A rare earth-based hydrogenation catalyst and its preparation method

Abstract

The present invention relates to the field of catalyst technology, and in particular to a rare earth-based hydrogenation catalyst and a preparation method thereof. The present invention uses a phosphate-modified carrier, constructs a core-shell structure of a magnesium oxide-cerium oxide precursor, and introduces an yttrium-cerium solid solution, and prepares a catalyst through ultrasonic dispersion, calcination, and reduction treatment. The catalyst utilizes oxygen vacancies to reduce the hydrogen dissociation energy barrier, combines phosphate to inhibit green oil formation, and resists sulfur poisoning of the core-shell structure, thereby achieving low-temperature and efficient hydrogenation. The catalyst prepared by the present invention has the advantages of high dealkyne rate, good monoolefin selectivity, strong sulfur and carbon deposition resistance, and is suitable for industrial application in selective hydrogenation and dealkyne removal of pyrolysis gasoline.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a rare earth-based hydrogenation catalyst and a preparation method thereof. Background Art

[0002] Pyrolysis gasoline, a byproduct of ethylene cracking units, is rich in C8- to C10-monoolefins. However, the presence of alkynes (such as vinyl acetylene and methyl acetylene) and dienes can easily cause irreversible poisoning of downstream polymerization catalysts. Catalytic hydrogenation is widely used industrially to remove alkynes to concentrations below parts per million, but existing catalyst systems have inherent flaws. While traditional palladium-based catalysts exhibit high hydrogenation activity, their active sites exhibit insufficient selectivity for alkynes versus alkenes, often resulting in over-hydrogenation of more than 15% of the olefins to low-value alkanes, significantly reducing olefin yields. Furthermore, sulfides in pyrolysis gasoline, which are difficult to completely remove, can irreversibly adsorb onto precious metal surfaces, causing severe sulfur poisoning. For example, hydrogen sulfide forms a dense palladium sulfide layer on the palladium surface, significantly reducing the catalyst's hydrogenation activity within a half-cycle.

[0003] A more severe challenge comes from catalyst deactivation induced by side reactions. Highly active dienes in pyrolysis gasoline are prone to polymerization under hydrogenation conditions, especially when there are acidic sites on the carrier surface. These will catalyze the polymerization of dienes to form a viscous green oil. The green oil covers the active metal surface and gradually carbonizes, causing permanent deactivation of the catalyst. Although sulfur-resistant catalysts developed in recent years can partially alleviate the problem of sulfur poisoning, it is still difficult to achieve long-term stable operation due to the failure to simultaneously solve the problems of carrier acidity and excessive hydrogenation of olefins. In response to the above pain points, it is urgent to develop catalysts that have high olefin selectivity, strong sulfur tolerance and resistance to green oil formation to break through the technical bottleneck of the pyrolysis gasoline refining process. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a rare earth-based hydrogenation catalyst and a preparation method thereof.

[0005] Based on the above objectives, the present invention provides a method for preparing a rare earth-based hydrogenation catalyst, comprising the following steps:

[0006] S1. Add triethyl phosphate to ethanol, adjust the pH to 5-6 with 1 mol / L sulfuric acid, stir for 20-30 minutes, then add γ-Al2O3, heat to 60-80°C, stir and react for 2-4 hours, filter while hot, wash with deionized water, and dry to obtain the phosphate-modified support Al2O3-P. The chemical reaction diagram is as follows:

[0007] Formula (1), the hydroxyl groups on the surface of γ-Al2O3 are basically completely replaced, which cannot catalyze the protonation of alkynes, blocking the path of alkyne polymerization reaction. At the same time, the steric hindrance of the ethoxy group in the phosphate group is large, which increases the distance between the alkyne and the carrier, further reducing the possibility of alkyne polymerization, thereby reducing the production of green oil in petroleum cracking and hydrogenation catalysis;

[0008] S2. Add magnesium nitrate hexahydrate to deionized water and stir for 20-30 minutes. Add ammonium bicarbonate solution dropwise while stirring. The ion reaction equation is: Mg 2+ +2HCO3 - →MgCO3↓+CO2↑+H2O, during the addition process, use 1mol / L ammonia solution to adjust the pH to between 8.5-9.5. After the addition is completed, continue stirring for 1-2 hours, then raise the temperature to 70-80℃ and add hexahydrate cerium nitrate solution dropwise. The ionic reaction equation is: 2Ce 3+ +3CO3 2- →Ce2(CO3)3↓, the surface of magnesium carbonate is rich in negatively charged carbonate (CO3 2- ), and the cerium ion carries a strong positive charge. The two are tightly combined by "electrostatic attraction + chemical bonding" to form a core-shell structure of magnesium carbonate core and cerium carbonate shell. During the addition process, the pH is adjusted to 8-9 with 1 mol / L ammonia water. After the addition is completed, stirring is continued for 1-3 hours, and the temperature is raised to 90-100 ° C again. The hydrothermal reaction is carried out for 5-7 hours, cooled to room temperature, filtered, washed, and dried. After that, it is placed in a muffle furnace and heated to 500-600 ° C at a heating rate of 5-7 ° C / min. It is calcined for 3-5 hours to obtain a magnesium oxide-cerium oxide precursor. The chemical reaction equation is: MgCO3→MgO+CO2, Ce2(CO3)3→2CeO2+3CO2. H2S is preferentially adsorbed by the oxygen vacancies on the surface of the CeO2 shell to generate S 2- , S 2- By lattice diffusion to MgO core to form MgS, in reducing atmosphere, Ce 3+ Reduction of MgS releases S 2- and regenerate MgO, forming an "adsorption-diffusion-fixation-regeneration" process;

[0009] S3. Add yttrium nitrate and cerium nitrate to deionized water to form a mixed solution, heat it to 55-65 ° C, and add sodium hydroxide solution dropwise to the mixed solution while stirring. The ion reaction equation is: Y 3+ +3OH - →Y(OH)3↓,Ce 3+ +3OH -→Ce(OH)3↓, after the addition is completed, adjust the pH of the reaction solution between 9.5-10.5, let it stand for 5-7 hours, then transfer it to a high-pressure reactor, heat it to 150-170℃, hydrothermally react for 10-14 hours, cool it to room temperature, filter it, wash it, put it in a muffle furnace and heat it to 480-520℃ at a heating rate of 3-5℃, calcine it for 2-4 hours to obtain yttrium-cerium solid solution. The chemical reaction is as follows: Y(OH)3+Ce(OH)3+O2→Y x Ce 1-x O 1.5 +H2O, through Y 3+ Doping induces the generation of high-density oxygen vacancies. 3+ , squeeze out a lattice oxygen, generate an oxygen vacancy, and achieve low-temperature and efficient catalysis by reducing the hydrogen molecule dissociation energy barrier and promoting interface hydrogen overflow. Its essence is to replace Ce in the CeO2 lattice with doped ions. 4+ To maintain charge balance, when two trivalent dopant ions replace two tetravalent cerium ions, the lattice releases an oxygen atom and forms a doubly positively charged oxygen vacancy defect. The reaction formula is: , which can dissociate H2 into highly reactive protons H + and negative hydrogen ions H - ,H + and H - overflow through the support-metal interface to the adjacent Ni 0 active sites, forming bifunctional hydrogenation centers (Ni-H + / Ni-H - ), increasing the hydrogenation rate of olefins. At the same time, oxygen vacancies can also absorb oxygen in the air to form superoxide radicals (•O2 - ), the carbon deposits are oxidized to CO2 / H2O at high temperature, which prolongs the life of the catalyst;

[0010] S4. Add magnesium oxide-cerium oxide precursor and yttrium cerium solid solution to ethanol / water mixed solution, stir for 30-40 minutes, then add phosphate modified carrier Al2O3-P, heat to 60-80℃, shake and react for 2-4 hours, magnesium oxide-cerium oxide precursor and yttrium cerium solid solution are electrostatically adsorbed around Al2O3-P, phosphorus oxygen double bond in Al2O3-P undergoes dehydration condensation with hydroxyl group on the surface of metal oxide to form phosphate-metal covalent bond, which is firmly bonded to the carrier. After cooling to room temperature, nickel nitrate aqueous solution is added under stirring, and then allowed to stand at room temperature for 1-3 hours for penetration. Nickel nitrate enters the pores of the carrier by capillary action, and then is ultrasonically dispersed at 300-500w for 30-40 minutes, filtered, washed, placed in a muffle furnace, and heated to 400-500℃ at a heating rate of 5-10℃ under a nitrogen atmosphere. It is calcined for 1-2 hours. At this time, the chemical reaction equation of nickel nitrate is: , cool to 140-160℃, continue to introduce H2O / H2 mixed gas at a gas flow rate of 1-2L / min for 1-3h. The chemical reaction equation at this time is: Finally, the mixture was dried in a muffle furnace under nitrogen atmosphere for 1-2 hours and cooled to room temperature to obtain a rare earth-based hydrogenation catalyst.

[0011] Preferably, the weight ratio of triethyl phosphate, γ-Al2O3 and ethanol in S1 is 0.12-0.16:1:5-7.

[0012] Preferably, the weight ratio of magnesium nitrate hexahydrate, ammonium bicarbonate solution, cerium nitrate hexahydrate solution and deionized water in S2 is 1:8-8.4:8-9:2-4.

[0013] Preferably, the concentration of the ammonium bicarbonate solution in S2 is 1.5 mol / L, and the concentration of the cerium nitrate hexahydrate solution is 0.5 mol / L.

[0014] Preferably, the weight ratio of yttrium nitrate, cerium nitrate, sodium hydroxide solution and deionized water in S3 is 1:2.8-3:30-36:18-20.

[0015] Preferably, the concentration of the sodium hydroxide solution in S3 is 1 mol / L.

[0016] Preferably, the weight ratio of the magnesium oxide-cerium oxide precursor, the yttrium-cerium solid solution, the phosphate-modified carrier Al2O3-P, the nickel nitrate aqueous solution and the ethanol / water mixed solution in S4 is 0.22-0.26:0.15-0.17:1:2-4:2.5-2.7.

[0017] Preferably, the concentration of the nickel nitrate aqueous solution in S4 is 1 mol / L, and the ethanol / water mixed solution refers to a mixture of ethanol and water in a weight ratio of 1:1.

[0018] Preferably, in the H2O / H2 mixed gas in S4, the volume ratio of H2O to H2 is 7:93.

[0019] Furthermore, the present invention also provides a rare earth-based hydrogenation catalyst, which is prepared using the above preparation method.

[0020] Furthermore, the present invention also provides an application of a rare earth-based hydrogenation catalyst in the selective hydrogenation and deacetylation of pyrolysis gasoline.

[0021] Preferably, the selectivity of the preferential addition of alkynes rather than alkenes is reflected in the elimination of acidic sites by modifying the carrier with phosphate, the use of steric hindrance of ethoxy groups to increase the distance between the compound to be hydrogenated and the carrier, weakening the adsorption of olefins, the oxygen vacancies in the yttrium-cerium solid solution promote hydrogen dissociation to form a bifunctional hydrogenation center to preferentially activate the triple bond addition of alkynes, and the metal-support covalent bonding regulates Ni0 The electronic structure makes the adsorption of alkynes stronger, and the water vapor forms a hydration layer to prevent excessive adsorption and coking of alkenes, thereby achieving preferential addition to alkynes.

[0022] Beneficial effects of the present invention:

[0023] 1. This invention modifies the γ-Al2O3 support with phosphate esters, effectively eliminating acidic sites on the support surface and blocking the diene polymerization pathway. It also utilizes the steric hindrance of the ethoxy groups to increase the distance between the reactants and the support, significantly reducing green oil production. This modification mechanism fundamentally suppresses byproduct formation, prevents active sites from being deactivated by coating, and enhances the catalyst's resistance to carbon deposition and operational stability.

[0024] 2. The present invention uses Y in yttrium-cerium solid solution 3+ Doping CeO2 lattice induces high-density oxygen vacancies, which greatly reduces the H2 dissociation energy barrier and forms Ni-H + / Ni-H - This bifunctional hydrogenation center allows the catalyst to efficiently activate hydrogen molecules even at low temperatures, achieving directional addition of alkynes. This overcomes the bottleneck of low-temperature activity of traditional nickel-based catalysts and broadens the temperature range of the catalytic reaction.

[0025] 3. The present invention uses the core-shell structure of magnesium oxide and cerium oxide precursors to resist sulfur poisoning by using the "adsorption-diffusion-fixation-regeneration" cycle mechanism. The oxygen vacancies in the CeO2 shell preferentially adsorb H2S to generate S 2- , diffuses into the MgO core through the lattice to form stable MgS, and Ce in a reducing atmosphere 4+ MgS can be reduced to regenerate MgO, avoiding direct poisoning of active centers by sulfur species and significantly extending the service life of the catalyst.

[0026] 4. The present invention achieves preferential addition of alkynes through the synergistic effect of multiple components. By modifying the carrier with phosphate to eliminate acidic sites and utilizing the steric hindrance of ethoxy groups to weaken olefin adsorption, the Ni-H + / Ni-H - The bifunctional center preferentially activates the alkyne triple bond addition, and the metal-support covalent bonding is combined to regulate Ni 0 Electronic structure, enhance the alkyne adsorption selectivity, at the same time, water vapor treatment forms a hydration layer on the Ni surface, further weakening the interaction between the olefin π bond and the Ni active site through physical coverage, avoiding excessive adsorption of olefins to cause coking or deep hydrogenation, in addition, ultrasonic dispersion and high temperature calcination process make the nickel active site uniformly dispersed in the three-dimensional network formed by the phosphate modified support and the rare earth composite oxide, forming a highly dispersed Ni 0The particles increase the specific surface area while inhibiting the agglomeration of active centers through covalent anchoring, achieving synergistic optimization of selectivity and stability.

[0027] 5. The catalyst prepared by the present invention integrates the advantages of sulfur resistance, carbon deposition resistance, high selectivity and low-temperature activity. The catalyst maintains stable and efficient hydrogenation performance over a wide temperature range. In addition, the preparation process is highly controllable, the raw material cost is low, and it is suitable for industrial scenarios such as pyrolysis gasoline refining. It can break through the technical bottleneck of traditional catalysts under complex working conditions. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0029] The sources of the reagents and raw materials used in the examples of the present invention are as follows:

[0030] Triethyl phosphate was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. with a purity of 98%; γ-Al2O3 was purchased from Beijing Zhongxin Yannuo New Material Technology Co., Ltd. with a purity of 99% and a particle size of 45-105 μm; magnesium nitrate hexahydrate was purchased from Nanjing Chemical Reagent Co., Ltd. with a purity of 98%; ammonium bicarbonate was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. with a purity of 99.995%; cerium nitrate hexahydrate was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. with a purity of 99.999%; yttrium nitrate was purchased from Shandong Xiya Chemical Co., Ltd. with a purity of 99.99%; cerium nitrate was purchased from Jiaxing Zhejia Biotechnology Co., Ltd. with a purity of 95%; and nickel nitrate was purchased from Nanjing Chemical Reagent Co., Ltd. with a purity of 98%.

[0031] Example 1: A specific method for preparing a rare earth-based hydrogenation catalyst comprises the following steps:

[0032] (1) Add 1.8 g of triethyl phosphate to 75 g of ethanol, adjust the pH to 5-6 with 1 mol / L sulfuric acid, stir for 20 min, then add 15 g of γ-Al2O3, heat to 60 °C, stir and react for 2 h, filter while hot, wash with deionized water, and dry to obtain the phosphate-modified support Al2O3-P;

[0033] (2) Add 2 g of magnesium nitrate hexahydrate to 4 g of deionized water and stir for 20 min. Keep stirring and dropwise add 16 g of 1.5 mol / L ammonium bicarbonate solution. During the dropwise addition, adjust the pH value between 8.5 and 9.5 with 1 mol / L ammonia solution. After the dropwise addition, continue stirring for 1 h. Then heat to 70 ° C. and dropwise add 16 g of 0.5 mol / L cerium nitrate hexahydrate solution. During the dropwise addition, adjust the pH value between 8 and 9 with 1 mol / L ammonia solution. After the dropwise addition, continue stirring for 1 h. Heat to 90 ° C again. Hydrothermal reaction for 5 h. Cool to room temperature. Filter, wash, dry, place in a muffle furnace, heat to 500 ° C at a heating rate of 5 ° C / min, and calcine for 3 h to obtain magnesium oxide-cerium oxide precursor.

[0034] (3) Add 2 g of yttrium nitrate and 5.6 g of cerium nitrate to 36 g of deionized water to prepare a mixed solution, heat it to 55 ° C, and add 60 g of 1 mol / L sodium hydroxide solution to the mixed solution under stirring. After the addition is completed, adjust the pH of the reaction solution to between 9.5 and 10.5, let it stand for 5 hours, and then transfer it to a high-pressure reactor, heat it to 150 ° C, and hydrothermally react for 10 hours. After cooling to room temperature, filter, wash, put it in a muffle furnace, heat it to 480 ° C at a heating rate of 3 ° C, and calcine it for 2 hours to obtain a yttrium-cerium solid solution;

[0035] (4) 2.2 g of magnesium oxide-cerium oxide precursor and 1.5 g of yttrium-cerium solid solution were added to 25 g of ethanol / water mixed solution (ethanol and water were mixed in a weight ratio of 1:1), stirred for 30 min, and then 10 g of phosphate modified carrier Al2O3-P was added. The temperature was raised to 40 ° C and oscillated for reaction for 2 h. After cooling to room temperature, 20 g of 1 mol / L nickel nitrate aqueous solution was added under stirring. The mixture was then allowed to stand at room temperature for 1 h. The mixture was then ultrasonically dispersed at 300 W for 30 min, filtered, washed, and placed in a muffle furnace. Under a nitrogen atmosphere, the temperature was raised to 400 ° C at a heating rate of 5 ° C, calcined for 1 h, cooled to 140 ° C, and H2O / H2 mixed gas (H2O and H2 were mixed in a volume ratio of 7:93) was continuously introduced at a gas flow rate of 1 L / min for 1 h. Finally, the mixture was kept in a nitrogen atmosphere in the muffle furnace, dried for 1 h, and cooled to room temperature to obtain a rare earth-based hydrogenation catalyst.

[0036] Example 2: A specific preparation method of a rare earth-based hydrogenation catalyst comprises the following steps:

[0037] (1) Add 2.1 g of triethyl phosphate to 90 g of ethanol, adjust the pH to 5-6 with 1 mol / L sulfuric acid, stir for 25 min, then add 15 g of γ-Al2O3, heat to 70 °C, stir and react for 3 h, filter while hot, wash with deionized water, and dry to obtain the phosphate-modified support Al2O3-P;

[0038] (2) Add 2 g of magnesium nitrate hexahydrate to 6 g of deionized water and stir for 25 min. Keep stirring and dropwise add 16.4 g of 1.5 mol / L ammonium bicarbonate solution. During the addition, adjust the pH value between 8.5 and 9.5 with 1 mol / L ammonia solution. After the addition is complete, continue stirring for 1.5 h. Then heat to 75 ° C. and dropwise add 17 g of 0.5 mol / L cerium nitrate hexahydrate solution. During the addition, adjust the pH value between 8 and 9 with 1 mol / L ammonia solution. After the addition is complete, continue stirring for 1.5 h. Heat to 95 ° C again. Hydrothermal reaction for 6 h. Cool to room temperature. Filter, wash, dry, place in a muffle furnace, heat to 550 ° C at a heating rate of 6 ° C / min, and calcine for 4 h to obtain magnesium oxide-cerium oxide precursor.

[0039] (3) Add 2 g of yttrium nitrate and 5.8 g of cerium nitrate to 38 g of deionized water to prepare a mixed solution, heat it to 60 ° C, and add 66 g of 1 mol / L sodium hydroxide solution to the mixed solution under stirring. After the addition is completed, adjust the pH of the reaction solution to between 9.5 and 10.5, let it stand for 6 hours, and then transfer it to a high-pressure reactor, heat it to 160 ° C, hydrothermally react for 12 hours, cool it to room temperature, filter it, wash it, put it in a muffle furnace, heat it to 500 ° C at a heating rate of 4 ° C, and calcine it for 3 hours to obtain a yttrium-cerium solid solution;

[0040] (4) 2.4 g of magnesium oxide-cerium oxide precursor and 1.6 g of yttrium-cerium solid solution were added to 26 g of ethanol / water mixed solution (ethanol and water were mixed in a weight ratio of 1:1), stirred for 35 min, and then 10 g of phosphate modified carrier Al2O3-P was added. The temperature was raised to 45 ° C and the reaction was shaken for 3 h. After cooling to room temperature, 30 g of 1 mol / L nickel nitrate aqueous solution was added under stirring, and then the solution was allowed to stand at room temperature for 2 h and then subjected to 400 w The product was ultrasonically dispersed for 35 minutes, filtered, washed, placed in a muffle furnace, and heated to 450°C at a heating rate of 7°C under a nitrogen atmosphere. It was calcined for 1.5 hours, cooled to 150°C, and H2O / H2 mixed gas (H2O and H2 were mixed in a volume ratio of 7:93) was continuously introduced at a gas flow rate of 1.5 L / min for 2 hours. Finally, the product was dried in a muffle furnace under a nitrogen atmosphere for 1.5 hours and cooled to room temperature to obtain a rare earth-based hydrogenation catalyst.

[0041] Example 3: A specific preparation method of a rare earth-based hydrogenation catalyst comprises the following steps:

[0042] (1) Add 2.4 g of triethyl phosphate to 105 g of ethanol, adjust the pH to 5-6 with 1 mol / L sulfuric acid, stir for 30 min, then add 15 g of γ-Al2O3, heat to 80 °C, stir and react for 4 h, filter while hot, wash with deionized water, and dry to obtain the phosphate-modified carrier Al2O3-P;

[0043] (2) Add 2 g of magnesium nitrate hexahydrate to 8 g of deionized water and stir for 30 min. While stirring, add 16.8 g of 1.5 mol / L ammonium bicarbonate solution dropwise. During the addition, adjust the pH value between 8.5 and 9.5 with 1 mol / L ammonia solution. After the addition is complete, continue stirring for 2 h. Then heat the mixture to 80 ° C. Add 18 g of 0.5 mol / L cerium nitrate hexahydrate solution dropwise. During the addition, adjust the pH value between 8 and 9 with 1 mol / L ammonia solution. After the addition is complete, continue stirring for 3 h. Heat the mixture to 100 ° C. again. Hydrothermally react for 7 h. Cool to room temperature. Filter, wash, dry, place in a muffle furnace, heat to 600 ° C. at a heating rate of 7 ° C / min, and calcine for 5 h to obtain a magnesium oxide-cerium oxide precursor.

[0044] (3) Add 2 g of yttrium nitrate and 6 g of cerium nitrate to 40 g of deionized water to prepare a mixed solution, heat it to 65 ° C, and add 72 g of 1 mol / L sodium hydroxide solution to the mixed solution under stirring. After the addition is completed, adjust the pH of the reaction solution to between 9.5 and 10.5, let it stand for 7 hours, and then transfer it to a high-pressure reactor, heat it to 170 ° C, and hydrothermally react for 14 hours. After cooling to room temperature, filter, wash, put it in a muffle furnace, heat it to 520 ° C at a heating rate of 5 ° C, and calcine it for 4 hours to obtain a yttrium-cerium solid solution;

[0045] (4) 2.6 g of magnesium oxide-cerium oxide precursor and 1.7 g of yttrium-cerium solid solution were added to 26 g of ethanol / water mixed solution (ethanol and water were mixed in a weight ratio of 1:1), stirred for 40 min, and then 10 g of phosphate modified carrier Al2O3-P was added. The temperature was raised to 50 ° C and oscillated for reaction for 4 h. After cooling to room temperature, 40 g of 1 mol / L nickel nitrate aqueous solution was added under stirring. The mixture was then allowed to stand at room temperature for 3 h and then ultrasonically dispersed at 500 W for 40 min. The mixture was filtered, washed, and placed in a muffle furnace. Under a nitrogen atmosphere, the temperature was raised to 500 ° C at a heating rate of 10 ° C, calcined for 2 h, cooled to 160 ° C, and H2O / H2 mixed gas (H2O and H2 were mixed in a volume ratio of 7:93) was continuously introduced at a gas flow rate of 2 L / min for 3 h. Finally, the mixture was kept in a nitrogen atmosphere in the muffle furnace, dried for 2 h, and cooled to room temperature to obtain a rare earth-based hydrogenation catalyst.

[0046] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that γ-Al2O3 is not modified with triethyl phosphate. The specific preparation process is as follows: A specific preparation method of a rare earth-based hydrogenation catalyst comprises the following steps:

[0047] (1) Add 2 g of magnesium nitrate hexahydrate to 6 g of deionized water and stir for 25 min. Keep stirring and dropwise add 16.4 g of 1.5 mol / L ammonium bicarbonate solution. During the addition, adjust the pH value between 8.5 and 9.5 with 1 mol / L ammonia solution. After the addition is complete, continue stirring for 1.5 h. Then heat to 75 ° C and dropwise add 17 g of 0.5 mol / L cerium nitrate hexahydrate solution. During the addition, adjust the pH value between 8 and 9 with 1 mol / L ammonia solution. After the addition is complete, continue stirring for 1.5 h. Heat to 95 ° C again and hydrothermally react for 6 h. Cool to room temperature, filter, wash, dry, place in a muffle furnace, heat to 550 ° C at a heating rate of 6 ° C / min, and calcine for 4 h to obtain magnesium oxide-cerium oxide precursor.

[0048] (2) Add 2 g of yttrium nitrate and 5.8 g of cerium nitrate to 38 g of deionized water to prepare a mixed solution, heat it to 60 ° C, and add 66 g of 1 mol / L sodium hydroxide solution to the mixed solution under stirring. After the addition is completed, adjust the pH of the reaction solution to between 9.5 and 10.5, let it stand for 6 hours, and then transfer it to a high-pressure reactor, heat it to 160 ° C, hydrothermally react for 12 hours, cool it to room temperature, filter it, wash it, put it in a muffle furnace, heat it to 500 ° C at a heating rate of 4 ° C, and calcine it for 3 hours to obtain a yttrium-cerium solid solution;

[0049] (3) 2.4 g of magnesium oxide-cerium oxide precursor and 1.6 g of yttrium-cerium solid solution were added to 26 g of ethanol / water mixed solution (ethanol and water were mixed in a weight ratio of 1:1), stirred for 35 min, and then 10 g of Al2O3-P was added. The temperature was raised to 45 ° C and oscillated for reaction for 3 h. After cooling to room temperature, 30 g of 1 mol / L nickel nitrate aqueous solution was added under stirring. The mixture was then allowed to stand at room temperature for 2 h. The mixture was then ultrasonically dispersed at 400 W for 35 min, filtered, washed, and placed in a muffle furnace. Under a nitrogen atmosphere, the temperature was raised to 450 ° C at a heating rate of 7 ° C. The mixture was calcined for 1.5 h, cooled to 150 ° C, and H2O / H2 mixed gas (H2O and H2 were mixed in a volume ratio of 7:93) was continuously introduced at a gas flow rate of 1.5 L / min for 2 h. Finally, the mixture was dried in a muffle furnace under a nitrogen atmosphere for 1.5 h and cooled to room temperature to obtain a rare earth-based hydrogenation catalyst.

[0050] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the yttrium-cerium solid solution is replaced by cerium oxide. The specific preparation process is as follows: A specific preparation method of a rare earth-based hydrogenation catalyst comprises the following steps:

[0051] (1) Add 2.1 g of triethyl phosphate to 90 g of ethanol, adjust the pH to 5-6 with 1 mol / L sulfuric acid, stir for 25 min, then add 15 g of γ-Al2O3, heat to 70 °C, stir and react for 3 h, filter while hot, wash with deionized water, and dry to obtain the phosphate-modified support Al2O3-P;

[0052] (2) Add 2 g of magnesium nitrate hexahydrate to 6 g of deionized water and stir for 25 min. Keep stirring and dropwise add 16.4 g of 1.5 mol / L ammonium bicarbonate solution. During the addition, adjust the pH value between 8.5 and 9.5 with 1 mol / L ammonia solution. After the addition is complete, continue stirring for 1.5 h. Then heat to 75 ° C. and dropwise add 17 g of 0.5 mol / L cerium nitrate hexahydrate solution. During the addition, adjust the pH value between 8 and 9 with 1 mol / L ammonia solution. After the addition is complete, continue stirring for 1.5 h. Heat to 95 ° C again. Hydrothermal reaction for 6 h. Cool to room temperature. Filter, wash, dry, place in a muffle furnace, heat to 550 ° C at a heating rate of 6 ° C / min, and calcine for 4 h to obtain magnesium oxide-cerium oxide precursor.

[0053] (3) Add 5.8 g of cerium nitrate to 38 g of deionized water to prepare a solution, heat it to 60 ° C, and add 66 g of 1 mol / L sodium hydroxide solution to the mixed solution under stirring. After the addition is completed, adjust the pH of the reaction solution to between 9.5 and 10.5, let it stand for 6 hours, and then transfer it to a high-pressure reactor, heat it to 160 ° C, and hydrothermally react for 12 hours. After cooling to room temperature, filter, wash, put it into a muffle furnace, heat it to 500 ° C at a heating rate of 4 ° C, and calcine it for 3 hours to obtain cerium oxide;

[0054] (4) 2.4 g of magnesium oxide-cerium oxide precursor and 1.6 g of cerium oxide were added to 26 g of ethanol / water mixed solution (ethanol and water were mixed in a weight ratio of 1:1), stirred for 35 min, and then 10 g of phosphate modified carrier Al2O3-P was added. The temperature was raised to 45 ° C and oscillated for reaction for 3 h. After cooling to room temperature, 30 g of 1 mol / L nickel nitrate aqueous solution was added under stirring. Then, the mixture was allowed to stand at room temperature for 2 h and then ultrasonically dispersed at 400 W for 35 min. After filtration and washing, the mixture was placed in a muffle furnace and heated to 450 ° C at a heating rate of 7 ° C under a nitrogen atmosphere. The mixture was calcined for 1.5 h and cooled to 150 ° C. H2O / H2 mixed gas (H2O and H2 were mixed in a volume ratio of 7:93) was continuously introduced at a gas flow rate of 1.5 L / min for 2 h. Finally, the mixture was dried in a muffle furnace under a nitrogen atmosphere for 1.5 h and cooled to room temperature to obtain a rare earth-based hydrogenation catalyst.

[0055] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that magnesium oxide-cerium oxide has no core-shell structure. The specific preparation process is as follows: A specific preparation method of a rare earth-based hydrogenation catalyst comprises the following steps:

[0056] (1) Add 2.1 g of triethyl phosphate to 90 g of ethanol, adjust the pH to 5-6 with 1 mol / L sulfuric acid, stir for 25 min, then add 15 g of γ-Al2O3, heat to 70 °C, stir and react for 3 h, filter while hot, wash with deionized water, and dry to obtain the phosphate-modified support Al2O3-P;

[0057] (2) Add 2 g of yttrium nitrate and 5.8 g of cerium nitrate to 38 g of deionized water to prepare a mixed solution, heat it to 60 ° C, and add 66 g of 1 mol / L sodium hydroxide solution to the mixed solution under stirring. After the addition is completed, adjust the pH of the reaction solution to between 9.5 and 10.5, let it stand for 6 hours, and then transfer it to a high-pressure reactor, heat it to 160 ° C, hydrothermally react for 12 hours, cool it to room temperature, filter it, wash it, put it in a muffle furnace, heat it to 500 ° C at a heating rate of 4 ° C, and calcine it for 3 hours to obtain a yttrium-cerium solid solution;

[0058] (3) Add 0.233g magnesium oxide, 2.09g cerium oxide, and 1.6g yttrium-cerium solid solution to 26g ethanol / water mixed solution (ethanol and water are mixed in a weight ratio of 1:1), stir for 35min, then add 10g phosphate modified carrier Al2O3-P, heat to 45℃, shake and react for 3h, cool to room temperature, add 30g 1mol / L nickel nitrate aqueous solution with stirring, then let it stand at room temperature for 2h, and then pass through 40 0w ultrasonic dispersion for 35min, filtered, washed, placed in a muffle furnace, heated to 450℃ under a nitrogen atmosphere at a heating rate of 7℃, calcined for 1.5h, cooled to 150℃, and continuously introduced H2O / H2 mixed gas (H2O and H2 are mixed in a volume ratio of 7:93) at a gas flow rate of 1.5L / min for 2h. Finally, in the muffle furnace, maintain a nitrogen atmosphere, dry for 1.5h, and cool to room temperature to obtain a rare earth-based hydrogenation catalyst.

[0059] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that only the phosphate-modified carrier Al2O3-P is used to support nickel. The preparation process is as follows: A specific preparation method of a rare earth-based hydrogenation catalyst comprises the following steps:

[0060] (1) Add 2.1 g of triethyl phosphate to 90 g of ethanol, adjust the pH to 5-6 with 1 mol / L sulfuric acid, stir for 25 min, then add 15 g of γ-Al2O3, heat to 70 °C, stir and react for 3 h, filter while hot, wash with deionized water, and dry to obtain the phosphate-modified support Al2O3-P;

[0061] (2) 10 g of phosphate-modified carrier Al2O3-P was added to 30 g of 1 mol / L nickel nitrate aqueous solution, stirred for 30 min, and then allowed to stand at room temperature for 2 h. It was then ultrasonically dispersed at 400 W for 35 min, filtered, washed, and placed in a muffle furnace. Under a nitrogen atmosphere, the temperature was raised to 450 ° C at a heating rate of 7 ° C, calcined for 1.5 h, cooled to 150 ° C, and H2O / H2 mixed gas (H2O and H2 were mixed in a volume ratio of 7:93) was continuously introduced at a gas flow rate of 1.5 L / min for 2 h. Finally, the mixture was dried in a muffle furnace under a nitrogen atmosphere for 1.5 h and cooled to room temperature to obtain a rare earth-based hydrogenation catalyst.

[0062] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that a commercial nickel / alumina catalyst purchased from Shanghai Xunkai New Material Technology Co., Ltd. is used.

[0063] Specific applications:

[0064] Catalytic hydrogenation object: cracked gasoline (C5-C9 fraction) from a petrochemical plant, composition:

[0065] Diolefins: 15wt%, Monoolefins: 50wt%, Alkynes (mainly vinyl acetylene and diacetylene): 2.0wt%, Saturated hydrocarbons: 20%, Aromatic hydrocarbons: 12%, Others: 1%, Sulfur content: 80ppm.

[0066] 1. A 100 ml autoclave was charged with 4 g of each of the catalysts prepared according to the preparation methods of Examples 1-3 and Comparative Examples 1-5. Hydrogenation was performed using the catalysts prepared as feedstock. The operating conditions were: reaction temperature 150°C, reaction pressure atmospheric pressure, and reaction time 2 h. The deacetylation efficiency, monoolefin selectivity, and green oil production of the catalysts are shown in Table 1.

[0067] 2. A 100 ml high pressure reactor was filled with 4 g of each catalyst obtained by the preparation method of Examples 1-3 and Comparative Examples 1-5, and a hydrogenation operation was performed using the above catalytic hydrogenation object as a raw material. The operating conditions were: reaction temperature 150 ° C, reaction pressure at normal pressure, reaction time 2 h, and 50 consecutive hydrogenation tests were performed to test the initial deacetylation rate of the catalyst and the deacetylation rate after 50 tests. The experimental results are shown in Table 1.

[0068] 3. A 100 ml autoclave was filled with 0.5 g of each catalyst obtained by the preparation method of Examples 1-3 and Comparative Examples 1-5, and the above catalytic hydrogenation object was used as a raw material for hydrogenation operation. A total of 4 experiments were carried out, and a new 0.5 g catalyst was replaced after each experiment. The weight of the raw materials used in each experiment was the same, and the temperatures were 150, 120, 90, and 60 ° C, respectively. The other operating conditions were the same: the reaction pressure was atmospheric pressure, the reaction time was 2 h, and the deacetylation rate of the catalyst at different temperatures was tested. The experimental results are shown in Table 2.

[0069] Table 1 Catalyst specific evaluation results, initial deacetylation rate and deacetylation rate after 50 tests

[0070] ;

[0071] Table 2 Deacetylation rate of catalyst at different temperatures

[0072] ;

[0073] Performance Analysis:

[0074] It can be seen from the experimental data in Table 1 and Table 2 that the catalysts prepared by the present invention in Examples 1-3 have excellent performance. This may be because the phosphate modified support Al2O3-P eliminates the acid sites and inhibits diene polymerization through ethoxy steric hindrance, reducing the formation of green oil. The Y in the yttrium-cerium solid solution 3+ Doping induces oxygen vacancies, which lower the H2 dissociation energy barrier and form Ni-H + / Ni-H _ The dual-functional hydrogenation center achieves low-temperature and efficient dealkyne removal. The core-shell structured magnesium oxide-cerium oxide precursor fixes H2S through an "adsorption-diffusion-regeneration" cycle to improve the ability to resist sulfur poisoning. The components are covalently bonded to regulate Ni 0 electronic structure, enhancing the alkyne adsorption selectivity, among which Example 2 has the best comprehensive performance.

[0075] Judging from the deacetylation rate at 150 ° C, this may be because the PO-Al bond of the phosphate modified support in Example 2 has high thermal stability and continuously inhibits the formation of green oil at high temperature; the magnesium oxide-cerium oxide precursor with a core-shell structure accelerates the S 2- Diffusion fixation prevents the formation of Ni-S bonds; oxygen vacancies in the yttrium-cerium solid solution promote the oxidation of carbon deposits at high temperatures. The reaction formula is: , maintaining a clean active surface. In contrast, the commercial catalyst in Comparative Example 5, while exhibiting a high deacetylation rate at 150°C, lacks selectivity and rapidly decays in activity due to sulfur poisoning and green oil coverage at high temperatures. Comparative Examples 1 and 3 exhibit significant high-temperature activity decay due to insufficient carrier acidity or sulfur resistance. Comparative Examples 2 and 4 lack multi-component synergy, resulting in lower selectivity and stability at high temperatures than Example 2.

[0076] From the perspective of monoolefin selectivity, this may be because the phosphate-modified carrier Al2O3-P in Example 2 replaces the surface hydroxyl groups with triethyl phosphate to form PO-Al covalent bonds, eliminating the L acid sites (Al 3+ ) and B acid sites (-OH), blocking the protonation path of olefins on the support surface; at the same time, the steric hindrance of the ethoxy group increases the interaction between olefins and Ni 0 The spacing of active sites weakens the π bond adsorption of olefins. In addition, the H + / H - The bifunctional center preferentially activates alkyne triple bonds, while the adsorption energy for monoolefin double bonds is lower, preventing overhydrogenation. In Comparative Example 1, the unmodified support exhibited acidic sites, leading to overhydrogenation of olefins. In Comparative Example 5, the commercial catalyst lacked selectivity, resulting in complete hydrogenation of monoolefins. In Comparative Examples 2, 3, and 4, the lack of phosphate modification or rare earth synergy resulted in residual acidic sites or insufficient electron density in the active centers, resulting in lower selectivity than in Example 2.

[0077] Judging from the amount of green oil produced, this may be because the Al2O3-P support of Example 2 is modified by phosphate, converting the hydroxyl groups on the surface of silicon oxide into phosphate groups, eliminating the acidic catalytic sites required for diene polymerization. The dienes cannot form carbon cation intermediates on the support surface, and the polymerization path is blocked; at the same time, the steric hindrance of the ethoxy group further inhibits the aggregation of dienes near the Ni active site, reducing the production of green oil precursors. In Comparative Example 1, the acidic sites of the unmodified support catalyze diene polymerization, and the amount of green oil is the highest; although Comparative Examples 2, 3, and 4 are partially modified or contain rare earths, the amount of green oil is still higher than that of Example 2 because the acidity of the support is not completely eliminated or there is a lack of synergistic anti-polymerization design; Comparative Example 5 has a strong acidity and is unmodified, and the amount of green oil produced is the highest.

[0078] It can be seen from the deacetylation rate after 50 tests that the cyclic stability of Example 2 is high, indicating that its anti-sulfur poisoning performance is good. This may be because the core-shell structure of the magnesium oxide-cerium oxide precursor of Example 2 is formed by "electrostatic attraction-hydrothermal synthesis", and the oxygen vacancies in the CeO2 shell preferentially adsorb H2S to generate S 2- , S 2- Oxygen ion channels diffuse into the MgO core through the CeO2 structure to form MgS, avoiding S 2- poisoning Ni active sites; during H2 / O2 treatment, Ce 4+ Oxidation of MgS to regenerate MgO, reaction formula: 2MgS+4Ce 4+ +O2→2MgO+4Ce 3+ +2S, forming an anti-sulfur cycle, comparative example 3 has no core-shell structure, mechanical mixing, MgO and CeO2 lack sulfur diffusion channels, S 2-Directly react with Ni; although Comparative Example 1 contains a core-shell structure of magnesium oxide-cerium oxide precursor and has a certain sulfur resistance, the green oil generated far exceeds the effect of sulfur poisoning, and the main reason for the activity decay is the green oil coverage rather than sulfur poisoning. Although Comparative Example 2 retains the core-shell structure of magnesium oxide-cerium oxide precursor, the oxygen vacancy concentration decreases, which weakens the ability of CeO2 shell to adsorb H2S. 2- The diffusion efficiency was reduced, and after 50 tests, the accumulated sulfur poisoning led to a decrease in the dealkyne rate. Comparative Example 4 had severe sulfur poisoning due to the absence of rare earth and core-shell structure.

[0079] From the catalyst deacetylation rate at different temperatures, this may be because the yttrium-cerium solid solution in Example 2 is converted into acetylation by Y 3+ Doped CeO2 lattice, every two Y 3+ Replace a Ce 4+ The release of a lattice oxygen forms an oxygen vacancy, which acts as a strong electron acceptor to reduce the H2 dissociation barrier compared to traditional Ni catalysts, and can also efficiently generate H at low temperatures. + / H - Dual-function center. + Forming a σ bond with the terminal carbon of the triple bond of the alkyne, H - Provide a negative hydrogen source to achieve directional addition of alkynes at low temperatures. 3+ doping, insufficient oxygen vacancy concentration, low H2 dissociation efficiency; Comparative Example 5 has no rare earth component, the Ni-H bond formation energy barrier is high, and H2 is difficult to dissociate at low temperatures; Comparative Examples 1, 3, and 4 lack yttrium-cerium solid solution or core-shell structure synergy, insufficient low-temperature active centers, and the deacetylation rate is significantly lower than that of Example 2.

[0080] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a rare earth-based hydrogenation catalyst, characterized in that: The following steps are involved: S1. Triethyl phosphate was added to ethanol, and the pH was adjusted to 5-6 with 1 mol / L sulfuric acid, stirred for 20-30 min, and then γ-Al2O3 was added. The temperature was raised to 60-80 ° C, and the reaction was stirred for 2-4 h. The mixture was filtered while hot, washed with deionized water, and dried to obtain a phosphate-modified support Al2O3-P. S2. Magnesium nitrate hexahydrate was added to deionized water and stirred for 20-30 min. Ammonium bicarbonate solution was added dropwise while stirring, and the pH was adjusted to 8.5-9.5 with 1 mol / L ammonia during the addition. After the addition was completed, stirring was continued for 1-2 h, and then the temperature was raised to 70-80 ° C. A cerium nitrate hexahydrate solution was added dropwise, and the pH was adjusted to 8-9 with 1 mol / L ammonia during the addition. After the addition was completed, stirring was continued for 1-3 h, and the temperature was raised to 90-100 ° C again. The hydrothermal reaction was carried out for 5-7 h, cooled to room temperature, filtered, washed, dried, placed in a muffle furnace, heated to 500-600 ° C at a heating rate of 5-7 ° C / min, and calcined for 3-5 h to obtain a magnesium oxide - cerium oxide precursor; S3. Yttrium nitrate and cerium nitrate were added to deionized water to form a mixed solution, which was heated to 55-65 ° C. The sodium hydroxide solution was added dropwise to the mixed solution under stirring. After the addition was completed, the pH of the reaction solution was adjusted to between 9.5 and 10.5, allowed to stand for 5-7 hours, and then transferred to an autoclave, heated to 150-170 ° C, hydrothermally reacted for 10-14 hours, cooled to room temperature, filtered, washed, placed in a muffle furnace at a heating rate of 3-5 ° C, heated to 480-520 ° C, and calcined for 2-4 hours to obtain a yttrium-cerium solid solution; S4. Add magnesium oxide-cerium oxide precursor and yttrium-cerium solid solution to an ethanol / water mixed solution, stir for 30-40 minutes, then add phosphate modified carrier Al2O3-P, heat to 40-50°C, oscillate for reaction for 2-4 hours, cool to room temperature, add nickel nitrate aqueous solution with stirring, then let stand for penetration at room temperature for 1-3 hours, then ultrasonically disperse at 300-500w for 30-40 minutes, filter, wash, put into a muffle furnace, heat to 400-500°C at a heating rate of 5-10°C under a nitrogen atmosphere, calcine for 1-2 hours, cool to 140-160°C, continuously introduce H2O / H2 mixed gas at a gas flow rate of 1-2L / min for 1-3 hours, finally, maintain a nitrogen atmosphere in the muffle furnace, dry for 1-2 hours, and cool to room temperature to obtain a rare earth-based hydrogenation catalyst.

2. The method for preparing a rare earth-based hydrogenation catalyst according to claim 1, wherein The weight ratio of triethyl phosphate, γ-Al2O3 and ethanol in S1 is 0.12-0.16:1:5-7.

3. The method for preparing a rare earth-based hydrogenation catalyst according to claim 1, wherein The weight ratio of magnesium nitrate hexahydrate, ammonium bicarbonate solution, cerium nitrate hexahydrate solution and deionized water in S2 is 1:8-8.4:8-9:2-4.

4. The method for preparing a rare earth-based hydrogenation catalyst according to claim 1, wherein The concentration of the ammonium bicarbonate solution in S2 is 1.5 mol / L, and the concentration of the cerium nitrate hexahydrate solution is 0.5 mol / L.

5. The method for preparing a rare earth-based hydrogenation catalyst according to claim 1, wherein The weight ratio of yttrium nitrate, cerium nitrate, sodium hydroxide solution and deionized water in S3 is 1:2.8-3:30-36:18-20, and the concentration of sodium hydroxide solution is 1 mol / L.

6. The method for preparing a rare earth-based hydrogenation catalyst according to claim 1, wherein The weight ratio of the magnesium oxide-cerium oxide precursor, the yttrium-cerium solid solution, the phosphate-modified carrier Al2O3-P, the nickel nitrate aqueous solution and the ethanol / water mixed solution in S4 is 0.22-0.26:0.15-0.17:1:2-4:2.5-2.

7.

7. The method for preparing a rare earth-based hydrogenation catalyst according to claim 1, wherein: The concentration of the nickel nitrate aqueous solution in S4 is 1 mol / L, and the ethanol / water mixed solution refers to a mixture of ethanol and water in a weight ratio of 1:

1.

8. The method for preparing a rare earth-based hydrogenation catalyst according to claim 1, wherein: In the H2O / H2 mixed gas in S4, the volume ratio of H2O to H2 is 7:

93.

9. A rare earth-based hydrogenation catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the rare earth-based hydrogenation catalyst according to claim 9 in the selective hydrogenation and deacetylation of pyrolysis gasoline.