Sunlight-assisted hydrogenation of CO2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites

[EN] The hydrogenation of CO2 into hydrocarbons promoted by the action of sunlight has been studied on Co nanoparticles covered by thin carbon layers. In particular, nearly 100% selectivity to hydrocarbons is obtained with increased selectivities towards C2 + hydrocarbons and alcohols (mainly ethanol) when using nanostructured materials comprising metallic cobalt nanoparticles, carbon layers, and sodium as promoter (NaCo@C). In the contrary, larger amount of CH4 and lower selectivity to C2 + hydrocarbons and alcohols were obtained in the conventional thermal catalytic process. When using Co@C nanoparticles in the absence of Na or bare Co3O4 as catalyst, methane is essentially the main product (selectivity > 96%). Control experiments in the presence of methanol as a hole scavenger suggest the role of light in generating charges by photon absorption as promoting factor. The reaction mechanism for photoassisted CO2 hydrogenation on the Co-based catalysts was investigated by near ambient-pressure X-ray photoelectron (AP-XPS) and in situ Raman spectroscopies, which provided information on the role of light and Na promoter in the modulation of product distribution for CO2 hydrogenation. Spectroscopic studies suggested that surface CO2 dissociation to CO, the stabilization of CO adsorbed on the surface of Na-Co@C catalyst and the easy desorption of reaction products is a key step for photothermal CO2 hydrogenation to ethanol and C2 + hydrocarbons.L.L. thanks ITQ for providing a contract. A.V.P. thanks the Spanish Government (Agencia Estatal de Investigacion) and the European Union (European Regional Development Fund) for a grant for young researchers (CTQ2015-74138-JIN, AEI/FEDER/UE). J.C. thanks the Spanish Government-MINECO for a "Severo Ochoa" grant (BES-2015-075748). The AP-XPS experiments were performed at NAPP endstation of CIRCE beamline at ALBA Synchrotron with the collaboration of ALBA staff. The authors also thank the Microscopy Service of UPV for kind help on FESEM, TEM and STEM measurements. Financial supports from the Spanish Government-MINECO through "Severo Ochoa" (SEV-2016-0683) program are also gratefully acknowledged.Liu, L.; Puga, AV.; Cored-Bandrés, J.; Concepción Heydorn, P.; Pérez-Dieste, V.; García Gómez, H.; Corma Canós, A. (2018). Sunlight-assisted hydrogenation of CO2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites. Applied Catalysis B Environmental. 235:186-196. https://doi.org/10.1016/j.apcatb.2018.04.060S18619623

FAT1 mutations cause a glomerulotubular nephropathy

Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease (CKD). Here we show that recessive mutations in FAT1 cause a distinct renal disease entity in four families with a combination of SRNS, tubular ectasia, haematuria and facultative neurological involvement. Loss of FAT1 results in decreased cell adhesion and migration in fibroblasts and podocytes and the decreased migration is partially reversed by a RAC1/CDC42 activator. Podocyte-specific deletion of Fat1 in mice induces abnormal glomerular filtration barrier development, leading to podocyte foot process effacement. Knockdown of Fat1 in renal tubular cells reduces migration, decreases active RAC1 and CDC42, and induces defects in lumen formation. Knockdown of fat1 in zebrafish causes pronephric cysts, which is partially rescued by RAC1/CDC42 activators, confirming a role of the two small GTPases in the pathogenesis. These findings provide new insights into the pathogenesis of SRNS and tubulopathy, linking FAT1 and RAC1/CDC42 to podocyte and tubular cell function

Modélisation des phénomènes de désactivation des catalyseurs à base de cobalt utilisés dans différent réacteurs de synthèse Fischer-Tropsch

La désactivation reste un enjeu important lors de la synthèse Fischer-Tropsch, car il limite la vie des catalyseurs, ainsi que leurs productivités catalytiques. Elle peut être liée à certains mécanismes selon la littérature. Le frittage a été proposé comme la source principale de désactivation initiale, et avec le cokage comme phénomène responsable de la désactivation à long-terme dans ce travail. Le but de cette thèse est de développer les modèles mécanistiques capables de prédire le changement d’activité catalytique des catalyseurs FT à base de cobalt avec le temps. Dans la première étape, le changement des propriétés physico-chimiques des particules avec le temps est considéré. Un modèle de frittage est développé, qui inclut l’effet d’accélération de l’eau par formation d’une couche d’oxyde de cobalt à la surface. Ce mécanisme nous permet de lier l’agglomération des particules à certaines conditions opératoires, notamment le rapport molaire de H2O/H2. Nous avons aussi développé un mécanisme pour l’empoisonnement des sites catalytiques par dépôt de carbone pour la désactivation à long-terme. Ce mécanisme permet d’évaluer le changement de fraction des sites libres avec le temps, ainsi que les fractions molaires de CO, H2, et H2O.Ces deux modèles microscopiques sont ensuite intégrés dans les modèles des réacteurs à lit fixe et slurry pour coupler les propriétés des catalyseurs et l’activité catalytique. L’effet des conditions opératoires sur la taille des cristallites, la fraction des sites actifs et la conversion sont considérés. Les modèles sont ensuite employés dans les réacteurs de laboratoire pour s’accorder avec les résultats expérimentaux.Catalyst deactivation remains a major challenge in Fischer-Tropsch synthesis; as it reduces the catalyst lifetime as well as its productivity. Deactivation can be attributed to certain mechanisms according to the literature. Sintering is proposed in this work to be responsible for the initial deactivation whereas coking is suggested to be the main cause of long-term deactivation. The final objective of this thesis is to develop the mechanistic models which could predict the extent of catalyst deactivation with time. In the first step, the change in the catalyst physico-chemical properties with time on stream is considered. A three-step sintering model is proposed which involves the effect of water acceleration through the formation of surface cobalt oxide layer. This mechanism allows correlating the crystallites growth with certain operating conditions especially the H2O/H2 molar ratio inside the reactor. We have also developed a mechanism for the active site poisoning by carbon deposition for the long-term deactivation. This mechanism helps to evaluate the change in the active sites coverage with time as well the CO, H2, and H2O mole fractions. The two microscopic models are then integrated in the reactor models in order to correlate the change in the catalytic activity with the catalyst properties. We have developed the models dedicated to fixed bed and slurry reactors. The effect of operating conditions on the crystallite size, active sites fraction, and conversion is considered by the simulations. The models are then employed in the laboratory scale reactors to fit the experimental data and to optimize the deactivation constants

Analysis of post-translational modifications of Fat1 cadherin

Research Doctorate - Doctor of Philoshphy (PhD)First identified in Drosophila as a tumour-suppressor gene, Fat cadherin (Ft) and the closely related Fat2 (Ft2) have been identified as giant members of the cadherin superfamily. Ft engages the Hippo signalling pathway during development and both receptors have been shown to function in different aspects of cell polarity and migration. There are four vertebrate homologues, Fat1-Fat4, all closely-related in structure to Drosophila ft and ft2. Over the past decade knock-out mouse studies, genetic manipulation and large sequencing projects have aided our understanding of the function of vertebrate Fat cadherins in tissue development and disease. The majority of studies of this family have focused on Fat1, with evidence now showing it can bind to ENA/VASP, β-catenin and Atrophin proteins to influence cell polarity and motility; Homer1 and 3 proteins to regulate actin accumulation in neuronal synapses; and Scribble to influence the Hippo signalling pathway. Fat2 and Fat3 can regulate cell migration in a tissue specific manner and Fat4 appears to influence both planar cell polarity and Hippo signalling recapitulating the activity of Drosophila Ft. Knowledge about the exact downstream signalling pathways activated by each family member remains in its infancy, but it is becoming clearer that each may have tissue specific and redundant roles in development. Importantly there is also evidence building to suggest that Fat cadherins may be lost or gained in certain cancers. This thesis represents the first in-depth biochemical investigation of human FAT1 cadherin, particularly its comparative expression in normal versus cancer cells. The first chapter studied the expression profile of all FAT cadherins in a panel of 20 cultured melanoma cells where all melanoma cell lines variably, but universally express FAT1 at the mRNA level and less commonly Fat2, Fat3 and Fat4. Both normal melanocytes and keratinocytes also express comparable FAT1 mRNA levels relative to melanoma cells. Analysis of the protein processing of FAT1 in keratinocytes revealed that human FAT1 was site-1 (S1) cleaved into a non-covalent heterodimer before achieving cell surface expression. A similar processing event had been reported in Drosophila Ft indicating that this was an evolutionary conserved mechanism. The use of inhibitors also established such cleavage is catalysed by a member of the proprotein convertase family, likely furin. However, in melanoma cells the non-cleaved pro-form of FAT1 was also expressed on the cell surface together with the S1-cleaved heterodimer. The appearance of both processed and non-processed forms of FAT1 on the cell surface demarked two possible biosynthetic pathways. Moreover FAT1 processing in melanoma cells generated a potentially functional proteolytic product in melanoma cells: a persistent 65kDa membrane-bound cytoplasmic fragment no longer in association with the extracellular fragment. Localisation studies of FAT1 both in vitro and in vivo showed melanoma cells display high levels of cytosolic FAT1 protein whereas keratinocytes, despite comparable FAT1 expression levels, exhibited mainly cell-cell junctional staining. The mechanisms deriving the unprocessed FAT1 and the p65 product were then further investigated to uncover the potential biological activities of these cancer specific products. The second chapter investigated the mechanisms behind dual processing of FAT1 in cancer cells including the mechanism of FAT1 heterodimerisation. Generally the S1 processing step and accompanying receptor heterodimerisation is thought to occur constitutively but the functional significance of this process in transmembrane receptors has been unclear and controversial. Using siRNA against a number of different proprotein convertases it was established that the S1-cleavage of FAT1 is catalysed only by furin. Mass spectrographic analysis identified the precise location of the cleavage site occurring between the laminin G and the second EGF domain on the extracellular domain of FAT1, consistent with an evolutionarily conserved region found in Drosophila DE-cadherin known to be involved in heterodimerisation. Utilising furin overexpressing studies in melanoma together with the furin deficient LoVo cells, indicated the likely reason behind partial heterodimerisation of FAT1 was deficiency in furin activity. Moreover, it was also determined from these experiments that only the heterodimer form of FAT1 was subject to a second cleavage step (S2) and subsequent release of the extracellular domain. This indicated that S1-processing was a prerequisite for FAT1 ectodomain shedding and established a general biological precedent with implications for the shedding of other transmembrane receptors that undergo heterodimerisation. Part of this work also established an ELISA assay against the extracellular domain of FAT1 that may find utility to investigate shed FAT1 as a potential new cancer biomarker in blood. Previous studies in Drosophila had shown that the interaction between Ft and its ligand, the large cadherin Dachsous (Ds) is regulated through ectodomain phosphorylation mediated by the atypical kinase, Four-jointed (Fj). The third chapter investigated the process of ectodomain phosphorylation of FAT1 on the basis that this important regulatory mechanism may be conserved. Using the known Fj-phosphorylation motif, in silico analyses were undertaken to determine if phosphorylation sites were conserved in human FAT cadherins. This search identified nine potential sites in FAT1 as potential substrates for the sole homologue of Fj in humans, FJX1. Using general antibodies against phospho-serine and phospho-threonine it was revealed that the extracellular domain of FAT1 was multiply phosphorylated on these residues. However, silencing FJX1 using either siRNA or stable shRNA transduction did not indicate any role for FJX1 in FAT1 ectodomain phosphorylation. Nevertheless, given that many regulatory processes are conserved between Drosophila and vertebrate Fat cadherins, the establishment that ectodomain phosphorylation occurs in FAT1 provides the strong likelihood that this process will be important in regulating the interaction of FAT1 with its presently unknown ligand. This knowledge may therefore provide an essential starting point for identifying the ligand of FAT1 and in helping to understand how their interaction is regulated between cells

Combined pinch and exergy analysis of an ethylene oxide production process to boost energy efficiency toward environmental sustainability

Ethylene oxide production process is one of the highest energy consumers in chemical industry, and therefore even a slight improvement in its overall efficiency can have a significant impact on the sustainability of the process. Efficiency improvement can be carried out using the exergy-aided pinch analysis outlined in this paper. The overall exergy loss distribution in different unit operations of an ethylene oxide process was first evaluated and mapped out in the form of "visualized exergetic process flowsheet". An initial analysis of the four main functional blocks of the process showed that the exothermic reaction block contained the largest exergy loss (6043 and 428 kJ/kg of internal and external losses, respectively) which can be reduced by isothermal mixing, as well as increasing reaction temperature and reduction in pressure drop. The absorption block was also estimated to have the second highest contribution with total exergy losses of 3640 kJ/kg which were mainly due to the cooling column. These losses were then recommended to be reduced by improvements in the concentration and temperature gradients along the tower. Following the block-wise analysis, exergy analysis was then carried out for individual unit operations in each block to pinpoint the main sources of thermal exergetic inefficiency. Thermal solutions to reduce losses were also proposed in accordance with the identified sources of inefficiency, leading to a comprehensive list of cold and hot process streams that could be introduced to reduce losses. Finally, pinch analysis was brought into action to estimate the minimum energy requirements, to select utilities, and to design heat exchanger network. Thus, the methodology used in this work took advantage of both exergy and pinch analyses. The combined thermal-exergy-based pinch approach helped to set energy targets so that all the thermal possible solutions supported by exergy analysis were considered, preventing exclusion of any hot or cold process stream with high potential for heat integration during pinch analysis. Results indicated that the minimum cold utility requirement could be reduced from 601.64 MW (obtained via conventional pinch analysis) to 577.82 MW through screening of streams by the combined methodology

Exergy aided pinch analysis to enhance energy integration towards environmental sustainability in a chlorine-caustic soda production process

This paper presents a case study on the improvement of energy integration in a chlorine-caustic soda process based on the main sources of thermal exergy losses. Exergy analysis has been performed to pinpoint the causes of thermal exergetic inefficiency. Thermal solutions have been then developed, leading to a comprehensive list of cold and hot process streams. Finally, pinch analysis has been brought into action to estimate the minimum energy requirement, to select utilities and to design heat exchanger network. As a result, the combined methodology followed here takes advantages of both exergy and pinch analyses. This bilateral thermal-exergy-based pinch approach helps to set energy targets in a way that all the possible thermal solutions supported by exergy analysis are considered, including all hot and cold process streams that have a high potential for heat integration during pinch analysis. To demonstrate this, energy targeting through conventional pinch analysis leads to 7.74 MW and 13.00 MW of hot and cold utility energy demand, respectively. These figures change to 8.17 MW and 0.40 MW of hot and cold utility energy demand, respectively through streams screening by the combined methodology. (C) 2017 Elsevier Ltd. All rights reserved

Diagnosis of an alternative ammonia process technology to reduce exergy losses

Ammonia production through more efficient technologies can be achieved using exergy analysis. Ammonia production is one of the most important but also one of most energy consuming processes in the chemical industry. Based on a panel of solutions previously developed, this study helps to identify potential areas of improvement using an exergy analysis that covers all aspects of conventional ammonia synthesis and separation. The total internal and external exergy losses are calculated as 3,152 and 6,364 kJ/kg, respectively. The process is then divided into five main functional blocks based on their exergy losses. The reforming block contains the largest exergy loss (3,098 kJ/kg) and thus the largest potential for improvement including preheating cold feed through an economizer, developing technology towards isobaric mixing, and pressure drop reduction in the secondary reformer as the main contributors to the irreversibility (1,302 kJ/kg) in this block. The second largest exergy loss resides in the ammonia synthesis block (3,075 kJ/kg) where solutions such as reduced temperature rise across the compressor, proper compressor isolation, reducing undesired components such as argon in the reactor feed, and using lower temperatures for reactor outlet streams, are proposed to decrease the exergy losses. Throttling process in the syngas separator is the key contributing mechanism for the irreversibility (1,635 kJ/kg exergy losses) in the gas upgrading block. The exergy losses in the residual ammonia removal block (833 kJ/kg exergy losses) are mainly due to the stripper and the absorber column where a modified column design might be helpful. The highest exergy loss in the preheating block belongs to the compressors (518 kJ/kg exergy losses) where a lower inlet temperature and better system isolation could help to reduce losses

Cleaner production of purified terephthalic and isophthalic acids through exergy analysis

The purified terephthalic and isophthalic acids production process was improved through the exergy analysis approach demonstrated in this work. The overall exergy losses and low-exergy-efficient units were first identified and presented using visualised exergetic flowsheets. Recommendations were then proposed to reduce losses based on the main cause(s) of irreversibility. Three out of the five constituent blocks contained the highest exergy losses. The oxidation block was the main player where it was suggested that using several reactors in series with gradually decreasing temperatures could lower losses. The product refining block had the second-largest irreversibilities, where improving coolers' performances were recommended. The crude terephthalic acid crystallisation block was the third-largest loss producer, where isothermal and isobaric mixing in the solvent dehydrator was suggested to reduce losses. The approach used in this work can be adapted to improve the energy footprint of other chemical processes

Exergy analysis as a scoping tool for cleaner production of chemicals:a case study of an ethylene production process

High energy consumption is one of the main challenges of the chemical industry. The energy footprint of most processes can, however, diminish through the solutions presented in the current paper, leading to cleaner ways of producing chemicals. Ethylene production process is selected as a case study to demonstrate the approach as it is one of the most energy consuming processes in the chemical industry. The study involves an exergetic diagnosis and does not only find the low-exergy-efficient unit operations, but also proposes tools to improve these units based on their key sources of irreversibility. For the ethylene production process, this is conducted by first splitting the flowsheet into four main functional blocks (namely cracking, compression, refrigeration, and separation and purification) according to their exergy losses. This results in identifying the cracking block as the most inefficient block with more than 45% of total exergy losses and thus the first block to be improved so that overall losses reduce (examples of which include increasing the number of furnace tubes while reducing their lengths). Although the compression block is-found to have the lowest contribution to internal exergy losses, the inefficient unit operations such as the water cooler (with an exergy loss of 214 4J/kg) can still be improved through solutions such as system isolation. The refrigeration block is also shown to have the second highest exergy losses with its ethylene and propylene compressors being the main contributors. Solutions are again provided to improve the block performance with specific focus on intercooler design improvement and system isolation. Finally, exergy losses in the purification and separation block are identified to be mainly due to demethanator, deethanator, and ethylene column where modifications in column design might be helpful as concentration and temperature gradients along the towers are the main sources of exergy losses. The approach used in the current study can also be applied to other chemical processes and the findings suggest that even for a well-developed process technology, there is still opportunity for thermodynamically justifiable energy efficiency improvements. Therefore, it is important for process developers to continuously revisit existing processes, in order to ensure lessons learned in one area can be applied to another one. Using a panel of solutions, which has been constructed from a number of previous case studies helps to make this approach more systematic and user-friendly. (C) 2016 Elsevier Ltd. All rights reserved