Catalysts For Toluene Combustion Research Articles

Mn-Ag bimetals supported on plate-like ZSM-5 as efficient and stable catalysts for the catalytic combustion of toluene: Synergistic effects and catalytic mechanisms

Ag-modified MnO2 loaded on plate-like ZSM-5 (PZ5) with different Ag/Mn ratios were synthesized by an in-situ growth method and used as catalysts for toluene combustion, as a probe molecule of volatile organic compounds (VOCs). The results showed that Ag doping greatly enhanced the toluene combustion activity (Mn50Agy/PZ5). Among them, Mn50Ag0.04/PZ5 showed the highest catalytic activity for toluene combustion with 90 % conversion of toluene at 234 °C (T90), and the reaction rate calculated per unit mass of Mn was 1.22×10−7 at 220 °C, which was 2.7 times higher than that of MnO2. In addition, Mn50Ag0.04/PZ5 exhibited excellent long-term stability and water resistance. Various characterizations indicated that the excellent performance of Mn50Ag0.04/PZ5 was attributed to its higher Mn2++Mn3+/Mn4+ ratios, higher reducibility, and more active surface adsorbed oxygen species. Finally, in-situ DRIFTS studies confirmed that Ag doping did not alter the catalytic combustion pathway of toluene over the Mn50Ag0.04/PZ5 catalyst but could accelerate the rate of conversion of toluene to the final products because the transfer of electrons from Ag+ to lattice oxygen persuaded the weaken of the Mn-O bond, and then made it easier for bulk lattice oxygen to migrate towards the Ag-MnO2 interface or catalysts’ surface, thus showing the better catalytic performance for toluene combustion.

Mesoporous Silica MCM-41 from Fly Ash as a Support of Bimetallic Cu/Mn Catalysts for Toluene Combustion.

The main outcome of this research was to demonstrate the opportunity to obtain a stable and well-ordered structure of MCM-41 synthesized from fly ash. A series of bimetallic (Cu/Mn) catalysts supported at MCM-41 were prepared via grinding method and investigated in catalytic toluene combustion reaction to show the material's potential application. It was proved, that the Cu/Mn ratio had a crucial effect on the catalytic activity of prepared materials. The best catalytic performance was achieved with sample Cu/Mn(2.5/2.5), for which the temperature of 50% toluene conversion was found to be 300 °C. This value remains in line with the literature reports, for which comparable catalytic activity was attained for 3-fold higher metal loadings. Time-on-stream experiment proved the thermal stability of the investigated catalyst Cu/Mn(2.5/2.5). The obtained results bring a valuable background in the field of fly ash utilization, where fly ash-derived MCM-41 can be considered as efficient and stable support for dispersion of active phase for catalyst preparation.

Promoting Pd/Al2O3 catalysts for toluene combustion by DBD plasma treating in different working gas atmospheres

To investigate the effects of plasma treatment on supported precious metals for VOCs combustion, a series of 1%Pd/Al2O3 catalysts were synthesized by DBD plasma treating in different working gases (H2/Ar, O2, N2, Air) and with reversed calcination sequences. It is revealed that both the working gas and treating sequence can alter the Pd dispersion degree, valence states and the concentration of surface acid sites, which subsequently impacts the catalytic activity. Usually, a Pd/Al2O3 catalyst with a higher active Pd surface area shows higher toluene combustion activity, due to the promoted ability to adsorb and activate toluene molecules. Therefore, Pd dispersion degree is the main factor to determine the reactivity of Pd/Al2O3 catalysts. Moreover, H2/Ar plasma treating can effectively create Pd0 sites, which is favorable to toluene and O2 molecule adsorption and activition. Due to the combination of these two factors, 1%Pd/Al2O3-C-H2P displays the best activity among all the samples.

Toluene combustion over Pd-based monolithic catalysts with a novel Ce x Zr 1−X O2 washcoat

A novel CexZr1−xO2 washcoat was prepared by impregnation, which acts as a host for the active Pd component to prepare a series of Pd-based monolithic catalysts for toluene combustion. The redox behavior and catalytic activity depend on the molar ratio of Ce to Zr.

Combustion of Toluene over Titanium(IV) Oxide Catalyst

Combustion catalysts free from precious metals, such as platinum, for removal of volatile organic compounds were investigated. Common metal oxides (titanium(IV) oxide (TiO2), alumina and silica) were selected as candidates for a catalyst for combustion of toluene at low concentrations. Complete conversion of toluene was not achieved even at 500°C without catalysts, although the ignition point of toluene is 480°C. TiO2 exhibited the highest activity for combustion of toluene among representative metal oxides. Toluene was almost quantitatively converted to carbon dioxide (>99% yield) over TiO2 under the condition of appropriate contact time at 500°C.