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Tian, Rui, et al. Chemical Engineering Journal (2025): 165923.
Tetrapropylammonium hydroxide (TPAH) has emerged as an effective alkaline pretreatment solvent for the selective fractionation of lignocellulosic biomass within integrated biorefinery strategies. In the reported study, an aqueous TPAH system was employed to simultaneously extract high-molecular-weight hemicellulose and uncondensed lignin from Bambusa sinospinosa, while enhancing the enzymatic digestibility of the residual cellulose.
Systematic evaluation of TPAH concentration (20-40 wt%) and pretreatment temperature (25-75 °C) demonstrated that 30 wt% TPAH at 75 °C for 1 h provided optimal fractionation performance. Under these conditions, hemicellulose was recovered with a high yield of 76.2% and a weight-average molecular weight of approximately 70,280 g mol⁻¹, indicating minimal polymer degradation. Simultaneously, lignin isolated from the TPAH system exhibited a high purity (92.7%) and a substantially increased retention of native β-O-4 linkages compared to conventional milled wood lignin.
Mechanistically, the formation of lignin-tetrapropylammonium complexes effectively suppressed alkaline cleavage of ether bonds, thereby preserving lignin's native structure. The cellulose-rich solid residues obtained after fractionation showed markedly improved enzymatic hydrolysis efficiency, achieving a glucose yield of 81.8%, nearly sevenfold higher than untreated biomass.
This case study highlights tetrapropylammonium hydroxide as a powerful and structure-preserving pretreatment reagent for biomass fractionation, enabling efficient valorization of hemicellulose, lignin, and cellulose within sustainable biorefinery applications.
Tian, Rui, et al. Industrial Crops and Products 218 (2024): 118891.
Tetrapropylammonium hydroxide (TPAH) has emerged as an efficient and selective alkaline reagent for the fractionation of lignocellulosic biomass, addressing key limitations of conventional caustic pretreatments. In this study, TPAH was applied to the pretreatment of BH to achieve high-value separation of hemicelluloses while simultaneously upgrading the quality of cellulose residues.
Compared with traditional NaOH extraction, TPAH pretreatment exhibited markedly higher selectivity toward hemicellulose dissolution. Hemicelluloses fractionated using TPAH retained relatively high molecular weights (~62,900 g/mol) and more intact chemical structures, indicating suppressed alkaline degradation. Under optimized conditions (20 wt% TPAH, 45 °C), hemicellulose yields were comparable to NaOH systems, but with significantly improved structural integrity.
Importantly, TPAH pretreatment demonstrated superior cellulose preservation. The cellulose retention rate reached 95.7%, with a high degree of polymerization (DP ≈ 635) and enhanced water retention value (284.8%). Unlike NaOH-treated residues, which typically undergo polymorphic transformation from cellulose I to cellulose II, the cellulose in TPAH-treated residues maintained the native cellulose I crystalline structure. Additionally, the α-cellulose content increased to 89.1%, reflecting improved purity and reactivity.
Mechanistically, the formation of tetrapropylammonium-associated structures is believed to moderate alkaline attack on glycosidic linkages, thereby inhibiting excessive depolymerization. Overall, tetrapropylammonium hydroxide provides a promising, structure-preserving pretreatment strategy for lignocellulosic biorefineries, enabling efficient hemicellulose recovery and high-quality cellulose upgrading for downstream valorization.
Zhao, Hongjie, et al. Microchemical Journal 201 (2024): 110600.
Tetrapropylammonium hydroxide (TPAH) has been successfully employed as a key reagent in the synthesis of a tailor-made fluorescent ionic liquid, [TBAOH][NA], for the development of a dual-emitting fluoroprobe targeting hydroquinone (HQ) in environmental water samples. The synthesis involved the reaction of TPAH with 1-naphthoic acid (1-NA) under a nitrogen atmosphere at 40 °C, yielding a light-yellow, transparent ionic liquid solution after overnight stirring and subsequent stationary settling.
The [TBAOH][NA]/Eu³⁺ system exhibited dual emission behavior, where HQ selectively enhanced the 365 nm fluorescence intensity (FI₃₆₅) without significantly altering the 615 nm emission (FI₆₁₅), enabling ratiometric self-calibration. Computational analysis indicated that HQ binding induced a complete π-π* electronic transition in S₁ and increased orbital overlap, facilitating photon transitions and enhancing sensitivity. Optimization using a central-composite-design approach achieved a linear detection range of 0.5-100 μM and a detection limit of 0.15 μM, comparable to conventional HPLC-DAD methods.
The TPAH-derived ionic liquid combines the environmental advantages of a "green solvent" with strong intrinsic luminescence due to the incorporation of 1-naphthoic acid, allowing for sensitive, selective, and rapid on-site HQ monitoring. The study demonstrates TPAH's versatility not only as a strong organic base for ionic liquid formation but also as a functional platform enabling high-performance analytical applications.
This work highlights TPAH's critical role in producing functional ionic liquids for environmental sensing, providing a practical, efficient, and environmentally benign approach for dual-emission ratiometric detection of hazardous phenolic compounds.
