hold about 3 grams of active ingredient. The release rate can be adjusted by varying the cell and pore sizes. For household-type "air fresheners," Accurel could offer both economic and perfor mance advantages over the gels currently used to hold and release the active agents, Armak says. In some cases, the active agent can be directly incorporated at the time of manufacture. For example, methyl nonyl ketone, a fairly effective cat repellent, is also a suitable solvent for making the microporous polymer. Ward Worthy, C&EN Chicago
Hydrogen peroxide used to oxidize propylene
Phillips Petro-Sulf ur Compounds. When your en gineers, research or other develop ment personnel need petro-sulfur compounds in individual or commercial quantities, contact Phillips. The leader in petrosulfur compounds. Mercaptans (Thiols)
Sulfides
Methyl Sulfide Ethyl Sulfide *Ethyl Mercaptan η-Butyl Sulfide *n-Propyl Mercaptan tert-Butyl Sulfide *n-Butyl Mercaptan Sec-Butyl Mercaptan Di- and *tert-Butyl Mercaptan Polysulfides Di-tert-Butyl Disulfide *n-Hexyl Mercaptan Di-tert-Dodecyl *n-0ctyl Mercaptan Disulfide *tert-Octyl Mercaptan Di-tert-Butyl *tert-Nonyl Mercaptan Polysulfide n-Decyl Mercaptan Sulfones *n-Dodecyl Mercaptan *Sulfolane *tert-Dodecyl (anhydrous) *Sulfolane W Mercaptan (3% water) *tert-TetradecyI *Sulfolene Mercaptan Miscellaneous *tert-Hexadecyl *Ethylthioethanol Mercaptan *Ethylthioacetate *Mixed Tertiary *2-Mercaptoethanol Mercaptans *Available in commercial volumes.
For more information write: Specialty Chemicals 14C4, Bartlesville, Oklahoma 74004. Or call 918 661-4872
' PHILLIPS PHILLIPS CHEMICAL COMPANY The Performance Company
CIRCLE 24 ON READER SERVICE CARD 24
C&EN Dec. 11, I978
Direct oxidation of propylene to propyl ene oxide using hydrogen peroxide now is possible. Catalyst systems developed at Produits Chimique Ugine Kuhlmann (PCUK) are the key (C&EN, Dec. 4, page 17). The continuous, one-step process is simple and entails high selectivity and conversion rates. The new catalysts overcome adverse effects of coproduct water. They also overcome problems arising from hydrogen peroxide's insta bility, Dr. Jean P. Schirmann told the American Chemical Society's 34th Southwest Regional Meeting, held re cently in Corpus Christi, Tex. Schirmann is a member of a team at PCUK's research center in Lyons, France, that for the past seven years or so, has been seeking a way to oxidize olefins with hydrogen peroxide directly. But the new finding has wider implications, he be lieves. It could open the way to use hy drogen peroxide in reactions for which it cannot now be used. "The discovery could prove very im portant as far as the future of hydrogen peroxide is concerned," he says. It is no accident that chemists at PCUK should be working to boost hydrogen peroxide's fortunes. The company is one of the world's leading producers of the chemical. Oxysynthèse, a joint venture between PCUK and Air Liquide, has capacity for making some 176 million lb per year of it at a plant near Grenoble, some 40 miles from Lyons. Worldwide propylene oxide output now approaches 2 billion lb annually. The chlorohydrin process is the oldest still used by Dow Chemical and others and, indeed, by PCUK. It involves reaction of propylene with hypochlorous acid, followed by hydrolysis of the resulting propylene chlorohydrin with lime. Yield averages about 80%, but chlorine is costly, and there is the added expense of ensuring against damage to the environment. Oxirane Chemical, jointly owned by Arco Chemical and Halcon International, has been expanding propylene oxide production rapidly by a process Halcon developed some 10 years ago. Referred to as direct oxidation, it is more complex than the name suggests.
In this process, isobutane, or ethylbenzene, first is oxidized to the corresponding hydroperoxide. This hydroperoxide interacts with propylene, yielding propylene oxide and by-product alcohol. The alcohol is dehydrated to the olefin and then hydrogenated to isobutane or ethylbenzene for re-use. Or the olefin—isobutene or styrene, depending on the starting material used—may be sold as such. Although propylene oxide yield is better than 90%, the Oxirane method does entail a number of processing steps. Also, the economics of the process are strongly dependent on the viability of by-product markets, Schirmann points out. More recently, several companies have been exploring alternate paths to propylene oxide. In Belgium, Interox S.A., jointly owned by the U.K.'s Laporte Industries and Belgium's Solvay, in partnership with Carbochimique of Belgium, has been pilot-testing a system at Jemeppe, Belgium, for the past two years. This system centers on interaction of a carboxylic acid, such as propionic acid, and hydrogen peroxide to form the corresponding percarboxylic acid. This, in turn, reacts with propylene to give propylene oxide and the carboxylic acid, which is recycled. Bayer and Degussa, both of West Germany, together are working along similar lines. In PCUK's direct oxidation process, propylene reacts with hydrogen peroxide in a solvent and in the presence of a special catalyst system. Catalysts tested so far are derivatives of arsenic, boron, and molybdenum. The degree of selectivity is of the order of 95%. Buildup of water that accompanies the reaction doesn't present a problem. The low-boiling propylene oxide is stripped off. Solvent, together with unused hydrogen peroxide, is recycled. Schirmann doesn't specify reaction conditions or the precise nature of the catalysts. However, he does say that metaboric acid may be used. This acts in the dual role of catalyzing the oxidation and combining with the liberated water to form orthoboric acid. Dehydration of the latter removes the water, and the recovered metaboric acid is re-used. Schirmann notes that Union Carbide chemists at South Charleston, W.Va., also claim to have directly oxidized propylene to propylene oxide with hydrogen peroxide using an arsenic catalyst. However, in contrast to PCUK's method, which employs 70% concentration hydrogen peroxide, that of Carbide calls for hydrogen peroxide concentrations approaching 90%, he points out. Also, Schirmann notes that coproduct water adversely affects Carbide's arsenic catalyst. Further expansion of the use of hydrogen peroxide for direct oxidations will be the subject of an intensive research effort at PCUK in the years ahead, Schirmann says. "It is quite certain that such a simple agent must have other uses in the area of direct oxidation in general. Epoxidation, in our opinion, is only part of what can be done." D
