Optimal separation of n-paraffins from Kuwait kerosene using a molecular sieve adsorbent

A study has been made of the vapour-phase adsorptive separation of n-alkanes from Kuwait kerosene using zeolite molecular sieves (LMS-5A). The object was to identify the optimum operating conditions, in terms of flow rate, adsorption temperature and zeolite particle size for the separation of n-alkanes from kerosene, so that the remaining stock would also be of marketable quality. The effect of these conditions on the height of the mass transfer zone (HMTZ) and the dynamic capacity (Ad) of zeolite was also investigated. The adsorptive separation process comprised one cycle of adsorption using a fixed bed of zeolite type-5A. The bed was fed with kerosene vapour until equilibrium had been achieved, whereby the n-paraffins were adsorbed and the denormalized material excluded. The processes were carried out isobarically at one atmosphere. The optimum operating conditions were found to be a feed flow rate of 33.33 × 10^?9 m³ s^?1, an adsorption temperature of 643 K and a zeolite pellet fraction size of 1.0–2.0 × 10^?3m. This yielded an HMTZ value of 0.206 m and an Ad of 9.653 × 10^?2 kg n-paraffins kg^?1 zeolite. The data will serve as a basis for the design of commercial plant.     

Validity generalization: Rejoinder to Schmidt, Hunter, and Raju (1988).

A rejoinder to the Schmidt, Hunter, and Raju (1988) critique of James, Demaree, and Mulaik (1986) is presented. It is proposed that the recommendations offered by James et al (1986) remain intact. These recommendations were that greater attention be given to alternative explanations of the results of validity generalization (VG) analyses, that use of the 75% rule be discontinued, and that VG analyses be predicated on Fisher z coefficients. In addition, the implication of low statistical power for interpreting results of a VG analysis is considered and the potential need for new mathematical models for VG is reviewed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Studies on rejuvenation of spent residue hydroprocessing catalysts by leaching of foulant metals: influence of inorganic salt additives on the leaching efficiency of organic acids

A comparative study has been made on the efficiency of oxalic, malonic and acetic acids for selective removal of metal foulants (e.g. vanadium) from spent residue hydrotreating catalysts in the presence and absence of aluminium nitrate. The influence of concentration of the added salt (aluminium nitrate) on the leaching efficiency of the three acids was also studied. The treated catalysts were characterized and the improvements in surface area, pore volume and HDS activity as a result of leaching with each reagent compared. The studies revealed that addition of aluminium nitrate enhanced the leaching efficiency of each acid to a different degree. The rate of vanadium leaching by oxalic acid was increased substantially by aluminium nitrate addition whereas for acetic acid there was only a moderate enhancement in leaching rate. The enhanced leaching by the aluminium nitrate-organic acid system may be explained in terms of a synergistic mechanism involving oxidizing and complexing reactions. The improvement in surface area and pore volume achieved on rejuvenation were related to the extent of removal of vanadium from the catalyst. The HDS activity of the catalyst was also increased significantly by leaching of the deposited metals. The selectivity for vanadium leaching (V/Mo ratio) was found to be an important factor for HDS activity recovery.     

Mechanisms of Drylng of Skin-Forming Materials; the Significance of Skin Formation and a Comparison Between Three Types of Material

ABSTRACT

Comparisons are drawn between the drying characteristics, and the mechanisms of skin formation on, three characteristic types of material. The significance of skin formation, which may be a major factor in valatiles retention in the drying of spray dried products, is discussed. The optimum drying conditions to achieve the highest volatiles retention for each type of skin-forming material are predicted. General comparisons are also drawn between the drvine of skin-formine i.e., materials which form a smooth flexible low- parosity skin at same slage, and normal crust-forming materials. The latter form only a rigid crust with a porosity which is system and drying-condition dependent.     

Mechanisms of Drying of Skin-Forming Materials. II.Droplets of Heat Sensitive Materials

ABSTRACT

Drying studies were carried out on single droplets of gelatin solution, typifying a skin forming, heat-sensitive material. Each droplet was suspended from a novel rotating glass nozzle which enabled direct measurement of its weight and temperature during drying. Observations using this appartatus successfully detected the decrease in core temperature and increase in drying rate resulting from granule dissolution at 30 °C.

The study covered air temperatures in the range 19 °C–175 °C. Scanning Electron Microscopy was used to examine the dried crusts. The resistance of the skin to vapour diffusion was significantly increased with an increase in the air temperature. At air temperature > 60 °C the dried particle lost the structure and properties of the original powder. The optimum drying conditions to avoid this were predicted for this type of skin forming-material.     

Smokeless tobacco use 1992-2002: trends and measurement in the Current Population Survey-Tobacco Use Supplements

Background

As smoking prevalence declines in the United States, it is important to understand if smokeless tobacco (SLT) use is also changing and if so, among what groups.

Methods

We examine the prevalence of SLT use and smoking, 1992–2002, using the Current Population Survey‐Tobacco Use Supplements (CPS‐TUS), which used US nationally representative samples based on stratified clusters of households.

Results

Consistent with declines in smoking, the prevalence of current SLT use declined over the period 1992–2002 for males and females ages 18 and older. The overall separate declines in SLT use and in smoking are mirrored by a decline in concurrent use of SLT and cigarettes. SLT use is becoming more associated with white males, but use is declining faster among the youngest males.

Conclusions

The findings indicate that relative reductions in smoking prevalence are exceeded by relative reductions in SLT use, with sizeable reductions in concurrent use. These results suggest that the stricter cigarette policies of recent years may not only reduce cigarette use, but also the use of alternative tobacco products. In light of potential policy implications of SLT use as a potential reduced exposure product (PREP), current survey methods require more careful measurement of SLT use in terms of initiation, duration, quantity, and cessation.     

Detection of antibodies against equine herpesvirus types 1 and 4 by using recombinant protein derived from an immunodominant region of glycoprotein B

The N-terminal fragment comprising residues +1 to +50 (gB1-50) of equine herpesvirus type 1 (EHV-1) glycoprotein B was expressed as a glutathione S-transferase fusion protein in Escherichia coli. Recombinant gB1-50 (rgB1-50) was recognized in immunoblots by sera from rabbits immunized with EHV-1 and by convalescent-phase sera from horses with natural EHV-1 infections. An enzyme-linked immunosorbent assay (ELISA) for monitoring antibody levels against EHV-1 was developed by using rgB1-50, and its specificity was assessed with a panel of reference antisera against other equine viruses. A specific cross-reaction was detected with EHV-4, which was confirmed by inhibition ELISA. Convalescent-phase sera from horses with natural EHV-1 or EHV-4 infections possessed antibody titers against rgB1-50 ranging from 1:2,000 to 1:64,000, indicating the presence of an immunodominant antigenic site. The study demonstrated the potential application of rgB1-50 as a diagnostic antigen and highlights the glutathione S-transferase fusion system as a simple and effective method of producing purified milligram quantities of antigen.     

The future of BSE from the global perspective

Although, the bovine spongiform encephalopathy (BSE) risk of most countries in Europe has been assessed and they have implemented both measures to control BSE and extensive surveillance systems, complete and valid data is still not consistently available. Globally, data is largely unavailable. Assessments based on incomplete or invalid information could lead to false conclusions. The BSE risk of countries throughout the world must continue to be assessed, and improvements in collection of surveillance data must be made, both in countries already reporting BSE cases and worldwide, in order to evaluate the global BSE picture and assure that cattle and products can be safely traded.     

Optimisation of a liquid extraction process

A mathematical model of a solvent extraction process has been developed which has been arranged into a form suitable for optimising the process by the indirect optimisation procedure and by the direct method developed by Hooke and Jeeves. These optimisation procedures have been compared by analysing an extraction process in which solvent recovery is by distillation.     

Natural Oxidant Demand of Aquifer Materials Using the Push-Pull Technique

The quantification of the natural oxidant demand (NOD) of aquifer materials is required to estimate the fate of reagents injected into contaminated aquifers during in situ chemical oxidation applications. Three push-pull tests were conducted at a horizontal spacing of 12–20 m within an uncontaminated region of the saturated zone in the Canadian Forces Base Borden aquifer located near Alliston, Ont., Canada to estimate the NOD for permanganate. Each test contacted a minimum of 270 kg of aquifer material. Upper estimates of NOD values from the three tests were 0.51–0.75 g/kg based on the initial mass of aquifer material contacted, and lower estimates were 0.29–0.42 g/kg based on additional aquifer material mass contacted during the drift or reaction phase. These results compared favorably to NOD values determined from bench-scale tests with high solids mass to solution volume ratios. If design and operational concerns can be overcome, the push-pull test offers significant advantages over the variety of bench-scale testing methods currently used to determine the NOD of aquifer materials.