Catalyst For Hydrodechlorination Research Articles

Co(PO3)2@CoP Heterojunction in CoPO/GC/NF Nanoarrays Modulate Proton Hydrogen-Promoted Electrocatalytic Hydrodechlorination.

Cobalt phosphide has received much attention as an efficient catalyst for electrocatalytic hydrodechlorination (EHDC). However, the active species proton hydrogen (H*) is consumed by the hydrogen evolution reaction (HER). Herein, we report a crystal regulation strategy for cobalt phosphate/graphitic nanocarbon/nickel foam (CoPO/GC/NF) catalysts applied for the EHDC of 2,4-dichlorophenoxyacetic acid (2,4-D). Characterization revealed that during the high-temperature phosphatization process, CoPO/GC/NF catalysts developed Co(PO3)2@CoP heterojunctions, enhancing charge transfer at the electrolyte-catalyst interface and water dissociation. The interaction between Co(PO3)2 and CoP induced the reconstitution of CoP into the Co-OH species, which facilitated the production of H* by accelerating the Volmer step, enhancing EHDC activity. Furthermore, Co(PO3)2 species improve the catalyst tolerance, with CoPO/GC/NF(450) maintaining over 71% yield of phenoxyacetic acid (PA) in continuous testing for up to 80 h under high-salt conditions. This work clarifies the surface transformation process of CoP/GC/NF during hydrodechlorination and demonstrates great potential for chlorophenol wastewater remediation.

Enhanced catalytic performance induced by synergistic interaction between Pd species with NiAl2O4 spinel support for aqueous-phase hydrodechlorination of 4-chlorophenols

4-Chlorophenol (4-CP) is a pervasive environmental pollutant commonly found in wastewater and groundwater, posing great risks to both human health and the ecosystem. Catalytic hydrodechlorination (HDC) of 4-CP by utilizing hydrogen (H2) as a reductant has emerged to be an efficient and sustainable way to treat pollutant water. This study focuses on the development of an efficient and stable Pd-based catalyst for the catalytic HDC of 4-CP. By incorporating an appropriate amount of Ni into Al2O3 support, a NiAl2O4 (NA) spinel was synthesized, enhancing the interaction between Pd and the support, leading to precise control over Pd species and oxygen vacancies. The tailored properties of the Pd/NA-1 catalyst result from meticulous adjustment of the Pd2+/Pd0 ratio and oxygen vacancies, which promotes electron transfer from Pd to Ni within the NiAl2O4 spinel. In comparison to the Pd/Al2O3 catalyst, the Pd/NA-1 catalyst exhibits exceptional stability, with continuous operation for over 120 h without deactivation. Comprehensive characterization analyses indicate that the Pd/NA-1 catalyst effectively prevented the aggregation of Pd nanoparticles, maintaining the Pd2+/Pd0 ratio at 1, which is crucial for its superior stability. This work provides valuable insights into the development of Pd-based catalysts for HDC reactions, highlighting the potential use of Pd/NA-1 catalysts in treating hazardous pollutants like 4-CP in waste systems.

Catalytic Dechlorination of Three Organochlorides by Recyclable Nano-Palladium-Engineered Natural Sponge with Formic Acid

Catalytic dechlorination of organic chlorides by palladium (Pd) with HCOOH represents one of the most effective and promising techniques for environmental remediation. In this study, we adopted alkaline-modified porous natural sponge as support of a Pd nanocatalyst (Pd@M-Sponge) and HCOOH as a hydrogen source for the hydrodechlorination of florfenicol (FF), o-chlorophenol (o-CP), and p-chlorophenol (p-CP). Favorable conversion efficiency of FF, o-CP, and p-CP was achieved at 25 °C and atmospheric pressure attributed to the small diameter and high catalytic reactivity of the prepared Pd NPs, in addition to the slight internal mass transfer limitation of the prepared Pd@M-Sponge. High reaction rate constants were obtained even in the conditions of a low molar ratio of HCOOH to p-CP (10:1) and a high concentration of p-CP (500 mg/L). The prepared catalyst also demonstrated superior recyclability without any obvious decrease in catalytic reactivity in 20 successive p-CP dechlorination cycles. This work provides an ideal recyclable and cost-effective catalyst based on renewable and biocompatible natural material for the catalytic hydrodechlorination of chlorinated organic pollutants with formic acid and a new view for the exploration and designing of highly reactive and stable catalysts for hydrodechlorination.

Solvent‐Free Synthesized Zeolites NaA‐Supported Binary Nickel‐Silver Nanoparticles and Their Use as an Efficient Catalyst for Hydrodechlorination of 2,4‐Dichlorophenol

Solvent‐Free Synthesized Zeolites NaA‐Supported Binary Nickel‐Silver Nanoparticles and Their Use as an Efficient Catalyst for Hydrodechlorination of 2,4‐Dichlorophenol

Efficient Palladium Catalysts: Application and Challenges of Electrocatalytic Hydrodechlorination Technology in Wastewater Treatment

AbstractThis review summarizes the research progress of palladium (Pd) catalysts in electrocatalytic hydrodechlorination (ECH) for the removal of chlorinated organic pollutants (COPs). ECH technology is a new type of green water treatment technology without secondary pollution, which has excellent removal effect on COPs. Pd is widely used in the field of ECH due to its excellent catalytic properties. However, the easy deactivation and high price of Pd have limited the application of Pd catalysts in practical wastewater treatment. Researchers have improved the performance of Pd catalysts for ECH by improving the morphological structure (dispersion, particle size, crystalline surface) and electronic states (electron‐rich Pd, electron‐deficient Pd). It is also found that modulation of the adsorption abilities of Pd catalysts can greatly improve the catalytic activity. The factors affecting the stability of Pd catalysts are also investigated, and the future large‐scale mature application of ECH technology is envisioned. The ability to prepare single‐atom Pd catalysts in a relatively simple way is a future direction, which will achieve 100 % atom utilization and thus significantly reduce the cost of Pd. This review details the frontier research on Pd catalysts in the field of ECH, which can provide some good strategies for related researchers.

Rational Design and Structural Regulation of Robust Catalysts for Electrocatalytic Hydrodechlorination: From Nanostructures to Single Atoms

Rational Design and Structural Regulation of Robust Catalysts for Electrocatalytic Hydrodechlorination: From Nanostructures to Single Atoms

Rod-Like Nanostructured Cu-Co Spinel with Rich Oxygen Vacancies for Efficient Electrocatalytic Dechlorination.

Dichloromethane (CH2Cl2) hydrodechlorination to methane (CH4) is a promising approach to remove the halogenated contaminants and generate clean energy. In this work, rod-like nanostructured CuCo2O4 spinels with rich oxygen vacancies are designed for highly efficient electrochemical reduction dechlorination of dichloromethane. Microscopy characterizations revealed that the special rod-like nanostructure and rich oxygen vacancies can efficiently enhance surface area, electronic/ionic transport, and expose more active sites. The experimental tests demonstrated that CuCo2O4-3 with rod-like nanostructures outperformed other morphology of CuCo2O4 spinel nanostructures in catalytic activity and product selectivity. The highest methane production of 148.84 μmol in 4 h with a Faradaic efficiency of 21.61% at -2.94 V (vs SCE) is shown. Furthermore, the density function theory proved oxygen vacancies significantly decreased the energy barrier to promote the catalyst in the reaction and Ov-Cu was the main active site in dichloromethane hydrodechlorination. This work explores a promising way to synthesize the highly efficient electrocatalysts, which may be an effective catalyst for dichloromethane hydrodechlorination to methane.

Bimetallic PdFe catalysts in hydrodechlorination of diclofenac: Influence of support nature, metal deposition sequence and reduction condition

Monometallic palladium and bimetallic palladium-iron catalysts (1 wt% Pd, 10 wt% Fe) were prepared by sequential (denoted as “-s”) and co- (denoted as “-c“) impregnation of alumina and silica – zirconia (ZS) supports with metal nitrates. After reduction with H2 at 320 and 30 °C the catalysts were tested in hydrodechlorination of diclofenac in water at 30 °C in batch and flow-type reactors. The alumina-supported catalysts were more active than the ZS-supported ones, while the bimetallic catalysts were more efficient than the monometallic Pd ones. The co-impregnated bimetallic catalysts showed higher efficiencies than the catalysts prepared by the sequential deposition of metals. Pd/Al2O3 and PdFe/Al2O3-c provided the same rate of DCF conversion in the batch reactor after both types of preliminary reduction, opening the way for energy saving. The catalysts were studied by XRD, TEM, SEM-EDX, low-temperature N2 physisorption, Mössbauer spectroscopy, DRIFT-CO and by XPS after in situ reduction at 320 °C and ex-situ reduction at 30 °C. The improvements in catalyst efficiency resulted from wider pores, formation of PdFe alloys or Pd-Fe-Ox species on the surface, high Pd0/Pd2+ ratio, low extent of Pd encapsulation with the support and especially its coordinately unsaturated sites. The encapsulation degree was the lowest in the co-impregnated catalysts.

Active site and adsorption behavior engineering of subsize PdNi nanoparticles for boosting electrocatalytic hydrodechlorination of 4-chlorophenol

Developing an efficient strategy to engineer the removal efficiency of catalysts for electrocatalytic hydrodechlorination (ECH) of acute toxic chlorophenols is of considerable importance but remains challenging. We report herein an efficient strategy to modulate the active site and adsorption behaviors of PdNi alloy nanoparticles (NPs) anchored on oxygen/nitrogen-doped porous carbon nanosheets (PdNi/NPCNs) through nanopore trapping. The competitive adsorption of PdCl42- and Ni2+ ions and subsequent reduction belowrmodynamic reduction temperature ensure the formation of highly dispersed subsize PdNi alloy NPs on the surface of NPCNs. More significantly, alloying of Pd with Ni not only provides abundant surface-active sites but also adjusts the adsorption behaviors of intermediates over PdNi/NPCNs because of the strong electronic interaction between the two metals, thereby considerably boosting the ECH performance for 4-chlorophenol (4-CP) removal. The complete removal of 4-CP (100 mg L−1) is achieved at 7.5 mA within 180 min, superior to that of monometallic Pd/NPCNs and many previous electrodes reported thus far. The catalyst also exhibits boosted stability toward the ECH of 4-CP with five successive recycling runs. This study provides an effective strategy to fabricate high-performance electrocatalysts for ECH reaction, which shows great promise in potential applications.

High performance of metal modified Pd catalyst for hydrodechlorination of chlorophenols to cyclohexanone

High performance of metal modified Pd catalyst for hydrodechlorination of chlorophenols to cyclohexanone

Nickel nanoparticles supported on titanium oxides nanotubes as an efficient catalyst for hydrodechlorination of 3-chlorophenol

Titanium oxides nanotubes (TNTs) were prepared by hydrothermal method and used as nano-support for nickel nanoparticles. Indeed, nickel nanoparticles supported TNTs (Ni-TNTs) were in situ synthesized from nickel salt and TNTs by chemical reduction method using sodium borohydride (NaBH4) as reducing agent. The physio-chemical properties of Ni-TNTs nano-catalysts were fully characterized such as Transmission Electron Microscopy (TEM), Scanning Electron Microscope (SEM), and X-ray diffraction (XRD). The results showed that nickel salt was completely reduced to Ni0 metal with an average particle size of 12 nm. On the other hand, the catalytic activity is tested by the hydrodechlorination of chlorinated organic compounds. The hydrode-chlorinated conversion of 3-chlorophenol was obtained over 97%.

In-Situ doping-induced crystal form transition of amorphous Pd–P catalyst for robust electrocatalytic hydrodechlorination

Developing catalysts with high activity and high atom utilization as well as exploring catalytic active sites are the biggest challenges for the electrocatalytic hydrodechlorination technology. Herein, a novel strategy of Pd crystal transformation induced by in-situ doping was proposed, and a series of amorphous Pd–P nanoparticles (NPs) with controllable coordination environment were synthesized successfully. The amorphous Pd–P NPs catalyst exhibits the highest activity for electrocatalytic hydrodechlorination and good cycling stability when the Pd–P coordination number is 3 and the Pd–Pd coordination number is 4. The 4-chlorophenol hydrodechlorination efficiency of Pd–P-60 NPs reaches 100 % within 2 h, and the mass activity is 8.58 min−1 g−1, which is 5.57 times as high as that for crystalline Pd NPs catalyst. Theoretical calculation shows that Pd–P catalyst facilitates the desorption of phenol and weakens the toxic effect on active sites. Density of states indicate that the doping of P results in a downshift of d-band center, facilitating the desorption of phenol. This work discovers the crystal effect and coordination effect of amorphous Pd–P NPs for electrocatalytic hydrodechlorination, which lays an important theoretical foundation for the design and development of high-performance Pd-based catalysts for electrocatalytic hydrodechlorination.

P‐doped Carbon as the Efficient Support of Nickel Catalysts for Hydrodechlorination of Chlorodifluoromethane

AbstractP‐doped carbon material (P−C) is successfully fabricated through directly combust phytic acid via microwave assistant. Then the as‐made P−C is selected as the support to load various amount of Ni. As the evaluated results show that 5 %Ni/P−C exhibits better catalytic performance than 5 %Ni/C for chlorodifluoromethane hydrodechlorination (HDC) reaction. It is because that the doped‐P is feasible to promote the dispersion of Ni species on the surface of P−C through the strong interaction between Ni and the P−C support. Therefore, combining the synergetic effect between Ni and heteroatom‐doped carbon could provide a promising way to improve the activity of HDC reaction.

Synthesis of functionalized mesoporous Ni-SBA-16 decorated with MgO nanoparticles for Cr (VI) adsorption and an effective catalyst for hydrodechlorination of chlorobenzene

In this research work the impact of MgO promoter tested on Ni-SBA-16 efficiency in aqueous media as an adsorbent for Cr(VI) and an effective catalyst for hydrodechlorination of chlorobenzene. New hydrothermal procedures were applied for the synthesis of Ni-SBA-16 and MgO/Ni-SBA-16 respectively. Results revealed that nanocomposites containing Ni nanocrystals of an average size distributed homogeneously within the pores of the amorphous silica matrix and also MgO was effectively coated on Ni-SBA-16 mesoporous silica walls, and that the mesoporous Ni-SBA-16 structure has been well preserved upon modification of MgO. The catalyst analysis results showed high interaction of unpromoted and MgO promoted catalyst Ni-SBA-16 as hydrodechlorination of chlorobanzene (≈ 96%) remained stable for 6 hours. The synthesized nanostructures were tested against Cr(VI) removal. 100% Cr(VI) adsorption was noted using 4 g/L and 200 mg/L of nanostructure and Cr(VI) respectively at temperature 75 °C, contact time 100 min and pH 3.

Pd-NCQD composite confined in SBA-15 as highly active catalyst for aqueous phase catalytic hydrodechlorination of 2,4-dichlorophenoxyacetic acid

A composite consisting of Pd particles and N-doped carbon quantum dots (NCQDs) confined in mesoporous SBA-15 (Pd-NC@SBA-15) was prepared. For comparison, Pd catalysts supported on SBA-15 (im-Pd/SBA-15), NCQDs modified SBA-15 (im-Pd/NC-SBA-15) and N-doped carbon nanotubes (Pd/NCNTs) were prepared using the impregnation method. The catalysts were characterized and the aqueous phase catalytic hydrodechlorination (HDC) of 2,4- dichlorophenoxyacetic acid (2,4-D) was investigated. Characterization results showed that Pd-NC@SBA-15 had a higher Pd dispersion and more homogeneous Pd particle distribution than other catalysts. Additionally, the presence of NCQDs led to increased content of positively charged Pd in Pd-NC@SBA-15. As a result, Pd-NC@SBA-15 exhibited a much higher catalytic activity. Furthermore, the turnover frequency value of the Pd-NC@SBA-15 catalyst increased with Pdn+ content and remained identical at Pdn+/Pd0 ratio above 1.20. The HDC of 2,4-D on Pd-NC@SBA-15 proceeded via both stepwise and concerted pathways and the stepwise dechlorination pathway was predominant. The present study highlights that substantial enhancement of the catalytic activity can be achieved by rational NCQDs modification of Pd based catalysts for the aqueous phase catalytic removal of pollutants.

Single-Atom Cobalt Catalysts for Electrocatalytic Hydrodechlorination and Oxygen Reduction Reaction for the Degradation of Chlorinated Organic Compounds.

Electrochemical reduction-oxidation processes with the aid of cathode catalysts are promising technologies for the decomposition of organic compounds. High-efficiency and low-cost catalysts for electrochemical reductive dechlorination and two-electron oxygen reduction reaction (ORR) are vital to the overall degradation of chlorinated organic compounds. This study reports electrochemical dechlorination using a single-atom Co-loaded sulfide graphene (Co-SG) catalyst via atomic hydrogen generated from the electrochemical reduction of H2O and electrolysis of hydrogen. The Co-SG electrocatalyst exhibited a remarkable performance for H2O2 synthesis with a half-wave potential of 0.70 V (vs RHE) and selectivity over 90%. The high electrochemical performance was achieved for bifunctional electrocatalysis with regard to the smaller overpotentials, faster kinetics, and higher cycling stability compared to the noble metal-based electrocatalysts. In this study, 2,4-dichlorobenzoic acid was well degraded and the TOC concentration was effectively reduced. This work introduces the preparation of a new active site for high-performance single-atom catalysts and also promotes its application in the electrochemical degradation of chlorinated organic pollutants.

Chloroform Hydrodechlorination on Palladium Surfaces: A Comparative DFT Study on Pd(111), Pd(100), and Pd(211)

Palladium has been shown to be an effective catalyst for chloroform hydrodechlorination, which serves as a promising treatment method for industrial chloroform waste. To investigate the structure sensitivity of this chemistry on Pd surfaces, we performed a density functional theory (DFT, GGA-PW91) study of the chloroform hydrodechlorination reaction on three distinct facets: Pd(111), Pd(100), and Pd(211). Based on the DFT results, the binding strengths of most surface intermediates generally increase in the following order: Pd(111) < Pd(100) < Pd(211). On all three Pd facets, methane is formed as the preferred reaction product through a pathway in which CHCl3* is fully dechlorinated to CH* first, and then hydrogenated to CH4. We constructed potential energy diagrams (PED) and compared the reaction energetics for chloroform hydrodechlorination on the three Pd facets. We propose that the competition between the desorption of chloroform and its initial dechlorination to form CHCl2* likely determines the hydrodechlorination activity of the catalyst. On Pd(111), the desorption of chloroform is energetically favored over its dechlorination while the dechlorination barriers are lower than the desorption barriers on Pd(100) and Pd(211). On the other hand, Pd(100) and Pd(211) bind atomic chlorine stronger and also catalyze the formation of atomic carbon effectively; both are potential site-blocking species. Our results suggest that the more open facets and step edge sites of a Pd nanoparticle may carry higher intrinsic activity towards chloroform hydrodechlorination than the close-packed facets, yet these under-coordinated sites are more prone to catalyst poisoning.

Pd nanoparticles supported on amphiphilic porous organic polymer as an efficient catalyst for aqueous hydrodechlorination and Suzuki‐Miyaura coupling reactions

Developing efficient and recyclable heterogeneous catalysts for organic reactions in water is important for the sustainable development of chemical industry. In this work, Pd nanoparticles supported on DABCO‐functionalized porous organic polymer was successfully prepared through an easy copolymerization and successive immobilization method. Characterization results indicated that the prepared catalyst featured big surface area, hierarchical porous structure, and excellent surface amphiphilicity. We demonstrated the use of this amphiphilic catalyst in two case reactions, i.e. the aqueous hydrodechlorination and Suzuki‐Miyaura coupling reactions. Under mild reaction conditions, the catalyst showed high catalytic activities for the two reactions. In addition, the catalyst could be easily recovered and reused for several times. Also, no obvious Pd leaching and aggregation of Pd nanoparticles occurred up during the consecutive reactions.

Functional Pd/reduced graphene oxide nanocomposites: effect of reduction degree and doping in hydrodechlorination catalytic activity

Pd catalysts supported on carbon have interesting features for chlorophenols-bearing water treatment by hydrodechlorination, including high stability, activity, and tunable support. In this work, a set of materials based on reduced graphene oxide (rGO) with different degrees of reduction, surface oxygen groups, nitrogen doping, and specific surface area were decorated with Pd nanoparticles, with diameter average size between 5 and 50 nm. Ethanol, hydrazine monohydrate, and sodium borohydride were used as reducing agents, and Pd(AcO)2 was used as a Pd precursor to obtain Pd/rGO nanocomposites in our developed one-pot synthesis approach. A thorough characterization revealed that a similar degree of reduction was obtained for sodium borohydride at 25 °C and hydrazine at 60 °C, although hydrazine also led to nitrogen doping. Pd nanoparticles were homogenously nucleated on the surface of the GO and the obtained nanocomposites were tested as catalysts for hydrodechlorination of 4-chlorophenol in the aqueous phase. The materials with a higher degree of reduction showed the best specific catalytic activity at 70 °C. However, the turnover frequency (TOF) only increased with the reduction degree for the N-doped Pd/rGO, indicating the important role of the nitrogenous functionalities in the catalytic activity. Therefore, the N doping of Pd/rGO catalysts is a feasible strategy to synthesize catalysts highly active for hydrodechlorination.

N-doped porous carbon supported Ni catalysts derived from modified Ni-MOF-74 for highly effective and selective catalytic hydrodechlorination of 1,2-dichloroethane to ethylene

Metal-organic frameworks (MOFs) have received significant attention as promising precursors or sacrificial templates in the preparation of porous carbon supported catalysts. In this study, N-doped porous carbon supported Ni catalysts (denoted as Ni/NC) were prepared using furfuryl alcohol (FA) loaded Ni-MOF-74 as the precursor followed by NH4OH treatment and pyrolysis under N2 atmosphere. For comparison purpose, Ni catalysts supported on porous carbon (denoted as Ni/C) were also prepared by direct pyrolysis of Ni-MOF-74. The selective gas phase catalytic hydrodechlorination of 1,2-dichloroethane to ethylene was carried out to evaluate the catalytic performances of the catalysts. It was found that for Ni catalysts prepared at the same pyrolysis temperature, Ni particle sizes in Ni/NC catalysts were significantly smaller (20–40% smaller) than that of Ni/C. This reflected that pre-modification of Ni-MOF-74 using FA and NH4OH could effectively increase Ni dispersion in Ni catalysts derived from Ni-MOF-74. Moreover, Ni/NC had a markedly stronger ability to form spillover H2 owing to the enhanced metal-support interactions by N-doping. Accordingly, Ni/NC catalysts exhibited much higher catalytic activities than Ni/C catalysts. The turnover frequencies of Ni/NC catalysts were found to be 1.22–1.65 times higher than Ni/C catalysts. Increasing pyrolysis temperature led to decreased catalytic activities of both Ni/C and Ni/NC catalysts, due to the aggregation of Ni particles at higher treatment temperature. The findings from this study demonstrate that the MOF-mediated synthesis method offers a promising way to prepare Ni-based catalysts for catalytic hydrodechlorination of chlorinated hydrocarbons.