Silicon-aluminum phosphate type molecular sieve, catalyst for preparing low-carbon olefin, and preparation method and application of silicon-aluminum phosphate type molecular sieve

Abstract

The invention discloses a silicoaluminophosphate type molecular sieve, a catalyst for preparing low-carbon olefin as well as a preparation method and application of the silicoaluminophosphate type molecular sieve. In the preparation process of the silicoaluminophosphate type molecular sieve, a phosphorus source simultaneously comprises an inorganic phosphorus source and an organic phosphorus source, so that the pore size distribution of the prepared silicoaluminophosphate type molecular sieve can be reduced, and the silicoaluminophosphate type molecular sieve has higher C2-3 olefin selectivity in a reaction for preparing low-carbon olefin from synthesis gas.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic chemistry and relates to a preparation method and application of a catalyst for directly converting synthesis gas into light olefins. Background Art

[0002] Low carbon olefins refer to olefins with carbon atoms less than or equal to 4. ), light olefins represented by ethylene and propylene are very important basic organic chemical raw materials. Foreign countries mostly produce light olefins by cracking light hydrocarbons, while domestically, they are mainly produced by cracking naphtha. With the decreasing petroleum resources, it is particularly important to study new technologies to replace traditional olefin production. From the perspective of large-scale equipment, producing methanol from synthesis gas, and then preparing light olefins (i.e., MTO route) and other oil products from methanol is the easiest route to achieve large-scale production, and it has been successfully commercialized so far. However, the direct conversion of synthesis gas into light olefins reduces the number of operating units and is actually a more cost-effective and energy-efficient approach.

[0003] Synthesis gas (CO+H 2 ) Chemistry is using coal, shale gas, biomass and CO 2 Synthesis gas plays an increasingly important role in the production of fuels, olefins, aromatics and other high-value chemicals to maintain the sustainable development of the chemical industry. As a key raw material for chemicals and polymers, the production of low-carbon olefins, especially ethylene and propylene, from syngas is increasingly receiving attention from academia and industry.

[0004] Fischer-Tropsch synthesis (FTS) is one of the process routes for directly producing light olefins from synthesis gas. As a non-petroleum-based technology for producing light olefins, it has attracted more and more attention. However, due to the limitation of Anderson-Schulz-Flory (ASF) rule, the existing catalysts have limited performance in C 2 -C 4 The total selectivity of olefins and alkanes can hardly exceed 58%. Based on this, in recent years, researchers have made continuous efforts to develop catalysts for the one-step conversion of syngas into light olefins. For example, the bifunctional catalyst developed, taking ZnCrOx & MSAPO as an example, showed excellent light olefin selectivity (about 70-87%), breaking through the distribution range of ASF (about 58%), but the selectivity of ethylene and propylene is still low.

[0005] However, from an economic point of view, the direct conversion of catalytic synthesis gas to light olefins (C 2-4 ＝), compared with butene, ethylene and propylene have higher economic value and practical application significance. Therefore, improving the selectivity of ethylene and propylene in low-carbon olefins has more application value and practical significance.

[0006] The Shanghai Research Institute of Petrochemicals of Sinopec Corporation disclosed in ZL2012103245177 the use of titanium silicon oxide-supported Fe-based catalysts, with a CO conversion rate of over 95%, but the selectivity of ethylene, propylene and butene was only about 60%. Similarly, patents ZL201410724028X, ZL2014107243818, and ZL201410724003X disclosed a series of modified alumina-supported iron-based catalysts, with the selectivity of ethylene, propylene and butene also maintained at about 60%.

[0007] It can be seen that in the process of preparing light olefins from synthesis gas, improving the selectivity of ethylene and propylene in light olefins has more application value and practical significance. Summary of the invention

[0008] 1. Problem to be solved

[0009] Based on the existing catalysts in the process of synthesizing light olefins from syngas, the selectivity of ethylene and propylene in light olefins is not ideal:

[0010] One of the purposes of the present invention is to provide a silicoaluminophosphate molecular sieve with different pore size characteristics; at the same time, a method for preparing the silicoaluminophosphate molecular sieve is provided;

[0011] The second object of the present invention is to provide a Zn x Cr y Al z Bifunctional catalysts of metal oxides and silicoaluminophosphate molecular sieves;

[0012] In addition, the present invention also provides the use of the silicoaluminophosphate molecular sieve and the bifunctional catalyst in the preparation of light olefins.

[0013] 2. Technical solution

[0014] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0015] The first aspect of the present invention provides a method for preparing a silicoaluminophosphate molecular sieve, comprising the following steps (a) to (c):

[0016] (a) preparing a mixture containing water, an aluminum source, a silicon source, a phosphorus source and a template;

[0017] (b) crystallizing the mixture by heat treatment;

[0018] (c) calcining the crystallized product;

[0019] Wherein, the phosphorus source includes an inorganic phosphorus source and an organic phosphorus source, and the molar proportion of the organic phosphorus source does not exceed 40%.

[0020] According to any embodiment of the first aspect of the present invention, the molar ratio of the silicon source, the aluminum source, the phosphorus source, the template, and the water is (0.1-1.0):1.0:(0.5-3):(1.0-4.0):(30-100); wherein,

[0021] The aluminum source is Al 2 O 3 count;

[0022] The phosphorus source is P 2 O 5 count;

[0023] The silicon source is SiO 2 count.

[0024] According to any embodiment of the first aspect of the present invention, in step (b), the heat treatment temperature is 170 to 200° C. and the time is 24 to 72 hours.

[0025] According to any embodiment of the first aspect of the present invention, in step (c), the calcination temperature is 350 to 600° C. and the calcination time is 2 to 12 hours.

[0026] According to any embodiment of the first aspect of the present invention, the molar ratio of the inorganic phosphorus source to the organic phosphorus source is not less than 2.

[0027] According to any embodiment of the first aspect of the present invention, the molar ratio of the inorganic phosphorus source to the organic phosphorus source is (2-30):(0.01-1); preferably (2-20):(0.02-1), and more preferably (2-15):(0.05-1).

[0028] According to any embodiment of the first aspect of the present invention, the inorganic phosphorus source comprises phosphoric acid (H 3 PO 4 ), diammonium hydrogen phosphate ((NH 4 ) 2 HPO 4 ), diammonium phosphate (NH 4 H 2 PO 4 ), metaphosphoric acid (HPO 3 ), pyrophosphate (H 4 P 2 O 7 ), polyphosphoric acid (H 6 P 4 O13 ), phosphorous acid (H 3 PO 3 ) in any one or two or more; preferably phosphoric acid H 3 PO 4 ;

[0029] The organic phosphorus source includes any one or two or more of phenylphosphonic acid, methylphosphonic acid, and hydroxyethylidene diphosphonic acid; preferably phenylphosphonic acid;

[0030] The template agent is tetraethylammonium hydroxide, triethylamine or a mixture of the two.

[0031] The second aspect of the present invention provides a silicoaluminophosphate molecular sieve, which is prepared by the method described in any embodiment of the first aspect of the present invention.

[0032] According to any embodiment of the second aspect of the present invention, the chemical formula of the silicoaluminophosphate molecular sieve is (Si x Al y P z ) 2 ;in,

[0033] The x is 0.01 to 0.98;

[0034] y is 0.01 to 0.60;

[0035] z is 0.01 to 0.52;

[0036] x+y+z=1;

[0037] Its powder X-ray diffraction peaks include characteristic peaks located at diffraction angles 2θ (±0.2°): 9.40°, 12.79°, 15.90°, 17.53°, and 20.45.

[0038] According to any embodiment of the second aspect of the present invention, in terms of pore distribution based on the DFT method, the silicoaluminophosphate type molecular sieve has:

[0039] The pores with a pore diameter of 0.8 nm or less have a volume S.

[0040] Pores with a pore size of less than 1 nm, the pores in this part have a volume L;

[0041] The volume S accounts for no less than 10% of the volume L.

[0042] According to any embodiment of the second aspect of the present invention, the proportion of the volume S to the volume L is not less than 20%; preferably, the proportion of the volume S to the volume L is not less than 30%.

[0043] According to any embodiment of the second aspect of the present invention, the ratio of the volume S to the volume L is 10% to 40%; preferably 20% to 40%; further preferably 30% to 40%; and most preferably 30% to 35%.

[0044] According to any embodiment of the second aspect of the present invention, in terms of pore distribution based on the DFT method, the molecular sieve has: pores with a pore size greater than 0.8 nm and not more than 1 nm, the pores of this part have a volume M,

[0045] The volume M accounts for no more than 80% of the volume L; preferably no more than 70%.

[0046] According to any embodiment of the second aspect of the present invention, in terms of pore distribution based on the DFT method, the silicoaluminophosphate type molecular sieve has:

[0047] The pores with a pore diameter of 0.8 nm or less have a volume S.

[0048] Pores with a pore diameter of less than 0.9 nm have a volume X;

[0049] The volume S accounts for no less than 10% of the volume X.

[0050] According to any embodiment of the second aspect of the present invention, the volume S accounts for no less than 20% of the volume X; preferably, the volume S accounts for no less than 30% of the volume X; further preferably, the volume S accounts for no less than 35% of the volume X.

[0051] According to any embodiment of the second aspect of the present invention, the ratio of the volume S to the volume X is 10% to 50%; preferably 20% to 45%; further preferably 30% to 40%; and most preferably 35% to 40%.

[0052] The third aspect of the present invention provides a catalyst for preparing light olefins, the catalyst comprising component I and component II;

[0053] The component I is a silicoaluminophosphate molecular sieve provided by any embodiment of the second aspect of the present invention, or a silicoaluminophosphate molecular sieve prepared by the method described in any embodiment of the first aspect of the present invention;

[0054] The component II is a metal oxide, and the metal oxide includes any one or two or more of a monovalent metal oxide, a binary metal oxide, and a ternary metal oxide.

[0055] According to any embodiment of the third aspect of the present invention, the monometallic oxide includes but is not limited to monometallic Mn-based oxide, monometallic Zn-based oxide, monometallic In-based oxide, monometallic Ga-based oxide, and monometallic Ce-based oxide.

[0056] According to any embodiment of the third aspect of the present invention, the binary metal oxide includes but is not limited to Zn, Cr oxide, Zn, Al oxide, Zn, Zr oxide, Zr, In oxide.

[0057] According to any embodiment of the third aspect of the present invention, the ternary metal oxide includes but is not limited to Zn, Ce, Zr oxides, Zr, Zn, Al oxides, Zn, Cr, Al oxides.

[0058] According to any embodiment of the third aspect of the present invention, the weight ratio of component I to component II is 1:(0.5-3); preferably 1:(0.5-2.5); more preferably 1:(1-2.5); and most preferably 1:(1-2).

[0059] The fourth aspect of the present invention provides a method for preparing low-carbon olefins by catalyzing synthesis gas using a catalyst, wherein the catalyst comprises a silicoaluminophosphate molecular sieve prepared by the method of any embodiment of the first aspect of the present invention or a silicoaluminophosphate molecular sieve provided by any embodiment of the second aspect of the present invention;

[0060] or,

[0061] The catalyst includes the catalyst for preparing light olefins as described in any embodiment of the third aspect of the present invention. DETAILED DESCRIPTION

[0062] The present disclosure may be more easily understood by reference to the following description in conjunction with the accompanying drawings and examples, all of which constitute a part of the present disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions or parameters described and / or shown herein. Further, the terms used herein are only used for the purpose of describing specific embodiments by way of example and are not intended to be limiting unless otherwise stated.

[0063] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, for the sake of simplicity, the various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure itself may also be considered to be an independent embodiment.

[0064] Unless otherwise indicated, it should be understood that each individual element in a list and each combination of individual elements in the list will be interpreted as a different embodiment. For example, a list of embodiments represented as "A, B, or C" should be interpreted to include embodiments "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C".

[0065] In the present disclosure, the singular forms of the articles "a," "an," and "the" also include the corresponding plural references, and a reference to a specific value includes at least that specific value unless the context clearly indicates otherwise. Thus, for example, a reference to "a substance" is a reference to at least one of that substance and equivalents thereof.

[0066] The terms including ordinal numbers such as "first" and "second" can be used to explain various components or fluids, but these components and fluids are not limited by these terms. Therefore, without departing from the teachings of the present disclosure, these terms are only used to distinguish the component / fluid from another component / fluid.

[0067] When items are described by using the conjunction terms "... and / or...," etc., the description should be understood to include any one of the associated listed items and all combinations of one or more thereof.

[0068] In general, the use of the term "about" indicates an approximate value that may vary depending on the desired properties obtained by the disclosed subject matter, and will be interpreted in a context-dependent manner based on function. Therefore, one of ordinary skill in the art will be able to interpret a certain degree of difference on a case-by-case basis. In some cases, the number of significant figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about". In other cases, a gradient in a range of values ​​can be used to determine the range of differences allowed by the term "about". Further, all ranges in this disclosure are inclusive and combinable, and reference to the values ​​stated in the range includes each value within the range.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0070] [1] Method for producing silicoaluminophosphate molecular sieve (hereinafter abbreviated as SAPO-34)

[0071] The first aspect of the present invention provides a method for preparing a silicoaluminophosphate molecular sieve, comprising the following steps (a) to (c):

[0072] (a) preparing a mixture containing water, an aluminum source, a silicon source, a phosphorus source and a template;

[0073] (b) crystallizing the mixture by heat treatment;

[0074] (c) calcining the crystallized product;

[0075] Step (a): preparing a gel mixture containing water, an aluminum source, a silicon source, a phosphorus source and a template;

[0076] The common operation process of step (a) is as follows: mixing the aluminum source and water to make the two in a relatively uniform state as much as possible, then sequentially adding the template, phosphorus source and silicon source, or phosphorus source, silicon source and template, and continuing to stir until a uniform gel is formed, and then stirring at room temperature for 0.5 to 12 hours to age it;

[0077] When preparing a mixture containing water, an aluminum source, a silicon source, a phosphorus source and a template, the aluminum source is Al 2 O 3 The phosphorus source is P 2 O 5 The silicon source is SiO 2 The molar ratio of the silicon source, the aluminum source, the phosphorus source, the template agent, and water is (0.1-1.0):1.0:(0.5-3):(1.0-4.0):(30-100);

[0078] As the aluminum source used in the present invention, for example, any one of aluminum isopropoxide, pseudo-boehmite, aluminum oxide and aluminum hydroxide or a mixture of any two, three, four or five thereof can be cited;

[0079] As the silicon source used in the present invention, for example, there can be cited any one of silica sol (silicon dioxide mass fraction is 30%), white carbon black (also known as fumed silica), ethyl orthosilicate and methyl orthosilicate, or a mixture of any two, three or four thereof;

[0080] The “inorganic phosphorus source” is any one or both of inorganic phosphoric acid and inorganic phosphate;

[0081] Examples of "inorganic phosphoric acid" include: phosphoric acid H 3 PO 4 , polyphosphate H 6 P 4 O 13 、Methophosphoric acid chemical formula HPO 3 , phosphorous acid H 3 PO 3 , pyrophosphate H 4 P 2 O 7 etc., preferably phosphate H 3 PO 4 ;

[0082] Examples of the “inorganic phosphates” include orthophosphates, pyrophosphates, metaphosphates, phosphites, and hypophosphites;

[0083] The orthophosphates include, for example:

[0084] ① Dihydrogen phosphate MH 2 PO 4 , also known as primary phosphate;

[0085] ② Hydrogen phosphate MHPO 4 , also known as diphosphate;

[0086] ③ Orthophosphate M 3 PO 4 , also known as tertiary phosphate;

[0087] Here, M is a metal, for example, lithium (Li), sodium (Na), potassium phosphate (K), etc.

[0088] The “organic phosphorus source” is any one or both of organic phosphoric acid and organic phosphate;

[0089] Examples of the “organic phosphoric acid” include phenylphosphonic acid, methylphosphonic acid, vinylphosphonic acid, and the like.

[0090] Examples of the “organic phosphate” include lithium salts, sodium salts, potassium salts, and the like of organic phosphoric acid, for example, lithium salts of phenylphosphonic acid and methylphosphonic acid, sodium salts of phenylphosphonic acid and methylphosphonic acid, and potassium salts of phenylphosphonic acid and methylphosphonic acid.

[0091] In order to increase the 2-4 ＝ ) 2-3 From the perspective of increasing the selectivity of ethylene and propylene, the phosphorus source used in the present invention needs to include both an inorganic phosphorus source and an organic phosphorus source, and the phosphorus source is selected according to P 2O 5Calculated, the molar ratio of the organic phosphorus source does not exceed 40%, and preferably the molar ratio of the inorganic phosphorus source to the organic phosphorus source is not less than 2; for example, the molar ratio of the inorganic phosphorus source to the organic phosphorus source can be (2:0.01), (2:0.02), (2:0.05), (2:0.1), (2:0.15), (2:0.2), (2:0.25), (2:0.3), (2:0.35), (2:0.45), (2:0.5), (2:0.55), (2:0.6), (2:0.65), (2:0.7), (2:0.75), (2:0.8), (2:0.85), (2:0.9), (2:0.95), (2:1), (3:0.01), (3:0.02), (3:0.03), (3:0.04), (3:0.05), (3:0.06), (3:0.07), (3:0.08), (3:0.09), (3:0.10), (3:0.11), (3:0.12), (3:0.13), (3:0.14), (3:0.15), (3:0.16), (3:0.17), (3:0.18), (3:0.19), (3:0.20), (3:0.21), (3:0.22), (3:0.23), (3:0.24), (3:0.25), (3:0.26), (3:0.27), (3:0.28), (3:0.29), (3:0.30), (3:0.31), (3:0.32), (3:0.33), (3:0.34), (3:0.35), (3:0.36 3:0.02)、(3:0.05)、(3:0.1)、(3:0.15)、(3:0.2)、(3:0.25)、(3:0.3)、(3:0.35)、(3:0.45)、(3:0.5)、(3:0.55)、(3:0.6)、(3:0.65)、(3:0.7)、(3:0.75)、(3:0.8)、(3:0.85)、(3:0.9)、(3:0.95)、(3:1)、(6:0.01)、(6:0.02)、(6:0.05)、(6:0.1)、(6:0.15)、(6:0.2)、(6:0.25)、(6:0.3)、(6:0.35)、(6:0 .45)、(6:0.5)、(6:0.55)、(6:0.6)、(6:0.65)、(6:0.7)、(6:0.75)、(6:0.8)、(6:0.85)、(6:0.9)、(6:0.95)、(6:1)、(8:0.01)、(8:0.02)、(8:0.05)、(8:0.1)、(8:0.15)、(8:0.2)、(8:0.25)、(8:0.3)、(8:0.35)、(8:0.45)、(8:0.5)、(8:0.55)、(8:0.6)、(8:0.65)、(8:0.7)、(8:0.75)、(8:0.8)、(8:0.85 )、(8:0.9)、(8:0.95)、(8:1)、(10:0.01)、(10:0.02)、(10:0.05)、(10:0.1)、(10:0.15)、(10:0.2)、(10:0.25)、(10:0.3)、(10:0.35)、(10:0.45)、(10:0.5)、(10:0.55)、(10:0.6)、(10:0.65)、(10:0.7)、(10:0.75)、(10:0.8)、(10:0.85)、(10:0.9)、(10:0.95)、(10:1)、(12:0.01)、(12:0.02)、(12:0.05)、(12:0.1)、(12:0.15)、(12:0.2)、(12:0.25)、(12:0.3)、(12:0.35)、(12:0.45)、(12:0.5)、(12:0.55)、(12:0.6)、(12:0.65)、(12:0.7)、(12:0.75)、(12:0.8)、(12:0.85)、(12:0.9)、(12:0.95)、(12:1)、(15:0.01)、(15:0.02 、(15:0.05)、(15:0.1)、(15:0.15)、(15:0.2)、(15:0.25)、(15:0.3)、(15:0.35)、(15:0.45)、(15:0.5)、(15:0.55)、(15:0.6)、(15:0.65)、(15:0.7)、(15:0.75)、(15:0.8)、(15:0.85)、(15:0.9)、(15:0.95)、(15:1)、(20:0.01)、(20 :0.02)、(20:0.05)、(20:0.1)、(20:0.15)、(20:0.2)、(20:0.25)、(20:0.3)、(20:0.35)、(20:0.45)、(20:0.5)、(20:0.55)、(20:0.6)、(20:0.65)、(20:0.7)、(20:0.75)、(20:0.8)、(20:0.85)、(20:0.9)、(20:0.95)、(20:1)、(30:0. 01), (30:0.02), (30:0.05), (30:0.1), (30:0.15), (30:0.2), (30:0.25), (30:0.3), (30:0.35), (30:0.45), (30:0.5), (30:0.55), (30:0.6), (30:0.65), (30:0.7), (30:0.75), (30:0.8), (30:0.85), (30:0.9), (30:0.95), (30:1). .

[0092] In fact, in the existing preparation method of SAPO-34 molecular sieve, a single inorganic phosphoric acid is basically used as the phosphorus source, especially H 3 PO 4In the process of research, the present invention found that replacing the phosphorus source in the synthetic raw material of SAPO-34 with a mixture of an inorganic phosphorus source and an organic phosphorus source from a traditional single inorganic phosphorus source, such as partially replacing phosphoric acid with phenylphosphonic acid (i.e., ensuring that it is a mixture of phosphoric acid and phenylphosphonic acid), can reduce the pore size distribution of the prepared SAPO-34 molecular sieve, so that it can be used in the synthesis gas to olefin reaction for butene and C 5+ The olefin production is further reduced, and the C 2-3 The proportion of olefins increased significantly. The resulting SAPO-34 molecular sieve has a higher C 2-3 Olefin selectivity.

[0093] As the template used in the present invention, for example, triethylamine (TEA), morpholine (Morpholine), tetraethylammonium hydroxide (TEAOH), tetraethylammonium hydroxide-triethylamine (TEAOH-TEA), tetraethylammonium hydroxide-morpholine (TEAOH-Morpholin) and the like can be cited. 2-4 ＝ ) 2-3 From the perspective of increasing the proportion of olefins and reducing the proportion of high-carbon products, the preferred template includes tetraethylammonium hydroxide (TEAOH), such as tetraethylammonium hydroxide (TEAOH), tetraethylammonium hydroxide-triethylamine (TEAOH-TEA) or tetraethylammonium hydroxide-morpholine (TEAOH-Morpholin).

[0094] Step (b): crystallizing the mixture by heat treatment;

[0095] The heat treatment process of step (b) is generally as follows: the mixture obtained in step (a) is transferred to a stainless steel synthesis reactor with a polytetrafluoroethylene liner, sealed and heated to cause hydrothermal crystallization; the "heat treatment" is performed at 170-200°C for 24-72 hours;

[0096] After the crystallization is completed, the synthesis kettle is taken out and cooled to room temperature. The obtained product is centrifuged and washed until it is neutral, and then dried to obtain the SAPO-34 molecular sieve raw powder. There are no special requirements for the method of "drying", which mainly removes moisture, for example, it can be placed in an oven at 100°C and dried overnight.

[0097] Step (c): calcining the crystallized product;

[0098] The usual operation process of the heat treatment for reference in step (c) is: subjecting the SAPO-34 molecular sieve raw powder obtained in step (b) to high-temperature calcination to obtain a calcined SAPO-34 molecular sieve.

[0099] The main purpose of the "calcination" is to remove the organic template. Therefore, there is no particular limitation on the "calcination method", and a conventionally known method can be used; for example, a muffle furnace can be used.

[0100] The "calcination" is usually carried out at 350-600°C in air atmosphere for 2-12 hours to achieve the basic purpose.

[0101] [2] The present invention can provide a chemical formula of (Si x Al y P z ) 2 Aluminosilicophosphate molecular sieve, wherein:

[0102] The x is 0.01 to 0.98;

[0103] y is 0.01 to 0.60;

[0104] z is 0.01 to 0.52;

[0105] x+y+z=1;

[0106] The powder X-ray diffraction peaks of the silicoaluminophosphate molecular sieve include characteristic peaks located at diffraction angles 2θ (±0.2°): 9.40°, 12.79°, 15.90°, 17.53°, and 20.45;

[0107] In terms of pore distribution based on the DFT method, the molecular sieve has:

[0108] The pores with a pore diameter of 0.8 nm or less have a volume S.

[0109] The pores with a diameter of 1 nm or less have a volume L.

[0110] The proportion of the volume S to the volume L is not less than 10%, preferably the proportion of the volume S to the volume L is not less than 20%; further preferably the proportion of the volume S to the volume L is not less than 30%.

[0111] As the silicoaluminophosphate molecular sieve, it can also selectively satisfy any one of the following (I) to (VI) or any combination of several of them; the (I) to (VI) are respectively:

[0112] (I) The ratio of the volume S to the volume L is 10% to 40%; preferably 20% to 40%; more preferably 30% to 40%; and most preferably 30% to 35%.

[0113] (II) The molecular sieve has pores with a pore size greater than 0.8 nm and not more than 1 nm, and the pores in this part have a volume M, and the proportion of the volume M to the volume L does not exceed 80%, preferably not more than 70%.

[0114] (III) The molecular sieve has pores with a pore size of less than 0.9 nm, and the pores in this part have a volume X, and the proportion of the volume S to the volume X is not less than 10%; preferably, the proportion of the volume S to the volume X is not less than 20%; further preferably, the proportion of the volume S to the volume X is not less than 30%; more preferably, the proportion of the volume S to the volume X is not less than 35%.

[0115] (IV) The ratio of the volume S to the volume X is 10% to 50%; preferably 20% to 45%; more preferably 30% to 40%; and most preferably 35% to 40%.

[0116] (V) The molecular sieve has pores with a pore size of less than 0.8 nm, and the volume S of the pores is not less than 0.02 cm 3 / g; preferably not less than 0.04cm 3 / g; further preferably not less than 0.05cm 3 / g; more preferably not less than 0.06cm 3 / g; the best choice is not less than 0.07cm 3 / g; for example, 0.02~0.08cm 3 / g, 0.04~0.08cm 3 / g, 0.05~0.08cm 3 / g, 0.06~0.08cm 3 / g, 0.07~0.08cm 3 / g, 0.04~0.07cm 3 / g, 0.05~0.07cm 3 / g, 0.06~0.07cm 3 / g, 0.04~0.06cm 3 / g, 0.05~0.06cm 3 / g.

[0117] (VI) The molecular sieve has pores with a pore size of less than 0.9 nm, and the pores have a volume X of not less than 0.12 cm 3 / g is preferably not less than 0.15cm 3 / g; further preferably not less than 0.18cm 3 / g; more preferably not less than 0.2cm 3 / g; for example, 0.12~0.3cm 3 / g, 0.15~0.3cm3 / g, 0.18~0.3cm 3 / g, 0.2~0.3cm 3 / g, 0.25~0.3cm 3 / g, 0.12~0.25cm 3 / g, 0.15~0.25cm 3 / g, 0.18~0.25cm 3 / g, 0.2~0.25cm 3 / g, 0.12~0.2cm 3 / g, 0.15~0.2cm 3 / g, 0.18~0.2cm 3 / g, 0.12~0.18cm 3 / g, 0.15~0.18cm 3 / g, 0.12~0.15cm 3 / g.

[0118] (VII) The molecular sieve has pores with a pore size of less than 1 nm, and the pores have a volume L of not less than 0.21 cm 3 / g; preferably not less than 0.25cm 3 / g; further preferably not less than 0.3cm 3 / g; for example, 0.21~0.4cm 3 / g, 0.25~0.4cm 3 / g, 0.3~0.4cm 3 / g, 0.35~0.4cm 3 / g, 0.21~0.35cm 3 / g, 0.25~0.35cm 3 / g, 0.3~0.35cm 3 / g, 0.21~0.3cm 3 / g, 0.25~0.3cm 3 / g, 0.21~0.25cm 3 / g.

[0119] (VIII) The molecular sieve has pores with a pore size greater than 0.8 nm and less than 1 nm, and the pores have a volume M less than 0.20 cm 3 / g; preferably not more than 0.17cm 3 / g; for example: no more than 0.25cm 3 / g, not more than 0.19cm 3 / g, not more than 0.18cm 3 / g, not more than 0.17cm 3 / g; or the pores in this part have a volume M of 0.07 to 0.19 cm 3 / g, 0.07~0.18cm 3 / g, 0.07~0.17cm 3 / g, 0.1~0.19cm 3 / g, 0.1~0.18cm 3 / g, 0.1~0.17cm 3 / g, 0.12~0.19cm 3 / g, 0.12~0.18cm 3 / g, 0.12~0.17cm 3 / g, 0.15~0.19cm 3 / g, 0.15~0.18cm 3 / g, 0.15~0.17cm 3 / g.

[0120] As a method for preparing the silicoaluminophosphate molecular sieve SAPO-34, it is preferred to use the method described in [1] above.

[0121] [3] The present invention can provide a bifunctional catalyst for preparing low-carbon olefins, wherein the catalyst comprises component I and component II; the component I and component II are mixed in a weight ratio of 1:(0.5-3).

[0122] As the “component I”, it is preferred to use the silicoaluminophosphate molecular sieve SAPO-34 prepared by the method described in [1] above, or the silicoaluminophosphate molecular sieve SAPO-34 described in [2] above;

[0123] As the "component II", any metal oxide known to have catalytic activity in converting synthesis gas to light olefins can be used, such as a monovalent metal oxide, a divalent metal oxide, or a ternary metal oxide.

[0124] The "monometallic oxide" includes but is not limited to monometallic Mn-based oxides, monometallic Zn-based oxides, monometallic In-based oxides, monometallic Ga-based oxides, and monometallic Ce-based oxides. For example, MnO x (MnO,Mn 2 O 3 and MnO 2 )、ZnO、CeO 2 , Ga 2 O 3 、In 2 O 3 ;

[0125] The "binary metal oxides" include but are not limited to Mn-based oxides and Zn-based oxides; for example, MnCr y O (x+1.5y) 、MnAl y O (x+1.5y) 、MnZr y O (x+2y) 、MnIn y O (x+1.5y) 、ZnCr y O (1+1.5y) 、ZnAl y O (1+1.5y) , ZnGa y O (1+1.5y) 、ZnIn y O (2+1.5y) , the value range of x is 0.1 to 4.5, the value range of y is 0.05 to 10; the value range of z is 0.01 to 10. The "Zn-based oxide" includes Zn-Cr oxide, Zn-Al oxide, Zn-Zr oxide, and Zr-In oxide. For example, ZnCr 2 O 4 、Zn / Al 2 O 3 、ZnO-ZrO 2 , Zr-doped In 2 O 3 、ZnAl 2 O 4 wait.

[0126] The "ternary metal oxides" include but are not limited to Zn, Ce, Zr oxides, Zr, Zn, Al oxides, Zn, Cr, Al oxides; for example, Zn y Al z MnO (x+1.5y+1.5z) 、In y Ga z MnO (x+1.5y+1.5z) 、Zn x Cr y Al z One or two or more of the above, wherein the value range of x is 0.1 to 4.5, the value range of y is 0.05 to 10, and the value range of z is 0.01 to 10; or Zn 0.3 Ce 2-x Zr x O 4 (x = 0 ~ 2), Zr-doped Zn / Al 2 O 3 、Zn x Cr y Al z(x=0.1~4.5, y=0.05~2; z=0.01~2.)

[0127] As the "Zn x Cr y Al z of metal oxides”; then,

[0128] The value range of x is 0.1 to 4.5; preferably 0.5 to 4; more preferably 0.5 to 3; and most preferably 1 to 2;

[0129] The value range of y is 0.05 to 2; preferably 0.07 to 1.8; more preferably 0.08 to 1.5; and most preferably 1 to 1.5;

[0130] The value range of z is 0.01 to 2; preferably 0.05 to 2; more preferably 0.08 to 1.5; and most preferably 1 to 1.5.

[0131] [4] The present invention can provide a method for preparing a bifunctional catalyst for preparing light olefins.

[0132] Component I and component II are granulated separately and then compounded together according to the proportion.

[0133] 【5】Catalysts for catalytic synthesis of syngas to form light olefins

[0134] The silicoaluminophosphate molecular sieve (SAPO-34) and / or bifunctional catalyst of the present invention can be preferably reduced in the presence of a reducing agent such as hydrogen; for example, it is usually reduced at 200-500°C for 2-8 hours while supplying hydrogen.

[0135] Then, the reduced silicoaluminophosphate molecular sieve (SAPO-34) and / or bifunctional catalyst are used to catalyze the synthesis gas to directly produce light olefins; for example, usually when the synthesis gas (H in the synthesis gas) is supplied 2 The molar ratio with CO is 0.5-3, and the total volume space velocity is 1000-10000h -1 ), the reaction is carried out at 300 to 600° C. and a pressure of 0.1 to 3 MPa.

[0136] The detection instruments used in the following specific embodiments are:

[0137] Pore ​​size distribution detection: physical adsorption instrument (model ASAP-2460), adsorbate: nitrogen;

[0138] X-ray diffraction peak detection: X-ray diffractometer (model PANalytical X'Pert3Powder);

[0139] Reaction product light olefins: gas chromatograph (model Agilent 7890B).

[0140] The present invention is further described below in conjunction with specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. The essential characteristics and remarkable effects of the present invention can be reflected from the following examples, and the described embodiments are part of the embodiments of the present invention, rather than all the embodiments, and therefore, they do not limit the present invention in any way, and those skilled in the art make some non-essential improvements and adjustments based on the content of the present invention, which all belong to the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0141] Figure 1 This is a comparison chart of the pore size distribution of the SAPO-34 molecular sieves obtained in Comparative Example 1, Example 1, and Example 2 of the present invention;

[0142] Figure 2 This is the XRD diagram of the SAPO-34 molecular sieve obtained in Comparative Example 1, Example 1, and Example 2 of the present invention.

[0143] Comparative Example 1

[0144] Preparation of silicoaluminophosphate molecular sieve (hereinafter referred to as SAPO-34)

[0145] Weigh 8.93g of pseudo-boehmite and stir evenly with 32.62g of deionized water, then slowly add 48.98g of tetraethylammonium hydroxide, 17.09g of phosphoric acid, and 2.24g of silica sol (silicon dioxide mass fraction is 30%), and continue stirring until a uniform gel is formed. The obtained gel is transferred into a 150mL stainless steel synthesis reactor with a polytetrafluoroethylene liner and crystallized at 170°C for 60h. After the crystallization is completed, the synthesis reactor is cooled to room temperature with water. The obtained product is centrifuged and washed to neutrality, and placed in an oven at 110°C for drying overnight to obtain the original SAPO-34 molecular sieve powder. After the original powder is calcined at 550°C in air to remove the organic template, a calcined SAPO-34 molecular sieve is obtained, and then tableting and granulation are performed, and 40-60 mesh particles are sieved out for standby use.

[0146] Preparation of bifunctional catalysts

[0147] The calcined SAPO-34 molecular sieve (40-60 mesh) and the metal oxide ZnCrAlOx (40-60 mesh) were uniformly mixed at a weight ratio of 1:2 between the molecular sieve and the metal oxide, and compounded together by mechanical mixing.

[0148] Application of catalytic synthesis gas to form light olefins

[0149] 1 mL of the bifunctional catalyst was measured and loaded into a Φ8 mm fixed bed reactor. Before the reaction, the prepared catalyst was heated in H 2 The reduction was carried out under the atmosphere, the reduction temperature was 300℃, the reduction time was 4h, and then the raw gas was introduced to carry out the reaction of directly preparing low-carbon olefins from synthesis gas, the reaction temperature was 375℃, the reaction pressure was 1MPa, and the space velocity was 3000h -1 , H 2 The molar ratio of CO to CO is 2.

[0150] The catalytic products were analyzed online by gas chromatography, and the performance evaluation results of the catalyst are shown in Table 1.

[0151] Comparative Example 2

[0152] Preparation of silicoaluminophosphate molecular sieve (hereinafter referred to as SAPO-34)

[0153] Weigh 10.12g of pseudo-boehmite and stir evenly with 51.7g of deionized water, then slowly add 16.14g of phosphoric acid, 2.75g of silica sol, and 20.25g of triethylamine in sequence, and continue stirring until a uniform gel is formed. The obtained gel is transferred into a 150mL stainless steel synthesis reactor with a polytetrafluoroethylene liner, heated to 170°C after 60min, crystallized at this temperature for 12h, and then heated to 200°C after 30min, and crystallized at this temperature for 10h. After the crystallization is completed, the synthesis reactor is cooled to room temperature with water. The obtained product is centrifugally washed to neutrality, placed in an oven at 110°C for drying overnight, and the original SAPO-34 molecular sieve powder is obtained. After the original powder is calcined at 550°C in air to remove the organic template, a calcined SAPO-34 molecular sieve is obtained, and then tableting and granulation are performed, and 40-60 mesh particles are sieved out for standby use.

[0154] The preparation conditions and process of the bifunctional catalyst are the same as those of Comparative Example 1.

[0155] The application conditions and process of catalytic synthesis gas to prepare light olefins are the same as those in Comparative Example 1.

[0156] The catalytic products were analyzed online by gas chromatography, and the performance evaluation results of the catalyst are shown in Table 1.

[0157] Example 1

[0158] Preparation of silicoaluminophosphate molecular sieve (hereinafter referred to as SAPO-34)

[0159] Weigh 8.93g of pseudo-boehmite and stir evenly with 32.77g of deionized water, then slowly add 48.98g of tetraethylammonium hydroxide, 1.02g of phenylphosphonic acid, 16.31g of phosphoric acid, and 2.24g of silica sol in sequence, and continue stirring until a uniform gel is formed. The obtained gel is transferred into a 150mL stainless steel synthesis reactor with a polytetrafluoroethylene liner and crystallized at 170°C for 60h. After the crystallization is completed, the synthesis reactor is cooled to room temperature with water. The obtained product is centrifuged and washed to neutrality, and placed in an oven at 110°C for drying overnight to obtain the original SAPO-34 molecular sieve powder. After the original powder is calcined at 550°C in air to remove the organic template, a calcined SAPO-34 molecular sieve is obtained, which is then pressed into tablets and granulated, and 40-60 mesh particles are sieved for standby use.

[0160] The preparation conditions and process of the bifunctional catalyst are the same as those of Comparative Example 1.

[0161] The application conditions and process of catalytic synthesis gas to prepare light olefins are the same as those in Comparative Example 1.

[0162] The catalytic products were analyzed online by gas chromatography, and the performance evaluation results of the catalyst are shown in Table 1.

[0163] Example 2

[0164] Preparation of silicoaluminophosphate molecular sieve (hereinafter referred to as SAPO-34)

[0165] Weigh 8.93g of pseudo-boehmite and stir evenly with 32.92g of deionized water, then slowly add 48.98g of tetraethylammonium hydroxide, 2.05g of phenylphosphonic acid, 15.52g of phosphoric acid and 2.24g of silica sol in sequence, and continue stirring until a uniform gel is formed. The obtained gel is transferred into a 150mL stainless steel synthesis reactor with a polytetrafluoroethylene liner and crystallized at 170°C for 60h. After the crystallization is completed, the synthesis reactor is cooled to room temperature with water. The obtained product is centrifuged and washed to neutrality, and placed in an oven at 110°C for drying overnight to obtain the original SAPO-34 molecular sieve powder. After the original powder is calcined at 550°C in air to remove the organic template, a calcined SAPO-34 molecular sieve is obtained, which is then pressed into tablets and granulated, and 40-60 mesh particles are sieved out for standby use.

[0166] The preparation conditions and process of the bifunctional catalyst are the same as those of Comparative Example 1.

[0167] The application conditions and process of catalytic synthesis gas to prepare light olefins are the same as those in Comparative Example 1.

[0168] The catalytic products were analyzed online by gas chromatography, and the performance evaluation results of the catalyst are shown in Table 1.

[0169] Example 3

[0170] Preparation of silicoaluminophosphate molecular sieve (hereinafter referred to as SAPO-34)

[0171] Weigh 10.12g of pseudo-boehmite and stir evenly with 52g of deionized water, then slowly add 1.91g of phenylphosphonic acid, 14.72g of phosphoric acid, 2.75g of silica sol, and 20.25g of triethylamine in sequence, and continue stirring until a uniform gel is formed. The obtained gel is transferred into a 150mL stainless steel synthesis reactor with a polytetrafluoroethylene liner, heated to 170°C after 60min, crystallized at this temperature for 12h, and then heated to 200°C after 30min, and crystallized at this temperature for 10h. After the crystallization is completed, the synthesis reactor is cooled to room temperature with water. The obtained product is centrifugally washed to neutrality, placed in an oven at 110°C for drying overnight, and the original SAPO-34 molecular sieve powder is obtained. After the original powder is calcined at 550°C in air to remove the organic template, a calcined SAPO-34 molecular sieve is obtained, and then tableting and granulation are performed, and 40-60 mesh particles are sieved out for standby use.

[0172] The preparation conditions and process of the bifunctional catalyst are the same as those of Comparative Example 1.

[0173] The application conditions and process of catalytic synthesis gas to prepare light olefins are the same as those in Comparative Example 1.

[0174] The catalytic products were analyzed online by gas chromatography, and the performance evaluation results of the catalyst are shown in Table 1.

[0175] Example 4

[0176] Preparation of silicoaluminophosphate molecular sieve (hereinafter referred to as SAPO-34)

[0177] Weigh 10.12g of pseudo-boehmite and stir evenly with 52.2g of deionized water, then slowly add 3.48g of phenylphosphonic acid, 13.48g of phosphoric acid, 2.75g of silica sol, and 20.25g of triethylamine in sequence, and continue stirring until a uniform gel is formed. The obtained gel is transferred into a 150mL stainless steel synthesis reactor with a polytetrafluoroethylene liner, heated to 170°C after 60min, crystallized at this temperature for 12h, and then heated to 200°C after 30min, and crystallized at this temperature for 10h. After the crystallization is completed, the synthesis reactor is cooled to room temperature with water. The obtained product is centrifugally washed to neutrality, placed in an oven at 110°C for drying overnight, and the original SAPO-34 molecular sieve powder is obtained. After the original powder is calcined at 550°C in air to remove the organic template, a calcined SAPO-34 molecular sieve is obtained, and then tableting and granulation are performed, and 40-60 mesh particles are sieved for standby use.

[0178] The preparation conditions and process of the bifunctional catalyst are the same as those of Comparative Example 1.

[0179] The application conditions and process of catalytic synthesis gas to prepare light olefins are the same as those in Comparative Example 1.

[0180] The catalytic products were analyzed online by gas chromatography, and the performance evaluation results of the catalyst are shown in Table 1.

[0181] Table 1. Performance evaluation results of syngas to light olefins catalyst

[0182]

[0183] It can be seen from the evaluation data in the table that from the comparative evaluation results of Comparative Example 1 with Examples 1 and 2 and Comparative Example 2 with Examples 3 and 4, it can be concluded that in the process of synthesizing SAPO-34, whether tetraethylammonium hydroxide or triethylamine is used as a template agent, the SAPO-34 prepared by partially replacing the phosphoric acid in the synthetic raw material with phenylphosphonic acid (PPA) can improve the low-carbon olefin (C 2-4 ＝ ) 2-3 The proportion of olefins is reduced, the proportion of high-carbon products is reduced, and as the proportion of PPA in the phosphorus source increases, butene and C 5+ Further reduction, C 2-3 The proportion of olefins gradually increased, indicating that the SAPO-34 prepared by partially replacing phosphoric acid with phenylphosphonic acid (PPA) during the synthesis of SAPO-34 molecular sieve can improve the content of low-carbon olefins (C 2-4 ＝ ) Ethylene and propylene in the product (C 2-3 ＝ )’s share.

[0184] And based on the DFT method, combined with Figure 1 By testing the SAPO-34 molecular sieves prepared in Example 1 and Comparative Example 1, it was found that, as shown in Table 2 below, replacing the phosphorus source in the synthetic raw material of SAPO-34 with a mixture of an inorganic phosphorus source and an organic phosphorus source from a traditional single inorganic phosphorus source can reduce the pore size distribution of the SAPO-34 molecular sieve prepared. This is the SAPO-34 molecular sieve prepared in Examples 1 and 2. In the synthesis gas to olefins reaction, the pore size distribution of butene and C 5+ The olefin production is further reduced, and the C 2-3 The main reason is the significant increase in the proportion of olefins.

[0185] Table 2. Pore size test results of SAPO-34 molecular sieve

[0186] Example 1 Example 2 Comparative Example 1 <![CDATA[Volume S (cm 3 / g)]]> 0.06 0.08 0 <![CDATA[Volume M (cm 3 / g)]]> 0.19 0.17 0.2 <![CDATA[Volume X (cm 3 / g)]]> 0.19 0.21 0.11 <![CDATA[Volume L (cm 3 / g)]]> 0.25 0.25 0.2 Volume S / Volume L (%) 24 32 0 Volume S / Volume X (%) 32 38 0

[0187] In the table:

[0188] Volume S represents: the total volume of pores with a pore diameter ≤ 0.8 nm;

[0189] Volume X represents: the total volume of pores with a pore diameter ≤ 0.9 nm;

[0190] Volume M represents the total volume of pores with a pore diameter of 0.8 nm < ≤ 1 nm;

[0191] The volume L represents the total volume of pores with a pore diameter ≤ 1 nm.

[0192] In addition, it was found that compared with the SAPO-34 synthesized in the system using TEA as the template, the SAPO-34 synthesized in the system using TEAOH as the template had a more significant C 2-3 Selection of olefins. In general, the SAPO-34 molecular sieves synthesized under the two systems have proved that the introduction of organic phosphorus sources plays a certain positive role in the bifunctional catalyst.

[0193] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a silicoaluminophosphate molecular sieve, characterized in that: The method comprises the following steps (a) to (c), (a) preparing a mixture containing water, an aluminum source, a silicon source, a phosphorus source and a template; (b) crystallizing the mixture by heat treatment; (c) calcining the crystallized product; Wherein, the phosphorus source includes an inorganic phosphorus source and an organic phosphorus source, and the molar proportion of the organic phosphorus source is no more than 40% calculated on the basis of P2O5.

2. The method for preparing the silicoaluminophosphate molecular sieve according to claim 1, characterized in that: In step (a), The molar ratio of the silicon source, aluminum source, phosphorus source, template agent and water is (0.1-1.0):1.0:(0.5-3):(1.0-4.0):(30-100); wherein, The aluminum source is calculated as Al2O3; The phosphorus source is calculated as P2O5; The silicon source is calculated in terms of SiO2.

3. The method for preparing the silicoaluminophosphate molecular sieve according to claim 1, characterized in that: In step (b), The heat treatment is carried out at a temperature of 170 to 200° C. and for a time of 24 to 72 hours.

4. The method for preparing the silicoaluminophosphate molecular sieve according to claim 1, characterized in that: In step (c), The calcination temperature is 350-600° C. and the calcination time is 2-12 hours.

5. The method for preparing the silicoaluminophosphate molecular sieve according to any one of claims 1 to 4, characterized in that: The molar ratio of the inorganic phosphorus source to the organic phosphorus source is not less than 2.

6. The method for preparing the silicoaluminophosphate molecular sieve according to any one of claims 1 to 4, characterized in that: The molar ratio of the inorganic phosphorus source to the organic phosphorus source is (2-30):(0.01-1); preferably (2-20):(0.02-1), and more preferably (2-15):(0.05-1).

7. The method for preparing the silicoaluminophosphate molecular sieve according to any one of claims 1 to 6, characterized in that: The inorganic phosphorus source includes phosphoric acid H3PO4, diammonium hydrogen phosphate (NH4)2HPO4, diammonium phosphate NH4H2PO4, metaphosphoric acid HPO3, pyrophosphate H4P2O7, polyphosphoric acid H6P4O 13 , any one or two or more of phosphorous acid H3PO3; preferably phosphoric acid H3PO4; The organic phosphorus source includes any one or two or more of phenylphosphonic acid, methylphosphonic acid, and hydroxyethylidene diphosphonic acid; preferably phenylphosphonic acid; The template agent includes one of tetraethylammonium hydroxide and triethylamine or a mixture of the two.

8. A silicoaluminophosphate molecular sieve, characterized in that: The molecular sieve is prepared by the method according to any one of claims 1 to 7.

9. The silicoaluminophosphate molecular sieve according to claim 8, or the silicoaluminophosphate molecular sieve prepared by the method according to any one of claims 1 to 7, characterized in that: Used to catalyze the preparation of syngas to form light olefins.

10. A catalyst for preparing light olefins, characterized in that: The catalyst comprises component I and component II; The component I is the silicoaluminophosphate molecular sieve according to claim 8, or the silicoaluminophosphate molecular sieve prepared by any of the methods described in claims 1 to 7; The component II is a metal oxide, and the metal oxide includes any one or two or more of a monovalent metal oxide, a binary metal oxide, and a ternary metal oxide.

11. The catalyst for preparing light olefins according to claim 10, characterized in that: The weight ratio of component I to component II is 1:(0.5-3); preferably 1:(0.5-2.5); more preferably 1:(1-2.5); and most preferably 1:(1-2).

12. Use of the catalyst for preparing light olefins according to claim 10 or 11, characterized in that: Used to catalyze the preparation of syngas to form light olefins.

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