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Oligomeric oxymethylene dimethyl ethers (OME n , CH 3 O(CH 2 O) n CH 3 ) bearing three to five CH 2 O units are promising diesel fuels for the reduction of soot and NO x emissions. Regarding the production of OMEs, a highly optimized process has not been realized yet. This work describes efficient synthesis of OMEs from dimethoxymethane (DMM) and trioxane in batch experiments at room temperature and atmospheric pressure. To ensure high reactivity and high OME yields, dry educts have been used and the influence of water has been investigated in detail. The ion exchange resin Amberlyst36 and zeolites have been employed as acidic catalysts. Zeolite BEA25 exhibited highest catalytic activity and the reaction could be completed within 12 min at 25 °C. Furthermore, the formation of byproducts could be fully eliminated. [ABSTRACT FROM AUTHOR]

A catalyst screening comprising zeolites and ion exchange resins for the synthesis of oligomeric oxymethylene dimethyl ethers (OME) from methanol (MeOH) and formaldehyde (FA) has been carried out. All catalysts led to the same product spectrum and parameters for chemical equilibrium have been determined. The ion exchange resin Dowex50Wx2 showed highest activity and reaction kinetics has been investigated employing this catalyst. The influence of the FA:MeOH ratio and water as well as refeeding of OMEs with undesired chain lengths have been considered in the kinetic model, which is based on a hyperbolic approach. Experiments have been carried out in the temperature range between 40 and 120 °C and variable FA:MeOH ratios from 0.5 to 1.5 g/g have been employed. Regarding water, up to 23 wt.% have been added to the reaction mixtures to investigate its influence on yield and reaction rate. Low water contents lead to high OME selectivities. By varying the FA:MeOH ratio, chain lengths of the OMEs can be influenced. Regarding the most active catalyst Dowex50Wx2, 90% of equilibrium conversion is reached after 5 min at 60 °C employing a catalyst loading of 1 wt.%. A study on the long term performance of the catalyst has been carried out and after 17 days the decrease of activity was below 10% while selectivity remained the same. For different Dowex catalysts a general kinetic model could be developed, which is not limited to Dowex50Wx2. [ABSTRACT FROM AUTHOR]

Oligomeric oxymethylene dimethyl ethers (OMDMEs, CH 3 O–(CH 2 O) n –CH 3 ) are promising diesel fuel additives, which can reduce soot formation as well as NO x emissions. Due to the poor availability of high purity OMDMEs a comprehensive characterization of diesel standards was not feasible until now. Two types of oxymethylene dialkylethers (OMDMEs and oxymethylene diethyl ethers, OMDEEs) were synthesized, purified and characterized with respect to their physico-chemical and fuel properties. Density, melting point, flash point, auto ignition point as well as lubricity, kinematic viscosity and surface tension of OMDMEs and OMDEEs were measured and compared to the corresponding n -alkanes. Fuel requirements such as boiling points, flash points and surface tensions can be fulfilled by OMDMEs and OMDEEs. Furthermore, OMDMEs ( n = 3–5) and OMDEEs ( n = 2–4) are, due to their high cetane numbers of 124–180 and 64–103, particularly promising since cetane numbers in this range can lead to improved motor efficiency and smoother fuel combustion. Additionally, the heat of combustion as well as the standard enthalpy of formation and reaction were determined. Apart from somewhat lower heating values, OMDMEs exhibit fuel properties similar to conventional diesel complying the required fuel standards without the need of changing engines or fuel infrastructures. [ABSTRACT FROM AUTHOR]

Abstract: Recent progress regarding the production of alternative liquid fuels is described with a focus on catalyst development. Fuels for spark ignition engines as well as diesel fuels are considered and their potentials regarding the reduction of harmful emissions are addressed. Two main strategies are described. The first implies production of synthesis gas from renewables or CO2 and subsequent synthesis of methanol or dimethyl ether. Both can be further converted to a series of valuable fuels, e.g., high‐quality gasoline or oxymethylene ethers. The second strategy comprises the production of ethanol and its conversion to gasoline. [ABSTRACT FROM AUTHOR]