Abstract
A series of Ru-(Mn-M)OX catalysts (M: Al, Ti, Zr, Zn) prepared by co-precipitation were investigated in the hydrogenolysis of xylitol in water to ethylene glycol, propylene glycol and glycerol at 200 °C and 60 bar of H2. The catalyst promoted with Al, Ru-(Mn-Al)OX, showed superior activity (57 h−1) and a high global selectivity to glycols and glycerol of 58% at 80% xylitol conversion. In comparison, the catalyst prepared by loading Ru on (Mn-Al)OX, Ru/(Mn-Al)OX was more active (111 h−1) but less selective (37%) than Ru-(Mn-Al)OX. Characterization of these catalysts by XRD, BET, CO2-TPD, NH3-TPD and TEM showed that Ru/(Mn-Al)OX contained highly dispersed and uniformly distributed Ru particles and fewer basic sites, which favored decarbonylation, epimerization and cascade decarbonylation reactions instead of retro-aldol reactions producing glycols. The hydrothermal stability of Ru-(Mn-Al)OX was improved by decreasing the xylitol/catalyst ratio, which decreased the formation of carboxylic acids and enabled recycling of the catalyst, with a very low deactivation.
Highlights
Ethylene glycol (EG) and propylene glycol (PG) are employed as raw or starting materials in various useful industrial applications, such as heat-transfer fluids and cosmetics, in the pharmaceutics and packaging sectors [1,2]
In the last few decades, it has been reported that the upgrading of alditols to glycols can be performed in the aqueous phase under harsh conditions with temperatures of 160–230 ◦ C and H2 pressure (40–120 bar)
The actual M loadings (i.e., Al, Ti, Zn, Zr) were very different from the nominal ones; in particular up to 97% of Al was lost (Table 1, entry 1). This might originate from the too high pH applied during the synthesis of the material, which is outside the limits of precipitation of aluminum hydrate and alkaline dissolution of amorphous Al(OH)3 to soluble sodium aluminate occurs
Summary
Ethylene glycol (EG) and propylene glycol (PG) are employed as raw or starting materials in various useful industrial applications, such as heat-transfer fluids and cosmetics, in the pharmaceutics and packaging sectors [1,2]. 2 intermediates by the reaction of theofaldose or ketose catalyzed by base such such as They are hydrogenated to glycols or glycerol. The decarbonylation reaction may be catalyzed by the metallic sites and forms base. At high conversion of the catalysts displayed high selectivity to glycols and glycerol (up to 85%) at high conversion of the alditols alditols in the presence of. Fe2 O3 ) showed a high global Ni selectivity to on glycols and glycerol (58%composed at 41% conversion). 2O3) showed a high global selectivity to glycols and glycerol (58% at 41% conversion) as well as as high hydrothermal stability for four consecutive runs [20]. We reported high activity promotion of reasonable a Ru/C catalyst for hydrogenolysis of xylitol(32%). −1) and reasonable selectivity to glycols and glycerol (32%) over a 3%Ru/MnO(4.5%)/C We demonstrated that the Ru-(Mn-Al)OX catalyst stability could be improved by varying the operating conditions
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