Methane pyrolysis over porous particles

Abstract

The deposition of carbon from methane pyrolysis on various porous media was investigated at 950–1100 ◦C. 7 Types of unfunctionalized carriers were used, with pore sizes varying between 4 nm and 250 µm. Carbon deposition over time was measured in a single particle reactor. It was found that the porous samples can exhibit both an induction period as well as a gradual stop in carbon deposition. An induction period was observed for α-Al2O3 samples, but not for γ-Al2O3, SiC and C carriers. Hence, the slow start of the carbon deposition may be caused by substrate material. Furthermore, for all samples, an apparent maximum carbon loading was observed. It was confirmed that this is not caused by pore blockage, as significant surface area remains in these samples at the point of maximum carbon loading. In fact, it was found that fraction of pore volume filled at maximum loading, is a function of the initial pore diameter. The smaller pores fill to a lesser extent than the bigger pores. This maximum achievable carbon fraction was incorporated in a particle model. Using only the fraction of volume filled as a single parameter, the measured loading over time could be described.