CN108212197B - Catalyst for preparing polymethoxy dimethyl ether from dimethyl ether and preparation and application thereof - Google Patents
Catalyst for preparing polymethoxy dimethyl ether from dimethyl ether and preparation and application thereof Download PDFInfo
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- 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
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- 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
- B01J29/076—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0201—Impregnation
- B01J37/0207—Pretreatment of the support
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- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
- C07C41/48—Preparation of compounds having groups
- C07C41/50—Preparation of compounds having groups by reactions producing groups
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- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/37—Acid treatment
Abstract
The invention provides a catalyst for preparing polymethoxy dimethyl ether from dimethyl ether, belonging to the technical field of catalysts for synthesizing polymethoxy dimethyl ether. The catalyst is a composite oxide/zeolite catalyst which takes zeolite as a carrier and loads composite oxide on the carrier; wherein the zeolite accounts for 95-99% of the total mass of the catalyst, and the composite oxide accounts for 1-5% of the total mass of the catalyst. The invention also provides a preparation method of the catalyst, which comprises the steps of soaking zeolite by using sulfuric acid, washing to be neutral, drying, then soaking the mixed salt solution of the composite oxide onto the zeolite modified by the sulfuric acid in the same volume, standing after fully oscillating and stirring, drying, grinding, sieving and roasting to obtain the composite oxide/zeolite catalyst. The composite oxide/zeolite catalyst is applied to the reaction of preparing polymethoxy dimethyl ether from dimethyl ether, and has the advantages of high conversion rate, high catalytic activity, good stability, DME conversion rate of 30-50 percent and DMMx selectivity of 80-95 percent.
Description
Technical Field
The invention belongs to the technical field of catalysts for synthesizing polymethoxy dimethyl ether, and particularly relates to a catalyst for preparing polymethoxy dimethyl ether from dimethyl ether, and preparation and application thereof.
background
automobile exhaust is the main reason for causing large-area haze in China, but the pollution caused by diesel vehicles is far higher than that of gasoline vehicles. In addition to further improving the quality of diesel and engine technology, the reduction of waste emissions is also one of the solutions to the problem through the development of novel diesel additives. The research of the Chinese environmental science research institute shows that polymethoxy dimethyl ether (DMMx, x is 1-8) can be well mixed with diesel oil, and the emission of particulate matters of motor vehicles can be greatly reduced, so that the polymethoxy dimethyl ether is an ideal diesel oil additive.
2DMMx is a low relative molecular mass acetal polymer with dimethoxymethane as a matrix and methyleneoxy as a main chain, has higher oxygen content and cetane number, can obviously improve the combustion performance of diesel oil, effectively improve the thermal efficiency, and reduce the formation of smoke during combustion, at present, DMMx can be prepared by condensing methanol, dimethyl ether (DME) or methoxy dimethyl ether (DMM) with Formaldehyde (FA), Trioxymethylene (TOM) or Paraformaldehyde (PF) through acid catalysis, acid catalysts used in the synthesis of DMMx mainly comprise liquid acid, ion exchange resin, ionic liquid, molecular sieves and the like, for example, CN102320941A uses methanol and FA as raw materials and solid acid as a catalyst to synthesize DMMx, US6166266 uses FA and methanol or DME as raw materials and macroporous sulfonic cation exchange resin as a catalyst to prepare DMMx, CN1020306A and CN101940940A use methanol as raw materials and molecular sieves as carriers, iron molybdenum oxides as active components to synthesize the Mx by direct oxidation, CN102249868A uses methanol solution and ionic liquid as a catalyst, and the ionic liquid as a catalyst to synthesize the DMMx carbon nano-carbon material, and the DMMx-carbon nano-carbon material is prepared by a one-step process with high energy consumption and high investment, high energy consumption, high carbon nano-carbon material, such as a chemical carbon nano-carbon material, a chemical carbon nano-carbon material, and a chemical carbon nano-carbon material, and a low-carbon nano-carbon material, and a low-carbon material, such as a low-carbon nano-carbon material is developed by-carbon material, and is developed by a low-.
Disclosure of Invention
The invention aims to provide a catalyst for preparing polymethoxy dimethyl ether from dimethyl ether, which has the advantages of low raw material cost, high conversion rate, high catalytic activity and good stability, and a preparation method and application thereof. The purpose of the invention is realized by the following technical scheme:
The catalyst for preparing the polymethoxy dimethyl ether by the dimethyl ether takes zeolite as a carrier, and a composite oxide/zeolite catalyst of a composite oxide is loaded on the carrier; wherein the zeolite accounts for 95-99% of the total mass of the catalyst, and the composite oxide accounts for 1-5% of the total mass of the catalyst.
Zeolite is a porous hydrous aluminosilicate mineral containing alkali metal and having a framework structure, and has a silicon-oxygen tetrahedron structure to make it have strong adsorption capacity and large adsorption capacity, and cavities and channels with uniform and fixed sizes are arranged in the zeolite. In addition, the alkali metal cations in the zeolite crystal framework are not firmly connected with the silicon-aluminum framework structure, so that reversible ion exchange is realized within a certain limit, and modification treatment is easy to realize. The currently disclosed catalyst carrier for preparing the polyoxymethylene dimethyl ethers from the dimethyl ethers can adopt carbon nanotubes, activated carbon, carbon fibers, carbon molecular sieves and graphene, and has high loading amount and better catalytic activity due to the porous characteristic of carbon-based materials, but on one hand, the cost of the materials such as the carbon nanotubes, the carbon fibers and the graphene is far higher than the price of the common molecular sieve carrier; on the other hand, in the reaction of preparing the polyoxymethylene dimethyl ether by one-step oxidation of dimethyl ether, the carbon-based catalyst is easy to deposit carbon in the reaction process, so that the pore channel in the catalyst is blocked, the performance of the catalyst is reduced, and meanwhile, the regeneration of the catalyst has a larger problem. The invention adopts zeolite as the carrier, on one hand, the zeolite reserves in China are abundant, the price is low, and the raw material sources are very wide; on the other hand, the composite oxide/zeolite catalyst prepared by the invention is composed of a zeolite carrier and a metal oxide, can be activated and regenerated at high temperature, and has better stability.
As a specific example of the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether, the composite oxide is one of TiO 2 -ZnO, TiO 2 -V 2 O 5 2 -Al 2 O 3, Al 2 O 3 -MoO 3 and Al 2 O 3 -Cr 2 O 3, and the molar ratio of the composite oxide is 1: 1.
The complex oxides such as TiO 2 -ZnO, TiO 2 -V 2 O 5 2 -Al 2 O 3, Al 2 O 3 -MoO 3 and Al 2 O 3 -Cr 2 O 3 adopted by the invention belong to solid acids, can provide enough L acid centers for the reaction, and are beneficial to improving the selection of DMMx.
a preparation method of a catalyst for preparing polymethoxy dimethyl ether from dimethyl ether comprises the steps of soaking zeolite with sulfuric acid, washing until the zeolite is neutral, drying, soaking a mixed salt solution of a composite oxide onto the zeolite modified by the sulfuric acid in an equal volume, oscillating, fully stirring, standing, drying, grinding, sieving and roasting to obtain the composite oxide/zeolite catalyst.
The zeolite is modified by sulfuric acid, Fe 2 O 3, SiO 2 and partial organic impurities in the zeolite are dissolved, so that internal channels and passages of the zeolite are smoother, and Lewis acid centers in the zeolite are exposed.
further, the volume fraction of the sulfuric acid is 2-15%; the solid-liquid ratio of the sulfuric acid to the zeolite is 1: 35-45; the drying temperature is 100-130 ℃; the slow stirring temperature is 55-65 ℃, and the time is 2-3 hours; the standing time is 6-10 hours; the roasting temperature is 400-600 ℃, and the roasting time is 5-8 h.
As a specific example of the preparation method of the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether, when the composite oxide is TiO 2 -ZnO, the preparation method of the catalyst is as follows:
soaking 12.5 volume percent of sulfuric acid into zeolite at a solid-to-liquid ratio of 1:40 for 24 hours, washing to be neutral, drying at 120 ℃, adding 0.454g of Zn (NO 3) 2.6H 2 O and 0.287g of TiCl 4 into a proper amount of distilled water, soaking in 4.681g of acid-modified zeolite in the same volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8 hours, drying at 120 ℃, grinding and sieving, and roasting at 600 ℃ for 5 hours to obtain the TiO 2 -ZnO/zeolite catalyst with the composite oxide content of 5%.
As a specific example of the preparation method of the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether, when the composite oxide is TiO 2 -V 2 O 5, the preparation method of the catalyst is as follows:
soaking 15 volume percent of sulfuric acid in zeolite at a solid-to-liquid ratio of 1:40 for 24 hours, washing to be neutral, drying at 120 ℃, adding 0.190g of vanadyl sulfate pentahydrate and 0.143g of TiCl 4 into a proper amount of distilled water, soaking in 8.360g of acid-modified zeolite in an equal volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8 hours, drying at 120 ℃, grinding and sieving, and roasting at 500 ℃ for 6 hours to obtain the TiO 2 -V 2 O 5/zeolite catalyst with the composite oxide content of 2.3%.
As a specific example of the preparation method of the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether, when the composite oxide is SiO 2 -Al 2 O 3, the preparation method of the catalyst is as follows:
Soaking 8% volume fraction sulfuric acid in solid-to-liquid ratio of 1:40 for 24 hr, washing to neutrality, stoving at 120 deg.c, soaking Al 2 (SO 4) 3.18H 2 O in 1.067g and H 2 SiO 3 in 0.125g in distilled water in the same volume to 6.068g acid modified zeolite, shaking and stirring at 60 deg.c for 2.5 hr, standing for 8 hr, stoving at 120 deg.c, grinding, sieving and roasting at 800 deg.c for 6 hr to obtain SiO 2 -Al 2 O 3/zeolite catalyst with composite oxide content of 4.1%.
As a specific example of the preparation method of the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether, when the composite oxide is Al 2 O 3 -MoO 3, the preparation method of the catalyst is as follows:
soaking zeolite in sulfuric acid with the volume fraction of 2% for 24H according to the solid-to-liquid ratio of 1:40, washing to be neutral, drying at 120 ℃, adding 0.981g of Al 2 (SO 4) 3.18H 2 O and 1.818g of ammonium molybdate tetrahydrate into a proper amount of distilled water, soaking the mixture on 10.945g of acid-modified zeolite in the same volume, shaking and stirring at 60 ℃ for 2.5H, standing for 8H, drying at 120 ℃, grinding and sieving, and roasting at 800 ℃ for 8H to obtain the Al 2 O 3 -MoO 3/zeolite catalyst with the composite oxide content of 3.2%.
As a specific example of the preparation method of the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether, when the composite oxide is Al 2 O 3 -Cr 2 O 3, the preparation method of the catalyst is as follows:
Soaking zeolite in sulfuric acid with the volume fraction of 12.5% for 24H at a solid-to-liquid ratio of 1:40, washing to be neutral, and drying at 120 ℃, adding 0.333g of Al 2 (SO 4) 3.18H 2 O and 0.196g of Cr 2 (SO 4) 3.6H 2 O into a proper amount of distilled water, soaking onto 12.558g of acid-modified zeolite in an equal volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8H, drying at 120 ℃, grinding and screening, and roasting at 800 ℃ for 6H to obtain the Al 2 O 3 -Cr 2 O 3/zeolite catalyst with the composite oxide content of 1%.
The application of the catalyst for preparing the polyoxymethylene dimethyl ethers from dimethyl ethers is to use the catalyst in preparing the polyoxymethylene dimethyl ethers from dimethyl ethers.
As a specific embodiment of the application of the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether, the application condition of the catalyst in the preparation of the polymethoxy dimethyl ether from the dimethyl ether is that a fixed bed is used as a reactor, the molar ratio of raw material dimethyl ether to mixed gas is 8.5: 1-1: 1, the reaction is carried out in a continuous flow fixed bed reactor, the reaction space velocity is 2500-4500 h -1, the reaction temperature is 200-320 ℃, the reaction pressure is normal pressure, and the reaction time is 10-40 h, wherein the mixed gas is nitrogen and oxygen with the molar ratio of 1: 1.
the structural formula of the dimethyl ether is CH 3 -O-CH 3, C-O bonds are broken through a catalyst, generated CH 3 -O-, CH 3 -groups are freely combined to synthesize CH 3 O-CH 2 O-CH 3 (DMM), DMM is used as raw material feeding, a-CH 2 O-group is more easily generated, carbon chain growth is promoted, and a CH 3 O- (CH 2 O) x-CH 3 polymer is obtained, so that the DMM and the dimethyl ether and the like are used as raw materials to be fed together, and the yield of the DMMx can be effectively improved to a certain extent.
Further, in the specific process of synthesizing DMMx, the catalyst of the invention takes a fixed bed as a reactor, and adopts a two-stage reaction mode: firstly, dimethyl ether and mixed gas are fed to synthesize DMM and pure DMM is separated out, and secondly, dimethyl ether, mixed gas and further generated DMM are fed to synthesize DMMx.
Compared with the prior art, the invention has the following beneficial effects:
1. The present invention adopts zeolite as catalyst carrier, and has wide material source and low cost.
2. The composite oxide/zeolite catalyst has high conversion rate, high catalytic activity and good stability, and under the reaction temperature of 200-320 ℃, the conversion rate of DME is 30-50%, and the selectivity of DMMx is 80-95%.
3. The reaction process adopted by the invention is not limited to two-step reaction, and has great reference value for the synthesis process of DMMx.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
In this example, TiO 2 -ZnO is used as the composite oxide, and the specific preparation process of the catalyst is as follows:
Soaking 12.5 volume percent of sulfuric acid into zeolite at a solid-to-liquid ratio of 1:40 for 24 hours, washing to be neutral, drying at 120 ℃, adding 0.454g of Zn (NO 3) 2.6H 2 O and 0.287g of TiCl 4 into a proper amount of distilled water, soaking in 4.681g of acid-modified zeolite in the same volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8 hours, drying at 120 ℃, grinding and sieving, and roasting at 600 ℃ for 5 hours to obtain the TiO 2 -ZnO/zeolite catalyst with the composite oxide content of 5%.
The catalyst of the embodiment is used for preparing polymethoxy dimethyl ether by dimethyl ether:
the molar ratio of dimethyl ether and mixed gas (nitrogen and oxygen, the molar ratio is 1:1) is 4.5:1, the reaction is carried out in a continuous flowing fixed bed reactor, the reaction space velocity, the reaction temperature and the reaction pressure of a first fixed bed reactor and a second fixed bed reactor are consistent, the reaction space velocity is 3200h -1, the reaction temperature is 220 ℃, the reaction pressure is normal pressure, the total reaction time of the two stages is 18h, the conversion rate of the dimethyl ether is 41.3 percent, and the total selectivity of DMMx is 94.8 percent.
Example 2
In the embodiment, TiO 2 -V 2 O 5 is used as a composite oxide, and the specific preparation process of the catalyst is as follows:
Soaking 15 volume percent of sulfuric acid in zeolite at a solid-to-liquid ratio of 1:40 for 24 hours, washing to be neutral, drying at 120 ℃, adding 0.190g of vanadyl sulfate pentahydrate and 0.143g of TiCl 4 into a proper amount of distilled water, soaking in 8.360g of acid-modified zeolite in an equal volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8 hours, drying at 120 ℃, grinding and sieving, and roasting at 500 ℃ for 6 hours to obtain the TiO 2 -V 2 O 5/zeolite catalyst with the composite oxide content of 2.3%.
The catalyst of the embodiment is used for preparing polymethoxy dimethyl ether by dimethyl ether:
The raw material dimethyl ether and the mixed gas (nitrogen and oxygen, the molar ratio is 1:1) have the molar ratio of 8.5:1, the reaction is carried out in a continuous flowing fixed bed reactor, the reaction space velocity, the reaction temperature and the reaction pressure of a first fixed bed reactor and a second fixed bed reactor are consistent, the reaction space velocity is 4000h -1, the reaction temperature is 250 ℃, the reaction pressure is normal pressure, the total reaction time of the two stages is 32h, the conversion rate of the dimethyl ether is 30.9 percent, and the total selectivity of DMMx is 82.5 percent.
Example 3
in the embodiment, SiO 2 -Al 2 O 3 is used as the composite oxide, and the specific preparation process of the catalyst is as follows:
soaking 8% volume fraction sulfuric acid in solid-to-liquid ratio of 1:40 for 24 hr, washing to neutrality, stoving at 120 deg.c, soaking Al 2 (SO 4) 3.18H 2 O in 1.067g and H 2 SiO 3 in 0.125g in distilled water in the same volume to 6.068g acid modified zeolite, shaking and stirring at 60 deg.c for 2.5 hr, standing for 8 hr, stoving at 120 deg.c, grinding, sieving and roasting at 800 deg.c for 6 hr to obtain SiO 2 -Al 2 O 3/zeolite catalyst with composite oxide content of 4.1%.
The catalyst of the embodiment is used for preparing polymethoxy dimethyl ether by dimethyl ether:
The raw material dimethyl ether and the mixed gas (nitrogen and oxygen, the molar ratio is 1:1) have the molar ratio of 6:1, the reaction is carried out in a continuously flowing fixed bed reactor, the reaction space velocity, the reaction temperature and the reaction pressure of a first-stage fixed bed reactor and a second-stage fixed bed reactor are consistent, the reaction space velocity is 2500h < -1 >, the reaction temperature is 200 ℃, the reaction pressure is normal pressure, and the total reaction time of the two-stage reaction is 10 h. The conversion of dimethyl ether was 38.8% with a total selectivity of DMMx of 81.2%.
Example 4
In the embodiment, Al 2 O 3 -MoO 3 is used as the composite oxide, and the specific preparation process of the catalyst is as follows:
soaking zeolite in sulfuric acid with the volume fraction of 2% for 24H according to the solid-to-liquid ratio of 1:40, washing to be neutral, drying at 120 ℃, adding 0.981g of Al 2 (SO 4) 3.18H 2 O and 1.818g of ammonium molybdate tetrahydrate into a proper amount of distilled water, soaking the mixture on 10.945g of acid-modified zeolite in the same volume, shaking and stirring at 60 ℃ for 2.5H, standing for 8H, drying at 120 ℃, grinding and sieving, and roasting at 800 ℃ for 8H to obtain the Al 2 O 3 -MoO 3/zeolite catalyst with the composite oxide content of 3.2%.
The catalyst of the embodiment is used for preparing polymethoxy dimethyl ether by dimethyl ether:
The raw material dimethyl ether and the mixed gas (nitrogen and oxygen, the molar ratio is 1:1) are reacted in a continuously flowing fixed bed reactor, the reaction space velocity, the reaction temperature and the reaction pressure of the first and second fixed bed reactors are consistent, the reaction space velocity is 4500h -1, the reaction temperature is 320 ℃, the reaction pressure is normal pressure, the total reaction time of the two stages is 40h, the conversion rate of the dimethyl ether is 41.5 percent, and the total selectivity of DMMx is 88.3 percent.
example 5
In the embodiment, Al 2 O 3 -Cr 2 O 3 is used as the composite oxide, and the specific preparation process of the catalyst is as follows:
soaking zeolite in sulfuric acid with the volume fraction of 12.5% for 24H at a solid-to-liquid ratio of 1:40, washing to be neutral, and drying at 120 ℃, adding 0.333g of Al 2 (SO 4) 3.18H 2 O and 0.196g of Cr 2 (SO 4) 3.6H 2 O into a proper amount of distilled water, soaking onto 12.558g of acid-modified zeolite in an equal volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8H, drying at 120 ℃, grinding and screening, and roasting at 800 ℃ for 6H to obtain the Al 2 O 3 -Cr 2 O 3/zeolite catalyst with the composite oxide content of 1%.
The catalyst of the embodiment is used for preparing polymethoxy dimethyl ether by dimethyl ether:
The molar ratio of dimethyl ether and mixed gas (nitrogen and oxygen, the molar ratio is 1:1) is 2.1:1, the reaction is carried out in a continuously flowing fixed bed reactor, the reaction space velocity, the reaction temperature and the reaction pressure of a first fixed bed reactor and a second fixed bed reactor are consistent, the reaction space velocity is 3800h -1, the reaction temperature is 240 ℃, the reaction pressure is normal pressure, the total reaction time of the two stages is 28h, the conversion rate of dimethyl ether is 49.2 percent, and the total selectivity of DMMx is 90.9 percent.
Comparative example 1
This comparative example is a comparison of example 1, with the composite oxide being changed to one of ZnO or TiO 2:
ZnO is adopted as an active component, and the specific preparation process of the catalyst is as follows:
taking 12.5 percent volume fraction sulfuric acid, soaking zeolite for 24 hours according to a solid-to-liquid ratio of 1:40, washing to be neutral, drying at 120 ℃, adding 0.935g of Zn (NO 3) 2.6H 2 O into a proper amount of distilled water, soaking the mixture on 4.681g of acid modified zeolite in an equal volume, shaking and stirring fully, slowly stirring the mixture for 2.5 hours at 60 ℃, standing for 8 hours, drying at 120 ℃, grinding and sieving, and roasting at 600 ℃ for 5 hours to obtain the TiO 2 -ZnO/zeolite catalyst with the composite oxide content of 5 percent.
The active ingredient is changed into TiO 2, and under the same catalyst preparation condition and reaction condition, the conversion rate of dimethyl ether is 14.8 percent, and the total selectivity of DMMx is 55.2 percent.
Comparative example 2
This comparative example is a comparison of example 5, with the composite oxide changed to only one of Al 2 O 3 or Cr 2 O 3:
the Cr 2 O 3 is adopted as an active component, and the specific preparation process of the catalyst is as follows:
taking 12.5 percent volume fraction sulfuric acid, soaking zeolite for 24 hours according to a solid-to-liquid ratio of 1:40, washing to be neutral, drying at 120 ℃, adding 0.327g of Cr 2 (SO 4) 3.6H 2 O into a proper amount of distilled water, soaking 12.558g of acid modified zeolite in the same volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8 hours, drying at 120 ℃, grinding and sieving, and roasting at 800 ℃ for 6 hours to obtain the Cr 2 O 3/zeolite catalyst with the composite oxide content of 1 percent.
The active ingredient is changed into Al 2 O 3, and under the same catalyst preparation condition and reaction condition, the conversion rate of dimethyl ether is 15.5 percent, and the total selectivity of DMMx is 56.1 percent.
Comparative example 3
This comparative example is that of example 1, with TiO 2 -ZnO as the composite oxide, the catalyst was specifically prepared without acidification:
0.454g of Zn (NO 3) 2 & 6H 2 O and 0.287g of TiCl 4 are added into a proper amount of distilled water, dipped on 4.681g of zeolite in equal volume, stirred sufficiently with shaking, stirred slowly at 60 ℃ for 2.5 hours, then kept stand for 8 hours, dried at 120 ℃, ground, sieved and calcined at 600 ℃ for 5 hours to obtain the TiO 2 -ZnO/zeolite catalyst with the composite oxide content of 5 percent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (9)
1. the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether is characterized in that zeolite is used as a carrier, and a composite oxide/zeolite catalyst of a composite oxide is loaded on the carrier, wherein the zeolite accounts for 95-99% of the total mass of the catalyst, the composite oxide accounts for 1-5% of the total mass of the catalyst, and the composite oxide is one of TiO 2 -ZnO, TiO 2 -V 2 O 5 2 -Al 2 O 3, Al 2 O 3 -MoO 3 and Al 2 O 3 -Cr 2 O 3.
2. The method for preparing catalyst of dimethyl ether to prepare polymethoxy dimethyl ether according to claim 1, wherein the preparation method comprises soaking zeolite with sulfuric acid, washing to neutrality, oven drying, soaking the zeolite modified with sulfuric acid with mixed salt solution of composite oxide in equal volume, shaking, stirring, standing, oven drying, grinding, sieving, and calcining to obtain the composite oxide/zeolite catalyst.
3. The method for preparing catalyst for preparing polyoxymethylene dimethyl ethers according to claim 2, wherein when the composite oxide is TiO 2 -ZnO, the method for preparing the catalyst is as follows:
soaking 12.5 volume percent of sulfuric acid into zeolite at a solid-to-liquid ratio of 1:40 for 24 hours, washing to be neutral, drying at 120 ℃, adding 0.454g of Zn (NO 3) 2.6H 2 O and 0.287g of TiCl 4 into a proper amount of distilled water, soaking the mixture on 4.681g of acid-modified zeolite in an equal volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8 hours, drying at 120 ℃, grinding and sieving, and roasting at 600 ℃ for 5 hours to obtain the TiO 2 -ZnO/zeolite catalyst with the composite oxide content of 5%.
4. The method for preparing catalyst for preparing polymethoxy dimethyl ether according to claim 2, wherein when the composite oxide is TiO 2 -V 2 O 5, the method for preparing catalyst is as follows:
Soaking 15 volume percent of sulfuric acid in zeolite at a solid-to-liquid ratio of 1:40 for 24 hours, washing to be neutral, drying at 120 ℃, adding 0.190g of vanadyl sulfate pentahydrate and 0.143g of TiCl 4 into a proper amount of distilled water, soaking in 8.360g of acid-modified zeolite in an equal volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8 hours, drying at 120 ℃, grinding and sieving, and roasting at 500 ℃ for 6 hours to obtain the TiO 2 -V 2 O 5/zeolite catalyst with the composite oxide content of 2.3%.
5. The method for preparing catalyst for preparing polymethoxy dimethyl ether from dimethyl ether according to claim 2, wherein when the composite oxide is SiO 2 -Al 2 O 3, the method for preparing catalyst is as follows:
soaking 8% volume fraction sulfuric acid in solid-to-liquid ratio of 1:40 for 24 hr, washing to neutrality, stoving at 120 deg.c, soaking 1.067g Al 2 (SO 4) 3.18H 2 O and 0.125g H 2 SiO 3 in distilled water in the same volume to 6.068g acid modified zeolite, shaking and stirring at 60 deg.c for 2.5 hr, standing for 8 hr, stoving at 120 deg.c, grinding, sieving and roasting at 800 deg.c for 6 hr to obtain SiO 2 -Al 2 O 3/zeolite catalyst with composite oxide content of 4.1%.
6. the method for preparing catalyst for preparing polymethoxy dimethyl ether according to claim 2, wherein when the composite oxide is Al 2 O 3 -MoO 3, the method for preparing catalyst is as follows:
Soaking zeolite in sulfuric acid with the volume fraction of 2% for 24H according to the solid-to-liquid ratio of 1:40, washing to be neutral, drying at 120 ℃, adding 0.981g of Al 2 (SO 4) 3.18H 2 O and 1.818g of ammonium molybdate tetrahydrate into a proper amount of distilled water, soaking the mixture on 10.945g of acid-modified zeolite in the same volume, shaking and stirring at 60 ℃ for 2.5 hours, standing for 8H, drying at 120 ℃, grinding and sieving, and roasting at 800 ℃ for 8H to obtain the Al 2 O 3 -MoO 3/zeolite catalyst with the composite oxide content of 3.2%.
7. The method for preparing catalyst for preparing polymethoxy dimethyl ether according to claim 2, wherein when the composite oxide is Al 2 O 3 -Cr 2 O 3, the method for preparing catalyst is as follows:
Soaking zeolite in 12.5 vol% sulfuric acid in solid-to-liquid ratio of 1 to 40 for 24 hr, washing to neutrality, stoving at 120 deg.c, soaking Al 2 (SO 4) 3.18H 2 O in 0.333g and Cr 2 (SO 4) 3.6H 2 O in 12.558g of acid modified zeolite in distilled water in the same volume, shaking and stirring at 60 deg.c for 2.5 hr, standing for 8 hr, stoving at 120 deg.c, grinding, sieving and roasting at 800 deg.c for 6 hr to obtain Al 2 O 3 -Cr 2 O 3/zeolite catalyst with composite oxide content of 1%.
8. The use of the catalyst for preparing polyoxymethylene dimethyl ethers according to claim 1, wherein the catalyst is used in the preparation of polyoxymethylene dimethyl ethers from dimethyl ethers.
9. The application of the catalyst for preparing the polymethoxy dimethyl ether from the dimethyl ether as claimed in claim 8 is characterized in that the application conditions of the catalyst in preparing the polymethoxy dimethyl ether from the dimethyl ether are that a fixed bed is adopted as a reactor, the molar ratio of raw material dimethyl ether to mixed gas is 8.5: 1-1: 1, the reaction is carried out in a continuous flow fixed bed reactor, the reaction space velocity is 2500-4500 h -1, the reaction temperature is 200-320 ℃, the reaction pressure is normal pressure, and the retention time is 10-40 h, wherein the mixed gas is nitrogen and oxygen with the molar ratio of 1: 1.
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