Modified Mg-Al spinel catalysts, for the pyrolysis of diesel fuel for the production of industrial gases and liquids, have been developed by self-propagating high-temperature synthesis (SHS). The substitution of Mg by Co in the MgAl2O4 spinel and the use of Al2O3, SiO2 and MgO, increases significantly the catalytic conversion efficiency of the spinel while at the same time it suppresses substantially the formation of coke. The ethene (ethylene) production yield at 1020 K increased from 23% for pure Mg-Al spinel - same as that for thermal pyrolysis - to 37% by the use of a small percentage of Co3O4 The addition of up to 50% Co in the structure did not change the catalytic activity appreciably, possibly due to the existence of an optimum number of active centres in the surface and an optimum concentration of lattice defects in the Mg-Al spinel structure at a very low concentration of CoAl2O4 in the catalyst. At very large Co oxide concentrations, excess Co oxide appeared in the SHS product which changed the function of the catalyst to that of dehydrogenation with a H-2 yield of up to 80%. Such enhanced hydrogen yield suppresses ethene production.