Visbreaking of Heavy Oil in Supercritical Benzene

Abstract

The visbreaking of heavy oil in supercritical benzene ( SC benzene) was investigated. By introducing SC benzene, the visbreaking originally occurring in the oil phase is transferred into SC benzene. The superior diffusivity in SC benzene improves the efficiencies of the initiation and propagation of visbreaking network, by which the reaction could be run in the desired tandem structure. By mitigating diffusion limitation to reaction kinetics, the cracking of alkyl substitutes of aromatics vital to viscosity reduction is accelerated. Being the secondary reaction of the cracking, condensation could be terminated promptly at the shortened reaction time necessary for visbreaking. A comparison between the visbreaking in SC benzene and supercritical water ( SC H 2 O) confirms the effectiveness of improving diffusion for the optimization on heavy oil visbreaking. Nevertheless, the optimal operating conditions involved must be determined experimentally because of the complicated interaction between phase structure and reaction kinetics. The visbreaking in SC benzene shows the advantages of milder operating conditions and better product stability over the visbreaking in SC H 2 O.

The Visbreaking of Heavy Oil in Supercritical Cyclohexane: The Effect of H-Donation

“…The purpose of introducing SCFs in heavy oil visbreaking is to transfer the reaction to SCFs with excellent diffusivity. Combined with literature reports, the effectiveness of process enhancement in various SCFs can be demonstrated [6,9]. Unlike benzene and cyclohexane, water shows good mutual solubility with heavy oil only in the supercritical region.…”

“…According to the reported visbreaking in SC C 6 H 6 and SC H 2 O at increasing solvent density, the unfavorable cage effect on dealkylation kinetics could be effectively compensated by improving diffusivity [6,9]. Similarly, it was expected that accelerated viscosity reduction would be observed with the increase in the SC C 6 H 12 density.…”

“…In order to compare the visbreaking in different SCFs, a heavy oil used in previous work was also used here [6,9]. For simplicity, the raw heavy oil provided by Sinopec Changling Refining and Chemical Company is referred to as Changling VR in the following text.…”

“…Since the diffusion coefficient of a substance is inversely proportional to the viscosity of the system, the diffusion coefficient of oil molecules in SC H 2 O is about one to two orders of magnitude higher than that in the heavy oil. After alleviating the limitation of diffusion to reaction kinetics, an acceleration in viscosity reduction was observed at moderate temperatures of 390 to 420 • C. To verify the advantage of the tandem structure in visbreaking, supercritical benzene ( SC C 6 H 6 , Tc = 289 • C, Pc = 4.9 MPa) was also tried [9]. Benzene remaining thermally stable up to 550 • C is completely miscible with heavy oil under ambient conditions, so the mixture of heavy oil and SC C 6 H 6 should exist in the single-phase structure.…”

Upgrading of Tsingtao Vacuum Residuum in Supercritical Water (I): A Preliminary Phase Structure Study by Molecular Dynamics Simulations

“…Meanwhile, those of resin and asphaltene molecules increase by 10–15 wt %, respectively. The stability of asphaltenes in heavy oil usually is evaluated by colloidal stability index (CSI), and the initial CSI of Tsingtao VR is 0.25. , By the data presented in Figure , the CSI values of the largest cluster or oil droplets formed at increasing temperatures of 380, 400, and 420 °C are 0.29, 0.43, and 0.46. In terms of the increasingly ordered stacking of heavy fractions and the increasing CSI value, the extraction of light fractions into SC H 2 O surroundings increases the risk of the aggregation of heavy fractions and the subsequent condensation to coke within the oil droplets.…”