Catalysts based on PdO_ZrO2 in the hydrodechlorination reaction of chlorobenzene

The possibility of using mixed oxides of palladium and zirconium obtained with biotemplates (cellulose and wood pulp) as the precursor of catalysts for the hydrodechlorination of chlorobenzene is analyzed. The properties of the samples are studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), the Brunauer-Emmet-Teller (BET) method, and temperature-programmed reduction (TPR). They are then compared to the properties of a supported analogue. The biomorphic precursors are characterized by high porosity and include micropores, mesopores, and macropores; the results from TPR reveal the presence in the precursors of several forms of PdO that differ by reduction temperature. It is shown that the distribution of palladium in the catalysts obtained by reducing the precursors with hydrogen depends on the method used in synthesizing the precursor. It is shown that the studied catalysts ensure 100% conversion of chlorobenzene at temperatures of 100 to 250°C. It is established that cyclohexane is the principal product in the presence of the supported catalyst across the range of temperatures, while cyclohexane and benzene are detected among the products in the presence of biomorphous samples at temperatures above 130°C. The effect the presence of an admixture of alkaline and alkaline-earth metals in the catalyst has on the selectivity of the process is noted. It is established that the catalysts operate in a stable manner for at least 27 h of use under experimental conditions.