N-doped carbon (N carbon) materials were prepared from a commercial polyacrylonitrile (PAN) by calcination and subsequent ammoxidation and these were used for a model reaction of Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. The catalytic activity of the calcined PAN for the reaction was very low, but it was greatly enhanced by the ammoxidation and the enhancement depended on both the calcination and ammoxidation temperatures. X-ray photoelectron spectra indicated the presence of pyridine-type and pyrrole-/pyridone-type N species and the amount of the former N species was well correlated with the catalytic activity. It was suggested that the presence of pyridine-type N in the graphene structure is significant for the emergence of the catalytic activity. The most active N-carbon catalyst prepared in the present study was much more active than solid-based catalysts reported so far including N carbon derived from activated carbon, N-doped carbon nanotubes, and a few metal oxide based catalysts.

Nitrogen-doped carbon materials were prepared by ammoxidation of commercial carbon sources (carbon black and activated carbon) and applied as base catalysts for Knoevenagel and transesterification reactions. It was shown that these carbon materials were active and the activities were different depending on the ammoxidation conditions (temperature and ammonia concentration in air) and carbon sources used. The bulk, textural, and surface properties of the nitrogen-doped carbon materials were examined by several methods to clarify possible factors determining their final catalytic activities. The activated carbon-derived catalysts were more active than the carbon black-derived ones. The surface area and porosity were not responsible for this difference between the two carbon sources but the difference in the reactivity with oxygen was important. The reactivity of carbon sources with oxygen should influence the doping of nitrogen onto their surfaces by ammoxidation with ammonia and air and the resulting activities as base catalysts. The catalytic activity increases with the amount of nitrogen doped and, therefore, the nitrogen doped should be responsible for the catalytic activities. In addition, the activities are maximal at a ratio of nitrogen to oxygen of around 1, suggesting the importance of cooperative functions of nitrogen and oxygen on the surface of carbons.

Heck coupling reactions of methyl acrylate with various aryl bromides have been investigated using a Pd/TPP catalyst in toluene under pressurized CO₂ conditions up to 13 MPa. Although CO₂ is not a reactant, the pressurization of the reaction liquid phase with CO₂ has positive and negative impacts on the rate of Heck coupling depending on the structures of the substrates examined. In the case of either 2-bromoacetophenone or 2-bromocinnamate, the conversion has a maximum at a CO₂ pressure of about 3 MPa; for the former, it is much larger by a factor of 3 compared with that under ambient pressure. For 2-bromobenzene, in contrast, the conversion is minimized at a similar CO₂ pressure, being half compared with that at ambient pressure. In the other substrates, including the other isomers of these three aryl bromides, the conversion simply decreases or does not change so much with the CO₂ pressure. To examine the factors responsible for the effects of CO₂ pressurization, the phase behavior and the molecular interactions with dense phase CO₂ have also been studied by visual observation and in situ high pressure FT-IR spectroscopy. In addition, impact of CO₂ pressurization was also studied for the Diels–Alder reactions of isoprene with a few dienophiles like methyl acrylate, methyl vinyl ketone, and acrolein in the same solvent, toluene, but a heterogeneous silica-alumina catalyst was used (the reaction system was liquid-solid biphasic). When the CO₂ pressure is raised, the conversion monotonously decreases for the three dienophiles; however, the product selectivity changes with the pressure, in particular for acrolein. The FT-IR spectroscopic measurements suggest that its reactivity is altered by interactions with CO₂ molecules under pressurized conditions.