关键区别 - 均质与异质催化剂
催化剂有许多类型,但它们可以主要分为两组为均质催化剂和异质催化剂。这key difference在均质和异质催化剂之间均相催化剂可以在liquid phase whereas heterogeneous catalysts can be found in all three物质阶段: solid phase, liquid phase, and gas phase.
催化剂是用于在轻度条件下获得最大产量的化合物。这意味着催化剂可以增加特定反应的产量并加快反应。
内容
1.Overview and Key Difference
2.What is a Homogeneous Catalyst
3.什么是异质催化剂
4.并排比较 - 表格形式的均质与异质催化剂
5.概括
什么是均匀的催化剂?
均质催化剂是与进入反应阶段的物质相同的催化化合物。这些均匀的催化剂通常处于液相。均质催化剂的恢复相对困难且昂贵,因为催化剂与反应混合物的相同相。这意味着催化剂分离很困难。均质催化剂的热稳定性也很差。均质催化剂的最常见示例是元配合物。
Homogeneous catalysts are efficiently active in low-temperature conditions (less than 250◦C). The catalytic activity of these catalysts is moderate when compared to heterogeneous catalysts. However, the selectivity is high. The recycling of the homogeneous catalyst is expensive since the catalytic recovery is difficult. But the modification of the catalyst is easy because it is in the liquid phase.
这diffusivity of homogeneous catalysts is high. This because all reactants and the catalyst are in the same liquid phase and proper stirring leads to proper diffusion of the catalyst throughout the reaction mixture. Homogeneous catalysts usually have well-defined active sites. This means there are many proper active sites on the surface of catalyst compound onto which the reactants are bound, and the reaction progresses in those active sites.
什么是异质催化剂?
Heterogeneous catalysts are catalytic compounds that are in a different phase from that of the phase of the reaction mixture. These catalysts can be found in all three phases of matter: solid phase, liquid phase or gas phase. The catalytic recovery is easy and cheap in heterogeneous catalysts since the catalyst is in a different phase from that of the phase of the reaction mixture. Common examples for heterogeneous catalysts are metals, metal oxides, etc.
这thermal stability of heterogeneous catalysts is very good compared to homogeneous catalysts. These catalysts efficiently act in high-temperature conditions, around 250-500◦C. The catalytic activity is also high when compared to homogeneous catalysts. However, the selectivity of reactants is poor than that of homogeneous catalysts. The active sites of heterogeneous catalysts are not well-defined. This reduces selectivity.
如果催化剂的表面积较低,则异质催化剂的扩散率很差,因为催化剂和反应混合物分为两个相。但是催化剂的分离通常很简单。那么催化剂的回收也很容易。
均质和异质催化剂有什么区别?
同质与异质催化剂 |
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均质催化剂是与进入反应阶段的物质相同的催化化合物。 | Heterogeneous catalysts are catalytic compounds that are in a different phase from that of the phase of the reaction mixture. |
阶段 | |
Homogeneous catalysts can be found mostly in the liquid phase. | Heterogeneous catalysts can be found in all three phases; solid phase, liquid phase or gas phase. |
热稳定性 | |
这thermal stability of homogeneous catalysts is poor. | 这thermal stability of heterogeneous catalysts is good. |
Catalyst Recovery | |
这recovery of homogeneous catalysts is difficult and expensive. | 这recovery of heterogeneous catalysts is easy and cheap. |
Active Site | |
这active site of homogeneous catalysts are well-defined and has good selectivity. | 异质催化剂的活性位点不明确,选择性差。 |
Catalyst Recycling | |
这recycling of homogeneous catalysts is difficult. | 异质催化剂的回收很容易。 |
Catalyst Separation | |
这separation of homogeneous catalyst from the reaction mixture is difficult. | 异质催化剂与反应混合物的分离很容易。 |
Temperature Dependence | |
Homogeneous catalysts work better in low-temperature conditions (less than 250◦C). | Heterogeneous catalysts work better in high-temperature conditions (around 250 to 500◦C). |
Catalyst Modification | |
均质催化剂的修饰很容易。 | 这modification of heterogeneous catalysts is difficult. |
概括– Homogeneous vs Heterogeneous Catalyst
催化剂是可以提高特定反应的反应速率以在短时间内获得最佳产量的化合物。有两种主要类型的催化剂,称为均质催化剂和异质催化剂。均质和异质催化剂之间的关键区别在于,始终可以在液相中找到均质催化剂,而在物质的所有三个阶段中都可以找到异质的催化剂。固相,液相和气相。
Reference:
1.催化类型,化学指导,Available here.
2. “Homogeneous Catalysis.” Wikipedia, Wikimedia Foundation, 25 Feb. 2018,Available here.
3. “Heterogeneous Catalysis.” Wikipedia, Wikimedia Foundation, 16 Mar. 2018,Available here.
Image Courtesy:
1. “CatalysisScheme” By Smokefoot assumed- Own work assumed (based on copyright claims) (Public Domain) viaCommons Wikimedia
2. “Heterogeneous Asymmetric Hydrogenation Pyridines” By Bmalbrecht – Own work(CC BY-SA 3.0)viaCommons Wikimedia
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