Catalysis of Organic..

Marincean et al. 435increasing from 0.05 to 0.1M led to PG yields of 16% and 33% - a similar increase.In contrast, for 0.1 M KOH the increase in PG yield from water to i-PrOH/water to i-PrOH is 13% to 32% to 45%. Thus, while we cannot exclude the possible role ofbase strength in different solvents, the solvent structure appears to have a largereffect.40PG Yield, %30201000 1 2 3 4 5 6Time, h0.05M KOH/iPrOH/H2O 0.1M KOH/iPrOH/H2O0.25M KOH/H2O 0.1M KOH/H2OFigure 6. PG Yield at Different Base Concentrations aa Reactions carried out on 100ml solution of 1M GO, 0.1 M KOH for 6h at 200ºCand 1000psig H 2 using 0.5g Ni/Re catalyst.Finally, we note that carbon balance closures are generally poorer in thealcohols than in water. A control experiment in which the entire reaction was carriedout without sample collection, and another in which reactor and contents werecarefully weighed at each stage of reaction, offered no hint as to the fate of lost GOor products. We measured gas formation in the reactor headspace and found < 1% ofinitial carbon present as gaseous products, primarily methane. We suspect thatglycerol and alcohols are forming ethers at the elevated reaction temperatures, andthat these ethers are not detected in HPLC. We are continuing efforts to betterunderstand interactions of the solvents with substrates and reaction products.ConclusionsGO hydrogenolysis to PG in presence of a Ni/Re catalyst is favored by a solvent thatpossesses both a hydroxyl group and a bulky carbon backbone. We attribute thisphenomenon to facilitated access of GO to the surface of the catalyst. We areconducting absorption experiments to elucidate in more detail the phenomena thattake place at the surface of the catalyst.