Pyrolysis Of Lignin Research Articles

Catalytic pyrolysis of lignin for the production of aromatic hydrocarbons: Effect of magnesium oxide catalyst

A base catalyst is expected to suppress coke formation of the catalyst, leading to less catalyst deactivation and more efficient production of bio-oil. To examine the feasibility of a solid-base catalyst as a lignin pyrolysis catalyst, MgO loaded on supports with different textural, acid, and base properties (i.e. carbon, Al2O3, and ZrO2) was applied. In addition, because the co-processing of biomass with plastic significantly improves the quality of bio-oil in the catalytic pyrolysis process, co-pyrolysis of lignin with linear low-density polyethylene was performed, and the effects of the MgO catalysts were analyzed. Thermogravimetric analysis and a tandem micro-reactor–gas chromatography/mass spectrometry system were used to evaluate the performance of the MgO catalysts in terms of thermal decomposition behavior and yield of monoaromatic hydrocarbons. Overall, MgO supported on carbon (MgO/C) showed the highest yield of aromatic hydrocarbons during the pyrolysis of lignin, due to its well-balanced acid/base sites and high surface area. Also, MgO/C exhibited the strongest positive synergy toward the production of aromatic hydrocarbons during co-pyrolysis, which suggests that a metal oxide with base properties supported on high-surface-area carbon could be an efficient catalyst for producing bio-oil with high energy density fuel additives from the lignin.

Aromatics from Beechwood Organosolv Lignin through Thermal and Catalytic Pyrolysis

Biomass fractionation, as an alternative to biomass pretreatment, has gained increasing research attention over the past few years as it provides separate streams of cellulose, hemicellulose, and lignin. These streams can be used separately and can provide a solution for improving the economics of emerging biorefinery technologies. The sugar streams are commonly used in microbial conversions, whereas during recent years lignin has been recognized as a valuable compound as it is the only renewable and abundant source of aromatic chemicals. Successfully converting lignin into valuable chemicals and products is key in achieving both environmental and economic sustainability of future biorefineries. In this work, lignin retrieved from beechwood sawdust delignification pretreatment via an organosolv process was depolymerized with thermal and catalytic pyrolysis. ZSM-5 commercial catalyst was used in situ to upgrade the lignin bio-oil vapors. Lignins retrieved from different modes of organosolv pretreatment were tested in order to evaluate the effect that upstream pretreatment has on the lignin fraction. Both thermal and catalytic pyrolysis yielded oils rich in phenols and aromatic hydrocarbons. Use of ZSM-5 catalyst assisted in overall deoxygenation of the bio-oils and enhanced aromatic hydrocarbons production. The oxygen content of the bio-oils was reduced at the expense of their yield. Organosolv lignins were successfully depolymerized towards phenols and aromatic hydrocarbons via thermal and catalytic pyrolysis. Hence, lignin pyrolysis can be an effective manner for lignin upgrading towards high added value products.

Lignin from Bioethanol Production as a Part of a Raw Material Blend of a Metallurgical Coke

Replacement of part of the coal in the coking blend with lignin would be an attractive solution to reduce greenhouse gas emissions from blast furnace (BF) iron making and for obtaining additional value for lignin utilization. In this research, both non-pyrolyzed and pyrolyzed lignin was used in a powdered form in a coking blend for replacing 5-, 10- and 15 m-% of coal in the raw material bulk. Graphite powder was used as a comparative replacement material for lignin with corresponding replacement ratios. Thermogravimetric analysis was performed for all the raw materials to obtaining valuable data about the raw material behavior in the coking process. In addition, chemical analysis was performed for dried lignin, pyrolyzed lignin and coal that were used in the experiments. Produced bio cokes were tested in a compression strength experiment, in reactivity tests in a simulating blast furnace shaft gas profile and temperature. Also, an image analysis of the porosity and pore shapes was performed with a custom made MatLab-based image analysis software. The tests revealed that the pyrolysis of lignin before the coking process has an increasing impact on the bio coke strength, while the reactivity of the bio-cokes did not significantly change. However, after certain level of lignin addition the effect of lignin pyrolysis before the coking lost its significance. According to results of this research, the structure of bio cokes changes significantly when replacement of coal with lignin in the raw material bulk is at a level of 10 m-% or more, causing less uniform structure thus leading to a less strong structure for bio cokes.

Controlled Radical Polymerization of Crude Lignin Bio-oil Containing Multihydroxyl Molecules for Methacrylate Polymers and the Potential Applications

In this work, methacrylate polymers with different thermal and viscoelastic properties were synthesized from red oak lignin bio-oil. The bio-oil, also called pyrolytic lignin (PL), consisted of various phenolic monomers and oligomers with average hydroxyl content of 3.04 mol/mol. The PL was first esterified with different amounts of methacryloyl chloride and acetyl chloride to form PL methacrylates and then subjected to reversible addition–fragmentation chain transfer polymerization. Polymerization of fully methacrylated PL caused gelation to yield a cross-linked polymer. On the other hand, gel-point suppression occurred in the polymerization of partially methacrylated PL to yield a thermoplastic polymer with glass transition temperature (Tg) of 161 °C and thermal decomposition temperature (Td) of 241 °C. In comparison, the functionalization of PL by partial methacrylation and subsequent acetylation resulted in a polymer with Tg of 130 °C and Td of 250 °C. Unlike other biobased methacrylate polymers that cannot withstand high temperatures and volatilize, the polymers produced from this study retained 25–28% mass when pyrolyzed to 1000 °C. The latter polymer was also melt-spinnable and demonstrated highly attractive properties as an ideal carbon fiber precursor. Other than its narrow molecular weight distribution and high isothermal stability, this lignin-based polymer also had a linear molecular orientation that is critical in producing high-quality carbon fiber.

Nitrogen, oxygen and sulfur co-doped hierarchical porous carbons toward high-performance supercapacitors by direct pyrolysis of kraft lignin

The O-N-S co-doped hierarchical porous carbons are prepared by direct pyrolysis of kraft lignin which is the byproduct from papermaking black liquor. The proposed preparation method is extremely facile, green-environmental, and low-cost without any additional activating agents, additives or templates. The kraft lignin-derived carbon materials possess large specific surface areas (338−1307 m2 g−1), hierarchical porous structures and abundant multi-heteroatoms co-doping (9.84–19.91 wt%). Benefiting from above synergistic advantages, the as-fabricated symmetric supercapacitor in aqueous electrolyte delivers a high specific capacitance of 244.5 F g−1 at 0.2 A g−1, excellent rate-capability (81.8% retention of initial capacitance at 40.0 A g−1), and outstanding cycling stability (91.6% retention over 10000 cycles). Importantly, this device in aqueous electrolyte delivers an energy density of 8.5 W h kg−1 at a power density of 100 W kg−1. Furthermore, a remarkable energy density of 66.8 W h kg−1 at a power density of 1.75 kW kg−1 has been achieved and 32.2 W h kg−1 is still maintained even at an ultrahigh power density of 40.0 kW kg−1 when ionic liquid serves as electrolyte. This study demonstrates the successful conversion of low-valued natural biomass derivative into sustainable high-performance supercapacitor electrode materials with a simple, low-cost, and green-environmental production process.

Techno‐economic comparative assessment of novel lignin depolymerization routes to bio‐based aromatics

AbstractThis paper presents a techno‐economic assessment of three novel routes for the production of bio‐based aromatics from lignin. It aims to provide insights into their feasibility and hotspots at an early stage of development to guide further research and development and to facilitate commercialization. The lignin conversion routes are: (non‐catalytic) lignin pyrolysis, direct hydrodeoxygenation (HDO), and hydrothermal upgrading (HyThUp). The products generated are mixed oxygenated aromatic monomers (MOAMON), light organics, heavy organics, and char. For the technical assessment, conceptual design followed by process modeling in Aspen Plus was based on experimental yields. The models generated indispensable data on material and energy flows. An economic assessment was then conducted by estimating operating and capital costs. Return on investment (ROI), payback period (PBP), and net present value (NPV) were used as key performance indicators. Downstream processing was especially demanding in the HyThUp process due to the presence of a significant flow rate of water in the system, which significantly increased external utility requirements. Due to complex separations, the HyThUp process showed the highest capital cost (35% more than pyrolysis). Operating costs were the highest for the direct HDO process (34% more than pyrolysis) due to the use of hydrogen. Overall, the direct HDO process showed the highest ROI (12%) and the shortest PBP (5 years) due to high yields of valuable heavy organics (32%) and MOAMON (24%). Direct HDO was found to be feasible with a positive NPV based on prices used in the assessment. Among the three processes investigated, the direct HDO process therefore appeared to be the most promising, and consideration should be given to further development and commercialization of this process. © 2019 The Authors. Biofuels, Bioproducts, and Biorefining published by Society of Chemical Industry and John Wiley & Sons, Ltd.

The selective cleavage of lignin aliphatic C–O linkages by solvent-assisted fast pyrolysis (SAFP)

We report the effect of an organic solvent on the selective cleavage of individual lignin model compounds and lignin C–O linkages during the fast thermal pyrolysis of lignin. During this process, it was possible to lower the aliphatic hydroxyl contents of lignin, along with increasing the amount of single and double bonded aliphatics. It was found that the addition of solvent during fast pyrolysis of lignin lowered the molecular weight distribution of the obtained bio-oil (~ 49–52% decrease) and at the same time inhibited the formation of a high amount of char. A detailed study of the cleavage of complex model compounds using Ethanol-Assisted Fast Pyrolysis (EAFP) revealed that the aliphatic hydroxyl groups and etheric linkages are very reactive during this process. By the use of deuterated lignin model compounds and solvent, it was then possible to elucidate the mechanism for cleavage of lignin in the EAFP process that involves the formation of a transition state between solvent and oxygen bonds of lignin. This transition state involves the cleavage of etheric bonds by the in situ transfer of hydrogen from ethanol to this linkage.

One-step pyrolysis of lignin and polyvinyl chloride for synthesis of porous carbon and its application for toluene sorption

The aim of this work aims to synthesize the high performance porous carbons from lignin and rice husk (RH) via one-step pyrolysis with KOH and PVC. And those porous carbons were evaluated for toluene sorption. The unactivated biochars had ultralow specific surface area (SBET). By co-pyrolysis of biomass with KOH, the SBET of bio-carbon was significantly improved. The addition of PVC can further enhance the SBET. Additionally, the SBET of lignin-carbons was higher than that of RH-carbons. It was attributed to the destruction of pore structures in the RH chars with high salts by the washing process. Compared with the RH carbons, the lignin carbons had a higher micro-porosity. As for toluene sorption, the maximum breakthrough time (2195 min) and sorption capacity (263.4 mg g−1) were achieved using LPKC. The textural properties (e.g., pore volume, micro-porosity, and hierarchically porous structure) can take significant effects on the sorption process.

Comprehensive Kinetic Study on the Pyrolysis and Combustion Behaviours of Five Oil Palm Biomass by Thermogravimetric-Mass Spectrometry (TG-MS) Analyses

Thermochemical conversion process is one of the most promising routes to harness the potential of oil palm biomass as renewable energy alternative in Malaysia. Despite this potential, there is a lack of comprehensive study that characterises the complete spectrum of oil palm biomass. In this work, thermogravimetric-mass spectrometry (TG-MS) results of five oil palm biomass, i.e., oil palm trunk (OPT), palm kernel shell (PKS), oil palm frond (OPF), mesocarp fibre (MF) and empty fruit bunch (EFB), in pyrolysis and combustion conditions are presented and analysed. Kinetic studies on the TG data of these biomass were performed using Coats–Redfern integral method and Sestak–Berggren function to determine the activation energy and the reaction mechanism at different thermal decomposition stages. Pyrolysis of hemicellulose, cellulose, and lignin occurs at 140–331, 235–435, and 380–600 °C, respectively, while combustion of hemicellulose, cellulose, and lignin took place at 140–313, 225–395, and 372–600 °C, respectively. The activation energy was the highest for cellulose decomposition in both pyrolysis and combustion cases. Phase boundary reaction dominated during hemicellulose and cellulose decompositions, while nucleation dominated during lignin decomposition and char oxidation. MS results show that majority of the gases came out between 250 and 600 °C, mainly from CH4 and H2O in pyrolysis case and from CH4, CO2 and H2O in combustion case. Other than these major gases, NO, NO2 and SO2 were also generated although in much lower proportion compared to these gases. Based on TG-MS results, the best potential application for each biomass was also identified where OPT and OPF are suggested for gasification and fermentation, PKS for bio-char production and combustion, MF for bio-oil production, combustion, and bio-char production and EFB for bio-oil and bio-char production.

Catalytic hydropyrolysis of lignin: Suppression of coke formation in mild hydrodeoxygenation of lignin-derived phenolics

Lignin, with its polyaromatic structure and as a main component of lignocellulosic biomass, is considered as an important renewable source of aromatics which are currently obtained from fossil fuels. Lignin pyrolysis gives a liquid product with a high content of phenolic compounds which can be further upgraded to aromatic hydrocarbons through catalytic approaches. In this work, in-situ catalytic hydropyrolysis combined with a subsequent ex-situ catalytic hydrodeoxygenation step was implemented to achieve an enhanced conversion of kraft lignin into aromatic hydrocarbons. The main point is that the ex-situ catalytic upgrading was conducted at mild conditions (temperature: 350 °C; pressure: 1 atm). HY was used as in-situ catalyst for enhanced decomposition of lignin. Fe/HBeta, FeReOx/MCM-41, Fe/ZrO2 and FeReOx/ZrO2 were used as ex-situ catalyst, among which the oxophilic, mesoporous and mild-acidic catalyst of FeReOx/ZrO2 revealed the highest HDO efficiency. Importantly, FeReOx/MCM-41, Fe/ZrO2 and FeReOx/ZrO2 led to significantly lower yield of coke compared to a zeolite-supported catalyst like Fe/HBeta. This suppression of coke formation is a result of reduced phenolic trapping inside catalyst mainly due to the mesoporosity and moderate acid strength of catalyst.

Electrocatalytic Upgrading of Phenolic Compounds Observed after Lignin Pyrolysis

Lignin valorization is increasingly important as biomass fractionation approaches achieve higher technology readiness levels. One approach to upgrade lignin first involves its deconstruction by fas...

Effect of volatiles interaction during pyrolysis of cellulose, hemicellulose, and lignin at different temperatures

Secondary reactions, including those caused by the interaction of volatiles, are unavoidable during biomass pyrolysis. This study investigated the interactions of the volatiles from cellulose, hemicellulose, and lignin in a two-stage fixed bed reactor without a pre-mixed feedstock. The yield distribution of the products and gases, and the composition of liquids were all affected by the interaction of the volatiles. The interactions increased the gas yield but inhibited the liquid yield. However, when temperature increased, the interactions weakened in the presence of cellulose but increased when hemicellulose and lignin were used. Independent of feedstock, the interactions also generated CO2 and H2 at 400–700 °C and inhibited the generation of CH4 and phenols below 500 °C and 400–700 °C, respectively. However, several feedstock-dependent interactions were also observed: 1) CH4 generation increased at temperatures above 600 °C in the presence of lignin volatiles; 2) both hemicellulose and lignin volatiles resulted in significant amounts of cellulose-derived sugars at temperatures above 500 °C; and 3) hemicellulose volatiles increased decomposition of cellulose volatiles, while the latter inhibited the decomposition of lignin volatiles, when the temperature was below 500 °C.

Effects of heating rate and gas atmosphere on the pyrolysis and combustion characteristics of different crop residues and the kinetics analysis

Abstract Efficient utilization of crop residues can help to solve the problem of global resource scarcity. The pyrolysis and combustion characteristics of 40 crop residues and 3 lignocellulosic components in different atmospheres by thermogravimetric analysis were analyzed. The results showed that with the increase of heating rate, the pyrolysis and combustion of cellulose, hemicelluloses, lignin and crop residues shifted to higher temperature zones. Meanwhile, the comprehensive combustibility index increased significantly, indicating that a higher heating rate could intensify and improve the pyrolysis and combustion performances. At the heating rate of 20 °C/min, the variation ranges of ignition temperatures of crop residues in N2, air and O2 were 253–295 °C, 247–275 °C and 245–268 °C, and the variation ranges of burnout temperatures were 555–682 °C, 466–596 °C and 323–357 °C, respectively. The comprehensive combustibility index in O2 was 144.24 × 10−7, which were much higher than those in air and N2. The variation ranges of activation energies of crop residues were 25.52–36.84, 27.96–43.35 and 41.07–69.35 kJ/mol in N2, air and O2 at 20 °C/min, respectively, and the combustion of crop residues in O2 is the most intense. Overall, rape stalk showed the best comprehensive pyrolysis and combustion performance, and rice straw was the poorest.

Co-pyrolysis of lignin and polyethylene with the addition of transition metals - Part I: Thermal behavior and kinetics analysis

In order to realize a promissing disposal of solid wastes, especially for biomass and plastics, and the recovery of high value-added products, lignin (LG) and polyethylene (PE) were co-pyrolyzed with the addition of transition metals. Thermal behavior and kinetics of the mixtures affected by the type of transition metals (0.5 mmol/g Ni, Co, Fe and Mn), the concentration of Ni (0–1 mmol/g Ni), the ratio of LG to PE (4:1-1:4) and heating rate (10–40 °C/min) were investigated according to thermogravimetric analysis (TGA). It is found that the treatment of LG/PE with 0.5 mmol/g Ni, Co, Fe or Mn results in the decrease of the initial decomposition temperature of LG and PE in the mixture by 10–53 °C and 9–18 °C, respectively. According to the difference of weight loss (ΔW), the introduction of Fe and Mn has slight influences on the interaction between LG and PE while a negative effect of PE on the devolatilization of LG in LG/PE can be largely diminished with the involvement of Ni and Co. Kinetic analysis reveals that the pyrolysis of LG and PE can be well fitted by a single first order model reaction while two consecutive first order model reactions are needed to exactly describe the co-pyrolysis of LG/PE with or without transition metals. The E value of LG and PE in the mixture is reduced by 6.11–21.62 kJ/mol and 7.67–50.11 kJ/mol, respectively, when 0.5 mmol/g Ni, Co, Fe or Mn was involved. Moreover, the concentration of Ni, the ratio of LG to PE and the heating rate play important roles on the thermal behavior and kinetics of the co-pyrolysis of LG/PE.

Influence of calcination temperature for LaTi0.2Fe0.8O3 on catalytic pyrolysis of bagasse lignin

LaTi0.2Fe0.8O3 (LTF) was prepared by the sol-gel method, and the effects of calcination temperature on the structure and properties were investigated. A new method of preparing aryl oxygen-containing compounds from bagasse lignin (BL) by the catalytic pyrolysis over LTF was proposed. The results show that LTF has cubic crystal phase and porous structure and its optimal calcination temperature is 800 °C (LTF-800). In the test for catalytic pyrolysis of BL, with the addition of LTF-800, the yield of liquid product reaches the maximum; the contents of phenolics, guaiacols, syringols, phenylates and furans increase obviously, while those of benzenes, esters and carboxylic acid decrease. The total content of aryl oxygen-compounds (including phenolics, guaiacols, syringols and phenylates) in liquid product is more than 74 wt% with the addition of LTF-800, larger than that obtained by single BL pyrolysis (62 wt%). LTF could avoid oxygen-containing functional groups from being excessively destroyed. It has nice regeneration performance by controlled combustion of char even after 5 cycles.

OH-Initiated Reactions of p-Coumaryl Alcohol Relevant to the Lignin Pyrolysis. Part I. Potential Energy Surface Analysis ⊥.

Cinnamyl alcohols such as p-coumaryl alcohol ( p-CMA) are lignin models and precursors (monolignols) and the most important primary products of lignin pyrolysis. However, the detection of monomers is not straightforward since they either undergo secondary transformations or repolymerize to contribute to the char formation. Both concerted-molecular and free-radical pathways are involved in these processes. Our recent fundamentally based theoretical and low-temperature matrix-isolation-EPR studies of cinnamyl alcohols highlighted the role of side-chain reactivity in diversity of pyrolysis products and provided a network of the chemically activated H + p-CMA reactions ( Asatryan J. Phys. Chem. A, 2017 , 121 , 3352 - 3371 ). The readily available hydroxyl radicals also can trigger a cascade of free-radical processes. Here, we present a comprehensive potential energy surface (PES) analysis of the OH + p-CMA reaction using various DFT and ab initio protocols. Since the p-CMA involves both an alkyl OH-group and a side-chain double bond, the title reaction can also serve as a relevant model for reactions of unsaturated alcohols with hydroxyl radicals to form various oxygenates including polyhydric alcohols which are abundant in nature. The newly identified pathways suggest certain alternatives to the known radical reactions. Of particular interest are the roaming-like low-energy dehydration reactions to generate a variety of O- and C-centered intermediate radicals, which are primarily transformed into the phenolic compounds observed in pyrolysis experiments. Several concerted unimolecular decomposition pathways for p-CMA are also revealed, not considered previously, such as the migration of terminal OH-group, and/or its splitting over the ipso-C and ortho-C atoms of the benzene ring to form bicyclic oxispiro- and chromene compounds represented in natural lignin.

Production of an upgraded lignin-derived bio-oil using the clay catalysts of bentonite and olivine and the spent FCC in a bench-scale fixed bed pyrolyzer

Lignocellulosic biomass is an abundant renewable energy source that can be converted into various liquid fuels via thermochemical processes such as pyrolysis. Pyrolysis is a thermal decomposition method, in which solid biomass are thermally depolymerized to liquid fuel called bio-oil or pyrolysis oil. However, the low quality of pyrolysis oil caused by its high oxygen content necessitates further catalytic upgrading to increase the content of oxygen-free compounds, such as aromatic hydrocarbons. Among the three different types of lignocellulosic biomass components (hemicellulose, lignin, and cellulose), lignin is the most difficult fraction to be pyrolyzed because of its highly recalcitrant structure for depolymerization, forming a char as a main product. The catalytic conversion of lignin-derived pyrolyzates is also more difficult than that of furans and levoglucosan which are the main pyrolysis products of hemicellulose and cellulose. Hence, the main purpose of this study was to develop a bench-scale catalytic pyrolysis process using a tandem catalyst (both in-situ and ex-situ catalysis mode) for an efficient pyrolysis and subsequent upgrading of lignin components. While HZSM-5 was employed as an ex-situ catalyst for its excellent aromatization efficiency, the potential of the low-cost additives of bentonite, olivine, and spent FCC as in-situ catalysts in the Kraft lignin pyrolysis at 500 °C was investigated. The effects of these in-situ catalysts on the product selectivity were studied; bentonite resulted in higher selectivity to aromatic hydrocarbons compared to olivine and spent FCC. The reusability of HZSM-5 (with and without regeneration) was examined in the pyrolysis of lignin mixed with the in-situ catalysts of bentonite, olivine, and spent FCC. In the case of using bentonite and spent FCC as in-situ catalysts, there were no obvious changes in the activity of HZSM-5 after regeneration, whereas using olivine as in-situ catalyst resulted in a remarkable decrease in the activity of HZSM-5 after regeneration.

Hydrotreatment of pyrolytic lignins to aromatics and phenolics using heterogeneous catalysts

The pyrolysis of lignocellulosic biomass generates a liquid product, known as pyrolysis oil, that can be further processed into biofuels and value-added chemicals. During pyrolysis, cellulose and hemicelulose fractions are converted into a range of water-soluble sugar derivatives, for which several valorisation strategies exist. On the other hand, lignin is broken down into so-called pyrolytic lignin, a water-insoluble complex mixture of aromatic oligomers that requires different upgrading strategies than the sugar rich fraction. Here, we report an experimental study on the valorisation of pyrolytic lignin via catalytic hydrotreatment in the absence of an external solvent. A variety of carbon-supported noble-metal heterogeneous catalysts were tested (Ru/C, Pd/C, Pt/C and Rh/C), as well as conventional hydrotreatment catalysts (sulphided NiMo/Al2O3 and CoMo/Al2O3) to obtain valuable low molecular weight aromatic and phenolic compounds. Overall, depolymerized liquids were obtained with organic yields of up to 63 wt%. Pd/C was shown to be the best catalyst, yielding 59 wt% of monomers based on the organic product (i.e. 33 wt% based on pyrolytic lignin intake). While noble metal catalysts favored higher monomer yields, though with some over-reduction of aromatic rings to saturated hydrocarbons, sulphided catalysts were more efficient in deoxygenation and aromatization reactions, but yielded less monomers. The hydrocracking efficiency was shown to be strongly dependent on the reaction temperature. Based on the experimental data, a global reaction network is proposed. The high monomer yields reveal the potential of catalytic hydrotreatment for the upgrading of pyrolytic lignin into valuable phenolics and aromatics.

CO2 as a reaction medium for pyrolysis of lignin leading to magnetic cobalt-embedded biochar as an enhanced catalyst for Oxone activation

Carbonaceous materials have been proven as advantageous supports for anchoring cobalt (Co) nanoparticles (NPs) to formulate Co/carbon composite catalysts for Oxone activation in degrading pollutants in water. While Co/carbon composites represent attractive catalysts, most carbonaceous supports are usually sophisticatedly fabricated using fine chemicals and immobilization of Co on carbon supports requires complicated post-modifications. As biochar appears as a versatile but easily-accessible carbon, pyrolysis of Co/lignin can result in a promising Co/biochar (CoBC) catalyst for Oxone activation. Especially, when CO2 is used to replace N2 as a reaction medium for pyrolysis of Co/lignin, the syngas production from pyrolysis can be enhanced and a magnetic CoBC is also obtained. This CoBC appears as a micro-sized composite of Co nanoparticles (NPs) well-distributed and embedded within carbon matrices, and exhibits several advantageous properties, such as high porosity, large surface area and magnetism, making it an advantageous catalyst for activating Oxone in water. As decolorization of Amaranth (AMR) dye is employed as a model test, CoBC successfully activates Oxone to fully decolorize AMR within 60 min with a rate constant of 0.33 min−1. CoBC also exhibits a much higher catalytic activity than CoBC prepared from pyrolysis in N2, and Co3O4, revealing its promising advantages. The activation energy of AMR decolorization by CoBC-activated Oxone is 48 kJ/mol, which is also lower than those reported in other studies. CoBC can be also re-used to activate Oxone over multiple cycles. These findings validate that CoBC is certainly a promising heterogeneous catalyst, which can be simply prepared from pyrolysis of Co/lignin in CO2 with concomitant enhanced syngas production.

Valorization of Pyrolysis Liquids: Ozonation of the Pyrolytic Lignin Fraction and Model Components

Pyrolytic lignin is the collective name of the lignin-derived fraction of pyrolysis liquids. Conversion of this fraction to biobased chemicals is considered an attractive valorization route. Here we report experimental studies on the ozonation of a pine-derived pyrolytic lignin dissolved in methanol (33 wt %). Results show a high reactivity of ozone, and a molecular weight reduction of up to 40% was obtained under mild conditions (0 °C, atmospheric pressure) without the need for catalysts. Detailed analysis of the product mixtures (GC/MS-FID, HPLC, GPC, NMR) showed the presence of low molecular weight (di)acids and esters, along with larger highly oxygenated aliphatics. A reaction network is proposed including the heterolytic cleavage of aromatic rings, followed by secondary reactions. The observations were supported by experimental studies using representative pyrolytic lignin model compounds and a biosynthetic lignin oligomer, which aided further elucidation on the reactivity trends for different chemic...