DISEÑO DE UNA TORRE DE SEPARACIÓN DE GASES UTILIZANDO MEMBRANAS DE REDES METAL ORGÁNICAS

Abstract

In the petrochemical industry, there has always been a great interest in the separation of mixtures derived from petroleum compounds, for which separation operations have been used, such as fraction distillation whose equipment and operation are usually commercially expensive and complicated processes. This due to the small differences in the volatility of the compounds present in these azeotropic mixtures. For this reason, since the last decade, research has been carried out in order to propose alternative separation processes based not only on the boiling points of the components of these mixtures, but also on their physical characteristics which allow their easy and more efficient separation, such as: its molecular diameter. This research work aims to design a gas separation tower based on a membrane system of well-structured, ordered, integrated MOFs with the ability to separate the components of a binary mixture by passing through it. Among the existing variety of MOFs, ZIF-8 (Zeolitic Imidazolate Framework-8) is one of the most studied so far, due to its great chemical, thermal stability and its strong covalent bonds, which make it a great alternative for the separation of hydrocarbons. Based on the foregoing, the synthesis of ZIF-8 membranes supported on 𝛼−𝐴𝑙2𝑂3 with disk-type and tubular geometries was initially carried out using the solvothermal method 1) in-situ and 2) with previous modification of the support surface. Subsequently, the membranes were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM), for the analysis of the crystalline phase and the morphology of the MOF, respectively. With the results obtained, it was concluded that the synthesis of membranes of ZIF-8 with previous modification of the support surface, promotes the nucleation and crystal growth in a more uniform way, avoiding empty spaces in the membrane, which would cause a reduction in the selectivity of this in the separation of gases. VII Next, the test were carried out on the permeation equipment with the proposed gases –𝐶𝑂2, 𝐻2 y 𝑁2–, with which the permeance data for the three gases were obtained, by means of the Time Lag Method. Consequently, these values were used to determine the ideal separation factor (selectivity) for the three possible binary mixtures, these being up to 4.35 in the 𝐻2/𝑁2 system. Taking into account the permeation values for the test gases and the normal operating conditions of the permeation equipment of the Membrane Laboratory of the Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, it was possible to calculate the necessary permeation area for a module of gas separation, by means of the molar balance of the perfect mixture model proposed in the literature. Based on the previous design calculations, it was possible to propose a cascade operation of a gaseous binary mixture separation tower in three cross-flow modules based on tubular membranes, which achieves a high selectivity due to the pore size of the MOF used, favoring the separation of the compounds present in the proposed binary mixtures. This becomes a good proposal to carry out studies for its possible scaling at an industrial level.