Reaction Of Propylene Oxide Research Articles

Influence of the crystallinity degree of vanadium containing catalysts on their activity in the propylene oxidation reaction

Influence of the crystallinity degree of vanadium containing catalysts on their activity in the propylene oxidation reaction

Controlled synthesis of CO2-diol from renewable starter by reducing acid value through preactivation approach

Synthesis of polyols from carbon dioxide (CO2) is attractive from the viewpoint of sustainable development of polyurethane industry; it is also interesting to adjust the structure of the CO2-polyols for versatile requirement of polyurethane. However, when renewable malonic acid was used as a starter, the copolymerization reaction of CO2 and propylene oxide (PO) was uncontrollable, since it proceeded slowly (13 h) and produced 40.4 wt% of byproduct propylene carbonate (PC) with a low productivity of 0.34 kg/g. A careful analysis disclosed that the acid value of the copolymerization medium was the key factor for controlling the copolymerization reaction. Therefore, a preactivation approach was developed to dramatically reduce the acid value to ~0.6 mg(KOH)/g by homopolymerization of PO into oligo-ether-diol under the initiation of malonic acid, which ensured the controllable copolymerization, where the copolymerization time could be shortened by 77% from 13 to 3 h, the PC content was reduced by 76% from 40.4 wt% to 9.4 wt%, and the productivity increased by 61% from 0.34 to 0.55 kg/g. Moreover, by means of preactivation approach, the molecular weight as well as the carbonate unit content in the CO2-diol was also controllable.

Direct synthesis of propylene oxide in the liquid phase under mild conditions

Here, we study the direct synthesis of propylene oxide (PO) on Pd-based catalysts operating under mild conditions (40°C, 5.5bar) and in a continuous flow microreactor. We show that the PO yield can be improved by a factor of two, with respect to the values present in literature, by using a Pd–Pt/TS-1 catalyst in excess of oxygen. Moreover, we compare the PO reaction with the hydrogen peroxide (H2O2) synthesis, being H2O2 (or OOH species) the intermediate and rate limiting step of the direct PO formation. We found that the optimal conditions for the PO synthesis are not advantageous for the H2O2 productivity. In this respect, the presence of Pt, which improves the PO selectivity by lowering the hydrogenation of propylene, negatively affects the H2O2 productivity due to an acceleration of its side reactions. This effect is more pronounced for the Pd–Au/TS-1 catalyst, which shows a high performance for H2O2 production. However, the PO formation remains relatively poor due to a very fast hydrogenation of propylene to propane. We conclude that the optimization of the H2O2 synthesis is not sufficient to improve the direct PO formation. Indeed, the hydrogenation of propylene needs also to be considered.

Synthetic and natural materials with the brucite-like layers as high active catalyst for synthesis of 1-methoxy-2-propanol from methanol and propylene oxide

The aim of this study was to investigate the correlation between the basic and catalytic properties of brucite and Mg,Al-layered double hydroxides (Mg,Al-LDHs) in the reaction of propylene oxide with methanol. The basic properties of the solids were investigated by FT-IR spectroscopy using CDCl3 as probe molecule and Hammett acidity titration with n-butylamine and benzoic acid. Both the increase in the activation temperature and the decrease in Al content favored the increase in the basicity of Mg,Al-LDH. The nature of “Mn+O2− Lewis acid-base” pairs was a key factor to control the catalytic behavior of the solids. The length of the M-O bond, the basicity of the oxygen ion and the strength of the metal ion on the surface affected the catalytic activity of the solids and their isomer selectivity in the reaction between methanol and propylene oxide to form 1-methoxy-2-propanol. It was demonstrated that brucite(150) can be applied as catalyst for at least four successive cycles without loss of activity.

The efficient synthesis of diethyl carbonate via coupling reaction from propylene oxide, CO2 and ethanol over binary PVEImBr/MgO catalyst

Direct synthesis of diethyl carbonate (DEC) from propylene oxide, CO2 and ethanol via coupling reaction over a heterogeneous catalyst was demonstrated. In this work, a cross linked poly(ionic liquid) containing poly(1-vinyl-3-ethylimidazolium bromide)(PVEImBr) moiety was prepared via a free radical polymerization. Meanwhile, the MgO nanoplatelet with abundant basic sites was prepared, which was combined with PVEImBr to form a composite catalyst of PVEImBr/MgO. N2 physisorption, TG, XRD, SEM, CO2-TPD and FT-IR were conducted to thoroughly characterize the structure and texture of the catalysts. The as-prepared heterogeneous catalyst, which simultaneously possessed the dual function of nucleophilicity and basicity, was used in the coupling reaction of propylene oxide, CO2 and ethanol to synthesize diethyl carbonate and propylene glycol. The composite catalyst could promote the reaction with high efficiency, and a good catalytic performance of 54.4% diethyl carbonate yield and 59.8% propylene glycol yield could be achieved. The 1H NMR and DFT calculation disclosed that greatly faster reaction rate was ascribed to the synergistic effect between the BrƟ anion of PVEImBr and hydroxyl group of ethanol. Accordingly, a mechanism of the sequential reaction consisting of cycloaddition and transesterification steps was proposed.

Design and synthesis of core-shell structured meso-Cu-SSZ-13@mesoporous aluminosilicate catalyst for SCR of NOx with NH3: Enhancement of activity, hydrothermal stability and propene poisoning resistance

A core-shell structured composite material with a mesoporous aluminosilicate (MAS) shell and mesopore-containing SSZ-13 (meso-SSZ-13) core was first synthesized by combining controlled desilication with subsequent self-assembly. The corresponding catalyst was subsequently prepared by a copper ion-exchange method. This catalyst can simultaneously solve three major problems existing in the previous Cu-SSZ-13 catalyst for NOx emission control from diesel engine exhaust, i.e., low temperature activity, hydrothermal stability and propene poisoning resistance. In comparison with Cu-SSZ-13, the meso-Cu-SSZ-13@mesoporous aluminosilicate (meso-Cu-SSZ-13@MAS) catalyst showed higher SCR activity across the entire temperature range. This increase was observed due to increasing the amount of active Cu species (isolated Cu2+ ions) and fewer pore diffusion limitations. The MAS shell with a “concrete with crushed stone”-like mesostructure could prevent the dealumination of meso-SSZ-13 core effectively, and therefore enhanced the hydrothermal stability of the meso-Cu-SSZ-13@MAS catalyst. Additionally, meso-Cu-SSZ-13@MAS exhibited higher hydrocarbon poisoning resistance because its external surface has fewer active sites for propene oxidation reaction.

The Synthesis of Styrene-Oligoester Copolymer and Investigation of Their Physico-mechanical Properties

<p>The copolymerization reaction of commercial propylene oxide with glycidylmethacrilate in the presence of BF<sub>3</sub>·O(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub> catalyst have been investigated. The composition and structure of copolymerization products and anchored functional groups have been determined using IR and gel chromatographic methods. The physico-mechanical properties and utility of polyfunctional unsaturated oligoester were investigated. The obtained thermoset product via the reaction of the oligoester with both styrene and oligostyrene obtained from the bottom of column as a waste material during the rectification operation of styrene in the presence of radicalic initiator has a good adhesion capability, hardness and high heat and water resistance. Thus the waste material was converted to the high valuable polymeric material.</p>

Oxide Nanocrystal Model Catalysts.

Model catalysts with uniform and well-defined surface structures have been extensively employed to explore structure-property relationships of powder catalysts. Traditional oxide model catalysts are based on oxide single crystals and single crystal thin films, and the surface chemistry and catalysis are studied under ultrahigh-vacuum conditions. However, the acquired fundamental understandings often suffer from the "materials gap" and "pressure gap" when they are extended to the real world of powder catalysts working at atmospheric or higher pressures. Recent advances in colloidal synthesis have realized controlled synthesis of catalytic oxide nanocrystals with uniform and well-defined morphologies. These oxide nanocrystals consist of a novel type of oxide model catalyst whose surface chemistry and catalysis can be studied under the same conditions as working oxide catalysts. In this Account, the emerging concept of oxide nanocrystal model catalysts is demonstrated using our investigations of surface chemistry and catalysis of uniform and well-defined cuprous oxide nanocrystals and ceria nanocrystals. Cu2O cubes enclosed with the {100} crystal planes, Cu2O octahedra enclosed with the {111} crystal planes, and Cu2O rhombic dodecahedra enclosed with the {110} crystal planes exhibit distinct morphology-dependent surface reactivities and catalytic properties that can be well correlated with the surface compositions and structures of exposed crystal planes. Among these types of Cu2O nanocrystals, the octahedra are most reactive and catalytically active due to the presence of coordination-unsaturated (1-fold-coordinated) Cu on the exposed {111} crystal planes. The crystal-plane-controlled surface restructuring and catalytic activity of Cu2O nanocrystals were observed in CO oxidation with excess oxygen. In the propylene oxidation reaction with O2, 1-fold-coordinated Cu on Cu2O(111), 3-fold-coordinated O on Cu2O(110), and 2-fold-coordinated O on Cu2O(100) were identified as the active sites, respectively, to produce acrolein, propylene oxide, and CO2. Ceria rods enclosed with the {110} and {100} crystal planes, ceria cubes enclosed with the {100} crystal planes, and ceria octahedra enclosed with the {111} crystal planes exhibit distinct morphology-dependent oxygen vacancy concentrations and structures that can be well correlated with the surface compositions and structures of exposed crystal planes. Consequently, the metal-ceria interactions, structures, and catalytic performances of ceria-supported catalysts depend on the CeO2 morphology. Our results comprehensively reveal the morphology-dependent surface chemistry and catalysis of oxide nanocrystals that not only greatly deepen the fundamental understanding of oxide catalysis but also demonstrate a morphology-engineering strategy to optimize the catalytic performance of oxide catalysts. These results adequately exemplify the concept of oxide nanocrystal model catalysts for the fundamental investigations of oxide catalysis without the "materials gap" and "pressure gap". With the structure-catalytic property relationships learned from oxide nanocrystal model catalyst studies and the advancement of controlled-synthesis methods, it is promising to realize the structural design and controlled synthesis of novel efficient oxide catalysts in the future.

Catalysis of Cycloaddition of Carbon Dioxide and Epoxides Using a Bifunctional Schiff Base Iron(III) Catalyst

AbstractCyclic carbonates are solvents with high boiling points and low toxicity. For synthesis of cyclic carbonates we report on bifunctional Schiff base iron(III) complex for catalytic coupling reaction of propylene oxide and CO2. Due to the presence of two imidazole groups in the ligand framework it facilitates the coupling reaction in the absence of co‐catalyst with good activity reaching TON value 225 within 4 h. Among various solvents used, the catalyst gives the highest activity in dichloromethane. Moreover, the complex catalyses also the cycloaddition reactions of CO2 and epichlorohydrin, styrene, 1‐hexene and cyclohexene oxides. The iron catalysed coupling reaction was followed with in situ infrared spectroscopy giving an apparent first order reaction (n ≈ 1) towards catalyst concentration. Accordingly, a monomolecular mechanism involving imidazole carbamate is proposed.

Deactivation of Pt/Al2O3 during propane oxidation at low temperatures: Kinetic regimes and platinum oxide formation

The kinetics of propane oxidation over Pt/Al2O3 are investigated in this work as a function of O2/C3H8 ratio in the 150–300°C temperature range. At high O2/C3H8 ratios, the platinum nanoparticles are saturated with oxygen and the reaction rate is zero-order with respect to the oxygen partial pressures in this regime. As the oxygen coverage decreases with decreasing O2/C3H8 ratio, the reaction rate increases and the reaction order changes from zero-order to negative-order in the oxygen partial pressure. The reaction rate is controlled to a large extent by the oxygen coverage on the platinum nanoparticles. However, at lower temperatures and higher oxygen pressures there is a slow deactivation of the catalyst that cannot be explained by a slow change in the oxygen coverage. Diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) of adsorbed CO was performed to track the evolution of the nanoparticle structure over the course of the propane oxidation reaction and to determine whether the slow deactivation was caused by reconstruction of the platinum nanoparticles. We found that the platinum nanoparticles are significantly reconstructed during the course of the reaction, including the formation of a platinum oxide (PtO) which has a characteristic CO-DRIFTS band at 2123cm−1. The extent of PtO formation decreases with increasing temperature and, as a result, deactivation of the catalyst is less severe at higher temperatures. Unexpectedly, increasing the oxygen partial pressure resulted in less PtO formation. We believe that a different platinum oxide phase (e.g. PtO2 or Pt3O4) is formed at higher oxygen pressures, which is reduced to metallic platinum during CO exposure at 25°C, and therefore is not detectable by CO-DRIFTS. These results are unique because they show how the nanoparticle structure evolves over many hours of propane oxidation, and how the temperature and oxygen pressure influence the reconstruction of the nanoparticles, which has implications for a wide range of reactions not limited to propane oxidation.

DFT studies on the origin of regioselective ring-opening of terminal epoxides during copolymerization with CO2

This report presents a detailed density functional theory (DFT) study on the difference in regioselectivity for the copolymerization reactions of styrene oxide versus propylene oxide with CO2 utilizing binary (salen)cobalt(III) catalyst systems. This study focuses on the discrepancy of regioselective ring-opening of two terminal epoxides during the copolymerization with CO2. It was found that the nucleophilic ring-opening of styrene oxide occurred predominantly at the methine C α -O bond due to the election delocalization of phenyl group to stabilize the transition state for the methine C―O bond cleavage.

Functionalized Polymers from α‐Hydroxyalkylated N‐Vinylcaprolactam

Hydroxyalkylation of N‐vinylcaprolactam (NVCL) in α‐position via ring‐opening reaction of propylene oxide and ε‐caprolactone, respectively, yields in precursors for multifunctional NVCL derivatives. Homo‐ and copolymers of hydroxyfunctionalized NVCL derivatives, synthesized by free radical mechanism, are further investigated regarding their thermoresponsive behavior. Esterification of hydroxypropylated NVCL derivative with methacrylic anhydride is carried out yielding a versatile bifunctional cross‐linker. Networks are obtained either via free radical polymerization of the cross‐linker or anionic polymerization of only the methacrylic function and subsequent polymer analogous cross‐linking of the vinylic side groups. The rheological behavior during and after curing is investigated by oscillatory rheology. Furthermore, N‐vinylcaprolactam anion is used as an initiator for the anionic ring‐opening polymerization of ε‐caprolactone. Copolymerization of poly(ε‐caprolactone) macromonomer with NVCL yields graft copolymers. A polymerizable thermotropic liquid crystalline (LC) derivative is prepared by coupling cholesteryl chloroformate to NVCL. The thermal behavior of LC derivative is investigated by differential scanning calorimetry and polarized light microscopy. image

Microwave-assisted polyol synthesis of bimetallic RuRe nanoparticles stabilized by PVP or oxide supports (γ-alumina and silica)

Uniform RuRe bimetallic nanoparticles (RuRe NPs) were successfully synthesized by a microwave-assisted polyol method using RuCl3 and NH4ReO4 as a precursor salts and ethylene glycol as a reducing agent. The obtained materials were characterized by UV–vis, TEM, SEM-EDS, XRD and XPS spectroscopy. Characterization by TEM showed that microwave-polyol synthesis using poly-N-vinyl-2-pyrrolidone (PVP) as a capping agent led to spherical RuRe NPs with mean size of 1.4nm or 1.6nm for the NPs with the nominal Ru/Re atomic ratio of 75:25 and 50:50, respectively, and a narrow particle size distributions (0.5–2.5nm). The size of the bimetallic NPs was slightly higher than monometallic Ru(PVP) NPs (1.3nm) prepared by the same method. XRD data confirmed small size of the obtained products. The “in situ” synthesis of γ-alumina or silica deposited NPs has been carried out without the addition of PVP, leading also to formation of bimetallic RuRe NPs. XPS analysis confirmed that the supported RuRe NPs consisted of Ru0, Re0 and oxidized Ru and Re species. However, the mean sizes and size distributions of the as-prepared bimetallic NPs depend greatly on the kind of the support used. In the case of γ-Al2O3 a narrow particle size distributions (0.5–5nm) were obtained and the mean sizes of RuRe and Ru NPs were slightly higher then for the PVP-stabilized NPs. The as-prepared silica deposited RuRe or Ru NPs were not well-dispersed and large aggregation of NPs was observed by TEM. However, diffraction data show that large agglomerates were composed from small bimetallic RuRe NPs (2.6nm) or nomometallic Ru NPs (9nm). Due to the weak interaction with silica surface, these small RuRe NPs lying very close to each other, were easily sintered during the hydrogen treatment at 400°C. In contrast, the bimetallic RuRe NPs deposited on the γ-Al2O3 under similar reducing conditions were very stable and have high activity for hydrogen chemisorption. Preliminary catalytic data show that alumina deposited RuRe nano-catalysts were more active then Ru nano-catalyst in the propane oxidation reaction.

Cell performance distribution in a low-temperature proton exchange membrane fuel cell stack during propene contamination

A 36-cell proton exchange membrane fuel cell (PEMFC) stack was contaminated with 50 ppm propene in air. Propene contamination amplified the uneven cell performance distribution along the stack length. End cells showed a larger performance change due to contamination than contiguous cells owing to a lower temperature and a larger effect of contamination at lower temperatures. The performance change of the inner cells linearly varied from cell 2 to cell 35 and was attributed to several causes including the uneven sub-saturated air flow distribution and the propene oxidation reaction involving a water molecule. The inner cells performance distribution was also credited to the uneven coolant flow distribution and a large effect of temperature on contamination. Higher cathode potentials acted as a cleaning method that minimized the contamination effect by promoting propene oxidation and led to weakly adsorbing CO2. As a consequence, higher cathode potentials also resulted in smoothing the uneven inner cells performance distribution.

Synthesis and utilization of non-metallic detergent/dispersant and antioxidant additives for lubricating engine oil

In the present work, different ashless detergent/dispersant additives based on propylene oxide (PO) were prepared via reaction of propylene oxide with different tertiary amines and the products which obtained were reacted with different organic acids. The structures of the prepared compounds were confirmed using fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC) for determination of molecular weight. All the prepared compounds were found to be soluble in lubricating oil. The efficiency of the prepared compounds as antioxidants and detergent/dispersant additives for lubricating oil was investigated. It was found that the additives have excellent power of dispersion, detergency and the most efficient additives as antioxidant those prepared by using n,n-dimethyloctadecylamine and di-n-butyl dithio phosphoric acid.

Utilization of olive tree branch cellulose in synthesis of hydroxypropyl carboxymethyl cellulose

This paper describes the functionalization of cellulose extracted from olive tree branches by subjecting it to successive etherification reactions, hydroxypropylation and carboxymethylation. Factors affecting the efficiency of etherification reactions like propylene oxide concentration, alkali concentration, reaction temperature and reaction duration were studied. The etherification efficiency was evaluated by analyzing the mixed cellulose ether to estimate its molar substitution and degree of substitution. Optimum conditions for hydroxypropylation reaction are to use 10% NaOH, together with 115% propylene oxide (all based on weight of cellulose), at 60°C for 120min. The obtained samples were characterized by estimating the molar substitution and the best value suitable for water solubility (0.39) was attained upon using the above optimum conditions. Optimum conditions for carboxymethylation of the hydroxypropylated cellulose were to use 20% (w/v) from NaOH during the alkalization step. This optimum condition gave carboxymethylated sample having degree of substitution 0.4 which is suitable for water solubility.

Green Process of Propylene Oxide Reaction for Thermal Hazard Assessment by Differential Scanning Calorimetry and Simulation

AbstractIn addition to polypropylene, acrylonitrile, and carbonyl alcohol, propylene oxide is the fourth major derivative among propylene derivatives and one of the important basic organic chemicals. A thermal stability test of catalyst, methanol, and hydrogen peroxide (H2O2) was conducted via differential scanning calorimetry (DSC). Propylene epoxidation with H2O2 over catalyst, methanol, and propylene evenly mixed by specific pressure was carried out, and then the runaway reaction under adiabatic conditions was further simulated by the vent sizing package 2 (VSP2) to measure temperature and pressure data with respect to time of the runaway excursion. Finally, the apparent activation energy of H2O2 and propylene oxide reaction was obtained via temperature variation equation to evaluate the degree of potential hazard in industry.

DMF and mesoporous Zn/SBA-15 as synergistic catalysts for the cycloaddition of CO2 to propylene oxide

A series of Zn/SBA-15 samples with Zn/Si molar ratios from 0.06 to 0.18 were prepared by one-pot synthesis method. XRD, N2 adsorption/desorption, TEM, FTIR and XPS techniques were used to determine the textual structures and physicochemical properties of Zn/SBA-15 samples. The mesoporous structure of SBA-15 was well preserved with Zn/Si molar ratio up to 0.18. Thereafter, Zn/SBA-15 was tested for the cycloaddition reaction of CO2 and propylene oxide to produce propylene carbonate in the presence of DMF. The catalytic results showed that Zn/SBA-15 and DMF synergistically catalyzed the cycloaddition of CO2 to propylene oxide. Moreover, the effects of various reaction factors, including different metal elements modified SBA-15, reaction temperature, CO2 pressure, reaction time and DMF amount were also discussed in detail. Propylene carbonate yield as high as 92.3% was achieved on Zn/SBA-15(0.15) catalyst at 160°C and 2MPa of CO2 pressure for 6h in the presence of DMF. In addition, the recycling property of Zn/SBA-15 catalyst was also investigated. A possible catalytic mechanism for the cycloaddition of CO2 to propylene oxide was proposed.

The relationship between the surface oxygen species and the acidic properties of mesoporous metal oxides and their effects on propane oxidation

Explore the impact of the surface oxygen species of mesoporous metal oxides on propane oxidation reaction.

Mechanism of fixation of CO2 with an epoxide catalyzed by ZnBr2 and a choline chloride co-catalyst: a DFT study

The cycloaddition mechanism of the reaction of propylene oxide with CO2 catalyzed by ZnBr2/choline chloride is elucidated using a DFT method.