Shape-selective N-methylation of melamine with methanol by use of Ru/mordenite catalyst in the liquid phase

• Published in: Applied catalysis. A, General General, 2000-03, Vol.194, p.375-381
• Main Authors: Shinoda, Sumio, Fujimura, Kaori, Ohnishi, Takeshi, Yamakawa, Tetsu
• Format: Article
• Language: English
• Subjects: Melamine; Methanol; Methylation; Ru/mordenite; Shape selectivity
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/S0926-860X(99)00383-X

A Ru/mordenite (Ru/M) catalyst with catalytically-active ruthenium species retained in the mordenite pores has been prepared by the ion-exchange of Na-mordenite with [Ru(NH 3) 6] 3+, followed by a very mild thermal treatment. While extended X-ray absorption fine structure (EXAFS) analysis showed the presence of both Ru–N and Ru–Ru bonds, HRTEM photographs evidenced the absence of metal particles larger than the diameter of a mordenite pore. The remaining NH 3 ligand was also observed from the characteristic IR bands appearing at 1640 and 1356 cm −1; the IR spectrum of adsorbed CO indicated the presence of multicarbonyl-type surface species (such as Ru n+ (CO) 3), consistent with the well-dispersed or coordinatively-unsaturated nature of ruthenium species. After the complete preparation procedure, a high degree of crystallinity was maintained for mordenite (XRD), and the decrease of S BET from 362 to 313 m 2 g −1 ensured the existence of ruthenium species in the mordenite pores. It was demonstrated that, by using this catalyst, N-methylation of melamine with methanol was able to proceed in a moderately shape-selective manner (suppression of the formation of N,N′ ,N″-tri-methylated melamine ( 3) as compared to that of N-methylated or N,N′-di-methylated melamine ( 1 or 2)), which is in harmony with the sizes of relevant molecules relative to the size of a mordenite pore.