Catalytic Conversion Of Carbohydrates To Produce 5-ethoxymethyl Furfural

With the worsening environmental quality,the development of alternative fuels and chemicals from renewable resources has been receiving much needed attention.Abundant renewable biomass is considered to be the most promising alternative carbon source for the sustainable supply of liquid fuels and chemicals,which has the potential to displace diminishing fossil fuel resources,especially through the transformation of carbohydrates that is the richest component of terrestrial biomass.Recently,5-ethoxymethylfurfural(EMF)has drawn increasing attention in recent years purporting its potential use as a biofuel alternative or diesel additive.It is known that EMF can be directly produced from one-pot conversion of carbohydrates in ethanol-containing medium catalyzed by acid catalyst.Currently,develop a competitive catalyst strategy is the key point for the selective synthesis of EMF.Herein,we first proposed to make use of lignosulfonate as a precursor to synthesize a novel carbonaceous solid acid catalyst by facile one-step simultaneous carbonization and sulfonation.Effect factors of catalyst preparation were explored,and the physicochemical properties of as-prepared catalysts were well characterized using a variety of techniques.The catalytic activities of as-prepared catalyst were evaluated for the one-pot conversion of biorenewable carbohydrates to furan derivatives including EMF and 5-hydroxymethylfurfural(HMF).On the other hand,inspired by the present research advances and existing issues,the objective of this study was to investigate the feasibility of Amberlyst-15 and Al(OTf)3 mixed-acid catalyst system in conjunction with the use of ethanol-DMSO co-solvent media for improving the yield of EMF directly from glucose conversion.The effects of multiple process parameters were evaluated and modeled to assess the optimal combination for maximizing EMF production via response surface methodology.Additionally,the reaction mechanism,as well as reusability and feedstock adaptability of the developed catalytic system were explored.In addition,it was well known that solvent composition enabled control of reactivity and selectivity for liquid-phase reactions,the effect of incorporation of co-solvent into ethanol as the reaction medium for the conversion of fructose was studied.An eco-friendly and low-cost lignosulfonate-based acidic carbonaceous catalyst(LS-SO3H)was first effectively fabricated using sulfite pulping by-product of sodium lignosulfonate as a precursor by facile one-step simultaneous carbonization and sulfonation,and employed for the synthesis of promising biofuel furan derivatives from biorenewable feedstocks.The catalyst preparation conditions significantly affected the preparation and properties of LS-SO3H.A relatively high catalyst preparation yield(40.4%)combined with strong-SO3H density(1.33 mmol/g)were obtained after treating at 120 C for 6 h.The preparation yield of LS-SO3H was nearly twice as much as that of one-step prepared catalyst using alkaline lignin(another technical lignin from pulping)as a precursor.The as-prepared LS-SO3H had similar textural characteristics to the frequently-used two-step prepared carbonaceous catalyst involving pyrolysis carbonization and sulfonation.The LS-SO3H was found to show good catalytic activity for the synthesis of EMF in ethanol medium,affording around 86%,57%and 47%yields from HMF,fructose and inulin,respectively.Also,a high HMF yield of 83%could be achieved from fructose when dimethyl sulphoxide(DMSO)was replaced as the reaction medium.The used LS-SO3H was readily recovered by filtration,and remained active in recycle runs.Presently,very few strategies are available for directly converting glucose-like compounds to EMF,a remarkable biofuel candidate.We report here on this conversion effectively using aluminum-based mixed-acid catalyst in co-solvent medium.The combination of aluminium triflate and Amberlyst-15 exhibited an admirable synergistic catalytic effect for the one-pot cascade conversion of glucose.Importantly,the interfusion of DMSO into ethanol as co-solvent medium can significantly promote the formation of EMF reducing the extent of side reactions.Based on this protocol,the effects of key process variables on the conversion of glucose was investigated via response surface methodology,leading to EMF in up to a 48.1%yield.The catalytic system can be separated with the reaction products and demonstrates reusability.Also,the generality of developed catalytic strategy can extended to synthesize EMF directly from glucose-based polysaccharides,such as sucrose and starch.Several organic compounds have been used to be co-solvents for the alcoholysis of fructose.To get more insight into the role of co-solvent in the conversion of fructose,the reaction was carried out in pure ethanol medium and various co-solvent media.All findings suggest that the type of co-solvent and the amount of co-solvent have a significant effect on product distribution and product selectivity.Among these organic solvent,N,N-dimethylacetamide(DMA)exhibits excellent properties in the system,which not only changes the selectivity of the product,but also significantly increases the total yield of furan derivatives.The reason for this is that the DMA will lead to a stronger hydrogen binding to the carbocation forms and increased stabilization of the transition state for the dehydration of fructose,thus stabilizing HMF and lessening side-reactions.On the other hand,a certain proportion of ethanol can shield DMA protection for HMF hydroxyl group to form EMF by etherification.An optimized furan derivatives yield of 84.4%could be achieved at 140 C for 4 h with substrate concentration of 50 g/L.In summary,this thesis develops an easy-prepared and low-cost recyclable solid acid catalyst(LS-SO3H)for the efficient synthesis of promising furan derivatives from biorenewable feedstocks.Furthermore,we have discovered that mixed-acid system consisting of Al(OTf)3 and Amberlyst-15 in ethanol-DMSO medium can be used as a facile and efficient catalytic strategy for the one-pot cascade transformation of glucose to produce the promising biofuel EMF in a competitive yield.Moreover,the influence of co-solvent on the distribution of products in fructose-ethanol system was further investigated.The findings of this dissertation can provide theoretical guidance and technical reference for further research and industrial scale production of biomass-based EMF.