Silica propylene oxidation

Epoxides such as ethylene oxide and higher olefin oxides may be produced by the catalytic oxidation of olefins in gas-liquid-particle operations of the slurry type (S7). The finely divided catalyst (for example, silver oxide on silica gel carrier) is suspended in a chemically inactive liquid, such as dibutyl-phthalate. The liquid functions as a heat sink and a heat-transfer medium, as in the three-phase Fischer-Tropsch processes. It is claimed that the process, because of the superior heat-transfer properties of the slurry reactor, may be operated at high olefin concentrations in the gaseous process stream without loss with respect to yield and selectivity, and that propylene oxide and higher... 

SMPO [styrene monomer propylene oxide] A process for making propylene oxide by the catalytic epoxidation of propylene. The catalyst contains a compound of vanadium, tungsten, molybdenum, or titanium on a silica support. Developed by Shell and operated in The Netherlands since 1978. 

For example, MSU-1 prepared using Tergitol is a disordered hexagonal mesoporous (25-48 A) silica. More recently, triblock copolymers based on ethylene oxide (EO) and propylene oxide (PO) have been used to make well-ordered mesoporous silicas having ID channels with pore sizes in the range of 50-300A... 

The reactor effluent is distilled and unreacted EB is recycled. The EB hydroperoxide is then reacted with propylene at 250°F and pressure in the range of 250-700 psi in the presence of a metal catalyst to produce propylene oxide and methylbenzyl alcohol B in Figure 8-7). The reactor mixture is separated by multiple fractionators. Unreacted propylene and EB are recycled. PO is recovered overhead. The methyl benzyl alcohol is easily dehydrated in the vapor stage at 450—500° F and 500 psi pressure over a titanium dioxide or silica gel catalyst to form styrene. Acephenone is one of the by-products. 

Olefin epoxidation is an important industrial domain. The general approach of SOMC in this large area was to understand better the elementary steps of this reaction catalyzed by silica-supported titanium complexes, to identify precisely reaction intermediates and to explain catalyst deachvahon and titanium lixiviation that take place in the industrial Shell SMPO (styrene monomer propylene oxide) process [73]. (=SiO) Ti(OCap)4 (OCap=OR, OSiRs, OR R = hydrocarbyl) supported on MCM-41 have been evaluated as catalysts for 1-octene epoxidation by tert-butyl hydroperoxide (TBHP). Initial activity, selechvity and chemical evolution have been followed. In all cases the major product is 1,2-epoxyoctane, the diol corresponding to hydrolysis never being detected. 

Copolymer of tetra-hydrofuran with propylene oxide OH 1000-1300 0.8-2.0 silica gel methylethyl ketone (i) LC 21,22)... 

However, the uncovered silica surface consisting in residual silanols could induce indesirable competitive reaction from propylene oxide treatment such as epoxide opening and alkoxylation of the surface. In order to overcome these drawbacks, the uncovered surface of the Cl-MTS 3 was previously passivate with hexamethyldisilazane treatment before the ligand 1 was anchored according to scheme 3. 

Certain bacterial strains convert propylene glycol to pyruvic acid in the presence of thiamine (15) other strains do the conversion without thiamine (16). Propylene oxide is the principal product of the reaction of propylene glycol over a cesium impregnated silica gel at 360°C in the presence of methyl ethyl ketone and xylene (17). 

Cleaners - [PROPYLENE OXIDE] (Vol 20) -defoamersm [DEFOAMERS] (Vol 7) -for electroplating [ELECTROPLATING] (Vol 9) -precipitated silica m [SILICA - AMORPHOUS SILICA] (Vol 21)... 

Sancier et al. (43) used oxygen-18 to examine the relative role of adsorbed versus lattice oxygen in propylene oxidation over a silica-supported bismuth molybdate catalyst as a function of temperature. At 400°C they observed the formation of predominantly acrolein[I60] rather than acrolein[I80], indicating significant participation of lattice oxygen. However, as the reaction temperature was decreased, the authors concluded that the role of adsorbed oxygen became more important. 

As a catalyst for propylene oxidation, Bi203 itself has fairly low activity and yields primarily the products of complete oxidation. Pure molybdenum trioxide has an even lower activity, but is fairly selective. In combination, however, remarkable activity and selectivity for propylene oxidation is obtained. Although industrial catalysts contain silica and phosphate as well as Bi203 and Mo03, many fundamental studies have employed catalysts containing only bismuth and molybdenum oxides in an attempt to determine the structure of the catalytically active phase. As a result of such studies, it is now known that bismuth molybdate catalysts display their superior properties only if the catalyst composition lies within the composition range of Bi/Mo = f to f (atomic ratio). 

An alternative method for the manufacture of styrene (the oxirane process), uses ethylbenzene that is oxidized to the hydroperoxide and reacts with propylene to give phenylmethylcarbinol (or methyl benzyl alcohol) and propylene oxide. The alcohol is then dehydrated at relatively low temperatures (180 to 400°C) by using an acidic silica gel (Si02) or titanium dioxide (Ti02) catalyst. 

The ordered mesoporous silica (pore diameter 6 nm) was kindly provided by Dr. Ulla Junges and was prepared as described previously by G.D. Stucky et al. [15]. A commercial triblock copolymer (Pluronic-123 ) was used in the synthesis process. This polymer contained ethylene oxide/ propylene oxide/ ethylene oxide blocks, which formed a hexagonal mesophase in the synthesis mixture during the hydrolysis of the silicon alkoxides. 

Propylene oxide isomerized over silica-magnesia and other oxides to give propionaldehyde and acetone on acidic and basic sites, respectively, and allyl alcohol on acid-base bifunctional catalysts. Methylvinyl ketone was formed selectively in the reaction of acetone and methanol with oxygen over silica-magnesia. Tanabe and co-workers have studied the alkylation of phenol... 

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