Synthesis of N-methylaniline by Aniline Alkylation with Methanol over Sn-MFI Molecular Sieve

Abstract

Sn-MFI molecular sieves (Tin silicalite-1) with SiO 2 /SnO 2 molar ratio of 50-150 were synthesized and characterized. Elemental analysis, XRD and DRUV-vis confirmed that prepared samples were of MFI zeolite structure and Sn was incorporated in MFI framework. Vapor phase methylation of aniline over Sn-MFI was systematically studied and optimizations of process parameters were carried out. Sn-MFI (SiO 2 /SnO 2 = 50) was found to be optimum catalyst with 55% aniline conversion and 60% N-methylaniline selectivity. At lower space velocity (higher contact time) of 1 h -1 , aniline conversion was found to be increased to 71% with reduction in N-methylaniline selectivity to 39% and increased in N,N-dimethylaniline selectivity to 58%. The reaction follows first order kinetics with respect to aniline having activation energy of 7.3 kcal/mol.

Characterization of surface acid sites in tin-silicalite-1 (Sn-MFI) molecular sieve by X-ray photoelectron spectroscopy

“…All samples exhibited similar TPAD profile which on deconvolution, resulted into three desorption peaks with maxima at 108 ± 04°C, 177 ± 15°C and 272 ± 15°C. These peaks can be assigned to desorption of physisorbed NH 3 , weak Lewis acid sites and strong Lewis acid sites, respectively [29,38]. The TPAD data for samples A, B and C are shown in Fig.…”

“…The acidity of the catalysts was also evaluated by TPAD using the procedure similar to described elsewhere [29].…”

“…Tin containing molecular sieves have shown potential applications as sorbent [22] and catalyst [22][23][24][25][26][27][28][29] for various reactions of commercial importance. Uniform micropore size distribution, high thermal and hydrothermal stability, flexible framework to tune the surface properties and high internal surface area of tin-silicalite-1 (Sn-MFI) make it attractive for potential applications.…”

“…Uniform micropore size distribution, high thermal and hydrothermal stability, flexible framework to tune the surface properties and high internal surface area of tin-silicalite-1 (Sn-MFI) make it attractive for potential applications. However, there is scanty information on its surface acidity [29,30]. The benefits of Sn-MFI molecular sieve and lack of adequate knowledge/method to measure the nature, type and strength of its acid sites have triggered our interest to employ XPS technique in combination with IR spectroscopy and TPAD to deduce the information on the surface acidity of Sn-MFI.…”

Thermal expansion properties of stannosilicate molecular sieve with MFI type structure

“…The isomorphous substitution of Si 4+ ions by other tetrahedrally coordinated elements in MFI structure [3][4][5][6][7][8] have opened a new class of compounds of academic and industrial importance. By virtue of higher electronegativity, atomic size and strong acidity, the incorporation of Sn (IV) in the tetrahedral silica frameworks possessing zeolitic structures led to yield promising sorbent [9] and catalysts [9][10][11][12][13][14][15][16] for various reactions of academic and commercial importance. Uniform micropore size distribution, high thermal and hydrothermal stability, flexible framework to tune the surface properties and high internal surface area of Sn (IV) incorporated silica MFI-type frameworks (SnSi-MFI) make it attractive for potential applications.…”