Recycling polystyrene into fuels by means of FCC: performance of various acidic catalysts

In accordance with the option of recycling plastics into fuels by dissolving them in standard feedstocks for the process of catalytic cracking of hydrocarbons, FCC, various acidic catalysts (zeolites ZSM-5, mordenite, Y, and a sulfur-promoted zirconia) were tested in the conversion of polystyrene dissolved into inert benzene at 550°C in a fluidized-bed batch reactor. Experiments were performed with very short contact times of up to 12 s. Main products were in the gasoline range, including benzene, toluene, ethylbenzene, styrene, and minor amounts of C_9–12 aromatics and light C₅₋ compounds. Coke was always produced in very significant amounts. All the products can be justified with basis on the properties of each catalyst and the various possible catalytic reaction pathways: cracking after protolytic attack on the polymer fragments, styrene oligomerization and subsequent cracking, or hydrogen transfer to styrene. Styrene would be mainly produced in this system from thermal cracking of the polymer as the initial step. If present, shape selectivity effects due to catalyst structure can influence significantly the prevalence of the various reactions, because they would interfere with those undergoing bulky transition states, like styrene oligomerization or hydrogen transfer. Even though sulfur-promoted zirconia is highly acidic, the low proportion of Brønsted-type acid sites does not allow the occurrence of secondary styrene reactions. It was shown that most favorable product distributions (higher yields of desirable products) are obtained on equilibrium commercial FCC catalysts.     

Spatial Cournot equilibrium: do branches matter?

This paper aims to contribute to the literature of Cournot spatial equilibria in two-dimensional spaces by considering branching. We study the case in which two firms compete on a circle and each one has the possibility of opening one or more branches. An innovative method—polar coordinates—is employed to obtain the complex profit functions. We show that there exists a symmetric subgame perfect Nash equilibrium where both firms place their n branches alternately and at the same distance from the center of the circle. Additionally, we show that this is, up to rotation, the unique symmetric equilibrium location.     

Management of R&D projects under uncertainty: a multidimensional approach to managerial flexibility

In this paper, we describe the practical application of a flexibility-based management approach to new product development, highlighting advantages, and limitations of this methodology. The model is concerned with the resolution of uncertainty over the product development life cycle and deals with technical, market, and cost factors all together. To this end, we consider a real options model, which uses multidimensional decision trees, to assess the development process of a high-technology product, namely, the Adaptive Optics Scanning Laser Ophthalmoscope. Moreover, we show how this project could be managed by estimating its value and determining optimal managerial actions to be taken at each review stage of the new product development process. Finally, we draw conclusions about this model's general utility and particular challenges associated with its use as a product development tool, and emphasize the need to consider a multidimensional model, instead of a single dimensional one.     

Study of the luminescent properties of KMgF3:Sm

The photoluminescence (PL), radioluminescence (RL) and thermoluminescence (TL) of KMgF₃ doped at several Sm concentrations have been investigated. The maximum TL and RL yield under beta irradiation has been observed in KMgF₃:Sm 0.02 mol%. The glow curve of this doped perovskite is made up of at least five peaks located at 95, 120, 160, 270, and 330 °C. The third peak appears to be the most convenient for personal or environmental dosimetry, since it shows no fading and good linearity within the investigated dose range (0.020-200 Gy). From the RL and PL spectra it has been found that most of KMgF₃:Sm emission is located at wavelengths higher than 650 nm. This emission, which is characteristic of Sm²⁺, makes this doped compound attractive for fiber-optic dosimetry.     

A multispectral imaging technique to determine concentration profiles of myoglobin derivatives during meat oxygenation

We have designed a multispectral imaging acquisition system to measure the relative concentration values of myoglobin forms inside meat during oxygenation. Images at 474, 525, 572 and 610 nm are used to compute the concentration of reduced myoglobin, oxymyoglobin and metmyoglobin with a spatial resolution of 0.0125 mm/pixel. From these images, pigment concentration profiles as a function of oxygenation time and depth beneath the surface were obtained. A model describing the diffusion of oxygen and the consumption of reduced myoglobin is numerically tested versus the measured concentration profiles. The model accurately fits the data with a Mean Root Squared Error equal to 0.253%. Precise definitions for position and width of pigment layers based in concentration profiles are given. The results suggest that multispectral imaging techniques combined with precise control and measurement of sample temperature and oxygen partial pressure will permit detailed studies of the myoglobin chemistry during oxygenation.     

Polymer Cocktail: A Multitask Supported Ionic Liquid‐Like Species to Facilitate Multiple and Consecutive C?C Coupling Reactions

Polymer‐supported ionic liquid‐like species (SILLPs) with different functionalities have been combined to obtain new catalytic systems (polymer cocktail) with improved properties towards their application for C C coupling reactions. The SILLPs have been synthesized in a simple way and combined to play different functions in the reaction medium. Those roles involve simultaneously (or consecutively) their actuation as supported reagents, precatalysts and scavengers of undesired reaction side‐products. The system has been tested by employing three different C C coupling reactions for 8 consecutive cycles. Moreover, different aryl bromides and iodides have proved to be efficiently transformed by the catalytic cocktail. Finally, the Heck reaction has been conducted in continuous‐flow conditions using a packed bed of this polymer cocktail and employing supercritical carbon dioxide (scCO₂) as a solvent, which cannot be carried out with the use of soluble bases as this would lead to the clogging of the reactor. Finally, the SILLPs cocktail enables one to combine different reaction steps and purification in a single vessel, which represents a significant improvement in terms of process intensification and green chemistry. This is particularly true in the case of the use of scCO₂ as this allows the direct production of crude materials not contaminated either by salts or by solvents.     

Polycyclic N-benzamido imides with potent activity against vaccinia virus

The synthesis and antiviral activity of a series of novel polycyclic analogues of the orthopoxvirus egress inhibitor tecovirimat (ST‐246) is presented. Several of these compounds display sub‐micromolar activity against vaccinia virus, and were more potent than cidofovir (CDV). The more active compounds were about 10‐fold more active than CDV, with minimum cytotoxic concentrations above 100 μM . Chemical manipulations of the two carbon–carbon double bonds present in the compounds were carried out to further explore the structure–activity relationships of these new polycyclic imides. Hydrogenation of the two carbon–carbon double bonds decreases antiviral activity, whereas either cyclopropanation or epoxidation of the double bonds fully eliminates the antiviral activity.     

Effect of maturity, processing, and storage on the furanocoumarin composition of grapefruit and grapefruit juice

Since the early 1990's, grapefruit juice has been implicated in drug interaction with various furanocoumarins (FCs) now associated with the effect. Although FCs are present in various fruits and vegetables, it is their presence in grapefruit that has attracted the most attention. Studies have shown that FCs in grapefruit juice can vary significantly and from multiple causes. Most of all, FCs are stress-induced molecules, their levels affected by many factors ranging from UV exposure to insect infestation. There are also varietal and seasonal factors. In this study, juice processing and storage parameters were investigated. Prolonged fruit storage prior to processing and most steps involved in juice processing had little influence on the levels of 6',7'-dihydroxybergamottin (DHB), paradisin C, or bergamottin. However, products that were hot filled or stored at room temperature had lower amounts of DHB and paradisin C and higher amounts of bergaptol compared to juices that were not hot filled and stored at refrigerated temperatures. Both DHB and paradisin C are potent CYP3A4 inhibitors, while bergaptol is a very weak inhibitor. Bergamottin amounts decreased to a lesser extent. Therefore, grapefruit juice products that were hot filled or have been stored at room temperature for an extended period of time will have a reduced drug interaction potential.