AbstractThis paper discusses the study of plant waste thermocatalytic conversion. The dependence of the conversion of agricultural waste on the pyrolysis temperature, reaction time and feedstock particle size was determined. The optimal temperature of fast pyrolysis providing the highest yield of gaseous products (over 30 wt. %) for all types of waste plant biomass was found to be 700 ºC. This temperature allows the lowest tar content in gases to be obtained. Further, ZSM-5 synthetic zeolites modified with iron subgroup metals were studied in the conversion of volatile products obtained by the fast pyrolysis of agricultural waste. It was found that the use of zeolite-based catalysts in the upgrading of gaseous products leads to a decrease in tar content and the increase in the volume concentration of С1-С4 hydrocarbons, CO, CO2, and hydrogen in comparison with the non-catalytic process.
AbstractHydrotreatment of bio-oil oxygen compounds allows the final product to be effectively used as a liquid transportation fuel from biomass. Deoxygenation is considered to be one of the most promising ways for bio-oil upgrading. In the current work, we describe a novel approach for the deoxygenation of bio-oil model compounds (anisole, guaiacol) using supercritical fluids as both the solvent and hydrogen-donors. We estimated the possibility of the use of complex solvent consisting of non-polar n-hexane with low critical points (Tc = 234.5 ºC, Pc = 3.02 MPa) and propanol-2 used as H-donor. The experiments were performed without catalysts and in the presence of noble and transition metals hydrothermally deposited on the polymeric matrix of hypercrosslinked polystyrene (HPS). The experiments showed that the presence of 20 vol. % of propanol-2 in n-hexane results in the highest (up to 99%) conversion of model compounds. When the process was carried out without a catalyst, phenols were found to be a major product yielding up to 95 %. The use of Pd- and Co-containing catalyst yielded 90 % of aromatic compounds (benzene and toluene) while in the presence of Ru and Ni cyclohexane and methylcyclohexane (up to 98 %) were the main products.
AbstractThe effects of catalyst loading, calcination and reaction temperatures on the structural properties and catalytic behavior of Ni/γ-Al2O3 catalyst system in relation to steam reforming of glycerol and catalyst deactivation were investigated. The results showed that catalyst loading, reaction and calcination temperatures had a profound influence on the structure and catalytic activity in glycerol conversion. Use of high calcination temperature (900-1000 °C) led to phase transformation of the active Ni/Al2O3 to less active spinel specie NiAl2O4 that resulted in a successive change of texture and color. The particle size growth and phase change at this temperature were responsible for the catalyst deactivation and low performance especially among the catalyst calcined at high temperatures. Conversely, at low reaction temperatures, catalyst surfaces were marred by carbon deposition. Whilethe polymeric carbon deposited at metal-support interface was associated with low reaction temperatures, high reaction temperatures were characterized predominantly by both amorphous carbon deposited on the active metal surface and polymeric or graphitic carbon deposited at metal-support interface respectively. Calcination temperature showed no significant influence on the location and type of coke deposited on the catalyst surface. Hence, catalyst loading, calcination and reaction temperatures could be tailored to enhance structural and catalytic properties and guard against catalyst deactivation.
AbstractAs a sustainable and renewable energy carrier for transition, hydrogen is considered as a key future fuel for the low carbon energy systems. During the past few decades, attention has been given to the conversion of waste materials, including plastics to the production of hydrogen. Studies in this field are of great importance because they resolve numerous problems brought about by plastic waste with other forms of waste. Polyethylene terephthalate (PET) is one of the major products of plastic waste which constitutes a major threat to environmental conservation efforts and harms living organism. Phenol has been chosen in this study as a solvent for PET to produce hydrogen because of unwanted liquid product in the bio-oil. This research investigates catalytic steam reforming of phenol with dissolved PET for hydrogen production. The aim of this study was the review of a highly active and stable catalyst for hydrogen production from steam reforming waste products. The analysis of product composition indicated that steam reforming of PET-phenol generally produced a high amount of aliphatic branched-chain compounds, together with a moderate amount of cyclic compounds. The reaction conditions also led to the alkylation of phenol by the reforming products from the PET-phenol solution with and without the catalyst. In conclusion, this study explored new ways to use l product derived from waste plastic materials. It provides a promising clean technology, which employed polyethylene terephthalate waste dissolved in phenol (as a solvent) for hydrogen production.
AbstractSome solid solutions have been strongly utilized over the years as good materials for the synthesis of electrocatalysts and photoctalysts. Sometimes, they are used as supports in order to improve electrocatalytic and photocatalytic properties. We show various achievements of solid solutions as good electrocatalysts, and also, good electrocatalysts support materials in oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Also, we demonstrate various works utilizing solid solutions as good photocatalysts, and good photocatalysts support materials in overall water splitting and carbon dioxide reduction. In all these reports, solid solutions proved to posses the necessary properties needed of any material as electrocatalysts and photocatalysts. In many cases, their use as catalysts supports recorded great improvements. X-ray photoelectron spectroscopy (XPS) was largely used to confirm the chemical environment of the results obtained, together with X-ray diffraction (XRD). In the electrochemical methods, cyclic voltammograms (CVA), chronoamperometry and rotating disk electrode (RDE), were also carried out. Linear sweep voltametry (LSV) curve was carried out in some cases to measure the current at a working electrode, and tables were shown for clear explanation. In addition, a photoluminescence spectrum (PL) was used to probe the electronic structure of the various solid solutions.
