Toward enhanced hydrogen production in a catalytic naphtha reforming process

Environmental regulations imposed on transport fuels, especially specifications on sulfur and nitrogen content, generally boost hydrogen requirements in refining industries. The catalytic naphtha reformer (CNR) process is one of the major sources of hydrogen in naphtha refinery, thus improving its hydrogen production would be of great importance for refining industries. Close examination of the reaction kinetics of CNR processes has identified temperature, hydrogen concentration and catalyst activity as key variables affecting the process's performance. In this paper, a new reactor concept is developed that better exploits these process variables. The proposed membrane moving-bed reactor promises to significantly outperform the conventional continuous catalyst regenerative (CCR) design. A case study identifies improvements of 23.6 mol% in hydrogen production, 18.8 mol% in aromatics production. Moreover, the reformate yield was found to increase by 10.6 wt%, while the production of light gases decreases to a value of 18.6 wt%.     

High pressure inactivation of Escherichia coli, Campylobacter jejuni, and spoilage microbiota on poultry meat

This study evaluated the high pressure inactivation of Campylobacter jejuni, Escherichia coli, and poultry meat spoilage organisms. All treatments were performed in aseptically prepared minced poultry meat. Treatment of 19 strains of C. jejuni at 300 MPa and 30°C revealed a large variation of pressure resistance. The recovery of pressure-induced sublethally injured C. jejuni depended on the availability of iron. The addition of iron content to enumeration media was required for resuscitation of sublethally injured cells. Survival of C. jejuni during storage of refrigerated poultry meat was analyzed in fresh and pressuretreated poultry meat, and in the presence or absence of spoilage microbiota. The presence of spoilage microbiota did not significantly influence the survival of C. jejuni. Pressure treatment at 400 MPa and 40°C reduced cell counts of Brochothrix thermosphacta, Carnobacterium divergens, C. jejuni, and Pseudomonas fluorescens to levels below the detection limit. Cell counts of E. coli AW1.7, however, were reduced by only 3.5 log (CFU/g) and remained stable during subsequent refrigerated storage. The resistance to treatment at 600 MPa and 40°C of E. coli AW1.7 was compared with Salmonella enterica, Shiga toxin-producing E. coli and nonpathogenic E. coli strains, and Staphylococcus spp. Cell counts of all organisms except E. coli AW 1.7 were reduced by more than 6 log CFU/g. Cell counts of E. coli AW1.7 were reduced by 4.5 log CFU/g only. Moreover, the ability of E. coli AW1.7 to resist pressure was comparable to the pressure-resistant mutant E. coli LMM1030. Our results indicate that preservation of fresh meat requires a combination of high pressure with high temperature (40 to 60°C) or other antimicrobial hurdles.     

Finite element analysis of ion-implanted diamond surface swelling

We present experimental results and numerical finite element analysis to describe surface swelling due to the creation of buried graphite-like inclusions in diamond substrates subjected to MeV ion implantation. Numerical predictions are compared to experimental data for MeV proton and helium implantations, performed with scanning ion microbeams. Swelling values are measured with white-light interferometric profilometry in both cases. Simulations are based on a model which accounts for the through-the-thickness variation of mechanical parameters in the material, as a function of ion type, fluence and energy. Surface deformation profiles and internal stress distributions are analyzed and numerical results are seen to adequately fit experimental data. Results allow us to draw conclusions on structural damage mechanisms in diamond for different MeV ion implantations.     

Experimental methodology and heat transfer model for identification of ignition kinetics of powdered fuels

A methodology for investigating and quantifying the thermal processes leading to ignition of rapidly heated metal powders was developed. The simple experiment involves observing ignition of a powder coated on the surface of an electrically heated filament and is well suited for a variety of powdered fuels. In an experimental case study, the ignition temperature of spherical Mg powder was detected optically at different heating rates. To interpret the results, a heat transfer model was developed for a multilayer powder coating on the heated cylindrical filament. The thermal contact resistance between particles was determined from the measured bulk thermal diffusivity of the powder considering the experimental particle size distribution. An Arrhenius type expression was used to describe the exothermic chemical processes leading to ignition with the pre-exponent as an adjustable parameter. For Mg, a pre-exponent value identified by matching the calculations with the experimental data was found to be 10¹⁰ kg/m² s. The match between the experimental and predicted temperatures and times of ignition was good for different heating rates, which validated the proposed heat transfer model and indicated that the developed methodology is practically useful.     

Studies addressing the importance of charge in the binding of fosmidomycin-like molecules to deoxyxylulosephosphate reductoisomerase

Fosmidomycin and its homologue FR900098 are inhibitors of 1-deoxy-D-xylulose-5-phosphate reductoisomerase, which is part of the mevalonate-independent isoprenoid biosynthetic pathway. Replacement of the phosphonate moiety by uncharged sulfone or sulfonamide partial structures resulted in complete loss of activity. Dropping one of the two negative charges resulted in a marked decrease in activity. Through occupation of a hydrophobic binding site, some activity could be regained, leading to compounds with micromolar activity against cultured malaria parasites.     

Advanced Knowledge of Three Important Classes of Grape Phenolics: Anthocyanins,Stilbenes and Flavonols

Grape is qualitatively and quantitatively very rich in polyphenols. In particular, anthocyanins, flavonols and stilbene derivatives play very important roles in plant metabolism, thanks to their peculiar characteristics. Anthocyanins are responsible for the color of red grapes and wines and confer organoleptic characteristics on the wine. They are used for chemotaxonomic studies and to evaluate the polyphenolic ripening stage of grape. They are natural colorants, have antioxidant, antimicrobial and anticarcinogenic activity, exert protective effects on the human cardiovascular system, and are used in the food and pharmaceutical industries. Stilbenes are vine phytoalexins present in grape berries and associated with the beneficial effects of drinking wine. The principal stilbene, resveratrol, is characterized by anticancer, antioxidant, anti-inflammatory and cardioprotective activity. Resveratrol dimers and oligomers also occur in grape, and are synthetized by the vine as active defenses against exogenous attack, or produced by extracellular enzymes released from pathogens in an attempt to eliminate undesirable toxic compounds. Flavonols are a ubiquitous class of flavonoids with photo-protection and copigmentation (together with anthocyanins) functions. The lack of expression of the enzyme flavonoid 3′,5′-hydroxylase in white grapes restricts the presence of these compounds to quercetin, kaempferol and isorhamnetin derivatives, whereas red grapes usually also contain myricetin, laricitrin and syringetin derivatives. In the last ten years, the technological development of analytical instrumentation, particularly mass spectrometry, has led to great improvements and further knowledge of the chemistry of these compounds. In this review, the biosynthesis and biological role of these grape polyphenols are briefly introduced, together with the latest knowledge of their chemistry.