Mechanistic modeling of pollutant removal, temperature, and evaporation in chemical air scrubbers

Chemical air scrubbers reduce the concentration of water-soluble components such as ammonia from the outgoing ventilation air through absorption in water, followed by chemical conversions and removal of the end products. A mechanistic model for a countercurrent air scrubber was set up. Mass balances for ammonia, hydrogen sulfide, nitrous oxide, and methane were implemented, as well as the water mass balance and heat balances. The model was validated against experimental data from a conventional fattening pig housing facility. The effect of influent characteristics, design parameters, and control handles on the removal efficiency, the temperature profile, and the water evaporation rate were investigated through simulation. The model was able to describe the behavior of a countercurrent chemical air scrubber

A synthetic biochemistry platform for cell free production of monoterpenes from glucose.

Cell-free systems designed to perform complex chemical conversions of biomass to biofuels or commodity chemicals are emerging as promising alternatives to the metabolic engineering of living cells. Here we design a system comprises 27 enzymes for the conversion of glucose into monoterpenes that generates both NAD(P)H and ATP in a modified glucose breakdown module and utilizes both cofactors for building terpenes. Different monoterpenes are produced in our system by changing the terpene synthase enzyme. The system is stable for the production of limonene, pinene and sabinene, and can operate continuously for at least 5 days from a single addition of glucose. We obtain conversion yields >95% and titres >15 g l-1. The titres are an order of magnitude over cellular toxicity limits and thus difficult to achieve using cell-based systems. Overall, these results highlight the potential of synthetic biochemistry approaches for producing bio-based chemicals

Selective hydrogenation of nitroarenes using an electrogenerated polyoxometalate redox mediator

The 2-electron reduced form of the polyoxometalate silicotungstic acid (H6[SiW12O40]) is shown to be an effective and selective hydrogenation agent for a range of nitroarenes without the need for any co-catalyst. The ease of generation of the active species and its recyclability suggest that a new approach to this important class of chemical conversions is possible

Strictosidine, the common precursor for monoterpenoid indole alkaloids with 3 α and 3 β configuration

Recently we reported that strictosidine (l> is the key intermediate in the formation of the three classes (ASDidOf3DeIm5, Iboga, Corynanthe) of monoterpenoid indole alkaloids In Catharanthus roseus and a variety of other plant species in cell culture using in vivo and in vitro techniques"2. These results were independently confirmed In Manchester 394 and subsequently also Scott et a1.5 were able to confirm the precursor role of (1) using Catharanthus material. All these results are in accord with reports on the biosynthesis of an alkaloid of taxonomically distant origin, camptothecln, for which strictosidine la&am6 was previously found to be a precursor, and recently7 also (1). The key intermediate in the biosynthesis of the majority of mono-terpenoid alkaloids is therefore (1) with 3 a (2) configuration, rather than vincoside (2) with 3 13 (lX> configuration as had previously been assumeda. However, a generalization of this precursor function of (1

Effect of molecular and electronic structure on the light harvesting properties of dye sensitizers

The systematic trends in structural and electronic properties of perylene diimide (PDI) derived dye molecules have been investigated by DFT calculations based on projector augmented wave (PAW) method including gradient corrected exchange-correlation effects. TDDFT calculations have been performed to study the visible absorbance activity of these complexes. The effect of different ligands and halogen atoms attached to PDI were studied to characterize the light harvesting properties. The atomic size and electronegativity of the halogen were observed to alter the relaxed molecular geometries which in turn influenced the electronic behavior of the dye molecules. Ground state molecular structure of isolated dye molecules studied in this work depends on both the halogen atom and the carboxylic acid groups. DFT calculations revealed that the carboxylic acid ligands did not play an important role in changing the HOMO-LUMO gap of the sensitizer. However, they serve as anchor between the PDI and substrate titania surface of the solar cell or photocatalyst. A commercially available dye-sensitizer, ruthenium bipyridine (RuBpy), was also studied for electronic and structural properties in order to make a comparison with PDI derivatives for light harvesting properties. Results of this work suggest that fluorinated, chlorinated, brominated, and iyodinated PDI compounds can be useful as sensitizers in solar cells and in artificial photosynthesis.Comment: Single pdf file, 14 pages with 7 figures and 4 table

Fast microwave-assisted oxidation of 1,4-dihydropyridines with FeCl 3.SiO 2

Pyridine derivatives are easily obtained in high yields by microwave-promoted rapid oxidation of the corresponding 1,4-dihydropyridines with ferric chloride hexahydrate and silica gel under solvent-free conditions

Dual isotopic composition of methane in Murchison meteorite

Dual isotopic composition (H and C) of methane extracted from a small sample of Murchison meteorite reveals a deuterium enrichment for this molecule, indicating the presence of interstellar hydrogen

Synthesis, Chemistry and Applications of 5-Hydroxymethyl-furfural And Its Derivatives

The prospect of exciting research activity in the chemistry of furfural derived compounds such as 5-hydroxymethylfurfural (HMF), 2,5-furandicarbaldehyde and 2,5-furan-dicarboxylic acid prompted the writing of this article. As the field of application of these compounds is really enormous, it is no wonder that research in this area, starting at the end of 19th century, is still being developed. Numerous important scientific groups are carrying out studies on the synthesis, and applications of HMF and its derivatives. Notable among these are, Gaset (Toulouse), Descotes (Lyon), Lichtenthaler (Darmstadt), and Gelas (Clermont-Ferrand). Not only academic scientists are interested in this subject, the chemical industry, is represented by sugar companies such as Beghin-Say, and Süddeutsche Zucker. Despite this interest, there are not many comprehensive monographs or reviews covering the chemistry of HMF. Two classic reviews, by Newth and by Feather and Harris, appeared in 1951 and 1973 respectively. Reviews by Gaset et al.,3 Faury et al. and by Kuster are more recent, but they are not detailed. An important review review by Cottier and Descotes6 appeared in 1991. This review is written to update those above, to summarize the contributions of the last 100 years; and to emphasize recent developments especially in electrochemistry, and on dialdehyde and diacid chemistry.HMF is a good starting material for the synthesis of precursors of various pharmaceuticals, thermo-resistant polymers and complex macrocycles. Among these precursors, one can find 2,5- furandicarbaldehyde and 2,5-furandicarboxylic acid; these two compounds are described in detail in this article. The field of their applications is enormous – the dialdehyde offers itself to be the precursor for the synthesis of complexing macrocycles, oxo-porphirines, oxo-annulenes as well as mono- and bis alkenyl and alkynyl furans. The diacid is a building block for numerous polyesters and polyamides; its derivatives were found to be useful in pharmacology. No wonder then, that numerous methods for their preparation have been worked out and published.N/