¹³C Solid-State NMR Analysis of the Chemical Structure in Petroleum Coke during Idealized In Situ Combustion Conditions

Abstract

Petroleum cokes with different chemical structures and oxygen-containing functional groups were obtained from two kinds of naphthenic- and paraffin-base crude oils by simulating an in situ combustion (ISC) process with the same reaction atmosphere and different reaction temperatures. 13 C wide-cavity solid-state nuclear magnetic resonance ( 13 C NMR) spectroscopy was used to identify and investigate the oxygen-containing functional groups of petroleum cokes obtained under different compositions and reaction temperatures. This study demonstrated that with the increase of coking temperature, the content of alkyl side chain and active oxygen-containing functional groups in naphthenic-base crude coke decreased obviously, while the content of aromatic carbon increased. The 13 C NMR analysis of the two kinds of petroleum cokes obtained at 500 °C further revealed that the paraffin-base petroleum coke retained a high content of oxygen- and nitrogen-rich functional groups, while the naphthenic-base petroleum coke had a lower amount of carbonyl groups and oxygen-containing functional groups.

Formation and Combustion Heat Release of Naphthenic-Based Crude Oil Cokes at Different Reaction Temperatures

“…In this stage, the oxidization of aromatic carbon elements of coke into carbon dioxide begins, and the graphitization degree of coke prepared at high temperature is significantly improved. 18 …”

“…In addition, oxygen elements connected to aromatic rings mainly exist in the carbonyl structure, which is consistent with the reported findings of solid 13 C NMR spectrum. 18 3.3. Combustion Characteristics of Cokes Prepared at Different Temperatures.…”

“… 17 With the increase in coke-forming temperature, the oxygen-containing functional groups in the coke molecules undergo conversion and bond-breaking reactions, which directly leads to a lower oxygen content but a higher hydrocarbon ratio in the petroleum coke produced at high temperatures. 18 …”

“…17 With the increase in coke-forming temperature, the oxygen-containing functional groups in the coke molecules undergo conversion and bond-breaking reactions, which directly leads to a lower oxygen content but a higher hydrocarbon ratio in the petroleum coke produced at high temperatures. 18 In this paper, thermogravimetric-differential scanning calorimetry (TG-DSC), elemental analysis, and 13 The results of the study show that under the same heating rate and air flow conditions, the two types of petroleum coke, 350 and 500 °C, exert essentially the same amount of heat, while 350 °C coke is able to burn completely at a lower temperature, and 500 °C coke burns completely at a higher temperature than 350 °C coke, which is more suitable as a fuel for air injection fire flooding.…”

A review on the applications of nuclear magnetic resonance (NMR) in the oil and gas industry: laboratory and field-scale measurements

“…More flexibility and diverse applications of NMR measurements are acquired using laboratory-scale experiments (Ouellette et al 2015). NMR has proven its robustness in the energy industry with the specific examples of lithium ion battery electrolytes (Wiemers-Meyer et al 2019), chemical structure during in-situ combustion conditions (Pan et al 2021), upstream (Chen et al 2018a, b), and downstream oil and gas industry (Abdul Jameel 2021). However, NMR is an immature field of research in the energy industry and opens several potential research projects.…”