A process by which the raw material, a gas comprising mainly hydrogen, carbon monoxide and carbon dioxide, is introduced into a first reactor together with a catalyst, in which one or more reactions take place that produce methanol or dimethyl ether or both, which are then introduced into a second reactor adding oxygen and a catalyst and producing formaldehyde and a minority of dimethyl ether, and where there may be an excess of water, such water being extracted from the process and the remaining products being introduced into the third reactor with, optionally, an additive, and such raw material is exposed to catalysts and under an atmosphere at medium temperature and pressure, in order to produce three or four groups of chemical reactions that, after extracting most of the water that is generated as a residue during the process, produces as a result a liquid multifunctional product that can be used as a solvent, a foaming agent or an oxygenated fuel; said product, normally a fluid, comprises polyoxymethylene dimethyl ethers with molecular formula CH3O(CH2O)nCH3 wherein n has a value between 1 and 7.