Application of templating-free chromium therephtalate for the adsorption of nitrogen-containing compounds in oil refinining feedstocks. Kinetics and thermodinamycs

Abstract

ABSTRACT A new simple and high scale hydrothermal synthesis of MIL-101Cr without the use of templating agent was carried out, with yields of up to 83% respective to Cr+3 with excellent textural properties. Four samples of MOF were prepared at different reaction times, and, after activation, these were studied for their nitrogen-containing compounds (NCCs) adsorption properties over straight run gasoil-light/cyclic oil (SRGO/LCO) feedstocks from oil refinery processes, containing 400 ppm of N. From the adsorption models studied, the Freundlich isotherm model better fitted the NCCs uptake, with R2 up to 0.9982 (RMSE = 0.3). According to the adsorption kinetics experiments, a pseudo second-order behavior (R2 = 0.99, RMSE = 0.067) was shown by the adsorbents with 10 min activation time. The max. NCCs adsorption capacity obtained was 19.49 mg/g. Furthermore, from the thermodynamic analysis, a ∆G0 as low as −24.6 kJ/mol showed that the adsorption process is extremely spontaneous, implicating excellent applicability at real industrial level. Up to 99.85% of non-reacted Cr+3 from MOF synthesis was perfectly recovered by precipitation with ammonia solution. Analysis of the mechanical stirring and static hydrothermal synthesis of MIL-101 Cr did not yield significant difference on the adsorption conditions, which represents an excellent energetically economic process.