Catalytic functionalities of nano Ru catalysts supported on TiO2–ZrO2 mixed oxide for vapor phase hydrogenolysis of glycerol to propanediols

Abstract

Vapor phase hydrogenolysis of glycerol was studied over Ru catalysts supported on TiO 2 -ZrO 2 binary oxide. Ru catalysts with various ruthenium loadings from 1.0 to 6.0 wt% were prepared by deposition-precipitation method on the TiO 2 -ZrO 2 mixed oxide support. These catalysts were characterized by X-ray diffraction, H 2 temperature-programmed reduction, NH 3 temperatureprogrammed desorption, transmission electron microscopy, BET surface area, XPS and CO chemisorption measurements. The catalysts exhibited superior performance for the vapor phase hydrogenolysis of glycerol at moderate temperature and atmospheric pressure. The mixed oxide support plays a significant role in improving the catalytic activity for the production of propanediols. The glycerol conversion and the selectivity of various products depend on the catalyst preparation method and also on the Ru content. The influence of acidity of the catalyst and its correlation to the catalytic performance (selectivity and conversion) has been studied. The weak and strong acidic sites of the catalysts measured by NH 3 -TPD play a key role in selective formation of 1,2-propanediol and 1,3-propanediol. XRD, TEM, XPS and CO chemisorption studies revealed that ruthenium was well dispersed on TiO 2 -ZrO 2 which further contributed to the superior catalytic activity for glycerol hydrogenolysis.

Support Screening Studies on the Hydrogenation of Levulinic Acid to γ-Valerolactone in Water Using Ru Catalysts

“…The acidity and type of active sites for various Ru/CNT catalysts reported in the literature varies considerably and is known to be a function of the preparation procedure (e.g., acid pre-treatment conditions) [39,40]. Weak and medium acid sites were observed for the Ru/ZrO2 catalyst with two desorption peaks below 400 °C ( Figure S1), in line with literature data [41,42]. For Ru/SiO2 and Ru/Al2O3, all three types of acid sites are present.…”

Effects of TiO2 structure and Co addition as a second metal on Ru-based catalysts supported on TiO2 for selective hydrogenation of furfural to FA

“…The crystallization of Ru particles was reported to be responsible for the reduction peak of Ru oxides. The reduction peak at lower temperature was attributed to the reduction of well-dispersed RuO x particles, while the reduction peak at higher temperature corresponded to the reduction of RuO x with larger particle size 23 , 24 , 32 . On the other hand, the Ru/TiO 2 -A and Ru/TiO 2 -sol showed only single sharp reduction peak, suggesting to the homogeneity in particle size distribution of Ru species.…”

“…All the Ru-based catalysts showed three main reduction peaks consisting of the first reduction peak at 100–250 °C corresponding to the reduction of Ru oxides to Ru 0 metal 27 – 29 , the reduction peak in the range of 300–450 °C corresponding to Ru interacting with TiO 2 support in the form of Ru-TiO x sites 27 – 30 , and the broad reduction peak at 570–730 °C assigning to the reduction of surface capping oxygen of TiO 2 support (partial reduction of TiO 2 ). Considering the reduction peak of Ru oxides to Ru 0 metal, a series of multiple reducible peaks of the Ru oxides reduction were observed on the Ru/TiO 2 -P25 and Ru/TiO 2 -R catalysts probably due to the presence of different Ru ion species and/or different Ru particle sizes in different environments on the surface of the support 23 , 30 , 31 . The crystallization of Ru particles was reported to be responsible for the reduction peak of Ru oxides.…”

“…The metal dispersion of the catalysts was evaluated by CO pulse chemisorption using a Micromeritics ChemiSorb 2750 pulse chemisorption system. The stoichiometry of CO chemisorption was CO/Ru = 1 23 . Prior to chemisorption, the catalyst was reduced under H 2 (25 cm 3 /min) at 300 °C for 2 h. Afterwards, the sample was maintained at 300 °C under helium flow (25 cm 3 /min) for 0.5 h for removing the physical adsorption of H 2 .…”

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“…In this vain, several glycerol valorization processes such as esterification [1], carbonylation [11,12], etherification [13], hydrogenolysis [14][15][16], acetylation dehydration, oligomerization, dehydrogenation, and glycerol reforming [5,17] have been proposed. Among all of these processes, upgrading glycerol by catalytic acetylation has received tremendous research attention, because it produces commercially valuable esters, namely, mono acetin (MAG), di acetin (DAG), and tri acetin (TAG) [4,7].…”