PolyE-IL, an Efficient and Recyclable Bronsted Acid Catalyst for Conversion of Rice Straw into Levulinic and Other Organic Acids

Abstract

The lignocellulosic biomass has been identified as a potential renewable feedstock for production of levulinic acid (LA). In the present study, the catalytic thermo liquefaction (CTL) process for liquefaction of rice straw into LA was studied by integrating the polyethyleneimine functionalized acidic ionic liquid (PolyE-IL) catalyst. The screening of various PolyE-IL catalysts with variable counter ions showed the remarkable formation of carbohydrates, LA, formic acid, and acetic acid (AA). Among the tested PolyE-IL catalysts, PolyE-IL with a [HSO4]− counter ion showed the maximum conversion efficiency. The process intensification study to evaluate the influence of reaction parameters such as catalyst concentration, reaction temperature, time, and slurry concentrations was conducted to achieve the maximum conversion and yield of organic acids. Moreover, the influence of feedstock pretreatment was also studied. The pretreated rice straw provided maximum yields of LA and FA. The intensified CTL process for untreated rice straw resulted in 49.8% LA, 50.5% FA, and 100% AA, while CTL of pretreated rice straw resulted in 65.5% LA, 75.8% FA, and 26.7% AA of the theoretical maximum at 210 °C for 120 min. The separation of the catalyst and other liquefaction products was achieved using adsorption followed by membrane separation processes. The adsorption process leads to separation of the undesired polymeric side products, while membrane separation provides efficient separation of the catalyst and organic acids with >98% efficiency. The undesired side products separated in the adsorption process were concentrated as CTL-Oil and characterized for physiochemical properties. CTL-Oil is C-, H-, and O-rich feedstock with a caloric value of 24–26 MJ/Kg and thus could be explored for multiple fuel and energy applications. Thus, an efficient valorization of rice straw was achieved using a recyclable, robust, and efficient catalyst.

Sustainable application of rice-waste for fuels and valuable chemicals-a mini review

“…Ukarde et al utilized polyethyleneimine-functionalized acidic ionic liquid catalysts for the conversion of rice straw into organic acids (formic, acetic, and levulinic acids), and it was observed that the catalyst with a [HSO 4 ] − counter ions exhibited superior efficiency compared to other tested catalysts since it has the highest hydrophilicity and Hammett acidity ( Ukarde and Pawar, 2022 ). Moreover, the sodium hydroxide pretreated rice straw was found to provide higher yields of levulinic acid (65.5%) and formic acid (75.8%) than untreated rice straw (levulinic acid: 49.8%; formic acid: 50.5%) ( Ukarde and Pawar, 2022 ). Typically, these organic acids are produced along with the furan derivatives ( Wanninayake et al, 2021 ).…”

Investigation of the Liquefaction Kinetics of the PolyE-IL-Catalyzed Catalytic Thermo Liquefaction Process for Organic Biodegradable Municipal Solid Waste

“…41 The PolyE-IL has serval distinctive properties such as effective solubilization of biomass, ease of separation, and tunable acidity. 42 In our most recent study, the PolyE-IL catalyst was used for CTL of organic biodegradable MSW, and potential indepth reaction pathways were examined. 43 It was observed that the PolyE-IL-catalyzed CTL process could serve as a potential alternative to convert MSW into CTL-Oil as a platform product.…”

“…The drawbacks associated with the separation of imidazole-based ILs can be overcome by integrating a polyethyleneimine-based polymeric Brønsted acid IL catalyst (PolyE-IL) . The PolyE-IL has serval distinctive properties such as effective solubilization of biomass, ease of separation, and tunable acidity . In our most recent study, the PolyE-IL catalyst was used for CTL of organic biodegradable MSW, and potential in-depth reaction pathways were examined .…”

PolyE‐IL: A polymeric Brønsted acid ionic liquid catalyst for catalytic thermo liquefaction of sugarcane bagasse into carboxylic acids

“…Thus, it can effectively solubilize and penetrate the cell wall structure of biomass. Moreover, in our previous study use of imidazole-based Bronsted acid ionic liquids catalysts and PolyE-ILs catalyst has been reported for efficient liquefaction of biomass and conversion of rice straw into LA, respectively 37,38. Thus, in the present study [PEI] + [HSO 4 ] − was explored as a catalyst for the catalytic liquefaction of sugarcane bagasse.…”