Decomposition Of Toluene Research Articles

Enhanced photo-degradation of gaseous toluene over MnOx/TiO2/activated carbon under a novel microwave discharge electrodeless lamps system

Traditional photocatalytic oxidation of volatile organic compounds (VOCs) suffers low oxidation and mineralization capability, the short lifetime of the lamps, etc. The usage of microwave discharge electrodeless lamps (MDELs) is an energetic approach to eliminate pollutants with lamps having a long lifetime. Herein, a novel MDELs-photocatalytic system using MnOx/TiO2/activated carbon (AC) as the photocatalyst was explored to degrade toluene. The system displayed a superior toluene removal efficiency (94%) and mineralization rate (91%), and there was nearly no ozone emission. Owing to the formation of MnTiO3, the photocatalytic degradation activity over MnOx/TiO2/AC was remarkably increased by producing more reactive oxygen species, such as O(1D) and OH·. MnO and MnTiO3 in MnOx/TiO2/AC also promoted the decomposition of ozone to further degrade toluene via catalytic ozonation. Moreover, the excellent microwave absorbing property of MnOx/TiO2/AC increased the catalyst bed temperature to nearly 150 °C, accelerating the thermal decomposition of toluene due to the “hot spots” effect. The degradation mechanism was proposed tentatively. This work shed new light on the effective removal of VOCs using a novel MDELs photodegradation system over multi-functional catalysts.

Tubular Membrane-Like Catalysts for the Oxidative Decomposition of Low-Concentrated Toluene in Air by Periodic Short-Term Plasma Discharge

A porous membrane-like alumina (MA) tube was employed as a catalyst to improve the energy efficiency of the oxidative decomposition of low-concentrated toluene in air by periodic short-term plasma discharge. The raw MA tube prepared by anodizing an aluminum tube had a relatively small surface area and toluene adsorption capacity, but they were remarkably increased by silica coating. Introducing the silica-coated catalyst into the dielectric-barrier discharge plasma generated for 5 s every 1 min resulted in a 3.6-fold increase in the rate of the toluene decomposition in a closed-circulating reaction system, suggesting that the toluene molecules were condensed by adsorption onto the catalyst surface and then decomposed by plasma. The energy efficiency was 14 g kWh−1, which was 9.3 times larger than that for the non-catalytic oxidation of toluene by continuous plasma irradiation. Palladium loading onto the catalyst slightly degraded the decomposition rate, but it suppressed the formation of organic by-products. These results clearly indicate the effectiveness of using a membrane-like catalyst in periodically-irradiated plasma reactors for VOC decompositions.

A Novel 3DOM TiO2 Based Multifunctional Photocatalytic and Catalytic Platform for Energy Regeneration and Pollutants Degradation

AbstractThe ternary 3D ordered macroporous (3DOM) heterojuncted nanocomposites (platinum/bismuth molybdate/3DOM TiO2: 3DOM‐Pt/Bi2MoO6/TiO2) are designed and synthesized as multifunctional platform for photocatalytic dye degradation, photoelectrocatalytic (PEC) water splitting, and thermal‐catalytic toluene decomposition with high performance. A series of structural, optical, and electronic characterizations demonstrates that the remarkably improved photocatalytic degradation and PEC water splitting activities are attributed to the combined effects of enhanced light harvesting, abundant reactive sites, facile reactants transfer, and efficient charges–holes pair separation. Through optimizing the loading amounts of Pt and Bi2MoO6, it is found that the 1%Pt/10%Bi2MoO6/TiO2 nanocomposite exhibits the highest photocatalytic Rhodamin B (RhB) degradation rate and PEC water splitting activity, which are 10 and 2.2 times higher than that of the titania photonic crystal (PC‐TiO2) photocatalyst, respectively. This work clearly illustrates that the ternary photocatalyst with 3DOM structure and intimate heterostructure can significantly facilitate the transfer of reaction intermediates and the separation of photogenerated carriers. Considering its unique 3DOM structure and excellent photocatalytic/PEC performances, the ternary nanocomposite has been used in catalytic toluene decomposition and inspiringly shows high efficiency, being very promising in thermocatalytic applications. This work provides new solutions in developing new ternary nanocomposites for versatile applications in photocatalytic, photoelectrochemical, and catalytic fields.

Nonthermal plasma catalysis for toluene decomposition over BaTiO3-based catalysts by Ce doping at A-sites: The role of surface-reactive oxygen species

The insights on the primary surface-reactive oxygen species and their relation with lattice defects is essential for designing catalysts for plasma-catalytic reactions. Herein, a series of Ba1−xCexTiO3 perovskite catalysts with high specific surface areas (68.6–85.6 m2 g−1) were prepared by a facile in-situ Ce-doping strategy and investigated to catalytically decompose toluene. Combining the catalysts with a nonthermal plasma produced a significant synergy effect. The highest decomposition efficiency (100%), COx selectivity (98.1%), CO2 selectivity (63.9%), and the lowest O3 production (0 ppm) were obtained when BC4T (Ce/Ti molar ratio = 4:100) was packed in a coaxial dielectric barrier discharge reactor at a specific input energy of 508.8 J L−1. The H2-TPR, temperature-programmed Raman spectra, EPR and OSC results suggested that superoxides (•O2−) were the primary reactive oxygen species and were reversibly generated on the perovskite surface. Molecular O2 was adsorbed and activated at the active sites (Ti3+-VO) via an electron transfer process to form •O2−. Surface-adsorbed •O2− had a greater effect on the heterogeneous surface plasma reactions than the dielectric constant, and enhanced the toluene decomposition and intermediate oxidation. A possible reaction path of toluene decomposition was also proposed.

Gold catalysts supported on cerium-modified mesoporous zirconia for total toluene oxidation. Effect of Ce/Zr molar ratio

Our study focused on the synthesis of gold catalysts supported on mixed Ce–ZrO2 (Ce/Zr = 0, 0.1, 0.4 and 0.9) mesoporous, which are mainly potential in the total oxidation of toluene and other volatile organic compounds. The mesoporous Ce–ZrO2 oxides (Ce/Zr = 0, 0.1, 0.4 and 0.9) were prepared via soft template strategy, using a triblock copolymer as a template. 1% of Au was loaded on mixed oxide mesoporous by deposition precipitation method. Ce–ZrO2 and Au/Ce–ZrO2 (Ce/Zr = 0, 0.1, 0.4 and 0.9) samples were characterized by XRD, N2 adsorption–desorption, H2-TPR and MET. The results showed that the dispersion of the gold particles on Ce–ZrO2 depends on the Ce/Zr ratio. These catalysts were then tested in the deep oxidation of toluene oxidation where they exhibited an excellent catalytic activity by complete decomposition of toluene at the reaction temperature equal to 576 K. This activity is correlated with the dispersion of the gold particles; itself is correlated with the Ce/Zr ratio.

Carbothermic reduction of carbon aerogel-supported Fe during the catalytic decomposition of toluene

Iron-catalyzed tar decomposition is studied by inspecting changes in catalytic activity and its correlation to the metal oxidation numbers. A carbon-aerogel-supported iron (Fe/CAG) catalyst was used herein to decompose toluene (model tar) at between 500 °C and 700 °C. The catalytic decomposition was studied in a conventional reaction system, and the catalyst was characterized prior to and after the reaction to understand the effect of the structural changes in the catalytic activity. The results demonstrated that the iron oxidation state and coke deposition strongly depend on the reaction temperature. The X-ray diffraction patterns confirmed that at T < 700 °C, several Fei+ are present, while at 700 °C, Fe° prevails, suggesting a reconstruction of the metal clusters on the surface. The Fe/C ratio determined by elemental mapping (EDS), as well as thermogravimetric analysis coupled to mass spectrometry (TGA-MS) of the spent catalysts, confirmed that this surface reconstruction is related to carbothermic reduction of the metal oxides and assisted by carbon deposition.

High-efficiency photocatalytic decomposition of toluene over defective InOOH: Promotive role of oxygen vacancies in ring opening process

The potential of oxygen vacancies (OVs) has been demonstrated in controlling photocatalytic activities by altering the electronic and/or band structures of photocatalysts. The effects of oxygen vacancies on photocatalytic reaction processes are yet unclear. In this work, indium oxyhydroxide (InOOH), well known as a wide band p-block metal compound with OVs, was synthesized through a one-pot solvothermal method to explore the roles of OVs in photocatalytic oxidation and ring opening of toluene. The defect level introduced by OVs enhanced light absorption and charge carrier separation, while promoting the activation of reactants to generate active oxygen species. As such, the modified InOOH was validated to enhance the photocatalytic performance by lowering the reaction energy barrier of the key intermediates during toluene oxidation (relative to the pristine InOOH). More strikingly, the energy barrier for the formation of benzoic acid was reduced with the increasing number of OVs on InOOH (accompanied by the increases in the ring opening reaction rates), in line with the results derived from the in situ DRIFTS investigation and theoretical calculation. Accordingly, it is possible to explain the mechanism regulating the photocatalytic oxidation of toluene on defective InOOH. This work could provide an electronic insight into oxygen vacancy engineering as a new strategy to enhance the photocatalytic selectivity and activity for VOC degradation.

Effect of supports on plasma catalytic decomposition of toluene using in situ plasma DRIFTS

Plasma catalysis technology has been demonstrated to be effective for the decomposition of volatile organic compounds (VOCs). It is highly desired to explore the effect of supports on VOCs oxidation processes during plasma catalysis. In this work, four supports of SiO2, ZSM-5–300, ZSM-5–38 and γ-Al2O3 loading with transition metal oxides were used to decompose toluene at room temperature. It was found that toluene decomposition with 1 wt%Mn/γ-Al2O3 was highest, which was strongly proportional to the ozone decomposition ability of the catalyst. The plasma catalytic decomposition of toluene over 1 wt% MnO2 on different supports were characterized using in situ plasma diffuse reflectance infrared Fourier transform spectrometer. The results showed that 1 wt%Mn/γ-Al2O3 could further catalyze toluene to carbonate and bicarbonate via the breakage of C-C bonds from benzoic acid, while that was difficult for 1 wt% Mn/SiO2, 1 wt%Mn/ZSM-5–300 and 1 wt%Mn/ZSM-5–38. The reaction mechanism of toluene decomposition on different catalysts were proposed.

Double redox process to synthesize CuO–CeO2 catalysts with strong Cu–Ce interaction for efficient toluene oxidation

In this study, a novel double redox (DR) method was developed to synthesize highly active CuO–CeO2 (CuCe-DR) catalyst for catalytic oxidative decomposition of toluene. Compare with CuCe-C catalyst prepared by co-precipitation method, CuCe-DR catalyst exhibits a higher Ce3+ ion and incorporated Cu2+ ion concentration, and has a stronger Cu–Ce interaction. Ce3+ and incorporated Cu2+ ions can induce the formation of oxygen vacancies, and thus increasing the amount of surface chemisorbed oxygen on CuCe-DR catalyst. The strong Cu–Ce interaction can promote the electron transfer between CuO and CeO2, which improves the redox properties of CuCe-DR catalyst. Although CuCe-DR catalyst has a lower toluene adsorption capacity, CuCe-DR exhibits much higher toluene oxidation performance than CuCe-C at the temperature below 300 °C. Moreover, CuCe-DR shows higher stability than CuCe-C during 100 h long-term test due to its high oxygen mobility which inhibits coking. Finally, the possible reaction pathways and promotional mechanism on CuCe-DR in toluene oxidation are proposed. We expect this study to shed more light on the nature of the surface active site(s) of CuCe catalyst for VOCs oxidation and the development of novel redox preparation method for the synthesis highly-active catalysts.

Nonthermal plasma in practical-scale honeycomb catalysts for the removal of toluene

Nonthermal plasma combined with a practical-scale honeycomb catalyst of 5.0 cm in height and 9.3 cm in diameter was investigated for the removal of toluene. The creation of plasma in the honeycomb catalyst greatly depended on the humidity of the feed gas and the presence of metals on the honeycomb surface. Compared to the bare ceramic honeycomb, the metal-loaded one gave higher toluene removal efficiency because the decomposition of toluene by the plasma-generated reactive species occurred not only homogeneously in the gas phase but also heterogeneously on the catalyst surface. The present plasma-catalytic reactor was able to successfully remove about 80% of dilute toluene (15 ppm in air) at a large flow rate of 60 L/min with a specific energy input of 58 J/L. The honeycomb-based plasma-catalytic reactor system is promising for practical applications since it can overcome such problems as high-pressure drop and difficulty in scale-up encountered in packed-bed reactors.

Carbon Quantum Dots Modified (002) Oriented Bi2O2CO3 Composites with Enhanced Photocatalytic Removal of Toluene in Air.

In work, (002) oriented flower-like Bi2O2CO3(BOC) composites are synthesized by a facile chemical route and carbon quantum dots (CQDs) are modified on their surfaces through a hydrothermal method. The synthesized samples (CQD/BOC) are characterized by X-ray diffraction (XRD), SEM, X-ray photoelectron spectroscopy (XPS), UV-Vis diffuser reflectances (DRS), BET and TEM/HRTEM. The morphologies of CQD/BOC composites are the flower-like shapes, the irregular flaky structures and the fine spherical particles of CQDs attached. Photocatalytic performances were investigated in terms of removing gaseous toluene at a concentration of 94.3ppm in air, with the assistance of CQD/BOC under artificial irradiation. Our results show that CQDs modified (002) oriented Bi2O2CO3 exhibits good photocatalytic activity for toluene decomposition, which can be attributed to the enhanced efficient charge separation. A certain ratio composite photocatalyst (BOC-CQD-15) shows a toluene removal rate of 96.62% in three hours, as well as great stability. CO2 was verified to be the primary product. The oriented flower-like Bi2O2CO3 with carbon quantum dots on the surface shows great potential in the field of solar driven air purification.

Regeneration of Hopcalite used for the adsorption plasma catalytic removal of toluene by non-thermal plasma

A dielectric barrier discharge reactor packed with both Hopcalite & glass beads has been investigated for the total oxidation of toluene adsorbed on Hopcalite. The catalytic activity and selectivity through the possible formation of by-products during the NTP discharge for the abatement of irreversibly adsorbed toluene have been investigated by FT-IR and mass spectrometer. The regeneration of the used Hopcalite by NTP discharge has been established by (i) determining the amount of toluene adsorbed on NTP regenerated Hopcalite, (ii) investigating the catalytic activity of NTP regenerated Hopcalite and (iii) comparing the bulk and surface properties of the fresh calcined and NTP regenerated Hopcalite. The ratio of amount of irreversibly adsorbed toluene to that of the total amount of adsorbed toluene adsorbed is similar for the fresh calcined and NTP (I) regenerated Hopcalite. The catalytic activity of the NTP (I) regenerated Hopcalite is slightly enhanced when compared to that of the fresh calcined Hopcalite. Although the first NTP treatment induces partial transformation of Hopcalite into Mn3O4 with no detected related CuOx and reduces specific surface area by a factor of 2, the toluene adsorption capacity remains less affected. A plausible reaction scheme for toluene decomposition in Hopcalite PBDBD reactor is proposed.

Decomposition of Toluene with a Combined Plasma Photolysis (CPP) Reactor: Influence of UV Irradiation and Byproduct Analysis

A combined plasma photolysis (CPP) reactor was used to study the effect of UV irradiation on the removal efficiency and byproducts of toluene decomposition. The influence of UV irradiation length on the removal rate and byproducts were compared. The results show that the toluene removal is obviously improved in the CPP reactor. The removal rate is enhanced with the increase of the UV irradiation length. The increase of removal efficiency is 7.94% and 19.1% under the UV irradiation with 5 cm and 15 cm length, respectively. UV also reduces the production of ozone significantly. It is interesting to find that the effect of UV on the carbon balance is not always increased as expected, but is related to the inlet toluene initial concentration. When the inlet toluene concentration is 300 ppm or 400 ppm, the carbon balance is enhanced by UV. When the inlet concentration is lower, in 60 ppm and 100 ppm, UV no longer plays a positive role. However, UV can change the trend of carbon balance at low initial concentrations and makes it positively related to specific input energy (SIE), which is contrary to the cases without UV.

Catalytic conversion of methylated aromatics over wood-derived chars – The role of reforming agents and the effect of methyl groups

Toluene steam reforming was performed over three wood-derived chars and compared with a previously-reported pyrolytic conversion study. The heterogeneous mechanism of toluene decomposition was not directly affected by the introduction of steam, but it caused gasification of char and toluene-derived coke, which prolonged the initial high conversion efficiency. Conversely, when oxygen was used as a substitute for steam, a direct ring-opening reaction of toluene was observed, rather than solid carbon combustion. A comparison of benzene, toluene, and p-xylene conversion revealed that the presence of a methyl group on the aromatic ring enhanced its decomposition, regardless of the catalyst’s activity. However, a second methyl group did not further improve the conversion and only served to increase the intensity of secondary recombination reactions.

Catalytic conversion of toluene over a biochar bed under an inert atmosphere – The comparison of chars from different types of wood and the role of selected metals

In this paper, toluene, a tar-representing compound, was used in pyrolytic conversion tests with a wood-derived char catalyst. The decomposition mainly occurred via two competing heterogeneous reactions; the favoured reaction led to coke formation on the catalyst bed. With char saturation of the carbon deposit, a second demethylation reaction gained significance, until selectivity towards benzene formation reached 12–16%. By-products of the secondary reaction (xylenes, ethylbenzene and styrene) were also detected; however, no gas-phase toluene decomposition occurred. The principles of toluene conversion were the same for all of the examined chars from the different tree species. However, a quantitative difference was observed between the chars from the wood from coniferous and deciduous trees. Pine yielded char with less mesopores and active sites and thus demonstrated a lower efficiency as a catalyst for toluene decomposition. An assessment of alkali and alkaline earth metals importance revealed that, while their presence in the char strongly enhances its oxidation rate, they did not affect the toluene pyrolysis.

Unveiling the unconventional roles of methyl number on the ring-opening barrier in photocatalytic decomposition of benzene, toluene and o-xylene

The ring-opening reaction is the rate-determining step for photocatalytic decomposition of aromatic VOCs with different methyl number. However, as a key challenge, the intrinsic relationship between the methyl number and ring-opening reaction efficiency has not been revealed. In order to clarify the ring-opening barriers and enhance the photocatalytic efficiency, the photocatalytic degradation pathway was systematically investigated aiming to elucidate the pivotal roles of methyl number on ring-opening mechanisms. The SnO2 is chosen as a photocatalyst to achieve highly efficient and stable photocatalytic degradation of benzene, toluene, and o-xylene respectively. It is unexpected to discover that the photocatalytic degradation performance and quantum efficiency are significantly elevated along with the increase of methyl number, reaching the highest efficiency for o-xylene with two methyl groups. The photocatalytic degradation efficiency of o-xylene on SnO2 is as high as 78.2 %, much higher than that of toluene (63.4 %) and benzene (55.9 %). The introduction of methyl groups could exert great influence on the distribution of electrons on the phenyl ring, enhance the adsorption and activation of benzene rings, and finally reduce the energy barrier of ring-opening reaction. The methyl number in the benzene ring is dominantly responsible for the elevated decomposition efficiency. This work proposes a new concept in mechanistic understanding of VOCs decomposition and propels the application of photocatalytic technology for efficient degradation of aromatic VOCs.

Three-dimensional hollow urchin α-MnO2 for enhanced catalytic activity towards toluene decomposition in post-plasma catalysis

Complete oxidation of volatile organic compounds (VOCs) with high energy efficiency remains a challenge in post-plasma catalysis (PPC) due to insufficient adsorption towards gas and relatively low catalytic activity at room temperature. Three-dimensional (3D) hollow urchin α-MnO2 for post-plasma catalytic decomposition of toluene is demonstrated in this study. Hollow urchin catalyst assembled by well-defined one-dimensional (1D) α-MnO2 nanorods is prepared by a simple one-step hydrothermal method without any template. The toluene decomposition, CO2 selectivity and carbon balance over hollow urchin α-MnO2 reach up to ~100%, ~59% and ~81% at an SIE of 240 J L−1, which are 43%, 96% and 44% superior to that of non-thermal plasma (NTP) process, respectively. The combination of NTP with hollow urchin α-MnO2 also significantly promotes the energy efficiency by 64%, reaching 13.1 g kWh−1 at an SIE of 119 J L−1. Moreover, hollow urchin α-MnO2 exhibits higher catalytic activity for toluene decomposition and ozone conversion compared with solid urchin α-MnO2. The hollow structure with an enlarged contact surface area is expected to enhance adsorption towards gas and prolong the retention of gas on the catalyst surface. Furthermore, the fully exposed non-agglomerated 1D α-MnO2 nanorods can promote oxygen vacancy density and low-temperature reducibility, facilitating the adsorption and conversion of ozone into active oxygen species (~100% ozone conversion), which leads to the deep decomposition of toluene in PPC. This work explores a new concept in designing 3D hollow urchin nanoarchitecture as a novel catalyst for efficient plasma-catalytic gas purification.

Radiation-induced transformations of isolated toluene molecules in low-temperature matrices: Towards better understanding of molecular radiation chemistry in condensed phases

The transformations of isolated toluene molecules under X-ray radiolysis in solid noble gas matrices at 6 K were characterized by FTIR spectroscopy. It was found that the efficiency of the radiation-induced decomposition of toluene was generally comparable to that of benzene. Meanwhile, a remarkable matrix effect was observed: toluene is more stable than benzene in an argon matrix, whereas it becomes more sensitive in the case of xenon matrix. This result was ascribed to the increasing role of upper triplet excited states in a xenon matrix. In all the matrices two main radiolysis products observed at moderate absorbed doses were benzyl radical and 5-methylene-1,3-cyclohexadiene (MCHD). Benzyl radical predominates in all the cases, while the relative contribution of MCHD strongly decreases in the row Ar-Kr-Xe. On the basis of this comparison, the formation of MCHD was tentatively attributed to the rearrangement of excited primary toluene radical cations. Possible scheme of the radiation-induced processes is discussed.

High energy efficient degradation of toluene using a novel double dielectric barrier discharge reactor

A double dielectric barrier discharge (DDBD) reactor was established to decompose toluene with high energy efficiency. Differences in discharge characteristics including visual images, voltage-current waveforms, Lissajous figures, and temperature variation, were determined between the DDBD and SDBD reactors. Removal efficiency, mineralization rate, CO2 selectivity, and energy yield were used to evaluate the toluene abatement performance of the two reactors. Compared to the SDBD reactor, the DDBD reactor exhibited more uniform and stable discharges due to a change in discharge mode. In addition, the DDBD reactor’s dissipated power and reactor temperature (including the gas, barrier and ground electrode) were significantly lower than those in the SDBD reactor. At 22−24 kV, the DDBD reactor showed a higher toluene removal efficiency and mineralization rate, while at 14−16 kV, the SDBD reactor exhibited higher respective value. The energy efficiency of the DDBD was 2.5–3 times that of the SDBD reactor, and the overall energy constant koverall of the DDBD reactor (1.47 mL/J) was significantly higher than that of the SDBD reactor (0.367 mL/J) as revealed by the kinetics study. Lastly, a plausible toluene degradation mechanism in the DDBD and SDBD reactors was proposed based on organic intermediates that formed during toluene decomposition.

Study of PAH formation in laminar premixed toluene and C8H10 aromatics flames

Toluene and C8H10 aromatic fuels are widely proposed as components of surrogate mixtures and usually employed as the prototypical fuels to investigate the combustion properties of aromatic fuels. In this study, the PAH formation of pure C8H10 aromatics (xylenes and ethylbenzene) and toluene was studied in a laminar premixed flame at atmospheric pressure using laser-induced fluorescence (LIF) diagnostic. The experimental results indicated the aromatic structure has a significant influence on the PAH tendency, and the observed LIF intensities were sequenced by toluene < xylenes < ethylbenzene. A detailed kinetic model was employed to validate against the experimental results based on the ROP analysis. The predicted mole fraction profiles of PAHs were consistent with the measured PAH tendency for toluene, o-xylene, and ethylbenzene. The chemical kinetic analysis indicated that benzyl is the most dominant intermediate product in toluene decomposition and precursor in PAH formation, corresponding to methylbenzyl in o-xylene flame, styrene and benzyl in ethylbenzene flame. In the comparison of o-xylene and toluene, the increased methylated groups on the benzenoid ring make the yield of benzylic radicals (mostly methylbenzyl) enhanced, increasing the probability of radical–radical recombination on PAH formation. In the ethylbenzene flame, two secondary CH bonds in the ethyl site are much easier to be abstracted than primary CH bonds in methyl sites of o-xylene. The different bond dissociation energies (BDEs) depended on the aromatic structure can change the distribution of the intermediate species in fuel decomposition, which can result in either an increase or decrease of PAH formation. Additionally, the weak benzylic CC bond makes the initiation of ethylbenzene decomposition easier, which could also explain the fated PAH formation in contrast with toluene and o-xylene. The experimental and kinetic analysis for C8H10 aromatics and toluene conducted in the present study contributed a deep insight into the PAH formation of aromatics fuels.