Parametric Studies on the Reduction of 4-Nitroacetophenone using Hydrogen Sulfide and Phase Transfer Catalyst

Abstract

Hydrogen Sulfide (H2S) is more often than not, found in the gas streams of Oil and Gas Industry. This is due to the fact that crude oil has in its composition, a small percentage of sulfur. Subduing the amount of sulfur in the crude oil is of paramount importance because it can cause corrosion of equipments and pipelines and also leads to unwanted side reactions leading to additional use of reactant and power. Conventionally, reduction in sulfur levels is achieved by subjecting the gas stream to ammonia absorption followed by Claus Process, the latter which converts H2S to elemental sulfur which is more productive (less poisonous) and used in rubber vulcanization and sulfuric acid production. The problem associated with Claus Process is that it is very expensive and the demand for elemental sulfur in the market is not as high to redeem the cost. So alternatively, H2S is absorbed into an aqueous alkanolamine and used in the reduction of Nitroarenes following the Zinin Reduction mechanism. Since the alkanolamine and Nitroarene are in two different phases, a phase transfer catalyst (PTC) is used to help increase the reaction rate, conversion of reactant and selectivity of products. This work is focused on the reduction of 4-Nitroacetophenone (NAP) to 4-Aminoacetophenone (AAP) using H2S rich N-Methyldiethanolamine (MDEA) and Tetrabutylphosphonium bromide (TBPB) as the PTC under Liquid-Liquid Phase transfer catalysis, and to study the process parameters involved to maximize the conversion of NAP to AAP. The parameters studied are variation in Stirring speed, Catalyst concentration, Temperature, Sulfide concentration, MDEA concentration etc. This Method can be used as an alternative to Claus Process to produce value added fine chemicals which have better use, in this case being Aminoacetophenone having applications in clinical microbiology, in the synthesis of Pyrimidines, Coumarins, as a drug metabolite. It also has antibacterial properties.