Title
Efficient microwave-assisted acid hydrolysis of lignocellulosic materials into total reducing sugars in ionic liquids
Authors
VIVIANE DA SILVA LACERDA JUAN BENITO LOPEZ SOTELOADRIANA CORREAGUIMARAES PABLO MARTIN-RAMOS SALVADOR HERNANDEZ-NAVARRO MERCEDES SANCHEZ-BASCONES LUIS M. NAVAS-GRACIA EDUARDO PEREZLEBENA and JESÚS MARTÍN-GIL

Received October 15, 2014
Published Volume 50 Issue 7-8 July-August
Keywords acid hydrolysis, deep eutectic solvents, lignocellulosic materials, microwave, total reducing sugars

Abstract
Different types of lignocellulosic materials (carnauba leaves, macauba shell and pine nut shell) and native cellulose have been studied for the production of total reducing sugars (TRS) through microwave-assisted acid-catalyzed hydrolysis in ionic liquids (ILs). Four reaction media have been assessed: two deep eutectic solvents (DES), choline chloride-oxalic acid (ChCl/ox) and choline chloride-urea (ChCl/urea), and two conventional ionic liquids, tetraethylammonium chloride (TEAC) and tetraethylammonium bromide (TEAB). Five acids (H2SO4, HCl, HNO3, H3PO4andp-toluensulfonic acid) have been evaluated in varying concentrations (5-30%) and time intervals (0-60 min), at different temperatures (100-140°C). Significant TRS production yields (as high as 83.7% in ChCl/ox for carnauba leaves) have been attained for both DES in combination with HNO3 10%, at 120°C for 30 min, with the additional advantage of low furfural and HMF by-products generation.