Liquid-phase hydrodechlorination of chlorobenzene over palladium-supported catalysts

“…In marked contrast, Shindler et al 98 obtained a constant HDC of 4‐CP in water over Pd supported on carbon cloths for up to 3 h without the addition of any base. In the HDC of chlorobenzene in methanol over Pd/AlPO 4 –SiO 2 , it was found that the beneficial effects of NaOH depended on Pd dispersion and support composition 101. It is fair to state that the consequences of base addition on liquid phase HDC activity/selectivity are still not well established and the role of the metal support remains unclear.…”

Section: Overview Of Catalytic Hydrodechlorination (Hdc)mentioning

confidence: 99%

A review of catalytic approaches to waste minimization: case study—liquid‐phase catalytic treatment of chlorophenols

Keane

2005

J of Chemical Tech & Biotech

101

View full text Add to dashboard Cite

Effective waste management must address waste reduction, reuse, recovery/recycle and, as the least progressive option, waste treatment. Catalysis can serve as an integral green processing tool, ensuring lower operating pressures/temperatures with a reduction in energy requirements while providing alternative cleaner synthesis routes and facilitating waste conversion to reusable material. The case study chosen to illustrate the role that catalysis has to play in waste minimization deals with the conversion of toxic chlorophenols in wastewater. The presence of chloro-organic emissions is of increasing concern with mounting evidence of adverse ecological and public health impacts. A critical overview of the existing treatment technologies is provided with an analysis of the available literature on catalytic dechlorination. The efficacy of Pd/Al 2 O 3 to promote the hydrogen-mediated dechlorination of mono-and dichlorophenols is demonstrated, taking account of both the physical and chemical contributions in this three-phase (solid catalyst and liquid/gaseous reactants) system. Hydrodechlorination activity and selectivity trends are discussed in terms of chloro-isomer structure, the influence of temperature is discussed, the role of base (NaOH) addition is examined and the feasibility of catalyst reuse is addressed.

show abstract

“…The same solvent was used for the entire seven‐week duration. Each time the soil was replaced (i.e., once per week), the solvent was spiked with 0.2 mL of ammonium hydroxide; this was to neutralize acidification of the solvent which might occur from the production of hydrochloric acid as a product of the catalytic hydrodehalogenation [6, 29–30].…”

Section: Methodsmentioning

confidence: 99%

Remediation of contaminated soil by solvent extraction and catalytic hydrodehalogenation: Semicontinuous process with solvent recycle

Wee¹,

Cunningham

2010

Env Prog and Sustain Energy

View full text Add to dashboard Cite

Halogenated hydrophobic organic contaminants (HHOCs), such as chlorinated benzenes and polychlorinated biphenyls, are common soil contaminants. We propose a new method for treating soils contaminated by HHOCs by extracting the contaminants with a solvent, then destroying the contaminants catalytically, enabling the solvent to be reused. Here, we report on the assessment of this technology at the lab scale, operating in a semicontinuous mode where the solvent is recycled in a closed loop. The solvent employed was a mixture of water and ethanol, the catalyst was 1% palladium (Pd) on porous alumina, and hydrogen gas was used as the reductant. We tested the process on two soils: Texas sandy loam contaminated in the laboratory, and Florida sandy clay loam collected from a contaminated field site. The technology worked successfully on the Texas soil: over 90% of the contamination (pentachlorophenol and 1,2,4,5-tetrachlorobenzene) could be extracted and destroyed within 1 week using a solvent flow rate of 0.005 L/(min-kg soil) and a residence time of $3.5 min in the catalytic reactor. Seven batches of soil were treated (one week each) without needing to replace the solvent. Catalyst activity decreased over time but was recovered by cleaning the catalyst with a dilute solution of hypochlorite. However, the process was unsuccessful at treating the Florida soil because of rapid catalyst deactivation. We believe that the proposed technology (called remedial extraction and catalytic hydrodehalogenation, or REACH) is a promising ''green'' technology if we can protect the catalyst from deactivation; possible methods for achieving this are discussed.

show abstract

Liquid-phase hydrodechlorination of chlorobenzene over palladium-supported catalysts

Cited by 75 publications

References 28 publications

Pd–Al pillared clays as catalysts for the hydrodechlorination of 4-chlorophenol in aqueous phase

Pd–Al pillared clays as catalysts for the hydrodechlorination of 4-chlorophenol in aqueous phase

A review of catalytic approaches to waste minimization: case study—liquid‐phase catalytic treatment of chlorophenols

Remediation of contaminated soil by solvent extraction and catalytic hydrodehalogenation: Semicontinuous process with solvent recycle

Contact Info

Product

Resources

About