阅读说明：本技术 一种含碱土金属的环烷烃脱氢催化剂及其制备方法 (Alkaline earth metal-containing cycloparaffin dehydrogenation catalyst and preparation method thereof ) 是由 李向伟 高忠民 于 2019-12-03 设计创作，主要内容包括：本发明涉及一种含碱土金属的环烷烃脱氢催化剂及其制备方法,以Pt为活性金属组分,以Sn为助剂组分,载体为含碱土金属、硫和钛的氧化铝载体。本发明提供的催化剂以含碱土金属和含钛的含硫型氧化铝为载体,以Pt为活性金属组分,以Sn为助剂组分。在载体原位制备载体的过程中所形成的碱土金属-Ti-Al骨架结构能够显著改善载体表面氧化铝酸性单一的特点,显著降低氧化铝载体的酸性,提高催化剂的抗积炭性能,提高催化剂的高温活性和稳定性。氧化铝载体中钛和硫的存在,不仅提高了载体表面活性金属的分散度,而且能够促进活性金属组分和助剂组分活性相的形成,提高催化剂的高温活性和稳定性。(The invention relates to a naphthene dehydrogenation catalyst containing alkaline earth metal and a preparation method thereof. The catalyst provided by the invention takes alkaline earth metal-containing and titanium-containing sulfur-containing alumina as a carrier, Pt as an active metal component and Sn as an auxiliary component. The alkaline earth metal-Ti-Al skeleton structure formed in the process of preparing the carrier in situ can obviously improve the characteristic of single acidity of the alumina on the surface of the carrier, obviously reduce the acidity of the alumina carrier, improve the carbon deposition resistance of the catalyst and improve the high-temperature activity and stability of the catalyst. The existence of titanium and sulfur in the alumina carrier not only improves the dispersion degree of active metal on the surface of the carrier, but also can promote the formation of active phases of active metal components and auxiliary components, and improves the high-temperature activity and stability of the catalyst.)

1. A naphthene dehydrogenation catalyst containing alkaline-earth metal is characterized in that Pt is used as an active metal component, Sn is used as an auxiliary component, and a carrier is an alumina carrier containing alkaline-earth metal, sulfur and titanium.

2. The catalyst of claim 1, wherein the catalyst comprises 0.05 to 3.0 wt% of Pt, 0.3 to 5.0 wt% of Sn, 0.3 to 4.0 wt% of an alkaline earth metal, 0.3 to 4.0 wt% of sulfur, and 1.0 to 3.0 wt% of Ti, based on the total weight of the catalyst; preferably, the content of Pt is 0.4-0.7 wt%, the content of Sn is 0.5-2.0 wt%, the content of alkaline earth metal is 0.4-2.0 wt%, the content of sulfur is 0.4-1.25 wt%, and the content of Ti is 1.5-3.0 wt%.

3. The catalyst according to claim 1 or 2, characterized in that the alkaline earth metal is magnesium and/or calcium; and/or the alumina carrier is gamma-Al₂O₃。

4. The catalyst according to any one of claims 1 to 3, wherein the support is in the form of a strip; and/or the equivalent diameter of the carrier is 0.2-5.0 mm; and/or the specific surface area of the carrier is 185-255 m²(ii)/g; and/or the density of the carrier is 0.50-0.90 g/cm³(ii) a Preferably, the equivalent diameter of the carrier is 0.5-2.0 mm, and the specific surface area is 190-230 m²A density of 0.55-0.70 g/cm³。

5. A method for producing an alkaline earth metal-containing cycloalkane dehydrogenation catalyst according to any one of claims 1 to 4, characterized by comprising the steps of:

1) preparing a carrier: adding a theoretical amount of alkaline earth metal sulfate into an aluminum salt solution to prepare an aluminum salt mixed solution, respectively and simultaneously adding the aluminum salt mixed solution, a pH regulator and a titanium salt solution into a gel forming tank by adopting a parallel-flow titration method, forming gel at 60-90 ℃, and after the gel forming is finished, aging, drying, forming and roasting to obtain an alkaline earth metal-containing alumina carrier;

2) impregnation aid and active metal component: impregnating and loading the auxiliary agent component, drying and roasting, impregnating and loading the active metal component, and performing secondary drying and roasting;

3) reduction: and (3) reducing the product obtained in the step (3) by taking hydrogen as a reducing agent to obtain the alkaline earth metal-containing cycloparaffin dehydrogenation catalyst.

6. The method as claimed in claim 5, wherein in the step 1), the aluminum salt solution takes one or more of aluminum trichloride, aluminum sulfate and aluminum nitrate as a solute; and/or the titanium salt solution takes one or more of titanium sulfate, titanium chloride and titanium nitrate as a solute, and preferably adopts titanium sulfate; and/or the alkaline earth metal sulfate is magnesium sulfate and/or calcium sulfate; and/or in the step 1), the pH regulator is ammonia water, preferably, the dosage of the pH regulator is based on the regulation of the pH value of the reaction system to 8-10.

7. The method according to claim 5 or 6, characterized in that step 1): preparing an aluminum trichloride aqueous solution with the concentration of 0.8-1.2M, and adding a theoretical amount of magnesium sulfate and/or calcium sulfate to obtain a mixed salt solution; under the stirring state, adding the mixed salt solution, ammonia water and titanium sulfate into a gel forming tank respectively and simultaneously by adopting a parallel flow titration method, controlling the flow rate to be 1-3 mL/min, and controlling the adding amount of the ammonia water to be based on the regulation of the pH value of a system to be 8-10; carrying out gelling reaction at 60-90 ℃; after the cementing, aging for 0.3-0.8 h, drying for 50-80 h at 40-70 ℃, molding, and roasting for 4-7 h at 500-800 ℃ to obtain the cement.

8. The method according to any one of claims 5 to 7, wherein in the step 2), the drying is performed at 40 to 70 ℃ for 50 to 80 hours; the roasting is carried out for 4-7 h at 500-800 ℃.

9. The method according to any one of claims 5 to 8, wherein in step 2) the promoter component is provided by tin tetrachloride and the Pt in the active metal component is provided by platinum chloride; and/or in the step 3), the reduction temperature is 500-700 ℃, and the reduction pressure is 0.05-0.5 MPa; preferably, the hydrogen-to-catalyst reduction is carried out at a volumetric flow rate ratio V per hour_H2/V_catIs 1000: 1.

10. Use of a catalyst according to any one of claims 1-4 in dehydrogenation reactions of cycloalkanes, preferably in dehydrogenation of cyclohexane to benzene or in dehydrogenation of methylcyclohexane to toluene.

Technical Field

The invention relates to the technical field of catalysts, in particular to a naphthenic hydrocarbon dehydrogenation catalyst containing alkaline earth metal and a preparation method thereof.

Background

Hydrogen energy is currently gaining wide attention as a representative sustainable new energy source. The research on hydrogen energy has been carried out in developed countries such as the united states, japan, europe, canada, and the like. Especially Japanese hydrogen energy sourceAnd (4) sending and utilizing. 26.12.2017, the japanese government issued "basic strategy for hydrogen energy source" (hereinafter referred to as "basic strategy"), and determined the goal of the construction of the hydrogen energy society in 2050 and the specific action plan by 2030. Hydrogen energy is regarded as an important hand for energy structure transformation, energy safety guarantee and climate change response in japan, and no country around the world is concerned with development of hydrogen energy as in japan. Actually, as early as 2014, the japanese government promulgates a "fourth energy basic plan" to accelerate the construction of a "hydrogen energy society". Hydrogen energy is so appreciated because it has many advantages, first of all, it is widely available, storable, transportable, flexible, and safe for energy. Second, CO reduction can be achieved₂And (4) discharging.

The difficulty in establishing an international hydrogen energy supply chain is storage and transportation. The storage and transportation method of hydrogen energy comprises the following steps: high pressure-liquefaction-pipeline (physical hydrogen storage), organic hydrogen compound (chemical hydrogen storage), hydrogen absorbing alloy (absorption hydrogen storage) and the like. The following two ways are preferred in japan: one is the same as the liquefied natural gas method, hydrogen is cooled and liquefied at ultralow temperature of 253 ℃ below zero, and is converted into a liquid form for storage. Japan is currently working in collaboration with australia to jointly develop the supply chain of the liquefied hydrogen industry. The brown coal is tried to be mined in Australia by companies such as Kawasaki heavy industry, the rock valley industry, power supply development and the like, prepared, cooled and liquefied locally, and then shipped to Japan by ships. The second method is a chemical hydrogen storage method, that is, a hydrogen storage technique using a reversible reaction of hydrogenation to dehydrogenation based on benzene and toluene. The four companies of Japan thousand generations of fields chemical engineering construction, Mitsubishi business, Mitsui products and Japan postal carriers jointly form a 'new generation of research society of hydrogen energy industry chain technology', the methane-cyclohexane is utilized to store hydrogen from Wenlai sea to Kawasaki in 2020, and the annual supply scale reaches 210 tons.

Cycloalkanes have received wide attention as organic liquid hydrogen storage materials. The dehydrogenation reaction of cycloalkane is the main reaction for producing hydrogen, and the core of the dehydrogenation reaction is the catalyst for dehydrogenation of cycloalkane. The dehydrogenation process is a strongly endothermic, highly reversible reaction process, and therefore, dehydrogenation is suitably carried out under high temperature conditions from both kinetic and thermodynamic considerations. However, high temperature easily causes carbon deposition and cracking reaction of the catalyst, reduces the activity of the catalyst, and is not favorable for the stability of dehydrogenation reaction. A large number of cycloalkane dehydrogenation catalysts have been studied to improve the dehydrogenation activity and stability of cycloalkanes.

Patent CN1201715 discloses a Pt-Sn-Mg/Al₂O₃A method for preparing the catalyst. Patent CN101066532 discloses a macroporous, low bulk density, but with a bimodal structure of gamma-Al₂O₃The pellet carrier is used for dehydrogenation catalysts of straight-chain alkanes, and has good dehydrogenation performance. USP6103103 discloses a dehydrogenation catalyst using borate and an alkaline earth metal as carriers, platinum as an active metal, and zinc as an adjuvant, which also exhibits good performance. However, these catalysts generally have the problems that the catalysts are easy to deposit carbon and deactivate, and the stability of the catalysts is not high.

The CN107537560A patent reports that the activity and the stability of a cycloparaffin dehydrogenation catalyst taking modified MCM-41 as a carrier are effectively improved. However, the MCM-41 molecular sieve is weak in acidity, carbon deposit is inhibited, and meanwhile, the dispersibility and activity of Pt metal have no obvious advantages, while the traditional Al is adopted₂O₃The carrier is too strong in acidity, and carbon deposition on the surface of the catalyst is serious.

The CN104785256B patent reports a Mg-Al-O composite oxide carrier, which aims to improve the carbon deposition resistance of the carrier. However, the reaction for preparing cyclohexene by dehydrogenation of cycloalkane is advantageous, and if the dehydrogenation activity is further improved to prepare benzene, the properties of active metal and carrier of the catalyst are still required to be further improved, and the carbon deposit resistance of the catalyst is improved.

CN103785423A discloses a preparation method of a sulfurized propane dehydrogenation catalyst, wherein a carrier of the catalyst is prepared into alumina by a sol-gel method, La, Sn and metal sulfide (magnesium sulfide or calcium sulfide) are introduced in the gelling process, and the catalyst shows good performance. However, the sulfur-containing catalyst prepared by the method takes sulfide as a raw material, and toxic gases such as hydrogen sulfide and the like can be generated in the preparation process, so that the production equipment is corroded, and the potential safety hazard of personnel is increased.

In summary, unlike the propane dehydrogenation catalyst, the main problems of the existing cycloalkane dehydrogenation catalyst are that the cycloalkane has a large molecular weight, is liquid at normal temperature, and has poor activity at low temperature, while carbon is easily deposited on the surface of the catalyst at high temperature, so that the catalyst is quickly deactivated, and has poor activity and stability. In order to solve the problems, the cycloparaffin dehydrogenation catalyst carrier has proper acidity, the large-amount generation of carbon deposit on the surface of the catalyst is inhibited, the dispersity of Pt on the surface of the carrier can be improved, more active phases are promoted to be generated on the surface of the catalyst, and the high-temperature activity and the stability of the catalyst are improved.

Disclosure of Invention

Aiming at the defects and shortcomings in the prior art, the invention provides an alkaline earth metal-containing cycloparaffin dehydrogenation catalyst and a preparation method thereof.

The invention aims to provide a naphthenic hydrocarbon dehydrogenation catalyst containing alkaline earth metal, which takes Pt as an active metal component, takes Sn as an auxiliary component and takes an alumina carrier containing alkaline earth metal, sulfur and titanium as a carrier. In the invention, the catalyst takes sulfur-containing alumina containing alkaline earth metal and titanium as a carrier, Pt as an active metal component and Sn as an auxiliary component. The existence of alkaline earth metal, Ti and sulfur on the carrier not only reduces the acidity of the carrier, is beneficial to improving the carbon deposition resistance of the catalyst, but also can improve the dispersion degree of active metal on the surface of the carrier and promote the formation of active phases of active metal components and auxiliary components.

In the process of preparing the alumina carrier by adopting an in-situ preparation method, a proper amount of sulfur-containing alkaline earth metal is introduced, and a Ti-containing compound is introduced as an auxiliary agent, so that the alumina carrier containing a certain amount of alkaline earth metal, sulfur and titanium is prepared. In the process of preparing the carrier in situ, the alkaline earth metal-Ti-Al skeleton structure can obviously improve the characteristic of single acidity of the alumina on the surface of the carrier, obviously reduce the acidity of the alumina carrier, improve the carbon deposition resistance of the catalyst and improve the high-temperature activity and stability of the catalyst. Secondly, the alkaline earth metal-Ti-Al skeleton structure in the carrier can be uniformly dispersed in the carrier, so that the phenomenon of uneven distribution of the active phase of the catalyst caused by partial uneven distribution is avoided, and the stability of the catalyst at high temperature is further improved. Thirdly, the existence of Ti and sulfur in the carrier can promote the dispersion degree of the active metal, and improve the generation of more active phases of the active metal and the auxiliary Sn, thereby further improving the high activity of the catalyst at high temperature. Compared with the post-vulcanization catalyst, the catalyst prepared by the method has more obvious dehydrogenation activity and stability at high temperature.

According to some preferred embodiments of the present invention, based on the total weight of the catalyst, the content of Pt is 0.05 to 3.0 wt%, the content of Sn is 0.3 to 5.0 wt%, the content of alkaline earth metal is 0.3 to 4.0 wt%, the content of sulfur is 0.3 to 4.0 wt%, and the content of Ti is 1.0 to 3.0 wt%; preferably, the content of Pt is 0.4-0.7 wt%, the content of Sn is 0.5-2.0 wt%, the content of alkaline earth metal is 0.4-2.0 wt%, the content of sulfur is 0.4-1.25 wt%, and the content of Ti is 1.5-3.0 wt%.

According to some preferred embodiments of the invention, the alkaline earth metal is magnesium and/or calcium; and/or the alumina carrier is gamma-Al₂O₃。

According to some preferred embodiments of the invention, the support is strip-shaped; and/or the equivalent diameter of the carrier is 0.2-5.0 mm; and/or the specific surface area of the carrier is 185-255 m²(ii)/g; and/or the density of the carrier is 0.50-0.90 g/cm³(ii) a Preferably, the equivalent diameter of the carrier is 0.5-2.0 mm, and the specific surface area is 190-230 m²A density of 0.55-0.70 g/cm³。

In another aspect, the present invention provides a method for preparing the alkaline earth metal-containing cycloalkane dehydrogenation catalyst, comprising the following steps:

1) preparing a carrier: adding a theoretical amount of alkaline earth metal sulfate into an aluminum salt solution to prepare an aluminum salt mixed solution, respectively and simultaneously adding the aluminum salt mixed solution, a pH regulator and a titanium salt solution into a gel forming tank by adopting a parallel-flow titration method, forming gel at 60-90 ℃, and after the gel forming is finished, aging, drying, forming and roasting to obtain an alkaline earth metal-containing alumina carrier; the molding can adopt the technical means commonly used in the field, such as dropping ball molding, extrusion molding and the like;

2) impregnation aid and active metal component: impregnating and loading the auxiliary agent component, drying and roasting, impregnating and loading the active metal component, and performing secondary drying and roasting;

3) reduction: and (3) reducing the product obtained in the step (3) by taking hydrogen as a reducing agent to obtain the alkaline earth metal-containing cycloparaffin dehydrogenation catalyst.

In the invention, a proper amount of sulfur-containing alkaline earth metal is introduced in the process of preparing the alumina carrier by adopting an in-situ preparation method, and a Ti-containing compound is introduced as an auxiliary agent, so that the alumina carrier containing a certain amount of alkaline earth metal, sulfur and titanium is prepared. In the process of preparing the carrier in situ, the alkaline earth metal-Ti-Al skeleton structure can obviously improve the characteristic of single acidity of the alumina on the surface of the carrier, obviously reduce the acidity of the alumina carrier, improve the carbon deposition resistance of the catalyst and improve the high-temperature activity and stability of the catalyst. Secondly, the alkaline earth metal-Ti-Al skeleton structure in the carrier can be uniformly dispersed in the carrier, so that the phenomenon of uneven distribution of the active phase of the catalyst caused by partial uneven distribution is avoided, and the stability of the catalyst at high temperature is further improved. Thirdly, the existence of Ti and sulfur in the carrier can promote the dispersion degree of the active metal, and improve the generation of more active phases of the active metal and the auxiliary Sn, thereby further improving the high activity of the catalyst at high temperature. Compared with the post-vulcanization catalyst, the catalyst prepared by the method has more obvious dehydrogenation activity and stability at high temperature. Meanwhile, the alkaline earth metal is not easy to run off, and the catalyst is ensured to have better stability at high temperature.

According to some preferred embodiments of the present invention, in step 1), the aluminum salt solution uses one or more of aluminum trichloride, aluminum sulfate and aluminum nitrate as a solute, preferably aluminum trichloride, and the concentration of the aluminum salt solution is 0.8 to 1.2M; and/or the titanium salt solution takes one or more of titanium sulfate, titanium chloride and titanium nitrate as a solute, and preferably adopts titanium sulfate; and/or the alkaline earth metal sulfate is magnesium sulfate and/or calcium sulfate; and/or in the step 1), the pH regulator is ammonia water, preferably, the dosage of the pH regulator is based on the regulation of the pH value of the reaction system to 8-10. According to the invention, the gelling reaction is controlled to be carried out under the condition of pH value of 8-10, which is beneficial to uniform precipitation of the alumina precursor, the specific surface area of the carrier is large, and uniform precipitation and dispersion of sulfate ions, alkaline earth metal ions and Ti ions in the carrier are ensured.

According to some preferred embodiments of the invention, step 1): preparing an aluminum trichloride aqueous solution with the concentration of 0.8-1.2M, and adding a theoretical amount of magnesium sulfate and/or calcium sulfate to obtain a mixed salt solution; under the stirring state, adding the mixed salt solution, ammonia water and titanium sulfate into a gel forming tank respectively and simultaneously by adopting a parallel flow titration method, controlling the flow rate to be 1-3 mL/min, and controlling the adding amount of the ammonia water to be based on the regulation of the pH value of a system to be 8-10; carrying out gelling reaction at 60-90 ℃; after the cementing, aging for 0.3-0.8 h, drying for 50-80 h at 40-70 ℃, molding, and roasting for 4-7 h at 500-800 ℃ to obtain the cement. In the preparation of the carrier, magnesium or calcium ions of alkaline earth metal, Ti ions and aluminum ions are subjected to coprecipitation to generate a certain amount of alkaline earth metal-Ti-Al skeleton structure, and the alkaline earth metal-Ti-Al skeleton structure is uniformly dispersed in the carrier and can play a role in weakening the acidity of the surface of the carrier, so that the carbon deposition on the surface of the carrier is reduced, the carbon deposition resistance of the catalyst is improved, and the high-temperature activity and the stability of the catalyst are improved. Meanwhile, the alkaline earth metal is not easy to run off, and the catalyst is ensured to have better stability.

According to some preferred embodiments of the present invention, in the step 2), the drying is performed at 40 to 70 ℃ for 50 to 80 hours; the roasting is carried out for 4-7 h at 500-800 ℃.

According to some preferred embodiments of the invention, in step 2), the promoter component is provided by tin tetrachloride and the Pt in the active metal component is provided by platinum chloride.

According to some preferred embodiments of the present invention, in the step 3), the reduction temperature is 500 to 700 ℃, and the reduction pressure is 0.05 to 0.5 MPa; preferably, the hydrogen-to-catalyst reduction is carried out at a volumetric flow rate ratio V per hour_H2/V_catIs 1000: 1.

In another aspect, the invention provides the use of said catalyst in dehydrogenation of cycloalkanes, preferably in dehydrogenation of cyclohexane to benzene or in dehydrogenation of methylcyclohexane to toluene.

The invention has the beneficial effects that: the catalyst of the invention has the space velocity of 2.0h at 430 DEG C^-1When the pressure was 1.0MPa and the hydrogen-oil volume ratio was 400, the yield of benzene after 30 days was 84.3% and the carbon deposit amount was less than 2 wt%. The results show that the catalyst has outstanding low-carbon alkane dehydrogenation activity and selectivity, has outstanding carbon deposit resistance and ensures the stability of the catalyst at high temperature.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. The technical solution of the present invention is not limited to the following specific embodiments, and includes any combination of the specific embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.

In the present invention, the specific techniques or conditions not specified in the examples are performed according to the techniques or conditions described in the literature in the art or according to the product specification. The instruments and the like are conventional products which are purchased by normal distributors and are not indicated by manufacturers. The chemical raw materials used in the invention can be conveniently bought in domestic chemical product markets.