Catalytic Deoxygenation of Guaiacol Using Methane

Guaiacol, produced by thermal degradation of lignin, represents a model compound for upgrading of fast pyrolysis bio-oils by deoxygenation. In our prior work, with Pt/C catalyst, such a process using H₂ was studied. To overcome the high cost of H₂, methane is used in this work to deoxygenate guaiacol. On Pt/C catalyst, in terms of guaiacol conversion and product distribution, methane is found to exhibit as good deoxygenation performance as H₂. The lifetime of this catalyst, however, is short (<3 h). The lifetime of Pt–Bi/C catalyst is extended (no significant deactivation in 5 h), by addition of bismuth as a promoter. This work provides a new approach for bio-oil upgrading using methane as a reductant instead of hydrogen

Highly Selective Nonoxidative Coupling of Methane over Pt-Bi Bimetallic Catalysts

There is widespread interest in converting methane, primary component of natural gas and shale gas, into valuable chemicals. As an important direct methane transformation technique, despite extensive research conducted for decades, oxidative coupling of methane (OCM) remains industrially uneconomical owing to low selectivity toward valuable target products (C₂ species, ethane/ethylene). In the present work, we describe that ZSM-5 zeolite supported bimetallic Pt-Bi catalysts stably and selectively convert methane to C₂ species with high carbon selectivity (>90%) at relatively moderate temperatures (600–700 °C). On the basis of experimental observations, it is proposed that the surface Pt in the catalysts functions as the active site for methane activation, while Bi addition as promoter plays an important role in C₂ species formation and catalyst stability

Conversion of Glycerol to Hydrocarbon Fuels via Bifunctional Catalysts

Utilization of byproduct glycerol improves biodiesel production in terms of both economics and sustainability. Conversion of glycerol to hydrocarbon (GTH) fuels is among the promising options, which provides additional renewable energy besides biodiesel and contributes further to independence from fossil fuels. In the present work, bifunctional catalysts (Pt/H-ZSM-5 and Pd/H-ZSM-5) were selected, prepared, characterized, and tested for GTH conversion. The addition of noble metals enhances aromatics’ yield, and both catalysts convert GTH fuels effectively. On the basis of the experimental observations and prior literature, it is proposed that GTH conversion follows sequential hydrodeoxygenation and aromatization steps. Under optimized conditions, ∼90% glycerol conversion and ∼60% yield of aromatic hydrocarbons were achieved over the Pd/H-ZSM-5 catalyst

Solution Combustion Synthesis of High Surface Area CeO₂ Nanopowders for Catalytic Applications: Reaction Mechanism and Properties

High surface area cerium oxide (CeO₂) is an important material as a catalyst component in many applications owing to its unique redox properties, high oxygen storage capacity, and ability to disperse metal on its surface. In this work, CeO₂ nanopowders were prepared by solution combustion synthesis (SCS), varying the synthesis parameters in terms of precursor oxidizer (cerium nitrate hexahydrate and cerium ammonium nitrate), fuel (glycine and hydrous hydrazine), fuel-to-oxidizer ratio (0.5–3), and gas generating agent (ammonium nitrate). These parameters strongly influence the combustion features, including combustion temperature and amount of gas evolved during combustion, and, in turn, the properties of formed CeO₂ powders. On the basis of the experimental results, the combustion reaction mechanism and correlation between the SCS parameters and properties of the resulting powder are discussed. The samples were characterized using X-ray diffraction, transmission electron microscopy, Raman, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller techniques. The tailored CeO₂ nanopowder synthesized using hydrous hydrazine fuel, fuel-to-oxidizer ratio 2, and ammonium nitrate/metal nitrate ratio 4 exhibited small CeO₂ crystallite size (7.9 nm) and high surface area (88 m²/g), which is the highest value among all prior reported SCS-derived CeO₂ powders

Solution Combustion Synthesis of High Surface Area CeO₂ Nanopowders for Catalytic Applications: Reaction Mechanism and Properties

High surface area cerium oxide (CeO₂) is an important material as a catalyst component in many applications owing to its unique redox properties, high oxygen storage capacity, and ability to disperse metal on its surface. In this work, CeO₂ nanopowders were prepared by solution combustion synthesis (SCS), varying the synthesis parameters in terms of precursor oxidizer (cerium nitrate hexahydrate and cerium ammonium nitrate), fuel (glycine and hydrous hydrazine), fuel-to-oxidizer ratio (0.5–3), and gas generating agent (ammonium nitrate). These parameters strongly influence the combustion features, including combustion temperature and amount of gas evolved during combustion, and, in turn, the properties of formed CeO₂ powders. On the basis of the experimental results, the combustion reaction mechanism and correlation between the SCS parameters and properties of the resulting powder are discussed. The samples were characterized using X-ray diffraction, transmission electron microscopy, Raman, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller techniques. The tailored CeO₂ nanopowder synthesized using hydrous hydrazine fuel, fuel-to-oxidizer ratio 2, and ammonium nitrate/metal nitrate ratio 4 exhibited small CeO₂ crystallite size (7.9 nm) and high surface area (88 m²/g), which is the highest value among all prior reported SCS-derived CeO₂ powders

Tailored Solution Combustion Synthesis of High Performance ZnCo₂O₄ Anode Materials for Lithium-Ion Batteries

A promising Li-ion battery anode material, nanostructured ZnCo₂O₄ spinel, is tailored by solution combustion synthesis to explore how reaction conditions can be tuned to enhance electrochemical performance. A strategy of using glycine and citric acid as fuels, ammonium nitrate as gas generating agent, and optimized fuel to oxidizer ratio results in a mild volume combustion mode with significant weight loss by gas evolution occurring during calcination to mitigate particle sintering. This yields a mesoporous product structure with a tap density of 1.48 g cm^–3, which accommodates volumetric changes during lithiation, resulting in a high stable capacity of 1000 mAh g^–1 (C/2 rate) and 950 mAh g^–1 (1 C rate) at 22 °C after initial formation cycles. This study demonstrates that with the use of mixed fuels, gas generating additives, and appropriate fuel to oxidizer ratio, ZnCo₂O₄ material synthesized by the efficient, one-step solution combustion synthesis method can be tuned to provide excellent electrochemical performance

Hydrodynamics of Trickle Bed Reactors with Catalyst Support Particle Size Distributions

Characterization of the hydrodynamics enables operation of trickle bed reactors within the desired flow regime and under conditions for uniform distribution of gas and liquid, resulting in an essentially plug flow contacting pattern. Studies reported in the literature are typically restricted to systems of beds packed with catalyst supports of a uniform size. This work addresses the impact of supports with particle size distributions on reactor hydrodynamics. An experimental database of pressure drop and liquid holdup was developed and, by careful definition of the particle diameter, literature models were adapted to account for the particle size distribution. The resulting models give improved predictions for packing media with a particle size distribution while maintaining applicability to uniform systems