INCAPE   05401
INSTITUTO DE INVESTIGACIONES EN CATALISIS Y PETROQUIMICA "ING. JOSE MIGUEL PARERA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
m-Cresol methylation: control of product distribution by shape selectivity
Autor/es:
NORA OKULIK; MARDELLY KATERYNE MONTAÑEZ VALENCIA; CRISTINA L. PADRÓ; MAURO ACEVEDO; MARIA EUGENIA SAD
Lugar:
Rio de Janeiro
Reunión:
Conferencia; 18th International Zeolite Conference; 2016
Institución organizadora:
SBCat (Sociedad Brasileira de Catalise) y International Zeolite Association
Resumen:
Valuable products can be obtained by m-cresol methylation. Dimethyl-phenols (DMP) and 3 methyl-anisole (3-MA), may be produced by C-alkylation and O-alkylation, respectively. In addition, trimethylphenols (TMP) and dimethylanisoles (DMA) could be formed by successive alkylation. Among the dimethylphenols, 2, 3-DMP is used in pesticides production, 3,4-DMP is raw material in the insecticide 3,4-dimethylphenyl methylcarbamate synthesis and 2,5 DMP is starting material in the manufacture of pharmaceuticals such as gemfibrozil (an oral drug used to lower lipid levels) and is also intermediate in synthesis of colorants, antiseptics and antioxidants. Furthermore, one of the trimethylphenols, 2,3,6-TMP, is employed in -tocopherol (vitamine E) synthesis, used as medicine and also as an antioxidant in stabilization of food, cosmetic and plastics. The catalytic activity and selectivity of acid catalysts in this reaction strongly depend on the nature and strength of the catalytic surface sites . HBEA, which contains acid sites of Brønsted and Lewis nature of considerable strength, is highly active but unselective forming 3-MA and DMP, as well as trimethylated phenols: TMP and DMA corresponding to C/O alkylation ratio of 1.9. On Al-MCM-41 (mostly acid Lewis sites of moderate strength) the main product of reaction was 3-MA (S3-MA=56%) giving a C/O- alkylation ratio of 0.72. However, the selectivity can be tuned by modifying the nature and principally the strength of the acid sites. In fact, ZnY (strong Lewis acidity) promote selectively the C-methylation (C/O alkylation ratio: 8.8). On another hand, the product distribution can also be modified by shape selectivity. In a previous paper , changes in product distribution in the methylation of phenol by shape selectivity have been reported on HMCM22 and HZSM5. Zeolite MCM-22 contains independent pore systems: large supercages (18.2 × 7.1 × 7.1 Å) connected by 10-MR openings (4.0×5.5 Å), bidimensional sinusoidal channels (4.1 × 5.1 Å), and large external cups, corresponding to hemisupercages (7.0 ×7.1 × 7.1 Å). HZSM5 zeolite has a three-dimensional channel system with elliptical aperture (5.1 x 5.5 Å) interconnected by zigzag channels with approximately circular cross section of 5.3 x 5.6 Å with no cages. In this work, we have studied the effect of porous structure and the role of internal and external acid sites on the product distribution of m-cresol methylation. In this aspect, we have tested in the reaction zeolites before and after poisoning with 2,4-dimethylquinoline (2,4-DMQ), which is a molecule too bulky to diffuse through the narrow porous of HZSM5 and HMCM22 zeolite