A Universal Descriptor for the Entropy of Adsorbed Molecules in Confined Spaces

Confinement of hydrocarbons in nanoscale pockets and pores provides tunable capability for controlling molecules in catalysts, sorbents, and membranes for reaction and separation applications. While computation of the enthalpic interactions of hydrocarbons in confined spaces has improved, understanding and predicting the entropy of confined molecules remains a challenge. Here we show, using a set of nine aluminosilicate zeolite frameworks with broad variation in pore and cavity structure, that the entropy of adsorption can be predicted as a linear combination of rotational and translational entropy. The extent of entropy lost upon adsorption is predicted using only a single material descriptor, the occupiable volume (Vocc). Predictive capability of confined molecular entropy permits an understanding of the relation with adsorption enthalpy, the ability to computationally screen microporous materials, and an understanding of the role of confinement on the kinetics of molecules in confined spaces

Steam-Induced Coarsening of Single-Unit-Cell MFI Zeolite Nanosheets and Its Effect on External Surface Brønsted Acid Catalysis.

Commonly used methods to assess crystallinity, micro-/mesoporosity, Brønsted acid site density and distribution (in micro- vs. mesopores), and catalytic activity suggest nearly invariant structure and function for aluminosilicate zeolite MFI two-dimensional nanosheets before and after superheated steam treatment. Yet, pronounced reaction rate decrease for benzyl alcohol alkylation with mesitylene, a reaction that cannot take place in the zeolite micropores, is observed. Transmission electron microscopy images reveal pronounced changes in nanosheet thickness, aspect ratio and roughness indicating that nanosheet coarsening and the associated changes in the external (mesoporous) surface structure are responsible for the changes in the external surface catalytic activity. Superheated steam treatment of hierarchical zeolites can be used to alter nanosheet morphology and regulate external surface catalytic activity while preserving micro- and mesoporosity, and micropore reaction rates

Can Modus Vivendi Save Liberalism from Moralism? A Critical Assessment of John Gray’s Political Realism

This chapter assesses John Gray’s modus vivendi-based justification for liberalism. I argue that his approach is preferable to the more orthodox deontological or teleological justificatory strategies, at least because of the way it can deal with the problem of diversity. But then I show how that is not good news for liberalism, for grounding liberal political authority in a modus vivendi undermines liberalism’s aspiration to occupy a privileged normative position vis-à-vis other kinds of regimes. So modus vivendi can save liberalism from moralism, but at cost many liberals will not be prepared to pay

Medical Staff Organization in Nursing Homes: Scale Development and Validation

PURPOSE: To construct a multidimensional self-report scale to measure nursing home (NH) medical staff organization (NHMSO) dimensions and then pilot the scale using a national survey of medical directors to provide data on its psychometric properties. DESIGN AND METHODS: Instrument development process consisting of the proceedings from the Nursing Home Physician Workforce Conference and focus groups followed by cognitive interviews, which culminated in a survey of a random sample of American Medical Directors Association (AMDA) affiliated medical directors. Analyses were conducted on surveys matched to Online Survey Certification and Reporting (OSCAR) data from freestanding nonpediatric nursing homes. A total of 202 surveys were available for analysis and comprised the final sample. RESULTS: Dimensions were identified that measured the extent of medical staff organization in nursing homes and included staff composition, appointment process, commitment (physiciancohesion; leadership turnover/capability), departmentalization (physician supervision, autonomy and interdisciplinary involvement), documentation, and informal dynamics. The items developed to measure each dimension were reliable (Cronbach's alpha ranged from 0.81 to 0.65).Intercorrelations among the scale dimensions provided preliminary evidence of the construct validity of the scale. IMPLICATIONS: This report, for the first time ever, defines and validates NH medical staff organization dimensions, a critical first step in determining the relationship between physician practice and the quality of care delivered in the NH

Up Up Down Down Left Right Left Right B A Start for the Catalytic Hackers of Programmable Materials

The valuable information of catalysis for the past century has been the composition and structure of high-performing catalytic materials. But a new class of programmable catalysts that change the electronic characteristics of their active sites on the time scale of the surface reaction are changing the catalyst design process by requiring additional information describing the input program that directs the temporal changes in the catalyst surface. Catalyst programs vary in complexity associated with the number of combined waveforms required to optimize surface chemistry rates and selectivity to products. The path forward for writing and optimizing catalyst programs will combine together the methods of parameter screening, rational design based on molecular models, and machine learning. This new approach to catalysis will change the nature of catalysis science, with researchers pursuing dynamic catalytic programs with improved catalytic performance over static catalyst compositions

Energy Flows in Static and Programmable Catalysts

Programmable catalysts that change on the time scale of a catalytic cycle provide a new opportunity to control the flow of energy to reactants and products to promote faster and more selective chemistry. While traditional chemical manufacturing processes consume energy to achieve favorable reaction conditions, programmable catalysts aim to dynamically add or remove energy to catalytic cycles through perturbations of the catalytic surface via strain, charge, or light. These surface energy flows are quantified by the changes in adsorbate binding energy with time, and the overall efficiency relating energy inputs to catalytic performance are defined by the characteristics of the undulating catalytic surface. Understanding and quantification of energy flows in programmable catalysts provides baseline definitions and metrics for comparing dynamic conditions and identifying optimal catalytic performance for more efficient chemical manufacturing

Glycosidic C-O Bond Activation in Cellulose Pyrolysis: Alpha Versus Beta and Condensed Phase Hydroxyl-Catalytic Scission

Mechanistic insights into glycosidic bond activation in cellulose pyrolysis were obtained via first principles density functional theory calculations that explain the peculiar similarity in kinetics for different stereochemical glycosidic bonds (β vs α) and establish the role of the three-dimensional hydroxyl environment around the reaction center in activation dynamics. The reported activating mechanism of the α-isomer was shown to require an initial formation of a transient C1-O2-C2 epoxide, that subsequently undergoes transformation to levoglucosan. Density functional theory results from maltose, a model compound for the α-isomer, show that the intramolecular C2 hydroxyl group favorably interacts with lone pair electrons on the ether oxygen atom of an α-glycosidic bond in a manner similar to the hydroxymethyl (C6 hydroxyl) group interacting with the lone pair electrons on the ether oxygen atom of a β glycosidic bond. This mechanism has an activation energy of 52.4 kcal/mol, which is similar to the barriers reported for non-catalytic transglycosylation mechanism (~50 kcal/mol). Subsequent constrained ab initio molecular dynamics (AIMD) simulations revealed that vicinal hydroxyl groups in the condensed environment of a reacting carbohydrate melt anchor transition states via two-to-three hydrogen bonds and lead to lower free energy barriers (~32-37 kcal mol-1) in agreement with previous experiments

Unique Biochar Phenomena

Paul Dauenhauer is director of the University of Massachusetts Reaction Engineering and Catalysis Laboratory and Assistant Professor of Chemical Engineering at the University of Massachusetts Amherst. Paul received his B.S. in Chemistry and Chemical Engineering from the University of Wisconsin Madison in 2004. In 2008, he received his Ph.D. in Chemical Engineering from the University of Minnesota with a focus on catalytic reforming of biomass advised by Professor Lanny Schmidt. Paul has also worked for the Dow Chemical Corporation as a Senior Research Engineer and Cargill, Inc. He currently serves as Thrust Leader of the DOE-funded Catalysis Center for Energy Innovation, associate editor of Chemical Engineering Science, and manager of the Waste-to-Energy engineering program at UMass. His work focusing on catalytic biomass conversion has been recognized for its achievements in renewable biofuels and chemicals, and Professor Dauenhauer has received the NSF-CAREER, the Dept. of Energy Early Career, and the 3M Nontenured Faculty awards supporting his research efforts.Production of Biochar: Multi-Scale Wood Pyrolysis Chemistry for Biochar Optimization Paul J. Dauenhauer, University of Massachusetts Amherst Utilization of non-food, lignocellulosic biomass such as trees and grasses provides unprecedented opportunity to sustain a lifestyle which benefits from renewable plastics, chemicals and fuels and relies heavily on agriculture. These feedstocks are rich in the carbohydrate polymers cellulose and hemicellulose, which can be broken down by pyrolysis to a solid product, called biochar, which has significant benefits for soil and farming. Production of biochar relies on a chemical process called pyrolysis, whereby the biopolymers of lignocellulosic feedstocks thermally degrade to vapors and solid char. Our research aims to understand the chemical reaction pathways that produce biochar from woody biomass and to integrate these chemical mechanisms within heat transfer models capable of describing the biochar process within wood fibers. Using a new experimental technique called ‘thin-film pyrolysis,’ we reveal that biochar is produced by two competing pathways: (1) direct dehydration of intact biopolymers, and (2) indirect re-formation of intermediate polymer fragments. These chemistries are studied within porous wood fibers using a diffuse reflectance spectroscopy technique capable of characterizing spatio-temporal compositional profiles of carbohydrates within wood fibers during the biochar reaction process. This research provides fundamental insight into the development of new chemical reactors which exhibit increased yield to higher quality biochar. INFLUENCE OF PYROLYTIC TEMPERATURE ON NUTRIENT AVAILABILITY IN PLANT-DERIVED BIOCHAR: Z. WANG This session will discuss the influence of pyrolytic temperature on nutrient availability based on research using biochars produced from giant reed, and the release of N, P and K. With increasing temperature, more N was lost and residual N was transformed into heterocyclic-N, resulting in less available NH4 from high temperature biochars, whereas no P and K losses were observed. P was transformed less soluble minerals, resulting in a reduction in available P in high temperature biochars. The available K content in biochars increased with increasing pyrolysis temperature. The results indicated that the low-temperature biochar produced from giant reed may be a good amendment for improving the availability of nutrients in acidic soils exhibiting N, P and/or K deficiency. BIOCHARS FROM ANIMAL MANURE AS ADSORBENTS FOR ENVIRONMENTAL REMEDIATION Isabel M. Lima, K. Thomas Klasson, Minori Uchimiya USDA, Agricultural Research Service, New Orleans, LA ABSTRACT Water quality and public health impacts of animal manure produced at large concentrated animal facilities prompted the need for viable solutions for their conversion and reuse. There are a myriad of carbonaceous precursors that can be used advantageously to produce chars, due to their low cost, availability and intrinsic properties and our laboratory at the Southern Regional Research Center, as part of the Agricultural Research Service of the U.S. Department of Agriculture, has shown that it is feasible to convert animal manure into chars and activated chars used for heavy metals remediation. Toxic metals contamination of various water sources is a significant problem in many parts of the United States. Both chars and activated chars produced under different processing conditions and undergoing different pre- and post treatments have been characterized for their physical properties and most importantly their ability to adsorb metal ions. These properties depend on the source of the manure, and in general it has been determined that poultry manure-based chars and activated chars far exceed those sourced from coal, wood or coconut shells, in their ability to remove heavy metals from solution. Acid washing or water rinsing treatments to reduce ash content had no significant effect in the ability of the activated char to adsorb copper ions, however significantly affected surface area, pH, and ash and carbon contents. Strong positive correlations were found between copper uptake and concentration of certain elements in the activated char such as phosphorous, sulfur, and calcium. An estimated cost of production for the manure based value added chars and activated chars under different post treatment scenarios is also reported