Structure sensitivity in the hydrodechlorination of chlorophenols

The gas phase hydrodechlorination of methanolic and mixed methanol/water so lutions of 2-chlorophenol, 2,6-dichlorophenol, 2,4,5-trichlorophenol and pe ntachlorophenol has been studied at 573 K over nickel/silica catalysts of v arying (1.5-20.3 wt.% Ni) nickel loading. Each catalyst was 100% selective in promoting hydrodechlorination; the variation of catalytic activity and s electivity with time-on-stream is illustrated and catalyst deactivation is addressed. Dechlorination is quantified in terms of specific rate constants , phenol selectivity/yield and chlorine removal efficiencies. Increasing th e nickel loading resulted in a marked increase in dechlorination efficiency while the introduction of water into the fed lowered the activity.