Hydrolysis of Cellulose to Glucose over Solid Acid Carbon Catalysts in Flow Reactor
Renewable Plant Resources "Chemistry, Technology, Medicine"
18-22 Sep 2017
|| Gromov Nikolay V.
, Medvedeva Tatiana Borisovna
, Taran Oxana Pavlovna
, Aymonier Cyril
, Parmon Valentin Nikolaevich
Boreskov Institute of Catalysis SB RAS
Novosibirsk State Technical University
University of Bordeaux
Novosibirsk State University
Cellulose, as the main component of plant biomass, is a promising renewable alternative to fossil resources for the production of valuable chemicals and fuel components. Of particular interest is the search for new catalytic one-pot technologies for synthesis of glucose directly from inedible cellulose instead of food resources (starch, sucrose, etc). Glucose is a widely used chemical. It could be used for a synthesis of 5-hydroxymethylfurfural (5-HMF), levulinic acid and other most promising bio-based platform molecules for producing food additives, plastics, pharmaceutics and biofuels. To produce glucose from cellulose, solid acid carbon materials seem to be one of most promising catalysts for the process.
The aim of this work was a development of the solid acid catalysts based on graphite-like carbon Sibunit for the production of glucose from cellulose and an elucidation of the mechanism of the catalytic action.
Ten Sibunit carbon catalysts were prepared using sulfonation (H2SO4 at 80-200 °С), oxidation (by HNO3 or wet air ) and subsequent oxidation-sulfonation methods (by additional sulfonation of oxidized carbons at 200 °С). The catalysts were characterized by N2 absorption, titration with NaOH, XPS and XRF and tested in the one-pot hydrolysis-dehydration of a mechanically activated cellulose in a flow reactor at 200 °С under 200 bar.
The highest formation of the products was observed during the first hour of the reaction (about 70-80% of the total yield). All the catalysts could be divided into three groups in terms of the catalyst activity (Figure 1). Only one catalyst - untreated pure Sibunit - was in the group with the lowest activity (glucose yield 20%).
The second group consisted of sulfonated and oxidized catalysts. Carbon oxidized by wet air was the most active carbon in spite of the lowest acidity among all the samples in the group due to high specific surface area.
The third group was composed of oxidized-sulfonated carbons. They were noticeably (about 1.5-2 times) more active compared to other samples. Such a difference of the activities was in the agreement with the total acidity of the catalysts. The highest yield of glucose obtained under the flow conditions equal to 74% was reached in the presence of Sibunit oxidized by HNO3 and additionally sulfonated.
The results obtained make possible to assume a heterogeneous reaction mechanism: saccharide transformations take place on the surface of catalyst. Both specific surface aria and surface acidity are crucial parameters for the activity of solid Sibunit acid catalyst.