A 1H CRAMPS n.m.r. investigation of chemically and thermally treated asphalt ridge tar sand

Abstract

An exploratory investigation was conducted using the n.m.r. technique CRAMPS (combined rotation and multiple-pulse spectroscopy) to provide information on the types of organic hydrogen functionality present on the surface of tar sand residues. These residues were obtained from solvent extraction using solvents of different polarity and isothermal pyrolysis at four different temperatures. The solvents hexane, toluene, and methylene chloride were used to extract the bitumen from a native tar sand. From carbon and hydrogen analyses, all three solvents removed essentially all of the bitumen from the mineral matrix. However, solid-state 1H n.m.r. and diffuse reflectance infrared spectra show the presence of a small amount of organic material still in contact with the mineral matrix. After extraction with methylene chloride, the most polar solvent, tar sand residues contain less organic material than the tar sand residues obtained after solvent extraction with hexane, the least polar of the solvents. The hydrogen spectra of the tar sand residues show a greater amount of aromatic hydrogens than aliphatic hydrogens presumably because heteroaromatics associate more strongly with the mineral matrix. The 1H CRAMPS spectra of the tar sand residues obtained from the isothermal pyrolysis of the native tar sand show that a relatively large amount of unpyrolysed bitumen still remains with the mineral matrix even at a temperature of 380 °C. For the native tar sand pyrolysed above 400 °C, the 1H spectrum changed dramatically, but the spectrum of the pyrolysate tar sand residues still did not have the chemical shift resolution that was apparent in the spectra of the tar sand residues from solvent extraction. The major change in the 1H spectrum of the tar sand residue after pyrolysis above 400 °C was the loss of paraffinic hydrogens, as expected.