Synthesis Of Propylene Oxide Research Articles

Vapor–liquid equilibrium in the system of propylene oxide synthesis products

Vapor–liquid equilibrium data calculated for the systems formed by propylene oxide synthesis products have been compared to the same data available from the literature. Using the NRTL and UNIQUAC models, the vapor–liquid equilibrium data available from the literature for the systems have been optimized, the model parameters and their errors have been estimated, and the corresponding diagrams have been calculated and mapped. A process flowsheet for propylene oxide isolation from the reaction mixture is suggested.

Epoxidation of propylene to propylene oxide with molecular oxygen over Sb2O3–CuO–NaCl/SiO2 catalysts

Co-impregnated Sb2O3–CuO–NaCl/SiO2 catalysts were investigated for the direct gas-phase synthesis of propylene oxide (PO) from propylene and molecular oxygen at atmospheric pressure. The trimetallic system was optimized for PO formation by varying the Sb:Cu:Na ratios, total metal loadings and calcination temperatures. At a reaction temperature of 250°C and propylene/oxygen molar ratio=1:4, the highest performing catalyst achieved 40–45% PO selectivity with 0.4–0.7% propylene conversion without a co-feeding gas. The coexistence of Sb2O3 and CuO crystals was determined to play a vital role in propylene epoxidation, while NaCl helped to suppress combustion.

Design and optimization of a catalytic membrane reactor for the direct synthesis of propylene oxide

Using numerical simulations, a new membrane reactor is proposed for the direct synthesis of propylene oxide (PO) in liquid phase. The reactor is a combination of two consecutive catalytic reactor units, one for the hydrogen peroxide (H2O2) synthesis on a Pd/SiO2 catalytic membrane layer, and the second for the conversion of hydrogen peroxide with propylene (C3H6) to PO on a titanium silicalite-1 (TS-1) catalytic layer. The membrane reactor is described numerically by a set of kinetic-diffusion mass balance equations. The optimization of the reactor design is achieved by determining membrane pore size, thickness and gas pressures which provide conversion and selectivity performance comparable to the industrial requirements. An optimal pore size of 0.2–0.4μm was found for the Pd/SiO2 membrane layer. The results show that a Pd/SiO2 membrane thickness of 250μm and a TS-1 layer of 100μm are necessary to ensure conversion and selectivity performance of the catalytic membrane reactor comparable to the industrial ones. Calculated these optimized dimensions of the membrane reactor, a total membrane area of 84,000m2 is required for the production of 300kton/year of propylene oxide.

Effective separating agents for extractive distillation of a propylene oxide-methanol mixture

The activity coefficients at infinite dilution were determined and used for estimating the maximum selectivity of twenty different separating agents for the propylene oxide-methanol pair formed during propylene oxide synthesis. Protic and aprotic solvents were compared in terms of their effectivity. A relationship between the maximum selectivity and physicochemical properties of the solvent was established.

Key Mechanistic Insight into the Direct Gas‐Phase Epoxidation of Propylene by the RuO2–CuO–NaCl/SiO2 Catalyst

AbstractThe discovery of the RuO2–CuO–NaCl/SiO2 catalyst for the direct gas‐phase epoxidation of propylene to propylene oxide created a potentially promising path towards developing a high‐performing catalyst of substantial commercial value and opened a new challenge in catalysis research. In this work, studies following up this discovery are presented to reveal critical insight into the catalytic mechanism on the trimetallic catalyst. Small crystalline CuO particles, in close proximity of RuO2, were determined from temperature‐programmed reduction and high‐resolution transmission electron microscopy studies to be the site for propylene oxide synthesis. In addition, the presence of NaCl was confirmed to suppress the formation of CO2.

Trimodel hierarchical yolk–shell porous materials TS-1@mesocarbon: Synthesis and catalytic application

Abstract Trimodal hierarchical yolk–shell materials consisting of TS-1 core and mesoporous carbon shell (YS-TS-1@MC) was successfully synthesized by using TS-1@mesosilica as hard template, sucrose as carbon source and organic base tetrapropylammonium hydroxide (TPAOH) as silica etching agent. The resultant YS-TS-1@MC contains the micropores (0.51 nm) in TS-1 core, the mesopores (2.9 nm) in carbon shell as well as a void or a stack pore between TS-1 fragements (TS-1 intercrystal mesopores, ∼18.4 nm). Under the rigorous etching conditions, the crystalline structure of TS-1core was well retained. The YS-TS-1@MC served as a good support for palladium nano-particles (Pd NPs) or Rh(OH)x species, giving rise to efficient bifunctional catalysts for the tandem reactions including one-pot synthesis of propylene oxide or amides.

New Catalytic Materials for the Direct Epoxidation of Propylene by Molecular Oxygen

AbstractThe direct vapor‐phase production of propylene oxide (PO) from propylene and molecular oxygen without the use of a co‐reactant remains a challenging problem in industrial catalysis, in spite of several decades of research. Herein, the discovery of a new class of silica‐supported multimetallic RuO2–CuOx–NaCl catalysts for the direct synthesis of PO from propylene and molecular oxygen is reported. This trimetallic catalyst exhibits durability and delivers PO selectivities of 40–50 % at propylene conversions of 10–20 % within 240‐270 °C and at atmospheric pressure. The best performing catalysts are characterized by powder X‐ray diffraction (PXRD) and transmission electron microscopy (TEM) and are determined to be composed of nanocrystalline domains of the three phases of RuO2, CuOx, and NaCl.

High Throughput Synthesis and Screening of New Catalytic Materials for the Direct Epoxidation of Propylene

Nanoparticles of 35 individual metals as well as their binary combinations were synthesized using High Throughput pulsed laser ablation (PLA), and collected on Al(2)O(3), CeO(2), SiO(2), TiO(2), and ZrO(2) pellets. These materials were then screened for their catalytic activities and selectivities for the partial oxidation of propylene, in particular for propylene oxide (PO), using array channel microreactors. Reaction conditions were the following: 1 atm pressure, gas hourly space velocity (GHSV) of 20,000 h-1, temperature 300 degrees C, 333 degrees C, and 367 degrees C, and feed gas composition 20 vol% O(2), 20 vol% C(3)H(6) and balance He. Initial screening experiments resulted in the discovery of SiO(2) supported Cr, Mn, Cu, Ru, Pd, Ag, Sn, and Ir as the most promising leads for PO synthesis. Subsequent experiments pointed to bimetallic Cu-on-Mn/SiO(2), for which the PO yields increased several fold over single metal catalysts. For multimetallic materials, the sequence of deposition of the active metals was shown to have a significant effect on the resulting catalytic activity and selectivity.

New Catalytic Materials for the Direct Epoxidation of Propylene by Oxygen: Application of High-Throughput Pulsed Laser Ablation

New catalytic materials were prepared by depositing nanoparticles of 35 different metals as well as their select binary combinations on Al2O3, CeO2, SiO2, TiO2, and ZrO2 supports. Nanoparticles were synthesized by high-throughput pulsed laser ablation (PLA). Catalytic materials were then screened for their selectivities towards the synthesis propylene oxide (PO) from propylene and oxygen using array channel microreactors at 1 atm and 300, 333, and 367 °C. A gas hourly space velocity (GHSV) of 20,000 h−1 was used at the feed gas composition of 20% O2, 20% C3H6 and the balance He. Initial screening experiments resulted in the discovery of SiO2 supported Cr, Mn, Cu, Ru, Pd, Ag, Sn, and Ir as the most promising leads for PO synthesis. Subsequent experiments pointed to bimetallic Cu-on-Mn/SiO2, for which the PO yields increased several fold over single metal catalysts. For multimetallic materials, the sequence of deposition of the active metals was shown to have a significant effect on the resulting catalytic activity and selectivity.

A new route for the synthesis of propylene oxide from bio-glycerol derivated propylene glycol

The synthesis of propylene oxide from propylene glycol, a derivative of bio-glycerol, was firstly realized in the presence of alkali-loaded silica catalysts to achieve 44% conversion and 70% selectivity.

One-pot green synthesis of propylene oxide using in situ generated hydrogen peroxide in carbon dioxide

In the one-pot green synthesis of propylene oxide using in situ generated hydrogen peroxide, a propylene oxide yield of 23% with 82% selectivity was achieved over a (0.2%Pd + 0.02%Pt)/TS-1 catalyst by using compressed (supercritical or liquid) carbon dioxide as the solvent and small amounts of water and methanol as co-solvents. The addition of an inhibitor effectively suppressed a number of common side-reactions, including the hydrogenation of propylene, the hydrolysis of propylene oxide and the reaction between propylene oxide and methanol. This suppression effect is due to the interaction between the inhibitor and TS-1 leading to the neutralization of its surface acidity.

A greener, pressure intensified propylene epoxidation process with facile product separation

A novel biphasic process concept for the synthesis of propylene oxide (PO) from propylene is presented, using the long known catalyst, methyl trioxorhenium and aqueous hydrogen peroxide as the oxidant. Propylene is fed as gas, which is transported to the liquid phase containing the oxidant, catalyst and methanol as a cosolvent that improves propylene solubility. The selective oxidation produces PO which is distilled easily from the liquid phase taking advantage of the relatively low normal boiling point of PO ( ∼ 34 ∘ C ) compared to those of methanol and water. The process satisfies the sustainability principles of waste minimization, use of benign reagents and process intensification at mild conditions. The process produces PO in yields exceeding 98%. It operates at essentially ambient temperature ( 20 – 35 ∘ C ) and moderate pressures ( ∼ 20 bar ) , using easily recyclable, low hazard aqueous methanol, as solvent. The catalyst, methyl trioxorhenium, is robust under the operating conditions. A key aspect of the innovation is the use of nitrogen gas pressure to enhance propylene availability in the liquid phase increasing its conversion from ∼ 80 % (without N 2 ) to complete (with ∼ 20 bar N 2 ) in a few hours. These findings pave the way for catalyst durability and recycle studies, aimed at demonstrating a continuous process that is economically and environmentally sustainable compared to existing processes.

Propylene Oxide Synthesis and Selective Oxidation over Supported Metal Oxide Photocatalysts with Molecular Oxygen

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Propylene Oxide Synthesis and Selective Oxidation over Supported Metal Oxide Photocatalysts with Molecular Oxygen

Abstract Recent progress of photocatalytic epoxidation of propylene with molecular oxygen is reviewed. Highly dispersed metal oxide photocatalysts, such as silica-supported V2O5, Nb2O5, and TiO2 with low loading, promote steady-state propylene oxide formation with high selectivity (>40%). The isolated tetrahedrally-coordinated species in the ligand-to-metal charge-transferred state is the photocatalytic active site. The photo-induced hole center localized on the lattice oxygen plays a significant role for the photocatalytic epoxidation. In the case of isolated TiO4 tetrahedra on silica, an electrophilic oxygen species is generated by the reaction between the hole center and molecular oxygen. The addition of alkali ions to surface VO4 tetrahedra improves the photocatalytic epoxidation ability of V2O5/SiO2 with low loading. The key step in the selective photocatalytic oxidation over isolated VO4 tetrahedra is the electron transfer from a hydrocarbon to the photo-induced hole center on the lattice oxygen, which is inserted in the photogenerated products.

Production of Propene Oxide by a Homogeneous Chain Reaction Initiated by Surface Radical Generation

Effective Ti catalysts were found for the vapor phase synthesis of propylene oxide, one of the most challenging reactions in heterogeneous catalysis. The observation that the reaction was enhanced by the presence of a post-catalytic bed volume indicated that the reaction occurred through a homogeneous chain reaction, likely initiated by surface radical generation. EXAFS analysis of the SiO2-supported catalysts indicated that active samples had Ti oxide clusters on the support. The catalytic activity was stable for 500-600 min, and indicated a promising catalytic system. [DOI: 10.1380/ejssnt.2006.74]

Synthesis of Propylene Oxide in CO2 as Solvent

AbstractFor Abstract see ChemInform Abstract in Full Text.

Oxidation reactions in CO2: academic exercise or future green processes?

Conducting oxidation reactions using CO2 as the solvent is a promising strategy for creation of greener chemical processes that are also economical, as CO2 and water are probably the only solvents that can be used in oxidation reactions without the formation of any solvent byproducts. However, it must be noted that the promise of CO2-based oxidation still dwarfs the actual realization of CO2-based oxidation processes. Nevertheless, there is extensive literature on the use of CO2 as the solvent for the oxidation of cyclohexane (adipic acid synthesis), cumene oxidation (phenol synthesis), and epoxidation (propylene oxide synthesis). In all of these studies, knowledge of the phase behavior is crucial toward understanding the effects of pressure and temperature on reaction outcomes. To date, much of the research in this field has involved simply using CO2 as a "drop-in" replacement for a conventional organic solvent; it will be interesting in the future to see if the use of CO2 can be combined with innovations in catalyst and reactor design to create truly green oxidation processes where the use of CO2 is not merely tolerated but truly supports process and chemistry innovation.

Direct Synthesis of Propylene Oxide with CO2 as the Solvent

Das Oxidationsmittel H2O2 entsteht in situ bei dieser sauberen einstufigen Umsetzung von Propylen in Propylenoxid. Entgegen den Erwartungen benötigt der Katalysator – Palladium auf Titan‐Silicalit – kein Methanol zur Aktivierung, und Nebenreaktionen mit dem Lösungsmittel lassen sich vermeiden, indem die Reaktion in CO2 ausgeführt wird.

Direct synthesis of propylene oxide with CO2 as the solvent.

The oxidant H2O2 is generated in situ in this clean, one‐step conversion of propylene into propylene oxide. Contrary to expectations, the catalyst—palladium on titanium silicalite—does not require methanol for activity, and solvent‐based side reactions are avoided by conducting the reaction in CO2.

‘One-pot’ reactions: a contribution to environmental protection

The direct oxidation of benzene, β-picoline and propylene, respectively, were carried out by ‘one-pot’ reactions. A steamed H-[Al]-ZSM-5 with strong Lewis acid sites yields the best results in the oxidation of benzene with N 2O. β-picoline can be directly oxidized with O 2 in the gas-phase to nicotinic acid in the presence of a V 2O 5 impregnated TiO 2 catalyst having Brönsted acid sites in addition to redox properties. Yields up to 98% can be achieved. The propylene oxide synthesis is based on the oxidation of propylene by using a O 2–H 2 gas mixture over Pd/Pt-impregnated TS-1. Selectivities up to 85% are obtained at conversions between 15 and 20%.