Sexc/SCat

The high activity of monometallic catalysts in HDS supports the afore given explanation that the absence of surface zero valent Co and Ni results in a decreased Scat, Sexc and HDS activity. 

Sulfur exchange between sulfided CoMoOx/AbOa catalyst and gas phase radioactivity of H2S has been studied by Qian et al. (1997) at high (1-5 MPa) pressure in a pressurised fixed bed flow reactor. The H2S sulfided catalyst was treated with H2/H2 S pulses (0.1% of H2 S). The differences in the flow rates did not affect practically the measured Sexc/Scat ratios. These increased with temperature from 15 to 44% of the total sulfur in the 503-673 K region. 

It is of interest to compare the Smob/Scat data with Sexc/Scat obtained in studies on the S-exchange of catalyst sulfide with H2S.I 1 The degree of MoOx sulfidation was 63% if sulfided with thiophene, [ 1 that by the H2S-sulfided sample — 48%.t l The fraction of exchangeable sulfur in the... 

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