Aqueous Ozonation Of Fatty Acids

The reactivity of a series of fatty acids toward ozone was examined in aqueous solution at low substrate concentration (μg.L^?1 range). Saturated fatty acids were unreactive, unsaturated fatty acids were readily consumed. A number of reaction products or their methylated derivatives were identified by gas chromatography and gas chromatography-mass spectrometry. The products identified are consistent with a 1,3-dipolar cyclo-addotion reaction.     

A new technique to derive particle size distributions and aerosol number concentrations directly from thermophoretic data

The manufacture of many high value-added powders takes place by the decomposition of gaseous precursors in aerosol tube reactors. Historically, process improvements were achieved by making changes on the outside of the reactor and observing what comes out at the end of the pipe. The development of increasingly accurate aerosol dynamics models based on engineering first principles has been limited because models were typically validated on integral properties of ex situ product, instead of particle properties measured at multiple positions inside the reactor. In this study, a model reactor was equipped to capture samples thermophoretically from 15 internal positions. Additional in-line measurements were achieved with a multi-stage inertial impactor and by traditional analysis of ex situ product. Calculations were performed to verify that thermophoresis was the dominant mechanism of particle capture. The thermophoretic samples were analyzed by electron beam microscopy and image analysis to develop particle size distributions at each of the internal positions inside the reactor. An approximation of Talbot's Equation for thermophoretic velocity allowed experimental measurements to be combined with thermophoretic sample data to give predictions of particle number concentration corresponding to the precise sampling locations. The combinations of particle size distributions and number concentrations provide powerful insights on particle nucleation and growth dynamics.     

Diamond-like carbon coating of alternative metal alloys for medical and surgical applications

The effectiveness of a plasma-deposited, diamond-like carbon (DLC) coating on aluminium alloy based surgical instruments is investigated. Surgical instruments must satisfy a number of important criteria including biocompatibility, functional performance, sterility and cleanability, structural integrity, and fatigue resistance. The integrity of the DLC layer and the diffusion barrier properties are of paramount importance due to biocompatibility considerations of the underlying aluminium metal. We investigate the optimisation of the coating with incorporation of silicon and variation in negative self bias, and highlight the design and manufacture of a lightweight laparoscopic assist instrument from aluminium alloy coated with diamond-like carbon, which has been used successfully in the clinical environment to improve operations such as cholecystectomy (gall bladder removal) and exploratory techniques for the diagnosis of cancer.     

EFFECTS OF ASPHALTENE PRECIPITATION AND REPRECIPTION ON THE METAL-CONTAINING COMPOUNDS IN HEAVY RESIDUA

ABSTRACT

Boscan vacuum residuum (VR) has been separated into isooctane insoluble asphaltenes and isooctane soluble maltenes. The asphaltenes were dissolved in a minimum of toluene and were further separated by two additional reprecipitations using isooctane as the precipitating solvent. We examined the fractions, including the recovered isooctane soluble material, by size exclusion chromatography (SEC) with inductively coupled plasma (ICP) emission spectroscopy to determine the effects, if any, the reprecipitations have on the size distribution of the metal-containing compounds.

The asphaltene fractions show little change in size upon reprecipitation, but removal of a small amount of the metal components does occur. The first reprecipitation produces isooctane soluble material which is very similar in size to the original maltene fraction. However, the second reprecipitation removes small amounts of material in the size range of the asphaltenes. When the amounts were weight balanced, the resulting separation did little to effect the overall maltene and asphaltene size profiles.     

CHARACTERIZATION OF NICKEL AND VANADIUM COMPOUNDS IN TAR SAND BITUMEN BY UV-VIS SPECTROSCOPY AND SIZE EXCLUSION CHROMATOGRAPHY COUPLED WITH ELEMENT SPECIFIC DETECTION

ABSTRACT

Previously, we have examined the Ni and V in heavy crude oils, residua, and processed products by several metal speciation techniques to ascertain molecular structure and processing behavior. Two classes of metal compounds were found -metallopetroporphyrins and metallo-nonporphyrins - each having unique reactivity during processing. In efforts to better understand the binding of metals in the oil medium, we have now examined Ni and V in tar sand bitumens, the bitumen was solvent extracted from the sand matrix and was separated by column chromatography and the petro-porphyrin content was quantitated by UV-vis spectroscopy. The petroporphyrin contents ranged from virtually none to over 36% of the total metals. Asphalt Ridge (Utah) has primarily Ni petroporphyrins; Big Clifty (Kentucky) and Athabasca (Canada) have primarily V petroporphyrins; Arroyo Grande and McKittrick (California) have roughly equal amounts of both types; and Surmyside (Utah) has virtually none of either.

Size characteristic profiles (SEC-ICP) were generated for the extracted bitumens. The profiles are generally bimodal in shape and resemble several different specific heavy crude oils and residua. For examples, Arroyo Grande and McKittrick appear to be similar to Kern River (California) 650°F+ residuum, while Athabasca resembles Morichal (Venezuela) 650°F+ residuum.     

EFFECT OF PREHYDROGENATION ON HYDROCONVERSION OF MAYA RESIDUUM,PART II: HYDROGEN INCORPORATION

ABSTRACT

Maya 650° F residuum (Maya AR) was prehydrogenated over a standard hydroprocessing catalyst. The 650°F residuum of this product lpar;HMaya ARrpar; and Maya AR were then separately hydroprocessed further at selected conditions. The products were examined by elemental, ¹H, and ¹³C NMR analyses to determine the how hydrogen was incorporated during processing.

For all processing steps, hydrogen was incorporated in capping fragments formed during cracking reactions, as well as in hydrogenation reactions, heteroatom removal, and hydrocarbon gas formation, but the distribution of the hydrogen was dependent upon the type and severity of the process: For the direct hydroconversion of Maya AR, 25 to 30% of the total hydrogen was incorporated for heteroatom removal and hydrocarbon gas formation. The remaining hydrogen was incorporated in hydrogenation and cracking reactions.

For the two-step hydroconversion process, 30 to 40% of the total hydrogen was incorporated for heteroatom removal and hydrocarbon gas formation. The remaining was primarily incorporated in hydrogenation reactions. Some was incorporated into cracking reactions in the moderate severity case, but almost none was seen in the low severity case.

The hydrogen incorporation during each specific processing step is discussed, along with an evaluation of the prehydrogenation step a residuum conversion process option. These results will be also compared to previously reported hydrogen incorporation measurements on other feeds and processing methods.     

Size Exclusion Chromatography-Inductively Coupled Plasma Atomic Emission Spectrographic Study of Fe In Bitumens Derived from Tar Sands

Abstract

Bitumens extracted from tar sands from various locations (Utah. California. Kentucky, and Alberta) were examined by size exclusion chromatography with on-line element-specific detection to study the Fe concentration as a function of size. In most cases, the resulting profiles exhibit unimodal distributions at relatively large molecular size with very similar times for maximum elution. Specifically, Sunnyside (Utah) and McKittrick (California) tar-sand bitumens exhibited very intense maxima consistent with extremely high bulk Fe contents. Arroyo Grande (California) exhibited an additional maximum at very large molecular size. This size behavior of the Fe appears to correlate with the large molecular size Ni and V components eluted under the same conditions.     

TRANSIENT THERMOELASTIC FRACTURE OF INTERFACE CRACKS

Abstract

The transient behavior of an interface crack at the center and edge of two finite dissimilar materials free to bend and subjected to a transient thermal load was studied. It was first assumed that the crack was insulated. The effect of allowing heat to conduct through the crack upon closing was also investigated. The effects of the mechanical and thermal material property ratios as well as the thickness ratio on the crack deformations and the transient strain energy release rate were calculated.     

Net energy for lactation of calcium salts of long-chain fatty acids for cows fed silage-based diets.

The NEL of calcium salts of long-chain fatty acids from palm oil was determined in mature Holstein cows. Twelve lactating (fed for ad libitum intake) and six nonlactating (restricted to near maintenance intake) Holstein cows were fed 0 or 2.95% fat supplement in diets formulated to contain 16 or 20% CP in a 2 x 2 factorial arrangement of treatments in a single reversal design within protein level. The fat supplement was substituted for ground corn and minerals. Two 6-d total collection balance trials were conducted during which cows were in open circuit respiration chambers. Intake of OM was lower for lactating cows fed the fat supplement (18.1 vs. 19.1 kg/d), but energy intake did not differ (93.2 Mcal/d). Total long-chain fatty acid intake was increased from 477 to 820 g/d with fat feeding. Apparent digestibility of long-chain fatty acids was increased 11.1 percentage units with increased dietary CP for lactating cows with no difference in fatty acid digestibility for the dry cows. Milk yield was higher (34.3 vs. 32.0 kg/d) with fat feeding, but milk energy yield did not differ (22.6 Mcal/d). The NEL of the fat supplement was estimated from the incremental differences in energy values within cows, assuming NEL of corn replaced by fat to be 1.96 Mcal/kg DM, and was determined to be 6.52 Mcal/kg DM (SE = 1.74). The efficiency of the use of metabolizable energy for lactation from dietary fat was 77.2%. The energy in calcium salts of long-chain fatty acids is utilized efficiently for lactation in mature cows.     

Net absorption of macrominerals by portal-drained viscera of lactating Holstein Cows and beef steers

Net absorption of macrominerals by portal-drained viscera of cattle was measured in two experiments. In Experiment 1, net portal-drained visceral and liver flux of Na, K, Ca, P, and Mg were measured in four lactating Holstein cows fed a 60:40 corn silage:concentrate diet ad libitum and milked at 12-h intervals. Twelve measurements of net flux (venous-arterial concentration difference x blood plasma flow) were obtained hourly at 4 and 8 wk postpartum. Intake of DM and milk yield averaged 15.6 and 32.2 kg/d, respectively. Excluding Na, net absorption of these macrominerals was measurable across portal-drained viscera. Flux of Na was negative at wk 4 postpartum (net removal from blood) and positive at wk 8 (net absorption into blood). Excluding Mg, differences in venous-arterial concentrations for macrominerals across the liver were not different from zero. In Experiment 2, net portal-drained visceral flux of Na, K, Ca, P, and Mg was partitioned into stomach and poststomach sections in two Hereford steers. Poststomach tissues accounted for essentially all such absorption of K, Ca, and P and, on a net basis, removed Na and Mg. Stomach tissues absorbed Mg and small amounts of K, Ca, and P. Net stomach flux of Na was positive, denoting net absorption, but highly variable. Net portal-drained visceral absorption of K increased with intake in both experiments. Net portal-drained visceral absorption of P was greater than total intake in both experiments, reflecting recycling of P via saliva and other digestive secretions.