A continuous catalytic process was developed to remove hydrogen sulfide from a natural gas stream using activated carbon as catalyst. The concentration range of hydrogen sulfide in the gas stream studied was 300–3000 ppmv (0.0126–0.126 moles/m3). Virtually 100 percent conversion of hydrogen sulfide was achieved by the combination of various parameters. The “field gas” employed in this study exhibited cracking of some heavier hydrocarbons and made the product sulfur slightly brown. These hydrocarbons should therefore be separated from the gas stream prior to the oxidation reaction. No carbon monoxide or carbon dioxide was produced during the oxidation of hydrogen sulfide. It is concluded that the process described herein has the potential for the removal of hydrogen sulfide as sulfur from a sour natural gas stream on a continuous basis and could therefore eliminate an environmental problem which now exists.

The oxidation of low concentrations of hydrogen sulfide with air over activated carbon was studied over the temperature range 24‐200°C using both fixed and fluid bed reactors. The predominant reaction, H2S + ½ Oa → H2O + S, was found to have an order of 0.5 with respect of H2S concentration. Activity of the catalyst decreased as the amount of sulfur deposited on it increased. Indirect evidence suggests that adsorption of water by the carbon also decreases its activity as a catalyst at lower temperatures. Values of the activation energy and the frequency factor were determined for various sulfur loadings using the fixed bed reaction system. Regeneration of the carbon loaded with sulfur was studied at temperatures between 150 and 500°C using steam as a carrier gas. Bright yellow sulfur was recovered. The regenerated carbon was shown to have its original activity.

A gas containing approximately 1000 ppm of methyl mercaptan (CH 3 SH) was used to test an oxidative reaction system for the purification of gas. Experiments were performed for 3.0 h periods in a fixed-bed reactor containing 0.25-5.0 g of Hydrodarco activated carbon in the temperature and pressure ranges 323-448 K and 122-364 kPa, respectively. The gas hourly space velocity was varied from 938 to 4000 h -1 , with the O 2 /CH 3 SH ratio varying from 1.1 to 1.33 times the stoichiometric ratio. Dimethyl disulfide was the main product, while CO 2 was produced in small amounts. At temperatures above 373 K, 99.99% conversion of the mercaptan was achieved. It was established that higher conversion of CH 3 SH could be achieved while keeping CO 2 production to a minimum by using an O 2 /CH 3 SH ratio in the feed gas close to 1.10 times the stoichiometric ratio. Catalyst deactivation occurred due to deposition of dimethyl disulfide on the catalyst. A kinetic study of this process was performed, and a rate equation for the conversion of CH 3 SH to (CH 3 ) 2 S 2 and H 2 O was obtained. Since catalyst deactivation occurred by fouling due to deposition of (CH 3 ) 2 S 2 on the catalyst, the initial rates were considered to be global rates without deactivation effects. According to the Langmuir-Hinshelwood model, the overall rate equation was derived on the basis of the mechanism where the rate-determining step is a surface reaction. The rate data obtained using granular activated carbon were collected well with the rate equation.

A process is proposed for the removal of H 2 S from sour produced wastewater at lower temperatures (<25 °C) using an activated carbon as a catalyst and oxygen in air as an oxidizing agent. Hydrodarco-activated carbon catalyst was successfully used in this process in a continuous-flow stirred-tank reactor (CFSTR) in an aqueous solution with a pH of 3-10, and temperature and residence time of the feed in the reactor ranging from 8 to 24 °C and 5.2 to 18.6 min, respectively. This catalyst has higher activity than that of Calgon catalyst in this process. The H 2 S conversion was increased with temperature, the conversion approaching 100% at 24 °C after 90 min of operation at a pH of 4.5 and a residence time of 11.4 min. The Hydrodarcoactivated carbon was capable of sorbing 0.66 g of sulfur/g of carbon before its activity decreased significantly giving conversions below 90%. In a CFSTR, for the sour water with a pH value of 4.5, the rate of H 2 S oxidation in the temperature range 8-24 °C was -r H2S ) (5.072 × 10 10 (µmol/L) 0.76 (1/min)) exp(-21.3 kJ/mol/RT)[H 2 S] 0.24 , [µmol/(L min)].

The kinetics of the hydrogen sulfide oxidation process, producing mostly sulfur and water, was studied using 0.25 to 1 .O g Hydrodarco activated carbon catalyst and varying the 02/H$ ratio (molar basis) in the feed gas between 0.5 to 0.6 in the temperature, and pressure ranges from 125 to 200°C and 225 to 780 kPa. SO, was obtained as an undesirable by-product during H S oxidation reaction or as a product during regeneration of the catalyst. The feed gas contained 0.9 -1.3 mol% HP with approximately 80 mol% CH, In this paper, the factors affecting the H$ conversion and SO, formation are presented. The rate expressions for (a) H$ conversion and (b) SO, formation were developed from the LangmuirHinshelwood surface control reaction model. The experimental data were well correlated by the rate equations. Also, the rate parameters were evaluated and correlated with temperature. The activation energies for H$ oxidation and SO, production reactions were calculated to be 34.2 and 62.5 kJimol, respectively. Partial pressures of oxygen and H S were found to influence H$ conversion whereas, the presence of water in the feed gas up to 10.5 mol% did not affect H P conversion significantly. Heats of adsorption for various species on the active sites were calculated. SO, production was, as expected, enhanced at higher temperature, and its rate was much smaller than the oxidation rate of H$ under the reaction conditions used.