Hybridizing HKUST-1 And Titania:a High-performance TiO₂ Supported Copper Nanocatalyst For Furfural Hydrogenation

Production of high-value downstream fine chemicals via traditional fossil fuels is vital to rapid economic growth.However,several drawbacks,such as reserve shortage,carbon emission,environmental pollution etc.,cannot be neglected.Alternatively,biomass valorization has attracted much attention due to its green chemistry and sustainability.Furfural is derived from the fermentation and hydrolysis of agricultural wastes and can be converted into hundreds of value-added fine hydrogenation chemicals.Therefore,preparing efficient,stable,low-cost,and recyclable catalysts has been the key to the biomass route.In recent years,metal-organic frameworks（MOFs）have been widely used in composites due to their high surface area,fractional porosity,tunability of metal nodes,and modification flexibility.It provides a new idea to prepare MOFs inorganic oxides hybrid by using MOFs as a precursor.Given the current problems of low activity,unstable selectivity,and easy sintering inactivation of nano-copper hydrogenation catalyst for furfural,this thesis proposes a novel preparation strategy of in-situ hybridizing MOFs with inorganic oxides was proposed to prepare the highly dispersed nano-copper catalyst,and the structure-activity relationship between the structure and the hydrogenation performance of furfural was investigated.Firstly,a metal-organic framework material HKUST-1 was uniformly hybridized with titanium dioxide and then calcinated to attain highly-dispersed titania supported copper catalyst（Cu O#TiO₂）.Distinctly from the copper catalysts prepared by the conventional routes（impregnation or co-precipitation）,this novel Cu O#TiO₂catalyst has a high copper dispersion（particle size of～5 nm）,easy-reducible copper species,and weakened Lewis acidity.As a result,it shows superior high activity(～20.8 mol _FUR/mol _Cu·h)and high furfural alcohol selectivity（100-%）at 140-°C and 2 MPa for furfural hydrogenation.Moreover,Cu O#TiO₂can be reused several times after regeneration at 200°C of air-calcination without significant activity attenuation.The comprehensive characterization of the structure and properties of the catalyst revealed that the high activity and stability of Cu O#TiO₂can be attributed to the in-situ hybridization manner,which can intensify the interaction between Cu O and TiO₂,provide more active sites,and depress side reactions.Then based on the above obtained Cu O#TiO₂catalyst from the in situ preparation strategy,we explored the promotion synergy raised by the co-catalyst K₂CO₃in the copper-catalyzed liquid-phase furfural hydrogenation.Assisted by the K₂CO₃,the Cu O#TiO₂acquired a high furfuryl alcohol productivity of 24.2 mol _FOL/mol _Cu·h at 100 ^oC and 1.4 Mpa,nearly four-fold higher than the single Cu O#TiO₂did,representing the top catalytic performance amongst these most state-of-the-art reports so far.Moreover,analogous promotion synergy is available in commercial copper nanoparticles and other substrates with excellent activity and selectivity,demonstrating its broad applicability.Catalyst structure characterizations and controlled experiments have unveiled that the K₂CO₃assistant served a prominent dual functional role,i)boosting the in situ generations of surface copper active sites and ii)promoting the gaseous hydrogen dissolvation in ethanol medium.Both contributions enabled a smoothed overall hydrogen dissociative adsorption kinetic,realizing a striking enhanced hydrogenation activity under a mild reaction.