Model-free analysis allows for determination of the activation energy of a reaction process without assuming a kinetic model for the process. Also, the reaction type is usually not required to calculate the activation energy. However, it is not possible to determine the number of reaction steps, their contribution to the total effect or the order in which they occur.

### Model-free analysis is based on two assumptions:

1. The reaction can be described by only one kinetic equation for the degree of reaction α:

where E(α) is the activation energy depending on the conversion α, and A(α) is the pre-exponential factor.

2. The reaction rate at a constant value of conversion is only a function of temperature.

## Model-Free Methods in Kinetics Neo

In Kinetics Neo, the following methods can be used:

- ASTM E698,
- ASTM E2890,
- ASTM E1641,
- Isothermal Arrhenius for time-to-event,
- Dynamic Arrhenius for failure temperature (ASTM E2070D),
- ASTM E2070(A) for isothermal data,
- Friedman,
- Ozawa-Flynn-Wall (OFW),
- Kissinger-Akahira-Sunose (KAS),
- Numerical Optimization (Kinetics Neo only).

## The Model-Free Analysis Methods — Advantages and Disadvantages

The ** Friedman **analysis is an isoconversional method whereas the

**and**

*Ozawa-Flynn-Wall (OFW)***analyses are integral isoconversional methods. In all methods, the measurements are analyzed for multiple conversion levels.**

*Kissinger-Akahira-Sunose (KAS)***requires at least two measurements.**

*Friedman*In addition to two dynamic measurements, ** OFW **and

**require positive heating rates.**

*KAS*The ** Numerical Optimization** uses digital simulation in determining the activation energy and pre-exponential factor to achieve the best agreement between simulated and experimental curves. At least two measurements are required.

In all of the methods, the activation energy is determined using the points at the same conversion (0.01, 0.02, …, 0.99) from the measurements at different heating rates or under different isothermal conditions (for ** Friedman **and

**).**

*Numerical Optimization*_{}

^{}

Model-Free Methods | Advantage | Disadvantage | |
---|---|---|---|

Methods based on a single conversion | ASTM E698 | Only for one-step reactions; for complex reactions, the points are not on a straight line
Only for dynamic measurements
Only one point is evaluated; all other information is not used | |

Conversion-dependent methods | ASTM E2070(A) | For multiple-step reactions without parallel reaction steps
Evaluation of each reaction point Suitable for isothermal measurements only
| For parallel and independent reactions, the mean values of Ea are given |

Friedman | For multiple-step reactions without parallel reaction steps
Evaluation of each reaction point Suitable for dynamic and isothermal measurements
| For parallel and independent reactions, the mean values of Ea are given | |

Ozawa-Flynn- Wall (OFW) | For multiple-step reactions without parallel reaction steps
Evaluation of each reaction point | Suitable only for dynamic runs For parallel and independent reactions, the mean values of Ea are given | |

Kissinger-Akahira-Sunose (KAS) | For multiple-step reactions without parallel reaction steps Evaluation of each reaction point | Suitable only for dynamic runs For parallel and independent reactions, the mean values of Ea are given | |

Numerical Optimization | For multiple-step reactions without parallel reaction steps Evaluation of each reaction point Suitable for dynamic and isothermal measurements | For parallel and independent reactions, the mean values of Ea are given |