Catalytic Combustion Of Chlorobenzene Research Articles

Effect of transition metal (M=Cr, Mn, Fe, Co) doping on catalytic combustion of chlorobenzene over Ce − Y composite oxide

Transition metal (Cr, Mn, Fe, Co)-doped CeYOx catalysts were prepared by a co-precipitation method and applied for chlorobenzene elimination. Metal doping caused significant changes in physical properties and chemical environment of CeY solid solution. Intrinsic activity of metals and their interaction with CeY significantly improved the redox performance and oxygen mobility, thus enhancing the catalytic activity and chlorine poisoning resistance. The enhanced concentration and mobility of reactive oxygen can effectively control chlorinated by-products. MnCeYOx can achieve 90 % chlorobenzene conversion at 235 °C, attributing to the promotion of the redox dynamic cycle by the enhanced mobility of active oxygen.

Formation of PCDD/Fs, PCBs and HCl during catalytic combustion of chlorobenzene over supported transition metal (Cr, V and Cu) oxide catalysts

As an efficient scheme, catalytic combustion can be used to eliminate chlorinated volatile organic compounds (CVOCs). To avoid the formation of more toxic by-products, it is essential to reveal the relationship between the chlorine-containing products and redox properties of catalyst. In the present study, the activity for chlorobenzene (CB) oxidation, HCl production, and formation of by-products polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs)were investigated over γ-Al2O3-supported transition metal (Cr, V and Cu) oxide catalysts. The results showed that the 10Cr-Al catalyst with relatively high specific surface areaand more oxygen absorbed than other catalysts exhibited higher catalytic oxidation activity for CB. The temperatures needed for 90% conversion of CB (T90) were 331, 353 and 386 °C for 10Cr-Al, 10V-Al and 10Cu-Al, respectively. The amount and type of acid sites on the surface of catalysts play an important role in the distribution of products and by-products. It was found that the increase of acid sites and the presence of Brønsted acid (B-acid) significantly improve the HCl selectivity of catalysts. More HCl was formed on the 10V-Al catalyst with B-acid sites. Meanwhile PCDD/Fs and PCBs detected in the by-products had a tight relationship with the acidity sites and redox performance of the catalyst. The yields of ∑PCDD/Fs and ∑PCBs were the largest on 10V-Al at T10, reaching 25.60, 66.93 mmol/mol CB, respectively. The obtained results provided theoretical support for the subsequent development of CVOCs catalytic oxidation catalysts and the control of toxic by-products.

Catalytic oxidation of chlorinated aromatics over Fe-based oxide catalysts modified by Mn

FexMny mixed oxide catalysts prepared by co-precipitation method are applied in catalytic combustion of chlorobenzene (CB) and 1,2-dichlorobenzene (1,2-DCB). Characterization shows that Mn species of Fe9Mn1highly disperse into α-Fe2O3 as Fe-O-Mn structure. With the increase in Mn content, a part of Mn is separated as MnO2 and α-Mn2O3. Fe-O-Mn structure greatly increases the acidity (especially for strong acid) and reducibility of α-Fe2O3. In CB and 1,2-DCB oxidations, FexMny catalysts are active, of which Fe9Mn1 catalyst presents the highest activity. At 5% – 20% O2 and 500 – 2000 ppm 1,2-DCB at space velocity of 15,000 mL g-1h−1, the apparent rates at 300 °C over Fe9Mn1 are estimated to be 0.056 – 0.112 μmol min−1 m−2, and the temperatures needed for 50% and 90% conversions are 294 – 342 °C and 346 – 375 °C, respectively. High availabilities of surface oxygen and acid sites are related to effective Cl removal in aid of active hydroxyls produced during the reaction (confirmed by in situ FT-IR tests), which are responsible for high activity of Fe9Mn1 catalyst. For the catalysts with MnO2 and Mn2O3 domains on the surface, Cl strong adsorption results in their deactivation. Moreover, Fe9Mn1 catalyst shows high stability at 350 °C on feed stream containing 1000 ppm 1,2-DCB within 600 min duration or for five runs. The selectivity for CO/CO2 approaches 98% or higher and no chlorination products are detected within FID limitation (1 ppm) under the above mentioned broad reaction conditions, which are highly desirable for industrial application.

A Facile Method to Synthesize Co3O4 Catalyst for Efficient Chlorobenzene Combustion

AbstractPreparation methods are essential for the synthesis of materials with diverse structures, which may lead to the different physicochemical properties. The activities of catalysts for volatile organic compounds (VOCs) combustion can be improved by optimizing the preparation methods. In this paper, a novel ammonium bicarbonate pyrolysis method is successfully applied to prepare Co3O4 catalyst (Co3O4‐A), which is not only facile in preparation, but also superior to the Co3O4 catalysts prepared by the hydrothermal, sol‐gel, MOFs pyrolysis and carbonate pyrolysis method in the performance of chlorobenzene catalytic oxidation with 90 % conversion and mineralization temperature at 310 and 325 °C, respectively (1000 ppm CB, Air, WHSV=60,000 mL ⋅ g−1 ⋅ h−1). Furthermore, Co3O4‐A catalyst can maintain high catalytic activity for a long time, and has high tolerance to water vapor, which indicates Co3O4‐A catalyst has a good potential application value in catalytic combustion of chlorobenzene.

Formation of Pcdd/Fs, Pcbs and Hcl During Catalytic Combustion of Chlorobenzene Over Supported Transition Metal (Cr, V and Cu) Oxide Catalysts

Formation of Pcdd/Fs, Pcbs and Hcl During Catalytic Combustion of Chlorobenzene Over Supported Transition Metal (Cr, V and Cu) Oxide Catalysts

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.

Formation of Pcdd/Fs, Pcbs And Hcl During Catalytic Combustion of Chlorobenzene Over Supported Transition Metal (Cr, V and Cu) Oxide Catalysts

Formation of Pcdd/Fs, Pcbs And Hcl During Catalytic Combustion of Chlorobenzene Over Supported Transition Metal (Cr, V and Cu) Oxide Catalysts

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.

Effect of Rare Earth Metal (RE = La, Pr, Nd, Y) Doping on Co–Ce Composite Oxide and Its Application in Catalytic Combustion of Chlorobenzene

Rare earth metal (RE = La, Pr, Nd, Y)-doped CoCeOx catalysts were prepared and evaluated for eliminating chlorobenzene (CB). Characterization results showed that the doped RE metal simultaneously a...

Catalytic Combustion of Chlorobenzene with VOx/CeO2 Catalysts： Influence of Catalyst Synthesis Method

Abstract VOx/CeO2 catalysts with various nanostructure were synthesized by the hydrothermal method and used in catalytic combustion of chlorobenzene (CB) at a low temperature. XRD, BET, TEM, Raman, XPS, and H2-TPR were employed to reveal that catalysts VOx on CeO2 support had considerable activity for CB combustion. VOx/CeO2 catalysts prepared with ammonium to adjust pH value and added P123 as a surfactant, showed the highest CB conversion ratio of 60 % at 250 °C and 100 % at 400 °C. It showed that preparation method could infect the shape evolution and surface species during the synthesis. The new phase CeVO4 formed in VOx/CeO2 catalysts improved the catalysts efficiency by increasing oxygen vacancies.

Enhancement mechanism of Sn on the catalytic performance of Cu/KIT-6 during the catalytic combustion of chlorobenzene

Sn promoted the redox capacity of Cu2+ and Sn4+, thus greatly reducing the surface chloride-deposition during the chlorobenzene catalytic combustion process.

Catalytic combustion of chlorinated aromatics over WOx/CeO2 catalysts at low temperature

WOx/CeO2 catalysts prepared by wet impregnation with (NH4)6H2W12O40 and (COOH)2 aqueous solution were used in the catalytic combustion of chlorobenzene (CB) and 1,2-dichloro- benzene (1,2-DCB). Characterization by XRD, N2 isothermal adsorption and desorption, Raman, XPS, H2-TPR, O2-TPD and NH3-TPD shows that CeO2 exists as a form of face-centered cubic fluorite structure, while WOx is identified as the forms of monoxo and dioxo monotungstate, polytungstate and nano-particle, depending on W content. W-O-Ce is formed as a result of interaction between WOx and CeO2, which increases oxygen vacancy and promotes the reducibility and acidity of WOx/CeO2 catalysts. In CB or 1,2-DCB oxidation, WOx/CeO2 catalysts with monotungstate WOx present excellent stable activity with TOF at 250 °C based on W-O-Ce in a range of 4.7–7.2 × 10−4 s-1. 90% conversion is obtained below 350 °C, at which chlorination is almost completely inhibited. The activity in feed containing 5% H2O or 5% CO2 is depending on their effects on the availability of surface oxygen. In situ FT-IR shows that the adsorbed CB species can be oxidized by surface lattice oxygen into phenolate, carboxylates and carbonate, while the formation of acetaldehyde on Brönsted acid sites is promoted by gas oxygen. Partial oxidation products are oxidized to COx by surface oxygen.

Ce-modified AlZr pillared clays supported-transition metals for catalytic combustion of chlorobenzene

In this article, we provided a one-step hydrothermal method to prepare composite AlZr pillaring agents, and synthesized AlZr-pillared clays (AlZr-PILC) via ion exchange. Compared with conventional methods, our method successfully shortened synthetic routes and greatly reduced consumption of the materials. Then, AlZr-PILC-supported manganese and cerium oxide catalysts were obtained by impregnation method. The compositions and properties of these catalysts were characterized by some technical means. The energy dispersive X-ray spectroscopy clearly shows the existence of Mn, Ce, and O, which indicates the successful loading of the active components on the surface of AlZr-PILC. Meanwhile, the results of X-ray diffraction (XRD) and N2 adsorption experiments demonstrate that the synthesized AlZr-PILC outperforms the raw clays (Na-mmt) and mononuclear Al-PILC in the catalytic combustion of chlorobenzene. XRD and high-resolution transmission electron microscopy also proves that the high activity of them is related to the high dispersion of the oxides and the exposure of more active sites. H2-temperature-programmed reduction shows that cerium can promote the redox cycles of the manganese system through the strong interactions between MnO2, CeO2 and AlZr-PILC. In particular, MnCe(9:1)/AlZr-PILC shows the best catalytic activity in the catalytic combustion of chlorobenzene.

Catalytic combustion of chlorobenzene over core–shell Mn/TiO2 catalysts

Core–shell Mn/TiO2 mixed oxide catalysts (Mn/Ti-cs) were prepared by incipient-wetness impregnation method, and tested in the catalytic combustion of chlorobenzene (CB) as a model of chlorinated aromatics. The obtained catalysts were characterized by XRD, TEM, XPS, BET, and H2-TPR. It was found that Mn/Ti-cs catalysts with different mass ratios of Mn/Ti were found to possess high activity for catalytic combustion of CB. Among these, Mn/Ti20-cs was the most active catalyst, for which the complete combustion temperature (T90) of CB was 296 °C, which was higher than the compared Mn/TiO2 nanoparticles with the same Mn/Ti mass ratio (Mn/Ti20-np). We found that the porous structure and special morphology are the main factors to increase the catalytic activity. Mn/Ti20-cs can provide more reaction and adsorption sites, surface active oxygen species than Mn/Ti20-np on the catalyst surface, which was beneficial to the diffusion and degradation of CB molecule and other intermediate products. By increasing the Mn/Ti mass ratio to 30%, T90 was raised to 400 °C. This is due to the decrease of Mn3+/Mn ratio and specific surface area. Conversion of CB over the MnTi20-cs catalyst was maintained at 90% or more for 900 min, indicating the excellent stability of this catalyst.

Novel metal loaded KIT-6 catalysts and their applications in the catalytic combustion of chlorobenzene

A series of metal-loaded mesoporous silica catalysts, M/KIT-6 (M = Mn, Cu, Fe, Cr, Sn), were prepared by incipient-wetness impregnation method, and tested in the catalytic combustion of chlorobenzene (CB) as a model of chlorinated aromatics. The effects of metal oxide species and concentration on the textural structure and catalytic properties were studied in detail. It was found that the dispersion, specific surface area and reducibility are the main factors influencing the catalytic activity. On the basis of T50 (temperature at which 50% conversion is attained), the catalytic activity for the CB degradation decreases in the following order: Mn/KIT-6>Cr/KIT-6>Cu/KIT-6>Fe/KIT-6>Sn/KIT-6, correlating with the redox properties of the catalysts. Mn/KIT-6 catalysts having different molar ratios of Mn/Si were found to possess high catalytic activity for catalytic combustion of CB. Among these, Mn3/KIT-6 was the most active catalyst, for which the complete combustion temperature (T90) of chlorobenzene was 210.7°C. By increasing the Mn/Si molar ratio to 1/2, T90 was raised to 238.5°C. This is due to the decrease of pore volume and specific surface area caused by increase in the amount of Mn in the channels of KIT-6, increased agglomeration of Mn, and the lowering of Oads/(Olatt+Oads+Owat) concentration ratio. Conversion of CB over the Mn3/KIT-6 catalyst was maintained at 90% or more for 1000min, indicating the excellent stability of this catalyst.

Catalytic combustion of chlorobenzene over VOx/CeO2 catalysts

VOx/CeO2 catalysts with various loadings of VOx were prepared by wet impregnation method and used in catalytic combustion of chlorobenzene (CB). Characterized by XRD, Raman, XPS, HRTEM, H2-TPR, and O2-TPD revealed that VOx on CeO2 support was identified as monomeric, oligomeric, or polymeric VOx and CeVO4. Monomeric VOx promoted oxygen vacancies and hence increased in surface oxygen and oxygen mobility. VOx/CeO2 catalysts had considerable activity for CB combustion. The highest value of TOF (0.023min−1) was obtained on VOx/CeO2 catalysts with monomeric VOx. VOx greatly improved the stability of VOx/CeO2 catalysts through retarding the exchange of Cl for basic surface lattice oxygen of CeO2. High stability maintained at 285°C for at least 1000min. In situ FTIR and Raman indicated that CB adsorption on CeO2 was much stronger than VOx, and different reaction pathways were related to different types of oxygen species existing on the surface of VOx/CeO2 catalysts.

Catalytic combustion of chlorobenzene on modified LaMnO3 catalysts

Modified LaMnO3 catalysts with perovskite structure prepared by co-precipitation method were tested in catalytic combustion of chlorobenzene. Characterizations show that the substitutions of different elements for Mn and La species affect significantly surface active oxygen species, H2 consumption and the ratio of surface oxygen to lattice oxygen of LaMnO3 catalysts. TOFSA of LaMnO3 catalysts is almost proportional to oxygen mobility. LSMO catalyst (substituted by Sr for La) with the largest oxygen mobility presents the highest stable activity which is ascribed to quickly remove the Cl species adsorbed on the surface of catalysts.

Removal of Cl adsorbed on Mn–Ce–La solid solution catalysts during CVOC combustion

Mn–Ce–La oxide-mixed catalysts prepared by the method of complexation followed by calcination at 750°C were tested in the catalytic combustion of chlorobenzene (CB) taken as a model of chlorinated aromatics. XRD analyses show that Mn and La enter CeO2 matrix with a fluorite-like structure to form solid solution. The catalysts with high ratio of Mn/Mn+Ce+La exhibit high activity for CB combustion, due to high oxygen mobility. For all Mn–Ce–La catalysts, deactivation due to Cl adsorption is observed at different temperatures, depending on composition. At 330°C or higher temperature, the removal of Cl species from the surface in the forms of Cl2 (produced through Deacon reaction) and HCl (produced through hydrolysis of Cl) occurs and the activity of catalysts for CB combustion becomes thus stable. Either the addition of water or the increase in gaseous oxygen concentration can promote the removal of Cl species, and thus to increase the activity for CB combustion. High stable activity of Mn–Ce–La catalysts can be related to the combination of good oxidation and Deacon reaction performances.

The effect of TiO2 doping on catalytic performances of Ru/CeO2 catalysts during catalytic combustion of chlorobenzene

The lower temperature catalytic combustion of chlorinated hydrocarbons (CHCs), including chlorobenzene (CB), 1,2-dichloroethane (DCE) and trichloroethylene (TCE), over RuO2 supported on Ti-doped CeO2 catalysts (Ru/Ti–CeO2) was investigated, and the effects of preparation methods, Ti content, Ru content, inlet CB concentration and space velocity, oxygen concentration and water were studied detailedly. Moreover, the doping of other different metals (Mn, Co, Sn and Mg) and the supporting of different precious metals (Pt, Pd, Rh, Au and Ag) also were briefly explored. The results show that the doping of Ti can improve obviously the catalytic activity and stability of CeO2 based catalysts. The better catalytic activity of Ru/Ti–CeO2 is ascribed to the expose of more oxygen vacancies and high energy lattice plane CeO2 (110) and (100), and the Cl dissociatively adsorbed at active sites of CeO2 can be oxidized into Cl2 catalyzed by RuO2 supported Ti–CeO2 at lower temperature (such as 200̊C) which be responsible to the excellent stability of Ru/Ti–CeO2 catalysts.

Catalytic combustion of chlorobenzene on the Ln modified Co/HMS

Lanthanide (Ln, including La, Ce and Nd) modified Co/HMS was prepared via two pathways: extra-framework modified post-loading and framework modified direct synthesis. The influence of modified methods, rare earths kind and rare earths loading on the catalytic performance of Co/HMS was studied by the catalytic combustion of chlorobenzene (CB). It was found that the extra-framework Ce modified catalysts show the better catalytic performance than the framework Ln modified ones due to that the forming of CeO2 is advantaged to obtain the fine Co3O4 crystal clusters and the reduction of Ce4+ ions to Ce3+ species probably will promote neighboring reduction of Co species. The suitable extra-framework Ce loading (6%, mass fraction) can effectively ameliorate the redox ability of Co species in the channel of HMS. Since the channel of HMS itself and Co(NO3)3·6H2O aqueous solution both are hydrophilic, the polarity adjusting function of framework Ln to the internal reaction between Co species and support is not great in this case. However, the slightly improved redox ability and weak acidity originated from framework Ln still can do some contribution to the catalytic performance. The electronic structure of Co and Ce is advantageous to the delocalization of π-electrons and the forming of radical species.