ABSTRACT:
Apart from all gaseous contaminants in air, sulfur dioxide is considered to be the principal pollutant. The emission of sulfur dioxide is generally caused by combustion of sulfur bearing fuels. This further gets converted into sulfuric acid in atmosphere as a result of its reaction with oxygen and moisture. This air borne acid is responsible to damage steel buildings, bridges and machinery. Hence there is a major need to decrease sulfur percentage in the environment in order to lead a better and healthy living. As we can see the world runs on energy, for which fossil fuels are the main constituents. As these all are the complex network of hydrocarbons, when they are combusted or utilized, the products or effluents are somewhat harmful to the atmosphere. Sulfur is one such effluent, which seriously harms the environmental conditions. So this has to be recovered up to appreciable levels. In India diesel is mostly utilized as fuel and it is up to 70%. So in order to reduce the sulfur content diesel is chosen as fuel oil. The reduction of sulfur is done by hydro desulfurization and the process is termed as diesel hydro desulfurization (DHDS). This is achieved by converting the mercaptane state sulfur to hydrogen sulfide (H2S) by reacting it with hydrogen alone on a cobalt molybdenum catalyst. By this the sulfur content is reduced from 1 wt% to 0.25 wt%. This is further reduced to 0.05 wt% using trickle bed reactors.