Technology
New process simplifies isoprene synthesis Japan's Takeda estimates its isobutene/formaldehyde route has capital cost edge of about 10% over competitive methods Michael K. McAbee Architect Mies van der Rohe's famous dictum, "less is more, " doesn't stop with the whisker-clean buildings he designed by its use. Cutting out steps in the synthesis route to a major commercial chemical is another instance—and the "more" here is not style, but money. Takeda Chemical Industries' new single-step isoprene synthesis from isobutene and formaldehyde (C&EN, Sept. 18, page 13) could well be an example. For a plant of given size, the Japanese firm estimates its route has a capital cost edge on the order of 10%, compared to any current commercial isoprene synthesis. A molecule each of isobutene and formaldehyde will condense to form a molecule of isoprene and one of water— an appealingly simple route, but one that in previous attempts at exploitation ran afoul of expensive problems like poor yields and short catalyst life. For industrial use, isobutene/formaldehyde routes such as that developed by Institut Français du Pétrole add another step. A cyclic intermediate is first formed, then cracked to isoprene, formaldehyde,
and water. (Competitive synthetic routes such as the SNAM and Goodyear/Scientific Design processes are also multistep routes using other raw materials.) Catalyst selection and development, department head Kenji Naito of Takeda's research laboratories tells C&EN, were the crux of the six-year project to base a practical process on the singlestep isobutene/formaldehyde route. Takeda, best known as Japan's largest pharmaceutical firm, became involved in isoprene process design through cooperation with the government-related Institute of Physical & Chemical Research in Tokyo, where the initial catalytic studies were made. Takeda's part was to amplify the catalysis study and to design a process around it. The company's plan is to supply process users with catalyst. The catalyst system will be excluded from technology transfers to users. The material used, says Mr. Naito, hasn't been reported previously as a catalyst. A recent Takeda patent (U.S. 3,662,016) indicates that the catalyst is a solid acid catalyst of silicon oxide and antimony oxide. According to the patent, addition of one of a list of metals as a minor ingredient enhances the conversion ratio of formaldehyde and /or the selectivity of the reacted formaldehyde to isoprene. Also, addition of aluminum as a minor ingredient, it says, prolongs the life of the catalyst. In Takeda's gas-phase reaction, which goes at 300° C. and nearly atmospheric pressure, catalyst life is about one year. The fixed-bed reactors must
operate cyclically in pairs—one on stream while the other is being airblasted to burn away coke and so regenerate the catalyst. A 60,000 metric-tona-year (of isoprene) unit would require a catalyst volume of 100 to 150 cubic meters, meaning several reactor pairs. Suitably sized reactors would operate on a cycle of about six hours on stream, six hours off. Catalyst cost per metric ton of product (including auxiliary chemicals) is put at about $5.50. Operating and cost data have been generated for about a year's time by a 170 kg.-per-day pilot plant. Feedstock isobutene is a stream of more than 95% isobutene concentrated by distillation or sulfuric acid extraction from spent C4 cut. tert-Butanol is an alternative feed, usable without change in operating conditions. It's dehydrogenated to isobutene in the reactors. Takeda claims lower raw material cost than the two-step synthesis, due to smaller consumption of methanol (as formaldehyde feedstock). Overall capital cost of a 60,000 metric-ton-a-year plant—assuming sulfuric acid extraction of isobutene from spent C4, silvercatalyst production of formaldehyde, and Japanese feedstock costs—is estimated at $10.7 million. Some 0.35 ton of by-product oligomers is formed per ton of isoprene made. Takeda has designed its own separators for feedstock recovery, and expects them in full-scale operation to cut total electric power requirement for the process by more than a third, compared to use of standard separators with the process. Cooling water de-
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Oligomer bottoms Oct. 16, 1972 C&EN
15
mand, though, is one third higher and steam load goes up by about 60%. Final product is more than 99.5% isoprene, containing under 3 p.p.m. cyclopentadiene and under 10 p.p.m. piperylene. ci's-l,4-Polyisoprene made from its monomer, Takeda maintains, has cis content as high as that made via the IFP two-step route or the Goodyear/SD three-step synthesis from propylene.
Dow tests backfilling method in coal mines If schedules are met, a start will be made late this week on a project that should relieve at least some worries of residents of Scranton, Pa. Dowell division of Dow Chemical will begin backfilling abandoned coal mines underlying a section of Scranton and threatening the area with subsidence. The operation is a scaled-up demonstration of a technique developed by Dowell. It is being carried out under a $900,000 contract from the U.S. Department of Interior's Bureau of Mines. The project facing Dowell consists of two abandoned mine strata—the waterfilled Clark bed about 200 feet beneath the surface, and the partially waterfilled New County bed, about 140 feet down. The method will thus get a test in both wet and dry mine areas.
Eureka Bank of mine refuse (above railroad) will be used to backfill mine voids At the same time, Scranton will be getting rid of an eyesore—the so-called Eureka Bank, a 100-foot pile of coal, rock, and dirt near the site. Since the project will remove two thirds of the bank, valuable real estate should also be reclaimable. Two backfilling methods have been used in the past for abandoned mines, not very successfully. In one method— controlled flushing—slurry is pumped into the mine and distributed there by workmen. Although effective when it can be used, it is decidedly uneconomical and requires conditions allowing workmen to descend into the mine. The other method—blind flushing—is simply a technique in which material is poured down a hole until the mine won't take any more. A conical fill usually results, leading to inadequate point support of the mine roof. Many boreholes must be used.
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Dowell's technique is called hydrostatic pumping. In initial tests in 1970 at Rock Springs, Wyo., the company found it could pump a slurry of water and crushed fill into a mine cavity at relatively high velocity. Fill deposits in the mine under the borehole but never quite reaches the mine roof. By controlling velocity, the company is able to keep pumping in slurry, which continues to travel over the pile of fill extending it outward in all directions through the mine. Dowell isn't sure how far slurry can be moved out from a single hole (assuming no blockage by mine walls or the like) since in its tests it hasn't reached a limit. At Scranton, Dowell has installed water wells in the Clark bed and will draw the water off for blending with crushed culm from the Eureka Bank. Slurry will be pumped back at about 2000 cubic yards of culm per day, a rate limited by the crushing rate. (Empire Contracting Co. has a separate Bureau of Mines contract for crushing the culm.) Using one borehole for the Clark bed and four for the New County bed, Dowell will, after about 30 weeks, have injected 177,000 cubic yards of fill into the Clark bed and 123,000 cubic yards into the New County bed.
Search system for mass spectroscopists For the past nine months, some 100 mass spectroscopists have been putting to the test a conversational mass spectral search and retrieval system developed at the National Institutes of Health, Bethesda, Md. Now that it has proved successful, the system's developers are hoping to broaden its use as far as possible. They are offering the service and computer time free—other than the cost of the telephone calls to tie users into the computer. There's no reason 1000 or more scientists couldn't be using the system, says Dr. Stephen R. Heller of the division of computer research and technology. The aim of the system's developers—Dr. Heller, along with Dr. Henry M. Fales and Dr. G. W. A. Milne of the National Heart and Lung Institute's chemistry laboratory—is to see if the system is indeed of broad usefulness and should be "put into production." Continued on page 18
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C&EN Oct. 16, 1972
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If the system proves useful with a wide user audience, the developers ex pect that it would be transferred to a commercial computer network, and NIH would bow out. In that case, users would pay regular fees for use of the network and probably a royalty that would go to the Mass Spectrometry Data Centre at Aldermaston, Berks., England, for maintenance of the data base. The heart and lung institute pro vides the financial support. For its data base, the NIH group has relied primarily on the Aldermaston file and has spectra of some 9000 com pounds. According to Dr. Heller, Alder maston has indicated it will be shipping another 5000 spectra within the next few months. As new spectra are added to the file, in addition to the basic data, structural information in the form of Chemical Abstracts registry numbers is being included. These additions will enable users to use a new and different type of search procedure called substructure searching—a method of finding chemi cal groups, fragments, or substructures imbedded in a chemical structure. The system offers users seven search options: peak and intensity search, molecular weight search, molecular formula search (complete or imbedded), molecular weight and peak search, molecular formula and peak search, molecular weight and molecular formula search, and spectrum printout. In addi tion, a user is able to type in from his terminal any comments or complaints to the NIH developers. And he can choose to receive any current news or information about the system.
A final option the user can exercise is to add spectra of his own. As the sys tem is now set up, the developers would send such spectra to Aldermaston for inclusion in its master file. NIH would then receive the data back from Alder maston as an update and add it to the data bank. The computer program is set up so that a user can carry out his search by interacting with the computer in con ventional language. For example, to call in a particular search program, a user would type "PEAK," or " M W , " or another program code depending on which he wanted (to comment or com plain, the code is "CRAB"). For a peak search, the computer would ask for an intensity range factor and then for a peak and intensity. The user would provide these, and the computer would respond with how many spectra were found in the data file with that peak and intensity. Narrowing down the choices by supplying other peaks and intensities, the user would finally end up with a small number of references for which he can have the chemical names printed out [Anal. Chem., 44, 1951 (1972)]. Experience so far has shown, Dr. Heller says, that a normal search uses only two to six seconds of computer time. In conducting a search, the aver age user spends five to 15 minutes at his terminal. Potential users of the system can find out how to gain access and can get a copy of the instruction manual from Dr. Fales, National Heart and Lung Institute, Bldg. 10, Room 7N-316, Bethesda, Md. 20014.
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18 C&EN Oct. 16, 1972
New macromolecular science institute dedicated Some 400 scientists gathered in Midland, Mich., late last month for the for mal dedication of the Midland Macromolecular Institute, an independent, privately funded laboratory devoted to basic research in macromolecular science (C&EN, Oct. 26, 1970, page 39). MM I was established by the Michi gan Foundation for Advanced Research "to do something for basic research in the U.S. Midwest," according to MFAR president H. D. (Ted) Doan. MFAR —a nonprofit organization supported by contributions from three Midlandbased family foundations—will provide an annual $500,000 grant for nine years; hopes are that other groups will also furnish financial support. MM I will also do contract research for industry, government, or other institutions, but only if the results can be made public not more than two years after ter mination of the contract. MM I director Hans-Georg Elias notes that a staff of three senior scientists and six postdoctoral workers has been assem bled. Dr. Elias adds that MM I will also carry on educational activities.
