阅读说明：本技术 一种临氢异构化催化剂及其制备方法和应用 (Hydroisomerization catalyst and preparation method and application thereof ) 是由 张在忠 赵兴涛 马俊青 张勇 于 2020-07-22 设计创作，主要内容包括：本发明公开了一种临氢异构化催化剂及其制备方法和应用,属于催化剂技术领域。所述催化剂包括如下原料：载体、贵金属和稀土元素；所述载体包括氢氧化铝干胶、HY分子筛和HZSM-5分子筛,所述氢氧化铝干胶为载体总重量的26%~43%,所述HY分子筛为载体总重量的49%~63%,所述HZSM-5分子筛为载体总重量的7%~21%；所述贵金属为载体总重量的0.1%~1%；所述稀土元素为载体总重量的1%~4%。本发明提供的临氢异构化催化剂,能够有效提高正构烷烃的转化率和异构化选择性,且裂化率低。(The invention discloses a hydroisomerization catalyst, a preparation method and application thereof, belonging to the technical field of catalysts. The catalyst comprises the following raw materials: a carrier, a noble metal and a rare earth element; the carrier comprises aluminum hydroxide dry glue, an HY molecular sieve and an HZSM-5 molecular sieve, wherein the aluminum hydroxide dry glue accounts for 26-43% of the total weight of the carrier, the HY molecular sieve accounts for 49-63% of the total weight of the carrier, and the HZSM-5 molecular sieve accounts for 7-21% of the total weight of the carrier; the noble metal accounts for 0.1-1% of the total weight of the carrier; the rare earth element accounts for 1-4% of the total weight of the carrier. The hydroisomerization catalyst provided by the invention can effectively improve the conversion rate and isomerization selectivity of normal paraffins, and has low cracking rate.)

1. A hydroisomerization catalyst is characterized by comprising the following raw materials: a carrier, a noble metal and a rare earth element; the carrier comprises aluminum hydroxide dry glue, an HY molecular sieve and an HZSM-5 molecular sieve, wherein the aluminum hydroxide dry glue accounts for 26-43% of the total weight of the carrier, the HY molecular sieve accounts for 49-63% of the total weight of the carrier, and the HZSM-5 molecular sieve accounts for 7-21% of the total weight of the carrier;

the noble metal accounts for 0.1-1% of the total weight of the carrier;

the rare earth element accounts for 1-4% of the total weight of the carrier.

2. The hydroisomerization catalyst according to claim 1, wherein said noble metal is Pt or Pd.

3. The hydroisomerization catalyst according to claim 1, wherein said rare earth element is La or Ce.

4. A process for the preparation of a hydroisomerization catalyst as claimed in any one of claims 1 to 3, comprising the steps of:

1) mixing aluminum hydroxide dry glue, an HZSM-5 molecular sieve and an HY molecular sieve, adding deionized water, and sequentially kneading, extruding and forming, drying and roasting to obtain a catalyst carrier;

2) respectively preparing noble metal and rare earth elements into solutions, soaking the catalyst carrier obtained in the step 1) with the obtained noble metal solution and rare earth element solution, and then sequentially drying and roasting to obtain the hydroisomerization catalyst.

5. The preparation method according to claim 4, wherein the roasting temperature in the steps 1) and 2) is 400-600 ℃ and the roasting time is 3.5-4.5 h.

6. The preparation method of claim 4, wherein the drying temperature in the step 1) is 100-120 ℃ and the drying time is 2-6 h.

7. The preparation method of claim 4, wherein the drying temperature in the step 2) is 100-120 ℃ and the drying time is 10-16 h.

8. The method for preparing a porous material according to claim 4, wherein the impregnation method in the step 2) is an equal-volume impregnation method.

9. Use of the hydroisomerization catalyst of any one of claims 1 to 3 in the hydroisomerization reaction of n-hexane.

10. The use according to claim 9, wherein the reaction conditions for the isomerization of n-hexane are: temperature: 220-300 ℃, hydrogen-oil molar ratio: 300: 1-700: 1, reaction pressure: 0.5Mpa to 2.5Mpa, and the volume space velocity is 0.5 to 2.5h^-1。

Technical Field

The invention relates to the technical field of catalysts, in particular to a hydroisomerization catalyst and a preparation method and application thereof.

Background

In the production of gasoline, the octane number can be improved by utilizing a hydroisomerization technology, and the higher the isomerization degree is, the more the octane number is favorably improved. In recent years, due to the requirement of environmental protection and the enhancement of environmental awareness of people, the quality requirement of the automobile fuel is higher and higher, and the gasoline is developed to low olefin, low aromatic hydrocarbon and high octane number.

The conventional zeolite type bifunctional catalyst mainly refers to a catalyst prepared by taking crystalline silicate as a carrier and alumina or other high-temperature-resistant oxides as a binder and loading noble metal platinum or palladium. The reaction mechanism is generally considered that normal paraffin firstly dehydrogenates on active metal to form olefin, then transfers to acidic site to protonate to form carbonium ion, and the carbonium ion isomerizes on the acidic site to form branched carbonium ion, and then the branched carbonium ion diffuses to the active metal center to hydrogenate, and finally isoparaffin is generated. The overall reaction process requires a suitable distribution of acidic sites and metal active sites, and generally the activity and isomerization selectivity of the bifunctional catalyst is optimal only when the hydrogenation/dehydrogenation active centers of the metal are in equilibrium with the acid function of the support. At the same time, the mechanism also shows that the side reaction of cracking can exist at the same time of isomerization reaction. In the prior art, the medium-temperature isomerization catalyst molecular sieve has single carrier, the strong and weak acid proportion is difficult to regulate and control, and the preparation process of the compound molecular sieve is complex and has high cost. Moreover, the acidity of the molecular sieve and the active center of the noble metal are difficult to balance, and better normal alkane conversion rate and isomerization selectivity are difficult to obtain.

Disclosure of Invention

Aiming at the technical problem that better normal paraffin conversion rate and isomerization selectivity are difficult to obtain in the background technology, the invention provides a hydroisomerization catalyst, a preparation method and application thereof, which can effectively improve the normal paraffin conversion rate and isomerization selectivity and have low cracking rate.

In order to solve the technical problems, the invention provides a hydroisomerization catalyst, which comprises the following raw materials: a carrier, a noble metal and a rare earth element; the carrier comprises aluminum hydroxide dry glue, an HY molecular sieve and an HZSM-5 molecular sieve, wherein the aluminum hydroxide dry glue accounts for 26-43% of the total weight of the carrier, the HY molecular sieve accounts for 49-63% of the total weight of the carrier, and the HZSM-5 molecular sieve accounts for 7-21% of the total weight of the carrier;

the noble metal accounts for 0.1-1% of the total weight of the carrier;

the rare earth element accounts for 1-4% of the total weight of the carrier.

Preferably, the noble metal is Pt or Pd.

Preferably, the rare earth element is La or Ce.

The invention provides a preparation method of the hydroisomerization catalyst, which comprises the following steps:

1) mixing aluminum hydroxide dry glue, an HZSM-5 molecular sieve and an HY molecular sieve, adding deionized water, and sequentially kneading, extruding and forming, drying and roasting to obtain a catalyst carrier;

2) respectively preparing noble metal and rare earth elements into solutions, soaking the catalyst carrier obtained in the step 1) with the obtained noble metal solution and rare earth element solution, and then sequentially drying and roasting to obtain the hydroisomerization catalyst.

Preferably, the roasting temperature is 400-600 ℃ respectively and independently, and the roasting time is 3.5-4.5 h respectively and independently.

Preferably, the drying temperature in the step 1) is 100-120 ℃, and the time is 2-6 h.

Preferably, the drying temperature in the step 2) is 100-120 ℃, and the time is 10-16 h.

Preferably, the impregnation method in the step 2) is an equal-volume impregnation method.

The invention provides an application of the hydroisomerization catalyst in the scheme in a normal hexane hydroisomerization reaction.

Preferably, the reaction conditions during the n-hexane isomerization reaction are as follows: temperature: 220-300 ℃, hydrogen-oil molar ratio: 300: 1-700: 1, reaction pressure: 0.5Mpa to 2.5Mpa, and the volume space velocity is 0.5 to 2.5h^-1。

Compared with the prior art, the invention has the following technical effects:

the hydroisomerization catalyst provided by the invention adopts aluminum hydroxide dry glue, an HY molecular sieve, an HZSM-5 molecular sieve, noble metal and rare earth elements as raw materials, the catalyst contains two molecular sieves HY and HZSM-5 with different acid strengths, and a molecular sieve carrier after mixing and screening has better acid distribution, so that not only are the medium-strong acid position and the strong acid position of the HZSM-5 molecular sieve obtained, but also the high cracking rate of the HZSM-5 molecular sieve caused by difficulty in diffusion of double-branched-chain molecules due to small pore diameters is weakened. The mixed optimized molecular sieve is modified by rare earth elements, so that the B acid site required by alkane isomerization is further increased, and meanwhile, the introduction of the rare earth elements improves the dispersion performance of active metals, so that better active metal-acid site matching is obtained. Has better conversion rate and isomerization rate.

Drawings

FIG. 1 is a graph showing the distribution of Pt/Pd grain sizes of catalysts prepared in examples 1-4 and comparative examples 1-4.

Detailed Description

The invention provides a hydroisomerization catalyst, which comprises the following raw materials: a carrier, a noble metal and a rare earth element; the carrier comprises aluminum hydroxide dry glue, an HY molecular sieve and an HZSM-5 molecular sieve, wherein the aluminum hydroxide dry glue accounts for 26-43% of the total weight of the carrier, the HY molecular sieve accounts for 49-63% of the total weight of the carrier, and the HZSM-5 molecular sieve accounts for 7-21% of the total weight of the carrier;

the noble metal accounts for 0.1-1% of the total weight of the carrier;

the rare earth element accounts for 1-4% of the total weight of the carrier.

In the invention, the carrier comprises aluminum hydroxide dry glue, HY molecular sieve and HZSM-5 molecular sieve. The aluminum hydroxide dry glue accounts for 26-43% of the total weight of the carrier, and is preferably 30%. The HY molecular sieve accounts for 49-63% of the total weight of the carrier, and is preferably 56%. The HZSM-5 molecular sieve accounts for 7-21% of the total weight of the carrier, and is preferably 14%.

In the invention, the noble metal is 0.1-1%, preferably 0.2-0.5%, and more preferably 0.4% of the total weight of the carrier. The noble metal is preferably Pt or Pd, more preferably Pt.

In the invention, the rare earth element accounts for 1-4% of the total weight of the carrier, and preferably accounts for 2%. In the present invention, the rare earth element is preferably La or Ce, more preferably La. In the invention, the rare earth element is a carrier modified element, and can improve the dispersion property of the active metal, thereby obtaining better active metal-acid site matching.

According to the invention, two molecular sieves with different acid strengths, namely HY and HZSM-5, are adopted, and the molecular sieve carrier after mixing and screening has better acid distribution, so that a medium strong acid position and a strong acid position of the HZSM-5 molecular sieve are obtained, and the high cracking rate of the HZSM-5 molecular sieve caused by difficulty in diffusion of double-branched-chain molecules due to small pore diameters is weakened. The mixed optimized molecular sieve is modified by rare earth elements, so that the B acid site required by alkane isomerization is further increased, and meanwhile, the introduction of the rare earth elements improves the dispersion performance of active metal, so that better active metal-acid site matching is obtained, and better conversion rate and isomerization rate are achieved.

The invention provides a preparation method of the hydroisomerization catalyst, which comprises the following steps:

1) mixing aluminum hydroxide dry glue, an HZSM-5 molecular sieve and an HY molecular sieve, adding deionized water, and sequentially kneading, extruding and forming, drying and roasting to obtain a catalyst carrier;

2) respectively preparing noble metal and rare earth elements into solutions, soaking the catalyst carrier obtained in the step 1) with the obtained noble metal solution and rare earth element solution, and then sequentially drying and roasting to obtain the hydroisomerization catalyst.

The preparation method comprises the steps of mixing aluminum hydroxide dry glue, an HZSM-5 molecular sieve and an HY molecular sieve, adding deionized water, and sequentially kneading, extruding, forming, drying and roasting to obtain the catalyst carrier. In the invention, the addition amount of the deionized water is preferably 5-20% of the total weight of the carrier, and more preferably 15%. In the present invention, in order to facilitate the binding of the components in the carrier, the catalyst carrier is prepared, and a binder is preferably added before kneading. In the invention, the volume of the binder is preferably 5-10% of the total weight of the carrier, and more preferably 7.5% by weight and volume percentage. In the present invention, the binder is preferably an aqueous citric acid solution, an aqueous acetic acid solution, or an aqueous nitric acid solution, and more preferably an aqueous nitric acid solution. The mass concentration of the binder is preferably 2.5-3.5%, and more preferably 3%. In the present invention, sesbania powder is preferably added before kneading for the convenience of extrusion molding. In the invention, the sesbania powder is preferably 1-2% of the total weight of the carrier, and more preferably 1.5%. In the present invention, the extrusion is preferably carried out using a twin-screw extruder. In the invention, the drying temperature is preferably 100-120 ℃, and more preferably 110 ℃; the drying time is preferably 2-6 h, and more preferably 4 h. In the invention, the roasting temperature is preferably 400-600 ℃, and more preferably 550 ℃; the roasting time is preferably 3.5-4.5 h, and more preferably 4 h.

After the catalyst carrier is obtained, noble metal and rare earth elements are respectively prepared into solution, the catalyst carrier is impregnated with the obtained noble metal solution and rare earth element solution, and then the catalyst carrier is dried and roasted in sequence to obtain the hydroisomerization catalyst. In the present invention, it is preferable to prepare a noble metal solution by mixing a metal acid or chloride of a noble metal with distilled water. In the present invention, it is preferable to use lanthanum nitrate and add distilled water to prepare a rare earth element solution. In the present invention, the impregnation method is preferably an equivalent-volume impregnation method. The isovolumetric impregnation method preferably comprises the steps of 1) drying the support to be impregnated at 120 ℃ for 2 h; 2) immersing the dried carrier into distilled water for 6h, and measuring the water absorption rate; 3) calculating the volume of the required impregnation liquid according to the mass of the impregnated carrier; 4) calculating the dosage of the required noble metal/rare earth element and distilled water according to the concentration of the noble metal solution/rare earth element solution required to be prepared and the volume of the required impregnation solution obtained by the calculation in the step 3), preparing the noble metal solution/rare earth element solution, and impregnating the catalyst carrier into the prepared noble metal solution/rare earth element solution. For example, a 200g catalyst carrier is prepared by 60g of alumina dry gel and 140g of HY molecular sieve, chloroplatinic acid is adopted to impregnate the catalyst carrier by an isometric method, the mass fraction of Pt in the catalyst is 0.4%, and the specific impregnation method is as follows: 1) drying the catalyst carrier at 120 ℃ for 2 h; 2) immersing the dried carrier into distilled water for 6h, and measuring the water absorption rate to be 35.87 mL; 3) 35.87mL of chloroplatinic acid aqueous solution is needed for dipping 200g of catalyst carrier; 4) when the mass fraction of Pt in the catalyst is 0.4%, 2.1248g of chloroplatinic acid is needed, 2.1248g of chloroplatinic acid is dissolved by distilled water until the volume of the solution is 35.87mL, and the chloroplatinic acid aqueous solution is prepared to impregnate the catalyst carrier.

In the invention, the drying temperature is preferably 100-120 ℃, and more preferably 110 ℃; the drying time is preferably 10-16 h, and more preferably 12 h. In the invention, the roasting temperature is preferably 400-600 ℃, and more preferably 500 ℃; the roasting time is preferably 3.5-4.5 h, and more preferably 4 h.

The present invention has no special limitation on the source of the material, reagent and apparatus for preparing the hydroisomerization catalyst, and may be prepared with conventional commercial products in the art.

The invention provides an application of the hydroisomerization catalyst in the scheme in a normal hexane hydroisomerization reaction.

Preferably, the reaction conditions during the n-hexane isomerization reaction are as follows: temperature: 220-300 ℃, hydrogen-oil molar ratio: 300: 1-700: 1, reaction pressure: 0.5Mpa to 2.5Mpa, and the volume space velocity is 0.5 to 2.5h^-1More preferably, the temperature: 280 ℃, hydrogen-oil molar ratio: 500:1, reaction pressure: 1.5Mpa, and the volume space velocity is 1h^-1。

In order to further illustrate the present invention, the following embodiments are described in detail, but they should not be construed as limiting the scope of the present invention.