The Kinetic and Thermodynamic Behavior of Gaseous
H2S and CO2 over a Heterogeneous Catalyst

The Stenger-Wasas Process (SWAP) as described, in which the gaseous reaction between hydrogen sulfide and carbon dioxide over treated solid heterogeneous catalyst (i.e. C09-0108t) was observed to be thermodynamically and kinetically favorable at or below 25°C to 150°C and above. The reaction process is spontaneous and liberates heat. This conclusion is based upon physical experiment data (adiabatic and isothermal calorimetry), as well as theoretical predictive methods.

It was also observed that the reaction performance increases:

• significantly at elevated temperatures (i.e. above 150°C); and
• upon transition from a closed static system to a continuous flow fixed bed system; and
  
• in the presence of an inert gas, such as (but not limited to) methane.

This reaction process was studied by physical experiment under different initial conditions. Spontaneous chemical interaction was observed between the gases, hydrogen sulfide (H2S) and carbon dioxide (CO2) in the presence of the heterogeneous catalyst, C09-0108. In fact, in this synthesis, the SWAP proceeds at or below 25°C and is highly exothermic. In corroborating studies, using two different laboratory test methods, (isothermal and adiabatic conditions), it was observed that this reaction is faster and most favorable at temperatures at or above 150°C and under pressures that range from atmospheric i.e. 15 psia (at sea level) to 700 psia. These experimental studies have also demonstrated that the nature of the chemistry is unaltered in the presence of up to 50% methane gas (sour gas mixture), which behaves in this scenario as an inert species. The experimental data were analyzed to provide the Heat of Reaction, the Gibbs Free Energy, the kinetic Rate Constant, the Activation Energy and Reaction Order for the SWAP.

While this study has confirmed that the SWAP system is very successful in reacting hydrogen sulfide and carbon dioxide using the solid catalyst C09-0108t, additional work is continuing to assess catalyst performance during continuous flow conditions as a function of gas flow rate at temperatures at and above 150°C. This additional experimental work will provide data for defining future pilot and demonstration plant process conditions.