Optimization of the oxidative dehydrogenation of ethane to ethylene over NiO-SnO2 catalysts in an industrial-scale packed-bed reactor

Nowadays, the development of new technologies for the manufacturing of key building blocks in the petrochemical sector, is becoming a priority. The well-known side effects that the growing worldwide energy demand has on the planet, is one of the main motivations. When it comes to olefins, ethylene is one of the most requested compounds in the world due to its versatility in the production of high added-value products. Although steam cracking is currently the dominant technology for the industrial production of light olefins, its disadvantages and limitations are vast, e.g. high endothermicity, low selectivity, thermodynamic limitations, coke formation, etc. This scenario has encouraged the study of alternative processes. The purpose of this document is to study the oxidative dehydrogenation of ethane (ODH-C2) in a multi-tubular packed-bed catalytic reactor in order to determine the optimum operating conditions for the production of ethylene. At that scope, the performance of a nickel-based catalyst (NiO-SnO2) is evaluated, aiming to determine its potential for the production of ethylene at industrial-scale. The work presented in this document can be divided into two main sections. First, a reactor-level analysis involves a multi-objective optimization in which important operating parameters are tested. On this regard, a pseudo-heterogeneous reactor model is numerically solved in order to obtain a detailed two-dimensional description of the reactor performance, in terms of ethylene selectivity and final conversion of the reactants. Due to the mathematical complexity involved in the pseudo-heterogeneous formalism, a multi-objective optimization would be remarkably expensive in terms of computational resources. Therefore, a novel model is proposed through a design of experiments (DoE), in which a set of algebraic multi-parametric equations are developed by the response surface methodology (RSM) approach. The global statistical significance of the model is evaluated through a series of ANOVA tests, where the estimation of the regression coefficients, has been conducted through the least square method. In addition, the statistical significance of each individual parameter is calculated by the t test. Once the accuracy of the model is verified, the goal is to analyze the full spectrum of the independent variables and their respective interactions; therefore, identifying promising configurations to maximize the reactor performance. The second section of this work involves the implementation of the model in ASPEN Plus®, with the aim of establishing a complete modelling framework of the case-study. At that scope, the catalytic reactor is modelized via an USER2 block. It follows the incorporation of additional processes, aiming to improve the overall energy integration of the simulation framework, and to simulate key processes for the production of polymer-grade ethylene, i.e. CO2 absorption with amine solutions and cryogenic distillation. The resulting system is further optimized aiming to achieve olefins commercial standards by minimizing both, product losses and energy requirements. Finally, the overall ODH-C2 process is compared with the dominant technology for worldwide ethylene production. On this matter, important parameters of sustainability are considered (i.e. energy consumption and CO2 emissions) in order to evaluate the feasibility of a gradual technological innovation within the petrochemical sector.