Catalytic Oxidation Of Chlorobenzene Research Articles

Catalytic Oxidation of Chlorobenzene over Amorphous Manganese-Chromium Catalysts Supported by UiO-66-Derived ZrOx.

The development of efficient catalysts with longevity to remove chlorobenzene is challenging due to Cl poisoning. Herein, a series of Mn-Cr/ZrOx catalysts supported by Zr-based metal-organic framework (UiO-66)-derived ZrOx was prepared and investigated for chlorobenzene (CB) catalytic oxidation. MnCr/ZrOx-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/ZrOx-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 ZrOx support. Furthermore, 40Mn7Cr3/ZrOx-M presented excellent stability for chlorobenzene oxidation.

Catalytic Oxidation of Chlorobenzene over HSiW/CeO2 as a Co-Benefit of NOx Reduction: Remarkable Inhibition of Chlorobenzene Oxidation by NH3.

There is an urgent need to develop novel and high-performance catalysts for chlorinated volatile organic compound oxidation as a co-benefit of NOx. In this work, HSiW/CeO2 was used for chlorobenzene (CB) oxidation as a co-benefit of NOx 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 NOx and CB over this catalyst operated more like a two-stage process rather than a synergistic one. Therefore, to achieve simultaneous NOx and CB removal, it would be more meaningful to focus on improving the performances of HSiW/CeO2 for NOx reduction and CB oxidation separately.

Enhanced catalytic elimination of chlorobenzene over Ru/TiO2 modified with SnO2—Synergistic performance of oxidation and acidity

The chlorine poisoning of catalyst caused by catalytic oxidation of CVOCs after long-term operation is still the bottleneck of its large-scale industrial application. In this work, Ru-xSn/TiO2 catalysts with oxidation and acid function were prepared by the typical impregnation method, and the catalytic oxidation of chlorobenzene (CB) was also investigated. Meanwhile, the doping of Sn could make the catalyst maintain excellent activity on the basis of reducing the content of noble metals. The optimal catalytic oxidation activity of CB was obtained by doping 10 % Sn on 0.4Ru/TiO2, and the T10 and T90 values were 140 °C and 195 °C, respectively, which were similar to that of 2.0Ru/TiO2. SnO2 improved the concentration of Ru4+ on the surface of the catalyst and formed a solid solution with TiO2 to promote the crystal phase structure of anatase-TiO2 to rutile, resulting in an increase of surface defect sites. The acidity of Ru-Sn/TiO2 catalyst was higher than that of Ru/TiO2 catalyst and the Lewis acid would increase with the formation of SnOTi, while RuO2 was mainly the Brönsted acid center, so it had a suitable B/L ratio. CO2 was almost the only carbon-containing product, the oxidation processproducts were mainly benzoquinone, maleate, acetate, aldehydes and other intermediates. Most chlorine species were removed as HCl and Cl2 under the promotion of Deacon reaction.

Rod‐Like MnOx Catalyst Derived from Mn‐MOF‐74 for Chlorobenzene Oxidation at Low Temperature

AbstractIn this study, a series of MnOx catalysts were prepared by pyrolysis of Mn‐MOF‐74 precursors. The calcination temperature had influence on the structure and catalytic performance of MnOx catalysts in the catalytic oxidation of chlorobenzene. Their physicochemical properties were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption, X‐ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2‐TPR) and Fourier transform infrared (FTIR), respectively. The order of catalytic activity was as follows: rod‐like MnOx‐700 > rod‐like MnOx‐600 > boat‐like MnOx‐800. The MnOx‐700 catalysts exhibited excellent activity for chlorobenzene (CB) decomposition, and the T90 (temperature with CB conversion of 90 %) was 225 °C. The main reason was that MnOx‐700 inherited the advantage of Mn‐MOF‐74 with high specific surface area, and had higher ratio of Mn3+/Mn4+ (2.51) and Osur/Ototal (0.53). Meanwhile, the MnOx‐700 can maintain over 90 % CB conversion at elevated temperature for 100 h. This work can provide an idea for the further development of high efficiency catalysts prepared via MOF‐template in the CB decomposition.

Catalytic oxidation of chlorobenzene and PCDD/Fs over V2O5-WO3/TiO2: insights into the component effect and reaction mechanism.

In this work, titania supported catalysts (V-W/Ti) with different vanadium-tungsten contents were prepared and evaluated in the catalytic oxidation of chlorobenzene, which was used as the model compound of dioxins. The results showed that V2O5 is the main active component for chlorobenzene oxidation, and doping of WO3 affects the valence distributions of vanadium, contributing a bimetallic synergistic effect. The catalysts were investigated by XRD, SEM-EDS mapping, Raman, and XPS, and the changes in V element valence state and chlorine content on fresh and used catalysts were observed by XPS. Moreover, in situ FTIR studies and chlorine balance were also conducted, the addition of WO3 is helpful to the breakage of C-Cl, and a reaction mechanism for the catalytic oxidation of chlorobenzene was proposed. 3V-5W/Ti catalyst with better catalytic activity was selected for catalytic oxidation of PCDD/Fs using a lab scale PCDD/Fs generating and decomposing system. The degradation efficiency was 66.5% at 200°C and 62.2% at 300°C, which indicated that the low reaction temperature of 200°C was conducive to the catalytic degradation of PCDDs, while the high temperature of 300°C was facilitated the degradation of PCDFs.

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.

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.

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.

Catalytic oxidation of chlorobenzene over noble metals (Pd, Pt, Ru, Rh) and the distributions of polychlorinated by-products.

Catalytic oxidation of chlorobenzene over noble metal catalysts Pd/TiO2, Pt/TiO2, Ru/TiO2, and Rh/TiO2 was evaluated, and Ru/TiO2 contributed the highest catalytic activity and CO2 selectivity. During the oxidation, polychlorinated benzenes PhClx (x ≥ 2) were observed, and Ru/TiO2 showed apparently lower PhClx concentrations than other three samples. With the improvement of temperature, the maximum concentration appeared in the sequence of dichlorobenzene (PhCl2), trichlorobenzene (PhCl3), tetrachlorobenzene (PhCl4), and pentchlorobenzene (PhCl5), whereas the concentration of hexachlorobenzene (PhCl6) was always low and showed no apparent regularity. Besides, the dioxin-like PCBs (dl-PCBs) were collected and analyzed for Pd/TiO2 and Ru/TiO2. The ∑dl-PCBs produced by Pd/TiO2 (0.0055 ng WHO-TEQ/Nm3) was about 1.5 times that of Ru/TiO2 (0.0027 ng WHO-TEQ/Nm3). XPS analyses revealed that Ru/TiO2-used and Rh/TiO2-used gave the lowest and the highest Cl content of 0.61% and 1.87%. Ru/TiO2-used afforded the lowest (Clad+Clor)/Cl value (22.1%) and the highest Clbr/Cl value (77.9%), which might be an important reason for its strongest chlorine removal ability and the lowest yields of polychlorinated by-products, whereas other three catalysts showed similarity in the Cl distributions. Additionally, systematic in-situ FTIR studies were conducted, and a reaction mechanism for the catalytic oxidation of chlorobenzene was proposed.

Catalytic Oxidation of Chlorobenzene over Ruthenium-Ceria Bimetallic Catalysts

A series of Ru-based mono and bimetallic materials were prepared and evaluated in the catalytic oxidation of chlorobenzene. Among the different Ru-based catalysts, 1Ru/TiO2(P25) was the most active catalyst and contributed the lowest complete oxidation temperature, suggesting that commercial P25 TiO2 was the best support for Ru catalysts. After ceria oxides were introduced into the Ru catalytic system, the catalytic activity of 1Ru-5Ce/TiO2(Rutile) dramatically improved and that of P25 supported catalysts was decreased. Comparing the chlorobenzene consumption rates for 1Ru/TiO2 and 1Ru-5Ce/TiO2 at 280 °C, it could be concluded that monometallic Ru catalytic system was appropriate for P25 support, and the Ru-Ce bimetallic catalytic system was suitable for the rutile TiO2 support. At 280 °C, for 1Ru-5Ce/TiO2(Rutile) and 1Ru-5Ce/TiO2(P25), the chlorobenzene conversion was stabilized at approximately 91% and 86%, respectively. According to the physicochemical properties of the catalysts as characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and Hydrogen temperature programmed reduction (H2-TPR), it can be concluded that (a) electrophilic Oads species play an important role in VOCs oxidation; (b) abundant RuO2 nanoparticles on the surface of 1Ru-5Ce/TiO2(Rutile) result in higher catalytic activity and stability; and (c) dispersion is not the major factor for the catalytic activity, rather the unique structure greatly facilitated the catalytic activity and stability.

Mechanism study on catalytic oxidation of chlorobenzene over MnxCe1-xO2/H-ZSM5 catalysts under dry and humid conditions

Developments on advanced catalysts for catalytic oxidation of chlorinated hydrocarbons still encounter bottlenecks in Cl deactivation, low HCl and CO2 selectivity, toxic by-products generation, etc. In this paper, a well-reported MnxCe1-xO2 catalyst was selected as active phase to access the role of H-ZSM5 in catalytic oxidation of chlorobenzene (CB) under both dry and humid conditions. The HCl and CO2 production, by-products generation and CB oxidation routes variation were evaluated by using a range of analytical techniques including XRD, BET, GC/MS, in situ DRIFT, Ion Chromatography, etc. It was noted that the presence of H-ZSM5 could induce ca. 90% CB conversion at ca. 230°C. However, only 20% CB was converted into CO2. There were nearly 25 by-products being detected in the off-gas. In situ DRIFT analyses revealed that under dry condition, the H-ZSM5 could promote Cl dissociation from the aromatic ring of CB, which transferred the CB into cyclohexanone or benzoquinone species, hence facilitating CB ring-opening process. Under humid condition, the presence of H2O could not only protect the active sites of Mn0.8Ce0.2O2 from accumulated chlorine poisoning but also act as H and OH radical source to deeply oxidize CB, promoting the HCl and CO2 production over the MnxCe1-xO2/H-ZSM5 catalyst.

Kinetics and mechanism study on catalytic oxidation of chlorobenzene over V2O5/TiO2 catalysts

In this article, we present a detailed study combining the kinetic studies and in-situ FTIR experiments to investigate the oxidation behavior of chlorobenzene over V2O5/TiO2 catalysts. The catalytic data show the 3–5wt.% V2O5/TiO2 catalysts are best fit for the oxidation of chlorobenzene. The calculated apparent reaction orders are about 0.6 and 0.2, respectively. The results of in-situ FTIR provided mechanism insights into the catalytic reaction, which supports the following proposal: (i) a nucleophilic substitution on VO species and (ii) attacking by surface oxygen through a electrophilic substitution, then (iii) followed by the cracking of ring structure, and further oxidation of the resulting species to form final products. The above results further suggest that the nucleophilic substitution process and surface reaction are kinetically significant steps for chlorobenzene oxidation, determining the overall rate of the reaction. Furthermore, 1,2-dichlorobenzene, 1,3-dichlorobenzene and 1,2,4-trichlorobenzene as additional reactants were tested together with chlorobenzene in binary mixtures to examine their competition reactions.

Catalytic oxidation of chlorinated hydrocarbons in two-component mixtures with selected VOCs

The catalytic oxidation of chlorobenzene (ChB) and 1,2-dichloroethane (DCE) oxidized alone and in two-component mixtures with selected non-chlorinated volatile organic compounds (VOCs) such as toluene, n-hexane, acetone ethanol, ethyl acetate, was investigated. The tests were carried out over Pt-based catalyst on a monolithic metallic support. Only both hydrocarbons and ethanol enhanced ChB oxidation. DCE conversion was inhibited in the presence of each non-chlorinated admixture. Both chlorinated compounds lowered the catalytic reactivity of non-chlorinated VOCs and increased the concentration of incomplete oxidation products, first of all acetaldehyde.

Catalytic oxidation of chlorobenzene on supported manganese oxide catalysts

Total oxidation of chlorinated aromatics on supported manganese oxide catalysts was investigated. The catalysts have been prepared by wet impregnation method and characterized by XRD and TPR. Among the catalysts with the supports of TiO2, Al2O3 and SiO2, titania-supported catalyst (MnOx/TiO2) gives the highest catalytic activity. MnOx/TiO2 (Mn loading, 1.9wt.%) shows the total oxidation of chlorobenzene at about 400°C. The activity can be stable for over 82h except for the first few hours. At lower Mn loadings for MnOx/TiO2, only one reduction peak appears at about 400°C due to the highly dispersed manganese oxide. With the increase of Mn loading, another reduction peak emerges at about 500°C, which is close to the reduction peak of bulk Mn2O3 at 520°C. TPR of the used catalyst is totally different from that of the fresh one indicating that the chemical state of the active species is changed during the chlorobenzene oxidation. The characterization studies of MnOx/TiO2 showed that the highly dispersed MnOx is the precursor of the active phase, which can be converted into the active phase, mainly oxychlorinated manganese (MnOyClz), under working conditions of chlorobenzene oxidation.