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CN117263203A - Method for preparing amine-free high-silicon ZSM-5 molecular sieve by changing alkalinity - Google Patents

Method for preparing amine-free high-silicon ZSM-5 molecular sieve by changing alkalinity Download PDF

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CN117263203A
CN117263203A CN202210676293.XA CN202210676293A CN117263203A CN 117263203 A CN117263203 A CN 117263203A CN 202210676293 A CN202210676293 A CN 202210676293A CN 117263203 A CN117263203 A CN 117263203A
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zsm
hydrothermal reaction
source
water
molecular sieve
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张云鹏
邢恩会
罗一斌
欧阳颖
朱远
舒兴田
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • C01B39/36—Pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
    • C01B39/38—Type ZSM-5
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C4/00—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms
    • C07C4/02—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by cracking a single hydrocarbon or a mixture of individually defined hydrocarbons or a normally gaseous hydrocarbon fraction
    • C07C4/06—Catalytic processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/16—After treatment, characterised by the effect to be obtained to increase the Si/Al ratio; Dealumination
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
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  • Silicates, Zeolites, And Molecular Sieves (AREA)

Abstract

The invention discloses a method for preparing an amine-free high-silicon ZSM-5 molecular sieve by changing alkalinity, which comprises the following steps: mixing a silicon source, an aluminum source, an alkali source, water and seed crystals to obtain a first mixture, and performing a first hydrothermal reaction to obtain a first hydrothermal reaction product; mixing the first hydrothermal reaction product with additional water, or mixing the first hydrothermal reaction product with additional water and ethanol to obtain a second mixture, and performing a second hydrothermal reaction. The invention forms small crystal nucleus under higher alkalinity, and the ZSM-5 molecular sieve with 35-60 silicon-aluminum mole ratio and high crystallinity can be prepared by supplementing water or further supplementing ethanol in the second step and continuing growing under low alkalinity.

Description

Method for preparing amine-free high-silicon ZSM-5 molecular sieve by changing alkalinity
Technical Field
The invention relates to preparation and application of a molecular sieve, in particular to a method for preparing a high-silicon ZSM-5 molecular sieve without amine and application of the obtained molecular sieve in light hydrocarbon catalytic cracking.
Background
The ZSM-5 molecular sieve has a unique three-dimensional cross pore system and zeolite with an MFI topological structure, and has two cross-linked ten-membered ring pore channels. The catalyst has strong selective adsorption performance, good thermal stability, good hydrothermal stability and moderate acidity, so that the catalyst is suitable for catalytic reactions of various hydrocarbon compounds, such as catalytic cracking, isomerization, aromatization, alkylation and the like, and is widely applied to the fields of petrochemical industry and industrial catalysis.
Traditional hydrothermal synthesis method has to add quaternary ammonium cation or other organic amine molecule as template agent, namely amine method. At present, the synthesis of ZSM-5 molecular sieves with high silica-alumina ratio is mostly synthesized by an amine method, although organic amine molecules with strong structure guiding effect are used as templates, ZSM-5 molecular sieves with uniform particle size, regular pore channels and regular crystal forms can be synthesized under wider conditions, the synthesized ZSM-5 molecular sieves have smaller crystal grains and lower stability in a reaction environment with severe catalytic cracking. In addition, the organic amine template agent has high toxicity, a large amount of organic wastewater can be generated in the synthesis process, and the air pollution can be caused when the template agent is roasted and decomposed, so that the performance of the molecular sieve can be influenced. The use of expensive templating agents in large amounts also greatly increases the cost of molecular sieve production.
The method for synthesizing the ZSM-5 molecular sieve without the organic amine template system is an amine-free method, has the characteristics of environment friendliness, low cost and the like, is favored by vast researchers in recent years, and more processes for synthesizing the ZSM-5 molecular sieve without the amine are emerging. However, the amine-free process requires longer crystallization times than conventional synthesis processes because of the lack of guiding of the organic amine molecules resulting in an increase in nucleation and growth activation energies; in addition, the lack of guiding function of organic amine molecules makes crystal nucleus formation difficult, and crystal transformation phenomenon is easy to occur, so that the phase area of the ZSM-5 molecular sieve synthesized by the amine-free method is narrower. If seed crystal containing formed crystal nucleus is added into synthetic liquid, a great amount of specific crystal nucleus can be induced to form in short time, so that the crystallization time is shortened, the synthetic phase area is widened, and the phenomena of eutectic and crystal transformation are avoided to a great extent, namely the seed crystal method. The seed crystal method for preparing the ZSM-5 molecular sieve with the silicon-aluminum ratio of about 25 has been industrially applied, but the ZSM-5 molecular sieve with the silicon-aluminum ratio of about 25 has higher acidity and has the defect of higher hydrogen transfer reaction degree. The ZSM-5 molecular sieve with the silicon-aluminum ratio of 35-50 is more suitable for catalytic cracking to produce more low-carbon olefin. The synthesis of ZSM-5 molecular sieve with high silica alumina ratio by the amine-free method is a difficult problem, because the seed crystal guiding effect can guide ZSM-5 molecular sieve with low silica alumina ratio, but the activation energy of nucleation growth is higher and nucleation is difficult to form in a short time when the seed crystal guiding effect is used for guiding the synthesis of ZSM-5 molecular sieve with high silica alumina ratio. Therefore, even if the ZSM-5 molecular sieve with high silica-alumina ratio is synthesized by adding seed crystal, the crystallinity is still low.
Regarding the synthesis of ZSM-5 molecular sieves by the amine-free method, CN105621451A, CN105692652A discloses a method for preparing a ZSM-5 molecular sieve without using a template. The preparation method comprises the steps of mixing a silicon source, an alkali source, an aluminum source, seed crystals and deionized water, and preparing the ZSM-5 molecular sieve through two-stage crystallization. The preparation method synthesizes the molecular sieve under the conditions of no template agent, low water-silicon ratio, temperature rising speed control and two-stage crystallization. Although the ZSM-5 molecular sieve with the silicon-aluminum ratio of 20 to 25 is synthesized by the preparation method, the crystallinity of the molecular sieve is lower when the silicon-aluminum ratio is 35 to 60 or higher. CN108190913a discloses a method for synthesizing a silicon-rich ZSM-5 zeolite molecular sieve by a seed crystal guiding method, wherein methanol or ethanol is introduced as a pore filler to obtain a molecular sieve with completely open pores.
Disclosure of Invention
The invention aims to provide a method for preparing ZSM-5 molecular sieve with a silicon-aluminum ratio of 35-60 and high crystallinity and provides application thereof, aiming at the defects of the existing amine-free method.
To achieve the above object, a first aspect of the present invention provides a method for preparing an amine-free high silica ZSM-5 molecular sieve with varying basicity, the method comprising:
S1, carrying out a first hydrothermal reaction on a first mixture obtained by mixing a silicon source, an aluminum source, an alkali source, water and seed crystals to obtain a first hydrothermal reaction product, wherein the mole ratio of the silicon source to the aluminum source to the alkali source to the water is (40-70): 1: (1-5): (400-700), the seed crystal being used in an amount of 1-10 wt% of the silicon source;
s2, mixing the first hydrothermal reaction product with additional water or mixing the first hydrothermal reaction product with the additional water and ethanol to obtain a second mixture for a second hydrothermal reaction;
wherein the molar ratio of the total amount of water described in step S1 and the additional supplemental water described in step S2 to the aluminum source is 720-1000:1, the mole ratio of the ethanol to the silicon source is 0.1-1, the silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 The alkali source is calculated by alkali metal oxide, and the seed crystal is calculated by SiO 2 And (5) counting.
In step S1, the conditions of the first hydrothermal reaction include: the temperature is 160-180 ℃ and the time is 1-8 hours; in step S2, the conditions of the second hydrothermal reaction include: the temperature is 160-180 ℃ and the time is 4-11 hours. The total crystallization time is 10-16 hours.
In the step S1, the molar ratio of the silicon source to the aluminum source to the alkali source to the water is (55-65): 1: (4-5): (500-700), the seed crystal being used in an amount of 8-10% by weight of the silicon source.
In step S2, when a scheme of mixing the first hydrothermal reaction product with additional water and ethanol is employed, the molar ratio of the ethanol to the silicon source is 0.1 to 1, preferably 0.1 to 0.5.
The method provided by the invention comprises the steps of adding water in the step S1 and additional water in the step S2 in a molar ratio of 720-1000 to an aluminum source: 1. preferably 800-1000:1.
the silicon source is selected from one or more of silica gel, water glass, silicon dioxide and white carbon black; the aluminum source is selected from one or more of sodium metaaluminate, SB powder, aluminum oxide, aluminum hydroxide and aluminum sulfate; the alkali sources are respectively and independently selected from one or more of sodium hydroxide and potassium hydroxide; the ethanol is absolute ethanol;
the seed crystal is ZSM-5 molecular sieve with the mol ratio of silicon oxide to aluminum oxide of 25-50.
Optionally, the method provided by the invention further includes step S3: and collecting a product obtained by the second hydrothermal reaction, and sequentially carrying out filtering, washing, ammonium exchange, drying and roasting on the product. The conditions of the calcination treatment include: the temperature is 400-800 ℃, the time is 0.5-8h, and the atmosphere is air atmosphere or water vapor atmosphere.
In order to achieve the above object, a second aspect of the present invention provides an amine-free high-silica ZSM-5 molecular sieve prepared by the method according to the first aspect of the present invention. SiO of the amine-free high-silicon ZSM-5 molecular sieve 2 With Al 2 O 3 The molar ratio of (2) is 35-60, the relative crystallinity is 80-95%, and the specific surface area is 240-360m 2 /g。
In order to achieve the above object, a third aspect of the present invention provides a light hydrocarbon catalytic cracking reaction method, which is characterized in that the amine-free high-silicon ZSM-5 molecular sieve provided in the second aspect of the present invention is used as a catalyst.
The method for preparing the ZSM-5 molecular sieve with high silicon-aluminum ratio by using the variable alkalinity and no amine provided by the invention adopts a mode of first crystallizing at one stage under higher alkalinity to form a small crystal nucleus primary product and then supplementing water or supplementing water and supplementing ethanol for secondary crystallization to enable the small crystal nucleus to continuously grow under the second stage crystallization under lower alkalinity, and the method continuously crystallizes an unutilized silicon source under lower alkalinity to further improve the crystallinity, so that the ZSM-5 molecular sieve with the silicon-aluminum ratio of 35-60 and high crystallinity can be prepared.
Drawings
FIG. 1 is an X-ray diffraction pattern of ZSM-5 molecular sieve sample A1 prepared in example 1;
FIG. 2 is an X-ray diffraction pattern of ZSM-5 molecular sieve sample A2 prepared in example 2;
FIG. 3 is a scanning electron micrograph of ZSM-5 molecular sieve sample A2 prepared in example 2;
FIG. 4 is an X-ray diffraction pattern of ZSM-5 molecular sieve sample A3 prepared in example 3;
FIG. 5 is a scanning electron micrograph of ZSM-5 molecular sieve sample A3 prepared in example 3;
FIG. 6 is an X-ray diffraction pattern of comparative sample D1 of the ZSM-5 molecular sieve prepared in comparative example 1;
FIG. 7 is a scanning electron micrograph of a ZSM-5 molecular sieve comparative sample D1 prepared in comparative example 1;
FIG. 8 is an X-ray diffraction pattern of comparative samples D3 and D4 of ZSM-5 molecular sieves prepared in comparative example 3 and comparative example 4;
FIG. 9 is an X-ray diffraction pattern of samples A7 and A8 of ZSM-5 molecular sieves prepared in example 7 and example 8.
FIG. 10 is a scanning electron micrograph of ZSM-5 molecular sieve sample A7 prepared in example 7.
FIG. 11 is a scanning electron micrograph of ZSM-5 molecular sieve sample A8 prepared in example 8.
FIG. 12 is an X-ray diffraction pattern of comparative sample D5 of the ZSM-5 molecular sieve prepared in comparative example 5.
FIG. 13 is an X-ray diffraction pattern of comparative sample D6 of the ZSM-5 molecular sieve prepared in comparative example 6.
FIG. 14 is a scanning electron micrograph of a ZSM-5 molecular sieve prepared in comparative example 6, comparative sample D6.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The first aspect of the invention provides a method for preparing an amine-free high-silicon ZSM-5 molecular sieve by changing alkalinity, which comprises the following steps:
S1, carrying out a first hydrothermal reaction on a first mixture obtained by mixing a silicon source, an aluminum source, an alkali source, water and seed crystals to obtain a first hydrothermal reaction product, wherein the mole ratio of the silicon source to the aluminum source to the alkali source to the water is (40-70): 1: (1-5): (400-700), the seed crystal being used in an amount of 1-10 wt% of the silicon source;
s2, mixing the first hydrothermal reaction product with additional water and ethanol to obtain a second mixture, and performing a second hydrothermal reaction, wherein the molar ratio of the ethanol to the silicon source is 0.1-1;
wherein the molar ratio of the total amount of water comprising the water of step S1 and the additional supplemental water of step S2 to the aluminum source is 720-1000:1, the silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 The alkali source is calculated by alkali metal oxide, and the seed crystal is calculated by SiO 2 And (5) counting.
The invention adopts a scheme of two-stage crystallization secondary water supplementing or a scheme of water supplementing and ethanol supplementing, namely small crystal nucleus is formed under higher alkalinity, and the alkalinity is diluted by adding water after one-stage crystallization, so that an environment which is more favorable for crystal growth is formed to improve the crystallinity; or on the basis of diluting the alkalinity by adding water, ethanol is further added, so that an environment which is more favorable for crystal growth is formed, further crystallization growth of a silicon source which is not completely utilized after one-stage crystallization is promoted, and the crystallinity is further improved. Compared with the method of one-time feeding and one-stage crystallization in the prior art, the method provided by the invention has the advantages that the operation is simple, no ammonia nitrogen wastewater is discharged, and the prepared ZSM-5 molecular sieve has higher silicon-aluminum ratio and higher relative crystallinity, and is more suitable for the catalytic cracking reaction of light hydrocarbon.
In one embodiment of the present invention, the conditions of the first hydrothermal reaction include: the temperature is 160-180deg.C, the time is 1-8 hr, the preferred temperature is 165-175 deg.C, and the time is 5-8 hr; the conditions of the second hydrothermal reaction include: the temperature is 160-180deg.C, the time is 4-11 hr, and the preferred temperature is 165-175 deg.C, and the time is 4-7 hr. Preferably, the total hydrothermal reaction time of the step S1 and the step S2 is 10 to 16 hours.
The first and second hydrothermal reactions may be carried out in devices conventionally employed by those skilled in the art, for example in a heat-resistant closed vessel, preferably an autoclave, as is well known to those skilled in the art. The reaction pressure of the first hydrothermal reaction and the second hydrothermal reaction in the present invention is not particularly limited, and may be, for example, the autogenous pressure of the reaction system or the reaction pressure applied thereto, preferably the autogenous pressure of the reaction system.
In step S1 of the present invention, the molar ratio of the silicon source, the aluminum source, the alkali source and the water amount may vary within a wide range. In step S1 of one embodiment, the molar ratio of the silicon source, the aluminum source, the alkali source and the water is (40-70): 1: (1-5): (400-700), preferably (50-65): 1: (4-5): (500-700) the seed crystal is used in an amount of 1-10 wt%, preferably 8-10 wt%, of the silicon source.
In the step S2 of the invention, the mol ratio of the ethanol to the silicon source is 0.1-0.5.
The invention comprises the water described in step S1 and the additional supplementary water described in step S2 in a molar ratio of 720-1000 to the aluminium source: 1. preferably 800-1000:1.
the silicon source, the aluminum source and the alkali source are well known to those skilled in the art, preferably, the silicon source is selected from one or more of silica gel, water glass, silica and white carbon black, the alkali source is selected from one or more of sodium hydroxide and potassium hydroxide, preferably, the alkali source is sodium hydroxide, the aluminum source is selected from one or more of sodium metaaluminate, SB powder, aluminum oxide, aluminum hydroxide and aluminum sulfate, and the ethanol is absolute ethanol; the seed crystal can be ZSM-5 molecular sieve with the silicon-aluminum ratio of 25-50.
The method provided by the invention further comprises the step S3: and collecting a product obtained by the second hydrothermal reaction, and sequentially carrying out collection, washing, ammonium exchange, drying and roasting on the product. For example, the product may be collected by filtration, centrifugation, or the like; the liquid used for washing may be any kind of liquid that does not react with the solid product, such as deionized water to wash the solid product to neutrality. The ammonium exchange, drying and calcination processes are well known to those skilled in the art and will not be described in detail herein. The calcination may be performed in a tube furnace, a muffle furnace, or the like, and preferable calcination conditions may include: the temperature is 400-800 ℃ and the time is 0.5-8 hours, and the roasting can be carried out in an air atmosphere or a water vapor atmosphere.
The second aspect of the invention provides an amine-free high-silicon ZSM-5 molecular sieve prepared by the method provided by the first aspect of the invention. The ZSM-5 molecular sieve of the invention has higher silicon-aluminum mole ratio and relative crystallinity.
In one embodiment of the present invention, the amine-free high silica ZSM-5 molecular sieve is SiO 2 With Al 2 O 3 The molar ratio of (2) is 35-60, the relative crystallinity is 80-95%, and the specific surface area is 280-360m 2 And/g. Wherein SiO is 2 With Al 2 O 3 The molar ratio of (2) can be detected by adopting X-ray fluorescence spectrum. The relative crystallinity is detected by a Siemens D5005 type X-ray diffractometer by taking a ZSM-5 molecular sieve standard sample of the Shike's institute as a reference, namely the relative crystallinity of the ZSM-5 molecular sieve standard sample of the China petrochemical Co., ltd. Specific surface area can be measured by a specific surface area tester according to N 2 The adsorption principle is determined according to BJH calculation method (see petrochemical analysis method (RIPP test method), RIPP151-90, scientific Press, 1990).
The third aspect of the invention provides an application of the high silica alumina ratio ZSM-5 molecular sieve prepared by the amine-free method provided by the second aspect of the invention in light hydrocarbon catalytic cracking reaction.
According to the present invention, the light hydrocarbon catalytic cracking reaction may be performed in a fixed bed reactor, and reaction conditions of the light hydrocarbon catalytic cracking reaction may include: the temperature is 600-650 ℃, and the reaction mass space velocity is 20-40h -1 The reaction pressure is 0.8-1.2MPa.
The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereby. The raw materials used in the following examples and comparative examples are commercially available unless otherwise specified.
Examples 1-5 illustrate the present invention in step S2 with the first hydrothermal reaction product supplemented with water only additionally.
Example 1
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 3 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water = 60:1:4.5:840, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 9h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ in air for 4h to obtain a ZSM-5 molecular sieve, namely A1, wherein the X-ray diffraction diagram is shown in figure 1.
Specific surface area S of A1 BET (m 2 Per g), total pore volume V total /(cm 3 ·g -1 ) Micropore volume V micro /(cm 3 ·g -1 ) Volume of mesopores V meso /(cm 3 ·g -1 ) The data are shown in Table 1.
Example 2
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 5 hours to obtain a first hydrothermal reaction product;
S2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water = 60:1:4.5:840, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 7h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ in air for 4h to obtain a ZSM-5 molecular sieve, namely A2, wherein an X-ray diffraction spectrum is shown in figure 2, and a scanning electron microscope is shown in figure 3.
Example 3
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 8 hours to obtain a first hydrothermal reaction product;
s2, the first hydrothermal reaction productTransferred to a beaker, 15.84g deionized water (in which, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water = 60:1:4.5:840, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 4 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air for 4 hours to obtain a ZSM-5 molecular sieve, which is denoted as A3, wherein an X-ray diffraction pattern is shown in FIG. 4, and a scanning electron microscope is shown in FIG. 5.
Example 4
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 6 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 21.12g of deionized water (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water = 60:1:4.5:900, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to stainless steel kettle again, performing second hydrothermal reaction at 170deg.C for 6 hr, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120deg.C for 12 hr, and then emptyingRoasting for 4 hours at 550 ℃ in the gas atmosphere to obtain the ZSM-5 molecular sieve which is denoted as A4.
Example 5
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 9 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 21.12g of deionized water (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water = 60:1:4.5:900, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 3 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air atmosphere for 4 hours to obtain a ZSM-5 molecular sieve, which is denoted as A5.
Comparative example 1
20g of silica gel and 5.99g of sodium metaaluminate (Na) were added in sequence with stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel,fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 12 hours to obtain a first hydrothermal reaction product; filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ for 4h in air atmosphere to obtain a ZSM-5 molecular sieve which is marked as D1. The X-ray diffraction spectrum is shown in figure 6 and the scanning electron microscope photo is shown in figure 7.
Comparative example 2
In comparison with example 2, it is demonstrated that the first stage crystallization time cannot be too short, and that too little crystallinity is not elevated.
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 1h to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water = 60:1:4.5:840, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 11 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air atmosphere for 4 hours to obtain a ZSM-5 molecular sieve which is denoted as D2.
Comparative example 3
In comparison with example 2, it is shown that the amount of water in the first stage cannot be too small, which would result in lower crystallinity.
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 40.13g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:540 in SiO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 5 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 10.56g of deionized water (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water = 60:1:4.5:660, siO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 7h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ in air for 4h to obtain a ZSM-5 molecular sieve, namely D3, wherein an X-ray diffraction diagram is shown in figure 8.
Comparative example 4
The temperature rise was the same as in example 3, except that the amount of water in the first stage was the same as in example 540, and in example 660. Too little water in the first stage has lower crystallinity.
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 40.13g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water =60:1:4.5:540 in SiO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 8 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 10.56g of deionized water (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water = 60:1:4.5:660, siO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 4 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air for 4 hours to obtain a ZSM-5 molecular sieve, which is denoted as D4, wherein an X-ray diffraction diagram is shown in figure 8.
Specific surface areas S of samples A1 to A5 and comparative samples D1 to D4 BET (m 2 Per g), total pore volume V total /(cm 3 ·g -1 ) Micropore volume V micro /(cm 3 ·g -1 ) Volume of mesopores V meso /(cm 3 ·g -1 ) The silica to alumina molar ratio and the relative crystallinity data are shown in Table 1.
Comparative example 1 is a comparison with example 1, example 1 is a two-step water make-up preparation, 190 ℃ for 3 hours +170 ℃ for 9 hours, and comparative example 1 is a one-step process, 190 ℃ for 12 hours. As can be seen, the one-step crystallinity of comparative example 1 was 80.1%, and the two-step water-replenishing crystallinity of example 1 was higher, 84.9%
Comparative example 2 was compared with example 2, example 2 was a two-step make-up preparation, 190 ℃ for 5 hours +170 ℃ for 7 hours, and comparative example 2 was a two-step make-up, but 190 ℃ for 1 hour +170 ℃ for 11 hours. The first period of time cannot be too small and the crystallinity is not raised too little. It can be seen that the crystallinity is too low and the first stage crystallization time of comparative example 2 is too low.
Comparative example 3 was compared with example 2, example 2 was prepared by two-step water make-up, 190 ℃ for 5 hours +170 ℃ for 7 hours, water make-up from 660 to 840; comparative example 3 was also two-step water make-up, 190℃for 5 hours +170℃for 7 hours, but water was made up from 540 to 660. Indicating that the amount of water in the first stage cannot be too small, which would result in lower crystallinity.
Comparative example 4 and example 3 are compared, the temperature rise process is the same, the difference is the water amount of the first stage, comparative example 4 is 540, and example 3 is 660. Too little water in the first stage has lower crystallinity.
Test example 1
The molecular sieves prepared in examples 1 to 5 and comparative examples 1 to 4 are used as catalysts in the catalytic cracking reaction of light hydrocarbons to perform the catalytic cracking reaction of n-tetradecane, and the specific method is as follows: the influence of the molecular sieve on the yield and conversion rate of the low-carbon olefin in the light hydrocarbon catalytic cracking is evaluated by adopting pure hydrocarbon micro-reaction. The reaction is carried out in a fixed bed reactor, the raw oil is n-tetradecane, the carrier gas is nitrogen, the flow is 30mL/min, the reaction temperature is 550 ℃, the regeneration temperature is 600 ℃, and the weight airspeed is 20h -1 The molecular sieve is sieved into particles with 20-40 meshes after being pressed into tablets, the filling amount is 2.0g, the agent-oil volume ratio is 1.28, the sample analysis is carried out after 900s of reaction, the material balance calculation is carried out, and the product distribution is shown in Table 1.
Wherein the micro-inverse conversion rate X of the raw material and the yield Y of the product are calculated by adopting the following formula i ：
X = 100% - (n-tetradecane content in oil phase-n-tetradecane feed) ×100%;
Y i the weight of component i in the product/n-tetradecane feed x 100%, i representing ethylene, propylene, butene or components above C5.
TABLE 1
As shown in Table 1, the ZSM-5 molecular sieve prepared by the alkalinity-changing method has a silicon-aluminum ratio of 35-55, a high relative crystallinity (the relative crystallinity can reach 87.8% as high as possible) and a large specific surface area (333 cm) 2 /g). It is used for light hydrocarbon catalysisThe cracking reaction has better low-carbon olefin yield and can produce more propylene.
Examples 6-11 illustrate the present invention scheme for additional make-up of water and ethanol for the first hydrothermal reaction product in step S2.
Example 6
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 5 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water and 1.8g of absolute ethyl alcohol (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water: total molar mass of absolute ethanol = 60:1:4.5:840:6, siO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 7h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ in air atmosphere for 4h to obtain a ZSM-5 molecular sieve which is denoted as A6.
Example 7
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Calculated mole of sodium metaaluminateThe molar mass: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 5 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water and 5.4g of absolute ethyl alcohol (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water: total molar mass of absolute ethanol = 60:1:4.5:840:18, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 7h, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ in air for 4h to obtain a ZSM-5 molecular sieve, denoted as A7, wherein an X-ray diffraction pattern is shown in FIG. 9, and a scanning electron microscope is shown in FIG. 10.
Example 6 and example 7 were fed the same as example 2 except that ethanol was further added, wherein the ratio of silicon alkoxide in example 6 was 0.1 and that in example 7 was 0.3. The crystallinity of the molecular sieve synthesized by adding ethanol is further improved, and the morphology is in a long strip shape.
Example 8
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferred to a stainless steel kettle at 19Carrying out a first hydrothermal reaction at 0 ℃ for 8 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water and 1.8g of absolute ethyl alcohol (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water: total molar mass of absolute ethanol = 60:1:4.5:840:6, siO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 4 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air for 4 hours to obtain a ZSM-5 molecular sieve, namely A8, wherein an X-ray diffraction pattern of the ZSM-5 molecular sieve is shown in FIG. 9, and a scanning electron microscope photo is shown in FIG. 11.
Example 9
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 8 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water and 5.4g of absolute ethyl alcohol (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water: total molar mass of absolute ethanol = 60:1:4.5:840:18, in SiO 2 The total amount of ZSM-5 seed crystals is calculated asIn SiO form 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 4 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air atmosphere for 4 hours to obtain a ZSM-5 molecular sieve which is denoted as A9.
Example 10
S1, adding 20g of silica gel and 4.79g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 1.01g sodium hydroxide, 50.53g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 75:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 5 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water and 5.4g of absolute ethyl alcohol (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water: total molar amount of absolute ethanol = 75:1:4.5:840:18, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10 weight percent of the total usage of the silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle again, performing a second hydrothermal reaction at 170 ℃ for 7 hours, filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12 hours, and roasting at 550 ℃ in air atmosphere for 4 hours to obtain a ZSM-5 molecular sieve which is denoted as A10.
Example 11
S1, adding 20g of silica gel and 4.79g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 1.01g sodium hydroxide, 50.53g deionized water, 2.01g ZSM-5 seed (wherein,in SiO form 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 75:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 5 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, sequentially adding 15.84g of deionized water under stirring, and fully and uniformly stirring; transferring to a stainless steel kettle again, and carrying out a second hydrothermal reaction for 3h at 170 ℃. 5.4g of absolute ethanol (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water: total molar mass of absolute ethanol = 60:1:4.5:840:18, in SiO 2 The total amount of ZSM-5 seed crystal is calculated as SiO 2 10% by weight of the total amount of silica gel. Transferring the mixture into a stainless steel kettle for the third time, and performing a second hydrothermal reaction for 4 hours at 170 ℃. Filtering, washing to pH=7-8, performing ammonium exchange, drying at 120 ℃ for 12h, and roasting at 550 ℃ for 4h in air atmosphere to obtain ZSM-5 molecular sieve which is marked as A11.
Comparative example 5
The condition of comparative example 5 is the result of one-step synthesis, at 190℃for 12 hours with less water (540), and a certain amount of ethanol (6) was added.
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 48.9g deionized water, 1.8g absolute ethanol, 2.01g ZSM-5 seed crystal (wherein, siO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water: absolute ethanol = 60:1:4.5:540:6, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10% by weight of silica gel) Fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 12 hours to obtain a first hydrothermal reaction product; filtering, washing to pH=7-8, ammonium exchanging, drying at 120 deg.C for 12 hr, roasting at 550 deg.C in air atmosphere for 4 hr to obtain ZSM-5 molecular sieve, and recording as D5, and its X-ray diffraction spectrum is shown in figure 12.
Comparative example 6
In comparison with example 6, the conditions such as temperature rising process are the same as those of example 6, but the ethanol is obviously increased, the ethanol amount of example 6 is 6, and the alcohol-silicon ratio is 0.1; comparative example 6 the ethanol amount was 90 and the alcohol to silicon ratio was 1.5.
S1, adding 20g of silica gel and 5.99g of sodium metaaluminate (Na) in sequence under stirring 2 O:156.3g/L，Al 2 O 3 103.8 g/L), 0.81g sodium hydroxide, 50.69g deionized water, 2.01g ZSM-5 seed (in which SiO 2 Calculated molar amount of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Molar amount of sodium hydroxide calculated as O: molar amount of deionized water = 60:1:4.5:660, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 190 ℃ for 5 hours to obtain a first hydrothermal reaction product;
s2, transferring the first hydrothermal reaction product into a beaker, and sequentially adding 15.84g of deionized water and 1.8g of absolute ethyl alcohol (wherein, siO 2 Total molar mass of silica gel: with Al 2 O 3 Molar mass of sodium metaaluminate: by Na 2 Total molar amount of sodium hydroxide calculated as O: total molar amount of deionized water: total molar mass of absolute ethanol = 60:1:4.5:840:90, siO 2 The ZSM-5 seed crystal is calculated as SiO 2 10 wt% of silica gel, and fully and uniformly stirring; transferring to a stainless steel kettle, and performing a first hydrothermal reaction at 170 ℃ for 7 hours to obtain a first hydrothermal reaction product; filtering, washing to pH=7-8, ammonium exchanging, drying at 120deg.C for 12 hr, roasting at 550deg.C in air atmosphere for 4 hr to obtain ZSM-5 molecular sieve, denoted as D6, with X-ray diffraction pattern shown in figure 13, The scanning electron microscope photograph is shown in FIG. 14.
Specific surface area S of samples A6-A11 and comparative samples D5-D6 BET (m 2 Per g), total pore volume V total /(cm 3 ·g -1 ) Micropore volume V micro /(cm 3 ·g -1 ) Volume of mesopores V meso /(cm 3 ·g -1 ) The silica to alumina molar ratio and the relative crystallinity data are shown in Table 2.
Test example 2
The molecular sieves prepared in examples 6 to 11 and comparative examples 5 and 6 were used as catalysts in the catalytic cracking reaction of light hydrocarbons to perform the catalytic cracking reaction of n-tetradecane.
The product distribution is shown in Table 2 under the same conditions as in test example 1.
TABLE 2
As can be seen from Table 2, the ZSM-5 molecular sieve prepared by the method of the invention has a silica/alumina ratio of 35-60, examples 6-9 show that the solution of adding water and ethanol has higher relative crystallinity (the relative crystallinity can reach 90.8%) than the solution of adding water alone, and examples 10 and 11 illustrate the solution of adding water and ethanol, and the relative crystallinity can also exceed 80 at a higher feed silica/alumina ratio (75). When used in the light hydrocarbon catalytic cracking reaction, the catalyst has better low-carbon olefin yield and can produce more propylene.

Claims (13)

1. A method for preparing an amine-free high-silicon ZSM-5 molecular sieve by changing alkalinity, which comprises the following steps: s1, mixing a silicon source, an aluminum source, an alkali source, water and seed crystals to obtain a first mixture, and performing a first hydrothermal reaction to obtain a first hydrothermal reaction product; s2, mixing the first hydrothermal reaction product with additional water or mixing the first hydrothermal reaction product with the additional water and ethanol to obtain a second mixture, and performing a second hydrothermal reaction.
2. The method of claim 1, wherein in the step S1, the molar ratio of the silicon source, the aluminum source, the alkali source and the water is (40-70): 1: (1-5): (400-700), the seed crystal being used in an amount of 1-10 wt% of the silicon source; preferably, the molar ratio of the silicon source, the aluminum source, the alkali source and the water is (50-65): 1: (4-5): (500-700), the seed crystal being used in an amount of 8-10% by weight of the silicon source.
3. The method of claim 1, wherein the molar ratio of the total amount of water comprising step S1 and additional make-up water comprising step S2 to the aluminum source is from 720 to 1000:1, the mole ratio of the ethanol to the silicon source is 0.1-1, the silicon source is SiO 2 The aluminum source is calculated as Al 2 O 3 The alkali source is calculated by alkali metal oxide, and the seed crystal is calculated by SiO 2 And (5) counting.
4. A method according to claim 3, wherein the molar ratio of the total amount of water comprising step S1 and the additional make-up water comprising step S2 to the aluminium source is 800-1000:1.
5. a method according to claim 3, wherein the molar ratio of S2 of said ethanol to said silicon source is between 0.1 and 0.5.
6. The method of claim 1, wherein the silicon source is selected from one or more of silica gel, water glass, silica and white carbon; the aluminum source is selected from one or more of sodium metaaluminate, SB powder, aluminum oxide, aluminum hydroxide and aluminum sulfate; the alkali source is selected from one or more of sodium hydroxide and potassium hydroxide; the seed crystal is an industrial ZSM-5 molecular sieve with the molar ratio of silicon oxide to aluminum oxide of 25-50.
7. The method of claim 1, wherein the conditions of the first hydrothermal reaction comprise: the temperature is 160-180 ℃ and the time is 1-8 hours; the conditions of the second hydrothermal reaction include: the temperature is 160-180 ℃ and the time is 4-11 hours.
8. A method according to claim 1, characterized in that the method further comprises the step S3 of: and collecting a product obtained by the second hydrothermal reaction, and sequentially carrying out filtering, washing, ammonium exchange, drying and roasting on the product.
9. The method of claim 8, wherein the conditions of the firing process include: the temperature is 400-800 ℃, the time is 0.5-8h, and the atmosphere is air atmosphere or water vapor atmosphere.
10. The amine-free high silica ZSM-5 molecular sieve prepared by the method of any one of claims 1-9.
11. The amine-free high silica ZSM-5 molecular sieve according to claim 10, siO 2 With Al 2 O 3 The molar ratio of (2) is 35-60, the relative crystallinity is 80-95%, and the specific surface area is 280-360m 2 /g。
12. The light hydrocarbon catalytic cracking reaction method is characterized in that the method takes the amine-free high-silicon ZSM-5 molecular sieve as a catalyst in claim 10 or 11.
13. The process of claim 12, wherein the process is carried out in a fixed bed reactor and the reaction conditions include: the temperature is 600-650 ℃, and the reaction mass space velocity is 20-40h -1 The reaction pressure is 0.8-1.2MPa.
CN202210676293.XA 2022-06-15 2022-06-15 Method for preparing amine-free high-silicon ZSM-5 molecular sieve by changing alkalinity Pending CN117263203A (en)

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