Production propylene oxide

Table 3. Global Propylene Oxide Production Capacities, t x lOVyr...

Fiaal purification of propylene oxide is accompHshed by a series of conventional and extractive distillations. Impurities ia the cmde product iaclude water, methyl formate, acetone, methanol, formaldehyde, acetaldehyde, propionaldehyde, and some heavier hydrocarbons. Conventional distillation ia one or two columns separates some of the lower boiling components overhead, while taking some of the higher boilers out the bottom of the column. The reduced level of impurities are then extractively distilled ia one or more columns to provide a purified propylene oxide product. The solvent used for extractive distillation is distilled ia a conventional column to remove the impurities and then recycled (155,156). A variety of extractive solvents have been demonstrated to be effective ia purifyiag propylene oxide, as shown ia Table 4. 

Safe Handling and Storage of DOW Propylene Oxide, Product Bulletin, Form 109-609-788 SMG, The Dow Chemical Co., Midland, Mich., 1988. 

Propylene Oxide, Product Safety Bulletin, ARCO Chemical Co., Newton Square, Pa., Mar. 24,1992. 

The most important chemical reaction of chi orohydrin s is dehydrochloriaation to produce epoxides. In the case of propylene oxide. The Dow Chemical Company is the only manufacturer ia the United States that still uses the chlorohydrin technology. In 1990 the U.S. propylene oxide production capacity was hsted as 1.43 x 10 t/yr, shared almost equally by Dow and Arco Chemical Co., which uses a process based on hydroperoxide iatermediates (69,70). More recentiy, Dow Europe SA, aimounced a decision to expand its propylene oxide capacity by 160,000 metric tons per year at the Stade, Germany site. This represents about a 40% iacrease over the current capacity (71). 

The main method to obtain propylene oxide is chlorohydrination followed by epoxidation. This older method still holds a dominant role in propylene oxide production. Chlorohydrination is the reaction between an olefin and hypochlorous acid. When propylene is the reactant, propylene chlorohydrin is produced. The reaction occurs at approximately 35°C and normal pressure without any catalyst ... 

Electrochemical processes high pressure, 73 429-431 hydrogen use in, 73 857-862 for propylene oxide production, 20 807-808... 

Hydrogen peroxide processes, for propylene oxide production, 20 806 Hydrogen peroxide stabilizer packages, 14 40... 

Hou, C.T., Propylene oxide production from propylene by immobilized whole cells of Methylosinus sp. CRL 31 in a gas-solid bioreactor, Appl. Microbiol. Biotech., 19 (1984) 1-4. 

Figure 7.4 Temperature dependence of propylene oxidation product yield. C3H6 20% H202 = 1 1 vCH = 800ml/h t = 1.86 s (1 propylene oxide 2 propionic aldehyde 3 allyl alcohol 4 acetone and "5 total propylene conversion).

Inserting oxygen into the C-H bond of an alkane initially leads to hydroperoxides. When this reaction is performed with atmospheric oxygen it is also called autooxidation. It usually leads to a multitude of products, because of further spontaneous reactions, so this reaction is of limited synthetic use. An exception is oxidation of isobutane with oxygen, which leads to 70 % yield of tert-butyl hydroperoxide at a conversion of 80% (Table 1, entry 7). Hydrogen bromide is used, among other compounds, as an initiator [15]. tert-Butyl hydroperoxide is used as an oxidant in propylene oxide production by the Halcon process. In the formation of phenol by the cumene process cumene is oxidized into the corresponding hydroperoxide in a similar way. 

The world installed capacity for propylene oxide production is ca. 5.9 Mt/a. It is a raw material for many end products and intermediates in the chemical... 

A novel route for making propylene oxide is by epoxidation of propylene using hydrogen peroxide. U.S. 6,103,915 (to Enichem) and U.S. 5,744,619 (to UOP) give yields for several catalysts. U.S. 5,252,758 describes a process for propylene oxide production. Estimate the cost of propylene oxide production and determine the best catalyst. 

The chlorohydrin process practiced by Dow Chemical in the United States, weds the chlorine component of chloralkali technology to propylene oxide production. Chlorine added to water produces hypochlorous acid and hydrochloric acid (Eq. 19.44). 

The first step is oxidation of EB to form EB hydroperoxide. The oxidation is carried out in the liquid phase with a target EB conversion of approximately 13%. Although higher conversions are attractive from an EB recovery and recycle standpoint, there is a significant disadvantage because the EB hydroperoxide selectivity declines sharply. The second step is epoxidation of propylene to form propylene oxide product and 1-phenylethanol. In the last step, the 1-phenylethanol is dehydrated to styrene and water. The dehydrated reaction mixture is typically stripped of light components and rerun in a styrene column to remove heavy by-products, resulting in a purified styrene product. 

Peroxide-based propylene oxide production makes headway, Chem. Eng. Prog., (October, 2003) 14. 

Dow Chemical Company, "Ethylene Oxide and Propylene Oxide - Product Bulletin , Midland, MI... 

FI, 7.4. Propylene oxide production by oxidation with peroxide compounds. ARCO Chemical (Oxirunc) process, isobutane version. 1 - I... 

Table 5 Propylene Oxide Production in the United States...

The epoxidation reactor effluent is sent to a propylene separation column where unreacted propylene is distilled from the propylene oxide product. The unreacted propylene is recycled to the epoxidation reactor and the propylene oxide is sent for further separation and recovery of propylene glycol by-products. 

This product can be used again in a second stage of polyoxypropylation wherein it acts as a solvent for fresh sucrose. The reaction conditions are basically as described before. Using this procedure 670 gm (0.8 mole) of sucrose-propylene oxide product is used for 670 gm (1.95 mole) of fresh sucrose. 

Figure 1.13 Simplified process flow diagram for propylene oxide production via oxidation of propylene catalyzed by TS-1 with H2O2 as the oxidizing agent (Dow-BASF HPPO process). Adapted from US 7,138,534.

Scheme I shows a simplified block diagram illustrating the four main stq>s of a new route to propylene oxide production. In die first step, an alkylanthrahydroquinone, propylene and air react through a series of reactors producing propylene oxide, a minor amount of solvolysis products and water. Propylene oxide is separated by distillation and recovered. In die next step, methanol, propylene glycol and its methyl ether derivatives are extracted widi water and purified. The remaining organic phase passes to the alkylanthraquinone purification/hydrogenation step and finally is fed widi methanol, back to the epoxidation reactors. The regeneration and purification of the working solution are not shown in Scheme I.

Horstmann, S. Gardeler, H. Fischer, K. Koester, F. GmehUng, J. Vapor pressure, vapor-hquid equihbrium, and excess enthalpy data for compounds and binary subsystems of the chlorohydrin process for propylene oxide production J. Chem. Eng. 

Only industrial producers (e.g. Dow) with a highly integrated and cost competitive supply chain of chlorine-caustic soda (through production from caustic soda by NaCl electrolysis) to provide chlorine for the chlorohydrin reactor and sodium hydroxide for the dehydrochlorination step can operate chlorohydrin units for propylene oxide production competitively with indirect oxidation units. 

Indirect oxidation of propylene is an important route for propylene oxide production that proceeds in two reaction steps. The first step is the formation of a peroxide from alkanes, aldehydes, or adds by oxidation with air or oxygen. The second reaction step is the epoxidation of propylene to PO by oxygen transfer from the peroxide with formation of water, alcohol, or acid. The catalytic oxidation of propylene with organic hydroperoxides is nowadays a successful commercial production route (51% of world capacity). Two organic hydroperoxides dominate the processes (i) a process using isobutane (peroxide tert-butyl hydroperoxide, co-product tert-butyl alcohol), which accounts for 15% of the world capacity and (ii) a process using ethylbenzene (peroxide ethylbenzene hydroperoxide, co-product styrene) that accounts for 33% of the world capacity. The process via isobutane is presented by ... 

Figure 6.12.6 Flow sheet of the Halcon process for propylene oxide production. Adapted from Kahlich et a. 2000) and Fedtke eto/. (1992).

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