ETA-CU3SI PERCENTAGE AND PARTICLE-SIZE IN VARIOUS ROCHOW CONTACT MASSES

Various Rochow contact masses have been characterized by catalytic tes ts as well as by X-ray diffraction with respect to eta-Cu3Si percentag e and particle size. The presence of eta-Cu3Si in the contact masses i s neither a necessary nor a sufficient precondition of catalytic activ ity, but a certain contribution of dispersed eta-Cu3Si to the activity cannot be excluded. The results can be explained consistently by assu ming highly dispersed or even two-dimensional Cu-Si species, not detec table by X-rays, as catalytically active species. The promoters zinc, antimony and tin do not significantly change the percentage and partic le size of eta-Cu3Si.