Deactivation of a Pd/AC catalyst in the hydrodechlorination of chlorinated herbicides

The Influence of Copper on Halogenation/Dehalogenation Reactions of Aromatic Compounds and Its Role in the Destruction of Polyhalogenated Aromatic Contaminants

The effect of copper and its compounds on halogenation and dehalogenation of aromatic compounds will be discussed in the proposed article. Cu oxidized to appropriate halides is an effective halogenation catalyst not only for the synthesis of halogenated benzenes or their derivatives as desired organic fine chemicals, but is also an effective catalyst for the undesirable formation of thermodynamically stable and very toxic polychlorinated and polybrominated aromatic compounds such as polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans accompanied incineration of waste contaminated with halogenated compounds or even inorganic halides. With appropriate change in reaction conditions, copper and its alloys or oxides are also able to effectively catalyze dehalogenation reactions, as will be presented in this review.

Theoretical and Applied Aspects of Hydrodechlorination Processes—Catalysts and Technologies

The commercial implementation of hydrodechlorination processes will be an essential step in resolving the problem of environmentally sound organochlorine wastes processing. By now, there is a number of fundamental, applied, and process elaborations of such processes, in which chlorine is almost completely removed from wastes. The review article contains a significant number of results including basic regularities of thermal hydrodechlorination, comprehensive and selective catalytic hydrodechlorination. It discusses thermodynamics, kinetics, and catalysts of gas and liquid phase processes. Considerable attention is paid to hydrodechlorination of vinyl chloride production wastes and utilization of tetrachloromethane, which is the ozone-depleting substance. It also discusses hydrodechlorination of mono- and (poly)chlorobenzenes. The important examples of liquid phase data include hydrogenation using complex hydrides of elements. It also includes several flow sheets of hydrodechlorination processes.

Degradation of diclofenac using palladized anaerobic granular sludge: Effects of electron donor, reaction medium and deactivation factors

Biogenic nanopalladium (Bio-Pd) was formed by Anaerobic Granular Sludge (AGS). The Bio-Pd hosted in AGS (Pd-AGS) was used to degrade a pharmaceutical compound diclofenac (DCF) under the conditions of various electron donors, Pd loadings and reaction media. Results showed that hydrogen was the most effective electron donor for the Pd-AGS, followed by formate, glucose and acetate. The Pd-AGS was able to produce effective hydrogen/electron donors from organic compounds via microbial metabolism to initiate Pd activity. Over 96% of DCF (initial concentration of 20 mg L^-1) was removed using the Pd-AGS within 90 min, and a maximum specific activity K_obs of 1.53 L g^-1 min^-1 was obtained at 3.0 wt% Pd loading, in the presence of hydrogen. The Pd-AGS exhibited a relatively high activity in the medium of PBS or Na₂SO₄ (25 mM) at pH = 7-7.5, but lost activity in the medium of Na₂CO₃ (40 mM) or NaOH (40 mM). The Pd-AGS was more resistant to deactivation by chloride or sulphide comparing to free Pd nanoparticles. The Pd-AGS could reduce DCF and nitrate simultaneously with high nitrogen selectivity. The Pd-AGS, as a novel form of Pd catalyst with AGS, shows promise for applications in reducing chlorinated organic compounds in contaminated water.

Reactivity of Aryl Halides for Reductive Dehalogenation in (Sea)water Using Polymer-Supported Terpyridine Palladium Catalyst

A polymer-supported terpyridine palladium complex was prepared. The complex was found to promote hydrodechlorination of aryl chlorides with potassium formate in seawater. Generally, reductive cleavage of aryl chlorides using transition metal catalysts is more difficult than that of aryl bromides and iodides (reactivity: I > Br > Cl); however, the results obtained did not follow the general trend. Therefore, we investigated the reaction inhibition agents and found a method to remove these inhibitors. The polymeric catalysts showed high catalytic activity and high reusability for transfer reduction in seawater.

Effective catalytic hydrodechlorination of chlorophenoxyacetic acids over Pd/graphitic carbon nitride

Catalytic hydrodechlorination (HDC) of chlorophenoxyacetic acids was performed over Pd/graphitic carbon nitride (Pd/g-C₃N₄) catalysts in the present work.

Enhanced catalytic hydrodechlorination of 2,4-dichlorophenol over Pd catalysts supported on nitrogen-doped graphene

Pd catalysts supported on graphene and N-doped graphene (GN-1, GN-2 and GN-3) with varied N-doping amounts were prepared, and liquid phase catalytic hydrodechlorination of 2,4-dichlorophenol was investigated over these catalysts.