Modified HZSM-5 molecular sieve, catalyst containing modified HZSM-5 molecular sieve as well as preparation and application of modified HZSM-5 molecular sieve

Abstract

The invention discloses an HZSM-5 molecular sieve catalyst and a preparation method thereof. The catalyst comprises, by weight, 60%-85% of an HZSM-5 molecular sieve, 0.1%-6% of sodium oxide and / or potassium oxide and 13%-35% of aluminum oxide. The molar ratio of silicon to aluminum of the HZSM-5 molecular sieve is 40 to 150, and the indication constant k is 100 to 550. The preparation method of the catalyst comprises the following steps: firstly, dissolving cinnamate in benzene to prepare a solution, and enabling the solution to fully fill molecular sieve pores; blowing with hot nitrogen, and carrying out addition reaction on C = C of the cinnamate and benzene to generate a macromolecular salt product, so as to achieve the purpose of modifying an acid center at a pore crossing part; and preparing the catalyst according to a conventional method. The catalyst provided by the invention has proper activity, relatively high p-diethylbenzene selectivity and longer one-way operation period.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a selective catalyst, in particular to a preparation method and application of a molecular sieve catalyst for synthesizing p-diethylbenzene by selective alkylation of ethylbenzene and ethylene (or ethanol). Background Art

[0002] p-Diethylbenzene is often used as a desorbent for p-xylene in industry. This process requires the p-diethylbenzene purity to be above 98%. Direct synthesis of p-diethylbenzene by selective alkylation of ethylbenzene and ethylene (or ethanol) on a solid acid catalyst is a common method for industrial production. The catalyst used is usually a modified HZSM-5 molecular sieve catalyst. On the acid center, ethylbenzene and ethylene (or ethanol) can generate three isomers, namely p-diethylbenzene, m-diethylbenzene and o-diethylbenzene. The molecular diameters of the ortho- and meta-products are larger than those of the para-products. The high selectivity of the para-products is achieved through the diffusion restriction effect of the selective catalyst pores.

[0003] The following methods are commonly used to modify HZSM-5 molecular sieve catalysts: steam treatment to kill the strong acid centers of the molecular sieve and reduce the density of the acid centers, such as patents CN94110202.5, US4365104, US4128592, CN200310116628.X, etc.; loading Mg oxide or rare earth metal oxide to adjust the number and strength of the acid centers in the molecular sieve pores, such as patents CN90101436.2, CN94110202.5, CN95118372. 9. CN200310116628.X, CN200410020397.9, CN200810246986.5, US4128592, etc.; silanization is used to adjust the pore diameter of the molecular sieve, such as patents US4465886 and CN200310116628.X, etc.; phosphorus oxide modification is used to increase the medium and strong acid centers of the molecular sieve, such as patents CN95118372.9, CN200310116628.X, US4128592, etc.

[0004] In the pore structure of HZSM-5 molecular sieve, there are two types of pore space, namely straight-through pores and pore intersections. The pore intersection is where two pores intersect each other at a certain angle (such as 90°) and are connected internally. The space at the intersection of such pores is open, and the acid centers are denser than those at non-intersections, which often become active areas for side reactions or carbon deposit precursors. The above-mentioned modification methods for the pores of HZSM-5 molecular sieves, such as steam treatment, loading of Mg oxides, loading of rare earth metal oxides, and loading of phosphorus oxides, modify both the pore intersections and the straight-through pores, which is a general modification method that is not targeted. After the above-mentioned modification, there are still relatively open spaces and a large number of acid centers at the intersection of the pores, which can continue to catalyze the product diethylbenzene to continue to react to generate triethylbenzene, tetralin and phenylcyclohexane with larger molecular weights, which not only affects the selectivity of the product to diethylbenzene, but also further forms carbon deposit precursors with a high carbon-hydrogen ratio until carbon deposits are formed. If the existing modification means are used to increase the loading of metal oxides to achieve the purpose of modifying the acid centers at the intersection of the pores, the loading of the modified material is too large, which affects the diffusion of the target product p-diethylbenzene in the pores, increases the decay rate of the catalyst ethylbenzene conversion rate, and shortens the single-pass operation cycle of the catalyst. The single-pass operation cycle of the industrial alkylation process for producing p-diethylbenzene catalyst is only 300-400 hours before it needs to be regenerated by burning carbon, resulting in high operating costs and few annual effective operating hours. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a modified HZSM-5 molecular sieve, a catalyst containing the same and a preparation method thereof. The HZSM-5 molecular sieve provided by the present invention has a suitable active center and pore structure, and the catalyst prepared by using the same as an acidic component is used in the alkylation reaction of ethylbenzene and ethylene (or ethanol), which can obtain a higher selectivity for p-diethylbenzene and excellent stability.

[0006] The first aspect of the present invention provides a modified HZSM-5 molecular sieve.

[0007] The modified HZSM-5 molecular sieve contains at least one metal oxide of sodium and potassium as an additive, and the additive content is 0.5% to 5%; Among them, the silicon-aluminum ratio (SiO 2 / Al 2 O 3 Molar ratio) is 40~150; The indicative constant k of the HZSM-5 molecular sieve is 100-550, preferably 101-500, wherein the indicative constant k is calculated as follows: k=Q / (0.5705×a -0.366 -c) Wherein, Q-cyclohexane adsorption capacity, in g / 100g; a-HZSM-5 molecular sieve silicon-aluminum ratio; c-the number of moles of metal oxides contained in 100gHZSM-5 molecular sieve.

[0008] Furthermore, the indicator constant k in the present invention is obtained by fitting based on a large amount of data on cyclohexane adsorption, silicon-aluminum ratio, amount of metal oxide substances, etc. measured on HZSM-5 molecular sieves.

[0009] Furthermore, the method for determining the cyclohexane adsorption amount is as follows: the determination is performed using an intelligent gravimetric analyzer (IGA-002). Before determining the cyclohexane adsorption amount, a molecular sieve de-impurity treatment is performed to remove moisture and impurities such as residual templates. The de-impurity treatment is to raise the temperature of the sample to be tested from room temperature to 300°C at a rate of 5°C / min under a vacuum state, and then return it to room temperature after its mass becomes constant, and then the cyclohexane adsorption amount is determined. Cyclohexane vapor is passed into the sample chamber after de-impurity, and the weight difference is recorded after the sample is completely adsorbed and saturated (i.e., the weight is constant).

[0010] Furthermore, the silicon to aluminum ratio of HZSM-5 molecular sieve is 50-150.

[0011] The second aspect of the present invention also provides a method for preparing the modified HZSM-5 molecular sieve.

[0012] Specifically, the preparation method of the modified HZSM-5 molecular sieve comprises the following steps: (1) Dissolve cinnamate in benzene and stir evenly to fully dissolve; (2) impregnating HZSM-5 molecular sieve with the solution obtained in step (1), and filtering out the HZSM-5 molecular sieve after the impregnation is completed; (3) purging the HZSM-5 molecular sieve filtered out in step (2) with hot nitrogen; (4) Washing the HZSM-5 molecular sieve obtained in step (3) with deionized water, followed by drying and calcining.

[0013] Furthermore, the cinnamate in step (1) can be a soluble carnitine silicate such as sodium cinnamate, potassium cinnamate, etc. The mass fraction of the cinnamate in benzene is 0.5% to 20%, preferably 1% to 15%.

[0014] Furthermore, the liquid-to-solid ratio of the impregnation in step (2) is 4-10 mL / g, preferably 5-8 mL / g; and the impregnation time is 1-10 hours, preferably 1-5 hours.

[0015] Furthermore, the temperature of the hot nitrogen in step (3) is 80°C to 180°C, preferably 85°C to 150°C. The conditions for hot nitrogen purging are conventional operations in the art. For example, the nitrogen volume space velocity is 100h / min. -1 ~3000h -1 , preferably 200h -1 ~2000h -1 The purge time is generally 2 hours to 24 hours, preferably 5 hours to 20 hours. At the end of the purge, the benzene content in the nitrogen after passing through the molecular sieve is no more than 1 μg / L.

[0016] Furthermore, the liquid-to-solid ratio of the washing in step (4) is 4-10 mL / g, preferably 5-8 mL / g; the washing temperature is room temperature-80°C, preferably 40°C-70°C; and the number of washings is 1-10 times, preferably 2-6 times.

[0017] Furthermore, the drying and calcining described in step (4) adopt conventional conditions in the art. The calcination needs to be carried out in an oxygen-containing atmosphere. For example, the drying conditions are generally: the drying temperature is 60°C to 150°C, preferably 80°C to 120°C, and the drying time is 8 hours to 24 hours, preferably 10 hours to 20 hours. The calcination conditions are: the calcination temperature is 300°C to 800°C, preferably 400°C to 700°C, and the calcination time is 2 hours to 24 hours, preferably 4 hours to 8 hours.

[0018] The third aspect of the present invention provides a catalyst for synthesizing p-diethylbenzene, wherein the catalyst contains the modified HZSM-5 molecular sieve described above.

[0019] Specifically, the catalyst for synthesizing p-diethylbenzene comprises, based on the weight of the catalyst: HZSM-5 molecular sieve 60%~85%, preferably 61%~83%; Sodium oxide and / or potassium oxide 0.1%~6%, preferably 0.2%~5%; Alumina: 13% to 35%, preferably 14% to 34%.

[0020] Furthermore, the silicon aluminum (SiO 2 / Al 2 O 3 ) molar ratio is 40~180, preferably 40~150.

[0021] Furthermore, the characteristic constant k of the HZSM-5 molecular sieve is 100-550, preferably 101-500.

[0022] Furthermore, the specific surface area of ​​the catalyst is generally 250-650 m 2 / g, preferably 300~600m2 / g; the specific pore volume is 0.20~0.50mL / g, preferably 0.25~0.45mL / g.

[0023] Furthermore, the catalyst is generally in the form of a bar or a sphere. When it is in the form of a bar, its cross section may be cylindrical, clover-shaped or four-leaf clover-shaped, with a diameter of 0.5 to 3.0 mm, preferably 1.0 to 2.0 mm; when it is in the form of a sphere, its diameter is 0.5 to 5.0 mm, preferably 1.0 to 3.0 mm.

[0024] Furthermore, in addition to the metal oxide introduced during the modification of the HZSM-5 molecular sieve, the catalyst may further contain other metal or non-metal oxides as second additives, such as one or more oxides of Li, La, Ce, Mg, Ca, Ba, Cu, Zn, Zr, Fe, Si, P, B, and C to further improve the catalyst's acid distribution, pore structure and other physical properties. The content of the second additive oxide in the catalyst is generally 0.1-5%.

[0025] A fourth aspect of the present invention provides a method for preparing a HZSM-5 molecular sieve catalyst.

[0026] Specifically, the preparation method of the HZSM-5 molecular sieve catalyst comprises the following steps: (1) Dissolve an appropriate amount of cinnamate in benzene, stir evenly and fully dissolve; use the solution to impregnate HZSM-5 molecular sieve, and filter out the molecular sieve after impregnation; (2) Purge the filtered molecular sieve with hot nitrogen and cool it naturally to room temperature after the purge is completed; (3) washing the molecular sieve obtained in step (2) with deionized water, drying and calcining the washed molecular sieve to obtain a modified HZSM-5 molecular sieve; (4) The modified HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried and calcined to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) is loaded with the second auxiliary agent oxide by conventional impregnation method, and then dried and calcined to obtain a finished catalyst.

[0027] Furthermore, the cinnamate described in step (1) can be a soluble cinnamate such as sodium cinnamate, potassium cinnamate, etc. The mass fraction of cinnamate in benzene is 0.5% to 20%, preferably 1% to 15%. The liquid-to-solid ratio during the impregnation of the molecular sieve is 4 to 10 mL / g, preferably 5 to 8 mL / g; the impregnation time is 1 to 10 hours, preferably 1 to 5 hours.

[0028] Furthermore, the temperature of the hot nitrogen in step (2) is 80°C to 180°C, preferably 85°C to 150°C. The conditions for hot nitrogen purging are conventional in the art. For example, the nitrogen volume space velocity is 100h / min. -1 ~3000h -1 , preferably 200h -1 ~2000h -1 The purge time is generally 2 hours to 24 hours, preferably 5 hours to 20 hours. At the end of the purge, the benzene content in the nitrogen after passing through the molecular sieve is no more than 1 μg / L.

[0029] Furthermore, the liquid-to-solid ratio of the washing in step (3) is 4-10 mL / g, preferably 5-8 mL / g; the washing temperature is room temperature-80°C, preferably 40°C-70°C; and the number of washings is 1-10 times, preferably 2-6 times.

[0030] Furthermore, in step (4), the extrusion aid may be sesbania powder, and the peptizing agent solution may be at least one of dilute nitric acid and citric acid. The mass concentration of the dilute nitric acid solution is generally 3% to 15%.

[0031] Furthermore, the proportions and operations of the materials in step (4) are well known to those skilled in the art. For example, the weight ratio of HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution is generally (60-85): (15-40): (3-20): (5-80), preferably (70-80): (20-30): (10-15): (20-50). In the material dosage, HZSM-5 molecular sieve and alumina precursor are weights calculated on a dry basis.

[0032] Furthermore, the drying conditions in steps (3), (4) and (5) are generally as follows: the drying temperature is 60°C to 150°C, preferably 80°C to 120°C, and the drying time is 2 hours to 24 hours, preferably 5 hours to 20 hours; the roasting conditions are as follows: the roasting temperature is 300°C to 800°C, preferably 400°C to 700°C, and the roasting time is 2 hours to 24 hours, preferably 3 hours to 8 hours; during the roasting, the molecular sieve or molecular sieve catalyst is purged with air flow, and the air volume space velocity is 100h -1 ~3000h -1 , preferably 200h -1 ~2000h -1 .

[0033] Furthermore, step (4) is preferably performed by naturally drying in the shade for 10 to 48 hours before drying.

[0034] Furthermore, the conventional impregnation method for loading the second additive oxide in step (5) is an operation well known to those skilled in the art.

[0035] A fifth aspect of the present invention provides a method for producing p-diethylbenzene by alkylation of ethylbenzene and ethylene (or ethanol), wherein the HZSM-5 molecular sieve catalyst described above is used.

[0036] A method for producing p-diethylbenzene by alkylation of ethylbenzene and ethylene (or ethanol), comprising the following steps: alkylation reaction of raw materials ethylbenzene and ethylene (or ethanol) in the presence of HZSM-5 molecular sieve catalyst under reaction conditions.

[0037] Further, the reaction conditions include: reaction pressure of 0.1MPa~4.0MPa, preferably 0.12MPa~3.5MPa; reaction temperature of 300℃~380℃, preferably 310℃~370℃; ethylbenzene mass space velocity of 1h -1 ~10h -1 , preferably 2h -1 ~8h -1 ; The molar ratio of ethylbenzene to ethylene (or ethanol) is 10~2:1, preferably 8~3:1.

[0038] The inventors of this application have made the following findings based on the research on the reaction of alkylation of ethylbenzene and ethylene (or ethanol) to produce p-diethylbenzene: the alkylation reaction of ethylbenzene is a typical acid-catalyzed selective catalytic reaction, and the acid properties and pore structure of the catalyst affect the selectivity of the para-product and the stability of the catalyst. At present, the catalyst for the alkylation of ethylbenzene and ethylene (or ethanol) to produce p-diethylbenzene in industry is a modified HZSM-5 molecular sieve catalyst. In the pore structure of HZSM-5 molecular sieve, there are two types of pore spaces, namely straight pores and pore intersections. The pore intersection is where two pores intersect each other at a certain angle (such as 90°) and are connected internally. This kind of pore intersection has a wide space, and the acid center is denser than the non-intersection, which often becomes an active zone for side reactions or carbon deposit precursors. The existing modification methods for the HZSM-5 molecular sieve pores, such as steam treatment, loading Mg oxide, loading rare earth metal oxide and loading phosphorus oxide, modify both the intersection of the pores and the straight pores, which is a general modification method that is not targeted. After the above modification, there is still a relatively open space and a large number of acid centers at the intersection of the pores, which can continue to catalyze the product diethylbenzene to continue to react to generate triethylbenzene, tetralin and phenylcyclohexane with larger molecular weight, which not only affects the selectivity of the product p-diethylbenzene, but also further forms a carbon deposit precursor with a high carbon-hydrogen ratio until carbon deposits are formed. If the existing modification means are used to increase the loading amount of metal oxides to achieve the purpose of modifying the acid centers at the intersection of the pores, the loading amount of the modified material is too large, which affects the diffusion of the target product p-diethylbenzene in the pores, increases the decay rate of the catalyst ethylbenzene conversion rate, and shortens the single-pass operation cycle. Industrially, the catalyst for producing diethylbenzene by the alkylation process has a single-pass operation cycle of only 300 to 400 hours before it needs to be regenerated by burning carbon. The operating costs of the device are high, and the annual effective operating hours are small.

[0039] The preparation method of the catalyst of the present invention is as follows: firstly, cinnamate is dissolved in benzene to prepare a solution, and then the solution is filled with the molecular sieve pores. Hot nitrogen is used for purging, and C=C in the cinnamate at high temperature reacts with benzene to generate a macromolecular salt product with two benzene rings. Since the molecular size of the reaction product is larger than the diameter of the molecular sieve straight-through pore, even if there is an acid center required for the reaction in the straight-through pore, it cannot be generated in the straight-through pore, but can only be generated at a location where there is both sufficient space and an acid center, such as the intersection of the pores. The hot nitrogen will also gasify the excess benzene in the pores and take out the molecular sieve, and the remaining unreacted cinnamate in the pores will be taken away during water washing, while the macromolecular product generated by the reaction cannot be taken out of the pores due to the limitation of the molecular size, and continues to remain at the intersection of the pores. The calcination process fully oxidizes and burns the carbon and hydrogen components in the macromolecular product, turning them into carbon dioxide and water vapor and escaping the molecular sieve. The remaining metal oxides continue to adhere to the intersection of the molecular sieve channels, playing a role in adjusting the acid center at the intersection of the channels and adjusting the size of the area, but will not affect the acid center at the straight-through channel, nor will it affect the smooth flow of the channel. Combined with the modification of other metal or non-metal oxides, the strong acid centers inside and outside the channels are further modified to obtain a catalyst with suitable activity, high selectivity for diethylbenzene, and a long single-pass operation cycle. Implementation

[0040] The technical scheme of the present invention is described in detail below in conjunction with the examples, but the present invention is not limited to the following examples. In the material dosage, the HZSM-5 molecular sieve and the alumina precursor are all measured by weight on a dry basis.

[0041] In the examples of the present invention and the comparative examples, the concentration of the product was analyzed by liquid chromatography, and the conversion rate and selectivity were obtained by calculation.

[0042] Ethylbenzene conversion rate = number of moles of ethylbenzene involved in the reaction / total number of moles of ethylbenzene feed × 100%; Selectivity for p-diethylbenzene = number of moles of p-diethylbenzene in the product / number of moles of diethylbenzene in the product × 100%. Example 1

[0043] This embodiment provides a method for preparing a HZSM-5 molecular sieve catalyst, comprising the following steps: (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, fully dissolve, and prepare a solution with a mass percentage of 4.5%; use the solution at a liquid-to-solid ratio of 5 mL / g to impregnate 200 g of HZSM-5 molecular sieve with a silicon-aluminum ratio of 40, and filter out the molecular sieve after impregnation for 3 hours; (2) The filtered molecular sieve was heated with 110℃ hot nitrogen for 800h -1 The air velocity was purged for 4 hours, and then naturally cooled to room temperature after the purging; (3) washing the molecular sieve obtained in step (2) with deionized water at a liquid-to-solid ratio of 6 mL / g, drying the washed molecular sieve at 110° C. for 5 hours and calcining at 550° C. for 5 hours to obtain a modified HZSM-5 molecular sieve; (4) The modified HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried at 110° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) was loaded with La oxide by conventional impregnation method, and then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was denoted as A. Example 2

[0044] This embodiment provides a method for preparing a HZSM-5 molecular sieve catalyst, comprising the following steps: (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, fully dissolve, and prepare a solution with a mass percentage of 3.5%; use the solution at a liquid-to-solid ratio of 6 mL / g to impregnate 200 g of HZSM-5 molecular sieve with a silicon-aluminum ratio of 80, and filter out the molecular sieve after impregnation for 4 hours; (2) The filtered molecular sieve was heated with 110℃ hot nitrogen for 1000h -1 The air velocity was purged for 5 hours, and then naturally cooled to room temperature after the purging; (3) washing the molecular sieve obtained in step (2) with deionized water at a liquid-to-solid ratio of 5 mL / g, drying the washed molecular sieve at 120° C. for 7 hours and calcining at 540° C. for 3 hours to obtain a modified HZSM-5 molecular sieve; (4) The modified HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried at 140° C. for 3 hours, and calcined at 550° C. for 6 hours to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) was loaded with Cu oxide by conventional impregnation method, and then dried at 130°C for 2 hours and calcined at 560°C for 3 hours to obtain a finished catalyst, which was denoted as B. Example 3

[0045] This embodiment provides a method for preparing a HZSM-5 molecular sieve catalyst, comprising the following steps: (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, fully dissolve, and prepare a solution with a mass percentage of 5%; use the solution at a liquid-to-solid ratio of 7 mL / g to impregnate 200 g of HZSM-5 molecular sieve with a silicon-aluminum ratio of 120, and filter out the molecular sieve after impregnation for 3 hours; (2) The filtered molecular sieve was heated with 110℃ hot nitrogen for 1200h -1The air velocity was purged for 5 hours, and then naturally cooled to room temperature after the purging; (3) washing the molecular sieve obtained in step (2) with deionized water at a liquid-to-solid ratio of 8 mL / g, drying the washed molecular sieve at 110° C. for 7 hours and calcining at 530° C. for 4 hours to obtain a modified HZSM-5 molecular sieve; (4) The modified HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried at 130° C. for 5 hours, and calcined at 550° C. for 6 hours to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) was loaded with P oxide by conventional impregnation method, and then dried at 150°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was denoted as C. Example 4

[0046] This embodiment provides a method for preparing a HZSM-5 molecular sieve catalyst, comprising the following steps: (1) Dissolve an appropriate amount of potassium cinnamate in benzene, stir evenly, fully dissolve, and prepare a solution with a mass percentage of 4.5%; use the solution at a liquid-to-solid ratio of 8 mL / g to impregnate 200 g of HZSM-5 molecular sieve with a silicon-aluminum ratio of 150, and filter out the molecular sieve after impregnation for 4 hours; (2) The filtered molecular sieve was heated with 140℃ hot nitrogen for 1300h -1 The air velocity was purged for 2 hours, and then naturally cooled to room temperature after the purging; (3) washing the molecular sieve obtained in step (2) with deionized water at a liquid-to-solid ratio of 5 mL / g, drying the washed molecular sieve at 110° C. for 3 hours and calcining at 550° C. for 6 hours to obtain a modified HZSM-5 molecular sieve; (4) The modified HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried at 130° C. for 5 hours, and calcined at 550° C. for 6 hours to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) was loaded with Mg oxide by conventional impregnation method, and then dried at 150°C for 3 hours and calcined at 550°C for 3 hours to obtain a finished catalyst, which was denoted as D.

[0047] Comparative Example 1 This comparative example provides a method for preparing a HZSM-5 molecular sieve catalyst, comprising the following steps: (1) Using potassium nitrate as a precursor, a HZSM-5 molecular sieve with a silicon-aluminum ratio of 40 was impregnated by a conventional impregnation method. After impregnation for 5 hours, the molecular sieve was filtered out, dried at 110°C for 7 hours, and calcined at 550°C for 3 hours; (2) After fully mixing and kneading HZSM-5 molecular sieve with a silicon-aluminum ratio of 40, alumina precursor, an extrusion aid and a peptizing agent solution, the mixture was shaped, dried at 110° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain a catalyst precursor; (3) The catalyst precursor obtained in step (2) was loaded with La oxide by conventional impregnation method, and then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was recorded as E1.

[0048] Comparative Example 2 This comparative example provides a method for preparing a HZSM-5 molecular sieve catalyst, comprising the following steps: (1) Using potassium nitrate as a precursor, a HZSM-5 molecular sieve with a silicon-aluminum ratio of 80 was impregnated by a conventional impregnation method. After impregnation for 5 hours, the molecular sieve was filtered out, dried at 110°C for 7 hours, and calcined at 550°C for 3 hours; (2) The HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (1) are fully kneaded, molded, dried at 110° C. for 5 hours, and calcined at 550° C. for 5 hours to obtain a catalyst precursor; (3) The catalyst precursor obtained in step (2) was loaded with La oxide by conventional impregnation method, and then dried at 110°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was recorded as E2.

[0049] Comparative Example 3 This comparative example provides a method for preparing a HZSM-5 molecular sieve catalyst, comprising the following steps: (1) Using potassium nitrate as a precursor, a HZSM-5 molecular sieve with a silicon-aluminum ratio of 120 was impregnated by a conventional impregnation method. After impregnation for 3 hours, the molecular sieve was filtered out, dried at 110°C for 5 hours, and calcined at 550°C for 6 hours; (2) The HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (1) are fully kneaded, molded, dried at 130° C. for 5 hours, and calcined at 550° C. for 6 hours to obtain a catalyst precursor; (3) The catalyst precursor obtained in step (2) was loaded with P oxide by conventional impregnation method, and then dried at 150°C for 5 hours and calcined at 550°C for 5 hours to obtain a finished catalyst, which was recorded as E3. Example 5

[0050] The properties of the HZSM-5 molecular sieve and the HZSM-5 molecular sieve catalyst obtained in the above examples and comparative examples are shown in Table 1 and Table 2.

[0051] Catalyst performance evaluation: The catalysts of the above-mentioned embodiments and comparative examples were used to carry out an evaluation experiment of synthesizing p-diethylbenzene by alkylation of ethylbenzene in a small evaluation device, with ethylbenzene and ethylene as raw materials and the mass space velocity of ethylbenzene being 5h -1 The molar ratio of ethylbenzene to ethylene was 5:1, the reaction temperature was 320°C, the reaction pressure was 1.0 MPa, and the reaction results are shown in Table 3, where the single-pass operation cycle is the operation time from the start of the reaction to the time when the ethylbenzene conversion rate drops to 10%.

[0052] Table 1 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 HZSM-5 molecular sieve Silicon to aluminum ratio, molar ratio 40 80 120 150 40 80 120 Cyclohexane adsorption g / 100g 15.32 15.11 14.28 14.01 7.45 6.23 5.45 Additives <![CDATA[K 2 O content*]]> 0.02 0.03 0.04 0.05 0.02 0.03 0.04 Indicative constant, k 117 179 238 350 58 73 93 *, the number of moles of metal oxide loaded per 100g of molecular sieve.

[0053] Table 2 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Molecular sieve catalyst HZSM-5 molecular sieve, wt% 68.5 72.7 70.4 76 68.5 73.5 69.4 Additives Second additive oxide, wt% 2.5 3.0 2.0 1.5 2.5 2.5 1.8 Alumina, % 29.0 24.3 27.6 22.5 29.0 24.0 28.8 Table 3 Catalyst No. Average conversion of ethylbenzene, mol% Average selectivity to diethylbenzene, mol% One-way operation cycle, h A 15.32 98.89 560 B 14.25 99.10 610 C 14.67 98.23 578 D 14.12 99.12 565 E1 15.23 95.33 269 E2 14.29 96.12 338 E3 15.46 96.33 277

Claims

1. A modified HZSM-5 molecular sieve, It is characterized in that The modified HZSM-5 molecular sieve contains at least one metal oxide of sodium and potassium as an additive, and the additive content is 0.5% to 5%; Wherein, the silicon-aluminum ratio of HZSM-5 molecular sieve is 40-150, preferably 50-150; The indicative constant k of the HZSM-5 molecular sieve is 100-550, preferably 101-500, wherein the indicative constant k is calculated as follows: k=Q / (0.5705×a -0.366 -c) Wherein, Q-cyclohexane adsorption capacity, in g / 100g; a-HZSM-5 molecular sieve silicon-aluminum ratio; c-the number of moles of metal oxides contained in 100gHZSM-5 molecular sieve.

2. The method for preparing the modified HZSM-5 molecular sieve according to claim 1, It is characterized in that The following steps are involved: (1) Dissolve cinnamate in benzene and stir evenly to fully dissolve; (2) impregnating HZSM-5 molecular sieve with the solution obtained in step (1), and filtering out the HZSM-5 molecular sieve after the impregnation is completed; (3) purging the HZSM-5 molecular sieve filtered out in step (2) with hot nitrogen; (4) Washing the HZSM-5 molecular sieve obtained in step (3) with deionized water, followed by drying and calcining.

3. The preparation method according to claim 2, It is characterized in that The cinnamate is one or more of sodium cinnamate and potassium cinnamate.

4. The preparation method according to claim 2, It is characterized in that The mass fraction of cinnamate in benzene is 0.5%~20%.

5. The preparation method according to claim 2, It is characterized in that The liquid-to-solid ratio of the impregnation in step (2) is 4-10 mL / g, and the impregnation time is 1-10 hours.

6. The preparation method according to claim 2, It is characterized in that The temperature of the hot nitrogen in step (3) is 80°C to 180°C.

7. A HZSM-5 molecular sieve catalyst for synthesizing p-diethylbenzene, It is characterized in that The catalyst contains the modified HZSM-5 molecular sieve according to claim 1.

8. The HZSM-5 molecular sieve catalyst according to claim 7, It is characterized in that The catalyst for synthesizing p-diethylbenzene comprises, based on the weight of the catalyst,: HZSM-5 molecular sieve 60%~85%, preferably 61%~83%; Sodium oxide and / or potassium oxide 0.1%~6%, preferably 0.2%~5%; Alumina, 13% to 35%, preferably 14% to 34%; The silicon-aluminum molar ratio of the HZSM-5 molecular sieve is 40-180, preferably 40-150; The indicative constant k of the HZSM-5 molecular sieve is 100-550, preferably 101-500.

9. The HZSM-5 molecular sieve catalyst according to claim 8, It is characterized in that The specific surface area of ​​the catalyst is 250-650m 2 / g, and the specific pore volume is 0.20~0.50mL / g.

10. The HZSM-5 molecular sieve catalyst according to claim 8, It is characterized in that The catalyst also contains one or more oxides of Li, La, Ce, Mg, Ca, Ba, Cu, Zn, Zr, Fe, Si, P, B, and C as a second auxiliary agent, and the content of the second auxiliary agent oxide in the catalyst is 0.1-5%.

11. A method for preparing the HZSM-5 molecular sieve catalyst according to any one of claims 7 to 10, It is characterized in that The steps include: (1) Dissolve an appropriate amount of cinnamate in benzene, stir evenly and fully dissolve; use the solution to impregnate HZSM-5 molecular sieve, and filter out the molecular sieve after impregnation; (2) Purge the filtered molecular sieve with hot nitrogen and cool it naturally to room temperature after the purge is completed; (3) washing the molecular sieve obtained in step (2) with deionized water, drying and calcining the washed molecular sieve to obtain a modified HZSM-5 molecular sieve; (4) The modified HZSM-5 molecular sieve, alumina precursor, extrusion aid and peptizing agent solution obtained in step (3) are fully kneaded, molded, dried and calcined to obtain a catalyst precursor; (5) The catalyst precursor obtained in step (4) is loaded with other metals or non-metal oxides by conventional impregnation method, and then dried and calcined to obtain a finished catalyst.

12. The preparation method according to claim 11, It is characterized in that The cinnamate is one or more of sodium cinnamate and potassium cinnamate.

13. The preparation method according to claim 11 or 12, It is characterized in that The mass fraction of cinnamate in benzene is 0.5% to 20%, preferably 1% to 15%.

14. The preparation method according to claim 11, It is characterized in that In step (1), the liquid-to-solid ratio of the HZSM-5 molecular sieve impregnation is 4-10 mL / g, and the impregnation time is 1-10 hours.

15. The preparation method according to claim 11, It is characterized in that The temperature of the hot nitrogen in step (2) is 80°C to 180°C.

16. A method for producing p-diethylbenzene by alkylation of ethylbenzene, ethylene or ethanol, It is characterized in that The HZSM-5 molecular sieve catalyst described in any one of claims 8 to 11 is used.

17. The method according to claim 16, It is characterized in that The method includes the following: The raw material ethylbenzene, ethylene or ethanol is subjected to an alkylation reaction in the presence of a HZSM-5 molecular sieve catalyst under reaction conditions.

18. The method according to claim 17, It is characterized in that The reaction conditions include: reaction pressure of 0.1 MPa to 4.0 MPa, reaction temperature of 300° C. to 380° C., and ethylbenzene mass space velocity of 1 h -1 ~10h -1 , the molar ratio of ethylbenzene to ethylene or ethanol is 2~10:1.