Organic solvent-free catalytic hydrogenation of diene-based polymer nanoparticles in latex form: Mass transfer of hydrogen in a semibatch process

• The level of bound hydrogen in the agitated aqueous phase was evaluated.
• Mass transfer of hydrogen is negligible in diffusing through the surfactant layer.
• Diffusion of hydrogen in the nanosize NBR particles was modeled.
• Mass transfer of hydrogen is not the rate-determining step of latex hydrogenation.

The mass transfer process of hydrogen during hydrogenation of diene-based latex nanoparticles remains as one of the most discussed and sought-after research topics particularly for potential commercial processes carried out in a semibatch reaction mode. In this research, in-house prepared nitrile butadiene rubber (NBR) nanoparticle latices were prepared as the substrate for the subsequent hydrogenation experiments. The mass transfer pathway of hydrogen molecules in a gas (hydrogen)–liquid (water)–solid (polymer) three phase hydrogenation system under semibatch operation was examined, wherein the hydrogen transports from the bulk gas phase to an intermediate liquid phase, and then to the solid polymer phase. The mass transfer of hydrogen across the interfacial surfactant layer at the water/polymer interface was studied. A one-dimensional, moving boundary model was developed to describe the diffusion of hydrogen into the polymer nanoparticles by incorporating the level of bound hydrogen in the aqueous phase and the mass diffusivity of hydrogen in the polymer phase. Our results show that the mass transfer of hydrogen cannot account for the rate-determining step of NBR latex hydrogenation. This research report provides some further insight into the mass transfer of hydrogen during catalytic latex hydrogenation.

Illustrative diagram representing the mass transfer pathway of hydrogen in the three-phase latex hydrogenation of unsaturated polymer under semibatch operation.Figure optionsDownload as PowerPoint slide