Synthesis of cordierite - MnOx - Block carriers co oxidation catalysts

Title : Synthesis of cordierite - MnOx - Block carriers co oxidation catalysts

Abstract:

Block carriers are widely used for the preparation of automotive catalysts. All known block catalysts contain platinum group metals. However, these catalysts are expensive and mechanically insufficiently strong due to the difficulty of achieving the necessary adhesion of the secondary carrier to the frame material. As the main active components and the secondary coating of the aluminosilicate block-cordierite Mn-Pd catalyst for CO oxidation, instead of heat-resistant oxides (CaO, MgO. Al₂O₃), stable manganese oxides are considered: MnO₂, Mn₂O₃, Mn₃O₄, MnO. The results of studying the synthesis conditions and determining the basic physicochemical properties of block cordierite - carriers with Mn - coating for the preparation of CO oxidation catalysts are presented. SEM pictures of the components of the cordierite on the cordierite - MnOx 400^oC and cordierite – MnOx 800^oC carriers at 1μm of the showed of the oxides of Mn are distributed uniformly on the surface. Heat treatment at 800^oC results in coarsening of manganese oxide particles from 10–100 nm to 500–600nm. Additional high-temperature heat treatment at 800^oC leads to the completion of the process of formation of the crystalline structure of the secondary Mn - block carrier coating. The introduction of Mn atoms in the framework structure of the carrier provides the required adhesion of the secondary Mn coating on the surface of the block catalyst. The successive application of a secondary coating of MnOx oxides increases the specific surface area of the cordierite block to 5.0 - 6.0 m². g^-1. The content of MnOx, in terms of Mn - metallic, reaches 5.5 - 6.0 wt. %. Activity of the Pd - MnOx - catalyst, was studied in the CO oxidation reaction. A positive effect on the activity of the Pd - MnOx / Cordierite catalyst was shown to be treated with aqueous ammonia. Exoeffects on the DTA thermal analysis wing with maxima at temperatures of 255^oC and 305^oC were attributed to the phase dissociation of the formed amine-palladium complex. X-Ray phase and thermal analyses of the catalyst showed the presence of PdO and PdO2 (traces). The endoeffect on the ??? curve at the temperatures 780oC ? 826^oC wich in indicative of the phase decomposition of PdO. On catalysts Pd - MnOx 400^oC / cordierite and Pd - MnOx 800^oC/cordierite, the maximum conversion of CO - 80-100% is achieved in the temperature range 170 - 190^oC. Modifications β - MnO₂ and a - Mn₂O₃ in Mn-Pd catalysts can be considered as active intermediate phases at the carrier-Pd interface.

Audience Take Away:
The formation of a secondary Mn-coating at the interface Cordierite - Pd improves the physico-chemical characteristics and positively affects the activity of Mn - Pd CO oxidation catalysts.

Biography:

Dr. Vitaly Bakhtadze graduated from the Georgian Polytechnic Institute with a degree in the technology of inorganic substances. 1964 - 1974 a post-graduate student and then a researcher at the catalysis laboratory of the Institute of Inorganic Chemistry and Electrochemistry of the Georgian Academy of Sciences. From 1974 to the present day, head of the catalysis laboratory. He published over 50 scientific articles.)