Abstract
Thermal cracking of C5-deasphalted oil\t\t\t\t\t\t(C5-DAO) was performed in a batch reactor at 410°C in\t\t\t\t\tthe absence and presence of H2 gas and catalysts. Coke\t\t\t\t\twas formed during the thermal cracking of C5-DAO even\t\t\t\t\tthough the feed contained no asphaltenes. Although H2\t\t\t\t\tsuppressed asphaltene formation and decreased the coke yield, coke was still\t\t\t\t\tformed in the absence of a catalyst. A slurry-phase dispersed catalyst inhibited\t\t\t\t\tthe transformation of resins into heavier fractions and facilitated <1 wt %\t\t\t\t\tasphaltene yield with no coke formation even under high conversion conditions.\t\t\t\t\tThe main function of the catalyst was the facilitation of hydrogenation\t\t\t\t\treactions and the stabilization of free radicals, leading to liquid production\t\t\t\t\tby inhibiting coke formation. Consequently, the product quality, in terms of\t\t\t\t\thydrogen to carbon ratio and microcarbon residue and S contents, was enhanced by\t\t\t\t\tcatalytic hydrocracking.
Highlights
Research and development of heavy oil upgrading technologies has recently attracted considerable attention because the demand for high quality fuel oils has increased while the proportion of low quality crude oil has grown [1,2,3,4,5]
Series experiments on thermal cracking and the non-catalytic hydrocracking of C5-deasphalted oil (C5-deasphalted oil (DAO)) as a function of reaction time were performed to elucidate the effect of H2 on the thermal cracking of C5-DAO
The aromatic carbon peaks decreased in the initial 4 h of the reaction, seemed to be unchanged between 8 and 12 h. This observation is consistent with the other results, as shown earlier. This could be attributed to the fact that some heavy fractions in C5-DAO were converted but still remained as a polyaromatic compound even after the catalytic hydrocracking reaction, and it took a long time to convert these heavy fractions into lighter products without coke formation
Summary
Research and development of heavy oil upgrading technologies has recently attracted considerable attention because the demand for high quality fuel oils has increased while the proportion of low quality crude oil has grown [1,2,3,4,5]. The coke yield increases significantly, and the liquid product yield decreases when feeds with high asphaltene content are used for hydrocracking reactions. The products obtained from DAO hydrocracking in the presence of NiMoS/Al2O3 and NiMoS–TiO2–USY catalysts were distilled into five fractions (gasoline, kerosene, gas oil, vacuum gas oil, and resins) and characterized by gas chromatography-atomic emission detection (GC-AED) to evaluate the hydrocracking performance by determining the distribution of C, S, and N species in the products [24]. The catalytic hydrocracking of C5-DAO was conducted in a semi-batch system to determine the role of the Mo-octoate catalyst precursor; catalytic hydrocracking was compared to non-catalytic hydrocracking in terms of hydrocracking activity, product quality, and saturates, aromatics, resins, and asphaltenes (SARA) distribution. The macrostructure parameters of asphaltenes and coke, such as aromaticity (fa-XRD), distance between the neighboring aromatic sheets (dm), average height of the stacked aromatic sheets perpendicular to the plane of the sheet (Lc), and number of aromatic sheets in a stacked cluster (M), were calculated using Eqs. (1)–(4), which have been mentioned in previous studies [6, 26,27,28]
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