Characterization Of Titanium Silicalite-1 Modified By Organic Bases And Its Performance In Ammoxidation Of Methyl Ethyl Ketone

The nano-scale TS-1 was synthesized by using self-made tetrapropylammonium hydroxide (TPAOH) solution as the template, tetraethyl orthosilicate (TEOS) as Si source and tetrabutyl orthotitanate as the Ti source in 2L autoclave. The as-synthesized TS-1 was modified by inorganic bases and organic bases. The modification conditions were investigated, including modification time, modification temperature, the concentration of TPAOH. The activity of all the TS-1 samples was evaluated by using the ammoxidation of methyl ethyl ketone (MEK) as a test reaction. The results show that the modification temperature has great influence on the catalytic properties in ammoxidation of MEK and 443K was optimal modification temperature. The modification time 6 h was sufficient to keep the catalyst repeated usage unchanged at 0.23mol/L of TPAOH. The concentration of TPAOH can be reduced to 0.0092mol/L with modification time 3 days, and MEK conversion can keep 99.0% after three times repeated use. The repeated usage of TS-1 modified by NaOH, Na₂CO₃, NH3H2O can not be improved effectively. The nano-scale TS-1 was modified by other organic bases such as TMAOH, TEAOH, TBAOH can keeps excellent activity.The ammoxidation of MEK to methyl ethyl ketoxime(MEKO) over TS-1 modified by TPAOH was studied. The effects of the solvent, mass ratio of catalyst to MEK, reaction temperature, molar ratio of H2O2 or NH3 to MEK were investigated. The results show that the optimal reaction conditions of ammoxidation of MEK over modified nano-scale TS-1 are as follows: water as the solvent, reaction temperature 343K, 9.0g/mol(MEK), NH3:H2O2:MEK= 4:1.5:1 (molar ratio). Under above reaction conditions, both conversion of MEK and the selectivity to MEKO can reach 99.0%. The nano-scale TS-1 was more suitable for ammoxidation of MEK than Ti-HMS, Ti-SBA-15, Ti-APO.The experiment was performed to prepare for TS-1 industrial synthesis. Effect of different preparation of TPAOH on synthesis of TS-1 were investigated. The ICP analysis of K+ in purchased TPAOH was much more excessive than self-made template, which may inhibit titanium into the framework in the zeolite synthesis. The NH4NO3 exchange can not improve the activity of catalyst. But the activity of nano-scale TS-1 can reach 99.0% in ammoxidation of MEK after the catalyst was modified by TPAOH. TPAOH made by electrolysis has great influence on synthesis TS-1. The activity of Micro TS-1 can not be improved effectively by crystal seed modified by TPAOH.