Review on Sulfur Compounds in Petroleum and Its Products: State-of-the-Art and Perspectives

Abstract

Sulfur compounds have significant geochemical information, and the removal of sulfur from petroleum products is one of the most important tasks in petroleum refining. However, it is a challenging task to reveal the chemical composition of sulfide at the molecular level because of its complex composition. Unremitting efforts have been made to develop methods for the separation and characterization of sulfur compounds in petroleum and its products in order to understand the mechanisms of their geological origin and their transformation in petroleum processing. Sulfur compounds include thiophenes, sulfides, thiols, sulfoxides, and sulfones, etc. The sulfur element is mainly from sulfate in the sedimentary environment, but the combination of sulfur into hydrocarbons could occur in different ways. Most sulfur compounds are generated in the early diagenetic period through the reaction of unsaturated organic matter with H2S or elemental sulfur released from sulfate via bacterial sulfate reduction. The composition of the sulfur compound in petroleum could be largely altered by thermal maturation, leading to an increase in the relative abundance of highly condensed aromatic sulfur compounds. Another important pathway of sulfur addition is thermochemical reactions between sulfate and hydrocarbons at high temperatures. Some sulfur compounds have a relatively weak chemical stability and are easily decomposed into small-molecule sulfur compounds in petroleum processing. Removing sulfur from petroleum is an essential task for petroleum refinement and upgrading, in which the steric hindrance effect is the most important factor affecting the desulfurization activity of sulfur compounds via hydrotreating. Some polar sulfur compounds are difficult to hydrogenate to remove sulfur; however, the chemical structures of these compounds are unclear. High-resolution mass spectrometry has revealed the high complexity of the molecular composition of sulfur compounds in heavy oils and their polar fractions. However, understanding of their molecular structure is limited, and further research should focus on the formation and transformation mechanism of these polar sulfur compounds. This review will focus on the molecular composition of petroleum sulfur compounds with a collection of topics of sulfur compounds that covers the upstream and downstream petroleum industry, including separation and characterization methods, molecular and structural composition of various sulfur compounds, mechanisms of their geological origin, and their transformation during petroleum processing.

Key Factors Affecting the Development of Oxidative Desulfurization of Liquid Fuels: A Critical Review

“…Some ILs can act as both extractant and catalyst such as [Omim]­[HSO 4 ], [BPy]­[BF 4 ], and [EimC 4 SO 3 H]­NTf 2 . Some ILs can be applied as only catalysts such as [Cn­(mim) 2 ]­Cl 2 /mFeCl 3 , [EMIM]­[NiCl 2 ], [EMIM]­[CoCl 2 ], [EMIM]­[MnCl 2 ], [PW 12 O 40 ], − …”

“…The combustion of fossil fuels releases sulfur oxides, which can cause adverse effects on the environment, health, and economy. , Nowadays, the strongest incentive to decrease sulfur in fossil fuels is strict environmental regulations. , Desulfurization is the removal of sulfur-containing compounds from solid, gas, or liquid fuels . Sulfur removal from petroleum products is one of the most challenges in petroleum refining. , As presented in Table , the sulfur in liquid fuels exists in various forms such as mercaptans, sulfides, disulfides, thiophene (Th), benzothiophene (BT), dibenzothiophene (DBT), 4,6-dimethyl dibenzothiophene (4,6-DMDBT), benzonaphthothiophene (BNT), and so on . One of the most important purposes of green chemistry is to reduce the negative effects of chemical and petroleum industries on human health and the environment .…”

Metal-Free Catalytic Oxidative Desulfurization of Fuels─A Review

“…While effective measures are being deployed and reviewed regularly in the developed countries, the developing countries have not been able to meet the demand of the international regulatory bodies, such as the European Emission Standard, for sulfur-free fuel . With the recent gradual reinforcement of stringent sulfur limit regulations in some developing countries, the scarcity of sweet (low-sulfur) crude oil, and the increasing demand for crude oil energy, as shown in Figure a, refineries in these regions will have to upgrade their hydrotreating units to accommodate the low-sulfur-level requirement or adopt other sulfur removal techniques as well-documented complementary sulfur removal technologies, such as adsorptive desulfurization (ADS), , biodesulfurization (BDS), , supercritical water-based desulfurization (SBD), , and oxidative desulfurization (ODS). , Sulfur in fuel commonly exists in the form of thiols (alkyl or other organic substituent), organic disulfide, thiophene, derivatives, etc., and these organosulfur components have been arranged in Figure b according to their ease of removal, with the arene-containing compounds occupying the region of desulfurization resistance, hence described as refractory organosulfur compounds. Accordingly, the quest for effective desulfurization techniques for high-sulfur-containing fuels has become an interesting topic among researchers in recent times.…”

Links of Hydrogen Sulfide Content With Fluid Components and Physical Properties of Carbonate Gas Reservoirs: A Case Study of the Right Bank of Amu Darya, Turkmenistan

“…As for the TDS, the required sulfur compounds such as thiol, thioether, and thiophene are rather scarce in natural gas reservoirs. Besides, the temperature threshold for sufficient thermal decomposition is commonly considered to be not lower than 150 °C (Shi and Wu, 2021). Therefore, TSR is regarded as the main contribution to the H 2 S in carbonate gas reservoirs (Li et al, 2019;Jia et al, 2021).…”