Process for the production and separation of 5-hydroxymethylfurfural with quaternary ammonium salts
The present invention relates to a process for the production and separation of 5-hydroxymethylfurfural (HMF) comprising the steps of: (1) dehydrating at least one saccharide selected from the group consisting of monosaccharides having 6 carbon atoms and disaccharides, oligosaccharides and polysaccharides formed from units having 6 carbon atoms or mixtures thereof, in the presence of water and of at least one quaternary ammonium salt, at a temperature between 80-130° C., obtaining a reaction mixture comprising the quaternary ammonium salt, HMF and any unreacted saccharide; and (2) subjecting the said reaction mixture to at least one membrane separation operation selected in the group consisting of nanofiltration, reverse osmosis, electrodialysis and their combinations, obtaining an aqueous permeate comprising HMF and a retentate comprising quaternary ammonium salt, wherein both the dehydration of step (1) and the separation operations of step (2) are carried out in the absence of organic solvents.
1 . A process for production and separation of 5-hydroxymethylfurfural (HMF), the process comprising steps of:
1) dehydrating a saccharide in the presence of water and a tetraalkylammonium salt, at a temperature between 80-130° C., obtaining a reaction mixture comprising the tetraalkylammonium salt, HMF and any unreacted saccharide;
wherein step 1) is carried out in the presence of an acid catalyst;
2) diluting the reaction mixture with water to form a diluted reaction mixture; and
3) subjecting said diluted reaction mixture to at least one membrane separation operation selected from the group consisting of nanofiltration, reverse osmosis, electrodialysis and their combinations, obtaining an aqueous permeate comprising HMF and a retentate comprising tetraalkylammonium salt and any unreacted saccharide;
wherein each of the steps of the process is carried out in the absence of an organic solvent,
wherein said saccharide is fructose, said tetraalkylammonium salt is tetrabutylammonium bromide (TBAB) and said acid catalyst is selected from sulfuric acid and nitric acid,
wherein said process comprises, before step 3), a preliminary purification step for removal of high molecular weight compounds, wherein in the said preliminary purification step comprises one or more operations selected from: decantation, centrifugation, microfiltration or ultrafiltration, and
wherein step 3) comprises one or more nanofiltration operations and said membrane separation operation of step 3) uses a nanofiltration membrane, the nanofiltration membrane having a mean pore size in a range of 0.7 nm to 2 nm.
2 . The process according to claim 1 , wherein the weight ratio between TBAB and fructose at the beginning of step 1) is less than 5:1.
3 . The process according to claim 2 , wherein at the beginning of step 1), water is present in amounts less than 10% by weight with respect to the sum of TBAB and fructose.
4 . The process according to claim 1 , wherein the reaction time of step 1) is comprised from 1 minute and 240 minutes.