FT-IR Study On The OH Vibration Of Different Zeolite Catalysts

The framework and hydroxyl vibration of different zeolites were summarized by FT-IR in this paper. At the same time, not only the thickness, position and the synthetic batch of TS-1 sample, but also the difference of hydroxyl groups of TS-1 under different synthesis conditions, such as the crystallization time, the molal ratio of silicon to titanium, the content of ammonium carbonate, the solvent of acetyl acetone and nitrogen protection were investigated. Furthermore, the effect of steaming and calcination on the framework structure and hydroxyl groups of low-cost TS-1 catalysts was investigated. The obtained results demonstrated as follows:1. The framework vibration,hydroxyl vibration and acidity of hydroxyl of different forms of zeolites have obvious differences.2. The thickness of TS-1 sample is quite appropriate to obtain preferable spectrogram in OH vibration region when the weight of TS-1 is 10.0 mg. The unique spectrogram could be acquired even if in different part of sample with same thickness and synthesis conditions.3. The low-cost TS-1 catalysts have complicated hydroxyl groups which include isolated hydroxyl groups, geminal hydroxyl groups, terminal hydroxyl groups and hydrogen-bonded hydroxyl groups. After 36 h crystallization, the framework of low-cost TS-1 are formed completely, the framework structure and hydroxyl groups are no longer change as the crystallization time extension.4. Terminal hydroxyl groups decrease while hydrogen-bonded hydroxyl groups increase with the molar ratio of silicon to titanium increasing from 40 to 180 for low-cost TS-1. When the molar ratio of silicon to titanium increasing from 180 to 270, hydroxyl groups don't change obviously. However, with the increase of aluminum and sodium content, geminal hydroxyl groups increase and the peak which is attributed to hydrogen-bonded hydroxyl groups shift to the lower wave number.5. With the increase of ammonium carbonate content, the peak which is attributed to isolated hydroxyl groups become weaker and the peak which is attributed to hydrogen-bonded hydroxyl groups shift to the lower wave number for classical TS-1. While the geminal hydroxyl groups and terminal hydroxyl groups increase and hydrogen-bonded hydroxyl groups decrease for low-cost TS-1. After the molar ratio of ammonium carbonate to silicon come up to 1.0, with the increase of (NH4)2CO3/Si, the hydroxyl groups of low-cost TS-1 get lessen. 6. Hydrogen-bonded hydroxyl groups increase with the acetyl acetone increase and nitrogen protection while low-cost TS-1 was synthesized. Isolated hydroxyl groups also increase with the acetyl acetone increase.7. The hydroxyl groups of low-cost TS-1 catalysts could be changed by high temperature steam passivation and calcinations.