Oxidation Of Chlorobenzene Research Articles

Study on catalytic combustion of chlorobenzene over TiO2-supported V-W composite bimetallic catalysts

A series of TiO2-supported V-W bimetallic catalysts were prepared by incipient wetness impregnation method. The effects of V/W ratios on the catalytic combustion performance for chlorobenzene were investigated. The results showed that proper W doping (5V5W-Ti and 3V7W-Ti) improved the catalytic combustion activity of chlorobenzene and the selectivity of HCl. In combination with BET, XRD, XPS, H2-TPR, NH3-TPD and Py-FTIR characterizations, it indicated that higher activity for chlorobenzene oxidation was attributed to the high dispersion of the active species and the abundant surface adsorbed oxygen. In addition, moderate doping of W significantly enhanced the surface acidity of catalysts, especially strong acids and Brønsted acids, and thus improved the selectivity to HCl in the products.

Improvement of Al2O3 on the multi-pollutant control performance of NOx and chlorobenzene in vanadia-based catalysts

We compared the influences of Al2O3 and SiO2 on a traditional V2O5–MoO3/TiO2 for the simultaneous removal of NOx and chlorobenzene (CB). The Al2O3 doping catalyst considerably broadens the active temperature window with higher NOx reduction and CB oxidation efficiencies than the SiO2 doping one and the V2O5–MoO3/TiO2. Furthermore, its resistance to SO2 was preserved and the quantities of polychlorinated byproducts also decreased. The increase in activity at low temperatures could be due to the promotion of vanadia reducibility via interactions between V2O5 and Al2O3. Moreover, the high temperature activity could be due to the additional surface acidities provided by Al2O3, in which the Lewis acid sites played the predominant role in both NH3 adsorptions and CB de-chlorination compared to the Brønsted acid sites. Finally, we proposed that Al2O3 is an effective addition for vanadia-based catalyst in NOx and CB simultaneous removal from stationary sources.

Non-thermal plasma coupled with MOx/γ-Al2O3 (M: Fe, Co, Mn, Ce) for chlorobenzene degradation: Analysis of byproducts and the reaction mechanism

Chlorinated volatile organic compounds (VOCs) such as chlorobenzene pose serious human health and environmental risks, but are resistant to elimination techniques that are traditionally applied to Cl-free VOCs. Non-thermal plasma (NTP) offers a promising technique to decompose chlorobenzene, but its application remains limited owing to low COx selectivity and the generation of toxic byproducts. To address these problems, this study investigated chlorobenzene degradation in NTP coupled with MOx/γ-Al2O3 (M: Fe, Co, Mn, Ce) catalysts. The combination of NTP with MOx/γ-Al2O3 remarkably improved the removal efficiency (RE), mineralization rate (MR), Cl selectivity (SCl) and energy yield (EY) of chlorobenzene abatement, and decreased the production of residual O3. CoOx/γ-Al2O3 exhibited the best performance among these tested catalysts with higher RE, MR, SCl and EY by 26.06%, 25.52%, 33.03% and 2.41 g/kWh, respectively, at 510 J/L, compared with those of the NTP alone system. Several catalyst characterizations were applied to explore the relation between the catalyst characteristics and chlorobenzene abatement efficacy in NTP. The results indicate that the NTP catalytic oxidation of chlorobenzene strongly depends on the reducibility and acidity of the MOx/γ-Al2O3 samples, whereas the textural properties of the catalysts exert a limited influence on chlorobenzene degradation. High-resolution gas chromatography and high-resolution mass spectrometry analyses verified for the first time that PCDD/Fs were generated during chlorobenzene degradation in NTP catalytic reactions. A plausible decomposition mechanism of chlorobenzene in the NTP catalytic system is speculated according to the organic intermediates generated during chlorobenzene decomposition.

Pt and Mo Co-Decorated MnO2 Nanorods with Superior Resistance to H2O, Sintering, and HCl for Catalytic Oxidation of Chlorobenzene.

MnO2 nanorods with exposed (110), (100), or (310) facets were prepared and investigated for catalytic oxidation of chlorobenzene, then the (110)-exposed MnO2 nanorod was screened as the candidate parent and further modified by Pt and/or Mo with different contents. The loading of Pt enhanced activity and versatility of the pristine MnO2, but the polychlorinated byproducts and Cl2 were promoted, conversely, as the decoration of Mo inhibited the polychlorinated byproducts and improved durability. Determination of structure and properties suggested that Pt facilitated the formation of more oxygen vacancies/Mn3+ and surface adsorbed oxygen weakened the bonds of surface lattice oxygen, while Mo stabilized surface lattice oxygen and increased acid sites, especially Brønsted acid sites. Expectedly, Pt and Mo bifunctionally modified MnO2 presented a preferable activity, selectivity, and durability along with the super resistance to H2O, high-temperature, and HCl, and no prominent deactivation was observed within 30 h at 300 °C under dry and humid conditions, even at high-temperature aging at 600 °C and HCl-pretreatment (7 h). In this work, the optimized Mo and Pt codecorated MnO2 was considered a promising catalyst toward practical applications for catalytic oxidation of actual Cl-VOCs emissions.

In-situ regulation of acid sites on Mn-based perovskite@mullite composite for promoting catalytic oxidation of chlorobenzene

A series of Sm-Mn perovskite@mullite composites with different amounts of acid sites were successfully synthesized by regulating the level of in situ etched-surface modification. X-ray diffraction (XRD) test showed that the crystal structure of catalyst gradually changed from perovskite to perovskite@mullite composites and mullite. The characterization of temperature programmed desorption with ammonia (NH3-TPD) confirmed the acid sites on the surface of catalyst can be deployed by the in-situ modification. The temperature-programmed reduction with hydrogen (H2-TPR), and N2 adsorption–desorption showed that the surface modification also increased the reducibility, surface area, and mesoporosity of catalyst. The catalytic activities were compared by a long-term catalytic oxidation of chlorobenzene evaluation for 20 h of uninterrupted reaction at a relatively low temperature of 300 °C, and the Sm-Mn perovskite@mullite composite (SMPM-1.2) possessed the best catalytic stability. The X-ray photoelectron spectroscopy (XPS) measurement determined that the high ratios of lattice oxygen and tetravalent manganese did not improve the stability of catalyst in the catalytic oxidation of chlorobenzene, but the activities trends of samples were consistent with the change of surface (Mn4++Mn3+)/Mn2+ ratios. Meanwhile, the catalytic experiments for benzene, toluene, o-xylene and acetone showed that the as-prepared catalyst was also suitable for the efficient removal of the different types of VOCs. This work supplied a method for the further development of high activity catalysts for the removal of VOCs.

Removal of pesticide chlorobenzene by anodic degradation: Variable effects and mechanism

The oxidation of chlorobenzene (CB) was studied by electrochemical electrolysis using boron-doped diamond (BDD), PbO2 or platine (Pt) as anode and graphite bar as cathode. The effect of applied current density, supporting electrolyte and initial pH value were also studied. The results demonstrated that BDD anode had the best effectiveness and accomplishment of electrochemical degradation of CB compared to PbO2 and Pt anodes. For a current density of 20 mA/cm2 and at pH = 3, the elimination of COD and TOC were about 97% and 98%, respectively, after 360 min of electrolysis with the BDD anode. Pseudo-first order kinetics appears to be the most appropriate to describe the degradation of chlorobenzene. The electrochemical mechanism of chlorobenzene on BDD was proposed based on the identified intermediates.

Catalytic feasibility of Ce-doped LaCoO3 systems for chlorobenzene oxidation: An analysis of synthesis method

A family of Ce-doped LaCoO3 perovskites are presented as possible catalysts for Cl–VOCs elimination. These materials with different contents of Ce were obtained through the citrate and the reactive grinding methods. The insertion of Ce in the original perovskite structure favours the presence of Co2+/Co3+ and Ce3+/Ce4+ redox pairs and a higher content of oxygen vacancies that enhances the catalytic performance in chlorobenzene combustion based on differential kinetics studies. The family obtained by the grinding method presents a performance as high as that synthesized by citrate method. Thus, the reactive grinding is a feasible green chemistry alternative to obtain a catalyst with the same performance as that obtained from traditional methods. Finally, the stability of samples was evaluated under total combustion reaction conditions showing an excellent activity during 45 h time on stream.

Catalytic combustion of chlorobenzene at low temperature over Ru-Ce/TiO2: High activity and high selectivity

Ru/TiO2 and Ru-Ce/TiO2 catalysts were prepared by the equal-volume impregnation method to test their catalytic oxidation of chlorobenzene(CB), with the aim to investigate the effect of Ce addition on the redox capacity of the catalysts under the premise of reducing the content of noble metals. It was found that the introduction of Ce conserved the high catalytic efficiency of the catalyst while reducing the content of noble metal, and the catalysis of CB was greatly improved at low temperatures. Compared with the 0.4Ru/TiO2 catalyst, the T10 and T90 of the 0.4Ru-1.0Ce/TiO2 catalyst decreased by 50 ℃ and 60 ℃ respectively. It presented high reaction rate at 170 ℃ with an increase from 1.21 × 10−8 mol/min‧m2 for the 0.4Ru/TiO2 catalyst to 10.45 × 10−8 mol/min‧m2, making it even better than the 2.0Ru/TiO2 catalyst. The structure and morphology of the Ru/TiO2 catalyst did not change with the Ce doping and the mesoporous structure of the catalysts was maintained. CeO2 can not only store and release oxygen, but also improve the activity and dispersion of precious metal loaded. The formation of RuOCe under the interaction between CeO2 and Ru species promoted electron transfer and improved the mobility of surface oxygen, thus forming RuOx with higher valance. The introduction of Ce improved the yield of COx and selectivity towards inorganic chlorine (HCl and Cl2) and prevented the catalyst from producing more chlorinated by-products, thus greatly reducing the chance of producing more toxic dioxins.

Catalytic deep degradation of Cl-VOCs with the assistance of ozone at low temperature over MnO2 catalysts

This paper conducted catalytic ozonation and oxidation of chlorobenzene (CB) and dichloroethane (DCE) over three synthesized MnO2 catalysts with different properties. Catalytic ozonation exhibited high efficiency with less catalyst dosage at low temperature, ca. 30 ~ 120 °C, excellent stability, and less byproducts formation for both CB and DCE conversion. MnO2–I exhibited the best performance for all experiments, attributing to its abundant oxygen vacancies, more acid sites, and excellent CO2 desorption properties. Catalytic ozonation exhibited excellent stability with much fewer organic byproducts in effluent gas at 120 °C·H2O had no effect on catalytic ozonation but recovered catalytic oxidation performance. Besides, O3 existence attained high activity over deactivated catalyst by Cl poisoning. In–situ DRIFTs measurements validated facilitated transformation of intermediates during catalytic ozonation. These findings comprehensively verify the superiority of catalytic ozonation to attain highly stable and complete degradation of chlorinated volitile organic compounds (Cl–VOCs) at mild conditions.

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.

Oxidative decomposition of chlorobenzene over iron titanate catalysts: The critical roles of oxygen vacancies and adsorption geometries

Iron titanate catalysts with various Fe/(Fe + Ti) ratios were prepared by sol-gel method and investigated in catalytic oxidation of chlorobenzene (CB). The catalysts exhibited good activity and sulfation further promoted the performance in both activity and stability. Ti3+-oxygen vacancy (Vo) was determined with Raman, EPR and O2-TPD, while the generation mechanism of Ti3+-Vo was investigated by XPS and UV–vis. The structure-activity relationship was established between oxygen vacancies (Vo) and CB oxidation. The generation of Ti3+-Vo was attributed from the electron transfer from Fe3+ to Ti4+ in FeOTi structure as well as the incorporation of S4+ into surface lattice (for the sulfated catalyst). Moreover. the adsorption geometries of CB were comparatively studied. CB adsorbed on a pair of adjacent Lewis acid sites over the iron titanate catalysts through the Cl atom and the π cloud. CB of this adsorption type was highly activated and essentially contributed to the high activities.

Synthesis of manganese ore/Co3O4 composites by sol–gel method for the catalytic oxidation of gaseous chlorobenzene

Manganese ore/cobalt oxide composites were synthesized by using natural manganese ore and Co(NO3)2·6H2O via oxalic acid-assisted sol–gel method and applied in the catalytic oxidation degradation of gaseous chlorobenzene. The catalytic properties of the manganese ore/Co3O4 composites were investigated by X-ray diffraction (XRD), the electron microscopy technique (FE-SEM), N2 adsorption–desorption (BET), X-ray photoelectron spectroscopy (XPS) and H2-temperature programmed reduction (H2-TPR), respectively. The results showed that the composite catalyst with the mass ratio of manganese ore/cobalt oxide was 0.4 and calcined at 450 °C had the optimal catalytic performance. It could achieve 94% conversion of chlorobenzene, 83% selectivity of CO2 and over 36 h sustainability at 300 °C for the gaseous chlorobenzene with the initial concentration of 1200 mg m−3. The composite catalyst had the abundant surface oxygen species, good anti-chlorine poisoning performance and strong redox properties of composites, which were due to the interaction between manganese ore and Co3O4, and played a key role in degradation of chlorobenzene.

Enhanced catalytic activities of MnOx/Co3O4 nanocomposites prepared via MOFs-templated approach for chlorobenzene oxidation

Chlorinated volatile organic compounds (CVOCs) existing widely in the industries are harmful to the environment and human’s health. It is urgent to develop highly efficient catalysts for their combustion. Herein, a series of porous MnOx/Co3O4 nanocomposites are synthesized by the pyrolysis of Mn@Co-ZIF-67 precursors, in which the Mn ions are introduced by impregnation method. XRD, Raman, ICP-OES, BET, SEM, TEM, XPS, O2-TPD, and H2-TPR have been performed to investigate the as-prepared catalysts’ physicochemical properties. The optimal catalyst MnOx/Co3O4-4h exhibits 90% and 100% chlorobenzene (CB) conversion (1000 ppm, Air, WHSV = 60,000 mL/(g h)) at 334 °C and 350 °C, respectively. And the better catalytic performance over MnOx/Co3O4-4h compared with the pure Co3O4 and other MnOx/Co3O4 nanocomposites mainly ascribes to its porous structures, homogeneous dispersion, optimal Mn/Co molar ratio, more lattice defects, and higher surface OLatt/OAds ratio. Meanwhile, MnOx/Co3O4-4h displays high stability and resistance to moisture. Main intermediates have been further investigated by in situ DRIFT, and the degradation mechanism has been proposed according to the analysis of intermediates.

Comparative Investigation on Chlorobenzene Oxidation by Oxygen and Ozone over a MnOx/Al2O3 Catalyst in the Presence of SO2.

Catalytic oxidation of volatile organic compounds (VOCs) usually encounters complicated components in flue gas causing severe deactivation that restrict its application in specific conditions. The Cl substitution in chlorobenzene further increases poisoning risks. Ozone assistance has unique superiority that can overcome these bottleneck problems. Herein, this study performs a comparative investigation of CB oxidation by oxygen and ozone over a simple Mn/Al2O3 catalyst. CB conversion suffered from slight deactivation in oxygen atmosphere (from 90 to 70%) and more severe deactivation in the presence of SO2 (from 90 to 45%) at 480 °C. Introduction of ozone successfully attained high CB conversion at low temperature (120 °C) with excellent stability and less byproducts. Especially, CB oxidation by ozone maintained its original conversion in the presence of SO2. The deactivation process was simulated by synthesizing several sulfated catalysts. Direct sulfation on Mn/Al2O3 attained more severe deactivation in CB conversion and CO2 formation than sulfation on the Al2O3 support. Ozone with a strong oxidation property promoted the CB oxidation cycle, facilitated desorption of carbonaceous intermediates, and protected MnOx species from severe erosion, thus exhibiting high and stable performance in CB oxidation.

Improved Activity and Stability of Chlorobenzene Oxidation Over Transition Metal-Substituted Spinel-Type Catalysts Supported on Cordierite

Industrial catalysts usually encounter great challenges in Cl· deactivation, toxic by-products generation, and stability with a long running operation for catalytic oxidation of chlorinated volatile organic compounds (CVOCs). In this research, spinel-type oxides with transition metal substituted as active oxides supported on cordierite (Crd) was identified to catalytic degradation of chlorobenzene (CB). The Cu1.4Mn1.6O4 spinel-type oxides considered as the main active oxides have been identified, which were confirmed by XRD and TEM. The activities of these CuMxMn2−xO4 catalysts were markedly improved by lower calcining temperature and shorter time. CuCe0.25Mn1.75O4/Crd catalyst displayed the highest activity and good stability due to that CeO2 nano-rods structure conducive to increase the Oads amount, the dispersion of active oxides, the strength of weak acidity, the surface areas and pore volume. Moreover, spinel-type with CeO2 doping exhibited high performance in CVOCs elimination attributed to the high storage capacity of oxygen, plentiful oxygen vacancies, good efficiency in breaking C–Cl bond and the easy shuttles between Ce3+ and Ce4+, which were demonstrated by XPS. The results indicate that CeO2, Oads, and ·OH have beneficial effects on the removing Cl· into benzene, and then improving the ring-opening of CB for CB degradation.

Multi-pollutant control (MPC) of NO and chlorobenzene from industrial furnaces using a vanadia-based SCR catalyst

NO and chlorobenzene (CB) coexist in the flue gas of industrial furnaces from waste incineration and iron sintering. We design the strategy to remove them simultaneously via SCR and catalytic combustion together (multi-pollutant control, MPC). The V5Mo5Ti exhibits excellent activity with 100 % NO conversions in 200–400 °C and 95 % CB conversions above 300 °C. 2,3-dichloromaleic anhydride (DCMA) and acetate are the primary intermediates during the CB oxidation, while the sum of 17 kinds of PCDD/Fs on the V5Mo5Ti is 0.0115 ng·I-TEQ·Nm−3. Partial DCMA is not deeply oxidized into CO2, reducing the COx selectivity below 350 °C. The final products of the accumulated species above 800 °C desorption are CCl4 and C2Cl4, generated from the hydrogenation of intermediates. The Cl desorption mainly occurs in two zones: HCl in 200–500 °C from CB oxidation and CCl4 and C2Cl4 above 800 °C from surface hydrocarbon decomposition.

Enhanced Catalytic Oxidation of Chlorobenzene over MnO2 Grafted In Situ by Rare Earth Oxide: Surface Doping Induces Lattice Oxygen Activation

A series of highly active MnO2@REOx (RE = Gd, Sm, Ce, and La) catalysts were successfully synthesized via in situ growth on the surface of MnO2, wherein the rare earth oxides were planted on the defect sites left by hydrogen peroxide etching of the surface of MnO2. Their physicochemical performance was investigated by scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction with hydrogen (H2-TPR), and temperature-programmed desorption of oxygen (O2-TPD). The catalytic properties are compared through the catalytic oxidation of chlorobenzene. Among all catalysts, MnO2@GdOx showed better mobility of surface lattice oxygen and higher molar ratios of Mn4+/Mn3+ (1.10) and Oads/Olatt (0.45), which promoted the superior low-temperature catalytic activity for chlorobenzene oxidation. The long-term chlorobenzene oxidation test (18 h) at different temperatures and the experiments with a mixture of VOCs showed that the as-prepared catalyst not only possessed a high stability but also was suitable for the efficient and simultaneous removal of multicomponent VOCs (toluene, benzene, acetone, and chlorobenzene). This work also provided an idea for the further development of high-efficiency catalysts for the purification of VOCs from complex atmosphere environment.

Antimony Substituted Ammonium 12-Molybdophosphoric Acid Catalysts for Gas Phase Chlorobenzene Oxidation

Antimony (Sb) substituted Keggin structured ammonium salt of 12-molybdophsphoric acid (AMPA) materials were synthesized by acid precipitation method. The samples were obtained by increase of Sb atoms from 1 to 3 and corresponding decrease of Mo atoms from 11 to 9. The synthesized materials were thermal treated in the range of 300–500 °C. The catalytic performance of thermally treated Sb incorporated AMPA materials were examined for oxidation of chlorobenzene and the catalytic activity of Sb-AMPA samples was compared with activity of bulk AMPA. The materials were thoroughly analyzed by different techniques such as elemental analysis, TG, powder XRD, FTIR, SEM, N2-physisorption, 31P MAS NMR, XPS, DR UV–Vis and H2-TPR techniques. The characterization results clearly indicated that Sb-AMPA samples possessed high thermal stability, relatively large surface area and easy reducibility compared to bulk AMPA. The synthesized samples also possessed high content of surface adsorbed oxygen species, which are responsible for superior catalytic activity.

Unveiling the importance of reactant mass transfer in environmental catalysis: Taking catalytic chlorobenzene oxidation as an example

To date, investigations onto the regulation of reactants mass transfer has been paid much less attention in environmental catalysis. Herein, we demonstrated that by rationally designing the adsorption sites of multi-reactants, the pollutant destruction efficiency, product selectivity, reaction stability and secondary pollution have been all affected in the catalytic chlorobenzene oxidation (CBCO). Experimental results revealed that the co-adsorption of chlorobenzene (CB) and gaseous O2 at the oxygen vacancies of CeO2 led to remarkably high CO2 generation, owning to their short mass transfer distance on the catalyst surface, while their separated adsorptions at Brönsted HZSM-5 and CeO2 vacancies resulted in a much lower CO2 generation, and produced significant polychlorinated byproducts in the off-gas. However, this separated adsorption model yielded superior long-term stability for the CeO2/HZSM-5 catalyst, owning to the protection of CeO2 oxygen vacancies from Cl poisoning by the preferential adsorption of CB on the Brönsted acidic sites. This work unveils that design of environmental catalysts needs to consider both of the catalyst intrinsic property and reactant mass transfer; investigations of the latter could pave a new way for the development of highly efficient catalysts towards environmental pollution control.

Silicotungstic acid modified CeO2 catalyst with high stability for the catalytic combustion of chlorobenzene

The catalysts’ redox capacity and surface acidity was important during the catalytic combustion of chlorobenzene (CB). CeO2 showed great attractiveness due to its high oxygen storage capacity. Furthermore, the increase of acidity on the catalyst surface could improve the resistance to the chlorine poisoning. In this work, the silicotungstic (HSiW) modified CeO2 catalysts prepared by four cerium salts and exhibited the different morphologies and catalytic activity. The HSiW modified CeO2 catalyst prepared by Ce(CH3COO)3 (Cat-A) exhibited the best catalytic activity due to its abundant surface weak acid sites, more Ce3+ species and surface adsorption oxygen. The HSiW mainly located on the CeO2 (111) planes of the Cat-A, which was conducive to redox property of CeO2, thus promoting the deep oxidation of CB. Meanwhile the redox ability together with the weak acidity influenced the catalytic efficiency at low temperature. And the redox ability played a major role at high temperature. In addition, the Cat-A still possessed high stability and water resistance and maintained high activity after continuous catalytic oxidation of CB at 235 and 295 °C for 100h, exhibiting the possibility of industrial application.