Catalytic Oxidation and Depolymerization of Lignin in Aqueous Ionic Liquid

Lignin is an integral part of the plant cell wall, which provides rigidity to plants, also contributes to the recalcitrance of the lignocellulosic biomass to biochemical and biological deconstruction. Lignin is a promising renewable feedstock for aromatic chemicals; however, an efficient and economic lignin depolymerization method needs to be developed to enable the conversion. In this study, we investigated the depolymerization of alkaline lignin in aqueous 1-ethyl-3-methylimidazolium acetate [C2C1Im][OAc] under oxidizing conditions. Seven different transition metal catalysts were screened in presence of H2O2 as oxidizing agent in a batch reactor. CoCl2 and Nb2O5 proved to be the most effective catalysts in degrading lignin to aromatic compounds. A central composite design was used to optimize the catalyst loading, H2O2 concentration, and temperature for product formation. Results show that lignin was depolymerized, and the major degradation products found in the extracted oil were guaiacol, syringol, vanillin, acetovanillone, and homovanillic acid. Lignin streams were characterized by Fourier transform infrared spectroscopy and gel permeation chromatography to determine effects of the experimental parameters on lignin depolymerization. The weight-average molecular weight (Mw) of liquid stream lignin after oxidation, for CoCl2 and Nb2O5 catalysts were 1,202 and 1,520 g mol−1, respectively, lower than that of Kraft lignin. Polydispersity index of the liquid stream lignin increased as compared with Kraft lignin, indicating wide span of the molecular weight distribution as a result of lignin depolymerization. Results from this study provide insights into the role of oxidant and transition metal catalysts and the oxidative degradation reaction sequence of lignin toward product formation in presence of aqueous ionic liquid

Lignin Valorization in Ionic Liquids and Deep Eutectic Solvent via Catalysis and Biocatalysis

This invention relates to a method for extracting valorized compounds from lignin by contacting lignins with an ionic liquid and/or a deep eutectic solvent and adding a catalyst and/or a biocatalyst to assist in breaking down the source material. Converting lignin into high value chemicals adds revenues for a bio-refinery and helps to improve the economic viability of biofuel production

Adsorption of p-cresol on Granular Activated Carbon

Swine farming emit several odorous volatile organic compounds, one of which is p-cresol. Considering the layout of a swine barn, adsorption is one of the most suitable technologies for mitigating organic pollutants. In this study, commercial granular activated carbon (GAC) was tested as an adsorbent for removing p-cresol from aqueous solution. The objectives were to: 1) determine the combined effect of temperature, pH, and adsorbent dose on adsorption, (2) investigate the effect of volatile fatty acids and aldehydes on adsorption of p-cresol, (3) determine adsorption kinetics and isotherms, (4) study the effect of solvent on adsorption, (5) propose a possible mechanism of adsorption, and (6) discuss practical implications and design calculations for estimating adsorption of p-cresol on activated carbon. Batch experiments with GAC were performed to assess the combined effects of temperature (15-35 °C), pH (6-8), and adsorbent dose (10-30 g L-1) on adsorption of p-cresol. The results indicated that adsorption capacity of p-cresol decreased with increasing adsorbent dose, whereas the effects of pH and temperature were not significant. Optimum adsorption capacity of 12.02 mg g-1 was observed at temperature of 25 °C, pH of 7, and adsorbent dose of 0.32g. It was also found that presence of isovaleric acid and formaldehyde enhanced adsorption of p-cresol. Kinetic analyses indicated that p-cresol adsorbed mainly via chemisorption and adsorption was limited mainly via intra-particle diffusion. The role of solvent was not significant suggesting that water did not compete with p-cresol. Furthermore, surface oxygen somewhat inhibited adsorption of p-cresol perhaps due to enhancement of hydrophilicity. It is proposed that adsorption occurred mainly via electron-transfer between p-cresol and activated carbon. Sample design calculations are also presented to aid the swine producers to estimate the carbon dosage.

Linking Lignin Source with Structural and Electrochemical Properties of Lignin-Derived Carbon Materials

Valorization of lignin to high-value chemicals and products along with biofuel production is generally acknowledged as a technology platform that could significantly improve the economic viability of biorefinery operations. With a growing demand for electrical energy storage materials, lignin-derived activated carbon (AC) materials have received increasing attention in recent years. However, there is an apparent gap in our understanding of the impact of the lignin precursors (i.e., lignin structure, composition and inter-unit linkages) on the structural and electrochemical properties of the derived ACs. In the present study, lignin-derived ACs were prepared under identical conditions from two different lignin sources: alkaline pretreated poplar and pine. The lignin precursors were characterized using composition analysis, size exclusion chromatography, and 2D HSQC nuclear magnetic resonance (NMR). Distinctive distributions of numerous micro-, meso- and macro-porous channels were observed in the two lignin-derived ACs. Poplar lignin-derived ACs exhibited a larger BET surface area and total mesopore volume than pine lignin-derived AC, which contributed to a larger electrochemical capacitance over a range of scan rates. X-ray photoelectron spectroscopic analysis (XPS) results revealed the presence of oxygen-containing functional groups in all lignin-derived ACs, which participated in redox reactions and thus contributed to an additional pseudo-capacitance. A possible process mechanism was proposed to explain the effects of lignin structure and composition on lignin-derived AC pore structure during thermochemical conversion. This study provides insight into how the lignin composition and structure affect the derived ACs for energy storage applications

Catalytic Oxidation and Depolymerization of Lignin in Aqueous Ionic Liquid

Lignin is an integral part of the plant cell wall, which provides rigidity to plants, also contributes to the recalcitrance of the lignocellulosic biomass to biochemical and biological deconstruction. Lignin is a promising renewable feedstock for aromatic chemicals; however, an efficient and economic lignin depolymerization method needs to be developed to enable the conversion. In this study, we investigated the depolymerization of alkaline lignin in aqueous 1-ethyl-3-methylimidazolium acetate [C2C1Im][OAc] under oxidizing conditions. Seven different transition metal catalysts were screened in presence of H2O2 as oxidizing agent in a batch reactor. CoCl2 and Nb2O5 proved to be the most effective catalysts in degrading lignin to aromatic compounds. A central composite design was used to optimize the catalyst loading, H2O2 concentration, and temperature for product formation. Results show that lignin was depolymerized, and the major degradation products found in the extracted oil were guaiacol, syringol, vanillin, acetovanillone, and homovanillic acid. Lignin streams were characterized by Fourier transform infrared spectroscopy and gel permeation chromatography to determine effects of the experimental parameters on lignin depolymerization. The weight-average molecular weight (Mw) of liquid stream lignin after oxidation, for CoCl2 and Nb2O5 catalysts were 1,202 and 1,520 g mol−1, respectively, lower than that of Kraft lignin. Polydispersity index of the liquid stream lignin increased as compared with Kraft lignin, indicating wide span of the molecular weight distribution as a result of lignin depolymerization. Results from this study provide insights into the role of oxidant and transition metal catalysts and the oxidative degradation reaction sequence of lignin toward product formation in presence of aqueous ionic liquid

Catalytic Oxidation and Depolymerization of Lignin in Aqueous Ionic Liquid

Lignin is an integral part of the plant cell wall, which provides rigidity to plants, also contributes to the recalcitrance of the lignocellulosic biomass to biochemical and biological deconstruction. Lignin is a promising renewable feedstock for aromatic chemicals; however, an efficient and economic lignin depolymerization method needs to be developed to enable the conversion. In this study, we investigated the depolymerization of alkaline lignin in aqueous 1-ethyl-3-methylimidazolium acetate [C2C1Im][OAc] under oxidizing conditions. Seven different transition metal catalysts were screened in presence of H2O2 as oxidizing agent in a batch reactor. CoCl2 and Nb2O5 proved to be the most effective catalysts in degrading lignin to aromatic compounds. A central composite design was used to optimize the catalyst loading, H2O2 concentration, and temperature for product formation. Results show that lignin was depolymerized, and the major degradation products found in the extracted oil were guaiacol, syringol, vanillin, acetovanillone, and homovanillic acid. Lignin streams were characterized by Fourier transform infrared spectroscopy and gel permeation chromatography to determine effects of the experimental parameters on lignin depolymerization. The weight-average molecular weight (Mw) of liquid stream lignin after oxidation, for CoCl2 and Nb2O5 catalysts were 1,202 and 1,520 g mol−1, respectively, lower than that of Kraft lignin. Polydispersity index of the liquid stream lignin increased as compared with Kraft lignin, indicating wide span of the molecular weight distribution as a result of lignin depolymerization. Results from this study provide insights into the role of oxidant and transition metal catalysts and the oxidative degradation reaction sequence of lignin toward product formation in presence of aqueous ionic liquid

Oxidative Depolymerization of Lignin Using Supported Niobium Catalysts

Valorization of lignin into aromatics has driven researchers for decades. In this research, niobium was deposited on oyster shells (OSNC) and carbon rods (CRNC) and tested as a catalyst for depolymerization of lignin. Catalysts (2%, 5%, and 8% loading) were synthesized via wet impregnation. Batch experiments were performed at 95 °C, using 8 g of lignin, and 1 g of catalyst. Our research indicates that niobium supported catalysts are effective in partial oxidation of lignin. Maximum vanillin concentration for OSNC was found to be 86.25 mg L−1 (0.1 wt%) at 5% niobium whereas, as for CRNC, maximum vanillin concentration was found to be 139.40 mg L−1 (0.17 wt%) at 2% niobium loading. Addition of hydrogen peroxide into the batch reactor decreased the concentration of vanillin production

Poređenje matematičkih modela i kinetike sušenja bukovače (pleurotus spp) u tankom fluidizovanom sloju sa ubrzanom temperaturom i brzinom vazduha

Effect of drying air temperature and velocity on thin-layer drying characteristics of oyster mushroom (Pleurotus spp.) was investigated using a fluidized bed dryer. Mushrooms were dried at three air temperatures 45, 55 and 65ºC coupled with the air velocity of 2, 3.5 and 5 m•s‒1. Dehydration of mushrooms occurred in falling rate period and temperature has significant (P=0.04) effect on drying. From the regression model, best quality of dried oyster mushroom was obtained at 65°C temperature and 5 ms‒1 air velocity and it was validated with sensory characteristics in terms of colour, crispy texture, flavour and comparatively less shrinkage. To determine the drying kinetics, experimental moisture ratio data were fitted to seven thin-layer drying models. Among the models studied, Page model was found to be the best fitted model to describe the drying behavior of oyster mushroom. At any given air velocity, with the increase in drying air temperature led to an increase in effective moisture diffusivity ranged from 7.78×10‒10 to 2.11×10‒9m2•s‒1. Drying at 5 m•s‒1 air velocity required minimum activation energy of 22.15 kJ•mol‒1 to remove water during the drying process by diffusion. Rehydration ratios (RR) values (1.95-2.75) increased with increase in drying air temperature and velocity. The results obtained could be for making appropriate design and operations of industrial drying system for further processing of mushrooms to value added products.Ispitivan je uticaj temperature i brzine vazduha na karakteristike sušenja tankog fluidizovanog sloja bukovače (Pleurotus spp.). Pečurke su sušene na tri temperature vazduha 45, 55 i 65ºC, kombinovane sa brzinama vazduha od 2, 3.5 i 5 ms‒1. Trajanje dehidracije pečurki se smanjivalo i temperatura je imala značajan (P=0.04) uticaj na sušenje. U regresionom modelu, najbolji kvalitet sušene bukovače postignut je pri temperaturi od 65°C i brzini vazduha od 5 ms‒1, a ocenjen je prema senzornim karakteristikama: boja, hrskava tekstura, ukus i komparativno manje kalo. Za određivanje kinetike sušenja, eksperimentalne vrednosti vlažnosti su poređene sa sedam modela sušenja tankog sloja. Među analiziranim modelima, Page model je najbolje opisivao tok sušenja bukovače. Pri svakoj brzini vazduha, povećanje temperature dovelo je do povećanja efektivne difuzivnosti vlage u interval od 7.78×10‒10 do 2.11×10‒9 m2s‒1. Sušenje strujom vazduha brzine 5 ms‒1 zahtevalo je minimalnu energiju aktivacije od 22.15 KJ mol‒1 za odstranjivanje vode difuzijom tokom sušenja. Odnosi rehidracije (RR) (1.95-2.75) povećali su se sa povećanjem temperature i brzine vazduha. Dobijeni rezultati se mogu koristiti za pravljenje odgovarajućih konstrukcija i operacija industrijskih sistema sušenja gljiva radi dalje prerade i dobijanja prozvoda veće vrednosti

Characterization and Catalytic Transfer Hydrogenolysis of Deep Eutectic Solvent Extracted Sorghum Lignin to Phenolic Compounds

Deep eutectic solvent (DES) is intrinsically cheaper than many ionic liquids (ILs) due to low precursor cost, simple synthesis, and improved recyclability. Meanwhile, DES can be as effective as ILs toward dissolving lignin from plant materials. However, the lignin depolymerization mechanism in DES, the structural and chemical properties of DES-extracted lignin (DES-EL), and the possible valorization pathways of DES-EL toward value-added products were not well understood. This study aims to characterize the lignin streams from DES (1:2 choline chloride:lactic acid) treated sorghum and further upgrade the extracted lignin to phenolic compounds. As revealed by HSQC, ¹³C, and ³¹P NMR analysis, DES cleaved nearly all ether linkages in native lignin, resulting in significant size reduction. We further catalytically upgraded DES-EL to phenolic compounds via catalytic transfer hydrogenolysis in the presence of isopropyl alcohol. Among the three tested catalysts (Ru/C, Pd/C, and Pt/C), Ru/C proved the most effective in deconstructing DES-EL, with oil, char, and gas yields of 36.3, 46.4, 17.3 wt %, respectively. Major lignin monomeric products in the oil were phenol, 4-ethylphenol, 4-ethyl-2-methoxyphenol, 2-methoxy-4-propylphenol, and 4-hydroxy-benzenepropanoic acid. This study provides a mechanistic understanding of lignin depolymerization in DES and demonstrates a possible way to catalytic upgrading of DES-EL to low molecular weight phenolic compounds

Understanding Lignin Fractionation and Characterization from Engineered Switchgrass Treated by an Aqueous Ionic Liquid

Aqueous ionic liquids (ILs) have received increasing interest because of their high efficacy in fractionating and pretreating lignocellulosic biomass while at the same time mitigating several challenges associated with IL pretreatment such as IL viscosity, gel formation during pretreatment, and the energy consumption and costs associated with IL recycling. This study investigated the fate of lignin, its structural and compositional changes, and the impact of lignin modification on the deconstruction of cell wall compounds during aqueous IL (10% w/w cholinium lysinate) pretreatment of wild-type and engineered switchgrass. The <i>4CL</i> genotype resulting from silencing of 4-coumarate:coenzyme A ligase gene (<i>Pv4CL1</i>) had a lower lignin content, relatively higher amount of hydroxycinnamates, and higher S/G ratio and appeared to be less recalcitrant to IL pretreatment likely due to the lower degree of lignin branching and more readily lignin solubilization. The results further demonstrated over 80% of lignin dissolution from switchgrass into the liquid fraction under mild conditions while the remaining solids were highly digestible by cellulases. The soluble lignin underwent partial depolymerization to a molecular weight around 500–1000 Da. ¹H–¹³C HSQC NMR results demonstrated that the variations in lignin compositions led to different modes of lignin dissolution and depolymerization during pretreatment of engineered switchgrass. These results provide insights into the impact of lignin manipulation on biomass fractionation and lignin depolymerization and lead to possible ways toward developing a more selective and efficient lignin valorization process based on aqueous IL pretreatment technology