Advanced Investigation On The Development And Utilization Of The Wood Tar From Almond Shell

Bitter almond shell is a kind of byproduct in the pruduction of bitter almond kernel that is used in traditional Chinese medicine or bervage industry.The shells are usually abondoned or burnt,resulting in the waste of this naturall resource.In order to use this biomass,previously,we carried out the pyrolysis on almond shell,and obtained solid product,i.e.,almond shell carchoal,which is further prepared to the value added products,acivated carbon.The liquid products include pyrolignous acid and wood tar that is formed during standing.In this study,we use the wood tar as material to conduct investigation on the advanced development and utilizaion by physical and chemical methods,in wich the content of phenols(a main group of the chemical constituents in the tar)was adopted as index constituent.The results are reported as follows.1.When the wood tar was distilled under atmospheric pressure,three kinds of the products were obtained from different temperature ranges based on the similarity of physico-chemical properties:A1(90-110℃),A2(110-219℃),and A3(219-260℃).Similarly,other three products were collected from the vacuum distillation of the wood tar:V1(90-110℃),V2(110-160℃),and V3(160-200℃).Higher contents of organic acids,ketones,and esters were found in A1 and V1,that were collected from the lower temperature range during atmospheric and vacuum distillation,Both A1 and V1 exhibited the lowest antioxidant and antimicrobial activities,whild A3 and V3 that were resulted from the high temperature range and were rich in phenolics and hydrocarbons presented the highest antioxidant and antimicrobial activities.Products A2 and V2 that were collected from the middle temperature ranges contained lower contents of organic acids,ketones,esters,and higher contents of phenolics,their antioxidant and antimicrobial activities were in the middle levels.The results indicated that both atmostpheric and vaccum distillation could be adopted to refine wood tar from almond shell,and vaccum distillation exhibited some advantages in the contents of chemical constituents.2.Creosote oil was prepared by basic and adcidic extraction methods from V2 and V3,which were obtained by vacume dilstillation.Single factors experiments demonstrated that the best process parameters were sodium hydrogen carbonate concentration:6%,sodium hydroxide concentration:2.5%,extraction volume ratio:2.0,and acidification pH:6.0.In the response surface experiments,optimized simulation equation was proved to be R=-744.12+1297.77×A+19.27B+31.95C-272.74A2(A:concentration;B:volume ratio;C:pH)and the best process parameters were proved to be:sodium hydroxide concentration of 2.25%,the extraction volume ratio of 2.0 and acidificationn pH 7.0.The confirmatory experiment proved that the analysis and prediction of the regression model for total phenolic content of the extract creosote was reliable.The total phenol content of creosote extracted by alkalineacid extraction was two times higher than distillate.3.In the separation of creosote by chromatography,we got petroleum ether phase(F1),ethyl acetate phase(F2),and methanol phase(F3),F2 had the highest total phenol content and yield,which was proved to be the most active one;F3 had the lower yield and total phenol content,and proved to be active one in antioxidant antimicrobial activities,while F1 had the lowest yield and total phenol content,and proved to have almost no activity.