Catalytic Transformation Of Cellulose Into Levulinic Acid And γ-Valerolactone

With the aim of sustainable future, increasing attentions have been devoted tovarious routes for the production of biofuels and biochemicals via chemical andbiological catalysis. Taking amount of feedstock, food supply and processingcapacity into consideration, chemical transformation of cellulosic materials intobiofuels and biochemicals has to be emphasized. Current investigations show thatefficient conversion of cellulose to glucose, sorbitol, glycol, syngas, aromatics andfurans has been achieved via hydrolysis, hydrogenation, catalytic pyrolysis anddehydration. All of them are“building blocks”for biorefinery which is of greatpotentials to be the future chemicals, materials, and energy base.Levulinic acid, also a“building block”derived from cellulose, is a fascinatingcompound because it offers several promising routes for biofuels as well asbiochemicals. Starting from levulinic acid, levulinic esters andγ-valerolactone canbe obtained through addition of alkenes and hydrogenation respectively. Both can beblended with gasoline as ethanol. With regard to energy density, polarity and boilingpoint, the derivatives of levulinic acid orγ-valerolactone, such as valerate,5-nonanone, butene and C8+ alkenes, are more attractive in fuel applications.Moreover, levulinic acid andγ-valerolactone can also be converted to monomers.For instance, reaction with levulinic acid and phenol provides bisphenol A which isusually synthesized from acetone and plays important roles in polycarbonate andepoxy resin production. However, problems including the use of wasteful andcorrosive mineral acid, the efficient separation of levulinic acid and external H2supply, remain as bottleneck of the routes from cellulose to levulinic acid andγ-valerolactone.In chapter 1, we introduced the current state of the transformation of biomasstowards biofuels and biochemicals as well as the concept of“building blocks”brieflyThe chemical conversion of cellulose, synthesis and application of leculinic acid andγ-valerolactone were carefully reviewed. Besides,the relationship between biomassconversion and green chemistry were also commented.In chapter 2, levulinic acid was produced from cellulose by magnetic solid acidwith mesopores. The process may find important applications for the liquid fuels andvaluable chemicals production based on levulinic acid. By contrast with H2SO4, the catalysts are more efficient to convert microcrystalline cellulose into LA and catalyst separation can be readily achieved by magnetic force.The in-situ reduction of levulinic acid using by-product formic acid was reported in chapter 3 and 4. We creatively proposed the transformation of levulinic acid in water with equimolar formic acid toγ-valerolactone. The success of this new route not only improves the atom economy of the process, but also avoids the energy-costly step to separate LA from the aqueous solution mixture of LA and formic acid. We have demonstrated that by using inexpensive RuCl3/PPh3, 1:1 aqueous mixture of levulinic acid and formic acid can be catalytically converted toγ-valerolactone in high yields. A striking positive CO2 effect on Ru-catalyzed hydrogenation is also observed, which may be used to explain the good performance of aqueous hydrogenation using water insoluble ligand. Moreover, by using heterogeneous catalyst Ru-P-SiO2 for decomposition of fomic acid and Ru/TiO2 for hydrogenation of levulinic acid, an efficient two-step process forγ-valerolactone production has been developed. The two catalysts can be used repetitively for at least 8 times without deactivationIn summary, two key problems concerning levulinic acid andγ-valerolactone production has been solved. First, levulinic acid has been prepared from cellulosic feed via a“green”dehydration process using magnetic mesoporous solid acids. Second, levulinic acid formed in aqueous medium can be reduced toγ-valerolactone by robust catalysts without using external H2.