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Multi-Step Reactions

Multi-Step Reactions

Chemical reactions often occur in a stepwise fashion involving two or more distinct reactions taking place in a sequence. A balanced equation indicates the reacting species and the product species, but it reveals no details about how the reaction occurs at the molecular level. The reaction mechanism (or reaction path) provides details regarding the precise, step-by-step process by which a reaction occurs. Each of the steps in a reaction mechanism is called an elementary reaction. These...

Chemical Equilibria: Systematic Approach to Equilibrium Calculations

Chemical Equilibria: Systematic Approach to Equilibrium Calculations

Equilibrium calculations for systems involving multiple equilibria are often complex. For example, to calculate the solubility of a sparingly soluble salt in an aqueous solution in the presence of a common ion, one must consider all the equilibria in this solution. Calculations for these systems can be complicated and tedious, so a systematic approach with a series of steps is often helpful. The process is detailed below.
The first step is to identify all the chemical reactions involved, The...

Reaction Mechanisms

Reaction Mechanisms

Chemical reactions often occur in a stepwise fashion, involving two or more distinct reactions taking place in a sequence. A balanced equation indicates the reacting species and the product species, but it reveals no details about how the reaction occurs at the molecular level. The reaction mechanism (or reaction path) provides details regarding the precise, step-by-step process by which a reaction occurs.
For instance, the decomposition of ozone appears to follow a mechanism with two steps:

Rate-Determining Steps

Rate-Determining Steps

Relating Reaction Mechanisms
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...

Molecular Weight of Step-Growth Polymers

Molecular Weight of Step-Growth Polymers

Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...

Free-Radical Chain Reaction and Polymerization of Alkenes

Free-Radical Chain Reaction and Polymerization of Alkenes

The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.

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相关实验视频

Updated: May 17, 2025

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics

Published on: April 12, 2019

催化脱聚合的种群平衡模型:从基本步骤到多相反应器

Lela K Manis¹, Jiankai Ge¹, Changhae Andrew Kim¹

¹Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.

Accounts of chemical research

|May 16, 2025

概括

此摘要是机器生成的。

开发先进的人口平衡模型 (PBMs) 能够为聚合物回收提供准确的动力建模. 这些模型将基本计算和复杂的聚合物转换相结合,以实现有效的废物回收利用.

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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

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相关实验视频

Last Updated: May 17, 2025

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics

Published on: April 12, 2019

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Published on: November 27, 2015

A Scalable Balz-Schiemann Reaction Protocol in a Continuous Flow Reactor

A Scalable Balz-Schiemann Reaction Protocol in a Continuous Flow Reactor

Published on: February 10, 2023

科学领域:

化学工程是化学工程的重要组成部分.
材料科学材料科学材料科学
计算化学计算化学

背景情况:

塑料废物积累需要创新的回收解决方案.
传统的动力学模型对于具有众多反应物和中间体的复杂聚合物系统是失败的.
先进的建模对于理解和优化聚合物上循环过程至关重要.

研究的目的:

开发和应用人口平衡模型 (PBMs) 来准确地分析聚合物回收的动力学.
为了将PBM与吸附,脱附和速率方程相结合,用于全面的过程模拟.
使用这些模型进行机械学假设测试,参数提取和催化剂设计.

主要方法:

开发结合种群平衡模型 (PBMs),考虑宏分子物种.
聚合物吸附/脱附模型和小分子反应动力学的整合.
使用PBM与实验数据进行参数提取和机械分析.
从基本利率和第一原则计算 ("自下而上") 和数据分析 ("自上而下") 构建PBM.

主要成果:

PBMs成功地模拟了复杂的聚合物回收动力学,包括宏分子反应物和中间体.
这些模型有助于对催化剂活动进行定量比较,并考虑质量转移效应.
使用这些模型可以设计模仿酶脱聚合的新型催化剂架构.
在第一原则计算和聚合物上循环动力学之间建立了定量联系.

结论:

人口平衡模型为了解和优化聚合物回收提供了一个强大的框架.
这些模型允许设计更高效的催化剂和塑料废物再循环的过程.
理论计算和实验数据的整合加速了聚合物科学和可持续性的进步.