Study On The Synthesis Of Alkyl Polyglucosides Using Tungstophosphoric Acid Catalysts Supported On Activated Carbon

The synthesis of alkyl polyglucosides(APG) using tungstophosphoric acid(TPA)catalysts supported on activated carbon were studied. This research consists of two sections, one of which is the preparation, the adsorption and desorption characteristics and the characterization of the carbon supported TPA catalysts. The other is the optimization of APG's synthesis technics and the testing of APG's performances.TPA catalysts supported on several kinds of activated carbon were prepared by impregnation technique and adsorption technique. During the adsorption progress, the main factors influencing the adsorption quantity of TPA onto activated carbon are adsorption time and the characteristic of the support. During the desorption progress, the main factors influencing the desorption quantity of TPA from activated carbon are desorption time, preparation method, TPA loading amount and the the characteristic of the support. The supported catalysts were characterized by IR, XRD and SEM. There are both L-acid points and B-acid points existing on the surface of supported catalysts. With the increase of TPA loading amounts the total acid increases for catalysts prepared by impregnation technique but decreases for catalysts prepared by adsorption technique. The Keggin structure of TPA remains unaltered after being supported on activated carbon. The adsorption form altered when TPA loading amounts get changing. The adsorption process can be devided into three phases which are monomolecular adsorption(TPA loading is between 0~8%), multimolecular adsorption(TPA loading is between 8~14%) and surface packing of bulk TPA(TPA loading is above 14%).APG was synthesized using a two-step process. The optimal technics of the first step(butylglycosidation)are as follows: the best support is C1, the optimal TPA loading is 20%, the optimal catalysts use level is 5%, the best mol proportion of butyl alcohol and glucose is 5:1, the best temperature of the oil base is 120℃and the optimal reaction time is 2 h. The optimal technics of the second step(exchangement of glycosides)are as follows: the best reaction temperature is 120℃, the best mol proportion of dodecyl alcohol and glucose is 2.5:1 and the optimal reaction time is 1 h. Under the optimal technics, the glucose conversion is 97.0%, the DP value of APG product is 1.35. The content of APG12 is 70.2%. The glucose conversion remained relatively high(79%) after being 8 times reclaimed and reused. The APG product has a cmc value of 65.5 mg/L and the corresponding surface tension is 25.2 mN/m. The foam height of APG is 160 mm, and 158 mm after 5 min.