In this paper the steam reforming of bioalcohols over Ni and Pt catalysts supported on bare Al2O3 and La2O3 and CeO2-modified Al2O3 to produce H2 was studied. Catalytic activity results showed that ...the glycerine and the intermediate liquid products may hinder the ethanol adsorption on metal active sites of the catalysts, especially at temperatures below 773 K. In fact, ethanol conversion was lower than glycerine conversion in the steam reforming reaction at low temperatures. H2 chemisorption revealed that La2O3 doping of the Ni/Al2O3 catalyst improved the metal dispersion providing a better behaviour to the Ni/Al2O3-O2 catalyst towards H2 production. In the case of Pt catalysts, the good reducibility and the H2 spillover effect provided to the Pt/Al2O3-O1 catalyst the capacity to produce higher H2 yields.
The comparison of Pt and Ni catalyst activities showed that the Pt catalysts produced lower H2 yields. This can be attributed to the lower Pt loading as compared to the metal content of the Ni based catalysts.
► Bioalcohol mixtures conversion mainly resulted in gaseous products at 773 K. ► Important quantities of intermediate liquid products were detected at 723 K and 673 K. ► La2O3 on Ni/Al2O3 catalyst improved Ni dispersion, resulting in higher H2 yield. ► CeO2 on Pt/Al2O3 catalyst enhanced reducibility and Pt surface exposure.
► Liquors from WO acid leaching can be treated to obtain metallic Zn by electrolysis. ► The most important parameters for the electrowinning of these liquors were found to be 4.5V and 180min. ► ...Operating under these conditions allowed at lab-scale zinc purities >99.5%. ► The conceptual design of a new process able to recover 210kg metallic Zn/t of WO was presented. ► The economic value and improved environmental impact of the process as alternative to the conventional method.
Waelz oxide is a zinc and lead concentrate pyrometallurgically derived from electric arc furnace dust. There are clear incentives to leaching and purify this oxide to produce liquors that can be electrowinned to obtain recycled metallic zinc. This study is focused on this electrolytic zinc production from previously obtained sulphuric liquor. This liquor was obtained from double leached Waelz oxide (DLWO) throughout a hydrometallurgical process. The electrolytic liquor, after the corresponding leaching and purification stages, contains around 49kg/m3. This liquor was fed to an electrowinning process where platinum or lead anodes and aluminium cathodes were used. After optimizing the different electrowinning critical parameters, and working at these optimal conditions, almost 88 secondary zinc kg were precipitated per each initial DLWO tonne in one-through process. The zinc purity was higher than 99.5%. After some mass balance calculations, it can be concluded that, optimizing the process configuration through internal recycling, around 210Znkg/DLWOt with purity near to 100% could be achieved.
PdCu membranes were prepared by the electroless plating of Pd membranes prepared on ceramic tubular supports. Different PdCu membranes were prepared with Pd content between 45 and 77 wt% and a total ...metal layer between 0.5 and 1.9 μm thickness. The alloying step was performed in two ways to compare and establish the required alloying time for obtaining high permeance membranes. The alloying was analysed with EDX composition measurements, and full alloying was not required to obtain a stable hydrogen flux. Finally, permeance tests were performed at different pressures, including temperature cycles in hydrogen and nitrogen, to observe membrane stability. The hydrogen permeance values of the membranes were high, between 1.5 × 10
−3 and 4.5 × 10
−3 mol/(s Pa
0.5 m
2) at 673 K. The membranes recorded stable permeance values even after thermal cycles in a hydrogen atmosphere. Metal layer thickness was calculated using both the weight difference method and SEM images. SEM images were also used to analyse the surface morphology of the membranes, which was generally fairly uniform and smooth.
► PdCu alloy membranes for hydrogen purification. ► PdCu membranes with metal thickness between 0.5 and 1.9 μm. ► The required alloying time has been established. ► No complete alloying is necessary to obtain a high hydrogen flux. ► Membranes were stable even after thermal cycles in hydrogen.
Energy storage is needed in order to sustain the energy system on renewable energies like wind and solar power. Power-to-Gas (PtG) is a technology that enables the storage of the renewable ...electricity in a chemical carrier such as hydrogen, via water electrolysis, or methane, via carbon dioxide methanation. In this work a series of catalysts based on nickel and alumina, the catalyst commonly employed for carbon dioxide methanation, have been synthesised employing different calcination temperatures to study the influence of this parameter in the activity of the catalysts. As a result of this study 673 K was determined as the most suitable Moreover, the catalysts have also been tested at different pressures to determine the most suitable operating pressure. Although due to Le Chatelier's Principle a higher pressure results in an increasing yield, the study carried out proved that 10 bar is the most suitable pressure as the difference in the yield when increasing the pressure it is not high enough taking into account the costs and risks associated with higher pressures.
•673 K was the optimal catalyst calcination temperature for CO2 methanation.•A calcination temperature of 673 K resulted in higher active Ni particles.•10 bar was selected as the optimal pressure for this reaction.
Electric Arc Furnace Dust (EAFD) is an important hazardous waste from the steel production industry, due to its heavy metals content. It is recycled through a pyrometallurgical process to generate a ...Zn and Pb concentrate called Waelz oxide. This concentrate can be processed hydrometallurgically in order to obtain high purity ZnO. But this hydrometallurgical process also generates as wastes different solid residues with high content of heavy metals and a liquid waste stream with significant concentrations of ammonia and heavy metals. This is why the objective of this work is to design a process that can simultaneously treat these solid and liquid wastes. In the developed process, an alkaline solution is used to leach solid residues so as to produce an inert final waste. After filtration, the leaching liquor is mixed with the liquid waste in order to increase its pH and to enhance the ammonia evaporation by air stripping. This stripped stream can be recycled to the leaching stage of the Waelz oxide treatment process. Furthermore, the ammonia stripping precipitates the dissolved heavy metals as a zinc concentrate that can be commercialized as a raw material for the metallic zinc production industry. Therefore, the developed process reduces by more than half the wastes generation, increases the Zn recycling yield >5% and recovers >75% of the needed ammonia for the fresh leaching liquor.
•Novel process developed to treat residual heavy metals from secondary zinc recycling.•Ammonia removal from hydrometallurgical exhausted liquors to be reused.•Improvement to increase the sustainability of the zinc and steelmaking industries•The study of benefits obtained combining the solid and the liquid wastes treatment.
The hydrothermal stability of Ni and NiPt-containing γ-Al2O3 catalysts in aqueous phase reforming (APR) of glycerol/water mixture (C3H8O3/H2O, 10% w/w) was investigated putting in evidence the ...influence of the preparation method; sol–gel in basic medium (SGB) and impregnation on an in-house prepared sol–gel γ-Al2O3 support (SGI). All developed catalysts were characterized by ICP-AES, TPR-H2, in-situ heating XRD-O2, DSC/TG-N2/O2 and ex-situ reduction of XRD-H2, N2 physisoption and TEM techniques. The results indicate that SGI method and calcination treatment at 750 °C were crucial in extending the catalytic useful life of NiPt-containing γ-Al2O3 catalysts, resulting in an adequate distribution of NiPt metallic particles and good stability of γ-Al2O3 support against the severe hydrothermal conditions of APR process. The SGI method led to form stable NiPt catalysts with relatively big Ni particles and stable hydrothermal properties of γ-Al2O3 support, while the SGB catalysts exhibited well-dispersed Ni particles but unstable catalytic behavior. These last catalysts presented high glycerol conversions during the first hours of APR glycerol/water reaction, however, an important decrease in terms of glycerol conversion was observed after 24 h time-on-stream. The experimental results suggested that the most suitable stable and active catalyst was the NiPt/ASGI7 (better than >NiPt/ASGI6 > NiPt/ASGI5 >>> NiPt/ASGB7). This catalyst showed best catalytic activity and good catalytic stability along 56 h of time-on-stream, reaching, at steady state, highest total glycerol conversion (≈79%) and glycerol into gaseous products (≈57%) in APR reaction of glycerol/water mixture for hydrogen generation.
•The hydrothermal stability of Ni/NiPt-containing γ-Al2O3 catalysts in glycerol APR was studied.•SGI method and calcination at higher T were crucial to develop well-stable NiPt/γ-Al2O3 catalyst.•SGI method form bigger Ni particles/stable γ-Al2O3, while SGB exhibited well-dispersed particles.•SGI catalysts are more stable in glycerol APR process but SGB catalysts shown to be more active.•The most suitable activity/stability behavior in glycerol APR was obtained by NiPt/ASGI7 catalyst.
Ni/MgO and Ni/Al
2O
3 catalysts were prepared, by wet impregnation, to compare their performance in hydrogen production from methane CPO, wet-CPO and SR. The catalytic activity was tested at 1073 K, ...1 bar and 600–1200 h
−1. Fresh and used catalysts were characterized by different techniques. Both supports, as expected, had a low surface area (27.1 m
2/g MgO and 6.2 m
2/g α-Al
2O
3), as determined by BET method. The images obtained with SEM and TEM revealed that the Ni was more dispersed in the MgO support than in the Al
2O
3 one. By XRD a strong interaction, as solid-solution, between NiO and MgO was found in the 30Ni/MgO and 40Ni/MgO catalysts. The fresh 40Ni/Al
2O
3 reduced catalyst was partially reduced. But after the activity tests the stability of the reduced Ni became bigger. Some Ni sintering was also observed in the 40Ni/Al
2O
3 after the wet-CPO and SR tests. The behaviour of the three catalysts was very good in CPO methane conversion (90–93%), but the gradual increase of the steam to carbon ratio, wet-CPO and SR, affected negatively the conversion.
•Very high conversions were reached by all tested catalysts and operation conditions.•For biogas SR at S/C=1.0 and TR, H2/CO ratios near to 2.0 were obtained.•The highest hydrogen yield was measured ...for the biogas OR process at O/C=0.25.•DR is the most appropriate process for the conversion of almost all the CO2.•The RhNi catalyst based on Zeolite L (30–60nm) seems to be a promising catalyst.
This study examined the use of three different Zeolites L as catalyst support for biogas valorisation – a renewable resource – through reforming processes. These aluminosilicates are characterised by their high surface areas, affinity for CO2, and thermal stability, which makes them an interesting and promising support for reforming reactions at high temperature. Three nickel monometallic and their homologous rhodium–nickel bimetallic catalysts were prepared by the incipient wetness impregnation method for each type of Zeolite L. Significant physicochemical differences between the Zeolites L and catalysts were noticed by the characterisation using scanning electron microscope (SEM), transmission electron microscope (TEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), H2 chemisorption, N2 physisorption, temperature programmed reduction (TPR) X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The catalysts were tested in dry reforming (DR), steam reforming (SR) with steam to carbon (S/C) ratio of 1.0 and 2.0; oxidative reforming (OR) at O2/CH4=0.25; and tri-reforming (TR) with S/C ratio of 1.0 and O2/CH4=0.25. For all the experiments, a synthetic biogas, which consisted of 60% CH4 and 40% CO2 (vol.), was fed to a fixed bed reactor system at 1073K and atmospheric pressure. The same experimental conditions and reactions were studied in previous works of the authors, in which γ-Al2O3 was used as a catalyst support. Thus, this work allows comparing the achieved activities by the tested catalysts supported on those different supports. Among the processes studied, for the biogas SR at S/C=1.0 and TR processes, H2/CO ratios near to 2.0 were obtained, which is an appropriate ratio for the Fischer–Tropsch synthesis (FTS). In the case of the catalysts tested, the Rhodium (Rh) incorporation improved their activity. RhNi catalyst based on Zeolite L (30–60nm) is the most active catalyst for hydrogen generation.
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