Methane cracking over cobalt molybdenum carbides

The catalytic behaviour of Co3Mo3C, Co6Mo6C, Co3Mo3N and Co6Mo6N for methane cracking has been studied to determine the relationship between the methane cracking activity and the chemical composition. The characterisation of post-reaction samples showed a complex phase composition with the presence of Co3Mo3C, α-Co and β-Mo2C as catalytic phases and the deposition of different forms of carbon during reaction

Catalytic steam reforming of volatiles released via pyrolysis of wood sawdust for hydrogen-rich gas production on Fe–Zn/Al2O3 nanocatalysts

Thermo-chemical processing of biomass is a promising alternative to produce renewable hydrogen as a clean fuel or renewable syngas for a sustainable chemical industry. However, the fast deactivation of catalysts due to coke formation and sintering limits the application of catalytic thermo-chemical processing in the emerging bio-refining industry. In this research, Fe-Zn/Al2O3 nanocatalysts have been prepared for the production of hydrogen through pyrolysis catalytic reforming of wood sawdust. Through characterization, it was found that Fe and Zn were well distributed on the surface with a narrow particle size. During the reactions, the yield of hydrogen increased with the increase of Zn content, as Zn is an efficient metal promoter for enhancing the performance of the Fe active site in the reaction. The 20% Fe/Al2O3 catalyst with Zn/Al ratio of 1:1 showed the best performance in the process in relation to the hydrogen production and resistance to coke formation on the surface of the reacted catalyst. All the catalysts showed ultra-high stability during the process and nearly no sintering were observed on the used catalysts. Therefore, the nanocatalysts prepared from natural-abundant and low-cost metals in this work have promising catalytic properties (high metal dispersion and stability) to produce H2-rich syngas with optimal H2/CO ratio from the thermo-chemical process of biomass

Thermal behavior of native, washed and steam exploded lignocellulosic biomass samples

The aim of this study was to evaluate the chemical changes in the main components (cellulose, hemicellulose and lignin) of various lignocellulosic biomass samples during the steam explosion pretreatment. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/mass spectrometry (TG/MS) measurements have been performed on different native, washed and steam exploded woody (willow and spruce) and herbaceous (hemp, wheat straw and sweet sorghum bagasse) biomass samples. The main differences between the thermal decomposition of the samples are interpreted in terms of the altered structure of the biomass samples by the effective steam explosion treatment and the different alkali ion contents which have been determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. In order to separate these two effects, the native biomass samples have been washed with hot water to remove the main parts of the potassium and sodium ions. The concentration of K+ and Na+ has been reduced in the treated biomass samples so the thermal decomposition mechanism has been altered due to the elimination of the catalytic effects. Principal Component Analysis (PCA) has been used to find statistical correlations between the data. The functional group compositions of the lignin molecules have been modified significantly as indicated by the pyrograms and the score plot of the PCA. The amount of hemicellulose has been reduced. On the other hand, the relative amount of the structurally modified cellulose has been increased in the samples by the steam explosion pretreatment step

Pyrolysis of latex gloves in the presence of y-zeolite

In this study we have investigated the possibility of processing waste rubber gloves using pyrolysis. Y-zeolite catalyst was employed to upgrade the pyrolysis products to give higher yields of valuable aromatic compounds such as toluene and xylenes. The composition of the pyrolysis products was determined using GC-MS, GC-FID, GC-TCD, and FT-IR. It was found that when rubber gloves were pyrolysed in the absence of a catalyst, the pyrolysis oil consisted mainly of limonene and oligomers of polyisoprene. When Y-zeolite was added to the reaction system, the yields of toluene, xylene, methylbenzenes, ethylbenzenes, and naphthalenes increased dramatically. The Y-zeolite also catalysed the decomposition of limonene, which was absent from the catalytic pyrolysis products. The presence of the Yzeolite catalyst also increased the yield of hydrocarbon gases. The tests were carried out at both 380°C and 480°C and it was found that the higher reaction temperature led to increased yields of all the major compounds, both in the presence and absence of the Y-zeolite catalyst

Carbon deposition in the Bosch process with ruthenium and ruthenium-iron alloy catalysts

The effectiveness of ruthenium and the alloys 50Ru50Fe and 33Ru67Fe as alternatives to iron, nickel, and cobalt catalysts in recovering oxygen from metabolic carbon dioxide was investigated. Carbon deposition boundaries over the unsupported alloys are reported. Experiments were also carried out over 50Ru50Fe and 97Ru3Fe3 catalysts supported on gamma-alumina to determine their performance in the synthesis of low molecular weight olefins. High production of ethylene and propylene would be beneficial for an improvement of an overall Bosch process, as a gas phase containing high olefin content would enhance carbon deposition in a Bosch reactor

Analytical Techniques as a Tool to Understand the Reaction Mechanism

Thermal decomposition of biomass samples and the major macromolecular constituents of lignocellulosic biomass are reviewed. Special emphasis has been placed on the results of the thermoanalytical methods and analytical pyrolysis. On the basis of the product distribution of the thermal decomposition, the possible major decomposition mechanisms are discussed. The influence of the inherent inorganic components of biomass on the thermal decomposition of cellulose, and lignin are demonstrated. Furthermore, the effect of the low temperature heat treatment, the torrefaction on the thermal conversions are summarized

Catalyzed sodium chlorate candles

The catalytic effect of cobalt powder on chlorate decomposition has been confirmed. Catalysis is enhanced by oxidation of the metal during burning. Catalysts other than cobalt compounds should also be effective; the complete elimination of fuel has shown that the oxidation of cobalt during decomposition is not a vital factor in the improved performance of catalyzed candles

Producción de CH4 mediante hidrogenación de CO2 usando catalizadores basados en Ni soportados sobre carbón biomórfico

Se ha investigado reacción de metanación de CO2 sobre catalizadores de Ni modificados Mg y/o Ce, con soportados en carbón biomórfico. Estos catalizadores se han preparado usando una técnica de mineralización biomórfica que incluye una etapa de descomposición térmica en una atmósfera reductora, de celulosa previamente impregnada con los precursores (nitratos) metálicos. El estudio de la composición química, estructura, morfología y textura de las muestras se ha llevado a cabo mediante diferentes técnicas de caracterización como fisisorción de N2, difracción de rayos X, análisis termogravimétrico con aire y microscopía electrónica de transmisión. Además, para optimizar la productividad y selectividad de la reacción, se ha estudiado el efecto de las principales condiciones de operación (temperatura de la reacción y composición de la alimentación), en condiciones de elevada velocidad espacial (60.000 h-1). Por otro lado, la estabilidad del catalizador se ha medido a lo largo 8h a 325 ᵒC. Un resultado notable obtenido es que la adición del promotor de Ce ha aumentado la superficie BET, la microporosidad del catalizador y la dispersión de Ni sobre la superficie del soporte carbonoso. Como consecuencia, se han mejorado las prestaciones (conversión de CO2, selectividad a CH4 y estabilidad) durante la reacción. Se ha obtenido que el catalizador Ni-MgCe/BC es el más activo de CO2 a 350 ᵒC, alcanzando un 68,7% de conversión de CO2 y una selectividad de CH4 del 93,5%, lo que da un rendimiento a CH4 del 64,2%.<br /

Optimization of Charcoal Production Process from Woody Biomass Waste: Effect of Ni-Containing Catalysts on Pyrolysis Vapors

Woody biomass waste (Pinus radiata) coming from forestry activities has been pyrolyzed with the aim of obtaining charcoal and, at the same time, a hydrogen-rich gas fraction. The pyrolysis has been carried out in a laboratory scale continuous screw reactor, where carbonization takes place, connected to a vapor treatment reactor, at which the carbonization vapors are thermo-catalytically treated. Different peak temperatures have been studied in the carbonization process (500-900 degrees C), while the presence of different Ni-containing catalysts in the vapor treatment has been analyzed. Low temperature pyrolysis produces high liquid and solid yields, however, increasing the temperature progressively up to 900 degrees C drastically increases gas yield. The amount of nickel affects the vapors treatment phase, enhancing even further the production of interesting products such as hydrogen and reducing the generated liquids to very low yields. The gases obtained at very high temperatures (700-900 degrees C) in the presence of Ni-containing catalysts are rich in H-2 and CO, which makes them valuable for energy production, as hydrogen source, producer gas or reducing agent.The authors thank the Basque Country Government (consolidated research groups funding and Programa predoctoral de formacion de personal investigador no doctor), Befesa Steel R&D company for financial assistance for this work and Biotermiak Zeberio 2009 S.L. for the supply of fresh biomass