Removal of sulfur from liquid fuels using various materials

What is it about?

This article expresses the concerns about the environmental pollution caused due to the automobiles. At the same time, it talks about the remedies. Automobiles use gasoline or diesel as a fuel. The fuel undergoes combustion in the engine and produces energy. It also produces the combustion gases such as carbon monoxide, carbon dioxide, oxides of sulfur, and oxides of nitrogen. The fuels are composed of hydrocarbons and nonhydrocarbons. Nonhydrocarbon part consists of compounds such as organic sulfur and nitrogen compounds, which upon combustion generate their oxides. The gases produced are released directly into the atmosphere through the exhaust pipes of vehicles. These are harmful gases. Oxides of sulfur such as sulfur dioxide are responsible for acid rains. Worldwide there is movement towards reducing levels of sulfur in these transportation fuels. The expected sulfur level is very low i.e., ultra-low. The sulfur content in both gasoline and diesel must be 10 ppm as per the latest norms. Refineries meet expected fuel specifications through conventional route, which is very costly. In addition, it consumes hydrogen, which is precious. Thus, to reduce the cost and also reduce the consumption of hydrogen in a conventional process, an alternative process is being searched. Removal of sulfur through adsorption is one of the alternatives. However, it needs certain adsorbent material over the surface of which, sulfur compounds can be adsorbed. Thus, concentration of sulfur in the liquid fuels can be reduced. A variety of adsorbent materials, carbon based, and zeolite based have been studied by the researchers. If these materials are used without any modification, then sulfur removal efficiency will be very low. Thus, to increase the efficiency, their modification is necessary. This modification can be done through ion exchange process. Metal ions can be exchanged with raw adsorbents, which enhances the sulfur removal efficiency of the materials. Ion exchange is possible through liquid state and solid state. The article focuses on solid state ion exchange of materials, as it has certain advantages in comparison with liquid state one. After successful ion exchange, the materials need to be tested either in a batch process or continuous process. A model or real fuel may be used for this testing. At the end of testing, the material become spent or deactivated. To impart them original activity, they need to regenerate and reuse in the same process. The methods of regeneration and reuse of spent adsorbents have also been a part of present article. Equilibrium, kinetic and thermodynamic studies form an integral part of the article.

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Photo by grayomm on Unsplash

Photo by grayomm on Unsplash

Why is it important?

The subject covered by the article is very broad. It covers various areas such as modification and testing of adsorbents. In addition to it, regeneration and reuse of spent adsorbents too, covered. The readers will also find a summary of models on equilibrium and kinetic studies. Thermodynamics of sulfur removal using different adsorbents also discussed.

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