Catalysis of Organic..

430Glycerol Hydrogenolysisreaction as a control experiment in which base was added to the reaction mixtureonly after heating to 200ºC showed no PG at t=0.Results and DiscussionThe distribution of GO hydrogenolysis products, PG, LA, and EG, is influencedby the catalyst used and the amount of base present in the reaction mixture (Table 2).When compared to Ru, Ni/Re appears to be more selective towards PG at theexpense of EG.Table 2. GO Hydrogenolysis in Aqueous Medium aSelectivity(%)Exp. Catalyst KOH(M) Conv(%) PG LA EG C Balance(%)1 Ru 1.00 92.0 38.8 47.2 8.4 94.92 Ru 0.50 70.5 38.7 45.3 11.3 96.73 Ru 0.25 52.1 51.0 33.7 15.0 99.84 Ru 0.10 47.1 46.9 13.7 16.0 89.05 Ni/Re 1.00 99.1 63.8 20.6 6.3 90.46 Ni/Re 0.50 74.4 44.1 35.9 8.6 91.57 Ni/Re 0.25 43.9 45.7 30.7 6.9 92.88 Ni/Re 0.10 22.9 60.9 26.6 8.1 99.0a Reactions carried out on 100ml samples of 1M GO for 6h in H 2 O at 200ºC and1000psig H 2 using 0.5g catalyst.Figure 1. GO conversion and solution pH apH14121086pre -1 0.5 1.25 2 5rxnTime, hr1.210.80.60.40.20[GO], MpH[GO]a Reaction carried out on 100ml solution of 1M GO and 0.25M KOH for 6h in H 2 O at200ºC and 1000psig H 2 using 0.5g Ni/Re catalyst.The C-C cleavage pathway that leads to EG takes place to a smaller extent in thepresence of Ni/Re, when keto-enol tautomerization is favored as is shown by thehigher sensitivity of the reaction to the amount of base. GO consumption rate closelyfollows the solution pH, slowing greatly when the reaction medium becomes close toneutral (Figure 1). The acids identified in the reaction mixture, formic and lactic, arenot present in high enough quantities to account entirely for the pH decrease (e.g. to