Zinc oxide (ZnO) is used as a pretreatment step to remove hydrogen sulfide (H2S) from natural gas following hydrogenation of any sulfur compounds prior to a methane reformer, which can poison the catalyst. At temperatures between about 230–430 °C (446–806 °F), H2S is converted to water by the following reaction:

H2S + ZnO → H2O + ZnS

The zinc sulfide (ZnS) is replaced with fresh zinc oxide when the zinc oxide has been consumed.