High activity and regenerability of a palladium–gold catalyst for chloroform degradation

Velázquez, Juan C.; Leekumjorn, Sukit; Hopkins, Gary D.; Heck, Kimberly N.; McPherson, J.; Wilkens, John A.; Nave, Bradley S; Reinhard, Martin; Wong, Michael S.

doi:10.1002/jctb.4851

Cited by 9 publications

(5 citation statements)

References 25 publications

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“…13,37 The fouled catalysts should be regenerable by flushing the reactor bed with a bleach (e.g., sodium hypochlorite) solution. 35,38 The simulated HFPW showed a stronger deactivation effect than DI water, which is most likely due to scale formation from the calcium in the water and the CO 2 in the inlet ambient air stream.…”

Section: Resultsmentioning

confidence: 99%

“…The phenol degradation rate constant using Pd/Al 2 O 3 catalyst in simulated HFPW (8.1 × 10 –4 min –1 ) decreased to 62% of that in DI water (5.0 × 10 –4 min –1 ) (Table ). The nonzero performance decay rate constant could be due to the fouling of the catalyst surface (i.e., blocking of the catalytic active sites) over time by carbonaceous deposits, mainly of condensation/polymerization byproducts formed from oxidative coupling side reactions. , The fouled catalysts should be regenerable by flushing the reactor bed with a bleach (e.g., sodium hypochlorite) solution. , The simulated HFPW showed a stronger deactivation effect than DI water, which is most likely due to scale formation from the calcium in the water and the CO 2 in the inlet ambient air stream.…”

Section: Resultsmentioning

confidence: 99%

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Room-Temperature Catalytic Treatment of High-Salinity Produced Water at Neutral pH

Yin

Coonrod

Heck

et al. 2020

Ind. Eng. Chem. Res.

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Produced waters from hydraulic fracturing (HFPW) operations greatly challenge traditional water treatment technologies due to the high concentrations of total dissolved solids (TDS), highly complex and variable water matrices, and significant residual hydrocarbon content. We recently reported the unusual ability of a PdAu catalyst to degrade phenol in simulated HFPW at room temperature by generating H 2 O 2 in situ from formic acid and air. Phenol removal occurred at TDS levels as high as ∼10 000 ppm (ionic strength I = 0.3 M), but the catalytic reaction required pH < 4 to proceed. Here, we find that PdAu, Pd, and Au degraded phenol in the pH 5−8 range by using hydroxylamine as the hydrogen source in place of formic acid. Pd exhibited the highest activity, and Au the least. Activity of the monometallic catalysts decreased >70% as TDS increased from 0 to ∼100 000 ppm (I = 3 M), whereas the PdAu was comparatively less affected (∼50% activity decrease). All catalysts remained active at TDS levels as high as 100 000 ppm. The majority of the hydroxylamine formed N 2 , however this reaction generated additional nitrite/nitrate anion byproducts with nitrogen selectivities ranging from 0.5% to 11.5%, depending on the catalyst identity and reaction salinity. To demonstrate one possible flow treatment process concept, we constructed and tested a recirculating trickle bed reactor that removed 28% phenol from simulated HFPW over 48 h. These results show the potential of oxidation catalysis as a treatment approach for produced water and other high-salinity industrial wastewaters.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Room-Temperature Catalytic Treatment of High-Salinity Produced Water at Neutral pH

Yin

Coonrod

Heck

et al. 2020

Ind. Eng. Chem. Res.

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“…Testing the reaction over larger particles showed a particle size effect: increasing the size of the Au NP core from 4 to 7 nm led to a decrease in the rate for NPs with identical Pd sc% due to less subsurface Pd migration into the smaller NPs. 28 Pd-on-Au NPs were shown to be effective for a number of different CVOCs, including PCE, 29 CF, 30,31 and DCE. 29 Catalysis fundamentals can also be learned from the surfacebound transition species.…”

Section: Heterogeneous Hydrogenation Catalysismentioning

confidence: 99%

“…69 We also tested Pd supported on alumina ("Pd/Al 2 O 3 ") and PdAu/Al 2 O 3 catalysts on CFcontaminated groundwater. Because the HDC reaction generates HCl, a combination of lower pH and generation of Cl − initially led to catalyst fouling, 31 which was amended with citrate additive. While deactivation was observed, it was reversible via exposure to bleach followed by reduction with aqueous H 2 .…”

Section: Implementation and Perspectivementioning

confidence: 99%

Catalytic Converters for Water Treatment

et al. 2019

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Fresh water demand is driven by human consumption, agricultural irrigation, and industrial usage and continues to increase along with the global population. Improved methods to inexpensively and sustainably clean water unfit for human consumption are desired, particularly at remote or rural locations. Heterogeneous catalysts offer the opportunity to directly convert toxic molecules in water to nontoxic products. Heterogeneous catalytic reaction processes may bring to mind large-scale industrial production of chemicals, but they can also be used at the small scale, like catalytic converters used in cars to break down gaseous pollutants from fuel combustion. Catalytic processes may be a competitive alternative to conventional water treatment technologies. They have much faster kinetics and are less operationally sensitive than current bioremediation-based methods. Unlike other conventional water treatment technologies (i.e., ion exchange, reverse osmosis, activated carbon filtration), they do not transfer contaminants into separate, more concentrated waste streams. In this Account, we review our efforts on the development of heterogeneous catalysts as advanced reduction technologies to treat toxic water contaminants such as chlorinated organics and nitrates. Fundamental understanding of the underlying chemistry of catalytic materials can inform the design of superior catalytic materials. We discuss the impact of the catalytic structure (i.e., the arrangement of metal atoms on the catalyst surface) on the catalyst activity and selectivity for these aqueous reactions. To explore these aspects, we used model metal-on-metal nanoparticle catalysts along with state-of-the-art in situ spectroscopic techniques and density functional theory calculations to deduce the catalyst surface structure and how it affects the reaction pathways and hence the activity and selectivity. We also discuss recent developments in photocatalysis and electrocatalysis for the treatment of nitrates, touching on fundamentals and surface reaction mechanisms. Finally, we note that despite over 20 years of growing research into heterogeneous catalytic systems for water contaminants, only a few pilot-scale studies have been conducted, with no large-scale implementation to date. We conceive of modular, on-or off-grid catalytic units that treat drinking water at the household tap, at a community well, or for larger-scale reuse of agricultural runoff. We discuss how these may be enhanced by combination with photocatalytic or electrocatalytic processes and how these reductive catalytic modules (catalytic converters for water) can be coupled with other modules for the removal of potential water contaminants.

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“…The bimetallic catalysts had smaller metal particles and larger numbers of exposed active sites than those of monometallic catalysts. (Zhou et al, 2016) (Velazquez et al, 2016) It was shown that the bimetallic catalyst outperformed the monometallic Pd catalyst. The same authors reported activity of this material in hydrodechlorination of trichloroethylene and perchloroethylene over PdAu catalysts to a single-carbon organohalide.…”

Section: Hydrodechlorination (Hdc)mentioning

confidence: 99%

Designing Pd-based supported bimetallic catalysts for environmental applications

Nowicka

Sankar

2018

J. Zhejiang Univ. Sci. A

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Supported bimetallic nanoparticulate catalysts are an important class of heterogeneous catalysts for many reactions including selective oxidation, hydrogenation/hydrogenolysis, reforming, biomass conversion reactions and many more. The activity, selectivity and stability of these catalysts depend on their structural features including particle size, composition and morphology. In this review, we present important structural features relevant to supported bimetallic catalysts focusing on Pd-based bimetallic systems and recently reported strategies to control them through different synthesis methodologies. Further, we focus on a few reactions that are relevant to environmental catalysis i.e. (a) CO oxidation, (b) hydrocarbon oxidation, (c) hydrodechlorination and (d) NOx decomposition where Pd-based catalysts are often used successfully. In spite of much progress in these areas, still there is a need for more advanced catalytic technologies to address the grand challenges like environmental remediation. Some of the recent advances in the design of bimetallic catalysts were made because of the combined efforts of material scientists, spectroscopists, microscopists, catalysis chemists and engineers through state-of-the-art characterisation methodologies, mechanistic investigations and structure-activity correlations. This review is aimed at inspiring scientists to rationally design catalysts for a green and sustainable future.

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High activity and regenerability of a palladium–gold catalyst for chloroform degradation

Cited by 9 publications

References 25 publications

Room-Temperature Catalytic Treatment of High-Salinity Produced Water at Neutral pH

Room-Temperature Catalytic Treatment of High-Salinity Produced Water at Neutral pH

Catalytic Converters for Water Treatment

Designing Pd-based supported bimetallic catalysts for environmental applications

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