Potassium and phosphorus represent inorganics commonly found in biomass and can significantly affect catalytic gasification of biomass. The alkaline and acidic nature of potassium and phosphorus, respectively, can introduce different reaction chemistries. In this paper, the effects of potassium and phosphorus on Rh catalysts for catalytic gasification have been studied at different file/oxygen ratios and temperatures. Catalytic partial oxidation (CPO) of ethanol, a biomass surrogate, was carried out over potassium, phosphorus, and monobasic potassium-phosphate-doped catalysts at loadings of 0.1, 1, 10, and 100% of Rh atoms over a range of fuel/oxygen ratios. In addition, time-on-stream studies were also carried out with methane by predosing inorganics on the catalyst (10% loading) and ethanol by introducing inorganics in the feed (0.05 mol %) to understand their effects on the stability of autothermal operation. With ethanol CPO, synthesis gas selectivities did not change significantly with potassium-doped catalysts, Whereas they decreased with phosphorus,doped catalysts. Monobasic potassium phosphate showed synergistic effects of potassium and phosphorus; however, at higher temperatures, the effect of phosphorus was predominantly observed as a result of volatilization of potassium. Similarly, with time-on-stream studies with methane CPO, potassium volatilized at higher temperatures, while phosphorus retained its catalytic activity at higher temperatures. With the introduction of potassium and phosphorus in ethanol feed, steady-state autothermal operation was possible without any deactivation of the catalyst. In all experiments, phosphorus exhibited a stronger poisoning effect on rhodium for catalytic partial oxidation than potassium at concentrations.