Process for the preparation of 5-hydroxymethylfurfural comprising the steps of: A) heating to a temperature of between 60 and 120°C for a time of between 10 minutes and 12 hours a mixture consisting of: a) a quaternary ammonium salt R 3 R'N + X - in which: - R, which is the same or different, represents a C 1 -C 4 alkyl group; - R' represents a C 1 -C 15 alkyl group; - X - represents an anion selected from chloride, bromide, iodide, fluoride or hydroxide; b) at least one catalyst selected from: b-i) titanium oxide supported on silica having a specific surface area of between 150 and 900 m 2 /g, calcined at a temperature of between 150 and 900°C; b-ii) phosphotungstic acid, H 3 [P(W 3 O 10) 4], supported on silica having a specific surface area of between 150 and 900 m 2 /g, calcined at a temperature of between 150 and 900°C; b-iii) zirconium phosphate Zr(HPO 4) 2; b-iv) titanium phosphate Ti(HPO 4) 2; c) water in a quantity comprised between 1 and 50 % by weight with respect to the quaternary ammonium salt; d) one or more saccharides selected from monosaccharides having 6 carbon atoms, disaccharides, oligosaccharides and polysaccharides formed from monosaccharide units having 6 carbon atoms; B) adding to the reaction mixture an organic solvent or a mixture of organic solvents in which the quaternary ammonium salt and the catalyst are highly insoluble and 5-hydroxymethylfurfural is soluble, at a temperature between 15°C and the boiling point of the organic solvent or of the mixture of organic solvents, obtaining the quaternary ammonium salt and the catalyst as solid phase, and the organic solvent or mixture of organic solvents and 5-hydroxymethylfurfural as liquid phase; C) removing the solid phase from the liquid phase of step B); D) separating off the organic solvent or mixture of organic solvents from the 5-hydroxymethylfurfural by distillation. A) heating to a temperature of between 60 and 120°C for a time of between 10 minutes and 12 hours a mixture consisting of: a) a quaternary ammonium salt R 3 R'N + X - in which: - R, which is the same or different, represents a C 1 -C 4 alkyl group; - R' represents a C 1 -C 15 alkyl group; - X - represents an anion selected from chloride, bromide, iodide, fluoride or hydroxide; b) at least one catalyst selected from: b-i) titanium oxide supported on silica having a specific surface area of between 150 and 900 m 2 /g, calcined at a temperature of between 150 and 900°C; b-ii) phosphotungstic acid, H 3 [P(W 3 O 10) 4], supported on silica having a specific surface area of between 150 and 900 m 2 /g, calcined at a temperature of between 150 and 900°C; b-iii) zirconium phosphate Zr(HPO 4) 2; b-iv) titanium phosphate Ti(HPO 4) 2; c) water in a quantity comprised between 1 and 50 % by weight with respect to the quaternary ammonium salt; d) one or more saccharides selected from monosaccharides having 6 carbon atoms, disaccharides, oligosaccharides and polysaccharides formed from monosaccharide units having 6 carbon atoms; a) a quaternary ammonium salt R 3 R'N + X - in which: - R, which is the same or different, represents a C 1 -C 4 alkyl group; - R' represents a C 1 -C 15 alkyl group; - X - represents an anion selected from chloride, bromide, iodide, fluoride or hydroxide; - R, which is the same or different, represents a C 1 -C 4 alkyl group; - R' represents a C 1 -C 15 alkyl group; - X - represents an anion selected from chloride, bromide, iodide, fluoride or hydroxide; b) at least one catalyst selected from: b-i) titanium oxide supported on silica having a specific surface area of between 150 and 900 m 2 /g, calcined at a temperature of between 150 and 900°C; b-ii) phosphotungstic acid, H 3 [P(W 3 O 10) 4], supported on silica having a specific surface area of between 150 and 900 m 2 /g, calcined at a temperature of between 150 and 900°C; b-iii) zirconium phosphate Zr(HPO 4) 2; b-iv) titanium phosphate Ti(HPO 4) 2; b-i) titanium oxide supported on silica having a specific surface area of between 150 and 900 m 2 /g, calcined at a temperature of between 150 and 900°C; b-ii) phosphotungstic acid, H 3 [P(W 3 O 10) 4], supported on silica having a specific surface area of between 150 and 900 m 2 /g, calcined at a temperature of between 150 and 900°C; b-iii) zirconium phosphate Zr(HPO 4) 2; b-iv) titanium phosphate Ti(HPO 4) 2; c) water in a quantity comprised between 1 and 50 % by weight with respect to the quaternary ammonium salt; d) one or more saccharides selected from monosaccharides having 6 carbon atoms, disaccharides, oligosaccharides and polysaccharides formed from monosaccharide units having 6 carbon atoms; B) adding to the reaction mixture an organic solvent or a mixture of organic solvents in which the quaternary ammonium salt and the catalyst are highly insoluble and 5-hydroxymethylfurfural is soluble, at a temperature between 15°C and the boiling point of the organic solvent or of the mixture of organic solvents, obtaining the quaternary ammonium salt and the catalyst as solid phase, and the organic solvent or mixture of organic solvents and 5-hydroxymethylfurfural as liquid phase; C) removing the solid phase from the liquid phase of step B); D) separating off the organic solvent or mixture of organic solvents from the 5-hydroxymethylfurfural by distillation.