Enhancing the capacity of oxygen carriers for selective oxidations through phase cooperation: bismuth oxide and ceria–zirconia

Interfacing selective catalysts with oxygen carriers enhances capacity without affecting the surface chemistry, simplifying the design of selective oxygen carriers.

11-interval PFG pulse sequence for improved measurement of fast velocities of fluids with high diffusivity in systems with short T2(∗)

Magnetic resonance (MR) was used to measure SF6 gas velocities in beds filled with particles of 1.1 mm and 0.5 mm in diameter. Four pulse sequences were tested: a traditional spin echo pulse sequence, the 9-interval and 13-interval pulse sequence of Cotts et al. (1989) and a newly developed 11-interval pulse sequence. All pulse sequences measured gas velocity accurately in the region above the particles at the highest velocities that could be achieved (up to 0.1 ms(-1)). The spin echo pulse sequence was unable to measure gas velocity accurately in the bed of particles, due to effects of background gradients, diffusivity and acceleration in flow around particles. The 9- and 13-interval pulse sequence measured gas velocity accurately at low flow rates through the particles (expected velocity <0.06 ms(-1)), but could not measure velocity accurately at higher flow rates. The newly developed 11-interval pulse sequence was more accurate than the 9- and 13-interval pulse sequences at higher flow rates, but for velocities in excess of 0.1 ms(-1) the measured velocity was lower than the expected velocity. The increased accuracy arose from the smaller echo time that the new pulse sequence enabled, reducing selective attenuation of signal from faster moving nuclei.

The interaction between CuO and Al2O3 and the reactivity of copper aluminates below 1000 °C and their implication on the use of the Cu–Al–O system for oxygen storage and production

This work investigates the interaction between CuO and different aluminas (and precursors) which are commonly used as support materials at temperatures between 700 and 1000 °C, as well as some chemical properties of the resulting copper aluminates.

Kinetic studies of CO2 methanation over a Ni/γ-Al2O3 catalyst

The production of methane by reacting CO₂ with H₂ (CO₂ methanation) has the potential for producing synthetic natural gas, which could be exported using the existing infrastructure for the distribution of natural gas. The methanation of CO₂ was investigated over a wide range of partial pressures of products and reactants using (i) a gradientless, spinning-basket reactor operated in batch mode and (ii) a laboratory-scale packed bed reactor operated continuously. The rate and selectivity of CO₂ methanation, using a 12 wt% Ni/γ-Al₂O₃ catalyst, were explored at temperatures 445–497 K and pressures up to 20 bar. Research with the batch reactor showed that the rate increased with increasing partial pressures of H₂ and CO₂ when the partial pressures of these reactants were low; however, the rate of reaction was found to be insensitive to changes in the partial pressures of H₂ and CO₂ when their partial pressures were high. A convenient method of determining the effect of H₂O on the rate of reaction was also developed using the batch reactor and the inhibitory effect of H₂O on CO₂ methanation was quantified. The kinetic measurements were compared with a mathematical model of the reactor, in which different kinetic expressions were explored. The kinetics of the reaction were found to be consistent with a mechanism in which adsorbed CO₂ dissociated to adsorbed CO and O on the surface of the catalyst with the rate-limiting step being the subsequent dissociation of adsorbed CO. The ability of the kinetic expressions to predict the results from the continuous, packed-bed reactor was explored, with some discrepancies discussed.

Inhibiting the interaction between FeO and Al2O3 during chemical looping production of hydrogen

Hydrogen of high purity can be produced by chemical looping using mixed oxides containing Fe, Al, Na and Mg.

The environmental and economic sustainability of potential bioethanol from willow in the UK

Life cycle assessment has been used to investigate the environmental and economic sustainability of a potential operation in the UK in which bioethanol is produced from the hydrolysis and subsequent fermentation of coppice willow. If the willow were grown on idle arable land in the UK, or, indeed, in Eastern Europe and imported as wood chips into the UK, it was found that savings of greenhouse gas emissions of 70-90%, when compared to fossil-derived gasoline on an energy basis, would be possible. The process would be energetically self-sufficient, as the co-products, e.g. lignin and unfermented sugars, could be used to produce the process heat and electricity, with surplus electricity being exported to the National Grid. Despite the environmental benefits, the economic viability is doubtful at present. However, the cost of production could be reduced significantly if the willow were altered by breeding to improve its suitability for hydrolysis and fermentation.

Magnetic resonance measurements of high-velocity particle motion in a three-dimensional gas-solid spouted bed

Magnetic resonance imaging has been used to measure particle velocities, exceeding 1 m s⁻¹ in a two-phase granular system, namely, a spouted bed. The measurements are complicated due to the high voidage, i.e., low particle density, in the region of the highest particle velocity. However, applying gradient shapes which allow fast switching and, thus, short encoding and observation times in combination with a short echo time enable these measurements. It was found that the profile of the particle velocity is nonparabolic. Based on these measurements it was possible to confirm observations made in numerical simulations that there must be a continuous momentum exchange between the annulus region and the spout along the entire length of the spout.

Time-of-flight variant to image mixing of granular media in a 3D fluidized bed

This paper describes a variant of time-of-flight magnetic resonance (MR) imaging that provides a method of measuring the inherent mixing in a fluidized bed without the introduction of tracer particles. The modifications to conventional time-of-flight imaging enable the measurement of the axial mixing of a precisely controlled initial particle distribution, thereby providing measurements suitable for a direct comparison with models of solids mixing in granular systems. The imaging sequence is applied to characterize mixing, over time scales of 25-1000 ms, in a gas-fluidized bed of Myosotis seed particles; mixing over short timescales, inaccessible using conventional tracer techniques, is studied using this technique. The mixing pattern determined by this pulse sequence is used in conjunction with MR velocity images of the motion of the particles to provide new insight into the mechanism of solids mixing in granular systems.

Environmental analysis of plastic production processes: Comparing petroleum-based polypropylene and polyethylene with biologically-based poly-β-hydroxybutyric acid using life cycle analysis

Polymers based on olefins have wide commercial applicability. However, they are made from non-renewable resources and are characterised by difficulty in disposal where recycle and re-use is not feasible. Poly-beta-hydroxybutyric acid (PHB) provides one example of a polymer made from renewable resources. Before motivating its widespread use, the advantages of a renewable polymer must be weighed against the environmental aspects of its production. Previous studies relating the environmental impacts of petroleum-based and bio-plastics have centred on the impact categories of global warming and fossil fuel depletion. Cradle-to-grave studies report equivalent or reduced global warming impacts, in comparison to equivalent polyolefin processes. This stems from a perceived CO(2) neutral status of the renewable resource. Indeed, no previous work has reported the results of a life cycle assessment (LCA) giving the environmental impacts in all major categories. This study investigates a cradle-to-gate LCA of PHB production taking into account net CO(2) generation and all major impact categories. It compares the findings with similar studies of polypropylene (PP) and polyethylene (PE). It is found that, in all of the life cycle categories, PHB is superior to PP. Energy requirements are slightly lower than previously observed and significantly lower than those for polyolefin production. PE impacts are lower than PHB values in acidification and eutrophication.

Rapid two-dimensional imaging of bubbles and slugs in a three-dimensional, gas-solid, two-phase flow system using ultrafast magnetic resonance

Ultrafast magnetic resonance has been applied to measure the geometry of bubbles and slugs in a three-dimensional gas-solid two-phase flow. A bed of particles of diameter 0.5 mm were fluidized with gas velocities in the range of 0.08-0.26 m/s. Bubbles were imaged in transverse as well as vertical planes with an acquisition time of down to 25 ms and a spatial resolution down to 1.7 mm. Owing to the ultrafast character of these measurements, it is not only possible to evaluate correlations, e.g., for the bubble diameter, but also evaluate models of complex hydrodynamic phenomena, such as the splitting and coalescence of bubbles.

Real-time measurement of bubbling phenomena in a three-dimensional gas-fluidized bed using ultrafast magnetic resonance imaging

Ultrafast magnetic resonance imaging has been applied for the first time to measure simultaneously both the rise velocities and coalescence of bubbles, and the dynamics of the solid phase in a gas-solid two-phase flow. Here, we consider the hydrodynamics within a gas-fluidized bed of particles of diameter 0.5 mm contained within a column of internal diameter 50 mm; gas velocities in the range of 0.18-0.54 m/s were studied. The data are of sufficient temporal and spatial resolution that bubble size and the evolution of bubble size and velocity following coalescence events are determined.

Mixing in process vessels used in biopharmaceutical manufacturing

The use of nonbaffled vessels for mixing applications is becoming common in the biopharmaceutical industry but is not sufficiently well studied. Orientation of the impellers off-centered and/or at an angle is necessary to enhance mixing and eliminate swirling that would result without a baffle in a standard tank. This study focuses on characterizing mixing in vessels with the hydrofoil axial flow impellers mounted off-center at 10 degrees to the vertical. Geometrically similar vessels ranging from 100 to 5000 L working volume were used in this study. Mixing performance was successfully correlated to vessel geometric factors.

Lymphocytic/plasmacytic colitis in cats: 14 cases (1985-1990)

Lymphocytic/plasmacytic colitis was diagnosed in 14 cats during a 5-year period. Purebred cats were affected significantly (P < 0.001) more often than were nonpurebred cats. Six cats were male and 8 were female. Mean age at onset of clinical signs was 5.1 years (range, 0.5 to 9 years). Hematochezia, observed in 13 cats, was the most commonly reported sign; diarrhea was reported in 11 cats. Mildly high serum alanine transaminase activity and hypokalemia were frequent biochemical abnormalities. Campylobacter sp was cultured from the feces of 1 cat. On endoscopic examination, petechia and hyperemia of the colonic mucosa were detected in 7 of 8 cats. Cats were initially treated with dietary management alone or with a combination of dietary and pharmacologic management. Clinical signs in 7 of 11 treated cats completely resolved, whereas signs in 3 cats were considered improved. One cat was euthanatized when an inadequate response to treatment was observed. Most cats were eventually maintained on dietary management alone.

Lymphocytic/plasmacytic gastroenteritis in cats: 14 cases (1985-1990)

Over a 5-year period, lymphocytic/plasmacytic gastroenteritis was diagnosed in 14 cats. Purebred cats were affected significantly (P less than 0.025) more often than nonpurebred cats. Mean age at onset of clinical signs was 6.8 years (range, 1 to 13 years); 11 cats were male. Vomiting and weight loss, each reported in 10 of 14 cats, were the most common clinical signs. Diarrhea was reported in 7 of 14 cats. Alopecia was found in 4 of 14 cats. High hepatic enzyme activities and low plasma protein concentrations were frequent biochemical findings. Hyperemia, hemorrhage, and a roughened or "cobblestone" mucosa were visualized by endoscopy in only 2 of 8 cats with duodenal disease and in 2 of 5 cats with gastric disease. Lymphocytic/plasmacytic inflammation was detected in biopsy specimens from the stomach or duodenum or both in all cats; the duodenum was affected most commonly. Degree of inflammation frequently varied among gastric, duodenal, and colonic specimens from the same cat. Glucocorticoid treatment and dietary management adequately controlled clinical signs in 7 cats, but treatment was ineffective in 6 cats, 5 of which were euthanatized because of severity of clinical signs.

Combined chemical and mechanical processes for the disruption of bacteria

Mechanical cell disruption by high pressure homogenisation or high speed bead mills is currently the general method of choice for the large scale disruption of micro-organisms; however, deleterious effects include the high energy requirement, the need for efficient cooling to prevent the excessive heating of the product and the micronisation of cell debris. Certain chemical treatments for microbial cell disruption alter the permeability of bacteria and yeasts, allowing partial release of soluble products. Such treatments are insufficient for the recovery of granular intracellular products. As cell wall strength has been cited as a major factor influencing the requirements for efficient mechanical disruption, the use of chemical pretreatment to decrease cell wall strength prior to mechanical breakage by homogenisation has been considered. The following treatments were shown to increase the sensitivity of the Gram-negative bacterium, Alcaligenes eutrophus, to disruption: alkaline pH shock, the addition of an anionic detergent, increase of the monovalent cation concentration, the addition of EDTA and enzymic lysis by lysozyme. These pretreatments allow equivalent disruption to be achieved at lower operating pressures or fewer passes through the homogeniser. Alkaline pH pretreatment at pH 10.5 allowed a 37.5% increase in soluble protein release on subsequent homogenisation. An increase of some 30% in soluble protein release was found following prior addition of 0.137 M monovalent cations (Na+ or K+) at 60 degrees C. Treatment with an anionic detergent showed a considerable decrease in the number of passes required through the homogeniser. Maximum cell rupture can thus be accomplished at reduced energy inputs.