Integration of Particle to Bubble Adhesion Model in Design and Scale-Up of Slurry Bubble Columns

In slurry bubble column reactors, catalyst particles may adhere to gas bubbles. Thus, mass transfer limited reactions can be significantly improved either by increasing G-L mass transfer coefficient kL or specific surface area a. The scope of this work is to study the influence of model parameters on coalescence and G-L mass transfer, in order to develop new rules for design and scale-up of slurry bubble columns. A novel model describing adhesion of particles to gas bubbles was developed. The effects of particle size, hydrophobicity and porosity on particle-to-bubble adhesion and bubble coalescence were determined experimentally in a bubble pick-up/coalescence cell. Total gas hold-up, bubble rise velocities and size distribution were measured in a 2-D column. Hydrogenation of methyl acrylate catalyzed by Pd/SiO2 catalysts was performed in a stirred reactor. Hydrophobic catalyst particles adhering at G-L interface slightly increases bubble coalescence rate, but leads to a mass transfer rate up to 450% higher. The particles adhere preferentially to small bubbles increasing G-L mass transfer while higher coalescence rate of large bubbles explains a decrease in gas hold-up.