Gasification of Glycerol Over Ni/γ-Al2O3 For Hydrogen Production: Tailoring Catalytic Properties to Control Deactivation

The 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.

Hydrogen Production from Catalytic Polyethylene Terephthalate Waste Reforming Reaction, an overview

As 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.

A study of fast pyrolysis of plant biomass assisted by the conversion of volatile products using Fe(Co, Ni)/ZSM-5 catalysts

This 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.

Hydrogen-Free Deoxygenation of Bio-Oil Model Compounds over Sulfur-Free Polymer Supported Catalysts

Hydrotreatment 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.

Solid-Solutions as Supports and Robust Photocatalysts and Electrocatalysts: A Review

Some 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.

Alkali Lignin Catalytic Hydrogenolysis with Biofuel Production

In this paper synthesized palladium (Pd)-containing catalysts were used in the hydrogenolysis of lignin in the presence of a hydrogen donor solvent, i-propanol, to obtain liquid fuel components. A study of the influence of the catalyst support nature, catalyst preparation method and supercritical solvent nature on the lignin depolymerization was completed. It was found that the use of Pd-containing catalysts results in the formation of aromatic compounds (mainly benzene and toluene) for both supercritical solvents used (i-propanol and CO2). The maximum conversion of lignin (50 %) was achieved when the supercritical i-propanol was used and maximum selectivity to aromatics (over 70 %) was observed in the presence of the Pd-containing catalyst synthesized by hydrothermal deposition on the polymeric matrix of hyper-crosslinked polystyrene.

Mesoporous carbon and microporous zeolite supported Ru catalysts for selective levulinic acid hydrogenation into γ-valerolactone

Ru supported on mesoporous carbon Sibunit and microporous zeolites (HZSM-5, SiO2/Al2O3 = 250; H-Beta, SiO2/Al2O3 = 30; H-Y, SiO2/Al2O3 = 5; H-USY, SiO2/Al2O3 = 30) synthesized by the sol-gel method (CSIR-National Chemical Laboratory, Pune India) were prepared by impregnation of the corresponding supports with RuCl3∙nH2O (0.1 M) followed by reduction in H2. Catalyst screening in levulinic acid (LA) (15 mL, 6.9 mmol) hydrogenation into g-valerolactone (GVL) with 1,4-dioxane (165°C, hydrogen pressure ca. 16 bar) as a solvent showed higher activity and selectivity to GVL of Ru/zeolites compared to carbon supported catalysts. Among Ru/zeolites LA conversion increased as follows Ru/HZSM-5 < Ru/H-Y < Ru/H-USY < Ru/H-Beta demonstrating a clear advantage of H-Beta preparation method. Optimization of the support microstructure and acidity opens a reliable way for selective catalytic LA hydrogenation to GVL. The catalysts were analyzed by TEM, XRD, H2-TPR and N2 physisorption to compare their physical chemical properties.

Au/TiO2 catalysts prepared by borohydride reduction for preferential CO oxidation at near-ambient temperature

Au nanoparticles were prepared in solution using HAuCl4.3H2O as Au precursor, sodium citrate as stabilizing agent and sodium borohydride as reducing agent. The influence of synthesis parameters such as BH4:Au and Citrate:Au ratios were studied. In a further step, the stabilized Au nanoparticles were supported on TiO2 with different Au loadings (wt%). The resulting Au/TiO2 catalysts were characterized by Energy-dispersive X-ray spectroscopy, X-ray diffraction and Transmission Electron Microscopy and tested for the preferential oxidation of carbon monoxide in hydrogen-rich stream. Au nanoparticles stabilized in solution were obtained with sizes in the range of 3-4 nm. After supported on TiO2, the Au nanoparticles size did not change and the Au/TiO2 catalysts exhibited excellent performance and stability in the temperature range of 20 - 50°C.

A review on CO oxidation, methanol synthesis, and propylene epoxidation over supported gold catalysts

The aim of this general review is to give an overview of the reaction pathways involving the transformation of carbon monoxide (CO), methanol synthesis and propylene epoxidation using gold (Au) and gold supported clusters. Over the catalyst system of Nano-gold (Au/SiO2), the process of methane to methanol was also highlighted. A reaction mechanism proposed, indicated that molecular oxygen was consumed in the oxidation–reduction cycle. Consequently, methane oxidation to methanol can be achieved as a green chemical process. The system can also be used in other green chemical processes of liquid phase or gas phase oxidations. Methanol is expected to be a potential solution to the partial deployment of fossil source-based economies. Moreover, it is a recognized energy carrier that is better than other alternatives in terms of transportation, storage and reuse. New or improved catalysts for methanol production are likely to be discovered in the near future.

Perovskite-structured Active Solid Catalyst for Biofuel Synthesis

A solid catalyst tailored to perovskite structure was synthesized and investigated for catalytic activity in a transesterification reaction to form biodiesel. The catalyst has demonstrated high catalytic activity and selectivity for biodiesel under very mild reaction conditions and short reaction times. The catalyst system has shown robust resistance to leaching of the active phase when reused. The performance was attributable to the perovskite structure and the dopant metal used. Hence, this work has shown that the structure and dopant metal of the solid catalyst could be tailored to enhance catalytic activity and durability for renewable fuel synthesis.