连续流动在有机/药物合成中的应用 [3]
论文作者:www.51lunwen.org论文属性:学术文章 Scholarship Essay登出时间:2016-07-01编辑:cinq点击率:11330
论文字数:5000论文编号:org201607011048114906语种:英语 English地区:美国价格:免费论文
关键词:英语论文医学药物连续流动化学
摘要:本文是医学英语学术论文范文,主要内容是针对连续流动化学的技术进行研究,主要围绕连续流动在有机/药物合成中的应用问题。
sis uses micron-sized channels to transport various reagents, products and wastes. There are some special characteristic features of the channel network. For example, the channel network can offer more effective and accurate temperature control by operating computer programs. Temperature is the most important factors for chemical reaction. The micron-sized channels have large surface to volume ratios compared to the normal channels. This feature has a great advantage in heat transfer. The heat can be rapidly released and make fast cooling needed in the micro reaction. And the reaction would be heated up rapidly to a required temperature as well. The greater surface to volume ratios in the continuous flow also makes it more efficient for various phase boundary reactions, including liquid to liquid, gas to liquid or solid to liquid chemical reactions7.
High temperatures and pressuresare required for the rapid heat transformation in the reactions. The main driving method for fluid transportation in the continuous flow synthesis is the electrokinetic, which would never be obstructed by high temperatures and pressures. Thus, the continuous flow can tolerate under high temperatures and pressures, and enable the micro reactors to work in unconventional processes and harsh environmental conditions1.
The continuous flow synthesis is frequently used in chemical reactions which consist of combination of two or more reagents. Mixing of the reagents is a critical process for the efficient reactions. Mixing is due to the chemical molecular diffusion, which can be effectively controlled by the fluid flow rate and length of diffusion path. According to this theory, the continuous flow synthesis can improve the mix process by shortening the length of diffusion path in channel network and increasing the flow speed1.
The medical reaction time is determined by the residence time that reagents remain in the reactors. The residence time is related to the length of the channels and fluid flow rates. The residence time can increase when the length of channels increasing and flow rate decreasing. The continuous flow system can reduce the reaction time by shortening the length of channel and speeding the fluid flow rate. The short reaction time is critical for the chemical reactions generating some unstable reactive intermediates under certain conditions8.
Compared to the traditional batch reactors, the continuous reactors are more safe handling. For example, the chemical reactions may consist of some highly explosive and toxic reagents, which could be very dangerous when mixing and reacting in batch reactors. But in the continuous flow system, the reagents mix and react in the micron-sized reactors, which minimizes the risk of explosion and toxic exposure9.
Although the continuous flow reactors are very useful and efficient especially in the chemical synthesis, and serve as the most powerful tools in the laboratory synthesis. There still are some disadvantages of the continuous flow reactors in industrial-scale productions. First, the materials for the micro reactors and the channel networks in continuous flow system are more expensive than the batch flow system, which commonly used stainless steel and PTFE. And micro reactor channels are too small in size and suffer from restricted fluid flow capacity. The continuous flow system is considered to be unsuitable for industrialpharmaceuticals product
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