Alkane isomerization catalyst and preparation method thereof

Abstract

The present invention provides an alkane isomerization catalyst and a preparation method thereof. The preparation method comprises the following steps: (1) subjecting a composite oxide gel to temperature-programmed sulfurization to obtain a sulfur-modified catalyst intermediate; and (2) impregnating the sulfur-modified catalyst intermediate in step (1) with a precious metal source, drying, and calcining the catalyst to obtain an alkane isomerization catalyst. The present invention utilizes temperature-programmed vapor-phase sulfurization technology to simultaneously perform the drying, sulfurization, and crystallization processes of the composite oxide gel, thereby improving the structure and acid strength of existing sulfated zirconia-based catalysts and enhancing their catalytic activity and product selectivity in alkane isomerization reactions.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic materials, and in particular relates to an alkane isomerization catalyst and a preparation method thereof. Background Art

[0002] The isomerization of light alkanes to produce isoparaffins is an important means of improving gasoline octane rating. Currently, the most widely used catalyst for light alkane isomerization in industry is noble metal-supported chlorinated alumina catalysts. The noble metal and chlorine on the catalyst surface provide metal active sites and acidic sites, respectively, for the isomerization reaction, endowing this catalyst with excellent isomerization activity.

[0003] However, these catalysts suffer from a serious drawback: unstable surface acidic sites. The chlorine on the catalyst surface is irreversibly destroyed by water, oxygen, sulfur, and their compounds, leading to surface chlorine loss during the hydroisomerization reaction. This presents two challenges: first, alkaline washing equipment is required to prevent chlorine loss, which can lead to product contamination and equipment corrosion; second, continuous chlorine replenishment is required during the reaction to maintain strong acidity on the catalyst surface.

[0004] To address the above issues, US Pat. No. 6,180,555 discloses a sulfated zirconia-based alkane isomerization catalyst support. The zirconia gel is prepared using an alkaline precipitation method. The zirconia gel is then impregnated in a sulfuric acid solution and activated at high temperature to obtain a sulfated zirconia catalyst. The catalyst has strong acidic sites and isomerization catalytic activity. To further increase the specific surface area and porosity of the sulfated zirconia catalyst, CN Pat. No. 1,213,806C discloses a method for preparing bulky sulfated zirconia. During the catalyst preparation process, the zirconia gel is washed with an organic polar solvent, increasing the porosity and isomerization activity of the sulfated zirconia. CN Pat. No. 1,159,099C discloses a sulfated zirconia catalyst. Silicon oxide and aluminum oxide are added during the preparation of the zirconia gel to improve the surface utilization efficiency and catalyst surface area of ​​the zirconia, increase the number of medium-to-strong acidic sites, and thus improve the catalyst's surface structure and catalytic isomerization performance.

[0005] Although sulfated zirconia-based catalysts have good catalytic activity in alkane isomerization reactions, the strong acidic solution causes uncontrollable and severe etching during acid leaching, causing the pores of the oxide support to collapse and the specific surface area to decrease, making its surface acidity lower than that of chlorided alumina-based catalysts. In addition, cracking side reactions occur during the catalytic isomerization reaction, resulting in a decrease in the selectivity of the isomerized products.

[0006] In summary, developing a new method for preparing sulfated zirconia-based catalysts and improving their surface acidity and stability are technical problems that need to be urgently solved by those skilled in the art. Summary of the Invention

[0007] The present invention aims to provide an alkane isomerization catalyst and a preparation method thereof. The invention adopts a temperature-programmed vapor-phase sulfation technology to synchronize the drying, sulfation and crystallization processes of the composite oxide gel, thereby improving the organizational structure and acid strength of the existing sulfated zirconia-based catalyst, and enhancing its catalytic activity and product selectivity in the alkane isomerization reaction.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing an alkane isomerization catalyst, the preparation method comprising:

[0010] (1) subjecting the composite oxide gel to programmed temperature sulfurization to obtain a sulfur-modified catalyst intermediate;

[0011] (2) The sulfur-modified catalyst intermediate of step (1) is impregnated in a noble metal source, and after drying and calcining, an alkane isomerization catalyst is obtained.

[0012] In the present invention, the alkane isomerization includes normal alkane isomerization or isoalkane normalization, specifically: normal alkane isomerization to generate isoalkane with alkyl side chain or isoalkane undergoes carbon chain skeleton rearrangement reaction to obtain normal alkane without alkyl side chain.

[0013] The present invention innovatively subjecting the composite oxide gel to programmed temperature sulfurization in a sulfur-containing atmosphere, and simultaneously carrying out the drying, sulfation and crystallization processes of the composite oxide, thereby improving the organizational structure of the sulfated composite oxide carrier in the prior art, while increasing the specific surface area, mesopore volume, pore size and sulfuric acid loading of the catalyst, enhancing the interaction between the sulfuric acid species and the carrier surface, and increasing the strength of the acidic sites on the catalyst surface, thereby improving its catalytic activity in the alkane isomerization reaction.

[0014] It is worth noting that the composite oxides gradually dehydrate during the drying process to form amorphous composite hydroxides with a loose structure. Once generated, such hydroxides quickly react with SO3 molecules in the oxidizing atmosphere through chemical adsorption to form Me-OS bonds. During the programmed temperature rise process, the Me-OS bond gradually becomes stronger. On the one hand, the strong electron-withdrawing effect of the S=O bond promotes the formation of a strong composite hydroxide on the surface of the oxide support. acidic sites and Lewis acidic sites; on the other hand, it promotes the transformation of amorphous hydroxides into crystalline oxides, and finally forms a super acidic material with a large specific surface area.

[0015] As a preferred technical solution of the present invention, the programmed temperature vulcanization in step (1) includes the following situations:

[0016] (A) heating the sample to a first set temperature in a sulfur-containing atmosphere and performing a first heat preservation, then heating the sample to a second set temperature and performing a second heat preservation, and then cooling the sample to room temperature in an air atmosphere; or

[0017] (B) The temperature is raised to a first set temperature in an air atmosphere and a first insulation is performed, a sulfur-containing atmosphere is introduced and sulfurization is performed, and then the temperature is raised to a second set temperature and a second insulation is performed, and then the temperature is cooled to room temperature in an air atmosphere.

[0018] As a preferred technical solution of the present invention, the sulfur-containing atmosphere comprises the following components in terms of volume fraction: 0.1-50% SO3, 0-25% O2, and the balance N2.

[0019] Preferably, the sulfur-containing atmosphere comprises the following components in terms of volume fraction: 1.0-20% SO3, 0-10% O2, and the balance N2.

[0020] In the present invention, the sulfur-containing atmosphere includes a static or flowing SO3-containing atmosphere, and the sulfur-containing atmosphere can be recycled after dehydration and drying.

[0021] In the present invention, the volume fraction of SO3 in the sulfur-containing atmosphere is 0.1-50%, for example, it can be 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%, etc., but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1.0-20%.

[0022] In the present invention, the volume fraction of O2 in the sulfur-containing atmosphere is 0-25%, for example, it can be 1%, 3%, 5%, 7%, 10%, 12%, 14%, 16%, 18%, 20% or 22%, etc., but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0-10%.

[0023] Preferably, the heating rate to the first set temperature is 2-5°C / min, for example, it can be 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min or 4.5°C / min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the first set temperature is 100-200°C, for example, it can be 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C or 190°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the first insulation time is 1-3h, for example, it can be 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h or 2.8h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the heating rate to the second set temperature is 2-10°C / min, for example, it can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min or 9°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the second set temperature is 600-750℃, for example, it can be 610℃, 630℃, 650℃, 670℃, 690℃, 700℃, 710℃, 730℃ or 740℃, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the second insulation time is 1-3h, for example, it can be 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h or 2.8h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] It is worth noting that the present invention controls process parameters such as SO3 concentration, first set temperature and second set temperature during the programmed temperature rising process, regulates the severity of sulfation on the surface of the composite oxide, realizes controllable treatment of dehydration and sulfation, avoids uncontrollable and severe etching of the strong acidic solution in the traditional sulfuric acid impregnation process, causing the collapse of the oxide carrier pores, reduction of specific surface area and other factors that are not conducive to the formation of super-strong acidic sites, and finally obtains a catalyst carrier with rich and developed mesoporous channels and high order, providing more favorable places for the formation of super-strong acidic sites.

[0030] Preferably, the vulcanization time is 1-3 hours, for example, it can be 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours or 2.8 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] In the present invention, the programmed temperature vulcanization in step (1) can be carried out in vacuum, reduced pressure or normal pressure; the reduced pressure pressure is 0.01-0.09 MPa, for example, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa or 0.08 MPa, etc.

[0032] As a preferred technical solution of the present invention, the preparation method of the composite oxide gel in step (1) includes: mixing the first metal source, the second metal source and the pH regulator, adjusting the pH, and preparing the composite oxide gel after solid-liquid separation, washing and drying.

[0033] Preferably, the first metal source is a zirconium source.

[0034] Preferably, the zirconium source includes any one or a combination of at least two of zirconium hydroxide, zirconium nitrate, zirconium acetate, zirconium formate, zirconium isopropoxide, zirconium tert-butoxide, zirconium oxychloride or zirconium oxynitrate.

[0035] Preferably, the second metal source comprises any one or a combination of at least two of an inorganic metal salt, an organic metal salt or a hydroxide of Hf, Al, Nb, Zn, Ga or Mg;

[0036] Preferably, the molar ratio of the first metal source to the second metal source is (5-50):1, for example, it can be 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1 or 45:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the pH is adjusted to 10.5-12.5, for example, 10.7, 11, 11.2, 11.5, 11.8, 12, 12.2 or 12.4, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] In the present invention, the acidity or alkalinity of the pH adjuster is not specifically limited, as long as it satisfies the precipitation of the mixed oxide precursor solution.

[0039] In the present invention, the washing is performed using a polar solvent until the filtrate becomes neutral. The polar solvent includes any one of water, acetone, methanol or ethanol, or a combination of at least two of them.

[0040] Preferably, the drying temperature is 40-65°C, for example, 42°C, 45°C, 50°C, 55°C, 60°C, 62°C or 64°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] As a preferred technical solution of the present invention, the composite oxide gel in step (1) is subjected to programmed temperature vulcanization, including the following situations:

[0042] (a) mixing a binder with a composite oxide gel, forming the carrier, and subjecting the carrier to programmed temperature sulfurization to obtain a sulfur-modified catalyst intermediate; or

[0043] (b) The composite oxide gel is subjected to programmed temperature vulcanization to obtain a sulfur-modified composite oxide, which is then mixed with a binder and an additive, and subjected to molding, drying, and calcination to obtain a sulfur-modified catalyst intermediate.

[0044] Preferably, the binder comprises any one of kaolin, pseudo-boehmite, rectorite, attapulgite or silica sol, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of kaolin and pseudo-boehmite, a combination of pseudo-boehmite and rectorite, or a combination of attapulgite and silica sol, etc.

[0045] Preferably, the forming method includes any one of extrusion, spheronization or coating, or a combination of at least two of them, preferably extrusion.

[0046] Preferably, the auxiliary agent comprises sesbania powder and nitric acid.

[0047] The present invention does not impose any specific limitation on the amount of the auxiliary agent used, as long as the sulfur-modified composite oxide is agglomerated; the auxiliary agent can be removed after the calcination in step (b).

[0048] In the present invention, the shape of the catalyst can be made into flake, spherical, cylindrical, clover-shaped or four-leaf clover-shaped according to different requirements. The diameter of the carrier is determined by the size of the orifice plate, preferably 1-8 mm.

[0049] As a preferred technical solution of the present invention, the precious metal source in step (2) includes a Pt source and / or a Pd source.

[0050] Preferably, the drying temperature in step (2) is 80-150°C, for example, it can be 90°C, 100°C, 110°C, 120°C, 130°C or 140°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the drying time in step (2) is 2-6 h, for example, it can be 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 2.4 h, 2.6 h or 2.8 h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] Preferably, the calcination temperature in step (2) is 400-600°C, for example, it can be 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C or 580°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] Preferably, the calcination time in step (2) is 2-4 h, for example, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h or 3.8 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] As a preferred technical solution of the present invention, the mass percentage of the precious metal in the alkane isomerization catalyst is 0.01 wt%-1 wt%, for example, it can be 0.05 wt%, 0.07 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt% or 0.9 wt%, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0055] Preferably, the mass percentage of S in the alkane isomerization catalyst is 2 wt%-10 wt%, for example, 2.5 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt% or 9 wt%, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] Preferably, the mass percentage of the binder in the alkane isomerization catalyst is 1 wt%-40 wt%, for example, 2 wt%, 3 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt% or 35 wt%, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0057] In a second aspect, the present invention provides an alkane isomerization catalyst, which is prepared by the preparation method described in the first aspect;

[0058] The alkane isomerization catalyst comprises a carrier and a noble metal active component and a sulfuric acid active component supported on the surface of the carrier;

[0059] The support includes a composite oxide and a binder.

[0060] As a preferred technical solution of the present invention, based on the mass of the alkane isomerization catalyst, the mass percentage of the noble metal active component is 0.01 wt%-1 wt%.

[0061] Preferably, based on the mass of the alkane isomerization catalyst, the mass percentage of S in the sulfuric acid active component is 2 wt%-10 wt%.

[0062] Preferably, based on the mass of the alkane isomerization catalyst, the mass percentage of the binder is 1 wt%-40 wt%.

[0063] Preferably, the noble metal active component includes Pt and / or Pd.

[0064] Preferably, the composite oxide includes a first oxide and a second oxide.

[0065] Preferably, the first oxide is ZrO2.

[0066] Preferably, the second oxide includes any one of HfO2, Al2O3, Nb2O5, ZnO, Ga2O3 or MgO, or a combination of at least two thereof.

[0067] Preferably, the binder includes any one of kaolin, pseudo-boehmite, rectorite, attapulgite or silica sol, or a combination of at least two of them.

[0068] As a preferred technical solution of the present invention, the specific surface area of ​​the alkane isomerization catalyst is greater than 150m 2 / g, for example, it can be 155m 2 / g, 160m 2 / g, 165m 2 / g, 170m 2 / g, 175m 2 / g, 180m 2 / g、185m 2 / g, 190m 2 / g or 200m 2 / g, etc., but not limited to the listed values, other values ​​not listed in the numerical range are also applicable, preferably 150-190m 2 / g.

[0069] Preferably, the pore volume of the alkane isomerization catalyst is greater than 0.14 cm 3 / g, for example, it can be 0.142cm 3 / g, 0.145cm 3 / g, 0.147cm 3 / g, 0.15cm 3 / g, 0.155cm 3 / g, 0.16cm 3 / g, 0.165cm 3 / g or 0.17cm 3 / g, etc., but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0070] Preferably, the pore size of the alkane isomerization catalyst is 3.5-4.0 nm, for example, 3.55 nm, 3.6 nm, 3.65 nm, 3.7 nm, 3.75 nm, 3.8 nm, 3.85 nm, 3.9 nm or 3.95 nm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0071] Preferably, the surface sulfur density of the alkane isomerization catalyst is greater than 3.5S / nm 2 , for example, it can be 3.6S / nm 2 、3.7S / nm 2 、3.8S / nm 2 、3.9S / nm 2 , 4S / nm 2 , 4.1S / nm 2 , 4.2S / nm 2 or 4.3nm, etc., but not limited to the listed values, other values ​​not listed in the numerical range are also applicable, preferably 3.8-4.1S / nm 2 .

[0072] Preferably, the alkane isomerization catalyst The acid site density is greater than 240 μmol / g, for example, it can be 245 μmol / g, 260 μmol / g, 270 μmol / g, 280 μmol / g, 290 μmol / g or 300 μmol / g, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 250-280 μmol / g.

[0073] It is worth noting that the alkane isomerization catalyst prepared by the present invention has a higher specific surface area, pore volume, pore diameter and sulfuric acid loading than the catalyst prepared by the sulfuric acid impregnation method, and also exhibits a higher reactant conversion rate and product selectivity in the alkane isomerization reaction, while the catalyst stability is also significantly improved.

[0074] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] (1) The preparation method of the present invention performs a programmed temperature treatment on the composite oxide in a sulfur-containing atmosphere, so that the drying, sulfation and crystallization processes of the composite oxide are carried out simultaneously, thereby improving the microstructure of the sulfated composite oxide support, increasing its specific surface area, mesopore volume, pore diameter, and sulfuric acid loading, enhancing the interaction between the sulfuric acid species and the support surface, and improving the strength of the acidic sites on the catalyst surface;

[0077] (2) The preparation method of the present invention controls the SO3 concentration and the treatment temperature during the temperature-programmed sulfidation process, which can regulate the severity of the sulfation of the composite hydroxide surface, realize the controllable treatment of dehydration and sulfation, and avoid the uncontrollable and severe etching of the strong acid solution in the traditional sulfuric acid impregnation process, which causes the collapse of the oxide support pores and the reduction of the specific surface area, which are not conducive to the formation of super acidic sites;

[0078] (3) The alkane isomerization catalyst of the present invention has the advantages of excellent reactant conversion rate, product selectivity, etc. in the alkane isomerization reaction, and the catalyst stability is also significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 A schematic diagram of the gas-phase temperature-programmed sulfurization reaction apparatus provided in Example 1;

[0080] Among them, 1-reaction raw materials, 2-heating device, 3-sulfation reaction device, 4-drying device;

[0081] Figure 2 The XRD patterns of the catalysts prepared in Examples 1-3 and Comparative Example 1 are shown;

[0082] Figure 3 The BET diagrams of the catalysts prepared in Examples 1-3 and Comparative Example 1 are shown;

[0083] Figure 4 The pore size distribution diagram of the catalysts prepared in Examples 1-3 and Comparative Example 1. DETAILED DESCRIPTION

[0084] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0085] Example 1

[0086] This embodiment provides a method for preparing an alkane isomerization catalyst, the preparation method comprising the following steps:

[0087] (1) 1360 g of zirconium oxychloride (ZrOCl2·8H2O), 47.5 g of aluminum nitrate (Al(NO3)3·9H2O), 31.2 g of lanthanum nitrate (La(NO3)3·6H2O), 49.6 g of nickel nitrate (Ni(NO3)2·6H2O) and 2000 g of deionized water were mixed, and 26 wt% ammonia water was added dropwise under vigorous stirring until the pH of the system reached 10.5, and then stirring was continued for 4 h to obtain Zr-La-Ni-Al gel. After solid-liquid separation, the gel was washed with deionized water until the filtrate was neutral, and dried at 60°C to obtain a composite hydroxide gel;

[0088] 48.5 g of pseudo-boehmite (alumina content of 68 wt%) was added to 500 g of deionized water, and the mixture was stirred uniformly in a 65° C. water bath. 10 g of hydrochloric acid (concentration of 37%) was then added and continued to stir. 1000 g of the Zr-La-Ni-Al composite hydroxide gel prepared in step (1) was added, and the mixture was fully kneaded 2-3 times on an extruder to obtain clover-shaped strips with a diameter of 1.6 mm and a length of 3-10 mm. The support was finally dried at 40° C.;

[0089] (2) Place 1000g of the carrier described in step (1) in a sulfurization reaction device (such as Figure 1 As shown), a mixed gas of SO3, O2 and N2 with a volume ratio of 10:5:85 was introduced at a flow rate of 100 mL / min, the temperature was raised to 120°C at a rate of 2°C / min at normal pressure and room temperature and the temperature was first kept for 2 h, then the temperature was raised to 650°C at a rate of 2°C / min and the temperature was secondly kept for 2 h, after which the sulfur-containing atmosphere was stopped, and then the mixture was cooled to room temperature under an air atmosphere to obtain a sulfur-modified catalyst intermediate;

[0090] (3) immersing the sulfur-modified catalyst intermediate of step (2) in a platinum nitrate solution, drying at 120° C. for 2 h, and calcining at 500° C. for 4 h to obtain an alkane isomerization catalyst;

[0091] The mass percentage of Pt in the alkane isomerization catalyst is 0.3 wt %; the mass percentage of S in the alkane isomerization catalyst is 3.2 wt %.

[0092] Example 2

[0093] The only difference between this embodiment and embodiment 1 is that a mixed gas of SO 3 , O 2 and N 2 with a volume ratio of 15:10:75 is introduced at a flow rate of 200 mL / min, and other conditions are the same as those in embodiment 1.

[0094] Example 3

[0095] The only difference between this embodiment and Example 1 is that: after air is introduced at a flow rate of 100 mL / min, the temperature is raised to 120°C at a rate of 2°C / min and kept warm for 2 hours, a mixed gas of SO3, O2 and N2 with a volume ratio of 15:10:75 is introduced at a flow rate of 100 mL / min and sulfurized for 2 hours, the temperature is raised to 650°C at a rate of 10°C / min and kept warm for 2 hours, and then the introduction of sulfur-containing atmosphere is stopped, and then the mixture is cooled to room temperature in an air atmosphere. Other conditions are the same as in Example 1.

[0096] Example 4

[0097] The only difference between this embodiment and embodiment 1 is that a mixed gas of SO 3 and N 2 with a volume ratio of 20:80 is introduced at a flow rate of 200 mL / min, and other conditions are the same as those in embodiment 1.

[0098] Example 5

[0099] The only difference between this embodiment and embodiment 1 is that a mixed gas of SO 3 and N 2 with a volume ratio of 60:40 is introduced at a flow rate of 200 mL / min, and other conditions are the same as those in embodiment 1.

[0100] Example 6

[0101] The only difference between this embodiment and embodiment 1 is that the temperature is raised to 300° C. at a rate of 2° C. / min and the temperature is first kept at this temperature for 2 h. Other conditions are the same as those in embodiment 1.

[0102] Example 7

[0103] The only difference between this embodiment and embodiment 1 is that the temperature is raised to 800° C. at a rate of 2° C. / min and the temperature is kept for a second time for 2 h. Other conditions are the same as those in embodiment 1.

[0104] Example 8

[0105] The only difference between this embodiment and embodiment 1 is that the temperature is raised to 550° C. at a rate of 2° C. / min and the temperature is kept for a second time for 2 h. Other conditions are the same as those in embodiment 1.

[0106] Example 9

[0107] This embodiment provides a method for preparing an alkane isomerization catalyst, the preparation method comprising the following steps:

[0108] (1) 1360 g of zirconium oxychloride (ZrOCl2·8H2O), 47.5 g of aluminum nitrate (Al(NO3)3·9H2O), 31.2 g of lanthanum nitrate (La(NO3)3·6H2O), 49.6 g of nickel nitrate (Ni(NO3)2·6H2O) and 2000 g of deionized water were mixed, and 26 wt% ammonia water was added dropwise under vigorous stirring until the pH of the system reached 10.5, and then stirring was continued for 4 h to obtain Zr-La-Ni-Al gel. After solid-liquid separation, the mixture was washed with deionized water until the filtrate was neutral, and dried at 60°C to obtain a composite hydroxide gel;

[0109] 1000g of the composite hydroxide gel is placed in a sulfurization reaction device (such as Figure 1 As shown), a mixed gas of SO3, O2 and N2 with a volume ratio of 10:5:85 was introduced at a flow rate of 100 mL / min, the temperature was raised to 120°C at a rate of 2°C / min at normal pressure and room temperature and the temperature was first kept for 2 h, then the temperature was raised to 650°C at a rate of 2°C / min and the temperature was secondly kept for 2 h, after which the introduction of the sulfur-containing atmosphere was stopped, and the mixture was then cooled to room temperature in an air atmosphere to obtain a sulfur-modified composite oxide;

[0110] (2) 300 g of pseudo-boehmite, 20 g of sesbania powder and 1000 g of the sulfur-modified composite oxide described in step (1) were mixed uniformly in a kneader, 800 g of nitric acid solution (50 g of nitric acid (65 wt%) dissolved in 750 g of deionized water) were added and fully kneaded, and the mass material was extruded to obtain a clover-shaped strip sample with a diameter of 1.6 mm and a length of 3-10 mm, followed by drying at 120° C. for 6 h and calcining in a muffle furnace at 650° C. for 4 h to obtain a sulfur-modified catalyst intermediate;

[0111] (3) immersing the sulfur-modified catalyst intermediate of step (2) in a platinum nitrate solution, drying at 120° C. for 2 h, and calcining at 500° C. for 4 h to obtain an alkane isomerization catalyst;

[0112] The mass percentage of Pt in the alkane isomerization catalyst is 0.3 wt %; the mass percentage of S in the alkane isomerization catalyst is 3.6 wt %.

[0113] Example 10

[0114] The only difference between this embodiment and embodiment 9 is that a mixed gas of SO 3 , O 2 and N 2 with a volume ratio of 15:10:75 is introduced at a flow rate of 200 mL / min, and other conditions are the same as those in embodiment 9.

[0115] Example 11

[0116] The only difference between this embodiment and embodiment 9 is that: air is introduced at a flow rate of 100 mL / min, the temperature is raised to 120°C at a rate of 2°C / min and the mixture is kept warm for 2 hours, then a mixed gas of SO3, O2 and N2 with a volume ratio of 15:10:75 is introduced at a flow rate of 100 mL / min and sulfurized for 2 hours, the temperature is raised to 650°C at a rate of 10°C / min and the mixture is kept warm for 2 hours, and then the introduction of the sulfur-containing atmosphere is stopped, and then the mixture is cooled to room temperature in an air atmosphere. The other conditions are the same as those in embodiment 9.

[0117] Comparative Example 1

[0118] The only difference between this comparative example and Example 1 is that 1000 g of the carrier described in step (1) was immersed in 5 L of 0.5 mol / L sulfuric acid solution for 30 min, dried at 120° C. for 2 h after solid-liquid separation, and then calcined in a muffle furnace at 650° C. for 4 h. Other conditions were the same as in Example 1.

[0119] Comparative Example 2

[0120] The only difference between this comparative example and Example 9 is that 1000 g of the composite hydroxide gel is immersed in 5 L of 0.5 mol / L sulfuric acid solution for 30 min, and after solid-liquid separation, it is dried at 120° C. for 2 h and then calcined in a muffle furnace at 650° C. for 4 h. Other conditions are the same as those in Example 9.

[0121] Comparative Example 3

[0122] The only difference between this comparative example and Example 1 is that a mixed gas of SO3, O2 and N2 with a volume ratio of 15:10:75 is introduced at a flow rate of 100 mL / min, then the temperature is raised to 650°C at a rate of 2°C / min and the first sulfur-containing atmosphere is stopped after the first insulation for 2 hours, and then the mixture is cooled to room temperature in an air atmosphere. Other conditions are the same as in Example 1.

[0123] Comparative Example 4

[0124] The only difference between this comparative example and Example 1 is that air is introduced at a flow rate of 100 mL / min, the temperature is raised to 650°C at a rate of 2°C / min and the temperature is kept for 2 hours. Then, a mixed gas of SO3, O2 and N2 with a volume ratio of 15:10:75 is introduced at a flow rate of 100 mL / min and sulfurized for 2 hours. The introduction of the sulfur-containing atmosphere is stopped, and the mixture is then cooled to room temperature in an air atmosphere. The other conditions are the same as those in Example 1.

[0125] The catalysts prepared in the above examples and comparative examples were characterized for their physical properties. The characterization results are shown in the following table. Figure 2-4 and as shown in Table 1.

[0126] Depend on Figure 2It can be seen that the catalysts prepared by temperature-programmed sulfidation in Examples 1-3 of the present invention have higher tetragonal zirconia crystallinity than the catalyst prepared by sulfuric acid leaching in Comparative Example 1.

[0127] Depend on Figure 3 and Figure 4 It can be seen that the catalysts prepared by temperature-programmed sulfidation in Examples 1-3 of the present invention have higher specific surface area and mesopore volume than the catalyst prepared by sulfuric acid leaching in Comparative Example 1, while the mesopore diameter does not change significantly and is concentrated in the range of 3.7-4.0 nm, indicating that the temperature-programmed sulfidation method used in the present invention can provide more sites for the loading of sulfuric acid species.

[0128] Table 1

[0129]

[0130]

[0131] The catalysts prepared in the above examples and comparative examples were tested for their alkane isomerization catalytic performance. The alkane isomerization performance was evaluated in a 100 mL fixed-bed microreactor using n-butane and isobutane as raw materials under hydrogen conditions. The evaluation results are shown in Table 2.

[0132] The specific test conditions are as follows: the catalyst loading amount is 50 mL, the catalyst is activated in air at 500°C for 2 hours before the reaction to desorb the water adsorbed on the catalyst surface, and then reduced with hydrogen at 450°C for 2 hours. The temperature is then lowered to the reaction temperature, and alkane and hydrogen are introduced to start the reaction.

[0133] n-Butane isomerization reaction conditions: reaction temperature 180°C, reaction pressure 0.1 MPa, mass space velocity 0.8 h -1 , the volume ratio of n-butane to hydrogen was 1:1, sampling and analysis began after 5 hours of reaction, and the reaction period was 200 hours;

[0134] Isobutane normalization reaction conditions: reaction temperature 230℃, reaction pressure 0.1MPa, mass space velocity 0.8h -1 The volume ratio of isobutane to hydrogen was 1:1. Sampling and analysis began after 5 hours of reaction. The reaction cycle was 200 hours.

[0135] Table 2

[0136]

[0137]

[0138] The following points can be drawn from Tables 1 and 2:

[0139] (1) The catalysts prepared by the preparation methods provided in Examples 1-4 and Examples 9-11 of the present invention still have strong sulfur-binding capabilities after high-temperature calcination, i.e., higher surface sulfur content and sulfur density, and have excellent specific surface area, pore volume, and number of surface acid sites, resulting in high reactant conversion and product selectivity in the n-butane isomerization and isobutane normalization reactions;

[0140] (2) Based on Example 1 and Example 5, it can be seen that when the SO3 content in the sulfur-containing atmosphere is high, the sulfurization process is intense, resulting in a decrease in the specific surface area and pore volume of the prepared catalyst, which in turn reduces the catalyst reaction activity.

[0141] (3) Based on Example 1 and Examples 6-8, it can be seen that when the first set temperature in the programmed temperature rise is too high, the dehydration process of the composite oxide gel is too intense, resulting in a decrease in the specific surface area of ​​the prepared catalyst; when the second set temperature in the programmed temperature rise is too high, the sulfur holding capacity of the catalyst surface is reduced, resulting in a decrease in the sulfur content and specific surface area of ​​the prepared catalyst surface; when the second set temperature in the programmed temperature rise is too low, the transformation of the amorphous composite support into tetragonal zirconia is incomplete, resulting in a low crystallinity of the prepared catalyst;

[0142] (4) Based on Examples 1 and 9 and Comparative Examples 1-2, it can be seen that when the catalyst is prepared by traditional sulfuric acid impregnation, the strong acidic solution in the impregnation process causes uncontrollable and severe etching, resulting in the collapse of the pores of the oxide support and a decrease in the specific surface area. During the heat treatment after acid leaching, the dehydroxylation of the support surface causes a decrease in the adsorption sites of sulfuric acid species, resulting in the activity (reactant conversion rate and product selectivity) of the prepared catalyst in the n-butane isomerization and isobutane normalization reactions being significantly lower than that of the catalyst prepared by temperature-programmed sulfurization.

[0143] (5) Based on Example 1 and Comparative Examples 3-4, it can be seen that when programmed temperature sulfurization is not adopted, the dehydration, crystallization and sulfurization processes are too intense and the controllability is poor, resulting in reduced crystallinity, specific surface area and surface sulfur content of the prepared catalyst, and reduced catalytic isomerization activity.

[0144] In summary, the present invention adopts a gas-phase programmed temperature sulfation technology to synchronize the drying, sulfation and crystallization processes of the composite hydroxide carrier. Once the composite hydroxide undergoes dehydration and dehydroxylation reactions during the drying process to form an amorphous hydroxide with a loose structure, it immediately undergoes Me-OS bonding with the SO3 molecules in the heat-treated airflow. By controlling the process parameters of the gas-phase sulfation, the severity of the dehydration and sulfation of the composite hydroxide is regulated, and a controllable operation of dehydration and sulfation is achieved, resulting in an alkane isomerization catalyst with rich and well-developed mesoporous channels, highly ordered, and a large number of acidic sites. It has the advantages of high conversion rate and good selectivity in the alkane isomerization reaction.

[0145] The applicant declares that the present invention is intended to illustrate the detailed structural features of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed structural features. This does not mean that the present invention must rely on the above-described detailed structural features in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing an alkane isomerization catalyst, characterized in that: The preparation method comprises the following steps: (1) subjecting the composite oxide gel to programmed temperature sulfurization to obtain a sulfur-modified catalyst intermediate; The programmed temperature vulcanization includes the following situations: (A) heating the sample to a first set temperature in a sulfur-containing atmosphere and performing a first heat preservation, then heating the sample to a second set temperature and performing a second heat preservation, and then cooling the sample to room temperature in an air atmosphere; or (B) heating the sample to a first set temperature in an air atmosphere and performing a first heat preservation, introducing a sulfur-containing atmosphere and performing sulfurization, then heating the sample to a second set temperature and performing a second heat preservation, and then cooling the sample to room temperature in an air atmosphere; The sulfur-containing atmosphere comprises the following components by volume fraction: 0.1-50% SO3, 0-25% O2, and the balance N2; the first set temperature is 100-200°C; the second set temperature is 600-750°C; (2) The sulfur-modified catalyst intermediate of step (1) is impregnated in a noble metal source, and after drying and calcining, an alkane isomerization catalyst is obtained.

2. The preparation method according to claim 1, characterized in that The sulfur-containing atmosphere includes the following components in terms of volume fraction: 1.0-20% SO3, 0-10% O2, and the balance N2.

3. The preparation method according to claim 1, characterized in that The heating rate for heating to the first set temperature is 2-5°C / min.

4. The preparation method according to claim 1, characterized in that The first insulation time is 1-3 hours.

5. The preparation method according to claim 1, characterized in that The heating rate for heating to the second set temperature is 2-10°C / min.

6. The preparation method according to claim 1, characterized in that The second insulation time is 1-3 hours.

7. The preparation method according to claim 1, characterized in that The vulcanization time is 1-3 hours.

8. The preparation method according to claim 1, characterized in that The preparation method of the composite oxide gel in step (1) comprises: mixing a first metal source, a second metal source and a pH regulator, adjusting the pH, and performing solid-liquid separation, washing and drying to obtain the composite oxide gel.

9. The preparation method according to claim 8, characterized in that The first metal source is a zirconium source.

10. The preparation method according to claim 9, characterized in that The zirconium source includes any one of zirconium hydroxide, zirconium nitrate, zirconium acetate, zirconium formate, zirconium isopropoxide, zirconium tert-butoxide, zirconium oxychloride or zirconium oxynitrate, or a combination of at least two thereof.

11. The preparation method according to claim 8, characterized in that The second metal source includes any one or a combination of at least two of an inorganic metal salt, an organic metal salt or a hydroxide of Hf, Al, Nb, Zn, Ga or Mg.

12. The preparation method according to claim 8, characterized in that The molar ratio of the first metal source to the second metal source is (5-50):

1.

13. The preparation method according to claim 8, characterized in that The pH adjustment is to adjust the pH to 10.5-12.

5.

14. The preparation method according to claim 8, characterized in that The drying temperature is 40-65°C.

15. The preparation method according to claim 1, characterized in that The composite oxide gel in step (1) is subjected to programmed temperature vulcanization, including the following situations: (a) mixing a binder with a composite oxide gel, forming the carrier, and subjecting the carrier to programmed temperature sulfurization to obtain a sulfur-modified catalyst intermediate; or (b) The composite oxide gel is subjected to programmed temperature vulcanization to obtain a sulfur-modified composite oxide, which is then mixed with a binder and an additive, and subjected to molding, drying, and calcination to obtain a sulfur-modified catalyst intermediate.

16. The preparation method according to claim 15, characterized in that The binder includes any one of kaolin, pseudo-boehmite, rectorite, attapulgite or silica sol, or a combination of at least two of them.

17. The preparation method according to claim 15, characterized in that The forming method includes any one of extrusion, spheronization or film coating, or a combination of at least two of them.

18. The preparation method according to claim 17, characterized in that: The forming method is extrusion.

19. The preparation method according to claim 15, characterized in that The auxiliary agents include sesbania powder and nitric acid.

20. The preparation method according to claim 1, characterized in that The noble metal source in step (2) includes a Pt source and / or a Pd source.

21. The preparation method according to claim 1, characterized in that The drying temperature in step (2) is 80-150°C.

22. The preparation method according to claim 1, characterized in that The drying time in step (2) is 2-6 hours.

23. The preparation method according to claim 1, characterized in that The calcination temperature in step (2) is 400-600°C.

24. The preparation method according to claim 1, characterized in that The calcination time in step (2) is 2-4 hours.

25. The preparation method according to claim 1, characterized in that The mass percentage of the noble metal in the alkane isomerization catalyst is 0.01 wt%-1 wt%.

26. The preparation method according to claim 1, characterized in that The mass percentage of S in the alkane isomerization catalyst is 2 wt%-10 wt%.

27. The preparation method according to claim 1, characterized in that The mass percentage of the binder in the mass of the alkane isomerization catalyst is 1 wt%-40 wt%.

28. An alkane isomerization catalyst, characterized in that The alkane isomerization catalyst is prepared by the preparation method according to any one of claims 1 to 27; The alkane isomerization catalyst comprises a carrier and a noble metal active component and a sulfuric acid active component supported on the surface of the carrier; The support includes a composite oxide and a binder.

29. The alkane isomerization catalyst according to claim 28, characterized in that Based on the mass of the alkane isomerization catalyst, the mass percentage of the noble metal active component is 0.01wt%-1wt%.

30. The alkane isomerization catalyst according to claim 28, characterized in that Based on the mass of the alkane isomerization catalyst, the mass percentage of S in the sulfuric acid active component is 2wt%-10wt%.

31. The alkane isomerization catalyst according to claim 28, characterized in that Based on the mass of the alkane isomerization catalyst, the mass percentage of the binder is 1wt%-40wt%.

32. The alkane isomerization catalyst according to claim 28, characterized in that The noble metal active component includes Pt and / or Pd.

33. The alkane isomerization catalyst according to claim 28, characterized in that The composite oxide includes a first oxide and a second oxide.

34. The alkane isomerization catalyst according to claim 33, characterized in that The first oxide is ZrO2.

35. The alkane isomerization catalyst according to claim 33, characterized in that The second oxide includes any one of HfO2, Al2O3, Nb2O5, ZnO, Ga2O3 or MgO, or a combination of at least two thereof.

36. The alkane isomerization catalyst according to claim 28, characterized in that The binder includes any one of kaolin, pseudo-boehmite, rectorite, attapulgite or silica sol, or a combination of at least two of them.

37. The alkane isomerization catalyst according to claim 28, characterized in that The specific surface area of ​​the alkane isomerization catalyst is greater than 150m 2 / g.

38. The alkane isomerization catalyst according to claim 37, characterized in that The specific surface area of ​​the alkane isomerization catalyst is 150-190m 2 / g.

39. The alkane isomerization catalyst according to claim 28, characterized in that The pore volume of the alkane isomerization catalyst is greater than 0.14 cm 3 / g.

40. The alkane isomerization catalyst according to claim 28, characterized in that The pore diameter of the alkane isomerization catalyst is 3.5-4.0 nm.

41. The alkane isomerization catalyst according to claim 28, characterized in that The surface sulfur density of the alkane isomerization catalyst is greater than 3.5S / nm 2 .

42. The alkane isomerization catalyst according to claim 41, characterized in that The surface sulfur density of the alkane isomerization catalyst is 3.8-4.1 S / nm 2 .

43. The alkane isomerization catalyst according to claim 28, characterized in that The alkane isomerization catalyst Acidic site density>240μmol / g.

44. The alkane isomerization catalyst according to claim 43, characterized in that The alkane isomerization catalyst The acid site density is 250-280 μmol / g.

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