Total Aromatics Research Articles

Is nitrogen-modified atmosphere packaging a tool for retention of volatile terpenes and cannabinoids in stored Cannabis sativa inflorescence?

Modified atmosphere packaging (MAP) alters the gaseous composition of air surrounding packaged goods to prevent deleterious oxidation associated reactions. MAP has been adopted for the storage of cannabis, though a recent study revealed little difference in terpene content under MAP conditions. Questions regarding its efficacy for preservation of high value compounds like terpenes and cannabinoids lost during postharvest storage remain. The goal of this research is to determine weather N2 MAP preserves high value compounds of cannabis during its postharvest storage. This experiment followed a completed randomized block design. There were two factors of interest. The first was storage atmosphere (atmospheric or N2 MAP). The second was storage duration (18, 46, or 74 days). The experiment was then blocked by cannabis chemovar using 5 different chemovars. The concentration of 17 cannabinoids was evaluated through UPLC-UV and 61 volatile terpene compounds through GC–MS. Concentrations were compared over time and between storage treatments. There were no significant differences in total cannabinoids and volatile terpene compounds over time or between storage treatments. Individual cannabinoids Δ9-THC, CBG, CBNA, CBC, THCV, and THCVA all increased during storage time while THCA decreased. CBG and THCV only increased under MAP storage. Individual aromatics limonene, β-pinene, α-pinene, camphene, and terpinolene all only decreased during storage under N2 MAP. Only caryophyllene oxide and α-humulene increased under N2 MAP storage. β-Myrcene decreased under atmospheric storage, but not under N2 MAP. While N2 MAP had no effect on the preservation of total cannabinoids and aromatics during storage, it did influence several individual compounds. CBG, THCV, and α-humulene all increased under N2 MAP. N2 MAP also maintained the concentration β-myrcene over time, though the preservation of β-myrcene was offset by a decrease limonene. Overall, N2 MAP was not needed for preservation of most high value compounds but did have an effect of some compounds with reputed therapeutic benefits.

Thermal and catalytic pyrolysis of automotive plastic wastes to diesel range fuel

This study investigated the pyrolysis of automotive plastic wastes (APW) for the production of diesel-grade oil products using a modified calcium bentonite clay catalyst. The research aimed to optimize the process for maximum oil yield and diesel range organics yield. The APW was characterized by its chemical composition and physical properties and the optimal temperature and catalyst amount were determined for maximum oil yield and diesel range hydrocarbons. The results showed that the APW contained mixed Acrylonitrile Butadiene Styrene (ABS), High/Low Density Polyethylene (H/LDPE), Polypropylene (PP), Polystrene (PS) and fiberglass, with a large quantity of volatiles and ash. The average oil yield was higher in the catalytic process compared to that in the thermal process. Generally, higher temperature above 450 °C produced waxy oil, thus lower temperature favoured more Diesel Range Organics (DRO). Both processes yield similar yields of C8–C24 DRO, and in both cases, lower temperature favoured high yield of C8-C24 hydrocarbons. The catalyst significantly increased the yield of oil, but did not significantly increase C8–C24 DRO yield. The optimal conditions for a maximum oil yield of 78.6 % and DRO yield of 79.5 % was a temperature of 416 °C and 24.3 wt% clay. Thus, the modified calcium bentonite clay can be used to improve oil yield from pyrolysis of APW. The oil produced had properties such as calorific value (49.85 MJ/kg), flash point (113 °C) and total aromatics 3.55 area%, similar to those of commercial diesel, and comprised mostly of 2,4-Dimethyl-1-heptene (25.37 ± 2.01 %) of thermal and 2, 4 – Dimethyl – 1 – heptane (23.44 ± 2.42) in the catalytic process. The study suggests further research to explore different catalysts, maximization of both DRO and gasoline range organics, recover energy from residues, and conduct techno-economic assessments for plant-scale operations. Additionally, policies on the management of end-of-life vehicles should include provisions for stripping and segregation of plastic components by accredited providers for the purpose of plastics recycling.

Regulation of acidity properties of ZSM-5 and proximity between metal oxide and zeolite on bifunctional catalysts for enhanced CO2 hydrogenation to aromatics

Herein, Ga-ZnZrOx&ZSM-5 bifunctional catalysts were designed for CO2 thermal hydrogenation to aromatics, particularly, aiming to enhance the selectivity of high-value BTX (i.e., benzene, toluene, and xylene). It was evident that the exterior surface properties and acidity of ZSM-5 can be effectively tailored by in-situ silicon deposition originating from the rice husk template. Catalytic performance assessments demonstrate an optimized catalyst achieving 88.1 % aromatics selectivity (exclusive CO) in a single pass, with a notable 45.2 % BTX selectivity within total aromatics and a low CO selectivity of 23.6 %. This superior performance is attributed to the in-situ silicon deposition on ZSM-5 during one-pot synthesis and the optimized spacing between Ga-ZnZrOx and ZSM-5 facilitated by the rice husk platform. Furthermore, in-situ DRIFTS analysis identifies key reaction intermediates. This study offers an effective strategy for tuning zeolite acidity using rice husks, while modulating metal oxide-zeolite proximity on the bio-SiO2 platform, thus boosting CO2 conversion to aromatics.

Study on ex-situ catalytic pyrolysis of poplar to produce aromatics over a dual-catalyst system of hydroxyapatite and HZSM-5

The ex-situ catalytic pyrolysis of poplar in a dual-catalyst system of hydroxyapatite (HAP) and HZSM-5 was performed using a bench-scale device to enhance the aromatics production. Results indicated that the introduction of HAP could effectively achieve the deoxygenation of macromolecular oxygenates, which were then converted into hydrocarbon precursors. The combination of HAP and HZSM-5 exceedingly promoted the production of aromatics especially monocyclic aromatics (MAHs) than single HZSM-5. The effects of operating conditions on aromatics yield and distribution were investigated. Under the catalyst layout of mode B, with the optimum conditions reaching the catalytic temperature of 500 °C, HAP to HZSM-5 ratio of 2:4, and catalyst to biomass ratio of 1:1, the maximum aromatics yield of 9.10 wt% was achieved, accompanied by the monocyclic aromatics/polycyclic aromatics ratio enhanced to 2.33. At this point, the synergistic effect for MAHs and total aromatics reached 170.09% and 214.14%, respectively. Compared to the conventional metal oxides, the HAP/HZSM-5 dual-catalyst system exhibited superior performance in aromatics production. Besides, the anti-coking capability of HZSM-5 in the dual-catalyst system was also better than that of pure HZSM-5. This research provided a new perspective for the efficient utilization of biomass energy.

The σ+π dual aromaticity of typical bi-tetrazole ring molecule TKX-50.

Two complexes of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) were employed to evaluate the aromaticity of their tetrazole rings via deep analysis such as the electronic structure, the ZZ component of the natural chemical shielding tensor (NICSZZ) and component orbitals, localized orbital locator purely contributed by σ-orbitals (LOL-σ) and localized orbital locator purely contributed by π-orbitals (LOL-π), the anisotropy of the induced current density (AICD) and the ZZ component of iso-chemical shielding surface (ICSSZZ) of these tetrazole rings thereof. The conclusion shows: that all tetrazole rings and bi-tetrazole rings in complexes have strong σ and a comparable strength π double aromaticity; all these magnetic shields almost symmetrically increase from the central axis to the tetrazole ring atoms; tetrazole rings in complex II show a little stronger dual aromaticity than that in complex I mainly due to the different orientation of the fragment 2 encompassing two hydroxylamine groups resulting in different effects on the contributions of σ orbitals and π orbitals to total aromaticity of tetrazole rings thereof; the difference in aromaticity is fundamentally caused by the atoms O with stronger electron-withdrawing than atom N in fragment 2 interact with bi-tetrazole ring through O in complex I but through N in complex II.

Pollution characteristics and secondary formation potential of volatile organic compounds in the multi-industrial city of Ulsan, Korea

The secondary formation of ozone and aerosols due to volatile organic compounds (VOCs) has drawn increased attention in Ulsan, a multi-industrial city in South Korea. In this study, 52 VOCs were measured at 40 sites in four industrial (petrochemical, nonferrous, automobile, and shipbuilding) complexes and five urban sites using passive air samplers. The concentration of aromatics (44.6 μg/m3) accounted for 70.3% of the total VOC concentration (63.4 μg/m3), which was significantly higher than those of alkanes (27.5% and 17.4 μg/m3) and alkenes (2.15% and 1.37 μg/m3). The highest concentrations of total VOCs and aromatics were observed at the shipbuilding industrial complex, whereas the concentration of alkanes and alkenes was the highest in the petrochemical industrial complex. The positive matrix factorization (PMF) model suggested five major VOC sources in urban areas: (1) petrochemical production processes, (2) fuel combustion and evaporation, (3) urban emissions sources, (4) solvent use, and (5) painting and metal surface coating. The PMF result indicated that the distances from the four industrial complexes substantially affected VOC pollution in the urban areas. Moreover, aromatics (e.g., m,p-xylenes, toluene, ethylbenzene, o-xylene, and 1,2,4-trimethylbenzene) exhibited higher ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP), which were mainly emitted from solvent use and painting in the shipbuilding and automobile industrial complexes. The petrochemical industrial complex close to densely populated urban areas also contributed significantly to secondary formation potential. In conclusion, our study revealed that elevated levels of aromatics were associated with increased OFP and SOAFP. Additionally, the four industrial complexes exhibited varying impacts on pollution characteristics in urban areas. These findings have practical implications, as they can inform the development of industry-specific management strategies for mitigating VOC pollution and secondary formation in multi-industrial cities.

Application of high-performance liquid chromatography in determining saturates and aromatic hydrocarbons along with polars/additives in automotive finished and used lubricating oils

Lubricating oils help an internal combustion engine function effectively by reducing friction and wear on the engine's moving parts. They typically consist of petroleum-derived base oil and various additives to achieve the desired characteristics in automotive engine oils. Determination of aromatics and polar additives in the finished and used lubricating oils is not possible with existing methods hence their development is significant from the perspectives of environment and reuse/re-refining of used lubricating oils. This study reports the development of a new HPLC method to determine additives in the finished lubricating oils and/or polars in the used engine oils. The proposed method is simple, fast (runtime of 13 min), does not require sample pre-treatment, and exhibits high precision and superior limits of detection and quantification. The method demonstrated good linear response ranging from 0.1 to 30 mass for total aromatics and 0.1 to 20 % for additives. The method validation was carried out by analyzing brand-new commercial two and four-wheeler lubricants with used automotive lubricants. Based on the proposed method, the aromatics and additives concentration ranges in the studied finished lubricants were estimated between 0.20–1.70 % (mass) and 0.20–3.50 % (mass), respectively. Similarly, for used lubricants, the aromatics and additives were estimated to be 1.00–6.10 % and 0.60–2.40 % (mass), respectively.

Direct hydrogenation of CO2 to aromatics via Fischer-Tropsch route over tandem K-Fe/Al2O3+H-ZSM-5 catalysts: Influence of zeolite properties

Direct hydrogenation of CO2 to valuable aromatics using multifunctional catalysts is an attractive technology to produce low-carbon footprint chemicals. In this work, the relevant zeolite parameters driving the formation of total and BTEX aromatics from CO2 and H2 on tandem K-Fe/γ-Al2O3+H-ZSM-5 catalysts following the Fischer-Tropsch (FT)-mediated route were investigated. To this end, a set of H-ZSM-5 zeolites covering a wide range of physicochemical properties (density of Brønsted and Lewis acid sites, external acidity, crystallite size, and mesoporosity) was used, characterized by different techniques (ICP-OES, XRD, N2 physisorption, FTIR-pyridine, FTIR-2,6,-di-tert-butyl pyridine, XPS, 27Al MAS NMR, and electron microscopy), and evaluated in CO2 hydrogenation at 400 °C, 30 bar, H2/CO2 = 3.1, and GHSV of 4700 mL/(gFe-cat·h). At these conditions, high and stable CO2 conversions of 50 – 55% and low CO selectivity of ca. 10% were obtained for the Fe-based and tandem catalysts. The density and, to a certain extent, the strength of Brønsted acid sites were found the main parameters determining the selectivity of aromatics, reaching initial (TOS = 1.5 h) values of about 79% and 40% in liquid (C5+) and total hydrocarbons, respectively, for the catalyst based on the most acidic zeolite. Lewis acid sites associated to extraframework Al species (EFAL), by contrast, did not appear to play a relevant role in our conditions. Moreover, although a positive effect of the total amount and strength of Brønsted acid sites on the selectivity to the most valuable BTEX aromatics was inferred from our results, the external Brønsted acidity was the most influential factor in this case. Hence, a remarkable BTEX selectivity of 75% in aromatics was achieved for the zeolite previously submitted to a surface-passivation treatment by silylation.

Insight into the synergistic effect of copper and sodium over metal organic framework-derived Fe-based catalyst for CO2 hydrogenation to aromatics

One-step hydrogenation of carbon dioxide (CO2) to aromatics is a promising strategy for relieving the stress of fossil fuels. Here, a copper and sodium co-modified Fe-based catalyst (3-NFC-5) was synthesized through the pyrolysis of Cu-doped MIL-101(Fe) and Na impregnation. After combining with HZSM-5, 42.11% CO2 conversion and 50.68% total aromatics selectivity was achieved. Through multiple characterization and DFT calculations, the synergistic promotion of Na and Cu on light olefins intermediate production was revealed. Na was crucial for COOH* formation as the intermediate for reverse water gas shift reaction (RWGS), whose concentration could be further enhanced after Cu modification. Controlled C-C coupling towards C2-C4 hydrocarbons was realized by the enhanced CO non-dissociative activation and the increased content of χ-Fe5C2 after Cu doping, which was responsible for the inhibited surface CHx* concentration and selective production of light olefins, respectively.

Aromatic production from high-density polyethylene over zinc promoted HZSM-5

The nature of Zn species and their roles in catalytic cracking of high-density polyethylene (HDPE) thermal decomposing vapor over Zn-promoted HZSM-5 (Zn/Z5) for aromatics were investigated. The Zn/Z5 zeolites were prepared using ion exchange and impregnation methods followed by H2 reduction. Results indicated that hydrogen reduction of the Zn/Z5 significantly improved the aromatic yield. [ZnOH]+ and bridged Zn2+ species were critical species promoting BTX formation, with the former demonstrating higher activity. Besides, the synergistic effect between the Zn species and Brønsted acid sites on HZSM-5 boosts the aromatic yield. Incorporation of Zn was also found to promote long-chain scission. Among all the Zn/Z5, hydrogen reduced 2 wt% Zn/Z5 (SAR=25) is most effective in producing BTX, with a maximum yield of BTX (48%) and BTX selectivity (93%); hydrogen reduced 2 wt% Zn/Z5 (SAR=50) produced the highest yield of total aromatics (53%).

Impact of Solvent Emissions on Reactive Aromatics and Ozone in the Great Lakes Region

While transportation emissions have declined over the past several decades, volatile organic compound (VOC) emissions from solvent use applications have increased as urban areas expand. In this work, the Canadian air quality model (GEM-MACH-TEB) is used to assess the importance of solvent emissions during the Michigan Ontario Ozone Source Experiment (MOOSE). Model predictions are compared to ozone and total mono-substituted aromatics (TOLU) observations collected in Windsor, Ontario. For summer 2018, model estimates of TOLU from solvent emissions are smaller (30% for an 8 h daytime average) in Windsor than estimates from positive matrix factorization (44% for a 24 h average). The use of updated U.S. solvent emissions from the EPA’s VCPy (Volatile Chemical Product framework) for summer 2021 simulations increases the solvent use source contribution over Detroit/Windsor (30–50% for an 8 h daytime average). This also provides a more uniform spatial distribution across the U.S./Canada border (30–50% for an 8 h daytime average). Long-chain alkanes are the dominant speciation in the model’s air pollutant emission inventory and in the observation-derived solvent use factor. Summertime 8 h daytime ozone decreased by 0.4% over Windsor for a 10% solvent use VOC emission reduction scenario. A 10% mobile NOx emission reduction scenario resulted in a 0.6% O3 decrease over Windsor and more widespread changes over the study region.

Effect of kerosene aromaticity as a solvent on bulk and interfacial properties of Brazilian heavy crude oil with high asphaltene content

AbstractThis study investigated the effect of solvent aromaticity on asphaltene stability and interfacial behaviour using typical diluted heavy oils, which better represent the chemical diversity of petroleum components than previous studies that used simple solvent mixtures with low asphaltene concentrations. A Brazilian crude with high viscosity and asphaltene content was diluted with two kerosenes, one containing only saturated compounds (KeS), and the other a saturates/aromatics mixture (KeSA) to maintain total aromaticity in the oil mixture upon dilution. Viscosity, asphaltene stability, interfacial tension, and elasticity of the oil mixtures were measured, and correlated with emulsion stability, regarding the differences in solvent aromaticity and aromatics/saturates ratio. The results showed that the different kerosene compositions affected bulk viscosity and asphaltene flocculation, but had a lesser effect on oil/brine interfacial tension due to the high asphaltene content in the diluted oil. The elastic modulus decreased at higher dilutions with KeS, while it remained consistent for KeSA mixtures, which supported the differences obtained in emulsion stability, at solvent concentrations within the optimal aromaticity ratio reported for simple solvent mixtures. Interfacial segregation of the aromatics in KeSA was also observed, which has not been reported in previous studies using complex solvents. These findings suggest that the trends reported with model oils, such as heptol with added asphaltenes, can also be applied to more realistic complex oil mixtures with higher asphaltene concentrations. Nevertheless, it was suggested that maintaining the aromatic content may not be enough to prevent asphaltene flocculation upon dilution, due to the concurrent increase in saturates.

Construction of HZSM-5 with a Mesoporous Structure and Suitable Acidity: Application in Catalytic Syngas Conversion to Light Aromatics over Na–FeMn/HZSM-5 Zeolite

The diffusion of aromatics in pores has a great influence on the distribution of light aromatics and the stability of zeolites, and the aromatics selectivity is related to the acidity of the zeolite. Here, the HZSM-5 zeolite, rich in a mesoporous structure and suitable acidity, was manufactured by hydrothermal crystallization in the presence of a NaOH/TPAOH mixed solution. Because the mesoporous structure of the HZSM-5 zeolite facilitates the diffusion of reactants and products, it can regulate the distribution of light aromatics in total aromatics and attenuate coke deposition. Meanwhile, the treated HZSM-5 zeolite can adjust the acidity to enhance the aromatics selectivity. The reasonable design of zeolites with abundant mesopores and suitable acidity provides a new clue for directly converting syngas to light aromatics. Through catalytic performance testing, we obtained 46.89% aromatics selectivity and 55.86% light aromatics in total aromatics at 94.86% CO conversion over mesoporous HZSM-5. Furthermore, the modified mesoporous HZSM-5 zeolite with Ce could tune the acidity to promote the aromatics selectivity to 51.33%, maintaining 46.77% light aromatics in total aromatics and high catalytic stability in the meanwhile.

Study on separation of long carbon chain aromatics/alkanes in diesel systems with DBU-based ionic liquids

Based on the structural designability of ionic liquids (ILs), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-based ILs ([Bz-DBU]NTF2) were designed and synthesized. Their physical properties were analyzed by FT-IR, 1H NMR, DSC and TGA. Highly selective separation between aromatic and alkane by [Bz-DBU]NTF2 was achieved. Under the optimal conditions, the distribution coefficient (D) and separation selectivity (S) of [Bz-DBU]NTF2 for tetraline were 0.833 and 54.2. The IL was regenerated six times without decrease in separation selectivity, demonstrating good stability. For the multi-component simulated diesel, nearly 100% of the bicyclic alkanes could be removed by five-stage cross-flow extraction processes. While the removal rate of total aromatics reached up to 84.39 and the contents of alkanes and total saturated alkanes reached 56.64% and 96.69%, respectively. For the real diesel, after two-stage cross-flow extraction experiments, the removal rates of monocyclic, bicyclic, tricyclic aromatic hydrocarbons reached 63.9%, 91.3% and 100%, respectively. The final product reached the standard of high quality ethylene cracking feedstock.

Role of Catalyst Domain Size in the Hydrogenation of CO2 to Aromatics over ZnZrOx/ZSM-5 Catalysts

The direct conversion of carbon dioxide into aromatic compounds may provide an environmentally friendly resource for a family of chemical building blocks with high global demand─aromatic chemicals. An array of bifunctional catalysts composed of ZnZrOx for the conversion of CO2 to methanol and ZSM-5 for methanol aromatization is evaluated considering multiple operational and catalytic parameters, with a focus on the particle size of each catalyst functionality. Aromatic yields generally increase as the ZSM-5 domain size decreases for different configurations of catalyst domains─mixed powders, mixed pellets, and separate beds. However, for a physical mixture of the catalyst components prior to pelletization (mixed powder case), varying the ZSM-5 crystal size inversely impacts the particle size of ZnZrOx, leading to enlarged metal oxide domains and enhanced intermediate diffusion barriers for very small crystals of ZSM-5. Larger crystals of ZSM-5 can be employed to obtain a higher concentration of benzene, toluene, and xylene (BTX) among aromatics. Upon employing a physical mixture of the ZnZrOx/ZSM-5 catalyst with a Si/Al ratio of 300 and a ZSM-5 crystal size of 300 nm, a total aromatics selectivity of 44% at CO2 conversion of 6% was obtained at 320 °C, WHSV of 7200 mL gcatalyst–1 h–1, and H2/CO2 ratio of 3.

Crude oil conversion to chemicals over green synthesized ZSM-5 zeolite

The study reports the conversion of crude oil to basic chemicals over a template-free green synthesis of ZSM-5(40) zeolite using halloysite (HAL) and bolus alpha (BA) as silica and alumina precursors. The Z(40)HAL and Z(40)BA exhibited hierarchical pores with high surface area of 248 m2/g and 257 m2/g, respectively. The addition of soft template during the synthesis of Z(40)BA forms a Z(40)BAT zeolite with lower surface area. The synthesized zeolites were impregnated with 2wt%Mn and tested for the steam catalytic cracking of crude oil to light olefins and aromatics catalysts at 675 °C in a fixed-bed reactor. Maximum light olefins (C2=-C4=) yield (47 wt%) and total aromatics (14.7 wt%) were attained over 2Mn/Z(40)HAL catalyst. The conversion of crude oil (68.4%) is attributed to hierarchical pores and the presence of large weak and strong acid sites in the 2Mn/Z(40)HAL zeolite. Moreover, due to the high reaction temperature, some effects of thermal cracking such as protolytic cracking reactions with high ethylene yield (22%) were introduced. The addition of 1% phosphorus and 1%Mn to Z(40)HAL resulted in lower catalytic cracking activity. Similarly, the 2Mn/Z(40)BAT performed slightly lower than the template-free 2Mn/Z(40)BA additive. The experimental results demonstrate the technical feasibility of template-free green synthesis of ZSM-5 zeolite in the conversion of crude oil to basic chemicals.

Lignin depolymerization with alkaline ionic liquids and ethylene glycol in a continuous flow reactor

A novel alkaline ionic liquids N-allylpyridinium hydroxide ([APy]OH) was successfully designed and developed as a catalyst and co-solvent with ethylene glycol in the continuous depolymerization of lignin. Various reaction conditions, like lignin concentration, water content, and reaction temperature, were investigated under atmospheric pressure. Ethylene glycol was used as main solvent and repolymerization inhibitor of the aldehydes produced. The combination of [APy]OH and alkali metal salts exhibited a good synergistic effect for lignin depolymerization. Then, the depolymerization of three different lignins, including dealkaline lignin (DA-lignin), alkaline lignin (A-lignin), and sodium lignosulfonate (S-lignin), were also studied. S-lignin exhibited the highest yields of total liquid products (21.3 %) and aromatics (10.7 %). The change in lignin structure after depolymerization was observed by means of FT-IR and DTG-DTA techniques. Lastly, a hypothetical pathway for lignin depolymerization was proposed based on the catalytic results of lignin model compounds (LMCs) with different linkages.

Hydrothermal pretreatment of Eucalyptus by-product and refining of xylooligosaccharides from hemicellulosic hydrolysate

Xylooligosaccharides (XOS) are highly effective food bioproducts of value to the prebiotic market. The use of hydrothermal pretreatment (HP) on Eucalyptus by-product (EB) under suitable conditions can allow to obtain valuable XOS-rich hemicellulosic hydrolysate (HH). This work aimed to design an efficient methodology to refine XOS-rich HH, boosting the development of new applications for natural XOS obtained from EB. The approach includes the refining of XOS-rich HH, obtained after the HP, in which the HH was separated and fractioned using a liquid–liquid extraction (LLE) process with organic solvents, a vacuum evaporation, and an integrated downstream processing using the two operations. Both refining processes were efficient in removing unwanted components from HH, mainly total aromatics, including hydroxymethylfurfural (HMF) and furfural. LLE performance was maximized by adjusting the volumetric ratio of ethyl acetate (EtOAc). This operation was highly efficient for removing the aromatic fraction, with a removal efficiency of 63–82% of the total aromatics and only a small loss of XOS (of circa 15%). The use of vacuum evaporation to refine the HH allowed to remove 55.4% of total aromatics with an XOS average loss of 23.8%. The combination of vacuum evaporation and LLE (1:1 vol ratio of HH: EtOAc) was beneficial for the removal of total aromatics (75.7%), but negatively affected the content of XOS in the refined HH (average loss of XOS of 29.3%). Anyway, the integrated platform resulted in a purification index of 75.5%, which represents an increase of 34.1% when compared to raw HH. This work demonstrated that the use of LLE using EtOAc, vacuum evaporation and an integrated processing using both operations are effective and simple approaches to refine XOS-rich HH, especially for the removal of aromatics contaminants, presenting a potential to improve the industrial hemicellulose biorefining processes.

Accelerating syngas-to-aromatic conversion via spontaneously monodispersed Fe in ZnCr2O4 spinel

Spontaneous monodispersion of reducible active species (e.g., Fe, Co) and their stabilization in reductive atmospheres remain a key challenge in catalytic syngas chemistry. In this study, we present a series of catalysts including spontaneously monodispersed and enriched Fe on ZnCr2O4. Deep investigation shows remarkable performance in the syngas-to-aromatic reaction only when monodispersed Fe coupled with a H-ZSM-5 zeolite. Monodispersed Fe increases the turnover frequency from 0.14 to 0.48 s−1 without sacrificing the record high selectivity of total aromatics (80–90%) at a single pass. The increased activity is ascribed to more efficient activation of CO and H2 at oxygen vacancy nearest to the isolated Fe site and the prevention of carbide formation. Atomic precise characterization and theoretical calculations shed light on the origin and implications of spontaneous Fe monodispersion, which provide guidance to the design of next-generation catalyst for upgrading small molecules to synthetic fuels and chemicals.

Effects of zeolite morphologies on CO conversion to aromatics via a modified Fischer‐Tropsch synthesis pathway

AbstractBACKGROUNDSyngas conversion to olefins via Fischer‐Tropsch Synthesis (FTs) route and then subsequently into aromatics (syngas−olefins−aromatics (SOA)) was considered a promising industrialization route due to its ability to match reaction temperatures between syngas to olefins (300–400 °C) and olefins to aromatics (300–500 °C). In this reaction route, the syngas to olefin process can be efficiently and easily realized by Fe‐based FTs catalysts. However, the aromatization process occurring over the zeolite catalyst was still considered a big challenge due to zeolites' complex topology, variable morphology, and elusive acidic properties.RESULTSA series of ZSM‐5 zeolites with different morphologies, including nano ellipsoid, nano cube, nano aggregate, nano bead, and nano pile were successfully synthesized . The effects of the ZSM‐5 zeolite's morphology and reaction temperature on the aromatics synthesis from syngas based on a modified FTs route were systematically studied.CONCLUSIONIn all the studied ZSM‐5 zeolites, the nano cube ZSM‐5 zeolite (Z5‐NC) zeolite had the best aromatization ability. The hybrid catalyst combination of FeMnK&Z5‐NC obtained the highest xylene selectivity of 12% (2.8% + 9.2%), and its total aromatics selectivity was also the highest (42.5%). The study on reaction temperature suggested that a higher reaction temperature (320–360 °C) could efficiently impede the formation of CO2. However, the selectivity of aromatics was restrained to around 44% at higher temperatures because a high temperature facilitated the hydrocracking of higher hydrocarbons, leading to the increase of the selectivity of lighter CH4 and paraffin. © 2022 Society of Chemical Industry (SCI).