Modeling and experimental analysis of CO2 methanation reaction using Ni/CeO2 monolithic catalyst

In this study, the effect of the cell density of monolithic catalysts was investigated and further mathematically modeled on cordierite supports used in CO2 methanation. Commercial cordierite monoliths with 200, 400, and 500 cpsi cell densities were coated by immersion into an ethanolic suspension of Ni/CeO2 active phase. SEM–EDS analysis confirmed that, owing to the low porosity of cordierite (surface area < 1 m2 g−1), the Ni/CeO2 diffusion into the walls was limited, especially in the case of low and intermediate cell density monoliths; thus, active phase was predominantly loaded onto the channels’ external surface. Nevertheless, despite the larger exposed surface area in the monolith with high cell density, which would allow for better distribution and accessibility of Ni/CeO2, its higher macro-pore volume resulted in some introduction of the active phase into the walls. As a result, the catalytic evaluation showed that it was more influenced by increments in volumetric flow rates. The low cell density monolith displayed diffusional control at flow rates below 500 mL min−1. In contrast, intermediate and high cell density monoliths presented this behavior up to 300 mL min−1. These findings suggest that the interaction reactants-catalyst is considerably more affected by a forced non-uniform flow when increasing the injection rate. This condition reduced the transport of reactants and products within the catalyst channels and, in turn, increased the minimum temperature required for the reaction. Moreover, a slight diminution of selectivity to CH4 was observed and ascribed to the possible formation of hot spots that activate the reverse water–gas shift reaction. Finally, a mathematical model based on fundamental momentum and mass transfer equations coupled with the kinetics of CO2 methanation was successfully derived and solved to analyze the fluid dynamics of the monolithic support. The results showed a radial profile with maximum fluid velocity located at the center of the channel. A reactive zone close to the inlet was obtained, and maximum methane production (4.5 mol m−3) throughout the monolith was attained at 350 °C. Then, linear streamlines of the chemical species were developed along the channel.Funding for open access publishing: Universidad de Granada/CBUA. This work was supported by the Spanish project PID2021-127803OB-I00 funded by MCIN/AEI/ https://doi.org/10.13039/501100011033/ and by “ERDF A way of making Europe.” A. Parra-Marfil has received research support from CONACYT through the PhD grant 818974, E. Bailón-García is grateful to MICINN for her postdoctoral fellowship (RYC2020-029301-I), and A. Bueno-López thanks the financial support of Generalitat Valenciana (Projects CIPROM/2021/74 and MFA/2022/036) and the EU Next Generation funding

Auto-Pressurized Multi-Stage Tesla-Valve Type Microreactors in Carbon Monoliths Obtained Through 3D Printing: Impact of Design on Fluid Dynamics and Catalytic Activity

The present research exploits an innovative methodology for producing auto-pressurized carbon microreactors with a precise and controlled structure analyzing the influence of their design on the fluid dynamics and their catalytic performance. Carbon monoliths with Tesla-valve shape channels (Tesla, T, and modified Tesla, Tm) are synthesized through the combination of 3D printing and sol–gel process and further probed as Ni/CeO2 supports on CO2 methanation. The experimental results and mathematical modeling corroborated the improved performance obtained through the complex design compared to a conventional one. In addition to chaotic fluid flow induced by the deviation in flow direction, which improves the reagents-active phase interaction, local pressure increases due to convergence of flows may enhance the Sabatier reaction according to Le Châtelier's principle. Conversely to straight channels, T and Tm are not affected by flow rate and presented chemical control. Tesla-valve with curved angle (Tm) improved the mass transfer, achieving higher conversion and ≈30% reaction rate increase regarding right angle (T). Thus, this auto-pressurized multi-stage Tesla-valve monolith opens the gate to design specific and advanced functional materials for multitude chemical reactions where not only the reactant-active phase contact can be maximized but also the reaction conditions can be controlled to maximize the reaction kinetics.This research had been supported by the Spanish project PID2021-127803OB-I00 funded by MCIN/AEI/ 10.13039/501100011033/ and by “ERDF A way of making Europe”. Authors also thanks the “Unidad de Excelencia Química Aplicada a Biomedicina y Medioambiente” of the University of Granada (UEQ – UGR) for its technical assistance. A. Parra-Marfil appreciates the financial support provided by CONAHCYT through the PhD grant 818974. E. Bailón-García was grateful to MICINN for her postdoctoral fellowship (RYC2020-029301-I). A. Bueno López thanks the financial support of Generalitat Valenciana (Project CIPROM/2021/74)

Simulador para un yacimiento de gas basado en una solución numérica explícita

En este trabajo se presenta las ecuaciones fundamentales para desarrollar un simulador de yacimiento de gas acoplado a un pozo productor. El simulador se construye utilizando la ecuación gobernante para el pozo en estado estacionario, la cual está acoplada a la ecuación de flujo del yacimiento escrita en forma explícita. La ecuación del pozo se resuelve numéricamente utilizando un esquema de diferencias finitas hacia adelante, mientras que se usa un esquema iterativo para la ecuación explícita del yacimiento con el fin de encontrar la presión en cada bloque numérico a cada paso de tiempo. El simulador depende del tamaño del paso de tiempo para obtener soluciones numéricas estables y consistentes, por lo que el número de bloques para discretizar el yacimiento es reducido. A pesar de esta restricción, el simulador es de utilidad para estimar reservas y el influjo al pozo, realizar la interpretación de pruebas de presión y análisis nodal, etc. El simulador se aplicó en un caso base, donde se determinó las presiones a lo largo del pozo, en fondo de pozo, y en el yacimiento

Customizable Heterogeneous Catalysts: Nonchanneled Advanced Monolithic Supports Manufactured by 3D-Printing for Improved Active Phase Coating Performance

Three-dimensional (3D)-printed catalysts are being increasingly studied; however, most of these studies focus on the obtention of catalytically active monoliths, and thus traditional channeled monolithic catalysts are usually obtained and tested, losing sight of the advantages that 3D-printing could entail. This work goes one step further, and an advanced monolith with specifically designed geometry has been obtained, taking advantage of the versatility provided by 3D-printing. As a proof of concept, nonchanneled advanced monolithic (NCM) support, composed of several transversal discs containing deposits for active phase deposition and slits through which the gas circulates, was obtained and tested in the CO-PrOx reaction. The results evidenced that the NCM support showed superior catalytic performance compared to conventional channeled monoliths (CMs). The region of temperature in which the active phase can work under chemical control, and thus in a more efficient way, is increased by 31% in NCM compared to the powdered or the CM sample. Turbulence occurs inside the fluid path through the NCM, which enhances the mass transfer of reagents and products toward and from the active sites to the fluid bulk favoring the chemical reaction rate. The nonchanneled monolith also improved heat dispersion by the tortuous paths, reducing the local temperature at the active site. Thus, the way in which reactants and products are transported inside the monoliths plays a crucial role, and this is affected by the inner geometry of the monoliths.The authors are grateful for the financial support of the Spanish Ministry of Economy and Competitiveness (Project CTQ2015-67597-C2-2-R), The University of Alicante (Project GRE18-01A), Generalitat Valenciana (Project PROMETEO/2018/076, Ph.D. grant GRISOLIAP/2017/177, and contract APOSTD/2019/030), Junta de Andalucía (Project P18-RTJ-2974), and the UE (FEDER funding)

Mathematical Modeling of Preferential CO Oxidation Reactions under Advection–Diffusion Conditions in a 3D-Printed Reactive Monolith

In this study, the preferential CO oxidation (CO-PROX) reaction is simulated under advection–diffusion conditions in a CuO/CeO2 catalyst-supported monolith built by 3D-printing. The simulation incorporates the mass balances in the bulk of the fluid, the momentum balance, and the heterogeneous chemical reactions. In the monolith constricted channels, the fluid velocity is 80% larger than in the wider channels. Three reactive regimes are identified: the CO oxidation-dominated regime governing up to 85 °C and the early and late transition regimes where the H2 oxidation eventually increases. Up to 175 °C, a H2 oxidation-dominated reactive regime was not identified. The simulation accurately predicts experimental results of CO conversion and selectivity in the range from 25 to 175 °C. A sensitivity analysis demonstrates that the composition of gas mixture fed significantly affects the ratio of reaction rates and, consequently, the CO conversion and CO selectivity; meanwhile, the rate of gas injection yields moderate changes in reactivity

Empagliflozin in Patients with Chronic Kidney Disease

Background The effects of empagliflozin in patients with chronic kidney disease who are at risk for disease progression are not well understood. The EMPA-KIDNEY trial was designed to assess the effects of treatment with empagliflozin in a broad range of such patients. Methods We enrolled patients with chronic kidney disease who had an estimated glomerular filtration rate (eGFR) of at least 20 but less than 45 ml per minute per 1.73 m(2) of body-surface area, or who had an eGFR of at least 45 but less than 90 ml per minute per 1.73 m(2) with a urinary albumin-to-creatinine ratio (with albumin measured in milligrams and creatinine measured in grams) of at least 200. Patients were randomly assigned to receive empagliflozin (10 mg once daily) or matching placebo. The primary outcome was a composite of progression of kidney disease (defined as end-stage kidney disease, a sustained decrease in eGFR to &lt; 10 ml per minute per 1.73 m(2), a sustained decrease in eGFR of &amp; GE;40% from baseline, or death from renal causes) or death from cardiovascular causes. Results A total of 6609 patients underwent randomization. During a median of 2.0 years of follow-up, progression of kidney disease or death from cardiovascular causes occurred in 432 of 3304 patients (13.1%) in the empagliflozin group and in 558 of 3305 patients (16.9%) in the placebo group (hazard ratio, 0.72; 95% confidence interval [CI], 0.64 to 0.82; P &lt; 0.001). Results were consistent among patients with or without diabetes and across subgroups defined according to eGFR ranges. The rate of hospitalization from any cause was lower in the empagliflozin group than in the placebo group (hazard ratio, 0.86; 95% CI, 0.78 to 0.95; P=0.003), but there were no significant between-group differences with respect to the composite outcome of hospitalization for heart failure or death from cardiovascular causes (which occurred in 4.0% in the empagliflozin group and 4.6% in the placebo group) or death from any cause (in 4.5% and 5.1%, respectively). The rates of serious adverse events were similar in the two groups. Conclusions Among a wide range of patients with chronic kidney disease who were at risk for disease progression, empagliflozin therapy led to a lower risk of progression of kidney disease or death from cardiovascular causes than placebo

Doping Liquid Argon with Xenon in ProtoDUNE Single-Phase: Effects on Scintillation Light

Doping of liquid argon TPCs (LArTPCs) with a small concentration of xenon is a technique for light-shifting and facilitates the detection of the liquid argon scintillation light. In this paper, we present the results of the first doping test ever performed in a kiloton-scale LArTPC. From February to May 2020, we carried out this special run in the single-phase DUNE Far Detector prototype (ProtoDUNE-SP) at CERN, featuring 770 t of total liquid argon mass with 410 t of fiducial mass. The goal of the run was to measure the light and charge response of the detector to the addition of xenon, up to a concentration of 18.8 ppm. The main purpose was to test the possibility for reduction of non-uniformities in light collection, caused by deployment of photon detectors only within the anode planes. Light collection was analysed as a function of the xenon concentration, by using the pre-existing photon detection system (PDS) of ProtoDUNE-SP and an additional smaller set-up installed specifically for this run. In this paper we first summarize our current understanding of the argon-xenon energy transfer process and the impact of the presence of nitrogen in argon with and without xenon dopant. We then describe the key elements of ProtoDUNE-SP and the injection method deployed. Two dedicated photon detectors were able to collect the light produced by xenon and the total light. The ratio of these components was measured to be about 0.65 as 18.8 ppm of xenon were injected. We performed studies of the collection efficiency as a function of the distance between tracks and light detectors, demonstrating enhanced uniformity of response for the anode-mounted PDS. We also show that xenon doping can substantially recover light losses due to contamination of the liquid argon by nitrogen