Study on Catalytic Performance of Heteropoly Acid Supported on MCM-41 Molecular Sieve in Synthesized of Butyl lactate

Abstract

The supported heteropoly acid catalysts were prepared by loading Phosphotungstic acid on the MCM-41 molecular sieve via the impregnation method, which were characterized by FT-IR, N2 adsorption-desorption and applied in the synthesis of butyl lactate. The results show that heteropoly acids supported on porous molecular sieve, which can improve the catalytic performance of heteropoly acids, improve its catalytic activity and is good method to solve hard problem of recycling use. Introduction Heteropoly acid is a solid acid [1], which is applied as acid catalyst, redox catalyst and bifunctional catalyst in the chemical synthesis [2], shows high catalytic activity and selectivity, and has great advantages such as high reactivity, non-corrosion to equipments and no pollution. Consequently, it becomes the hot topic of research in catalysis. However, the application of heteropoly acid in the catalytic fields is limited because of its small specific surface area, poor stability, easily dispersing in polar solvents, difficulty of recycling and other reasons. In this report, the supported heteropoly acid catalysts were prepared by loading Phosphotungstic acid on the MCM-41 molecular sieve via the impregnation method, which were applied in the synthesis of butyl lactate. The experiment results show that MCM-41 molecular sieve was an excellent carrier for heteropoly acid, and the supported heteropoly acid catalysts possessed high catalytic activity in synthesis of butyl lactate. Experiments The preparation of MCM-41 molecular sieve [3]. Typically, 1.10g cetyltrimethylammonium bromide (CTAB) was dissolved in 25mL of distilled water, followed by adding 12mL of NH4OH (25%). Then 5mL of tetraethyl orthosilicate (TEOS) was slowly added to the resulting solution and kept stirring at room temperature for 3h. Next, the mixture was enclosed in reaction kettle for crystallization for 24h at 373K. The products were filtrated, washed with distilled water repeatedly and dried. At last, it was baked at 823K in air to remove template to obtain the products. Preparation of the supported heteropoly acid catalysts in the impregnation method [4, 5]. (0.43g, 0.67g, 1.0g) Phosphotungstic acid (HPW) was dissolved in 25mL of double-distilled water. After completely dissolving, 1g the above prepared MCM-41 molecular sieve was added into the resulting solution. And the resulting solution was stirred at 353K until the supported heteropoly acid catalysts were obtained. Based on the loading of active component, the catalysts were named as 30%HPW-MCM-41, 40%HPW-MCM-41, 50%HPW-MCM-41. Results and discussion FT-IR analysis. The FT-IR spectra images of HPW-MCM-41 samples that supported Phosphotungstic acid are shown in Fig.1. It can be seen clearly from Fig.1-a that the absorbance bond at 465 and 800 cm−1 is due to flexural vibration and symmetric stretching vibration of Si-O-Si, and International Conference on Materials, Environmental and Biological Engineering (MEBE 2015) © 2015. The authors Published by Atlantis Press 44 the band at 1080 cm−1 is attributed to the asymmetrical stretching vibrations of the Si-O-Si bond. The peaks at ca. 3450 cm−1 are related to the absorbance bond of OH, suggesting that there are massive hydroxyl groups on the surface of molecular sieve. The FT-IR images (Fig. 1-b, c) of the supported heteropoly acid catalysts indicate that the absorption peak in the region 800~1000cm-1 was extremely weak but very broad. With the increase of the loading, the characteristic absorption peak of Phosphotungstic acid emerges clearly (Fig. 1-d), which shows that Phosphotungstic acid could combine with support very well to form strong peaks. 4000 3500 300