Search

The environmental impact of Bitcoin mining has raised severe concerns considering the expected growth of 30% by 2030. This study aimed to develop a Life Cycle Assessment model to determine the carbon dioxide equivalent emissions associated with Bitcoin mining, considering material requirements and energy demand. By applying the impact assessment method IPCC 2021 GWP (100 years), the GHG emissions associated with electricity consumption were estimated at 51.7 Mt CO2 eq/year in 2022 and calculated by modelling real national mixes referring to the geographical area where mining takes place, allowing for the determination of the environmental impacts in a site-specific way. The estimated impacts were then adjusted to future energy projections (2030 and 2050), by modelling electricity mixes coherently with the spatial distribution of mining activities, the related national targeted goals, the increasing demand for electricity for hashrate and the capability of the systems to recover the heat generated in the mining phase. Further projections for 2030, based on two extrapolated energy consumption models, were also determined. The outcomes reveal that, in relation to the considered scenarios and their associated assumptions, breakeven points where the increase in energy consumption associated with mining nullifies the increase in the renewable energy share within the energy mix exist. The amount of amine-based sorbents hypothetically needed to capture the total CO2 equivalent emitted directly and indirectly for Bitcoin mining reaches up to almost 12 Bt. Further developments of the present work would rely on more reliable data related to future energy projections and the geographical distribution of miners, as well as an extension of the environmental categories analyzed. The Life Cycle Assessment methodology represents a valid tool to support policies and decision makers.

Solid sorbents based on silica and polyethyleneimine (PEI) are intensively investigated in the field of carbon capture and storage (CCS). Pyrolysis was proposed as a thermal process to recover the pure silica from exhausted sorbents and convert PEI into potentially useful products, such as alkylated pyrazines. A GC–MS method based on internal standardisation with 2-methoxypyrazine was developed and evaluated to determine the concentration of six pyrazines in the pyrolysis oils of exhausted silica-PEI sorbent pyrolysed at 400, 500, 600 and 650 °C. The most abundant pyrazines were 2-ethyl and 2,3-dimethyl, occurring at concentrations of 5–28 mg g–1, followed by pyrazine, 2-methyl, 2-ethyl-3-methyl and 2-propylpyrazine. The GC–MS results were compared to those from a HPLC-DAD method using the Welch's test. The 37 % discrepancy of concentrations was attributed to spectral interference in LC-DAD. GC was slightly less precise than HPLC, calibration errors were lower and enabled the identification of highly alkylated pyrazines. Both methods provided comparable values of total pyrazine yields (around 4–7 % by weight).

The search for alternative ways to give a second life to materials paved the way for detailed investigation into three silica-polyethylenimine (Si-PEI) materials for the purpose of CO2 adsorption in carbon capture and storage. A solvent extraction procedure was investigated to recover degraded PEIs and silica, and concomitantly, pyrolysis was evaluated to obtain valuable chemicals such as alkylated pyrazines. An array of thermal (TGA, Py-GC-MS), mechanical (rheology), and spectroscopical (ATR-FTIR, 1H-13C-NMR) methods were applied to PEIs extracted with methanol to determine the relevant physico-chemical features of these polymers when subjected to degradation after use in CO2 capture. Proxies of degradation associated with the plausible formation of urea/carbamate moieties were revealed by Py-GC-MS, NMR, and ATR-FTIR. The yield of alkylpyrazines estimated by Py-GC-MS highlighted the potential of exhausted PEIs as possibly valuable materials in other applications.

The most stable isomer of the 1:1 complex formed by 2,2,2-trifluoroacetophenone and water has been characterized by combining rotational spectroscopy in supersonic expansion and state-of-the-art quantum-chemical computations. In the observed isomer, water plays the double role of proton donor and acceptor, thus forming a seven-membered ring with 2,2,2-trifluoroacetophenone. Accurate intermolecular parameters featuring one classical O-H···O hydrogen bond and one weak C-H···O hydrogen bond have been determined by means of a semi-experimental approach for equilibrium structure. Furthermore, insights on the nature of the established non-covalent interactions have been unveiled by means of different bond analyses. The comparison with the analogous complex formed by acetophenone with water points out the remarkable role played by fluorine atoms in tuning non-covalent interactions.

Hydrogen is the cleanest energy vector among any fuels, nevertheless, many aspects related to its distribution and storage still raise serious questions concerning costs, infrastructure and safety. On this account, the chemical storage of renewable-hydrogen by conversion into green-fuels, such as: methanol, via CO2 hydrogenation assumes a role of primary importance, also in the light of a cost-to-benefit analysis. Therefore, this paper investigates the effects of chemical composition on the structural properties, surface reactivity and catalytic pathway of ternary CuO-ZnO-CeO2 systems, shedding light on the structure-activity relationships. Thus, a series of CuZnCeO2 catalysts, at different CuO/CeO2 ratio (i.e. 0.2-1.2) were performed in the CO2 hydrogenation reactions at 20 bar and 200-300 °C, (GHSV of 4800 STP L∙kg∙cat-1∙h-1). Catalysts were characterized by several techniques including X-ray Diffraction (XRD), N2-physisorption, single-pulse N2O titrations, X-ray Photoelectron Spectroscopy (XPS), and Temperature-programmed Reduction with H2 (H2-TPR). Depending on preparation method, the results clearly diagnostics the occurrence of synergistic structural-electronic effects of cerium oxide on copper activity, with an optimal 0.5 copper-to-cerium content. The rise of CuO loading up to 30% drives to a considerable increase of hydrogenation activity: C2Z1-C catalyst obtains the best catalytic performance, reaching methanol yield value of 12% at 300 °C. Catalyst activity proceeds according to volcano-shaped relationships, in agreement with a dual sites mechanism. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Use of liquid fuels in fuel cells is advantageous due to the easier and safer handling, transportation, and storage. Among the different options, hydrazine is of interest since the formation of highly poisoning carbonaceous species is avoided, in addition to its high energy density. In the search for more active direct hydrazine fuel cells (DHFC), this study analyzes the influence of Cu as an auxiliary metal on Pd. Three different PdxCu/C (x = 3, 1, and 0.33) catalysts were prepared by chemical reduction with NaBH4. The materials were physiochemically characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electrochemical analysis in a three-electrode glass cell and a single-cell DHFC was also carried out to study the impact on the electroactivity. Cu exerts a beneficial effect by reducing the adsorption energies of the adsorbed species and donating oxidized species for the completion of the hydrazine electro-oxidation, optimally balanced in the Pd1Cu/C (maximum power density of 180 mW cm−2). As a counterpoint, Cu slightly promotes the non-faradaic decomposition of hydrazine, seen by a larger H2 signal in mass spectroscopy in the anode exhaust at high current densities, which results in a slight loss in faradaic efficiency.

The conversion of carbon dioxide into value-added products is progressively gaining momentum. Several strategies have been used to develop technologies that reduce the net emissions of CO2. The utilisation of CO2 could either contribute to carbon recycling. In this paper, the transformation of CO2 was investigated in a coelectrolysis cell constituted of a solid polymer electrolyte, a carbon-supported CuO-Ag composite cathode and NiFeOx anode. Noncritical raw materials were synthesised according to the oxalate method and investigated in an alkaline environment. Low-carbon alcohols were obtained with a specific selectivity for ethanol and methanol over the CuO-Ag/KB cathode. The reaction rates at 1.6 V and 1.8 V cell voltages have been determined in steady-state experiments using NaHCO3 supporting electrolyte recirculated at the anode.

Fe2O3 and Fe2O3:Ge nanofibers (NFs) were prepared via electrospinning and thoroughly characterized via several techniques in order to investigate the effects produced by germanium incorporation in the nanostructure and crystalline phase of the oxide. The results indicate that reference Fe2O3 NFs consist of interconnected hematite grains, whereas in Fe2O3:Ge NFs, constituted by finer and elongated nanostructures developing mainly along their axis, an amorphous component coexists with the dominant α-Fe2O3 and γ-Fe2O3 phases. Ge4+ ions, mostly dispersed as dopant impurities, are accommodated in the tetrahedral sites of the maghemite lattice and probably in the defective hematite surface sites. When tested as anode active material for sodium ion batteries, Fe2O3:Ge NFs show good specific capacity (320 mAh g−1 at 50 mA g−1) and excellent rate capability (still delivering 140 mAh g−1 at 2 A g−1). This behavior derives from the synergistic combination of the nanostructured morphology, the electronic transport properties of the complex material, and the pseudo-capacitive nature of the charge storage mechanism.

The effect of the type of dopant (titanium and manganese) and of the reduced graphene oxide content (rGO, 30 or 50 wt %) of the α-Fe2O3@rGO nanocomposites on their microstructural properties and electrochemical performance was investigated. Nanostructured composites were synthesized by a simple one-step solvothermal method and evaluated as anode materials for sodium ion batteries. The doping does not influence the crystalline phase and morphology of the iron oxide nanoparticles, but remarkably increases stability and Coulombic efficiency with respect to the anode based on the composite α-Fe2O3@rGO. For fixed rGO content, Ti-doping improves the rate capability at lower rates, whereas Mn-doping enhances the electrode stability at higher rates, retaining a specific capacity of 56 mAhg−1 at a rate of 2C. Nanocomposites with higher rGO content exhibit better electrochemical performance.

Transition metal sulfide catalysts are actually the most performing catalytic materials in crude oil hydrotreating (HDT), for energetic purposes. However, these systems suffer from several drawbacks that limit their exploitation. Aiming to meet the even more stringent environmental requirement, through a remarkable improvement of HDT performance in the presence of refractory feedstock (i.e., in terms of activity, selectivity, and stability), a deeper knowledge of the structure−activity relationship of catalysts must be achieved. Therefore, in this study, CoMo/γ-Al2O3 and NiMo/γ-Al2O3 catalysts were characterized and tested in the o-xylene hydrogenation model reaction, assessing the influence of both support acidity and catalyst acid strength on reaction pathway by employing γ-Al2O3 and Y-Type zeolite as acid reference materials. A clear relationship between concentration and strength of acid sites and the performance of the catalytic materials was established. Cobalt based catalyst (CoMoSx) proves a higher acidic character with respect to Nickel (NiMoSx), prompting isomerization reactions preferentially, also reflecting a greater o-xylene conversion. The different chemical properties of metals also affect the catalytic pathway, leading on the CoMoSx system to the preferential formation of p-xylene isomer with respect to m-xylene.

The use of hydrogen as an energy vector and raw material for “very clean liquid fuels” manufacturing has been assessed by the catalytic conversion of CO2 to methanol over copper based catalysts. A systematic evaluation of copper based catalysts, prepared varying the chemical composition, has been carried out at 0.1–5.0 MPa of total pressure and in the range of 453–513 K by using a semi-automated LAB-microplant, under CO2/H2 reactant mixture (1/3), fed at GHSV of 8.8 NL∙kgcat−1∙h−1. Material’s properties have been investigated by the means of chemical-physical studies. The findings disclose that the addition of structure promoters (i.e., ZrO2/CeO2) strongly improves the textural properties of catalysts, in term of total surface area and exposure of metal surface area (MSA), also reducing the sintering phenomena. The results of the catalytic study clearly prove a structure-activity relationship at low reaction pressure (0.1 MPa), while at higher pressure (3.0–5.0 MPa) the reaction path is insensitive to structure and chemical composition.

Ethanimine, a possible precursor of amino acids, is considered an important prebiotic molecule and thus may play important roles in the formation of biological building blocks in the interstellar medium. In addition, its identification in Titan’s atmosphere would be important for understanding the abiotic synthesis of organic species. An accurate computational characterization of the molecular structure, energetics, and spectroscopic properties of the E and Z isomers of ethanimine, CH3CHNH, has been carried out by means of a composite scheme based on coupled-cluster techniques, which also account for extrapolation to the complete basis-set limit and core-valence correlation correction, combined with density functional theory for the treatment of vibrational anharmonic effects. By combining the computational results with new millimeter-wave measurements up to 300 GHz, the rotational spectrum of both isomers can be accurately predicted up to 500 GHz. Furthermore, our computations allowed us to revise the infrared spectrum of both E- and Z-CH3CHNH, thus predicting all fundamental bands with high accuracy. [ABSTRACT FROM AUTHOR]