Effect Of Lanthanide Elements On Catalytic Performance Of MoO₃-Bi₂O₃ Catalysts

The catalytic system of MoO3-Bi2O3 were used widely, mainly in olefinic oxidation, e.g. propylene oxidation, isobutene oxidation etc. . The catalytic behaviour of multiphasic catalyst based on MoOs-IOa by adding lanthanide elements was studied in the selective oxidation of isobutene to methacrolein(MAL).Some former researches indicated that pure MoO3 was lowly active and Bi2O3 was totally inactive. But considering the mixture of MoOs and Bi2O3, very strikingly catalytic performance has been observed.The influence , which lanthanide oxides (La2(V CeO Pr6Oi Nd2O3. Sm2(V Eu203, Gd2O3, Tb407 Dy2O3, Ho2O3 Er203, Tm2O3, Yb2O3) exerted on the catalytic performance of Mo-Bi-O catalysts for the selective oxidation of isobutene to methacrolein, was studied. The reaction temperature, concentration of isobutene in the reactant gases, LnOx proportion in the Mo-Bi-O catalysts, lanthanide varieties play very important roles in the reaction. The most optimal conditions were found, which are very helpful to design the catalysts in the future.Catalysts were prepared by two different means: mechanical mixture and copreciphation. The effects of preparation means were examined. A detailed physicochemical characterization was carried out on catalytic structure before and after the test. The joint use of these techniques indicated that no new phase formed during the preparation by mechanically mixing the corresponding powders. The mechanism for selective oxidation of isobutene with the Mo-Bi-O catalysts comprising lanthanide elements, was explained within the framework of the remote control mechanism, i.e., that LnOx produce a mobile oxygen species, namely spillover oxygen, which, byflowing onto the surface of Mo-Bi-O catalysts, create on the surface of the latter new selective sites and/or regenerate those which have become deactivated. There were molybdates after the activated of catalysts in a high temperature.The experiments showed that the selectivity of isobutene oxidation to methacrolein was improved by adding lanthanide elements. A strong synergy existed between the different components of Mo-Bi-O catalysts.The development of catalysts used in the preparation of methyl metnacrylate by oxidation of isobutene was induced simply. Catalysts used in industrial processes were manufactured. Catalytic performances were carried out in laboratory. The results are satisfying. All these work will lay the foundation for the use of lanthanide elements in industrial catalysts.