1,721,062 research outputs found
to Formic Acid at an Applicative Scale: Technical and Economic Analysis of Most Promising Routes
Full text linkIn the last decade, the electrochemical conversion of CO 2 to formic acid, FA, using Sn‐based cathodes, was widely investigated. In this work, the technical feasibility and economic viability of this process were evaluated considering the most promising electrochemical routes reported in the literature. Five case studies, based on the utilisation of GDE technologies or high CO 2 pressures, were analysed. The cost for producing FA by the electrochemical route was compared with that of the conventional chemical route. Several scenarios were envisioned finding the target figures of merit, the potential bottlenecks (including low FA concentration, GDE cost and high energy consumption) of each technology and the challenges that need to be faced. It was shown that the performances of these processes are not still adequate from an economic point of view and the improvements that should be achieved were identified. To be suitable for the commercialisation, the process should reach simultaneously high current density, faradaic efficiency and actual FA concentration as well as good stability with time and a limited cost of electrodes. In addition, it was shown that the utilisation of the excess electric energy generated from renewable sources could significantly reduce the costs of the process
Pressurized CO2 Electrochemical Conversion to Formic Acid: From Theoretical Model to Experimental Results
Full text linkTo curb the severely rising levels of carbon dioxide in the atmosphere, new approaches to capture and utilize this greenhouse gas are currently being investigated. In the last few years, many researches have focused on the electrochemical conversion of CO2 to added-value products in aqueous electrolyte solutions. In this backdrop, the pressurized electroreduction of CO2 can be assumed an up-and-coming alternative process for the production of valuable organic chemicals [1-3]. In this work, the process was studied in an undivided cell with tin cathode in order to produce formic acid and develop a theoretical model, predicting the effect of several operative parameters. The model is based on the cathodic conversion of pressurized CO2 to HCOOH and it also accounts for its anodic oxidation.
In particular, the electrochemical reduction of CO2 to formic acid was performed in pressurized filter press cell with a continuous recirculation of electrolytic solution (0.9 L) at a tin cathode (9 cm2) for a long time (charge passed 67’000 C). It was shown that it is possible to scale-up the process by maintaining good results in terms of faradaic efficiency and generating significantly high concentrations of HCOOH (about 0.4 M) [4]. It was also demonstrated that, for pressurized systems, the process is under the mixed kinetic control of mass transfer of CO2 and the reduction of adsorbed CO2 (described by the Langmuir equation), following our proposed reaction mechanism [5].
Moreover, the theoretical model is in good agreement with the experimental results collected and well describes the effect of several operating parameters, including current density, pressure, and the type of reactor used.
1. Ma, S., & Kenis, P. J. (2013). Electrochemical conversion of CO2 to useful chemicals: current status, remaining challenges, and future opportunities. Current Opinion in Chemical Engineering, 2(2), 191-199.
2. Endrődi, B., Bencsik, G., Darvas, F., Jones, R., Rajeshwar, K., & Janáky, C. (2017). Continuous-flow electroreduction of carbon dioxide. Progress in Energy and Combustion Science, 62, 133-154.
3. Dufek, E. J., Lister, T. E., Stone, S. G., & McIlwain, M. E. (2012). Operation of a pressurized system for continuous reduction of CO2. Journal of The Electrochemical Society, 159(9), F514-F517.
4. Proietto, F., Schiavo, B., Galia, A., & Scialdone, O. (2018). Electrochemical conversion of CO2 to HCOOH at tin cathode in a pressurized undivided filter-press cell. Electrochimica Acta, 277, 30-40.
5. Proietto, F., Galia, A., & Scialdone, O. (2019) Electrochemical conversion of CO2 to HCOOH at tin cathode: development of a theoretical model and comparison with experimental results. ChemElectroChem, 6, 162-172
ELECTROCHEMICAL CONVERSION OF CARBON DIOXIDE TO FORMIC ACID IN A PRESSURIZZED FILTER PRESS CELL
No full textTo limit the negative effect of carbon dioxide as a greenhouse gas, an interesting approach is the utilization of Carbon Capture and Conversion (CCC) methodology, which is focused on the use of CO2 waste as a feedstock to produce added-value product by using the excess electric energy from renewable source [1]. In this framework, an increasing attention has been devoted in the electrochemical conversion of carbon dioxide to formic acid in water [2,3], which is considered one of the more attractive pathway to convert CO2. Since the main hurdle of the CO2 reduction from aqueous solution is the low CO2 solubility in water, in this work, the effect of some operating parameters, including pressure, current density, and flow rate, on the conversion of CO2 at tin flat cathodes to formic acid was studied using a pressurized filter-press cell with a continuous recirculation of the solution (0.9 L)
Hydrothermal liquefaction of wet biomass in batch reactors: Critical assessment of the role of operating parameters as a function of the nature of the feedstock
Full text linkA scientometric analysis of articles published from 1986 to 2022 on batch hydrothermal liquefaction of microalgae, macroalgae, lignocellulosic biomass, sewage sludge and organic wastes in water was performed. We found that biocrude yield can be correlated with the kinetic severity factor (KSF) and scattering of experimental data increases in the supercritical region probably for uncertainty in the medium density affecting the kinetics of reactions involved in the process. The level of correlation and the yield increased when fast heating rates of the reactor, higher than 25 ◦C/min, were adopted. Energy recovery of biocrude obtained in fast heating experiments changes linearly with biocrude yield independently on the adopted biomass. From this analysis, it seems interesting to assess more systematically the role of KSF, nominal density of reaction medium and heating rate with costless not algal biomass
Premio di Laurea “Ametek Scientific Instruments”: Electrochemical Conversion of Carbon Dioxide to Formic Acid. Study of the Effect of the Operating Parameters
No full textElectrochemical conversion of CO2 is considered one of the more appealing approaches to introduce renewable energy in the chemical and energy chain and to mitigate the greenhouse gases effect. In this work, the reduction of carbon dioxide was performed in undivided electrochemical cell to produce formic acid, which is one of the highest value-added chemicals and economically feasible for large-scale applications (1). It is well known that the main hurdle of the reduction of CO2 from water solution is the low CO2 solubility in water. In order to overcome this obstacle, a specific investigation on the effect of the CO2 pressure and other operating parameters at tin flat cathodes was carried out. It was shown that an increase of the pressure leads to a drastic enhancement of the formic acid concentration. Indeed, the utilization of moderately high CO2 pressures (15–30 bar) allowed to obtain high concentrations of formic acid (up to 0.46 mol L-1) at high current density (up to 90 mA cm-2) employing cheap and simple undivided cell (2)
Development of a membrane-less microfluidic thermally regenerative ammonia battery
No full textThermally regenerative ammonia battery is a promising approach to make use of waste heat and generate electrical energy. However, according to literature, the price of the energy obtained by this device is much higher than alternative renewable technologies (such as wind, solar, geothermal, etc.). To make the process more viable for applicative purposes, it would be necessary to reduce dramatically the cost of the membrane or to avoid it. Hence, the aim of the present work is to increase the economic figures of thermally regenerative ammonia battery avoiding the use of membranes. It was concluded that this result can be obtained by developing the process in a microfluidic flow cell with laminar flow conditions. In particular, it has been demonstrated for the first time that it is possible to obtain quite high power densities in the absence of a membrane in a micro cell. By operating the process at proper flow rates and inter-electrode distances, the membrane-less microfluidic thermally regenerative ammonia battery allowed to achieve even higher power densities than conventional TRAB operated under batch mode and similar operating conditions. In addition, it was shown that the process can be improved using copper deposited on carbon electrodes and moderate temperatures. In fact, at 50 degrees C a power density of 73.4 W m(-2) was obtained. (C) 2021 Elsevier Ltd. All rights reserved
Thermally Regenerative Ammonia Batteries for Waste-Heat Exploitation
No full textIt is widely accepted that one of the most important issue to be faced by the scientific community is how to sustain the modern way of living and the related energy demand. While a long term target is the transition to a full-renewable energy system, a closer exigency is the optimization of the processes already existing. It has been calculated that about 370.41 TWh of potential energy is annually lost in Europe in the form of waste-heat from the industrial sector [1]. Waste heat comprises all the thermal energy with a temperature below 130 °C [2] (or 300 °C [1]), that hardly can find a useful application with the state of the art industrial technologies. Indeed, electrochemical technologies are nowadays under investigation for the potentiality they own to harvest, at least, part of this energy [2]. Among the others, Thermally Regenerative Ammonia Batteries (TRAB) were reported to have very high current density and simple operation [3], but most of the work accomplished up to now was devoted to the optimization of the generation phase in conventional divided reactors. In this work, our efforts for the optimization of the regeneration phase are reported, along with a detailed exposure of the apparatus adopted. In addition, the use of an undivided continuous-flow, microfluidic reactor is proposed to sustain higher current densities with reduced investment cost. The effect of some relevant operative parameters on the maximum current density that can be gained in such a microfluidic device is also discussed
Electrochemical Treatment of Wastewater by ElectroFenton, Photo-ElectroFenton, Pressurized- ElectroFenton and Pressurized Photo ElectroFenton: A First Comparison of these Innovative Routes
Full text linkIn the last few years increasing attention has been devoted to the utilization of electroFenton (EF) and EF based technologies for the treatment of wastewater polluted by recalcitrant organics. It has been shown that the performances of EF can be strongly improved using ultraviolet (UV) irradiation, e.g., by the photo-electroFenton (PEF) method, or pressurized air or oxygen, e.g., by the pressurized-electroFenton (PrEF) one. Although several studies were carried out on the degradation of many organic pollutants using EF, PEF or PrEF, a systematic comparison between PEF and PrEF was never reported as well as the possibility to couple the irradiation with pressurized air. In this study the performances of EF, PEF and PrEF were systematically compared using synthetic solutions of three model organic substrates (e. g., formic acid, oxalic acid and Acid Orange 7). In addition, the pressurized-photo-electroFenton (PrPEF) process was proposed for the first time
Toward the exploitation of plastic wastes as C- sources to produce molten salt-based micro- and nano- dispersed fluid as novel heat transfer media
No full textProcess integration with molten salt-based CSP plants may replace fossil fuels as heat source, however their thermal conductivity together with the limited stability of coatings of receivers restricts utilization beyond 550–560°C. Nanofluids are a revolutionary high thermal conductive heat transfer fluid designed by dispersing appropriate nanoparticles in liquid media that can absorb volumetrically the concentrated solar radiation thus overcoming both aforementioned limitations.
Current plastic waste is burnt or dumped in landfills. This wastes have considerable residual organic content, allowing for energy valorization. Molten salt activated catalytic carbonization is a new appealing route to achieve negative CO2 emissions and a circular carbon economy with organic waste. A very interesting result would be the conversion of the carbon content of the low-value waste into high value solid carbon particles dispersed in the molten salt media with the simultaneous recovery of the hydrogen content under the form of a low carbon hydrogen rich fuel gas.
In this context we started a study of the thermochemical conversion of polyolefinic plastic wastes in ZnCl2 based molten salts to test the possibility of: i) preparing in a one pot process a C-nanoparticles loaded molten salt-based micro-/nano-nanofluid that can be used in CSP plants equipped with direct absorption solar collectors; ii) quantify the impact of coupling nanofluid-based CSP with chemical processes; and iii) assess the potentiality of the process to achieve sustainable valorization of organic waste materials to be disposed of
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