Nitrogen Sorption in a Transition Metal Complex Solution for N2 Rejection from Methane

Abstract

Nitrogen is a ubiquitous impurity in natural gas that has to be removed for the production of liquefied natural gas (LNG). The most widely used technology for N2 rejection, cryogenic distillation, is a capital and energy intensive process. In this work, a nitrogen selective K[RuII(EDTA)] aqueous solution was prepared and tested for nitrogen sorption with the aim of reducing the N2 rejection costs by using a continuous recirculation absorption process analogous to the acid gas removal process in LNG production. The overall equilibrium amount of N2 sorption in the K[RuII(EDTA)] solution was obtained at 20 °C (0.075 mol N2/L solution at 2860 kPa), 30 °C (0.061 mol N2/L solution at 2873 kPa), and 40 °C (0.052 mol N2/L solution at 3049 kPa) using a custom-built volumetric sorption measurement apparatus. The corresponding specific N2 sorption amounts were 0.54 mol N2/mol Ru at 20 °C and 2860 kPa; 0.43 mol N2/mol Ru at 30 °C and 2873 kPa; and 0.34 mol N2/mol Ru at 40 °C and 3049 kPa. These specific N2 sorption a...