Synthesis And Modification Of Titanium Silicalite-1 And Its Performance In Ammoxidation Of Methyl Ethyl Ketone

Titanium silicalite-1 (TS-1) exhibits excellent catalytic and oxidative performance with dilute H₂O₂ as the oxidant in the mild reaction conditions because of the incorporation of titanium into the framework of zeolites. Synthesis, characterization of TS-1 and its industrial application have become the highlight in the zeolite catalysis field since synthesis of TS-1 in 1980.The nano-TS-1 was synthesized by using self-made tetrapropylammonium hydroxide (TPAOH) solution as the template, tetraethyl orthosilicate (TEOS) as Si source and tetrabutyl orthotitanate (TBOT) as Ti source in 100 ml and 2L autoclave, respectively. XRD, FT-IR, UV-Vis, TEM and phenol hydroxylation reaction have been used to study nano-TS-1 samples. The results show that the crystal size of TS-1 is 80¹00nm, the catalytic activities in phenol hydroxylation are high, the conversion of phenol is above 27%, the utility of H₂O₂ is above 86%.The ammoxidation of methyl ethyl ketone (MEK) to methyl ethyl ketone oxime (MEKO) over TS-1 was studied. The effects of the addition modes of hydrogen peroxide and ammonia, solvent, mass ratio of catalyst to MEK, reaction temperature, molar ratio of H₂O₂ or NH₃ to MEK and crystal size of catalyst were investigated. The results show that the optimal reaction conditions of ammoxidation of MEK over nano-TS-1 are as follows: hydrogen peroxide and ammonia were added slowly and continuously in one hour, t-butanol or mixed liquid of t-butanol and water as the solvent, reaction tempetature 75℃, 21.6gTS-l/mol(methyl ethyl ketone), NH₃:H₂O₂:MEK= 4:1.5:l(mol ratio). Under the most suitable reaction conditions, 99.4% conversion of MEK and 99.8% selectivity to MEKO could be obtained. Ammoxidation of MEK was considered to follow hydroxylamine mechanism.In ammoxidation of MEK that the regeneration properties of catalyst has been studied, the results show the cataliytic activity of TS-1 regenarated by calcination can be remained after several times reaction. While, if the used catalyst was not calcined at high temperature, and directly used in the next reaction, the conversion of MEK decreased drastically. The TS-1 was modified with TPAOH and other methods and was characterized by using XRD, FT-IR, UV-Vis, TEM, XRF and N₂ physical absorption. The results show that the modification does not affect the framework and bulk Ti content in the TS-1, while the amount of framework Tiwas decreased and the amount of non-framework Ti was increased, lots of micropore (diameter about 1.1nm), cavum and pit (diameter 2⁹0nm) were formed in the TS-1 particle. The TS-1 sample modified by TPAOH exhibits excellent activity on phenol hydroxylation, the conversion of phenol is above 31.6%, the utility of H₂O₂ is above 97.5%.