Propylene oxide plant

The modified Reppe process was installed by Rohm and Haas at thek Houston plant in 1948 and later expanded to a capacity of about 182 X 10 kg/yr. Rohm and Haas started up a propylene oxidation plant at the Houston site in late 1976. The combination of attractive economics and improved product purity from the propylene route led to a shutdown of the acetylene-based route within a year. 

Although this process has not been commercialized, Daicel operated a 12,000-t/yr propylene oxide plant based on a peracetic acid [79-21-0] process during the 1970s. The Daicel process involved metal ion-catalyzed air oxidation of acetaldehyde in ethyl acetate solvent resulting in a 30% peracetic acid solution in ethyl acetate. Epoxidation of propylene followed by purification gives propylene oxide and acetic acid as products (197). As of this writing (ca 1995), this process is not in operation. 

The process was commercially so superior to the chlorohydrin route, that by the 1970s, the new chemistry had completely replaced the old. Adding some momentum to this transition was the fact that the obsolete and abandoned chlorohydrin plants could be readily converted to propylene oxide plants. The silver bullet for that process has yet to be found. 

The hydrogen peroxide process is characterized by lower environmental impact, a simpler process scheme and lower investment. However hydrogen peroxide is relatively expensive and still produced in plants with relatively low nameplate capacities, though the construction of a 300 kt/a propylene oxide plant has been announced by Dow Chemical and BASF. 

Allyl alcohol can be made by the isomerization of propylene oxide. ARCO Chemical has obtained an exclusive worldwide license from Kuraray in Osaka, Japan for their hydroformulation technology to produce 1,4-butanediol from allyl alcohol. In 1990, ARCO commissioned both the alcohol and the 1,4-butanediol process at their Channelview, Texas propylene oxide plant [91. 1,4-Butanediol is a versatile chemical intermediate that can be used to produce tetrahydrofuran, polybutylene teraphthalate resins, polyurethanes, and pyrrolidone. At this time only a relatively small quantity of propylene oxide is used for this purpose. However, it is growing... 

The estimated capital cost for a propylene oxide plant to produce 540 million pounds per year of propylene oxide by the isobutane peroxidation process is given in Table 6. This estimate includes the equipment and offsites to coproduce isobutylene from TBA for feed to an MTBE plant. 

The production costs for a propylene oxide plant coproducing isobutylene are shown in Table 7. 

A variety of processes have been used for the production of esters of acrylic (propenoic) acid, including the solvolysis of acrylonitrile with c. H2SO4 and an alcohol. The Reppe process, commercialized by BASF and associated companies, is based on the reaction of acetylene with carbon monoxide, nickel carbonyl and an alcohol. However, the last U.S. operator of this process commissioned a propylene oxidation plant in October, 1982. 

A preliminary evaliiation shows that a process based on Scheme II is advantageous with respect to the method using pinified preformed hydrogen peroxide (72). It requires, however, that both the hyckogen peroxide and the propylene oxide plants are located in close proximity to each other. 

Modern propylene oxide plants in which the chlorohydrin route is followed have reached a close integration of the chlorine cycle with a conventional chlor-alkali plant. 

Figure 6.12.5 Flowsheet of a propylene oxide plant using the chlorohydrin process. Adapted from Kahlich eta/. (2000) and Fedtke eto/. (1992).

Although some very minor manufacturers of acryhc acid may still use hydrolysis of acrylonitrile (see below), essentially all other plants woddwide use the propylene oxidation process. 

Propylene oxide-based glycerol can be produced by rearrangement of propylene oxide [75-56-9] (qv) to allyl alcohol over triUthium phosphate catalyst at 200—250°C (yield 80—85%) (4), followed by any of the appropriate steps shown in Figure 1. The specific route commercially employed is peracetic acid epoxidation of allyl alcohol to glycidol followed by hydrolysis to glycerol (5). The newest international synthesis plants employ this basic scheme. 

Synthesis. The total aimual production of PO in the United States in 1993 was 1.77 biUion kg (57) and is expected to climb to 1.95 biUion kg with the addition of the Texaco plant (Table 1). There are two principal processes for producing PO, the chlorohydrin process favored by The Dow Chemical Company and indirect oxidation used by Arco and soon Texaco. Molybdenum catalysts are used commercially in indirect oxidation (58—61). Capacity data for PO production are shown in Table 1 (see Propylene oxide). 

The hydroperoxide process involves oxidation of propjiene (qv) to propylene oxide by an organic hydroperoxide. An alcohol is produced as a coproduct. Two different hydroperoxides are used commercially that result in / fZ-butanol or 1-phenylethanol as the coproduct. The / fZ-butanol (TBA) has been used as a gasoline additive, dehydrated to isobutjiene, and used as feedstock to produce methyl tert-huty ether (MTBE), a gasoline additive. The 1-phenyl ethanol is dehydrated to styrene. ARCO Chemical has plants producing the TBA coproduct in the United States, Erance, and the Netherlands. Texaco has a TBA coproduct plant in the United States. Styrene coproduct plants are operated by ARCO Chemical in the United States and Japan, Shell in the Netherlands, Repsol in Spain, and Yukong in South Korea. 

Production of propylene oxide in the United States in 1993 was estimated at 1,240,000 metric tons, and as having a 10-yr average aimual growth rate of 3.9% (229). Projections were for continued growth at about 4%/yr. Producers include Dow Chemical s chlorohydrin plants in Ereeport, Texas, and Plaquemine, Louisiana, and ARCO Chemical s hydroperoxide plants in Bayport and Chaimelview, Texas. Texaco started up a 180,000-t/yr plant in Port... 

Two options are being developed at the moment. The first is to produce 1,2-propanediol (propylene glycol) from glycerol. 1,2-Propanediol has a number of industrial uses, including as a less toxic alternative to ethylene glycol in anti-freeze. Conventionally, 1,2-propanediol is made from a petrochemical feedstock, propylene oxide. The new process uses a combination of a copper-chromite catalyst and reactive distillation. The catalyst operates at a lower temperature and pressure than alternative systems 220°C compared to 260°C and 10 bar compared to 150 bar. The process also produces fewer by-products, and should be cheaper than petrochemical routes at current prices for natural glycerol. The first commercial plant is under construction and the process is being actively licensed to other companies. 

Montoro A process for making styrene and propylene oxide. Named after the eponomous company. The process was to be used in Repsol Quimica s plant in Tarragona. 

The dominant share of styrene production comes from dehydrogenation of EB in plants like that shown in Figure 8-5. Some comes as a coproduct in propylene oxide/styrene plants. An even smaller amount is recovered from the gasoline fraction of olefins plants cracking heavy liquids. 

A few plants are designed to produce styrene from EB but as a coproduct with propylene oxide (PO). In this process, EB is oxidized to a hydroperoxide (A in Figure 8—8) by bubbling air through the liquid EB in the presence of a catalyst. Hydroperoxides are, by their nature, very unstable compounds (one of the reasons that bleach, another hydroperoxide, works so well). So exposure to high temperatures has to be limited. The reactions are usually run at about 320°F and 500 psi pressure. Heat exchangers and multiple vessels are used to control the temperatures. Pressures are not critical in this process. 

You have to talk about propylene oxide and propylene glycol after ethylene oxide and glycol. Its not that the chemical configurations are so similar (they are), or that the process chemistry is about the same (it is). The Fact is that much of the propylene oxide is now made in plants originally designed and constructed to produce EO, not PO. As you read in the last chapter, the chlorohydrin route to EO was abandoned by the 1970s in favor of direct oxidation. At the same time, the EO producers found that the old EO plants were suitable for the production of PO and certainly the cheapest hardware available to satisfy growing PO demands. 

The epoxidation of propylene to propylene oxide is a high-volume process, using about 10% of the propylene produced in the world via one of two processes [127]. The oldest technology is called the chlorohydrin process and uses propylene, chlorine and water as its feedstocks. Due to the environmental costs of chlorine and the development of the more-efficient direct epoxidation over Ti02/Si02 catalysts, new plants all use the hydroperoxide route. The disadvantage here is the co-production of stoichiometric amounts of styrene or butyl alcohol, which means that the process economics are dependent on finding markets not only for the product of interest, but also for the co-product The hydroperoxide route has been practiced commercially since 1979 to co-produce propylene oxide and styrene [128], so when TS-1 was developed, epoxidation was looked at extensively [129]. 

Biological. Bridid et al. (1979) reported BOD and COD values of 0.17 and 1.77 g/g using filtered effluent from a biological sanitary waste treatment plant. These values were determined using a standard dilution method at 20 °C for a 5 d period. When a sewage seed was used in a separate screening test, a BOD value of 0.20 g/g was obtained. The ThOD for propylene oxide is... 

There are two important methods for the manufacture of propylene oxide, each accounting for one half the total amount produced. The older method involves chlorohydrin formation from the reaction of propylene with chlorine water. Before 1969 this was the exclusive method. Unlike the analogous procedure for making ethylene oxide from ethylene, which now is obsolete, this method for propylene oxide is still economically competitive. Many old ethylene oxide plants have been converted to propylene oxide synthesis. 

The activity of titanium based catalysts for the oxidation of organic compounds is well known. Wulff et al. in 1971 [1] patented for Shell Oil a process for the selective epoxidation of propylene with hydroperoxides like ethylbenzene hydroperoxide (EBH) or tertiary-butyl hydroperoxide (TBH) with the use of a catalyst made of Ti02 deposited on high surface area Si02. A Shell Oil plant for the production of 130,000 tons/y of propylene oxide at Moerdijk, Holland, is based on this technology. 

One US plant manufd, since about 1948, Gc starting with petroleum, chlorine and caustic soda. At first a mixt of ethylene- and propylene oxides was obtd and this was treated with Na hypochlorite (obtd from NaOH+Cl2) and then hydrolyzed with NaOH. (Ref 15)... 

Explosion at Olin Mathieson. A blast in the propylene oxide-ethylene glycol area of Olin Mathieson s Brandenburg, Ky org chemicals, plant injured 29 persons and caused an esti- mated 8 million dollars damage in April 1962. 

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