Apparent Rate Constant for Diffusion-Controlled Three molecular   (catalytic) reaction
  We present simple explicit estimates for the apparent reaction rate constant for three molecular reactions, which are important in catalysis. For small concentrations and $d> 1$, the apparent reaction rate constant depends only on the diffusion coefficients and sizes of the particles. For small concentrations and $d\le 1$, it is also time -- dependent. For large concentrations, it gains the dependence on concentrations. 
S. F. Burlatsky (1), M. Moreau (2) ((1) University of Washington,   Seattle, (2) Universit\'e Paris VI)