Aromatic Yield Research Articles

Investigating the oxidation characteristic of a hydro-processed bio-jet fuel: Experimental and modeling study

A rapid transition from conventional jet fuels to sustainable aviation fuels (SAFs) is imperative in order to reduce carbon emissions. Hydro-processed esters and fatty acids synthetic paraffinic kerosene (HEFA-SPK), as a type of SAF, exhibits broad applications. In this study, a new HEFA-SPK named ZH-HEFA was investigated. The fuel comprises 14% n-alkanes, 85% iso-alkanes and only 1% cycloalkanes by weight, with the majority of alkanes ranging from C9 to C17. Oxidation experiments of the fuel were conducted using an atmospheric pressure flow reactor at temperatures ranging from 550 K to 1075 K under three equivalence ratios (0.5, 1.0 and 1.5). Species mole fraction profiles were measured by an on-line gas chromatographic (GC). For comparison purposes, an experiment was also performed on RP-3, a conventional jet fuel commonly used in China, under the equivalence of 0.5. Compared to RP-3, ZH-HEFA exhibited significantly stronger low temperature reactivity and higher combustion conversion rates while demonstrating considerably lower yields of aromatics at high temperatures. The kinetic simulation of ZH-HEFA was achieved by proposing two surrogates and their corresponding kinetic models. Surrogate S-1 consisted solely of n-dodecane, while S-2 comprised 35% n-dodecane and 65% 2,6,10-trimethyl dodecane by weight. Both surrogate models were validated by the experimental data. S-1 exhibited a closer resemblance to the global oxidation characteristics of ZH-HEFA, whereas S-2 demonstrated improved accuracy in predicting the formation of small hydrocarbon intermediates during the fuel oxidation. Rate of production analysis revealed that the branched alkane component in S-2 possessed more pathways and greater capability than S-1 in generating C3 intermediates, which are important for the generation of aromatics. Furthermore, both models displayed good predictive performance for the auto-ignition properties of HEFA-SPK fuels.-

Catalytic pyrolysis of Padina sp. with ZSM-5 and Amberlyst-15 catalysts to produce aromatic-rich bio-oil

The growing demand for renewable energy has increased interest in bio-oil production from biomass, particularly through catalytic co-pyrolysis. However, research on marine biomass like Padina sp. is limited. This study investigates the catalytic co-pyrolysis of Padina sp. using ZSM-5 and Amberlyst-15 catalysts to enhance aromatic-rich bio-oil production. Systematic experiments were conducted with varying catalyst loadings (1 %, 2 %, and 3 %) and temperatures (400 °C, 500 °C, and 600 °C). GC/MS analysis revealed that Amberlyst-15 at 600 °C and 3 % loading achieved a 65 % aromatic hydrocarbon yield, surpassing ZSM-5, which reached 50 %. Additionally, the highest conversion efficiency, 50 %, was attained with Amberlyst-15 at 500 °C and 3 % loading. These findings highlight the viability of Padina sp. as a renewable biofuel source and emphasize the importance of catalyst selection and process optimization in refining bio-oil production techniques, suggesting that further improvements in catalyst compositions and parameters could advance sustainable bio-oil production for renewable energy.

Catalytic pyrolysis of wheat straw based on dual catalyst CaO/ZSM-5 with acid washing and torrefaction pretreatment to enhance aromatic yield in bio-oils

In this paper, the catalytic pyrolysis integrating combined pretreatment (acid washing and torrefaction) and dual catalysts was adopted to improve the quality of bio-oil and the selectivity of aromatic hydrocarbons. Combined pretreatment is a highly effective method to improve the quality of biomass feedstock. It was capable of the removal of alkali and alkaline earth metals from wheat straw, with a K removal rate of 97.79 %. Under the combined pretreatment, the aromatic hydrocarbon content in bio-oil increased to 68.8 % using the ZSM-5 catalyst alone. Compared with ZSM-5, CaO could remove part of the oxygenated functional groups and had a better acid removal effect, but the aromatic hydrocarbon yield was low to 7.95 %. After combined pretreatment using simulated aqueous phase bio-oil for acid washing, catalytic pyrolysis using CaO/ZSM-5 dual catalysts greatly enhanced the quality of the bio-oil. The oxygenated compounds content was reduced to 17.58 %, and the total hydrocarbon yield was increased to 82.42 %, especially the aromatic hydrocarbons yield was increased to 79.91 %, of which the monocyclic aromatic hydrocarbons were as high as 68.38 %, and the benzene, toluene, and xylene content reaching 49.39 %. Thus, integrating dual catalysts (CaO/ZSM-5) with combined pretreatment can effectively increase the aromatic yield for producing high-quality bio-oil.

Effects of Acid Sites on Thin MCM‐22 Zeolite Catalysts and Their Catalytic Applications for Acetylene Aromatization

AbstractTwo types of thin zeolite MCM‐22 catalysts were prepared by using a carbon sphere template. By applying different calcination methods, a hollow sphere‐type MCM‐22 catalyst (HS‐MCM‐22) and a nanosheet‐type MCM‐22 catalyst (NS‐MCM‐22) were synthesized. Those catalysts were tested and evaluated for acetylene aromatization to see the effects of thin structures. The two types of thin catalysts were found to have higher amounts of acid sites than those of the conventional MCM‐22 catalyst. It was found that the extremely short diffusion length not only enhanced the aromatic yield, but also suppressed the formation of graphitic coke. Notably, the diffusion length of NS‐MCM‐22 was found to be at least 15 times shorter than that of conventional MCM‐22, leading to an 11% and 18% increase in benzene yield, respectively. The thin structure seemed to help the produced aromatics efficiently desorb before they were further converted into carbon precursors and coke. According to the thermogravimetric analysis, the carbon species in the spent thin catalysts were found less graphitic than that of the conventional MCM‐22 catalyst. Because of this, the thin MCM‐22 catalysts were believed to show higher coke removal capability. Especially, the coke removal rate of NS‐MCM‐22 was estimated over 90% despite the severe carbon deposition during the reaction.

Decoupling Aromatic Yield and Coke Formation in Methanol‐to‐Aromatic Reaction on Zn(II) Exchanged H‐ZSM‐5 Zeolite

AbstractMethanol to aromatic reaction is an alternative pathway to produce aromatics from non‐petroleum resources. Zn‐modified ZSM‐5 zeolite is the widespread catalyst for MTA due to its high activity and selectivity to aromatics. However, a desired high yield of aromatics is usually accompanied with undesired coke formation and fast deactivation of catalyst, because aromatic molecules also serve as the precursor for coke formation. To decouple the aromatic yield and coke formation rate, in this work we use Zn‐ZSM‐5 to investigate coke formation and catalyst deactivation. The coke distribution along the catalyst bed was analyzed and its correlation with the concentration gradient of methanol, olefins and aromatics along the bed was deciphered. Coke was found to form very fast at catalyst bed in the copresence of methanol and aromatics. On the contrary, much less coke was observed at the later layers of the catalyst bed where methanol had been fully converted and aromatics were present in the highest concentration. Based on this finding, we adjusted the reaction conditions to successfully improve the yield of aromatics without reducing catalyst lifetime in compromise, by applying a higher methanol partial pressure that enables a faster consumption of methanol and reduces the period of copresence of methanol and aromatics.

Integrated approach for co-production of bioethanol and light aromatics from lignocellulose through polyethylene glycol-aided acidic glycerol pretreatment

Acid-catalyzed glycerol organosolv (GO) pretreatment is a promising method for lignocellulosic biomass (LCB) fractionation. However, this method often leads to lignin repolymerization, intensifying lignin's inhibitory effects on subsequent enzymatic hydrolysis and limiting the production of highly active lignin, thereby hindering its valorization. This study explored incorporating polyethylene glycol (PEG) into acidic-catalyzed GO to improve bioethanol and bio-oil yields, with a focus on improving the yield of light aromatics, from LCB. Optimized PEG-aided GO pretreatment achieved a significantly higher bioethanol yield (23.7 g/L) compared to GO (17 g/L) and dilute acid (DA: 11.3 g/L) pretreatments. This improvement is attributed to the ability of PEG to mitigate lignin inhibition and modify the physicochemical properties of the pretreated substrate. Furthermore, thermal pyrolysis of PEG-aided GO lignin, obtained after the fermentation process, resulted in a substantially increased bio-oil yield (45.5 %) compared to GO (19 %) and DA (12 %). The enhanced bio-oil yield from PEG-aided GO lignin is ascribed to the promotion of β-O-4 linkages and the formation of β-O-4′ linkages. Characterization of the pyrolysis bio-oil revealed that light aromatic compounds were the dominant fraction, with their relative abundance significantly increasing from DA (5.9 %) to GO (9.7 %) and PEG-aided GO lignin (24.9 %). The PEG-aided GO method achieved an energy output of 8.85 MJ/kg, exceeding that of the GO and DA methods by 31 % and 57 %, respectively. The energy conversion efficiency of the PEG-aided GO method was 70 %, demonstrating a significant improvement compared to GO (57 %) and DA (51 %). This approach promotes the circular economy by upcycling LCB for bioethanol and valuable light aromatic compound production.

Ex-situ catalytic fast pyrolysis of waste polycarbonate for aromatic hydrocarbons: Utilizing HZSM-5/modified HZSM-5

Catalytic pyrolysis has been proven as a highly efficient process for transforming waste polycarbonate (PC) into valuable aromatic hydrocarbons, especially benzene, toluene, ethylbenzene, and xylene (BTEX). In the present work, the ex-situ catalytic fast pyrolysis of PC on metal- or alkali-modified HZSM-5 was investigated using the double micro-fixed bed system. Experimental results indicate that the rapid pyrolysis of PC may follow a homolytic chain scission mechanism, resulting in pyrolysis products dominated by phenols. Metal- or alkali-modified HZSM-5 significantly enhances the cleavage of C-OH bonds in phenols, improving the yield of aromatics. The yield of aromatics in the liquid product is 91 %, 72 %, and 77 % when loaded with nickel (Ni), iron (Fe), and cobalt (Co), respectively, all of which are higher than unmodified HZSM-5 with the yield of 43 %. Among them, the Ni/HZSM-5 has significantly enhanced the yield of BTEX reaching 81.64 %. When using alkali-modified HZSM-5 with a larger pore volume and higher specific surface area, the yield of aromatics can be increased to 60 %. Furthermore, the dual modification of alkali treatment and Ni loading on HZSM-5 simultaneously enhanced catalytic activity and resistance to coke formation. The yield of BTEX reaches 94.47 %. The BTEX formation mechanism can be explained by direct deoxygenation (DDO) of the pyrolytic volatiles of PC and the “phenol pool” mechanisms of primary products on the catalyst surface. This study enriches the understanding of catalytic pyrolysis of PC and provides a theoretical foundation for the harmless treatment of PC.

Synergistic Interaction during Copyrolysis of Soybean Straw and Tire Waste: Improving Emissions and Product Quality.

This study explores copyrolysis of soybean straw (SS) with hydrogen-rich tire waste (TW) to enhance pyrolytic product quality and reduce pollutant emissions. Addition of TW increased SS biomass conversion from 67.19 to 72.46% and decreased coke/residue formation from 32.81 to 27.54%. The activation energy dropped to 121.84 kJ/mol from 160.73 kJ/mol (as calculated by the Kissinger-Akahira-Sunose method) and 122.78 kJ/mol from 159.76 kJ/mol (as calculated by the Ozawa-Flynn-Wall method). Thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TG-FTIR) showed lowered CO2, NO2, and SO2 emissions (5.58, 5.72, 3.38) compared to conventional SS pyrolysis (18.38, 11.55, 12.37). Yields of value-added chemicals (phenols, olefins, aromatics) increased (32.38, 22.17, 30.18%) versus conventional SS pyrolysis (23.56, 13.78, 20.36%). Pyrolysis gas chromatography-mass spectrometry (Py/GC-MS) analysis reveals that the addition of TW leads to a decrease in the production of oxygenates and polycyclic aromatic hydrocarbons, reducing their yields to 8.96 and 7.67%, respectively, down from 19.37 and 14.37%. Simultaneously, it enhances the yields of olefins, aromatics, phenols, and aliphatic hydrocarbons to 23.38, 26.78, 26.17, and 25.78%, respectively, compared to 15.37%, 15.29, 18.36, and 17.25%, respectively, in the absence of TW. In summary, copyrolysis of TW with SS improves product quality and reduces pollutant emissions, marking a significant research contribution.

Co-aromatization of methane and methanol over MoxZn/HZSM-5 to increase aromatic hydrocarbon yield: experimental and kinetic studies

Co-aromatization of methane and methanol over MoxZn/HZSM-5 was conducted to improve hydrocarbon yield and methane conversion. Natural gas, coalbed methane, and coke oven gas are rich in methane. The utilization of methane-rich gas is particularly important as energy demand continues to increase and environmental requirements continue to rise. The efficient conversion to light aromatics is obtained using a co-feed of methane and methanol under relatively mild conditions and catalyzed by MoxZn/HZSM-5. In general, Mo species promote the C-H bond breaking of methane to produce intermediates. Mo is transformed into Mo2C in the co-aromatization reaction as observed by FT-IR and XPS, which leads to the higher activity and aromatic selectivity of the catalyst and can also avoid carbon deposition of the catalyst. Furthermore, kinetic analysis results indicate that olefins play an important role during the co-aromatization of methane and methanol. Olefins are the key reaction intermediates to form aromatics and olefins initially formed in the transformation reaction of methanol perhaps promote the conversion of methane.

Boron doped Mo/HMCM-22 catalyst for improving coke resistance in methane dehydroaromatization

Mo/HMCM-22 is one of the candidate catalysts for methane dehydroaromatization (MDA) reaction. However, serious coke deposition would deactivate the catalyst, resulting in a rapid decrease of aromatics yield. Here, we adjusted the acidity of MCM-22 zeolite by doping boron into the framework. Boron species replace some of framework aluminum and prompt aluminum to locate in sinusoidal channel. It optimizes the ratio of strong/weak Brønsted acid, as well as enhances the interaction between molybdenum and HMCM-22 to facilitate the dispersion of molybdenum species. After 10 h of MDA reaction, the yield of aromatics over Mo/H[B]MCM-22 (SBR 30) is 3.5 times higher than that of Mo/H[B]MCM-22 (SBR 5). It decreases by only 4.8 % in comparison to the initial yield. Meanwhile, Mo/H[B]MCM-22 (SBR 30) shows significantly better resistance to coke deposition. Therefore, the established structure–activity relationships provide valuable insights for future research on the modification of zeolite acidity in methane dehydroaromatization reaction.

The effects of in situ-produced hydrogen on catalytic upgrading of lignite pyrolysis volatiles over ZSM-5 zeolites to produce light aromatics

The introduction of in situ hydrogen donors to obtain a high H/Ceff ratio is an effective way to upgrade coal pyrolysis volatiles to light aromatics. In this study, the influence of different in-situ hydrogen suppliers in catalytic reforming of coal pyrolysis vapors was explored. The abilities of active hydrogen donation were greatly corresponded to structures of hydrogen donors. Isopropanol showed the best catalytic performance due to the release of a large amount of active α-H as a result of negative inductive effect of hydroxyl. Whereas tertbutanol showed the poorest catalytic performance owing to the lack of α-H. Meanwhile, the effect of in-situ hydrogen production via steam reforming with different alcohols on light aromatic yields was investigated. The highest BTEXN yield was obtained under in-situ hydrogen production from isopropanol steam reforming. Two circumstances of hydrogen supply were further compared. Relatively higher BTEXN yield was presented in the reaction of methanol steam reforming than that of using methanol solely. However, higher BTEXN yield was contrarily obtained from sole isopropanol as a hydrogen donor despite lower H2 production was gained compared to the case of isopropanol steam reforming. The fact was probably ascribed that high electron-withdrawing effect of hydroxyl for isopropanol promoted the cleavage of α-C-H bond and favored the transfer of active hydrogen to reactants over acid sites.

Pyrolysis and catalytic upgrading of pine wood sawdust over modified biochar catalyst in a tandem microreactor

A series of novel catalysts were prepared by modifying biochar (BC) with different metal loading (Fe, Zn) and thermal activation in different atmospheres (CO2, H2O). The catalysts were further used to upgrade the pyrolysis vapor from pine wood sawdust, aiming to produce high-quality bio-oil. The modified biochar catalyst exhibited strong deoxygenation ability to acids and ketones in bio-oil and effectively converted lignin-derived compounds into aromatic hydrocarbons and phenols. Subsequently, the catalyst (BC-Fe-CO2) demonstrating the highest yields of phenols and aromatics was selected for condition optimization. Different catalytic temperatures and biomass-to-catalyst ratios were compared to determine the optimal conditions for producing high-quality bio-oil. Phenolics and aromatic hydrocarbons content in the bio-oil reached 70 % at the optimal condition and the selectivity of monocyclic aromatic hydrocarbons in aromatic hydrocarbons reached 77 %. The properties of the biochar catalysts were characterized using BET, SEM, XRD, and XPS. The superior performance of the modified BC catalysts not only relied on its enhanced surface area and porous structure but also due to active Fe sites. The detail reaction pathways of the bio-oil catalytic upgrading were also proposed. These findings underscore the potential of modified biochar in pyrolysis and catalytic upgrading for bio-oil with improved quality.

Synergistic effects of Fe@C catalysts prepared at different carbonization temperatures on microwave co-pyrolysis of biomass and plastic for high-value oil and gas production

This study explores the impact of Fe@C catalysts, prepared at different carbonization temperatures, on the microwave co-pyrolysis of bamboo and polyethylene (BP) for the production of high-value oil and gas. In the synthesis of MIL-101(Fe), bamboo-derived pyrolytic carbon was added, and this was used as a precursor to synthesize Fe@C catalysts through microwave carbonization. Various properties and characteristics of Fe@C catalysts were analyzed using XRD, BET, SEM, FT-IR, and Raman spectroscopy to understand its structure and performance comprehensively. The composition of bio-oil, pyrolysis gas, and product distribution were analyzed. The results show that Fe@C catalysts enhances the yield of pyrolysis gas, as well as the selectivity of H2 in the pyrolysis gas and aromatic hydrocarbons in the bio-oil. Among them, Fe@C-700 catalysts achieved the highest synthesis gas yield (89.35 vol%) and aromatic hydrocarbon yield (27.13 %). Additionally, the proportion of light aromatic hydrocarbons (BTX) in the aromatic hydrocarbon compounds can reach up to 31.33 %. This study provides valuable insights into the synergistic effects of Fe@C catalysts during BP microwave co-pyrolysis, highlighting their potential for the production of high-value oil and gas from biomass and plastic.

Catalytic co-pyrolysis of woody biomass with polypropylene: Effects of Korean loess hybrid catalysts and pyrolysis temperatures

This paper describes an effort to improve the catalytic characteristics of Korean loess (KL) for the co-pyrolysis of biomass and polypropylene, resulting in a unique multifunctional catalyst. Korean loess was physically and chemically transformed into a microporous structure (ZSM) fitting for co-pyrolysis. Using the catalysts manufactured above, analytical co-pyrolysis was carried out using a Py-GC/MS system with pinewood sawdust and polypropylene mixed at a ratio of 1:1 (w/w). To investigate the impacts of the use of catalysts and the pyrolysis temperatures on the distribution of volatile pyrolytic products, the experiments were designed to mix 2- or 8-fold catalyst mass quantities with feedstock and pyrolyze at temperatures of 500 °C, 600 °C, and 700 °C. Compared to pure Korean loess, the catalytic activity of the optimal hybrid catalyst (0.2KL/ZSM) favored decarbonylation over dehydration, making it more effective than mesoporous ZSM. Pyrolytic products generated using the hybrid catalyst (0.2KL/ZSM) had a higher hydrogen concentration (9.8 wt%) than pyrolytic products produced using ZSM catalysts (6.5 wt%). Because of this, the pyrolytic products were expected to be more compatible as a fuel over 0.2KL/ZSM, with an HHV of 27.4 MJ/kg as opposed to 26.5 MJ/kg over ZSM. Zeolite framework catalysts could promote the production of aromatic chemicals (3.0 mg/g for non-catalyst, 34.7 mg/g for KL, and 53.9 mg/g for 0.2KL/ZSM) in the co-pyrolysis of PP with pine, which synergistically enhance oligomerization, cyclization, and aromatization reactions at catalyst acid sites. Concerning aromatic hydrocarbon yields, 0.2KL/ZSM could be expected to perform very similarly to ZSM in producing 74.7 mg/g of MAH+PAH at 600 °C.

The effect of Ce promotor on catalytic performance of Zn/ZSM-5 in coaromatization of methanol and n-hexane

Ce modified Zn/ZSM-5 catalyst was prepared and the effect of Ce promotor on coaromatization of methanol and n-hexane was studied. The physical and chemical properties of Zn–Ce/HZ were tested by XRD, XPS, TEM, N2 adsorption-desorption and Py-FTIR. The loading of Ce tuned the acidity distribution and increased the LAS/BAS ratio, and mainly reduced the microporous specific surface area. Most of Zn and Ce elements entered the zeolite channels. The loading of Ce enhanced the interactions between Zn species and support and significantly increased the numbers of active centers of ZnOH+ species. Under the optimized conditions, the yield of aromatics was greatly improved from 25.2 % of HZ to 62.6 %. The reasons of deactivation were also analyzed. The higher the aromatization activity, the more the formed carbon deposit. The blockage of micropores and the greatly coverage of acid sites by carbon deposit thus resulted in poor catalytic performance.

Coke formation on different metal-modified (Co, Mo and Zr) ZSM-5 in the catalytic pyrolysis of cellulose to light aromatics

Catalytic pyrolysis of biomass is regarded as a promising method for preparing value-added products. However, the main factors limiting the development of the process at present are the low yield of value-added products and poor selectivity, especially for rapid catalyst deactivation due to coke deposition. The present study focuses on the catalytic pyrolysis of cellulose over metal Co-, Mo-, and Zr-loaded catalysts using a falling fixed bed at 600 °C to evaluate the type of coking of the catalysts as well as the effect of the different metal active sites on the formation of coke deposits. The introduction of Co and Mo metal sites increased the light aromatics yield of ZSM-5 from 128.9 mg/g to 147.2 mg/g and 143.0 mg/g. And the yield of coke deposits decreased from 8.3 to 6.8 and 5.1 wt%. The stability evaluation of the catalyst showed that the deactivation degree of ZSM-5 of the supported metal Co was lower than that of commercial ZSM-5, while the ZSM-5 of the supported metal Mo was rapidly deactivated. The deactivation of the catalysts depended more on the morphology or location of the accumulated coke than on the total amount deposited. The clogging of metal and acidic sites on the surface of the zeolite and the pore channels by the amorphous encapsulating coke was the main cause of catalyst deactivation. The metal Mo active sites promoted dehydrogenation coupling and hydrogen transfer during coke formation, forming a more highly disordered multiring structure, and the metal Co active sites were more capable of decomposing macromolecular compounds, olefins and alkanes, and promoted the formation of graphite-like structural carbon.

Catalytic co-pyrolysis of cabbage waste and plastics with Ni/ZSM-5 catalysis to produce aromatic-rich oil

This study investigates the selective production of aromatics through the co-pyrolysis of cabbage waste and plastics followed by catalytic reforming with Ni-modified ZSM-5. Co-pyrolysis significantly improves the inflection point (a parameter for determining thermal stability) to 251.3 °C from 232.7 °C. This process also enhances the relative yield of olefins and phenols, which are precursors for aromatic production to 25.46 and 17.23 respectively, up from 13.87 to 12.05. Furthermore, catalytic pyrolysis elevates the relative yield of aromatics to 53.4, as confirmed by Thermogravimetric Analysis (TGA) and Thermogravimetric-Fourier Transform Infrared Spectroscopy (TG-FTIR) analyses. GC-MS confirms the enhanced formation of valuable chemical precursors via co-pyrolysis such as phenols and olefines to 18.67 % and 22.13 % leading to a 63.81 % selective yield of aromatics in the final oil with 10Ni/ZSM-5. Ni modification of ZSM-5 is influential in decreasing PAH formation (7.26 % from 20.37 %), indicating that this two-step process is an effective method for transforming waste into high-quality bio-oil with enriched aromatic content.

Aqueous-Phase Photoreactions of Mixed Aromatic Carbonyl Photosensitizers Yield More Oxygenated, Oxidized, and less Light-Absorbing Secondary Organic Aerosol (SOA) than Single Systems.

Aromatic carbonyls have been mainly probed as photosensitizers for aqueous secondary organic aerosol (aqSOA) and light-absorbing organic aerosol (i.e., brown carbon or BrC) formation, but due to their organic nature, they can also undergo oxidation to form aqSOA and BrC. However, photochemical transformations of aromatic carbonyl photosensitizers, particularly in multicomponent systems, are understudied. This study explored aqSOA formation from the irradiation of aromatic carbonyl photosensitizers in mixed and single systems under cloud/fog conditions. Mixed systems consisting of phenolic carbonyls only (VL + ActSyr + SyrAld: vanillin [VL] + acetosyringone [ActSyr] + syringaldehyde [SyrAld]) and another composed of both nonphenolic and phenolic carbonyls (DMB + ActSyr + SyrAld: 3,4-dimethoxybenzaldehyde [DMB], a nonphenolic carbonyl, + ActSyr + SyrAld) were compared to single systems of VL (VL*) and DMB (DMB*), respectively. In mixed systems, the shorter lifetimes of VL and DMB indicate their diminished capacity to trigger the oxidation of other organic compounds (e.g., guaiacol [GUA], a noncarbonyl phenol). In contrast to the slow decay and minimal photoenhancement for DMB*, the rapid photodegradation and significant photoenhancement for VL* indicate efficient direct photosensitized oxidation (i.e., self-photosensitization). Relative to single systems, the increased oxidant availability promoted functionalization in VL + ActSyr + SyrAld and accelerated the conversion of early generation aqSOA in DMB + ActSyr + SyrAld. Moreover, the increased availability of oxidizable substrates countered by stronger oxidative capacity limited the contribution of mixed systems to aqSOA light absorption. This suggests a weaker radiative effect of BrC from mixed photosensitizer systems than BrC from single photosensitizer systems. Furthermore, more oxygenated and oxidized aqSOA was observed with increasing complexity of the reaction systems (e.g., VL* < VL + ActSyr + SyrAld < VL + ActSyr + SyrAld + GUA). This work offers new insights into aqSOA formation by emphasizing the dual role of organic photosensitizers as oxidant sources and oxidizable substrates.

Coupled conversion of polyethylene and carbon dioxide catalyzed by a zeolite-metal oxide system.

Zeolite-catalyzed polyethylene (PE) aromatization achieves reduction of the aromatic yield via hydrogenation and hydrogenolysis reactions. The hydrogen required for CO2 hydrogenation can be provided by H radicals formed during aromatization. In this study, we efficiently convert PE and CO2 into aromatics and CO using a zeolite-metal oxide catalyst (HZSM-5 + CuZnZrOx) at 380°C and under hydrogen- and solvent-free reaction conditions. Hydrogen, derived from the aromatization of PE over HZSM-5, diffuses through the Brønsted acidic sites of the zeolite to the adjacent CuZnZrOx, where it is captured in situ by CO2 to produce bicarbonate and further hydrogenated to CO. This favors aromatization while inhibiting hydrogenation and secondary hydrogenolysis reactions. An aromatic yield of 62.5 wt % is achieved, of which 60% consisted of benzene, toluene, and xylene (BTX). The conversion of CO2 reaches values as high as 0.55 mmol gPE-1. This aromatization-hydrogen capture pathway provides a feasible scheme for the comprehensive utilization of waste plastics and CO2.

Upgrading CO2 to sustainable aromatics via perovskite-mediated tandem catalysis

The directional transformation of carbon dioxide (CO2) with renewable hydrogen into specific carbon-heavy products (C6+) of high value presents a sustainable route for net-zero chemical manufacture. However, it is still challenging to simultaneously achieve high activity and selectivity due to the unbalanced CO2 hydrogenation and C–C coupling rates on complementary active sites in a bifunctional catalyst, thus causing unexpected secondary reaction. Here we report LaFeO3 perovskite-mediated directional tandem conversion of CO2 towards heavy aromatics with high CO2 conversion (> 60%), exceptional aromatics selectivity among hydrocarbons (> 85%), and no obvious deactivation for 1000 hours. This is enabled by disentangling the CO2 hydrogenation domain from the C-C coupling domain in the tandem system for Iron-based catalyst. Unlike other active Fe oxides showing wide hydrocarbon product distribution due to carbide formation, LaFeO3 by design is endowed with superior resistance to carburization, therefore inhibiting uncontrolled C–C coupling on oxide and isolating aromatics formation in the zeolite. In-situ spectroscopic evidence and theoretical calculations reveal an oxygenate-rich surface chemistry of LaFeO3, that easily escape from the oxide surface for further precise C–C coupling inside zeolites, thus steering CO2-HCOOH/H2CO-Aromatics reaction pathway to enable a high yield of aromatics.