Gas-Phase Hydrodechlorination of Dichloromethane at Low Concentrations with Palladium/Carbon Catalysts

Abstract

The behavior of a commercial (CE) and homemade (CH) palladium/carbon catalyst in the gas-phase hydrodechlorination of dichloromethane (DCM) has been investigated, at low concentration, in a fixed-bed microreactor, with a view of application to the treatment of residual gas streams. The influence of space time (1.0-6.6 kg h mol -1 ), reaction temperature (423-623 K), and H 2 /DCM molar ratio (50-400) was investigated. The catalysts showed high performance, with DCM conversions up to 97% and selectivities to nonchlorinated products of ∼80%. Modification of the operating conditions highly affects the activity of the catalyst while also showing scarce influence on the selectivity. At equal palladium loadings, the CH catalyst showed higher activity than the CE catalyst; however, the product distribution was fairly similar. This was attributed to a different dispersion and distribution of palladium particles, but a similarity in the nature of the palladium species involved in both types of catalysts.

Gas-phase hydrodechlorination of mixtures of chloromethanes with activated carbon-supported platinum catalysts

“…The HDC experiments were conducted in a continuous flow reaction system described elsewhere [1], consisting in a quartz fixed bed micro-reactor coupled to a gas-chromatograph The results on the characterization and the catalysts performance experiments were reproducible in more than 95%. At least two measurements were done for each experimental result reported.…”

“…They are also employed in the manufacture of aerosols, adhesives, and for dry cleaning [1]. The main problem of these compounds is their high toxicity and carcinogenic character.…”

“…In previous studies [1,[13][14][15][16], we have investigated the HDC of individual chloromethanes (mainly DCM and TCM) using catalysts based on Pd, Pt, Rh and Ru supported on activated carbon. The catalysts were found to be effective in the HDC of DCM and TCM individually.…”

Deactivation behavior of Pd/C and Pt/C catalysts in the gas-phase hydrodechlorination of chloromethanes: Structure–reactivity relationship

“…Although HDC of CMs has been investigated to a lesser extent than HDC of other organochlorine compounds, several publications have appeared in recent years including a number reporting on the deep gas-phase HDC of CMs over different supported metal catalysts [4,5,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. It is well known that precious metals are active catalysts for the hydrogenolysis of the carbon-chlorine bond [8,9].…”

“…Among them, palladium has been reported to be a very good option because of its high activity and selectivity to nonchlorinated products [21,25,26]. These studies report on the use of a wide variety of supports including SiO2 [5,10], Al2O3 [11][12][13], TiO2 [14][15][16] and carbon materials [4,[17][18][19][20][21][22][23][24]. However, in all cases where the performance as a function of time on stream has been evaluated, Pd catalysts have been shown to suffer severe and rapid deactivation.…”