Abstract
The aim of this work was to study the fractional composition of super-viscous oil resins from the Ashalcha field, as well as the catalytic aquathermolysis product in the presence of a cobalt-containing catalyst precursor and a hydrogen donor. The study was conducted at various durations of thermal steam exposure. In this regard, the work enabled the identification of the distribution of resin fractions. These fractions, obtained by liquid adsorption chromatography, were extracted with individual solvents and their binary mixtures in various ratios. The results of MALDI spectroscopy revealed a decrease in the molecular mass of all resin fractions after catalytic treatment, mainly with a hydrogen donor. However, the elemental analysis data indicated a decrease in the H/C ratio for resin fractions as a result of removing alkyl substituents in resins and asphaltenes. Moreover, the data of 1H NMR spectroscopy of resin fractions indicated an increase in the aliphatic hydrogen index during catalytic aquathermolysis at the high molecular parts of the resins R3 and R4. Finally, a structural group analysis was carried out in this study, and hypothetical structures of the initial oil resin molecules and aquathermolysis products were constructed as well.
Highlights
The refining industry is tending toward an increase in the mass of the feedstock being processed and this in turn is leading to the development and implementation of additional processes for the preparation of oils based on the destruction of the structures of high molecular mass compounds in the oil, which leads to an increase in the content of light fractions in oil feedstock [1,2,3,4,5]
It is important to know the structure of resins and asphaltenes, as well as the number and nature of molecular fragments, as these contain heteroatoms that play a significant role in the destruction of high molecular mass compounds [6,7,8,9,10]
The oil resin fractions of the Ashalcha field consisted of a set of molecules with average molecular masses from 900 to 1080 amu, and the resin fractions of the catalytic aquathermolysis product with a 6 h treatment time had molecular masses from 698 to
Summary
The refining industry is tending toward an increase in the mass of the feedstock being processed and this in turn is leading to the development and implementation of additional processes for the preparation of oils based on the destruction of the structures of high molecular mass compounds in the oil, which leads to an increase in the content of light fractions in oil feedstock [1,2,3,4,5]. One of the most common methods for increasing the yield of light fractions is the method of component destruction of heavy oil feedstock (thermal, thermal radiation, etc.). In this regard, it is important to know the structure of resins and asphaltenes, as well as the number and nature of molecular fragments, as these contain heteroatoms that play a significant role in the destruction of high molecular mass compounds [6,7,8,9,10]. Sulfur-containing model compounds of different classes demonstrate different abilities to generate hydrogen sulfide under conditions simulating the process of cyclic thermal steam exposure (CSS) [18], while the formation of H2 S increases with increasing temperature. It has been shown that thiophenols and n-alkyl and aryl sulfides undergo desulfurization more than the cyclic sulfur-containing compounds—thiophenes and benzothiophenes [19,20]—while treatment of 15% aqueous formic acid under supercritical conditions promotes the occurrence of these reactions [19]
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