CN110605125B - Light alkane isomerization catalyst and preparation method thereof - Google Patents

Abstract

The invention relates to the field of solid superacid catalysts, and discloses a light alkane isomerization catalyst and a preparation method thereof. The method comprises (1) dissolving Fe-containing soluble salt, Ga-containing soluble salt and Zr-containing soluble salt (2) under stirring conditions, drop the ammonia solution into the mixed solution to obtain the suspension containing the precipitation; (3) subject the suspension containing the precipitation to water; Thermal reaction, washing, filtering and drying after the hydrothermal reaction is completed to obtain a Fe-Ga doped zirconium hydroxide precursor; (4) after immersing the Fe-Ga doped zirconium hydroxide precursor in a sulfuric acid solution, drying, calcining; (5) impregnating the calcined product obtained in step (4) with a solution of a soluble salt containing Pt, drying and calcining to obtain a light alkane isomerization catalyst. The invention increases the specific surface area and pore volume of the zirconium hydroxide precursor, and improves the light alkane isomerization performance of the catalyst.

Description

Light alkane isomerization catalyst and preparation method thereof

technical field

The invention relates to the field of solid superacid catalysts, in particular to a light alkane isomerization catalyst and a preparation method thereof.

Background technique

With the gradual application of National V and National VI high-standard gasoline across the country, in the production of light alkane isomerization, the provision of high-octane isomerized oil without olefins and aromatics will surely develop rapidly. Isomerization of light alkanes in Fischer-Tropsch naphtha into high value-added isomerized gasoline components will greatly improve the efficiency of the naphtha part, increase the added value of Fischer-Tropsch products, and enhance the Fischer-Tropsch product market Competitiveness, but also in line with the market environment of rising gasoline standards.

Light alkane isomerization is generally carried out under hydrogen conditions, and is a process in which normal alkanes generate corresponding isoalkanes. This reaction is a mildly reversible exothermic reaction. Therefore, low temperature favors the formation of isomeric products. Metal oxide-type solid superacid catalytic materials have the advantages of strong acidity, high thermal stability, easy to separate from the reaction products, environmental friendliness, non-corrosion equipment, and regeneration. Especially, they can catalyze alkane at low temperature The isomerization reaction is thus considered to be the most promising isomerization catalyst with broad application prospects. For example, Pt-SO ₄ ^2- /ZrO ₂ catalysts are low temperature isomerization catalysts with high activity and selectivity, which can produce isomerized oils with higher octane levels. _The preparation parameters of the zirconium hydroxide precursor of this catalyst will affect the structure of ZrO2 and thus the reactivity of the catalyst.

At present, the commonly used method for preparing sulfated zirconia catalyst is zirconium salt hydrolysis precipitation method _. For example, Monoclinic and Tetragonal High Surface Area Sulfated Zirconias in ButaneIsomerization:CO Adsorption and Catalytic Results, Journal of Catalysis 2001, 198: 277–285 reported in the literature that the hydrothermal method was used for hydrothermal treatment at 150 °C for 2-20 hours, respectively, The sulfated ZrO ₂ with high specific surface area was prepared, and the product had higher butane isomerization performance. However, the ZrO ₂ prepared by this method is mainly monoclinic, and has poor activity in the isomerization reaction of C5 and C6.

CN1395995A discloses a mesoporous superacid material with high specific surface and its preparation method. The super acid material is composed of sulfurized metal oxides (such as ZrO ₂ /SO ₄ ^2- ), with P123 or P84 or P65 or polyethylene glycol as surfactants, and water and soluble salts of metal oxides according to a certain formula By mixing, the superacid material is obtained by preparing the precursor, aging, re-vulcanizing, and calcining, and its specific surface area is between 150-200 m ² /g. Monoclinic superacid material.

The surface doping assistant of SO ₄ ^2- /ZrO ₂ is one of the ways to improve the isomerization performance of the catalyst. For example, CN106140198A discloses a Fe and W doped SO ₄ ^2- /ZrO ₂ type catalyst. The invention is to drop an ammonia solution into a mixed solution of Zr and Fe to cause co-precipitation, filter and wash the precipitate and put it away It is dried in an oven to obtain the Fe-doped zirconium hydroxide precursor, and then the corresponding catalyst is obtained by impregnating sulfuric acid and Pt, drying, calcining, and reducing the mixed gas. The preparation process of the invention is complicated, the catalyst with tetragonal phase doped monoclinic phase is prepared, the isomerization reaction activity is low and unstable, the conversion rate of isoparaffin is not high, the highest conversion rate of n-pentane is only 57.2%, and the production cost is at the same time. It is still high, and a certain amount of carbon species remains on the surface after calcination in a hydrogen-nitrogen mixed gas atmosphere, which also affects the activity of the catalyst to a certain extent.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the problems of the light alkane isomerization catalyst existing in the prior art, such as the small specific surface area, the conversion rate of n-hexane and the low selectivity of the target reaction product 2,2-DMB, to provide a light alkane. Preparation method of isomerization catalyst.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing a light alkane isomerization catalyst, comprising the following steps:

(1) Dissolving Fe-containing soluble salt, Ga-containing soluble salt and Zr-containing soluble salt in a solution containing surfactant to obtain a mixed solution;

(2) under stirring conditions, the ammonia solution is added dropwise to the mixed solution to obtain a suspension containing precipitation;

(3) carrying out a hydrothermal reaction with the suspension containing the precipitation, washing, filtering and drying after the hydrothermal reaction to obtain a Fe-Ga doped zirconium hydroxide precursor;

(4) after immersing the Fe-Ga doped zirconium hydroxide precursor in a sulfuric acid solution, drying and calcining;

(5) After impregnating the calcined product obtained in step (4) with a solution of a Pt-containing soluble salt, drying and calcining to obtain a light alkane isomerization catalyst.

The second aspect of the present invention provides a light alkane isomerization catalyst prepared by the above method, which is a Fe- and Ga-doped tetragonal SO ₄ ^2- /ZrO ₂ catalyst supported with Pt.

The method of the invention utilizes surfactant, co-precipitation method and hydrothermal treatment method to synthesize a solid super acid catalyst with tetragonal phase crystals, and by increasing the specific surface area and pore volume of the zirconium hydroxide precursor, the adsorption and adsorption of alkanes in the catalyst are promoted. At the same time, Fe and Ga can be uniformly doped in the tetragonal SO ₄ ^2- /ZrO ₂ catalyst. The light paraffin isomerization catalyst of the present invention can be used in the hydroisomerization reaction of n-paraffin, for example, in the isomerization reaction of n-hexane, and can improve the conversion rate of n-hexane and the target reaction product 2,2- Selectivity of DMB.

Description of drawings

FIG. 1 is the XRD pattern of the light paraffin isomerization catalyst prepared in Examples 1 and 2.

Detailed ways

The endpoints of ranges and any values disclosed herein are not limited to the precise ranges or values, which are to be understood to encompass values proximate to those ranges or values. For ranges of values, the endpoints of each range, the endpoints of each range and the individual point values, and the individual point values can be combined with each other to yield one or more new ranges of values that Ranges should be considered as specifically disclosed herein.

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, but not to limit the present invention.

The invention provides a preparation method of a light alkane isomerization catalyst, comprising the following steps:

(1) Dissolving Fe-containing soluble salt, Ga-containing soluble salt and Zr-containing soluble salt in a solution containing surfactant to obtain a mixed solution;

(2) under stirring conditions, the ammonia solution is added dropwise to the mixed solution to obtain a suspension containing precipitation;

(3) carrying out a hydrothermal reaction with the suspension containing the precipitation, washing, filtering and drying after the hydrothermal reaction to obtain a Fe-Ga doped zirconium hydroxide precursor;

(4) after immersing the Fe-Ga doped zirconium hydroxide precursor in a sulfuric acid solution, drying and calcining;

(5) After impregnating the calcined product obtained in step (4) with a solution of a Pt-containing soluble salt, drying and calcining to obtain a light alkane isomerization catalyst.

The invention simultaneously utilizes the surfactant and the hydrothermal treatment method to increase the specific surface area and pore volume of the zirconium hydroxide precursor, obtains the Fe and Ga doped SO ₄ ^2- /ZrO ₂ type catalyst with high specific surface area, and simultaneously The catalysts Fe and Ga can be uniformly doped in the tetragonal phase ZrO2 _- based catalyst, so that it has good isomerization performance, especially the C6 conversion rate and target product selectivity are high.

According to the present invention, in order to improve the activity of the isomerization reaction and facilitate the doping of additives Fe and Ga, in step (1), the mass ratio of the Fe-containing soluble salt, the Ga-containing soluble salt and the Zr-containing soluble salt 1:2.5-3.5:70-90.

According to the present invention, the Zr-containing soluble salt is zirconium oxychloride, the iron-containing soluble salt can be ferric nitrate, and the Ga-containing soluble salt can be gallium nitrate.

According to the present invention, in order to avoid the formation of agglomeration and collapse of the zirconium hydroxide precursor, thereby increasing the specific surface area and pore volume of the zirconium hydroxide precursor, in step (1), in the solution containing the surfactant, the surfactant The content is 0.1-0.5% by weight, and the solvent is water and ethanol. Preferably, the volume ratio of water to ethanol is 1:0.5-2.

According to the present invention, the surfactant is preferably polyethylene glycol, which is not particularly limited in the present invention, and can be selected with reference to the prior art, for example, it can be PEG400, PEG600, and the addition of polyethylene glycol is easy for subsequent roasting, and During the formation of the zirconium hydroxide precursor, it is beneficial to release Fe ³⁺ and Ga ³⁺ slowly and promote the uniform doping of Fe and Ga.

According to the present invention, in order to avoid agglomeration of the suspension containing the precipitate, in step (2), the stirring speed is preferably 650-950 r/min, and the dropping time is preferably 30-50 min.

According to the present invention, in order to improve the dispersibility and doping amount of Fe and Ga, in step (2), the concentration of the ammonia solution is preferably 1-7 mol/L, and the pH of the suspension containing the precipitate is 9.8- 10.5.

According to the present invention, in order to better build a tetragonal phase structure and make the structure more stable, in step (3), the hydrothermal reaction conditions are that the hydrothermal temperature is 60-150° C., and the hydrothermal reaction is 5-36 h.

According to a preferred embodiment, the Fe-Ga-doped zirconium hydroxide precursor obtained in step (3) has a specific surface area of 300-500 m ² /g, and a pore volume of 0.4-0.6 cm ³ /g.

According to the present invention, in order to prevent the active metal elements from being sintered, in step (4), the concentration of the sulfuric acid solution is preferably 0.1-1.0 mol/L, relative to 1 g of the Fe-Ga doped zirconium hydroxide precursor, so The amount of the sulfuric acid solution is 5-30 mL. In this step, preferably, the calcination temperature is 600-800° C., and the calcination time is 2-12 h.

According to the present invention, in step (5), preferably, the impregnation makes the Pt loading amount to be 0.01-0.10 wt %, which is beneficial to improve the carbon deposition phenomenon. In this step, preferably the calcination temperature is 400-700°C, and the calcination time is 3-10h, which can increase the specific surface area and pore volume of the light alkane isomerization catalyst, increase the surface Fe and Ga content and reduce the surface acid content, The carbon content on the surface of the catalyst is reduced, and the isomerization reaction activity of the light alkane isomerization catalyst is improved.

According to the present invention, the drying conditions of the above steps may include: a temperature of 100-130° C. and a time of 12-24 hours. And the specific drying conditions of each step may be the same or different.

The present invention also provides a light paraffin isomerization catalyst prepared by the above method. The catalyst prepared by the method of the invention is a Fe- and Ga-doped tetragonal SO ₄ ^2- /ZrO ₂ catalyst loaded with Pt.

The method of the invention utilizes surfactant, co-precipitation method and hydrothermal treatment method to synthesize a solid super acid catalyst with tetragonal phase crystals, and by increasing the specific surface area and pore volume of the precursor of the catalyst, the adsorption of alkanes in the catalyst and the increase of the pore volume are promoted. At the same time, Fe and Ga can be uniformly doped in the tetragonal SO ₄ ^2- /ZrO ₂ catalyst.

The present invention will be described in detail below by means of examples. In the following examples, the test methods and raw materials involved are as follows:

The catalyst specific surface area and pore volume were measured by N adsorption _- desorption method;

Unless otherwise specified, the raw materials used are all commercially available products.

Example 1

Take 100mL of water, 100mL of ethanol and 0.556g of polyethylene glycol (PEG400), stir evenly to obtain a solution containing surfactant; take 50g of zirconium oxychloride, 0.7g of iron nitrate, 2.0g of gallium nitrate, dissolve in the above In the solution of the active agent, a mixed solution was obtained; under the stirring condition of the rotating speed of 800 r/min, the ammonia water with a concentration of 6moL/L was dropped into the mixed solution for 40 minutes to be hydrolyzed to form a precipitate to obtain a suspension containing the precipitate; The precipitated suspension was put into a hydrothermal kettle, hydrothermally heated at 110 °C for 22 h, the suspension in the hydrothermal kettle was taken out, filtered, the precipitate was washed with ethanol, and dried at 110 °C for 24 h to obtain Fe-Ga doped The zirconium hydroxide precursor, the pore structure parameters of the zirconium hydroxide precursor are shown in Table 1; Zirconium hydroxide precursor, the amount of sulfuric acid solution was 15 mL), dried at 110 °C for 24 h, calcined at 700 °C for 3 h; finally impregnated the calcined product with an aqueous solution of H ₂ PtCl ₆ , then dried at 110 ° C for 24 h, 500 ° C After calcination for 3 h, Fe- and Ga-doped tetragonal SO ₄ ^2- /ZrO ₂ catalysts loaded with 0.5 wt% Pt were prepared. It can be seen from Figure 1 that the characteristic peaks of standard tetragonal ZrO ₂ appear in the XRD pattern of the tetragonal SO ₄ ^2- /ZrO ₂ catalyst.

Example 2

Take 125mL of water, 125mL of ethanol and 0.556g of polyethylene glycol (PEG400), stir evenly to obtain a solution containing surfactant; The mixed solution was obtained in the solution of the agent; under the stirring condition of the rotating speed of 950r/min, 6moL/L ammonia water was dropped into the mixed solution for 30 minutes to hydrolyze to form a precipitate, and a suspension containing the precipitate was obtained; the suspension containing the precipitate was The turbid liquid was put into a hydrothermal kettle, hydrothermally heated at 110 °C for 22 hours, the suspension in the hydrothermal kettle was taken out, then filtered, the precipitate was washed with ethanol, and dried at 110 °C for 24 hours to obtain Fe-Ga doped zirconium hydroxide For the precursor, the pore structure parameters of the zirconium hydroxide precursor are shown in Table 1; 15mL) with stirring and immersion for 1 hour, dried at 110°C for 24h, and calcined at 700°C for 3h; finally impregnated the calcined product with an aqueous solution of H ₂ PtCl ₆ , then dried at 110° C for 24h, and calcined at 500° C for 3h. A Fe- and Ga-doped tetragonal SO ₄ ^2- /ZrO ₂ catalyst loaded with 0.5 wt% Pt was obtained, and its XRD pattern is shown in Fig. 1 . It can be seen from Figure 1 that the characteristic peaks of standard tetragonal ZrO ₂ appear in the XRD pattern of the tetragonal SO ₄ ^2- /ZrO ₂ catalyst.

Example 3

Take 125mL of water, 125mL of ethanol and 0.556g of polyethylene glycol (PEG600), stir evenly to obtain a solution containing surfactant; The mixed solution was obtained in the solution of the solvent; under the stirring condition of the rotating speed of 800 r/min, 6moL/L ammonia water was dropped into the mixed solution for 40 minutes to make it hydrolyzed to form a precipitate, and a suspension containing the precipitate was obtained; the suspension containing the precipitate was The turbid liquid was put into a hydrothermal kettle, hydrothermally heated at 130 °C for 22 hours, the suspension in the hydrothermal kettle was taken out, then filtered, the precipitate was washed with ethanol, and dried at 110 °C for 24 hours to obtain Fe-Ga doped zirconium hydroxide For the precursor, the pore structure parameters of the zirconium hydroxide precursor are shown in Table 1; , the amount of sulfuric acid solution was 15mL), stirred and immersed for 1 hour, dried at 110°C for 24h, calcined at 700°C for 3h; finally impregnated the calcined product with an aqueous solution of H ₂ PtCl ₆ , then dried at 110° C for 24h, 500° C. After calcination for 3h, Fe- and Ga-doped tetragonal SO ₄ ^2- /ZrO ₂ catalysts loaded with 0.5wt% Pt were prepared. The characteristic peaks of standard tetragonal ZrO ₂ also appeared in the XRD pattern.

Comparative Example 1

The light alkane isomerization catalyst was prepared according to the method of Example 1, except that manganese nitrate was used instead of gallium nitrate to prepare the catalyst. The pore structure parameters of the zirconium hydroxide precursor are shown in Table 1.

Comparative Example 2

The light alkane isomerization catalyst was prepared according to the method of Example 1, except that the surfactant polyethylene glycol (PEG400) was not added to prepare the catalyst. The pore structure parameters of the zirconium hydroxide precursor are shown in Table 1. .

Comparative Example 3

The light alkane isomerization catalyst was prepared according to the method of Example 1, except that the suspension containing the precipitate was not subjected to hydrothermal reaction, and the catalyst was prepared. The pore structure parameters of the zirconium hydroxide precursor are shown in Table 1.

test case

The performance evaluation of the catalysts prepared in Example 1-3 and Comparative Example 1-3 was carried out on a continuous micro-reverse-chromatography device, using n-hexane as the reaction raw material, and the reaction conditions were: pressure 2MPa, temperature 160 ° C, and the hydrogen-hydrocarbon molar ratio was 5. The volume space velocity was 4.0h ^-1 . The catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were evaluated. The results of C6 conversion and 2,2-DMB selectivity are shown in Table 1.

Table 1

It can be seen from the results in Table 1 that, compared with Comparative Examples 1-3, the preparation method of Example 1-3 effectively improves the specific surface area and pore volume of the catalyst, and at the same time, the prepared catalyst makes the C6 conversion rate (8h) It can reach more than 93%, and the selectivity of the target product 2,2-DMB can reach more than 38%.

The preferred embodiments of the present invention have been described above in detail, however, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, a variety of simple modifications can be made to the technical solutions of the present invention, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed in the present invention. All belong to the protection scope of the present invention.

Claims (10)

1. a preparation method of light alkane isomerization catalyst, is characterized in that, comprises the following steps: (1) Dissolving Fe-containing soluble salt, Ga-containing soluble salt and Zr-containing soluble salt in a solution containing surfactant to obtain a mixed solution; (2) under stirring conditions, the ammonia solution is added dropwise to the mixed solution to obtain a suspension containing precipitation; (3) carrying out a hydrothermal reaction with the suspension containing the precipitation, washing, filtering and drying after the hydrothermal reaction to obtain a Fe-Ga doped zirconium hydroxide precursor; (4) after immersing the Fe-Ga doped zirconium hydroxide precursor in a sulfuric acid solution, drying and calcining; (5) after impregnating the calcined product obtained in step (4) with a solution of a soluble salt containing Pt, drying and calcining to obtain a light alkane isomerization catalyst; Wherein, the surfactant is polyethylene glycol. 2. The preparation method according to claim 1, wherein in step (1), the mass ratio of the Fe-containing soluble salt, the Ga-containing soluble salt and the Zr-containing soluble salt is 1: 2.5-3.5 : 70-90; and/or, the Zr-containing soluble salt is zirconium oxychloride. 3. preparation method according to claim 1, is characterized in that, in step (1), in described solution containing surfactant, the content of surfactant is 0.1-0.5 weight %, and solvent is water and ethanol; And/or, the volume ratio of water to ethanol is 1:0.5-2. 4. preparation method according to claim 1 is characterized in that, in step (2), the speed of described stirring is 650-950r/min, and described dropping time is 30-50min. 5. preparation method according to claim 1 is characterized in that, in step (2), the concentration of described ammonia solution is 1-7mol/L, and the pH of the described suspension containing precipitation is controlled to be 9.8-10.5 . 6 . The preparation method according to claim 1 , wherein, in step (3), the hydrothermal reaction conditions include: a temperature of 60-150° C. and a time of 5-36 h. 7 . 7. The preparation method according to any one of claims 1-6, wherein in step (3), the specific surface area of the Fe-Ga-doped zirconium hydroxide precursor is 300-500 m ² / g, the pore volume is 0.4-0.6 cm ³ /g. 8. The preparation method according to claim 1, wherein in step (4), the concentration of the sulfuric acid solution is 0.1-1.0 mol/L; relative to 1 g of the Fe-Ga doped zirconium hydroxide Precursor, the consumption of the sulfuric acid solution is 5-30mL; And/or, the calcination temperature is 600-800°C, and the calcination time is 2-12h. 9. The preparation method according to claim 1, wherein in step (5), the impregnation makes the loading of Pt be 0.01-0.10wt%; And/or, the calcination temperature is 400-700°C, and the calcination time is 3-10h. 10. The light paraffin isomerization catalyst prepared by the preparation method according to any one of claims 1-9.

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