Catalytic Pyrolysis Research Articles

Examination of in situ and ex situ catalytic fast pyrolysis and liquid fractionation utilizing a free-fall reactor

This study examines biomass valorization through thermochemical conversion by an integrated catalytic fast pyrolysis process with liquid fractionation using a free-fall reactor, γ-alumina, as a catalyst and methanol for direct quenching. The novelty lies within the process intensification (i.e., a single-step conversion and fractionation pathway) to improve pyrolysis oil yield and quality. In particular, the conversion bioprocess utilizes in situ or ex situ catalytic free-fall fast pyrolysis reactors at 550°C and 10–15 psi to produce pyrolysis oil and char (bio-oil and biochar) from pinewood feedstocks. The results from the gas chromatography–mass spectrometry show that the main volatile fractions of bio-oil compounds are levoglucosan, furfural, hydroxy acetone, methyl acetate, and catechol. The electrospray ionization–mass spectrometry results determine the average molar mass, revealing improved cracking, thermal treatment, and fraction stabilization. The Fourier transform infrared spectroscopy and thermal aging provide insight into the change in functional groups in relation to experimental parameters. The outcomes indicate that γ-alumina successfully decreased acidic compounds and increased esters and phenolic content in the bio-oil. The bio-oil produced from the ex situ catalytic pyrolysis also shows the highest liquid yield (~41%), high phenolic content, and thermally stable properties. The in situ catalytic pyrolysis exhibits lower yields but favors high ketone formation. Fractions condensed in methanol exhibit the highest thermal stability and esterification potential; however, they still possess relatively high amounts of acidic compounds. It is concluded that ex situ catalytic pyrolysis, using γ-alumina catalyst and fractionation with methanol, can improve conversion reactions, particularly bio-oil quality, yield, and thermal stability.

Catalytic Fast Pyrolysis of Biomass over Hierarchical Zeolites: Comparison of Mordenite, Beta, and ZSM-5

Catalytic Fast Pyrolysis of Biomass over Hierarchical Zeolites: Comparison of Mordenite, Beta, and ZSM-5

Kinetics study of catalytic pyrolysis of polystyrene polymer using response surface method

Kinetics study of catalytic pyrolysis of polystyrene polymer using response surface method

Recycling the polyethylene into fuels via an olefin-intermediate tandem catalysis over Fe2O3/USY catalysts

Catalytic pyrolysis of waste plastics using iron-based metal-acid catalysts is a promising waste-to-energy technology to deliver clean renewable fuels. While these catalysts show valid catalytic activity during pyrolysis, their ability to guide tandem reactions over metal and acid sites remains uncertain. In this study, we employ the Fe2O3/USY catalysts to recycle polyethylene (PE) into liquid fuels, and demonstrate the tandem catalysis of the Fe2O3/USY catalysts during PE depolymerization. The highest fuel oil yield obtained was 78.1 % after Fe2O3/USY catalysis (5 % Fe loading, Si/Al ratio = 80). The resulting oil predominantly falls within the gasoline range, with a carbon number distribution rich in C5–C9 range. The oil composition comprises 71.3 % olefins and 16.7 % paraffins, mostly isomeric, while few aromatics were obtained. Comparative experiments confirm that PE depolymerization over the metal and acid sites of Fe2O3/USY catalysts involves an olefin-intermediate tandem pathway: the Fe2O3 enhances olefin-intermediate generation through its dehydrogenation activity, while the USY allows these olefin-intermediates to undergo further cleavage over the acid sites. Although the Fe2O3 loading on USY enhances PE cracking by facilitating olefin-intermediate generation in tandem catalysis, the reduced acidity inhibits PE cracking. Therefore, when aiming for oil production via PE pyrolysis, the delicate balance between reduced acidity and increased dehydrogenation activity after Fe2O3 loading must be taken into account.

Pyrolytic Decomposition of Polyethylene in the Presence of Aluminosilicate Materials Containing Nickel Oxide

The work is devoted to the study of the pyrolysis of high-density polyethylene (PE) in the presence of aluminosilicate materials containing nickel oxide. The process of catalytic pyrolysis of plastics makes it possible to convert polymers into chemical compounds, which can later be used as an additional source of fuels, raw materials for the chemical industry or polymer production. The physicochemical parameters of materials containing nickel oxide have been established using the following methods: IR-Fourier spectroscopy; x-ray diffraction analysis; N2 physical adsorption method; thermogravimetric analysis; pyrolytic gas chromatography. The dependences of the chemical composition of PE pyrolysis products on the type of support used and the presence of nickel oxide. The presence of nickel oxide in the studied aluminosilicates increases the Lewis acidity, which increases the content of aromatic compounds in the pyrolysis products. The activation energy of the PE pyrolysis process in the presence of MCM-41 containing nickel oxide was calculated from experimental data.

Closing the loop: Biochar-supported nickel catalyst for efficient hydrogen-rich syngas production

Thermochemical conversion of agricultural by-products into hydrogen-rich syngas is a technology that offers both economic and environmental benefits. In this work, we investigated a biochar-supported nickel-based catalyst for the catalytic pyrolysis of straw biomass to produce hydrogen-rich syngas. The by-product, straw biochar, was used as a material for synthesizing fresh catalysts, achieving a closed-loop process. We explored gas yields under various conditions. The highest yields of CO and H2, reaching 0.52 L/g and 0.48 L/g, respectively, were obtained under the conditions of a pyrolysis temperature of 900 °C, a residence time of 20 min, a calcination temperature of 400 °C, a nickel loading of 15 wt%, and a citric acid to potassium hydroxide ratio of 1:4. The catalysts were characterized using XRD, H2-TPR, SEM, and TEM. The results demonstrated that biochar provides excellent support and synergy, enabling the catalyst to function at high temperatures and offering antioxidative protection to the active metals during the thermal process. Overall, this catalytic pyrolysis process, aiming for green and efficient conversion, achieved high yields of syngas and hydrogen.

Study on the key influencing factors of KOH-catalyzed coal pyrolysis for direct preparation of carbon nanotubes

The environmental pollution and greenhouse gas emission caused by the traditional utilization of coal such as combustion, coking and gasification are becoming increasingly apparent. Green and environmentally friendly coal utilization technology is an effective way to solve this problem. In this study, high-value carbon nanotubes (CNTs) were directly prepared from coal by catalytic pyrolysis with low KOH content. It was found that when the KOH additive amount was 50 wt%, the influence of three main factors on the preparation of CNTs was as follows: pyrolysis temperature＞residence time＞heating rate. Pyrolysis temperature of 900 °C, heating rate of 15 °C/min, and residence time of 60 min were the best combination of KOH-catalyzed coal pyrolysis to prepare CNTs, and the content of CNTs in the corresponding sample was 10.01 wt%. This study has a specific contributes to the high-value transformation and utilization of coal resources and the preparation of CNTs.

Plastic upgrading via catalytic pyrolysis with combined metal-modified gallium-based HZSM-5 and MCM-41

Plastic upgrading via catalytic pyrolysis with combined metal-modified gallium-based HZSM-5 and MCM-41

Identification of coke species on Fe/USY catalysts used for recycling polyethylene into fuels.

The Fe/USY catalyst used for converting plastic waste into fuels faces coking problems. A comprehensive understanding of coke distribution and structure is crucial for catalyst design, enabling resistance to coke deposition and facilitating regeneration. In this study, we analyze the coke deposition on Fe/USY catalysts after catalytic pyrolysis of polyethylene for fuel oil, and present insights into the coke distribution over the metal and acid sites, as well as its specific molecular structure. The coke distributes over both the metal and acid sites, exhibiting distinct TPO peaks corresponding to metal-site coke (370 °C) and acid-site coke (520 °C). The total coke yields range from 2.0% to 2.4%, with distribution on metal and acid sites dependent on Fe loading and acidity. Structurally, the coke is highly-condensed, containing more than four aromatic rings with limited alkyl groups. The acid-site coke is more condensed than the metal-site coke, showing lower H/C ratios (0.5-0.75) relative to the acid-site coke (0.75-0.9). Identified by MALDI-TOF mass analysis, the predominant molecular structures of the coke located on metal and acid sites are illustrated. The metal-site cokes typically exhibit 4-7 aromatic rings, while the acid-site cokes display even greater condensation with 5-12 aromatic rings.

Obtaining Zeolites from Natural Materials of Volcanic Origin for Application in Catalytic Pyrolysis for the Sustainable Chemical Recycling of Polymers

Obtaining Zeolites from Natural Materials of Volcanic Origin for Application in Catalytic Pyrolysis for the Sustainable Chemical Recycling of Polymers

Syngas production through CO2-assisted catalytic pyrolysis of ethylene vinyl acetate (EVA) with a cobalt-based catalyst

Ethylene vinyl acetate (EVA) is a representative copolymer widely adopted across various sectors owing to its superior physiochemical properties; however, an environmentally benign protocol for the disposal of EVA waste has not yet been established owing to the various ratios of acetate to polyethylene. Therefore, in this study, we proposed an innovative thermochemical technique for converting EVA waste into energy resources, specifically syngas. CO2 was used to enhance the environmental sustainability of pyrolysis. Thermogravimetric analysis revealed that most of the EVA (approximately 99 wt%) was converted into pyrolytic oil and gases. However, the mechanistic features of CO2 in the pyrolysis of EVA could not be fully elucidated through single- or double-stage pyrolysis owing to the slow kinetics of the homogeneous reaction between CO2 and volatiles. To expedite the reaction kinetics, we used a cobalt (Co)-based catalyst (Co/SiO2). In the presence of Co/SiO2, the concentration of CO produced under CO2 was approximately 30-fold higher than that under N2. Furthermore, the homogeneous reactions resulted in fewer benzene derivatives and polycyclic aromatic hydrocarbons (PAHs) in the pyrolytic oil under CO2 conditions. These experimental findings suggest that CO2 and EVA could serve as valuable feedstocks for the production of energy.

An Industrial Perspective for Sustainable Polypropylene Plastic Waste Management via Catalytic Pyrolysis—A Technical Report

Recycling plastics on an industrial scale is a key approach to the circular economy. This study presents a techno-economic analysis aimed at recycling polypropylene waste, one of the main consumer plastics. Specifically, it evaluates the technical and economic feasibility of achieving a large-scale cracking process that converts polypropylene waste into an alternative fuel. Pyrolysis is considered as a promising technique to convert plastic waste into liquid oil and other value-added products, with a dual benefit of recovering resources and providing a zero-waste solution. This study concerns a fast catalytic pyrolysis in a fluidized bed reactor, with the presence of a fluid catalytic cracking catalyst of low acidity for high heat transmission, for an industrial plant with a capacity of 1 t/h of polypropylene waste provided by the Greek Petroleum Industry. From the international literature, the operational conditions were chosen pyrolysis temperature at 430 °C, pressure at 1atm, heating rate at 5 °C/min, and yields of products to 71, 14, and 15 wt.%, for liquid fuel, gas, solid product, respectively. The plant design includes a series of apparatuses, with the main one to be the pyrolyzer. The catalytic method is selected over the non-catalytic because the presence of catalyst increases the quantity and quality of the liquid product, which is the main product of the plant. The energy loops of recycling pyrolysis gas and char as a low-carbon fuel in the plant were considered. The production cost, annual revenue, for 2023, are anticipated to reach €13.7 million (115 €/t) and €15 million (15 €/t), respectively, with an estimated investment equal to €5.3 million. The Payback Time is estimated to 2.4 years to recover the cost of investment. The endeavor is rather economically sustainable. A critical parameter for large scale systems is securing feedstock with low or negligible price.

Investigation of sawdust microwave-assisted pyrolysis by machine learning, Part I: Optimization insights by large language models

Microwave-assisted catalytic pyrolysis shows promise for efficiently converting waste biomass, such as sawdust, into valuable bio-oil. However, current research on pyrolysis characteristics predominantly relies on conventional trial-and-error experimentation. This work pioneers the first use of large language models (LLMs) to gain insights into optimizing bio-oil yield by analyzing the effects of catalyst loading and pretreatment temperature on product distribution. Additionally, we encode the textual LLM outputs into distributed vectors via Word2Vec and concatenate them with artificial neural network (ANN) embeddings, capitalizing on the complementary strengths of data-driven and language models. Our results demonstrate superior accuracy and interpretability, providing better optimization insights on heating dynamics and energy efficiency while avoiding extensive experimental costs. This research establishes the prospects of LLMs as supplementary tools for thermochemical conversion studies, potentially reducing resource-intensive lab trials through reliable data-driven predictions.

Sustainable valorisation of sewage sludge via carbon dioxide-assisted pyrolysis

The escalating volume of sewage sludge (SS) generated poses challenges in disposal, given its potential harm to the environment and human health. This study explored sustainable solutions for SS management with a focus on energy recovery. Employing CO2-assisted pyrolysis, we converted SS into flammable gases (H2 and CO; syngas). Single-stage pyrolysis of SS in a CO2 conditions demonstrated that CO2 enhances flammable gas production (especially CO) through gas phase reactions (GPRs) with volatile matter (VM) at temperatures ≥520 °C. Specifically, the CO2 partially oxidized the VM released from SS and concurrently underwent reduction into CO. To enhance the syngas production at temperatures ≤520 °C, multi-stage pyrolysis setup with additional heat energy and a Ni/Al2O3 catalyst were utilized. These configurations significantly increased flammable gas production, particularly CO, at temperatures ≤520 °C. Indeed, the flammable gas yield in the catalytic pyrolysis of SS increased from 200.3 mmol under N2 conditions to 219.2 mmol under CO2 conditions, representing a 4.4-fold increase compared to single-stage pyrolysis under CO2 conditions (50.0 mmol). By integrating a water-gas-shift reaction, the flammable gases produced from CO2-assisted catalytic pyrolysis were expected to have the potential to generate revenue of US$4.04 billion. These findings highlight the effectiveness of employing CO2 in SS pyrolysis as a sustainable and effective approach for treating and valorising SS into valuable energy resources.

Sustainable Al2O3 nanoparticles in catalytic pyrolysis: Unlocking high-yield bio-oil from Melia azedarach fruit biomass with comprehensive physicochemical analysis

The catalytic pyrolysis of Melia azedarach fruit biomass in the presence of aluminium oxide (Al2O3) nanoparticles was studied using a fixed bed reactor. Cost-effective and sustainable Al2O3 nanoparticles were employed as a catalyst in biomass pyrolysis and these nanoparticles were synthesized by using the extract of Phyllanthus emblica seeds as a reducing and capping agent. The confirmation of fabricated Al2O3 nanoparticles was analyzed by EDS, SEM and XRD characterization techniques. The potential effects of pyrolysis process parameters including catalyst dose, temperature and time were investigated. The optimized catalytic bio-oil was further characterized by FTIR spectroscopy. Moreover, physiochemical analyses were also performed to examine the bio-oil properties as fuel. This study demonstrates that catalytic bio-oil produced from Melia azedarach fruit biomass has the potential to be used as a substitute for fossil fuel for the generation of energy and industrial applications.

Reaction synergy of bimetallic catalysts on ZSM-5 support in tailoring plastic pyrolysis for hydrogen and value-added product production

Hydrogen, viz. a green energy carrier, is poised to considerably contribute to the empowerment of a sustainable society. By valorizing plastics, catalytic pyrolysis was envisaged as a promising route to produce green hydrogen and value-added product here. Firstly, the screening of optimal catalyst support (from activated carbon and four zeolites: M-zeolite, B-zeolite, Y-zeolite, ZSM-5) was executed by studying catalytic polypropylene (PP) pyrolysis over supported Ni catalysts. In view of the highest H2 yield (19.2 mmol/gPP) of Ni/ZSM-5, ZSM-5 was put forth as the optimal catalyst support. Then, the identification of optimal active metal (from Ni, Fe, Co, FeNi, FeCo, and NiCo) was performed by running the catalytic PP pyrolysis over ZSM-5 supported catalysts. For catalytic PP pyrolysis, NiCo/ZSM-5 was the optimal catalyst with the highest H2 yield (28.7 mmol/gPP), while the resulting pyrolysis oil demonstrated potential for use as jet fuel. From catalytic pyrolysis of various plastics over NiCo/ZSM-5, polystyrene gave the highest H2 composition (83.2 vol%) of pyrolysis gas and high composition (52.8 area%) of benzocyclobutene (useful chemicals for semiconductor and microelectronics fields) in pyrolysis oil. Lastly, the catalytic mechanism was discussed based on the results, revealing NiCo's remarkable enhancement in H2 yield to 28.7 mmol/g, which surpassed the individual yields of Ni (19.2 mmol/g) and Co (10.2 mmol/g), thereby underscoring the synergistic effect of NiCo. This study supports the recycling of plastics waste into hydrogen energy and valuable products, contributing to environmental pollution mitigation.

Microwave-assisted catalytic rapid pyrolysis of soybean straw for the preparation of high-value indole-rich bio-oils

Microwave-assisted catalysed rapid pyrolysis of soybean straw to prepare high-value bio-oils rich in indoles achieved value-added use of biomass. The effects of different urea doping ratios, two typical Al-based catalysts (γ-Al2O3, HZSM-5), and different HZSM-5 doping ratios on the preparation of N-rich bio-oils (NCBs) from soybean straw by microwave-assisted pyrolysis were investigated. It was shown that the yield of the liquid product at 40 % urea addition was 39.63 %, in which pyridine compounds were enriched to the extent of 20.86 %. On this basis, the effects of γ-Al2O3 and HZSM-5 on N-containing compounds (NCCs) in bio-oil were analyzed in detail. The yield of NCCs increased significantly with the addition of HZSM-5. The best parameter combinations were obtained through orthogonal experiments: urea addition of 50 %, HZSM-5 catalyst type, and catalyst doping ratio of 200 %. At this point, the bio-oil yield reached 29.575 wt%. Among them, indole yield reached 41.66 wt% and exhibited high selectivity of 68.92 % in NCCs. The formation mechanism of indoles during microwave-assisted N-rich pyrolysis was further investigated on the basis of experimental studies. In addition, the inhibitory effect of the HZSM-5 catalyst on the formation of pyridine compounds during pyrolysis process and the enhancement mechanism of the formation of indole compounds were deeply investigated. This provided a green pathway for the preparation of indoles by microwave-assisted fast pyrolysis directional catalytic conversion of biomass.

Catalytic pyrolysis of polypropylene waste for liquid fuels production using Ni/Al-MOF-derived catalysts

Waste plastics pose significant environmental risks due to their non-biodegradable nature and accumulation in the environment. The pandemic has exacerbated this issue by increasing the production of plastic medical waste such as surgical masks. This study developed Ni/Al-MOF-derived catalysts for pyrolysis, an effective plastic waste utilization technology. By optimizing conditions, the study successfully converted waste surgical masks, made primarily of polypropylene, into gasoline or diesel range chemicals. The oil yield from polypropylene waste reached 72.8 % using Ni/Al-MOF-derived catalysts with 5 % Ni loading at 450°C, while surgical masks yielded 58.9 % oil under the same conditions. Catalyst characterization revealed a high surface area and evenly distributed Ni particles in MOF-derived Al2O3, maximizing catalytic performance. This catalyst provides a promising solution for converting waste surgical masks into liquid fuels, reducing the environmental impact of plastic products, and promoting plastic waste recycling.

Biomass Valorization through Catalytic Pyrolysis Using Metal-Impregnated Natural Zeolites: From Waste to Resources.

Catalytic biomass pyrolysis is one of the most promising routes for obtaining bio-sustainable products that replace petroleum derivatives. This study evaluates the production of aromatic compounds (benzene, toluene, and xylene (BTX)) from the catalytic pyrolysis of lignocellulosic biomass (Pinus radiata (PR) and Eucalyptus globulus (EG)). Chilean natural zeolite (NZ) was used as a catalyst for pyrolysis reactions, which was modified by double ion exchange (H2NZ) and transition metals impregnation (Cu5H2NZ and Ni5H2NZ). The catalysts were characterized by nitrogen adsorption, X-ray diffraction (XRD), ammonium programmed desorption (TPD-NH3), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). Analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) allowed us to study the influence of natural and modified zeolite catalysts on BTX production. XRD analysis confirmed the presence of metal oxides (CuO and NiO) in the zeolite framework, and SEM-EDS confirmed successful metal impregnation (6.20% for Cu5H2NZ and 6.97% for Ni5H2NZ). Py-GC/MS revealed a reduction in oxygenated compounds such as esters, ketones, and phenols, along with an increase in aromatic compounds in PR from 2.92% w/w (without catalyst) to 20.89% w/w with Ni5H2NZ at a biomass/catalyst ratio of 1/5, and in EG from 2.69% w/w (without catalyst) to 30.53% w/w with Ni5H2NZ at a biomass/catalyst ratio of 1/2.5. These increases can be attributed to acidic sites within the catalyst pores or on their surface, facilitating deoxygenation reactions such as dehydration, decarboxylation, decarbonylation, aldol condensation, and aromatization. Overall, this study demonstrated that the catalytic biomass pyrolysis process using Chilean natural zeolite modified with double ion exchange and impregnated with transition metals (Cu and Ni) could be highly advantageous for achieving significant conversion of oxygenated compounds into hydrocarbons and, consequently, improving the quality of the condensed pyrolysis vapors.

Gas-phase and liquid-phase purification of plastic waste derived carbon nanotubes: Effect of purification agent and operational parameters

The preparation of carbon nanotubes (CNTs) by catalytic pyrolysis of waste plastics is one of the most promising technologies to realize the harmless and high-value recycling of waste plastics. However, there are limited studies on the purification of waste-derived carbons, which is of significance for downstream applications. In this paper, the effects of different gas-phase purification conditions (temperature, gas type), liquid-phase purification (hydrochloric and nitric acid reflux), and combined gas-liquid purification on the properties of CNTs prepared from waste plastics were investigated. The as-obtained and purified CNTs were characterized using SEM, TEM, TPO, XRD, XPS, Raman spectroscopy, and FTIR spectroscopy. Results showed that operational temperatures have distinct impacts on the properties of CNTs during gas-phase purification. An appropriate temperature range for gas-phase purification was determined, with temperatures around 450 °C for air, 650 °C for CO2, and 700 °C for steam respectively, so that the amorphous carbon could be removed and the graphitization of CNTs was retained. Approximately 93 wt% of the metal catalyst particles could be removed with acid treatment for 4 h. In addition, carboxyl and hydroxyl functional groups were introduced to CNTs after acidic treatment. Furthermore, it was found that the approach combining CO2 treatment and nitric acid washing yielded CNTs with relatively higher quantities and lower defect levels. Results showed the properties of CNTs varied from the purification methods, which could meet different needs based on the downstream specific application requirements.