(323c) Gas- and Aqueous-Phase Hydrogenation of Acetic Acid Over Ru Catalysts

Research on biofuel production from biomass has rapidly increased due to the depletion in fossil fuel reserves and to the rising concerns with greenhouse gas emissions. Hydrogenation reactions, and particularly the hydrogenation of organic acids, are critical in most pathways for production of biofuels. This work presents and compares the results of Ru catalyzed acetic acid hydrogenation in both gas and liquid phases in various types of reactor configurations. In this presentation we will show that the aqueous phase does not change the catalytic properties, and that the catalytic activity is a function of the concentration of both the acetic acid and the hydrogen in the reactor. We will compare our experimental results with density functional theory (DFT) studies to gain a better understanding of the reaction chemistry.

All experiments were carried out with a Ru/Carbon catalyst. We studied the effect of water concentration at 175?aC in a flow reactor by keeping the acetic acid and hydrogen concentrations constant (0.0016 M and 0.061 M, respectively), and by varying the water/water vapor concentration in the system (0-0.13 M). We have observed that the presence of liquid water has very little effect on the activity and selectivity of the catalyst. It has been concluded that the hydrogen and acetic acid concentration on the catalyst surface changes the catalytic properties.

We also compared acetic acid hydrogenation in both batch and flow reactors. Again in these experiments the hydrogen and acetic acid partial pressures are the controlling variables. In the flow reactor the hydrogen partial pressure is typically significantly higher than in typical batch reactors. Therefore, flow reactors are significantly better hydrogenation reactors than batch reactors.

These results provide important insights as to how hydrogenation reactions can be improved.