Sample records for dimethoxymethane

  1. Thermal Decomposition of Dimethoxymethane Electrolyte Solution.


    DIMETHOXYMETHANE ELECTROLYTE SOLUTION by J. S. Foos and V. Meltz Prepared for Publication in the Journal of the Electrochemical Society EIC...Journal of the Electrochemical Society . III. KEY WORDS (Conitiue onl reverse side It neci’eay and Identify by block nsinibor) Lithium Battery, Organic...Batteries, B. B. Owens and N. Margalit, eds., Vol. 80-4, The Electrochemical Society , Pennington, NJ, 384 (1980). .2. K. M. Abraham, J. L. Goldman and D. L

  2. Catalytic Oxidation of Dimethyl Ether to Dimethoxymethane over Cs Modified H3PW12O40/SiO2 Catalysts

    Qingde Zhang; Yisheng Tan; Caihong Yang; Yizhuo Han; Jun Shamoto; Noritatsu Tsubaki


    The attractive utilization route for one-step catalytic oxidation of dimethyl ether to dimethoxymethane was successfully carried out over the H3PW12O40(40%)/SiO2 catalyst,modified by Cs,K,Ni,and V.The Cs modification of H3PW12040(40%)/SiO2 gave the most promising result of 20%dimethyl ether conversion and 34.8% dimethoxymethane selectivity.Dimethoxymethane could be synthesized via methoxy groups decomposed from dimethyl ether through the synergistic effect between the acid sites and the redox sites of Cs modified H3PW12040(40%)/SiO2.

  3. Reforming and synthesis of dimethoxymethane and dimethyl ether for H{sub 2} production; Reformage et synthese des dimethoxymethane et dimethylether pour la production d'hydrogene

    Sun, Q


    This work is related to the subject 'Clean Energy'. Dimethoxymethane (DMM) is a suitable H{sub 2} storage material for mobile application due to its high H{sub 2} content and non-toxicity. It was found that DMM can be 100% reformed to produce H{sub 2} on a complex catalyst composed of an acid component such as Nb{sub 2}O{sub 5} or niobium phosphate (NbP) combined with CuZnO/Al{sub 2}O{sub 3} catalyst. Moreover, V{sub 2}O{sub 5}/NbP and V{sub 2}O{sub 5}-TiO{sub 2}-SO{sub 4}{sup 2-} catalysts were prepared and evaluated in the reaction of selective oxidation of methanol to DMM. The surface acidic and redox properties of V{sub 2}O{sub 5}-TiO{sub 2}-SO{sub 4}{sup 2-} were correlated to the reactive performance of the catalysts. The adsorption properties of Nb{sub 2}O{sub 5} and NbP used in methanol dehydration reaction were also studied. (author)

  4. Phenylsulfonic Acid Functionalized Mesoporous Silica Catalyzed Transetherification of Alcohols with Dimethoxymethane

    杨建明; 吕剑


    Phenylsulfonic acid functionalized mesoporous silica was synthesized by condensation of tetraethylorthosilicate with phenyltrimethoxysilane, and then sulfonation using 30% fuming sulfuric acid. The material was characterized using FT-IR, DSC, XPS, TEM and N2 adsorption/desorption measurements. DSC revealed that sulfonic acid group of the catalyst was decomposed at 354.8℃, indicating that the catalyst exhibited high thermal stability. XPS showed that there existed three kinds of different silicon species on surface of the catalyst. The catalytic performance of the catalyst was evaluated using transetherification of alcohols with dimethoxymethane. It was found that among primary alcohols, the selectivities of the two long-chain alcohols for n-dedocanol and n-tetradecyl alcohol were higher than 97.0% at the conversions of 43.6% and 65.3%, respectively, while the selectivities of the short-chain alcohols except for n-hexanol were less than 90.0% at the conversions of over 80.0%. Due to steric bartier, the secondary alcohols such as /so-butanol and cyclohexanol afforded conversions of 79.4% and 60.5%, and the selectivities of the two alcohols were more than 90.0%. The sequence in conversion of the substituted phenols isas follows: p-nitrophenol>p-fluorophenol≥p-bromophenol>p-cresol>m-cresol.

  5. Imaging momentum orbital densities of conformationally versatile molecules: a benchmark theoretical study of the molecular and electronic structures of dimethoxymethane.

    Huang, Y R; Knippenberg, S; Hajgató, B; François, J-P; Deng, J K; Deleuze, M S


    The main purpose of the present work is to predict from benchmark many-body quantum mechanical calculations the results of experimental studies of the valence electronic structure of dimethoxymethane employing electron momentum spectroscopy, and to establish once and for all the guidelines that should systematically be followed in order to reliably interpret the results of such experiments on conformationally versatile molecules. In a first step, accurate calculations of the energy differences between stationary points on the potential energy surface of this molecule are performed using Hartree-Fock (HF) theory and post-HF treatments of improving quality (MP2, MP3, CCSD, CCSD(T), along with basis sets of increasing size. This study focuses on the four conformers of this molecule, namely the trans-trans (TT), trans-gauche (TG), gauche-gauche (G+G+), and gauche-gauche (G+G-) structures, belonging to the C2v, C1, C2, and Cs symmetry point groups, respectively. A focal point analysis supplemented by suited extrapolations to the limit of asymptotically complete basis sets is carried out to determine how the conformational energy differences at 0 K approach the full CI limit. In a second step, statistical thermodynamics accounting for hindered rotations is used to calculate Gibbs free energy corrections to the above energy differences, and to evaluate the abundance of each conformer in the gas phase. It is found that, at room temperature, the G+G+ species accounts for 96% of the conformational mixture characterizing dimethoxymethane. In a third step, the valence one-electron and shake-up ionization spectrum of dimethoxymethane is analyzed according to calculations on the G+G+ conformer alone by means of one-particle Green's function [1p-GF] theory along with the benchmark third-order algebraic diagrammatic construction [ADC(3)] scheme. A complete breakdown of the orbital picture of ionization is noted at electron binding energies above 22 eV. A comparison with available

  6. Thermodynamic analysis of dimethoxymethane synthesis reaction%二甲氧基甲烷合成反应的热力学分析

    郑妍妍; 张宏达; 王金福


    The standard enthalpy of formation, entropy and heat capacity of dimethoxymethane were calculated by using Benson group contribution method. The mole enthalpy changes, the Cibbs free energies and the equilibrium constants of the reaction of dimethoxymethane synthesis from methanol and formaldehyde were calculated as a function of temperature. The liquid activity coefficients of formaldehyde-methanol-water-dimethoxymethane system were predicted with UNIFAC group contribution model. The effects of temperature and the formaldehyde/methanol mole ratio on formaldehyde equilibrium conversion were studied as well, and the results were compared with the experimental data. The results provided a thermodynamic basis for the synthesis of dimethoxymethane and laid a solid foundation for study of polyoxymethylene dimethyl ethers.%用Benson基团贡献法估算了二甲氧基甲烷的标准摩尔生成焓△fHmθ、标准摩尔熵Smθ和摩尔等压热容Cp,m,计算了缩醛化合成二甲氧基甲烷的标准摩尔焓变△rHmθ、吉布斯自由能变△rGmθ以及反应平衡常数K与温度T的关联式;用UNIFAC基团贡献模型关联甲醛-甲醇-水-二甲氧基甲烷四元体系液相活度系数.考察了反应温度T以及原料醇醛物质的量比M对甲醛平衡转化率Xe的影响,并与实验数据比较.本热力学分析为二甲氧基甲烷合成的实验研究及生产工艺优化提供了理论指导,并为后续聚甲氧基二甲醚的研究开发奠定了基础.

  7. Synthèse directe du 1,1-diméthoxyméthane à partir de méthanol moyennant une modification mineure du procédé de production de formaldéhyde sur catalyseurs FeMo Direct Synthesis of 1,1-dimethoxymethane from Methanol by Minor Modification of the Formaldehyde Production Process over FeMo Catalysts

    Gornay J.


    éthanol de l’ordre de 56 % et une sélectivité en DMM d’environ 90 %. Ces travaux ouvrent d’intéressantes perspectives de reconversion d’unités de production de formaldéhyde (catalyseur FeMo en réacteur multitubulaire en unités de production de DMM, en ne modifiant pratiquement que la pression partielle de méthanol dans la charge, tout entravaillant avec de l’air comme diluant/oxydant. The partial oxidation reaction of methanol over redox catalysts mainly leads to the formation of formaldehyde. Over optimized FeMo-based catalysts, small quantities of products like formic acid or COx are also detected. When the catalysts have also acidic properties, condensation/dehydration reactions take place in addition to the consecutive oxidation reactions, which leads to the formation of 1,1-dimethoxymethane (DMM or methylal, dimethylether and methyl formate. Among the aforementioned products, DMM is especially interesting for industrial applications owing to its good physical properties (very good solvent, low viscosity, low superficial pressure, etc.. The main industrial applications are a use as a green solvent or a chemical intermediate; it is further suitable as a fuel additive in replacement of the petro-chemistry-derived products. At the industrial scale, DMM is conventionally produced in two steps: – formaldehyde synthesis followed by; – reaction between formaldehyde and methanol over an acid catalyst to finally obtain DMM. However, in order to reduce the DMM production costs, the development of a catalyst and of the associated process enabling the direct conversion of methanol to DMM are necessary. As aforementioned, over a FeMo-based catalyst, the main product obtained by methanol partial oxidation is formaldehyde. This process is carried out at a low methanol partial pressure, the rich methanol composition area – over the explosivity zone – being not industrially operated. Using a rich methanol composition, we observed over the same Fe

  8. Conversion from Dimethyl Ether to Dimethoxymethane and Dimethoxyethane Using Dielectric-Barrier Discharge Plasma

    Wang Yu; Liu Changjun; Zhang Yueping


    Experimental investigation was conducted to convert dimethyl ether (DME) in thepresence of steam using dielectric barrier discharge (DBD) at atmospheric pressure and 373 K.The flow rate of DME was 20 ml/min. The introduction of steam resulted in an increase in theDME conversion and the selectivity of oxygenates. Plasma steam-enhanced dimethyl ether (DME)conversion led to a direct synthesis of DMMT and DMET, with a high selectivity of 5.78% and17.99%, respectively. The addition of steam promoted the formation of "plasma aerosol" that wasfavored for the formation of liquid oxygenates. The reaction pathway of plasma DME conversionwas proposed.

  9. Structure and Dynamics of Solutions of Lithium Salts Relevant to Battery Construction.


    with M. Delsignore and H. Farber. P2+P3. "Molecular Relaxation Dynamics and Ionic Association of LiBF4 in dimethoxymethane" J. Phys. Chem 90 (1986...copyright owner. Molecular Relaxation Dynamics and Ionic Association of LiBF4 in Dimethoxymethane M. Delsignore, H. Farber, and S. Petrucci* Departments of...Electrical conductance data for LiBF4 in dimethoxymethane (DMM) at 25 *C reveal the electrolyte to be heavily associated to ion pairs and triple ions. A

  10. Part A. Molecular Dynamics and Ionic Associations of LiAsF6 in 4-Butyrolactone Mixtures with 2-Methyl Tetrahydrofuran. Part B. Molecular Dynamics and Ionic Associations of LiBF4 in 1,2-Dimethoxymethane.


    relaxations. LIAsF. solutions in pure 2MeTHF (3) show only a single Debye process, and -12- at this time we cannot determine which solvent component ...expression KFj- 4 7rL ds e- /2 e b KJ= ’ e-~ e(II) 3000 It results in a charge to charge separation in the pair d = 5.1xlO- Scm . Similarly by equating...gx1l- Scm , a value that seems too high to be reconciled with the triple ions model and definition envisaging the three Ions at contact, whereas, the value

  11. Part A. Molecular dynamics and ionic associations of LiAsF6 in 4-butyrolactone mixtures with 2-methyl tetrahydrofuran. Part B. Molecular dynamics and ionic associations of LiBF4 in 1,2-dimethoxymethane

    Harada, Y.; Salomon, M.; Petrucci, S.; Delsignore, M.; Farber, H.


    Solutions of LiAsF6 at 298.2 K were studied by audiofrequency conductance in the concentrations range .0001-.01 Mol/Cu dm and by radiofrequency ultrasonic absorption in the concentration range 0.05 - 0.5 mol/cu dm. The solvents employed were mixtures of 4-butyrolactone with 2-methyl tetrahydrofuran varying in compositions from mole fractions X subscript BL = 0.10 X subscript BL = 0.75. In dilute solutions the audiofrequency conductivity data yield ion association constants which appear to represent both contact and solvent-separated ion pairs for mixtures up to X subscript BL = 0.36. At higher LiAsF6 concentrations and in solvent mixtures of composition X subscript BL = 0.75, and X subscript BL = 0.35, the ultrasonic spectrum shows a single relaxation process which again is attributed to the formation of both contact and solvent separated ion pairs. Part B: Electrical conductance data for LiBF4 in 1,2-Dimethyoxymethane (DMM)at 25 C reveal the electrolyte to be heavily associated to ion-pairs and triple ions. A theoretical expression for the triple ion association constant similar to the Bjerrum one for ion-pairs and to the Maaser-Bjerrum theory of dimers has been developed and applied to the present conductance data. Ultrasonic relaxation absorption data at much higher concentrations than the conductance data reveal association to dimers. This is also evident from the microwave dielectric data showing no electrolyte dielectric effect on the solvent and apparent lack of presence of dipoles. The ultrasonic data can be rationalized by a two-step dimerization mechanism.


    Guo-xiang Xu; Lu Qi; Bi-tao Yu; Lei Wen


    PVC disulfide (2SPVC) was synthesized by solution crosslink and its molecular structure was confirmed by the particle size of d0.5 = 11.3 μm. With SEM (Scanning Electron Microscope) experiment the surface morphology and obvious S-S redox reaction in charge-discharge process. When 2SPVC was used as cathode material for secondary lithium mixture of o-xylene (oxy), diglyme (DG) and dimethoxymethane (DME) at 30℃, the first discharge capacity of 2SPVC is very promising cathode candidate for rechargeable lithium batteries.

  13. Stable, Electroinactive Wetting Agent For Fuel Cells

    Prakash, Surya G.; Olah, George A.; Narayanan, Sekharipuram R.; Surampudi, Subbarao; Halpert, Gerald


    Straight-chain perfluorooctanesulfonic acid (C8 acid) identified as innocuous and stable wetting agent for use with polytetrafluoroethylene-containing electrodes in liquid-feed direct-oxidation fuel cells suggested for use in vehicles and portable power supplies. C8 acid in small concentrations in aqueous liquid solutions of methanol, trimethoxymethane, dimethoxymethane, and trioxane enables oxidation of these substances by use of commercially available electrodes of type designed originally for use with gases. This function specific to C8 acid molecule and not achieved by other related perfluorolkanesulfonic acids.

  14. Comparative study between gas phase and liquid phase for the production of DMC from methanol and CO2

    Ahmed Aouissi; Salem S. Al-Deyab


    Direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide over Co1.5PW12O40 in liquid and in gas phase is investigated.The synthesized catalyst has been characterized by means of FTIR and XRD.Liquid phase experiment results showed that high pressures are favorable for the synthesis of DMC.However,DMC formation is limited by the reaction with co-produced water.DMC selectivity is more strongly dependent on the temperature than on the pressure of CO2.As for the reactions in gas phase,it has been found that both CH3OH conversion and DMC selectivity decreased with increasing temperature,owing to the decomposition of DMC at high temperatures.High temperatures and more amount of Co1.5PW12O40 catalyst favor the formation of dimethoxymethane (DMM) and methyl formate (MF).

  15. Aqueous liquid feed organic fuel cell using solid polymer electrolyte membrane

    Surampudi, Subbarao (Inventor); Narayanan, Sekharipuram R. (Inventor); Vamos, Eugene (Inventor); Frank, Harvey A. (Inventor); Halpert, Gerald (Inventor); Olah, George A. (Inventor); Prakash, G. K. Surya (Inventor)


    A liquid organic fuel cell is provided which employs a solid electrolyte membrane. An organic fuel, such as a methanol/water mixture, is circulated past an anode of a cell while oxygen or air is circulated past a cathode of the cell. The cell solid electrolyte membrane is preferably fabricated from Nafion.TM.. Additionally, a method for improving the performance of carbon electrode structures for use in organic fuel cells is provided wherein a high surface-area carbon particle/Teflon.TM.-binder structure is immersed within a Nafion.TM./methanol bath to impregnate the electrode with Nafion.TM.. A method for fabricating an anode for use in a organic fuel cell is described wherein metal alloys are deposited onto the electrode in an electro-deposition solution containing perfluorooctanesulfonic acid. A fuel additive containing perfluorooctanesulfonic acid for use with fuel cells employing a sulfuric acid electrolyte is also disclosed. New organic fuels, namely, trimethoxymethane, dimethoxymethane, and trioxane are also described for use with either conventional or improved fuel cells.

  16. Organic fuel cell methods and apparatus

    Vamos, Eugene (Inventor); Surampudi, Subbarao (Inventor); Narayanan, Sekharipuram R. (Inventor); Frank, Harvey A. (Inventor); Halpert, Gerald (Inventor); Olah, George A. (Inventor); Prakash, G. K. Surya (Inventor)


    A liquid organic, fuel cell is provided which employs a solid electrolyte membrane. An organic fuel, such as a methanol/water mixture, is circulated past an anode of a cell while oxygen or air is circulated past a cathode of the cell. The cell solid electrolyte membrane is preferably fabricated from Nafion.TM.. Additionally, a method for improving the performance of carbon electrode structures for use in organic fuel cells is provided wherein a high surface-area carbon particle/Teflon.TM.-binder structure is immersed within a Nafion.TM./methanol bath to impregnate the electrode with Nafion.TM.. A method for fabricating an anode for use in a organic fuel cell is described wherein metal alloys are deposited onto the electrode in an electro-deposition solution containing perfluorooctanesulfonic acid. A fuel additive containing perfluorooctanesulfonic acid for use with fuel cells employing a sulfuric acid electrolyte is also disclosed. New organic fuels, namely, trimethoxymethane, dimethoxymethane, and trioxane are also described for use with either conventional or improved fuel cells.

  17. Highly stable CO2/N2 and CO2/CH4 selectivity in hyper-cross-linked heterocyclic porous polymers.

    Saleh, Muhammad; Lee, Han Myoung; Kemp, K Christian; Kim, Kwang S


    The largest obstacles for landfill/flue gas separation using microporous materials are small adsorption values and low selectivity ratios. This study demonstrates that these adsorption and selectivity challenges can be overcome by utilizing a series of hyper-cross-linked heterocyclic polymer networks. These microporous organic polymers (MOPs) were synthesized in a single step by inexpensive Friedel-Crafts-catalyzed reactions using dimethoxymethane as an external linker. The amorphous networks show moderate Brunauer-Emmett-Teller surface areas up to 1022 m(2) g(-1), a narrow pore size distribution in the range from 6 to 8 Å, and high physicochemical stability. Owing to the presence of the heteroatomic pore surfaces in the networks, they exhibit maximum storage capacities for CO2 of 11.4 wt % at 273 K and 1 atm. Additionally, remarkable selectivity ratios for CO2 adsorption over N2 (100) and CH4 (15) at 273 K were obtained. More importantly, as compared with any other porous materials, much higher selectivity for CO2/N2 (80) and CO2/CH4 (15) was observed at 298 K, showing that these selectivity ratios remain high at elevated temperature. The very high CO2/N2 selectivity values are ascribed to the binding affinity of abundantly available electron-rich basic heteroatoms, high CO2 isoteric heats of adsorption (49-38 kJ mol(-1)), and the predominantly microporous nature of the MOPs. Binding energies calculated using the high level of ab initio theory showed that the selectivity is indeed attributed to the heteroatom-CO2 interactions. By employing an easy and economical synthesis procedure these MOPs with high thermochemical stability are believed to be a promising candidate for selective CO2 capture.

  18. Biofiltration of high formaldehyde loads with ozone additions in long-term operation.

    Maldonado-Diaz, G; Arriaga, S


    Formaldehyde (FA) biofiltration was evaluated over 310 days with and without ozone addition. Without ozone, the biofilter was able to treat formaldehyde at inlet loads (ILs) lower than 40 g m(-3) h(-1), maintaining, under this condition, an average removal efficiency (RE) of 88 % for a few days before collapsing to zero. The continuous addition of ozone (90 ppbv) helped to recover the RE from zero to 98 ± 2 % and made it possible to operate at an IL of 40 g m(-3) h(-1) for long periods of operation (107 days). Furthermore, the ozone addition aided in operating the biofilter at a formaldehyde IL of up to 120 g m(-3) h(-1) values that have never before been reached. GC-mass spectrometry (MS) analysis showed that dimethoxymethane was the common compound in leachate during the performance decay. Also, the addition of ozone aided in maintaining an optimal pH in the biofilter with values between 7.5 and 8.2, due to the carbonate species formed during the ozone reactions with formaldehyde and its by-products. Thus, the pH control was confirmed and the alkalinity of the biofilter increased from 334.1 ± 100.3 to 1450 ± 127 mg CaCO3 L(-1) when ozone was added. Ozone addition diminished the exopolymeric substances (EPS) content of biofilm and biofilm thickness without affecting cell viability. Kinetic parameters suggested that the best conditions for carrying out FA biofiltration were reached under ozone addition. The addition of ozone during formaldehyde biofiltration could be a good strategy to maintain the pH and the steady state of the system under high ILs and for long periods of operation.

  19. Tröger’s Base Ladder Polymer for Membrane-Based Hydrocarbon Separation

    Alhazmi, Abdulrahman


    The use of polymeric membranes for natural gas separation has rapidly increased during the past three decades, particularly for carbon dioxide separation from natural gas. Another valuable application is the separation of heavy hydrocarbons from methane (fuel gas conditioning), more importantly for remote area and off-shore applications. A new potential polymeric membrane that might be utilized for natural gas separations is a Tröger’s base ladder polymer (PIM-Trip-TB-2). This glassy polymeric membrane was synthesized by the polymerization reaction of 9, 10-dimethyl-2,6 (7) diaminotriptycene with dimethoxymethane. In this research, the polymer was selected due to its high surface area and highly interconnected microporous structure. Sorption isotherms of nitrogen (N2), oxygen (O¬2), methane (CH4), carbon dioxide (CO2), ethane (C2H6), propane (C3H8), and n-butane (n-C4H10) were measured at 35 °C over a range of pressures using a Hiden Intelligent Gravimetric Analyzer, IGA. The more condensable gases (C2H6, CO2, C3H8, and n-C4H10) showed high solubility due to their high affinity to the polymer matrix. The permeation coefficients were determined for various gases at 35 °C and pressure difference of 5 bar via the constant-pressure/variable-volume method. The PIM-Trip-TB-2 film exhibited high performance for several high-impact applications, such as O2/N2, H2/N2 and H2/CH4. Also, physical aging for several gases was examined by measuring the permeability coefficients at different periods of time. Moreover, a series of mixed-gas permeation tests was performed using 2 vol.% n-C4H10/98 vol.% CH4 and the results showed similar transport characteristics to other microporous polymers with pores of less than 2 nm. The work performed in this research suggested that PIM-Trip-TB-2 is suitable for the separation of: (i) higher hydrocarbons from methane and (ii) small, non-condensable gases such as O2/N2 and H2/CH4.

  20. Literature Research Report of Polyoxymethylene Dimethyl Ethers Synthyesis%聚甲氧基二烷基醚合成文献调研报告

    李臻; 宋河远


    adding 20% DMM3-8 in the diesel oil, the amounts of powderous pollutants and NOx released upon combustion can be reduced by 80%~90% and 50%, respectively. DMMn molecule is composed of formaldehyde oligomer in the midst and methyl in two ends; therefore, DMMn can be synthesized from the compounds providing methyl ends (such as methanol, dimethyl ether, and dimethoxymethane) and those compounds supplying formaldehyde oligomer (such as formaldehyde, trioxymethylene and polyformaldehyde). As a result, the conversion of methanol to DMMn as an additive of diesel oil may not only extend the methanol industry chain and digest the large surplus production capacity of methanol, but also bring enormous benefits with respect to economics and environmental protection. At early stage, DMMn was obtained from methanol and formaldehyde, polyformaldehyde, or dioxacyclopentane, with sulfuric acid and hydrochloric acid as catalyst. In this respect, BASF Group used H2SO4 or CF3SO3H as catalyst to get DMM1-10, with methanol, DMM, trioxymethylene, and polyformaldehyde as raw materials, but the catalyst is corrosive and the conversion and selectivity to DMM3-8 is low. With zeolites or acidic ion exchange resins as catalyst, BP produced DMMn by conversion of dimethyl ether with formaldehyde through a complicated process; however, the DMM3-8 yield was still lower than 10%. In recent years, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences has made progress to synthesize DMM3-8 by using ionic liquid as catalyst in a homogeneous reaction system with methanol and trioxymethylene as feed; single-pass yield of DMMn reached 50% with the selectivity to DMM3-8 being 70%~80%.