Production Of Levulinic Acid Research Articles

The Chemistry of Levulinic Acid: Its Potential in the Production of Biomass‐based Chemicals

Biomass has been identified as the ultimate sustainable resource for all carbon‐based consumer products of the chemical industries in the future. Its catalytic conversion leads to the formation of various platform chemicals that could partially or even fully replace the fossil‐based building blocks that have been currently used in synthetic chemical processes. Among these compounds, levulinic acid (LA) has been recognized as a member of the "Top Value Added Chemicals from Biomass" and has attracted significant attention since the seminal paper reported by Werpy and Petersen in 2004. This review summarizes the properties, recent advances, and developments in the chemistry of levulinic acid. The production of LA from both plant and animal‐based carbohydrate feedstocks via 5‐hydroxymethylfurfural or furfuryl alcohol is discussed from a mechanistic perspective, highlighting intrinsic molecular‐level limitations to LA formation. The efficiencies of recently developed catalytic systems are also summarized and compared. Furthermore, the conversion of LA into high‐value‐added downstream chemicals, including its role in the synthesis of complex molecular structures, is overviewed. This section discussed the reactions of LA in the points of view of its various transformations on carbonyl‐, carboxy‐, methyl‐, and methylene functional groups. The reactions of these functionalities with C‐ ,N‐, O‐, and S‐nucleophiles, alcohols, amines, organometallic reagents, oxygen etc. were thematically summarized. Our review also outlooks to highlight the challenges and opportunities associated with the extensive research area of organic chemistry of levulinic acid.

Levulinic Acid Production from Artichoke Leaves (Cynara Scolymus L.) by Catalytic Hydrothermal Reaction

In addition to examining the highest yield production of Levulinic acid (LA) from artichoke leaves by the subcritical catalytic hydrothermal decomposition, the studies were carried out on also increasing the production yields of 5-Hydroxymethylfurfural (HMF), Acetic and Formic acid from this biomass. In order to obtain the most suitable reaction conditions, the effect of different reaction conditions, including different temperature, reaction time, pH and catalyst types, on the decomposition of artichoke leaves and product yields were investigated. The subcritical thermal decomposition studies of artichoke leaves were carried out in an autoclave system at temperatures (120°C, 140°C, 160°C, and 180°C) for reaction times of 10, 20, 30, 40, and 50 min in the presence of H2SO4, HNO3, and HCL catalysts with different pH values; these reactions were realized also without adding a catalyst. As a result of the detailed research, it was seen that the most suitable experimental conditions for the production of LA with the highest yield from artichoke leaves could be achieved by adding sulfuric acid with a pH of 0.5 at a reaction temperature of 180°C and a reaction time of 50 min. The investigations were continued till achieving the highest product yields. After carrying out the experiments stated above, the optimal yields of the products produced from the artichoke biomass by the reactions were found as 209.39 g/kg biomass for LA, 117.40 g/kg biomass for formic acid, 72.27 g/kg biomass for acetic acid, and 39.04 g/kg biomass for 5-HMF.

Microbial production of levulinic acid from glucose by engineered Pseudomonas putida KT2440

Levulinic acid(LA) is produced through acid-catalyzed hydrolysis and dehydration of lignocellulosic biomass. It is a key platform chemical used as an intermediate in various industries including biofuels, cosmetics, pharmaceuticals, and polymers. Traditional LA production uses chemical conversion, which requires high temperatures and pressures, strong acids, and produces undesirable side reactions, repolymerization products, and waste problems Therefore, we designed an integrated process to produce LA from glucose through metabolic engineering of Pseudomonas putida KT2440. As a metabolic engineering strategy, codon optimized phospho-2-dehydro-3-deoxyheptonate aldolase (AroG), 3-dehydroshikimate dehydratase (AsbF), and acetoacetate decarboxylase (Adc) were introduced to express genes of the shikimate and β-ketoadipic acid pathways, and the 3-oxoadipate CoA-transferase (pcaIJ) gene was deleted to prevent loss of biosynthetic intermediates. To increase the accumulation of the produced LA, the lva operon encoding levulinyl-CoA synthetase (LvaE) was deleted resulting in the high LA-producing strain P. putida HP203. Culture conditions such as medium, temperature, glucose concentration, and nitrogen source were optimized, and under optimal conditions, P. putida HP203 strain biosynthesized 36.3 mM (4.2 g/L) LA from glucose in a fed-batch fermentation system. When lignocellulosic biomass hydrolysate was used as the substrate, this strain produced 7.31 mM of LA. This is the first report of microbial production of LA from glucose by P. putida. This study suggests the possibility of manipulating biosynthetic pathway to produce biological products from glucose for various applications.

Understanding the effect of reaction parameters on the production of levulinic acid from glucose

AbstractA significant and sustainable feedstock for many value added products is levulinic acid, which is basically a short‐chain fatty acid. The current study aims to comprehend how multiple factors affect the hydrothermal reactions that convert glucose to levulinic acid. Glucose can be readily obtained from lignocellulosic biomass and hence it is selected in the work as representative sustainable source. The effect of various operating parameters, including time (0–180 min), temperature (140–180°C), nitrogen pressure (0–25 bar), glucose concentration (3%–10%), agitation speed (100–300 RPM), and acid concentration (2%–6%); use of different salts (NaCl, AlCl3 6H2O, FeCl3); and different acids (HCl, H3PO4, H2SO4) on the reaction progress has been studied in a batch autoclave reactor. It was elucidated that pressure (only nitrogen purge was essential for reaction progress) or salt content changes did not affect sugar conversion significantly. The process was seriously influenced by the presence of acids, mostly in the form of homogeneous catalysts, and the most significant results were obtained for H2SO4. The highest levulinic acid yield (39.7 g/g) at 90 min, with nearly complete sugar conversion, was obtained under the ideal conditions of 160°C, 5% sugar loading, and 5% H2SO4 concentration. The current study indicates that the two primary operating parameters in this conversion process are temperature and time, with higher temperature and lower sugar concentration showing a rising tendency in sugar conversion. Overall, the study establishes a sustainable process for levulinic acid synthesis.

Life cycle GHG emissions and economic viability of two levulinic acid production processes from biomass: A case study of Japan and Canada

We evaluated CO2 equivalent (CO2eq) greenhouse gas (GHG) emissions and minimum selling price of levulinic acid (LA) produced in two biomass-waste-based processes: the AlCl3/choline chloride (ChCl) process, and the formic acid (FA) process, with catalysts recycling. Six scenarios were synthesized to compare the performances of the two processes in Japan and Canada. In the AlCl3/ChCl process, the total GHG emission was 11.35–11.56 kg-CO2eq/kg-LA and those from the energy input to the pretreatment and ChCl production were 5.22 and 3.90 kg-CO2eq/kg-LA, respectively. In the FA process, the total GHG emission was 9.46–9.68 and 22.29–22.51 kg-CO2eq/kg-LA for 60 wt% and 80 wt% FA, respectively. The operational emissions for makeup FA input were 7.65 and 20.80 kg-CO2eq/kg-LA (60 wt% and 80 wt%, respectively), which accounted for more than 80% in all scenarios. The optimization of the product purge volume, FA concentration in the pretreatment, and FA production using biomass and/or renewable energy are critical parameters to reduce overall environmental impacts of the processes. The liquid content of the solid residue (moisture, water soluble organic matters, and catalyst) had insignificant influences on the GHG emission and minimum selling price. In the FA process, combustion of solid residue can compensate the GHG emissions from the reaction and separation units.

An improved coking model for simulating reactive transport phenomena and coking behavior in sucrose hydrolysis

Levulinic acid (LA) holds great significance as a biomass platform chemical in the production of bio-aviation fuel and the utilization of bioenergy. Heterogeneous acid-catalyzed polysaccharide hydrolysis has emerged as a promising method for LA production. Understanding the coupling mechanisms of the physicochemical processes are fundamentally important to optimize the reaction system. In this work, a pore-scale multicomponent reactive transport model based on lattice Boltzmann method was developed to simulate the hydrolysis of sucrose. Considering the significant effect of active sites distribution density on coking formation, an improved coking model was proposed. Systematic investigations of reactive transport and coking behavior were conducted. Simulation results demonstrated that, initial sucrose concentration had a substantial impact on the coking rate of catalyst, when sucrose concentration exceeded 250 mmol/L, the catalyst became fully deactivated before complete hydrolysis of reactant occurred. Furthermore, a marginal benefit was found for the synergistic effect of protons in solution and solid catalysts on sucrose hydrolysis, when proton concentration reached the marginal value of 0.12 mol/L, further increases in proton concentration resulted in only marginal improvements in reaction efficiency. This work underscores the importance of the catalyst morphological character engineering and processes controlled for enhancing overall performance in LA production.

Antimicrobial and antioxidant activities of lignin by-product from sugarcane leaf conversion to levulinic acid and hydrochar

To enhance the sustainability of lignocellulosic biomass utilization process, a significant attention is given to a high-value lignin byproduct of this process. Herein, antimicrobial, antioxidant, and physicochemical properties of lignin in black liquor extracted from sugarcane leaf (SCL) for levulinic acid (LA) and hydrochar production were investigated. The lignin was extracted from SCL through an alkaline pretreatment process using 5–25 wt% of either NaOH or KOH at 120–160 °C. Disk diffusion susceptibility tests, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) revealed that the SCL lignin is effective against Gram-positive bacteria (S. aureus) rather than Gram-negative bacteria (E. coli and S. typhimurium). Different alkaline reagents marginally affected the antimicrobial and antioxidant activities of the lignin. Py-GC/MS analysis results determined that the SCL lignin contained mainly p-hydroxyphenyl (H) and guaiacyl (G) with a small amount of syringyl (S) lignin. Furthermore, the structural alterations and linkages of SCL lignin during alkaline pretreatment were examined using 2D-HSQC NMR, providing valuable insights into the transformation processes. The conversion of delignified SCL to LA through a catalytic hydrothermal process using various acid catalysts indicated that the alkaline pretreatment could enhance LA yield with a maximum yield of 33.4 wt%. Additionally, fuel property characterization of the hydrochar co-product from LA production determined that the hydrochar can be used as a coal substitute.

Optimisation of the biological production of levulinic acid in a mixed microbial culture fed with synthetic grape pomace.

Levulinic acid (LA) is a polymer with a vast industrial application range and can be co-produced as a minor by-product during the biological production of polyhydroxyalkanoates (PHA). However, the influence of key parameters as tools for favouring the production of LA over PHA is still unclear. In this study, we investigated how several critical operational conditions, i.e., carbon-nitrogen ratio (C/N), organic loading rate (OLR) and airflow, can be optimised to favour LA accumulation over PHA production by a mixed microbial culture (MMC), using synthetic grape pomace (GP) hydrolysate as the substrate. The results showed that it was possible to direct the MMC towards LA accumulation instead of PHA. The maximum LA yield was 2.7 ± 0.2g LA/(L·d) using a C/N of 35, an airflow of 5L/min and an OLR of 4g sCOD/(L·d). The OLR and, to a lesser extent, the C/N ratio were the main factors significantly and positively correlated with the biological synthesis of LA.

Integrated biorefinery approach for utilization of wood waste into levulinic acid and 2-Phenylethanol production under mild treatment conditions

In a bid to explore the on-site biorefinery approach for conversion of forestry residues, lignocellulosic biomass into value-added products was studied. The bark white pine wood was subjected to the microwave technique of fast and slow hydrolysis under varying acid and biomass concentrations to produce levulinic acid (LA). The HCl (2% v/v) and plant biomass (1% w/v) were identified as the optimum conditions for fast wood hydrolysis (270 ºC for 12 sec), which led to maximum LA yield of 446.68 g/kgPB. The proposed sustainable approach is mild, quick, and utilized a very low concentration of the HCl for the production of LA. The hydrolysate was used as a medium for Kluyveromyces marxianus growth to produce 2-phenylethanol (2-PE). K. marxianus used 74–95% of furfural from hydrolysate as a co-substrate to grow. The proposed model of the integrated biorefinery is an affordable on-site approach of using forest waste into localized solutions to produce LA and 2-PE.

Production of levulinic acid from macroalgae by hydrothermal conversion with ionic resin catalyst

Gracilaria verrucosa is red algae (Rhodophyta) that is particularly significant because of its potential for bioenergy production as a sustainable and environmentally friendly marine bioresource. This study focuses on the production of levulinic acid from G. verrucosa using hydrothermal conversion with an ionic resin Purolite CT269DR as the catalyst. By optimization of the conversion condition, a 30.3 % (22.58 g/L) yield of levulinic acid (LA) (based on carbohydrate content) was obtained at 200 °C for 90 min with 12.5 % biomass and 50 % catalyst loading of biomass quantity. Simultaneously, formic acid yielded 14.0 % (10.42 g/L). The LA yield increased with increasing combined severity (CS) levels under tested ranges. Furthermore, the relationship between CS and LA synthesis was effectively fitted to the nonlinear sigmoidal equation. However, as the yield of sugar decreased, LA yield was linearly increased. Thus, the use of ionic resin as a heterogeneous catalyst presents significant potential for the manufacture of platform chemicals, specifically LA, through the conversion of renewable marine macroalgae.

Design and synthesis of SO3H-based ionic liquids for direct catalytic conversion of straw to levulinic acid

The utilization of ionic liquids (ILs) in the conversion of lignocellulose to levulinic acid (LA) is a significant pathway in the field of bio-refinery. In this study, a series of sulfonic-based ILs with elongated alkyl chains were synthesized using density functional theory. These ILs were then utilized for the conversion of straw into LA in a single reaction vessel. The yield of LA was compared between a single solvent (water) and a biphasic system comprising water and methyl isobutyl ketone (MIBK). Among the investigated ILs, [C3SO3HEim]Cl exhibited a higher yield of LA, reaching up to 11.3 wt% in the aqueous phase and 17.8 wt% in the MIBK-water biphasic system. Furthermore, [C3SO3HEim]Cl displayed a high catalytic efficiency (90.4%) and a yield of LA (16.3 wt%) after 5 cycles. These findings suggest that the elongation of alkyl side chains in ILs enhances the solubility of cellulose and increases the yield of LA. The MIBK-water biphasic system promotes the rehydration of hydroxymethylfurfural (HMF) and reduces the residence time of LA in the aqueous phase, thereby optimizing its yield. This innovative approach involving ILs and the MIBK-water biphasic system presents a novel perspective for the production of LA from biomass.

Integrated Preparation of Hollow Lignin Nanoparticles as a Drug Carrier and Levulinic Acid from the Poplar Wood Prehydrolysis Liquor.

Prehydrolysis liquid (PHL) from dissolving pulp and biorefinery industries is rich in saccharides and lignin, being considered as a potential source of value-added materials and platform molecules. This study proposed an environmentally friendly and simple method to prepare morphologically controllable hollow lignin nanoparticles (LNPs) and levulinic acid (LA) from PHL. In the first step, after hydrothermal treatment of PHL with p-toluenesulfonic acid (p-TsOH), lignin with a uniform molecular weight was obtained to prepare LNPs. The prepared LNPs have an obvious hollow structure, with an average size of 490-660 nm, and exhibit good stability during 30 days of storage. When the as-obtained LNPs were used as a sustained-release agent for amikacin sulfate, the encapsulation efficiency reached over 70% and the release efficiency within 40 h reached 69.2% in a pH 5.5 buffer. Subsequently, the remaining PHL that contains saccharides was directly used for LA production under the catalysis of p-TsOH. At 150 °C for 1.5 h, the LA yield reached 58.4% and remained at 56% after 5 cycles of p-TsOH. It is worth noting that only p-TsOH was used as a reactive reagent throughout the entire preparation process. Overall, this study provided a novel pathway for the integrated utilization of PHL and showed the immense potential of the preparation and application of LNPs.

Wet torrefaction of biomass waste into high quality hydrochar and value-added liquid products using different zeolite catalysts

Wet torrefaction (WT) proves to be a highly efficient pretreatment method for biomass waste, resulting in the production of hydrochar and valuable liquid products. In this study, a groundbreaking chemocatalytic approach is introduced, employing various zeolite catalysts (H-ZSM-5, H-Beta, H–Y, H-USY, and H-Mordenite) in a batch reactor under a nitrogen atmosphere. This method enables the simultaneous one-pot production of levulinic acid (LA) and/or bio-ethanol during the WT process of wood cellulose pulp residue (WCPR), ultimately yielding high-quality solid fuel. The WT process involves at 220 and 260 °C, H2O/WCPR = 10, and torrefaction time at 15, 30 and 60 min. The study identifies that at 220 °C and 15 min, as the optimal temperature and time, for bio-ethanol production, achieving a selectivity of 59.0 % with the H–Y catalyst, while the highest amount of bio-ethanol (75.6 %) was detected in presence of H-USY zeolite at 260 °C after 60 min. In addition, it was found the formation of relatively high amount of LA (62.0 %) at 220 °C after 60 min but using the H-ZSM-5 catalyst. For the WT + Mordenite sample (220 °C, 60 min), the highest carbon content of 71.5 % is achieved, resulting in the higher heating value (HHV) of 27.3 MJ/kg, an enhancement factor of 1.36, and carbon enrichment of 1.48, with the sequence of element removal during WT prioritized as DO > DH > DC and the weight loss of 68 %. Finally, the reaction mechanism was proposed to elucidate the formation of liquid products after WT of WCPR with participation of zeolite catalysts. The main pathway involving the direct conversion of cellulose into hydroxyacetone, followed by the subsequent generation of ethanol through the C–C cleavage of hydroxyacetone while LA formed via well-known route which includes cellulose hydrolysis to form glucose, conversion to 5-HMF and the subsequent transformation of 5-HMF into LA.

Wet torrefaction of biomass waste into levulinic acid and high-quality hydrochar using H-beta zeolite catalyst

Wet torrefaction (WT) is an effective pretreatment method of biomass waste for producing high-quality hydrochar and valuable liquid products. This study delves into how acid catalysts and reaction conditions in WT impact the resulting hydrochar's surface characteristics and elemental composition, as well as the distribution of liquid products. The focus is on utilizing wood cellulose pulp residue (WCPR) as the feedstock with H-Beta zeolite catalyst in a nitrogen-rich environment. The WT process involves a temperature range of 180–260 °C, and reaction durations spanning 15–60 min. The findings reveal that WT conditions, including the catalyst for WCPR, significantly influence the hydrochar's properties and liquid product distribution. With increasing temperature and reaction time, the hydrochar experiences changes, including increased carbon content and reduced oxygen content. The study identifies 260 °C and 30 min as the optimal temperature and time for levulinic acid production, achieving a remarkable selectivity of 62.8% with the H-Beta zeolite catalyst using H2O/WCPR = 10. Various properties of the resulting hydrochar are assessed, including higher heating values (HHVs), decarbonization (DC), dehydrogenation (DH), deoxygenation (DO), enhancement factor, carbon enrichment, surface area, pore diameter, weight loss as well as solid, carbon, hydrogen, and energy yields. The WT + Beta_220 sample, processed at 220 °C for 30 min, exhibited the highest HHV at 30.3 MJ/kg and carbon content at 78.9% in hydrochar compared to various biomass types, with an enhancement factor of 1.51 and carbon enrichment of 1.63, while the sequence of element removal during WT prioritized as DO > DH > DC. Furthermore, it is worth highlighting that the most significant weight loss, increasing from 17.0 to 60.7%, was observed under the same WT conditions. Lastly, a comprehensive reaction pathway is proposed to elucidate the WT of WCPR with the presence of H-Beta zeolite catalyst under these optimized conditions.

Hydrothermal Valorization via Liquid Hot Water and Hydrothermal Carbonization of Pea Pod Waste: Characterization of the Biochar and Quantification of Platform Molecules

Pea pod cultivation spans various regions and climates, with a global production of around 20 million tons. The pea peel wastes, which make up 30–40% of the total weight of the peas, are freely available in large quantities. The biomass used was characterized via ultimate, proximate, and structural analysis, obtaining 20.2%w of cellulose and 17.4%w of hemicellulose, which, via valorization processes, can be transformed into platform chemicals. Hydrothermal valorization presents itself as a clean form of treatment for these wastes, ranging from 120 to 180 °C (LHW) and from 180 to 260 °C (HTC). The use of LHW can lead to the production of sugars (up to 70%w yield) and levulinic acid (4%w yield), while the use of HTC leads to formic acid (40%w yield) and levulinic acid (4%w yield). The use of LHW for longer periods favors the production of HMF and furfural. The use of homogeneous catalysts (H2SO4, CH3COOH, KOH, and NaHCO3) was implemented, and their selectivity was described. Solid fractions of LHW and HTC were characterized via FTIR and elemental analysis, and the change in their structure was described as they shifted from biomass to biochar. Optimal conditions for each platform chemical were reported to best utilize the pea pod waste.

A Clever Application of a Recycled Waste Solution for Levulinic Acid and Adsorbent Production from Apple Pomace Using a Hydrothermal Process

A Clever Application of a Recycled Waste Solution for Levulinic Acid and Adsorbent Production from Apple Pomace Using a Hydrothermal Process

Sustainable management of wine-derived leftovers: Enhanced extraction of antioxidants and production of levulinic acid by microwave-assisted processing

Within the framework of circular economy and process intensification, this work aimed to develop a two-way, microwave (MW)-assisted valorisation protocol for winemaking waste, namely grape stalk (GS), grape marc (GM) and exhausted grape marc (EGM). The first step evaluates the recovery of biologically active compounds (BACs). In this context, MW-assisted extraction (MAE) (200 W, 100 ºC, 2 h) demonstrated to be an intensified approach for processing EGM, enhancing the total antioxidant capacity (TAC) by up to 436% (TAC) compared to conventional soaking. Various polyphenols including flavonols (quercetin), flavanols (catequin, epicatechin), anthocyanins (procyanidins (B1-B7)), as well as glycosylated structures (i.e., kaempferol 3-O-glucoside), were detected by LC-MS analysis in this matrix. Simultaneously, the conversion to the bio-based chemical levulinic acid (LevA) was carried out. Considering the environmental factor involved in the dimension of sustainability, environmentally friendly practices were adopted, based on an aqueous single-phase without organic solvent, reusable catalysts as p-toluenesulfonic acid (p-TsA), and short reaction times (20 min). LevA yield reached 33.09% molar from the extractives-free (EF)-EGM matrix, surpassing the 22.31% obtained from the untreated one. Nonetheless, GS exhibited higher efficiency, yielding up to 34.75 and 59.83% from the untreated- and EF-GS matrices, respectively.

Valorization of lignocellulosic platform products based on biorefinery schemes through sequential pretreatments

AbstractPretreatments have been identified as the core of lignocellulosic biorefinery design due to biomass fractionation and the influence on subsequent reaction and downstream processes. However, most pretreatments are described as single-step, maximizing the valorization of a side stream. Therefore, sequential pretreatments could better describe the integral valorization of lignocellulosic biomass to obtain platform products that can be further used for value-added products. This work experimentally analyzed the sequential pretreatments for the fractionation of rice husks to obtain individual lignocellulosic fractions. It was demonstrated that the dilute acid-wet air oxidation (DA-WAO) sequence is suitable for biorefinery designs since it is possible to solubilize up to 80% of hemicellulose during the first stage and subsequently fractionate almost 90% of lignin after the second stage, obtaining a pretreated solid with high cellulose content. The isolated lignocellulosic fractions were used as platform products to obtain furfural, levulinic acid, and phenolic compounds. As a main result, yields and conversions were improved when valorizing the cellulose platform based on sequential pretreatment. In contrast, valorizing the black liquor after a combination scheme decreased aldehyde yields such as vanillin and syringaldehyde by 4.8–11.9%. The findings indicate that from the biorefinery approach, sequential pretreatments improve the yield of platform products. Despite the decrease of phenolic compounds, levulinic acid and furfural production is significantly enhanced.

Oil Palm Empty Fruit Bunch (OPEFB) Pretreatment Simulation with Ammonia Soaking and Ammonia Expansion Method for Levulinic Acid and Furfural Production

OPEFB is a waste product from oil palm mills and is abundant in quantity. OPEFB is a lignocellulosic compound containing cellulose, hemicellulose, and lignin. The cellulose in OPEFB can be converted into levulinic acid, while hemicellulose can be converted into furfural. The consumption of furfural and levulinic acid in Indonesia is increasing, and so far, the demand has been met through imports. Pretreatment is the first stage in converting OPEFB into valuable products. In this paper, we have simulated furfural and levulinic acid production from OPEFB using two pretreatment methods: ammonia soaking and ammonia expansion. Both process simulations were carried out using Superpro Designer v9.0, with 17,520 metric tons OPEFB/year capacity as input raw material. The simulation of furfural and levulinic acid production using the ammonia expansion pretreatment process resulted in feasibility indicators including a payback period of 2.56 years, an ROI (Return on Investment) of 34.07%, and an IRR (Internal Rate of Return) of 28.62%. On the other hand, using the ammonia-soaking process resulted in an IRR of 22.26%. These parameters indicate that furfural and levulinic acid production is more economically viable using the ammonia expansion pretreatment process than the ammonia soaking pretreatment process.

One-pot directly conversion of passion fruit husk to levulinic acid using highly efficient and recyclable SO3H-functionalized ionic liquids

In this study, hydrothermal conversion of passion fruit husk powder (PFHP) into levulinic acid (LA) was achieved using SO3H-functionalized ionic liquids (ILs) as catalyst. The investigation focused on the impact of IL types and reaction conditions (temperature, time, water quantity and catalyst loading) on LA yield. Among the selected ILs, [C4SO3Hmim][HSO4] exhibited the highest LA yield at 66.6%, achieved under specific conditions: 4 h of reaction time, 180 °C temperature, 0.2 g of PFHP, 1.5 g of IL, and 6.0 g of deionized water. Remarkably, [C4SO3Hmim][HSO4] displayed consistent stability and catalytic efficiency throughout four recycling cycles. Comprehensive analyses, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), were conducted on the solid residues of passion fruit husk obtained at different reaction times. These analyses revealed significant alterations in surface morphology, functional groups, and crystallinity index of the solid residues with prolonged reaction times. Notably, hemicellulose and lignin removal occurred within the first 0.5–1 h of the reaction, leading to the formation of by-products after 3 h. This one-pot process for LA production from agricultural waste showcases a promising avenue for converting sustainable biomass resources into valuable chemicals, emphasizing the potential for future biomass utilization.