Super Or Sub-critical Alcoholysis Of Starch To Prepare Alkyl Polyglucosides

Alkyl polyglucosides?APG?,produced from renewable natural resources,are a new type of green non-ionic surfactants.Combined with many characteristics of anionic and nonionic surfactants,they have broad spectrum of antibacterial activity,high surface activity,low toxicity,good dermatological compatibility and good biodegradability.Therefore,they are widely used in in many fields including cosmetics,food ingredients,pharmaceuticals and detergents.Recent the main materials used for synthesis of alkyl polyglycosides are natural fatty alcohols and glucose which is commonly produced from starch and cellulose with complex process.Restricted by product variety and productivity,people began to look for new raw material.The synthesis technology of APG is developing towards higher efficiency and lower cost.Besides,acid catalyst is necessary for the traditional industrial process,which increasing the cost of catalyst recovery and the burden on environment.Hence,The research of starch alcoholysis under sup-critical or sub-critical condition to obtain two kinds of alkyl polyglycosides with different carbon chain lengths was carried out in this paper.The direct utilization of starch can save production cost and rich source of raw materials.In addition,the whole research is easy for the separation of products due to no need of any catalysts during the glycosylation process.First,with starch and isooctyl alcohol as raw materials,the product of isooctyl glucosides were prepared by direct glycosylation under super or sub-critical condition.The whole process can be divided into three processes:alcoholysis,dealcoholization,and decolorization.The products were characterized by FT-IR,HPLC and ¹H NMR.The characteristic absorption peaks of alkyl polyglycosides resulted from branched-chain ether group around at 1150 and 1040 cm^-1 were found in alcoholysis products by FT-IR.HPLC spectra showed that the alcoholysis products has a main peak around at 6.981 similar to the standard isooctyl glucoside.Furthermore,The ¹H NMR peaks of the alcoholysis products were entirely in accord with the molecular structure of isooctyl glucosides.Therefore,the main alcoholysis product was confirmed as isooctyl glucosides,eventually.After single factor analysis and orthogonal test,The optimum reaction conditions were determined to be:the weight ratio of isooctyl alcohol to starch 10,temperature 260°C and reaction time 2 h,the yield of isooctyl glucosides can attain 73.45%.Then,dodecyl polyglucosides were synthesized by transglycosidation of methyl polyglucosides which obtained from super or sub-critical methanolysis of starch.After steps including methanolysis of starch,double alcohol exchange,dealcoholization and decolorization,light yellow products were produced finally.The methanolysis and transglycosidation products were determined to be methyl glucosides and dodecyl polyglucosides by FT-IR,Agilent 1200 HPLC and ¹H NMR,respectively.With the weight ratio of methanol to starch 7.5,temperature 220°C and reaction time 2 h,the yield of methyl glucosides was 84.53%.The alcohol exchange glycosidation was carried out under conditions of the weight ratio of 1-dodecanol to starch 2.5,p-toluene-sulfonic acid to starch 0.01,reaction temperature 110°C and time 1 h,the yield of dodecyl polyglucosides products can reach 82.79%.Finally,the surface tension,foam,emulsification and wetting properties of the two kinds of products were analyzed.The results showed that the CMC value of the isooctyl glucosides and dodecyl polyglucosides products were 2.5 g/L?0.22 g/L,?_cmc=34.1 mN/m?32.42 mN/m,HLB=17?12,the average degree of polymerization were 1.215?1.477 and the average molecular weight were 326.83?425.27,respectively.Moreover,For both of them,the single glycosides and solids content were greater than 50%,residual alcohol content was close to 1%.Basically,the main physical and chemical indicators of isooctyl glucosides and dodecyl polyglucosides products were all in line with national standards.