Some Foundational Investigations On The Structure Of Heavy Oil

Average molecular weight is an important parameter describing the structure of heavy oil. It's the necessary basic data for illustration of petroleum's natures and for calculating average molecular structure for heavy oil. However, large differences exist in the average molecular weights of resins especially of asphaltenes measured by different methods. The main reason for this difficulty is that there isn't a perfect and effective method which can split resins and asphaltenes into single molecules without breaking the chemical bonds in these molecules. Fortunately, Matrix assisited laster desorption ionization time of flight mass spectroscopy (MALDI-TOF-MS) can make up the limitation because of its'soft'ionization ability as well as that of analyzing infinite mass molecules. In this thesis, we employ the MALDI-TOF-MS method to measure the average molecular weights of vacuum residue fractions from Liaohe crude oil. Mass and 1H-NMR spectra of these fractions before and after a thermal reaction have been tested. Average molecular weight for each fraction is derived from MALDI-TOF-MS data. In conjuction with 1H-NMR spectra we obtain the average structure parameters of these fractions, e. g., aromatic rates, aromatic ring numbers, saturate carbon numbers, total ring numbers, naphthene ring numbers. We use these parameters to study the law of the structural varieties of each fraction in the thermal reaction. In order to discuss the chemical properties about a unit sheet of asphaltene, density functional theory at its B3LYP functional has been employed to investigate HOMO-LUMO gaps, ionization potentials, as well as harmonic oscillator model of aromaticity (HOMA) for acridine and acridine derivatives. The analysis of these parameters permit us to make a quantitative prediction that meta-positioned C2 (with respect to N atom) is more reactive than C6 located also meta with respect to N. Ionization potentials for the position 2 substituted derivatives are larger than those of the corresponding position 6 substitutes. In addition, substituent effect in position 2 is more notable than that in position C6.