Lean methane combustion over zeolite-supported Pd catalysts: Structure-performance relationship and deactivation mechanism.

Zeolites are a promising support for Pd catalysts in lean methane (CH4) combustion. Herein, three types of zeolites (H-MOR, H-ZSM-5 and H-Y) were selected to estimate their structural effects and deactivation mechanisms in CH4 combustion. We show that variations in zeolite structure and surface acidity led to distinct changes in Pd states. Pd/H-MOR with external high-dispersing Pd nanoparticles exhibited the best apparent activity, with activation energy (Ea) at 73 kJ/mol, while Pd/H-ZSM-5 displayed the highest turnover frequency (TOF) at 19.6 × 10-3 sec-1, presumably owing to its large particles with more step sites providing active sites in one particle for CH4 activation. Pd/H-Y with dispersed PdO within pore channels and/or Pd2+ ions on ion-exchange sites yielded the lowest apparent activity and TOF. Furthermore, Pd/H-MOR and Pd/H-ZSM-5 were both stable under a dry condition, but introducing 3 vol.% H2O caused the CH4 conversion rate on Pd/H-MOR drop from 100% to 63% and that on Pd/H-ZSM-5 decreased remarkably from 82% to 36%. The former was shown to originate from zeolite structural dealumination, and the latter principally owed to Pd aggregation and the loss of active PdO.

Unveiling the Function of Oxygen Vacancy on Facet-Dependent CeO2 for the Catalytic Destruction of Monochloromethane: Guidance for Industrial Catalyst Design.

Secondary pollution remains a critical challenge for the catalytic destruction of chlorinated volatile organic compounds (CVOCs). By employing experimental studies and theoretical calculations, we provide valuable insights into the catalytic behaviors exhibited by ceria rods, cubes, and octahedra for monochloromethane (MCM) destruction, shedding light on the elementary reactions over facet-dependent CeO2. Our findings demonstrate that CeO2 nanorods with the (110) facet exhibit the best performance in MCM destruction, and the role of vacancies is mainly to form a longer distance (4.63 Å) of frustrated Lewis pairs (FLPs) compared to the stoichiometric surface, thereby enhancing the activation of MCM molecules. Subsequent molecular orbital analysis showed that the adsorption of MCM mainly transferred electrons from the 3σ and 4π* orbitals to the Ce 4f orbitals, and the activation was mainly caused by weakening of the 3σ bonding orbitals. Furthermore, isotopic experiments and theoretical calculations demonstrated that the hydrogen chloride generated is mainly derived from methyl in MCM rather than from water, and the primary function of water is to form excess saturated H on the surface, facilitating the desorption of generated hydrogen chloride.

Surface-Phosphorylated Ceria for Chlorine-Tolerance Catalysis.

An improved fundamental understanding of active site structures can unlock opportunities for catalysis from conceptual design to industrial practice. Herein, we present the computational discovery and experimental demonstration of a highly active surface-phosphorylated ceria catalyst that exhibits robust chlorine tolerance for catalysis. Ab initio molecular dynamics (AIMD) calculations and in situ near-ambient pressure X-ray photoelectron spectroscopy (in situ NAP-XPS) identified a predominantly HPO4 active structure on CeO2(110) and CeO2(111) facets at room temperature. Importantly, further elevating the temperature led to a unique hydrogen (H) atom hopping between coordinatively unsaturated oxygen and the adjacent P═O group of HPO4. Such a mobile H on the catalyst surface can effectively quench the chlorine radicals (Cl•) via an orientated reaction analogous to hydrogen atom transfer (HAT), enabling the surface-phosphorylated CeO2-supported monolithic catalyst to exhibit both expected activity and stability for over 68 days during a pilot test, catalyzing the destruction of a complex chlorinated volatile organic compound industrial off-gas.

Palladium Encapsulated by an Oxygen-Saturated TiO2 Overlayer for Low-Temperature SO2 -Tolerant Catalysis during CO Oxidation.

The development of oxidation catalysts that are resistant to sulfur poisoning is crucial for extending the lifespan of catalysts in real-working conditions. Herein, we describe the design and synthesis of oxide-metal interaction (OMI) catalyst under oxidative atmospheres. By using organic coated TiO2 , an oxide/metal inverse catalyst with non-classical oxygen-saturated TiO2 overlayers were obtained at relatively low temperature. These catalysts were found to incorporate ultra-small Pd metal and support particles with exceptional reactivity and stability for CO oxidation (under 21 vol % O2 and 10 vol % H2 O). In particular, the core (Pd)-shell (TiO2 ) structured OMI catalyst exhibited excellent resistance to SO2 poisoning, yielding robust CO oxidation performance at 120 °C for 240 h (at 100 ppm SO2 and 10 vol % H2 O). The stability of this new OMI catalyst was explained through density functional theory (DFT) calculations that interfacial oxygen atoms at Pd-O-Ti sites (of oxygen-saturated overlayers) serve as non-metal active sites for low-temperature CO oxidation, and change the SO2 adsorption from metal(d)-to-SO2 (π*) back-bonding to much weaker σ(Ti-S) bonding.

Defect Engineering in 0D/2D S-Scheme Heterojunction Photocatalysts for Water Activation: Synergistic Roles of Nickel Doping and Oxygen Vacancy.

Photocatalytic hydrodechlorination (HDC) is a promising method for eliminating chlorinated organic compounds (COCs) from water, but it requires catalysts with excellent water activation ability. Defect engineering is a feasible way to enhance the catalytic performance of photocatalysts by improving light adsorption, charge carrier dynamics, and surface reactions. Herein, a well-designed 0D/2D S-scheme heterojunction with favorable band structures and defective interfaces was constructed via defect tailoring on TiO2 quantum dots (QDs) and the interface structure. The optimized catalyst Ni-TiO2-x/g-C3N4 with 1% Ni doping after thermal treatment at 300 °C under nitrogen resulted in superior visible-light-driven activity in trichloroethylene (TCE) photocatalytic HDC, approximately an 18.2-fold increase as compared with g-C3N4. Ni doping and thermal-induced oxygen vacancies were verified to synergistically endow the catalyst with improved visible-light absorption efficiency, ameliorated charge separation and migration, and enhanced redox potential. Experimental and theoretical results showed that the synergy of multifold defects in promoting visible-light harvesting was mainly due to the characteristic multiple midgap states, in terms of different intermediate energy levels and narrowed bandgap. Furthermore, the contradicting effects of midgap states on photogenerated charge carrier dynamics were mediated by the defective S-scheme heterojunction, where the detrimental charge recombination relating to excessive defects was considerably inhibited via superior spatial charge separation and promoted surface redox reactions. The design of defect-engineered heterojunctions and the role of controlled defects in adjusting band structures provide valuable insights for creating highly efficient artificial photosystems in the visible region.

Polymerization State of Vanadyl Species Affects the Catalytic Activity and Arsenic Resistance of the V2O5-WO3/TiO2 Catalyst in Multipollutant Control of NOx and Chlorinated Aromatics.

The conventional V2O5-WO3/TiO2 catalyst suffers severely from arsenic poisoning, leading to a significant loss of catalytic activity. The doping of Al or Mo plays an important role in promoting the arsenic resistance on NH3 selective catalytic reduction (NH3-SCR), but their promotion mechanism remains in debate and has yet to be explored in multipollutant control (MPC) of NOx and chlorinated organics. Herein, our experimental characterizations and density functional theory (DFT) calculations confirmed that arsenic species preferentially adsorb on both Al and Mo to form arsenate, thereby avoiding bonding to the catalytically active V sites. More importantly, Al doping partially converted the polymeric vanadyl species into monomeric ones, thereby inhibiting the near-surface and bulk lattice oxygen mobility of the V2O5-WO3/TiO2 catalyst, while Mo doping resulted in vanadyl polymerization with an enriched V5+ chemical state and exhibited superior MPC activity and COx selectivity. Our work shows that antipoisoning catalysts can be designed with the combination of site protection and occurrence state modification of the active species.

Catalytic destruction of chlorobenzene over K-OMS-2: Inhibition of high toxic byproducts via phosphate modification.

In the process of catalytic destruction of chlorinated volatile organic compounds (CVOCs), the catalyst is prone to chlorine poisoning and produce polychlorinated byproducts with high toxicity and persistence, bringing great risk to atmospheric environment and human health. To solve these problems, this work applied phosphate to modify K-OMS-2 catalysts. The physicochemical properties of catalysts were determined by using X-ray powder diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), hydrogen temperature programmed reduction (H2-TPR), pyridine adsorption Fourier-transform infrared (Py-IR) and water temperature programmed desorption (H2O-TPD), and chlorobenzene was selected as a model pollutant to explore the catalytic performance and byproduct inhibition function of phosphating. Experimental results revealed that 1 wt.% phosphate modification yielded the best catalytic activity for chlorobenzene destruction, with the 90% conversion (T90) at approximately 247°C. The phosphating significantly decreased the types and yields of polychlorinated byproducts in effluent. After phosphating, we observed significant hydroxyl groups on catalyst surface, and the active center was transformed into Mn(IV)-O…H, which promoted the formation of HCl, and enhanced the dechlorination process. Furthermore, the enriched Lewis acid sites by phosphating profoundly enhanced the deep oxidation ability of the catalyst, which promoted a rapid oxidation of reaction intermediates, so as to reduce byproducts generation. This study provided an effective strategy for inhibiting the toxic byproducts for the catalytic destruction of chlorinated organics.

Selective Ru Adsorption on SnO2/CeO2 Mixed Oxides for Efficient Destruction of Multicomponent Volatile Organic Compounds: From Laboratory to Practical Possibility.

Ru-based catalysts have been extensively employed for the catalytic destruction of chlorinated volatile organic compounds (VOCs), but their versatility for other routine VOCs' destruction has been less explored. Herein, we show that Ru-decorated SnO2/CeO2 mixed oxides can sustain H2O and HCl poisonings and are endowed with extraordinary versatility for a wide range of VOCs' destruction. Selective adsorption of Ru on the cassiterite SnO2 and CeO2 nanorods through a Coulomb force can rationally tune the oxidation and dechlorination centers on decorated catalysts, where the epitaxial growth of RuOx on top of SnO2 is endowed with excellent dechlorination ability and that on CeO2 is functional as an oxidation center; the latter could also activate H2O to provide sufficient H protons for HCl formation. Our developed Ru/SnO2/CeO2 catalyst can steadily destruct mono-chlorobenzene, ortho-dichlorobenzene, trichloroethylene, dichloromethane, epichlorohydrin, N-hexane, ethyl acetate, toluene, and their mixtures at an optimum temperature of 300 °C, and its monolithic form is also functional at this temperature with few dioxins being detected in the off-gas. Our results imply that the Ru-decorated SnO2/CeO2 catalyst can meet the demands of regenerative catalytic oxidation for the treatment of a wide range of VOCs from industrial exhausts.

Tribocatalysis of homogeneous material with multi-size granular distribution for degradation of organic pollutants.

Recently, tribocatalysis driven by mechanical energy has been developed by rubbing two kinds of different materials. In this work, we firstly demonstrated that the friction of the single material also could initiate the tribocatalysis for degrading organic dyes. Under magnetic stirring, the multi-size granular polytetrafluoroethylene (PTFE) particles were triboelectrically charged, among which the collision between large and small particles would cause high energy electrons on large particles to transfer to small ones. These triboelectric charges on PTFE particles could react with adsorbed oxygen molecules or water to generate reactive oxygen species, and then promoted the degradation process of organic dyes together with oxidant holes. We further investigated the experimental parameters, such as stirring speed, size and quantity of stirring bar, to optimize the tribocatalytic performance. What's more, the PTFE tribocatalysis possessed high durability for multiple recycling runs with > 90% degradation efficiency of Rhodamine B, as well as well universality for eliminating other pollutants. Finally, we proposed a plausible tribocatalytic mechanism of multi-size granular PTFE according to the detected reactive oxygen species and the determined intermediates. This study provides new insights into tribocatalysis, and demonstrates that the single material with different particle sizes can also be used as catalyst to drive tribocatalytic process.

Synergistic Elimination of NOx and Chlorinated Organics over VOx/TiO2 Catalysts: A Combined Experimental and DFT Study for Exploring Vanadate Domain Effect.

Vanadium-based catalysts have been extensively applied for the synergistic control of NOx and chlorinated organics. However, how the vanadia species affect the reaction activity and products distribution, and what are the dominant reaction sites of these vanadia species are still unknown. Herein, we investigated the reaction characteristics of monomeric and polymeric vanadate domains for the catalytically synergistic elimination of NOx and chlorobenzene (CB). Density functional theory (DFT) calculations and experimental investigations have been combined to clarify the effects of different vanadyl species on the synergistic reaction. It was noted that the main adsorption site of CB on the monomeric domain was V-OH bond, and that on the polymeric one was V═O bond. The monomeric vanadyl was favorable for converting the Lewis V═O into Brønsted V-OH, which provided sufficient H protons for HCl formation, whereas the polymeric species could effectively retain the V4+/V5+ redox cycle, and yielded superior activity in CB catalytic oxidation (CBCO) reaction. However, the abundant oxygen vacancies and the inclined accumulation of Cl by forming the V-Cl bands led to significant polychlorinated byproducts on the polymeric vanadyl catalysts. Our work gives the first insight into different vanadate domain effects on the synergistic reaction, and is expected to provide theoretical basis for efficient design of the vanadium-based catalysts toward multipollutants elimination.

V2O5-WO3/TiO2 Catalyst for Efficient Synergistic Control of NOx and Chlorinated Organics: Insights into the Arsenic Effect.

Municipal solid waste incineration and the iron and steel smelting industry can simultaneously discharge NOx and chlorinated organics, particularly polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). Synergistic control of these pollutants has been considered among the most cost-effective methods. This work combined experimental and computational methods to investigate the reaction characteristics of a catalytically synergistic approach and gives the first insight into the effect of arsenic (As) on the multipollutant conversion efficiency, synergistic reaction mechanism, and toxic byproduct distribution over a commercial V2O5-WO3/TiO2 catalyst. The loaded As2O3 species were shown to distinctly decrease the formation energy of an oxygen vacancy at the V-O-V site, which likely contributed to the extensive formation of more toxic polychlorinated byproducts in the synergistic reaction. The As2O5 species strongly attacked neighboring V═O sites forming the As-O-V bands. Such an interaction deactivated the deNOx reaction, but led to excessive NO being oxidized into NO2 that greatly promoted the V5+-V4+ redox cycle and in turn facilitated chlorobenzene (CB) oxidation. Subsequent density functional theory (DFT) calculation further reveals that both the As2O3 and As2O5 loadings can facilitate H2O adsorption on the V2O5-WO3/TiO2 catalyst, leading to competitive adsorption between H2O and CB, and thereby deactivate the CB oxidation with water stream.

Effect of Cr doping in promoting the catalytic oxidation of dichloromethane (CH2Cl2) over Cr-Co@Z catalysts.

A core-shell catalyst which consists of a Co3O4 core and ZSM-5 shell, was prepared by microwave hydrothermal method and subjected for dichloromethane (DCM) oxidation. Chromium, cerium, niobium, and manganese species were separately introduced into the core-shell catalyst using the wet precipitation method and denoted as M-Co@Z (M = Cr, Ce, Nb, Mn). The catalytic activity of the Cr-Co@Z catalyst was significantly increased due to the interaction between Cr2O3 and Co3O4. The results of Raman spectra indicated the incorporation of chromium into the Co3O4 lattice and revealed the existence of the interaction between Cr2O3 and Co3O4. The synergistic effect between Cr2O3 and Co3O4 might be conducive to the generation of highly defective structure and increase the ratio of Co3+/Co2+ of the sample, leading to its better oxygen mobility. The dechlorination ability of Cr-Co@Z was also promoted due to the enhanced mobility of lattice oxygen. Based on in situ DRIFT studies, a possible reaction route of CH2Cl2 oxidation over Cr-Co@Z catalyst was proposed.

The role of surface sulfation in mediating the acidity and oxidation ability of nickel modified ceria catalyst for the catalytic elimination of chlorinated organics.

Surface sulfation has shown to be an effective way in modifying the acidity and oxygen mobility of metal oxide catalysts. Both of the properties were crucial in the catalytic elimination of chlorinated organics from industrial source of emission. Herein, sulfation of a dry-mixed NiO/CeO2 catalyst was conducted. The catalyst was subsequently utilized for eliminating chlorobenzene (CB) under a simulated realistic condition. A range of analytical techniques, including XRD, XPS, in situ DRIFT and NH3-DRIFT were employed to elucidate the sulfation effect on the physiochemical property and reaction activity of NiO/CeO2. Enhanced Lewis acidity and enriched surface oxygen vacancies originating from the interaction of sulfates and metal ions were observed, which led to improved conversion efficiency and COx (CO + CO2) selectivity in CB oxidation. In particular, qualitative analyses of reaction byproducts in the off-gas indicated that sulfation modification did not cause severe electrophilic chlorination of NiO/CeO2, and resulted in limited production of polychlorinated byproducts and less secondary pollution of the catalyst.

Deactivation effects of Pb(II) and sulfur dioxide on a γ-MnO2 catalyst for combustion of chlorobenzene.

Mn-based catalysts are extensively used; herein, the poisoning mechanism of Pb2+ and SO2 on the γ-MnO2 catalyst during the combustion of chlorobenzene (CB) was studied. The oxidizability/reducibility, surface acidity and water activation property of the Pb/SO42- modified γ-MnO2 were analyzed by using XPS, H2-TPR/O2-TPD, NH3-TPD/Pyridine-IR and H2O-TPD. Catalytic performance and byproduct selectivity towards CB combustion were explored, indicating that Pb2+ and SO2 both impacted CB conversion and CO2 selectivity as indicated by the loss of oxidation properties and surface acidity. Analysis of the byproducts showed that Pb2+ and SO2 induced the formation of more toxic polychlorinated byproducts, thereby introducing new secondary environmental pollution risks.

Elimination of chloroaromatic congeners on a commercial V2O5-WO3/TiO2 catalyst: The effect of heavy metal Pb.

Catalytic elimination of chlorinated volatile organic compounds (CVOCs) from the industrial sources of emission usually confronted with catalyst deactivation and secondary pollution. As a widely used catalyst in selective catalytic reduction (SCR) of nitric oxides, V2O5-WO3/TiO2 catalysts (denoted as VWT) have been also applied for eliminating the CVOCs, especially those from the municipal solid waste (MSW) incineration. However, the effect of heavy metals on the reaction characteristics of this catalyst is lack of exploration, which has been considered to be a main cause for catalyst deactivation. Herein, we investigated the effect of lead (Pb), a critical heavy meal in the flue gas of MSW incineration, on the catalytic elimination of chlorobenzene (CB) over the VWT catalyst. Variations of catalytic activity, CO2/HCl selectivity and chlorine adsorption/desorption behaviors were evaluated. In particular, the reaction byproducts with and without Pb loadings were qualitatively and quantitatively analyzed. It was noted that the loading of excessive Pb could change the reaction route over the VWT catalyst, leading to low CB oxidation efficiency and CO2 selectivity. However, these Pb spices likely acted as "a sink" to capture the dissociated Cl that hindered the electrophilic chlorination reaction, and avoided the formation of more toxic polychlorinated byproducts.

Efficient Elimination of Chlorinated Organics on a Phosphoric Acid Modified CeO2 Catalyst: A Hydrolytic Destruction Route.

The development of efficient technologies to prevent the emission of hazardous chlorinated organics from industrial sources without forming harmful byproducts, such as dioxins, is a major challenge in environmental chemistry. Herein, we report a new hydrolytic destruction route for efficient chlorinated organics elimination and demonstrate that phosphoric acid-modified CeO2 (HP-CeO2) can decompose chlorobenzene (CB) without forming polychlorinated congeners under the industry-relevant reaction conditions. The active site and reaction pathway were investigated, and it was found that surface phosphate groups initially react with CB and water to form phenol and HCl, followed by deep oxidation. The high on-stream stability of the catalyst was due to the efficient generation of HCl, which removes Cl from the catalyst surface and ensures O2 activation and therefore deep oxidation of the hydrocarbons. Subsequent density functional theory calculations revealed a distinctly decreased formation energy of an oxygen vacancy at nearest (VO-1) and next-nearest (VO-2) surface sites to the bonded phosphate groups, which likely contributes to the high rate of oxidation observed over the catalyst. Significantly, no dioxins, which are frequently formed in the conventional oxidation route, were observed. This work not only reports an efficient route and corresponding phosphate active site for chlorinated organics elimination but also illustrates that the rational design of the reaction route can solve some of the most important challenges in environmental catalysis.

Synergistic Elimination of NOx and Chloroaromatics on a Commercial V2O5-WO3/TiO2 Catalyst: Byproduct Analyses and the SO2 Effect.

The synergistic control of multipollutants is the frontier of environmental catalysis. This research is in the infancy stage, and many uncertainties still remain. Herein, we investigated the reaction characteristics of synergistic elimination of NOx and chloroaromatics on a commercial V2O5-WO3/TiO2 catalyst. The reaction byproducts were qualitatively and quantitatively analyzed, and their origins were clarified. In particular, the origins of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the synergistic reaction with or without SO2 were first explored; this is crucial for assessing the environmental risk by applying such a synergistic system. Experimental results indicate that during the synergistic reaction, the V2O5-WO3/TiO2 catalyst was deactivated at 200 and 250 °C, whereas the 300 °C was sufficient to durably convert the NO and chlorobenzene at the turnover frequency (TOF) of 7.23 × 10-4 and 1.32 × 10-4 s-1, respectively. A range of aromatics, alkenes, and alkanes, particularly their chlorinated congeners, were observed in the off-gases and on the catalyst surface, where those of 3-chlorobenzonitrile, 4-chloro-2-nitrophenol, and inorganic CS2 were first discovered. In the time-on-stream test at 250 °C, the PCDD/Fs collected from the off-gases was measured at 0.0514 ng I-TEQ Nm-3, but the most toxic dioxins congener, 2,3,7,8-TCDD, was not observed. The alkalinity of selective catalytic reduction reaction likely facilitated the chlorophenol formation, which eventually promoted PCDD/F generation. The SO2 was found to benefit polychlorinated byproduct generation, but the addition of which distinctly inhibited PCDD/F formation.

Catalytic Oxidation of Chlorinated Organics over Lanthanide Perovskites: Effects of Phosphoric Acid Etching and Water Vapor on Chlorine Desorption Behavior.

In this article, the underlying effect of phosphoric acid etching and additional water vapor on chlorine desorption behavior over a model catalyst La3Mn2O7 was explored. Acid treatment led to the formation of LaPO4 and enhanced the mobility of lattice oxygen of La3Mn2O7 evidenced by a range of characterization (i.e., X-ray diffraction, temperature-programmed analyses, NH3-IR, etc.). The former introduced thermally stable Brönsted acidic sites that enhanced dichloromethane (DCM) hydrolysis while the latter facilitated desorption of accumulated chlorine at elevated temperatures. The acid-modified catalyst displayed a superior catalytic activity in DCM oxidation compared to the untreated sample, which was ascribed to the abundance of proton donors and Mn(IV) species. The addition of water vapor to the reaction favored the formation and desorption of HCl and avoided surface chlorination at low temperatures. This resulted in a further reduction in reaction temperature under humid conditions ( T90 of 380 °C for the modified catalyst). These results provide an in-depth interpretation of chlorine desorption behavior for DCM oxidation, which should aid the future design of industrial catalysts for the durable catalytic combustion of chlorinated organics.

Alkali Potassium Induced HCl/CO2 Selectivity Enhancement and Chlorination Reaction Inhibition for Catalytic Oxidation of Chloroaromatics.

Industrial combustion of chloroaromatics is likely to generate unintentional biphenyls (PCBs), polychlorinated dibenzo- p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). This process involves a surface-mediated reaction and can be accelerated in the presence of a catalyst. In the past decade, the effect of surface nature of applied catalysts on the conversion of chloroaromatics to PCBs/PCDD/PCDF has been well explored. However, studies on how the flue gas interferent components affect such a conversion process remain insufficient. In this article, a critical flue gas interferent component, alkali potassium, was investigated to reveal its effect on the chloroaromatics oxidation at a typical solid acid-base catalyst, Mn xCe1- xO2/HZSM-5. The loading of alkali potassium was found to improve the Lewis acidity of the catalyst (by increasing the amounts of surface Mn4+ after calcination), which thus promoted the CO2 selectivity for catalytic chlorobenzene (CB) oxidation. The KOH with a high hydrophilicity has favored the adsorption/activation of H2O molecules that provided sufficient hydroxyl groups and possibly induced a hydrolysis process to promote the formation of HCl. The K ion also served as a potential sink for chorine ions immobilization (via forming KCl). Both of these inhibited the formation of phenyl polychloride byproducts, thereby blocking the conversion of CB to chlorophenol and then PCDDs/PCDFs, and potentially ensuring a durable operation and less secondary pollution for the catalytic chloroaromatics combustion in industry.