LPG (liquid petroleum gas) sweetening is a very important refining process in which mercaptans are extracted from LPG by caustic solution, resulting in mercaptide salts. Subsequently, these mercaptides are oxidized in the presence of air and catalyst to disulphides involving gas liquid (G‐L) reactions in an oxidizer. This review discusses design and operational aspects of a laboratory G‐L oxidizer which are essential for determination of intrinsic kinetic parameters of the mercaptide oxidation step. These kinetic parameters are subsequently used for scale‐up and design of grass root industrial scale oxidizers. The sweetening is categorized as a slow reaction. Hence, reaction takes place both in the film and the bulk. Transport of oxygen across the air to the aqueous alkaline phase in the oxidizer is critical and controlled by the liquid film mass transport term. Thus, oxygen transportation limitations need to be overcome and ensured before conducting kinetic studies. This paper fills the gap between laboratory reactor design and operational aspects by presenting a detailed review on chemical engineering analysis for maximization of the volumetric mass transfer coefficient using operational aspects of an agitated sparged G‐L reactor.
Thiols in liquefied petroleum gas are undesirable due to their foul odor and corrosive nature. The process of removing these thiols is termed as sweetening. Metal phthalocyanines are reported to be the most effective sweetening catalyst. However, the solubility of metal phthalocyanine is low in aqueous medium. Thus, in an effort to further improve upon the existing catalysts, a novel cobalt phthalocyanine sulfonamide catalyst was developed. Laboratory and commercial evaluation of this catalyst showed enhanced activity as compared to a commercial catalyst with comparable stability. With proven higher activity, comparable stability, design of grass root oxidizer using this catalyst is the next step. Design of oxidizers for an extractive sweetening process based on this catalyst in grass root refineries requires a rigorous kinetic model. The paper reviews the literature on sweetening kinetics and focuses on the concepts of design of laboratory reactors for reaction kinetics studies for such gas-liquid reactions. Laboratory reactor systems can be useful for accurate estimation of kinetic parameters which can then be used to design industrial reactors and predict their performance.
Hydrodesulfurization (HDS) of straight‐run naphtha (SRN) reformer feed significantly improves reformer catalyst life, gasoline yield, and its stability. HDS of SRN helps in protecting the expensive platinum‐based reforming catalyst. HDS is usually catalyzed by sulphided Co–Mo/Al2O3 or sometimes Ni–Mo/Al2O3. The design of naphtha HDS units requires the development develop a kinetic model. It is well‐known that among the sulphur types present in naphtha, the most persistent sulphur compound is thiophene. Therefore, the design of naphtha HDS units is governed by thiophene HDS rates. It is essential to have experimental conditions free from intraparticle diffusional limitations in order to obtain intrinsic kinetics data. This Communication discusses the calculation procedures involved in ensuring experimental conditions free from pore diffusional resistances before conducting detailed kinetics studies. The pore diffusional resistance was quantified in terms of Thiele modulus (Φ).
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