Analysis of volatiles from the thermal decomposition of Amadori rearrangement products in the cysteine-glucose Maillard reaction and density functional theory study.

The Amadori rearrangement products are an important flavor precursor in the Maillard reaction. Its thermal decomposition products usually contribute good flavors in foods. Therefore, investigating the thermal breakdown of Amadori products is significant for understanding the flavor forming mechanism in the Maillard reaction. In this study, volatiles from thermal decomposition of Amadori products in cysteine and glucose Maillard reaction was investigated by a thermal desorption cryo-trapping system combined with gas chromatography-mass spectrometry (GC-MS). A total of 60 volatiles were detected and identified. Meanwhile, the forming mechanism of 2-methylthiophene, a major decomposition product, was also investigated by using density functional theory. Seventeen reactions, 12 transition states, energy barrier and rate constant of each reaction were finally obtained. Results reveal that it is more likely for Amadori products of cysteine and glucose to undergo decomposition under neutral or weakly alkaline conditions.

In-Depth Understanding of the Oxidative Compatibility of Volatile Organic Compounds with Mn2O3 and Pt-Loaded Catalysts.

Designing suitable catalysts for efficiently degrading volatile organic compounds (VOCs) is a great challenge due to the distinct variety and nature of VOCs. Herein, the suitability of different typical VOCs (toluene and acetone) over Pt-based catalysts and Mn2O3 was investigated carefully. The activity of Mn2O3 was inferior to Pt-loaded catalysts in toluene oxidation but showed superior ability for destroying acetone, while Pt loading could boost the catalytic activity of Mn2O3 for both acetone and toluene. This suitability could be determined by the physicochemical properties of the catalysts and the structure of the VOC since toluene destruction activity is highly reliant on Pt0 in the metallic state and linearly correlated with the amount of surface reactive oxygen species (Oads), while the crucial factor that affects acetone oxidation is the mobility of lattice oxygen (Olat). The Pt/Mn2O3 catalyst shows highly active Pt-O-Mn interfacial sites, favoring the generation of Oads and promoting Mn-Olat mobility, leading to its excellent performance. Therefore, the design of abundant active sites is an effective means of developing highly adaptive catalysts for the oxidation of different VOCs.

Characterization of Key Aroma Compounds and Main Contributing Amino Acids in Hot-Pressed Oil Prepared from Various Peanut Varieties.

The production of peanut oil in the industrial sector necessitates the utilization of diverse raw materials to generate consistent batches with stable flavor profiles, thereby leading to an increased focus on understanding the correlation between raw materials and flavor characteristics. In this study, sensory evaluations, headspace solid-phase micro-extraction gas chromatography mass spectrometry (HS-SPME-GC-MS), odor activity value (OAV) calculations, and correlation analysis were employed to investigate the flavors and main contributing amino acids of hot-pressed oils derived from different peanut varieties. The results confirmed that the levels of alcohols, aldehydes, and heterocyclic compounds in peanut oil varied among nine different peanut varieties under identical processing conditions. The OAVs of 25 key aroma compounds, such as methylthiol, 3-ethyl-2,5-dimethylpyrazine, and 2,3-glutarone, exceeded a value of 1. The sensory evaluations and flavor content analysis demonstrated that pyrazines significantly influenced the flavor profile of the peanut oil. The concentrations of 11 amino acids showed a strong correlation with the levels of pyrazines. Notably, phenylalanine, lysine, glutamic acid, arginine, and isoleucine demonstrated significant associations with both pyrazine and nut flavors. These findings will provide valuable insights for enhancing the sensory attributes of peanut oil and selecting optimal raw peanuts for its production.

Unravelling caramelization and Maillard reactions in glucose and glucose + leucine model cakes: Formation and degradation kinetics of volatile markers extracted during baking.

A large number of volatile compounds are formed during the baking of foods by reactions such as caramelization and Maillard reactions. Elucidating the reaction mechanisms may be useful to predict and control food quality. Ten reaction volatile markers were extracted during baking of solid model cakes implemented with known amounts of precursors (glucose with or without leucine) and then quantified by Thermal desorption-Gas chromatography-Mass spectrometry. The kinetic data showed that the level of air convection in the oven had no significant influence on the reaction rates. In contrast, increasing baking temperatures had a nonlinear accelerating impact on the generation of newly formed volatile compounds with a bell-shaped kinetic curve found for most of the markers at 200 °C. The presence of leucine triggered the activation of the Maillard and Strecker routes with a specific and very rapid formation of 3-Methylbutanal and pyrazines. A dynamic model was developed, combining evaporation flow rate and kinetic formation and consumption of reaction markers. It can be used to describe, for two furanic compounds of different volatilities, the vapor concentrations in the oven from the concentrations measured in the model cakes.

Formation of Volatile Pyrazinones in the Asparagine Maillard Reaction Systems and Novel Pyrazinone Formation Pathways in the Amidated-Alanine Maillard Reaction Systems.

Maillard reaction (MR) plays a pivotal role in the food flavor industry, including a cascade of reactions starting with the reaction between amino compounds and reducing sugars, and thus provides various colors and flavors. A new group of volatile compounds called pyrazinones found in MR are now getting more attention. In this study, eight volatile pyrazinones were found in the asparagine MR systems, in which 3,5-dimethyl- and 3,6-dimethyl-2(1H)-pyrazinones were reported for the first time. The major formation pathways were the reactions between asparagine and α-dicarbonyls, with decarboxylation as a critical step. Besides, novel alternative pathways involving alanine amidation and successive reactions with α-dicarbonyls were explored and successfully formed eight pyrazinones. The major differences between alanine-amidated pathways and decarboxylation pathways are the amidation step and absence of the decarboxylation step. For the alanine-amidated pathways, the higher the temperature, the better the amidation effect. The optimal amidation temperature was 200 °C in this study. The reaction between the alanine amide and α-dicarbonyls after amidation can happen at low temperatures, such as 35 and 50 °C, proposing the possibility of pyrazinone formation in real food systems. Further investigations should be conducted to investigate volatile pyrazinones in various food systems as well as the biological effects and kinetic formation differences of the volatile pyrazinones.

HS-SPME-GC-MS and Chemometrics for the Quality Control and Clustering of Monovarietal Extra Virgin Olive Oil: A 3-Year Study on Terpenes and Pentene Dimers of Italian Cultivars.

Terpenes and pentene dimers are less studied volatile organic compounds (VOCs) but are associated with specific features of extra virgin olive oils (EVOOs). This study aimed to analyze mono- and sesquiterpenes and pentene dimers of Italian monovarietal EVOOs over 3 years (14 cultivars, 225 samples). A head space-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method recently validated was used for terpene and pentene dimer quantitation. The quantitative data collected were used for both the characterization and clustering of the cultivars. Sesquiterpenes were the molecules that most characterized the different cultivars, ranging from 3.908 to 38.215 mg/kg; different groups of cultivars were characterized by different groups of sesquiterpenes. Pentene dimers (1.336 and 3.860 mg/kg) and monoterpenes (0.430 and 1.794 mg/kg) showed much lower contents and variability among cultivars. The application of Kruskal-Wallis test-PCA-LDA-HCA to the experimental data allowed defining 4 clusters of cultivars and building a predictive model to classify the samples (94.3% correct classification). The model was further tested on 33 EVOOs, correctly classifying 91% of them.

Comparison of Techniques for the Quantitation of Reductive Aroma Compounds in White Wine: Links to Sensory Analysis and Cu Fractions.

Multiple analytical methodologies allow quantitation of H2S and methanethiol (MeSH) in wine, but confirmation that the determined concentrations are related to perceived off-aromas, or "reductive" faults, is yet to be provided. Fifty white wines underwent sensory evaluation and measurement of free and salt-treated H2S and MeSH concentrations by gas chromatography with sulfur chemiluminescence detection and/or gas detection tubes. The determined concentrations were compared across techniques and different analysis laboratories. Sulfhydryl off-odors in the wines were best described by boiled and rotten egg and natural gas/sewerage/durian aroma attributes. The wines with the highest ratings for both aromas had high concentrations of free H2S, free MeSH, and/or salt-treated MeSH but were unrelated to salt-treated H2S. The free sulfhydryl concentrations and their associated aromas appeared to be suppressed by specific Cu fractions in the wines. This study provides evidence of the relevant measures of reductive aroma compounds and their relation to off-odors and Cu fractions.

Formation of Key Aroma Compounds During 30 Weeks of Ripening in Gouda-Type Cheese Produced from Pasteurized and Raw Milk.

Gouda-type cheeses were produced on a pilot-scale from raw milk (RM-G) and pasteurized milk (PM-G). Sixteen key aroma compounds previously characterized by the sensomics approach were quantitated in the unripened cheeses and at five different ripening stages (4, 7, 11, 19, and 30 weeks) by means of stable isotope dilution assays. Different trends were observed in the formation of the key aroma compounds. Short-chain free fatty acids and ethyl butanoate as well as ethyl hexanoate continuously increased during ripening but to a greater extent in RM-G. Branched-chain fatty acids such as 3-methylbutanoic acid were also continuously formed and reached a 60-fold concentration after 30 weeks, in particular in PM-G. 3-Methylbutanal and butane-2,3-dione reached a maximum concentration after 7 weeks and decreased with longer ripening. Lactones were high in the unripened cheeses and increased only slightly during ripening. Recent results have shown that free amino acids were released during ripening. The aroma compounds 3-methylbutanal, 3-methyl-1-butanol, and 3-methylbutanoic acid are suggested to be formed by microbial enzymes degrading the amino acid l-leucine following the Ehrlich pathway. To gain insight into the quantitative formation of each of the three aroma compounds, the conversion of the labeled precursors (13C6)-l-leucine and (2H3)-2-keto-4-methylpentanoic acid into the isotopically labeled aroma compounds was studied. By applying the CAMOLA approach (defined mixture of labeled and unlabeled precursor), l-leucine was confirmed as the only precursor of the three aroma compounds in the cheese with the preferential formation of 3-methylbutanoic acid.

Influence of Milk Pasteurization on the Key Aroma Compounds in a 30 Weeks Ripened Pilot-Scale Gouda Cheese Elucidated by the Sensomics Approach.

Gouda cheese was produced from pasteurized milk and ripened for 30 weeks (PM-G). By application of gas chromatography/olfactometry and an aroma extract dilution analysis on the volatiles isolated by extraction/SAFE distillation, 25 odor-active compounds in the flavor dilution (FD) factor range from 16 to 4096 were identified. Butanoic acid, 2- and 3-methylbutanoic acid, and acetic acid showed the highest FD factors, and 2-phenylethanol, δ-decalactone, and δ-dodecalactone were most odor-active in the neutral-basic fraction. Quantitations by stable isotope dilution assays followed by a calculation of odor activity values (OAVs) revealed acetic acid, 3-methylbutanoic acid, butanoic acid, and butane-2,3-dione with the highest OAVs. Finally, an aroma recombinate prepared based on the quantitative data well agreed with the aroma profile of the PM-G. In Gouda cheese produced from raw (nonpasteurized) milk (RM-G), qualitatively the same set of odor-active compounds was identified. However, higher OAVs of butanoic acid, hexanoic acid, and their corresponding ethyl esters were found. On the other hand, in the PM-G, higher OAVs for 3-methylbutanoic acid, 3-methylbutanol, 3-methylbutanal, and butane-2,3-dione were determined. The different rankings of these key aroma compounds clearly reflect the aroma differences of the two Gouda-type cheeses. A higher activity of lipase in the RM-G and higher amounts of free l-leucine in PM-G on the other side were responsible for the differences in the concentrations of some key aroma compounds.

Antifungal activity of bio-active cell-free culture extracts and volatile organic compounds (VOCs) synthesised by endophytic fungal isolates of Garden Nasturtium.

Antimicrobial resistance in fungal pathogens (both human and plant) is increasing alarmingly, leading to massive economic crises. The existing anti-fungal agents are becoming ineffective, and the situation worsens on a logarithmic scale. Novel antifungals from unique natural sources are highly sought to cope sustainably with the situation. Metabolites from endophytic microbes are the best-fitted alternatives in this case. Endophytes are the untapped sources of 'plants' internal microbial population' and are promising sources of effective bio-therapeutic agents. Fungal endophytes were isolated from Tropaeolum majus and checked for antifungal activity against selected plant and human pathogens. Bioactive metabolites were identified through chromatographic techniques. The mode of action of those metabolites was evaluated through various spectroscopic techniques. The production of antifungal metabolite was optimized also. In particular VOCs (volatile organic compounds) of TML9 were tested in vitro for their anti-phytopathogenic activity. Ethyl acetate (EA) extract of cell-free culture components of Colletotrichum aenigma TML3 exhibited broad-spectrum antifungal activity against four species of Candida and the major constituents reported were 6-pentyl-2H-pyran-2-one, 2-Nonanone, 1 propanol 2-amino. The volatile metabolites, trans-ocimene, geraniol, and 4-terpinyl acetate, produced from Curvularia lunata TML9, inhibited the growth of some selected phyto pathogens. EA extract hampered the biofilm formation, minimised the haemolytic effect, and blocked the transformation of Candida albicans (MTCC 4748) from yeast to hyphal form with a Minimum Fungicidal Concentration (MFC) of 200-600 µg mL-1. Central carbohydrate metabolism, ergosterol synthesis, and membrane permeability were adversely affected and caused the lethal leakage of necessary macromolecules of C. albicans. Volatile metabolites inhibited the growth of phytopathogens i.e., Rhizoctonia solani, Alternaria alternata, Botrytis cinerea, Cercospora beticola, Penicillium digitatum, Aspergillus fumigatus, Ceratocystis ulmi, Pythium ultimum up to 89% with an IC50 value of 21.3-69.6 µL 50 mL-1 and caused leakage of soluble proteins and other intracellular molecules. Citrusy sweet odor volatiles of TML9 cultured in wheat-husk minimised the infections of Penicillium digitatum (green mold), in VOC-exposed sweet oranges (Citrus sinensis). Volatile and non-volatile antifungal metabolites of these two T. majus endophytes hold agricultural and pharmaceutical interests. Metabolites of TML3 have strong anti-Candida activity and require further assessment for therapeutic applications. Also, volatile metabolites of TML9 can be further studied as a source of antifungals. The present investigational outcomes bio-prospects the efficacy of fungal endophytes of Garden Nasturtium.

Extraction of tannin, colour and aroma compounds in pinot noir wines as affected by clone selection and whole bunch addition.

Our previous study revealed stem inclusion fermentation reduced anthocyanin, and increased tannin and aroma compounds responsible for green notes. This study further investigated the effect of clone selection and whole bunch fermentation on Pinot noir wine composition, with focus on tannin composition. Three treatments were conducted using two clones (AM10/5 and UCD5) in 2021 and 2022: 100% destemmed (DS), 30% whole bunch (WB30), and 60% whole bunch (WB60). WB60 increased stem and skin derived tannins but reduced seed derived tannin proportion in wines. Clone selection had an impact on tannin composition and an even greater impact on tannin concentration, colour, and aroma compounds. AM10/5 produced wines with higher tannin, polymeric pigments and darker colour. AM10/5 wines also had higher concentration of phenylethyl alcohol, but lower concentrations of 3-isobutyl-2-methoxypyrazine and ethyl esters, indicating more floral but less fruity and green notes.

Efficient Catalytic Elimination of Toxic Volatile Organic Compounds via Advanced Oxidation Process Wet Scrubbing with Bifunctional Cobalt Sulfide/Activated Carbon Catalysts.

Advanced oxidation process (AOP) wet scrubber is a powerful and clean technology for organic pollutant treatment but still presents great challenges in removing the highly toxic and hydrophobic volatile organic compounds (VOCs). Herein, we elaborately designed a bifunctional cobalt sulfide (CoS2)/activated carbon (AC) catalyst to activate peroxymonosulfate (PMS) for efficient toxic VOC removal in an AOP wet scrubber. By combining the excellent VOC adsorption capacity of AC with the highly efficient PMS activation activity of CoS2, CoS2/AC can rapidly capture VOCs from the gas phase to proceed with the SO4•- and HO• radical-induced oxidation reaction. More than 90% of aromatic VOCs were removed over a wide pH range (3-11) with low Co ion leaching (0.19 mg/L). The electron-rich sulfur vacancies and low-valence Co species were the main active sites for PMS activation. SO4•- was mainly responsible for the initial oxidation of VOCs, while HO• and O2 acted in the subsequent ring-opening and mineralization processes of intermediates. No gaseous intermediates from VOC oxidation were detected, and the highly toxic liquid intermediates like benzene were also greatly decreased, thus effectively reducing the health toxicity associated with byproduct emissions. This work provided a comprehensive understanding of the deep oxidation of VOCs via AOP wet scrubber, significantly accelerating its application in environmental remediation.

Investigations on the Diffusion Behavior of Smoke-Associated Aroma Compounds into the Sausage Matrix as Affected by Casing, Caliber, and Packaging.

The aim of the study was to investigate how smoke-associated flavoring substances behave during storage in Frankfurter-type sausages. The diffusion behavior of seven selected aroma substances in the sausage matrix and the influence of the packaging and the casing were examined over a storage period of 28 days. The sausages were cut into uniformly thick layers at defined time intervals and examined by headspace-solid phase microextraction-gas chromatography-mass spectrometry. In general, three different groups could be distinguished: (1) even distribution over the entire product on the first day after smoking; (2) clear concentration gradient from outside to inside on the first day of storage, which leveled out until day 28 of storage; and (3) a clear concentration gradient that remained present throughout the storage period. In addition, only small effects were found in the distribution of flavorings between two types of packaging, selected casing, or different calibers.

Effect of Light Conditions, Trichoderma Fungi and Food Polymers on Growth and Profile of Biologically Active Compounds in Thymus vulgaris and Thymus serpyllum.

The research investigates the influence of different lighting conditions and soil treatments, in particular the application of food polymers separately and in combination with spores of Trichoderma consortium, on the growth and development of herbs-Thymus vulgaris and Thymus serpyllum. The metabolic analysis focuses on detecting changes in the levels of biologically active compounds such as chlorophyll a and b, anthocyanins, carotenoids, phenolic compounds (including flavonoids), terpenoids, and volatile organic compounds with potential health-promoting properties. By investigating these factors, the study aims to provide insights into how environmental conditions affect the growth and chemical composition of selected plants and to shed light on potential strategies for optimising the cultivation of these herbs for the improved quality and production of bioactive compounds. Under the influence of additional lighting, the growth of T. vulgaris and T. serpyllum seedlings was greatly accelerated, resulting in an increase in shoot biomass and length, and in the case of T. vulgaris, an increase in carotenoid and anthocyanin contents. Regarding secondary metabolites, the most pronounced changes were observed in total antioxidant capacity and flavonoid content, which increased significantly under the influence of additional lighting. The simultaneous or separate application of Trichoderma and food polymers resulted in an increase in flavonoid content in the leaves of both Thymus species. The increase in terpenoid content under supplemental light appears to be related to the presence of Trichoderma spores as well as food polymers added to the soil. However, the nature of these changes depends on the thyme species. Volatile compounds were analysed using an electronic nose (E-nose). Eight volatile compounds (VOCs) were tentatively identified in the vapours of T. vulgaris and T. serpyllum: α-pinene, myrcene, α-terpinene, γ-terpinene; 1,8-cineole (eucalyptol), thymol, carvacrol, and eugenol. Tendencies to increase the percentage of thymol and γ-terpinene under supplemental lighting were observed. The results also demonstrate a positive effect of food polymers and, to a lesser extent, Trichoderma fungi on the synthesis of VOCs with health-promoting properties. The effect of Trichoderma and food polymers on individual VOCs was positive in some cases for thymol and γ-terpinene.

Evaluation of the effect of Torulaspora delbrueckii on important volatile compounds in navel orange original brandy using E-nose combined with HS-SPME-GC-MS.

Simultaneous inoculation of non-Saccharomyces cerevisiae during the alcoholic fermentation process has been found to be an effective strategy for enhancing wine flavor. This study aimed to investigate the effect of Torulaspora delbrueckii NCUF305.2 on the flavor of navel orange original brandy (NOOB) using E-nose combined with HS-SPME-GC-MS. The results showed a significant increase (p < 0.05) in the sensitivity of NOOB to W5C, W3C, W1S, and W3S sensors by mixed fermentation (MF). Esters in NOOB increased by 4.13%, while higher alcohols increased by 21.93% (p < 0.001), terpenes and others increased by 52.07% and 40.99% (p < 0.01), respectively. Notably, several important volatile compounds with relative odor activity values above 10 showed an increase. Sensory analysis revealed that a more pronounced citrus-like flavor and higher overall appearance scores were found in MF than in pure fermentation (PF). These findings offer valuable theoretical guidance for enhancing the quality of fruit brandies.

Chemical and sensorial profile of Tempranillo wines elaborated with toasted vine-shoots of different varieties and micro-oxygenation.

The positive impact of use SEGs ("Shoot from vines - Enological - Granule") in winemaking for wines of the same variety has been extensively demonstrated, but their combination with different SEGs varieties and micro-oxygenation (MOX) remains unstudied. In this study, Tempranillo wines were in contact along 35 days with two doses of Tempranillo and Cabernet Sauvignon SEGs (12 and 24 g/L) and two fixed doses of MOX (LOTR, 6.24 mg/L·month, and HOTR, 11.91 mg/L·month). Chemical composition and sensory profiles were analyzed after SEGs-MOX treatments. Results indicated a greater impact of MOX on volatile composition when Cabernet Sauvignon SEGs were used, with similar results for CS12-HOTR and CS24-LOTR wines. Phenolic compounds showed a total concentration decrease in all treated wines, though trans-resveratrol increased in all cases, particularly with the highest MOX dose. In sensory evaluation, MOX accelerated the integration of characteristic SEGs aromas into the wine, reducing the required bottle time for round them.

Metabolomics, volatolomics, and bioinformatics analyses of the effects of ultra-high pressure pretreatment on taste and flavour parameters of cured Culter alburnus.

The effects of ultra-high pressure (UHP) pretreatment (50-250 MPa) on the fish curing were studied. UHP increased the overall volatile compound concentration of cured fish. Among 50-250 MPa five treatment groups, 150 MPa UHP group exhibited the highest total free amino acid content (294.34 mg/100 g) with that of the control group being 92.39 mg/100 g. The activity of cathepsin L was increased under 50-200 MPa UHP treatment (62.28-58.15 U/L), compared with that in the control group (53.80 U/L). UHP treatment resulted in a significant increase in small molecule compounds, especially the amino acid dipeptides and ATP metabolic products. Under UHP treatments, the bacterial phyla Actinobacteriota (1.04-5.25 %), Bacteroidota (0.20-4.47 %), and Deinococcota (0.00-0.05 %) exhibited an increased abundance, and they promoted taste and flavor formation. Our results indicated that UHP is a promising pretreatment method to improve taste and flavour in cured fish by affecting the microorganisms, cathepsin, and proteins.

In-depth analysis of volatolomic and odorous profiles of novel craft beer by permutation test features selection and multivariate correlation analysis.

This research explored the impact of binary cereal blends [barley with durum wheat (DW) and soft wheat (CW)], four autochthonous yeast strains (9502, 9518, 14061 and 17290) and two refermentation sugar concentrations (6-9 g/L), on volatolomics (VOCs) and odour profiles of craft beers using unsupervised statistics. For the first time, we applied permutation test to select volatiles with higher significance in explaining variance among samples. The unsupervised approach on the 19 selected VOCs revealed cereal-yeast interaction to be the main source of variability and DW-9502-6/9, DW-17290-6, CW-17290-6 and CW-9518-6 being the best technological strategies. In particular, in samples DW-9502-6/9, concentrations of some of the selected volatiles were observed to be approximately three to more than seven times higher than the average. PLS-correlation between VOCs and odour profiles proved to be very useful in assessing the weight of each of the selected VOCs on the perception of odour notes.

The role of hydrogen-rich water in delaying the pulp breakdown of litchi fruit during postharvest storage.

Previous studies have indicated that hydrogen-rich water (HW) treatment can delay fruit ripening and senescence. However, little is known about the HW-delaying pulp breakdown. In this study, eight physiological characteristics revealed that HW treatment delayed both pericarp browning and pulp breakdown of litchi fruit. To gain a comprehensive understanding of the changes in litchi pulp, a combination of multiple metabolomics and gene expression analyses was conducted, assessing 67 primary metabolites, 103 volatiles, 31 amino acids, and 13 crucial metabolite-related genes. Results showed that HW treatment promoted starch degradation, decelerated cell wall degradation and glycolysis, and maintained the flavor and quality of litchi fruit. Furthermore, HW treatment stimulated the production of volatile alcohols, aldehydes, ketones, olefins, and amino acids, which might play a vital role in HW-delaying pulp breakdown. This study sheds light on the mechanism by which HW delayed pulp breakdown by investigating small molecule metabolites and metabolic pathways.

Effect of support structure of Pt/silicaite-1 catalyst on non-thermal plasma (NTP) assisted chlorobenzene degradation and PCDD/Fs formation.

Development of efficient catalysts for non-thermal plasma (NTP) assisted catalysis to mitigate the formation of harmful by-products is a significant challenge in the degradation of chlorinated volatile organic compounds (Cl-VOCs). In this study, catalytically active Pt nanoparticles supported on non-porous SiO2 and silicalite-1 zeolites (S1) with different pore structure were comparatively investigated for catalytic chlorobenzene degradation under NTP condition. It was shown that the pore structure could significantly impact the metal size and metal dispersion rate. Pt supported on modified S1 hierarchical meso-micro-porous silicalite-1 (Pt/D-S1) exhibited the smallest particle size (∼6.19 nm) and the highest dispersion rate (∼1.87). Additionally, Pt/D-S1 demonstrated superior catalytic performance compared to the other catalysts, achieving the highest chlorobenzene conversion and COx selectivity at about 80% and 75%, respectively. Furthermore, the pore structure also affected the formation of by-products according to the findings from GC-MS analysis. Pt/SiO2 generated a total of 18 different species of organic compounds, whereas only 12 species of organic by-products were identified in the Pt/D-S1 system (e.g. polychlorinated compounds like 3,4 dichlorophenol were exclusively identified in Pt/SiO2). Moreover, dioxin-like polychlorinated biphenyl and other chlorinated organic compounds, which have potential to form highly toxic dioxins, were detected in the catalysts. HRGC-HRMS confirmed and quantified the 17 different dioxin/furans formed on Pt/SiO2 (25,100 ng TEQ kg-1), Pt/S1 (515 ng TEQ kg-1) and Pt/D-S1 (367 ng TEQ kg-1). The correlation between synthesis-structure-performance in this study provides insights into the design of catalysts for deep oxidation of Cl-VOCs in NTP system.