What is a shrinking core model?

The shrinking core model is used to describe situations in which solid particles are being consumed either by dissolution or reaction and, as a result, the amount of the material being consumed is “shrinking.” This model applies to areas ranging from pharmacokinetics (e.g., dissolution of pills in the stomach) to the …

What is progressive conversion model?

Progressive-Conversion Model (PCM): In present model, we assume that reactant gas enters and reacts throughout the particle at all times, most likely at different rates at different locations within the particle.

What are the limitations of shrinking core model?

Shrinking core model exhibits inherent limitations to the reactions with a porous particle. Ahn and Choi (2017) indicated that the shrinking core model for a porous pellet would become 837 valid only when the reaction was controlled by inward diffusion (i.e., the reaction proceeded with the core-shell structure). …

What is the significance of Hatta number?

The Hatta number (Ha) was developed by Shirôji Hatta, who taught at Tohoku University. It is a dimensionless parameter that compares the rate of reaction in a liquid film to the rate of diffusion through the film.

How do you calculate effectiveness factor?

For the heterogeneous systems with known constants to define the Thiele module φ, the effectiveness factor η can be obtained by calculating the Thiele module φ and then referring to the η–φ curve.

What is porous catalyst?

In this study, a porous catalyst pellet is defined to mean the material formed by compressing a large number of small porous particles. This compression in- troduces a macroscopic pore-size dis- tribution between the particles whose pores are within the range 200 to 10,000 A.

What is enhancement factor?

The enhancement factor E in Eq. ( 10) is defined as the ratio of the liquid mass-transfer coefficients for absorption with and without a chemical reaction.

Can effectiveness factor be greater than 1?

Thus, because the effectiveness factor is the ratio of the actual reaction rate to the rate at surface conditions, the effectiveness factor can be greater than 1, depending on the magnitude of the parameters and .

Why is effectiveness factor important?

The internal effectiveness factor is more useful. It characterizes the utilization of the internal surface of a catalyst particle and can provide guidance for catalyst manufacture and use.

How do you calculate enhancement?

The SERS enhancement factor (EF) is given by: EF= NvolIsurf/NsurfIvol where Nvol and Nsurf are the number of molecules probed in the aqueous sample and on the SERS substrates, respectively. Ivol and Isurf are the corresponding normal Raman and SERS intensities.

What is the enhancement factor?