Preparation & Evaluation of Deoxo Catalyst for the Purification of Inert Gases

Abstract

There has been phenomenal growth in the development of adsorptive technologies for the separation and purification of multi-component gas mixtures during the last three decades. They are being used to serve the chemical, petrochemical, pharmaceutical, environmental, and electronic gas industries. Two generic process concepts called “Pressure swing adsorption (PSA)” and “Thermal swing adsorption (TSA)”, are most frequently used for industrial gas separations. An important technique for producing nitrogen from air is pressure swing adsorption (PSA). Carbon molecular sieves and zeolites are the most well-known adsorbents in PSA frameworks for production of nitrogen, yet the primary disadvantages of presently accessible adsorbents are their high cost of production and final product fluctuation. A significant challenge around there of innovation is to improve the structure of carbon molecular sieves or to change the support from CMS to activated alumina to achieve higher air recoveries, higher nitrogen productivity, and better consistency in adsorbent properties-all at a lower cost. A simple PSA unit produces nitrogen upto 99.99% purity, with trace of (< 100 ppm) of oxygen impurities. The ever increasing demands for high purity gases, used not only in chemical industries, are stimulating the use of high activity catalysts for the removal of impurities. Oxygen is a major impurity in inert or reactive gases; and hence, reducing its concentration has significant importance in industries. Adsorption of oxygen impurity from inert gases has become more popular now a days. Use of beverages and packed food stuff is increased and hence it is necessary to remove oxygen impurities from the atmosphere to preserve food stuff for a longer time. Inertization of reactors and reaction space in many polymerization processes is required to enhance the productivity of catalyst and to avoid undesired products. Therefore, high purity gases with purity of > 99.9999 % and < 1 ppm oxygen impurity is needed. Chemisorption with subsequent catalytic reaction always offers and economical and effective way to purify gases. In the present study, adsorptive separation of oxygen from partially purified nitrogen was considered by chemisorption route using in-house developed Deoxo type catalyst/adsorbent. Catalyst/adsorbent samples were prepared using dissolution technique. Different synthetic parameters such as metal salt loading, calcination temperature, effect of co-metal were extensively studied to get the optimize recipe for the catalyst preparation. Prepared adsorbents were characterized by various analytical techniques such as ICP-OES, Surface area measurements. The prepared adsorbent samples were evaluated through gas phase equilibrium adsorption isotherms using volumetric set-up and oxygen adsorption capacity was measured at 230 ̊C. Sample prepared with transition metal salts like copper (Cu) and manganese (Mn) supported on γ-alumina (Al2O3) has maximum oxygen adsorption capacity and was found equivalent with reference samples. All the data were fitted into Temkin adsorption isotherm model to calculate the adsorbent/adsorbate parameters and temkin constants for chemisorption process with regression value (R2) in the range of 0.99.