Brendan F. Graham

Solubility of p-t-butylcalixarenes in supercritical carbon dioxide: a comparison of static and dynamic measurement techniques

Abstract The solubilities of p - t -butylcalix[ n ]arenes ( n =4,6,8) and calix[4]arene have been measured in supercritical carbon dioxide. Solubility measurements were conducted in a high pressure cell with in situ spectrophotometric detection. Measurements were taken over the ranges of 10 to 20 MPa and 40 to 60°C. The p - t -butylcalix[4]arene showed solubility approximately 10 fold higher than both p - t -butylcalix[6]arene and p - t -butylcalix[8]arene with a maximum measured solubility over the studied pressure and temperature ranges of 1.84×10 −5 mol/l. A comparison of these results with measurements made with a commercially available analytical SFE unit for p - t -butylcalix[4]arene showed less than 10% deviation between the two sets of data over a common range of conditions. The SFE unit allows measurements to be made over significantly wider ranges of pressure and temperature than are currently available using the solubility cell.

Evidence of a Host:Guest Complex between p-t-Butylcalix(4)arene and Carbon Dioxide ∗

In this paper we report evidence for an inclusion complex between carbon dioxide and p-t-butylcalix[4]arene. The complex was studied with infrared spectroscopy,single-crystal X-ray diffraction, solid-state NMR, and thermogravimetric analysis.Results indicate that 70% of the p-t-butylcalix[4]arene cavities could be occupiedby a CO2 molecule following exposure at 30 MPa and 40 °C.

Quantitative produced water analysis using mobile 1H NMR

Measurement of oil contamination of produced water is required in the oil and gas industry to the (ppm) level prior to discharge in order to meet typical environmental legislative requirements. Here we present the use of compact, mobile 1H nuclear magnetic resonance (NMR) spectroscopy, in combination with solid phase extraction (SPE), to meet this metrology need. The NMR hardware employed featured a sufficiently homogeneous magnetic field, such that chemical shift differences could be used to unambiguously differentiate, and hence quantitatively detect, the required oil and solvent NMR signals. A solvent system consisting of 1% v/v chloroform in tetrachloroethylene was deployed, this provided a comparable 1H NMR signal intensity for the oil and the solvent (chloroform) and hence an internal reference 1H signal from the chloroform resulting in the measurement being effectively self-calibrating. The measurement process was applied to water contaminated with hexane or crude oil over the range 1–30 ppm. The results were validated against known solubility limits as well as infrared analysis and gas chromatography.