Composite catalytic tubular membranes for selective hydrogenation in three-phase systems

• Membranes reactors reduce hydrogen starvation at catalyst.
• Membranes reactors produces about ½ the trans-fats of slurry reactor.
• Near zero reaction order in hydrogen pressure (order = −0.1 ± 0.2).
• Increased temperature does not significantly increase trans-fat produced.
• Membrane reactors have potential to replace slurry reactors.

Catalytic membrane contact reactors (CMCRs) were evaluated for the selective three-phase hydrogenation of the model reaction, the partial hydrogenation of soybean oil (PHSO). PHSO produces copious amounts of trans-fats when carried out in a batch slurry reactor due to hydrogen starvation at the catalyst, caused by inherent mass transfer limitations of the system. In this study composite ceramic/polymer membranes were rendered catalytically active by depositing a polymer-palladium complex, (poly(N-vinyl-2-pryyolidone) (PVP)-palladium (Pd)), onto the selective skin of the membrane. Hydrogen gas was supplied to the support side of the membrane, the hydrogen gas permeated from the support side to the skin side of the membrane, where it dissociated onto the catalyst surface. Liquid reactant was circulated over the skin side of the membrane, allowing the three components to come into contact and react. Our system is shown to be nearly zero order in hydrogen, indicating that the catalyst surface maintains high hydrogen coverage throughout. CMCRs produced 50% less trans-fat at equivalent levels of hydrogenation compared to slurry reactors. It was further demonstrated that an increase in temperature had minimal effects on trans-fat formation, while significantly increasing hydrogenation rates; allowing the system to capture higher reaction rates without adversely affecting product quality.

Figure optionsDownload high-quality image (182 K)Download as PowerPoint slide