Rare earths show promise as antiknocks Rare-earth metals and their com pounds could well replace tetraethyllead as antiknock additives for motor fuels. Preliminary testing of several such compounds at the Air Force's Aerospace Research Laboratories at Wright-Patterson Air Force Base, Ohio, indicates that some of the com pounds are better than TEL in some applications. In other applications they are not as good but encouraging. According to Dr. Robert E. Sievers, the senior scientist who directed inves tigation of the rare-earth antiknock compounds, development of a suitable replacement for TEL is a matter of crucial importance for the Air Force and for the average motorist. Unless a suitable substitute is developed, the only alternative is to increase the aromatics content of gasolines. And this approach may be intolerable because aromatics yield undesirable engine emissions. Moreover, the refinery in vestment required to increase aromat ics production probably would increase the price of gasolines, and would fur ther drain dwindling natural resources that have greater value as chemical raw materials. Dr. Sievers and his associates have surveyed the properties of rare-earth chelates and find that a number of them are effective antiknock com pounds. The most noteworthy com pounds contain cerium, and the best compound discovered to date is cerium ( 2,2,6,6-tetramethyl-3,5-heptanedionate) 4 , or Ce(thd) 4 . Tests with
Ce(thd)4 have been carried out with two types of engines, supercharged and conventional. The supercharged engine simulates an aircraft engine during takeoff. Two different fuels tested with Ce(thd)4 in this engine showed better performance than with TEL. The results of the tests conducted in conventional vehicle engines were less encouraging but still good. Used in a synthetic fuel composed of 80% isooctane and 20% heptane, Ce(thd)4 exhib its significant antiknock properties but less than TEL at all concentrations. In a full-boiling-range fuel, containing 19.7% aromatics, only slight antiknock activity was obtained from Ce(thd)4. However, if the engine's fuel heater is turned off, Ce(thd)4 has greater effect. Dr. Sievers concluded that it may be possible to improve the antiknock ef fect of Ce(thd)4 with minor changes in the operating condition of the engine. Road tests are being conducted but the results are not all in. Some prelim inary results suggest that Ce(thd) 4 may be more effective in road tests than first thought. One oil company is known to be testing Ce(thd)4 in a 1973 Ford Galaxie, Dr. Sievers says. In addition to its antiknock quali ties, Ce(thd)4 shows unexpected prom ise in reducing noxious engine emis sions. Dr. Sievers believes that this ef fect is due to catalysis by the Ce(thd)4. The effect is particularly noticeable in the reduction of hydrocarbon emis sions, although not enough tests have been run to warrant firm conclusions.
carbon in water? Β :
total organic carbon volatile organic carbon total carbon Dohrmann's DC-50 organic analyzer makes of these measurements accurately and rapidly. Based on proven methods, it avoids interferences and undesirable pyrolysis re actions that historically have resulted in significant errors. Here's why the DC-50 is the complete solution for the analysis of carbon in water: Four-digit presen tation shows carbon content directly in mg/liter or ppm. No recorder needed! E M E N T . A single sample injection gives either Organic Car bon or Total Carbon content directly, not by difference. INDEPENDENT MEASUREMENT Volatile Organics are determined sepa rately from Total Organics to aid in source identification. Deter mines important, lightweight volatiles such as low molecular weight alcohols and ke tones, normally lost by acidification and sparging. 5 minutes per determination repeatability of ± 1 m g / liter or ± 2% 1 to 2,000 mg/liter (ppm) without dilution $7,500, including start-up assist ance and operator training E P A E V A L U A T E D : Newsletter # 1 5 Oct. 1972 AQCL, N E R C , E P A Cincinnati, Ohio 45268 Contact: D O H R M A N N Division, Envirotech Corporation, 1062 Linda Vista Ave. Mountain View, CA 94040 (415)968-9710
ENVIROTECH Robert Bausman, Dr. Robert Sievers, Dr. Karl Scheller (front), Robert Tischer, and Dr. Kent Eisentraut (left to right) observe an engine test of a new lanthanide antiknock additive that could replace tetraethyllead in gasoline CIRCLE 24 ON READER SERVICE CARD March 25, 1974 C&EN
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Du Pont instruments azm
Measure surface characteristics to tell if children's pajamas are durably flame retardant. New Federal laws require children's sleepwear to be "durably" flame retardant, through repeated washing. Generally durable flame retardant treatments have been achieved by empirical experimentation. Now Du Ponts Electron Spectrometer can provide a more definitive analysis of these treatments. ESC A (Electron Spectroscopy for Chemical Analysis) is highly sensitive to surface chemistry; it non-destructively analyzes organic and polymer substances, detecting chemical bonding characteristics of the uppermost layers. For example, THPOH* is a common flame retardant for cotton. When applied to fabric, and treated with a nitrogenous material (NH 3 , etc.), it is still "non-durable." Figure 1 shows a mixture of phosphorus 4-3 and + 5 species in a THPOH/ NH3-treated sample measured by ESCA. Figure 2 is an ESCA-measured sample further treated with H 2 0 2 / indicating predominantly phosphorus + 5 species, in the more durable finish. Flame retardancy is just one of many applications for ESCA. If you need to know more about the composition and characterization of surfaces you deal with—catalytic, polymeric, metallic, circle 38 on Reader Service Card.
Help prevent $100,000 shutdowns of black liquor furnaces. A major impetus for continuous monitoring of SO2 is the need to record sulfur emissions, to comply with existing and proposed State and Federal Regulations. But a significant benefit in using on-line photometric monitoring lies in keeping furnace equipment operative. Process monitoring with the Du Pont 460 Photometric Analyzer System enables you to control operating conditions more effectively, avoiding downtime. The Du Pont 460 System uses the UV absorption technique. It is highly selective and reliable, with minimum sample conditioning, responds rapidly, and is sensitive to ± 1 ppm. If S 0 2 control is a problem in your process, look into the Du Pont 460. It could save you a lot of costly downtime. For more information, circle 39 on Reader Service Card. Du Pont Instruments—a growing line of scientific, process, and biomedical instrumentation. Du Pont Company, Wilmington, DE 19898. tetrakishydroxymethylphosphonium hydroxide
MPÔNÎ) instruments "EG. US. PAT OF*
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C&EN March 25, 1974
Any substitute for TEL will have to have properties other than the ability to suppress engine knock. The substitute must be soluble in gasoline and insoluble in water. It must be stable to light and heat in storage, and should not foul any catalytic converters that may be used in the future. According to Dr. Sievers, Ce(thd)4 meets all these requirements. It also has acceptable hardness (5.0 on the Moh scale)—comparable to other materials tried in the past. This is a major requirement in controlling engine wear. A big advantage of Ce(thd)4 is low toxicity. Under normal conditions of inhalation or ingestion of cerium, the compound is virtually nontoxic. Dr. Sievers says that, even when it was fed to test animals for 90 days in dosages equivalent to 1% of the total diet, no detectable organ damage was observed. At high concentrations of cerium and its compounds there is only mild toxicity, much less than with TEL. The basic raw materials from which Ce(thd)4 is made are rare-earth ores, neopentanoic acid, and acetone. It isn't necessary to use highly purified rare earths to make Ce(thd)4· At the present time, Dr. Sievers says, mixed rareearth chlorides cost about 20 cents per pound and may become even cheaper in the future as by-products from the production of thorium for nuclear fuel. The rare earths are not really rare, and U.S. reserves would be capable of supplying the needed cerium for at least as long as petroleum supplies last. There are extensive deposits of rare earths in California, Tennessee, Idaho, South Carolina, and Florida. Ce(thd)4 can be synthesized in quantitative yield by the inexpensive solvent extraction technique. The process can be carried out either continuously or in batch. Neither method requires heat or special equipment. The low toxicity of Ce(thd)4 also eliminates the need for elaborate safeguards during manufacture. Dr. Sievers regards Ce(thd)4 as the first step in the investigation of possible substitutes for TEL. Work is continuing with other promising compounds, including naturally occurring beta-ketones from wheat straw and other agricultural wastes. At the moment Ce(thd)4 has not been fully evaluated as an antiknock additive. However, the preliminary results are encouraging and Dr. Sievers believes that an aggressive research effort should be started to evaluate Ce(thd)4 and other compounds that show promise of replacing TEL. Meanwhile, a patent (U.S. 3,794,473) on Ce(thd)4 has been issued to Dr. Kent J. Eisentraut and Robert L. Tischer, along with Dr. Sievers, and assigned to the Air Force. Licenses are being negotiated. Molybdenum Corp. of America has acquired exclusive rights to make and sell the additives under patents that may issue from applications filed in 14 foreign countries.
