CN-122010699-A - Polymethoxy dimethyl ether synthesis process based on high-load acidic catalyst

CN122010699ACN 122010699 ACN122010699 ACN 122010699ACN-122010699-A

Abstract

The invention discloses a polymethoxy dimethyl ether synthesis process based on a high-load acidic catalyst, and belongs to the technical field of chemical production processes. The process takes methanol or dimethyl ether as a raw material, adopts a molecular sieve for dehydration pretreatment, adopts a high-load acid catalyst in a fixed bed reactor to perform one-step oxidation condensation, and then performs standing liquid separation, double-tower rectification, molecular sieve dehydration and filter membrane filtration to finish product refining, wherein a Mo-V/W composite oxidation active center is constructed by taking mesoporous silica of the high-load acid catalyst as a carrier, and is matched with a gradient acid site of strong acid in a strong acid-pore inlet/surface in a pore channel, and the outer surface is subjected to hydrophobic passivation treatment to realize multifunctional synergistic catalysis. The process simplifies the traditional complex flow, greatly improves the selectivity and the product purity of the target product, has stable structure and long service life, and the obtained product meets the diesel oil mixing requirement, can effectively support combustion and reduce emission in high altitude scenes and the like, and has good industrial application prospect.

Inventors

Ding Zhenjing
LI HAIYUN
XU XINWANG
DU YINGLING
LIU SHUNJIANG
BAI PENG

Assignees

义乌市嘉坤新能源有限公司
山东省天大金达生命科学工程研究院有限公司

Dates

Publication Date: 20260512
Application Date: 20260129

Claims (10)

1. The polymethoxy dimethyl ether synthesis process based on the high-load acid catalyst is characterized by comprising the following steps of: (1) Dehydrating the raw materials by using a molecular sieve until the moisture content is less than or equal to 0.1 weight percent to obtain a pretreated raw material; (2) Mixing a high-load acid catalyst with an equal-volume ceramic ring, filling the mixture in the middle of a fixed bed reactor, and filling both ends with quartz sand; (3) Purging the reactor with nitrogen for 30-60min, heating to 200-240 ℃, regulating the pressure to 0.5-1.5MPa, introducing raw materials and oxygen, controlling the space velocity of the feed to 0.8-2.0h -1 , introducing nitrogen as carrier gas, continuously reacting, and collecting condensed liquid phase products; (4) Standing and layering the liquid phase product at room temperature, separating to remove water phase, adopting a double-tower rectification process, removing light components by adopting a light component removal tower top pressure of 0.08-0.12MPa and a temperature of 38-50 ℃, collecting a 130-160 ℃ fraction by adopting a product rectification tower top pressure of 0.04-0.06MPa, introducing the 130-160 ℃ fraction into a 3A molecular sieve column to dehydrate until the water content is less than or equal to 0.05wt%, and filtering by adopting a 0.22 mu m filter membrane to obtain the polymethoxy dimethyl ether.
2. The process for synthesizing polymethoxy dimethyl ether based on the high-load acidic catalyst according to claim 1, wherein the raw material in (1) is methanol or dimethyl ether.
3. The process for synthesizing polymethoxy dimethyl ether based on high load acid catalyst according to claim 1, wherein the loading of the high load acid catalyst in (2) is 30% -40% of the effective volume of the fixed bed reactor.
4. The process for synthesizing polymethoxy dimethyl ether based on the high-load acidic catalyst according to claim 1, wherein the volume space velocity of nitrogen purging in the step (3) is 600-1200h -1 based on the effective volume of the fixed bed reactor, the temperature is raised to 200-240 ℃ when the raw material is methanol, the temperature is raised to 210-240 ℃ when the raw material is dimethyl ether, the pressure is regulated to 0.5-1.5MPa when the raw material is methanol, the pressure is regulated to 0.5-1.0MPa when the raw material is dimethyl ether, the pressure is regulated to 0.8-1.5MPa when the raw material is dimethyl ether, the introducing molar ratio of the raw material and oxygen is methanol: oxygen=1:0.5-1, the volume fraction of the introduced nitrogen is 20-35% of the total feed gas volume, and the total feed gas volume is the sum of the feed gas volumes of the raw material, oxygen and nitrogen.
5. The process for synthesizing polymethoxy dimethyl ether based on high-load acidic catalyst according to claim 1, wherein the theoretical plate number of the light component removing tower in the step (4) is 18-22, and the theoretical plate number of the product rectifying tower is 28-32.
6. The process for synthesizing polymethoxy dimethyl ether based on the high-load acid catalyst according to claim 1, wherein the preparation method of the high-load acid catalyst is as follows: S1, adding mesoporous silica into a dilute nitric acid solution, stirring for 1-3 hours at room temperature, filtering, washing with deionized water until the pH value of filtrate is neutral, and drying to obtain a pretreatment carrier; S2, adding one of ammonium molybdate and ammonium metavanadate or ammonium tungstate into deionized water, stirring until the ammonium molybdate and the ammonium metavanadate or the ammonium tungstate are dissolved to obtain a precursor aqueous solution, dripping the precursor aqueous solution onto a pretreatment carrier until the liquid level just drops out of the pretreatment carrier, performing ultrasonic treatment and stirring for 2-3 hours at room temperature, standing for 12-24 hours, filtering, drying, then placing in a tube furnace, introducing nitrogen-hydrogen mixed gas, heating to 400-600 ℃ at a rate of 3-7 ℃ per minute, preserving heat for 3-5 hours, and cooling to room temperature to obtain a carrier loaded with oxidative active centers; S3, placing a carrier carrying an oxygen active center in a quartz boat, placing the quartz boat in a constant temperature area of a horizontal tube furnace, introducing nitrogen as carrier gas, heating to 120-140 ℃, then introducing SO 3 steam, performing constant temperature deposition for 1-2h, stopping introducing SO 3 steam after the deposition is finished, heating the furnace to 180-220 ℃, treating for 30-60min at the temperature, cooling to room temperature, adding an ethanol solution of p-toluenesulfonic acid, stirring for 3-5h at room temperature, filtering, drying, transferring to a muffle furnace, heating to 200-240 ℃ under the air atmosphere, performing heat treatment for 1.5-2.5h, and cooling to room temperature to obtain a high-load acidic catalyst precursor; S4, dispersing the high-load acid catalyst precursor in ethanol, adding dimethyl dichlorosilane, stirring for 4-8 hours at room temperature, filtering, washing with anhydrous toluene for 2-3 times, and drying to obtain the high-load acid catalyst.
7. The process for synthesizing polymethoxy dimethyl ether based on the high-load acidic catalyst according to claim 6, wherein the pore diameter of the mesoporous silica S1 is 2-5nm, the specific surface area is more than or equal to 600m 2 /g, the dosage ratio of the mesoporous silica to the dilute nitric acid solution is 1g:5-10ml, and the concentration of the dilute nitric acid solution is 5-10wt%.
8. The process for synthesizing polymethoxy dimethyl ether based on the high-load acidic catalyst according to claim 6, wherein the molar ratio of ammonium molybdate to ammonium metavanadate or ammonium tungstate in S2 is 3-5:1, the total mass fraction of solutes in the precursor aqueous solution is 5-8wt%, the introducing rate of the nitrogen-hydrogen mixed gas is 1000-2000h -1 based on the effective volume of the tubular furnace, and the volume ratio of nitrogen to hydrogen in the nitrogen-hydrogen mixed gas is 95:5.
9. The process for synthesizing polymethoxy dimethyl ether based on the high-load acidic catalyst according to claim 6, wherein the introducing rate of nitrogen in the S3 is based on the effective volume of a horizontal tube furnace, the introducing rate of steam with the volume space velocity of 800-1500h -1 ;SO 3 is 0.3-1.0 ml/min.10 g of carrier with an oxygen active center, the using amount ratio of the carrier with the oxygen active center to the ethanol solution of p-toluenesulfonic acid is 1g:4-8ml, and the concentration of p-toluenesulfonic acid in the ethanol solution of p-toluenesulfonic acid is 8-15wt%.
10. The process for synthesizing polymethoxy dimethyl ether based on the high-load acid catalyst according to claim 6, wherein the dosage ratio of the high-load acid catalyst precursor, the ethanol and the dimethyl dichlorosilane in the S4 is 1g:8-12ml:0.06-0.15g.

Description

Polymethoxy dimethyl ether synthesis process based on high-load acidic catalyst Technical Field The invention relates to the technical field of chemical production processes, in particular to a polymethoxy dimethyl ether synthesis process based on a high-load acidic catalyst. Background The polymethoxy dimethyl ether (PODE n) is used as a novel clean fuel additive, has the characteristics of high oxygen content, excellent cetane number, good intersolubility with diesel oil and the like, can obviously improve the combustion efficiency of the diesel oil, reduces the emission of carbon monoxide (CO), nitrogen oxide (NO x) and Particulate Matters (PM), has important application value in the field of fuel oil optimization under special environments such as high altitude hypoxia and the like, and becomes a research hotspot in the fields of chemical industry and energy. At present, the synthesis process of PODE is mainly focused on the oxidative condensation reaction using methanol or dimethyl ether as raw materials, but the prior art still has a plurality of key problems to be solved urgently. Firstly, in the aspect of a synthetic route, the traditional process mostly adopts a two-step method, namely, a formaldehyde intermediate is prepared by oxidizing methanol, and then formaldehyde and methanol/dimethyl ether are subjected to condensation reaction to generate PODE, and the route has the defects of long flow, high energy consumption for separating the intermediate product, low overall production efficiency and the like, and is difficult to meet the requirement of industrial continuous production. Secondly, the catalyst performance is a core bottleneck for limiting the product quality, the existing catalyst mostly adopts a single acid site or single metal active center design, the acid sites are unordered in distribution, the active centers are easy to agglomerate, the raw material activation efficiency is low, the chain growth process cannot be accurately regulated, the selectivity of the target product is low, the ratio of byproducts such as low-polymerization PODE 1-2, high-polymerization PODE 7+ and the like is too high, and the combustion performance of the mixed fuel is seriously influenced. Meanwhile, the traditional catalyst lacks effective control on oxidation depth, so that excessive oxidation of raw materials is easy to generate CO x byproducts, the utilization rate of raw materials is reduced, and the subsequent separation cost is increased. In addition, the existing catalyst has insufficient structural stability, the active center is easy to be deactivated due to sintering and carbon deposition blockage, the activity is greatly reduced after long-time operation, and the requirement of long-term industrial application is difficult to be met. Furthermore, the problems of wide distribution of polymerization degree and high impurity content of the product are prominent. Because the catalyst lacks the structural design of directional regulation and control chain growth, the polymerization degree distribution in the PODE product obtained by the prior art is scattered, the content of impurities such as residual moisture, paraformaldehyde and the like is higher, the problems of poor atomization, blockage of an oil nozzle and the like are easy to occur after the PODE product is mixed with diesel, and the combustion-supporting and emission-reducing effects cannot be fully exerted especially in a high-altitude low-oxygen environment. Disclosure of Invention The invention aims to solve the defects in the prior art, and provides a polymethoxy dimethyl ether synthesis process based on a high-load acidic catalyst. In order to achieve the aim, the invention adopts the following technical scheme that the polymethoxy dimethyl ether synthesis process based on the high-load acid catalyst comprises the following steps: (1) Dehydrating the raw materials by using a molecular sieve until the moisture content is less than or equal to 0.1 weight percent to obtain a pretreated raw material; (2) Mixing a high-load acid catalyst with an equal-volume ceramic ring, filling the mixture in the middle of a fixed bed reactor, and filling both ends with quartz sand; (3) Purging the reactor with nitrogen for 30-60min, heating to 200-240 ℃, regulating the pressure to 0.5-1.5MPa, introducing raw materials and oxygen, controlling the space velocity of the feed to 0.8-2.0h -1, introducing nitrogen as carrier gas, continuously reacting, and collecting condensed liquid phase products; (4) Standing and layering the liquid phase product at room temperature, separating to remove water phase, adopting a double-tower rectification process, removing light components by adopting a light component removal tower top pressure of 0.08-0.12MPa and a temperature of 38-50 ℃, collecting a 130-160 ℃ fraction by adopting a product rectification tower top pressure of 0.04-0.06MPa, introducing the 130-160 ℃ fraction into a 3A molecular sieve column to dehydrat