极性和非极性分子在微波化学

关于这项研究

微波化学是化学过程的研究使用微波辐射。微波加热任何介质包含移动电荷,如极性分子在固体,液体或进行离子作为高频电场。极性溶剂加热因为其组成分子被迫旋转场和失去能量的碰撞。当离子或电子在半导体或进行样本产生电流,能量损失是由于材料的电阻。微波加热后,在实验室被广泛接受的文章发表于1986年,尽管微波加热化学改性可以追溯到1950年代。传统加热需要使用炉或油浴加热反应堆的墙通过对流和传导。当加热陶瓷砖的大样本,例如,示例的核心需要更长的时间达到所需的温度。

微波吸收,它充当一个内部热源,可以热目标化合物没有整个炉或油浴加热,节省时间和精力。它也可以热细项均匀地在他们的体积(而不是只有外表面),导致更加平等的加热。微波场通常不均匀,局部过热发生由于大多数微波炉的结构和不平等的吸收被加热的对象。通过提供一个强大的、均匀的微波,微波加热体积克服不均匀吸收。当考虑到组件的损失切线,异构系统(包括各种物质或阶段)可能是各向异性。因此,各种能量的微波场预计将被转换成热系统的不同部分。由于不均匀能量耗散,选择性加热材料是可以想象的截然不同的地区,这可能导致非温度梯度。尽管如此,传热过程域之间必须接触区域的存在比别人更高的温度。热门领域不会持续很长时间,系统域之间的传热率高,随着组件快速达到热平衡。在系统传热缓慢,很多早期作品在微波化学推测特定的分子或基团分子内可能是兴奋。 However, because the time it takes for thermal energy to be partitioned from such moieties is significantly shorter than the period of a microwave pulse, such molecular hot spots cannot exist under normal laboratory settings. Collisions with nearby molecules would instantly transmit the oscillations caused by the radiation in these target molecules, bringing them to thermal equilibrium at the same time. Solid-phase processes behave in a somewhat different way. Much higher heat transport resistances are involved in this situation, and the likelihood of stationary hot-spots should be considered. Although many people perceive the distinction between two types of hot spots to be arbitrary, it has been highlighted in the literature. All huge non-isothermal volumes that can be detected and measured with optical pyrometers were designated macroscopic hot spots. Under microwave irradiation, these methods can be used to visualize thermal in homogeneities inside solid phases. Non-isothermal areas exist at the micro or Nano scale or at the molecular scale. However, post-mortem approaches have identified minuscule hotspots similar as those postulated to explain catalyst behavior in various gas-phase catalytic reactions, therefore the distinction is meaningless. Due to the presence of metals in supported catalysts and the likelihood of arcing occurrences in the presence of flammable solvents, the application of MW heating to heterogeneous catalysis reactions has not been thoroughly investigated. Using nanoparticle-sized metal catalysts, however, this scenario becomes implausible.