The Spectroscopic Signature Nitrogen-Substituted Zeolites

Nanoporous acid catalysts in the form of zeolites are the foundation of catalytic technologies in petroleum refining. Recent interest in fuel production from biomass, however, has created demand for similarly shape-selective base catalysts because of the high oxygen content of biomass-derived feeds. Strongly basic zeolites, however, are notoriously difficult to make due to the strongly acidic nature of aluminosilicates. Much research has been conducted into the production of strongly basic zeolites by treating ordinary zeolites with amines, but to date there is little direct evidence that nitrogen is actually incorporated into the zeolite framework during such treatments. We detail synthesis, NMR spectroscopy, and quantum chemical calculations showing that nitrogen likely adds to both surface and interior sites, preserving the framework structure. The resulting zeolites show unique catalytic activity. This finding is of critical importance to the rational design of biomass refining catalysts, and allows over fifty years of zeolite science to be applied to the catalytic synthesis of biofuels.