Kinetic study of methanol dehydration over Zro2 supported-activated carbons

The growing concerns about climate change and energy consumption have been the driving force in seek of alternative fuels such as DME, mainly produced via methanol dehydration over a solid acid catalyst. The use of activated carbons for this aim has been little studied up to date. Only a few studies can be found in the literature, reporting all of them materials with a low thermal stability of the acid surface groups, which results into a fast deactivation of the catalyst. In this work, the preparation of activated carbons via chemical activation with phosphoric acid, their modification with different ZrO2 loads, and their application as methanol dehydration catalysts have been studied. The catalytic results showed that the best methanol conversion and selectivity towards DME were achieved with the activated carbon prepared with an impregnation mass ratio value (H3PO4 /precursor) of 2 and an activation temperature of 800 ºC, loaded with a 7 % (wt) of ZrO2 . This catalyst exhibits high steady state methanol conversion values even at temperatures as high as 400 ºC (XCH3OH= 80%, 0.1 g·s/μmol, PCH3OH= 0.08 atm in helium), keeping a selectivity to DME higher than 96%. The effect of oxygen in the reaction atmosphere was also analysed. In this sense, an increase of 15 % in the DME yield was obtained when using air instead of helium as reaction atmosphere (350 ºC, 0.1 g·s/μmol, PCH3OH= 0.04 atm). A kinetic study has been carried out on this catalyst in which two mechanisms (Eley Rideal and Langmuir Hinshelwood) for methanol dehydration have been analysed. The models proposed also consider the presence of oxygen in the reaction media.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MECD (FPU13/02413)

Biomass-derived activated carbon catalysts for the direct dimethyl ether synthesis from syngas

The direct DME synthesis from syngas was studied by using activated carbon-based bifunctional catalytic beds. Two kinds of activated carbons, prepared by physical (by CO2 partial gasification) and chemical (with phosphoric acid) activation of olive stones, were used as supports for the preparation of the catalysts. The chemically activated carbon presented a considerable amount of thermally and chemically stable surface phosphorus complexes, which played an important role on the catalytic performance of the prepared catalysts. A Zr-loaded P-containing activated carbon presented a relatively high activity, selectivity and stability for the production of DME from methanol and was used as methanol dehydration catalyst. On the other hand, Cu-Zn was loaded on both P-containing and P-free activated carbon supports for the preparation of methanol synthesis catalysts. The presence of surface-phosphorus on the carbon support resulted in a strong metal-support interaction, hindering the catalytic activity for the hydrogenation of CO to methanol. However, the catalyst that did not contain phosphorus showed noticeable activity for this reaction. The physical mixing of the methanol synthesis and methanol dehydration catalysts resulted in the preparation of carbon-based bifunctional catalytic beds, which performed very efficiently in the direct DME synthesis from syngas in a fixed-bed reactor. Different mass ratios of the individual (metallic and acid) catalysts were studied. An acid/metallic catalyst mass ratio of 2 provided the catalytic bed with enough acid sites to promote methanol dehydration to its maximum extent and make the overall product distribution controlled by the methanol synthesis reaction on the metallic phase.Funding for open access charge: Universidad de Málaga / CBUA. This work was supported by MCIN (PID2022-140844OB-I00 and TED2021-131324B-C21) and European Union “NextGenerationEU”/ PRTR (MCIN/AEI/10.13039/501100011033). J. Palomo acknowledges the assistance of the Spanish Ministry Education for the award of FPU grant (FPU13/02413). M. A. Rodríguez-Cano also acknowledges the assistance of the Spanish Ministry of Sciences Innovation and Universities for the concession of a FPU grant (FPU18/02796)

Biomass derived activated carbon catalysts for the one-step dimethyl ether synthesis from syngas

Se trata de un resumen extendido de una comunicación a congreso internacional.In this work we study the behaviour of a carbon-based catalyst for this one-step synthesis process. Two kinds of activated carbons, prepared by chemical (with H3PO4) and physical (by CO2 partial gasification) activation of olive stones, were used as catalysts support. The main difference between the activated carbons was the presence of chemically stable phosphorus surface groups, mainly in form of C-O-PO3 groups1, on the activated carbon prepared via chemical activation. The addition of Zr to the chemically activated carbon (ACPZr) resulted in the formation of zirconium phosphate species on the carbon surface, which were capable of promoting the selective methanol dehydration to DME. Cu-Zn loading on the chemically activated carbon resulted in strong interactions between the metallic phase and the phosphate surface groups due to the formation Cu phosphate species. The bifunctional catalyst, ACPZrCuZn showed less conversion that the physical mixture. This fact is related with the presence of phosphorus species that avoids the reduction of the metal (copper).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Efficient methanol dehydration to DME and light hydrocarbons by submicrometric ZrO2-ZSM-5 fibrillar catalysts with a shell-like structure

Zeolites are widely used in many applications, such as catalysis and adsorption processes. The use of these materials in a nanometric size would be of great interest for these applications, due to the better performance they could exhibit in terms of avoiding intraparticle mass and heat transfer limitations. However, this small particle size results in high pressure drops in adsorption columns and fixed-bed reactors, making these materials non-applicable directly in the nanometric size. In this work, ZrO2 fibers with a mean diameter of 275 nm and the presence of small well-defined ZSM-5 zeolite aggregates of 550 nm in size around the ZrO2 submicrometric fibers, in the form of a shell-like structure, have been prepared by electrospinning technique, which resulted very active for the synthesis of DME and light olefins via methanol dehydration. The submicrometric fibrillar catalysts, without any further modification, could be easily structured inside a fixed-bed reactor, which worked very efficiently in terms of heat and mass transfer, avoiding, at the same time, the usual pressure drops problems of fixed-bed reactors working with catalyst particles of submicrometric size. Methanol conversion and selectivity to DME and light hydrocarbons could be finely controlled, for a given set reaction conditions, by tuning the zeolite loading in the structured catalyst. Apparent kinetic parameters for the selective methanol dehydration to DME were calculated assuming a reversible second order rate expression and an activation energy of 75 kJ/mol was obtained.RTI2018-097555-B-I00 FPU13/02413 FPU18/0279

Dynamic learning rates for continual unsupervised learning.

The dilemma between stability and plasticity is crucial in machine learning, especially when non-stationary input distributions are considered. This issue can be addressed by continual learning in order to alleviate catastrophic forgetting. This strategy has been previously proposed for supervised and reinforcement learning models. However, little attention has been devoted to unsupervised learning. This work presents a dynamic learning rate framework for unsupervised neural networks that can handle non-stationary distributions. In order for the model to adapt to the input as it changes its characteristics, a varying learning rate that does not merely depend on the training step but on the reconstruction error has been proposed. In the experiments, different configurations for classical competitive neural networks, self-organizing maps and growing neural gas with either per-neuron or per-network dynamic learning rate have been tested. Experimental results on document clustering tasks demonstrate the suitability of the proposal for real-world problems

Carbon-based materials as Catalyst Supports for Fischer–Tropsch Synthesis: a review

The use of carbon-based materials as catalyst supports for Fischer–Tropsch synthesis (FTS) is thoroughly reviewed. The main factors to consider when using a carbonaceous catalyst support for FTS are first discussed. Then, the most relevant and recent literature on the topic from the last 2 decades is reviewed, classifying the different examples according to the carbon structure and shape. Some aspects such as the carbon textural properties, carbon support modification (functionalization and doping), catalyst preparation methods, metal particle size and location, catalyst stability and reducibility, the use of promoters, and the catalyst performance for FTS are summarized and discussed. Finally, the main conclusions, advantages, limitations, and perspectives of using carbon catalyst supports for FTS are outlined

Planificación para la implantación de un Sistema de Gestión de la Calidad en el RAAA 74: Definición de Fases y Responsabilidades

Actualmente todo el mundo sabe de la importancia que posee la calidad en el Ejército de Tierra, sin ella las unidades de fuerza terrestre serían incapaces de ejercer sus cometidos con unas garantías de seguridad y aptitud mínimas. No obstante, dicha función de la calidad debe gestionarse para lograr llegar a su objetivo. Debido a lo expuesto en este proyecto se ha investigado como se implantaría un Sistema de Gestión de la Calidad en la Unidad de Reparaciones III/ 74, San Roque, la cual es encargada de ejercer las funciones logísticas en el Regimiento de Artillería Antiaérea 74 sobre todo lo relacionado del sistema HAWK.Para la realización de este trabajo se va a comenzar dando unas nociones básicas sobre definiciones y principios a día de hoy que plantea la norma ISO 9001:2015 para un SGC; ya que sobre estos se van a desarrollar. Acto seguido se van a describir los objetivos y metodología que se va a seguir en este TFG para su desarrollo; así como el contexto de la unidad donde se ha desarrollado e investigado. Sobre esta última se estudiará además el estado en la actualidad en el que se encuentra respecto a su gestión de la calidad, señalando su respectiva problemática, para así entender mejor su elaboración y en qué aspectos se debe centrar el trabajo a desarrollar.En primer lugar se realizará un estudio sobre los procesos que componen el SGC; esto se compondrá primero de una clasificación de ellos en tipos de procesos, ya que no todos los procesos tienen la misma finalidad dentro del sistema .A continuación, se hará una descripción breve de todos ellos, señalando los elementos de entrada y salida de los que se componen; además se desarrollarán unas fichas técnicas de todos los procesos, en los que se describan todos los ámbitos recalcados en la norma que debe contener un proceso de un SGC. Por último se mostrará como interaccionan dichos procesos en el sistema, señalando los vínculos que existen entre los procesos y sus tipos.Por otro lado, se realizará un procedimiento de implantación del SGC, siendo una de las más importantes partes del presente TFG. Este consistirá en una adaptación al Ciclo Gestor del Tiempo [13], en el cual primeramente se definirán las fases de las que va a consistir dicho procedimiento, proporcionando las tareas y herramientas para su realización. En un segundo lugar se van a proporcionar los recursos de los que se va a disponer para dicha implantación, así como la asignación de estos a las distintas responsabilidades a hacer de cada fase. Acto seguido se estimará la duración de las que se va a componer cada fase y el procedimiento en general; estas duraciones servirán para desarrollar el calendario en el que se va a implantar el SGC, estipulando además la secuenciación que tendrán dichas fases en el calendario. En último lugar, se analizarán los principales riesgos a los que está expuesto dicho procedimiento, proporcionando en su caso medidas para su inmediata respuesta.Por último, se desarrollará unas conclusiones de lo que ha supuesto este proyecto, analizando los puntos claves y la problemática surgida en los distintos apartados que suponen. Además se contará alguna de las líneas futuras y recomendaciones posibles para este trabajo.<br /

A novel continual learning approach for competitive neural networks

Continual learning tries to address the stability-plasticity dilemma to avoid catastrophic forgetting when dealing with non-stationary distributions. Prior works focused on supervised or reinforcement learning, but few works have considered continual learning for unsupervised learning methods. In this paper, a novel approach to provide continual learning for competitive neural networks is proposed. To this end, we have proposed a different learning rate function that can cope with non-stationary distributions by adapting the model to learn continuously. Experimental results performed with different synthetic images that change over time confirm the performance of our proposal.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

CADICA: a new dataset for coronary artery disease detection by using invasive coronary angiography

Coronary artery disease (CAD) remains the leading cause of death globally and invasive coronary angiography (ICA) is considered the gold standard of anatomical imaging evaluation when CAD is suspected. However, risk evaluation based on ICA has several limitations, such as visual assessment of stenosis severity, which has significant interobserver variability. This motivates to development of a lesion classification system that can support specialists in their clinical procedures. Although deep learning classification methods are well-developed in other areas of medical imaging, ICA image classification is still at an early stage. One of the most important reasons is the lack of available and high-quality open-access datasets. In this paper, we reported a new annotated ICA images dataset, CADICA, to provide the research community with a comprehensive and rigorous dataset of coronary angiography consisting of a set of acquired patient videos and associated disease-related metadata. This dataset can be used by clinicians to train their skills in angiographic assessment of CAD severity and by computer scientists to create computer-aided diagnostic systems to help in such assessment. In addition, baseline classification methods are proposed and analyzed, validating the functionality of CADICA and giving the scientific community a starting point to improve CAD detection

Long-term outcome of patients after a single interruption of antiretroviral therapy: a cohort study

Background: To describe the long term outcome of patients who interrupted highly active antiretroviral therapy (HAART) once, identify the variables associated with earlier need to re-start HAART, and the response when therapy was resumed. A retrospective observational cohort of 66 adult patients with HIV-1 infection who interrupted HAART with a CD4+cell count ≥350 cells/μL and undetectable viral load (VL) was performed. The pre-established CD4+ cell count for restarting therapy was 300cells/μL. Cox regression was used to analyse the variables associated with earlier HAART reinitiation. Results: The median follow-up was 209 weeks (range, 64–395). Rates of HIV-related or possible HIV-related events were 0.37 (one case of acute retroviral syndrome) and 1.49 per 100 patient-years, respectively. Two patients died after re-starting therapy and having reached undetectable VL. Three patients suffered a sexually transmitted disease while off therapy. Fifty patients (76%) resumed therapy after a median of 97 weeks (range, 17–267). Age, a nadir of CD4+ 10,000 copies/ml were independent predictors for earlier re-start. The intention-to-treat success rate of the first HAART resumed regimen was 85.4%. There were no differences by regimen used, nor between regimens that were the same as or different from the one that had been interrupted. Conclusions: Our data suggest highly active antiretroviral therapy may be interrupted in selected patients because in these patients, when the HAART is restarted, the viral and clinical response may be achieved