Yields Of Carboxylic Acids Research Articles

Ionizing radiation as a pretreatment technique on the valorization of rice straw

ABSTRACT The current study focuses on investigating the efficacy of gamma radiation exposure as a pretreatment technique on the valorization of rice straw using advanced analytical pyrolysis technology. The results obtained shed light on the impact of gamma radiation on the composition of functional groups within the rice straw. Specifically, the weaker C-H and C-O bonds appear to be affected, leading to slight modifications in their composition. Furthermore, the crystallinity of the sample experiences minor changes, indicating some level of structural disruption caused by radiation exposure. To delve deeper into the effects of gamma radiation on the rice straw, fast pyrolysis is performed on both the exposed and raw samples. Notably, the exposed samples demonstrate a substantial increase in the formation of carboxylic acids during the pyrolysis process. This finding suggests that exposure to gamma radiation influences the chemical reactions occurring within the rice straw, leading to the production of a higher yield of carboxylic acids compared to the unexposed samples. A tentative reaction pathway leading to the formation of different products is visualized and presented in the study. The changes in functional group composition, the minor disruption in crystallinity, and the increased formation of carboxylic acids collectively indicate the transformative effects of gamma radiation on the rice straw samples.

Crucial role of sulfonated ionic liquids as promoter for efficient production of valuable carboxylic acids by H5PMo10V2O40-catalyzed aerobic oxidation of lignite

To explore the effect of adding acidic ionic liquids (ILs) to the heteropoly acid/H2SO4 catalytic system on the aerobic oxidation of lignite, acidic ILs functionalized with -SO3H were synthesized accordingly and mixed with H5PMo10V2O40 (HPA-2) in various molar ratios. The optimum combination of HPA-2 and 1-methyl-3-(4-sulfobutyl) imidazolium (MIMBS) with molar ratio of 0.3 showed excellent performance for the catalytic oxidation of lignite, with the yields of carboxylic acids (CAs) (including benzene carboxylic acids, formic acid and acetic acid) reaching 326.21 ± 12.86 mg/g lignite, which considerably exceeded the 136.08 ± 6.23 mg/g lignite of pure HPA-2. Highest occupied molecular orbital energy of CAs calculated by Gaussian 09 on 6-31G(d) basis set and Hammett function analysis confirmed that the oxidative activity and acidity of the catalytic system could be moderately modulated by sulfonated ILs, thereby increasing the yield of CAs. In addition, the effect of H2SO4 concentration on the oxidation of lignite was investigated via the HPA-2/H2SO4/MIMBS system with different molar ratios, and the results showed that CAs yield increased first and then decreased with increasing H2SO4 concentration, but the concentration of H2SO4 at the maximum yield of CAs was significantly reduced from 0.28 wt% to 0.14 wt% once MIMBS was added. A possible process for the catalytic oxidation of lignite by sulfonated ILs/HPA-2/H2SO4 in aerobic aqueous solution is proposed, which generally involves the reactions of hydrolysis, oxidation and re-oxidation. Due to the good reproducibility, the robust homogeneous catalytic system of HPA-2/sulphonated ILs has the advantages of including increased yields of CAs and reduced H2SO4 dosage, which will pave the way for the efficient utilization of lignite.

Influence of Temperature and Residence Time on Torrefaction Coupled to Fast Pyrolysis for Valorizing Agricultural Waste

Torrefaction is a promising pretreatment technology for valorizing biomass and upgrading pyrolysis products. This study sets out an original procedure consisting of subjecting the biomass to torrefaction before fast pyrolysis to increased value-added compounds based on agricultural waste biomasses production. This study uses a combined biomass treatment consisting of torrefaction (280–320 °C) and subsequent fast pyrolysis (500 °C) using the same reactor. Under different torrefaction temperatures and residence times, olive pomace (OP) and almond shell (AS) have been evaluated. The study demonstrated OP rather than AS was thermally unstable. The highest total yield of carboxylic acids (mainly acetic acid) was obtained by means of torrefaction at 280 °C with a residence time of 20 s for OP, and at 300 °C and 20 s for AS. Higher torrefaction temperature and residence time promoted phenolic compounds production for OP. However, OP had a higher lignin content and inherent metals that promoted a catalytic reaction during the procedure. The highest yield (47.7%) was obtained using torrefaction at 320 °C with a residence time of 240 s. Overall, the torrefaction of biomass combined with fast pyrolysis constituted a very simple and efficient strategy for valorizing the conversion of agricultural waste biomass into value-added chemicals.

Influence of different salts of alkali and alkaline earth metals on the pyrolysis of Prosopis juliflora

AbstractThis study explores the effect of acetate, oxide and chloride salts of alkali and alkaline earth metals (AAEMs) on the pyrolysis of lignocellulosic biomass. Prosopis juliflora samples were infused using 2% acetate and chloride salts of potassium (CH3COOK, KCl) and the oxide and chloride salts of magnesium (MgO, MgCl2). Dry impregnation technique was employed for the infusion of salts into the biomass matrix. The AAEM salt‐infused biomass was pyrolyzed using a semi‐batch pyrolysis reactor, and the bio‐oils were characterized for variation in chemical composition using gas chromatography–mass spectroscopy. The AAEM salts significantly influenced the pyrolysis process by catalyzing different degradation pathways. Potassium salts catalyzed the ring fission reactions of carbohydrates, resulting in an increase in carboxylic acid yield. On the other hand, magnesium salts promoted the cyclization of the fragmented radicals of the ring fission, resulting in enhanced furan and cycloketone yield. AAEM salts were most effective in catalyzing carbohydrate degradation pathways over the lignin degradation reactions owing to their ability to easily influence polysaccharide C–C bond cleavage over those of lignin aromatic rings. This study also revealed that the anions of AAEM salts also play a major role in biomass pyrolysis. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd

Conversion of carbon dioxide to value added products through anaerobic fermentation and electro fermentation: A comparative approach

Increasing carbon footprint alters the carbon balance in nature, thereby worsening global climate change. The conversion of carbon dioxide (CO 2 ) into value-added products through biological routes is the pathway of the future because of its ecological and sustainable character. The present study evaluated the conversion of CO 2 into short-chain fatty acids (SCFA)/volatile fatty acids (VFA) and methane using four experimental conditions (R1-R4). The experimental conditions are R1 was an anaerobic fermenter (AF) operated as control, R2 consisted of an AF with electrodes operated in open circuit, R3 was an AF with electrodes operated in a closed circuit with 100 Ω as load and R4 was an electro-fermentation reactor with an applied cathodic potential of −0.8 V vs. Ag/AgCl. The results were assessed in terms of production of SCFA, methane, current density and inorganic carbon reduction. Electro-fermentation (R4) setup achieved the highest production of SCFA (2050 mg/L) and methane (41.2 mL/day) compared to other reactors. R3 reported 1800 mg/L and 24 mL/day, R2 reported 1560 mg/L and 15 mL/day and R1 reported 1430 mg/L and 10 mL/day of methane and SCFA production. The study-inferred that electro-fermentation could effectively catalyse the biochemical reactions and enhance the conversion of CO 2 to organic compounds in a sustainable manner. • Presence of electrode in the anaerobic fermentation enhanced the yield of carboxylic acids and biofuels. • The redox conditions are balanced in the microbial catalysed systems than the conventional anaerobic fermentations. • Enriched microbes showed different yield based on the operational conditions. • Electrofermentation is an effective processes to convert CO 2 to Value added products.

Integrating the Carboxylate Platform into a Red Seaweed Biorefinery.

Macroalgae are an important source of food, fertilizer, hydrocolloids, and healthful bioactive components. Macroalgae are also being considered sources of biofuels, which require minimal demands for arable land, fresh water, or fertilizers. In this study, we explored the possibility of developing a red seaweed biorefinery process to extract carrageenan while producing chemical or biofuel co-products derived from the carrageenan extraction wastes. A common approach to processing organic wastes is to generate biogas; however, in this study, we targeted a potentially higher value option by applying acidogenic digestion to convert extraction wastes to carboxylic acids and derived compounds. Using an open culture of microorganisms, wastes from a carrageenan extraction plant were converted to mixed carboxylic acids, which were then neutralized and thermally decomposed to a variety of ketones. Batch digestions of the wastes were carried out at temperatures of 35°C and 55°C. Either calcium carbonate or ammonium bicarbonate was used as buffer. A solid-liquid counter-current percolation fermentation was operated in four stages at 35°C. Digestion produced carboxylic acids ranging in chain length from one to seven carbons. The mesophilic temperature gave higher carboxylic acid yield and longer chain acids, with the highest acid titer reaching 18g L-1. Thermal decomposition of carboxylate salts produced a mixture of ketones which contained acetone, 3-pentanone, 2-hexanone, 2-heptanone, 3-heptanone, and 4-octanone as major products. These ketones could be sold as chemicals or hydrogenated to form corresponding chain length secondary alcohols which deliver higher energy density than ethanol.

Solvent‐Promoted Oxidation of Aromatic Alcohols/Aldehydes to Carboxylic Acids by a Laccase‐TEMPO System: Efficient Access to 2,5‐Furandicarboxylic Acid and 5‐Methyl‐2‐Pyrazinecarboxylic Acid

AbstractLaccase coupled with 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO) is a well‐known catalytic system for the oxidation of alcohols to the carbonyl compounds. In this work, a simple yet effective solvent engineering strategy is developed to enable aromatic alcohols/aldehydes to be efficiently oxidized to carboxylic acids by a laccase‐TEMPO system. Citrate buffer (100–300 mm, pH 6) rather than the widely used acetate buffer (pH 4–5) proves to be optimal for this purpose. The roles of citrate are discussed in laccase‐TEMPO‐catalyzed synthesis of carboxylic acids. 5‐Hydroxymethylfurfural (HMF) of 200 mm is oxidized to 2,5‐furandicarboxylic acid (FDCA), a top‐value biobased chemical in the polymer industry, in 28 h with a yield of up to 97%. Of the 18 substrates examined, 11 alcohols are converted to target carboxylic acids with >90% yields by this method, with 2 alcohols giving >60% yields of carboxylic acids. Gram‐scale preparation of FDCA and 5‐methyl‐2‐pyrazinecarboxylic acid, an important drug intermediate, is demonstrated with total turnover numbers up to 110 000 for laccase and space‐time yields up to 1.0 g/(L•h). This chemoenzymatic approach may be a promising alternative to traditional chemical oxidations for the synthesis of carboxylic acids.

Towards high carbon conversion efficiency by using a tailored electrodialysis process for in-situ carboxylic acids recovery

Production of carboxylic acids from anaerobic fermentation has gained increasing attention. However, acidogenic fermentation is still facing challenges such as low yield of carboxylic acids and difficulties in product recovery and purification. The emission of acidogenic off-gas CO2 leads to a reduced carbon recovery (∼70%) and also increases the carbon footprint of the anaerobic treatment process. In this study, a tailored electrodialysis stack was integrated with a fermenter to recover the products and hence to improve quantity and quality of the produced carboxylic acids. Three levels of currents, i.e., 0.4, 1, and 4 A (T1, T2, and T3), were applied during electrodialytic separation of carboxylic acids and 12 cycles of electrodialysis were carried out to evaluate the performance of the integrated system. Results showed that different degrees of carboxylic acids removal led to varied impacts on the yield of carboxylic acids, economic viability, and the instability of microbial community. Compared with the case without coupling electrodialysis process, the carbon conversion rate increased by 28.04% in T3, which was due to the reuse of inorganic carbon introduced by a tailored electrodialysis process. After 12 cycles of fermentation, the percentage of Clostridiales finally increased from 0.11% (inoculum) to 31.15% in T3, which also confirmed the possible autotrophic acidogenesis by using inorganic carbon. This work would provide a promising solution to improve the recovery of carboxylic acids from organic wastes and achieve minimum carbon footprint in the organic waste management process.

Characteristics of small molecule compounds produced from the co-pyrolysis of cotton stalk and coal

Pyrolysis experiments of cotton stalk (CS) and Shenmu coal (SM) were conducted in a tubular furnace. The pyrolysis temperature was 600 °C at 5 °C/min and sustained for 15 min. The water-soluble small molecule compounds (WSMC) were derived from the liquid products obtained during pyrolysis with the methods of toluene entrainment and ultrasonic extraction. The compositions of WSMC were further characterized by gas chromatography–mass spectrometry (GC-MS). The components of the syngas were analyzed by gas chromatography (GC). The results showed that the phenol yield was promoted by the interaction of CS and SM during co-pyrolysis. Moreover, the co-pyrolysis interaction blocked the radical reaction pathway that produces amides and accelerated the formation of pyridines. Because the ester yield increased, the esterification was clearly enhanced and the yield of carboxylic acids in WSMC was reduced during co-pyrolysis. In addition, the inhibition of furan generation resulted in an increased yield of C2–C4 hydrocarbons in the co-pyrolysis syngas. The maximal yields of C2–C4 hydrocarbons all occurred at a 20/100 ratio of CS/SM. Lastly, the formation mechanisms of small molecule compounds were proposed.

Valorization of olive oil industry subproducts: ash and olive pomace fast pyrolysis

Environmental problems have encouraged investigation of renewable energies. The organic waste treating through fast pyrolysis seems to be a highly promising option for decreasing pollutants. Olive pomace, a major source of waste in countries with high production of olive oil (mainly Spain, Italy, and Greece), is a clear target for valorisation. Dried olive pomace together with the ashes obtained during the drying process was blended to study the influence of the inorganic metals inherently present in the ashes (K, Na, Ca and Mg) for fast pyrolysis product distribution. The results determined that these metals increased yields of phenolic compounds until a maximum was reached, whereas carboxylic acid yield fell due to the action of metals. In addition, aromatic hydrocarbons and polyphenols were obtained for those samples with a large amount of ash. Moreover, the formation of organic acids, such as acetic acid, requires a smaller proportion of ash in the blend. Finally, it has been found that the ashes could be used as a catalyst for producing better quality bio-oil, thereby avoiding extra costs and thus valorizing the industrial treatment olive pomace.

Enhanced short-chain carboxylic acids yield in dark fermentation by cyclic product removal

Disposal of carbon-rich wastes, such as food waste, is one of the several environmental concerns raised nowadays. Conversion of organic residues by dark fermentation produces short-chain (C1–C6) carboxylic acids, which are valuable chemical building blocks. The objective of this study was to optimize the operational parameters and perform comparative studies of cyclic and batch mode dark fermentation for carboxylic acid production from food waste. A maximum yield of short-chain carboxylic acids (SCCAs) 0.21 ± 0.012 g-SCCAs/g-TS in 50 g-TS/L was obtained in the cyclic mode as compared with the 0.13 ± 0.011 g-SCCAs/g-TS in the batch mode. The results showed that the use of the cyclic mode increased the carboxylic acid yield from 54 (batch mode) to 88%.

Oxidative Depolymerization of Kraft Lignin for Microbial Conversion

The valorization of lignin is being increasingly recognized as crucial to improve the economic viability of integrated biorefineries. Because of its inherent heterogeneity and recalcitrance, lignin has been treated as a waste product in the pulp and paper industry, but new technologies are now being explored to transform lignin into a sustainable resource and enhance its value chain. In the present study, alkaline oxidative depolymerization was investigated as a potential form of pretreatment to enable further biological conversion of LignoBoost kraft lignin (LB). LB lignin oxidation reactions were studied at various temperatures (120-200 °C) and O2 partial pressures (3-15 bar) to identify the optimal conditions for obtaining a biocompatible, oxidatively depolymerized lignin (ODLB) stream. The low molecular weight compounds resulting from this treatment consisted mainly of aromatic monomers and carboxylic acids. The highest yield of aromatic monomers, 3 wt %, was obtained at 160 °C and 3 bar O2. The yield of carboxylic acids increased with both increasing temperature and O2 pressure, exceeding 13% under the harshest conditions investigated. The growth of four aromatic-catabolizing bacterial strains was examined on reaction product mixtures, all of which showed growth on agar plates utilizing ODLB as the sole source of carbon and energy. Rhodococcus opacus and Sphingobium sp. SYK-6 were found to consume most of the aromatic monomers present in the ODLB (e.g., vanillin, vanillate, acetovanillone, and guaiacol). The findings of this study indicate that pretreatment by oxidative depolymerization has potential in the biological valorization of technical lignin streams, for the production of valuable chemicals and materials. (Less)

Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed

BackgroundDuckweeds (Lemnaceae) are efficient aquatic plants for wastewater treatment due to their high nutrient-uptake capabilities and resilience to severe environmental conditions. Combined with their rapid growth rates, high starch, and low lignin contents, duckweeds have also gained popularity as a biofuel feedstock for thermochemical conversion and alcohol fermentation. However, studies on the acidogenic anaerobic digestion of duckweed into carboxylic acids, another group of chemicals which are precursors of higher-value chemicals and biofuels, are lacking. In this study, a series of laboratory batch experiments were performed to determine the favorable operating conditions (i.e., temperature and pH) to maximize carboxylic acid production from wastewater-derived duckweed during acidogenic digestion. Batch reactors with 25 g/l solid loading were operated anaerobically for 21 days under mesophilic (35 °C) or thermophilic (55 °C) conditions at an acidic (5.3) or basic (9.2) pH. At the conclusion of the experiment, the dominant microbial communities under various operating conditions were assessed using high-throughput sequencing.ResultsThe highest duckweed–carboxylic acid conversion of 388 ± 28 mg acetic acid equivalent per gram volatile solids was observed under mesophilic and basic conditions, with an average production rate of 0.59 g/l/day. This result is comparable to those reported for acidogenic digestion of other organics such as food waste. The superior performance observed under these conditions was attributed to both chemical treatment and microbial bioconversion. Hydrogen recovery was only observed under acidic thermophilic conditions, as 23.5 ± 0.5 ml/g of duckweed volatile solids added. More than temperature, pH controlled the overall structure of the microbial communities. For instance, differentially abundant enrichments of Veillonellaceae acidaminococcus were observed in acidic samples, whereas enrichments of Clostridiaceae alkaliphilus were found in the basic samples. Acidic mesophilic conditions were found to enrich acetoclastic methanogenic populations over processing times longer than 10 days.ConclusionsOperating conditions have a significant effect on the yield and composition of the end products resulting from acidogenic digestion of duckweed. Wastewater-derived duckweed is a technically feasible alternative feedstock for the production of advanced biofuel precursors; however, techno-economic analysis is needed to determine integrated full-scale system feasibility and economic viability.

Facile oxidation of alcohols to carboxylic acids in basic water medium by employing ruthenium picolinate cluster as an efficient catalyst

Selective transformation of alcohols into carboxylic acids is a crucial process in industry for the synthesis of bulk chemicals. Current methods for the production of acids involve oxygen under pressure or toxic reagents like ruthenium chlorite or iodate or chromium oxides. Herein, we report the preparation of [Ru3(CO)8(C5H4NCO2)2] cluster which is an efficient catalyst precursor for the conversion of primary alcohols into carboxylic acids under aerobic conditions. The catalytic process involves the use of NaOH in a water–isopropanol medium which gives a 90% yield of carboxylic acid (90% yield for benzoic acid in standard reaction). This clean process appears to be safe for the synthesis of various benzoic acids for both laboratory and also industrial purposes.

Catalytic fast pyrolysis of a wood-plastic composite with metal oxides as catalysts

The catalytic fast pyrolysis of a poplar wood-polypropylene composite (WPP) was investigated using Py-GC/MS in the presence of ZnO, CaO, Fe2O3 and MgO. The synergistic effects between wood and plastic components in both non-catalytic and ZnO-catalyzed pyrolysis of WPP were studied. CaO facilitated the removal of oxygen due to its strong basicity, eliminating carboxylic acids and phenols from the products, while slightly increasing cyclopentanones and alkenes. MgO has weaker deoxygenation but stronger chain scission activities versus CaO, and significantly enhanced the alkene yields. Alkene yields were highest using ZnO among the four catalysts. ZnO increased ketone and phenol yields while reducing carboxylic acids. Aromatics were identified in the presence of Fe2O3. A synergistic effect between poplar wood and PP in the uncatalyzed pyrolysis of WPP increased the yields of carboxylic acids, phenols and light alkenes, while it reduced carbonyl-containing oxygenates such as aldehydes, ketones and furans. The synergy in the ZnO-catalyzed pyrolysis of WPP further enhanced the formation of monomeric phenols and alkenes.

Effects of various additives on the pyrolysis characteristics of municipal solid waste

Additives can have a significant impact on the pyrolysis process. The effects of three additives (CaO, MSW char and biomass) on the pyrolysis characteristics of municipal solid waste (MSW) were investigated using a fixed-bed reactor. In addition, the effects of additives and temperature on the MSW pyrolysis product yield, the composition of MSW pyrolysis gases, and the composition of MSW pyrolysis tar were investigated using fixed bed reactor, GC–MS and FTIR, respectively. The results showed that the maximum tar yield of the MSW reached 28.73% at 600 °C and the tar yield decreased with increasing amounts of CaO and MSW. The tar yield began to decrease when the additive amount of CaO was 5% and decreased to 23.05% when the additive amount of MSW char (C) was 30%. Synergistic pyrolysis of the biomass and MSW was observed when the additive amount of the pine increased to 75% (with a tar yield of 37.91%). Regarding gas composition, with increasing additives content, the CO2 yield decreased, while the CO yield increased. According to the FTIR analysis of the tar, CaO enhanced the condensation of the aromatic rings and converted the aliphatic hydrocarbons, while C reduced the oxygenic groups of the tar. The GC–MS results revealed that the additives decreased the yield of carboxylic acid and ethanol, and increased the ester yield. The additives were also found to have a deoxidation effect that decreased the acid content, potentially improving the quality and stability of the tar.

Valorization of Lignin by Partial Wet Oxidation Using Sustainable Heteropoly Acid Catalysts.

The production of carboxylic acids by partial wet oxidation of alkali lignin at elevated temperatures and pressures was studied experimentally. Two different heteropoly acids, phosphotungstic acid (H3PW12O40) and phosphomolybdic acid (H3PMo12O40), were used to catalyze the oxidation of lignin under hydrothermal conditions. Factors influencing the total yield of carboxylic acids formed during the partial oxidation of lignin were investigated. Formic, acetic and succinic acids were the major products identified. Of the two catalysts used, phosphomolybdic acid gave the most promising results, with carboxylic acid yields and lignin conversions of up to 45% and 95%, respectively.

Production of Benzene Carboxylic Acids and Small-Molecule Fatty Acids from Lignite by Two-Stage Alkali-Oxygen Oxidation

Carboxylic acids are widely used in industry as a kind of important chemical materials, and it is very promising to produce carboxylic acids from lignite. The traditional alkali-oxygen oxidation of lignite does not consider the complex structure of lignite, and the structures with different reactivities are treated under identical and harsh reaction conditions, resulting in a low yield of carboxylic acids. We propose a two-stage oxidation process of lignite to increase the yield and mitigate the harsh reaction conditions. First, lignite was extracted using a NaOH aqueous solution to yield two parts (extract and residue) with different reactivities. The extract and residue then were oxidized separately with alkali-oxygen oxidation under different conditions. In this way, high yields of benzene carboxylic acids (BCAs, 12 types) and small-molecule fatty acids (SMFAs) could be obtained. The extraction conditions and the alkali-oxygen oxidation conditions of the extract and the residue were investigated. Compa...

Production of Benzene Poly(carboxylic acid)s and Small-Molecule Fatty Acids from Lignite by Catalytic Oxidation in NaVO3/H2SO4 Aqueous Solution with Molecular Oxygen

Carboxylic acids are widely used in industry and are considered an important type of chemicals. The production of carboxylic acids through oxidation of lignite is very promising. The traditional alkali−oxygen oxidation of lignite can produce high yields of carboxylic acids, but the process consumes a great deal of alkali and acids and the high reaction temperature increases the energy consumption. In the present work, we found that carboxylic acids, including small-molecule fatty acids and benzene poly(carboxylic acid)s, could be obtained by catalytic oxidation of lignite in NaVO3/H2SO4 aqueous solution with molecular O2. The effects of NaVO3/coal mass ratio, H2SO4 content, reaction temperature, initial O2 pressure and reaction time on the conversion of lignite and yield of carboxylic acids were investigated. In the process of reaction, lignite is first converted into water-soluble intermediates, which are then converted into carboxylic acids. The second step is the rate controlling step. It has been foun...

Assessment of Shock Pretreatment of Corn Stover Using the Carboxylate Platform

Corn stover was pretreated with lime and shock, a mechanical process that uses a shockwave to alter the biomass structure. Two pretreatments (lime-only and lime + shock) were evaluated using enzymatic hydrolysis, batch mixed-culture fermentations, and continuous countercurrent mixed-culture fermentation. In a 120-h enzymatic hydrolysis, shock pretreatment increased the glucan digestibility of submerged lime pretreatment (SLP) corn stover by 3.5 % and oxidative lime pretreatment (OLP) corn stover by 2.5 %. The continuum particle distribution model (CPDM) was used to simulate a four-stage continuous countercurrent mixed-culture fermentation using empirical rate models obtained from simple batch experiments. The CPDM model determined that lime + shock pretreatment increased the total carboxylic acids yield by 28.5 % over lime-only pretreatment in a countercurrent fermentation with a volatile solids loading rate (VSLR) of 12 g/(L/day) and liquid retention time (LRT) of 30 days. In a semi-continuous countercurrent fermentation performed in the laboratory for 112 days with a VSLR of 1.875 g/(L day) and LRT of 16 days, lime + shock pretreatment increased the total carboxylic acid yield by 14.8 %. The experimental results matched closely with CPDM model predictions (4.05 % error).