(384c) Aliphatic Amine and Nitrile Synthesis through Catalytic CO Hydrogenation in the Presence of Ammonia

The global demand for amines and nitriles is growing rapidly ($2.9 billion by 2025). Traditional routes of aliphatic amine and nitrile synthesis involve multi-step processes, so little regioselectivity is reached this way. In the present paper, we report a regioselective “one-step one-pot” synthesis of aliphatic amines and nitriles as feedstock for emulsifiers and detergents using the catalytic CO hydrogenation as a vehicle to produce hydrocarbon chain lengthening and ammonia as an agent to provide terminal nitrogen functionalization.

Materials and Methods

For the studies presented here, a Co₄Mn₁K_0.1 (indices indicating atom %) was used [1]. High-pressure catalytic tests were performed in a fixed-bed plug-flow reactor at 17 bar and 260°C. Experiments always started by running the Fischer Tropsch (FT) synthesis before introducing ammonia up to 15 % of the total volumetric feed.

Results and Discussion

According to the table 1(see attached), adjusting the reactant feed (in absence of ammonia) to H₂/CO=3 and, subsequently, to 0.5 causes alcohols and, respectively, aldehydes to form. Interestingly, these oxygenates are replaced by aliphatic amines and nitriles when using feeds containing 15 vol% NH₃. The single-pass CO conversion in these experiments drops to 31% for H₂/CO=3 and to 11 % for H₂/CO=0.5, respectively. Chain-lengthened nitriles provide linear C₄₊ Anderson−Schulz−Flory (ASF) characteristics with chain growth probabilities of about 0.5, Remarkably, all experiments described here are completely reversible, i.e. the initial Fischer-Tropsch catalytic performance, whatever H₂/CO ratio, is reproduced once ammonia is being removed from the reactant feed.

A reaction scheme will be provided including transient kinetic studies (fast compositional changes of reactant feeds) along with XRD and XPS, which clearly show that catalysts undergo reconstruction to Co₂C and Co-carbonitrides.

References

1. Xiang, Y.; Kruse, N., Tuning the catalytic CO hydrogenation to straight- and long-chain aldehydes/alcohols and olefins/paraffins. Nature Communications 2016, 7, 13058