Analysis of montmorillonite affecting coke formation during the thermal conversion of heavy oil. (15th March 2021)

• Record Type: Journal Article
• Authors: Zheng, Ruonan; Liu, Dong; Tang, Junshi; Song, Qiang; Yao, Qiang
• Is Part Of: Fuel. Volume 288(2021)
• Publication Date: 2021-03-15
• Subjects: Montmorillonite -- Heavy oil -- Coke formation -- Catalysis; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2020.119687
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Montmorillonite catalyzes aromatization and polymerization during oil pyrolysis. Its large specific surface area also affects coking during oil pyrolysis. Montmorillonite affects coke formation under the oxidizing atmosphere via catalysis. It catalyzes oxygen-adding, polycondensation, decarbonylation and decarboxylation. Abstract: Coke formation during the process of in-situ combustion is affected by clay minerals, among which montmorillonite shows the most significant effect. A fixed-bed reactor was used to conduct the thermal conversion experiments of heavy oil and model compounds to reveal the mechanism of montmorillonite affecting the coke formation. Under the inert atmosphere, in the presence of montmorillonite, the temperature at which aromatic C–C groups of coke appeared decreased from 500 °C to 450 °C and polymers were formed when toluene was heated, indicating that montmorillonite catalyzed aromatization and polymerization, respectively. The increase in the supporter surface area promoted the formation of coke from pyrolysis by shortening the induction of coking. Under the oxidizing atmosphere, in the presence of montmorillonite, the initial temperature of O2 consumed by heavy oil decreased from 270 °C to 250 °C, indicating that montmorillonite catalyzed oxygen-adding reaction. The temperature of COx released by acetaldehyde and acetic acid decreased, and the release amounts increased, indicating that montmorillonite catalyzed decarbonylation and decarboxylation. Polymers were formed when acetaldehyde, acetic acid, ethanol, and acetone were heated, indicating that montmorillonite catalyzed polycondensation. When the oil mass fraction in the sample was within 18%, further increase in the supporter surface area did not affect the formation of coke from oxidation. The catalysis of montmorillonite was the main mechanism affecting coke formation during the thermal conversion of heavy oil under the inert and oxidizing atmospheres.