Abstract
Proton and carbon-13 NMR spectroscopic methods were developed for determining hydrogen and carbon contents in petroleum products. These methods are applicable to a wide range of petroleum streams. A new reference standard, bis(trimethylsilyl)methane, BTMSM, is introduced for both proton and carbon-13 NMR for the first time, which offers several advantages over those customarily employed. These methods are important for the calculation of the mass balance and hydrogen consumption in pilot plant studies. Unlike the ASTM D-5291 combustion method, the NMR methods also allow for the measurement of hydrogen and carbon content in low-boiling fractions and those containing hydrogen as low as 1%. The NMR methods can also determine aromatic and aliphatic hydrogens and carbons in a given sample without additional experimentation. The precision and accuracy of the newly developed NMR methods are compared with those of currently employed ASTM D-5291 combustion method. Using the proton NMR method, hydrogen content was determined in fifteen model compounds and sixty-eight petroleum fractions. The NMR and ASTM methods show an agreement within +/-5% for 48 out of a total number of 68 oil fractions. Using carbon-13 NMR, the carbon content was determined for four representative compounds and three fractions of crude oil. Both carbon-13 NMR and ASTM methods give comparable carbon content in model compounds and crude oil fractions.