The Elimination Of H₂S In The Methane By Photocatalytic Oxidation

In recent twenty years, environmental photocatalysis has been widely applied in purifying air and eliminating organic contamination of water. It becomes one of the most important applied facets of heterogeneous catalysis.The photocatalytic-elimination of H2S in the methane on the TiO2 was studied. Only by UV-light without TiO2 catalyst the degradation of H2S couldn't occur at room temperature. Without O2 the photocatalytic-elimination of H2S on the TiO2 was very small (5%). When there were TiO2 catalyst and oxygen (the mol ratio of 02: H2S was 250:1), the photocatalytic-oxidation of H2S was remarkable and the conversion rate could increase to 97%. These showed that the oxygen was indispensable to the photocatalytic-oxidation of H2S. The reaction activity was influenced by the velocity of gas, and the conversion rate was inverse ratio to the velocity of flow.During the photocatalytic-oxidation of H2S, TiO2 was inactive because of the resultant of S. After TiO2 was inactive, TiO2 could get back to some 80% of the initial activity by regeneration. The initial activity of Pt/TiO2 was higher than that of TiO2 because it restrained the recombination of electron and hole with supported Pt, however the regenerated ability of the Pt/TiO2 was lower than that of TiO2. After the regeneration, the activity could come back to some 60% of the original activity and the reaction activity declined rapidly. The reason might be that after regeneration on the surface of Pt/TiO2 the incomplete oxidation of H2S to produce S was enhanced.The amplifing experiments were carried based on the use of methane in the country. The photocatalytic-oxidation of H2S was carried by augmenting the reactor, enhancing the light intensity and increasing the quantum of TiO2. The result showed that it was unreality to destruct the H2S in the methane in the country by photocatalysis. The main reasons were no oxygen in methane, the high speed of the gas in use and the small pressure difference. Because the photocatalytic destruction of H2S needed the quitequantum oxygen. It was still a technical problem on how to add the air to the reactor in so small pressure difference. In addition, the photocatalytic reaction efficiency was very low at the high speed. The reactor will be large, the price will be very high and the electricity will be enormously consumed during the photocatalytic-oxidation of H2S in the methane. The peasants could not afford them.Though the photocatalytic destruction the HiS in methane in the country was unreality, it is entirely feasible to get rid of the low concentration of HiS in the local atmosphere.