Nitrogen distribution in the pyrolysis products of a type II kerogen (Cenomanian, Italy). Timing of molecular nitrogen production versus other gases

A type II kerogen (NN8, Cenomanian, Italy) was submitted to isothermal closed pyrolyses, in sealed gold tubes, under various temperature/time conditions (ranging from 280 to 550 degrees C and from 1 to 72 h). Nitrogen distributions were determined, via independent measurements, in the different pyrolysis fractions. Complete nitrogen mass balances were thus obtained, for the first time to the best of our knowledge, for pyrolyses of a type II kerogen. The nature and the abundance of the individual gases generated under each temperature/time condition were also examined. Taken together the above results provided information on (i) the amounts of N-2, CH4, CO2, and H2S produced from the NN8 kerogen upon thermal stress, (ii) the timing of such productions, and (iii) the composition to be expected for the gas fractions generated from such a type II kerogen at different stages of natural maturation. In addition, these observations were compared with those derived from a similar study recently carried out on a type I kerogen.