Thermal Cracking and Catalytic Hydrocracking of a Colombian Vacuum Residue and Its Maltenes and Asphaltenes Fractions in Toluene

Abstract

Thermal cracking and catalytic (molybdenum naphthenate) hydrocracking processes in toluene solvent were carried out in a batch reactor for a typical Colombian heavy vacuum residue and its corresponding separated maltenes and asphaltenes fractions. The thermal cracking and catalytic hydrocracking tests were performed at 430 °C and 13.5 MPa for 25 min in the presence of nitrogen and hydrogen, respectively. Additionally, catalytic hydrocracking was also conducted after conditioning the vacuum residue at 380 °C, and 12.2 MPa of H 2 for 60 min with activated carbon. The cracking and catalytic hydrocracking performances of the vacuum residue and its components (maltenes and asphaltenes) were assessed by evaluating the effects on the yield and quality of the products (gas, toluene-insoluble solid, and liquid) utilizing SARA (saturates, aromatics, resins, and asphaltenes) composition and removal of sulfur and heavy (Ni, V) metals analyses. The vacuum residue showed asphaltene conversions of 53.1 and 43.1 wt % (excluding the yield of toluene-insoluble solids) under conditions of thermal cracking and catalytic hydrocracking, respectively. When the vacuum residue was pretreated with activated carbon and then catalytically hydrocracked, the asphaltenes conversion was higher (68.7 wt %, excluding the yield of toluene-insoluble solids) when compared to that during thermal cracking and catalytic hydrocracking in the absence of such pretreatment. Overall, the results showed that the hydrocracking of a vacuum residue in toluene with a molybdenum naphthenate catalyst is effective in forming liquid products that are lighter and with a lower concentration of sulfur and Ni and V heavy metals. These heteroatoms are removed in the toluene-insoluble solid products that concentrate recalcitrant sulfur and nickel complex (i.e., porphyrinic) aromatic compounds to a greater extent. The primary function of the thermally activated carbon pretreatment was to increase the yield of lighter liquid products as a likely result of the conversion of more reactive vanadium-containing complex structures into simpler components that remain in the liquid product and which otherwise would have been rejected in the toluene-insoluble solid fractions.

NMR Spectroscopy Analysis of Asphaltenes

“…Asphaltenes also have a greater number of aromatic carbons such as peri-condensed and cata-condensed ones and smaller fraction of alkyl substituents in the aromatic rings. Leon et al have claimed that these results are similar to the previous findings. , Most of the studies on vacuum residue analysis by NMR spectroscopy have utilized Dickinson’s equations for determining average structural parameters. In a recent report on NMR analysis of asphaltene probes obtained from an oil sand and of two vacuum remains from petroleum refining, Zheng et al argued that the Dickinson’s equation has its own limits as it supposes only that the carbon to hydrogen ratio of the α-alkyl groups matches that of the other alkyl groups at various locations of the asphaltene molecules.…”

“…Leon et al have investigated not only thermal cracking but also hydro-breaking treatment with molybdenum naphthenate as the catalyst in toluene in a batch apparatus for a characteristic Colombian heavy vacuum remaining and its corresponding segregated maltenes and asphaltene portions. Both of the thermal breaking treatments are conducted at 430 °C and 13.5 MPa for 25 min under the flow of N 2 and H 2 , respectively.…”

Application of Ethylene Tar as an Additive in Visbreaking of Petroleum Vacuum Residue

“…40,41 Probably, due to the different activity of vanadium-and nickel-containing structures, they are released to varying degrees with coke. 42 The data on the fractional composition of liquid visbreaking products are presented in Table 4. The highest yield of distillate fractions was obtained for VR + ET products (35.01 wt %), and the lowest was for VR + HCO (22.90 wt %).…”

Effect of WC/Ni–Cr additive on changes in the composition of an atmospheric residue in the course of cracking

“…At the same time, a deep destruction of resins is observed. It results in the formation of low molecular weight hydrocarbon components, which are part of light fractions (León et al 2017).…”