One-pot conversion of D-Glucose into liquid straigh-chain alkanes over Ru-based catalysts

Regarding the shortage of fossil resources and energy sustainability, a great piece of attention has been paid to look for novel alternatives in order to obtain fuels, chemicals and energy.  Due to its high oxygen-to-carbon ratio, cellulosic biomass appears as a promising feedstock for its valorization into chemicals and building blocks. In recent years, direct hydrogenolysis of sugars and sugar alcohols or other platform chemicals (HMF, levulinic acid) has been presented in the literature as one of the major routes in order to produce new generation biofuels. Nowadays, production of alkanes from cellulose is in its infancy. In the present research work, synthesis and characterization of Ru/Al-MCM-48 and Ru/MCM-48/TPA is presented. The catalysts were tested in the direct hydrogenolysis of D-Glucose towards alkanes and their catalytic behaviour was compared with that from a commercial Ru/C.

Mesoporous Al-MCM-48 with a Si/Al = 20 was prepared by a similar hydrothermal sol-gel procedure than that described by Schumacher. Tungstophosphoric acid (TPA) was deposited over MCM-48 in order to improve its acidity. Ru was deposited over Al-MCM-48 and MCM-48/TPA by the typical wet impregnation method. Catalysts were activated at 150 ºC with hydrogen under H2-TPR conditions. Commercial 5% Ru/C supplied by Alfa Aesar was reactivated at 200 ºC under hydrogen atmosphere. Biphasic catalytic experiments (decane/water) were performed in a stainless steel high-pressure reactor of 200 mL equipped with an electrically heated jacket, a turbine agitator with a magnetic driver, and a liquid sample line.

Figure 1. Hydrogenolysis of D-Glucose over different catalysts
Figure 1. Hydrogenolysis of D-Glucose over different catalysts

Ru/Al-MCM-48 presented a metal loading of 3.5%, while Ru/MCM-48/TPA presented 4.9 %. Catalysts were tested in the hydrogenolysis of D-Glucose into alkanes (Figure1). Ru/Al-MCM-48 achieved a yield to alkanes of 56 %, where pentane and hexane were the major compounds in the organic phase. However, Ru/C showed a yield to alkanes of 29 %. The addition of Al-MCM-48 or TPA in the reaction media with Ru/C improved the production of alkanes up to 82 and 70 % respectively. Using Ru/C, hexane was the main product in all cases. Ru/MCM-48/TPA demonstrated low activity in this reaction.

This research has been developed under the Predoctoral Grants Program of  Junta de Castilla y León (E-47-2015-0062773 )

Alberto Romero (1), C. Pinel (2), A. Nieto-Márquez (3), E. Alonso (1), N. Essayem (2)

(1) Chemical Engineering Department, Valladolid, Castilla y León, Spain. 

(2) IRCELyon – CNRS, Lyon, Rhône-Alpes, France.

(3) Optical Characterization of Materials Lab., Madrid, Spain.

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