Improving bio-oil properties through the fast co-pyrolysis of lignocellulosic biomass and waste tyres

Valorization of pyrolysis oils recycled from waste car tires as potential collector in coal flotation: Production, characterization, and collecting mechanism

The present research study investigates the performance of pyrolysis oils recycled from waste tires as a collector in coal flotation. Three different types of pyrolysis oils (namely, POT1, POT2, and POT3) were produced through a two-step pressure pyrolysis method followed by an oil rolling process. The characteristics of POTs were adjusted using various oil-modifying additives such as mineral salts and organic solvents. The chemical structure of POTs was explored by employing necessary instrumental analysis techniques, including microwave-assisted acid digestion (MAD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), Fourier-transform infrared spectroscopy (FT-IR), and gas chromatography-mass spectrometry (GC-MS). The collecting performance of POTs in coal flotation was evaluated using an experimental design based on Response Surface Methodology (RSM), considering the ash content and yield of the final concentrate. The effect of the type and dosage of POTs was evaluated in conjunction with other important operating variables, including the dosage of frother, dosage of depressant, and the type of coal. Results of POTs characterization revealed that the pyrolysis oils were a complex composition of light and heavy hydrocarbon molecules, including naphthalene, biphenyl, acenaphthylene, fluorene, and pyrene. Statistical analysis of experimental results showed that among different POTs, POT1 exhibited remarkable superiority, achieving not only a 15% higher coal recovery but also a 12% lower ash content. The outstanding performance of POT1 was attributed to its unique composition, which includes a concentrated presence of carbon chains within the optimal range for efficient flotation. Additionally, the FT-IR spectra of POT1 reveal specific functional groups, including aromatic and aliphatic compounds, greatly enhancing its interaction with coal surfaces, as confirmed by contact angle measurement. This research provides valuable insights into the specific carbon chains and functional groups that contribute to the effectiveness of POT as a collector, facilitating the optimization of coal flotation processes and underscoring the environmental advantages of employing pyrolysis oils as sustainable alternatives in the mining industry.

Enhanced biofuel production by co-pyrolysis of distiller's grains and waste plastics: A quantitative appraisal of kinetic behaviors and product characteristics

Pyrolysis of biomass feedstocks can produce valuable biofuel, however, the final products may present excessive corrosion and poor stability due to the lack of hydrogen content. Co-pyrolysis with hydrogen-rich substances such as waste plastics may compensate for these shortcomings. In this study, the co-pyrolysis of a common biomass, i.e. distiller's grains (DG), and waste polypropylene plastic (PP) were investigated towards increasing the quantity and quality of the production of biofuel. Results from the thermogravimetric analyses showed that the reaction interval of individual pyrolysis of DG and PP was 124-471 °C and 260-461 °C, respectively. Conversely, an interaction effect between DG and PP was observed during co-pyrolysis, resulting in a slower rate of weight loss, a longer temperature range for the pyrolysis reaction, and an increase in the temperature difference between the evolution of products. Likewise, the Coats-Redfern model showed that the activation energies of DG, PP and an equal mixture of both were 42.90, 130.27 and 47.74 kJ mol-1, respectively. It thus follows that co-pyrolysis of DG and PP can effectively reduce the activation energy of the reaction system and promote the degree of pyrolysis. Synergistic effects essentially promoted the free radical reaction of the PP during co-pyrolysis, thereby reducing the activation energy of the process. Moreover, due to this synergistic effect in the co-pyrolysis of DG and PP, the ratio of elements was effectively optimized, especially the content of oxygen-containing species was reduced, and the hydrocarbon content of products was increased. These results will not only advance our understanding of the characteristics of co-pyrolysis of DG and PP, but will also support further research toward improving an efficient co-pyrolysis reactor system and the pyrolysis process itself.

Synergistic optimization of bio-oil quality and heavy metal solidification during microwave co-pyrolysis of cow dung and red mud

To decrease the environmental risks caused by heavy metals (HMs) in red mud (RM) and improve the quality of pyrolysis oil from biomass, high-temperature pretreated RM and cow dung (CD) were microwave co-pyrolyzed. Then, the optimization potential of energy consumption was evaluated and the interaction mechanism between RM and CD was explored. The results showed that the increase in transition metal oxides and specific surface area improved the microwave-absorption and catalytic capacity of the pretreated RM. By optimizing the parameters, a pretreatment temperature of 650 °C resulted in a 21.65% reduction in acid content of bio-oil, higher HMs immobilization rates (>91%) and a 7.44% reduction in energy consumption. The synergistic optimization of bio-oil quality, HMs immobilization and energy consumption was achieved. After microwave co-pyrolysis with cow dung, the larger specific surface area (92.90 m² g^-1) and higher carbon crystallinity (I_D/I_G = 1.02) of pyrolysis residues enhanced the physical adsorption to HMs. The complexation of HMs with -OH could further enhance the solidification of HMs. This work will provide support to efficient resource utilization of solid waste, and demonstrate the great potential of microwave co-pyrolysis in HMs immobilization.

Biomass pyrolysis: A review on recent advancements and green hydrogen production

Biomass pyrolysis has recently gained increasing attention as a thermochemical conversion process for obtaining value-added products, thanks to the development of cutting-edge, innovative and cost-effective pyrolysis processes. Over time, new and novel pyrolysis techniques have emerged, and these processes can be tuned to maximize the production of high-quality hydrogen. This review examines recent advancements in biomass pyrolysis by classifying them into conventional, advanced and emerging approaches. A comprehensive overview on the recent advancements in biomass pyrolysis, highlighting the current status for industrial applications is presented. Further, the impact of each technique under different approaches on conversion of biomass for hydrogen production is evaluated. Techniques, such as inline catalytic pyrolysis, microwave pyrolysis, etc., can be employed for the sustainable production of hydrogen. Finally, the techno-economic analysis is presented to understand the viability of pyrolysis at large scale. The outlook highlights discernments into future directions, aimed to overcome the current shortcomings.

Study on co-pyrolysis and products of Chlorella vulgaris and rice straw catalyzed by activated carbon/HZSM-5 additives

The weight loss characteristics, product distribution and bio-oil composition of co-pyrolysis of rice straw (RS) and Chlorella vulgaris (CV) were investigated by microwave oven. Then, the catalytic effect of activated carbon (AC) and HZSM-5 on these characteristics were studied. Results showed that AC strongly improved co-pyrolysis weight loss characteristics and obtained maximum average weight loss rate (R_a) at 30% addition with 0.01639 wt.%/s. While HZSM-5 promoted the characteristics as addition was lower than 10%. In the case of compound additives, 20% A7H3 obtained the maximum R_a (0.01413 wt.%/s). Furthermore, both single AC and HZSM-5 showed negative effect on bio-oil production, while 20% A7H3 (AC/HZSM-5 = 7:3) achieved the maximum production (24%). For bio-oil composition, 30% A10H0 showed strong selectivity for phenol and N-heterocycle and 10% A0H10 showed strong aromatization capacity, and the addition of 20% A7H3 increased the hydrocarbons content from 20.79% to 31.63% compared with the blank group.

Valorization of Hazardous Materials along with Biomass for Green Energy Generation and Environmental Sustainability through Pyrolysis

Increased population growth, industrialization, and modern culture create a variety of consequences, including environmental pollution, heavy metal accumulation, and decreasing energy resources. This perilous position necessitates the development of long-term energy resources and strategies to address environmental threats and power shortages. In this study, an investigation into the use of castor seed oil cake and waste tyres as a feed material for the copyrolysis process for yielding maximum oil production was performed. The copyrolysis experiments were performed by changing the mass percentage of waste tyres with oil cake to make different ratios of 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100. At 50 : 50 ratio, the maximum positive synergy on oil production was obtained. At that condition, a maximum of 59.8 wt% oil was produced and characterized to analyze its physiochemical properties. The coprocessing of the selected two feed materials enables the stabilization of the oil, as the produced oil has a lower oxygen content with a maximum heating value of 38.72 MJ/kg. The Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) analysis of the oil showed the existence of aromatic hydrocarbons and phenolic elements. Adding waste tyres to the biomass improved the quality of the oil by increasing carbon content with reduced oxygen content.

An integrated utilization strategy of printed circuit boards and waste tire by fast co-pyrolysis: Value-added products recovery and heteroatoms transformation

Fast co-pyrolysis has been suggested as a promising technique to solve the environmental issues and simultaneously recover value-added products from polymer wastes. However, to date, no studies have focused on fast co-pyrolysis of printed circuit boards (PCB) and waste tire (WT). Therefore, we comprehensively investigated the fast co-pyrolysis of PCB and WT using pyrolysis-gas chromatography/mass spectrometry. The results show that an increase in temperature during fast pyrolysis improved the interactions between the PCB and WT pyrolyzates, increasing the formation of aliphatic and aromatic compounds. The formation of p-cymene was greatly induced by the isomerization and dehydrogenation reactions of D-limonene. Co-pyrolysis reduced the formation of brominated phenols and benzothiazole from PCB and WT pyrolysis, respectively, whereas promoted the interactions between Br- and S/N-containing radicals, concentrating them into heavy compounds. Increasing the temperature enhanced the release of heteroatom compounds. The findings suggest that debromination of PCB achieved via dehydrogenation of WT pyrolysis provoked secondary reactions of olefins and interactions of heteroatom radicals. The major products were accurately predicted by different fitting models using response surface methodology, indicating the synergistic interactions during co-pyrolysis. The results were beneficial for optimizing the experimental parameters to obtain the maximum yield of desired products.

Effect of pretreatment and biomass blending on bio-oil and biochar quality from two-step slow pyrolysis of rice straw

This study investigated biomass blending and water washing to improve product quality from two-step pyrolysis of rice straw. Rice straw (RS) was mixed with groundnut shells (GNS) and wheat straw (WS) in different weight ratios. Blending RS with GNS/WS in a 1:1 ratio increased the total bio-oil yields by 7-9% and reduced the pyrolysis gas and char yields by 5-7% and < 2%, respectively. RS was washed with water separately to examine the effect of removing water-soluble ash elements. The optimum washing duration was 60 min; the ash removal efficiency was then 26%. The bio-oil yields from washed straw increased by 4% over unwashed straw, and pyrolysis gas yields decreased. Combining the washing and blending processes increased the levoglucosan yield by 1.6-2.1 times compared to unwashed RS, and the water content in bio-oil was reduced by ∼ 10%. Moreover, the biochar samples obtained after pyrolysis of washed biomass blends had potential fuel applications owing to low fouling or slagging propensity. They also had possible use in the soil for adsorption of soil contaminants and increasing acidic soil pH, with likely stability of ∼ 1000 years in the ground. These results provide a promising alternative for efficiently converting rice straw to multiple value-added products.

Bio-Oil: The Next-Generation Source of Chemicals

Bio-oil, although rich in chemical species, is primarily used as fuel oil, due to its greater calorific power when compared to the biomass from which it is made. The incomplete understanding of how to explore its chemical potential as a source of value-added chemicals and, therefore, a supply of intermediary chemical species is due to the diverse composition of bio-oil. Being biomass-based, making it subject to composition changes, bio-oil is obtained via different processes, the two most common being fast pyrolysis and hydrothermal liquefaction. Different methods result in different bio-oil compositions even from the same original biomass. Understanding which biomass source and process results in a particular chemical makeup is of interest to those concerned with the refinement or direct application in chemical reactions of bio-oil. This paper presents a summary of published bio-oil production methods, origin biomass, and the resulting composition.

Microwave assisted carbonization and activation of biochar for energy-environment nexus: A review

Conventional thermochemical conversion techniques for biofuel production from lignocellulosic biomass is often non-selective and energy inefficient. Microwave assisted pyrolysis (MAP) is cost and energy-efficient technology aimed for value-added bioproducts recovery from biomass with less environmental impacts. The present review emphasizes the performance of MAP in terms of product yield, characteristics and energy consumption and further it compares it with conventional pyrolysis. The significant role of biochar as catalyst in microwave pyrolysis for enhancing the product selectivity and quality, and the influence of microwave activation on product composition identified through sophisticated techniques has been highlighted. Besides, the application of MAP based biochar as soil conditioner and heavy metal immobilization has been illustrated. MAP accomplished at low temperature creates uniform thermal gradient than conventional mode, thereby producing engineered char with hotspots that could be used as catalysts for gasification, energy storage, etc. The stability, nutrient content, surface properties and adsorption capacity of biochar was enhanced by microwave activation, thus facilitating its use as soil conditioner. Many reviews until now on MAP mostly dealt with operational conditions and product yield with limited focus on comparative energy consumption with conventional mode, analytical techniques for product characterization and end application especially concerning agriculture. Thus, the present review adds on to the current state of art on microwave assisted pyrolysis covering all-round aspects of production followed by characterization and applications as soil amendment for increasing crop productivity in addition to the production of value-added chemicals, thus promoting process sustainability in energy and environment nexus.

Slow Pyrolysis as a Method for Biochar Production from Carob Waste: Process Investigation and Products’ Characterization

The zero-waste city challenge of the modern society is inevitably addressed to the development of model’s waste-to-energy. In this work, carob waste, largely used in the agro-industrial sector for sugar extraction or locust beangum (LBG) production, is considered as feedstock for the slow pyrolysis process. According to the Food and Agriculture Organization of the United Nations (FAO), in 2012, the world production of carobs was ca. 160,000 tons, mainly concentrated in the Mediterranean area (Spain, Italy, Morocco, Portugal, and Greece). To evaluate the biomass composition, at first, the carob waste was subjected to thermo-gravimetric analysis. The high content of fixed carbon suggests that carobs are a plausible candidate for pyrolysis conversion to biochar particles. The thermal degradation of the carob waste proceeds by four different steps related to the water and volatile substances’ removal, degradation of hemicellulose, lignin and cellulose degradation, and lignin decomposition. Considering this, the slow pyrolysis was carried out at three different temperatures, specifically, at 280, 340, and 400 °C, and the obtained products were characterized. Varying the processing temperature, the proportion of individual products’ changes with a reduction in the solid phase and an increase in liquid and gas phases, with an increase in the pyrolysis temperature. The obtained results suggest that carob waste can be considered a suitable feedstock for biochar production, rather than for fuels’ recovery.

Colored cotton wastes valuation through thermal and catalytic reforming of pyrolysis vapors (Py-GC/MS)

This study aims to analyze the products of the catalytic pyrolysis of naturally colored cotton residues, type BRS (seeds from Brazil), called BRS-Verde, BRS-Rubi, BRS-Topázio and BRS-Jade. The energy characterization of biomass was evaluated through ultimate and proximate analysis, higher heating value, cellulose, hemicellulose and lignin content, thermogravimetric analysis and apparent density. Analytical pyrolysis was performed at 500 °C in an analytical pyrolyzer from CDS Analytical connected to a gas chromatograph coupled to the mass spectrometer (GC/MS). The pyrolysis vapors were reformed at 300 and 500 °C through thermal and catalytic cracking with zeolites (ZSM-5 and HZSM-5). It has been noticed that pyrolysis vapor reforming at 500 °C promoted partial deoxygenation and cracking reactions, while the catalytic reforming showed better results for the product deoxygenation. The catalyst reforming of pyrolysis products, especially using HZSM-5 at 500 °C, promoted the formation of monoaromatics such as benzene, toluene, xylene and styrene, which are important precursors of polymers, solvents and biofuels. The main influence on the yields of these aromatic products is due to the catalytic activity of ZSM-5 favored by increased temperature that promotes cracking reactions due expanded zeolites channels.

Sustainable green strategy for recovery of glucose from end-of-life euro banknotes

Usually, Euro banknotes are made from cotton substrates and their waste is disposed of in landfill or is incinerated. In order to valorize the end-of-life euro banknotes (ELEBs), the substrates were used in this research for cellulase production via submerged fungal fermentation (SFF), and the resultant fungal cellulase w s used in ELEBs hydrolysis process for extraction of glucose. The experiments were started by exposing the ELEBs to different types of pretreatments, including milling process, alkali (NaOH/urea solution), and acid leaching to remove any contamination (e.g. dyes) and to decrease the crystallinity of cellulose (the main element in cotton substrate) thus increasing the degradation rate during the fermentation process. The effect of pretreatments on the morphology and chemical composition of ELEBs was observed using Scanning Electron Microscope and Energy Dispersive Spectrometry. Afterwards, Trichoderma reesei-DSM76 was used for cellulase production from the treated ELEBs with high cellulase activity (12.97 FPU/g). The resultant cellulase was upscaled in a bioreactor and used in ELEBs hydrolysis. Finally, the results showed that the optimized pretreatment methods (milling followed by leaching process) significantly improved the cellulase activity and glucose recovery, which was estimated by 96%. According to the obtained results, the developed strategy has a great potential for conversion of ELEBs into a glucose product that could be used in biofuels and bioplastics applications.

Waste-to-energy nexus: A sustainable development

An upsurge in global population due to speedy urbanization and industrialization is facing significant challenges such as rising energy-demand, enormous waste-generation and environmental deterioration. The waste-to-energy nexus based on the 5R principle (Reduce, Reuse, Recycle, Recovery, and Restore) is of paramount importance in solving these Gordian knots. This review essentially concentrates on latest advancements in the field of 'simultaneous waste reduction and energy production' technologies. The waste-to-energy approaches (thermal and biochemical) for energy production from the agricultural residues are comprehensively discussed in terms environmental, techno-economic, and policy analysis. The review will assess the loopholes in order to come up with more sophisticated technologies that are not only eco-friendly and cost-effective, but also socially viable. The waste-to-energy nexus as a paradigm for sustainable development of restoring waste is critically discussed considering future advancement plans and agendas of the policy-makers.

On the pyrolysis of different microalgae species in a conical spouted bed reactor: Bio-fuel yields and characterization

The aim of this work was to study fast pyrolysis of three microalgae species in a continuous bench-scale conical spouted bed reactor at 500 °C. Bio-gas, bio-oil and bio-char yields have been determined and characterized by using GC, GC/MS, elemental analyzer and SEM. Bio-oil was the main product obtained through pyrolysis of microalgae. The non-condensable gaseous stream is made up of mainly hydrogen, carbon monoxide and carbon dioxide, apart from other light hydrocarbons detected in lower concentration, as are methane, ethane, ethylene, propane and propylene. The compounds identified in the bio-oil have been categorized into hydrocarbons, nitrogen containing compounds, ketones, alcohols, acids, lactones, phenols and aldehydes. The nitrogen and carbon contents of the microalgae bio-chars are higher than those for bio-chars derived from other biomasses. Pyrolysis improved the morphology and porous structure of microalgae. Finally, the mechanism involving microalgae pyrolysis has been approached and the main reaction pathways have been proposed.

Recent advances in catalytic co-pyrolysis of biomass and plastic waste for the production of petroleum-like hydrocarbons

The global economy is threatened by the depletion of fossil resources and fluctuations in fossil fuel prices, and thus it is necessary to exploit sustainable energy sources. Carbon-neutral fuels including bio-oil obtained from biomass pyrolysis can act as alternatives to fossil fuels. Co-pyrolysis of lignocellulosic biomass and plastic is efficient to upgrade the quality of bio-oil because plastic facilitates deoxygenation. However, catalysts are required to produce bio-oil that is suitable for potential use as transportation fuel. This review presents an overview of recent advances in catalytic co-pyrolysis of biomass and plastic from the perspective of chemistry, catalyst, and feedstock pretreatment. Additionally, this review introduces not only recent research results of acid catalysts for catalytic co-pyrolysis, but also recent approaches that utilize base catalysts. Future research directions are suggested for commercially feasible co-pyrolysis process.

Ex situ catalytic fast pyrolysis of soy sauce residue with HZSM-5 for co-production of aromatic hydrocarbons and supercapacitor materials

A promising approach is proposed for the efficient conversion of soy sauce residue (SSR) into aromatic hydrocarbons and a supercapacitor electrode material by ex situ catalytic fast pyrolysis (CFP) technology with HZSM-5. The thermal decomposition behaviors of SSR were first investigated via thermogravimetry (TG) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analyses. The ex situ CFP of SSR was conducted to elucidate the aromatic hydrocarbons production under different pyrolysis temperatures and HZSM-5-to-SSR (HZ-to-SSR) ratios using both Py-GC/MS and lab-scale instruments. The results indicated that the aromatic hydrocarbons reached the maximal yields of 22.20 wt% from Py-GC/MS with an HZ-to-SSR ratio of 11 at 650 °C, and 17.61 wt% from the lab-scale device with an HZ-to-SSR ratio of 2, respectively. The as-obtained yield of aromatic hydrocarbons was far higher than those obtained from typical lignocellulosic biomass materials, confirming that SSR is a promising material for aromatics production. The pyrolytic solid product collected with this method was further activated by KOH to synthesize N-doped activated carbon (NAC) for supercapacitors. The physicochemical analysis showed that NAC possessed N-incorporated hierarchical pores, and exhibited a promising capacitance of 274.5 F g⁻¹ at 1 A g⁻¹.

A new method to co-produce aromatic hydrocarbons and a supercapacitor material from the catalytic fast pyrolysis of soy sauce residue has been developed.

Enhancement of hydrocarbons production through co-pyrolysis of acid-treated biomass and waste tire in a fixed bed reactor

The elution of metallic content from cotton stalk (CS) and its co-pyrolysis with waste tires (WT) was investigated in fixed bed reactor. Hydrochloric acid (HCl) was used for leaching and successful removal of metals from cotton stalk was observed. Removal efficiencies of 86%, 58%, 48%, 58% and 35% for potassium, calcium, magnesium, sodium, and iron metals were achieved, respectively. Pyrolysis and co-pyrolysis using various mixing ratios of raw (R-CS) and acid washed cotton stalk (W-CS) with waste tire were carried out at 550 °C. Co-pyrolyzing W-CS with WT not only resulted in increased liquid yield with reduced char and gas yields, but also improved the quality of pyrolytic oil evincing the occurrence of strong positive synergistic effect. The addition of WT reduced oxygenates, density and water content of oil whilst pH and calorific value are increased compared to both, R-CS and W-CS pyrolytic oils. Relative percentage area of hydrocarbons increased to 65% in co-pyrolysis of WT with W-CS as compared to 47% for that of R-CS at optimum blend ratio (CS:WT 1:3). Likewise, 19% higher reduction in oxygenated compounds was observed in W-CS and WT co-pyrolytic oil. Co-pyrolyzing WT with R-CS and W-CS resulted in improved quality of oil. However, the synergistic effect was less significant for R-CS suggesting that the presence of intrinsic metals in R-CS hampered the occurrence of synergistic effects.

A study on the performance of coke resistive cerium modified zeolite Y catalyst for the pyrolysis of scrap tyres in a two-stage fixed bed reactor

Catalytic pyrolysis is a useful technique for the conversion of scrap tyres into liquid fuels. Zeolite catalysts were employed in the pyrolysis of scrap tyres for the production of aromatic rich fuel. Deactivation of zeolite catalysts during pyrolysis reaction was investigated which played an important role in the product quality and composition. Herein, the performance of microporous zeolite catalysts and mesoporous MCM-41 catalyst was evaluated in a two-stage fixed bed reactor for the pyrolysis of scrap tyres. Comparative studies showed the increase in the production of aromatic compounds up to 23.7% over zeolite catalyst as compared to 18.7% over MCM-41 catalyst. However, Zeolite Y catalyst exhibited higher coke formation led to the rapid deactivation. The stability of zeolite catalysts is addressed by the incorporation of Cerium metal within the framework of two zeolite catalysts namely Zeolite Y and ZSM-5 through the ion-exchange technique. Parent and spent catalysts were characterised using synchrotron FT-IR spectroscopy, temperature-programmed desorption of ammonia (NH₃-TPD), N₂ Physisorption, scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), energy-dispersive X-ray spectroscopy (EDX), and hydrogen temperature-programmed reduction (H₂-TPD). A higher percentage of aromatics were produced over the large pore Zeolite Y. Cerium ion-exchange decreased the formation of coke from 8.1% to 5.7% over submicron and large pore Zeolite Y catalyst. Moreover, naphthalene production decreased over both Ce-Zeolite Y and Ce-ZSM-5.

Ca-based Catalysts for the Production of High-Quality Bio-Oils from the Catalytic Co-Pyrolysis of Grape Seeds and Waste Tyres

The catalytic co-pyrolysis of grape seeds and waste tyres for the production of high-quality bio-oils was studied in a pilot-scale Auger reactor using different low-cost Ca-based catalysts. All the products of the process (solid, liquid, and gas) were comprehensively analysed. The results demonstrate that this upgrading strategy is suitable for the production of better-quality bio-oils with major potential for use as drop-in fuels. Although very good results were obtained regardless of the nature of the Ca-based catalyst, the best results were achieved using a high-purity CaO obtained from the calcination of natural limestone at 900 °C. Specifically, by adding 20 wt% waste tyres and using a feedstock to CaO mass ratio of 2:1, a practically deoxygenated bio-oil (0.5 wt% of oxygen content) was obtained with a significant heating value of 41.7 MJ/kg, confirming its potential for use in energy applications. The total basicity of the catalyst and the presence of a pure CaO crystalline phase with marginal impurities seem to be key parameters facilitating the prevalence of aromatisation and hydrodeoxygenation routes over the de-acidification and deoxygenation of the vapours through ketonisation and esterification reactions, leading to a highly aromatic biofuel. In addition, owing to the CO2-capture effect inherent to these catalysts, a more environmentally friendly gas product was produced, comprising H2 and CH4 as the main components.

A study on catalytic co-pyrolysis of kitchen waste with tire waste over ZSM-5 using TG-FTIR and Py-GC/MS

Co-pyrolysis characteristics of kitchen waste (KW) with tire waste (TW) were studied by TGA-FTIR and Py-GC/MS. The kinetic parameters were calculated by Ozawa-Flynn-Wall (OFW) and the Kissinger-Akahira-Sunose (KAS) methods. TGA-FTIR results indicated that CO₂, CO, NO, NH₃, SO₂, CH and CC groups were the main gases released from the pyrolysis process, finding that a certain coupling synergistic interaction occurred between KW and TW. Co-pyrolysis of KW and TW displayed positive synergy in pyrolysis kinetics, especially at the ratio of 5:5 whose apparent activation energy declined 16.78% (by FWO) and 17.54% (by KAS). The Py-GC/MS results found that co-pyrolysis could increase the total peak area of volatile matters (10.92-15.34%). Moreover, co-pyrolysis could increase hydrocarbons (especially for olefins (13.25-37.42%)) and inhibit non-hydrocarbon compounds (about 63%) of volatile products. In brief, co-pyrolysis of KW and TW could be a potential way for improving quality of pyrolysis oil.