5-Hydroxymethylfurfural Conversion To Liquid Fuel Over Pt Based Catalysts

With the massive use of non-renewable fossil fuels,more and more carbon dioxide is emitted into the atmosphere,causing a series of environmental problems such as the greenhouse effect.Biomass has received increasing attention due to its abundant storage,wide distribution and renewable nature.Among them,inedible lignocellulose is widely studied and5-hydroxymethylfurfural（HMF）,obtained by hydrolysis of cellulose under acidic conditions,is known as one of the most important platform molecules.A variety of high value-added chemicals or liquid fuels can be obtained from HMF.This paper focuses on the preparation of the liquid fuel 2,5-dimethylfuran（DMF）and etherification products from HMF.DMF has the advantages of low oxygen content,high boiling point,high octane number,high energy density and low water solubility,and is known as a"second generation biofuel".In addition,direct or reductive etherification of HMF has been shown to increase the octane rating of fuels,making it a potential fuel additive.In this thesis,a low loading Pt-FeO_x/AC bimetallic catalyst was prepared by impregnation and its catalytic performance for the selective hydrolysis of HMF to DMF was investigated.The synergistic effect between Pt and FeO_x was explored using XRD,ICP,TEM,XPS and Py-FTIR characterisation.It was found that the addition of a suitable amount of FeO_ximproved the dispersion of Pt,while Pt promoted the reduction of Fe,leading to the formation of more Lewis acidic sites,thus facilitating the hydrogenolysis of HMF.Optimizing the reaction conditions,the DMF yield was up to 91.1%at 180°C and 1.5 MPa H₂ for 6 h.It was also observed that the reaction temperature affected the reaction pathway,with the intermediate product being 2,5-dihydroxymethylfuran（BHMF）at low temperature and5-methylfurfural（MF）at high temperature.The stability testing of 0.5%Pt-2%FeO_x/AC revealed that the easy leaching of Fe resulted in a metal-acid imbalance,which led to a decrease in DMF selectivity and a large amount of over-hydrogenated by-product2,5-dimethyltetrahydrofuran（DMTHF）.In addition,the catalytic performance of Pt-based catalysts with different metal oxides as support for the etherification reaction of HMF was also investigated.The Pt/Nb₂O₅ catalyst was found to be more selective for the hydrogenated product BHMF and gave a yield of up to91.9%with only minimal etherification products produced,mainly due to its strong Lewis acid site.The Pt/Zr O₂ showed better reductive etherification performance,yielding 52.0%of the monoether product 5-butoxymethylfurfuryl alcohol（BMFA）,presumably due to its high Br?nsted/Lewis acidity ratio.In contrast,Pt/Sn O₂ was less reductive etherification compared to Pt/Zr O₂,but when the inorganic acid H₃PO₄ was added,it showed high selectivity for the direct etherification product 5-butoxymethylfurfural（BMF）and up to 82.4%yield was obtained,presumably due to the strong B acid inhibiting the hydrogenation of C=O at the Lewis acid site.Its main product changed to butyl 4-oxopentanoate（BO）when H₂SO₄ was used,probably due to its over-acidity leading to ring opening.