Highly efficient methyldiethanolamine (MDEA) removal and light naphtha purification via synergistic effect of molecular sieves and fixed adsorption bed

Abstract

Light naphtha is an important raw material for the production of benzene, toluene, and xylene from cracking in tubular furnaces for the production of ethylene and propylene. Light naphtha contains MDEA which is left behind after desulfurization. MDEA remaining in light naphtha will cause high alkalinity of light naphtha, which decreases product quality and increases costs. Additionally, MDEA itself is not easy to degrade and is harmful to human skin, so the removal of MDEA is of great significance for the purification of light naphtha and the protection of the environment. In this paper, a molecular sieve (13X) is compared with silica gel and resin (NKA-9) as a means of removing MDEA from light naphtha via synergism with a fixed adsorption bed. The adsorption capacity decreased in the order of 13X > NKA-9 > silica gel, with values of 53.189, 45.889 and 34.863 mg g^–1, respectively. Similarly, the effectiveness of steam for 13X regeneration after adsorption saturation was investigated, and the steam regeneration restored 95% of the activity of the fresh 13X. Furthermore, the adsorption mechanism of MDEA in light naphtha by 13X was studied, and it was confirmed that the adsorption process was dominated by chemisorption, supplemented by physisorption. The –OH and –NH₂ functional groups were the main groups involved in the chemisorption, and capillary action and hydrogen bond action may be involved in physisorption.