Microwave-assisted Catalytic Pyrolysis Research Articles

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.

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 29.575wt.%. Among them, indole yield reached 41.66wt.% 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.

Utilization of coffee waste for biofuel production through catalytic microwave-assisted pyrolysis approach

Utilization of coffee waste for biofuel production through catalytic microwave-assisted pyrolysis approach

Temperature-Dependent NiFeAl catalysts for efficient microwave-assisted catalytic pyrolysis of polyethylene into value-added hydrogen and carbon nanotubes

Polyolefins, comprising the majority of disposable plastics, face challenges in catalytic upcycling due to their inert saturated C(sp3)-C(sp3) bonds. This work demonstrates microwave-assisted catalytic pyrolysis, demonstrating the direct conversion of low-density polyethylene (LDPE) into valuable H2 and multi-walled carbon nanotubes (MWCNTs) over a porous ternary NiFeAl-T composite catalyst that serve as a microwave absorber. Optimizing the calcination temperature promoted metal nanoparticle dispersion, leading to enhanced catalytic performance. Specifically, lower temperatures favored metal–metal interactions, inducing porous architectures with superior microwave absorption and energy dissipation capabilities. This facilitated cleavage of C–C and C–H bonds in LDPE during microwave irradiation. An optimal NiFeAl-450 catalyst achieved a maximum H2 yield of 60.5 mmol gLDPE-1, with an H2 concentration of 85.1 vol% in gas products, alongside high-value MWCNTs. Moreover, successive recycling test displayed stable H2 and MWCNTs yields from LDPE. This work elucidates a promising pathway for upcycling plastic waste via microwave-assisted catalytic pyrolysis.

Co-, Ni-, and Cu-Doped Fe-Based Catalysts for the Microwave-Assisted Catalytic Pyrolysis of Polyethylene.

Environmental issues caused by waste polyethylene are becoming increasingly severe. Among potential treatment processes, microwave-assisted catalytic pyrolysis is promising for converting waste plastics into valuable products owing to its energy efficiency and environmental sustainability. Herein, a modified citric acid combustion method was used to prepare a series of metal oxide catalysts with loose porous structures. The prepared Fe-based catalysts doped with Co, Ni, or Cu were employed in the microwave-assisted catalytic pyrolysis of polyethylene. The bimetallic Co1Fe1Ox catalyst exhibited the best performance, yielding hydrogen at a rate of 60.7 mmol/gplastic. Further variation in the Co : Fe ratio revealed that the Co1Fe9Ox catalyst achieved the highest hydrogen production efficiency (63.64 mmol/gplastic). Similar oil-phase products were obtained over the various catalysts, as revealed by infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. Furthermore, scanning electron microscopy (SEM) identified carbon nanotubes as the major solid product of pyrolysis, which were attached to the catalyst surface. Finally, a combination of thermogravimetric analysis, SEM, and energy-dispersive X-ray spectroscopy indicated that the reduction in catalytic activity following recycling was caused by the accumulation of carbonaceous products on the catalyst surface. Overall, Co1Fe9Ox catalysts were favorable for obtaining H2 and carbon nanotubes by the microwave-assisted pyrolysis of polyethylene.

Microwave-assisted catalytic pyrolysis with char-supported Fe-Mn catalysts: A new method for utilizing furfural residue

The primary objective of this study was to investigate the effects of bimetallic-modified biochar catalysts on the products obtained from microwave-assisted catalytic pyrolysis (MACP) of furfural residue (FR). Bimetallic modified biochar catalysts were prepared by the impregnation method with FeCl3 and MnCl2. The results showed that iron (Fe) had a greater erosion effect on the pore structure of the catalyst. Moreover, the presence of bimetals increased the contents of H2 and CO2, decreased the contents of CO and CH4 in the pyrolysis gas, with Fe demonstrating significantly higher selectivity for H2 compared to Mn. The bimetallic modification additionally increased the relative content of phenols, with 2F6M (xFyM, where x and y represent the weight percentages of Fe and Mn) reaching the highest value at 62.22 % with a total loading mass of 8 wt%. Nevertheless, the catalytic effect of the catalyst was influenced by the pore structure, resulting in the lowest phenolic content for 4F4M. At a loading mass of 2 wt%, the catalytic effect of Fe modification surpassed that of Mn. Furthermore, as the Mn content increased, the catalytic effect became more pronounced, particularly when the loading mass exceeded 4 wt%. The results demonstrated that the bimetallic modification effectively enhanced the catalytic performance of the catalyst, promoting the generation of both phenols and H2.

Bio-fuel production from catalytic microwave-assisted pyrolysis of the microalgae Schizochytrium limacinum in a tandem catalytic bed

The formation of oxygenated and nitrogenated compounds during microalgae pyrolysis interferes with bio-oil usage as a viable competitor against fossil fuels. Aiming to reduce these undesirable substances and improve aromatic hydrocarbon production, the catalytic microwave-assisted pyrolysis of the microalgae Schizochytrium limacinum in a tandem catalytic bed was investigated. This study evaluated the effects of the reaction temperature and the tandem catalytic bed (NiHTC/SiC and NiHZSM 5/SiC: hydrotalcite and zeolite catalysts) on the product distribution and bio-oil composition. Experimental results showed that ex-situ catalytic microwave-assisted pyrolysis was able to produce satisfactory liquid yields, reaching 58 % in the optimal test. The results showed that NiHTC/SiC (hydrotalcite) favored de-acidification and de-nitrification reactions, leading to more intermediate compounds, such as ketones and alcohols. These compounds were then converted into hydrocarbons over the acid sites of the NiHZSM-5/SiC (zeolite) catalyst. Maximum hydrocarbon and benzene yields of 95 % and 78 %, respectively, were reached at 500 °C and a NiHTC/SiC:NiHZSM-5/SiC catalyst ratio of 1:1. In addition, the regeneration and recycling of the catalytic bed were successfully performed and did not affect catalytic activity regarding hydrocarbon generation. This study also provided crucial data on improving energy recovery (which ranged from 70 to 94 %) and bio-oil quality during the catalytic pyrolysis of microalgae. The satisfactory results indicated that the biomass energy was successfully stored as a liquid fuel.

Microwave-assisted catalytic pyrolysis of commercial residual lignin with in-situ catalysts to produce homogenous bio-oil and high-yield biochar with enriched pores

Microwave-assisted catalytic pyrolysis of commercial residual lignin with in-situ catalysts to produce homogenous bio-oil and high-yield biochar with enriched pores

Synthesis of alkoxyphenols-rich bio-oil by microwave-assisted catalytic pyrolysis of wood over MoS2 catalyst

Microwave-assisted pyrolysis (MAP) is widely concerned as a high-efficiency treatment of forestry solid waste to produce value-added products. In this study, alkoxyphenols-rich bio-oil was selectively produced from wood powder through MAP process using self-made MoS2 catalysts. First of all, the yield of bio-oil was selectively controlled by changing the process parameters of microwave power, temperature and catalyst weight content. Under the conditions of 1200 W, 600 °C and 10 wt% of catalyst to feedstock, an optimal bio-oil yield of 54.3 wt% was achieved over the MoS2 catalysts. Notably, compared with commercial MoS2-catalyzed and non-catalyzed MAP, the self-made MoS2-catalyzed process realized the improvement for the content of both general phenol species and specific alkoxyphenols component, reaching up to 90.1 % and 77.3 %, respectively at 1200 W, 600 °C and 10 wt% of catalyst to feedstock, which was superior to most of the previously reported candidates. The contrast experiment evidenced the bifunctional roles of MoS2 as both microwave absorbent and catalyst. It could not only promote the production of bio-oil but also inhibit the carbonization, selectively upgrade non-condensable gas to bio-oil, and simultaneously limit the second pyrolysis of alkoxyphenols, which jointly leads to the efficient synthesis of alkoxyphenols-rich bio-oil. This work provides guidance for producing phenols-rich bio-oil and other highly value-added products through the microwave-assisted catalytic pyrolysis of biomass over transition metal dichalcogenides materials.

Assessment of biochar, bio-oil and biogas production from lemon myrtle waste via microwave assisted catalytic pyrolysis using CaO based catalyst and zeolite catalyst

This work fashioned the conventional pyrolysis by introducing a microwave process to assess the feasibility of lemon myrtle waste (LMW) to produce biochar, bio-oil and biogas in the presence of catalyst. Microwave assisted pyrolysis (MAP) of LMW was established as a control before introducing five different catalysts in the Microwave Assisted Catalytic Pyrolysis (MACP) reaction. The catalyst includes CaO based catalyst (Dolomite and Eggshell (CES)) and Zeolite based catalyst (ZSM-5, HY-Zeolites and FCC). These catalysts were characterized using the X-Ray Diffraction (XRD) method, Brunauer-Emmet-Teller (BET) surface area, Particle Size Analyzer (PSA) and Scanning Electron Microscope (SEM) to determine their physical properties. These characterizations proved that all catalysts are suitable for the MACP reaction. The biochar, bio oil and biogas yield were determined using mass balance. Biochar quality was evaluated by its calorific value content while the bio-oil and biogas produced from the MACP was characterized using Gas Chromatography-Mass Spectrometry (GC–MS) and GC-Thermal Conductivity Detector (GC-TCD) analysis. The result shows that more than 95 % of MACP yield were biochar and biogas. MAP of LMW produced highest calorific value biochar at 21.72 MJ/kg. Dolomite catalyst produced the highest bio-oil yield of 2.27 % with the highest hydrocarbon content of 86.35 %. MACP of LMW proved that the bio-oil yield produced was increase by 0.7 % while hydrocarbon percentage was increased by 11.4 % in the presence of Dolomite catalyst. The feasibility of LMW to be used as solid fuel is successfully proven form this study.

Catalytic microwave-assisted pyrolysis of plastic waste to produce naphtha for a circular economy

Catalytic cracking of plastics into naphtha as a substitute for new plastic production has the potential to contribute to the plastic circular economy. However, mitigating catalyst deactivation in large-scale processes poses a significant challenge. Here, we demonstrate a remarkable improvement (4.3 × to 12.3 ×) in catalyst lifetime by utilizing hierarchical ZSM-5 catalysts compared to conventional analogues. Increasing the Brønsted acid concentration from 0 to 302 µmol/g enhances catalyst lifetime by over 46 × and boosts cumulative aromatic selectivity from 6 to 73%. Catalyst characterization reveals the development of significant voids after modification, enhancing molecular transport within the hierarchical ZSM-5. Economic analysis shows a pilot system with a 10 ton/day capacity yielding an annual profit of $344,999 and an 11.5% return on investment. Life cycle assessment indicates a reduction of 817.6 kg CO2 eq compared to traditional plastic-to-fuels technology. These findings advance the plastic circular economy and bring us closer to commercial implementation.

Catalytic Microwave-Assisted Pyrolysis of the Main Residue of the Brewing Industry

Most agro-industrial wastes are lignocellulosic biomass. Several technologies have been developed to convert these residues to value-added products. Among these processes, pyrolysis refers to the thermal degradation of organic materials. Microwave-assisted pyrolysis (MAP) is more advantageous than conventional pyrolysis because it offers time savings, increases heating efficiency, and promotes a more precise process control. In this work, the microwave-assisted pyrolysis (MAP) of brewer’s spent grain (BSG), the main waste of the brewing industry, was studied, focusing on its liquid product. The effects of temperature, moisture content, and catalyst (calcium oxide) percentage on the product distribution and hydrocarbon content in the liquid product obtained were investigated. Although a high liquid yield of 71.8% was achieved with a BSG moisture content of 14%, the quality of the product (hydrocarbon yield) in this condition was not so attractive (21.60%). An optimization study was carried out to simultaneously maximize bio-oil yield and quality. The optimum conditions obtained were a temperature of 570 °C and a catalyst/biomass ratio of 12.17%. The results of the liquid product composition at the optimum point are promising given the presence of aromatic hydrocarbons, organic compounds of great interest to the industry.

Microwave-assisted catalytic pyrolysis of ferulic acid, as a lignin model compound

Microwave-assisted catalytic pyrolysis of ferulic acid, as a lignin model compound

Formation mechanism of hydrogen production from catalytic pyrolysis of waste tires: A ReaxFF molecular dynamics and experimental study

The mechanism for the formation of gaseous products, especially hydrogen, from the catalytic pyrolysis of waste tires by using Ni-based catalysts has been studied. The catalytic pyrolysis of the three essential components of waste tires such as natural rubber (NR), styrene-butadiene rubber (SBR), and cis-polybutadiene rubber (BR) was simulated and the pyrolysis fracture of the molecular chain was investigated. This work aims to provide a deeper understanding of the reaction thermodynamics and kinetics for the formation mechanisms of gaseous products, primarily hydrogen. Microwave-assisted catalytic pyrolysis of the waste tires over Ni-based catalysts was carried out and used to assent to the simulation results. The study revealed that with the incorporation of 10 wt% Ni/ZSM-5 catalyst, the relative content of H2 from the catalytic pyrolysis of waste tires can be significantly improved by about 41.3 % in comparison to the same measurement done in the absence of the catalyst. Kinetic and thermodynamic simulations for the catalytic pyrolysis of waste tires were also performed and the corresponding energy barriers and Gibbs free energy changes were calculated. Accordingly, the optimal reaction path for the hydrogen production was determined by comparing and analyzing the values of those parameters. It was confirmed that the addition of Ni, ZSM-5, and Ni/ZSM-5 catalysts promote the hydrogen production reaction pathways. Among those catalysts, the simulation result verified that Ni/ZSM-5 brings a pronounced hydrogen production capacity, which was consistent with the experimental findings.

ReaxFF MD simulation of microwave catalytic pyrolysis of polypropylene over Fe catalyst for hydrogen

Microwave-assisted catalytic pyrolysis of waste plastics is promising for hydrogen generation. To study the mechanism of microwave in Fe catalyzed pyrolysis of plastics. Molecular dynamics (MD) simulation was carried out using the ReaxFF method to compare the bonded and non-bonded interatomic interactions at the same temperature under conventional heating and microwave heating at different powers. The results show that the microwave improves the adsorption capacity of Fe clusters, reduces the dissociation energy of CH bonds, and promotes the cleavage of CC bonds due to H radicals at low temperature. Therefore, microwave enhances the generation of H2, reduces the required reaction temperature, and suppresses the generation of small gaseous hydrocarbon molecules and tar. These results prove the reliability of ReaxFF MD and provide a theoretical basis for valorising waste plastics aided by microwave.

Plasma catalytic microwave-assisted pyrolysis of stable substrates to give synthesis gas and hydrocarbons in the presence of cobalt-containing systems

Plasma catalytic microwave-assisted pyrolysis of stable substrates to give synthesis gas and hydrocarbons in the presence of cobalt-containing systems

Microwave-assisted pyrolysis spent bleaching clay for aromatic bio-oil production: Exploration of heating pathway based on microwave response characteristics of feedstock

Spent bleaching clay (SBC) is a waste generated from the refining process of edible oils. SBC contains some residual oils, with excellent potential to produce aromatic bio-oil. For the first time, microwave-assisted pyrolysis was used to treat SBC, which has unique microwave response characteristics. The products of microwave heating and electric heating were investigated, under three conditions: no catalyst, in-situ catalysis, and ex-situ catalysis. Microwave heating saved 50% of the reaction time and up to 53% of the energy consumption, compared to electric heating. Microwave heating facilitated the formation of aromatic hydrocarbons by promoting hydrogen transfer and cyclization reactions. In comparison with electric heating, the aromatic hydrocarbons relative content was increased by 15.46% under no catalyst. In addition, the optimal pyrolysis temperature, catalytic temperature, feedstock to catalyst mass ratio (F/C) and nitrogen flow rate based on microwave heating pathway were 500 °C, 500 °C, 10/1, and 50 mL/min, respectively. Under these conditions, the relative content of aromatic hydrocarbons was 87.89%. Microwave-assisted catalytic pyrolysis is a fast and energy efficient pathway to produce aromatic bio-oil from SBC, which can provide a theoretical basis for resource utilization of SBC.

Microwave-assisted in-situ catalytic pyrolysis of polystyrene: Analysis of product formation and energy consumption using machine learning approach

Microwave-assisted catalytic pyrolysis is a prominent technology for the production of high-quality fuel intermediates and value-added chemicals from polystyrene waste. The objectives of this study were to understand the role of catalyst (KOH) on polystyrene (PS) pyrolysis. Pyrolysis experiments were conducted using a microwave oven at a power of 450 W and a temperature of 600 °C. Graphite susceptor (10 g) was used to achieve the required pyrolysis conditions. In addition, the design of experiments (DoE) with machine learning (ML) was used to understand the loading of PS (5 g, 27.5 g, and 50 g), and KOH (5 g, 7.5 g, and 10 g). The products including oil, gas, and char were collected in every experiment. The average heating rates achieved were in the range of 30–50 °C/min. The specific microwave power (microwave power per unit mass of feedstock) decreased with an increase in PS amount from 90 to 9 W/g. However, the specific microwave energy (microwave energy per unit mass of feedstock) (27–73 kJ/g) was in line with the average heating rate. The maximum yield of pyrolysis oil was found to be 95 wt%, which was obtained with a PS:KOH ratio of 27.5 g: 7.5 g. The oil yield increased from 80 to 95 wt% when the mass of the catalyst increased from 5 to 7.5 g. On the other hand, the gas yield (3–18 wt%) varied significantly and char yield (1–2 wt%) was not influenced. The yields predicted by ML matched well with the experimental yields. This study demonstrated the potential of KOH as a catalyst for PS pyrolysis technology as the formation of aliphatic hydrocarbons in the oil fraction was significantly promoted.

Effect of dry torrefaction pretreatment of the microwave-assisted catalytic pyrolysis of biomass using the machine learning approach

This study employs the Leave-One-Out cross-validation approach to build a machine-learning model using polynomial regression to predict pyro product yield through microwave-assisted pyrolysis of sawdust over KOH catalyst and graphite powder a susceptor. The determination of coefficient (R2) validates the developed models. All the developed models achieved a high prediction accuracy with R2 > 0.93, which signifies that the experimental values are in good agreement with the predicted one. The dependence of the catalyst loading and pretreatment temperature on dominating process parameters such as heating rate, pyrolysis temperature, susceptor thermal energy, and pyro products, namely bio-oil, biochar, and biogas, are explored. The yield of biochar is reduced; however, bio-oil and biogas are enhanced as the catalyst loading increased. On the other hand, increasing the temperature of pretreated sawdust decreased bio-oil and biogas yields while increasing biochar yields. Further, microwave conversion efficiency, and susceptor thermal energy increased with increased catalyst quantity and pretreatment temperatures of sawdust. It was observed that the average heating rate was increased by increasing the catalyst quantity while maintaining the same pyrolysis time until pretreatment temperatures of 150 °C were reached, after which the heating rate dropped due to the continuous microwave energy input to the system.

An economic and environmental assessment of biofuel produced via microwave-assisted catalytic pyrolysis of forest residues

The conversion of forest residues into biofuels will enhance the decarbonization of the transportation sector and help the world reach its net-zero targets. Microwave-assisted catalytic pyrolysis (MACP) is an emerging thermo-catalytic conversion technology which, when coupled with low-carbon electricity, will result in negative emissions. The work described here assessed the economic feasibility and environmental impact of a novel MACP system for co-production of upgraded biofuel and high-quality biochar from forest residues. The cradle-to-gate (CTG) carbon intensity of MACP biofuel ranged from −57.3 to 27.4 g CO2-eq/MJ respectively when using either low-carbon electricity or carbon-intense electricity. Compared to petroleum fuels, a 43% to 162% reduction of GHG emissions could be achieved depending on electricity mix and methods to treat biochar co-product. The use of electricity to produce MACP biofuel as compared to directly charge electric vehicles was justified as a preferred use based on the finding that the advanced utilization of waste biomass via MACP could contribute significantly to GHG reduction of transportation fuel without sacrificing the travel distance of vehicles. The minimum selling price (MSP) of MACP biofuel was $1.02/L in the absence of any policy support and could be reduced to a comparable price of petroleum fuels at $0.53/L or increased to $1.32/L depending on the co-product revenue from biochar’s higher or lower-value applications. MACP biofuel could also be priced competitively with petroleum fuels by as early as 2026 under the planned carbon tax schedule in Canada. This co-production of upgraded biofuel and value-added biochar could bring flexibility to the biorefinery to seek the highest possible economic and environmental benefits facing the changing market and policy.