Thermal steam cracking of naphtha in packed bed reactors has been compared with cracking in an empty tube. A laboratory-scale packed bed reactor has been used to investigate the effects of inert and catalytic active materials on the steam cracking of naphtha, Different sizes of ceramic materials as inert materials have been tested at various reactor temperatures. The results show that lower molecular weight products, such as hydrogen, methane, and ethylene, have been increased by steam cracking in packed bed reactors compared to a conventional approach in an empty tube. Steam cracking of naphtha over six different catalysts consisting of mixtures of alumina and metal oxides, such as CaO, TiO2, SrO, MgO, Cr2O3, and MnO, has been tested, and the results are compared with those for a ceramic packed bed reactor. It could be demonstrated that the catalysts used do not improve the yields of ethylene and propylene as main products. However, the same catalysts have shown significant gasification activity, indicated by the increased yield of H-2, CO, and CO2 with a reduction of the yields of ethylene, propylene, and other cracking products. Among those catalysts, it has been found that calcium aluminate (12CaO(.)7Al(2)O(3)) selectively gasifies aromatics produced during the cracking reactions without any reduction of ethylene and propylene.