Catalytic Selective Synthesis Of Sucrose Fatty Acid Monoester And Its Properties

Sucrose fatty acid monoesters with high purity are a kind of safe non-toxic,biodegradable green non-ionic surfactants.They are found to have strong and stable hydrophilic emulsifying capacity,as well as antibacterial,anti-tumor and insecticidal activities.It can be applied in as value-added substate in the field of cosmetics,food emulsifiers,and bio-based pesticides,pharmaceutical preparations,etc.However,due to the similar activity among sucrose hydroxyl groups,it is difficult to achieve selective esterification of hydroxyl groups to directly prepare monoester products.Therefore,in this paper,based on the transesterification of sucrose and methyl caproate as the model,the alkali modified mesoporous silica catalyst was constructed.By adjusting the amount of alkali and pore structure,the transesterification of sucrose and methyl caproate was restricted to form diesters by limiting the amount of alkali and pore structure.The main research results are as follows:Sucrose octanoate,sucrose decanoate,sucrose laurate and sucrose palmitate were synthesized by dimethyl sulfoxide（DMSO）solvent method.The unreacted sucrose and some impurities in the products were removed by butanone and 10%sodium chloride solution with volume ratio of 2:1.Using the mixture of V（chloroform）:V（methanol）:V（acetic acid）:V（water）=75:15:3:2 as eluent,the corresponding sucrose fatty acid monoesters were isolated and purified by silica gel column chromatography,and identified by TLC,FT-IR,MS and ¹H-NMR.HPLC-ELSD was used to establish qualitative and quantitative analysis methods for pure sucrose octanoate monoester and diester,and GC-FID was used for quantitative analysis of methyl caproate and sucrose.The short-pore mesoporous silica nanospheres（MSN）were synthesized by the sol-gel method and supported with 1,5,7-Triazabicyclo[4.4.0]dec-5-ene（TBD）to form TBD/MSN catalyst.The results of XRD,TEM and SEM show that MSN and TBD/MSN have highly ordered hexagonal mesoporous structure（p6mm）,which are honeycomb and monodisperse nanospheres.The BET analysis realized that both MSN and TBD/MSN had typical type IV adsorption isotherms with mesoporous structure.The specific surface area of MSN and TBD/MSN were about 1000 m²g^-1.With the increase of loading,the total pore volume and micropore volume of TBD/MSN decrease.Sucrose octanoate was synthesized from sucrose and methyl caproate in vacuum at 130℃for 6 h with TBD and TBD/MSN as catalysts.The conversion of methyl caproate was44.0%,38.1%,and the selectivity of sucrose caprylate was 76.2%and 84.1%,respectively.It can be concluded that TBD/MSN has selectivity and the yield of monoester is slightly reduced.Through the determination of sucrose fatty acid monoester hydrophilic lipophilic balance value（HLB value）,critical micelle concentration（CMC）,foaming performance and antibacterial performance and correlation analysis;The results realized:sucrose fatty acid monoester increases with the carbon chain,both CMC and HLB values decrease;With the increase of HLB value,its foaming performance and foam stability first increase and then decrease.Among them,sucrose capric acid monoester and sucrose lauric acid monoester have the best foaming performance,which can reach 162.5%,192.5%,the thermal stability of sucrose caprate monoester and sucrose lauric acid monoester can reach 70%.The initial degradation temperature of sucrose fatty acid monoester is basically around 200℃,and its properties can remain unchanged below 200℃in the food industry.Sucrose decanoate monoester has the best antibacterial effect on E.coli.Sucrose caprylate monoester,sucrose decanoate monoester,sucrose palmitate monoester,S1 670 has almost100%antibacterial effect on Staphylococcus aureus.