Search Results (37)

Here, we report a highly efficient and stable catalytic system based on monometallic oxides supported on HY zeolites for the catalytic oxidation of chlorobenzene (CB). Among the transition and rare-earth metal oxides screened, the 30Cu/HY catalyst demonstrates exceptional performance, achieving near 100% CB conversion at 300 °C (500 ppm CB, 10,000 h⁻¹) alongside outstanding 24 h continuous stability without deactivation. Quantitative Py-IR analysis reveals that this superior activity is fundamentally driven by extensive solid-state ion exchange, forming robust Lewis acid centers (Cu-Y structures) that synergize with zeolitic Brønsted acid sites to efficiently polarize and cleave C-Cl bonds. Through an integrated approach combining in situ DRIFTS, real-time mass spectrometry, TGA, and NLDFT pore size analysis, we elucidate that the exceptional deep-oxidation capability of Cu/HY continuously mineralizes carbonaceous intermediates. This property minimizes coke deposition (2.91 wt%) and preserves the hierarchical pore architecture, preventing the coverage of active sites and severe pore blockage by partially oxidized intermediates (such as phenolic, aldehydic, and quinonic species) and stable carbonate species responsible for the deactivation of other metal oxides. These insights provide a mechanistic framework for the rational design of robust, chlorine-resistant catalysts for the sustainable abatement of persistent organic pollutants. Full article

The development of low-temperature, high-efficiency catalysts for the catalytic elimination of chlorinated volatile organic compounds (CVOCs) remains a significant challenge. Investigating the influence mechanism of catalyst physicochemical properties on chlorobenzene oxidation performance and degradation pathways is particularly important. CuO/WO₃ catalysts were developed using a hydrothermal method in this work. The effects of simultaneous or separate addition of ammonium sulphate and ammonium persulphate on the catalytic performance of the CuO/WO₃ series catalysts were investigated. The results showed that the introduction of ammonium sulphate alone can facilitate the formation of CuWO₄, thereby increasing the chemisorbed oxygen concentration of the CuO/WO₃, and making the overall structure of the catalyst looser and increasing the active sites on the catalyst surface. As the optimal catalyst, CuO/WO₃-2 exhibited 55.9% of chlorobenzene conversion and 32.9% of CO₂ selectivity at 500 °C. Interestingly, although the surface acidity in this work seemed to be one of the reasons for promoting the chlorobenzene oxidation, it could be clearly found that the strong solid acidity of WO₃ was actually a key factor in inhibiting the chlorobenzene oxidation. Finally, based on in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis, the primary mechanism for chlorobenzene oxidation on CuO/WO₃ catalysts proceeds through a sequential conversion: chlorobenzene was first transformed into phenolic intermediates, followed by quinone compounds, maleates, aldehydes, bidentate carbonates, and ultimately carbonate species. Full article

Nano zero-valent iron (nZVI) particles have received much attention in environmental science and technology due to their unique electronic and chemical properties. While sulfate radical-based advanced oxidation processes (SR-AOPs) activated by nZVI show promise for mono-chlorobenzene (MCB) degradation, their efficiency is severely limited by surface oxidation of nZVI and Fe³⁺ accumulation. This study aims to enhance the nZVI/persulfate (PS) system using L-cysteine (Cys) to achieve effective MCB removal. The work involved synthesizing nZVI via borohydride reduction, followed by comprehensive characterization and batch experiments of the Cys/nZVI/PS degradation system of MCB were carried out to evaluate the key influencing factors and analyze the reaction mechanism of Cys-enhanced MCB degradation. Under optimal conditions (0.1 g/L nZVI, 3 mM PS, 0.1 mM Cys, pH 3), 92.6% of MCB was degraded within 90 min—an 18.7% improvement compared to the Cys-free system. Acidic pH promoted Fe²⁺ release and significantly enhanced degradation, while HCO₃⁻ strongly inhibited the process. Mechanistic studies revealed that sulfate radicals (SO₄^•−) played a dominant role, and Cys served as an electron shuttle that facilitated the Fe³⁺/Fe²⁺ cycle and enhanced Fe⁰ conversion, thereby sustaining PS activation. This study demonstrates that Cys effectively mitigates the limitations of nZVI/PS systems and provides valuable insights for implementing efficient SR-AOPs in treating chlorinated organic contaminants. Full article

The hydrolysis oxidation of 1,2-chlorobenzene (1,2-DCB) over Pd-Ti-Ni/ZSM-5(25) catalysts has been investigated as a safe and environmentally friendly method for the removal of chlorinated aromatic organic compounds. Experimental results demonstrate that hydrolysis oxidation technology can effectively suppress the formation of polychlorinated organic compounds. Among the catalysts studied, the 0.5%Pd-2%Ti-8%Ni/ZSM-5(25) catalyst exhibited optimal hydrolysis oxidation performance, achieving complete conversion of 1,2-DCB at 425 °C. Notably, this technology significantly inhibits the formation of polychlorinated organic by-products during the catalytic degradation of 1,2-DCB. Although trace amounts of chlorobenzene were still detected, the overall reduction in hazardous by-products is remarkable. Characterization techniques, including X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Pyridine adsorption infrared Spectroscopy (pyridine IR) and Fourier transform infrared spectroscopy (FT-IR) analysis, revealed that the acidity and redox properties of the catalyst surface play a pivotal role in the hydrolysis oxidation process. The hydrolysis oxidation of chlorinated volatile organic compounds not only effectively reduces pollutant concentrations but also prevents the generation of more toxic by-products. This dual benefit not only protects the environment but also minimizes ecological risks, highlighting the potential of this technology for sustainable environmental remediation. Full article

Particulate matter coexists with persistent organic pollutants (POPs) in the atmosphere, which can enter the human body by accompanying inhalable particles in the respiratory tract. Photochemical conversion further alters the chemical composition of the precursor particles and secondary products. This study investigated the effects of nanoscale iron–chlorobenzene mixtures and their photochemical conversion products on early lung development in rat pups. Using network toxicology and animal experiments, we constructed a compound toxicity–target network and developed air exposure models. This study revealed that both pollutants, before and after photochemical conversion, bound to the aryl hydrocarbon receptor (AhR), increased oxidative stress, altered lung tissue morphology, and reduce inflammatory factor expression. Rat pups were highly sensitive to pollutants during critical stages of lung development. However, no significant differences in oxidative stress or inflammation were observed between the pollutants, likely because of immature lung tissues. Once tissue damage reached a threshold, the response to increasing pollutant concentrations diminished. This study provides insights into atmospheric pollutant toxicity and scientific evidence for the risk assessment of dioxin-like nanoscale mixtures. Full article

Nitrogen oxides (NO_x) and chlorobenzene (CB) released during waste incineration and iron ore sintering pose significant threats to both the atmosphere and human health, necessitating effective control measures. Vanadium-based catalysts are commonly employed for the simultaneous control of NO_x and CB; however, their catalytic performance requires further enhancement. In this study, the NH₃-SCR activity and CB catalytic oxidation (CBCO) activity were significantly enhanced by doping the V10W/Ti catalyst with Ce. During the multi-pollutant control (MPC) reaction, the optimized 15CeV10W/Ti catalyst demonstrated NO_x conversion approaching 100% and N₂ selectivity exceeding 95% at temperatures between 210 and 450 °C. Additionally, it achieved CB conversion nearing 100% and CO₂ selectivity above 80% at temperatures above 350 °C. These results were markedly superior to those of the conventional commercial 1%V₂O₅–10%WO₃/TiO₂ catalyst. Characterization studies indicated that the 15CeV10W/Ti catalyst possessed improved redox performance and more acidic sites. In the MPC reaction, the declined CBCO activity, compared to the CB separate oxidation, can be attributed primarily to the competitive adsorption of NH₃ with CB. Conversely, the observed decrease in NO_x conversion at lower temperatures was primarily due to the suppression of the oxidation of NO to NO₂ by CB. Full article

A series of Fe–Ba mixed oxides, including a pure Fe-containing sample as a reference, have been synthesized via a sol–gel process using Fe³⁺ or Fe²⁺ salts and BaSO₄ as raw materials, with Pluronic P123 serving as a template. These oxides have been thoroughly characterized and subsequently utilized as catalysts for the chlorination of various organic molecules. Commercial hydrochloric acid, known for its relative safety, and environmentally friendly aqueous hydrogen peroxide were employed as the chlorine source and oxidant, respectively. The pure Fe-containing catalyst displays excellent thermal stability between 600 and 800 °C and exhibited moderate to high conversions in the chlorination of toluene, benzene, and tert-butyl hydroperoxide, with remarkable ortho-selectivity in chlorination of toluene. The combination of Fe³⁺ salt with BaSO₄ in the sol–gel process results in a Fe–Ba mixed oxide catalyst composed of BaO₂, BaFe₄O₇, and Fe₂O₃, significantly enhancing the chlorination activity compared to that displayed by the pure Fe catalyst. Notably, the chlorination of tert-butyl hydroperoxide (TBHP) does not require additional oxidants such as H₂O₂, and involves both electrophilic substitution and nucleophilic addition. Notably, the chlorination of bromobenzene yields chlorobenzene as the sole product, a transformation that has not been previously reported. Overall, this catalytic chlorination system holds promise for advancing the chlorination industry and enhancing pharmaceutical production. Full article

Porous polymeric microspheres are among the most effective adsorbents. They can be synthesized from numerous monomers using different kinds of polymerization techniques with a broad selection of synthesis factors. The main goal of this study was to prepare copolymeric microspheres and establish the relationship between copolymerization parameters and the porosity and thermal stability of the newly synthesized materials. Porous microspheres were obtained via heterogenous radical copolymerization using 3-(trimethoxysilyl)propyl methacrylate (TMPSM) as functional monomers and trimethylolpropane trimethacrylate (TRIM) as the crosslinker. In the course of the copolymerization, toluene or chlorobenzene was used as the pore-forming diluent. Consequently, highly porous microspheres were produced. Their specific surface area was established by a nitrogen adsorption/desorption method and it was in the range of 382 m²/g to 457 m²/g for toluene and 357–500 m²/g in the case of chlorobenzene. The thermal degradation process was monitored by thermogravimetry and differential scanning calorimetry methods in inert and oxidative conditions. The copolymers were stable up to 269–283 °C in a helium atmosphere, whereas in synthetic air the range was 266–298 °C, as determined by the temperature of 5% mass loss. Thermal stability of the investigated copolymers increased along with an increasing TMPSM amount in the copolymerization mixture. In addition, the poly(TMSPM-co-TRIM) copolymers were effectively used as the stationary phase in GC analyses. Full article

The development of efficient catalysts with longevity to remove chlorobenzene is challenging due to Cl poisoning. Herein, a series of Mn-Cr/ZrO_x catalysts supported by Zr-based metal-organic framework (UiO-66)-derived ZrO_x was prepared and investigated for chlorobenzene (CB) catalytic oxidation. MnCr/ZrO_x-M prepared via a wet impregnation method presented an amorphous structure, indicating the homogeneous dispersion of Cr and Mn, which improved acid and redox properties. 40Mn7Cr3/ZrO_x-M exhibited the best catalytic activity for chlorobenzene oxidation with T₉₀ of 293 °C, which is mainly due to the strong interaction between manganese and chromium promoted by the large specific surface area of the ZrO_x support. Furthermore, 40Mn7Cr3/ZrO_x-M presented excellent stability for chlorobenzene oxidation. Full article

Ce–based catalysts exhibit a poor stability and activity in chlorinated volatile organic compound (Cl–VOC) oxidation due to their rapid Cl poisoning. Herein, phosphotungstic acid (HPW) was coated on CeO₂ to improve its activity and stability for chlorobenzene (CB) oxidation. The HPW coating not only promoted CB adsorption onto CeO₂, but also provided Brønsted acid sites to CeO₂ for Cl species removal as HCl, thus avoiding Cl poisoning. Hence, a synergistic effect of CeO₂ and HPW on HPW/CeO₂ was observed, resulting in superior CB oxidation activity and stability. Additionally, to improve the sulfur resistance of the catalyst, the inhibition mechanism of SO₂ on CB oxidation by HPW/CeO₂ was explored. HPW/CeO₂ was prone to sulfation due to the formation of Ce₂(SO₄)₃ from the reaction of SO₂ and CeO₂. Thus, the oxidation ability of HPW/CeO₂; the amount of adsorption sites for CB adsorption; and the amounts of Ce⁴⁺ bonded with O²⁻, lattice oxygen species, and adsorbed oxygen species were decreased by SO₂. Meanwhile, SO₂ competed with CB for the adsorption sites on HPW/CeO₂. Therefore, CB oxidation by HPW/CeO₂ was remarkably restrained by SO₂. The present work promotes further work on Cl–VOC removal by Ce-based catalysts for anti-SO₂ poisoning modification in the future. Full article

There is an urgent need to develop novel and high-performance catalysts for chlorinated volatile organic compound oxidation as a co-benefit of NO_x. In this work, HSiW/CeO₂ was used for chlorobenzene (CB) oxidation as a co-benefit of NO_x reduction and the inhibition mechanism of NH₃ was explored. CB oxidation over HSiW/CeO₂ primarily followed the Mars–van–Krevelen mechanism and the Eley-Rideal mechanism, and the CB oxidation rate was influenced by the concentrations of surface adsorbed CB, Ce⁴⁺ ions, lattice oxygen species, gaseous CB, and surface adsorbed oxygen species. NH₃ not only strongly inhibited CB adsorption onto HSiW/CeO₂, but also noticeably decreased the amount of lattice oxygen species; hence, NH₃ had a detrimental effect on the Mars–van–Krevelen mechanism. Meanwhile, NH₃ caused a decrease in the amount of oxygen species adsorbed on HSiW/CeO₂, which hindered the Eley-Rideal mechanism of CB oxidation. Hence, NH₃ significantly hindered CB oxidation over HSiW/CeO₂. This suggests that the removal of NO_x and CB over this catalyst operated more like a two-stage process rather than a synergistic one. Therefore, to achieve simultaneous NO_x and CB removal, it would be more meaningful to focus on improving the performances of HSiW/CeO₂ for NO_x reduction and CB oxidation separately. Full article

With the rapid development of the economy and the demands of people’s lives, the usage amount of polymer materials is significantly increasing globally. Chlorobenzenes (CB_S) are widely used in the industrial, agriculture and chemical industries, particularly as important chemical raw materials during polymers processes. CB_S are difficult to remove due to their properties, such as being hydrophobic, volatile and persistent and biotoxic, and they have caused great harm to the ecological environment and human health. Electrochemical oxidation technology for the treatment of refractory pollutants has been widely used due to its high efficiency and easiness of operation. Thus, the electrochemical oxidation system was established for the efficient treatment of monochlorobenzene (MCB) waste gas. The effect of a single factor, such as anode materials, cathode materials, the electrolyte concentration, current density and electrode distance on the removal efficiency (RE) of MCB gas were first studied. The response-surface methodology (RSM) was used to investigate the relationships between different factors’ conditions (current density, electrolyte concentration, electrode distance), and a prediction model was established using the Design-Expert 10.0.1 software to optimize the reaction conditions. The results of the one-factor experiments showed that when treating 2.90 g/m³ MCB gas with a 0.40 L/min flow rate, Ti/Ti₄O₇ as an anode, stainless steel wire mesh as a cathode, 0.15 mol/L NaCl electrolyte, 10.0 mA/cm² current density and 4.0 cm electrode distance, the average removal efficiency (RE), efficiency capacity (EC) and energy consumption (Esp) were 57.99%, 20.18 g/(m³·h) and 190.2 (kW·h)/kg, respectively. The results of the RSM showed that the effects of the process parameters on the RE of MBC were as follows: current density > electrode distance > electrolyte concentration; the interactions effects on the RE of MBC were in the order of electrolyte concentration and current density > current density and electrode distance > electrolyte concentration and electrode distance; the optimal experimental conditions were as follows: the concentration of electrolyte was 0.149 mol/L, current density was 18.11 mA, electrode distance was 3.804 cm. Under these conditions, the RE achieved 66.43%. The response-surface variance analysis showed that the regression model reached a significant level, and the validation results were in agreement with the predicted results, which proved the feasibility of the model. The model can be applied to treat the CB_S waste gas of polymer processes through electrochemical oxidation. Full article

Hydrodechlorination (HDC) is a reaction that involves the use of hydrogen to cleave the C−Cl bond in chlorinated organic compounds such as chlorophenols and chlorobenzenes, thus reducing their toxicity. In this study, a palladium (Pd) catalyst, which is widely used for HDC due to its advantageous physical and chemical properties, was immobilized on alumina (Pd/Al) and graphene-based materials (graphene oxide and reduced graphene oxide; Pd/GO and Pd/rGO, respectively) to induce the HDC of 4-chlorophenol (4-CP). The effects of the catalyst dosage, initial 4-CP concentration, and pH on 4-CP removal were evaluated. We observed that 4-CP was removed very rapidly when the HDC reaction was induced by Pd/GO and Pd/rGO. The granulation of Pd/rGO using sand was also investigated as a way to facilitate the separation of the catalyst from the treated aqueous solution after use, which is to improve practicality and effectiveness of the use of Pd catalysts with graphene-based support materials in an HDC system. The granulated catalyst (Pd/rGOSC) was employed in a column to induce HDC in a continuous flow reaction, leading to the successful removal of most 4-CP after 48 h. The reaction mechanisms were also determined based on the oxidation state of Pd, which was observed using X-ray photoelectron spectroscopy. Based on the results as a whole, the proposed granulated catalyst has the potential to greatly enhance the practical applicability of HDC for water purification. Full article

Mineralization of gaseous chlorobenzene (major VOC from cement plants) was studied in a continuous reactor using three advanced oxidation processes: (i) photocatalysis, (ii) Dielectric Barrier Discharge (DBD) plasma and (iii) DBD/TiO₂-UV coupling. The work showed an overproduction of OH * and O * radicals in the reaction medium due to the interaction of Cl * and O₃. A parametric study was carried out in order to determine the evolution of the removal efficiency as a function of the concentration, the flow rate and the applied voltage. Indeed, a variation of the flow rate from 0.25 to 1 m³/h resulted in a decrease in the degradation rate from 18 to 9%. Similarly, an increase in concentration from 13 to 100 mg/m³ resulted in a change in degradation rate from 18 to 4%. When the voltage was doubled from 6 to 12 kV, the degradation rate varied from 22 to 29 % (plasma) and from 53 to 75% (coupling) at 13 mg/m³. The evolution of CO_X and O₃ was monitored during the experiments. When the voltage was doubled, the selectivity increased from 28 to 37% in the plasma alone and from 48 to 62 % in the coupled process. In addition, at this same voltage range, the amount of ozone formed varied from 10 to 66 ppm in plasma and 3 to 29 ppm in coupling. This degradation performance can be linked to a synergistic effect, which resulted in an increase in the intensity of the electric field of plasma by the TiO₂ and the improvement in the performance of the catalyst following the bombardment of various high-energy particles of the plasma. Full article

This study focused on the elimination of chlorobenzene by dual adsorption/catalytic oxidation over activated carbon fibers (ACFs) loaded with transition metal oxides (TMOs). The TMOs were successfully loaded on the ACFs by the incipient wetness impregnation method, which has the advantages of easy preparation, low cost, and size uniformity. The removal effects for chlorobenzene (CB) were investigated on pristine ACFs and TMOs@ACFs in a fix-bed reactor. The adsorption/catalytic oxidation experiments result demonstrated that ACFs can be used as a very efficient adsorbent for the removal of low-concentration CB at the low temperature of 120 °C; the breakthrough time of CB over pristine ACFs can reach 15 h at an inlet concentration of 5000 ppmv and space velocity of 20,000 h⁻¹. As the bed temperature rose above 175 °C, the CB removal mainly contributed to the catalytic oxidation of MnO₂; a preferable CB removal ratio was achieved at higher temperatures in the presence of more MnO₂. Therefore, CB can be effectively removed by the dual adsorbent/catalyst of MnO₂@ACF at the full temperature range below 300 °C. Full article