A method for catalytically synthesizing dimethoxymethane and dimethyl carbonate from carbon monoxide, methanol and methyl nitrite in the gas phase

Abstract

The present invention discloses a novel process for catalytic gas-phase synthesis of dimethoxymethane and dimethyl carbonate from carbon monoxide, methanol and methyl nitrite, belonging to the technical field of chemical production. This process uses carbon monoxide, methanol and methyl nitrite as raw materials, and the catalyst is a novel and efficient molecular sieve catalyst containing Pd and / or Ti metal. The molecular sieve support is one or a combination of two of Ti-MWW, TS-1, MCM-22, ITQ-1, S-1, and NaY molecular sieves. By using a fixed-bed reactor, under the conditions of a reaction temperature of 80-160 °C and a reaction pressure of 0.1-2.0 MPa, the efficient and green synthesis of dimethoxymethane and dimethyl carbonate is realized, and it has certain industrial application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical fields of chemical raw material production and new catalyst development, and particularly relates to a method for catalytically synthesizing dimethoxymethane and dimethyl carbonate from carbon monoxide, methanol and methyl nitrite in the gas phase and a preparation method of a catalyst used therefor. Background Art

[0002] Dimethoxymethane (DMM), also known as methylal, has the molecular formula C3H8O2 and is an important chemical raw material, mainly used for the production of anion exchange resins and as a green solvent to replace toxic organic solvents. Due to its high oxygen content and physical properties similar to diesel, dimethoxymethane and its derivatives can be used as diesel additives to improve the cetane number of diesel, promote the conversion of combustion energy into kinetic energy, and reduce the emission of harmful substances in diesel engine exhaust. Due to the increasing concern about the exhaust gas and carbon dioxide emissions generated by the combustion of fossil fuels, researchers have conducted in-depth studies on the search for clean fuels and renewable fuels. OMEs (Oxymethylene dimethyl ethers) are considered to be promising oxygenates for solving the diesel engine exhaust problem. Dimethoxymethane (OME1), as the simplest compound in the OME family, can provide a high yield of OME when reacting with formaldehyde. 3-5 However, at present, the industrial methods for synthesizing dimethoxymethane at home and abroad are mainly the alcohol-aldehyde condensation method, using liquid acid as a catalyst, which has strict requirements for equipment, high energy consumption, long process flow, a large amount of three wastes, and serious environmental pollution. Therefore, there is an urgent need for an efficient and environmentally friendly dimethoxymethane synthesis process.

[0003] At present, the direct synthesis of dimethoxymethane from carbon dioxide hydrogenation, the direct synthesis of dimethoxymethane from methanol dehydrogenation, and the direct oxidation of methanol to dimethoxymethane are three synthesis routes that have been studied more.

[0004] Katharina Thenert et al. described an organometallic catalytic system for the direct synthesis of dimethoxymethane by hydrogenating carbon dioxide using a ruthenium triphosphate catalyst (Ruthenium-Catalyzed Synthesis of Dialkoxymethane Ethers Utilizing Carbon Dioxide and Molecular Hydrogen, Katharina Thenert et al., Angew. Chem. Int. Ed., 2016, Vol. 55, p. 12266). The direct synthesis of dimethoxymethane by hydrogenating carbon dioxide first requires reducing CO2 to formaldehyde, and then the aldol condensation reaction of formaldehyde with methanol to synthesize dimethoxymethane. However, in the process of reducing CO2 to formaldehyde, the thermodynamic stability of the by-product formic acid is better than that of formaldehyde, resulting in extremely low selectivity of formaldehyde. Therefore, the selective synthesis of formaldehyde remains a challenge, and the reaction conditions are harsh. The low catalytic activity makes this attractive reduction route far from industrial application. Wu et al. further synthesized DMM by dehydrogenating methanol through Cu / SiO2 in a batch reactor. The selectivity is close to 100%, but the poor activity and the batch operation pose obstacles to practical application, and the catalytic mechanism is still unclear, and more efforts are needed in the dehydrogenation route (Direct Synthesis of Hydrogen and Dimethoxylmethane from Methanol on Copper / Silica Catalysts with Optimal Cu+ / CuO Sites, Wu et al., ChemCatChem, 2018, Vol. 10, p. 1140).

[0005] The above studies show that the two routes of directly synthesizing dimethoxymethane by hydrogenating carbon dioxide and directly synthesizing dimethoxymethane by dehydrogenating methanol require the participation of the intermediate formaldehyde. However, due to thermodynamic limitations in the direct synthesis of dimethoxymethane by hydrogenating carbon dioxide, the selectivity of the currently reported catalysts for formaldehyde is too low. The formation mechanism of formaldehyde and the final product in the direct synthesis of dimethoxymethane by dehydrogenating methanol is not clear, and the research on both routes is currently only at the laboratory stage. The low catalytic performance is also the key problem existing in both routes.

[0006] The direct oxidation of methanol to dimethoxymethane is a process that has been extensively studied. Researchers have made certain progress in the study of bifunctional catalysts based on rhenium, ruthenium, vanadium, molybdenum, etc. Yuan et al. discovered a binary metal oxide (SbRe2O6) composed of Re and Sb, which showed a 92.5% selectivity for dimethoxymethane when used to catalyze the oxidation of methanol, with a methanol concentration of 4 vol% and a conversion rate of 6.5% (Performance and Characterization of a NewCrystalline SbRe2O6 Catalyst for Selective Oxidation of Methanol to Methylal, Youzhu Yuan et al., J. Catal., 2000, Vol. 195, p. 51). Re / SiO2 prepared by Anthony Yoboue et al. via a one-pot sol-gel method exhibited an 89.1% selectivity for dimethoxymethane, with a methanol concentration of 4 vol% and a conversion rate of 40% (An easily accessible Re-based catalyst for the selective conversion ofmethanol: evidence for an unprecedented active site structure through combinedoperando techniques, Anthony Yoboue et al., Chem. Commun., 2011, Vol. 47, p. 4285). The SbRe2O6 catalyst used in US Patent US6403841 had a methanol concentration of 4 vol%, a methanol conversion rate of 12.3%, and a dimethoxymethane selectivity of 89%. The expensive rhenium element was introduced into the catalysts of the above patents, and the high-valent oxide of rhenium is volatile at high temperatures and easily causes the inactivation of the catalyst, which limits the practical application of this type of catalyst. The bifunctional catalyst Mo:Fe(2) / HZSM-5 designed by Yuanyu Tian et al. achieved a methanol conversion rate and a dimethoxymethane selectivity of 87.44% and 93% respectively, far higher than other research results. However, the preparation process of this catalyst is complex and the catalyst life is short (Effects of reaction conditions on one-step synthesis of methylal viamethanol oxidation catalyzed by Mo:Fe(2) / HZSM-5catalyst, Yuanyu Tian et al., nt JEnergy Res., 2021, Vol. 45, p. 7487).Chinese Patent Application Publication No. CN103933965A publicly reported a vanadium-titanium-based catalyst with methanol conversion and dimethoxymethane selectivity reaching 55.17% and 98.45% respectively, and the volume percentage of methanol in the feed gas being 2-15%. Chinese Patent Application Publication No. CN 112536048 A publicly reported a vanadium-titanium-based catalyst with methanol conversion and dimethoxymethane selectivity reaching 62.5% and 93.8% respectively.

[0007] The above research shows that the catalysts used in the direct oxidation of methanol to synthesize dimethoxymethane are still in the research stage. Catalyst deactivation is one of the main problems faced by this method. For example, the SbRe2O6 catalyst uses expensive rhenium element, and rhenium is volatile at the reaction temperature, resulting in catalyst deactivation. The lifespan of the Mo:Fe(2) / HZSM-5 bifunctional catalyst is short. Moreover, due to the explosion hazard of methanol in air, the concentration of methanol must be controlled within a certain range throughout the production process. Therefore, the industrial synthesis of dimethoxymethane by the direct oxidation of methanol has relatively high safety risks and difficulties in terms of process implementation.

[0008] Dimethyl carbonate (DMC), as an environmentally friendly chemical raw material, has a wide range of uses. As an important organic chemical intermediate, it can be used to produce polycarbonate, pharmaceuticals, pesticides and other products, replace phosgene, halogenated methane, and dimethyl sulfate as carbonylation and methylation reagents, and can be used as a solvent in the lithium battery electrolyte and paint and coating industries (accounting for more than 50% of the total DMC consumption in China). It is also expected to replace toxic methyl tert-butyl ether (MTBE) as a gasoline and diesel additive. According to statistics, since 2007, the market demand for DMC in China has shown exponential growth, and the demand for DMC in 2019 has reached 810,000 tons / year. At present, the methods for directly synthesizing dimethyl carbonate can be mainly divided into: phosgene method, oxidative carbonylation method, nitrite carbonylation method, transesterification method, one-step synthesis method of methanol / carbon dioxide, and urea alcoholysis method. The phosgene method has been gradually phased out due to the high toxicity of raw materials, poor safety, and serious environmental pollution; although the transesterification method is simple to operate and the reaction conditions are relatively mild, the process cost is high, and the separation and purification of products are relatively difficult; due to the use of homogeneous catalysts in the urea alcoholysis method, there are also problems with subsequent separation and purification; although the one-step synthesis method of methanol and carbon dioxide has the advantage of simple process, the reactant carbon dioxide is difficult to be activated, so the catalytic activities of the catalysts developed at present are generally low. The catalyst reported in Chinese Patent CN110479287A for the one-step synthesis of dimethyl carbonate from methanol and carbon dioxide has a methanol conversion rate of only 11%, a selectivity for dimethyl carbonate of 75%, and a yield of only 8%. The process route for synthesizing dimethyl carbonate by carbonylation of methyl nitrite and carbon monoxide has no pollution to the environment during the production process, and its catalysts mainly include chlorine-containing and chlorine-free Pd-based catalyst systems. The chlorine-containing catalyst needs to continuously add chlorine to the raw materials, which causes serious corrosion of the equipment. The chlorine-free catalyst has low conversion rate and selectivity and poor stability (Vapor Phase Carbonylation Reactions Using MethylNitrite Over Pd Catalysts, Yasushi Yamamoto, Catal.Surv.from Asia., 2010, Vol. 14, p. 103). The method for synthesizing dimethoxymethane and dimethyl carbonate from methanol, carbon monoxide and methyl nitrite described in the present invention has no pollution to the environment, and the chlorine-free catalyst used has the advantages of good stability, high catalytic activity and selectivity, and has certain industrial application prospects.

[0009] In summary, compared with the direct synthesis of dimethoxymethane by hydrogenation of carbon monoxide and the direct synthesis of dimethoxymethane by dehydrogenation of methanol, the one-step synthesis of dimethoxymethane from methanol has higher conversion and product selectivity. However, due to the explosion hazard of methanol in air, the concentration of methanol in air should be lower than 7%, which poses a great safety hazard in production. (Dimethoxymethane as a Cleaner Synthetic Fuel: Synthetic Methods, Catalysts, and Reaction Mechanism, Ruiyan Sun et al., ACS Catal., 2019, Vol. 9, p. 1298). The method of catalytically synthesizing dimethoxymethane and dimethyl carbonate from methanol, carbon monoxide and methyl nitrite avoids the direct contact between methanol and oxygen, so there is no need to consider the explosion risk. The catalyst for the process of synthesizing dimethyl carbonate by carbonylation of methyl nitrite and carbon monoxide mainly includes chlorine-containing and chlorine-free Pd-based catalyst systems. The chlorine-containing catalyst seriously corrodes the equipment, while the chlorine-free catalyst has low conversion, low selectivity and poor stability. There is no relevant literature report on the gas-phase synthesis of dimethoxymethane and dimethyl carbonate from methanol, carbon monoxide and methyl nitrite. Therefore, it is of great significance to develop a new process for synthesizing dimethoxymethane and dimethyl carbonate and design a catalyst with high stability, high selectivity and high activity. Summary of the Invention

[0010] Aiming at the above problems existing in the prior art, the purpose of the present invention is to provide a new process for synthesizing dimethoxymethane and co-producing dimethyl carbonate. This process proposes a process for catalytically synthesizing dimethoxymethane and dimethyl carbonate from methanol, carbon monoxide and methyl nitrite over a molecular sieve catalyst containing Pd and / or Ti metals, which solves the problems of complex process, high energy consumption and environmental pollution in the traditional industrial synthesis of dimethoxymethane and dimethyl carbonate. Compared with the currently studied one-step oxidation method of methanol to synthesize dimethoxymethane and the commonly used methods for synthesizing dimethyl carbonate, this process does not need to consider the explosion risk, and the catalyst used has high activity, high selectivity and high stability.

[0011] To achieve the above invention purpose, the present invention adopts the following technical solutions:

[0012] A method for synthesizing dimethoxymethane and dimethyl carbonate, using carbon monoxide, methanol and methyl nitrite as raw materials, loading a molecular sieve catalyst in a continuous reactor, continuously introducing carbon monoxide, methanol and methyl nitrite, and mainly undergoing three catalytic reactions to obtain dimethoxymethane, dimethyl carbonate and by-product methyl formate under the conditions of a reaction temperature of 80 to 160 °C and a reaction pressure of 0.1 to 2.0 MPa; the molecular sieve catalyst is a supported catalyst, including an active component and a carrier, the active component is one or two of Pd and Ti, the mass fraction of the active component is 0.01 to 2.50%, the carrier is one or a combination of two of Ti-MWW, TS-1, MCM-22, ITQ-1, S-1, NaY molecular sieves, the average particle size of the molecular sieve particles is 0.05 to 6.0 microns, and the three catalytic reactions are respectively 2CH3ONO + CO → (CH3O)2CO + 2NO, CH3OH + 2CH3ONO → (CH3O)2CH2 + 2NO + H2O and 4CH3ONO → CHOOCH3 + 2CH3OH + 4NO.

[0013] A method for synthesizing dimethoxymethane and dimethyl carbonate, and the preparation method of the modified catalyst containing Pd and / or Ti metal used therein includes the following steps:

[0014] 1) Molecular sieve pretreatment: Place the molecular sieve in an alkali solution with a concentration of 0.001 to 5 mol / L, pretreat it at 0 to 100 °C for 0.5 to 30 h, after treatment, perform solid-liquid separation, then place the molecular sieve solid in an ammonium chloride solution and stir for 1 to 3 hours, filter and wash the obtained sample until it is neutral, and dry it at 25 to 100 °C for 1 to 48 hours. In a muffle furnace, raise the temperature of the dried molecular sieve from room temperature to 200 to 600 °C at a certain heating rate and maintain it for 1 to 6 hours. Thereby, defect positions are formed inside the molecular sieve to facilitate the anchoring of metals later;

[0015] 2) Dissolve the Pd precursor and / or Ti precursor in one or a combination of two of water, dilute hydrochloric acid, acetic acid, methanol, ethanol, acetone, petroleum ether, benzene, toluene, dichloromethane, acetonitrile or ether, stir evenly to form a clear Pd and / or Ti precursor solution;

[0016] 3) Mix the modified molecular sieve obtained in step 1) with one or a combination of two of water, dilute hydrochloric acid, acetic acid, methanol, ethanol, acetone, petroleum ether, benzene, toluene, dichloromethane, acetonitrile or ether in a mass ratio of 1:0.5 - 50, stir for 1 - 3 hours, and gradually add a certain mass of the Pd and / or Ti precursor solution obtained in step 2) so that the theoretical mass content of Pd and / or Ti in the molecular sieve is 0.01% - 2.50%. Stir for 1 - 3 hours, filter and wash the obtained sample until it is neutral, and dry it at a temperature of 25 - 100 °C for 1 - 48 hours to obtain the molecular sieve loaded with the Pd and / or Ti precursor;

[0017] 4) In a muffle furnace, heat the molecular sieve obtained in step 3) from room temperature to 200 - 600 °C at a certain heating rate and hold for 1 - 6 hours to obtain the described molecular sieve catalyst.

[0018] As a preferred embodiment, in a method for synthesizing dimethoxymethane and dimethyl carbonate, the molar ratio of carbon monoxide:methanol:methyl nitrite:inert gas in the raw materials is 1:0.01 - 10:0.5 - 10:0.5 - 10, and the reaction space velocity is 1000 - 10000 h -1 , the inert gas is one or a combination of two of carbon dioxide, nitrogen, and argon, and the continuous reactor is a fixed-bed or fluidized-bed reactor.

[0019] In the method for synthesizing dimethoxymethane and dimethyl carbonate according to the present invention, the methanol conversion rate is 3 - 90%, the carbon monoxide conversion rate is 5 - 90%, the methyl nitrite conversion rate is 5 - 90%, and the selectivity S DMM / MN / % of dimethoxymethane is 20 - 95%, and the selectivity S DMC / MN / % of dimethyl carbonate is 1 - 50%, and the selectivity S MF / MN / % of methyl formate is 1 - 20%.

[0020] In the method for synthesizing dimethoxymethane and dimethyl carbonate according to the present invention, the reactant methyl nitrite is industrially produced by the reaction of methanol, air, and recycled NO, and the catalytic reaction equation is 2NO + 2CH3OH + 1 / 2O2 → 2CH3ONO + H2O.

[0021] As a preferred embodiment, the alkali solution in step 1) is one or a combination of two of methyl chloroalkali solution, ethyl chloroalkali solution, propyl chloroalkali solution, triethylamine solution, sodium carbonate solution, potassium carbonate solution, cesium carbonate solution, sodium hydroxide solution, lithium hydroxide solution, potassium hydroxide solution, and ammonia water solution.

[0022] As a preferred embodiment, the concentration of the ammonium chloride solution in step 1) is 0.001 - 5 mol / L, preferably 0.002 - 4 mol / L, the temperature of the ammonium chloride solution is 25 - 100 °C, preferably 30 - 90 °C, the treatment time is 0.5 - 6 h, preferably 0.5 - 6 h. The molecular sieve obtained by treating the ammonium chloride solution is calcined, and the temperature is raised from room temperature to 200 - 600 °C at a heating rate of 0.1 - 10 °C / min and maintained for 1 - 6 hours.

[0023] As a preferred embodiment, the Pd precursor in step 2) is one or a combination of two of palladium nitrate, palladium acetate, palladium chloride, ammonium chloropalladate, potassium chloropalladate, tetraamminepalladium chloride, tetraamminepalladium nitrate, dichlorodiamminepalladium, and sodium chloropalladate. The Ti precursor in step 2) is one or a combination of two of titanium tetrachloride, tetrabutyl titanate, isopropyl titanate, and titanium oxysulfate.

[0024] As a preferred embodiment, the heating rate in step 3) is 0.1 - 10 °C / min. For the molecular sieve catalyst obtained in step 4), the average particle size of the Pd particles is 0.2 - 10 nanometers.

[0025] For the method for synthesizing dimethoxymethane and dimethyl carbonate of the present invention, the catalyst used can introduce a forming step.

[0026] Compared with the prior art, the method for synthesizing dimethoxymethane and dimethyl carbonate from methanol, carbon monoxide, and methyl nitrite of the present invention and the preparation method of its catalyst have the following remarkable features:

[0027] (1) It solves the problems of complex process, high energy consumption, and environmental pollution in the traditional industrial synthesis of dimethoxymethane. Compared with the method for synthesizing dimethoxymethane by the one-step oxidation of methanol, which is studied more currently, this process synthesizes dimethoxymethane and dimethyl carbonate by the gas-phase reaction of carbon monoxide, methanol, and methyl nitrite. After separation, the non-condensable gas containing NO reacts with methanol and air through a non-catalytic reaction for the regeneration of CH3ONO. This process avoids the direct contact between oxygen and methanol, does not need to consider the risk of explosion, and the catalyst used has high activity, high selectivity, and high stability;

[0028] (2) There is currently no relevant literature report on the synthesis of dimethoxymethane and dimethyl carbonate from methanol, carbon monoxide, and methyl nitrite. The molecular sieve-supported Pd and / or Ti metal catalyst in the present invention exhibits excellent catalytic performance in the reaction of synthesizing dimethoxymethane and co-producing dimethyl carbonate by the low-pressure gas-phase method of methanol, carbon monoxide, and methyl nitrite;

[0029] (3) Treat the molecular sieve with a modified solution to form defect sites inside the molecular sieve, and load Pd and / or Ti metals. The formed Ti active sites and Pd active sites have higher catalytic activity and higher selectivity for dimethoxymethane and dimethyl carbonate. The defect sites formed inside the molecular sieve help the Pd and Ti metal particles to be evenly dispersed in the molecular sieve framework, preventing the agglomeration of Pd and Ti metals. The uniformly dispersed metals in the framework have higher catalytic activity and selectivity. By using modified solutions with different alkalinities and physical properties, different degrees and types of defects can be formed in the molecular sieve, and the active metals are located on the formed defects to regulate the content of metals in the framework. In addition, the Ti metal in the modified catalyst framework increases its Lewis acid amount, significantly improving the catalytic decomposition efficiency of methyl nitrite in the raw materials, thereby achieving high activity and high selectivity catalysis of the catalyst. Description of the Drawings

[0030] Figure 1 SEM diagram of the catalyst prepared in Example 1;

[0031] Figure 2 XRD diagram of the catalyst prepared in Example 1;

[0032] Figure 3 TEM diagram of the catalyst prepared in Example 1;

[0033] Figure 4 SEM diagram of the catalyst prepared in Example 2;

[0034] Figure 5 XRD diagram of the catalyst prepared in Example 2;

[0035] Figure 6 TEM diagram of the catalyst prepared in Example 2;

[0036] Figure 7 SEM diagram of the catalyst prepared in Example 3;

[0037] Figure 8 XRD diagram of the catalyst prepared in Example 3;

[0038] Figure 9 TEM diagram of the catalyst prepared in Example 3;

[0039] Figure 10 Schematic diagram of the gas-phase synthesis of dimethoxymethane and dimethyl carbonate from carbon monoxide, methanol and methyl nitrite. Detailed Description of the Invention

[0040] For the convenience of understanding the content of the present invention, the present invention will be described in detail below through embodiments. The embodiments are only for helping to understand the present invention and are not intended to limit the scope of the present invention. Since the present invention can also be described and explained by other solutions that do not deviate from the technical features of the present invention, all changes within the scope of the present invention or within the scope of equivalent inventions should fall within the protection scope of the present invention.

[0041] The present invention will be further elaborated below in conjunction with examples, comparative examples and application examples.

[0042] Example 1

[0043] 1) Molecular sieve pretreatment: Place the Ti-MWW molecular sieve in a lithium hydroxide alkali solution with a concentration of 0.001 mol / L, pretreat it at 25 °C for 30 h. After treatment, perform solid-liquid separation. Then place the molecular sieve solid in an ammonium chloride solution and stir for 3 hours. Filter and wash the obtained sample until it is neutral, and dry it at 25 °C for 48 hours. In a muffle furnace, heat the dried molecular sieve from room temperature to 200 °C at a heating rate of 0.1 °C / min and hold for 6 hours.

[0044] 2) Dissolve palladium chloride and titanium tetrachloride in a mixed solution of dilute hydrochloric acid and ethanol, stir evenly to form a clear Pd and Ti precursor solution;

[0045] 3) Mix the modified molecular sieve obtained in step 1) with a mixed solution of petroleum ether and benzene in a mass ratio of 1:50, stir for 1 hour, and gradually add a certain mass of the Pd and Ti precursor solution obtained in step 2) so that the theoretical mass content of Pd metal in the molecular sieve is 0.5%, and the theoretical mass content of Ti metal in the molecular sieve is 2.5%. Stir for 1 hour, filter and wash the obtained sample until it is neutral, and dry it at 30 °C for 48 hours to obtain a molecular sieve loaded with Pd and Ti precursors;

[0046] 4) In a muffle furnace, heat the molecular sieve obtained in step 3) from room temperature to 200 °C at a heating rate of 2 °C / min and hold for 6 hours to obtain the molecular sieve catalyst.

[0047] Figure 1 is the SEM image of the catalyst prepared in Example 1. It can be seen that the average particle size of the catalyst is 3 μm. Figure 2 is the XRD pattern of the catalyst prepared in Example 1. As can be seen from the figure, the prepared catalyst has high crystallinity. Figure 3 is the TEM image of the catalyst prepared in Example 1 after 3 hours of catalytic reaction. The average particle size of the metal particles is 2 nm, indicating that the two metals have a high degree of dispersion.

[0048] Example 2

[0049] 1) Molecular sieve pretreatment: Place the molecular sieve NaY in a KOH alkaline solution with a concentration of 0.2 mol / L and pretreat it at 50 °C for 20 h. After the treatment, perform solid-liquid separation. Then place the molecular sieve solid in an ammonium chloride solution and stir for 3 hours. Filter and wash the obtained sample until it is neutral, and dry it at 100 °C for 2 hours. In a muffle furnace, heat the dried molecular sieve from room temperature to 600 °C at a heating rate of 10 °C / min and hold for 1 hour.

[0050] 2) Dissolve ammonium chloropalladate and titanium isopropoxide in a mixed solution of ether and acetone, stir evenly to form a clear Pd and Ti precursor solution;

[0051] 3) Mix the modified molecular sieve obtained in step 1) with a mixed solution of ether and acetone in a mass ratio of 1:20, stir for 2 hours, and gradually add a certain mass of the Pd and Ti precursor solution obtained in step 2) so that the theoretical mass content of Pd metal in the molecular sieve is 2.5%, and the theoretical mass content of Ti metal in the molecular sieve is 2%. Stir for 2 hours, filter and wash the obtained sample until it is neutral, and dry it at 80 °C for 24 hours to obtain a molecular sieve loaded with Pd and Ti precursors;

[0052] 4) In a muffle furnace, heat the molecular sieve obtained in step 3) from room temperature to 600 °C at a heating rate of 10 °C / min and hold for 1 hour to obtain the described molecular sieve catalyst.

[0053] Figure 4 is the SEM image of the catalyst prepared in Example 2. It can be seen that the average size of the catalyst particles is 2 μm. Figure 5 is the XRD pattern of the catalyst prepared in Example 2. As can be seen from the figure, the prepared catalyst has high crystallinity. Figure 6 is the TEM image of the catalyst prepared in Example 2 after 3 hours of catalytic reaction. The average particle size of the metal particles is 5 nm, indicating that the two metals have high dispersion.

[0054] Example 3

[0055] 1) Place the S-1 molecular sieve in a triethylamine solution with a concentration of 4 mol / L and pretreat it at 60 °C for 5 h. After the treatment, perform solid-liquid separation. Then place the molecular sieve solid in an ammonium chloride solution and stir for 3 hours. Filter and wash the obtained sample until it is neutral, and dry it at 80 °C for 12 hours. In a muffle furnace, heat the dried molecular sieve from room temperature to 400 °C at a heating rate of 2 °C / min and hold for 4 hours.

[0056] 2) Dissolve palladium acetate and titanium isopropoxide in a mixed solution of acetone and methanol, stir evenly to form a clear Pd and Ti precursor solution;

[0057] 3) Mix the modified molecular sieve obtained in step 1) with the mixed solution of acetone and methanol in a mass ratio of 1:2, stir for 3 hours, and gradually add a certain mass of the Pd and Ti precursor solution obtained in step 2) so that the theoretical mass content of Pd metal in the molecular sieve is 2%, and the theoretical mass content of Ti metal in the molecular sieve is 0.02%. Stir for 3 hours, filter and wash the obtained sample until neutral, and dry it at 80 °C for 12 hours to obtain the molecular sieve loaded with Pd and Ti precursors.

[0058] 4) In a muffle furnace, heat the molecular sieve obtained in step 3) from room temperature to 300 °C at a heating rate of 1 °C / min and hold for 6 hours to obtain the described molecular sieve catalyst.

[0059] Figure 7 It is the SEM image of the catalyst prepared in Example 3. It can be seen that the a-axis of the S-1 molecular sieve crystal size is 170 - 240 nm, the b-axis is 60 - 130 nm, and the c-axis is 410 - 460 nm. Figure 8 It is the XRD pattern of the catalyst prepared in Example 3. As can be seen from the figure, the prepared catalyst has high crystallinity. Figure 9 It is the TEM image of the catalyst prepared in Example 3 after 3 hours of catalytic reaction. The average particle size of the metal particles is 2.1 nanometers, indicating that the two metals have high dispersion.

[0060] Comparative Example 1

[0061] 1) Dissolve appropriate amounts of palladium acetate and isopropyl titanate in the mixed solution of acetone and methanol, stir evenly to form a clear Pd and Ti precursor solution.

[0062] 2) Mix the commercially purchased α-Al2O3 with the mixed solution of acetone and methanol in a mass ratio of 1:2, stir for 3 hours, and gradually add a certain mass of the Pd and Ti precursor solution obtained in step 1) so that the theoretical mass content of Pd metal in α-Al2O3 is 2%, and the theoretical mass content of Ti metal in α-Al2O3 is 0.02%. Stir for 3 hours, filter and wash the obtained sample until neutral, and dry it at 80 °C for 12 hours.

[0063] 3) In a muffle furnace, heat the α-Al2O3 containing Pd and Ti precursors obtained in step 2) from room temperature to 300 °C at a heating rate of 1 °C / min and hold for 6 hours to obtain the α-Al2O3 catalyst containing palladium and titanium metals.

[0064] Comparative Example 2

[0065] 1) Dissolve ammonium chloropalladate and titanium isopropoxide in a mixed solution of diethyl ether and acetone, stir evenly to form a clear Pd and Ti precursor solution;

[0066] 2) Mix commercially purchased SiO2 with a mixed solution of diethyl ether and acetone at a mass ratio of 1:20, stir for 2 hours, gradually add a certain mass of the Pd and Ti precursor solution obtained in step 1) so that the theoretical mass content of Pd metal in SiO2 is 2.5%, and the theoretical mass content of Ti metal in SiO2 is 2%. Stir for 2 hours, filter and wash the obtained sample until neutral, and dry it at 80 °C for 24 hours.

[0067] 3) In a muffle furnace, heat the SiO2 containing Pd and Ti precursors obtained in step 2) from room temperature to 600 °C at a heating rate of 10 °C / min and hold for 1 hour to obtain a SiO2 catalyst containing palladium and titanium metals.

[0068] Application Example 1

[0069] Evaluate the catalytic activity of the catalysts prepared in Examples 1 to 3 and Comparative Examples 1 and 2 in a fixed-bed reactor. The catalyst loading is 1 g. The reaction uses carbon monoxide, methanol, and methyl nitrite as raw material gases, and nitrogen as a diluent gas. The molar ratio of carbon monoxide, methanol, methyl nitrite, and nitrogen gases is 1:0.01:3:10, and the reaction space velocity is 2000 h -1 , the reaction temperature is 150 °C, and the reaction pressure is 0.1 MPa. The products are analyzed by on-line gas chromatography. The products include the main products dimethoxymethane (DMM) and dimethyl carbonate (DMC), and the by-products methyl formate (MF) and dimethyl oxalate (DMO). From this, the conversion rate X of methyl nitrite (MN) is calculated MN , the selectivity S of dimethoxymethane based on methyl nitrite DMM / MN , the selectivity S of dimethyl carbonate based on methyl nitrite DMC / MN , the total selectivity S of dimethoxymethane and dimethyl carbonate based on methyl nitrite (DMM+DMC) / MN and the selectivity S of by-products based on methyl nitrite MF / MN , S DMO / MN .

[0070] Application Example 2

[0071] Evaluate the catalytic activity of the catalysts prepared in Examples 1 to 3 and Comparative Examples 1 and 2. The gas molar ratio is carbon monoxide: methanol: methyl nitrite: nitrogen (CO:CH3OH:CH3ONO:N2) = 1:6:6:10,, and the reaction space velocity is 10000 h -1 , the reaction temperature is 100 °C, and the reaction pressure is 2 MPa. Other conditions are the same as in Application Example 1.

[0072] As can be seen from Tables 1 and 2, in the novel reaction process for synthesizing dimethoxymethane and dimethyl carbonate from carbon monoxide, methanol and methyl nitrite of the present invention, a novel molecular sieve catalyst is designed, and high catalytic performance can be achieved under mild reaction conditions. The conversion rate of methyl nitrite and the selectivities of dimethoxymethane and dimethyl carbonate are significantly superior to the catalytic performances of Comparative Examples 1 and 2.

[0073] Table 1 Catalytic performances of the catalysts of Examples 1 to 3 and Comparative Examples 1 and 2 under the reaction conditions of Application Example 1

[0074] Catalyst <![CDATA[X MN / %]]> <![CDATA[S DMM / MN / %]]> <![CDATA[S DMC / MN / %]]> <![CDATA[S (DMM+DMC) / MN / %]]> <![CDATA[S MF / MN / %]]> <![CDATA[S DMO / MN / %]]> Example 1 75.5 60.1 20.4 80.5 19.5 0 Example 2 60.0 59.9 20.5 80.4 19.6 0 Example 3 45.5 40.0 41.5 81.5 18.5 0 Comparative Example 1 9.0 20.0 2.4 22.4 58.6 19.0 Comparative Example 2 6.9 19.8 5.4 25.2 58.0 16.8

[0075] Table 2 Catalytic performances of the catalysts of Examples 1 to 3 and Comparative Examples 1 and 2 under the reaction conditions of Application Example 2

[0076] Catalyst <![CDATA[X MN / %]]> <![CDATA[S DMM / MN / %]]> <![CDATA[S DMC / MN / %]]> <![CDATA[S (DMM+DMC) / MN / %]]> <![CDATA[S MF / MN / %]]> <![CDATA[S DMO / MN / %]]> Example 1 50.1 92.4 1.5 93.9 6.1 0 Example 2 41.3 90.9 1.2 92.1 7.9 0 Example 3 32.8 89.5 2.3 91.8 8.2 0 Comparative Example 1 4.7 9.5 0 9.5 90.5 0 Comparative Example 2 3.3 8.7 0 8.7 91.3 0

[0077] After stability evaluation, Example 1 stably operated for more than 500 hours, and the conversion rate of methyl nitrite and the selectivities of dimethoxymethane and dimethyl carbonate basically remained unchanged. Moreover, through TEM characterization, the metal particle size of Example 1 was 2.2 nanometers, and its metal particle size was basically the same as that before the reaction. It can be seen that the catalyst used in the method for catalytically synthesizing dimethoxymethane and dimethyl carbonate from carbon monoxide, methanol and methyl nitrite of the present invention has high stability.

[0078] From the results of the above examples and comparative examples, it is found that: the catalyst prepared in the present invention is a catalyst with high stability, high selectivity, high conversion rate and easy to realize industrialization, and is particularly suitable for the reaction of catalytically synthesizing dimethoxymethane and dimethyl carbonate from carbon monoxide, methanol and methyl nitrite.

[0079] As Figure 10 shown, under the action of a novel and efficient molecular sieve catalyst of Pd and / or Ti metal, carbon monoxide, methanol and methyl nitrite are catalytically gas-phase synthesized into dimethoxymethane and dimethyl carbonate. After separation, the non-condensable gas containing NO and methanol and air undergo a non-catalytic reaction for the regeneration of CH3ONO. This process avoids the direct contact between oxygen and methanol, does not need to consider the risk of explosion, and the used catalyst has high activity, high selectivity and high stability, and has certain industrial application prospects.

Claims

1. A method for synthesizing dimethoxymethane and dimethyl carbonate, characterized in that, Using carbon monoxide, methanol and methyl nitrite as raw materials, a molecular sieve catalyst is loaded into a continuous catalytic reactor, and carbon monoxide, methanol and methyl nitrite are continuously introduced. Under the conditions of a reaction temperature of 80-160 °C and a reaction pressure of 0.1-2.0 MPa, three catalytic reactions mainly occur to obtain dimethoxymethane, dimethyl carbonate and the by-product methyl formate; the molecular sieve catalyst is a supported catalyst, including an active component and a carrier. The active component is Pd and Ti, and the mass fraction of the active component in the catalyst is 0.01-2.50%. The carrier is one or a combination of two of Ti-MWW, TS-1, MCM-22, ITQ-1, S-1, and NaY molecular sieves. The average particle size of the molecular sieve particles is 0.05-6.0 microns. The three catalytic reactions are 2CH3ONO + CO → (CH3O)2CO + 2NO, CH3OH + 2CH3ONO → (CH3O)2CH2 + 2NO + H2O, and 4CH3ONO → CHOOCH3 + 2CH3OH + 4NO. The preparation method of the molecular sieve catalyst includes the following steps: 1) Molecular sieve pretreatment: The molecular sieve is placed in an alkali solution with a concentration of 0.001-5 mol / L and pretreated at 0-100 °C for 0.5-30 h. After treatment, solid-liquid separation is carried out. The molecular sieve solid is then placed in an ammonium chloride solution and stirred for 1-3 hours. The obtained sample is filtered, washed to neutrality, and dried at 25-100 °C for 1-48 hours. In a muffle furnace, the dried molecular sieve is heated from room temperature to 200-600 °C at a certain heating rate and maintained for 1-6 hours, so as to form defect positions inside the molecular sieve for facilitating the loading of Pd and Ti metals in the subsequent steps; 2) Dissolve the Pd precursor and the Ti precursor in one or a combination of two of water, dilute hydrochloric acid, acetic acid, methanol, ethanol, acetone, petroleum ether, benzene, toluene, dichloromethane, acetonitrile or ether, and stir evenly to form a clear Pd and Ti precursor solution; 3) Mix the modified molecular sieve obtained in step 1) with one or a combination of two of water, dilute hydrochloric acid, acetic acid, methanol, ethanol, acetone, petroleum ether, benzene, toluene, dichloromethane, acetonitrile or ether according to a mass ratio of 1:0.5-50, stir for 1-3 hours, and gradually add a certain mass of the Pd and Ti precursor solution obtained in step 2) so that the theoretical mass content of Pd and Ti in the molecular sieve is 0.01%-2.50%. Stir for 1-3 hours, filter and wash the obtained sample to neutrality, and dry at 25-100 °C for 1-48 hours to obtain a molecular sieve loaded with Pd and Ti precursors; 4) In a muffle furnace, heat the molecular sieve obtained in step 3) from room temperature to 200-600 °C at a certain heating rate and maintain for 1-6 hours to obtain the molecular sieve catalyst.

2. The synthesis method of dimethoxymethane and dimethyl carbonate according to claim 1, characterized in that, The molar ratio of carbon monoxide: methanol: methyl nitrite: inert gas in the raw materials is 1: 0.01-10: 0.5-10: 0.5-10, and the reaction space velocity is 1000-10000 h -1 , the inert gas is one or a combination of two of carbon dioxide, nitrogen, and argon, and the continuous catalytic reactor is a fixed bed reactor or a fluidized bed reactor.

3. A method for synthesizing dimethoxymethane and dimethyl carbonate according to claim 1, characterized in that, The conversion rate of methanol is 3-90%, the conversion rate of carbon monoxide is 5-90%, the conversion rate of methyl nitrite is 5-90%, and the selectivity S DMM / MN / % of dimethoxymethane is 20-95%, and the selectivity S DMC / MN / % of dimethyl carbonate is 1-50%, and the selectivity S MF / MN / % of methyl formate is 1-20%.

4. A method for synthesizing dimethoxymethane and dimethyl carbonate according to claim 1, characterized in that, The reactant methyl nitrite is industrially produced by the reaction of methanol, air and recycled NO, and the catalytic reaction equation is 2NO + 2CH3OH + 1 / 2O2 → 2CH3ONO + H2O.

5. A method for synthesizing dimethoxymethane and dimethyl carbonate according to claim 1, characterized in that, The alkali solution in step 1) is one or a combination of two of methyl chloro alkali solution, ethyl chloro alkali solution, propyl chloro alkali solution, triethylamine solution, sodium carbonate solution, potassium carbonate solution, cesium carbonate solution, sodium hydroxide solution, lithium hydroxide solution, potassium hydroxide solution, and ammonia water solution.

6. The synthesis method of dimethoxymethane and dimethyl carbonate according to claim 1, characterized in that, In step 1), the concentration of the ammonium chloride solution is 0.001 - 5 mol / L, the temperature of the ammonium chloride solution is 25 - 100 °C, the treatment time is 0.5 - 6 h. The molecular sieve obtained by treating the ammonium chloride solution is calcined, heated from room temperature to 200 - 600 °C at a heating rate of 0.1 - 10 °C / min, and maintained for 1 - 6 hours.

7. A method for synthesizing dimethoxymethane and dimethyl carbonate according to claim 1, characterized in that, The Pd precursor in step 2) is one or a combination of two of palladium nitrate, palladium acetate, palladium chloride, ammonium chloropalladate, potassium chloropalladate, tetramminepalladium chloride, tetramminepalladium nitrate, dichlorodiamminepalladium, and sodium chloropalladate. The Ti precursor in step 2) is one or a combination of two of titanium tetrachloride, tetrabutyl titanate, isopropyl titanate, and titanium oxysulfate.

8. A method for synthesizing dimethoxymethane and dimethyl carbonate according to claim 1, characterized in that, The heating rate in step 3) is 0.1 - 10 °C / min. For the molecular sieve catalyst obtained in step 4), the average particle size of the Pd particles is 0.2 - 10 nanometers. After step 4), a catalyst shaping step can be introduced.

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