Structural and superacidity study of bifunctional catalyst, sulfated-titanium/TS-1

Abstract

Abstract : Bifunctional oxidative and acidic catalysts are prepared in this study. The sulfated titanium silicalite is prepared by first, synthesizing the titanium silicalite (TS-1) having oxidative properties, followed by the deposition of titanium on the surface of TS-1, and finally, treatment of the solid with sulfuric acid. The structure of the solid samples are characterized by XRD, FTIR, and UV-Vis DR spectroscopy techniques, while the strength and the type of acid site are monitored by Hammet indicator and pyridine adsorption method, respectively. The results show that the MFI structure of TS-1 is maintained even after the treatment with sulfuric acid. However, a part of the tetrahedral titanium framework of the TS-1 has been expelled from the framework and becomes nonframework octahedral titanium after contacting with sulfuric acid. The acidity study by Hammet indicator indicates that sample possesses superacidic property, measured by Hammet indicator 2,4- dinitrobenzene (pKa = -14.52), in which the acid type is Lewis, from the pyridine adsorption. Abstrak : Mangkin dwifungsi pengoksidaan dan asid telah disediakan. Titanium silicalite bersulfat disediakan dengan mensintesis titanium silicalite (TS-1) dahulu yang mempunyai tapak pengoksidan, diikuti oleh penambahan titanium di atas permukaan TS-1, dan akhir sekali, pepejal dirawat dengan asid sulfuric. Struktur pepejal dicirikan dengan menggunakan kaedah XRD, FTIR, dan UV-Vis DR spektroskopi, sementara kekuatan dan jenis tapak asid dicirikan dengan kaedah penunjuk Hammet dan penjerapan piridina. Hasil pencirian menunjukkan bahawa struktur MFI daripada TS-1 masih utuh selepas sampel dirawat dengan asid sulfuric. Bagaimanapun, sebahagian titanium bingkaian dalam struktur tetrahedron daripada TS-1 telah terkeluar dan berubah menjadi oktahedron titanium luar bingkaian setelah tindak balas dengan asid sulfuric. Kajian keasidan dengan penunjuk Hammet menunjukkan bahawa sampel mempunyai sifat superasid, mengikut penunjuk Hammet 2,4-dinitrobenzena (pKa = -14.52). Penjerapan piridina menunjukkan bahawa sampel mempunyai tapak asid daripada jenis asid Lewis.