Benzene, Toluene And Xylene Research Articles

Bifunctional Catalytic Performance of Zn/ZSM-5 in the Aromatization of LPG and the Conversion of Pyrolytic Gases from Recycled Polypropylene

Zn-modified ZSM-5 zeolites with different zinc contents were successfully prepared by the impregnation method and compared with unmodified ZSM-5. Their potential for LPG (liquefied petroleum gas) aromatization and the conversion of pyrolysis gases obtained from recycled polypropylene was subsequently evaluated. In this process, various characterization tests were performed on the prepared catalysts, including SEM-EDS (scanning electron microscopy with energy-dispersive spectroscopy), TPD-NH₃ (temperature-programmed desorption of ammonia), and FTIR (Fourier-transform infrared spectroscopy). Under optimized conditions, the best results were obtained with 2% Zn/ZSM-5, which generated a higher production of BTX (benzene, toluene, and xylene) isomers, which are major components of gasoline. Likewise, in catalytic pyrolysis of recycled polypropylene, this catalyst generated a higher production of aromatic compounds. Therefore, this catalyst showed excellent performance in generating valuable hydrocarbons of great industrial interest, particularly aromatics.

Microwave-enhanced catalytic conversion of fatty acid ester to olefins by Na-ZSM-5

The bio-based production of essential chemicals is important for the sustainability of the chemical industry. Here, we demonstrate efficient olefin production from methyl oleate using Na substituted ZSM-5 (Na-ZSM-5) and microwave irradiation. Na-ZSM-5 exhibits superior microwave heating properties compared to H-ZSM-5 and other zeolites. It was more effective in converting methyl oleate to olefins such as ethylene and propylene than H-ZSM-5 or Y zeolites. Microwave irradiation promoted the conversion efficiency of methyl oleate by Na-ZSM-5, achieving an olefin yield over four times higher than that obtained with conventional heating (CH) using an electric furnace. Meanwhile, the aromatization to benzene, toluene and xylene (BTX) was suppressed using Na-ZSM-5, which was attributed to the removal of strong acid sites. In addition, in situ microwave XRD revealed that microwaves promoted temperature-dependent structural changes in Na-ZSM-5 at lower temperatures than CH, suggesting that microwaves form localized high temperatures in the zeolite. These localized high temperatures effectively enhance olefin production via microwave irradiation.

Boosting visible-light response for the complete decomposition of volatile organic compounds on the Cu-oxide deposited WO3 photocatalyst by the synergistic effects of TiO2

The degradation of volatile organic compounds (VOCs) by photocatalytic systems is the most practical strategy due to its cost performance, simplicity, and environmental sustainability. To address such issues, the photocatalytic activities of tungsten trioxide (WO3) were developed by the deposition of various cocatalysts. In particular, the Cu-oxide (CuO/Cu2O)-deposited WO3 (Cu-WO3) photocatalyst could efficiently decompose acetic acid and acetaldehyde into CO2 under visible-light irradiation, although it exhibited low activity for the decomposition of benzene, toluene and xylene (BTX). Furthermore, a composite Cu-WO3/TiO2 photocatalytic system, which was fabricated by the simple physical mixing of Cu-WO3 with TiO2, was found to exhibit unprecedented reactivity for the complete decomposition of persistent BTX pollutants into CO2 under visible light irradiation. The synergistic effects of Cu-WO3 and the interfacial surface complex (ISC) formed by toluene-adsorbed TiO2 contribute to the efficient visible light response by excitation up to around 600 nm. The reaction mechanism for the enhancement of photocatalytic activity by the Cu-WO3/TiO2 composite photocatalyst is examined in this study.

Effect of different ligands on the preparation of Pt-xMn@HZSM-5 and their catalytic performance for iso-butane catalytic cracking

ZSM-5 has emerged as a promising catalyst for iso-butane catalytic cracking due to its unique pore structures and abundant acid sites. And the optimization of catalytic performance has attracted more and more attention. Herein, a series of Pt and Mn-embedded Pt-xMn@HZSM-5 catalysts with different Mn complexes were successfully synthesized via the one-pot hydrothermal method (x refers to the Mn/Pt ratio). The ligand effects of both ethylenediamine and ethylenediaminetetraacetic acid disodium salt on the nature of target samples in terms of crystallinity, porosity, morphology, metal state, and acidity, were investigated in detail. It has been demonstrated that ethylenediamine served as a ligand enabled Pt-xMn@HZSM-5 more metal nanoparticles and acid sites, thereby delivering improved catalytic performance and high yields of ethylene, propylene and BTX (benzene, toluene, and xylene) for iso-butane catalytic cracking.

Catalytic Oxidation of BTX (Benzene, Toluene, and Xylene) Using Metal Oxide Perovskites

AbstractThe high toxicity, volatility, and dispersion of the light aromatics, benzene, toluene, and xylene (BTX) pose a serious threat to the environment and human health. Compared to incineration, catalytic oxidation technologies for BTX removal offer benefits such as low energy consumption, high efficiency, and low pollution. ABO3–type perovskite catalysts (ABO3–PCs) are particularly promising materials for the catalytic oxidation of BTX due to their high activity and thermal stability, as well as their adjustable elemental composition and flexible structure allowing their properties to be improved. Nonetheless, the full potential of ABO3–PCs for the oxidation of BTX has yet to be reached. This review systematically and critically analyses progress in the catalytic oxidation of BTX by ABO3–PCs. Catalytic performance is assessed for each category of perovskite, including non–doped, doped (A–, B–, or A/B–site doped), and loading type (noble metal, metal oxide, and matrix composite), with structure–activity relationships are established. A kinetic model and proposed mechanism for the catalytic oxidation of BTX are also presented. Finally, the challenges and opportunities of ABO3–PCs applied to BTX oxidation and other reactions are highlighted.

Catalytic pyrolysis of rape straw to produce light aromatic hydrocarbons over HZSM-5 loaded by metal ions from spent lithium batteries extracted with citric acid

In this study, metal-loaded HZSM-5 was prepared with metal ion extracted from the cathode materials of spent lithium batteries (lithium iron phosphate, LFP; lithium nickel-cobalt manganate, NCM) with citric acid for the improved production of light aromatic hydrocarbons by catalytic pyrolysis of rape straw. Because of the dealuminization effect of citric acid on HZSM-5, mesopores were introduced, and the diffusion and conversion of pyrolysis gas over acid sites were improved. After metal loading with acid-leaching solution, the amount of weak and total acids in metal-loaded HZSM-5 increased a lot, which was conducive to the dehydration, deoxygenation, decarbonylation and aromatization of pyrolysis, and the production of monocyclic aromatic hydrocarbons (MAHs). With 0.1 mol/L citric acid for LFP and NCM treatment, the metal-loaded catalyst showed a higher yield of benzene, toluene and xylene (BTX) of 11.10 wt% during catalytic pyrolysis of rape straw. Compared with 0.1-NCM-H5, a higher yield of MAHs was obtained over 0.1-LFP-H5 with a more favorable pore structure and higher amounts of weak and total acid sites. In general, the high-valued utilization of agricultural wastes and spent lithium batteries was realized in this study to produce clean energy.

CO2-facilitated upcycling of polyolefin plastics to aromatics at low temperature.

Plastics are one of the most produced synthetic materials and largest commodities, used in numerous sectors of human life. To upcycle waste plastics into value-added chemicals is a global challenge. Despite significant progress in pyrolysis and hydrocracking, which mainly leads to the formation of pyrolysis oil, catalytic upcycling to value-added aromatics, including benzene, toluene and xylene (BTX), in one step, is still limited by high reaction temperatures (>500°C) and a low yield. We report herein CO2-facilitated upcycling of polyolefins and their plastic products to aromatics below 300°C, enabled by a bifunctional Pt/MnOx-ZSM-5 catalyst. ZSM-5 catalyzes cracking of polyolefins and aromatization, generating hydrogen at the same time, while Pt/MnOx catalyzes the reaction of hydrogen with CO2, consequently driving the reaction towards aromatization. Isotope experiments reveal that 0.2kg CO2 is consumed per 1.0kg polyethylene and 90% of the consumed CO2 is incorporated into the aromatic products. Furthermore, this new process yields 0.63kg aromatics (BTX accounting for 60%), comparing favorably with the conventional pyrolysis or hydrocracking processes, which produce only 0.33kg aromatics. In this way, both plastic waste and the greenhouse gas CO2 are turned into carbon resources, providing a new strategy for combined waste plastics upcycling and carbon dioxide utilization.

Occupational exposure to organic solvents and risk of bladder cancer

BackgroundBladder cancer has been linked to several occupations that involve the use of solvents, including those used in the dry-cleaning industry.ObjectivesWe evaluated exposure to solvents and risk of bladder cancer in 1182 incident cases and 1408 controls from a population-based study.MethodsExposure to solvents was quantitatively assessed using a job-exposure matrix (CANJEM). Exposure to benzene, toluene and xylene often co-occur. Therefore, we created two additional sets of metrics for combined benzene, toluene and xylene (BTX) exposure: (1) CANJEM-based BTX metrics and (2) hybrid BTX metrics, using an approach that integrates the CANJEM-based BTX metrics together with lifetime occupational histories and exposure-oriented modules that captured within-job, respondent-specific details about tasks and chemicals. Adjusted odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated using logistic regression.ResultsBladder cancer risks were increased among those ever exposed to benzene (OR = 1.63, 95% CI: 1.14–2.32), toluene (OR = 1.60, 95% CI: 1.06–2.43), and xylene (OR = 1.67, 95% CI: 1.13–2.48) individually. We further observed a statistically significant exposure-response relationship for cumulative BTX exposure, with a stronger association using the hybrid BTX metrics (ORQ1vsUnexposed = 1.26, 95% CI: 0.83–1.90; ORQ2vsUnexposed = 1.52, 95% CI: 1.00–2.31; ORQ3vsUnexposed = 1.88, 95% CI: 1.24–2.85; and ORQ4vsUnexposed = 2.23, 95% CI: 1.35–3.69) (p-trend=0.001) than using CANJEM-based metrics (p-trend=0.02).ImpactThere is limited evidence about the role of exposure to specific organic solvents, alone or in combination on the risk of developing bladder cancer. In this study, workers with increasing exposure to benzene, toluene, and xylene as a group (BTX) had a statistically significant exposure-response relationship with bladder cancer. Future evaluation of the carcinogenicity of BTX and other organic solvents, particularly concurrent exposure, on bladder cancer development is needed.

Acid-site control of ZSM-5 zeolites using quaternary ammonium hydroxides for shale gas dehydroaromatization

The direct non-oxidative shale gas dehydroaromatization is a promising route for BTX (benzene, toluene, and xylenes) production, offering an effective alternative to conventional crude-oil-based processes. However, it faces crucial challenges such as rapid catalytic deactivation in Mo/ZSM-5 catalysts and limited regenerability due to the formation of external hard coke, resulting from external Mo active sites. This study introduces a hydrothermal post-treatment approach that can selectively control the external Al sites in ZSM-5 zeolites using quaternary ammonium hydroxides, aimed at reducing external Mo anchoring sites. This method successfully reduced the external Al and Mo-site densities in Mo/ZSM-5 catalysts, concurrently introducing mesoporosity, eventually leading to improved catalytic stability, reduced hard coke formation, and enhanced regenerability of spent catalysts. We highlight the significance of the roles of quaternary ammonium cations in the hydrothermal post-treatment, contrasting their effects with the NaOH treatment and analogous processes conducted at lower temperatures.

Simultaneous determination of benzene, toluene and xylene (BTX) by Au nanoparticles (AuNP) anchored in reduced graphene oxide electrode

AbstractThis work reports the development of an electrochemical sensor for the simultaneous determination of benzene, toluene and xylene (BTX). The sensor was prepared by coating the glassy carbon electrode (GCE) with reduced graphene oxide (RGO) film, decorated with gold nanoparticles (AuNP), by electrodeposition. Surface modification with AuNP/RGO‐GCE favored the electron transfer process and increased the active area, providing greater sensitivity for the sensor. The AuNP/RGO‐GCE sensor was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM). Quantitative analyses of BTX were carried out using the differential pulse voltammetry (DPV) technique, after optimization of the parameters that influence the sensor performance. The sensor showed a linear response in the 30–240 μM concentration range, with a detection limit range of 1.8–2.2 μM, 2.2–2.7 μM, and 2.0–2.6 μM, and quantification limit range of 6.2–7.3 μM, 7.2–8.9 μM, and 6.6–8.8 μM, respectively for B, T and X. In addition to the satisfactory repeatability and stability, in the determination of BTX, the method still showed good selectivity even in the presence of molecules with similar chemical structure, such as: catechol, p‐benzoquinone, resorcinol, ethanol, pyrene and in the presence of K+, Mg2+ and Pb2+ ions. The device was successfully applied for the determination of the analytes (BTX) in water samples from fuel station separator boxes, where recovery rates close to 100 % (97.8 % to 103.1 %) were obtained. The results obtained suggest that the AuNP/RGO‐GCE sensor has strong potential for detecting BTX in wastewater discharge from industrial processes.

Catalytic conversion of lignin into monoaromatic hydrocarbons over a Ni/Al hydrotalcite-derived catalyst

Lignin is the most abundant aromatic biopolymer. Thus, preparation of BTX (benzene, toluene and xylenes) by catalytic fast pyrolysis (CFP) of lignin is attractive. Ni-Al mixed metal oxide (MMO) catalysts, derived from pyrolyzing Ni-Al layered double hydroxides (LDH), were prepared for the catalytic fast pyrolysis of lignin. The effects of catalyst Ni/Al ratio, catalyst dosage and pyrolysis temperature on the liquid products were investigated by Py-GC/MS. The Ni3Al3-MMO produced the best liquid product distribution from lignin at 700 ℃. The selectivity of Ni3Al3-MMO for aliphatic hydrocarbons and monocyclic aromatic hydrocarbons (MAHs) was 18.0% and 78.2%, respectively. The selectivity to polyaromatic hydrocarbons (PAHs) was 3.8%. No phenols and phenolic derivatives were produced. This is related to the mesoporous catalytic structure (pore size of 14.37 nm), large external surface area (134.74 m2/g) and strong acidity (4.92 mmolNH3/g) of Ni3Al3-MMO. In addition, a mechanistic study was performed with the lignin model compound (guaiacol) showing that Ni3Al3-MMO exhibits strong deoxygenation activity for aromatic C–O bond cleavage of lignin.

Screening of Commercial Organic Solvent Nanofiltration Membranes for Purification of Plastic Waste Pyrolysis Liquids.

Increasing consumption rates of plastics, combined with the waste generated from their production, leads to several environmental problems. Presently, plastic recycling takes account of only about 10% of the plastic waste, which is achieved mainly through mechanical recycling. Chemical recycling methods, such as pyrolysis, could significantly increase overall recycling rates and reduce the need for the production of fossil-based chemicals. Produced pyrolysis oil can be used for the production of benzene, toluene and xylene (BTX) through catalytic upgrading or for the production of alkanes if used directly. Separation of high-value components in pyrolysis oil derived from plastic waste through traditional separation methods can be energy intensive. Organic solvent nanofiltration has been recognised as an alternative with very low energy consumption, as separation is not based on a phase transition. This work focuses on the screening of several (semi-) commercially available membranes using a simplified model mixture of pyrolysis oil obtained from plastics. Based on membrane performance, a selection of membranes was used to treat a feedstock obtained from the direct pyrolysis of plastics. This work shows that currently, commercial OSN membranes have promising separation performance on model mixtures while showing insufficient and non-selective separation at very low flux for complex mixtures derived from the pyrolysis of plastics. This indicates that OSN is indeed a promising technology but that membranes should likely be tailored to this specific application.

Biomass pyrolysis in a circulating fluidized bed reactor: Evaluating two strategies for the reduction of oxygen content in bio-oil

The use of a circulating fluidised bed (CFB) reactor promotes higher heat transfer to the biomass pyrolysis process and has the advantage of being energy self-sufficient through the continuous burning of biochar. CFB’s similarity with the fluidised catalytic cracking (FCC) of fossil streams represents a promising scenario of integration of lignocellulosic biomass in a conventional refining scheme. In this paper, two approaches were studied to enhance the deoxygenation reactions of biomass components in a pilot pyrolysis CFB reactor. First, in a noncatalytic pyrolysis, a lignocellulosic biomass was cofed with hydrogen-rich compounds produced in the oil refinery (methane and propane). In the second part, using a ZSM-5 catalyst in the bed, the effect of different catalyst-to-biomass ratios (CTB) in the bio-oils’ properties was evaluated. Compared with conventional pyrolysis, the cofeeding of methane or propane produced bio-oils with less oxygen content. The use of propane achieved better performance in terms of hydrocarbon concentrations in bio-oils, hence increasing benzene, toluene and xylene (BTX) production and being comparable with the results of catalytic pyrolysis. It was also shown that the increase of CTB in catalytic pyrolysis led to the enhancement of deoxygenation reactions, producing more O-free compounds. Both strategies were promising for improving the quality of bio-oil. Issues such as the cost of the catalyst and gases must be evaluated for possible integration into a conventional refining process.

Aromatic hydrocarbons rich bio-oil production from Miscanthus pyrolysis by coupling torrefaction and MoO3/ZSM-5 dual catalysis process

The valorization of Miscanthus pyrolysis by coupling torrefaction and MoO3/ZSM-5 dual catalysis process was studied to generate the aromatic hydrocarbons rich bio-oil, biochar, and combustible gas. With the optimal conditions of torrefied Miscanthus at 280 °C, MoO3/ZSM-5 catalysis process converted 24.17 % bio-oil, 30.27 % biochar, and 45.56 % gas. The coupled system accessed bio-oil phase deoxygenation by reducing the oxygen-containing compound content to 6.27 %. The aromatic yield reached 91.38 %, with an outstanding benzene, toluene and xylene (BTX) selectivity of 52.24 %. Isolating investigations revealed that torrefaction declined the oxygen content of Miscanthus to 5.24 %, increasing their calorific value and promoting subsequent catalytic pyrolysis through deoxygenation. When only using the ZSM-5 catalyst, the increase in torrefaction temperature enhanced aromatic hydrocarbon compounds conversion in the bio-oil, leading to a boost in their content from 55.01 % to 75.97 %. Correspondingly, MoO3 promoted deoxygenation, decreased the ketone content from 40.4 % to 21.92 %, and inhibited the generation of aldehydes. The combination of MoO3 and ZSM-5 with torrefaction delivered a superimposed effect on yielding aromatic hydrocarbons and BTX, which allowed a promising product upgrading method for obtaining high-quality bio-oil.

Effects of parameters in the preparation of Mo/MWW-type catalysts on the dehydroaromatization of shale gas

The direct non-oxidative aromatization of shale gas offers an unconventional production route for BTX (benzene, toluene, and xylene), potentially alleviating the heavy dependence of BTX supply on petroleum-based processes. Zeolite-supported transition metal catalysts have been successfully applied in the aromatization of light alkanes, where the zeolites provide the appropriate shape selectivity and acidity that are beneficial for the production of aromatics. In addition to HZSM-5, MCM-22 has also been recognized to be an effective support, owing to the characteristic topology of MWW structure. Here, we present a systematic investigation into the preparation and optimization of Mo/MWW-type catalysts, aiming to maximize their performance in shale gas aromatization. Mo/MCM-22 exhibited a superior initial BTX yield compared to Mo/ZSM-5 with a comparable Si/Al ratio, but was rapidly deactivated. A moderate value of Si/Al (∼ 11) was required for optimal catalytic performance, as an excessive amount of Al during the synthesis of MCM-22 led to insufficient amount of strong acid sites that are favorable for the reaction. The inclusion of Ga in MCM-22 greatly deteriorated the aromatization activity, owing to a significant degree of degalliation under reaction conditions. Contrary to ZSM-5, pelletization of MCM-22 also had a noticeable impact on catalytic performance, which was attributed to the nature of MWW topology. These results provide a comprehensive understanding of designing MWW-type zeolites for their application in shale gas aromatization.

Atmospheric VOCs in an industrial coking facility and the surrounding area: Characteristics, spatial distribution and source apportionment

Industrial coking facilities are an important emission source for volatile organic compounds (VOCs). This study analyzed the atmospheric VOC characteristics within an industrial coking facility and its surrounding environment. Average concentrations of total VOCs (TVOCs) in the surrounding residential activity areas (R1 and R2), the coking facility (CF) and the control area (CA) were determined to be 138.5, 47.8, 550.0, and 15.0 µg/m3, respectively. The cold drum process and coking and quenching areas within the coking facility were identified as the main polluting processes. The spatial variation in VOCs composition was analyzed, showing that VOCs in the coking facility and surrounding areas were mainly dominated by aromatic compounds such as BTX (benzene, toluene, and xylenes) and naphthalene, with concentrations being negatively correlated with the distance from the coking facility (p < 0.01). The sources of VOCs in different functional areas across the monitoring area were analyzed, finding that coking emissions accounted for 73.5%, 33.3% and 27.7% of TVOCs in CF, R1 and R2, respectively. These results demonstrated that coking emissions had a significant impact on VOC concentrations in the areas surrounding coking facility. This study evaluates the spatial variation in exposure to VOCs, providing important information for the influence of VOCs concentration posed by coking facility to surrounding residents and the development of strategies for VOC abatement.

MP22-13 OCCUPATIONAL EXPOSURE TO ORGANIC SOLVENTS AND RISK OF BLADDER CANCER

You have accessJournal of UrologyCME1 Apr 2023MP22-13 OCCUPATIONAL EXPOSURE TO ORGANIC SOLVENTS AND RISK OF BLADDER CANCER Shuai Xie, Melissa Friesen, Dalsu Barus, Molly Schwenn, Nathaniel Rothman, Alison Johnson, Margaret Karagas, Debra Silverman, and Stella Koutros Shuai XieShuai Xie More articles by this author , Melissa FriesenMelissa Friesen More articles by this author , Dalsu BarusDalsu Barus More articles by this author , Molly SchwennMolly Schwenn More articles by this author , Nathaniel RothmanNathaniel Rothman More articles by this author , Alison JohnsonAlison Johnson More articles by this author , Margaret KaragasMargaret Karagas More articles by this author , Debra SilvermanDebra Silverman More articles by this author , and Stella KoutrosStella Koutros More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003247.13AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Bladder cancer has been linked to several occupations that involve the use of solvents, but only perchloroethylene, used in the dry-cleaning industry, is classified as probably carcinogenic to humans. The role of other commonly used solvents is still unclear. Here, we evaluated exposure to solvents and risk of bladder cancer in 1182 incident cases and 1408 controls from a population-based study. METHODS: Exposure to 21 specific solvents was quantitatively assessed using a job-exposure matrix (CANJEM). Because exposure to benzene, toluene and xylene often co-occur, we created two additional sets of metrics of combined benzene, toluene and xylene (BTX) exposure: 1) CANJEM based BTX metrics and 2) Hybrid BTX metrics, which used a novel approach that integrated the CANJEM based BTX metrics together with responses to lifetime occupational histories and exposure-oriented modules to incorporate within-job, subject-specific details about tasks and chemicals into the exposure assessment. Odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated using logistic regression. RESULTS: Bladder cancer risks were significantly increased among those ever exposed to benzene (OR=1.63, 95%CI: 1.14-2.32), toluene (OR=1.60, 95%CI: 1.06-2.43), and xylene (OR=1.67, 95%CI: 1.13-2.48) individually. We observed a statistically significant exposure-response relationship for cumulative BTX exposure, with a stronger association observed with hybrid BTX metrics (ORQ1vsUnexposed=1.26, 95% CI: 0.83-1.90; ORQ2vsUnexposed=1.52, 95% CI: 1.00-2.31; ORQ3vsUnexposed=1.88, 95% CI: 1.24- 2.85; and ORQ4vsUnexposed=2.23, 95% CI: 1.35- 3.69) (p-trend=0.001) than with CANJEM based BTX metrics (p-trend=0.02). CONCLUSIONS: In our population-based study, BTX exposure was frequent among automobile mechanics, shoemakers, and painters. The identification of an increased risk for these solvents highlights a little recognized occupational exposure that may play a role in the etiology of bladder cancer. Source of Funding: This work was supported by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, Division of Cancer Epidemiology and Genetics (ZIA CP010125-27) © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e301 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Shuai Xie More articles by this author Melissa Friesen More articles by this author Dalsu Barus More articles by this author Molly Schwenn More articles by this author Nathaniel Rothman More articles by this author Alison Johnson More articles by this author Margaret Karagas More articles by this author Debra Silverman More articles by this author Stella Koutros More articles by this author Expand All Advertisement PDF downloadLoading ...

Mutual inhibition effects on the synchronous conversion of benzene, toluene, and xylene over MnOx catalysts

Advancing the practical application of catalytic oxidation technology demands for illustrating the synchronous conversion behavior of various volatile organic compounds (VOCs) over catalysts. Here, the mutual effects of benzene, toluene and xylene (BTX) were examined for their synchronous conversion on the surface of the MnO2 nanowire. Competitive adsorption of xylene (absorption energy (Eads): −0.889 eV) facilitated its prior conversion and impeded the oxidization of toluene and benzene over the catalyst. The turnover frequencies were 0.52 min−1 (benzene), 0.90 min−1 (toluene) and 2.42 min−1 (xylene) for mixed BTX conversion over the MnO2. Doping MnO2 with K+, Na+ and Ca2+ could enhance its ability to oxidize the individual VOCs but did not alter the conversion mechanism of mixed BTX over the catalyst. When reducing the competitive effects in the adsorption of BTX, the oxidation performance of catalysts would depend on their ability to oxidize toluene and benzene. K-MnO2 showed superior properties, i.e. specific surface area, highly low-valent Mn species, high lattice oxygen content, and abundant oxygen vacancy, and then exhibited superior performance during long-term operation (90% conversion in 800 min). The present study uncovered the co-conversion mechanism of multiple VOCs and significantly leveraged the catalytic oxidization technology for VOCs removal in practical application.

Catalytic pyrolysis of biomass to produce aromatic hydrocarbons in a cascade dual-catalyst system: Design of red mud based catalyst assisted by the analysis of variance

Theoretical and experimental study on the catalytic pyrolysis of rape straw was carried out for the production of aromatic hydrocarbons using the composite red mud (RM) and zeolite HZSM-5 catalyst as the combined catalysts. In the orthogonal tests and analysis of variance (ANOVA), it was originally established that Fe2O3 and CaO acted as the active metal oxides in the red mud, which played the notable role in the production of benzene, toluene and xylene (BTX) as hydrocarbon fuels. Subsequently, the physicochemical property of the Fe2O3 and CaO loaded red mud (Fe2O3-RM and CaO-RM) was investigated and their performance in the catalytic pyrolysis of rape straw combined with HZSM-5 were investigated. It was revealed that the further cracking of the primary pyrolysis gas was promoted with more active Fe2O3 involved, and the heavy component was converted into the light fraction entering HZSM-5 for deoxygenation and aromatization to produce aromatic hydrocarbons. The yield of BTX over Fe2O3-RM was boosted by 10.15 wt% compared with the original red mud catalyst, while that of BTX was further promoted to 11.37 wt% over the composite red mud catalyst with 6% CaO loading. In addition to the strong bond-breaking performance of CaO, calcium carboxylate was easily generated and then decomposed to form CaCO3 and ketones, and then BTX were produced from ketones over HZSM-5 by deoxygenation and aromatization. In this study, the high-performance red mud-based catalysts was designed and utilized in the thermochemical conversion of biomass, providing a potential way for the utilization of two solid wastes, rape straw and red mud to produce hydrocarbon fuels in a high-valued way.

Comparing the effects of hollow structure and mesoporous structure of ZSM-5 zeolites on catalytic performances in methanol aromatization

Comparing the effects of hollow and mesoporous structures over ZSM-5 zeolites on catalytic behaviors in methanol aromatization was done. Hollow zeolites possessing larger voids, increasing Bronsted acid sites and more framework Al in channel crossings promoted higher benzene, toluene and xylene (BTX) selectivity. Zero-length column (ZLC) desorption of cyclohexane stated that higher diffusion rate was observed over mesopores zeolite and hollow zeolite. However, lower effective diffusion constants (Deff) and higher activation energy of hollow zeolite demonstrated that mass transfer was not only limited by microporosity but by surface barriers resulting from surface defects and pore blockage. The highest diffusion rate of cyclohexane over hollow zeolite was presented indicating that surface barrier was not dominant in diffusion limitation. The stability of hollow ZSM-5 was lower compared to mesoporous ZSM-5 as a result of more strong acid sites and higher external silanol groups, which favored to carbon deposition. Additionally, the collapse of hollow structures with thinner shells also contributed to higher deactivation rate.