Regulation and control method for acid intensity distribution of solid acid, solid acid and application

Abstract

The invention relates to the field of solid acids, and discloses a regulation and control method for acid strength distribution of a solid acid, the solid acid and application. The invention relates to a method for regulating and controlling the acid intensity distribution of solid acid, which comprises the following steps: (1) in the presence of ammonium cations, carrying out ammonium cation reversible adsorption on the solid acid, and then carrying out first desorption; and (2) in the presence of metal cations, carrying out metal cation directional adsorption on the product after the first desorption in the step (1), and then carrying out second desorption. According to the method, reversible adsorption of ammonium cations and directional adsorption of metal cations are combined, so that the acid intensity distribution can be conveniently regulated and controlled while the acid amount of the solid acid is kept, and different application environments are met.

Description

Technical Field

[0001] The invention relates to the technical field of solid acids, and in particular to a method for regulating the acid strength distribution of solid acids, solid acids and applications thereof. Background Art

[0002] Solid acid catalysts are commonly used catalysts in petrochemical processes, such as alkylation, isomerization, catalytic cracking, catalytic cracking and other important petrochemical reactions. Due to the structural problems of solid acids themselves, there are differences in the strength of acid sites on the surface of solid acids, with a wide acid strength distribution, and it is difficult to control the acid strength of solid acids. There is no convenience of liquid acids to control the acid density and strength by using the acid proton concentration. However, different catalytic reactions have different requirements for acid strength. For example, alkylation reactions require higher acid strength. The acid strength of molecular sieve-type solid acids is generally achieved by regulating the silicon-aluminum ratio of the molecular sieve. However, unlike the simultaneous increase of acid strength and acid density of liquid acids with acid proton concentration, the higher the silicon-aluminum ratio of the molecular sieve, the higher the acid strength, but the acid density will be significantly reduced, which is very difficult for reactions that require both high acid strength and acid density.

[0003] In the literature, molecular sieve catalysts are generally regulated by regulating the molecular sieve silicon-aluminum ratio to regulate the acid strength distribution. For example, Xu Ruren et al. pointed out that the molecular sieve silicon-aluminum ratio is closely related to its acidity and catalytic activity. Regulating the molecular sieve framework silicon-aluminum ratio is a common method for regulating the molecular sieve acid strength (Molecular Sieve and Porous Materials Chemistry (Second Edition)), Science Press, 2014.8, 345-359); Bao et al. Regulated the silicon-aluminum ratio of HZSM-5 molecular sieves by means of dealumination and re-insertion of aluminum, and successfully adjusted the acid amount and acid strength of the molecular sieve (J.Phys.Chem.B 2006,110,15411-15416). For other types of solid acids, there is a method of suppressing strong acids by alkali adsorption, but there is no method for accurately controlling the required catalyst acid strength. Therefore, how to conveniently regulate the acid strength of solid acid catalysts has important theoretical and practical significance. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem in the prior art that the acid strength and acid amount of solid acids cannot be achieved at the same time, and to provide a method for regulating the acid strength distribution of solid acids and solid acids and applications. The method combines the reversible adsorption of ammonium cations and the directional adsorption of metal cations, and can conveniently regulate the acid strength distribution while maintaining the acid amount of the solid acid to meet different application environments.

[0005] In order to achieve the above object, the present invention provides a method for regulating the acid strength distribution of a solid acid in a first aspect, wherein the method comprises the following steps:

[0006] (1) in the presence of ammonium cations, reversibly adsorbing the solid acid with ammonium cations, and then performing a first desorption;

[0007] (2) In the presence of metal cations, the product after the first desorption in step (1) is subjected to directional adsorption of metal cations, and then subjected to a second desorption.

[0008] Preferably, the temperature of the directional adsorption of the metal cation is 5-30°C higher than that of the reversible adsorption of the ammonium cation, and more preferably 10-25°C higher.

[0009] Preferably, in step (2), the metal ion exchange degree of the second desorption product is 15-80%, more preferably 30-50%.

[0010] The second aspect of the present invention provides a solid acid obtained by the control method described in the first aspect.

[0011] The third aspect of the present invention provides a use of the solid acid described in the second aspect in the alkylation reaction of light olefins.

[0012] The inventors of the present invention have found through research that the alternating reversible adsorption of ammonium cations and the directional adsorption (irreversible adsorption) of other cations can selectively cover acid centers of different strengths, so as to achieve the purpose of conveniently controlling the distribution of solid acid strength while maintaining the acid content of the solid acid.

[0013] The method of the present invention can regulate the catalyst to have only a certain acid strength such as a medium-strong acid based on the reaction requirements. The method is simple and convenient, has strong applicability, and has great advantages over the prior art. DETAILED DESCRIPTION

[0014] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0015] A first aspect of the present invention provides a method for regulating the acid strength distribution of a solid acid, wherein the method comprises the following steps:

[0016] (1) in the presence of ammonium cations, reversibly adsorbing the solid acid with ammonium cations, and then performing a first desorption;

[0017] (2) In the presence of metal cations, the product after the first desorption in step (1) is subjected to directional adsorption of metal cations, and then subjected to a second desorption.

[0018] The inventors of the present invention have found through research that the alternating reversible adsorption of ammonium cations and the directional adsorption (irreversible adsorption) of other cations can selectively cover acid centers of different strengths, so as to achieve the purpose of conveniently controlling the distribution of solid acid strength while maintaining the acid content of the solid acid.

[0019] The method of the present invention can regulate the catalyst to have only a certain acid strength such as a medium-strong acid based on the reaction requirements. The method is simple and convenient, has strong applicability, and has great advantages over the prior art.

[0020] The present invention utilizes the reversible adsorption of ammonium cations to desorb at a certain temperature to expose acidic sites of a certain strength, and then utilizes metal cations to irreversibly adsorb ions to occupy them, and finally removes all or part of the reversibly adsorbed cations to expose some acidic sites, thereby facilitating and simply regulating the acid distribution to be suitable for different industrial scenarios.

[0021] In the present invention, by controlling the reversible adsorption of ammonium cations and the directional adsorption of metal cations in step (1) and step (2), each reaction condition interacts with each other so that the obtained solid acid has a higher medium-strong acid amount and medium-strong acid distribution. Preferably, the medium-strong acid amount of the solid acid is 450-1400 μmol / g, more preferably 950-1200 μmol / g, for example, it can be 950 μmol / g, 1000 μmol / g, 1050 μmol / g, 1100 μmol / g, 1150 μmol / g, 1200 μmol / g and values ​​between any two groups. Preferably, the amount of medium-strong acid in the solid acid accounts for 40-85% of the total acid amount, and more preferably 65-80%, for example, it can be 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80% and values ​​between any two groups.

[0022] In the present invention, the reversible adsorption means that the medium after low-temperature adsorption can be completely desorbed at high temperature.

[0023] In the present invention, the directional adsorption of metal cations refers to the directional adsorption of metal ions covering part of the acidic sites.

[0024] In the present invention, preferably, the temperature of the directional adsorption of the metal cation is 5-30°C higher than the temperature of the reversible adsorption of the ammonium cation, preferably 10-25°C higher, for example, it can be 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C and values ​​between any two groups. The advantage of adopting this preferred embodiment is that the migration of cations during high-temperature desorption may cause changes in the coverage of acidic sites, which is higher than the reversible adsorption temperature, and can ensure better stability of metal cations.

[0025] In the present invention, step (1) is carried out in the presence of ammonium cations to expose acidic sites on the solid acid, provide acidic sites for subsequent directional adsorption of metal cations, and facilitate acid intensity control. The present invention does not particularly limit the source of ammonium cations, as long as the required ammonium cations can be provided. Preferably, the ammonium cations are provided by an atmosphere containing ammonia and / or a compound containing ammonium cations.

[0026] In the present invention, there is no particular limitation on the concentration of ammonia in the ammonia-containing atmosphere, as long as the required ammonium cations can be provided. Preferably, the volume concentration of ammonia in the ammonia-containing atmosphere is 5-100%. By selecting ammonium cations within the above preferred range, liquid filtering and drying processes are avoided, and adsorption is convenient and efficient.

[0027] In the present invention, there is no particular limitation on the specific type of the compound containing ammonium cations, as long as it can provide the required ammonium cations. Preferably, the compound containing ammonium cations is provided by a solution of the compound containing ammonium cations.

[0028] In the present invention, preferably, the concentration of the solution of the compound containing ammonium cations is 1-5 mol / L.

[0029] In the present invention, there is no particular limitation on the type of solid acid, and any solid acid conventionally defined in the art can be applied to the control method of the present invention. Preferably, in step (1), the solid acid is selected from at least one of a heteropoly acid, a solid superacid, a mixed oxide, a supported solid acid and a molecular sieve, and is more preferably a molecular sieve.

[0030] In the present invention, preferably, the molecular sieve is selected from at least one of Y-type molecular sieve, Beta-type molecular sieve, ZSM-5-type molecular sieve, MOR-type molecular sieve and MCM-22-type molecular sieve, and more preferably Y-type molecular sieve. The method provided by the present invention is particularly suitable for acid stress control of molecular sieves, so that the molecular sieves are suitable for different application scenarios.

[0031] In the present invention, by controlling the conditions for reversible adsorption of ammonium cations, the acidic sites are fully exposed, more acidic sites are provided for subsequent directional adsorption of cations, and the acid strength is controlled. According to a preferred embodiment of the present invention, the ammonium cations are provided by an atmosphere containing ammonia gas, and the conditions for reversible adsorption of the ammonium cations include: an adsorption temperature of 20-100° C., a time of 0.5-3 h, and a flow rate of the atmosphere containing ammonia gas of 5-50 mL / min relative to 1 g of solid acid.

[0032] According to another preferred embodiment of the present invention, the ammonium cation is provided by a compound containing ammonium cation, and the ammonium cation reversible adsorption is carried out by ion exchange. The advantage of adopting this preferred embodiment is that the ammonium cation is only exchanged to the acidic site by ion exchange, and has no effect on the pores and the outer surface.

[0033] In the present invention, the conditions for ammonium cation exchange by ion exchange method are selected in a wide range. Preferably, the ammonium cation is provided by a compound containing ammonium cation, and the conditions for reversible adsorption of the ammonium cation include: adsorption temperature of 50-90°C, time of 1-5h, and the amount of the solution of the compound containing ammonium cation is 2-10g relative to 1g of solid acid.

[0034] In the present invention, by controlling the conditions of the first desorption, the requirements of different application environments for the acid strength distribution of the solid acid can be met, and the operation process is simple and has strong adaptability. Preferably, in step (1), the conditions of the first desorption include: a temperature of 200-350°C and a time of 2-8h.

[0035] In the present invention, preferably, in step (1), the first desorption is carried out in the presence of an inert atmosphere, and preferably the inert atmosphere is selected from at least one of nitrogen, argon and helium.

[0036] In the present invention, preferably, in step (1), the first desorption condition further comprises: the flow rate of the inert atmosphere is 5-50 mL / min relative to 1 g of the solid acid.

[0037] In the present invention, preferably, step (1) further comprises drying the solid acid and then reversibly adsorbing the ammonium cations. In the present invention, there is no particular limitation on the drying method and conditions, and those skilled in the art can adjust them according to actual conditions.

[0038] In the present invention, preferably, in step (2), the metal ion exchange degree of the second desorption product is 15-80%, more preferably 30-50%, for example, 30%, 35%, 40%, 45%, 50% and values ​​between any two groups.

[0039] In the present invention, the metal ion exchange degree refers to the ratio of the amount of cations exchanged into the molecular sieve (the amount of substance) to the amount of Al atoms in the molecular sieve. The exchange degree is determined by performing a composition test on the final molecular sieve (XRF or ICP can be used to determine the relative amounts of exchange metals and Al atoms in the molecular sieve).

[0040] In the present invention, step (2) selectively covers the acid sites of the solid acid in the presence of metal cations to achieve convenient regulation of the acid strength of the solid acid. The present invention does not particularly limit the source of the metal cations, as long as the required metal cations can be provided. Preferably, the metal cations are provided by a compound containing metal cations, preferably by at least one of a compound containing a metal element of Group IIA, a compound containing a metal element of Group VIIB, and a compound containing a metal element of Group IB, and more preferably by a compound containing Ca 2+ Compounds containing Ag + Compounds and Re 2+ Preferably, in the present invention, the compound containing metal cations is provided by a solution containing metal cation compounds. In the present invention, there is no particular limitation on the concentration of the solution containing metal cation compounds. Preferably, the concentration of the solution containing metal cation compounds is 1-10% by weight, and those skilled in the art can select according to actual needs.

[0041] In the present invention, there is no particular limitation on the method of metal cation adsorption, as long as the metal cation can cover the acid sites of the solid acid. Preferably, in step (2), the metal cation adsorption is selected from at least one of ion exchange, isovolumetric impregnation and vacuum impregnation, preferably ion exchange. By adopting ion exchange to achieve directional adsorption of metal cations, it is possible to avoid excessive metal ion residues affecting pore diffusion.

[0042] In the present invention, preferably, in step (2), the conditions for the directional adsorption of metal cations include: temperature of 40-95°C, time of 1-10h, and an amount of the compound containing metal cations of 0.05-3g relative to 1g of the product after the first desorption; further preferably, in step (2), the conditions for the directional adsorption of metal cations include: temperature of 60-90°C, time of 2-6h, and an amount of the compound containing metal cations of 0.1-1.3g relative to 1g of the product after the first desorption.

[0043] In the present invention, by controlling the conditions of the second desorption, the requirements of different application environments for the acid strength distribution of the solid acid can be met, and the operation process is simple and has strong adaptability. Preferably, in step (2), the conditions of the second desorption include: a temperature of 400-650°C and a time of 1-8h; further preferably, in step (2), the conditions of the second desorption include: a temperature of 450-600°C and a time of 1-6h.

[0044] In the present invention, preferably, in step (2), the second desorption is carried out in the presence of an inert atmosphere, and preferably the inert atmosphere is selected from at least one of nitrogen, argon and helium.

[0045] In the present invention, preferably, in step (2), the conditions for the second desorption further include: the flow rate of the inert atmosphere is 5-50 mL / min relative to 1 g of the product after the first desorption.

[0046] The second aspect of the present invention provides a solid acid obtained by the control method described in the first aspect.

[0047] The solid acid provided by the present invention has a relatively high acid content of medium-strong acid. Preferably, the acid content of medium-strong acid of the solid acid is 450-1400 μmol / g, and more preferably 950-1200 μmol / g.

[0048] The solid acid provided by the present invention has a relatively high distribution of medium-strong acids. Preferably, the medium-strong acid content of the solid acid accounts for 40-85% of the total acid content, and more preferably 65-80%.

[0049] The third aspect of the present invention provides a use of the solid acid described in the second aspect in the alkylation reaction of light olefins.

[0050] In the present invention, preferably, the low-carbon olefin is selected from C3-C6 low-carbon olefins. The present invention has no particular limitation on the specific type of low-carbon olefin, for example, it may be butene.

[0051] The solid acid provided by the present invention has a specific ratio of medium-strong acid content and separation, provides alkylation performance of low-carbon olefins, and improves the selectivity of the target product C8.

[0052] In the present invention, the acid strength and acid amount are determined by the NH3-TPD method, which is as follows: a chemical adsorption instrument is used for determination, 0.15g of a sample with a particle size of 20-40 mesh is weighed and loaded into a quartz sample tube, and placed in a thermal conductivity cell heating furnace. First, a He gas with a flow rate of 50mL / min is used as a carrier gas to heat up to 250°C and purge for 2h to remove adsorbed impurities on the sample surface. Then the temperature is lowered to 100°C, constant temperature is maintained for 30min, and NH3 / He mixed gas (10 volume % NH3+90 volume % He) is switched to saturated adsorption for 30min, and then switched to He gas purge for 90min until the baseline is stable to remove NH3 on the sample surface by physical adsorption. The temperature is raised to 250°C at a heating rate of 10°C / min and maintained for 30min to remove ammonia that can be desorbed below 250°C, and a TCD detector is used to detect changes in gas components, and the temperature is continued to be raised to 350, 450, and 550°C, and the above steps are repeated. The TCD detector was used to detect gas changes, and the adsorption curves obtained at different temperature sections were integrated to automatically calculate the acid distribution at different temperatures. The desorption amount at 250°C represented the weak acid amount, the desorption amounts at 350°C and 450°C represented the medium-strong acid amount, and the desorption amount at 550°C represented the strong acid amount.

[0053] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all raw materials used are commercially available.

[0054] In the following examples 1-4, 6 and comparative examples, the solid acid is a Y-type molecular sieve (n Si / n Al =3.5, Na2O mass fraction 0.1%, crystallinity 95%).

[0055] Example 1

[0056] (1) After the HY molecular sieve was vacuum dried at 150°C for 24 hours, an ammonia-containing atmosphere was introduced at room temperature for reversible adsorption of ammonium cations. The volume concentration of ammonia in the ammonia-containing atmosphere was 5%. The flow rate of the ammonia-containing atmosphere was 5 mL / min relative to 1 g of the HY molecular sieve. The conditions for reversible adsorption of ammonium cations were: 50°C for 2 hours. After saturated adsorption, the temperature was raised to 350°C and maintained for 2 hours under nitrogen for the first desorption. The flow rate of nitrogen was 5 mL / min relative to 1 g of the HY molecular sieve. When nitrogen was introduced into water, the first desorption was completed when the pH change of the water was less than 0.1.

[0057] (2) The molecular sieve after the first desorption was subjected to ion exchange with a silver nitrate solution (temperature 75°C, mass ratio of AgNO3:H2O: molecular sieve after the first desorption = 1:60:6, exchange time 1h). When the pH change of the solution was less than 0.1, the Ag +Directed adsorption. The catalyst after the directed adsorption was heated to 450°C and subjected to the second desorption under nitrogen for 1 hour. The flow rate of nitrogen was 5 mL / min relative to 1 g of the molecular sieve after the first desorption. When nitrogen was introduced into water and the pH change of the water was less than 0.1, the second desorption was completed. The metal ion exchange degree of the second desorption product was 45%. The acid strength and acid amount of the obtained catalyst were determined by NH3-TPD characterization. The results are shown in Table 1.

[0058] Example 2

[0059] (1) After the HY molecular sieve was vacuum dried at 150° C. for 24 h, an ammonia-containing atmosphere was introduced at room temperature for reversible adsorption of ammonium cations. The volume concentration of ammonia in the ammonia-containing atmosphere was 100%. The flow rate of the ammonia-containing atmosphere was 15 mL / min relative to 1 g of the HY molecular sieve. The conditions for reversible adsorption of ammonium cations were: 80° C. for 0.5 h. After saturated adsorption, the temperature was raised to 200° C. and maintained for 8 h under nitrogen for the first desorption. The flow rate of nitrogen was 15 mL / min relative to 1 g of the HY molecular sieve. When nitrogen was introduced into water, the first desorption was completed when the pH change of the water was less than 0.1.

[0060] (2) The molecular sieve after the first desorption was subjected to ion exchange with a silver nitrate solution (temperature 95°C, mass ratio of AgNO3:H2O: molecular sieve after the first desorption = 0.6:60:6, exchange time 1h). When the pH change of the solution was less than 0.1, the Ag + Directed adsorption. The catalyst after the directed adsorption was heated to 600°C and subjected to the second desorption under nitrogen for 6 hours. The flow rate of nitrogen was 15 mL / min relative to 1 g of the molecular sieve after the first desorption. When nitrogen was introduced into water and the pH change of the water was less than 0.1, the second desorption was completed. The metal ion exchange degree of the second desorption product was 30%. The acid strength and acid amount of the obtained catalyst were determined by NH3-TPD characterization. The results are shown in Table 1.

[0061] Example 3

[0062] (1) After the HY molecular sieve was vacuum dried at 150°C for 24 hours, an ammonia-containing atmosphere was introduced at room temperature for reversible adsorption of ammonium cations. The volume concentration of ammonia in the ammonia-containing atmosphere was 20%. The flow rate of the ammonia-containing atmosphere was 50 mL / min relative to 1 g of the HY molecular sieve. The conditions for reversible adsorption of ammonium cations were: 20°C, 3 hours. After saturated adsorption, the temperature was raised to 300°C and maintained for 1 hour under nitrogen for the first desorption. The flow rate of nitrogen was 50 mL / min relative to 1 g of the HY molecular sieve. When nitrogen was introduced into water, the first desorption was completed when the pH change of the water was less than 0.1.

[0063] (2) The molecular sieve after the first desorption was subjected to ion exchange with a silver nitrate solution (temperature 40°C, AgNO3:H2O: molecular sieve after the first desorption mass ratio = 1.2:60:6, exchange time 1h), and when the pH change of the solution was less than 0.1, the Ag + Directed adsorption. The catalyst after the directed adsorption was heated to 500°C and subjected to the second desorption for 3 hours under nitrogen. The flow rate of nitrogen was 50 mL / min relative to 1 g of the molecular sieve after the first desorption. When nitrogen was introduced into water and the pH change of the water was less than 0.1, the second desorption was completed. The metal ion exchange degree of the second desorption product was 50%. The acid strength and acid amount of the obtained catalyst were determined by NH3-TPD characterization. The results are shown in Table 1.

[0064] Example 4

[0065] (1) After the HY molecular sieve was vacuum dried at 150°C for 24 hours, an ammonia-containing atmosphere was introduced at room temperature for reversible adsorption of ammonium cations. The volume concentration of ammonia in the ammonia-containing atmosphere was 5%. The flow rate of the ammonia-containing atmosphere was 5 mL / min relative to 1 g of the HY molecular sieve. The conditions for reversible adsorption of ammonium cations were: 100°C for 2 hours. After saturated adsorption, the temperature was raised to 350°C and maintained for 2 hours under nitrogen for the first desorption. The flow rate of nitrogen was 5 mL / min relative to 1 g of the HY molecular sieve. When nitrogen was introduced into water, the first desorption was completed when the pH change of the water was less than 0.1.

[0066] (2) The molecular sieve after the first desorption was subjected to ion exchange with a silver nitrate solution (temperature 75°C, mass ratio of AgNO3:H2O: molecular sieve after the first desorption = 1:60:6, exchange time 1h). When the pH change of the solution was less than 0.1, the Ag + Directed adsorption. The catalyst after the directed adsorption was heated to 450°C and subjected to the second desorption under nitrogen for 1 hour. The flow rate of nitrogen was 5 mL / min relative to 1 g of the molecular sieve after the first desorption. When nitrogen was introduced into water and the pH change of the water was less than 0.1, the second desorption was completed. The metal ion exchange degree of the second desorption product was 40%. The acid strength and acid amount of the obtained catalyst were determined by NH3-TPD characterization. The results are shown in Table 1.

[0067] Example 5

[0068] The method of Example 1 was followed, except that the molecular sieve was Hβ molecular sieve (nSi / nAl=10, Na2O mass fraction 0.08%, crystallinity 90%), and the other conditions were the same, and the final metal ion exchange degree was 35%. The acid strength and acid amount were determined by NH3-TPD characterization, and the results are shown in Table 1.

[0069] Example 6

[0070] (1) After the HY molecular sieve was vacuum dried at 150°C for 24 hours, an ammonia-containing atmosphere was introduced at room temperature for reversible adsorption of ammonium cations. The volume concentration of ammonia in the ammonia-containing atmosphere was 5%. The flow rate of the ammonia-containing atmosphere was 5 mL / min relative to 1 g of the HY molecular sieve. The conditions for reversible adsorption of ammonium cations were: 50°C for 2 hours. After saturated adsorption, the temperature was raised to 350°C and maintained for 2 hours under nitrogen for the first desorption. The flow rate of nitrogen was 5 mL / min relative to 1 g of the HY molecular sieve. When nitrogen was introduced into water, the first desorption was completed when the pH change of the water was less than 0.1.

[0071] (2) The molecular sieve after the first desorption was subjected to ion exchange with a silver nitrate solution (temperature 25°C, mass ratio of AgNO3:H2O: molecular sieve after the first desorption = 0.3:60:6, exchange time 1h). When the pH change of the solution was less than 0.1, the Ag + Directed adsorption. The catalyst after the directed adsorption was heated to 450°C and subjected to the second desorption under nitrogen for 1 hour. The flow rate of nitrogen was 5 mL / min relative to 1 g of the molecular sieve after the first desorption. When nitrogen was introduced into water and the pH change of the water was less than 0.1, the second desorption was completed. The metal ion exchange degree of the second desorption product was 15%. The acid strength and acid amount of the obtained catalyst were determined by NH3-TPD characterization. The results are shown in Table 1.

[0072] Example 7

[0073] The method of Example 1 is followed, except that step (2) adopts vacuum impregnation method, the solution ratio remains unchanged, and the impregnation is carried out in a rotary evaporator for 1 hour. After the impregnation is completed, the temperature is raised and vacuum is drawn to remove water, and the water is dehydrated at 75°C and 0.08MPa vacuum for 3 hours, and then dried in an oven at 110°C for 4 hours, and then the corresponding desorption process is carried out. The final ion exchange degree is 60%. The acid strength and acid amount are determined by NH3-TPD characterization, and the results are shown in Table 1.

[0074] Comparative Example 1

[0075] The HY molecular sieve of Example 1 was selected and vacuum dried at 150°C for 24 hours. Ammonia was then introduced at room temperature for adsorption. After saturated adsorption, the molecular sieve was heated to 350°C and maintained for 1 hour for the first desorption step. The obtained catalyst was characterized by NH3-TPD (note that NH3-TPD was only desorbed to 350°C) to determine its acid strength and acid amount. The results are shown in Table 1.

[0076] Comparative Example 2

[0077] The HY molecular sieve of Example 1 was selected, treated with ammonium fluorosilicate solution (0.25 mol / L, 1 g molecular sieve 30 mL solution) at 80°C for 2 h, washed with a large amount of water, dried at 110°C for 12 h, and then calcined at 450°C for 3 h to obtain a HY molecular sieve with nSi / nAl=9.5, Na2O mass fraction of 0.08%, and crystallinity of 85%, which was used to compare the comparative example of the catalyst obtained by the conventional post-treatment method. The acid strength and acid amount were determined by NH3-TPD characterization (it should be noted that NH3-TPD was desorbed to 550°C), and the results are shown in Table 1.

[0078] Table 1

[0079]

[0080]

[0081] It can be seen from the above table that the molecular sieve prepared by the method of the present invention can conveniently control the catalyst with medium-strong acid distribution, and the total acid content is not greatly affected. Compared with the conventional post-treatment method catalyst, the strong acid content can be more than doubled.

[0082] Test Case

[0083] The solid acid obtained in the above examples and comparative examples was subjected to an alkylation reaction of isoparaffin and olefin in a fixed bed reactor, and the reaction conditions were as follows: the molar ratio of isobutane to mixed butenes (1-butene and 2-butene) was 220, the reaction temperature was 75°C, the reaction pressure was 2.5MPa, and the feed flow rate of isobutane and mixed butenes was 200mL / h. When butene was detected in the product, it was considered that the catalyst was deactivated, and the reaction time before the catalyst was deactivated was defined as the catalyst cycle life. The results are shown in Table 2.

[0084] Table 2

[0085]

[0086]

[0087] It can be seen from the above table that the solid acid prepared by the preparation method of the present invention has a higher acid content and acid strength distribution, a smaller amount of weak acid, and thus has a better alkylation reaction cycle life and target product selectivity.

[0088] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for regulating the acid strength distribution of a solid acid, characterized in that: The method comprises the following steps: (1) in the presence of ammonium cations, reversibly adsorbing the solid acid with ammonium cations, and then performing a first desorption; (2) In the presence of metal cations, the product after the first desorption in step (1) is subjected to directional adsorption of metal cations, and then subjected to a second desorption.

2. The method according to claim 1, wherein: The temperature at which the metal cations are directional adsorbed is 5-30°C higher than the temperature at which the ammonium cations are reversibly adsorbed, preferably 10-25°C higher.

3. The method according to claim 1 or 2, wherein: The ammonium cations are provided by an atmosphere containing ammonia and / or a compound containing ammonium cations; Preferably, the volume concentration of ammonia in the ammonia-containing atmosphere is 5-100%; Preferably, the compound containing ammonium cations is provided by at least one selected from ammonia water, organic amines, urea and ammonium salts, and is further preferably provided by ammonia water; Preferably, the compound containing ammonium cations is provided from a solution of a compound containing ammonium cations; Preferably, the concentration of the solution of the compound containing ammonium cations is 1-5 mol / L; Preferably, in step (1), the solid acid is selected from at least one of heteropolyacids, solid superacids, mixed oxides, supported solid acids and molecular sieves, and is more preferably a molecular sieve; Preferably, the molecular sieve is at least one selected from the group consisting of Y-type molecular sieve, Beta-type molecular sieve, ZSM-5-type molecular sieve, MOR-type molecular sieve and MCM-22-type molecular sieve, and more preferably Y-type molecular sieve.

4. The method according to claim 3, wherein: The ammonium cation is provided by an atmosphere containing ammonia gas, and the conditions for the reversible adsorption of the ammonium cation include: an adsorption temperature of 20-100° C., a time of 0.5-3 h, and a flow rate of the atmosphere containing ammonia gas of 5-50 mL / min relative to 1 g of solid acid; Preferably, the ammonium cation is provided by a compound containing an ammonium cation, and the ammonium cation is reversibly adsorbed by using an ion exchange method to exchange the ammonium cation; Preferably, the ammonium cations are provided by a compound containing ammonium cations, and the conditions for the reversible adsorption of the ammonium cations include: an adsorption temperature of 50-90°C, a time of 1-5h, and an amount of 2-10g of the solution of the compound containing ammonium cations relative to 1g of solid acid.

5. The method according to any one of claims 1 to 4, wherein: In step (1), the first desorption conditions include: temperature of 200-350° C. and time of 1-8 h.

6. The method according to any one of claims 1 to 5, wherein: In step (2), the metal ion exchange degree of the second desorption product is 15-80%, preferably 30-50%.

7. The method according to any one of claims 1 to 6, wherein: In step (2), the metal cation is provided by a compound containing a metal cation, preferably provided by at least one of a compound containing a metal element of Group IIA, a compound containing a metal element of Group VIIB, and a compound containing a metal element of Group IB, and more preferably provided by a compound containing Ca 2+ Compounds containing Ag + Compounds and Re 2+ At least one of the compounds is provided.

8. The method according to any one of claims 1 to 7, wherein: In step (2), the metal cation adsorption is selected from at least one of an ion exchange method, an equal volume impregnation method and a vacuum impregnation method, preferably an ion exchange method.

9. The method according to any one of claims 1 to 8, wherein: In step (2), the conditions for the directional adsorption of the metal cation include: a temperature of 25-95° C., a time of 1-10 h, and an amount of the metal cation-containing compound of 0.05-3 g relative to 1 g of the product after the first desorption; Preferably, in step (2), the conditions for directional adsorption of the metal cations include: temperature of 60-90°C, time of 2-6h, and an amount of the metal cation-containing compound of 0.1-1.3g relative to 1g of the product after the first desorption.

10. The method according to any one of claims 1 to 9, wherein: In step (2), the second desorption conditions include: temperature of 400-650°C and time of 1-8h; Preferably, in step (2), the second desorption conditions include: temperature of 450-600° C. and time of 1-6 h.

11. A solid acid obtained by the regulation method according to any one of claims 1 to 10.

12. Use of the solid acid according to claim 11 in the alkylation reaction of light olefins; Preferably, the light olefin is selected from C3-C6 light olefins.

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