Reaction Of Propylene Oxide Research Articles

Incorporation of Mg/Al metal oxide into ionic liquids for CO2 capture and conversion into cyclic carbonate under solvent-free conditions: Effect of coordination ability, recyclability, and catalytic study

The direct conversion of carbon dioxide (CO2) and propylene oxide (PO) into propylene carbonate (PC) offers a green way to utilize anthropogenic CO2. However, this reaction is limited by low conversion of PO and harsh reaction conditions. In this study, we solve this problem using ionic liquids (ILs)/metal oxide composites (ILs@MAO). The catalytic activity of MAO-500 (500 = annealing temperature) is poor evidenced by its low conversion of PO (24.94%). However, ILs@MAO-500 has a high conversion of PO (97.54%) under similar reaction conditions (2 h at 1.5 MPa CO2 pressure, 90 °C, and 0.85 g catalyst). The ILs consist of imidazolium cation with weak coordinated [NTf2]– anion leading to outward movement of anion resulting in the formation of “heterodinuclear complex”. This complex generates an amorphous-crystalline intermediate with balanced acid-base sites that activate PO and stabilize the catalytic intermediate. In large part, the high PO conversion is theorized to be primarily due to the abundant reactive sites in the ILs that are covalently immobilized on the MAO-500 carrier. Furthermore, even after multiple recycling, ILs@MAO-500 remains stable and exhibits high yield and selectivity. The proposed solvent-free catalytic system is mild, kinetically fast, and naturally safe for coupling CO2 and PO into PC synthesis.

Influence of the synthesis route on Au-Ir/Al2O3 catalysts performing the total propane oxidation reaction at low temperature

The current study highlights synthesis as a key parameter for obtaining Au-Ir/Al2O3 bimetallic catalysts using the deposition-precipitation with urea (DPU) method. Both co-deposition and sequential deposition (first by adding Au and then Ir and vice versa) were employed. These approaches were compared with the sol-gel and impregnation methods, revealing notable differences in the catalytic oxidation of C3H8 at low temperatures. The Au-Ir/Al2O3 catalysts prepared via co-deposition and sequential deposition demonstrated outstanding results, producing nanoparticles as small as 1 nm when thermally reduced in hydrogen at 400 °C; also, these catalysts exhibited greater capacity for oxidizing C3H8 below 280°C than the Ir/Al2O3 and Au/Al2O3-based catalysts. Characterization of the catalysts was conducted by employing various techniques, including in-situ DRIFTS, UV-Vis, H2-TPR, HAADF-STEM-EDS, XPS and surface acidity determinations by pyridine thermo-desorption. This last technique showed differences in total acidity (Brönsted and Lewis) provoked by the Au-Ir interaction in the different catalysts, which significantly influenced their ability to oxidize C3H8 towards CO2. The results emphasize the effectiveness of the co-deposition and sequential deposition methods using the DPU approach compared to the sol-gel and impregnation methods.

Green and rational design of Ln4Zn2L2 heteromultimetallic complexes for mild and highly efficient CO2 conversion

Reasonable and high efficient utilization of carbon dioxide (CO2) has always been considered as a kind of green and sustainable development strategy. However, the efficient chemical conversion of CO2 into value-added products has been limited due to lack of efficient catalysts. Herein, two novel heterometallic hexanuclear complex catalysts (viz Nd4Zn2L2 (1) and Eu4Zn2L2 (2)) were designed and synthesized, which featuring unique hetero-multinuclear units. The heterometallic hexanuclear complex catalysts not only have multi-bimetallic catalytic sites (Ln3+ and Zn2+) which can absorb more molecules and be beneficial to the improvement of catalytic performance, but also have the potential to further expand the chemical fixation of CO2 with epoxides avoid the harsh reaction conditions. Using the synthesis of propylene carbonate (PC) by cycloaddition reaction of propylene oxide (PO) and CO2 as a model reaction, the as-prepared catalysts and catalytic system showed high turnover frequencies (TOFs) under the mild condition instead of harsh reaction conditions. More importantly, these catalysts can be reused to preserve the structure's integrity and retain their catalytic activity at the same level even after five rounds of catalysis. The excellent regeneration performance indicated that the as-prepared heterometallic hexanuclear complex catalysts can be reused many times. In addition, the catalytic system also exhibited a wide range of substrates for epoxide. These results predict that the proposed heterometallic hexanuclear complex catalysts and catalytic system have great potential toward CO2 adsorption and catalytic conversion. This work may build up a new synthetic route for tailoring more new heterometallic complex catalysts with excellent catalytic activity and applied in various fields of application.

Less Is More: Selective-Atom-Removal-Derived Defective MnOx Catalyst for Efficient Propane Oxidation.

Defect manipulation in metal oxide is of great importance in boosting catalytic performance for propane oxidation. Herein, a selective atom removal strategy was developed to construct a defective manganese oxide catalyst, which involved the partial etching of a Mg dopant in MnOx. The resulting MgMnOx-H catalysts exhibited superior low-temperature catalytic activity (T50 = 185 °C, T90 = 226 °C) with a propane conversion rate of 0.29 μmol·gcat.-1·h-1 for the propane oxidation reaction, which is 4.8 times that of pristine MnOx. Meanwhile, a robust hydrothermal stability was guaranteed at 250 °C for 30 h of reaction time. The comprehensive experimental characterizations revealed that the catalytic performance improvement was closely related to the defective structures including the abundant (metal and oxygen) vacancies, distorted crystals, valence imbalance, etc., which prominently weakened the Mn-O bond and stimulated the mobility of surface lattice oxygen, leading to the elevation in the intrinsic oxidation activity. This work exemplifies the significance of defect engineering for the promotion of the oxidation ability of metal oxide, which will be valuable for the further development of efficient non-noble metal catalysts for propane oxidation.

Enhancing Efficiency and High-Value Chemicals Generation through Coupling Photocatalytic CO2 Reduction with Propane Oxidation.

Conversion of CO2 into high-value chemicals using solar energy is one of promising approaches to achieve carbon neutrality. However, the oxidation of water in the photocatalytic CO2 reduction is kinetically unfavorable due to multi-electron and proton transfer processes, along with the difficulty in generating O-O bonds. To tackle these challenges, this study investigated the coupling reaction of photocatalytic CO2 reduction and selective propane oxidation using the Pd/P25 (1 wt%) catalyst. Our findings reveal a significant improvement in CO2 reduction, nearly fivefold higher, achieved by substituting water oxidation with selective propane oxidation. This substitution not only accelerates the process of CO2 reduction but also yields valuable propylene. The relative ease of propane oxidation, compared to water, appears to increase the density of photogenerated electrons, ultimately enhancing the efficiency of CO2 reduction. We further found that hydroxyl radicals and reduced intermediate (carboxylate species) played important roles in the photocatalytic reaction. These findings not only propose a potential approach for the efficient utilization of CO2 through the coupling of selective propane oxidation into propylene, but also provide insights into the mechanistic understanding of the coupling reaction.

Ring Opening Copolymerization of Epoxides with CO2 and Organic Anhydrides Promoted by Dinuclear [OSSO]‐type Metal Complexes

AbstractThe ternary copolymerization of a series of cyclic anhydrides with epoxides and carbon dioxide using dinuclear [OSSO]‐type chromium (III),1, and ‐iron(III), 2, complexes (0.1 mol %) in combination with (bis(triphenylphosphine)iminium chloride) (PPNCl, 0.5–1.0 mol with respect to catalyst) as co‐catalyst is reported in this study. The results have yielded copolymers with polyester and polycarbonate segments with high molecular weights and narrow dispersity. The catalytic systems 1–2/PPNCl were tested in the copolymerization of different epoxides, such as propylene oxide (PO), cyclohexene oxide (CHO), and vinylcyclohexene oxide (VCHO), with a variety of cyclic anhydrides, such as phthalic (PA), diglycolic (DGA) and succinic (SA), with CO2 pressure of 20 bar, temperature range of 45–80 °C in 24 h. Anhydride reaction, affording the polyester segments, exceeded the conversion of 99 % in all the explored cases. On the other hand, in the case of epoxide copolymerization with CO2, for the propylene oxide (PO) reaction, the selectivity towards polypropylene carbonate (PPC) without polyether linkage consistently was >99 %. For the terpolymerization of PO, CO2 and diglycolic anhydride (DGA), a notable epoxide conversion of 86 %, selectively to polycarbonate, with TOF value as high as 36 h−1, was achieved.

Modulating the Electronic States of Pt Nanoparticles on Reducible Metal-Organic Frameworks for Boosting the Oxidation of Volatile Organic Compounds.

The adsorption and activation of pollutant molecules and oxygen play a critical role in the oxidation reaction of volatile organic compounds (VOCs). In this study, superior adsorption and activation ability was achieved by modulating the interaction between Pt nanoparticles (NPs) and UiO-66 (U6) through the spatial position effect. Pt@U6 exhibits excellent activity in toluene, acetone, propane, and aldehyde oxidation reactions. Spectroscopic studies, 16O2/18O2 kinetic isotopic experiments, and density functional theory (DFT) results jointly reveal that the encapsulated Pt NPs of Pt@U6 possess higher electron density and d-band center, which is conducive for the adsorption and dissociation of oxygen. The toluene oxidation reaction and DFT results indicate that Pt@U6 is more favorable to activate the C-H of toluene and the C═C of maleic anhydride, while Pt/U6 with lower electron density and d-band center exhibits a higher oxygen dissociation temperature and higher reactant activation energy barriers. This study provides a deep insight into the architecture-performance relation of Pt-based catalysts for the catalytic oxidation of VOCs.

Br-doped Ga2O3/MCM-41 catalyzed synthesis of propylene carbonate from carbon dioxide and propylene oxide

In this paper, Br-doped Ga2O3/MCM-41 has been synthesised for the reaction of CO2 and propylene oxide, which has the advantages of high efficiency, greenness and recyclability.

OEEFs precisely regulating the propane oxidation reaction catalyzed by O–Fe-corrolazine

Oriented external electric fields can precisely regulate the oxidation of propane to produce propylene catalyzed by O–Fe-corrolazine under mild conditions.

Ionic liquids bonded in mesoporous HAP serve as efficient catalysts for CO2 fixation

In this study, hydroxyapatite (HAP) with abundant surface hydroxyl and large pores was used as the ionic liquid ([DMCA]X) immobilization carrier, where the surface hydroxyl groups of HAP were used as binding sites and the n-halogen-acids were used as bonding agents. The supported ionic liquid catalysts [DMCA]X-n-HAP were characterized by XRD, TEM, TG and FTIR, proving that the ionic liquids were successfully bonded onto the surface of HAP. The utilization of hydroxyl sites on the surface of HAP was as high as 90%. The above catalysts were used to catalyze the cycloaddition reaction of CO2 and propylene oxide (PO), and the yield and selectivity of propylene carbonate (PC) were up to 98.7% and 100%, respectively. The length effect of the bonding agents on the catalyst performance was also studied, and found that n-chlorine-butyric acid was the most suitable chemical for channel structure of HAP and spatial freedom of ionic liquid. In addition, the effects of halogen anion and hydroxyl hydrogen on the performance of the reaction were also studied. Importantly, autocatalysis was discovered in the reaction. Finally, the reaction intermediates and reaction mechanism of CO2 cycloaddition were investigated by in situ-DRIFTS, revealing that ring-open of PO is rate-determining step.

Highly efficient CO2 and propylene oxide co-polymerization using Zn glutarate/Zn-Cr double metal cyanide composite catalyst

A highly active zinc glutarate-double metal cyanide (DMC) composite catalyst (ZnGA/Zn-CrDMC) was designed for the carbon dioxide (CO2) and propylene oxide (PO) copolymerization reaction. The composite catalyst was synthesized in a rheological phase reaction and characterized using Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The synthesized composite catalysed the solvent free reactions of PO and CO2 to afford biodegradable polypropylene carbonate (PPC) copolymer. 1H NMR,13C NMR, FT-IR and ESI-TOF mass spectrometry measurements were employed to confirm the characteristics of the PPC produced. Under optimal reaction conditions (50 bar CO2, 70 °C, 24 h), the ZnGA-Zn3[Cr(CN)6]2 composite displayed higher catalytic activities in the copolymerization reactions than the individual catalysts. The ZnGA:Zn3[Cr(CN)6]2 ratio of 15:1 gave PPC yield of 47.9 g polymer/g cat compared to ZnGA that produced 42.6 g polymer/ g cat in 24 h. In addition, the PPC produced from the composite catalyst displayed higher carbonate linkage content (Fc = 85.4 %) compared to the value of Fc = 33.9 %. obtained using the Zn3[Cr(CN)6]2 catalyst. Similaly, the composite catalsyt produced PPC with molecular weight of 4200 g/mol and narrow polydispersity index of 2.2. The resultant PPC copolymer displayed good thermal stability, exhibiting a high degradation temperatures (TGA-10%) of 229 °C and complete decomposition at 350 °C.

Unveiling the self-activation of exsolved LaFe0.9Ru0.1O3 perovskite during the catalytic total oxidation of propane

The exsolution process enables to produce and control the formation of stable and catalytically active nano particles via reductive extraction of uniformly incorporated precious metal ions from a solid oxide solution. Here we consider the simple and stable perovskite LaFeO3 (LFO) where 10% of Fe on B sites are substituted by ruthenium (LFRO). Hydrogen reduction of LFRO at 800 °C leads to the formation of socketed ruthenium particles whose low-temperature activity in the total propane oxidation reaction at 210 °C is substantially lower than that of the original LFRO. Upon increasing the reaction temperature once to 400 °C, the exsolved catalyst undergoes self-activation so that the activity at 210 °C turns out to be five times higher than that of the original LFRO. High-resolution transmission electron microscopy and nanometer-resolved element mapping, together with averaging characterization methods, including X-ray diffraction and X-ray photoelectron spectroscopy, Raman spectroscopy, and diffuse infrared spectroscopy, unveil that after reduction at 800 °C the exsolved Ru particles are slightly alloyed with Fe and encapsulated by an inert and protecting LaOx layer. Mild oxidative treatment at 400 °C leads to the removal of the conforming LaOx layer, while the uncovered RuFe alloy particle transforms to catalytically active oxidic Ru species, with no indication of a separate FeOx phase. We exemplify with our case study of LaFe0.9Ru0.1O3 that careful redox treatment enables to control the exsolution process and to avoid deactivation. This may be of importance for the whole class of exsolvable materials.

Zn-Co bimetallic catalysts before and after calcination: Research on their different properties for cycloaddition and Friedel-Crafts acylation reactions

A series of bimetallic Zn-Co catalysts before and after calcination were prepared by simple MOFs template methods. The effects of calcination on their structures were investigated by XRD, FT-IR, TPD, XPS and EPR characterization methods, and their catalytic performances were compared in the cycloaddition reactions of CO2 and propylene oxide and acylation reactions of anisole and acetyl chloride, respectively. The results show that uncalcined ZnCo2-MOFs catalyst has excellent catalytic performance for cycloaddition reaction due to the presence of acid-base synergism, whereas the strong acidity of calcined ZnCo2OX catalyst is very favorable for acylation reaction. This is due to the fact that calcination changes the structure of ZnCo2-MOFs catalyst, causes charge migration on the surface and results in the conversion of lattice oxygen to oxygen vacancies, which brings a large difference in the acidity and basicity of catalysts.

Continuous process for CO2 cycloaddition reaction in a fixed bed reactor: Kinetic model of reaction transport

Immobilized ionic liquids (ILs) catalysts are often used in fixed bed reactors (FBR) to continuously catalyze the reaction of CO2 and propylene oxide (PO). However, the kinetics and mass transfer characteristics of this reaction in FRB are rarely reported. In this work, two methods were used to calculate the apparent kinetics in FBR, and the apparent kinetics and mass transfer limiting performance were correlated based on the Arrhenius equation. Simultaneously, the reactor model with mass transfer coefficient was established to determine the modified empirical relationship of external mass transfer at low Reynolds number, and the continuous reaction process in FBR was predicted by the relationship between the effective factor (η) of internal mass transfer and the Thiele modulus (Φ). Additionally, the FBR reaction model was verified and compared with the actual experimental data. This study provides a valuable reference for further optimization of FBR configuration and reaction conditions.

3D Cyclophane for the Selective Conversion of Epoxide to Cyclic Carbonate.

A novel three-dimensional (3D) cyclophane molecule 1 was synthesized and fully characterized. Cyclophane 1, which can form a N heterocyclic carbene, was tested for conversion of certain epoxides (3-6) [scheme 2] to cyclic carbonates in the presence of CO2. Propylene oxide (3) was found to have more reactivity with cyclophane 1 compared to the other epoxides. The theoretical calculations based on N,N'-disubstituted imidazol(in)ium-2-carboxylates derived from N,N' disubstituted imidazole as the source of N-heterocyclic carbene show lower activation energy in the case of the reactivity of epoxides 5 and 6 as compared to 3 and 4. However, cyclophane 1, which possesses a 3D geometry, can form the open intermediate with CO2 and propylene oxide more feasibly than the other three epoxides, which have larger sizes as compared to propylene oxide. Hence, the reaction of propylene oxide, CO2, and cyclophane 1 can follow the mechanistic path 1, whereas the epoxides 4-6 can follow a different mechanistic path 2. Cyclophane 1 is the first example of a cyclophane to act as an organocatalyst for the conversion of CO2 and epoxide to cyclic carbonate via the N heterocyclic carbene pathway.

Outstanding synergistic effect of Au–Ir/Al2O3 catalysts on the total oxidation of propane

Bimetallic Au–Ir catalysts supported on ɣ-Al2O3 were synthesized by a sequential deposition-precipitation with urea (DPU) method. These materials displayed outstanding synergistic performance in the propane oxidation reaction at low reaction temperatures. A T50 of 150 °C was obtained for a bimetallic Au–Ir catalyst (Au loading of 3 wt % and Ir loading of 5 wt %), while for their gold and iridium monometallic counterparts it was of 370 and 190 °C, respectively. The synthesized materials were characterized by XRD, HRTEM-HAADF, H2-TPR, O2-TPD, UV–vis, and pyridine thermo-desorption, followed by FTIR and XPS, showing distinct characteristics that were correlated with their catalytic activity. Outcomes revealed a strong interaction among the gold and iridium particles when the catalysts were activated in H2 and that the thermal treatment atmosphere (hydrogen or air) modified the active sites; likewise, gold-iridium and monometallic iridium catalysts supported on ɣ-Al2O3 showed considerable endurance to activity loss because they hardly presented metal sintering at high reaction temperatures. Moreover, XPS results revealed electron transfer between Au–Ir (Au0 and Ir2+ species). Only the bimetallic system presented Lewis and Brønsted acidity (2.95 and 0.25 μ-mol m−2, respectively), which may have been responsible for enhancing the total oxidation of C3H8 at a low temperature. Likewise, the 3Au–5Ir/Al2O3 catalyst exhibited high stability and reusability during five reaction cycles and using a GHSV of 41,000 h−1.

Metal-polyacrylic acid complex aerogels for efficient cycloaddition of CO2 with propylene oxide

The cycloaddition reaction of carbon dioxide with propylene oxide captures considerable attention owing to its environmental friendliness, economy and 100% atomic utilization. Homogeneous metal catalysts exhibit excellent performance in cycloaddition reactions, but their widespread applications are limited by complicated preparation and recovery processes. It is important to develop effective strategies to immobilize homogeneous catalysts, and even immobilize active metal ions into solid carriers. Herein, we developed an innovative and universal strategy to immobilize metal ions through the complexation of metal ions with organic polymerization. The Zinc-manganese bifunctional polyacrylic acid complex (ZnMn-PAA) aerogels prepared using this strategy exhibited remarkable catalytic activity and stability in the cycloaddition reaction of carbon dioxide (CO2) and propylene oxide (PO). Mechanism studies revealed that the Zn and Mn central sites respectively enhanced the activation of PO and CO2, and the synergistic effect of bimetallic sites guaranteed to the excellent catalytic performance.

Asymmetric Synthesis of the Contact Sex Pheromone of the Emerald Ash Borer, Agrilus planipennis Fairmaire

AbstractAgrilus planipennis Fairmaire is a wood‐boring pest of ash trees. The contact sex pheromone of this pest was synthesized from chiral propylene oxide. This asymmetric synthesis was efficient and mainly involved the ring‐opening reaction of chiral propylene oxide, the stereospecific inversion of secondary tosylate and Wittig coupling of chiral aldehyde.

Unveiling geometric and electronic effects of Pt species on water-tolerant Pt/ZSM-5 catalyst for propane oxidation

Si/Al ratio of ZSM-5 affecting Pt/ZSM-5 catalyst water-tolerance has been investigated for propane oxidation. Under wet condition (5 % H2O), it is found that Pt/ZSM-5 (18) catalyst contains both irreversible and reversible deactivation Pt active sites; Pt/ZSM-5 (130) and Pt/ZSM-5 (500) catalysts have only reversible deactivation Pt active sites; all the Pt active sites in the Pt/ZSM-5 (1200) catalyst are water tolerant. It is further found that the Si/Al ratio of ZSM-5 determines the geometrical and electronic states of Pt particles, and amount of surface acid sites on catalysts, thereby affecting the water tolerance of Pt/ZSM-5 catalyst. Low Si/Al ratio of ZSM-5 benefits to anchor the Pt species and form small Pt particles, but Pt particle with small size and more oxidized state Pt species (Ptδ+) on Pt/ZSM-5 (18) is easily poisoned by H2O. More Pt0 species generating on large Pt particle during propane oxidation reaction and low surface acid sites on Pt/ZSM-5 (1200) catalyst are responsible for its high water tolerance.

Data-Centric Heterogeneous Catalysis: Identifying Rules and Materials Genes of Alkane Selective Oxidation.

Artificial intelligence (AI) can accelerate catalyst design by identifying key physicochemical descriptive parameters correlated with the underlying processes triggering, favoring, or hindering the performance. In analogy to genes in biology, these parameters might be called "materials genes" of heterogeneous catalysis. However, widely used AI methods require big data, and only the smallest part of the available data meets the quality requirement for data-efficient AI. Here, we use rigorous experimental procedures, designed to consistently take into account the kinetics of the catalyst active states formation, to measure 55 physicochemical parameters as well as the reactivity of 12 catalysts toward ethane, propane, and n-butane oxidation reactions. These materials are based on vanadium or manganese redox-active elements and present diverse phase compositions, crystallinities, and catalytic behaviors. By applying the sure-independence-screening-and-sparsifying-operator symbolic-regression approach to the consistent data set, we identify nonlinear property-function relationships depending on several key parameters and reflecting the intricate interplay of processes that govern the formation of olefins and oxygenates: local transport, site isolation, surface redox activity, adsorption, and the material dynamical restructuring under reaction conditions. These processes are captured by parameters derived from N2 adsorption, X-ray photoelectron spectroscopy (XPS), and near-ambient-pressure in situ XPS. The data-centric approach indicates the most relevant characterization techniques to be used for catalyst design and provides "rules" on how the catalyst properties may be tuned in order to achieve the desired performance.