Thermal and thermo-oxidative characterisation of rice straw for its use in energy valorisation processes

[EN] The processes of pyrolysis and combustion of rice straw will be carried out in a spouted bed reactor. Both thermo-chemical processes were simulated in the first stage by multi-rate linear non-isothermal thermogravimetric (TGA) experiments using Ar and O-2 as carrier gas respectively. The results obtained from the TGA measurements, the kinetic methodology based on the combination of the iso-conversional methods Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Vyazovkin and the use of Master Plots assessed by Perez-Maqueda criterion have permitted to describe mathematically both thermo-chemical reactions. Lower operational temperatures and higher kinetic parameters (Ea, n, A) were required to carry out combustion reactions respect to those for pyrolysis. These results will be the initial parameters that will define both thermo-chemical processes in a spouted bed reactor. (C) 2016 Elsevier Ltd. All rights reserved.Moliner, C.; Bosio, B.; Arato, E.; Ribes-Greus, A. (2016). Thermal and thermo-oxidative characterisation of rice straw for its use in energy valorisation processes. Fuel. 180:71-79. https://doi.org/10.1016/j.fuel.2016.04.021S717918

Steam reforming of phenol as biomass tar model compound over Ni/Al₂O₃ catalyst

Catalytic steam reforming of phenol over Ni/Al₂O₃ catalyst with 10 wt% of Ni loading was carried out in a fixed bed reactor. The effect of temperature (650–800 °C), reaction time (20–80 min) and catalyst amount (0–2 g corresponding to 0–4.5 gcat h gphenol−1) on carbon conversion, H2 potential and catalyst deactivation was studied. High efficiency of Ni/Al₂O₃ catalyst in steam reforming of phenol is observed at 750 °C for a reaction time of 60 min when 1.5 g of catalyst (3.4 gcat h gphenol−1) is used, with carbon conversion and H2 potential being 81 and 59%, respectively. An increase in temperature enhances phenol reforming reaction as well as coke gasification, minimizing its deposition over the catalyst. However, at high temperatures (800 °C) an increase in Ni crystal size is observed indicating catalyst irreversible deactivation by sintering. As catalyst time on stream is increased the coke amount deposited over the catalyst increases, but no differences in Ni crystal size are observed. An increase in catalyst amount from 0 to 1.5 g increases H2 potential, but no further improvement is observed above 1.5 g. It is not observed significant catalyst deactivation by coke deposition, with the coke amount deposited over the catalyst being lower than 5% in all the runs

Development of Ni- and Fe- based catalysts with different metal particle sizes for the production of carbon nanotubes and hydrogen from thermo-chemical conversion of waste plastics

Co-production of valuable hydrogen and carbon nanotubes (CNTs) has obtained growing interest for the management of waste plastics through thermo-chemical conversion technology. Catalyst development is one of the key factors for this process to improve hydrogen production and the quality of CNTs. In this work, Ni/SiO2 and Fe/SiO2 catalysts with different metal particle sizes were investigated in relation to their performance on the production of hydrogen and CNTs from catalytic gasification of waste polypropylene, using a two-stage fixed-bed reaction system. The influences of the type of metals and the crystal size of metal particles on product yields and the production of CNTs in terms of morphology have been studied using a range of techniques; gas chromatography (GC); X-ray diffraction (XRD); temperature programme oxidation (TPO); scanning electron microscopy (SEM); transmission electron microscopy (TEM) etc. The results show that the Fe-based catalysts, in particular with large particle size (∼80 nm), produced the highest yield of hydrogen (∼25.60 mmol H2 g−1 plastic) and the highest yield of carbons (29 wt.%), as well as the largest fraction of graphite carbons (as obtained from TPO analysis of the reacted catalyst). Both Fe- and Ni-based catalysts with larger metal particles produced higher yield of hydrogen compared with the catalysts with smaller metal particles, respectively. Furthermore, the CNTs formed using the Ni/SiO2-S catalyst (with the smallest metal particles around 8 nm) produced large amount of amorphous carbons, which are undesirable for the process of CNTs production

Hydrogen and Carbon Nanotubes from Pyrolysis-Catalysis of Waste Plastics: A Review

More than 27 million tonnes of waste plastics are generated in Europe each year representing a considerable potential resource. There has been extensive research into the production of liquid fuels and aromatic chemicals from pyrolysis-catalysis of waste plastics. However, there is less work on the production of hydrogen from waste plastics via pyrolysis coupled with catalytic steam reforming. In this paper, the different reactor designs used for hydrogen production from waste plastics are considered and the influence of different catalysts and process parameters on the yield of hydrogen from different types of waste plastics are reviewed. Waste plastics have also been investigated as a source of hydrocarbons for the generation of carbon nanotubes via the chemical vapour deposition route. The influences on the yield and quality of carbon nanotubes derived from waste plastics are reviewed in relation to the reactor designs used for production, catalyst type used for carbon nanotube growth and the influence of operational parameters

Dolomitization in Cretaceous/Tertiary boundary sediments at Quecedo Section (northern Burgos, Spain)

Diagenetic processes of dolomitization and calcitization have been recorded from the upper Maastrichtian -lower Danian shallow-marine carbonate rocks at Quecedo. Dolomitization is associated to a first order sequence boundary, evolved from upper to lower and affected very shallow marine sediments. A diagenetic sequence from evaporative, to marine and meteoric mixing ambients, to a later freshwater generalized input can be inferred from both the study of micro textures and cathodoluminescence observation

Dolomitization below unconformities: a comparative study of dolomites from Turonian-Coniacian (El Ribero) and Upper Maastrichtian (Quecedo) of Northern Burgos (Spain)

Substantial dolomitization and calcitization processes occurred in upper Turonian-lower Coniacian and upper Maastrichtian-lower Danian carbonates at El Ribero and Quecedo sections, respectively. Carbonate precipitation is in both cases related to first order sequence boundaries. Textures under S.E.M. reveal m o re im p o rta n t processes o f dissolution at El Ribero in comparison to those a t Quecedo, suggesting an aggressive meteoric phreatic zone. C and O isotopic relations tend to become positive just below the unconformities as a result of the influence of marine waters. A general comparison show more heavy isotopic values at Quecedo. A marine/mixing water model of dolomitization is proposed for both dolomites, but with a major influence of marine waters at Queced