为获得一种绿色高效的羧甲基多孔淀粉制备工艺,本研究以酶解制得的多孔木薯淀粉为原料,氯乙酸钠为醚化剂,氢氧化钠为催化剂,采用机械活化协同固相醚化法制备羧甲基多孔淀粉,通过单因素实验探究各因素对羧甲基多孔淀粉取代度(Degree of s...为获得一种绿色高效的羧甲基多孔淀粉制备工艺,本研究以酶解制得的多孔木薯淀粉为原料,氯乙酸钠为醚化剂,氢氧化钠为催化剂,采用机械活化协同固相醚化法制备羧甲基多孔淀粉,通过单因素实验探究各因素对羧甲基多孔淀粉取代度(Degree of substitution,DS)的影响,并探讨羧甲基多孔淀粉在酱油中的应用。结果表明,机械活化协同固相法制备羧甲基多孔淀粉的最佳工艺条件为:多孔淀粉与氯乙酸钠的物质的量之比为1:1,氢氧化钠质量分数为18.8%,球磨时间1.5 h,反应温度50℃,此条件下制备得到的羧甲基多孔淀粉取代度最高为0.2532。通过红外光谱仪(Infrared spectrometer,FTIR)、X-射线粉末衍射仪(X-ray powder diffractometer,XRD)和扫描电镜(Scanning electron microscope,SEM)等表征,进一步证实多孔淀粉发生了羧甲基化反应。随着羧甲基多孔淀粉DS的增大其冷水溶解度、吸水率和柠檬黄吸附量增大;当DS为0.2532时,羧甲基多孔淀粉的冷水溶解度达到64.94%,吸水率达到180.73%,柠檬黄吸附量达到2.5086 mg·g^(-1)。羧甲基多孔淀粉所制备的粉末酱油相比于木薯淀粉和多孔淀粉所制备的粉末酱油溶解性更好,吸潮性更低,氨基酸态氮含量更高,与原酱油最接近。因此,机械活化协同固相醚化法可有效制备羧甲基多孔淀粉,该法操作简单,绿色环保,取代高,为多孔淀粉的开发利用提供了科学依据。展开更多
Carbon coated LiFePO4 cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances o...Carbon coated LiFePO4 cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances of the material as cathode in lithium-ion battery were investigated at medium and elevated temperature (30 and 55 ℃) by galvanostatic charge-discharge and A.C. impedance tests. The results show that carbon coated LiFePO4 powder exhibits a well-crystallized olivine structure and spherical morphology with an average particle size of about 500 nm. Galvanostatic charge-discharge tests show that the reversible discharge capacity at 1 C and 1.5 C rates was improved from 121 and 105 mAh·g-1 at 30 ℃ to 136 and 123 mAh·g-1 at 55℃, respectively, while the enhancement of high temperature on electrochemical performance is less obvious at a rate lower than 0.5 C. Impedance spectra analyses indicate that the cathode material has a remarkably higher lithium-ion diffusivity at 55 ℃ than that at 30 ℃, which improves the electrochemical performance at high temperature.展开更多
文摘为获得一种绿色高效的羧甲基多孔淀粉制备工艺,本研究以酶解制得的多孔木薯淀粉为原料,氯乙酸钠为醚化剂,氢氧化钠为催化剂,采用机械活化协同固相醚化法制备羧甲基多孔淀粉,通过单因素实验探究各因素对羧甲基多孔淀粉取代度(Degree of substitution,DS)的影响,并探讨羧甲基多孔淀粉在酱油中的应用。结果表明,机械活化协同固相法制备羧甲基多孔淀粉的最佳工艺条件为:多孔淀粉与氯乙酸钠的物质的量之比为1:1,氢氧化钠质量分数为18.8%,球磨时间1.5 h,反应温度50℃,此条件下制备得到的羧甲基多孔淀粉取代度最高为0.2532。通过红外光谱仪(Infrared spectrometer,FTIR)、X-射线粉末衍射仪(X-ray powder diffractometer,XRD)和扫描电镜(Scanning electron microscope,SEM)等表征,进一步证实多孔淀粉发生了羧甲基化反应。随着羧甲基多孔淀粉DS的增大其冷水溶解度、吸水率和柠檬黄吸附量增大;当DS为0.2532时,羧甲基多孔淀粉的冷水溶解度达到64.94%,吸水率达到180.73%,柠檬黄吸附量达到2.5086 mg·g^(-1)。羧甲基多孔淀粉所制备的粉末酱油相比于木薯淀粉和多孔淀粉所制备的粉末酱油溶解性更好,吸潮性更低,氨基酸态氮含量更高,与原酱油最接近。因此,机械活化协同固相醚化法可有效制备羧甲基多孔淀粉,该法操作简单,绿色环保,取代高,为多孔淀粉的开发利用提供了科学依据。
文摘Carbon coated LiFePO4 cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances of the material as cathode in lithium-ion battery were investigated at medium and elevated temperature (30 and 55 ℃) by galvanostatic charge-discharge and A.C. impedance tests. The results show that carbon coated LiFePO4 powder exhibits a well-crystallized olivine structure and spherical morphology with an average particle size of about 500 nm. Galvanostatic charge-discharge tests show that the reversible discharge capacity at 1 C and 1.5 C rates was improved from 121 and 105 mAh·g-1 at 30 ℃ to 136 and 123 mAh·g-1 at 55℃, respectively, while the enhancement of high temperature on electrochemical performance is less obvious at a rate lower than 0.5 C. Impedance spectra analyses indicate that the cathode material has a remarkably higher lithium-ion diffusivity at 55 ℃ than that at 30 ℃, which improves the electrochemical performance at high temperature.
