Acidic ionic liquid catalyzed liquefaction of untreated switchgrass biomass in acetone and Pd-La(OTf)3 catalyzed reduction of the products

Highlights: • Switchgrass was liquefied in acetone using acidic ionic liquid catalysts at 120 °C. • Sixteen C5-C15 range products were found in the switchgrass liquefied product. • Liquefied product was reduced using H₂, 200 °C, 1.38 MPa and Pd-La(OTf)₃ catalyst. • Mainly alcohol and ketone products were found in the reduced product. -- Abstract: The cellulosic fraction of untreated switchgrass was partially liquefied by using acidic ionic liquid catalysts and heating in acetone at 120 °C for 3.5 h. The Brønsted acidic ionic liquids 1-(3-propylsulfonic)-3-methylimidazolium chloride and 1-(4-butylsulfonic)-3-methylimidazolium as catalysts produced 39.5% and 31.75% w/w liquefactions of switchgrass biomass and the lignin fraction remains unaffected by the mild conditions used. Sixteen C5-C15 range products were observed in the switchgrass liquefied product and 13 compounds were identified using GC-MS, including three products arising from dimerization of acetone under acidic conditions used. The liquefied product could be partially reduced by catalytic hydrogenation using Pd-La(OTf)₃ catalyst system in 50% aq. acetic acid at 200 °C, 1.38 MPa for 16 h. Thirteen, mainly alcohol and ketone products were identified in the catalytically reduced liquefied product.