Water–gas shift reaction over sulfided molybdenum catalysts supported on TiO2–ZrO2 mixed oxides: Support characterization and catalytic activity

Supported sulfided molybdenum and nickel–molybdenum catalysts were applied in the water–gas shift (WGS) reaction with sulfided feed. TiO2, ZrO2 and binary systems of TiO2–ZrO2, in which composition was changed in 10 wt.% intervals, were used as the supports for sulfided Mo and Ni–Mo catalysts. The concentration of Mo (8 wt.%) and Ni (3 wt.%) was the same in all studied catalysts. Supports and selected catalysts were characterized with XRD, BET, TPR (H2), TPD of ammonia, FTIR and NO adsorption measurements. The comparison of pure TiO2 or ZrO2 with TiO2–ZrO2 systems shows that introduction of the second component always resulted in almost duplication of the surface area of the supports. No simple relationship between surface area and catalytic activity was found. The choice of the support with appropriate ratio of surface acid–base sites, high dispersion of supported Ni–Mo–S surface species as well as much easier reductivity of Mo6+ ions in the presence of nickel ions can lead towards high activity in the WGS reaction with sulfided feed. The highest activity was obtained for Ni–Mo–S catalysts supported on TiO2 (40)–ZrO2 (60).