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Li, Yang, et al. Fuel 283 (2021): 118858.
Tetrabutylammonium hydrogen sulfate (THS) has been reported as a highly effective liquid-phase additive for enhancing the simultaneous removal of NO₂ and SO₂ in wet flue gas desulfurization (WFGD) systems under NO pre-oxidation conditions. Conventional WFGD processes exhibit poor NO₂ absorption efficiency, typically below 20%, which severely limits integrated NOx-SO₂ control. The introduction of THS addresses this limitation by modifying the aqueous reaction environment and stabilizing reactive sulfur species.
Laboratory-scale and pilot-scale gas-liquid absorption experiments demonstrated that THS significantly improves NO₂ absorption by stabilizing sulfite ions (SO₃²⁻), which act as key reductive intermediates facilitating NO₂ capture. Under controlled conditions (pH 6.5-7.0, CaCO₃ slurry buffering), the presence of SO₂ was found to promote NO₂ absorption, while excess O₂ in flue gas and accumulated nitrite (NO₂⁻) inhibited NO₂ removal. THS effectively mitigated these inhibitory effects, leading to enhanced synergistic removal performance.
Importantly, the applicability of Tetrabutylammonium hydrogen sulfate was validated in an engineering-scale demonstration on a 35 t/h industrial boiler. In this real-world system, NO₂ absorption efficiency increased dramatically from approximately 13% to 70% following THS addition, without compromising SO₂ removal. These results highlight THS as a promising and scalable additive for advanced flue gas treatment, offering substantial potential for cost-effective, integrated control of sulfur and nitrogen oxides in industrial combustion processes.
Parmar, Narsidas J., et al. Tetrahedron letters 52.22 (2011): 2853-2856.
Tetrabutylammonium hydrogen sulfate (TBA-HS) has been successfully applied as an efficient reaction mediator for the one-pot synthesis of novel benzopyran-annulated pyrano[2,3-c]pyrazole derivatives via a domino Knoevenagel-hetero-Diels-Alder (DKHDA) reaction. In the reported study, TBA-HS enabled a cascade transformation between substituted salicylaldehydes and 5-pyrazolones, affording structurally complex heterocyclic frameworks in a streamlined and operationally simple manner.
The reaction proceeds through an initial Knoevenagel condensation, followed by an intramolecular hetero-Diels-Alder cycloaddition, all within a single reaction vessel. Tetrabutylammonium hydrogen sulfate plays a dual role by providing an ionic reaction environment that promotes efficient intermediate formation and stabilizes charged transition states, thereby facilitating smooth progression of the multistep sequence. Compared with conventional multi-step protocols, the TBA-HS-mediated process offers reduced reaction time, improved atom economy, and simplified work-up.
The resulting benzopyrano[4',3':4,5]pyrano[2,3-c]pyrazoles are synthetically valuable scaffolds, combining multiple pharmacologically relevant heterocycles in a single molecular architecture. Such compounds are of interest for further biological evaluation due to their potential bioactivity profiles. This study highlights Tetrabutylammonium hydrogen sulfate as a versatile and effective ionic mediator for complex heterocyclic synthesis, reinforcing its utility in modern synthetic and medicinal chemistry.
Khansole, Gopinath S., et al. Materials Today: Proceedings 9 (2019): 653-660.
Tetrabutylammonium hydrogen sulfate (Bu₄NHSO₄) has been demonstrated as an efficient and environmentally benign catalyst for the multicomponent synthesis of pharmaceutically relevant thiadiazolo[2,3-b]quinazolin-6-(7H)-one derivatives. In the reported protocol, Bu₄NHSO₄ (10 mol%) mediates a one-pot condensation of 2-amino-5-phenyl-1,3,4-thiadiazole, dimedone (5,5-dimethylcyclohexane-1,3-dione), and substituted aromatic aldehydes in an ethanol-water medium under mild reflux conditions (60 °C).
The reaction proceeds smoothly within two hours, affording the target heterocyclic frameworks in high yields with excellent atom economy. Tetrabutylammonium hydrogen sulfate plays a crucial role in promoting the multicomponent cyclocondensation by enhancing substrate activation and facilitating proton transfer in the aqueous-organic solvent system. The use of a benign solvent mixture, low catalyst loading, and straightforward work-up via precipitation and recrystallization further underscore the green chemistry advantages of this approach.
Importantly, the synthesized thiadiazoloquinazolinone derivatives exhibit notable antioxidant activity, highlighting their potential pharmaceutical relevance. Compared with conventional synthetic routes, the Bu₄NHSO₄-catalyzed method offers operational simplicity, reduced cost, and minimized environmental impact. This case study underscores Tetrabutylammonium hydrogen sulfate as a versatile ionic catalyst for sustainable heterocyclic synthesis, particularly in the development of biologically active fused-ring systems.
