The role of fuel chemistry in dictating nanostructure evolution of soot toward source identification

Abstract

Laser derivatization is proposed as a diagnostic technique toward identifying the sources contributing to combustion produced soot. Fuel chemistry and the resultant oxygen content in nascent soot have been shown to influence the evolution of soot nanostructure upon laser derivatization. This is illustrated using the spectroscopic and microscopic characterization of biodiesel soot, with a systematic variation in fuel chemistry used to generate the soot. Functionalized carbon black is used as the control to independently verify the influence of material chemistry on nanostructure upon laser heat treatment. Results track with those observed for biodiesel soot. Reciprocally, the similarity in soot nanostructure observed after laser heating is tied to the likeness in fuel chemistry of biomass-fueled sources. Understanding the origin of differences or similarities in soot nanostructure upon laser heat treatment can help differentiate sources based on their contribution, thereby aiding in effective air quality control.

Copyright © 2019 American Association for Aerosol Research     

Clath rates in Analytical Separations

Abstract

Recent advances in clathrate chemistry and their use for analytical and preparative chemistry are discussed. The effect of molecular geometry and sub-stituent groups of guest species on the capabilities of various clathrating compounds is reviewed.     

AQUEOUS COMPLEXES IN SEPARATIONS OF f-ELEMENTS: OPTIONS AND STRATEGIES FOR FUTURE DEVELOPMENT

ABSTRACT

Powerful and/or selective extractant molecules/sorbents are a necessary component of efficient metal ion separation processes. However, selectivity in extraction and efficiency in process design often rely on reactions occurring in or moderated by the aqueous medium. This report describes the role of the aqueous phase and reactions that occur in aquo in defining separation efficiency and metal ion selectivity. As our programmatic focus is on actinide solution chemistry, the separations chemistry of the f-elements will be used to illustrate the principal role of aqueous chemistry in metal ion separations. Most of the arguments developed apply to metal ion separations chemistry and processes in general. The discussion will emphasize the role of complexation and the effect of properties of the aqueous medium on separation efficiency and selectivity. Historically important separations processes will be considered along with recent efforts in our laboratories to design and characterize new water soluble complexants for improved f element separations.

     

SIMULATION OF FLOW THROUGH THE PREHEATER OF A COAL LIQUEFACTION REACTOR

Applications of the fundamentals of turbulent mixing become clear once those fundamentals are understood. The first article in this series presented those fundamentals, in order to show how to apply turbulent mixing fundamentals modelling and scaleup, this article covers the following topics:

1. reaction types and their interaction with mixing;

2. closure of the Reynolds equations for mixing and reactions;

3. application to complex geometries;

4. random coalescence-dispersion modelling;

5. application to complex chemistry.

The most difficult problem in applying our knowledge of turbulence to mixer modelling and scaleup is the choice of model complexity. The levels of model complexity available and how to apply them to various problems are presented following the introduction.     

The Scent of Ant Brood: Caste Differences in Surface Hydrocarbons of Formica exsecta Pupae

Chemical communication is common across all organisms. Insects in particular use predominantly chemical stimuli in assessing their environment and recognizing their social counterparts. One of the chemical stimuli used for recognition in social insects, such as ants, is the suite of long-chain, cuticular hydrocarbons. In addition to providing waterproofing, these surface hydrocarbons serve as a signature mixture, which ants can perceive, and use to distinguish between strangers and colony mates, and to determine caste, sex, and reproductive status of another individual. They can be both environmentally and endogenously acquired. The surface chemistry of adult workers has been studied extensively in ants, yet the pupal stage has rarely been considered. Here we characterized the surface chemistry of pupae of Formica exsecta, and examine differences among sexes, castes (reproductive vs. worker), and types of sample (developing individual vs. cocoon envelope). We found quantitative and qualitative differences among both castes and types of sample, but male and female reproductives did not differ in their surface chemistry. We also found that the pupal surface chemistry was more complex than that of adult workers in this species. These results improve our understanding of the information on which ants base recognition, and highlights the diversity of surface chemistry in social insects across developmental stages.

     

Thiohydantoins: synthetic strategies and chemical reactions

The chemistry of thiohydantoins has gained increased interest in both synthetic organic chemistry and biological fields. Many of these compounds exhibit considerable biological activities in various fields. This review covers the literature regarding the synthesis, reactions, and applications of such compounds.

     

Linear Free Energy Relationships in Kinetic Analyses: Applications of Quantum Chemistry

Abstract

The role of linear free energy relationships and quantum chemistry in kinetic analyses is discussed and applied to a representative sequence of molecular pathways important in hydrocracking chemistry. Experimental data on adsorption, hydrogenation, cracking, isomerization, and coking for various aromatic, heteroatom-containing aromatics, and alkylaromatics were compiled from the literature and correlated with a set of reactivity indices which describe important structural, electronic, and/or energetic features of the reactants, products, or intermediates. All reactivity indices were computed from serniempirical quantum chemical calculations. The equilibria of adsorption were correlated with the proton affinity. Hydrogenation kinetics were related to the atomic site containing the highest π-electron density. Cracking kinetics were explained by the correlation with the heat of hydride transfer. Isomerization appeared dependent upon the heat of carbocation formation. Coke formation was related to the proton affinity. These LFERs provided a concise organizational summary of the chemistry of hydrocracking. Their potential in the prediction of the kinetics of unstudied systems is also discussed.     

Role of inorganic and theoretical chemistry in ceramics: past,present, and future

Abstract

Theoretical inorganic chemistry has evolved since Professor Mellor's time to include a new generation of quantum mechanics based calculational methods to understand and predict chemical reaction pathways. Semi-empirical molecular orbital (MO) calculations have been used in the fields of glass and silica structure analysis, fracture mechanics, sol–gel processing of net shape optics, porous matrixes for hybrid optics, sensors, and tissue engineering scaffolds. Applications of MO calculations in biomaterials interface reactions, biomimetics, and biomineralisation have also been made. Future directions for use of theoretical inorganic chemistry in the ceramic industry are forecast.     

Characterization of titanium alkoxide sol–gel systems designed for anti-icing coatings: I. Chemistry

Recent interest in sol–gel chemistry involving titanium alkoxide precursors has been prompted by the ability to control the morphology of the final TiO₂ structure. The ligands used in these processes are typically sacrificial and are removed once the process is complete. In contrast, the sol–gel chemistry presented here is used to facilitate the slow release of the attached alkoxide ligands: tripropylene glycol (TPG) and glycerol. These compounds are first chemically reacted with titanium isopropoxide (TIP), then are slowly released through subsequent hydrolysis and condensation reactions. TPG and glycerol depress the freezing point of water and this sol–gel chemistry has been incorporated into a coating which has anti-icing properties. This article analyzes the precursor chemistry for various experimental conditions using TGA, FTIR, ¹H NMR, and model calculations.     

Size-Exclusion Chromatography of Highly-active Organometallic and Multifunctional Metal-Containing Compounds

Abstract

Some results of size-exclusion chromatography (SEC) investigations of highly-active organometallic and metal-containing highly-active compounds (OMC) are reviewed. Until recently these classes of compounds have not been investigated by chromatography. New labile multifunctional metal-containing oligomers is revealed. The further application of SEC investigation for MW-analysis of highly-active OMC and multifunctional elementoxide compounds are outlined. The basises of labile multifunctional hetero-organic oligomers chemistry are founded.     

Surface Dynamics vs. Adhesion in Oxygen Plasma Treated Polyolefins

Polyethylene (PE) and polypropylene (PP) were oxygen plasma treated and aged in carefully reproducible conditions. The effect of aging on the surface chemistry, wettability and adhesion were studied using a combination of techniques: contact angle measurements, XPS, SSIMS, adhesion tests (shear and pull).

PE was found to be relatively insensitive to aging both in terms of wettability and adhesion, due to crosslinking during plasma treatment, which is likely to reduce macromolecular mobility within the surface layer.

In the case of PP, dramatic decreases of wettability occur with time, due to macromolecular motions leading to minimization of oxygen-containing functions at the surface. This behavior was shown to affect the adhesion performance of treated PP.     

Combination of atom transfer radical polymerization and click chemistry toward cellulose-rosin derived UV-absorbent copolymers

UV absorption coating is an important function material, which can protect the substrates from photoaging. In this work, a class of sustainable UV-absorbent copolymers derived from ethyl cellulose (EC), fatty acid and rosin were prepared by a combination of atom transfer radical polymerization (ATRP) and click chemistry. To fulfill this strategy, the pendant azides were first attached onto the backbone of EC. Then, ATRP was applied to fabricate well-defined poly(lauryl methacrylate) (PLMA) bearing terminal alkynes. Finally, click chemistry between the pendant azides in EC and the alkynes in PLMA as well as in rosin esters (DAPE), was performed to achieve the cellulose-rosin graft copolymers (EC-(g-DAPE)-g-PLMA) with UV absorption property. The chemical structure of cellulose-rosin graft copolymers was confirmed by FTIR, ¹H NMR and GPC. Thermodynamic performance analysis indicated that these EC-rosin graft copolymers showed better thermal stability than EC. Due to the synergistic hydrophobic interaction of rosin and the hydrophobic lauryl groups in PLMA, these graft copolymers showed excellent hydrophobic property, and the static contact angles were all above 90°. In addition, all the EC-rosin graft copolymers showed outstanding and stable UV absorption capability, and maintained excellent UV absorption capability after continuous UV-irradiation for 1 h or being heated to 100 °C for 0.5 h, which had potential application in UV absorption materials.

     

Fluid Mechanics–Foam Flotation Interactions

Abstract

Foam flotation methods have been used for years for ore concentration and show considerable promise for the removal of a variety of pollutants from wastewaters. However, scant attention has been given to the critical interaction in these processes of surface chemistry and fluid mechanics. A numerical model of an air bubble with an attached floc particle rising in a Stokes flow regime through a liquid pool at the bottom of a batch foam flotation column was developed. This model computed the viscous forces acting to separate the bubble and particle, and these forces were compared with those given by previous investigators. This research demonstrates that, while previous methods have correctly estimated the magnitudes of the viscous forces, they have failed to correctly estimate the directions. Based on the results of this work, a much simpler model for describing the interaction of fluid mechanics and surface chemistry in particle attachment to bubbles in foam flotation columns is suggested.     

The Truex Process and the Management of Liquid Tru Uwaste

Abstract

The TRUEX (TRansUranium Extraction) process is a new generic actinide extraction/recovery process for the removal of all actinides from acidic nitrate and chloride nuclear waste solutions. A brief review of the relevant chemistry of the TRUEX process and a summary of the current status of development and deployment of TRUEX process flowsheets to treat specific acidic waste solutions at several U.S. DOE sites is presented.     

Colloidal Fouling during Ultrafiltration

Abstract

Colloidal fouling causes serious problems in many membrane plants. Two different kinds of flux-reducing phenomena occur when treating colloidal dispersions. When treating stable dispersions the flux is reversible and can be restored after changing the operating parameters, such as the transmembrane pressure or the cross flow velocity. The flux reduction experienced when treating unstable colloidal dispersions is irreversible. In this study the DLVO theory, well-known from colloid chemistry, has been used to illustrate the mechanisms underlying the difference in filtration characteristics between stable and unstable colloidal dispersions.     

Extraction of Actinides with Different 6,6′‐Bis(5,6‐Dialkyl‐[1,2,4]‐Triazin‐3‐yl)‐[2,2′]‐Bipyridines (BTBPs)

Abstract

The extraction of Am(III), Th(IV), Np(V), and U(VI) from nitric acid by 6,6′‐bis(5,6‐dialkyl‐[1,2,4]‐triazin‐3‐yl)‐[2,2′]‐bipyridines (C2‐, C4‐, C5‐, and CyMe₄‐BTBP) was studied. Since only americium and neptunium extraction was dependent on the BTBP concentration, computational chemistry was used to explain this behavior. It has been shown that the coordination of the metal played an important role in forming an extractable complex into the organic phase, thus making it possible to extract pentavalent and trivalent elements from tetravalent and hexavalent elements. This is very important, especially because it shows other possible utilizations of a group of molecules meant to separate the actinides from the lanthanides. In addition, the level of extraction at very low or no BTBP concentration was explained by coordination chemistry.     

Glycerol Esters from Real Waste Cooking Oil Using a Robust Solid Acid Catalyst

Notwithstanding the food-for-fuel debate, turning waste cooking oil and fat (WCO) into a valuable product is a classic example of green chemistry. We demonstrate that sulfated zirconia and lanthanum-supported sulfated zirconia are good catalysts for the esterification of WCO free fatty acids (FFAs) with glycerol, giving high-value monoglycerides. Various catalysts were first screened using palmitic acid as a model FFA. Subsequently, six 10-kg batches of actual WCO were collected from commercial cookeries over a period of 28 weeks, pre-treated in a purpose-built decanter and esterified with industrial grade glycerol using heterogeneous catalysis. Good yield and turnovers were obtained. The pre-treatment stage and the catalytic esterification experiments are described and discussed.

     

Synthesis and Utilization of New Extractants for Nuclear Hydrometallurgy

Abstract

Recent progress in organic chemistry increases the possibility of controlling metal ions/organic molecules interaction. The use of macrocycles or polypodands (1) makes possible the creation of specific extractants for each metal ion. According to the actual needs in pollution elimination and precious metal recovery, this approach can lead to important renewals of extractants used in hydrometallurgy. In the present work, selective extraction of plutonium by dicyclohexano-18-crown-6 (DCHI8C6) and paladium by thiapolypodands from high-level nuclear waste solutions is investigated, and the results are modeled and discussed.     

Foreword

The effect of surface treatments and fiber sizings on the stress transfer characteristics and composite properties of AS-4 carbon/epoxy materials has been determined. Fiber surface chemistry was systematically varied from acidic to basic with RF glow discharge plasmas of CO₂ and NH₃ and characterized with ESCA techniques. Sizings applied to some of the treated fibers consisted of diglycidyl ether of bisphenol-A(DGEBA). Single fiber tension tests were used to measure the interfacial shear strength of samples made with DGEBA/metaphenylene diamine resin. Short beam shear and transverse flexure tests were used to examine the composite properties of modified materials.

Results showed that the plasma treatments were effective in altering the surface chemistry of the fiber but that changes in surface chemistry had surprisingly little effect on the critical stress transfer length. Sizing had a more significant effect on the transfer length. The interlaminar shear strength of the composites were unaffected by the treatments. Transverse flexure tests were more sensitive to the changes in surface characteristics. The work indicates that the interface properties of AS-4 fibers are close to optimal but that improvements in composite performance are possible through interphase formation.     

Gordon Research Conference on Chemicals and Materials From Renewable Resources

Abstract

This Conference will be held July 2-6, 1984 at Brewster Academy, Wolfeboro, New Hampshire. Among the topics to be discussed are the following: solid state ^iJC NMR spectra of celluloses, ultrastructure ofcellulose fibers - some new aspects, plant cell wall polysaccharides, 13 structural C NMR studies of lignin and lignin-like materials from flash utohydrolyzed wood, isolation of lignins from wood, electron transfer reactions in lignin and pulping chemistry, and structural inhomogeneity of lignin in wood cell walls.