2806
Ind. Eng. Chem. Res. 1992,31, 2806-2807
The rates of methane consumption at 550 and 600 " C were, respectively, 4.8 x and 5.12 x mol min-' ~ m - ~The . difference between the two rates is too small to be considered significant, and is not compatible with Arrhenius' law. It should also be noted that the catalytic rate of methane consumption was 4.23 X mol min-' ~ m -which ~ , was slightly lower than the rate of homogeneous reaction (runs 7 and 9). Thus it would be difficult to draw any conclusion about the contribution of homogeneous reactions in experiments where a catalyst was used. We would suggest that the interpretation of the results should take into account complete conversion of oxygen, and the effects of residence time and reaction temperature
on the product distribution should be investigated with excess oxygen at the exit of the reactor. Registry No. CHI, 14-82-8; 02, 1182-44-1.
Literature Cited Walsh, D. E.; Martenak, D.J.; Han, S.; Palermo, R. E. Direct Oxidative Methane Conversion at Elevated Pressure and Moderate Temperatures. Ind. Eng. Chern. Res. 1992, 31, 1259.
0. Olaofe, P. L. Yue* School of Chemical Engineering University o f Bath Bath BA2 7AY, U.K.
Response to Comments on "Direct Oxidative Methane Conversion at Elevated Pressure and Moderate Temperatures" Sir: Based on their comments on our paper (Walsh et al., 1992), it would appear that Olaofe and Yue are restating remarks already presented in the article, and are interpreting more in the data than we, the authors, intended, asserted, or believed was justified. Their general observation that oxygen is the limiting reactant in this study is self-evident; it is also characteristic of most current direct oxidative methane conversion studies in the literature. Likewise, the discussion of the range over which methane conversion can vary and its limiting values which are governed by different stoichiometries has been appreciated by those working in the field. Their discussion that longer residence times can promote further reactions among products appears to be a restatement of our remarks in the article (p 1261, column 1,paragraphs 1and 2). In particular, we noted that oxygen consumption remained complete when residence time was reduced by a factor of 3; consequently, we suspected that since more residence time was available in most runs than was required to achieve complete oxygen consumption, certain thermodynamically feasible secondary reactions might occur. As reported, the similarity of the product distributions (and associated methane conversions) in two runs at substantially different residence times suggested that such reactions "do not proceed extensively" during the available incremental time (
