Development of nitrogen-doped bamboo-like carbon nanotubes coated zeolite beads as \u201csupport on support\u201d catalyst for the catalytic hydrogenation of olefins

Abstract

“Support on support” type catalysts were developed by applying catalytic chemical vapour deposition (CCVD). Nitrogen-doped bamboo-like carbon nanotubes (N-BCNT) were synthetized on the surface of zeolite beads by using four different metals (Ni, Fe, Co and V). Based on the thermogravimetric analysis (TGA), the Ni, Co and Fe were catalytically active for nanotube production on the zeolite surface. It was confirmed by SEM measurements, that the surface of the beads was extensively covered by N-BCNTs. Based on the TGA and SEM results, two SoS systems were selected for further catalysts development, which differed the most in their nanotube content (difference 11.63 wt%) and surface coverage. These were two nickel containing samples with 6.72 and 18.35 wt% N-BCNT. Palladium nanoparticles were deposited (1 wt%) on the surface of the N-BCNT/zeolite systems, and the final Pd/SoS catalysts were tested in hydrogenation of 1-butene. The conversion maximum (X = 100%) was reached after 6 min in both cases independently of the nanotube content and coverage (WHSV: 5.49). To measure the lifetime of the selected catalysts, the WHSV was increased from 5.49 to 11 (by increasing the gas flow) and the systems were still active after 6 h. Thus, the lifetime of the catalysts is longer than 6 h. Furthermore, by increasing the gas flow (WHSV = 11), higher conversion was achieved (98%) with the sample which has a higher nanotube content Therefore, smaller carbon nanotube content is still as catalyst support. The final Pd/SoS catalysts were active, easy to treat and removable from the reactors and could work with smaller carbon nanotube content as well. Thus, a more economical catalysts was developed, than a solely carbon nanotube-based counterparts which lack the zeolite core.