Quinoline hydrogenation, nitrogen-containing

Polycyclic aromatic nitrogen compounds, such as quinoline, indole, acridine, and carbazole, are the main nitrogen-containing compounds in oil fractions, and monocyclic pyridine and pyrrole as well as anilines are present in coal tar (Scheme 11). Saturated cyclic amines are found as products of ring hydrogenation of the compounds shown in Scheme 11 after HDN. Aliphatic amines are rarely found in fuels and only in low concentrations after HDN since their nitrogen atoms are easily removed. 

Quinoline is hydrogenated selectively in the nitrogen-containing ring by means of carbon monoxide and water... 

In contrast, nitrogen-containing bases are contained in many crude-oil fractions. In a typical starting material, 25 35 % of the nitrogen compounds have basic character. The sensitivity of solid acids towards these poisons correlates directly with their basicity. For example, pyridine, quinoline, amines, and indoles are basic, while pyrrole and carbazole are nonbasic. These poisons are best removed by hydrogenation, together with sulfur and most of the heavy metal poisons. 

Transfer hydrogenation has also been used for the reduction of the nitrogen-containing rings in the quinoline and isoquinoline systems (Scheme... 

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