Steam reforming of chlorocarbons:: chlorinated aromatics

Effective dechlorination of chloroaromatics, such as C6H5Cl, 1,2-C6H4Cl2, 1,3-C6H4Cl2 and 1,2,4-C6H3 Cl-3, using catalytic steam reforming has been confirmed with laboratory experiments on nickel and platinum catalysts. Using a feed comprising a mixture of steam and chlorocarbon with a H2O/C ratio of 10, complete conversions (>0.99999) were obtained with GHSVs of less than 4-5 x 10(5) h(-1) for a 23 wt.% Ni/CaAl2O4, catalyst and 1-2 x 10(5) h(-1) for a 0.5 wt.% Pt/gamma-Al2O3 catalyst in the temperature range 500-700 degrees C; The reactions followed pseudo-first-order kinetics for these catalysts and chloroaromatics, and kinetic parameters obeyed a compensation effect that was statistically sound, with isokinetic temperatures of 596 and 650 degrees C for Ni and Pt, respectively. Product distributions indicated two parallel catalytic reactions: steam reforming, leading to complete destruction of the aromatic ring and production of H-2, CO, CO2, and HCl; and hydrogenolysis, giving less chlorinated aromatic intermediates, C6H6 and HCl. The aromatic intermediates further react by steam reforming. Platinum was found more selective towards C6H6 formation than Ni, with selectivity increasing at lower temperatures. Comparisons between C6H11Cl and C6H5Cl revealed that saturation of the ring increases the rate of overall dechlorination. Above 596 degrees C for Ni and 650 degrees C for Pt, reactivities increase for higher chlorine levels of the aromatic ring. (C) 2000 Elsevier Science B.V. All rights reserved.