Reaction Mechanism of H₂S Generation during Tetrahydrothiophene Aquathermolysis Reaction

Abstract

The generation of H2S causes many problems during steam injection thermal recovery. To make clear the formation rule of H2S under the condition of steam injection thermal recovery, tetrahydrothiophene was selected as a model compound, and then reaction mechanism and kinetics were explored based on indoor thermal simulation. The results showed that tetrahydrothiophene aquathermolysis reaction can generate a large amount of H2S. The C–S bond formed by heteroatom S broke at first and then opening-ring occurred, which produced small molecular alkanes or alkenes. The decarbonylation of aldehydes and other organic compounds resulted in the formation of CO, hydrocarbons, and other related compounds. High-temperature water played a key role in the process of tetrahydrothiophene aquathermolysis reaction and would directly participate in the elementary reactions such as hydrolysis and water–gas shift reaction (WGSR). These elementary reactions would finally lead to the migration of hydrogen from water to gas-phase or liquid-phase products. In addition, a kinetic model of H2S formation during tetrahydrothiophene aquathermolysis reaction was established through kinetic experiments, the activation energy is 54.55 kJ/mol, and the frequency factor is 166.47 day–1.

In-Situ Heavy Oil Aquathermolysis in the Presence of Nanodispersed Catalysts Based on Transition Metals

“…Moreover, the transition metal species can accelerate certain chemical reactions as illustrated in Figure 1. Lin et al reported that catalyst particles are retained on the surface of silicate particles and accelerate the chemical rupture of carbon-heteroatom bonds [14]. They draw our attention to the significant amount of H 2 S generation after catalytic aquathermolysis of tetra-hydro-thiophene, as a model compound [14].…”

“…Lin et al reported that catalyst particles are retained on the surface of silicate particles and accelerate the chemical rupture of carbon-heteroatom bonds [14]. They draw our attention to the significant amount of H 2 S generation after catalytic aquathermolysis of tetra-hydro-thiophene, as a model compound [14]. The authors consider C-S bond cleavage and ring opening reactions, which lead to the formation of low-molecular alkanes and alkenes ( Figure 2).…”

“…These simple reactions will eventually lead to the transfer of hydrogen from water into gaseous or liquid phase products. In addition, the kinetic model of H 2 S formation after aquathermolysis of tetrahydro-thiophene was established, the activation energy of which was 54.55 kJ/mole [14].…”

“…The key factor in successful application of the aquathermolysis process is introduction of catalysts that promote the overall chemical reactions occurring down in the reservoir, such as hydrogenation, hydrodesulfurization, water-gas shift reaction, etc. The influence of catalysts on aquathermolysis reactions has been widely investigated [2,9,10,14]. The aquathermolysis catalysts can be roughly divided into four groups: nanocatalysts, watersoluble catalysts, oil-soluble catalysts and rock minerals.…”

“…The authors proposed the catalytic role of metal ions in the aquathermolysis process. Since then, substantial advances in catalysis have made the catalytic aquathermolysis a distinct process, and catalytic steam-based heavy oil recovery techniques has been investigated as a promising technology to recover heavy oil resources [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. More importantly, this process occurs in the cheapest high-pressure reactor of all, petroleum formations [3][4][5][6].…”