Greening experiments by reducing hazardous reagents and waste has become a primary focus for many academic institutions.  Electrophilic aromatic substitutions typically use Lewis Acids as the catalyst.  Aromatic compounds with ring-activating groups containing nitrogen cannot be catalyzed by Lewis acids since they react with the non-bonded electron pair.  Graphite is known as a greener catalyst for electrophilic aromatic substitution reactions.  In this paper we present the results of implementing graphite as a catalyst in electrophilic aromatic substitution reactions on strongly activated and deactivated aromatic compounds.  This can potentially be applied to many similar organic experiments as a new, greener alternative technique.

Green electrophilic aromatic substitution reactions using graphite as a catalyst

Advances in the synthesis and performance of nanoscale magnetic-abrasive fluids, used for magnetic field-assisted finishing (MAF), are needed to overcome current surface roughness limitations. Thus, we are exploring how to tailor the magnetic behavior of transition metal ferrite (MFe2O4, M = Co, Ni, Cu, Zn) nanoparticles.  Varied cation stoichiometries and particle sizes of MFe2O4, (CoWNiXCuYZnZ)Fe2O4, and other solid solutions  were examined.  Using a solution precipitation route, 10-50 nm particles with the spinel phase were prepared by the thermal decomposition of Fe(CO)5 and various transition metal acetylacetonates (M(acac)2, M = Cu, Ni, Co), and Zn(Et)2. X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Super Quantum Inference Device (SQUID) Magnetometery was used to characterize and study each synthesized nanomaterial. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Tailoring the magnetic behavior of transition metal ferrite nanoparticles

Advances in coatings, to prevent biofouling and corrosion, are needed to support marine hydrokinetic (MHK) device operation, performance, and reliability. MHK devices are being developed to produce renewable energy from ocean waves, tides, and thermal gradients.  Due to the promise of enhanced protection, nanobased coatings are being pursued to determine performance�which is critical before they can be accepted by the MHK industry.  To investigate fundamental properties, self-assembled monolayers and nanocomposites of: Ag, ZnFe2O4, CNT, CeO2, SiO2 were explored. The nanoparticles were prepared through either a solution precipitation or solvothermal route.  Corrosion resistance was characterized from electrochemical impedance spectroscopy while High-Throughput and CDC reactor techniques were used to determine biofouling prevention.  Results were compared to commercially available coatings.  Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Nanobased coatings for the prevention of corrosion and biofouling for marine hydrokinetic energy devices

Solution routes to SnE, and PbxSn1-xE [E= S, Se, Te] nanoparticles are of interest for bioimaging and solar panels due to their size-tunable infrared properties. To explore the influence of precursor selection on morphology and phase, SnE and PbxSn1-xE  particles were prepared using solution precipitation or solvothermal routes and various tin carboxylates: Sn(OCCH3)2 (1 ), Sn(O4C2)2 (2 ), Sn(O2C(C2H5)CH(CH2)3CH3)2 (3 ), and Sn(O2C(CH2)7CH=CH(CH2)7CH3 (4 ), and chalcogenides (S, Se, and Te) were used. The yield was characterized with X-ray Diffraction and Transmission Electron Microscopy. Through these synthetic routes, we have prepared nanosheets and particles with various phases of SnO, SnSe, SnTe, and PbxSn1-xE. This work was supported by the Laboratory Directed Research and Development (LDRD) program at Sandia National Laboratories.  Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Phase and morphological control of SnE and PbxSn1-xE [E= S, Se, Te] (E= S, Se, Te) nanomaterials through tin carboxylate precursor selection

The coverage of surface adsorbates influences both the number and types of sites available for catalytic reactions at a heterogeneous surface, but accounting for adsorbate-adsorbate interactions and understanding their implications on observed rates remain challenges for simulation. Here we demonstrate the use of a density-functional-theory (DFT) parameterized cluster expansion (CE) to incorporate accurate adsorbate-adsorbate interactions into a surface kinetic model. The distributions of adsorbates and reaction sites at a metal surface as a function of reaction conditions are obtained through Grand Canonical Monte Carlo simulations on the CE Hamiltonian. Reaction rates at those sites are obtained from the CE through a DFT-parameterized Br�nsted-Evans-Polyani (BEP) relationship or through a separate CE. The approach provides ready access both to steady-state rates and rate derivatives, and further provides insight into the microscopic factors that influence observed rate behavior. We demonstrate the approach for O2 temperature-programmed desorption and for steady-state O2 dissociation at an O-covered surface, for a range of metals.

Accurate coverage-dependence incorporated into first-principles kinetic models

Metal oxide materials may be used in two-step solar thermochemical water-splitting cycles to renewably produce hydrogen.  Here, we use first-principles density functional calculations to investigate promising oxide materials for use in these cycles.  We present a general analysis of the equilibrium thermodynamics of a two-step metal oxide water splitting cycle, and survey a large number (more than 100) binary oxide redox couples.  CeO2 is promising, but the reoxidation at low temperature is kinetically limited due to slow surface processes, however, very little is known about the mechanism.  We use DFT to identify stable surface structures containing surface or subsurface oxygen vacancies, H2O or H. We calculate barriers for diffusion of oxygen vacancies, and barriers for dissociation of water and the desorption of hydrogen.  Our results show that the surface coverage of adsorbed H may play a key role in the kinetics of water splitting on ceria surfaces.

Solar fuels from thermochemical gas splitting

Diels-Alder reactions are used extensively throughout chemistry as a means to form six member carbon rings. Generally Lewis acids are used as a catalyst for the Diels-Alder reaction. Green chemistry techniques are becoming increasingly popular among academic institutions for their safety and economic reasons. In this research, we studied the novel use of graphite as a catalyst in Diels-Alder reactions with both traditional organic solvent and environmentally friendly ionic solvents. We present a green laboratory procedure for Diels-Alder reactions that can be used in academic institutions. This can reduce the need to purchase expensive catalysts and use of flammable or hazardous solvents which will reduce the environmental impact.

Novel application of graphite as a catalyst for Diels-Alder reactions

The cost of oil is increasing tremendously. On the other hand, bioethanol can be produced very efficiently, but there are alternate techniques that could be used to utilize the reagents and make the process more cost effective and greener for the environment. Immobilization of the saccharomyces cerevisiae strain on maple bark pieces was investigated in order to determine the efficiency of ethanol production. The maple bark proves to be an excellent support for yeast absorption due to the presence of sugars and its local availability. Using the sugars from molasses and the immobilized yeast cells on the maple bark pieces the ethanol can be fermented rather quickly and easily. In addition, maple bark support can be reused for multiple fermentations resulting and yeast makes this process more efficient. The immobilization technique and the local supports used prove to be an adequate way to attain the goal of generating greener ethanol.

Green ethanol synthesis using Saccharomyces cerevisiae supported on maple bark

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.