NOVELTY - Preparation (P1) of hydroxymethylfurfural involves i) providing a reaction mixture comprising saccharide and metal complex of N-heterocyclic carbene, where the saccharide is a hexose or a mixture of hexoses, or a dimer, oligomer or polymer or copolymer of a hexose or their mixture; and ii) allowing the saccharide to react in the reaction mixture to form hydroxymethylfurfural, where the steps (i) and (ii) are conducted at less than or equal to 70 degrees C.    USE - For preparing hydroxymethylfurfural useful for making fuel (claimed) e.g. biofuel.    ADVANTAGE - The heterocyclic carbene-metal complexes are capable of catalyzing the conversion of saccharides such as glucose or fructose to hydroxymethylfurfural (5-(hydroxymethyl)-2-furaldehyde; HMF). The reaction proceeds in relatively high yield, particularly when an ionic liquid solvent is employed. The method uses relatively inexpensive and/or readily available substrates, which, in some cases, represent waste materials. 30% HMF yield is achieved by conversion of cellulose according to the process. The method enables recycling of the metal complex of the N-heterocyclic carbene and/or of the solvent without a separate step of removing the volatiles. The N-heterocyclic carbene (NHC)/ionic liquid system selectively produce hydroxymethylfurfural (HMF) from glucose and fructose. The HMF yields are as high as 96% and 82% from fructose and glucose respectively. The system provides high selectivity towards HMF, and tolerance towards high substrate loading. It also allows ease of recycling of catalyst and ionic liquid. The high efficiency of the catalyst and the high substrate loading render the process is very attractive for industrial scale-up. This reaction process also allows for the continuous extraction of product. The ionic liquid-metal catalyst system has excellent stability and selectivity in HMF conversion from carbohydrates. The process facilitates continuous or semi-continuous operation; and/or facilitates reuse/recycling of the metal complex; and/or facilitates separation of the product; and/or higher yield of HMF. The ionic liquid-tungsten salt catalyst system can effectively convert fructose to HMF at a much lower temperature ( less than or equal to 50 degrees C) than previously used. This system offers a feasible large-scale continuous HMF production protocol under moderate temperatures and ambient pressure.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for making (P2) fuel involving carrying out steps (i) and (ii); and iii) converting the hydroxymethylfurfural obtained to the fuel.