Preparation Of Modified MMT And Its Catalytic Activity For Esterification Of Long Chain Acid

The purpose of this paper is developing a notive solid acid catalyst suitable for fatty acid esterification. Specifically, the preparation, characterization and its catalystic activities of acidic MMT are studied in the paper.A series of acidic catalysts were prepared by a variety of inorganic acids, and then the conditions of preparing acidic catalysts were investigated systematically. The optimum preparation conditions of catalysts were attained as follow: concentration of nitric acid was 2mol/L, acidification temperature was 50℃, acidification time was 24 h and the ratio of liquid to solid was 12 m L/g. The structure and performance of catalysts were characterized by Fourier transform infrared spectroscopy(FTIR), Nitrogen physisorption-desorption(BET), X-ray diffraction(XRD), Scanning electron microscope(SEM), Thermogravimetric analyzer(TGA) and Ultraviolet-visible absorption spectrometry(UV). The IR spectra of pyridine adsorbed showed that the montmorillonite had both Br?nsted acid sites and Lewis acid sites. The results of XRD indicated that acid activation did not affect the layer structure and the interlayer space of the catalyst expanded. The results of BET indicated that the surface area was larger and the pore size was more uniform. The analysis of SEM showed that acid activation leaded the catalysts to delaminate and the re-accumulation of these fragments formed larger pore channels. The TGA and UV revealed that the thermodynamic stability and acid amount of catalysts were significantly improved.The acidic catalyst H-MMT was prepared at the optimum prepared conditions and used to produce pentaerythritol tetraisostearate. The effects of catalyst dosage, reaction time, acid / methanol molar ratio and reaction temperature were also investigated. The esterification rate was over 94% under the conditions of catalyst dosage 2.5%(based on the isooctadecanoic acid mass), reaction time 6h, acid / methanol molar ratio 5.6:1 and reaction temperature 190 ℃. The thermal stability, physical and chemical properties of the product were investigated. The results showed that pentaerythritol tetraisostearate had high thermal stability and good viscosity temperature performance. The Acid Value of purified product was 1.9 mg KOH/g, Saponification Value was 187.43 mg KOH/g, Refractive Index was 1.468(25℃) and Pour Point was-21℃.Also, the acidic catalyst H-MMT was used to produce palmityl palmitate through esterification of palmitic acid with cetyl alcohol. The effects of reaction time, catalyst dosage, methanol / acid molar ratio and reaction temperature were also investigated. The esterification rate was over 95% under the conditions of reaction time 3.5h, catalyst dosage 5%(based on the palmitic acid mass), methanol / acid molar ratio 1.3:1 and reaction temperature 180℃.In addition, the reusability of the catalyst was discussed. The results showed that the catalytic activity of the catalyst decreased when it was used five times. The catalytic activity could be improved significantly after regenerated. The regenerated catalyst’s activity could reached 94%.