•Pyrolysis of olive tree cuttings in two reactors connected in series.•First step for obtaining metallurgical grade biochar.•Second step for thermal and catalytic upgrading of pyrolysis ...vapours.•Ni/Al2O3–CeO2 and Ni/Al2O3–ZrO2 catalysts were tested.•Ni/Al2O3–CeO2 gave rise to less tars and higher H2 and CO.
Slow pyrolysis of biomass at high temperatures yields a solid product (biochar or charcoal) with useful properties to be used as a reducing agent in metallurgical applications. In such conditions tar yields are much lower than those obtained in biomass fast pyrolysis. The permanent gases obtained are rich in carbon monoxide (CO) and hydrogen (H2) which makes them valuable for energy production or as reducing agent. Pyrolysis liquids are claimed to be useful as fuels or chemical feedstock. However, biomass pyro-oils obtained in slow pyrolysis are frequently oxygenated, corrosive, relatively unstable and chemically very complex. Consequently, catalytic upgrading of the pyrolysis vapours to reduce tars and increase the amount of gases and its CO and H2 contents is of special interest.
Pyrolysis experiments of waste biomass (olive tree cuttings) have been carried out. This type of biomass is available in big quantities, is hardly used in industrial applications and its consumption does not lead to potential conflicts with food markets. The experiments were conducted in two reactors connected in series: a first non-stirred batch 3.5L pyrolysis reactor where 100g of biomass were pyrolyzed at 750°C, and a second catalytic reactor with a previous biochar bed, where the gases were immediately treated at different temperatures; both reactors were swept with 1Lmin−1 nitrogen (N2). Two different nickel/alumina supported monolithic catalysts modified with ceria and zirconia were prepared for this study. Ni/Al2O3 is a typical reforming catalyst and the addition of ceria and zirconia aimed to enhance the Ni/Al2O3 performance, especially at high temperatures. Two different methods for preparing the Ni/Al2O3–CeO2 catalyst were used (dissolution sequential method and suspension in ethanol method).
The initial sample, as well as the solid, liquid and gaseous products obtained in the experiments were characterized. No influence of the catalyst preparation method was observed. The use of catalyst leads to a lower liquid yield and a higher gas yield, while the solid yield remains unaltered. Additionally, the organic content of the aqueous phase is decreased by the use of catalyst. Concerning gases the use of catalyst gave rise to higher H2 and CO and lower methane (CH4) production. The ceria modified catalyst has better performance than the zirconia modified catalyst.
In this paper, the hydrogen storage capacity of some synthetic and natural iron oxides is presented. The results of the activity tests and characterization techniques of natural and synthetic iron ...oxides (N
2
adsorption–desorption isotherms, temperature-programmed reduction, X-ray diffraction, and plasma atomic emission spectroscopy) suggest that the use of chromium on iron oxide systems improved their hydrogen storage capacity. This is related to the capacity of chromium to modify the iron oxide reduction profile when Cr was incorporated. A direct reduction from Fe
3
O
4
to Fe was observed as the mechanism for H
2
storage. In addition, natural oxides as commercial Superfine and Densinox-L oxides are proved to be suitable materials to store and purify H
2
due to their high stability during different cycles of reduction and oxidation. The best results among the natural ones were Densinox-L and among the synthetic ones Fe–10Cr.
In this work carbon dioxide methanation was performed in order to produce methane. This process is known as “Power-to-Gas”, which uses the excess of electricity produced from renewable sources to ...generate hydrogen via water electrolysis. This hydrogen can react with carbon dioxide, obtained from different industrial processes, to generate methane that can be stored, burned or injected into the existing natural gas grid. Thus, different catalysts supported on alumina and cerium/zirconium modified alumina were prepared, using nickel as main active metal and with the addition of small amounts of noble metals, rhodium and ruthenium, in order to increase their catalytic activity. Addition of noble metals increased the dispersion and the reducibility of the nickel species, whilst support modifiers increased the amount of nickel oxide with moderate interaction with the support and non-stoichiometric nickel aluminate species. These species proved to be related with the catalytic activity. For the catalysts tested, promising results were obtained between 640 and 700 K with a methane yield of 70%.
•Thermodynamic equilibrium reached at high temperatures.•Noble metals enhanced catalytic activity at low temperatures.•Nickel oxide and non-stoichiometric nickel aluminate proved to be the active phases for methanation reaction.
Silica–alumina supported Pd catalysts with a second metal such as Cu, Ru or Pt have been prepared (nominal content: 1
wt%) and tested in the naphthalene hydrogenation (HYD) and dibenzothiophene ...hydrodesulfurization (HDS) model reactions. These catalysts were characterized by means of temperature-programmed reduction, NH
3 temperature-programmed desorption and photoelectron spectroscopy techniques. The combined use of all these techniques revealed that only in the case of PtPd system a rather uniform distribution of the metals across the pore network is achieved. Another important observation was that the PtPd system exhibited strong Brönsted acid sites. The highest HYD and HDS activities of the PtPd bimetallic catalyst can be related not only to a high dispersion of the metals and their uniform distribution but also to its strong Brönsted acidity. The PtPd system presented the highest DBT conversion (83.1%) and the highest C–S hydrogenolysis activity as illustrated by the lowest S-containing products (21.9
wt%) as compared with the much higher S-containing products (54.8
wt%) obtained with the monometallic Pd/ASA catalyst under the same experimental conditions.
Cuando el relato es demasiado corto Cambra, Francisco Jose; Bobillo-Perez, Sara
Anales de pediatría,
October 2019, Letnik:
91, Številka:
4
Journal Article
Nickel- and palladium–nickel catalysts supported on silica–alumina have been studied in the simultaneous hydrogenation of naphthalene and toluene. These catalysts were characterised by means of X-ray ...diffraction, CO chemisorption, temperature-programmed reduction, NH
3 temperature-programmed desorption, diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy of adsorbed CO and X-ray photoelectron spectroscopy techniques. All the catalysts studied showed higher initial intrinsic activity in the hydrogenation of toluene than of naphthalene. Regarding the hydrogenation of toluene, the 1Pd–8Ni/SA sample displayed the strongest resistance to deactivation by coke precursors as compared with the Ni-free 1Pd/SA catalyst. For the 1Pd–8Ni catalyst, the characterisation data pointed not only to a high degree of reducibility of nickel but also the greatest exposure of Pd species. Both findings appear to be related to the development of nickel hydrosilicate species at the support interface. Indeed, a better resistance towards deactivation was obtained by Pd incorporation and by increasing Ni-loading.
Alumina-supported nickel catalysts modified with redox (Mo, Mn and Sn) oxides were tested in the catalytic partial oxidation (CPO) of methane and the wet catalytic partial oxidation (wet-CPO) of ...methane for syngas production. The influence of different reaction parameters on the performance of these systems was studied for both reactions. Certain insights on catalyst surface structure were revealed by means of X-ray photoelectron spectroscopy (XPS) and thermal programmed reduction (TPR). The joint analysis of all the results led to certain correlations between the structure of the catalysts and catalytic activity, indicating that the redox additives to some extent modify the stability of the active nickel phase by altering the nickel-alumina interface interaction.
In the present work, Ni/α-Al
2O
3 catalysts modified with different amounts of CaO and MgO were used for the production of hydrogen by catalytic partial oxidation (CPO) and wet-CPO processes of ...methane. In the wet-CPO process, small additions of water were introduced into the feed of the reactor to improve both the H
2 yield and methane conversion. The addition of water is also beneficial because coke formation becomes thermodynamically unfavorable. The catalysts were characterized before and after the reaction with XRD, XPS, TPR and TPO techniques. Several methane decomposition tests and methane pulse experiments were carried out with a view to correlating the ability of metal sites to activate methane in the absence of oxygen with the performance for CPO and wet-CPO reactions.
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