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

Data for Process Design and Economic Analysis of Renewable Isoprene from Biomass via Mesaconic Acid

The data consists of a single spreadsheet file for Microsoft Excel which contains the data for each figure as a separate tab.The data contain the process design and economic information for the design and optimization of a chemical process to manufacture isoprene from biomass via mesaconic intermediate.Minnesota Corn Growers AssociationCenter for Sustainable Polymers, NSF (CHE-1413862

Kinetics and reaction chemistry for slow pyrolysis of enzymatic hydrolysis lignin and organosolv extracted lignin derived from maplewood

The kinetics and reaction chemistry for the pyrolysis of Maplewood lignin were investigated using both a pyroprobe reactor and a thermogravimetric analyser mass spectrometry (TGA-MS). Lignin residue after enzymatic hydrolysis and organosolv lignin derived from Maplewood were used to measure the kinetic behaviours of lignin pyrolysis and to analyse pyrolysis product distributions. The enzymatic lignin residue pyrolyzed at lower temperature than that of organosolv lignin. The differential thermogravimetric (DTG) peaks for pyrolysis of the enzymatic residue were more similar to the DTG peaks for pyrolysis of the original Maplewood than DTG of the organosolv lignin. The condensable liquid volatile products were collected from a Pyroprobe reactor with a liquid nitrogen trap. The primary monomeric phenolic compounds were guaiacol, syringol, and vanillic acid. However, only 14–36 carbon% of the sample could be detected by GC-MS. Over 60 carbon% of the condensable products were heavy tar molecules that are not detectable by GC-MS. These heavy tar molecules are the primary products from pyrolysis of lignin. Intermediate solid samples were also collected at various pyrolysis temperatures and characterized by elemental analysis, FT-IR, DP-MAS 13C NMR, and TOC. The methoxy groups and ether linkages decreased and the non-protonated aromatic carbon–carbon bonds increased in the solid residues as the pyrolysis temperature increased. The carbon content of the initial lignin feed (derived from enzymatic hydrolysis) and the solid polyaromatics residue (obtained at 773 K) was 58 wt% and 74 wt% respectively. This polyaromatic residue contained about 69 wt% of the original lignin feed. The solid polyaromatics undergo further slow decomposition accompanied by a constant release of carbon dioxide as the pyrolysis reaction continues. The pyrolysis of the enzymatic lignin residue was modelled by two reactions in series. In the first pyrolysis step the lignin was decomposed with an apparent activation energy of 74 kJ mol−1 and a heat of reaction of −8,780 kJ kg−1. The second pyrolysis step had an apparent activation energy of 110 kJ mol−1 and a heat of reaction of −2,819 kJ kg−1. Lignin pyrolysis has lower activation energies and higher heats of reaction than cellulose pyrolysis

Millisecond Autothermal Steam Reforming of Cellulose for Synthetic Biofuels by Reactive Flash Volatilization

Three biomass-to-liquid process steps (volatilization of cellulose, tar-cleaning of organic products, and water-gas-shift of the gaseous effluent) have been integrated into a single autothermal catalytic reactor for the production of high quality synthesis gas at millisecond residence times ([similar]30 ms). Particles of cellulose ([similar]300 μm) were directly impinged upon the hot, catalytic bed of Rh–Ce/γ-Al2O3 catalyst on 1.3 mm α-Al2O3 spheres in the presence of O2, N2, and steam in a continuous flow fixed-bed reactor at 500–1100 °C. Complete conversion to gases was observed for all experimental parameters including N2/O2, S/C, the total flow rate of cellulose, and the fuel-to-oxygen ratio (C/O). The addition of steam increased the selectivity to H2 and decreased the selectivity to CO in agreement with water-gas-shift equilibrium. Optimal conditions produced a clean gaseous effluent which exhibited [similar]80% selectivity to H2 at a synthesis gas ratio of H2/CO = 2.3 with no dilution from N2 at a fuel efficiency of [similar]75%. Carbon-free processing was explained by relating the domain of experimental parameters to the thermodynamic prediction for the formation of solid carbon, CS

Improved utilization of biomass-derived carbon by millisecond co-processing with hydrogen rich feedstocks

A reactor capable of improving the utilization of biomass-derived carbon during thermochemical conversion to synthesis gas is demonstrated experimentally. By co-processing hydrogen-deficient biomass (H/C[similar]2) with hydrogen-rich feedstocks (H/C≥4) through catalytic partial oxidation, 100% of the fuel carbon atoms fed to the reactor can be converted to CO

Writing the Programs of Programmable Catalysis

It has long been known that non-steady state and periodic catalytic reactor operation in temperature, pressure, and composition can lead to higher overall productivity or product selectivity than the best steady operation. Recently, the emergence of catalysts whose intrinsic properties can oscillate with time introduces novel forcing capabilities that can be "programmed" into the catalysts, so to broaden the scope and applicability of periodic operation to surface chemistry. In this work, an algorithmic approach was implemented to significantly accelerate the discovery and optimization of periodic steady states. Decomposition of complex dynamics into fundamental mechanistic fast-slow steps improves conceptual understanding of the relationship between binding energy oscillation protocols and overall catalytic rates. Finding the structured forcing protocols, optimally tailored to the multiple time scales of a given individual mechanism, requires efficient search of high-dimensional parameter spaces. This is enabled here through active learning (Bayesian Optimization enhanced by our proposed Bayesian Continuation). Implementation of these methods is shown to accelerate the evaluation of catalyst programs by up to several orders of magnitude. Faster screening of programmable catalysts to discover periodic steady states enables the optimization of catalytic operating protocols; it thus opens the possibility for catalyst engineering based on optimal forcing programs to control rate and product selectivity, even for complex multi-step catalytic mechanisms