为提高蛋清蛋白凝胶性,本研究以蛋清蛋白(Egg white protein,EWP)为研究对象,通过分析质构、持水率、分子作用力、傅里叶红外色谱、圆二色谱、粒径、电位、巯基含量、表面疏水力及扫描电镜的变化,探究超高压处理(Ultra-high pressure,U...为提高蛋清蛋白凝胶性,本研究以蛋清蛋白(Egg white protein,EWP)为研究对象,通过分析质构、持水率、分子作用力、傅里叶红外色谱、圆二色谱、粒径、电位、巯基含量、表面疏水力及扫描电镜的变化,探究超高压处理(Ultra-high pressure,UHP)、谷氨酰胺转胺酶处理(Transglutaminase,TG)及超高压协同TG酶处理(Ultra-high pressure synergistic Transglutaminase,UTG)的蛋清蛋白热诱导凝胶机理及结构的变化。结果表明:UHP-EWP、TG-EWP、UTG-EWP的硬度、弹性和持水性均有所提高,疏水相互作用力是维持凝胶的主要作用力;UHP-EWP、TG-EWP、UTG-EWP的α-螺旋含量均不同程度下降、β-折叠含量均上升;UHP-EWP的平均粒径值下降、电位绝对值下降,TG-EWP、UTG-EWP的变化与之相反;UHP-EWP、TG-EWP、UTG-EWP的游离巯基含量上升、总巯基含量下降、表面疏水性升高;凝胶结构更加致密光滑,平整度提高。本研究为蛋清蛋白热诱导凝胶改性提供了理论基础及研究思路。展开更多
海底充油电缆的安全稳定运行至关重要,但内部的十二烷基苯(DDB)绝缘油在热故障导致的局部高温下会快速热解和产气。基于反应分子动力学模拟(Reax FF-MD)和热重-红外光谱(TG-IR)实验,对十二烷基苯绝缘油的热解和产气过程进行探究。热解...海底充油电缆的安全稳定运行至关重要,但内部的十二烷基苯(DDB)绝缘油在热故障导致的局部高温下会快速热解和产气。基于反应分子动力学模拟(Reax FF-MD)和热重-红外光谱(TG-IR)实验,对十二烷基苯绝缘油的热解和产气过程进行探究。热解模拟结果表明:十二烷基苯分子初始裂解反应主要为C—C键的断裂产生长链大分子,后逐渐热解产生小烷基自由基和烯烃分子,DDB最终会热解为侧链为·C_(2)H_(5)、·CH_(3)和·C_(3)H_(7)基团的短链烷基苯分子。热解过程中主要特征气体为C_(2)H_(4)、H_(2)、CH_(4),与IR实验结果相同,特征气体生成的主要反应机理分别为:β位C—C键的断裂、加氢反应和脱氢反应;·H自由基攻击其他自由基上的H原子;甲基自由基(·CH_(3))与游离的氢(·H)自由基反应。动力学结果表明TG实验与Reax FF-MD的活化能分别为86.606 k J/mol以及99.867 k J/mol,相近的活化能进一步验证了仿真结果的合理性。研究结论为深入了解十二烷基苯绝缘油的裂解和产气机理提供了理论支持。展开更多
Despite the fact that a few countries in the Mediterranean and the Middle East have limited crude oil reserves, they have abundant biomass feedstocks. For instance, Jordan relies heavily on the importation of natural ...Despite the fact that a few countries in the Mediterranean and the Middle East have limited crude oil reserves, they have abundant biomass feedstocks. For instance, Jordan relies heavily on the importation of natural gas and crude oil for its energy needs;but, by applying thermochemical conversion techniques, leftover olive oil can be used to replace these energy sources. Understanding the chemical, physical, and thermal characteristics of raw materials is essential to obtaining the most out of these conversion processes. Thermogravimetric analysis was used in this study to examine the thermal behavior of olive-solid residue (kernel) at three different heating rates (5, 20 and 40 C/min) in nitrogen and oxygen atmospheres. The initial degradation temperature, the residual weight at 500 and 700˚C and the thermal degradation rate during the devolatilization stage (below 400˚C) were all determined. It was found that in N<sub>2</sub> and O<sub>2</sub> atmospheres, both the initial degradation temperature and the degradation rate increase with increasing heating rates. As heating rates increase in the N<sub>2</sub> atmosphere, the residual weight at 500 or 700˚C decreases slightly, but at low heating rates compared to high heating rates in the O<sub>2</sub> atmosphere, it decreases significantly. This suggests that a longer lignin oxidation process is better than a shorter one. Coats and Redfern approach was used to identify the mechanism and activation energy for the devolatilization stage of pyrolysis and oxidation reactions. The process mechanism analysis revealed that the model of first-order and second-order reactions may adequately describe the mechanism of heat degradation of the devolatilization step of olive-solid waste for pyrolysis and oxidation processes, respectively.展开更多
文摘海底充油电缆的安全稳定运行至关重要,但内部的十二烷基苯(DDB)绝缘油在热故障导致的局部高温下会快速热解和产气。基于反应分子动力学模拟(Reax FF-MD)和热重-红外光谱(TG-IR)实验,对十二烷基苯绝缘油的热解和产气过程进行探究。热解模拟结果表明:十二烷基苯分子初始裂解反应主要为C—C键的断裂产生长链大分子,后逐渐热解产生小烷基自由基和烯烃分子,DDB最终会热解为侧链为·C_(2)H_(5)、·CH_(3)和·C_(3)H_(7)基团的短链烷基苯分子。热解过程中主要特征气体为C_(2)H_(4)、H_(2)、CH_(4),与IR实验结果相同,特征气体生成的主要反应机理分别为:β位C—C键的断裂、加氢反应和脱氢反应;·H自由基攻击其他自由基上的H原子;甲基自由基(·CH_(3))与游离的氢(·H)自由基反应。动力学结果表明TG实验与Reax FF-MD的活化能分别为86.606 k J/mol以及99.867 k J/mol,相近的活化能进一步验证了仿真结果的合理性。研究结论为深入了解十二烷基苯绝缘油的裂解和产气机理提供了理论支持。
文摘Despite the fact that a few countries in the Mediterranean and the Middle East have limited crude oil reserves, they have abundant biomass feedstocks. For instance, Jordan relies heavily on the importation of natural gas and crude oil for its energy needs;but, by applying thermochemical conversion techniques, leftover olive oil can be used to replace these energy sources. Understanding the chemical, physical, and thermal characteristics of raw materials is essential to obtaining the most out of these conversion processes. Thermogravimetric analysis was used in this study to examine the thermal behavior of olive-solid residue (kernel) at three different heating rates (5, 20 and 40 C/min) in nitrogen and oxygen atmospheres. The initial degradation temperature, the residual weight at 500 and 700˚C and the thermal degradation rate during the devolatilization stage (below 400˚C) were all determined. It was found that in N<sub>2</sub> and O<sub>2</sub> atmospheres, both the initial degradation temperature and the degradation rate increase with increasing heating rates. As heating rates increase in the N<sub>2</sub> atmosphere, the residual weight at 500 or 700˚C decreases slightly, but at low heating rates compared to high heating rates in the O<sub>2</sub> atmosphere, it decreases significantly. This suggests that a longer lignin oxidation process is better than a shorter one. Coats and Redfern approach was used to identify the mechanism and activation energy for the devolatilization stage of pyrolysis and oxidation reactions. The process mechanism analysis revealed that the model of first-order and second-order reactions may adequately describe the mechanism of heat degradation of the devolatilization step of olive-solid waste for pyrolysis and oxidation processes, respectively.
