Ultraviolet absorption spectra are used in conjunction with multivariate calibration methods to predict the percent content of saturates (61-99%), monoaromatics (1-34%), diaromatics (0-5%), and polyaromatics (0-1%) in light gas oil and diesel fuel samples. A total of 114 samples taken from three pilot plant studies between 1992 and 1994 were used to develop the calibration models. Supercritical fluid chromatography with flame ionization detection was employed as the reference method for quantifying hydrocarbon types. Several multivariate calibration methods (classical least squares, multiple linear regression, principal components regression (PCR), and partial least squares (PLS)) were examined. PCR and PLS gave the best overall performance, with root-mean-squared errors of prediction (absolute) of 0.9% (saturates), 0.8% (monoaromatics), 0.2% (diaromatics), and 0.05% (polyaromatics) based on 44 prediction samples. Relative errors (absolute × 100/range) for these same species were 2.4%, 2.4%, 3.2%, and 5.3%.Key words: light gas oil, diesel, hydrocarbon content, UV spectroscopy, multivariate calibration, aromatics, petroleum.

A simple and rapid method has been developed to measure the bitumen, water, and solids content of Athabasca oil sand samples in order to efficiently serve both plant operations and research needs. A solvent blend of 74% toluene and 26% isopropyl alcohol extracts both the bitumen and the water from the solids producing a homogeneous liquid phase. The bitumen is determined gravimetrically on an aliquot of this solution. A Karl Fischer titration is used to measure the water concentration. Solids are measured gravimetrically or can be reported by difference. Mass balances between 99.05 and 100.25% are achieved routinely.

Oxalate over the range of 0.4 M to 1 × 10−5 M can be determined with an accuracy of about 2% by injection of sample solutions into a photolytic cell containing an acidic solution of iron(III). Ultraviolet irradiation decomposes the iron(III) oxalate complex to iron(II) and carbon dioxide. The carbon dioxide then is purged from the cell in a stream of helium, dried, separated from other gases on a column of silica gel, and measured with a thermal conductivity detector. Interference from calcium, magnesium, thorium, aluminum, and several carboxylic acids is slight, while that from malonic. citric, formic, and tartaric acids is moderate. Strong ultraviolet absorbing species affect results by reducing the efficiency of photolysis.

Oxalate concentrations were measured by photochemical oxidation with iron(III) to carbon dioxide. Technicon AutoAnalyzer components were used to automate the sampling and mixing steps, and the carbon dioxide produced in the radiation step was measured with a CO2 electrode. Variables in the System were evaluated and the optimum conditions identified. A theoretical study was made of the effect on ionic species concentrations of variations in iron(III), acid, and counter ion concentrations. A linear calibration curve could be obtained for oxalate concentrations in the range of 2 × 10−4 to 0.02 M; by modifying conditions linearity could be achieved at both higher and lower concentration ranges. Several other acids are partially oxidized under optimum conditions for oxalate. Tartrate, citrate, and malonate introduce errors of 2% or less at concentrations equivalent to oxalate; malate and pyruvate cause errors on the order of 10%. Several small carboxylic acids were found to interfere with the CO2 electrode.