purine antimetabolites limits design of new drugs, Dr. Montgomery says. He suggests three knowledge limits on which design can be based. One of these is the amount of metabolism of purine analogs. Another is the mechanism of action of these analogs in how they affect cells. The third is the effects of alterations in the chemical makeup of the analog on the amount of metabolism and on the mechanism.
PETROCHEMICALS:
Clear Sailing at Taft Union Carbide's trouble-plagued complex at Taft, La., is entering a new phase of its short lifetime—smooth operation. All of the units are now running at capacity or at rates needed for current market demands, except for an acrylates unit being started up, says Carbide's chemicals and plastic operations division president, Robert D. Bower. In fact, Mr. Bower optimistically remarks, the Taft plant "is running as well as any plant in the chemical industry." Mr. Bowrer indicates that the major problems that plagued the Taft plant for more than two years were mostly solved by last August. Its operation since then has continuously improved, he says. Many lessons have been learned from the engineering, construction, and startup problems of the plant, Mr. Bower notes. Especially, he adds, plant officials have learned the importance of a stable system of utilities for a plant with new technology used in units larger than ever before built. Experience developed at Taft will be helpful in building and staffing the Carbide plant under construction at Ponce, P.R., Mr. Bower says.
Many of the problems at Taft were not caused by design, size, or technology, company officials explain. Personnel was stretched too thin initially, and the plant was staffed for computer control over the long term. Result: During startup of various units, the available staff couldn't handle all the "bugs" in the equipment. Timing caused other difficulties. Because of construction labor problems, completion of the basic-oleflns complex was a year late. It had to be started up at about the same time as was a peracetic acid complex that uses raw materials from the olefins complex. Now, except for the new acrylates unit, all of the plant's units have demonstrated full-capacity production, says George H. Daniels, plant manager. Currently, the plant is using as feedstock 12,000 barrels per day of a medium naphtha (250° to 400° F. boiling range), 3000 barrels per day of ethane, and 4000 barrels per day of propane. An all-naphtha feed could be used in the plant, the company says, but not an all-ethane feed, because the mixture from the cracking furnaces would be too low in density to permit the cracked-gases compressor to operate economically.
GASOLINE:
Tax on Lead The impact on the chemical industry of President Nixon's proposed tax of about 2.3 cents a gallon on leaded gasoline is uncertain at this time. Some oil and chemical company officials view the proposed additional tax as unlikely to go into effect soon. These officials point out that by the time the tax is in effect, gasoline may contain
THE CHEMICAL WORLD THIS WEEK
less lead alkyls because auto manufacturers will have modified car engines beginning with the 1971 models to require lower octane fuels. The proposed tax is actually $4.25 per pound of lead used in gasoline. If refiners use less lead alkyls in gasoline, as some plan to do this fall, the added tax per gallon will be less than 2.3 cents. Government officials arrive at the proposed tax of 2.3 cents a gallon by using an average of about 2.5 grams of lead (added as lead alkyls) per gallon of gasoline in the U.S. The first effect of the tax, if it significantly affects competitive positions of various gasoline marketers, will be to increase prices for aromatics. To make more aromatics for fuels containing small amounts of lead or no lead at all, refiners first will increase use of catalytic reformers that make aromatics and will increase operating severity when possible. Aromatics have relatively high octane values and are relatively less sensitive to the absence of lead alkyls to raise octane than are paraffins. Additional quantities of low-octane paraffins, which could be useful feedstocks for olefin units, will be made if more reforming is done. If the raffmate (largely paraffins) left after extraction of aromatics from reformate is used in olefin plants, there could be increased output of olefins for possible use in alkylate for gasoline. Alkylates of olefins and isobutane do not have as high an unleaded octane value as do aromatics, but the octane is high enough to be suitable for regular-grade gasoline. The net impact on supplies of olefins as raw materials for other chemicals and polymers could be mild over the long term.
Carbide's Taft plant produces these major volume products Product
Capacity (millions of pounds per year)
Ethylene^ Propylene b Butadiene Alkylamines Acrylates c Peracetic acid Peracetic acid derivatives Glyoxal Ethylene oxide Ethylene glycol Benzene Other a r o m a t i c s Glycol e t h e r s Ethyleneamines
500 250 95 100 200 120 200 100 350 300 100l1 103'1
:i
Wulff unit makes additional 16 million pounds per year. Also makes 8 million h pounds of acetylene. Current output; varies with feedstock. c Startup; not yet demonstrated capacity. d Millions of gallons per year. ° Varies widely depending on product mix. 18 C&EN JUNE 1, 1970
Carbide's Taft, La., complex consists entirely of large-scale units
