Search

Due to its significant aromatic content, lignin is an attractive source of valuable organic chemicals. As most of the proposed lignin depolymerization processes are expected to be liquid-phase, it is necessary to understand the effect of solvent quality on the structure and dynamics of lignin. Here we use all-atom molecular dynamics simulations to understand the evolution of lignin structure as a function of methanol concentration in methanol/water solution at different temperatures. We utilize two different lignin models: softwood consisting of guaiacyl (G) monomer and hardwood consisting of heteropolymer containing guaiacyl/syringyl (S) with a 1.35:1 ratio. The presence of additional methoxy groups in the hardwood lignin leads to a more extended configuration than softwood lignin with increasing methanol concentration. Structural features (radius of gyration and solvent accessible surface area) of lignin correlate with the strength of intermolecular forces quantified using cohesive energy density. We find that methanol preferentially solvates the nonpolar segments of the lignin polymer while water molecules solvate the polar functional groups. Thus, as the methanol concentration increases, methanol can better solvate lignin polymer, leading to a more extended configuration suitable for catalytic transformation to value-added chemicals.

Lignin is the essential building block of lignocellulosic biomass, an excellent renewable source of different aromatic monomers for the polymer and biofuel industry. The depolymerization of lignin into value-added chemicals and fuels through the catalytic process poses a significant challenge due to the complex structure of lignin. Understanding lignin's conformational diversity and dynamics in the liquid phase is crucial for designing an effective depolymerization process. Here, we conducted all-atom molecular dynamics simulations to understand the conformation and dynamics of softwood lignin on the all-silica zeolite nanosheet based on the MFI topology in a binary mixture of water-methanol at three different molar compositions (0%, 50%, 100% methanol). We observed that methanol-surface interaction is stronger than water-surface, and methanol readily diffused into the MFI core. Lignin and surface contact decreases with increasing methanol composition due to higher solubility and dynamics. Lignin dynamics on the surface in neat water is an order of magnitude smaller than methanol. We also found that lignin adopts a slightly extended conformation when it stays on the surface than in the bulk solution phase for the pure water case, whereas for pure methanol and the binary structures are statistically similar.

Hypothyroidism is classified as congenital and acquired according to the time of onset. Consequences of thyroid gland dysfunction also depend on the life stage at which they occur. Peripheral and central nervous system dysfunction are important clinical features of congenital as well as acquired hypothyroidism. Although thyroid hormone effects on the brain are most prominent in development, also in adult-acquired hypothyroidism symptoms such as sensory impairments, disagreeable smells and taste, slowness of thought and action, changes of speech, irritability, headaches ,sleep disturbances, confusion up to delusions and Hallucinations, impairments of memory, of vision as well as of hearing frequently occur. The most prominent and first significant clinical symptom to develop in hypothyroidism is a slowing of speech and of visual perception. These findings indicate CNS involvement in hypothyroidism. VEP may be a useful test to detect these changes in early stage of disease.

High-spin quintet polyradicals are reported by embedding the electron-deficient 6,6-dicyanofulvene group. We present a design strategy delineating control of the ground state from closed-shell to open-shell polyradical character.

Most organic semiconductors have closed-shell electronic structures, however, studies have revealed open-shell character emanating from design paradigms such as narrowing the bandgap and controlling the quinoidal-aromatic resonance of the π-system. A fundamental challenge is understanding and identifying the molecular and electronic basis for the transition from a closed- to open-shell electronic structure and connecting the physicochemical properties with (opto)electronic functionality. Here, we report donor-acceptor organic semiconductors comprised of diketopyrrolopyrrole and naphthobisthiadiazole acceptors and various electron-rich donors commonly utilized in constructing high-performance organic semiconductors. Nuclear magnetic resonance, electron spin resonance, magnetic susceptibility measurements, single-crystal X-ray studies, and computational investigations connect the bandgap, π-extension, structural, and electronic features with the emergence of various degrees of diradical character. This work systematically demonstrates the widespread diradical character in the classical donor-acceptor organic semiconductors and provides distinctive insights into their ground state structure-property relationship., The classical narrow bandgap donor-acceptor organic semiconductors show great application potential in organic electronics, bio-imaging and other fields. Here, the authors systematically and rigorously demonstrate their open-shell diradical character via experimental and theoretical investigation.

High-spin ground-state organic materials with unique spin topology can significantly impact molecular magnetism, spintronics, and quantum computing devices. However, strategies to control the spin topology and alignment of the unpaired spins in different molecular orbitals are not well understood. Here, we report modulating spin distribution along the molecular backbone in high-spin ground-state donor-acceptor (D-A) conjugated polymers. Density functional theory calculations indicate that substitution of different heteroatoms (such as C, Si, N, and Se) alters the aromatic character in the thiadiazole unit of the benzobisthiadiazole (BBT) acceptor and modulates the oligomer length to result in high-spin triplet ground-state, orbital and spin topology. The C, Si, and Se atom substituted polymers show a localized spin density at the two opposite ends of the polymers. However, a delocalized spin distribution is observed in the N substituted polymer. We find that the hybridization (sp

Stable organic semiconductors (OSCs) with a high-spin ground-state can profoundly impact emerging technologies such as organic magnetism, spintronics, and medical imaging. Over the last decade, there has been a significant effort to design π-conjugated materials with unpaired spin centers. Here, we report new donor–acceptor (D–A) conjugated polymers comprising cyclopentadithiophene and cyclopentadiselenophene donors with benzobisthiadiazole (BBT) and iso-BBT acceptors. Density functional theory calculations show that the BBT-based polymers display a decreasing singlet–triplet energy gap with increasing oligomer chain length, with degenerate singlet and triplet states for a N = 8 repeat unit. Furthermore, a considerable distance between the unpaired electrons with a pure diradical character disrupts the π-bond covalency and localizes the unpaired spins at the polymer ends. However, replacing the BBT acceptor with iso-BBT leads to a closed-shell configuration with a low-spin ground-state and a localized spin density on the polymer cores. This study shows the significance of the judicious choice of π-conjugated scaffolds in generating low- (S = 0) and high-spin (S = 1) ground-states in the neutral form, by modulation of spin topology in extended π-conjugated D–A polymers for emergent optoelectronic applications.

Liquid-phase heterogeneous catalysis using zeolites is important for biomass conversion to fuels and chemicals. There is a substantial body of work on gas-phase sorption in zeolites with different topologies; however, studies investigating the diffusion of complex molecules in liquid medium into zeolitic nanopores are scarce. Here, we present a molecular dynamics study to understand the sorption and diffusion of aqueous β-d-glucose into β-zeolite silicate at

Metal phosphides have been investigated as promising catalysts for many hydrogenation reactions, including CO2 reduction. Due to the vast compositional space available to discover active and select...

Dye-sensitized solar cells (DSCs) have drawn a significant interest due to their low production cost, design flexibility, and the tunability of the sensitizer. However, the power conversion efficiency (PCE) of the metal-free organic dyes is limited due to the inability of the dye to absorb light in the near-infrared (NIR) region, leaving a large amount of energy unused. Herein, we have designed new DSC dyes with open-shell character, which significantly red-shifts the absorption spectra from their counterpart closed-shell structure. A small diradical character (y < 0.10) is found to be beneficial in red-shifting the absorption maxima into the NIR region and broadening up to 2500 nm. Also, the open-shell dyes significantly reduce the singlet–triplet energy gaps (ΔEST), increase the total amount of charge-transfer to the semiconductor surface, reduce the exciton binding energy, and significantly increase the excited-state lifetimes compared to the closed-shell systems. However, the closed-shell dyes have higher injection efficiency with increased intramolecular charge transfer (ICT) character. Our study reveals the design rule for open-shell DSC dyes to be able to absorb photons in the NIR region, which can increase the efficiency of the solar cell device.

Microbial cell disruption using pressurized gases (e.g., CO2) is a promising approach to improve the lipid recovery from wet oleaginous microorganisms by eliminating the energy-intensive drying required for conventional methods. In this study, we perform cell disruption of Rhodotorula glutinis using pressurized CH4, N2, and Ar where we find the efficacy of these gases on cell viability is minimal. Since CO2 is found to be the only viable gas for microbial cell disruption among these four gases, we use a combination of Box–Behnken design and response surface methodology (RSM) to find the optimal cell disruption by tuning different parameters such as pressure (P), temperature (T), exposure time (t), and agitation (a). From RSM, we find 6 log reduction of viable cells at optimized conditions, which corresponds to more than 99% cell death at P = 4000 kPa, T = 296.5 K, t = 360 min, and a = 325 rpm. Furthermore, from the scanning electron microscope (SEM), we find a complete morphological change in the cell structure when treated with pressurized CO2 compared to the untreated cells. Finally, we find that up to 85% of total lipid can be recovered using optimized pressurized CO2 from wet biomass compared to the untreated wet cells where up to 73% lipid can be recovered.

The catalytic properties of monometallic and bimetallic Ru and Mo phosphides were evaluated for their ability to selectively hydrogenate furfural to furfuryl alcohol. Monometallic MoP showed high selectivity (98%) towards furfuryl alcohol, while RuP and Ru2P exhibited lower selectivity at comparable conversion. Bimetallic promotional effects were observed with Ru1.0Mo1.0P, as the pseudo-first order reaction rate constant for furfural hydrogenation to furfuryl alcohol, k1, was at least 5× higher than MoP, RuP, and Ru2P, while maintaining a 99% selectivity. Composition-directed catalytic studies of RuxMo2−xP (0.8 Ru1.2Mo0.8P > MoP > Ru0.8Mo1.2P > RuP > Ru2P. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to examine the configuration of adsorbed furfural on the synthesized catalysts, but the results were inconclusive and no correlation could be found with the selectivity due to the possible IR inactive surface modes with furfural adsorption. However, gas phase density functional theory calculations suggested the x = 1.0 material in RuxMo2−xP (0.8 < x < 1.2) had the most favorable furfural adsorption energy. Experimentally, we also observed that the solvent greatly influenced both the conversion and selectivity, where isopropanol provided the highest selectivity to furfuryl alcohol. Finally, recycling experiments showed a 12% decrease in k1 after 3 cycles without any regeneration, but the activity could be fully recovered through a re-reduction step.

The knowledge of solubility of different gases in triglycerides is required to design efficient cell disruption processes for biodiesel production from wet biomass. In this combined experimental and simulation study, we determine carbon dioxide solubility in long (C18) and short (C4) chain triglycerides, and provide microscopic picture of CO2–triglyceride interaction. The solubility of CO2 in tributyrin (a small chain triglyceride) was determined using a pressure drop gas apparatus at P = 800–1700 kPa and T = 283.2–303.2 K. Gibbs ensemble Monte Carlo simulations with configurational biased Monte Carlo algorithm were used to compute the solubility of CO2 in both a long chain triglyceride (to mimic canola oil) and tributyrin at different pressures and temperatures. The transferable potentials for phase equilibria force field was used for modeling triglycerides and CO2. Predicted densities and viscosities of both canola oil and tributyrin were in good agreement with the experimental data. We find that the computed solubilities are in excellent agreement with the experimental results for both CO2–canola oil and CO2–tributyrin where the mean deviation were 2.85% and 9.51%, respectively. The structural analysis of liquid phase indicates that CO2 has slightly higher preference to bind with carbonyl group than the nonpolar segments.

Summary Polyradical character and global aromaticity are fundamental concepts that govern the rational design of cyclic conjugated macromolecules for optoelectronic applications. Here, we report donor-acceptor (D−A) conjugated macromolecules with and without π-spacer derivatives to tune the antiferromagnetic couplings between the unpaired electrons. The macromolecules without π-spacer have a closed-shell electronic configuration and show global nonaromatic character in the singlet and lowest triplet states. However, the derivatives with π-spacer develop a nearly pure open-shell diradical and a very high polyradical character, not reported for D−A type macromolecules. Furthermore, the π-spacer derivatives display global nonaromaticity in the singlet ground state, but global aromaticity in the lowest triplet state, according to Baird's rule. The absorption spectra of the open-shell macromolecules calculated with time-dependent density functional theory indicate intensive light absorption in the near-infrared region and broadening to 2,500 nm, making these materials suitable for numerous optoelectronic applications., Graphical Abstract, Highlights • Donor-acceptor macromolecules with open-shell polyradical character are reported. • The antiferromagnetic coupling between the unpaired electrons is modulated with pi-spacer. • The open-shell macrocycles show Baird’s aromaticity in the lowest triplet state. • Open-shell macrocycles red-shift absorption spectra., Chemistry; Supramolecular Chemistry; Computational Chemistry; Macromolecules

Molecular gels are formed by the supramolecular assembly of low molecular weight gelators (LMWGs) in organic solvents or water. Despite significant advances in the field, our understanding of how gelator molecules lead to complex self-assembled fibrillar network (SAFIN) is rather poor. Here, we present molecular dynamics simulations to gain insights into the early-stage aggregation of self-assembled fibrillar network (SAFIN) of 12-hydroxyoctadecanamide (12-HSAm) in octane. Our simulations reveal that the hydroxyl group located at the 12th carbon position plays an important role in the fiber formation. If the hydroxyl group is removed from the backbone, then we find that the aggregates adopt a bilayer morphology rather than cylindrical fibers. Analysis of fibers reveals different morphologies such as cylindrical, tape, and junction zones. A typical cylindrical fiber diameter is 2.4-3.4 nm, while the tape-like fibers are 4.4-8.6 nm in width and 2.4-4.2 nm in depth. In the fibers, we observe that the majority of the gelator molecules interact with neighboring molecules with only one interaction site, leading to growth of the fiber in one dimension. Our simulations help explain the role of functional groups in the self-assembly of small molecules leading to gel formation.

Polyradical character and global (anti)aromaticity are fundamental concepts that govern rational design of cyclic conjugated macromolecules for optoelectronic applications. Here, we have designed donor-acceptor (D-A) macromolecules with ring topology along with their pi-spacer derivatives, and analyzed their unique electronic properties with density functional theory (DFT). The macromolecules with n = 8 and 16 repeat D-A units display similar singlet-triplet energy gap and have closed-shell electronic configuration with no diradical character (y0 = 0). These macromolecules also display global nonaromatic character, which is supported by NICS(0), AICD, and 2D-ICSS analysis. However, the derivatives with pi-spacer (n = 8-pi) develop near pure open-shell character (y0=1) with increased singlet-triplet gap. Furthermore, these derivatives display global antiaromaticity in the singlet ground-state according to Huckel's rule, and global aromaticity in the lowest triplet state following Baird's rule, and have a very high polyradical character, which is not reported for D-A type macromolecules. The calculated absorption spectra with time-dependent DFT (TDDFT) indicates intensive light absorption in the near-infrared (NIR) region broadening to 2500 nm. These macrocycles also display a size-dependent absorption maxima when the number of repeat units increased from n = 8 to 16. Furthermore, due to the development of open-shell character in the pi-spacer derivatives, a significant red-shift in the absorbance wavelength is observed.

Author(s): Wang, Kaiping; Huang, Lifeng; Eedugurala, Naresh; Zhang, Song; Sabuj, Md Abdus; Rai, Neeraj; Gu, Xiaodan; Azoulay, Jason D; Ng, Tse Nga

Catalytic hydrodeoxygenation (HDO) of phenolics is a necessary step for upgrading bio-oils to transportation fuels. Bimetallic catalysts offer the potential of increased activities and selectivities for desired products. Adding non-metallic elements, such as phosphorous, allows for charge distribution between the metal and nonmetal atoms, which improves Lewis acid character of catalytic surfaces. This work utilizes experimental and density functional theory (DFT) based calculations to identify potential C–O bond cleavage pathways and product selectivities for HDO reactions on FeMoP, RuMoP, and NiMoP catalysts. Our work demonstrates that FeMoP catalyst favors direct deoxygenation pathway due to a lower activation energy barrier for C–O bond cleavage whereas RuMoP and NiMoP catalysts promote ring hydrogenation first, followed by the cleavage of C–O bond. The Bader charge analysis indicates that for these catalytic systems Moδ+ site bears a large positive charge which acts as a Lewis acid site for HDO reactions. Overall, we find that trends in the experimental product selectivities are in good agreement with that predicted with DFT calculations.

Vapor liquid equilibria (VLE) and condensed phase properties of carbon dioxide and sulfur dioxide are calculated using first principles Monte Carlo (FPMC) simulations to assess the performance of several density functionals, notably PBE-D3, BLYP-D3, PBE0-D3, M062X-D3, and rVV10. GGA functionals were used to compute complete vapor liquid coexistence curves (VLCCs) to estimate critical properties, while the hybrid and nonlocal van der Waals functionals were used only for computing density at a single state point due to the high computational cost. Our results show that the BLYP-D3 functional performs well in predicting VLE properties for both molecules when compared with other functionals. In the liquid phase, pair correlation functions reveal that there is not a significant difference in the location of the peak for the first solvation shell while the peak heights are different for different functionals. Overall, the BLYP-D3 functional is a good choice for modeling VLE of acidic gases with significant environmental implications such as CO2 and SO2 . © 2017 Wiley Periodicals, Inc.

Lignin, a major biomass component, can be an excellent source for different monomers in the polymer industry. However, the complex and heterogeneous structure of lignin poses a significant challenge for designing energy-efficient processes for depolymerization. As many proposed depolymerization processes are solvothermal, it is essential to understand the structure and dynamics of lignin in solution, in particular aqueous solution. Here, we utilize molecular dynamics simulations to understand the effect of water models on the structure and dynamics of different model lignin oligomers (softwood and hardwood) as a function of temperature. We have examined three different water models: TIP3P, TIP4P/Ew, and flexible SPC/Fw. We find that the diffusion constant of lignin oligomers in an aqueous solution differs significantly depending on the water model used. The diffusion constant of lignin in the TIP3P water model is almost twice as large as that in SPC/Fw and TIP4P/Ew. The softwood and hardwood oligomers adopt an extended structure in TIP3P water compared to SPC/Fw and TIP4P/Ew. Given the different levels of sensitivity of transport and structural properties of aqueous lignin on water models, it is important to take these into account when discussing results from a specific water model.

The study of in situ gas explosion to lyse the triglyceride-rich cells involves the solubilization of gas (e.g., carbon dioxide, CO2 ) in lipid-rich cells under pressure followed by a rapid decompression, which allows the gas inside the cell to rapidly expand and rupture the cell from inside out. The aim of this study was to perform the cell disruption using pressurized CO2 as well as to determine the solubility of CO2 in Rhodotorula glutinis cell suspension, sugar broth media, and spent media. Cell disruption of R. glutinis was performed at two pressures of 2,000 and 3,500 kPa, respectively, at 295.2 K, and it was found from both scanning electron microscopy (SEM) and plate count that a substantial amount of R. glutinis was disrupted due to the pressurized CO2 . We also found a considerable portion of lipid present in the aqueous phase after the disruption at P = 3,500 kPa compared to control (no pressure) and P = 2,000 kPa, which implied that more intracellular lipid was released due to the pressurized CO2 . Solubility of CO2 in R. glutinis cell suspension was found to be higher than the solubility of CO2 in both sugar broth media and spent media. Experimental solubility was correlated using the extended Henry's law, which showed a good agreement with the experimental data. Enthalpy and entropy of dissolution of CO2 were found to be -14.22 kJ mol-1 and 48.10 kJ mol-1 K-1 , 9.64 kJ mol-1 and 32.52 kJ mol-1 K-1 , and 7.50 kJ mol-1 and 25.22 kJ mol-1 K-1 in R. glutinis, spent media, and sugar broth media, respectively. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:737-748, 2017.

The development of task-specific bimetallic phosphide catalysts can be accomplished by exploiting the electronic and bi-functional effects of multiple metal combinations, thus providing materials with tunable catalytic properties. Here, we present the modulation of metal compositions (i.e., Fe and Mo) in the synthesis of FeXMo2−XP (0.88 ≤ X ≤ 1.55), leading to a series of iso-structural, orthorhombic FeXMo2−XP catalysts via reduction at 750 °C. Hydrodeoxygenation of phenol was selected as a probe reaction to showcase the effect of metal composition on the catalytic performance. In particular, catalysts with Fe compositions between 0.99 and 1.14 (i.e., Fe0.99Mo1.01P and Fe1.14Mo0.86P) exhibited high selectivities to C–O bond cleavage of phenol with H2 to form benzene. The catalysts with the highest selectivities to C–O scission also exhibited the highest acidity as determined from NH3 temperature programmed desorption experiments. Density functional theory (DFT) calculations indicate the high Lewis acidity for the ∼1 : 1 Fe : Mo compositions resulted from a greater charge separation between metallic species and P species. These compositions led to greater selectivities to benzene due to desired coordination environment of the phenol on catalytic surface, as evidenced by both DFT calculations and a time on stream study using a benzonitrile poison. Enhanced TOFs were also observed with catalysts exhibiting greater Lewis acid character, which reduce the activation energy required to cleave the C–O bond of phenol, as evidenced by DFT calculations. This structure–property study highlights the effects of metal composition in bimetallic phosphides to enhance the activity and selectivity for C–O bond cleavage reactions.

A new pressure drop solubility gas apparatus was developed to determine the solubility of carbon dioxide in canola oil, a triglyceride consisting primarily of oleic, linoleic, and alpha linoleic acid radicals. Solubility of CO2 in triglycerides was determined at different temperatures (283.2–303.2 K) and pressures (600–2450 kPa). It was found that the solubility of CO2 in triglycerides is higher than that of pure water because triglycerides lack strong hydrogen bond networks that exist in liquid water at the ambient conditions. The experimental solubility was correlated using Krichevsky–Kasarnovsky (KK), Mather-Jou (MJ), and Carvalho-Coutinho (CC) correlations. We find that KK and MJ equations can predict the solubility with higher accuracy. The enthalpy and entropy of absorption of CO2 were calculated using the van’t Hoff plot and were found to be −7.165 kJ.mol−1, and −28.791 J.mol−1.K−1, respectively.

Lignin as a potential renewable source of biofuels, chemicals, and other value-added products has gained much attention. However, the complexity of lignin structure poses a significant challenge for developing efficient valorization techniques. As most processes involve solvothermal conditions to minimize energy cost, lignin depolymerization is governed by reaction conditions (temperature and pressure) and solvents. In this work, binding of β-O-4 linkage consisting lignin dimers on MWW two-dimensional (2D) zeolite is investigated using periodic density functional theory. Furthermore, the effect of different terminated surfaces (H:OH% = 100:0; 50:50; 0:100%), different temperatures (323, 353, 373 K), and different solvents (water and methanol) on the binding modes is quantified. Our work shows that in the gas phase the binding strength increases 10-15 kcal/mol upon increasing the number of hydroxyl groups on the surface. Also, the phenolic dimer binds more strongly than the nonphenolic dimer, and the binding strength of model compounds increases in the presence of the solvent. Analysis of structural changes in the presence of the solvent reveals that the aromatic rings are parallel to the zeolite surface and primary interaction with zeolite is through the hydroxyl groups near the β-O-4 linkage. Furthermore, while the solvation energy decreases with increasing temperature, the opposite trend is observed for the binding energy with the surface.

A conjugated polymer semiconductor was synthesized, which exhibits a high-spin ground state and robust stability., Interest in high-spin organic materials is driven by opportunities to enable far-reaching fundamental science and develop technologies that integrate light element spin, magnetic, and quantum functionalities. Although extensively studied, the intrinsic instability of these materials complicates synthesis and precludes an understanding of how fundamental properties associated with the nature of the chemical bond and electron pairing in organic materials systems manifest in practical applications. Here, we demonstrate a conjugated polymer semiconductor, based on alternating cyclopentadithiophene and thiadiazoloquinoxaline units, that is a ground-state triplet in its neutral form. Electron paramagnetic resonance and magnetic susceptibility measurements are consistent with a high-to-low spin energy gap of 9.30 × 10−3 kcal mol−1. The strongly correlated electronic structure, very narrow bandgap, intramolecular ferromagnetic coupling, high electrical conductivity, solution processability, and robust stability open access to a broad variety of technologically relevant applications once thought of as beyond the current scope of organic semiconductors.

Selective hydrogenation of α,β-unsaturated aldehydes is challenging due to the competition between unsaturated functional groups (C C and C O) with the catalyst. This study probes the use of metal phosphides as selective catalysts for cinnamaldehyde hydrogenation. Monometallic phosphides (MP; M = Ni, Co, Ru) showed high affinity to C C hydrogenation, with 98 % selectivity to hydrocinnamaldehyde with both Ni2P and Co2P. Bimetallic RuMoP improved the cinnamyl alcohol (COL) selectivity up to 91 %, while bimetallic NiMoP preferred C C hydrogenation to hydrocinnamaldehyde. Density functional theory (DFT) suggested greater charge transfer between the carbonyl oxygen and Mo sites on the surface leading to a lower activation energy barrier for cinnamaldehyde hydrogenation to COL. Product and pyridine doping studies resulted in an increased selectivity to COL possibly through surface coverage effects. Lastly, diffuse reflectance infrared Fourier transform spectra and DFT provided insights into the CAL adsorption mode and the reaction mechanism that supported the experimental observation.

Microbial cell disruption using pressurized gases (e.g., CO

Actinyl ions (AnO2n+), the form in which actinides are commonly found in aqueous solution, are important species in the nuclear fuel cycle. These ions can form stable complexes with ionic ligands such as OH-, NO3-, Cl-, and even other actinyl ions in the aqueous phase. Knowledge of the relative stabilities of these complexes is important for the efficient design of separation processes used in recycling. These complexes also play a major role in the formation of actinide nanoclusters. A quantitative treatment of the stability of these actinyl ion complexes is therefore warranted. In the present work, molecular dynamics (MD) simulations have been performed to calculate the potential of mean force (PMF) between two actinyl ions (UO22+ and NpO2+) and various ligands (F-, Cl-, OH-, NO3-, SO42-, CO32-, Na+, and H2O) in explicitly-modeled aqueous solution. Equilibrium constants were calculated from the PMFs, and are consistent with experimental trends. Dication actinyls show stronger affinity for anions compared to monocation actinyls, whereas the opposite is true for cation-cation interactions between actinyls. Finally, the dynamics of actinyl-ligand contact ion pair (CIP) dissociation were characterized by calculating rate constants from transition state theory. The transmission coefficient, a dynamical correction factor used to correct for reaction barrier recrossing, was calculated for each actinyl-ligand CIP dissociation event.

Lipid extraction directly from the wet oleaginous microorganisms for biodiesel production is preferred as it reduces the energy input for traditional processes which require extensive drying of the biomass prior to the extraction. The high water content (≥80% on cell dry weight) in the wet biomass hinders the extraction efficiency due to the mass transfer limitation. This limitation can be overcome by pretreating wet biomass prior to the lipid extraction using pressurized gas that can be used alone or combined with other pretreatments to disrupt the cell wall. In this review, an extensive discussion on different pretreatments and the subsequent lipid extraction using these pretreatments is presented. Furthermore, a detailed account of the cell disruption using pressurized gas (e.g., CO2) treatment for microbial cell lysing is also presented. Finally, a new technique on lipid extraction directly from wet biomass using the combination of pressurized CO2 and microwave pretreatment is proposed.