Search

The application of non-noble metal catalysts in the catalytic direct gas-phase epoxidation of propylene with H2 and O2 to produce propylene oxide is valuable and challenging. The introduction of alkali metal promoters is one of the effective methods to improve the catalytic activity of catalysts. Herein, a series of alkali metal (Li, Na, K, Rb, and Cs)-promoted Ni/TS-1 catalysts were prepared to deeply understand the effect of alkali metals on the structure-activity relationship for gas-phase epoxidation of propylene. Among them, the Na-Ni/TS-1 catalyst exhibits the highest catalytic activity (propylene conversion of 7.35% and PO formation rate of 157.9 g h−1 kgcat−1) and the best stability (long-term stability exceeding 140 h at 200 °C). X-ray absorption and photoelectron spectroscopy revealed that the electronic structure of Ni can be tuned by the addition of alkali metal promoters. NH3-TPD-MS, CO2-TPD-MS, and C3H6-TPD-MS results indicate that the acidity of the catalyst can also be adjusted by the introduction of alkali metal, whereas the Na-Ni/TS-1 catalyst exhibits the strongest C3H6 adsorption capacity. Thus, the suitable acid-base properties, unique electronic properties of Ni species, and the strongest propylene adsorption capacity resulted in improved propylene gas-phase epoxidation activity of Na-Ni/TS-1 catalyst. This study not only provides a new strategy for the practical application of nickel-based catalysts in the gas-phase epoxidation of propylene but also provides insights into the promoting effect of alkali metals. [ABSTRACT FROM AUTHOR]

A series of hollow VOx/SiO2 nanofiber catalysts (nV/S-f) with vanadium content ranging from 0.25 wt% to 4.0 wt% were prepared by electrospinning-calcination, and characterized by ICP-MS, XRD, N2 adsorption–desorption, SEM, XPS, UV–Vis-DRS and H2-TPR. Subsequently, the performance of these catalysts in the oxidative dehydrogenation of propane (ODHP) was evaluated. It was found that vanadium species with high dispersivity were obtained when the V content was less than 1.5 wt%. By comparison, 1.0V/S-f catalyst had the best catalytic performance, especially in terms of the propylene selectivity at high-temperature: ~ 77% at 550 °C and ~ 74% at 575 °C. In contrast to the conventional impregnation technique, the catalyst with one-dimensional nanostructure has more catalytic advantages. [ABSTRACT FROM AUTHOR]

Hierarchical ZSM‐5 zeolite materials with different SiO2/Al2O3 molar ratios in the range of 60–300 were synthesized using soft templating and microemulsion methods to generate zeolite materials with narrow mesopore size distributions. The resulting materials were characterized by X‐ray flourescence (XRF), Fourier transform infra‐red (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature programmed desorption (NH3‐TPD), thermo‐gravimetric analysis (TGA), Brunauer‐Emmett‐Teller (BET) surface area measurements, and products from the catalytic tests were analyzed by gas chromatography (GC). The XRF analysis determined that the Si/Al ratios for the synthesized ZSM‐5 were close to the batch ratios. The XRD and FTIR results revealed that the synthesized samples had crystalline ZSM‐5 zeolite structures. The small angle observed from the XRD patterns confirmed the presence of mesopores in the structure of the prepared materials. The SEM results showed that the ZSM‐5 synthesized materials had different morphologies and particle sizes, as well as worm‐like holes indicating that some macropores with average pore sizes ranging between 68 and 85 nm were successfully generated in these materials. NH3‐TPD results showed that the total acidity of the prepared materials decreased with an increase in the Si/Al (SA) ratio following this trend: SA = 71 > 177 > 345. This may be due to the decrease in the aluminum content, which is largely responsible for the formation of acidic sites in zeolites. The acid strength was found to increase with a decrease in the Si/Al ratio, highlighted by the peak shifts to higher temperatures. From the BET results, the SA = 71 was observed to have the highest SSA of 618 m2/g given by its micropore area of 103 m2/g and an external surface area of 515 m2/g. The high external surface area present in the material was due to the development of mesopores with narrow pore size distribution of approximately 6 nm indicating the success of the microemulsion method for the generation of hierarchical zeolites with well controlled pore sizes. The hierarchical ZSM‐5 catalysts were tested for the cracking of various hydrocarbon chain lengths. Low conversions, less than 10%, were obtained in the cracking of hexane; however, when cracking longer chain C12 hydrocarbons, the conversion increased remarkably to 100%. The catalyst with SA = 71 had the highest selectivity towards ethylene and propylene olefins due to its higher acidity in comparison with the other prepared catalysts. Improved activity, selectivity towards ethylene and propylene greater than 60%, and enhanced catalyst stability were demonstrated when using a hierarchical ZSM‐5 compared to the commercial catalyst in the cracking of dodecane. High selectivity towards light olefins was obtained for the cracking of waste tire‐derived oil. The results suggest that these hierarchical materials are suited to the cracking of long chain hydrocarbons and are promising materials for the valorization of waste tire‐derived oils. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main patterns of oxidative chlorination (oxychlorination) with such unsaturated hydrocarbons as propylene, acetylene, 1,3-butadiene, and benzene are considered. It is shown that when the processes are conducted in the gas phase, having heterogeneous copper or palladium based catalysts in the system is preferable. It is shown that palladium in a catalyst promotes processes of substitutive oxychlorination. Stagewise schemes of reactions are given for processes of propylene, acetylene, and benzene oxychlorination along with corresponding kinetic equations. Applied aspects of the above processes are discussed. [ABSTRACT FROM AUTHOR]

The development of green route for preparing propylene oxide (PO) with molecular oxygen is of significance both in academic and industrial. In this work, propylene epoxidation coupled with furfural oxidation catalyzed by platinum meso-tetraphenylporphyrin (Pt (II)TPP) has been developed. Propylene conversion and PO selectivity reached up to 56% and 83%, respectively. Meanwhile, furfural was almost completely converted to furoic acid. Based on operando characterizations and electron paramagnetic resonance (EPR) tests, a mechanism involved high-valent Pt species was proposed. This work is expected to provide a potential application prospects for producing PO and furoic acid simultaneously in chemical industry.

Industrial Bi-Mo-Fe-Co composites catalysts for propylene oxidation, are consist of two main components: Bi-Mo oxidate for propylene activation and Fe-Co oxidate for oxygen activation. But there are three different Bi-Mo crystalline phases, i.e., α-Bi2Mo3O12, β-Bi2Mo2O9, γ-Bi2MoO6, their role in catalytic oxidation process is unclear. In this paper, above three kinds of Bi-Mo phase are prepared at first, then coupled them respectively with Fe-Co oxidates by ball milling method to manufacture Cat-α, Cat-β, and Cat-γ. It is showed that their catalytic performance for propylene oxidation to acrolein, has the order of Cat-α > Cat-β > Cat-γ, and the Cat-α exhibit the best propylene conversion (90.1%) and highest acrolein selectivity (91.7%). The result shows that Cat-α exhibited a lower redox temperature, and possessed a high Olattice content, which benefit to its excellent oxidant ability. Meanwhile, α-Bi2Mo3O12 exhibit rich Co2+/Co3+ pairs in Cat-α, prompt oxygen migration efficiency, and had a low interaction with propylene confirmed by DFT calculation, which inhibited the excessive oxidation, benefits to acrolein yield. Our study provides a new insight over Bi-Mo catalyst for selective oxidation. [ABSTRACT FROM AUTHOR]

Liquefied petroleum gas (LPG) is known as clean fuel and its importance will be continued in the future. However, most of LPG is currently produced from fossil resources. Thus, producing LPG from CO2 as a renewable source is significant for achieving carbon neutrality. One possible way to produce LPG from CO2 is through an indirect pathway via methanol/dimethyl ether and propylene/butene. The final step of this pathway is the hydrogenation reaction of olefins to produce paraffins. Although H2O may coexist in this reaction, there have been few studies to investigate reaction kinetics of propylene hydrogenation in the presence of H2O. Here, we measured the propylene conversion over different four catalysts: Pt/α-Al2O3, Pd/α-Al2O3, Pt/ZrO2, and Pd/ZrO2. We varied a reaction temperature and concentrations of propylene, H2 and H2O in the feed. We found that above 200 °C the propylene conversion was negatively affected by the reaction temperature and the propylene concentration, while it was positively affected by the H2 concentration. We also found that the dependence of propylene conversion on H2O concentration depended on the catalysts. To reproduce the measured results, a kinetic model based on the Langmuir-Hinshelwood mechanism was developed over Pt/ZrO2 which showed the best reaction performance among the catalysts used. A two-dimensional reactor model consisting of mass and heat balance equations was developed for exploring the desirable reactor type. The simulations showed that the externally cooled reactor with a catalyst density gradient was the most suitable for propylene hydrogenation in terms of heat management and propylene conversion. [ABSTRACT FROM AUTHOR]

Products made from light olefins play an important role in our daily lives. Traditional light olefins production based on steam cracking and fluid catalytic cracking suffer from high energy consumption and CO2 emissions. Thereby, the continually increasing demand for light olefins needs to be met through more environmentally sustainable procedures. On‐purpose production routes are preferred choice among petrochemicals manufacturers, being energy efficient and having lower carbon footprint. Among them, oxidative dehydrogenation (ODH) of light paraffins is a thermodynamically favourable exothermic process as compared to non‐oxidative routes. They can be operated at lower temperatures and have propensity of low coke deposition on catalyst, thereby resisting rapid catalyst deactivation. Herein, we have analysed various catalytic systems utilised in the oxidative dehydrogenation process. We have reviewed role of support, chemical composition of catalyst, presence of dopant, oxidation state of active metal, controlled surface modification by oxidative and reductive pretreatments, and reaction factors for each system. The performance of various catalytic systems for ODH of ethane, propane and butane in the presence of O2, CO2, N2O and special oxidants have been reviewed. A short critical overview on emerging on‐purpose routes for the production of renewable 1,3 butadiene has also been discussed. [ABSTRACT FROM AUTHOR]

Small additions of hydrocarbons, such as propylene, which are widely studied as combustion and explosion inhibitors of hydrogen-air mixtures, sometimes exhibit specific properties. The known mechanism of the inhibitory effect of these additives is associated with the intensification of the termination of branching chains due to the addition of hydrogen atoms; however, conditions also exist in which these compounds, instead of inhibiting, have a neutral and even promoting effect. Such conditions and the reasons leading to the fact that inhibition is practically absent have not yet been studied. This article shows the results of numerical modeling, which make it possible to more fully outline the range of conditions where the addition of propylene practically does not inhibit hydrogen-air mixtures and outline possible reasons for this effect. The solution to three model problems is presented: self-ignition in a constant-volume reactor, laminar flame propagation, and gas ignition with a heated wire. The calculations are carried out with the detailed kinetic mechanism of chemical reactions NUIGMech 1.1 (2020). The objects of the study are three air mixtures containing hydrogen in amounts of 15, 29.6, and 50 vol % (lean, stoichiometric, and rich mixtures, respectively) without additives and with the addition of 1% propylene. [ABSTRACT FROM AUTHOR]

The self-ignition of a propylene–oxygen–argon stoichiometric mixture with a volumetric argon content of 95% is studied. The experiments are performed on a shock tube, which is part of the Shock Tube Experimental Complex of the Institute of Mechanics of Moscow State University, in conditions behind the reflected shock wave. The time dependencies of signals from a piezoelectric pressure sensor, a thermoelectric detector, and an optical section configured to record the radiation of electronically excited radicals OH• (λ = 302 nm), CH• (λ = 427 nm, and molecular carbon (λ = 553 nm) are analyzed. The ignition delay times τign are measured in the temperature range T = 1200–2460 K and pressures p = 4.5–25 atm. The data obtained are compared with the results of other authors. [ABSTRACT FROM AUTHOR]

Propylene is an essential chemical feedstock, which needs efficient and stable production technology to meet its increasing industrial demand. In this work, the Pt–Sn/MgAl2O4 catalysts fabricated via the incipient wetness impregnation method were used for propane dehydrogenation to propylene (PDH). The effect of Sn on reaction performance was investigated to determine the optimal loading amount. The characterization results from XRD, N2 physisorption, TEM, H2-TPR, NH3-TPD, and TGA elucidated the physicochemical characteristic evolution with varied Sn content in the catalysts. The Pt0.3Sn/MgAl2O4 achieved the best propane conversion of 40.9% and propylene selectivity of 82.5% at 600 °C. Sn addition promoted Pt dispersion, enhanced metal-support interactions, and inhibited the side reactions. The MgAl2O4 support could suppress the coke formation and maintain propylene selectivity. This work demonstrates the Pt–Sn/MgAl2O4 catalysts are effective and durable for PDH to meet propylene demand. [ABSTRACT FROM AUTHOR]

Pt-based catalysts have been widely investigated for propane dehydrogenation (PDH) due to their superior activation of C-H bonds. It is still a challenge to develop highly dispersed Pt-based catalysts with an excellent PDH performance. Herein, we designed in situ-formed PtMn intermetallic nanoclusters on Mn-doped mesoporous Al2O3 as efficient catalysts for PDH. A series of characterizations demonstrated that well-dispersed PtMn intermetallic nanoclusters were in situ-formed and did not aggregate into large ensembles during PDH reactions. The PtMn intermetallic nanoclusters reduced the activation temperature of C-H cleavage and improved the PDH performance. The specific activity of the Pt/2Mn-Al2O3 catalyst was 0.81 molC3H6 molPt-1 s-1 at 600°C, which is comparable to that of most of the state-of-the-art PtM bimetallic nanocatalysts. Moreover, the catalyst exhibited better stability than the undoped catalyst, which resulted from the antisintering effect of the PtMn intermetallic nanoclusters and the migration of coke from the Pt sites to the support. Thus, the Pt/2Mn-Al2O3 catalyst exhibited excellent regeneration stability with recoverable propane conversion and selectivity for propylene after removing coke. [ABSTRACT FROM AUTHOR]

PtSn/Al2O3 and PtSnSr/Al2O3 were prepared by the incipient wetness impregnation method. The added Sn and Sr are uniformly distributed on the surface without damaging the original crystal structure and surface texture properties. The addition of Sn not only changes the dispersion of Pt, reduces the reduction temperature of Pt, but also provides electrons to Pt, increases the electron cloud density on the surface of Pt, and reduces the deep propylene adsorption. The addition of Sr reduces the number of total acid sites and strong acid sites, reduces the generation of adverse effects and carbon deposition, slows down the deactivation of the catalyst, and improves the selectivity of propylene. Pt1.5Sn1.5Sr/Al2O3 showed the best catalytic reaction performance and remained stable after five cycles of regeneration. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petrochemical Universities / Shiyou Huagong Gaodeng Xuexiao Xuebao is the property of Journal Editorial Department Of Liaoning Shihua University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Four different samples of pure scheelite α-Bi2Mo3O12 were synthesized by the fast microwave-assisted hydrothermal method. By adjusting the pH in the preparation process, the morphologies and structures of the synthesized catalysts were changed. TG, XRD, SEM, TEM, BET, and XPS analyses were used to investigate the characteristics of the catalyst. The sample of α-Bi2Mo3O12 was prepared at a calcination temperature of 500 °C and pH = 1 had the highest specific surface area propylene selective oxidation properties. The conversion of propylene was 28.3% and the selectivity of acrolein was 86.4%. Compared with α-Bi2Mo3O12 prepared by co-precipitation and normal hydrothermal method, α-Bi2Mo3O12 prepared by microwave hydrothermal method has higher propylene oxidizing activity. The conversion of propylene is negatively correlated with the crystallinity of the catalyst. This is due to the fact that higher crystallinity inhibits the lattice oxygen flow between the lattices, thus inhibiting the selective oxidation and reducing the conversion of the reaction. The oxygen mobility of α-Bi2Mo3O12 samples was characterized by XPS. The results showed that the conversion of propylene of α-Bi2Mo3O12 were positively correlated with its oxygen mobility strength. A probable mechanism for the selective oxidation of propylene was proposed. This work not only offers a high-efficiency method for the rapid preparation of bismuth molybdate catalysts but also extends the application of microwave-assisted hydrothermal synthesis in the field of selective oxidation of propylene. [ABSTRACT FROM AUTHOR]

Pt single atoms catalysts with precise coordination environment and high stability are expected to achieve high performance of propane dehydrogenation (PDH). In this work, an innovative synthetic strategy is proposed to construct the S-1@0.1Pt9Zn@DPS-1 nanocomposite as a highly efficient PDH catalyst. Defect engineering is applied to induce the formation of defective porous silicalite-1 (DPS-1), which is favorable for achieving the uniformly distributed ZnO nanoclusters. The ZnO nanoclusters were further served as anchoring sites to stabilize the isolated Pt atoms. The structural characterization revealed that penta-O coordinated Pt single atom coupled with ZnO nanoclusters decorated on the DPS-1. Moreover, the atomically dispersed Pt atoms with the ideal coordination environment could act as the predominant active sites for PDH process. As expected, the optimal S-1@0.1Pt9Zn@DPS-1 catalyst delivered an excellent PDH performance (propane conversion of 40.7%, propylene selectivity of 97.5%) and good cycling regeneration stability. This work provides a new way for improving the activity and stability of catalysts in the field of industrial catalysts. [ABSTRACT FROM AUTHOR]

Isomerization Metathesis (ISOMET) reaction is an emerging tool for "open loop" chemical recycling of polyethylene to propylene. Novel, latent N‐Alkyl substituted Cyclic(Alkyl)(Amino)Carbene (CAAC)–ruthenium catalysts (5a‐Ru, 3b‐Ru – 6c‐Ru) are developed rendering "inverted" chemical structure while showing enhanced ISOMET activity in combination with (RuHCl)(CO)(PPh3)3 (RuH) double bond isomerization co‐catalyst. Systematic investigations reveal that the steric hindrance of the substituents on nitrogen and carbon atom adjacent to carbene moiety in the CAAC ligand have significantly improved the catalytic activity and robustness. In contrast to the NHC‐Ru and CAAC‐Ru catalyst systems known so far, these systems show higher isomerization metathesis (ISOMET) activity (TON: 7400) on the model compound 1‐octadecene at as low as 3.0 bar optimized pressure, using technical grade (3.0) ethylene. The propylene content formed in the gas phase can reach up to 20% by volume. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We summarize the patent literature related to the direct oxidation of propylene‐to‐propylene oxide (DOPO) over silver catalysts. Inventions claiming new compositions, preparation methods, and/or alternative process options are illustrated with data sampled from patent documents. Early claims focused on powders of silver (silver oxide) alloyed with and/or surface‐modified with one‐two promoterswhere silver was in large excess (>80 wt%). In the following decades, inventors refined their approach and pursued alternative bulk synthetic methods supplemented with impregnation to produce formulationscontaining lower amounts of silver in combination with various other transition metals, halides, alkalis and/or alkaline earth elements. Simultaneously, process development has facilitated increased PO selectivity via the co‐feeding of water and/or carbon dioxide at volume percent levels combined with smaller ppmV concentrations of organic chlorides and nitrogenoxides. At the end we briefly discuss how non‐catalytic oxidative routes to propylene oxide provide additional insights for new catalyst development. While these approaches hardly exceed 60 % PO selectivity, they may shed light on design criteria for catalysts capable of achieving that goal. Success in the field will require strong fundamental understanding of the activation of dioxygen on catalytic surfaces to define design requirements for silver catalystswith high selectivity to PO via direct oxidation. [ABSTRACT FROM AUTHOR]

Objective To develop the process of catalytic cracking of C4 olefins to propylene and the catalyst preparation technology, the pilot test and industrial side line test are completed. Methods The fixed-bed evaluation apparatus was used to investigate the impact of catalyst formulation, modification, and industrial conditions on catalyst activity, selectivity, and stability. Results The catalyst with ZSM-5 zeolite as the active component had good activity, selectivity, stability and regeneration performance in the conversion of C4 olefins to propylene. The introduction of phosphorus did not change the crystal structure of the catalyst, but it reduced the number of acidic sites on the catalyst, and adjusted the molar ratio of B acid and L acid of ZSM-5 zeolite. With the increase of phosphorus loading to 5wt * 0/0 the interaction between phosphorus and aluminum in molecular sieves was gradually strengthened, and phosphorus could interact with framework aluminum and non-framework aluminum. Conclusions The conversion rate of C4 olefins is more than 80%, the selectivity of propylene is 35% - 45% the once-through life of catalyst is more than one month, and the regeneration recovery rate is 95%. [ABSTRACT FROM AUTHOR]

A series of Zn-modified HBeta (Zn/HBeta) catalysts were prepared via the wetness impregnation method with different zinc precursors such as ZnSO4·7H2O, ZnCl2, C4H6O4Zn·2H2O and Zn(NO3)2·6H2O, and their catalytic performance in the conversion of ethanol to propylene reaction was evaluated. Results indicate that the amount and strength distribution of the acid sites of the Zn/HBeta catalysts were easily tuned by employing different types of zinc precursors. More importantly, when the zinc species were introduced to the HBeta, the propylene yield was significantly enhanced, whereas the yields of ethylene and C2–C4 alkanes were remarkably suppressed. For the catalyst prepared by using the ZnCl2 precursor, a higher propylene yield of up to 43.4% for Zn/HBeta-C was achieved as a result of the moderate amount and strength distribution of acid sites. The average coking rate of the used Zn/HBeta catalysts strongly depended on the amount of total acid sites, especially the strong acid sites, i.e., the higher the amount of total acid sites of the catalyst, the greater the average coking rate. For the catalyst prepared by using the ZnSO4·7H2O precursor, Zn/HBeta-S exhibited a better stability even after depositing more coke, which was due to the higher amount of strong acid sites. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Half-sandwich titanium complexes, specifically Cp*TiCl3 and Cp*Ti[O(2,6-iPr2-Ph)]Cl2, were investigated as catalytic precursors for the synthesis of ethylene/propylene copolymers and ethylene/propylene/5-ethylidene-2-norbornene terpolymers. For this purpose, a variety of activators were tested: modified polymethylaluminoxane; boron-containing compounds such as B(C6F5)3 and Ph3CB(C6F5)4 in combination with triisobutylaluminum (TIBA); isobutylaluminoxane (IBAO), and isobutylaluminum aryloxide (2,6-tBu2,4-Me-PhO-)AliBu2 (AlBHT). In the copolymerization of ethylene and propylene, the catalysts exhibited high activity when activated by MMAO-12 and TIBA+Ph3CB(C6F5)4 but low activity with TIBA+B(C6F5)3 and AlBHT. With IBAO as an activator, these catalysts were found to be totally ineffective. The catalysts exhibited low activity in terpolymerization. It was further revealed that more than one type of active sites was generated in the catalytic systems: these sites were responsible for simultaneous formation of low-molecular-weight and ultrahigh-molecular-weight polymers. The composition of the copolymers as well as their thermophysical and physicomechanical properties were shown to depend on the type and composition of the catalytic system. [ABSTRACT FROM AUTHOR]

The energy pathways of possible decomposition and isomerization reactions of iso-propyl (i-C3H7) and n-propyl (n-C3H7) radicals are studied by computational methods of quantum chemistry. The B3LYP, M062X, MP2, and CBS-QB3 methods are used to localize stationary points on the potential energy surface of a system containing propyl radicals. A number of intermediate compounds formed during the isomerization and decomposition of propyl radicals are identified and information is obtained on their structure and thermochemical parameters. Based on the results of the research, a diagram of the energy levels of the system under consideration is constructed. [ABSTRACT FROM AUTHOR]

The influence of adding Cr(III) compounds into Zn−BEA zeolite samples (with silicate modulus Si/Al=17, 100, and 1000) on the redox and acid–base characteristics of Cr/Zn−BEA zeolites were studied, and their catalytic properties in propane dehydrogenation with CO2 to propylene. It was established (based on the XRD, low–temperature (77 K) ad/desorption of N2, TPR−H2, TPD−MSC−NH3(CO2), C3H8(C3H6), FTIR−Py data) that the acid–base characteristics of the surface of bifunctional Cr/Zn−BEA catalysts, namely the amount, strength, and nature (Lewis and Brønsted sites), determine their activity/selectivity, and operation stability in the process of CO2−PDH. This indicates that over Cr/Zn−BEA catalysts, the process runs along the route of direct propane dehydrogenation combined with the reverse water gas shift reaction. [ABSTRACT FROM AUTHOR]

Compared to the currently widely used propane dehydrogenation process for propylene production, propane oxidative dehydrogenation (ODHP) offers the advantage of no thermodynamic limitations and lower energy consumption. However, a major challenge in ODHP is the occurrence of undesired over-oxidation reactions of propylene, which reduce selectivity and hinder industrialization. MOFs possess a large number of metal sites that can serve as catalytic centers, which facilitates the easier access of reactants to the catalytic centers for reaction. Additionally, their flexible framework structure allows for easier adjustment of their pores compared to metal oxides and molecular sieves, which is advantageous for the diffusion of products within the framework. This property reduces the likelihood of prolonged contact between the generated propylene and the catalytic centers, thus minimizing the possibility of over-oxidation. The research on MOF catalyzed oxidative dehydrogenation of propane (ODHP) mainly focuses on the catalytic properties of MOFs with cobalt oxygen sites and boron oxygen sites. The advantages of cobalt oxygen site MOFs include significantly reduced energy consumption, enabling catalytic reactions at temperatures of 230 °C and below, while boron oxygen site MOFs exhibit high conversion rates and selectivity, albeit requiring higher temperatures. The explicit structure of MOFs facilitates the mechanistic study of these sites, enabling further optimization of catalysts. This paper provides an overview of the recent progress in utilizing MOFs as catalysts for ODHP and explores how they promote progress in ODHP catalysis. Finally, the challenges and future prospects of MOFs in the field of ODHP reactions are discussed. [ABSTRACT FROM AUTHOR]

The epoxidation reaction of propylene (C3H6) for propylene oxide (PO) production was, for the first time of its kind, investigated in a low-temperature parallel-plate dielectric barrier discharge system with two frosted glass plates and a separate C3H6 feed under ambient condition. For the mixed feed experiments, the maximum PO selectivity was found at a feed molar air-to-C3H6 ratio of 0.5:1, an applied voltage of 7 kV, an input of 550 Hz, and a feed flow rate of the mixed gas of 100 cm3/min (corresponding to a residence time (RT) of 12.1 s). At the optimum operational conditions, a separate C3H6 feed position fraction of 1 (complete separation of C3H6) with total reactant feed flow rate of 100 cm3/min (corresponding to an O2 residence time (RT) of 24.1 s), the greatest propylene oxide selectivity of 16.40% was achevied. The relatively high PO selectivity with very low selectivities for all other products and with the absence of both CO and CO2 obseved in this studied resulted from less active of C3H6 due to the separate feed of C3H6. The C3Hseparate feed is fundamentally responsible for the reduction in all the undesired reactions including cracking, dehydrogenation, coupling, and oxidations of C3H6. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE), octenidine dihydrochloride (OCT), and zinc oxide (ZnO) were used to modify the polypropylene nonwoven material by the methods of 'wet chemistry' and low-energy electron beam deposition (EBD). The influence of nonwoven material modification on the morphology, chemical composition, filtration, and antibacterial properties was established. The modified material has antibacterial activity against the gram-positive strain Staphylococcus aureus and against gram-negative strains of Escherichia coli and Klebsiella pneumoniae (suppression of bacterial growth for materials with OCT was 100%, with ZnO--70%). PTFE application to Aquaspun leads to a significant increase in the contact angle (from 141.3[degrees] to 152.7[degrees]) and air filtration efficiency (from 78.3% to 83.4%), which provides the barrier properties of the material. It was established that the material obtained using low-energy EBD demonstrated a more pronounced antimicrobial potential against the tested strains of St. aureus. Highlights * The influence of polypropylene nonwoven materials surface modification methods is systematically investigated. * Low-energy electron beam deposition increases antibacterial and filtration properties of nonwoven materials. * Surface modification methods increase barrier properties of polypropylene nonwoven materials. KEYWORDS coatings, fibers, modification, poly(propylene) (PP), 1 | INTRODUCTION In recent years, in the manufacture of personal protective equipment (PPE) from nonwoven polymeric materials, the most successful areas associated with both the modification of the source [...]

The study of the oxidation of propane-ethylene mixtures by numerical kinetic modeling allowed us to establish that in the range of 400–600°C with an increase in the conversion of propane with an increase in temperature, the selectivity of propylene formation passes through a maximum whose position depends on the concentration of ethylene in the initial mixture. The addition of ethylene to the initial mixture leads to a reduction in propane consumption and an increase in the selectivity of propylene formation. The conditions under which ethylene introduced into the initial mixture is not consumed during the process are determined; thus, formally it can be considered as a catalyst, and the process of propane oxidation as proceeding in a pseudo-catalytic regime. [ABSTRACT FROM AUTHOR]

Nonoxidative dehydrogenation of propane to propylene using Pt-based supported catalysts is an active research area in catalysis because catalyst attributes of Pt sites can be controlled by careful design of active sites. One way to achieve this is by the addition of a second metal that may impart a change in the electron density of active sites, which in turn affects catalytic performance. In this study, bimetallic Pt and B sites were deposited on powder SiO2 using atomic layer deposition (ALD). Boron was first deposited on SiO2 via half-cycle ALD using triisoproplyborate as the B source. Following calcination, Pt deposition was performed via half-cycle ALD using trimethyl(methylcyclopentadienyl)platinum(IV) as the Pt source. The synthesized catalysts were reduced under H2 at 550 °C and characterized using inductively coupled plasma optical emission spectroscopy for elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO to examine the properties of Pt, and time-resolved X-ray absorption near edge structure spectroscopy to examine the changes in the reducibility of Pt sites. The samples were then tested for nonoxidative dehydrogenation of propane at 550 °C using a fixed-bed plug-flow reactor to examine the role of B on the catalytic performance. Characterization results showed that the addition of B imparted an increase in electron density and affected the reducibility of Pt sites. In addition, incorporating B on SiO2 created anchoring sites for Pt ALD. The amount of Pt deposited on B/SiO2 was 2.2 times that on SiO2. Catalytic activity results revealed the addition of B did not change the initial activity of Pt sites significantly, but improved propylene selectivity from 80% to 87% and stability almost threefold. The enhanced selectivity and stability of PtB/SiO2 is most presumably due to favored desorption of propylene and mitigating coke formation under reaction conditions, respectively. [ABSTRACT FROM AUTHOR]

A series of C1-symmetric ethylene-bridged ansa-(3-R-cyclopentadienyl)(fluorenyl) metallocene complexes (Zr: 1–5; Hf: 6) have been synthesized, characterized and investigated as catalyst precursors for the high temperature ethylene polymerization. Using methylaluminoxane (MAO) as the cocatalyst, zirconium complexes 1–5 bearing a bulky substituent on the 3-position of the cyclopendienyl ring showed high catalytic activities up to 1.48×107 gPE·molZr−1·h−1 toward the polymerization of ethylene and afforded polyethylenes with high molecular weights (1.49×105−6.31×105 g/mol), meanwhile exhibting great thermal stability at high temperatures up to 120 °C together with a long catalytic life time up to 2 h. By adopting low Al/Zr ratios, such as 125, polyethylenes with ultra high molecular weights up to 2.86×106 g/mol were obtained. It is worthy of noting that zirconium complexes 1–4 bearing a substituent with an aryl pendant showed temperature-dependent activities, which increased rapidly with the increase of polymerization temperature, thus weak interaction of the pendent aryl group with the cationic active center is proposed to account for the very low activities displayed at low temperatures. In contrast to zirconocene complexes 1–5, hafnocene complex 6 only displayed very low catalytic activities toward the polymerization of ethylene and afforded polyethylenes with molecular weights ten times smaller than those obtained by zirconocene complexes 1–5. Zirconocene complexes 1–5 were also able to catalyse the polymerization of propylene at high temperatures, but only afforded waxes with low molecular weights. [ABSTRACT FROM AUTHOR]

The development of energy‐saving technology for the efficient separation of olefin and paraffin is highly important for the chemical industry. Herein, we report a self‐assembled Fe4L6 capsule containing a hydrophobic cavity, which can be used to encapsulate and separate propylene/propane. The successful encapsulation of propylene and propane by the Fe4L6 cage in a water solution was documented by NMR spectroscopy. The binding constants K for the Fe4L6 cage toward propylene and propane were determined to be (5.0±0.1)×103 M−1 and (2.1±0.7)×104 M−1 in D2O at 25 °C, respectively. Experiments and theoretical studies revealed that the cage exhibited multiple weak interactions with propylene and propane. The polymer‐grade propylene (>99.5 %) can be obtained from a mixture of propylene and propane by using the Fe4L6 cage as a separation material in a U‐shaped glass tube. This work provides a new strategy for the separation of olefin/paraffin. [ABSTRACT FROM AUTHOR]

The urgent need for branched‐chain α‐olefin (4‐methyl‐1‐pentene) with excellent characteristics promotes the development of efficient catalysts for the selective dimerization of propylene to it. Based on the concept of supported catalytically active liquid metal solutions (SCALMS), the highly efficient K−M/K2CO3 (M=Fe, Co, Ni, Cu, and Zn) catalysts are prepared by the melting method for the dimerization of propylene. The K−Cu SCALMS catalyst presents highly efficient and excellent selective C−C linkage, as well as limits the isomerization of C6 products. The highest conversion of propylene (64.3 %) with 80.6 % selectivity to 4‐methyl‐1‐pentene with thermodynamic instability is reached at 160 °C, 6 MPa and 20 h. Furthermore, the post‐reaction K−Cu SCALMS catalyst can be successfully reactivated in the H2 atmosphere. Therefore, it is proposed that it may be achieved the continuous selective dimerization of propylene to 4‐methyl‐1‐pentene over K−Cu SCALMS catalyst by the application of fluidized bed technology. [ABSTRACT FROM AUTHOR]

Studies on the development of a homogeneous chloride-free two-stage process (target reaction (first stage) and catalyst regeneration (second stage)) for propylene oxidation to acetone with oxygen in the presence of a + Mo–V–P heteropoly acid (HPA-x, where x is the number of V atoms) catalyst have been described. A kinetic equation of the target reaction has been derived; a mechanism of the reaction has been proposed. It has been shown that the most efficient catalysts are those based on high-vanadium modified (non-Keggin) HPA-xM compositions. It has been found that the kinetics of C3H6 oxidation in the presence of Keggin HPA-x and HPA-xM solutions is identical; however, only + HPA-xM catalysts are technologically feasible. They exhibit high thermal stability (up to 180°C) and, therefore, can be rapidly regenerated with oxygen. Owing to this feature, catalysts based on HPA-xM compare favorably with those based on Keggin HPAs-x, the thermal stability of which is limited to 140°C. The possibility of rapidly regenerating the catalyst has made it possible to close the two-stage catalytic cycle of C3H6 oxidation to acetone with oxygen and opened up prospects for the practical implementation of the process in the presence of + HPA-xM. The catalyst has effectively passed stability tests. [ABSTRACT FROM AUTHOR]

The effect that introduction of cerium oxide into oxide systems based on chromium and silicon exerts on the catalytic properties of these systems in nonoxidative propane dehydrogenation in a flow-through system with a fixed catalyst bed was studied. The characteristics of the catalysts CrOx–SiO2 and CrOx–CeO2–SiO2, both containing 9 wt % CrOx assuming the Cr2O3 stoichiometry, were compared. The СеО2 content of the ternary system was 52 wt %. The catalysts were characterized by X-ray diffraction analysis, scanning electron microscopy, Raman spectroscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, temperature-programmed reduction with hydrogen, and thermal analysis. In the initial period of the reaction, the catalyst containing CeO2 demonstrated higher propane conversion at 500 and 550°С and higher deactivation rate compared to CrOx–SiO2. Both catalysts can be regenerated by treatment in an air stream at 550°С for 30 min. Cerium dioxide favors the reduction of chromium in high oxidation states to form active reaction sites, Cr3+ ions, ensures higher dispersity of the chromium oxides, and favors partial oxidation of coke deposits in the initial period of the catalyst operation. [ABSTRACT FROM AUTHOR]

• This paper presents R290 (propane) and R1270 (propylene) local boiling heat transfer coefficients inside a BPHE. • R1270 exhibits boiling heat transfer coefficients very similar in trend, and 5–10% higher in magnitude, than those of R290. • Nucleate boiling seems to be the governing heat transfer regime both in R290 and R1270 tests. • Longo et al. (2015) model exhibits the best predicting performance with a MAPE of 7.7% and 6.9% for R290 and R1270, respectively. • R290 and R1270 exhibit boiling heat transfer performance between those of R404A and those of R410A. This paper presents the local heat transfer coefficients of R290 (propane) and R1270 (propylene) boiling inside a Brazed Plate Heat Exchanger (BPHE). A new test section was designed for measuring the local heat transfer coefficient in refrigerant two-phase heat transfer in a BPHE. The test section includes two thick AISI316L stainless steel corrugated plates instrumented with 36 T-type thermocouples for measuring the local plate surface temperature, the local heat flux and the local heat transfer coefficient in 9 positions along the refrigerant channel. The experimental tests were carried out at a boiling temperature of 10 °C, in the refrigerant mass flux range 5 − 17.5 kg m −2 s−1 with an inlet vapour quality ranging from 0.24 to 0.37 and an outlet vapour quality around 1.00. The global uncertainty of the local heat transfer coefficient measurement is within ±12.7%, and ±15.6%, for R290, and R1270, respectively. Nucleate boiling seems to be the governing heat transfer regime both in R290 and R1270 tests. Consolidated correlations for nucleate boiling inside BPHE show a fair agreement with all the experimental data. R290 and R1270 exhibit boiling heat transfer performance between those of R404A and those of R410A. [ABSTRACT FROM AUTHOR]

A simple method for the two-stage synthesis in one reactor on one catalyst of heterophase thermoplastic elastomers based on isotactic polypropylene and an ethylene-propylene copolymer or an ethylene-propylene-1,4-hexadiene terpolymer is developed. The obtained materials, depending on the composition, have good elastomeric properties or behave like thermoplastics. Polymers in which ethylene units form long sequences have the best set of basic characteristics: high values of the elastic modulus, strength, and elongation at a break, as well as a low residual deformation. [ABSTRACT FROM AUTHOR]

Abstract Isomerization Metathesis (ISOMET) reaction is an emerging tool for “open loop” chemical recycling of polyethylene to propylene. Novel, latent N‐Alkyl substituted Cyclic(Alkyl)(Amino)Carbene (CAAC)–ruthenium catalysts (5a‐Ru, 3b‐Ru – 6c‐Ru) are developed rendering “inverted” chemical structure while showing enhanced ISOMET activity in combination with (RuHCl)(CO)(PPh3)3 (RuH) double bond isomerization co‐catalyst. Systematic investigations reveal that the steric hindrance of the substituents on nitrogen and carbon atom adjacent to carbene moiety in the CAAC ligand have significantly improved the catalytic activity and robustness. In contrast to the NHC‐Ru and CAAC‐Ru catalyst systems known so far, these systems show higher isomerization metathesis (ISOMET) activity (TON: 7400) on the model compound 1‐octadecene at as low as 3.0 bar optimized pressure, using technical grade (3.0) ethylene. The propylene content formed in the gas phase can reach up to 20% by volume.

Ethylene Propylene Diene Monomer (EPDM) rubber foams are widely employed for thermal and acoustic insulation in building construction. However, their installation in confined spaces is often complicated, and the capability of EPDM foams to exhibit shape memory behavior could be a desirable property. In the literature, several works have demonstrated that blending elastomeric matrices with paraffin, a well-known Phase Change Material (PCM), could be an interesting method to obtain shape memory polymers with a tunable switching temperature. In this work, EPDM foams filled with paraffin wax, having a melting temperature of 70[degrees] C, were produced and characterized from a microstructural and thermo-mechanical point of view. By melt compounding and hot pressing, samples were produced, and the PCM content in the foams was varied between 0 and 60 wt% (with respect to the EPDM matrix). The results of the shape memory tests evidenced the crucial role played by the PCM in providing excellent shape fixability for the expanded rubber. Even a limited amount of paraffin (i.e., 20 wt%) was able to raise the strain fixity parameter to a value higher than 80%, and it reached 100% when the paraffin content was increased to 60 wt %. On the other hand, an increased PCM fraction caused a slower recovery process. Consequently, a compromise between a fast recovery and optimum shape fixability should be accepted. These results are promising for the development of novel thermal and acoustic EPDM insulating foams easier to be installed. KEYWORDS EPDM, paraffin, polymer foams, rubber, shape memory polymers, 1 | INTRODUCTION Shape memory polymers (SMPs) are smart materials that have drawn much interest due to their practical functions and potential uses in a multitude of sectors, including aeronautical [...]

[Display omitted] Conversion of isobutyl alcohol over the HMFI/SiC composite has been for the first time studied. Isobutanol (bioisobutanol) considered as a promising product of biomass processing was catalytically converted into aromatic hydrocarbons of the benzene–toluene–xylene fraction (BTX) and olefins C 2 –C 4 (mainly propylene and butenes). Compared with the pure zeolite, the incorporation of HMFI into the SiC matrix enhanced the yields of C 2 –C 4 olefins and BTX in the isobutanol conversion due to increased densities of Brønsted and Lewis acid centers [ABSTRACT FROM AUTHOR]

Non-oxidative propane dehydrogenation (PDH) is becoming an increasingly important approach to propylene production, while cobalt-containing catalysts have recently demonstrated great potential for use in this reaction, providing efficiencies comparable to those of industrially employed Pt- and Cr-based catalytic systems. It is therefore essential to clarify the nature of their active sites, especially since contradictory opinions on this issue are expressed in the literature. In this study, efforts were made to determine the state of Co in cobalt aluminates (CoAl2O4-Al2O3) responsible for PDH under typical operating conditions (600 °C, 1 atm). It is shown that the catalyst with a low cobalt content (Co/Al = 0.1) ensured the highest selectivity to propylene, ca. 95%, while maintaining significant propylene conversion. The structural motifs such as cobalt oxide and metallic cobalt nanoparticles, in addition to tetrahedral Co2+ species in the CoAl2O4 spinel system, were evaluated as potential active-site ensembles based on the obtained catalytic performance data in combination with the XRD, H2-TPR, TEM and XPS characteristics of as-synthesized, spent and spent–regenerated catalysts. It is revealed that the most likely catalytic sites linked to PDH are the Co-oxide forms tightly covering alumina or embedded in the spinel structure. However, additional in situ tuning is certainly needed, probably through the formation of surface oxygen vacancies rather than through a deeper reduction in Co0 as previously thought. [ABSTRACT FROM AUTHOR]

It is shown that the initial reaction pathways of the processes of steam reforming of ethanol (SRE) or ethanol to propylene (ETP) conversion can be the same and include dehydrogenation and condensation reactions with the formation of acetaldehyde and acetone. The equilibrium yields of propylene and hydrogen in the ETP process, in contrast to SRE, depend little on both temperature and ethanol concentration. An equation for the determination of hydrogen yield as the function of selectivity of carbon-containing compounds has been proposed, based on which the hydrogen concentration in products of the SRE and ETP processes can be calculated. [ABSTRACT FROM AUTHOR]