Effects of organic nitrogen compounds on hydrotreating and hydrocracking reactions

A major issue encountered in hydrotreating and hydrocracking reactions, as in many others fixed bed catalytic processes, is the decrease of catalytic activity with time on stream. The organic nitrogen compounds act as temporary poisons in hydroprocessing catalysts besides being coke precursors. The inhibiting effects of nitrogen compounds present in crude oil have been studied on SRGO hydrotreating reactions and VGO hydrocracking reactions. The results show that selective removal of nitrogen by adsorption using silica and alumina in varying proportions, would not only increase the HDS catalyst activity by more than 60%, but would also reduce hydrogen consumption. This step of nitrogen removal can be installed additionally in the upstream of an existing SRGO HDS reactor to achieve higher desulphurization or can be designed with the grass roots units.

The inhibition effects of nitrogen on VGO hydrocracking have been studied at different temperatures and the reaction has been found to be highly non-linear in nature and the conversion rapidly drops and the slope becomes less steep as the nitrogen level increases. At higher reaction temperature, the drop in activity or conversion with feed nitrogen is less than that in lower temperatures due to the higher rate of desorption of nitrogen compounds at elevated temperatures. The drop in conversion with nitrogen compounds present in VGO indicates the presence of organo nitrogen compounds having higher basicity compared to the nitrogen compounds by pyridine doping. The hysteresis exists in adsorption/desorption of nitrogen compounds and it indicates that desorption is a very slow process. With the increase of nitrogen compounds in the feed, the conversion drops rapidly and it takes long time to reach an equilibrium value. Similarly, with the step increase in reactor temperature, nitrogen desorption takes place at a slow rate and the conversion level comes to an equilibrium value after 8 days.

The observed effects of nitrogen inhibition on SRGO hydrotreating and VGO hydrocracking conversion are explained reasonably well by kinetic models.     

Substituent effect on the optoelectronic properties of poly(p‐phenylenevinylene) based conjugated‐nonconjugated copolymers

Two classes of light emitting Poly(p‐phenylenevinylene) (PPV) based conjugated‐nonconjugated copolymers (CNCPs) have been synthesized. The conjugated chromophores containing 2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene (MEHPV) and 2,5‐dimethyl‐1,4‐phenylenevinylene (DMPV) moieties are rigid segments and nonconjugated portion containing hexyl units are flexible in nature. All copolymers were synthesized by well‐known Wittig reaction between the appropriate bisphosphonium salts and the dialdehyde monomers. The resulting polymers were found to be readily soluble in common organic solvents like chloroform, THF and chlorobenzene. The effect of chromophore substituents on the optical and redox properties of the copolymers has been investigated. Color tuning was carried out by varying the molar percentage of the comonomers. The UV‐Vis absorption and PL emission of the copolymers were in the range 314–395 nm and 494–536 nm respectively. All the polymers show good thermal stability. Polymer light‐emitting diodes (PLEDs) were fabricated in ITO/PEDOT:PSS/emitting polymer/cathode configurations of selected polymers using double‐layer, LiF/Al cathode structure. The emission maxima of the polymers were around 499–536 nm, which is a blue‐green part of the color spectrum. The threshold voltages of the EL polymers were in the range of 5.4–6.2 V. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dual Electric Field Induced Alignment of Electrospun Nanofibers

A dual‐field method is described to produce aligned fibers by electrospinning. By applying a secondary electric field perpendicular to the primary field, control over the orientation of the fibers on the collector is obtained. The dual‐field approach is used in conjunction with dual electrodes and a rotating collector. Both approaches were used to electrospin poly(lactic acid) fibers under conditions intended to produce fibers with a diameter greater then 400 nm to aid observation by optical microscopy and digital photography. Digital photography was used to visualize a large area of aligned fiber and image analysis software was used to quantify the degree of alignment. Fibers aligned with the aid of a dual field showed better alignment than those from a single electric field under otherwise identical conditions.

     

Preparation and characterization of poly(lactic acid)/poly(ethylene oxide) blend film: effects of poly(ethylene oxide) and poly(ethylene glycol) on the properties

Poly(lactic acid) (PLA) film plasticized with poly(ethylene oxide) (PEO) at various weight percentages (1–5 wt%) was prepared to improve the elongation, thus overcoming the inherent brittleness of the material. After optimization of the amount of PEO (4 wt%) through mechanical analysis, poly(ethylene glycol) (PEG), a well‐established plasticizer of PLA, was added (0.5–1.5 wt%) without hampering the transparency and tensile strength much, and again its amount was optimized (1 wt%). Neat PLA and PLA with the other components were solvent‐cast in the form of films using chloroform as a solvent. Improvement in elongation at break and reduction in tensile strength suggested a plasticizing effect of both PEO and PEG on PLA. Thermal and infrared data revealed that the addition of PEO induced β crystals in PLA. Scanning electron micrographs indicated a porous surface morphology of the blends. PEO alone in PLA exhibited the best optical clarity with higher percentage crystallinity, while PEG incorporation in PLA/PEO resulted in superior barrier properties. Also, the stability of the blends under a wide range of pH means prospective implementation of the films in packaging of food and non‐food‐grade products. © 2018 Society of Chemical Industry     

Brain Metastasis-Initiating Cells: Survival of the Fittest

Brain metastases (BMs) are the most common brain tumor in adults, developing in about 10% of adult cancer patients. It is not the incidence of BM that is alarming, but the poor patient prognosis. Even with aggressive treatments, median patient survival is only months. Despite the high rate of BM-associated mortality, very little research is conducted in this area. Lack of research and staggeringly low patient survival is indicative that a novel approach to BMs and their treatment is needed. The ability of a small subset of primary tumor cells to produce macrometastases is reminiscent of brain tumor-initiating cells (BTICs) or cancer stem cells (CSCs) hypothesized to form primary brain tumors. BTICs are considered stem cell-like due to their self-renewal and differentiation properties. Similar to the subset of cells forming metastases, BTICs are most often a rare subpopulation. Based on the functional definition of a TIC, cells capable of forming a BM could be considered to be brain metastasis-initiating cells (BMICs). These putative BMICs would not only have the ability to initiate tumor growth in a secondary niche, but also the machinery to escape the primary tumor, migrate through the circulation, and invade the neural niche.     

The interphasial regions in interlayer fiber composites

The interaction between the fiber and matrix in a fiber-reinforced material plays an important role in determining the mechanical behavior of the composite. An efficient technique to simultaneously improve fiber-matrix interfacial shear strength and impact behavior of the composite is to deposit a flexible interlayer onto the fiber. This results in the creation of three bulk phases, the fiber, matrix, and the interlayer and two interphasial regions. A phenomenological model that defines the variation of the fiber-interlayer interphase and that of the interlayer-matrix interphase has been developed. In the model, the elastic moduli of these regions vary continuously, so as to bridge the two bulk phases on either side of the interphase. The interaction between the bulk phases is also taken into consideration. The model has the potential for the use of dynamic mechanical analysis to obtain, relatively, adhesion/interaction parameters of different fiber-interlayer-matrix systems. These parameters can be used to determine the optimum interlayer thickness for improved toughness and good stress transfer efficiency.     

Photoinduced graft copolymerization. IX. Graft copolymerization of methyl methacrylate onto nylon 6 in the presence of pyridine–bromine charge–transfer complex as photoinitiator

Photoinduced graft copolymerization of methyl methacrylate onto nylon 6 was investigated by using pyridine–bromine (Py–Br₂) charge–transfer complex as initiator. The graft yield increased with increasing monomer and initiator concentration at the initial stages, and therefore it decreased. The initiator exponent was computed to be 0.5. The reaction was carried out at three different temperatures, and the overall activation energy was computed. A suitable mechanism has been suggested.     

Some numerical experiments on Higgs model

The kink interactions in the Higgs model are studied numerically using a finite element Galerkin method and a clear picture regarding the ‘resonances’ is presented. It is found that these ‘resonances’ are dependent on spatial increment and time step.     

Biofabrication of silver nanoparticles using bacteria from mangrove swamp

The last decade has observed a rapid advancement in utilising biological system towards bioremediation of metal ions in the form of respective metal nanostructures or microstructures. The process may also be adopted for respective metal nanoparticle biofabrication. Among different biological methods, bacteria‐mediated method is gaining great attention for nanoparticle fabrication due to their eco‐friendly and cost‐effective process. In the present study, silver nanoparticle (AgNP) was synthesised via continuous biofabrication using Aeromonas veronii, isolated from swamp wetland of Sunderban, West Bengal, India. The biofabricated AgNP was further purified to remove non‐conjugated biomolecules using size exclusion chromatography, and the purified AgNPs were characterised using UV–visible spectroscopy, X‐ray diffraction, field emission scanning electron microscopy and transmission electron microscopy (TEM). Additionally, the presence of proteins as capping and stabilising agents was confirmed by the amide‐I and amide‐II peaks in the spectra obtained using attenuated total reflection Fourier transform infrared spectroscopy. The size of biofabricated AgNP was 10–20 nm, as observed using TEM. Additionally, biofabricated AgNP shows significant antibacterial potential against E. coli and S. aureus. Hence, biofabricated AgNP using Aeromonas veronii, which found resistant to a significant concentration of Ag ion, showed enhanced antimicrobial activity compared to commercially available AgNP.Inspec keywords: silver, nanoparticles, microorganisms, nanofabrication, purification, chromatography, ultraviolet spectra, visible spectra, X‐ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, proteins, molecular biophysics, biochemistry, molecular configurations, attenuated total reflection, Fourier transform infrared spectra, particle size, antibacterial activity, biomedical materials, nanomedicineOther keywords: capping agents, stabilising agents, amide‐I peaks, amide‐II peaks, attenuated total reflection Fourier transform infrared spectroscopy, antibacterial potential, E. coli, S. aureus, Aeromonas veronii, antimicrobial activity, size 10 nm to 20 nm, Ag, proteins, TEM, transmission electron microscopy, field emission scanning electron microscopy, X‐ray diffraction, UV‐visible spectroscopy, size exclusion chromatography, nonconjugated biomolecules, purification, swamp wetland, Aeromonas veronii, cost‐effective process, eco‐friendly, bacteria‐mediated method, biological methods, metal nanoparticle biofabrication, microstructures, metal nanostructures, metal ions, bioremediation, biological system, mangrove swamp, bacteria, silver nanoparticles     

A production–inventory model with remanufacturing for defective and usable items in fuzzy-environment

This paper investigates a production–remanufacturing system for a single product over a known-finite time horizon. Here the production system produces some defective units which are continuously transferred to the remanufacturing unit and the constant demand is satisfied by the perfect items from production and remanufactured units. Remanufacturing unit uses the defective items from production unit and the collected used-products from the customers and later items are remanufactured for reuse as fresh items. Some of the used items in the remanufacturing unit are disposed off which are not repairable. The remanufactured units are treated as perfect items. Normally, rate of defectiveness varies in a production system and may be approximated by a constant or fuzzy parameter. Hence, two models are formulated separately with constant and fuzzy defective productions. When defective rate is imprecise, optimistic and pessimistic equivalent of fuzzy objective function is obtained by using credibility measure of fuzzy event by taking fuzzy expectation. Here, it is assumed that remanufacturing system starts from the second production cycle and after that both production and remanufacturing units continue simultaneously. The models are formulated for maximum total profit out of the whole system. Here the decision variables are the total number of cycles in the time horizon, the duration for which the defective items are collected and the cycle length after the first cycle. Genetic Algorithm is developed with Roulette wheel selection, Arithmetic crossover, Random mutation and applied to evaluate the maximum total profit and the corresponding optimum decision variables. The models are illustrated with some numerical data. Results of some particular cases are also presented.