Interaction of oxalate with β-glucan: Implications for the fungal extracellular matrix, and metabolite transport.

β-glucan is the major component of the extracellular matrix (ECM) of many fungi, including wood degrading fungi. Many of these species also secrete oxalate into the ECM. Our research demonstrates that β-glucan forms a novel, previously unreported, hydrogel at room temperature with oxalate.

Hydroxyapatite catalyzed hydrothermal liquefaction transforms food waste from an environmental liability to renewable fuel.

Food waste is an abundant and inexpensive resource for the production of renewable fuels. Biocrude yields obtained from hydrothermal liquefaction (HTL) of food waste can be boosted using hydroxyapatite (HAP) as an inexpensive and abundant catalyst. Combining HAP with an inexpensive homogeneous base increased biocrude yield from 14 ± 1 to 37 ± 3%, resulting in the recovery of 49 ± 2% of the energy contained in the food waste feed.

Rational design of solid-acid catalysts for cellulose hydrolysis using colloidal theory.

Solid-acid catalysts functionalized with catalytic groups have attracted intense interest for converting cellulose into soluble products. However, design of solid-7 acid catalysts has been guided by molecular level interactions and the actual mechanism of cellulose-solid-acid catalyst particles adsorption remains unknown. Here, colloidal stability theory, DLVO, is used to rationalize the design of solid acids for targeted cellulose adsorption.

Critical Role of Tricyclic Bridges Including Neighboring Rings for Understanding Raman Spectra of Zeolites.

Raman spectroscopy of network solids such as zeolites is critical for shedding light on collective vibrations of medium-range structures such as rings that exist in crystals and that form during crystallization processes. Despite this importance, assignments of Raman spectra are not completely understood, though it is often assumed that Raman bands can be assigned to individual rings. We report a systematic zeolite synthesis, spectroscopy, and periodic DFT study of several all-silica zeolites to test this assumption and to determine the fundamental structural motifs that explain Raman spectral features.

ZSM-5 decrystallization and dealumination in hot liquid water.

Zeolites have recently attracted attention for upgrading renewable resources in the presence of liquid water phases; however, the stability of zeolites in the presence of liquid-phase water is not completely understood. Accordingly, the stability of the ZSM-5 framework and its acid sites was studied in the presence of water at temperatures ranging from 250 to 450 °C and at pressures sufficient to maintain a liquid or liquid-like state (25 MPa). Treated samples were analyzed for framework degradation and Al content and coordination using a variety of complementary techniques, including X-ray diffraction, electron microscopy, N sorption, Al and Si NMR spectroscopy, and several different types of infrared spectroscopy.

Engineered microbial biofuel production and recovery under supercritical carbon dioxide.

Culture contamination, end-product toxicity, and energy efficient product recovery are long-standing bioprocess challenges. To solve these problems, we propose a high-pressure fermentation strategy, coupled with in situ extraction using the abundant and renewable solvent supercritical carbon dioxide (scCO), which is also known for its broad microbial lethality. Towards this goal, we report the domestication and engineering of a scCO-tolerant strain of Bacillus megaterium, previously isolated from formation waters from the McElmo Dome CO field, to produce branched alcohols that have potential use as biofuels.

Electrocatalytic reduction of acetone in a proton-exchange-membrane reactor: a model reaction for the electrocatalytic reduction of biomass.

Acetone was electrocatalytically reduced to isopropanol in a proton-exchange-membrane (PEM) reactor on an unsupported platinum cathode. Protons needed for the reduction were produced on the unsupported Pt-Ru anode from either hydrogen gas or electrolysis of water. The current efficiency (the ratio of current contributing to the desired chemical reaction to the overall current) and reaction rate for acetone conversion increased with increasing temperature or applied voltage for the electrocatalytic acetone/water system.

Searching for microporous, strongly basic catalysts: experimental and calculated 29Si NMR spectra of heavily nitrogen-doped Y zeolites.

Nitrogen substituted zeolites with high crystallinity and microporosity are obtained by nitrogen substitution for oxygen in zeolite Y. The substitution reaction is performed under ammonia flow by varying the temperature and reaction time. We examine the effect of aluminum content and charge-compensating cation (H(+)/Na(+)/NH(4)(+)) on the degree of nitrogen substitution and on the preference for substitution of Si-O-Al vs Si-O-Si linkages in the FAU zeolite structure.

Microwave synthesis of zeolites: effect of power delivery.

The effect of microwave power magnitude and pulsing frequency on the synthesis enhancement of zeolites, silicoaluminophosphate SAPO-11, silicalite, and NaY, was studied. Pulsing the microwave power compared to continuous delivery at the same averaged fed microwave power showed no effect on the nucleation and crystallization rates of SAPO-11, silicalite, or NaY. However, SAPO-11 synthesized with continuous microwave power delivery produced larger particles compared to pulsed microwave power with the same reaction time (3.

Temperature distributions within zeolite precursor solutions in the presence of microwaves.

While microwave enhancement of chemical syntheses has been demonstrated for a broad variety of chemical reactions, there is no accepted universal mechanism. Is the enhancement due to more efficient heating, to overheating, to nonuniform heating, or to nonthermal effects? Analyses are complicated due to the often significant spatial and temporal temperature variations in microwave reactor systems, particularly within microwave ovens. To address this, we employ multiple fiber-optic temperature probes throughout a cylindrical reactor with a focus on zeolite synthesis solutions being the dielectric medium.

Microwave synthesis of SAPO-11 and AlPO-11: aspects of reactor engineering.

AlPO-11 and SAPO-11 are synthesized using microwave heating. The effects of precursor volume, reaction temperature, reactor geometry, stirring, applicator type and frequency on the microwave synthesis of SAPO-11 and AlPO-11 are studied. The nucleation time and crystallization rate are determined from crystallization curves for SAPO-11 (and/or AlPO-11), for the various parameters investigated.

Spectroscopic signatures of nitrogen-substituted zeolites.

Nanoporous acid catalysts such as zeolites form the backbone of catalytic technologies for refining petroleum. With the promise of a biomass economy, new catalyst systems will have to be discovered, making shape-selective base catalysts especially important because of the high oxygen content in biomass-derived feedstocks. Strongly basic zeolites are attractive candidates, but such materials are notoriously difficult to make due to the strong inherent acidity of aluminosilicates.

How could and do microwaves influence chemistry at interfaces?

Many chemical reactions may be accelerated by order(s) of magnitude when exposed to microwaves. Reaction selectivities are often enhanced. Reasons for microwave reaction enhancements are speculative, often conflicting.

Microwave synthesis of zeolites. 2. Effect of vessel size, precursor volume, and irradiation method.

The enhancement of synthesis reactions under microwave heating is dependent on many complex factors. We investigated the importance of several reaction engineering parameters relevant to microwave synthesis. Of interest to this investigation were the reaction vessel size, volume of precursor reacted, microwave power delivery, and microwave cavity design.

Physical adsorption analysis of intact supported MFI zeolite membranes.

We compare the adsorption properties of intact supported silicalite membranes with those of silicalite powder and of alumina supports using nitrogen and argon as adsorbates at 77 K. We disentangle contributions from the membrane and support and find that the support contributes significantly to the total quantity adsorbed due to its relative thickness. The micropore-filling regions of the adsorption isotherms of the powder and the supported membrane are nearly identical for the membranes studied, but the isotherms differ at higher pressures--the supported membranes exhibit a much higher quantity adsorbed than the powders.

In situ SAXS/WAXS of zeolite microwave synthesis: NaY, NaA, and beta zeolites.

A custom waveguide apparatus is constructed to study the microwave synthesis of zeolites by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WR-284 waveguide is used to heat precursor solutions using microwaves at a frequency of 2.45 GHz.

Microwave synthesis of nanoporous materials.

Studies in the last decade suggest that microwave energy may have a unique ability to influence chemical processes. These include chemical and materials syntheses as well as separations. Specifically, recent studies have documented a significantly reduced time for fabricating zeolites, mixed oxide and mesoporous molecular sieves by employing microwave energy.