esterification catalyst using discarded vanadium-titanium SCR catalyst

[0057] A: Use a blower to remove the dust on the surface of the discarded vanadium-titanium SCR catalyst, then crush it into 100-120 mesh and set aside;

[0058] B: 32 parts by weight of the waste vanadium-titanium SCR catalyst powder crushed in step A, 1.7% by weight of the coke catalyst of the waste vanadium-titanium SCR catalyst, and 262 parts by weight of thionyl chloride were added to the autoclave 1 in sequence. Stirring was started, the autoclave was sealed, and the temperature was raised to 165° C. to carry out a primary chlorination reaction.

[0059] C: Sampling and testing the titanium dioxide content in the autoclave 1. When the titanium dioxide content reaches 8 wt%, the temperature is lowered to 60°C, and the vent valve of the autoclave 1 is slowly opened to vent the gas to discharge sulfur dioxide gas, a byproduct of the chlorination reaction in the autoclave, to promote the chlorination reaction. The discharged sulfur dioxide gas is absorbed by a tank filled with 20 wt% ammonia water to obtain ammonium sulfate as a byproduct;

[0060] D: When there is almost no gas discharged from the vent valve of the high-pressure reactor 1 and the pressure in the reactor returns to normal pressure, it means that the sulfur dioxide is basically discharged. At this time, the high-pressure reactor 1 is sealed again and the temperature is raised to 180°C for secondary chlorination reaction;

[0061] E: Sampling and testing the titanium dioxide content in the autoclave 1. When the titanium dioxide content is less than 0.5 wt %, indicating that the secondary chlorination reaction has been completed, the temperature is lowered to 64° C. again and the sulfur dioxide gas is evacuated for the second time. The discharged sulfur dioxide gas is still absorbed by a tank filled with 13 wt % ammonia water to obtain ammonium sulfate by-product;

[0062] F: After the evacuation is completed, the contents of the autoclave 1 are placed in a reactor 2 equipped with a distillation apparatus, the stirring of the reactor 2 is started, and the temperature is gradually raised to 94° C. to distill and remove excess thionyl chloride, and the recovered thionyl chloride is used in the next batch; after no obvious thionyl chloride is distilled out (less than 1 drop in 20 seconds), indicating that the excess thionyl chloride in the reactor has been completely removed, 159 parts by weight of n-butanol is added, and the temperature is raised to 110° C. to carry out an esterification reaction, while continuously blowing nitrogen into the reactor to discharge hydrogen chloride gas generated by the reaction; the discharged hydrogen chloride gas is absorbed and treated with a 10% sodium carbonate solution;

[0063] G: Sampling and testing the contents of reactor 2. When the titanium tetrachloride content is less than 0.5 wt %, the esterification reaction of the chloride in the reactor is essentially complete, resulting in a mixture of tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten. The reaction mixture is then cooled to 50° C., and decolorized for 30 min by adding activated clay (0.4% by weight of n-butanol). The mixture is then filtered to remove insoluble matter from the reaction system, yielding a filtrate containing a mixture of butanol, tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten. The filtrate is then pumped to a distillation kettle for vacuum distillation to remove excess n-butanol (the vacuum degree of the vacuum distillation is controlled at -0.098 MPa, and the distillation temperature is 104° C.), yielding the final catalyst product 3, which is a light yellow, transparent, viscous liquid.

[0064] Example 4 Preparation of esterification catalyst using discarded vanadium-titanium SCR catalyst

[0065] A: Use a blower to remove the dust on the surface of the discarded vanadium-titanium SCR catalyst, then crush it into 100-120 mesh and set aside;

[0066] B: 35 parts by weight of the waste vanadium-titanium SCR catalyst powder crushed in step A, 1.8% by weight of the coke catalyst of the waste vanadium-titanium SCR catalyst, and 278 parts by weight of thionyl chloride were added sequentially into the autoclave 1, stirring was started, the autoclave was sealed, and the temperature was raised to 163° C. to carry out a primary chlorination reaction;

[0067] C: Sampling and testing the titanium dioxide content in the autoclave 1. When the titanium dioxide content reaches 12 wt%, the temperature is lowered to 64°C, and the vent valve of the autoclave 1 is slowly opened to vent the gas to discharge sulfur dioxide gas, a byproduct of the chlorination reaction in the autoclave, to promote the chlorination reaction. The discharged sulfur dioxide gas is absorbed by a tank filled with 19 wt% ammonia water to obtain ammonium sulfate as a byproduct;

[0068] D: When there is almost no gas discharged from the vent valve of the high-pressure reactor 1 and the pressure in the reactor returns to normal pressure, it means that the sulfur dioxide is basically discharged. At this time, the high-pressure reactor 1 is sealed again and the temperature is raised to 178°C for secondary chlorination reaction;

[0069] E: Sampling is performed to detect the titanium dioxide content in the autoclave 1. When the titanium dioxide content is lower than 0.5 wt %, indicating that the secondary chlorination reaction has been completed, the temperature is lowered to 63° C. again and the sulfur dioxide gas is evacuated for the second time. The discharged sulfur dioxide gas is still absorbed by a tank filled with 13 wt % ammonia water to obtain ammonium sulfate by-product;

[0070] F: After the evacuation is completed, the contents of the autoclave 1 are placed in a reactor 2 equipped with a distillation apparatus, the stirring of the reactor 2 is started, and the temperature is gradually raised to 93° C. to distill and remove excess thionyl chloride, and the recovered thionyl chloride is used in the next batch; after no obvious thionyl chloride is distilled out (less than 1 drop in 20 seconds), indicating that the excess thionyl chloride in the reactor has been completely removed, 168 parts by weight of n-butanol is added, and the temperature is raised to 114° C. to carry out an esterification reaction, while continuously blowing nitrogen into the reactor to discharge hydrogen chloride gas generated by the reaction; the discharged hydrogen chloride gas is absorbed and treated with a 10% sodium carbonate solution;

[0071] G: Sampling and testing the contents of reactor 2. When the titanium tetrachloride content is less than 0.5 wt %, the esterification reaction of the chloride in the reactor is essentially complete, resulting in a mixture of tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten. The reaction mixture is then cooled to 54° C., and decolorized for 28 min by adding activated clay at a concentration of 0.35% by mass of n-butanol. The mixture is then filtered to remove insoluble matter from the reaction system, yielding a filtrate containing a mixture of butanol, tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten. The filtrate is then pumped to a distillation kettle for vacuum distillation to remove excess n-butanol (the vacuum degree of the vacuum distillation is controlled at -0.097 MPa, and the distillation temperature is 103° C.), yielding the final catalyst product 4, which is a light yellow, transparent, viscous liquid.

[0072] Performance evaluation of test example catalysts

[0073] (1) Catalyst stability evaluation

[0074] The catalyst products prepared in Examples 1-4 and a commercially available tetrabutyl titanate catalyst were sealed and stored at room temperature, and their properties were observed for 12 months. The results are shown in Table 1.

[0075] (2) Evaluation of esterification catalytic performance of catalyst

[0076] The catalytic esterification reaction of terephthalic acid and isooctyl alcohol was used to verify the catalytic esterification effect of the catalyst products prepared in Examples 1-4 and commercially available tetrabutyl titanate catalyst. The reaction conditions are as follows:

[0077] The molar ratio of terephthalic acid to isooctyl alcohol is 1:2.1; the reaction temperature is 150°C; the stirring speed is 200 rpm; the reaction time is 3 hours; and the amount of catalyst used is 0.3% of the mass of terephthalic acid.

[0078] After 3 hours of reaction, the acid value of the esterified product in each reaction system was measured (the acid value test was conducted in accordance with HG / T2708-1995, "Determination of Acid Value in Polyester Polyols"), and the esterification rate was calculated (esterification rate = acid value of the system mixture before reaction - acid value of the esterified product after 3 hours / acid value of the system mixture before reaction * 100%). The results are shown in Table 1.

[0079] Table 1

[0080] sample Storage stability (12 months) 3h esterification rate (%) Example 1 No settlement, no stratification 86.5 Example 2 No settlement, no stratification 87.7 Example 3 No settlement, no stratification 86.1 Example 4 No settlement, no stratification 87.4 Commercially available tetrabutyl titanate catalyst No settlement, no stratification 86.8

[0081] As can be seen from Table 1, the mixed catalyst products of titanium butoxide, vanadium butoxide, and tungsten butoxide prepared by the present invention using specific raw materials and processes have a relatively transparent appearance and good storage stability, with no sedimentation or stratification for 12 months. When used in an esterification catalytic system (tested using the esterification of terephthalic acid and isooctyl alcohol as an example), the esterification rate reached over 86% in 3 hours, which is comparable to the catalytic effect of the commercially available industrial-grade tetrabutyl titanate used in Comparative Example 1. This indicates that the catalyst product prepared by the present invention can replace tetrabutyl titanate in conventional catalytic fields such as esterification.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an esterification catalyst using a waste vanadium-titanium-based SCR catalyst, comprising the following steps: S1: A waste vanadium-titanium-based SCR catalyst that has been deashed and crushed to 100-120 mesh is reacted with thionyl chloride in the presence of coke at 160-180°C. After the reaction is complete, excess thionyl chloride is removed to obtain a chlorinated product; S2: The chlorinated product obtained in step S1 is subjected to an esterification reaction with an alcohol at 110-115° C. After the reaction is completed, the target catalyst product is obtained after separation and purification.

2. The method according to claim 1, characterized in that The waste vanadium-titanium-based SCR catalyst is a waste product obtained by scrapping a high-temperature denitration catalyst V2O5·WO3 / TiO2 after long-term use due to a decrease in catalyst strength and / or activity; the waste vanadium-titanium-based SCR catalyst comprises 85-90 wt% of TiO2, 1.5-2.5 wt% of V2O5, and 7-12 wt% of WO3; and the remainder is impurities; and / or The alcohol substance includes n-propanol, n-butanol, n-pentanol, preferably n-butanol; and / or In parts by mass, the usage ratio of the waste vanadium-titanium-based SCR catalyst, thionyl chloride and alcohol substances is: (30-35): (250-280): (150-170), and the amount of coke used is 1.5-2wt% of the waste vanadium-titanium-based SCR catalyst.

3. The method according to claim 1, characterized in that Step S1 adopts a secondary chlorination method, comprising the following steps: S1-1: A primary chlorination reaction is carried out in a sealed autoclave at 160-165°C in the presence of coke, using a discarded vanadium-titanium-based SCR catalyst that has been ash-removed and crushed to 100-120 mesh. The reaction is then cooled to 60-65°C and the by-product sulfur dioxide gas generated in the autoclave is vented. S1-2: Seal the autoclave again and heat it to 175-180°C for secondary chlorination reaction; when the titanium dioxide content in the reaction system is lower than 0.5wt%, cool it down to 60-65°C again and vent the by-product sulfur dioxide gas generated in the autoclave.

4. The method according to claim 1, wherein In step S1, the chlorination product includes titanium tetrachloride, vanadium trichloride and tungsten chloride.

5. The method according to claim 1, wherein In step S1, the sulfur dioxide gas generated as a byproduct of the chlorination reaction is recovered, for example, the discharged sulfur dioxide gas is absorbed by ammonia water containing 10-20 wt% concentration to obtain ammonium sulfate as a byproduct; and / or In step S1, the method for removing excess thionyl chloride is carried out by distilling the reactants, and the distillation temperature is 90-95°C.

6. The method according to claim 1, characterized in that In step S2, an inert gas is introduced into the reaction system to discharge the hydrogen chloride gas generated by the reaction; and / or the generated hydrogen chloride gas is recovered; and / or In step S2, when the content of titanium tetrachloride in the reaction system is lower than 0.5 wt%, the reaction is determined to be complete.

7. The method according to claim 1, characterized in that In step S2, the separation and purification are carried out by the following steps: (1) Cooling the reaction product to 50-55°C, adding a decolorizing agent and performing decolorization treatment for 20-30 minutes; (2) filtering and removing insoluble matter in the reaction system to obtain a filtrate containing a mixture of butanol, tetrabutoxytitanium, tributoxyvanadium, and butoxytungsten; (3) removing excess n-butanol from the filtrate to obtain the final catalyst product.

8. The method according to claim 7, characterized in that In step (1), activated clay with a content of 0.3-0.5% by mass of n-butanol is used as a decolorizing agent; and / or In step (3), the excess n-butanol in the filtrate is removed by vacuum distillation. The conditions of the vacuum distillation are: vacuum degree: -0.095 MPa to -0.098 MPa, and distillation temperature is 100-105°C.

9. The esterification catalyst prepared by the method according to any one of claims 1 to 8.

10. Use of the esterification catalyst according to claim 9 in catalytic esterification reaction.