Effect of sodium ions in synthesis of titanium silicalite-1 on its catalytic performance for cyclohexanone ammoximation

Titanium silicalite-1（TS-1） has been hydrothermally synthesized with tetrapropylammonium hydroxide（TPAOH） as the template in the presence of various amounts of Na+,characterized by inductively coupled plasma,X-ray diffraction,scanning electron microscope,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy and ultro-violet-visible spectroscopy and studied in cyclohexanone ammoximation.The characterization results show that with the increase of Na+concentration in the synthesis,both the crystal sizes of TS-1 and extra framework Ti increase but framework Ti decreases.The addition of Na+ below 3 mol-%of TPAOH in the synthesis does not influence the catalytic properties with above 98%conversion of cyclohexanone and 99.5%selectivity to cyclohexanone oxime.However,at the concentrations of Na+≥3 mol-%of TPAOH in the synthesis,the catalysts are deactivated faster with the increase of Na+ addition,which can be attributed to more high molecular weight byproducts deposited in the large TS-1 particles and the loss of the frame-work titanium.The results of this work are of great importance for the industry.