A process utilizing a particulate catalyst, or particulate catalyst admixed with particulate heat transfer solids for conducting high temperature fluidized bed syn gas operations. Hydrogen and carbon monoxide are produced from a low molecular weight hydrocarbon by contact thereof, at high temperature in the presence of oxygen, or steam and oxygen, with a fluidized bed comprising said particulate solids. In one of its forms, barium hexaluminate is employed as a heat transfer solid, in concentrations ranging generally from about 10 wt. % to about 99.9 wt. %, in admixture with a particulate catalyst containing a metal, or metals, component catalytic for the production of hydrogen and carbon monoxide from low molecular weight hydrocarbons contacted with a fluidized bed of the catalyst at high temperature hydrothermal conditions. The catalyst, suitably one having a barium hexaluminate carrier component, is employed in concentration ranging generally from about 0.1 wt. % to about 90 wt. %. Such an admixture provides a particularly useful catalytic contact mass for conducting fluidized bed synthesis gas generation operations. This type of bed promotes continuous, highly efficient heat and mass transfer within the reacting gas phase. The presence of the catalyst having a barium hexaluminate carrier component, or barium hexaluminate heat transfer solid as a bed component maintains excellent bed fluidization characteristics, suppressing the normal tendency of the catalyst to sinter or agglomerate; tendencies which promote defluidization of the bed. Moreover, the heat transfer particles of the bed are highly attrition resistant, and are chemically compatible with the catalyst particles of the admixture.