Enhancement of N-2 formation from the nitrogen in carbon and coal by calcium

The effects of Ca catalysts on nitrogen release during heat treatment of po lyacrylonitrile-derived carbon and pyrolysis of low rank coals have been st udied with a fixed bed quartz reactor in a stream of high purity He. In the temperature-programmed treatment at 10 degreesC/min of the carbon with 3 w t % Ca, the Ca promotes Nz formation at 850-1000 degreesC and the catalytic effect is larger at a higher temperature. When a low rank coal, after demi neralization and subsequent addition of 3 wt % Ca, is pyrolyzed in the same manner as above, the Ca enhances the rate of N-2 formation at 850-1100 deg reesC at largest by a factor of 15. In the fast heating pyrolysis at 400 de greesC/min of the demineralized samples, the Ca at loading of 1-3 wt % also increases N-2 yields at 1200-1350 degreesC irrespective of type of coal. T hese observations and nitrogen distribution indicate that the N-2 increased by Ca addition arises mainly from solid-phase reactions of heterocyclic ni trogen forms. The X-ray diffraction measurements after heat treatment and p yrolysis reveal that catalyst particles are too fine on the carbon to be de tected and as small as 45-65 nm in size on the chars. The catalysis of N-2 formation at solid phase by the Ca is discussed in terms of the mobility of CaO particles, their agglomeration, and sulfur poisoning.