Dominant Reaction Pathways in the Catalytic Partial Oxidation of CH4 on Rh

Reforming technologies are at the heart of converting fossil fuels and biofuels to syngas and hydrogen for novel energy applications and, among reforming technologies, catalytic partial oxidation is appealing for decentralized energy production due to the compactness of reactors. Yet, the mechanisms of these reactions are poorly understood. Here we combine fundamental surface chemistry and detailed reactor models to elucidate the pathways leading to syngas and propose strategies for optimizing the process.     

A C1 microkinetic model for methane conversion to syngas on Rh/Al2O3

A microkinetic model capable of describing multiple processes related to the conversion of natural gas to syngas and hydrogen on Rh is derived. The parameters of microkinetic models are subject to (intrinsic) uncertainty arising from estimation. It is shown that intrinsic uncertainty could markedly affect even qualitative model predictions (e.g., the rate‐determining step). In order to render kinetic models predictive, we propose a hierarchical, data‐driven methodology, where microkinetic model analysis is combined with a comprehensive, kinetically relevant set of nearly isothermal experimental data. The new, thermodynamically consistent model is capable of predicting several processes, including methane steam and dry reforming, catalytic partial oxidation, H₂ and CO rich combustion, water‐gas shift and its reverse at different temperatures, space velocities, compositions and reactant dilutions, using the measured Rh dispersion as an input. Comparison with other microkinetic models is undertaken. Finally, an uncertainty analysis assesses the effect of intrinsic uncertainty and catalyst heterogeneity on the overall model predictions. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Discovery of Potent Vascular Endothelial Growth Factor Receptor‐2 Inhibitors

Substantial evidence over the last decades has implicated uncontrolled angiogenesis with various pathological states, including cancer. Vascular endothelial growth factor (VEGF) plays a critical role in its regulation. Because the tyrosine kinase VEGF receptor‐2 (VEGFR‐2) is the major mediator of the mitogenic, angiogenic, and permeability‐enhancing effects of VEGF, it has become one of the most profound anti‐angiogenesis targets. Inspired by the anthranilamide class of VEGFR‐2 inhibitors, we performed a computational analysis of some potent representative members, using docking and molecular dynamics calculations. Based on the observations drawn from introducing the effect of the receptor's flexibility in implicit aqueous environment, we designed, synthesized, and characterized several new analogues of related scaffolds with modifications in their steric and electronic characteristics. In vitro evaluation of these compounds revealed several novel VEGFR‐2 inhibitors that are less cytotoxic and more potent than the parent compounds.     

A Hybrid Support Vector Fuzzy Inference System for the Classification of Leakage Current Waveforms Portraying Discharges

Several techniques have been applied on leakage current waveforms in order to extract information regarding electrical activity on high-voltage insulators. However, a fully representative value is yet to be defined. In this article, a hybrid support vector fuzzy inference system is introduced as a classification tool. The system incorporates fuzzy logic, genetic algorithms, and support vector machines. Apart from the classification accuracy achieved, the system also produces a set of fuzzy rules under which the classification is made, allowing a further insight of the process. A comparison is made to other classification tools previously applied on the same data set.     

Palygorskite–TiO2 nanocatalysts for photocatalytic degradation of tebuconazole in water

Palygorskite–TiO₂ nanoparticles are frequently used as nanocatalysts. In the present study, two different nanocatalysts were developed based on the use of different palygorskite–TiO₂ ratios: 40–60 and 10–90. The nanocomposites were investigated for the photocatalytic degradation of the common fungicide tebuconazole (TEB), under aquatic conditions. The samples were extensively characterized by X-ray powder diffraction, attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy and N₂ specific surface area (SSA) by Brunauer–Emmett–Teller (BET) analytical techniques. The TiO₂ nanoparticles were successfully dispersed on the mineral's surfaces and the photocatalytic activity reached 88.4% for the palygorskite–TiO₂ ratio of 40:60, where the dispersion was better as proved by the total pore volume and BET parameters (0.49 cm³/g and 258 m²/g compared to 0.33 cm³/g and 220 m²/g of the 10:90 ratio). The photocatalytic efficiency of the proposed materials was significantly higher than Degussa P25 (33.2%), and that makes the palygorskite–TiO₂ nanocomposites very promising for advanced application in fungicides' degradation in aquatic environments.     

Comparison of Ethylene Glycol Steam Reforming Over Pt and NiPt Catalysts on Various Supports

Steam reforming of ethylene glycol (EG) was studied on Pt and NiPt catalysts supported on γ-Al₂O₃, TiO₂, and carbon. On all supports bimetallic NiPt catalysts show higher activity for H₂ production than the corresponding Pt catalysts as predicted from model surface science studies. The kinetic trends are similar for all catalysts (Pt and NiPt) with the H₂ production rate being zero-order and fractional order with respect to water and ethylene glycol, respectively. Slight differences in selectivity to minor products are observed depending both on active metal and support. On γ-Al₂O₃, NiPt shows higher H₂ and less alkane formation than Pt. TiO₂ supported catalysts show increased water-gas shift activity but also increased selectivity to alkane precursors. NiPt/C is identified as an active and selective catalyst for EG reforming.     

Reactive adsorption for the selective dehydration of sugars to furans: Modeling and experiments

5‐hydroxymethylfurfural (HMF) can be produced from the acid‐catalyzed dehydration of fructose, but its yield is limited due to subsequent HMF degradation to side products. A reactive adsorption process is proposed to improve the yield to HMF. Separate experimental single‐component isotherms of fructose, HMF, formic acid, and levulinic acid on carbon BP2000 and reaction kinetics of the fructose dehydration to HMF in aqueous solution of HCl are presented to develop empirical isotherms and kinetic rate constants, respectively. These submodels are subsequently integrated in an adsorptive reactor at a range of temperatures (100–150^°C) with different loadings of adsorbent. It is shown that the adsorbent improves HMF yield compared to the single‐solution phase (adsorbent‐free case). Low temperatures and high‐adsorbent loadings improve HMF yield. Under certain conditions both reactive adsorption and the commonly used reactive extraction can result in a similar improvement in HMF yield. HMF recovery from the solid adsorbent has been identified as a major challenge that can be ameliorated through adsorbent and solvent selection. The framework outlined here can be applied to any aqueous phase chemistry where the desired product is an intermediate in a reaction cascade. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3378–3390, 2013