Highly selective Ru/HBEA catalyst for the direct amination of fatty alcohols with ammonia

The present study describes the synthesis of primary amines from long-chain fatty alcohols and ammonia using supported ruthenium catalysts over different acid supports, including a variety of zeolites with different topologies and Si/Al ratios. The morphology, acidity and location of ruthenium in the catalysts was studied in detail by combining XRD, BET, HR-TEM, NH3-TPD, octylamine-TPD, H-2-TPR, XPS, EXAFS / XANES, Al-27 MAS NMR and TGA. In particular, Ru/HBEA (Si/Al = 25) with 5 wt% Ru afforded more than 90 % conversion and 90 % selectivity to 1-octylamine in the liquid-phase amination reaction of 1-octanol with ammonia at 180 degrees C in a batch reactor. The high selectivity of Ru/HBEA (Si/Al = 25) can be explained by the presence of Brunsted / Lewis acid centers with medium strength in the proximity of ruthenium nanoparticles. The catalyst was further tested in a pre-pilot continuous stirred-tank reactor (2 L) with flash separation of 1-octylamine. In this configuration, a steady 92 % selectivity of octylamine was obtained at 87 % 1-octanol conversion during 120 h on steam. The catalyst kept its integrity during the reaction.

Automated summary

This study successfully synthesized primary amines from long-chain fatty alcohols and ammonia using supported ruthenium catalysts on different acid supports. The catalyst Ru/HBEA (Si/Al = 25) showed the best performance with high selectivity attributed to the presence of medium strength acidity centers near the ruthenium nanoparticles. In a continuous reaction, the catalyst maintained a stable 92% selectivity.