AmericanChemicalSociety.com

With the support of the Petroleum Research Fund we are seeking to investigate the possibility of using photocatalytic degradation with visible light to remove chlorine-containing impurities from petroleum. Our initial tests were, and will be, run with chloroform dissolved in cyclohexane.

The grant became active on July 1, 2009, at which point one undergraduate student (Anton Seidl) began a series of experiments to test one of our hypotheses, which was that photocatalysis will be effective on chloroform even at the low concentrations typically found in petroleum streams. The hypothesis is based on the premise that until the concentration of CHCl₃ is extremely small, the rate-determining step will be the absorption of light by the photocatalyst. Using (Bu₄N)₂FeCl₄, which has high photocatalytic activity in pure chloroform, the rate of photodecomposition was measured in different ratios of chloroform to cyclohexane. What was observed was a small diminution in the degradation rate as the concentration of chloroform decreased. A solution with 10% chloroform had a rate about 80% of the rate found in pure chloroform. Unfortunately, we could not carry the experiments down to lower concentrations, because the catalyst was no longer soluble. We expect this to be a common problem.

In September I began a year-long sabbatical leave at the University of Ferrara, in Italy. I worked with Prof. Andrea Maldotti, whose area of specialty is heterogeneous catalysis by  coordination complexes. I did not do any work related to the PRF project, but given what I picked up during this year, I now plan to completely revise our approach to the photodecomposition of chloroform in petroleum by heterogenizing the catalysts. This will eliminate solubility problems, although the reactivity may turn out to be different than in homogeneous solution. Heterogeneous catalysis is much more practical in actual applications in any case (and we proposed eventually moving in that direction), but I expect we will be using heterogeneous catalysis exclusively in our studies.