Hemicellulose arabinogalactan hydrolytic hydrogenation over Ru-modified H-USY zeolites

Abstract

a b s t r a c tThe hydrolytic hydrogenation of hemicellulose arabinogalactan was investigated in the presence of protonic and Ru (1-5 wt.%)-modified USY zeolites (Si/Al ratio = 15 and 30). The use of the purely acidic materials was effective in depolymerizing the macromolecule into free sugars. While the latter partly dehydrated into 5-hydroxymethylfurfural and furfural, the generation of high molecular-weight compounds (aggregates of sugars and humins) was not favored, in contrast to previous evidences over beta zeolites. Application of the bifunctional Ru/USY catalyst, comprising well-dispersed metallic nanoparticles on the aluminosilicate support, resulted in the formation of galactitol and arabitol, in the suppression of dehydration side products, and further inhibition of polymerization reactions, which only yielded low molecular-weight oligomers. Detailed analysis of the reaction pathways as well as kinetic modeling of hydrolytic hydrogenation was performed with an advanced reaction mechanism.

Gallium Modified HUSY Zeolite as an Effective Co‐support for NiMo Hydrodesulfurization Catalyst and the Catalyst's High Isomerization Selectivity

“…The NH 3 ‐TPD profiles in Figure B reveal more than two peaks for the catalysts at temperatures of 495 K and higher, indicating the presence of complex acid types with different acid strengths. As the gallium content increased, the lower NH 3 desorption peak shifted to an even lower temperature, suggesting a decrease in the acid strength of the weak acid sites . However, the other NH 3 desorption peak shifted to higher temperatures, suggesting an increase in the acid strength of the stronger acid sites.…”

“…As the gallium content increased, the lower NH 3 desorption peak shifted to an even lower temperature, suggesting ad ecrease in the acid strength of the weak acid sites. [39] However,t he other NH 3 desorption peak shifted to higher temperatures, suggesting an increase in the acid strength of the stronger acid sites. These results are similar to the observations of Meng et al [40] over Y/ASA composites.…”

Catalytic Upgrading of Biomass‐Derived Sugars with Acidic Nanoporous Materials: Structural Role in Carbon‐Chain Length Variation

“…As shown in Scheme a, arabinogalactan (arabinoxylan) is first hydrolyzed to give arabinose and galactose (xylose and arabinose) in water over acid sites followed by being hydrogenized to yield arabitol and galactitol (xylitol and arabitol) in the presence of metal species . Ru (5 wt %)/USY‐15, which was prepared by the incorporation of Ru into USY zeolite through spray deposition, was developed for the hydrolytic hydrogenation of arabinogalactan in water and afforded 23 % yield of alditols in the presence of 2 MPa H 2 at 185 °C within 4 h . Dehydration side products (e.g., furfural and HMF) were also generated over different Ru/USY‐15 catalysts (i.e., Ru (1 wt %)/USY‐15, Ru (2.5 wt %)/USY‐15 and Ru (5 wt %)/USY‐15), owing to the presence of Brønsted acidity in USY‐15 zeolite, but an increase in the metal loading (i.e., Ru(5 wt %)/USY‐15) could suppress dehydration side reactions associated with sugar dehydration and thereby improve the yield of alditols .…”

“…Ru (5 wt %)/USY‐15, which was prepared by the incorporation of Ru into USY zeolite through spray deposition, was developed for the hydrolytic hydrogenation of arabinogalactan in water and afforded 23 % yield of alditols in the presence of 2 MPa H 2 at 185 °C within 4 h . Dehydration side products (e.g., furfural and HMF) were also generated over different Ru/USY‐15 catalysts (i.e., Ru (1 wt %)/USY‐15, Ru (2.5 wt %)/USY‐15 and Ru (5 wt %)/USY‐15), owing to the presence of Brønsted acidity in USY‐15 zeolite, but an increase in the metal loading (i.e., Ru(5 wt %)/USY‐15) could suppress dehydration side reactions associated with sugar dehydration and thereby improve the yield of alditols . Analogously, acid–metal bifunctionalized Ru/USY, which was fabricated through an ion‐exchange method, accomplished highly effective conversion of arabinoxylan into pentitols (xylitol+arabitol), giving a total yield of pentitols of up to 90 mol % over 5 MPa H 2 at 160 °C after 5 h .…”

Concepts of modern technologies of obtaining valuable biomass-derived chemicals

“…A process of hydrolytic hydrogenation of arabinogalactan from hemicellulose into 5-hydroxymethylfurfural and furfural in the presence of a modified Ru-USY zeolite (Si/Al = 15 and 30, 1-5% ruthenium) has also been developed [56]. Another example is the usage of H-ZSM-5 zeolite in the dehydration of xylose to furfural.…”