羧甲基木薯淀粉和羧甲基壳聚糖混合物不仅可有效改善淀粉物化性质,还可引入抑菌性能好的羧甲基壳聚糖。以木薯淀粉、壳聚糖为原料,氯乙酸钠为醚化剂,氢氧化钠为催化剂,采用机械活化固相醚法制备羧甲基木薯淀粉和羧甲基壳聚糖混合物。以...羧甲基木薯淀粉和羧甲基壳聚糖混合物不仅可有效改善淀粉物化性质,还可引入抑菌性能好的羧甲基壳聚糖。以木薯淀粉、壳聚糖为原料,氯乙酸钠为醚化剂,氢氧化钠为催化剂,采用机械活化固相醚法制备羧甲基木薯淀粉和羧甲基壳聚糖混合物。以黏度为评价指标,通过单因素和正交试验设计优化确定最佳制备工艺,采用红外光谱(Fourier transform infrared spectroscopy,FTIR)、X-射线衍射(X-ray diffraction,XRD)、扫描电镜(Scanning electron microscope,SEM)对羧甲基淀粉的结构进行表征,并考察混合物的取代度和溶解度。结果表明,机械活化破坏了淀粉、壳聚糖的结晶结构,降低结晶度,醚化试剂更容易渗透到内部使淀粉、壳聚糖发生羧甲基化反应。最佳工艺参数为:淀粉与壳聚糖质量比0.5:0.5、淀粉与氯乙酸钠的摩比1:0.9、氢氧化钠质量分数18.8%(占淀粉干基质量)、球磨温度50℃、球磨时间60 min、转速380 r/min、磨球体积500 m L。在该试验条件下制备得到的羧甲基木薯淀粉和羧甲基壳聚糖混合物的黏度为1025 m Pa·s,其中羧甲基木薯淀粉的取代度为0.79,羧甲基壳聚糖的总取代度为1.17,溶解度为90.87%,且随着壳聚糖比例增大,混合物溶解度不断减小。FTIR、XRD、SEM进一步证实木薯淀粉、壳聚糖均发生了羧甲基化反应。展开更多
The transformation of CO_(2)into cyclic carbonates via atom-economical cycloadditions with epoxides has recently attracted tremendous attention.On one hand,though many heterogeneous catalysts have been developed for t...The transformation of CO_(2)into cyclic carbonates via atom-economical cycloadditions with epoxides has recently attracted tremendous attention.On one hand,though many heterogeneous catalysts have been developed for this reaction,they typically suffer from disadvantages such as the need for severe reaction conditions,catalyst loss,and large amounts of soluble co-catalysts.On the other hand,the development of heterogeneous catalysts featuring multiple and cooperative active sites,remains challenging and desirable.In this study,we prepared a series of porous organic catalysts(POP-PBnCl-TPPMg-x)via the copolymerization metal-porphyrin compounds and phosphonium salt monomers in various ratios.The resulting materials contain both Lewis-acidic and Lewis-basic active sites.The molecular-level combination of these sites in the same polymer allows these active sites to work synergistically,giving rise to excellent performance in the cycloaddition reaction of CO_(2)with epoxides,under mild conditions(40℃ and 1 atm CO_(2))in the absence of soluble co-catalysts.POP-PBnCl-TPPMg-12 can also efficiently fixate CO_(2)under low-CO_(2)-concentration(15%v/v N2)conditions representative of typical CO_(2)compositions in industrial exhaust gases.More importantly,this catalyst shows excellent recyclability and can easily be separated and reused at least five times while maintaining its activity.In view of their heterogeneous nature and excellent catalytic performance,the obtained catalysts are promising candidates for the transformation of industrially generated CO_(2)into high value-added chemicals.展开更多
文摘羧甲基木薯淀粉和羧甲基壳聚糖混合物不仅可有效改善淀粉物化性质,还可引入抑菌性能好的羧甲基壳聚糖。以木薯淀粉、壳聚糖为原料,氯乙酸钠为醚化剂,氢氧化钠为催化剂,采用机械活化固相醚法制备羧甲基木薯淀粉和羧甲基壳聚糖混合物。以黏度为评价指标,通过单因素和正交试验设计优化确定最佳制备工艺,采用红外光谱(Fourier transform infrared spectroscopy,FTIR)、X-射线衍射(X-ray diffraction,XRD)、扫描电镜(Scanning electron microscope,SEM)对羧甲基淀粉的结构进行表征,并考察混合物的取代度和溶解度。结果表明,机械活化破坏了淀粉、壳聚糖的结晶结构,降低结晶度,醚化试剂更容易渗透到内部使淀粉、壳聚糖发生羧甲基化反应。最佳工艺参数为:淀粉与壳聚糖质量比0.5:0.5、淀粉与氯乙酸钠的摩比1:0.9、氢氧化钠质量分数18.8%(占淀粉干基质量)、球磨温度50℃、球磨时间60 min、转速380 r/min、磨球体积500 m L。在该试验条件下制备得到的羧甲基木薯淀粉和羧甲基壳聚糖混合物的黏度为1025 m Pa·s,其中羧甲基木薯淀粉的取代度为0.79,羧甲基壳聚糖的总取代度为1.17,溶解度为90.87%,且随着壳聚糖比例增大,混合物溶解度不断减小。FTIR、XRD、SEM进一步证实木薯淀粉、壳聚糖均发生了羧甲基化反应。
文摘The transformation of CO_(2)into cyclic carbonates via atom-economical cycloadditions with epoxides has recently attracted tremendous attention.On one hand,though many heterogeneous catalysts have been developed for this reaction,they typically suffer from disadvantages such as the need for severe reaction conditions,catalyst loss,and large amounts of soluble co-catalysts.On the other hand,the development of heterogeneous catalysts featuring multiple and cooperative active sites,remains challenging and desirable.In this study,we prepared a series of porous organic catalysts(POP-PBnCl-TPPMg-x)via the copolymerization metal-porphyrin compounds and phosphonium salt monomers in various ratios.The resulting materials contain both Lewis-acidic and Lewis-basic active sites.The molecular-level combination of these sites in the same polymer allows these active sites to work synergistically,giving rise to excellent performance in the cycloaddition reaction of CO_(2)with epoxides,under mild conditions(40℃ and 1 atm CO_(2))in the absence of soluble co-catalysts.POP-PBnCl-TPPMg-12 can also efficiently fixate CO_(2)under low-CO_(2)-concentration(15%v/v N2)conditions representative of typical CO_(2)compositions in industrial exhaust gases.More importantly,this catalyst shows excellent recyclability and can easily be separated and reused at least five times while maintaining its activity.In view of their heterogeneous nature and excellent catalytic performance,the obtained catalysts are promising candidates for the transformation of industrially generated CO_(2)into high value-added chemicals.
