Catalytic Pyrolysis Of Lignin Research Articles

Presence of oxygen in catalytic pyrolysis of lignin impacts evolution of both coke and aromatic hydrocarbons

Coking is a major issue in catalytic pyrolysis of biomass over zeolite catalysts. Using oxidative gas might mitigate formation of carbonaceous deposits. This was verified herein by catalytic pyrolysis of lignin with different oxygen concentrations (0 %, 3 %, 6 %, 9 % and 12 %) in carrier gas using ZSM-5 as the catalyst at 600 °C. The results indicated that the O2 introduced oxidized both volatiles and biochar, reducing bio-oil yield from 29.2 to 20.7 % and biochar yield from 56.8 to 53.7 % with increasing O2 concentration from 0 to 12 %. Oxidation of intermediates in “hydrocarbon pool” on surface of catalyst decreased the yield of BTX from 11.5 % in inert gas to 6.1–8.0 % and also other aromatics with 1 or 2 benzene rings. The aromatics with rigid polycyclic aromatic structures were more resistant towards oxidation. However, toluene, xylene, and other aromatic hydrocarbons or phenolics with side chains were more prone to be oxidized, abundance of which decreased more significantly at high O2 concentrations. Such results were also observed in catalytic pyrolysis of guaiacol or vanillin. The benefit of using O2 was diminished formation of coke and/or precursors of coke over ZSM-5. Characterization of reaction intermediates in catalytic pyrolysis of lignin with in-situ IR showed that O2 presence remarkably decreased the abundance of aliphatic intermediates containing –OH, -C-H and C=O through oxidation reactions and also interrupted aromatization organics in both coke and biochar.

Characterization of the decomposition behaviors of catalytic pyrolysis of alkaline lignin with the addition of different concentrations of potassium

Investigating the influence of potassium concentration on alkali lignin pyrolysis is beneficial for advancing the technology of biomass catalytic pyrolysis. This study examined the catalytic effects of different concentrations of various potassium compounds on alkali lignin pyrolysis. The impregnation method was employed to load potassium compounds (KCl, K2CO3, and CH3COOK) onto alkali lignin at varying concentrations. The results showed a significant influence of potassium concentration on the catalytic pyrolysis of lignin. Increasing the potassium concentration resulted in higher pyrolysis char yield and lower pyrolysis gas yield. Furthermore, the pyrolytic char with a high concentration of potassium exhibited a distinct surface pore structure that was noticeably eroded by potassium. Furthermore, with an increase in potassium concentration, the removal of side chains, including methoxy, acetyl, and hydroxyethyl groups, became increasingly pronounced, resulting in higher yields of CO2 and phenol. The elevated potassium concentration facilitated the depolymerization of lignin through Cβ-O bond cleavage, promoted the decomposition of intermediate products, and enhanced the formation of small molecule products. Ultimately, a hypothetical mechanism explaining the influence of potassium concentration on alkali lignin pyrolysis was proposed. This study establishes a scientific foundation for the high-value utilization and resource development of alkaline lignin.

Jet fuel range hydrocarbon generation from catalytic pyrolysis of lignin and polypropylene with iron-modified activated carbon

In this study, iron was used to modify pyrolytic activated carbon (AC) to synthesize a bifunctional catalyst (Fe/AC). It was applied to the catalytic co-pyrolysis of lignin with polypropylene (PP) for the preparation of jet fuel range hydrocarbons. Relationships between iron loading, reaction temperature, catalyst/feedstock ratio, and lignin/PP ratio were investigated in connection to the yield, component distribution, carbon number distribution, and chain structure of pyrolysis products. The results indicated that the hydrocarbons with carbon numbers in the jet fuel range dominated the products obtained from the catalytic co-pyrolysis of lignin and polypropylene. Owing to the oxytropism of Fe3 + , the selectivity of oxygenated chemicals in pyrolysis oil decreased as the Fe loading rose. Consequently, the production of hydrocarbons in the jet fuel range was increased. Furthermore, the deoxygenation and alkylation reactions of phenols to high-carbon aromatics were facilitated by Fe3 + . The cyclization and dehydrogenation reactions were promoted with the reaction temperature increased, thus enhancing the selectivity of cyclic hydrocarbons (cycloalkanes and aromatics) in the jet fuel range. However, secondary reactions were boosted with the excessive temperature, reducing the yield of hydrocarbons and the percentage of high-carbon hydrocarbons in the jet fuel range. The reduction of the proportion of oxygenated compounds was facilitated by the use of catalysts. Thus, the selectivity of hydrocarbons in the jet fuel range was improved, but the yield of high-carbon hydrocarbons would be reduced. In addition, the cleavage of PP-derived chain hydrocarbons was promoted by the hydrogen abstraction reaction of lignin-derived oxygenates during co-pyrolysis. The hydrogen transfer reaction between hydrocarbons and phenols was enhanced, it was pushed for phenols to convert to aromatics. Thus, the yield of hydrocarbons in the range of jet fuel was improved. A new approach to the efficient application of lignin with PP might be offered by the current work.

In-situ synthesis of micro/mesoporous HZSM-5 zeolite for catalytic pyrolysis of lignin to produce monocyclic aromatics

Catalytic pyrolysis of lignin is a promising way for lignin upgrading. To date, commercial zeolites have been demonstrated to be active in lignin catalytic pyrolysis for monocyclic aromatics production, but usually exhibit low selectivity and fast deactivation during reaction. These are mainly attributed to the inadequate of mesoporous structure and improper acidic property of commercial zeolites. Herein, HZSM-5 zeolites with different micro/mesoporous morphology were synthesized via the green and energy-efficient in-situ synthesis method. The porous structure of the zeolites was regulated by adjusting the synthesis conditions, i.e., the concentration of tetrapropylammonium hydroxide (TPAOH, used as the microporous templating agent), the synthesis temperature, and synthesis duration. With the HZSM-5 sample synthesized under the optimal condition (S8HZ), the relative content of monocyclic aromatics achieved during lignin catalytic pyrolysis reached 39.3 % at 500 °C, which was much higher than that attained over the commercial HZSM-5 (17.3 %). In addition, the acidic property and pore structure of the S8HZ catalyst was further modulated by cobalt impregnation. The introduction of cobalt, rendered a good balance between the structural property and acidity of the catalyst, which eventually facilitated the generation of monocyclic aromatics by both improving mass transfer and reducing coke formation. As it turned out, 1 wt% of cobalt introduction to the S8HZ boosted the generation of monocyclic aromatics to 46.3 % at 550 °C. Moreover, the catalyst retained good stability in catalytic lignin pyrolysis after 10 reaction cycles. Overall, this work demonstrates the feasibility of using in-situ synthesized HZSM-5 catalyst with rich micro/mesoporous structure as well as Co modification for catalytic lignin upgrading to monocyclic aromatics, which offers new insights for lignin upgrading via catalytic pyrolysis.

Integral techno-economic comparison and greenhouse gas balances of different production routes of aromatics from biomass with CO2 capture

The techno-economic performance and CO2 equivalent (CO2eq) reduction potential of bio-based aromatic production cases with and without CO2 capture and storage (CCS) have been evaluated and compared to those of fossil-based aromatic production. The bio-cases include tail gas reactive pyrolysis (TGRP), catalytic pyrolysis (CP), hydrothermal liquefaction (HTL), gasification-methanol-aromatics (GMA), and Diels-Alder of furan/furfural combined with catalytic pyrolysis of lignin (FFCA). The crude oil-based naphtha catalytic reforming (NACR) routes have GHG emissions of 43.4 and 43.9 t CO2eq/t aromatics with and without CCS (NACR-CCS), respectively. Except for HTL, all the biomass cases with CCS show negative emissions between −6.1 and −1.1 t CO2eq/t aromatics with avoidance costs ranging from 27.7 to 93.3 $/t CO2eq. Under favorable conditions, GMA with CCS (GMA-CCS) has the lowest emissions (−14.6 t CO2eq/t aromatics), while CP with CCS (CP-CCS) shows the lowest avoidance cost (12.3 $/t CO2eq). All biomass based aromatics production techniques are currently at the laboratory or demonstration stages, except for CP, which has pilot plants. The results indicate that bio-based aromatics production, with their reasonable avoidance costs and low, or potentially negative, greenhouse gas (GHG) emissions, are an attractive option to compensate for the expected aromatic production shortages in the coming decades.

Improving catalytic production of aromatic hydrocarbons with a mesoporous ZSM-5 modified with nanocellulose as a green template

ZSM-5 is an important class of acid catalyst for producing bio-oil rich in petrochemicals; however, continuous efforts are required to improve the conversion efficiency of the biomass-derived oxygenates with large molecular sizes. The mesoporous ZSM-5 (N-ZSM-5) was prepared in a post-treatment method with nanocellulose as a green template in this study to induce additional surface and porous features. The post-treatment promoted the mesoporous properties in N-ZSM-5, which effectively converted lignocellulosic biomass to deoxygenated aromatic products in catalytic pyrolysis. Moreover, compared to the conventional or alkali-treated mesoporous ZSM-5, higher selectivity of monocyclic aromatic hydrocarbons (MAHs) was attained in catalytic pyrolysis of lignin while mitigating the coke accumulation. The product distribution was evaluated using the response surface methodology with reaction temperature (°C) and catalyst loading (g/g feedstock). The compositions of upgraded volatile products measured MAHs (~46.55 area%) and monophenols (~98.09 area%) depending on the process conditions.

Catalytic pyrolysis of lignin with metal-modified HZSM-5 as catalysts for monocyclic aromatic hydrocarbons production

This work aimed to investigate the feasibility of using metal-modified (Fe, Co, Ni, Cu, Zn, Ga) HZSM-5 zeolite as catalysts for high-value monocyclic aromatic hydrocarbons production via lignin catalytic pyrolysis in a two-stage fixed bed reactor. The structure-performance relationship of the catalysts was revealed based on the catalytic reaction testing results along with the acidity and textural properties obtained via systematic physicochemical characterization techniques, thus guiding the selection of the best modification metal and the optimal loading amount. As demonstrated, the 1 wt% Co modified HZSM-5 (1%Co-HZ) exhibited relatively slight coverage effect on the active sites, while increased the mesoporous surface area and average pore size of the parent HZSM-5 zeolite. Consequently, enhanced mass-transfer efficiency was attained by the 1%Co-HZ catalyst, which achieved the highest monocyclic aromatic hydrocarbons content (29.3%) among all the investigated metal-modified HZSM-5 catalysts. In addition, the Co modified sample showed better resistance to carbon deposition than that of the unmodified one. Overall, 1%Co-HZ can be used as an effective catalyst for monocyclic aromatic hydrocarbons production in lignin catalytic pyrolysis.

Catalytic pyrolysis of lignin over ZSM-5, alkali, and metal modified ZSM-5 at different temperatures to produce hydrocarbons

Temperature and catalyst type greatly influence the chemical processes as well as the quality of the pyrolysis products. Catalytic fast pyrolysis (CFP) of lignin isolated from rice straw using three different catalysts was performed at different pyrolysis temperatures (450, 500, 550, and 600 °C) using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) to explore the suitable catalytic performance for hydrocarbon production. The shape selectivity and acidity of the three catalysts (ZSM-5, NaOH-modified ZSM-5 (0.4 M), and nickel modified ZSM-5 (8 wt.%)), showed a substantial effect on the product distribution during CFP of lignin. Ni-ZSM-5 (8 wt.%) demonstrated effective performance for the transformation of oxygenated compounds through demethoxylation and dehydroxylation into aromatics. The most suitable pyrolysis temperature for catalytic pyrolysis of lignin was 550 °C in which a maximum selectivity of 72% for hydrocarbon was obtained over Ni-ZSM-5 (8 wt.%) followed by ZSM-5 (0.4 M) and ZSM-5. This research provides a suitable pyrolysis temperature and catalyst for high hydrocarbon production from catalytic pyrolysis of lignin.

Influence of the Porosity and Acidic Properties of Aluminosilicate Catalysts on Coke Formation During the Catalytic Pyrolysis of Lignin

Influence of the Porosity and Acidic Properties of Aluminosilicate Catalysts on Coke Formation During the Catalytic Pyrolysis of Lignin

Experimental study on catalytic pyrolysis of lignin under char and ZSM-5 for preparation of aromatics

In order to improve yield of aromatics from catalytic pyrolysis of lignin, alkali lignin was used for rapid pyrolysis experiments under a binary catalysis system of alkali lignin char and ZSM-5. Influence of catalyst ratio and pyrolysis temperature as well as pyrolysis time on aromatics quantity and mechanism of synergistic catalysis of alkali lignin char and ZSM-5 were investigated. The results show that quantity of aromatics has increased from 17 mg/g (without char) to 33 mg/g (with char addition of 1g), which is about doubled. The optimal conditions for preparation of aromatics are under alkali lignin: alkali lignin char: ZSM-5=1:1:1 at 500°C for 10 min. Meanwhile, the mechanism analysis shows that alkali lignin char mainly plays a role in bond breaking during pyrolysis, while ZSM-5 can act as selective aromatization to obtain higher aromatics yield, whose synergistic effects result in higher aromatic yield.

Catalytic Pyrolysis Mechanism of β-O-4 Type of Lignin Dimer: The Role of H Proton

In the preparation of monocyclic benzenes by catalytic pyrolysis of lignin, how to break the bonds of pyrolysis macromolecules into small molecules is the key point for the transformation. In this ...

Renewable aromatic hydrocarbons production from catalytic pyrolysis of lignin with Al-SBA-15 and HZSM-5: Synergistic effect and coke behaviour

With a focus on converting waste to energy, this study integrated the macromolecular reaction ability of Al-SBA-15 and the shape selectivity of HZSM-5 for the production of renewable aromatic hydrocarbons. Results demonstrated that the catalytic pyrolysis of lignin with both Al-SBA-15 and HZSM-5 was able to improve the mono-aromatic hydrocarbons (MAHs) production while inhibiting the formation of undesirable poly-aromatic hydrocarbons (PAHs), thus controlling the MAHs and PAHs content in the bio-oil. At optimal operation conditions (pyrolysis temperature: 550 °C, Al-SBA-15/HZSM-5 ratio: 1:3), the MAHs content was 42.57% higher than that catalyzed by HZSM-5 only (28.30%). The PAHs content was only 27.13%. Typical MAHs (benzene, toluene and xylene, denoted as BTX) and PAHs selectivities were determined as 55.91% and 38.92%, respectively. Thermogravimetry-differential thermogravimetric (TG-DTG) analysis indicated that the used HZSM-5 was principally composed of graphite-like coke and a negligible content of fibrous-like coke. The coke content was observed as 5.65% compared to 10.52% in the HZSM-5 only. Furthermore, the efficient synergistic effect of Al-SBA-15 and HZSM-5 resulted in the deep conversion and directional reforming of the lignin pyrolysis vapors. This study can promote the high-grade utilization of lignin through the application of feasible fixed-bed catalytic pyrolysis technology.

The Effect of Ni-ZSM-5 Catalysts on Catalytic Pyrolysis and Hydro-Pyrolysis of Biomass.

With the demand of energy and re-utilization of wastes, the renewable lignocellulosic biomass, has attracted increasing and significant attention for alleviating the growing energy crisis and environment problems. As main components of lignocellulosic biomass, lignin, cellulose, and hemicellulose are connected by hydrogen bond to form a compact skeleton structure, resulting the trenchant condition of biomass pyrolysis. Also, pyrolysis products of above three main constituents contain a large amount of oxygenates that cause low heating value, high corrosiveness, high viscosity, and instability. Meanwhile, zeolites are of considerable significance to the conversion of lignocellulosic biomass to desirable chemical products on account of fine shape selectivity and moderate acid sites and strength. Among numerous zeolites, ZSM-5-based catalysts have been most extensively studied, and the acidity and porosity of ZSM-5 can be tuned by changing the content of Si or Al in zeolite. Beyond that, doping of other metal elements, such as Mn, Co, Ni, Ga, Ce, Pt, into ZSM-5 is also an efficient way to regulate the strength and density of acid sites in zeolite precisely. This review focused on the recent investigation of Ni-modified microporous ZSM-5 used in catalytic pyrolysis of lignin and cellulose. The application of metal-modified hierarchical ZSM-5 is also covered.

The Threshold Photoelectron Spectrum of Fulvenone: A Reactive Ketene Derivative in Lignin Valorization.

Unveiling reaction mechanisms by isomer-selective detection of reactive intermediates requires advanced spectroscopic knowledge. We study the photoionization of fulvenone (c-C5 H4 =C=O), a reactive ketene species relevant in catalytic pyrolysis of lignin, which was generated by pyrolysis of 2-methoxy acetophenone. The high-resolution threshold photoelectron spectrum (TPES) with vacuum ultraviolet synchrotron radiation revealed well-resolved vibrational transitions, assigned to ring deformation modes of the cyclopentadiene moiety. The adiabatic ionization energy was determined to be 8.25±0.01 eV and is assigned to the 2 A2 ← 1 A1 transition. A broad and featureless band arising at 9 eV is associated with the 2 B1 ← 1 A1 excitation. A conical intersection is responsible for the ultrafast relaxation of the fulvenone cation from the into the state resulting in a featureless and lifetime broadened band. These insights will increase the detection capabilities for fulvenone and thereby help to elucidate reaction mechanisms in lignin catalytic pyrolysis.

Catalytic Effect of Alkali and Alkaline Earth Metals in Lignin Pyrolysis: A Density Functional Theory Study

Catalytic pyrolysis is a promising technology for the production of renewable fuels and chemicals from lignin. The yield of aromatic compounds from the catalytic pyrolysis of lignin is significantl...

Preparation of graphene by catalytic pyrolysis of lignin and its electrochemical properties

The lignin residue produced by straw fermentation or straw acid hydrolysis is used as a carbon source to synthesize graphene. After adding tetrahydrofuran as a modifier and Fe(NO3)3 as a catalyst to lignin for pretreatment, the resulting product was heat treated at 900℃ for 3 h. The prepared graphene was characterized by XRD, Raman, HRTEM, and the electrochemical properties of the prepared graphene also were tested. The results of this study open up a new way for the efficient preparation of graphene based on renewable resources lignin. The prepared lignin-based graphene was used for electrochemical testing and found to be a good electrode material for super capacitors.

Microwave-Assisted Catalytic Conversion of Lignin to Liquid Products

The catalytic pyrolysis of lignin under microwave (MW) irradiation in the presence of iron-containing systems deposited directly on the lignin surface from various precursors has been studied using iron acetylacetonate, diacetylferrocene, and potassium trioxalatoferrate(III) as the precursors. The study has been focused on the effect of the argon eluent gas flow rate (300–60 mL/min) on the yield of the liquid product fraction. The effect of the gaseous medium (Ar, H2/Ar, O2/Ar) on the yield of liquid products formed by MW treatment has been studied. It has been shown that a maximum yield of liquid products is achieved in a medium of the inert gas argon or in a hydrogen/argon mixture (33 or 36%), whereas this yield in an oxygen/argon mixture is twofold lower (17%). The gas chromatography–mass spectrometry method has been used to determine the qualitative composition of the liquid product fraction, which is mostly represented by phenol and anisol, the derivatives of the monomeric units of lignin (coumaryl and coniferyl alcohols). In studying the effect of the iron precursor deposited on the lignin surface, it has been found that the liquid yield increases twofold from 18 to 36 or 34% in the presence of iron acetylacetonate Fe(C5H7O2)3 or potassium trioxalatoferrate K3[Fe(C2O4)3] ⋅ 3H2O, respectively, at a feed gas flow rate of 300 mL/min and a temperature of 700°C.

Catalytic pyrolysis of lignin using low-cost materials with different acidities and textural properties as catalysts

Catalytic fast pyrolysis of lignin was performed using low-cost materials with different acidities and textural properties as catalysts in the present work. The main focus is to understand the role of low-cost catalysts in the fast pyrolysis of lignin. The four most commonly used low-cost catalysts, ilmenite (FeTiO3), bentonite (Al-Si-OH), activated carbon (AC) and red mud (RM), were selected. The results show that bentonite, red mud and activated carbon effectively enhance the dehydration reaction, which is regarded as the dominant way to eliminate oxygen during the pyrolysis process, due to the existence of strong acidic sites. However, only activated carbon is found to be effective in promoting the production of monocyclic aromatic hydrocarbons (MAHs). Two metallic catalysts, i.e., bentonite and red mud, have strong acidities but quite low surface areas and less porous structures. Therefore, the dehydrated intermediates produced are especially easy to repolymerize to form char or coke without the restriction of obtaining a porous structure during the pyrolysis process. Activated carbon has not only a certain acidity but also a rich porous structure. Lignin fast pyrolysis-derived oxygenates can diffuse and react on the well-dispersed active sites within the pores of activated carbons. The catalytic performance of the activated carbon are supposed to be determined by the pore size. Only pores of similar size to lignin fast pyrolysis-derived oxygenates (0.6–1 nm) seems to be effective for the production of MAHs. Pores larger or smaller than lignin fast pyrolysis-derived oxygenates both tend to cause coke deposition rather than MAHs formation.

Catalytic pyrolysis of lignin in a cascade dual-catalyst system of modified red mud and HZSM-5 for aromatic hydrocarbon production

Catalytic pyrolysis of lignin over a dual-catalyst system of modified red mud and HZSM-5 was carried out in a bench-scale micro-reactor. Effects of pyrolysis temperature, modified red mud to HZSM-5 ratio, catalysts to lignin ratio on the yield of products and selectivity of aromatic hydrocarbons were investigated. Results indicated that 550 °C was the optimal pyrolysis temperature with the maximal yield of bio-oil (20.16 wt%). At a modified red mud to HZSM-5 ratio of 1:1, the content of monocyclic aromatic hydrocarbons (MAHs) increased to 41.27% whereas that of polycyclic aromatic hydrocarbons (PAHs) decreased to 22.65%. Likewise, at a catalysts to lignin ratio of 2:1, a higher content of MAHs was produced with a decreased content of PAHs. The cascade dual-catalyst system may serve as an efficient approach to disposing lignin and red mud wastes with significant environmental impact. Besides, this study provides a solution for the valorization of lignin-rich resources.

Catalytic pyrolysis of lignin over hierarchical HZSM-5 zeolites prepared by post-treatment with alkaline solutions

The application of hierarchical HZSM-5 zeolite catalysts in the catalytic fast pyrolysis (CFP) of lignin was investigated using a pyrolyzer coupled with gas chromatography-mass spectrometry (Py-GC–MS). A series of modified HZSM-5 zeolites were prepared by the post-treatment desilication of commercial HZSM-5 zeolite with varying concentrations of sodium hydroxide (NaOH) solutions (0.1 – 0.5 mol/L) and the following solutions: 0.3 mol/L of sodium aluminate (NaAlO2), 0.3 mol/L of sodium carbonate (Na2CO3), and 0.3 mol/L of tetrapropylammonium hydroxide (TPAOH). The catalyst samples were characterized by XRD, XRF, TEM, N2 adsorption–desorption, and NH3-TPD techniques. The crystallinity, the SiO2/Al2O3, the morphology, the pore properties, and the density of acid sites of the HZSM-5 zeolites were changed after alkali treatment. The alkali treatment improved the catalytic performance of HZSM-5 zeolite for cracking bulky oxygenates released from lignin (such as guaiacol, syringol, and their derivatives from the pyrolysis of lignin) to produce aromatic hydrocarbons. The HZSM-5 zeolite treated with 0.3 mol/L NaOH was the optimal choice for the catalytic fast pyrolysis of lignin for producing aromatic hydrocarbons.