Hydrodesulfurization of 4,6–Dimethyldibenzothiophene on NiMoP/γ–Al2O3 catalyst under reactive distillation conditions in a micro trickle bed reactor: solvent and temperature effect

In this work, the influence of pressure and temperature experimentally applied on reactive distillation (RD) under lower conditions than conventional hydrotreating (HDT) processes, the hydrodesulfurization (HDS) reaction of 4,6–dimethyldibenzothiophene (4,6–DMDBT) molecule and the experimental performance of a down-flow micro trickle bed reactor (micro-TBR) with n–dodecane and decalin were studied. Thermodynamic analyses to evaluate hydrogen solubility in liquid hydrocarbons and evaporation for n–dodecane and decalin as lineal and cyclic representative solvents, respectively, were considered. It was possible to define experimental conditions, producing a small deviation of the plug flow model (PFM) and diminished the gas–liquid (G–L) mass transfer limitation as determined from a reactor model at 2.5 MPa. The axial dispersion model (ADM) and PFM models adjust the experimental data at 2.5 MPa operational pressure and the 4,6–DMDBT conversion obtained was ca. 20–50% using n–dodecane; 1.5 times higher when decalin was using. This behavior was due to the liquid hydrogen fraction of n–dodecane was two times higher than for decalin for all operational pressures. In this sense, the use of n–dodecane as a solvent decreased the mass transfer resistance at the G–L and liquid–solid (L–S) interphases. The internal mass transfer resistance in the G–L interphase not only depends on the diffusivity of the solvent, but it also depends on both, the temperature and hydrogen pressure, finding that the RD conditions with n–dodecane are viable in the treatment of sterically impaired molecules in HDS processes.

Effect of Adding Chelating Ligands on the Catalytic Performance of Rh-Promoted MoS2 in the Hydrodesulfurization of Dibenzothiophene

Hydrodesulfurization (HDS) is a widely used process currently employed in petroleum refineries to eliminate organosulfur compounds in fuels. The current hydrotreating process struggles to remove organosulfur compounds with a steric hindrance due to the electronic nature of the current catalysts employed. In this work, the effects of adding chelating ligands such as ethylenediaminetetraacetic acid (EDTA), citric acid (CA) and acetic acid (AA) to rhodium (Rh) and active molybdenum (Mo) species for dibenzothiophene (DBT) HDS catalytic activity was evaluated. HDS activities followed the order of RhMo/ɣ-Al2O3 (88%) > RhMo-AA/ɣ-Al2O3 (73%) > RhMo-CA/ɣ-Al2O3 (72%) > RhMo-EDTA/ɣ-Al2O3 (68%). The observed trend was attributed to the different chelating ligands with varying electronic properties, thus influencing the metal–support interaction and the favorable reduction of the Mo species. RhMo/ɣ-Al2O3 offered the highest HDS activity due to its (i) lower metal–support interaction energy, as observed from the RhMo/ɣ-Al2O3 band gap of 3.779 eV and the slight shift toward the lower BE of Mo 3d, (ii) increased Mo-O-Mo species (NMo-O-Mo ~1.975) and (iii) better sulfidation of Rh and MoO in RhMo/ɣ-Al2O3 compared to the chelated catalysts. The obtained data provides that HDS catalytic activity was mainly driven by the structural nature of the RhMo-based catalyst, which influences the formation of more active sites that can enhance the HDS activity.

Trimetallic RuxMoNi Catalysts Supported on SBA-15 for the Hydrodesulfurization of Dibenzothiophene

In this work, novel trimetallic catalysts based on transition metal sulphides (Ru, Mo and Ni) supported on SBA-15 were synthesized. Citric acid (CA) was used as chelating agent in order to enhance the dispersion of the active phase and minimize the metal-support interaction. Sulfided catalysts were evaluated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 320 °C and 54.5 atm of total H2 pressure. The effects of different Ru/(Ni + Mo) atomic ratios on the active phase were studied. The catalysts were characterized using Micro-Raman spectroscopy, DRIFTS, XRD, XPS, HR-TEM and SEM techniques. Results have shown that there was a better dispersion of the metallic phases, which improves the physicochemical properties of the catalysts, increasing the catalytic activity. The trimetallic RuxMoNi catalyst with the lowest atomic ratio, have shown superior catalytic activity compared to their higher atomic ratio counterparts. The interaction of the chelating agent improved the catalytic activity, which was superior to that observed for NiMo based catalysts, considered one of the most active hydrotreating catalysts.

Nitrogen Adsorption Compounds in the Presence of Dibenzothiophene on Mesoporous Materials for Obtaining Ultra-Low-Sulfur Diesel

This work presents the adsorption process of nitrogen compounds, namely quinoline (Q), pyridine (Pyr), and indole (In), from liquid fuels such as gasoline and diesel containing dibenzothiophene (DBT) as sulfur-containing molecules. These compounds were adsorbed on mesoporous materials, namely SBA-15 and SBA-16, in calcined form in batch mode using dodecane as a solvent represent to a diesel mixture. The main conclusion of this research is that SBA-15 showed a higher nitrogen adsorption capacity than SBA-16 for all molecules containing nitrogen and sulfur. A comparative study of nitrogen and sulfur adsorption confirms that selective removal of nitrogen compounds from fuels using SBA-15 was better than that of sulfur compounds. Moreover, an increase in the adsorption of Q was found with SBA-15 material compared to SBA-16. To explain this behavior, the solids were characterized using X-ray diffraction (XRD), nitrogen physisorption, and High-Resolution Transmission Electron Microscopy (HRTEM). A pseudo-second-order kinetic model, rather than a first-order one, fitted the nitrogen adsorption data best. Moreover, the Langmuir model was suitable for describing the adsorption of nitrogen compounds from simulated diesel fuel, instead of the Freundlich model, which means that nitrogen compounds are adsorbed in a monolayer.

Numerical Simulation of a Kinetic Cell for in-situ Combustion. A Parametric Study and History Matching Aspects

The in-situ combustion method is an enhanced oil recovery technique based on the injection of air in petroleum reservoirs with the aim to burn a portion of hydrocarbons. This reduces the oil viscosity improving substantially the oil mobility. Simultaneously other phenomena take place as: distillation, segregation, oil upgrading, among others. In this work, a mathematical model to simulate oil combustion for kinetic cell experiments is presented. The model includes four-phases, nine components and four chemical reactions: coke formation, heavy oil fraction combustion, light oil fraction combustion and coke combustion. This formulation is commonly used to simulate in-situ combustion projects at combustion tubes- and petroleum reservoir-scales. The mass and energy balances were formulated leading to one set of highly coupled ordinary differential equations, which was numerically solved. The predictive model capabilities were tested by comparison with lab data, and it was found that CO and CO2 productions, oxygen uptake and cell temperature evolution agree well with experimental results. At one preliminary stage, the parameters fitting experimental results were inferred by individual manipulation until the best results were found. These parameters were perturbed in order to identify those parameters dominating the global dynamic of process. We found that energy activations and the mass density of oil components are the dominant parameters. We suggest that history matching processes must be focused over these parameters, and for this end, the implementation of advanced computational routines to solve multivariable inverse problems is recommended. In this work, we developed two automatic history matching techniques: one process based on Newton’s method and the second one based on evolutionary algorithms. The Newton’s method showed problems to find the minimum error, meanwhile the evolutionary algorithm was able to optimize the dominant parameters, but at the expense of slow convergence.

On the Understanding of the Adsorption of 2-Phenylethanol on Polyurethane-Keratin based Membranes

Polymers and specifically hybrid polymeric membranes have been identified as effective formulations in adsorption processes. Nevertheless, the adsorption mechanisms associated with their thermodynamics and kinetics are not fully understood, particularly when these polymeric membranes are used to adsorb 2-Phenylethanol (2-PE) to intensify its production in a specific bioconversion process. This work was aimed at giving phenomenological insights on the adsorption of 2-PE on a set of novel porous hybrid membranes based on polyurethane and keratin biofiber obtained from chicken feathers. Feathers, considered as a waste by-product of the poultry industry, represent an alternative source of keratin, a biopolymer that can be used to design low-cost materials from natural resources. Two types of hybrid membranes were prepared. i. e. composite and copolymer. Firstly, these materials were characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR) (before and after the adsorption process) and X-Ray (WAXD) analysis. Secondly, these materials, including the reference ones (keratin biofiber and polyurethane), were evaluated during the removal of 2-PE, relating their adsorption capabilities to physiochemical properties elucidated during the characterization. Particularly a composite with 0.1 g of chicken-feather-keratin (C1) presented the highest removal percentage (60.68%), a significant initial adsorption rate (0.2340 mgPE.h−1.gA −1), the maximum adsorption capacity (12.13 mgPE.gA −1) and the best stability and mechanical properties at studied operating conditions. In comparison with results reported in literature, in this composite carbonyl functional groups from polyurethane showed rather major affinity to 2-PE than amino groups from the keratin biofiber. To this end, parameters associated with its industrial application were obtained, namely thermodynamic and kinetic information was obtained from a proper design of experiments and phenomenological models based on adsorption macroscopic fundamentals.