Addition Of Catalyst Research Articles

Hydrothermal liquefaction of representative to Israel food waste model

In this study, we examined the hydrothermal liquefaction (HTL) pathway to reduce food waste environmental impacts by converting it into bio-crude and biochar. The yield and properties of these products depend on the composition of the feedstock and process parameters. We developed a model of household food waste based on Israel national waste survey. To investigate the effects of catalysts type, we examined the influence of dolime, dolomite, phosphate and potassium carbonate on products yields and composition. Additionally, we analyzed the role of the process parameters, including solid load, residence time, catalyst concentration, and temperature, on the yield and the properties of the hydrothermal liquefaction reaction products, such as bio-crude, biochar, and aqueous phase solubles. The experimental results show absolute bio-crude yield ranging from 6.61w% to 29.36w% and biochar yield ranging from 12.29w% to 40.73w% from the initial waste. Furthermore, 13.78w% to 33.98w% of the feed material was found in the aqueous phases and 6.15w% to 8.94w% was measured in the gas phase. The addition of catalysts positively influenced the bio-crude yield. A process temperature of 280 °C improved the energy recovery and increased product yield, resulting in a reduction in the oxygen content of the bio-crude. All bio-crudes showed undetectable sulfur levels and exhibited HHVs ranging from 30.24 MJ/kg to 37.94 MJ/kg, while biochar had HHVs of 31.29 MJ/kg to 31.84 MJ/kg. On the Israel national level, the bio-crude derived from food waste demonstrates the potential to meet up to 31.4 % of Israel's marine fuel demand assuming bio-crude yield of 29 %, as achieved in this study.

The regulation of ferrocene-based catalysts on heat transfer in high-pressure combustion of ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum composite propellants

The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum (AP/HTPB/Al) composite propellants under high pressures is a crucial step for its application in high-pressure solid rocket motors. In this work, the combustion characteristics of AP/HTPB/Al composite propellants containing ferrocene-based catalysts were investigated, including the burning rate, thermal behavior, the local heat transfer, and temperature profile in the range of 7–28 MPa. The results showed that the exponent breaks were still observed in the propellants after the addition of positive catalysts (Ce-Fc-MOF), the burning rate inhibitor ((Ferrocenylmethyl)trimethylammonium bromide, FcBr) and the mixture of FcBr/catocene (GFP). However, the characteristic pressure has increased, and the exponent decreased from 1.14 to 0.66, 0.55, and 0.48 when the addition of Ce-Fc-MOF, FcBr and FcBr/GFP in the propellants. In addition, the temperature in the first decomposition stage was increased by 7.50 °C and 11.40 °C for the AP/FcBr mixture and the AP/FcBr/GFP mixture, respectively, compared to the pure AP. On the other hand, the temperature in the second decomposition stage decreased by 48.30 °C and 81.70 °C for AP/FcBr and AP/FcBr/GFP mixtures, respectively. It was also found that FcBr might generate ammonia to cover the AP surface. In this case, a reaction between the methyl in FcBr and perchloric acid caused more ammonia to appear at the AP surface, resulting in the suppression of ammonia desorption. In addition, the coarse AP particles on the quenched surface were of a concave shape relative to the binder matrix under low and high pressures when the catalysts were added. In the process, the decline at the AP/HTPB interface was only exhibited in the propellant with the addition of Ce-Fc-MOF. The ratio of the gas-phase temperature gradient of the propellants containing catalysts was reduced significantly below and above the characteristic pressure, rather than 3.6 times of the difference in the blank propellant. Overall, the obtained results demonstrated that the pressure exponent could be effectively regulated and controlled by adjusting the propellant local heat and mass transfer under high and low pressures.

Scrutinizing different catalytic processes in the (Gd–La) codoped CeO2–NiO-carbonate membrane reactor, implying CO2 permeation mechanisms

In recent years, new and novel ceramic carbonate membrane reactors have received attention due to their high capabilities. Within this context, a membrane reactor system implies a gas permeation combined with a catalytic reaction process, resulting in a synergetic effect of a bifunctional material, which intensifies the whole process. This work presents the use of a (Gd–La) codoped CeO2–NiO-carbonate membrane reactor, for two different processes; i) carbon monoxide (CO) oxidation and ii) dry methane (CH4) reforming, in which carbon dioxide (CO2) permeation is needed. The (Gd–La) codoped CeO2–NiO powder was obtained by the so called one-pot method, obtaining a Gd–La codoped ceria and nickel oxide mixture, determined by X-ray diffraction and high resolution transmission electron microscopy. In any case, the formation of these phases probed to possess a better CO2 permeation than that obtained when a mechanical mixture of Ce0.85Gd0.15O2-δ and LaNiO3 was evaluated. This membrane reactor showed efficient CO oxidation and CO2 permeation yields, which were highly improved through the oxygen (O2) addition in the feed and/or sweep membrane sides. In the dry CH4 reforming reaction, this composition was able to perform the reaction, although it was importantly improved by a catalyst addition (LaNiO3) being the CO2 permeation the limiting step of the whole reaction process.

Insight into the pathways of biochar/smectite-induced humification during chicken manure composting

As representative organic and inorganic additives, both biochar and smectite exhibit an excellent capacity to improve humification efficiency during composting. Nevertheless, the mechanisms underlying biochar/smectite-induced compost humification have still not been fully explored from the perspective of overall organic substances. In this study, three composting treatments were performed as follows: 10 % biochar-amended composting, 10 % smectite-amended composting and natural composting without any additive. UV–visible parameters and synchronous hetero two-dimensional correlation spectra showed that biochar accelerated dissolved organic matter (DOM) complications, unsaturation and aromatization. For example, biochar promoted the C2 and simple C3 peaks to convert into a sophisticated C3/360 peak. However, the effect of smectite was negligible in complicating the DOM structure. Both biochar and smectite displayed an invigorating role in promoting humic substance (HS) formation. The strengthened relations between bacterial richness and physicochemical indicators and HS fractions might contribute to the positive action of biochar/smectite on HS synthesis. Network analysis showed that both bacterial functional omnipotence and specialization in response to the addition of catalysts may contribute to compost humification. The chemical pathway involved in DOM humification was intensified by enhancing the role of pH in biochar composting and weakening the degradation of unsaturated aromatic compounds of DOM with smectite addition. These findings benefit the practical application of biochar/smectite in promoting composting efficiency.

A Review on Biolubricants Based on Vegetable Oils through Transesterification and the Role of Catalysts: Current Status and Future Trends

The use of biolubricants as an alternative to petroleum-based products has played an important role in the last decade. Due to the encouragement of global policies, which mainly support green chemistry and circular economy, there has been an increasing interest in bio-based products, including biolubricants, from scientific and industrial points of view. Their raw materials, production, and characteristics might vary, as biolubricants present different applications for a wide range of practical uses, making this field a continuously changing subject of study by researchers. The aim of this work was to study biolubricant production from vegetable oil crops from a bio-refinery perspective, paying attention to the main raw materials used, the corresponding production methods (with a special focus on double transesterification), the role of catalysts and some techno-economic studies. Thus, the main factors affecting quality parameters such as viscosity or oxidative stability have been covered, including catalyst addition, reaction temperature, or the use of raw materials, reagents, or additives were also analyzed. In conclusion, the search for suitable raw materials, the use of heterogeneous catalysts to improve the effectiveness and efficiency of the process, and the optimization of chemical conditions seem to be the most interesting research lines according to the literature.

Mathematical modeling of tar conversion on downdraft biomass gasification processes

AbstractThe article concerns some problems associated with the use of low‐grade fuels for the production of syngas in fixed‐bed gasifiers. Syngas is typically used to feed internal combustion engines in small power systems. Gas quality can be understood as its various characteristics, such as calorific value, the content of individual components (for example, hydrogen), low tar and soot content, and so forth. Achieving these quality criteria often requires specific conditions for the gasification process, in addition, some of them may be limited by additional requirements that are associated with thermal stability or fuel conversion requirements. When evaluating the technical and economic characteristics of gasification‐based power plants, the optimal efficiency does not always correspond to the higher efficiency of the gasification process and the quality of producer gas. In this regard, the aim is to develop optimization methods for different criteria and to create regime maps that cover physically achievable options. Novel mathematical models of tar conversion are proposed, allowing investigation of the dependencies of tar yield on gasification conditions, including the addition of catalysts or staged air supply. Computational tools based on thermodynamic and kinetic models make it possible to solve some of these problems, first of all, to consider and compare the efficiency of various methods for reducing tar content in producer gas (staged gasification, fuel mixing, thermal, and catalytic methods of tar elimination). The choice of relatively simple mathematical models allows us to conduct numerical calculations in a wide range of conditions and to optimize the parameters of biofuel conversion plants. This approach allows a more flexible choice of gasifier operating conditions, including its work as a part of a power unit. Optimal parameters are calculated for specific conditions: secondary air ratio (1–20%) and fraction of catalytic material (5–10%). The results may be used in the analysis and choice of biofuel gasification conditions at small power plants.

Diffusion Effect on Octogen Coating-Curing Kinetics with Polyurethane Using Infrared Spectroscopy

The kinetic analysis of octogen coating with a polyurethane base containing hydroxyl-terminated polybutadiene (HTPB) was investigated using infrared spectroscopy. The coating process involved a solvent method, where octogen and liquid polyurethane were mixed, the solvent was evaporated, and curing took place at an elevated temperature. The ratio of HTPB to diisocyanate was equimolar. About 200 g octogen was coated with mixture of 2 mL HTPB, 50 mL ethyl acetate, and 0.2 mL TDI in the glass beaker at 30 °C for 1 h. The filtrated ethyl acetate was then evaporated, and the residue was dried in a vacuum oven for 15 min at 30 °C. The resulting film-coated octogen was cast into a KBr pellet and cured in the oven for 7 days at 40 °C, then infrared-analyzed every hour during the curing process. After curing, the shape of the coated octogen particles was analyzed using SEM Initially, the curing process occurred in the solvent system, followed by further curing in the bulk system. The kinetic analysis was performed using a modified diffusion-autocatalytic model, which includes noncatalytic, autocatalytic, and diffusion components. This model was compared with others during the bulk reaction and proved to be effective in correcting errors, particularly in the gel time region. Thermodynamic parameters were evaluated using the Arrhenius and Eyring equations. The reaction rate was initially controlled by chemical reactivity, but after the gel time, diffusion became the controlling factor. In the HTPB-TDI system, both the noncatalytic and autocatalytic parts decreased with increasing temperature, while diffusivity increased. It is worth noting that diffusivity is temperature-dependent. Different di-isocyanates, namely toluene diisocyanate (TDI), iso-phorone diisocyanate (IPDI), and hexamethylene diisocyanate (HMDI), were studied, revealing that HMDI exhibited higher reactivity than TDI and IPDI. The catalyst effect on reaction rate of the HTPB-TDI system was investigated. The addition of catalysts (0.1%) to the HTPB-TDI system decreased their activation energy in the order DBTL > FeAA > TPB. Catalysts did not change their diffusivity.

Catalyst‐Free, Self‐Healing, and Recyclable Tung Oil‐Based Epoxy Vitrimers with Dynamic Ester Bonds

AbstractLow toughness and nonrecyclability severely limit the applications of traditional thermosets and are not in line with the concept of sustainable development. To solve these problems, water is used as the solvent, and a tung oil‐based tetrafunctional carboxylic acid (TFA) curing agent is obtained through a “one‐pot” method based on previous works. This green synthesis method is suitable for synthesizing tung oil‐based polycarboxylic acid curing agents from various olefin‐containing polyacids. At the same time, the vitrimers (DGEBA‐TFA) are prepared with diglycidyl ether of bisphenol (DGEBA) as the skeleton, and applied to carbon fiber reinforced composites (CFRCs). The tensile strength, tensile modulus and elongation at break of DGEBA‐TFA are 64.62 MPa, 2.55 GPa, and 4.31%, respectively, which are comparable to previous works. Hence, the performance of the vitrimers is not reduced while simplifying the experimental steps. Meanwhile, DGEBA‐TFA exhibits excellent self‐healing, shape memory, and recycling abilities. The vitrimers can be reprocessed without additional catalysts, and the recovery rate remained at 91.3% in the third cycle. DGEBA‐TFA‐CFs exhibite excellent tensile strength. This work solves the problems in previous works and makes TFA more likely to be applied into practical industrial production.

Dielectric Barrier Discharge Plasma Coupled with Cobalt Oxyhydroxide for Methylene Blue Degradation.

In this study, the coupled use of a double dielectric barrier discharge (DDBD) and CoOOH catalyst was investigated for the degradation of methylene blue (MB). The results indicated that the addition of CoOOH significantly promoted MB degradation performance compared to the DDBD system alone. In addition, both the removal rate and energy efficiency increased with an increase in CoOOH dosage and discharge voltage. After 30 min of discharge treatment in the coupled system (with CoOOH of 150 mg), the removal rate reached 97.10% when the discharge voltage was 12 kV, which was 1.92 times that in the single DDBD system. And when the discharge time was 10 min, the energy efficiency could reach 0.10 g (k·Wh)-1, which was 3.19 times better than the one in the single DDBD system. Furthermore, the addition of CoOOH could also significantly enhance the TOC and COD removal rates of MB. In the DDBD-coupled-with-CoOOH system, TOC and COD were 1.97 times and 1.99 times those of the single DDBD system after 20 min of discharge treatment with a discharge voltage of 12 kV and 100 mg of CoOOH. The main active substances detected in the coupled system indicated the conversion of the active species H2O2 and O3 into a more oxidizing ·OH was enhanced through the addition of a CoOOH catalyst, resulting in the more effective decomposition of MB and intermediate molecules.

Solvent-less carboxymethylation-induced electrostatic crosslinking of chitosan

The successful N-carboxymethylation and concomitant crosslinking of solid chitosan upon heating its mixture with solid monochloroacetic acid, without the use of solvents or catalysts, is reported. The N-carboxymethylation was confirmed through the analysis of the partially depolymerized product using NMR spectroscopy, as well as a control reaction with lysine. This transformation was facilitated by the nucleophilic nature of the free amine group in the repeating unit of chitosan, which possesses lone pair of electrons capable of attacking the carbon center bearing the leaving group and displacing the leaving group in a concerted manner. The crosslinking, on the other hand, was established by the observed insolubility in aqueous acidic solutions, even when subjected to prolonged heating at 60 °C. This crosslinking occurs due to the electrostatic interactions between the carboxylate groups and the adjacent ammonium groups, as supported by evidence from FTIR spectroscopy and a control reaction involving ethyl chloroacetate. The resulting crosslinked carboxymethyl chitosan demonstrated its usefulness in the adsorption of methyl orange and fluorescein, as well as functioning as an organic catalyst for aza-Michael addition, Hantzsch reaction, and substituted perimidine synthesis.

Microwave catalytic co-pyrolysis of sugarcane bagasse and Chlorella vulgaris over metal modified bio-chars: Characteristics and bio-oil analysis

Bio-char (BC) is a cheap, environmentally friendly and easy-to-produce material, which is widely used as pyrolysis catalyst. In this study, the modified catalysts (Fe/BC, Co/BC and Mg/BC) were prepared using BC produced by the co-pyrolysis of sugarcane bagasse and Chlorella vulgaris. The characterization of the modified catalysts showed that they had a higher surface area (SBET) and pore volume compared with BC. Besides, the influence of modified catalysts on co-pyrolysis was analyzed at different additions. Except for 10% Mg/BC, the catalysts effectively increased the average weight loss rate (Rv) and decreased the reaction time (ts) of co-pyrolysis at all additions, and 40% Fe/BC addition had the highest Rv and lowest ts. The catalyst addition increased the bio-oil yield of the co-pyrolysis, and the maximum bio-oil yield (25.94%) was obtained under 40% Mg/BC addition. Moreover, the catalysts not only facilitated the formation of hydrocarbons, but also suppressed the generation of amines/nitriles and acids/esters. After adding 40% Fe/BC, the hydrocarbons content reached the highest (26.01%), while the amines/nitriles content (3.23%) and acids/esters content (4.66%) reached the lowest. The results provided theoretical support for improving microwave pyrolysis characteristics and bio-oil quality using modified BC catalysts.

Advancements, Challenges, and Prospects in Rechargeable Solid‐State Lithium‐Air Batteries

AbstractSolid‐state lithium‐air batteries (SSLABs) are attracting widespread research interest as emerging energy storage systems with ultra‐high theoretical energy density. However, due to their relatively short development history, the practical capacity and cyclic performance of SSLABs still fail to meet application requirements. The selection of solid electrolytes and the design and optimization of air cathodes are key factors for developing high‐performance solid‐state lithium‐air batteries. In this review, we focus on recent scientific advances and challenges in SSLABs, providing a comprehensive overview of solid electrolytes, air cathodes, and interface issues. Strategies such as electrolyte modification, composite cathodes, interface engineering, and the addition of catalysts which have been effective in addressing issues related to low ionic conductivity of electrolytes, high interfacial impedance, sluggish kinetics of electrochemical reactions, and poor cycling stability, were reviewed and discussed. Furthermore, this review also discusses the prospects of SSLABs, aiming to inspire and provide references for the development of solid‐state lithium‐air batteries, as well as other metal‐air batteries.

Effects of Nitrogen-Doping or Alumina Films on Graphene as Anode Materials of Lithium-Ion Batteries Verified by in Situ XRD

First, graphene is directly grown on nickel foil without additional catalysts by chemical vapor deposition (CVD). Next, the graphene is modified by nitrogen-doping and alumina is deposited onto the graphene by magnetron sputtering. The charge specific capacity of N-doped graphene is higher than that of graphene since 2 Theta of in situ XRD characteristic peaks for N-doped graphene moves toward a lower angle (about 24) which is smaller than that (about 25) for graphene, then the gap between graphene layers for N-doped graphene is larger than that for graphene according to Bragg’s Law and N-doped graphene demonstrates the additional in situ XRD characteristic peak (LiC6) in comparison to graphene only with the in situ XRD characteristic peak (LiC12). Furthermore, because 2 Theta of in situ XRD characteristic peaks for Al2O3/graphene also moves toward a lower angle (about 24) and Al2O3/graphene also shows the additional in situ XRD characteristic peak (LiC6), the charge specific capacity of Al2O3/graphene is also higher than that of graphene.

Advancements in Thin, Reinforced Proton Exchange Membranes for Water Electrolysis

Proton exchange membrane water electrolysis (PEMWE) is emerging as one of the most promising methods to produce clean hydrogen at industrial scale. New PEMWE stack designs require high voltage efficiency and differential pressure operation without sacrificing low hydrogen in oxygen concentrations in the anode stream. Membranes used in current stack designs, such as Chemours Nafion™ N115, are thick to provide strong mechanical stability. However, employing a thinner and mechanically supported membrane can enhance both the electrochemical performance and mechanical properties. With the demand for cheaper hydrogen, these new membrane designs are needed to achieve advanced performance metrics. In this presentation, recent improvements in membrane design at Chemours will be summarized.Novel architectures comprise a thin, reinforced composite membrane approach, utilizing a lower equivalent weight (EW) polymer that can surpass the performance of the current commercial membranes. For example, overpotential is reduced by >150 mV at 3 A/cm2 for novel membranes compared to Nafion™ N115 at 80°C. However, one concern with having a thinner film is the increase in hydrogen crossover, since the lower explosive limit (LEL) for hydrogen in oxygen is only 4 vol %. PEMWE differential pressures of up to 30 bar on the cathode side can exacerbate these hydrogen crossover challenges. To mitigate this hazard, gas recombination catalyst (GRC) additives have been implemented within the membrane where the GRC recombines hydrogen and oxygen to form water. A reduction in anodic hydrogen in oxygen content of >50x has been observed, assuring the safe operation at high differential pressures for these thin membranes. Polarization curves across different membrane constructions were analyzed as well as hydrogen crossover for various GRC designs. Comparisons will be presented demonstrating the improved performance and reduced hydrogen crossover. Figure 1

The synthesis of multifunctional cellulose graft alternating copolymers of 3,4-dihydrocoumarin and epoxides in DBU/DMSO/CO2 solvent system

Cellulose graft copolymers having well-defined structures could incorporate the characteristics of both the cellulose skeleton and side chains, providing a new method for the preparation functionalised cellulose derivatives. Herein, a series of multifunctional cellulose grafted, alternating 3,4-dihydrocoumarin (DHC) and epoxide (EPO) copolymers (cell-g-P(DHC-alt-EPO)) were prepared in a metal-free DBU/DMSO/CO2 solvent system without adding additional catalyst. Four examples of cell-g-P(DHC-alt-EPO) with tunable thermal and optical properties were synthesized by copolymerization of DHC with styrene oxide (SO), propylene oxide (PO), cyclohexene oxide (CHO) or furfuryl glycidyl ether (FGE) onto cellulose. The nonconjugated cell-g-P(DHC-alt-EPO) showed UV absorption properties with the maximum absorption peak at 282 nm and 295 nm and photoluminescence performance. A clustering-triggered emission mechanism was confirmed and consistent with DFT theoretical calculations. In DMSO solution, the copolymer (DHCSO5) with DP of 11.64 showed ACQ behaviour as the concentration increased. In addition, DHCSO5 had good antioxidant capacity with an instantaneous radical scavenging activity of 2,2-diphenyl-1-picrylhydrazine (DPPH) up to 65 % at a concentration of 40 mg/ ml and increased to 100 % after 30 min. Thus, the multifunctional cell-g-P(DHC-alt-EPO) materials had a variety of potential applications in the fields of fluorescent printing, bio-imaging, UV- shielding and antioxidants.

The promotion of NH3-SCR performance and its mechanism on Sm modified birnessite

To develop novel NH3-SCR catalysts with low-temperature and high-efficency, a series of birnessite (δ-MnO2) catalysts with different Sm doping by methanol reduction are synthesized. The results showed that the introduction of Sm successfully inhibited the crystallization of MnOX, promoted the specific surface area, the contents of chemisorbed oxygen species and the formation of surface acid sites. It also increased the relative content of (Mn4+ + Mn3+)/Mn, which was beneficial to low-temperature SCR activity. The catalytic performance of xSm/Mn (δ-MnO2 based with xSm doping) catalysts was evaluated by NH3-SCR performances. Among them, 0.05 Sm/Mn showed 100% NOX conversion and high N2 selectivity compared to the other Sm addition catalysts within the operating low-temperature window (25–200 °C), at a high GHSV (gas hourly space velocity) of 60,000 h−1. The modified 0.05 Sm/Mn catalysts followed the L-H and E-R reaction mechanisms and were dominated by L-H, as revealed by in-situ DRIFTs analysis.

Essential role of lattice oxygen in methanol electrochemical refinery toward formate.

Developing technologies based on the concept of methanol electrochemical refinery (e-refinery) is promising for carbon-neutral chemical manufacturing. However, a lack of mechanism understanding and material properties that control the methanol e-refinery catalytic performances hinders the discovery of efficient catalysts. Here, using 18O isotope-labeled catalysts, we find that the oxygen atoms in formate generated during the methanol e-refinery reaction can originate from the catalysts' lattice oxygen and the O-2p-band center levels can serve as an effective descriptor to predict the catalytic performance of the catalysts, namely, the formate production rates and Faradaic efficiencies. Moreover, the identified descriptor is consolidated by additional catalysts and theoretical mechanisms from density functional theory. This work provides direct experimental evidence of lattice oxygen participation and offers an efficient design principle for the methanol e-refinery reaction to formate, which may open up new research directions in understanding and designing electrified conversions of small molecules.

Non-Catalytic and Catalytic Conversion of Fruit Waste to Synthetic Liquid Fuel via Pyrolysis

Plum stone stands out as an alternative biomass source in terms of obtaining fuel and chemicals with or without catalysts under different conditions. Under variable heating rates (10, 50, and 100 °C min−1) and pyrolysis temperatures (400, 450, 500, 550, and 600 °C), plum stone was pyrolyzed at a constant rate in a constant sweep gas flow (100 cm3 min−1) in a tubular fixed-bed reactor. According to the results, an oil yield reaching a maximum of 45% was obtained at a heating rate of 100 °C min−1 and pyrolysis temperature of 550 °C in the non-catalytic procedure. The catalytic pyrolysis was carried out with two selected commercial catalysts, namely ZSM-5 and PURMOL-CTX and clinoptilolite (natural zeolite, NZ) under optimum conditions with a catalyst ratio of 10% of the raw material. With the addition of catalyst, the quantity and quality of bio-oil increased, including calorific capacity, the removal of oxygenated groups, and hydrocarbon distribution. In the presence of catalysts, an increase was observed in terms of desirable products such as phenol, alkene, and alkane, and a decrease in terms of undesirable products such as acids. Considering and evaluating all the results, the use of zeolite materials as catalysts in pyrolysis is a recommended option for obtaining enhanced chemicals and fuels.

Theoretical study on the catalytic pyrolysis mechanism of polyethylene terephthalate dimer

ABSTRACT In this paper, the density functional theory of B3P86/6–31++G(d,p) method was used to study the mechanism of the catalytic pyrolysis reactions of PET dimer. The calculated results show that the reaction energy barrier for calcium oxide to capture a proton on carboxyl group (at 112.6 kJ/mol) is lower than that on alkyl group (at 153.3 ~ 170.0 kJ/mol), which is more conducive to decarboxylation reaction. The protons provided by the acid catalyst attack the oxygen atoms of the C=O bond of PET main chain to form the cationic intermediate, and then the cleavage reaction occurs on the Calkyl-O bond, of which the bond dissociation energy is the lowest at 46.9 ~ 62.4 kJ/mol. Compared with pure pyrolysis, catalysts have little effect on the components of initial pyrolysis products, but it has effects on the components of secondary pyrolysis products of PET. The addition of catalysts can change the components of secondary pyrolysis products by changing the optimal reaction path of degradation. During the reaction processes, both alkaline and acidic catalysts can reduce the reaction energy barriers of the main elementary reactions to a certain extent (from 251.3 ~ 264.6 kJ/mol to 112.6 ~ 170.0 and 46.9 ~ 169.1 kJ/mol, respectively), making the reactions easier to proceed.

Multicomponent Radical Cross‐Coupling Reaction of [1.1.1]Propellane: Synthesis of 1‐Arylthiol‐3‐Heteroaryl Bicyclo[1.1.1]pentanes †

AbstractHerein, a visible light‐mediated multicomponent radical cross‐coupling reaction of [1.1.1]propellane with N‐heterocycles and disulfides is described. The mild conditions enabled the installation of the BCP motif in a wide variety of compounds in the absence of photocatalyst, additive and metal catalyst, with excellent functional group tolerance, This methodology opens a approach for the synthesis of potentially bioactive 1‐arylthiol‐3‐heteroaryl bicyclo[1.1.1]pentanes in moderate to good yield.