Propylene Oxide Production Research Articles

Gas-phase epoxidation of propylene through radicals generated by silica-supported molybdenum oxide

Abstract It was found that silica-supported molybdenum oxide was high effective for the epoxidation of propylene among various silica-supported metal oxides. The post-catalytic bed volume played an important role in its formation. On a MoO x /SiO 2 with 0.255 mmol/g-SiO 2 , a propylene conversion of 17.6% and a PO selectivity of 43.6% were obtained at 5 atm, 573 K and flow rates of C 3 H 6 /O 2 /He = 10/5/10 cm 3 min −1 . The characterization studies indicated that crystalline MoO 3 nano-particle species was more effective for propylene epoxidation to PO than molecularly dispersed Mo oxide species. The reaction mechanism of propylene epoxidation on MoO x /SiO 2 catalysts is hypothesized to involve gas-phase radicals generated at relatively low temperature by the dispersed molybdenum oxide species. These radicals participated in homogeneous reactions with molecular oxygen to produce propylene oxide.

Trimethylamine as a Gas‐Phase Promoter: Highly Efficient Epoxidation of Propylene over Supported Gold Catalysts

The probable reaction pathways for propylene epoxidation with O2 and H2 in the presence of trimethylamine on trimethylsilylated Au-Ba(NO3)2/titanosilicate catalyst are discussed (see figure). The use of trimethylamine as a gas-phase promoter for nanoparticulate gold catalysts leads to a direct one-stage production of propylene oxide (PO) with steady space–time yields comparable to values for current industrial ethylene oxide production.

Selective oxidation of propylene to propylene oxide using combinatorial methodologies

Direct oxidation of propylene by oxygen to propylene oxide (PO) has been studied through the application of the techniques of combinatorial catalysis. Catalytic materials containing single and binary metal components were prepared by impregnating standard γ-Al 2O 3 pellets. In the first stage, 34 single component catalytic materials at three different metal loading levels were prepared and screened for PO activity and selectivity using array channel microreactors and mass spectrometry. Experiments were conducted at a GSHV of 20,000 h −1, 101 kPa pressure and over a temperature range of 200–350 °C. Following a matrix inversion technique to deconvolute the mass spectrometric intensity measurements, signals that were directly attributable to PO were calculated. From these determinations, the elements Rh, Mn, and Mo were the most PO active single metal catalysts on γ-Al 2O 3. For acetone (AT) Rh, Pb, and Ir were somewhat effective, while Cu, Mn, and W favored some acrolein (AL) formation. In the second step, catalytic materials containing binary combinations of metals were prepared using a variety of strategies. However, the binary catalytic materials that exhibited the highest PO production levels always contained Rh. The binary combinations that exhibited superior PO production levels were Rh–V, Rh–Cr, Rh–Sn, Rh–In, Rh–Mo, and Rh–Sm, albeit substantial CO 2 formation. On the other hand, Rh–Ag, Rh–Zn, and Rh–Cr combinations were significant leads with regard to high PO and low CO 2 production. These findings call for the undertaking of detailed secondary screening studies to confirm the primary screening results reported here and to obtain information on the durabilities of these catalytic materials.

Dramatic innovation of propene epoxidation efficiency derived from a forced flow membrane reactor

AbstractIt is possible to develop a selective epoxidation process for propene using heterogeneous catalysis in a forced‐flow membrane reactor. The most innovative processes required two catalysts, Cs–Ag and Re–Ag, which were immobilized in the membrane pores of a micro‐porous glassy (MPG) substance, and three different reactor systems for reaction gas flows in the membrane pores. The systems included a convection‐flow reactor (CFR), a diffusion‐flow reactor (DFR), and a packed‐bed‐flow reactor (PFR). The three types were examined over temperatures ranges from 420 to 525 K, while keeping the total conversion of propene to less than 10%. The membrane reactor systems followed two common Langmuir‐type equations of reaction rates for CO2 and propylene oxide (PO) formation under steady state operations at atmospheric pressure. The amount of the intermediate for CO2 formation, whose structure retained the CCC bond of a propene molecule, was sensitively controlled by the types of catalysts and reactor systems used. Comparing the three immobilized catalysts, Cs–Ag, Re–Ag, and Ag2O, the larger the amount of intermediate formed on the catalysts the higher was the propylene oxide (PO) selectivity and thus the PO selectivity followed the order of Re–Ag > Cs–Ag > Ag2O. The CFR with Re–Ag/MPG clearly demonstrated hysteresis kinetics depending on the increase (C‐up) or decrease (C‐down) in the propene concentration. The PO selectivity was separately evaluated as 73–35% for the C‐up and 35–21% for the C‐down. The convection flow rate of reactants in the pores effectively contributed to an enhancement of the PO production rate from 18 to 41% of PO selectivity, for the reactant flow rate of 70–130 cm3 min−1 at 483 K.© 2003 Society of Chemical Industry

Comparing kinetic design of propene partial oxidation between a CsAg and a ReAg immobilized membrane reactors

The efficiency of the partial oxidation of propene (PP) to propylene oxide over a CsAg and a ReAg catalysts immobilized in two porous ceramic tube membrane reactors (designated Cs-membrane and Re-membrane respectively) was compared by using three different flow reactors (convection flow (CFR), diffusion flow (DFR) and plug flow (PFR) reactors). In the Cs- and Re-membranes, the CFR was commonly designed as the best efficient reactor at 420–524 K and, as a common reaction kinetics, two steady state rate equations, for the production of propylene oxide (PO) and CO 2 were separately proposed by two different reaction pathways. The reactor efficiency of CFR for the PO production selectivity was evaluated as 11.2–17.5% for the Cs-membrane reactor and 18–75% for the Re-membrane reactor because of an advantage of PO production rate constant as a rate determining step, which was effectively regulated by the amount of a stable intermediate formed on the catalyst surface in a CO 2 formation pathway.

Study on process integration of the production of propylene oxide and hydrogen peroxide

Titanium silicalite (TS-1) is an effective catalyst for selective oxidation of hydrocarbons and their derivatives with hydrogen peroxide under mild conditions. The industrialization of these processes is at present penalized by the high cost of hydrogen peroxide. The process integration of the production of propylene oxide (PO) with the production of hydrogen peroxide (H 2O 2) by the anthraquinone route is presented in this paper. Two integrated processes are discussed: in the first process, the solvent for the epoxidation step is recycled to extract H 2O 2 from the anthraquinone working solution; while in the second process, two oxidation processes, the epoxidation of propylene and the oxidation of anthrahydroquinone, are carried out in one circulating reactor. The influences of various reagents on the performance of TS-1 and the compatibility of the two oxidation processes were investigated. The results show that it is better to integrate the production of PO with the production of H 2O 2 when TS-1 is used as catalyst.

Copolymerization of maleic acid with acetophenone-containing bottoms from styrene distillation

The feasibility was studied for producing polymeric materials by high-temperature copolymerization of maleic acid with styrene distilation bottoms from joint production of styrene and propylene oxide. Regression equations were derived to predict the conditions for preparing the copolymer with the required properties. The structure, properties, and fields of possible application of the copolymer were studied.

Processing of Acetophenon Bottoms from Distillation of Styrene with Maleic Acid

The kinetic features of dehydration of maleic acid during preparation of a copolymer based on the styrene distillation bottoms from joint production of styrene and propylene oxide were studied. The potential application fields for the copolymer synthesized were analyzed.

Selective oxidation of propylene to propylene oxide over Ti–MCM-41 supporting metal nitrate

The direct gas-phase oxidation of propylene with molecular oxygen was carried out over Ti–MCM-41 impregnated with metal nitrates to produce propylene oxide (PO) selectively. The effects of Ti-loading on MCM-41, nitrate additives, acid treatment of the support, and the presence of molecular oxygen were investigated. The PO yield increased with increasing Ti content of Ti–MCM-41 and reached a maximum at an optimum Si/Ti ratio of 100. Calcium nitrate was the most suitable additive among various nitrates of alkali and alkaline earth metals investigated, and the acid treatment of Ti–MCM-41 effectively improved its catalytic performance for the PO formation. The presence of both nitrate and molecular oxygen was essential for the PO formation. A synergetic mechanism between the Ti species and metal nitrate was proposed to be responsible for the selective formation of PO.

Epoxidation of propylene over gold catalysts supported on non-porous silica

Non-porous silica was used as a carrier of Au/Ti-SiO 2 catalysts for the direct vapor-phase epoxidation of propylene in the copresence of H 2 and O 2, because the smooth surfaces were expected to facilitate the desorption of propylene oxide (PO). Their catalytic performances were inferior to those of Au/TS-1 and Au/Ti-MCM catalysts, however, an interesting feature was that propylene epoxidation over Au/Ti-SiO 2 appreciably depended on calcination temperature of the Ti-SiO 2 support. Higher calcination temperature benefits PO production at reaction temperatures above 100°C. IR and HRTEM analyses showed that the interaction between titanium oxides and silica was intensified to form more isolated TiO 4 units with tetrahedral coordination on the surfaces of Ti-SiO 2 supports with an increase in heat treatment temperature. These isolated TiO 4 sites incorporated in silica surface layers are assumed to be an important structural factor for the selective deposition of Au particles and the selective PO formation.

A GREENER ROUTE TO PROPYLENE OXIDE

A TUNGSTEN CATALYST SYStem developed by a team of researchers in China holds promise for a more economical and environmentally friendly route to production of propylene oxide. The apparent front-runner among several possible processes that have emerged to replace the two industrial methods currently in use is the catalytic epoxidation of propylene with hydrogen peroxide. Researchers at the Chinese Academy of Sciences' Dalian Institute of Chemical Physics have now come up with a novel catalyst system for that process [ Science , 292, 1139 (2001)]. Chemistry professor Xi Zuwei and coworkers Zhou Ning, Sun Yu, and Li Kunlan discovered a tungsten-containing catalyst, {C 5 H 5 NC 16 H 33 } 3 {PO 4 (WO 3 ) 4 }, that initially is insoluble in organic solvents. But under the action of in situ-generated H 2 O 2 it forms a soluble active species that catalyzes propylene epoxidation. As H 2 O 2 is used up, the catalyst becomes insoluble again, simplifying its recovery The only products of the reaction are propylene ...

Reaction-controlled phase-transfer catalysis for propylene epoxidation to propylene oxide.

The epoxidation of olefins with H2O2 was performed with a tungsten-containing catalyst. This insoluble catalyst forms soluble active species by the action of H2O2, and when the H2O2 is used up, the catalyst precipitates for easy recycling. Thus, the advantages of both homogeneous and heterogeneous catalysts are combined in one system through reaction-controlled phase transfer of the catalyst. When coupled with the 2-ethylanthraquinone/2-ethylanthrahydroquinone redox process for H2O2 production, O2 can be used for the epoxidation of propylene to propylene oxide with 85% yield based on 2-ethylanthrahydroquinone without any co-products. This approach avoids the problematic co-products normally associated with the industrial production of propylene oxide.

Vapor Pressure, Vapor−Liquid Equilibrium, and Excess Enthalpy Data for Compounds and Binary Subsystems of the Chlorohydrin Process for Propylene Oxide Production

Vapor−liquid equilibrium (VLE), excess enthalpy (HE), and vapor pressure (Pis) data for eight binary systems containing cis-1-chloropropene, trans-1-chloropropene, 1,2-dichloropropane, 1,2-propanediol, 1,2-propylene glycol diacetate, propylene oxide, and water are presented in a temperature range from 276 to 368 K. The VLE and vapor pressure data were obtained by means of a computer-controlled static apparatus, and the heat of mixing data were measured using an isothermal flow calorimeter. Temperature-dependent NRTL interaction parameters were regressed by a simultaneous correlation of the experimental VLE and HE data. These parameters are required for a proper simulation of the different separation steps in the chlorohydrin process for the production of propylene oxide.

Selective Vapor-Phase Epoxidation of Propylene over Au/TiO2Catalysts in the Presence of Oxygen and Hydrogen

Gold has long been thought to be chemically inert, however, it has recently been proven that its catalytic performance is dramatically tunable by control of the particle size and by careful selection of the support metal oxide. A typical example is the selective oxidation of propylene in a gas containing oxygen and hydrogen. When gold is deposited on TiO2by a deposition–precipitation technique as hemispherical particles with diameters smaller than 4.0 nm it produces propylene oxide with selectivities higher than 90% and conversions of 1–2% at temperatures of 303–393 K. The oxidation of hydrogen to form water is depressed by propylene, whereas propylene oxidation is not only enhanced but also restricted to partial oxidation by hydrogen. The depression of hydrogen combustion by the presence of propylene and a new peak due to gold deposition in TPD spectra have indicated that propylene is adsorbed on the surfaces of both gold particles and the TiO2support. The reaction rate is almost independent on the concentration of propylene and increases linearly with increasing concentrations of O2and H2. The above results suggest that propylene adsorbed on a gold surface may react with oxygen species formed at the perimeter interface between the gold particles and the TiO2support through the reaction of oxygen with hydrogen. The effect of gold loading is surprising in that the reaction product switches from propylene oxide to propane when gold loading is decreased to 0.1 wt%. Careful TEM observation indicates that gold particles larger than 2.0 nm in diameter produce propylene oxide, whereas smaller gold particles produce propane.

Technical and economic evaluation of different reactors for methanotrophic cultures for propylene oxide production

Technical and economic evaluation of different reactors for methanotrophic cultures for propylene oxide production

Technical and economic evaluation of different reactors for methanotrophic cultures for propylene oxide production

A two-stage process for the manufacture of propylene oxide is described. The preliminary economics based on use of methanol as a regeneration factor has resulted in a production cost of $12.10/lb of propylene oxide based on propylene oxide production rate of 40 mg/g-cell/h in conventional reactor. Increasing the propylene oxide production from 40 to 500 mg/g-cell/h resulted in a cost reduction from $12.10 to 5.8/lb of propylene oxide. The granular-activated, carbon-fluidized bed reactor (GAC-FBR) absorbs the propylene oxide and when saturated is eluted with ethyl acetate, and the bed is regenerated by steam to drive off the residual solvents. The estimated manufacturing costs are approx 59% lower (from $12.10/lb in conventional reactors to $5.00/lb for GAC-FBRs) for products that are highly inhibitory such as epoxides. In the GAC-FBR reactor, enhancing the propylene oxide production rate from 120 to 1500 mg/g-cell/h has resulted in the cost reduction to $2.00/lb. Enhancing the production capacity from 1 million lb to 10 million lb/yr has further reduced the cost of production to $1.00/lb.

Selective oxidation of propylene over gold deposited on titanium-based oxides

Gold supported on titanium-based metal oxides can assist the selective partial oxidation of propylene at temperatures from 313 K to 573 K in a gas containing both H2 and O2. The preparation method was found to be crucial in controlling the selectivities. In general, impregnation and chemical vapor deposition methods do not produce selective catalysts. Only the deposition-precipitation method makes gold selective to propylene oxide or propanal, suggesting that a strong contact between the gold particles and the titanium ion sites on the support is important. The effect of changing the support was also dramatic; the use of the anatase form of TiO2 and Ti-MCM-41 results in propylene oxide production, while the rutile structure of TiO2 caused complete oxidation to CO2. Microporous crystalline titanium silicates such as TS-1, TS-2, and Ti-β zeolite make gold relatively selective to propanal and of the three TS-1 gives the highest selectivity. These results indicate that the oxidation of propylene in the copresence of H2 must involve the surface of the supports and that the reaction takes place at the interface perimeter around the gold particles.

Mortality from pancreatic and lymphopoietic cancer among workers in ethylene and propylene chlorohydrin production.

OBJECTIVES: A previous study reported a fivefold increase in mortality from pancreatic cancer and a threefold increase in lymphopoietic and haematopoietic cancer among 278 men who were assigned to a...

Coplanar interdigitated band electrodes for electrosynthesis—Part 3: Epoxidation of propylene

Interdigitated coplanar band electrodes were made from platinum ink printed on alumina. Their application to the epoxidation of propylene was investigated under different experimental conditions, in both a tank cell and a flow cell. It was found for this coupled reaction that the agitation should be minimised to allow the products formed at the anodes to react with the products formed at the cathodes. The rate of bromine formation had to be high enough to allow a consequent production of propylene oxide, but low enough to avoid the formation of bromate. Therefore, the optimum potential was set between 3 and 4V, and the bromide concentration was found to be 1% by weight. The temperature was also optimised by choosing intermediate values between 6 and 10 °. The compromise in this case lies between having fast reactions at high temperature and high propylene concentration at low temperature. The inter-electrode distance of the different arrays was varied between 250 μm and 1mm and figures of merit were improved by using smaller inter-electrode gaps. For an array used in a tank cell, with an inter-electrode gap of 250 μm, an applied voltage of 3V, a cell temperature of 10 ° and a bromide concentration of 1%, the current efficiency reached 68%, for an energy consumption of 2.0 kWh kg −1 and a production rate of 0.12mol h −1 dm −2, which compared well with results previously obtained in a pump cell or a trickle tower.

The role of copper in the pMMO of Methylococcus capsulatus Bath: A structural vs. catalytic function

Methanotrophs convert methane to methanol by the methane monooxygenase (MMO). It is well known that two forms of the MMO can be expressed: one form is found in the cytoplasm, or in the soluble fraction (sMMO); the other is associated with the membranes, or particulate fraction (pMMO). The sMMO has been extensively examined, and much is known about its structure and mechanism of dioxygen activation. The pMMO, however, is less well understood: the enzyme has proven difficult to purify as it loses activity once the membranes become solubilized. Furthermore, although copper is known to be important for the stability and activity of the pMMO, its role is still unclear. In a recent study, we reported the use of electron paramagnetic resonance (EPR) spectroscopy to probe the nature of the copper ions in these membranes. Two EPR signals were uncovered for the highly oxidized membranes: one set of signals arises from the type 2 Cu(II) centers, and the other has been assigned to trinuclear copper(Cu(II)) clusters (H.-H. Nguyen, et al., J. Biol. Chem., 269, 14995 (1994). Here, we attempt to correlate the EPR spectra of the membrane fraction of Methylococcus capsulatus Bath with the amount of copper present in the membranes and to the activity of the pMMO as measured by the production of propylene oxide from propene by the pMMO. From these studies, we conclude that the primary role of copper is in the active site of the pMMO rather than simply a structural one.