A light olefin skeletal isomerization catalyst, a preparation method and application thereof

Abstract

The application discloses a light olefin skeleton isomerization catalyst and a preparation method and application thereof. The catalyst is prepared from small-grained B acid-rich HZSM-35 molecular sieves; the small-grained B acid-rich HZSM-35 molecular sieves have a sheet-shaped crystalline structure, the thickness of the crystal grains is less than 50 nm, and the length or width is less than 500 nm; the B acid content of the small-grained B acid-rich HZSM-35 molecular sieves is greater than 1.0 mmol / g; and the B acid content of the catalyst is greater than 0.9 mmol / g. The catalyst prepared from the small-grained B acid-rich HZSM-35 molecular sieves has high light olefin skeleton isomerization activity and selectivity, and can convert linear olefins into branched olefins at a relatively low reaction temperature.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of material chemistry and catalytic chemistry, and particularly relates to a light olefin skeletal isomerization catalyst as well as a preparation method and application thereof. BACKGROUND

[0002] ZSM-35 molecular sieve is a molecular sieve with FER topology, which has vertically intersecting ten-membered ring-eight-membered ring two-dimensional pore system, wherein the size of the ten-membered ring pore is 0.42*0.54 nm; the size of the eight-membered ring pore is 0.35*0.48 nm. ZSM-35 molecular sieve is widely used in catalytic reactions of hydrocarbon conversion due to its unique vertically intersecting two-dimensional pore structure, such as catalytic reactions of linear olefin isomerization, aromatization, polymerization and cracking.

[0003] Patent application CN1660721A reports an olefin skeletal isomerization catalyst, which contains at least one molecular sieve with a pore diameter of 0.4-0.8 nm, wherein the molecular sieve is a molecular sieve with twelve-membered ring pores, and the content of non-framework silicon in the crystal grains is less than 300 nm, and the content of the silicon is 1-20 wt% based on the total amount of the molecular sieve in terms of oxides.

[0004] Patent application CN1511637A reports a catalyst for high-conversion and high-selectivity skeletal isomerization reaction of a normal olefin-containing raw material (or pure normal olefin) into isomerized olefin and a preparation method thereof. The catalyst is prepared from a molecular sieve, modified kaolin and a binder as raw materials, wherein the molecular sieve is SAPO-11 or / and ZSM-35 molecular sieve, the modified kaolin is obtained by calcining kaolin at a high temperature of 500-800 DEG C, acid treatment, addition of magnesium chloride or / and calcium chloride or ammonium phosphate auxiliary agent, and calcination activation.

[0005] Patent application CN103301876A provides a preparation method of a linear olefin skeletal isomerization catalyst, and the specific synthesis steps are as follows: a synthesized rare earth ZSM-35 molecular sieve is treated with an alkali solution at 30-90 DEG C for 0.5-10 hours; the obtained product is washed to neutral, extruded into a strip with a binder, ion exchanged with an ammonium nitrate solution, filtered, washed with deionized water, dried, calcined; the obtained sample is treated with water vapor at 400-700 DEG C for 1-8 hours to prepare an isomerization catalyst. Compared with the ZSM-35 molecular sieve catalyst without treatment, the alkali water treatment modified ZSM-35 molecular sieve catalyst has obviously improved reaction stability.

[0006] The existing olefin skeletal isomerization catalyst has a high reaction temperature, and the initial temperature is usually above 350 DEG C. Moreover, the selectivity of the catalyst is poor at the initial stage of the reaction, and there are more cracking products. SUMMARY

[0007] An object of the present application is to provide a light olefin skeleton isomerization catalyst and a preparation method thereof to solve the problems of low activity at low temperature and poor product selectivity at the initial stage of reaction of the existing catalyst.

[0008] Another object of the present application is to provide an application method of the light olefin skeleton isomerization catalyst.

[0009] To achieve the above object, the present application adopts the following technical solutions:

[0010] The present application provides a light olefin skeleton isomerization catalyst, which is prepared from small-grained B-rich HZSM-35 molecular sieve;

[0011] The small-grained B-rich HZSM-35 molecular sieve has a sheet-like crystalline structure, with a grain thickness of less than 50 nm, preferably 10-50 nm, and more preferably 40-50 nm, and a length or width of less than 500 nm, preferably 100-500 nm, and more preferably 150-200 nm. The B acid content of the small-grained B-rich HZSM-35 molecular sieve is greater than 1.0 mmol / g, preferably 1.0-1.5 mmol / g, and more preferably 1.0-1.3 mmol / g. The B acid content of the catalyst is greater than 0.9 mmol / g, preferably 0.9-1.5 mmol / g, and more preferably 0.9-1.1 mmol / g.

[0012] Molecular sieve catalysts are a class of catalysts with high shape selectivity. So far, the catalysts that have successfully achieved selective isomerization of linear olefins are all molecular sieves with ten-membered ring structures. The common feature of these molecular sieve catalysts is strong acidity and one-dimensional pore structure. Studies have shown that the shape selectivity of the pore and the appropriate acidity are the key to whether various molecular sieve materials can have excellent olefin skeleton isomerization performance.

[0013] Small-grained molecular sieves have short pores and high accessibility of active sites. Therefore, small-grained molecular sieves generally have relatively high catalytic activity. In addition, because the molecular sieve pores are short, the reaction products can quickly leave the reaction zone, avoiding the occurrence of secondary reactions and improving the selectivity of the reaction. The number of small-grained molecular sieve pore openings is much larger than that of ordinary molecular sieves, which are not easily blocked by the carbon deposition generated by side reactions, improving the carbon deposition resistance of the molecular sieve. Therefore, small-grained molecular sieve catalysts often show better activity, selectivity, and activity stability compared to ordinary molecular sieve catalysts.

[0014] The B acid site on the molecular sieve is the main catalytic active site, and high B acid amount often shows high catalytic reaction activity. The catalytic activity of HZSM-35 molecular sieve is lower than that of HY and Hbeta molecular sieves in many catalytic reactions, but the channel structure of HZSM-35 molecular sieve often shows good selectivity of target products. Therefore, increasing the B acid amount of HZSM-35 molecular sieve is an important direction to improve the catalyst activity and the catalyst performance.

[0015] According to the light olefin skeletal isomerization catalyst of the present application, preferably, the length or width of the small-grained B acid-rich HZSM-35 molecular sieve is less than 200 nm, and the B acid amount of the small-grained B acid-rich HZSM-35 molecular sieve is greater than 1.2 mmol / g; and the B acid amount of the catalyst is greater than 1.1 mmol / g.

[0016] Another aspect of the present application provides a preparation method of the light olefin skeletal isomerization catalyst, which comprises the following steps:

[0017] The small-grained B acid-rich HZSM-35 molecular sieve is mixed with deionized water, a binder, an acid and a extrusion aid, and the mixture is formed, dried and calcined to prepare the light olefin skeletal isomerization catalyst. The forming is, for example, extrusion forming using an extruder. Preferably, the drying temperature is 120-140℃, and the time is 4-8 hours; and the calcination temperature is 450-500℃, and the time is 4-8 hours.

[0018] According to the preparation method of the present application, preferably, the mass ratio of the small-grained B acid-rich HZSM-35 molecular sieve, the binder, the extrusion aid, the acid and the deionized water is (50-100):(5-10):(1-5):(5-10):(50-100).

[0019] The present application does not limit the type of binder used in the preparation of the catalyst, which can be one or a combination of two or more of silica sol, alumina sol, alumina, pseudo-boehmite and the like; and pseudo-boehmite is recommended as the binder.

[0020] The present application does not particularly limit the extrusion aid used in the preparation method of the catalyst, and any extrusion aid commonly used in the prior art can be used, and the extrusion aid is preferably pearl millet powder and / or methyl cellulose.

[0021] The present application does not particularly limit the acid used in the preparation method of the catalyst, and any acid commonly used in the prior art can be used, and the organic acid is preferably one or a combination of two or more of acetic acid and citric acid; and the inorganic acid is preferably nitric acid.

[0022] According to the preparation method of the present application, preferably, the small-grained B acid-rich HZSM-35 molecular sieve is prepared by the following steps:

[0023] mixing the silicon source, ZSM-35 molecular sieve, water and inorganic base, reacting at 100-150℃ in a reaction kettle for 4-16 hours to obtain intermediate product 1;

[0024] mixing the silicon source, aluminum source, water, inorganic base, intermediate product 1 and template agent, crystallizing at 120-180℃ in a crystallization kettle for 36-96 hours to obtain crystallized product; washing, drying and calcining the crystallized product with deionized water to obtain ZSM-35 molecular sieve;

[0025] carrying out ion exchange (preferably 3 times) of the obtained ZSM-35 molecular sieve with ammonium nitrate solution (preferably with mass concentration of 5-10%); washing the ion-exchanged ZSM-35 molecular sieve with deionized water, and then drying and calcining to obtain the small-crystal B acid-rich HZSM-35 molecular sieve.

[0026] According to the preparation method of the present application, preferably, in the preparation step of the intermediate product 1, the silicon source is in terms of SiO2, the ZSM-35 molecular sieve is in terms of SiO2, the inorganic base is in terms of OH - , the molar ratio of the silicon source to the ZSM-35 molecular sieve is (0.05-0.5):1, the molar ratio of the inorganic base to the ZSM-35 molecular sieve is (0.1-1):1, and the molar ratio of the water to the ZSM-35 molecular sieve is (10-100):1.

[0027] According to the preparation method of the present application, preferably, in the preparation step of the ZSM-35 molecular sieve, the silicon source is in terms of SiO2, the aluminum source is in terms of Al2O3, the inorganic base is in terms of OH - , the molar ratio of the silicon source to the aluminum source is (20-100):1, the molar ratio of the inorganic base to the silicon source is (0.1-1):1, and the molar ratio of the water to the silicon source is (10-100); the silicon source, aluminum source, water and inorganic base are recorded as a mixture, the weight ratio of the intermediate product 1 to the mixture is (0.05-0.5):1; and the weight ratio of the template agent to the mixture is (0.05-0.5):1.

[0028] According to the preparation method of the present application, preferably, in the preparation step of the ZSM-35 molecular sieve, the temperature of the drying is 120-140℃, and the time is 4-8 hours; the temperature of the calcining is 500-550℃, and the time is 4-8 hours.

[0029] According to the preparation method of the present application, preferably, in the ion exchange process, the liquid-solid ratio is (5-10):1, and the temperature is 50-80℃; when washing the ion-exchanged ZSM-35 molecular sieve with deionized water, the liquid-solid ratio is (5-10):1.

[0030] According to the preparation method of the present application, preferably, after the ion-exchanged ZSM-35 molecular sieve is washed with deionized water, the drying temperature is 120-140°C, and the time is 4-8 hours; the calcination temperature is 450-500°C, and the time is 4-8 hours.

[0031] According to the preparation method of the present application, preferably, the silicon source in the preparation of the intermediate product 1 is independently selected from one or more than two combinations of solid silica gel, silica sol and white carbon black, which can be the same or different from the silicon source in the preparation of the ZSM-35 molecular sieve;

[0032] The aluminum source is selected from one or more than two combinations of sodium metaaluminate, aluminum hydroxide and aluminum sulfate;

[0033] The inorganic base in the preparation of the intermediate product 1 is independently selected from one or more than two combinations of sodium hydroxide and potassium hydroxide, which can be the same or different from the inorganic base in the preparation of the ZSM-35 molecular sieve;

[0034] The template agent is selected from one or more than two combinations of ethylenediamine, cyclohexylamine and cyclohexanediamine.

[0035] In another aspect of the present application, there is provided a method for using the above light olefin skeletal isomerization catalyst to convert light straight-chain olefins into isomeric branched-chain olefins under non-hydrogen-impingement conditions. More specifically, under non-hydrogen-impingement conditions, light straight-chain olefins containing olefin components are added into a reactor, and under the action of the catalyst, the light straight-chain olefins are converted into isomeric branched-chain olefins; preferably, the isomerization reaction conditions include a pressure of 0.05-0.5 MPa, a space velocity of 1.0-8.0 h -1 , and a temperature of 240-400°C. More preferably, the initial reaction temperature of the isomerization reaction is not higher than 260°C.

[0036] In a specific embodiment of the present application, the light straight-chain olefins can be n-butene, n-pentene, etc., or a mixture rich in (volume fraction ≮15%) n-butene and / or n-pentene, etc. For example, carbon four components, carbon five components, etc. after the production of MTBE, TAME in a refinery or an ethylene plant.

[0037] When the raw material contains olefin components, a fixed bed reactor can be used, or a moving bed, a fluidized bed, etc. can also be used. The reaction pressure can be normal pressure, or the reaction can be carried out under a higher pressure.

[0038] The beneficial effects of the present application include:

[0039] The isomerization catalyst provided by the present application can be applied to the isomerization catalysis of light straight-chain olefins, can catalyze the isomerization reaction at a lower temperature condition, and meanwhile has higher catalytic activity and selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 X-ray diffraction (XRD) spectrum of the HZSM-35 molecular sieve obtained from the present application comparative example 1.

[0041] Figure 2 Scanning electron microscope (SEM) image of the HZSM-35 molecular sieve obtained from the present application comparative example 1.

[0042] Figure 3 X-ray diffraction (XRD) spectrum of the HZSM-35 molecular sieve obtained from the present application example 1.

[0043] Figure 4 Scanning electron microscope (SEM) image of the HZSM-35 molecular sieve obtained from the present application example 1.

[0044] Figure 5 Process flow diagram of the present application example 7.

[0045] BRIEF DESCRIPTION OF DRAWINGS

[0046] 1 - raw material tank; 2 - oil inlet pump; 3 - reactor; 4 - gas-liquid separation tank; 5 - back pressure valve; 6 - wet flowmeter; 7 - diaphragm pneumatic valve; 8 - product tank. DETAILED DESCRIPTION

[0047] In order to more clearly illustrate the present application, the present application will be further described below in conjunction with preferred examples. It should be understood by those skilled in the art that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the present application.

[0048] All numerical designations (e.g., temperature, time, amount, and concentration, etc., including each of these in ranges) herein are approximations, and generally can be varied (+) or (-) by 0.1 or 1.0, as appropriate. All numerical designations are understood to be preceded by the term "about".

[0049] The small-grained B-rich acid HZSM-35 molecular sieve in the present application is prepared by the following three steps:

[0050] Step 1: ZSM-35 molecular sieve, silicon source, alkali, and water are mixed, and reacted in a reaction kettle at 100-150℃ for 4-16 hours to obtain intermediate product 1. Preferably, the reaction is carried out at 120-140℃ for 8-12 hours.

[0051] silicon source in terms of SiO2, ZSM-35 molecular sieve in terms of SiO2, inorganic base in terms of OH - silicon source in terms of SiO2, ZSM-35 molecular sieve in terms of SiO2, inorganic base in terms of OH

[0052] Step 2: the silicon source, the aluminum source, the water, the inorganic base, the intermediate product 1 and the template agent are mixed, and the mixture is crystallized in a crystallization kettle at 120-180℃ for 36-96 hours to obtain a crystallization product; the crystallization product is washed, dried and calcined to obtain the ZSM-35 molecular sieve. Preferably, the crystallization temperature is 140-160℃, and the crystallization time is 48-72 hours. Preferably, the drying temperature is 120-140℃, the drying time is 4-8 hours, the calcination temperature is 500-550℃, and the calcination time is 4-8 hours.

[0053] silicon source in terms of SiO2, ZSM-35 molecular sieve in terms of SiO2, inorganic base in terms of OH - silicon source in terms of SiO2, ZSM-35 molecular sieve in terms of SiO2, inorganic base in terms of OH

[0054] Step 3: the ion exchange step of the calcined ZSM-35 molecular sieve is as follows: the ZSM-35 molecular sieve is ion exchanged with a 5-10% ammonium nitrate solution according to a liquid-solid ratio of (5-10) : 1 and a temperature of 50-80℃ for 3 times; the ion-exchanged ZSM-35 molecular sieve is washed with deionized water according to a liquid-solid ratio of (5-10) : 1 for 3 times; and the ZSM-35 molecular sieve is dried at 120-140℃ for 4-8 hours and calcined at 450-500℃ for 4-8 hours to obtain a small-crystal B-rich HZSM-35 molecular sieve.

[0055] In the above preparation process, the silicon source in step 1 and the silicon source in step 2 are at least one of solid silica gel, silica sol and white carbon black; the inorganic base in step 1 and the inorganic base in step 2 are at least one of sodium hydroxide and potassium hydroxide. The aluminum source in step 2 is at least one of sodium aluminate, aluminum hydroxide and aluminum sulfate, and the template agent is one or a mixture of two or more of ethylenediamine, cyclohexylamine and cyclohexanediamine.

[0056] In step 2, the silicon source, the aluminum source, water and the inorganic base are mixed to form a mixture, and then the intermediate product 1 obtained in step 1 and the template agent are added, and crystallization is performed to obtain the ZSM-35 molecular sieve. In addition, step 2 can also be that the silicon source, the aluminum source, water, the inorganic base and the template agent are mixed, and then the intermediate product 1 obtained in step 1 is added, and crystallization is performed to obtain the ZSM-35 molecular sieve.

[0057] The small-grained B-rich HZSM-35 molecular sieve prepared by the above three steps has a thickness of less than 50 nm and a length or width of less than 500 nm, and has a high B acid amount, with the B acid amount being greater than 1.0 mmol / g. More preferably, the HZSM-35 molecular sieve has a thickness of less than 50 nm, a length or width of less than 200 nm, and a B acid amount of greater than 1.2 mmol / g.

[0058] The light olefin skeletal isomerization catalyst in the present application is prepared by the following steps:

[0059] The small-grained B-rich HZSM-35 molecular sieve is mixed with deionized water, a binder, an acid and a extrusion aid, extruded into a strip by an extruder, dried at 120-140℃ for 4-8 hours, and calcined at 450-500℃ for 4-8 hours to obtain the catalyst.

[0060] The acid can include an organic acid and / or an inorganic acid. The organic acid can include acetic acid and / or citric acid; the inorganic acid can include nitric acid. The binder can be a commonly used binder, for example, including one or a combination of two or more of aluminum sol, aluminum oxide and pseudo-boehmite; preferably, pseudo-boehmite. The extrusion aid can be a commonly used aid, for example, including sesbania gum and / or methyl cellulose. Preferably, the mass ratio of the small-grained B-rich HZSM-35 molecular sieve, the binder, the extrusion aid, the acid and the deionized water is (50-100):(5-10):(1-5):(5-10):(50-100).

[0061] The light olefin skeletal isomerization method in the present application specifically includes:

[0062] Under non-hydrogen conditions (i.e. in a gas environment without hydrogen), the above isomerization catalyst is used to catalyze the isomerization reaction of C6 and below light straight-chain olefins to convert into isomerized C6 and below light branched-chain olefins.

[0063] Specifically, the pressure of the olefin isomerization reaction is 0.05 MPa-0.5 MPa, the space velocity is 1.0 h -1 -8.0 h -1 , and the temperature is 240℃-400℃; preferably, the pressure of the isomerization reaction is 0.1 MPa-0.4 MPa, the space velocity is 3.0 h -1 -6.0 h -1 , and the temperature is 260℃-380℃.

[0064] The light straight-chain olefins can be n-butene, n-pentene, etc., or a mixture rich in (volume fraction ≮15%) n-butene and / or n-pentene, etc. For example, carbon four components, carbon five components, etc. after the production of MTBE, TAME in a refinery, an ethylene plant, etc.

[0065] The technical solutions of the present application are further described in detail below through specific examples.

[0066] The relevant test methods in each example include:

[0067] XRD characterization is performed using a smartlab X-ray diffractometer of Rigaku Corporation. CuKα line is used as the radiation source, tube voltage 40KV, tube current 50mA, scanning rate 5° / min, and scanning range 2θ=5-85°.

[0068] SEM characterization is performed using a 200F field emission scanning electron microscope of Quanta chrome company. The test high voltage is 200KV. The size of the molecular sieve crystal grains is measured by the 200F field emission scanning electron microscope.

[0069] Pyridine adsorption characterization is performed using a Nicolet-6700 Fourier transform infrared spectrometer. The B acid and L acid of the molecular sieve are determined. After the sample is pressed into a tablet and fixed in a reaction cell, the sample is purified at 1×10 -3 Pa, 450℃ for 2 hours, cooled to 90℃, saturated with adsorption of the probe molecule pyridine, then programmed to the specified temperature, vacuum desorption for 20 min, and the Py-FTIR spectrum is recorded.

[0070] There are two important indicators for evaluating the performance of the olefin skeletal isomerization catalyst: the first is the conversion rate of n-pent(en) (or but(en)); the second is the selectivity of iso-pent(en) (or but(en)), which is defined as:

[0071]

[0072]

[0073]

[0074]

[0075] Comparative Example 1

[0076] The comparative example prepared a HZSM-35 molecular sieve, including the following steps:

[0077] (1) into the crystallization kettle in turn added deionized water 300 g, silica sol (SiO2 mass content 30%) 270 g, sodium hydroxide solution (sodium hydroxide mass content 30%) 40 g, aluminum sulfate solution (mass content of Al2O3 8.0%) 60 g, ethylenediamine 80 g, ZSM-35 molecular sieve (SiO2 / Al2O3 molar ratio 20) crystal seeds 5 g. While adding, stirring. After uniform stirring, seal, crystallization at 140℃ for 72 hours. After crystallization, cooling, filtering, washing, drying to obtain ZSM-35 molecular sieve.

[0078] (2) ZSM-35 molecular sieve was calcined at 530℃ for 4 hours to remove the template agent, then ion exchanged with 10% mass concentration of ammonium chloride solution, liquid-solid ratio 5:1, temperature 60℃. After ion exchange for 3 times, washed with deionized water for 3 times, then dried at 130℃ for 4 hours, calcined at 530℃ for 4 hours to obtain HZSM-35 molecular sieve.

[0079] The HZSM-35 molecular sieve was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and pyridine infrared analysis. From Figure 1 It can be seen that the HZSM-35 molecular sieve has obvious characteristic diffraction peaks of ZSM-35 in 2θ = 5°-30°, and the molecular sieve has no characteristic diffraction peaks of other zeolites in 2θ = 5°-85°, indicating that the synthesized molecular sieve is pure phase ZSM-35. From Figure 2 It can be seen that the HZSM-35 molecular sieve crystal presents a sheet-like crystalline structure, but the crystal size is large, the thickness is 332 nm, the length or width is 1109 nm, and the B acid amount of the HZSM-35 molecular sieve is 0.576 mmol / g.

[0080] Comparative Example 2

[0081] The comparative example prepared a HZSM-35 molecular sieve, including the following steps:

[0082] (1) Into a crystallization kettle, deionized water 600 g, potassium hydroxide solution (mass content of potassium hydroxide 30%) 100 g, white carbon black (mass content of SiO2 95%) 85 g, aluminum hydroxide (mass content of Al2O3 45%) 8.0 g, cyclohexylamine 100 g were added in sequence, and stirring was not stopped during the addition. Then ZSM-35 molecular sieve (molar ratio of SiO2 / Al2O3 20) seed crystal 8 g was added, and after stirring was uniform, it was sealed, crystallized at 150°C for 60 hours. After cooling, washing and drying, ZSM-35 molecular sieve was obtained.

[0083] (2) After the ZSM-35 molecular sieve was calcined at 530°C for 4 hours to remove the template agent, ion exchange was carried out with 5% mass concentration of ammonium chloride solution, the exchange liquid to solid ratio was 10:1, and the temperature was 80°C. After three times of exchange, it was washed with deionized water for three times, and then dried at 140°C for 4 hours and calcined at 530°C for 4 hours to obtain a HZSM-35 molecular sieve.

[0084] The HZSM-35 molecular sieve was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and pyridine infrared analysis. The thickness of the HZSM-35 molecular sieve was 265 nm, the length or width was 972 nm, and the B acid amount of the HZSM-35 molecular sieve was 0.456 mmol / g.

[0085] Comparative Example 3

[0086] This comparative example used the HZSM-35 molecular sieve of Comparative Example 1 to prepare a light olefin skeletal isomerization catalyst A, including the following steps:

[0087] 1000 g of the HZSM-35 molecular sieve synthesized in Comparative Example 1 was mixed with 100 g of pseudoboehmite (specific surface area 288 m 2 / g, dry basis 68%) and 30 g of sesbania powder. 100 g of acetic acid was added to 850 g of deionized water and stirred uniformly. Then it was added to the above mixture, and a kneader was used for kneading, and then an extruder was used for extrusion molding. After drying at 130°C in an oven for 4 hours, it was moved into a muffle furnace. The temperature was increased to 450°C for 4 hours, and the temperature was kept constant for 4 hours, and the calcination was completed. A light olefin skeletal isomerization catalyst A was prepared. Pyridine infrared analysis of the catalyst A showed that the B acid amount was 0.526 mmol / g.

[0088] Comparative Example 4

[0089] This comparative example used the HZSM-35 molecular sieve of Comparative Example 2 to prepare a light olefin skeletal isomerization catalyst B, including the following steps:

[0090] 1000 g of the HZSM-35 molecular sieve synthesized in Comparative Example 2 was mixed with 100 g of pseudoboehmite (specific surface area 288 m 2HZSM-35 molecular sieve was prepared by the following steps:

[0091] Example 1

[0092] HZSM-35 molecular sieve was prepared by the following steps:

[0093] (1) 360 g of deionized water, 35 g of silica sol (SiO2mass content 30%), 100 g of sodium hydroxide solution (sodium hydroxide mass content 30%), and 100 g of ZSM-35 molecular sieve (SiO2 / Al2O3molar ratio 20) seed crystals were added to a reaction kettle at one time, stirred uniformly, and then sealed. The reaction was carried out at 120°C for 12 hours.

[0094] (2) 300 g of deionized water, 270 g of silica sol (SiO2mass content 30%), 40 g of sodium hydroxide solution (sodium hydroxide mass content 30%), 60 g of aluminum sulfate solution (aluminum oxide content 8.0%), and 80 g of ethylenediamine were sequentially added to a crystallization kettle while stirring. Then, 160 g of the product of step (1) was added, stirred uniformly, and then sealed. Crystallization was carried out at 140°C for 72 hours. After crystallization, the ZSM-35 molecular sieve was obtained after cooling, filtration, washing, and drying.

[0095] (3) After the ZSM-35 molecular sieve was calcined at 530°C for 4 hours to remove the template, ion exchange was carried out using a 10% mass concentration of ammonium chloride solution at a liquid-to-solid ratio of 5:1 and a temperature of 60°C. After three exchanges, the molecular sieve was washed three times with deionized water, and then dried at 130°C for 4 hours and calcined at 530°C for 4 hours to obtain the HZSM-35 molecular sieve.

[0096] The HZSM-35 molecular sieve was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and pyridine infrared analysis. From Figure 3 It can be seen that the HZSM-35 molecular sieve has obvious characteristic diffraction peaks of ZSM-35 in the range of 2θ = 5°-30°, and no characteristic diffraction peaks of other zeolites in the range of 2θ = 5°-85°, indicating that the synthesized molecular sieve is a pure-phase ZSM-35. From Figure 4It can be seen that the HZSM-35 molecular sieve crystals exhibit a sheet-like crystalline structure, the grain size is greatly reduced compared to Comparative Example 1, the thickness is 43 nm, and the length or width is 195 nm. The B acid amount of the HZSM-35 molecular sieve is 1.216 mmol / g.

[0097] Example 2

[0098] In this example, a HZSM-35 molecular sieve is prepared by the following steps:

[0099] (1) 500 g of deionized water, 50 g of white carbon black (SiO2 mass content 95%), 200 g of potassium hydroxide solution (potassium hydroxide mass content 30%), and 150 g of ZSM-35 molecular sieve (SiO2 / Al2O3 molar ratio 20) seed crystals are added to a reaction kettle at one time, stirred uniformly, sealed, and reacted at 130°C for 12 hours.

[0100] (2) 600 g of deionized water, 100 g of potassium hydroxide solution (potassium hydroxide mass content 30%), 85 g of white carbon black (SiO2 mass content 95%), 8.0 g of aluminum hydroxide (Al2O3 mass content 45%), and 100 g of cyclohexylamine are sequentially added to a crystallization kettle while stirring continuously. Then, 200 g of the reaction product of step (1) is added, stirred uniformly, sealed, and crystallized at 150°C for 60 hours. After cooling, washing, and drying, a ZSM-35 molecular sieve is obtained.

[0101] (3) After the ZSM-35 molecular sieve is calcined at 530°C for 4 hours to remove the template agent, it is exchanged with a 5% mass concentration ammonium chloride solution, the exchange liquid to solid ratio is 10:1, and the temperature is 80°C. After 3 exchanges, it is washed with deionized water 3 times, then dried at 140°C for 4 hours, calcined at 530°C for 4 hours, and a HZSM-35 molecular sieve is obtained.

[0102] The HZSM-35 molecular sieve is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and pyridine infrared analysis. The thickness of the HZSM-35 molecular sieve is 48 nm, the length or width is 310 nm, and the B acid amount of the HZSM-35 molecular sieve is 1.135 mmol / g.

[0103] Example 3

[0104] In this example, a HZSM-35 molecular sieve is prepared by the following steps:

[0105] (1) Into a reactor, 500 g of deionized water, 100 g of sodium hydroxide solution (sodium hydroxide mass content 30%), 50 g of solid silica gel (SiO2 mass content 92%), and 120 g of ZSM-35 molecular sieve seed crystals (SiO2 / Al2O3 molar ratio 20) were added at one time, and stirred uniformly, and then sealed, and reacted at 140°C for 8 hours.

[0106] (2) Into a crystallization reactor, 500 g of deionized water, 30 g of sodium hydroxide solution (sodium hydroxide mass content 30%), 30 g of potassium hydroxide solution (30%), 27 g of sodium aluminate solution (alumina mass content 10%), 90 g of solid silica gel (SiO2 mass content 92%), and 80 g of cyclohexanediamine were added in sequence while stirring. Then, 180 g of the reaction product of step (1) was added, stirred uniformly, and then sealed, and crystallized at 150°C for 48 hours. After cooling, washing, and drying, a ZSM-35 molecular sieve was obtained.

[0107] (3) After the ZSM-35 molecular sieve was calcined at 530°C for 4 hours to remove the template agent, it was exchanged with 8% mass concentration of ammonium chloride solution, with a liquid-to-solid ratio of 6:1 and a temperature of 70°C. After three exchanges, it was washed three times with deionized water, and then dried at 120°C for 8 hours and calcined at 500°C for 4 hours to obtain a HZSM-35 molecular sieve.

[0108] The HZSM-35 molecular sieve was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and pyridine infrared analysis. The thickness of the HZSM-35 molecular sieve was 49 nm, the length or width was 185 nm, and the B acid content was 1.012 mmol / g.

[0109] Example 4

[0110] This example used the HZSM-35 molecular sieve of Example 1 to prepare a light olefin skeletal isomerization catalyst C, including the following steps:

[0111] 1000 g of the HZSM-35 molecular sieve synthesized in Example 1 was mixed uniformly with 100 g of pseudoboehmite (specific surface area 288 m 2 / g, dry basis 68%) and 30 g of sesbania powder. 100 g of acetic acid was added to 850 g of deionized water and stirred uniformly. Then, it was added to the above mixture, kneaded with a kneader, and then extruded into a shape with an extruder. After drying at 130°C in an oven for 4 hours, it was moved into a muffle furnace. The temperature was increased to 450°C for 4 hours, and then kept constant for 4 hours, to obtain a light olefin skeletal isomerization catalyst C. Pyridine infrared analysis of the catalyst C showed that the B acid content was 1.116 mmol / g.

[0112] Example 5

[0113] This example uses the HZSM-35 molecular sieve of Example 2 to prepare a light olefin skeletal isomerization catalyst D, including the following steps:

[0114] 1000 g of the HZSM-35 molecular sieve synthesized in Example 2 is mixed with 100 g of pseudoboehmite (specific surface area 288 m 2 / g, dry basis 68%), 30 g of sesbania powder. 30 g of nitric acid, 50 g of acetic acid are added to 850 g of deionized water and stirred uniformly. Then added to the above mixture, kneaded with a kneader, and then extruded into a strip with an extruder. After drying in an oven at 140°C for 4 hours, it is moved into a muffle furnace. After 4 hours of temperature increase to 500°C, it is kept at a constant temperature for 4 hours to produce a light olefin skeletal isomerization catalyst D. Pyridine infrared analysis of catalyst D shows that the B acid amount is 1.012 mmol / g.

[0115] Example 6

[0116] This example uses the HZSM-35 molecular sieve of Example 3 to prepare a light olefin skeletal isomerization catalyst E, including the following steps:

[0117] 1000 g of the HZSM-35 molecular sieve synthesized in Example 3 is mixed with 100 g of pseudoboehmite (specific surface area 288 m 2 / g, dry basis 68%), 50 g of methyl cellulose. 50 g of nitric acid is added to 900 g of deionized water and stirred uniformly. Then added to the above mixture, kneaded with a kneader, and then extruded into a strip with an extruder. After drying in an oven at 140°C for 4 hours, it is moved into a muffle furnace. After 4 hours of temperature increase to 500°C, it is kept at a constant temperature for 4 hours to produce a light olefin skeletal isomerization catalyst E. Pyridine infrared analysis of catalyst E shows that the B acid amount is 0.918 mmol / g.

[0118] Example 7

[0119] Using the catalysts prepared in the above examples and comparative examples, isomerization reactions are carried out using mixed C5 light hydrocarbons as raw materials:

[0120] The experimental device is a normal pressure reaction device, using an isothermal fixed bed reactor, with a one-pass product flow. The catalyst is packed in the constant temperature section of the reactor. 20-30 mesh quartz sand is packed in the upper and lower parts of the catalyst. After packing is complete, the reactor is connected to the system. Nitrogen is introduced for airtightness test. The airtightness pressure is gradually increased to 1.0 MPa. After 2 hours of constant temperature, the pressure drops by no more than 0.1 MPa, and the device is airtight.

[0121] As Figure 5As shown, the C4, C5 olefin-containing raw material from the raw material tank 1 is pressurized by the oil feed pump 2 and then enters the reactor 3, is heated to a certain temperature at the upper stage of the reactor, enters the catalyst bed layer to occur olefin skeletal isomerization reaction, the reaction product enters the gas-liquid separation tank 4, the gas product is discharged from the upper part of the gas-liquid separation tank, is depressurized by the back pressure valve 5 and then discharged through the wet flowmeter 6; the liquid product is discharged from the bottom of the gas-liquid separation tank, is depressurized by the diaphragm pneumatic valve 7, is sampled and analyzed and then enters the product tank 8. The N2 pipeline provides nitrogen for system replacement and gas tightness, and is in a closed state during the isomerization reaction.

[0122] The test raw material is a refinery mixed C5 light hydrocarbon, and its composition is shown in Table 1.

[0123] Table 1 Composition analysis of mixed C5 light hydrocarbon

[0124] Component Content m% 1-pentene 4.27 2-methyl-1-butene 0.82 trans-2-pentene + cis-2-pentene 18.72 2-methyl-2-butene 8.14 isopentane 42.19 n-pentane 6.44 other 5.12

[0125] The above C5 light hydrocarbon is subjected to light olefin skeletal isomerization experiment under the conditions of a pressure of 0.1 MPa, a space velocity of 4.0 h-1 and a temperature of 260℃, and then the hydrocarbon composition of the product is analyzed. -1

[0126] The catalysts of Comparative Examples 3-4 and Examples 4-6 are respectively used for evaluation experiment, and the experimental results are shown in Table 2.

[0127] Table 2 Experimental results of different comparative examples and examples

[0128] Item Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Catalyst No. A B C D E n-pentene conversion % 61.5 58.2 72.1 69.1 71.2 isopentene selectivity % 95.8 96.1 97.8 98.5 98.1

[0129] From the above data, it can be seen that in the light olefin skeletal isomerization experiment, the catalyst of the present application has higher conversion rate of normal olefins and selectivity of isomerized olefins.

[0130] Obviously, the above examples of the present application are merely examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. For those skilled in the art, other different forms of changes or modifications can be made on the basis of the above description, and it is impossible to enumerate all the implementation modes here. Any changes or modifications which belong to the technical solutions of the present application and are derived from the obvious changes or modifications still fall within the protection scope of the present application.​

Claims

1. A light olefin skeletal isomerization catalyst, characterized in that, The catalyst was prepared using small-grained Brønsted acid-rich HZSM-35 molecular sieve. The small-crystal HZSM-35 molecular sieve rich in Brønsted acid exhibits a plate-like crystalline structure with a grain thickness of less than 50 nm and a length or width of less than 500 nm. The amount of Brønsted acid in the small-crystal HZSM-35 molecular sieve is greater than 1.0 mmol / g. The catalyst has a Brønsted acid content greater than 0.9 mmol / g.

2. The light olefin skeletal isomerization catalyst according to claim 1, characterized in that, The length or width of the small-crystal Brønsted acid-rich HZSM-35 molecular sieve is less than 200 nm, and the amount of Brønsted acid in the small-crystal Brønsted acid-rich HZSM-35 molecular sieve is greater than 1.2 mmol / g. The catalyst has a Brønsted acid content greater than 1.1 mmol / g.

3. A method for preparing the light olefin skeletal isomerization catalyst according to claim 1 or 2, characterized in that, The preparation method includes the following steps: The small-crystal Brønsted acid HZSM-35 molecular sieve is mixed with deionized water, binder, acid and extrusion aid, and then dried and calcined to produce the light olefin skeleton isomerization catalyst.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the small-crystal β-rich acid HZSM-35 molecular sieve, binder, extrusion aid, acid and deionized water is (50-100):(5-10):(1-5):(5-10):(50-100).

5. The preparation method according to claim 3 or 4, characterized in that, The adhesive is selected from one or more of silica sol, alumina sol, alumina, and boehmite; The acid is selected from one or more of nitric acid, acetic acid, and citric acid; The extrusion aid is guar gum powder and / or methylcellulose.

6. The preparation method according to claim 3, characterized in that, The drying temperature is 120-140℃ and the time is 4-8 hours; the calcination temperature is 450-500℃ and the time is 4-8 hours.

7. The preparation method according to claim 3, characterized in that, The small-crystal Brønsted acid-rich HZSM-35 molecular sieve is prepared by the following steps: A silicon source, ZSM-35 molecular sieve, water, and inorganic base are mixed and reacted in a reactor at 100-150°C for 4-16 hours to obtain intermediate product 1. The silicon source, aluminum source, water, inorganic alkali, intermediate product 1 and template agent are mixed and crystallized in a crystallization kettle at 120-180℃ for 36-96 hours to obtain the crystallized product. The crystallized product was washed with deionized water, dried and calcined to obtain ZSM-35 molecular sieve; The obtained ZSM-35 molecular sieve was subjected to ion exchange with ammonium nitrate solution; the ion-exchanged ZSM-35 molecular sieve was washed with deionized water, then dried and calcined to obtain the small-crystal Brønsted acid-rich HZSM-35 molecular sieve.

8. The preparation method according to claim 7, characterized in that, In the preparation step of intermediate product 1, the silicon source is calculated as SiO2, the ZSM-35 molecular sieve is calculated as SiO2, and the inorganic base is calculated as OH. - The molar ratio of the silicon source to the ZSM-35 molecular sieve is (0.05-0.5):1, the molar ratio of the inorganic alkali to the ZSM-35 molecular sieve is (0.1-1):1, and the molar ratio of the water to the ZSM-35 molecular sieve is (10-100):

1.

9. The preparation method according to claim 7, characterized in that, In the preparation steps of the ZSM-35 molecular sieve, the silicon source is calculated as SiO2, the aluminum source as Al2O3, and the inorganic base as OH-. - The molar ratio of silicon source to aluminum source is (20-100):1, the molar ratio of inorganic base to silicon source is (0.1-1):1, and the molar ratio of water to silicon source is (10-100):

1. The silicon source, aluminum source, water, and inorganic base are considered as a mixture, and the weight ratio of intermediate product 1 to the mixture is (0.05-0.5):

1. The weight ratio of the template agent to the mixture is (0.05-0.5):

1.

10. The preparation method according to claim 7, characterized in that, In the preparation steps of the ZSM-35 molecular sieve, the drying temperature is 120-140℃ and the time is 4-8 hours; the calcination temperature is 500-550℃ and the time is 4-8 hours.

11. The preparation method according to claim 7, characterized in that, During the ion exchange process, the liquid-to-solid ratio is (5-10):1, and the temperature is 50-80℃; When the ZSM-35 molecular sieve after ion exchange is washed with deionized water, the liquid-to-solid ratio is (5-10):

1.

12. The preparation method according to claim 7, characterized in that, After ion exchange, the ZSM-35 molecular sieve is washed with deionized water, and then dried at a temperature of 120-140℃ for 4-8 hours; the calcination temperature is 450-500℃ for 4-8 hours.

13. The preparation method according to claim 7, characterized in that, The silicon source used in the preparation of intermediate product 1 and the silicon source used in the preparation of ZSM-35 molecular sieve are independently selected from one or more combinations of solid silica gel, silica sol and fumed silica. The aluminum source is selected from one or more of sodium aluminate, aluminum hydroxide and aluminum sulfate; The inorganic base in the preparation of intermediate product 1 and the inorganic base in the preparation of ZSM-35 molecular sieve are independently selected from one or a combination of two of sodium hydroxide and potassium hydroxide. The template agent is selected from one or more of ethylenediamine, cyclohexylamine, and cyclohexanediamine.

14. A method for using the light olefin skeleton isomerization catalyst of claim 1 or 2 to convert light straight-chain olefins into isomerized branched olefins under non-hydrogenation conditions.

15. The application method according to claim 14, characterized in that, The isomerization reaction conditions include: pressure 0.05-0.5 MPa and space velocity 1.0-8.0 h⁻¹. -1 Temperature 240-400℃.

16. The application method according to claim 15, characterized in that, The initial reaction temperature of the isomerization reaction is no higher than 260°C.

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