Zongxian Wang

Characterization of molecular change of heavy oil under mild thermal processing using FT-IR spectroscopy

Abstract In order to quickly and economically obtain the information of molecular changes occurring in heavy oils during thermal processing, simulated mixtures of heavy oils and their pyrolyzed products were prepared from four model compounds, i.e., naphthalene, tetralin, decalin, and n-heptane. FT-IR absorption characteristics and average molecular parameters of the mixtures were correlated; the molecular parameters included the number ratio of methylene to methyl (NCH2/NCH3), hydrogen aromaticity (faH), atomic ratio of hydrogen to carbon of the aromatic sheet (NHar/NCar), etc. Considering heavy coker gas oil (HCGO) as a heavy oil feedstock, HCGO was thermally processed in an autoclave and its gas oil fraction (GOF) was separated into group fractions and analyzed by FT-IR. The results show that the simulated mixtures show good linearity between faH and the absorption area ratio of the bands at 3100 - 2750 cm −1 to 3100 - 3000 cm −1 (S3000-3100/S2750-3100), and so does (NCH2/NCH3) and absorbance ratio of the bands at 2920 - 2960 cm −1 (A2920/A2960). These correlations could be useful tools for illustrating molecular changes occurring in heavy oil during thermal processing. As the processing proceeds, the NCH2/NCH3 of the saturate molecules increases first and then declines, in sharp contrast to that of the aromatic molecules, which shows a consistent decline. As far as faH or NHar/NCar is concerned, however, the aromatic molecules show a rising trend. The chemistry behind these phenomena is also discussed in some detail.

Separation and composition characterization of acidic components in water produced by polymer flooding in Gudao Oilfield

Abstract The oily substances in the water produced by polymer flooding in Gudao, Shengli Oilfield were extracted by petroleum ether and trichloromethane and two fractions (marked as F1 and F2) were obtained. The acidic components from fraction F2 were separated by alkaline extraction and esterified by methanol. The methyl esters products were separated into three fractions I, II and III by silica gel column chromatography. The oily substances and the acidic components were characterized using elementary analysis, IR spectral analyses and acidimetry. The structures and compositions of the methyl ester fractions (fraction I) were identified using GC—MS technology. The results showed that the acidic emulsifying active substances in the produced water by polymer flooding were gathered in CHCl3 extracted fraction F2, and degradation products of hydrolyzed polyacrylamide (HPAM) constitute the major part of the acidic components. The compositions of fraction II and I were mainly petroleum acid methyl esters and aliphatic acid methyl esters with amide groups. The fraction III was mainly composed of aliphatic acid methyl esters with more amide groups and some strong polar compounds containing S=O group. The light petroleum acids in water produced by polymer flooding in Gudao Oilfield were mainly composed of C16—C18 aliphatic acids, C14—C18 naphthenic acids and C18—C21 tetracyclic naphthenic acids, and the amount of naphthenic acids were more compared with the aliphatic acids.