Sustainable ammonia production through process synthesis and global optimization

Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas-based reference case. A deterministic global optimization-based branch-and-bound algorithm is used to solve the resulting large-scale nonconvex mixed-integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019     

Simple solution-combustion synthesis of Fe2TiO5 nanomaterials with enhanced lithium storage properties

The porous Fe₂TiO₅ particles are successfully synthesized through a facile one step solution combustion method. The Fe₂TiO₅ negative materials exhibit remarkable electrochemical performance with discharge capacities of 371.4?mAh g^?1 at the 100 th cycle, and display promising rate stability with discharge capacities 76.6?mAh·g^?1 at a high current density of 3.2?A?g^?1. In addition, the mechanism of electrochemistry reaction is illustrated by the CV, raman and EIS measurements, the irreversible capacity mainly causes from the irreversible lithium insertion at 1.8?V. The results indicate that the one step solution combustion synthesis of porous Fe₂TiO₅ is a promising strategy for developing low-cost and high-performance Ti-based negative materials.     

Controllable Image‐Based Transfer of Flow Phenomena

Modelling flow phenomena and their related weathering effects is often cumbersome due their dependence on the environment, materials and geometric properties of objects in the scene. Example‐based modelling provides many advantages for reproducing real textures, but little effort has been devoted to reproducing and transferring complex phenomena. In order to produce realistic flow effects, it is possible to take advantage of the widespread availability of flow images on the Internet, which can be used to gather key information about the flow. In this paper, we present a technique that allows the transfer of flow phenomena between photographs, adapting the flow to the target image and giving the user flexibility and control through specifically tailored parameters. This is done through two types of control curves: a fitted theoretical curve to control the mass of deposited material, and an extended colour map for properly adapting to the target appearance. In addition, our method filters and warps the input flow in order to account for the geometric details of the target surface. This leads to a fast and intuitive approach to easily transfer phenomena between images, providing a set of simple and intuitive parameters to control the process.     

Electric transport properties of rare earth doped YbxCa1-xMnO3 ceramics (part I: Optimization of ceramic processing)

A comprehensive study was performed in order to find the effect of different calcination and sintering conditions on the physical properties of calcium manganite ceramics in dependence of temperature T and partial pressure of oxygen p(O₂). The eventual formation of oxygen vacancies during sintering was investigated and the results were confirmed by monitoring the release of oxygen using a ZrO₂ oxygen sensor. The phase transition behavior was studied using thermogravimetric analysis (TGA) in a wide range of p(O₂) ≈ 10^?1 MPa down to 10^-19 MPa at high temperatures accompanied by dilatometry- and XRD-measurements. Furthermore, the present study reveals for the first time a way for reducing and preventing crack formation that may occur during sintering. The present systematic research provides essential fundamental information before performing electrical measurements necessary in order to understand important factors about charge carriers and electrical transport mechanism.     

Efficient Enzymatic Cyclization of Disulfide-Rich Peptides by Using Peptide Ligases

Disulfide-rich macrocyclic peptides—cyclotides, for example—represent a promising class of molecules with potential therapeutic use. Despite their potential their efficient synthesis at large scale still represents a major challenge. Here we report new chemoenzymatic strategies using peptide ligase variants—inter alia, omniligase-1—for the efficient and scalable one-pot cyclization and folding of the native cyclotides MCoTI-II, kalata B1 and variants thereof, as well as of the θ-defensin RTD-1. The synthesis of the kB1 variant T20K was successfully demonstrated at multi-gram scale. The existence of several ligation sites for each macrocycle makes this approach highly flexible and facilitates both the larger-scale manufacture and the engineering of bioactive, grafted cyclotide variants, therefore clearly offering a valuable and powerful extension of the existing toolbox of enzymes for peptide head-to-tail cyclization.     

Production of (S)-β-Nitro Alcohols by Enantioselective C−C Bond Cleavage with an R-Selective Hydroxynitrile Lyase

Hydroxynitrile lyase (HNL)-catalysed stereoselective synthesis of β-nitro alcohols from aldehydes and nitroalkanes is considered an efficient biocatalytic approach. However, only one S-selective HNL—Hevea brasiliensis (HbHNL)—exists that is appropriate for the synthesis of (S)-β-nitro alcohols from the corresponding aldehydes. Further, synthesis catalysed by HbHNL is limited by low specific activity and moderate yields. We have prepared a number of (S)-β-nitro alcohols, by kinetic resolution with the aid of an R-selective HNL from Arabidopsis thaliana (AtHNL). Optimization of the reaction conditions for AtHNL-catalysed stereoselective C−C bond cleavage of racemic 2-nitro-1-phenylethanol (NPE) produced (S)-NPE (together with benzaldehyde and nitromethane, largely from the R enantiomer) in up to 99 % ee and with 47 % conversion. This is the fastest HNL-catalysed route known so far for the synthesis of a series of (S)-β-nitro alcohols. This approach widens the application of AtHNL for the synthesis not only of (R)- but also of (S)-β-nitro alcohols from the appropriate substrates. Without the need for the discovery of a new enzyme, but rather by use of a retro-Henry approach, it was used to generate a number of (S)-β-nitro alcohols by taking advantage of the substrate selectivity of AtHNL.     

Synthesis conditions effect on the of photocatalytic properties of MnWO4 for hydrogen production by water splitting

This work aims to study the synthesis conditions effect on the photocatalytic properties of manganese tungstate (MnWO₄) for H₂ production by the water splitting reaction under visible light irradiation. This is achieved by relating the materials characterization and photocatalytic evaluation of MnWO₄ at different synthesis conditions. MnWO₄ was synthesized through a precipitation reaction between Mn²⁺ and (WO₄)^2- ionic species, while adding oleic acid (OA) as surfactant at two concentrations (0.1% and 1% V) and using three different stirring methods: magnetic stirring (AM), ultrasound (US) and high-shear stirring (UT). Characterization was carried out by TGA, XRD, BET surface area, UV–Vis spectroscopy and FESEM. XRD patterns confirm the wolframite structure of MnWO₄. BET surface area increased by using UT stirring. UV–Vis spectroscopy results revealed indirect transition Eg values of ≈2 eV, favorable for the MnWO₄ photoactivation under visible light irradiation. During the photocatalytic evaluation, sample 1%-UT produced the highest H₂ amount among all samples with a value of 72 μmolH₂g⁻¹, which was far higher compared to WO₃, which was taken as a reference photocatalyst.     

Super-oleophilicity Co-doping Co2+/F-/TiO2 one-dimensional nanotubes for photocatalytic denitrification of light oil

In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co²⁺/F^-/TiO₂ nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co²⁺/F^-/TiO₂ revealed improved photocatalytic performance for denitrification of light oil compared to single TiO₂ photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co²⁺ and F^? in the photocatalyst.     

Biosynthesis of silver nanoparticles in collagen gel improves their medical use in periodontitis treatment

Silver nanoparticles (AgNP) suspensions were biosynthesized by silver ions reduction in the presence of collagen, a nontoxic, organic polymer, intending to improve their medical use in periodontitis treatment. Spectrophotometric measurements showed a time- and concentration-dependent increase of AgNP formation in each suspension variant. Transmission electron microscopy revealed spherical morphology of AgNP in collagen and their mean diameter size was around 30?nm. The particle size distribution and zeta potential values of AgNP in collagen were determined by dynamic light scattering measurements. The surface charge of AgNP in collagen was positive, while commercial AgNP stabilized in citrate had negative surface charge. In vitro cytotoxicity testing of AgNP in collagen showed that they were biocompatible with human gingival fibroblasts in a wider range of concentrations than commercial nanoparticles. The antibacterial activity of AgNP in collagen against two pathogenic strains present in the periodontal pocket was dose-dependent and higher than that of AgNP in citrate. All these results demonstrated that AgNP prepared in collagen gel had improved properties, like small diameter, positive surface charge, high biocompatibility in human gingival fibroblasts, efficiency against bacterial growth and, thus, better therapeutic potential in periodontal disease treatment.     

Impact of oxygenated cottonseed biodiesel on combustion,performance and emission parameters in a direct injection CI engine

In the present study, biodiesel production from the crude cotton-seed oil (CSO) and its feasibility to be used as fuel in compression ignition engine was analysed. Single-stage transesterification at molar ratio of 8:1 on crude CSO yielded 94% of cottonseed biodiesel (CBD). Gas chromatogram/mass spectrometry analysis revealed the presence of 19.5% unsaturated and 80.5% saturated esters in cotton seed biodiesel. Taguchi approach identified the stable fuel blend with oxygenate concentration. Increased oxygen concentration up to 20% were also analysed to understand the variation. Higher peak in-cylinder pressure was observed in D80CBD20 fuel blend. Diesel–biodiesel blend with oxygenate significantly affected the ignition delay and also resulted in varied exhaust gas temperature. D80CBD20nB10 showed an increase in brake thermal efficiency, whereas D80CBD20 exhibited higher brake specific energy consumption at full load. Carbon monoxide, hydrocarbon and smoke emission was found to be high in diesel with higher oxides of nitrogen in D80CBD20nB10. This experimental investigation finally revealed that, D80CBD20nB10 improved the combustion and performance characteristics with minimal emissions.

Abbreviations ASTM: American Society for Testing and Materials; BP: brake power; BSEC: brake specific energy consumption; BTE: brake thermal efficiency; CBD: cottonseed biodiesel; CI: compression ignition; CO: carbon monoxide; CO₂: carbon dioxide; CSO: cottonseed oil; DEE: diethyl ether; DOE: design of experiments; EGT: exhaust gas temperature; FTIR: Fourier transform infrared spectrometry; GC/MS: gas chromatogram/mass spectrometry; HC: hydrocarbon; HRR: heat release rate; HSDI: high speed direct injection; IDI: indirect injection; KOH: potassium hydroxide; MFB: mass fraction burned; NaOH: sodium hydroxide; NMR: nuclear magnetic resonance; N₂O: nitrous oxide; NO: nitric oxide; NO₂: nitrogen dioxide; NO _x : oxides of nitrogen; ROHR: rate of heat release; ROPR: rate of pressure rise; SOC: start of combustion; aTDC: after top dead centre; bTDC: before top dead centre