Supercritical water hydrolysis combined with silver mesoporous zeolite catalysts for the hydrolysis of cellulose into glucose

E. ALONSO; S. ASPROMONTE

Ciudad Real

Congreso; 17th European Meeting on supercritical fluids (EMSF 2019)-7th European Meeting on High Pressure Technology; 2019

The depolymerization of cellulose into glucose is an important process and remains a challenge for the conversion of lignocellulosic biomass to fuels and chemicals. Cellulose is formed by the binding of β-glucopyranose molecules via β-1,4-glucosidic bonds. Cellulose chains are coupled together in bundles hydrogen bridges. Additionally, the cellulose fibers do not dissolve either in water or in most organic solvents. Supercritical water (SCW) in ultrafast reactors with hydrolysis times of milliseconds has demonstrated to possess good ability to partially depolymerize cellulose without further degradation of sugars1. Although under such conditions more than 99 % of the cellulose is solubilized, the presence of oligomers remains high (> 60 % C)2. A possible approach to solve this problem is to complete the hydrolysis of cellulose by acid heterogeneous catalysts. The aim of the present work is to complete the hydrolysis of oligomers derived from supercritical water hydrolysis in ultrafast reactors into glucose, by using heterogeneous catalysts. For this purpose, the behaviour of Ag-based catalysts exchanged in mesoporous Na-mordenite was studied. This performance is compared to the commercial acid zeolite (HMOR, Si/Al=10) in an inert and reducing atmosphere. In addition, to achieve a global understanding of the observed catalytic behaviour several physicochemical techniques were applied, such as adsorption/desorption isotherms of N2 and measurements of X-ray photoelectron (XPS) and solid-state NMR spectroscopies, programmed-temperature reduction (TPR) and programmed-desorption temperature of ammonia (TPD-NH3).