Linked Strategy For The Production Of Fuels And Chemicals Via Formose Reaction

The world is currently faced with two significant problems:fossil fuel depletion and environmental degradation due to the consumption of fossil energy. As one of the solutions to these problems, the transformation of biomass into fuel and chemicals has drawn more and more attention. Current strategies for converting inedible lignocelluloses biomass to liquid fuels and chemicals involve two major methods:pyrolysis and hydrolysis. In these two methods, entire biomass can be converted to syn-gas through gasification in pyrolysis, but lots of energy will be lost in the Fischer-Tropsch synthesis (FTS) to convert syn-gas to alkanes. In contrast, hydrolysis method of converting soluble carbohydrates into liquid fuels and chemicals through aqueous phase-processing (APP) has advantages of benign reaction conditions and high energy efficiency. However, the pretreatment and acid hydrolysis of biomass to sugars are costly and may cause environmental concerns. In this respect, a low-cost and high-efficiency refinery technology still remains absence.Faced with these problems, this paper described a new catalytic path here which linked biomass gasification with APP via formose reaction to make liquid transportation fuels and chemicals. At first, formaldehyde from syn-gas was converted to triose. This was followed by aldol condensation and dehydration to4-hydroxymethylfurfural (4-HMF). Finally,4-HMF was hydrogenated to produce C9-C15branched-chain alkanes or2,4-dimethylfuran (2,4-DMF) as liquid transportation fuels. In the linked strategy, high energy-consuming pretreatment as well as expensive and polluting hydrolysis of biomass were omitted, but the high energy recovery of APP was inherited. Theoretically, about75%of the energy in methanol and almost50%of the energy in biomass was retained in the liquid fuel2,4-DMF, and by comprehensive utilization of reaction heat energy efficiency could be further improved. Inadditional, as a novel building block platform, this paper also described the application of4-HMF in preparing chemicals.In the first chapter, we briefly introduced the current development of conversion of biomass to liquid fuels, reviewed thoroughly current three routes for conversion of biomass to liquid fuels:gasification-FTS route, pyrolysis-upgrading route, and hydrolysis-APP route, and compared these three routes, proposed a new strategy of linking gasification with APP through formose reaction.In the second chapter, an important path was introduced in biomass APP——5-hydroxymethylfurfural (5-HMF) based refining path, as well as various influence factors. Furthermore the application of5-HMF in preparing liquid fuels and fine chemicals was briefly introduced.The third chapter is mainly about the preparation of triose sugars. In this chapter we proposed two methods to prepare triose sugars: glycerol catalytic oxidation method and selective formose reaction. In the study of glycerol catalytic oxidation, with Pt-Bi/C catalyst oxidized glycerol aqueous solution with oxygen, we got the highest selectively of80%to prepare1,3-dihydroxyacetone (DHA). In the study of selective formose reaction, we at first briefly introduced the development history of formose technique as well as the advancement of DHA technique. Then, we synthesized DHA by using N-alkylation benzothiazole carbene catalyst for selective catalysis of paraformaldehyde. Moreover, considering the cost of feedstock, we designed a dual towers system using solvent azeotropic water method regenerated the catalyst in situ to achieve the continuous conversion of formaldehyde solution to DHA.In the forth chapter, we mainly studied the catalytic condensation of triose sugars. Studies indicated that with base catalysts glyceraldehyde (GLYD) isomerized into DHA at first, and then cross condensation occured between GLYD and DHA to form straight-chain hexoketoses (SCS); while under base catalysis DHA self-condensation happened to form branch-chained hexoketose (BCS). Also, through the research on fixed bed flow reactor, we find out that the activation energy of DHA isomerizing to GLYD is higher than that of DHA’s self condensation. Therefore, reaction temperature can also control the distribution of DHA condensation products. Moreover, we used in situ nuclear magnetic tracking and for the first time confirmed that when the condensation of DHA in room temperature, the molar ratio of products of BCS and SCS is9:1, instead of2:1as reported before.The fifth chapter was mainly about the dehydration of hexoketose. Studies indicate that SCS dehydrate into5-HMF and that BCS dehydrate into4-HMF. We studied the dehydration of BCS into4-HMF in non aqueous system and two phase system respectively with batch procedure or continuous process.In the next chapter, we focused on the conversion of4-HMF into high octane branched alkane fuels and new furyl oxygenated fuels——2,4-DMF. We introduced the application of4-HMF and its derivatives as2,4-disubstituted furan compounds in chemicals such as cantharidin precursor molecules and liquid crystal molecules in the seventh chapter.The last chapter was the summary and outlook of this article.In conclusion, this article represented a linked strategy which linked biomass gasification with APP via formose reaction. In the condensation process of triose sugars, it was confirmed at the first time that DHA can be converted to BCS with selectivity of over95%. At the same time we found serendipitously that BCS could be converted to a new platform molecule——4-HMF. Through process integration, we achieved the continuous production of4-HMF, and presented the application of4-HMF in fuels and chemicals respectively, opens up a new aqueous refining path based on4-HMF.