Precombustion system cuts smog, saves gas
CARBONYLATOR. Dr. G. Biale of Union Oil adjusts controls of oxidative carbonylator as Dr. K. L. Olivier (left) and Dr. D. M. Fenton look on
Union Oil finds new route to acrylic acid PETROLEUM Oxidative carbonylation of ethylene is a new route to acrylic acid de veloped by chemists at Union Oil Co. of California. Although the process hasn't been commercialized, possibili ties are good that it will be. The catalyst system used is closely akin to that used in the Wacker process to oxidize ethylene to acetaldehyde, and preliminary economic studies show the process to compete favorably with other routes to acrylic acid such as propylene oxidation. In addition to acrylic acid, major amounts of β-acetoxypropionic acid are coproduced, Dr. D. M. Fenton of Union Oil told a symposium on cata lytic oxidation of hydrocarbons. The β-acetoxypropionic acid can be counted as a useful product because on heating it cracks to give acrylic acid and acetic acid. The chief unwanted by-products are carbon dioxide, polymers, and very small amounts of propionic acid, vinyl acetate, and acetaldehyde. No net production or consumption of water occurs in the oxidative car bonylation process, but some water is produced by spurious oxidations in the regeneration of the palladiumcopper chloride catalyst. The catalyst system operates simi larly to that of the Wacker process. Palladium chloride becames reduced to zero-valent palladium as the car bon monoxide-ethylene system is oxi dized to make acrylic acid. The pal ladium is chlorinated and reoxidized later by reaction with cupric chloride, which is reduced to cuprous chloride. The cuprous chloride is converted to the cupric form with H Cl and oxygen. Other ingredients of the catalyst sys tem include lithium or sodium chloride 72 C&EN SEPT. 22, 1969
and acetate dihydrate. Ferric chloride and nitric acid are alternate cocatalysts for reoxidation of the palladium. The reaction is affected by a num ber of unusual variables in addition to temperature and pressure. Conver sion to acrylic acid is highest at about 138° C , but selectivity to acrylic acid is best at about 127° C , Dr. Fenton says. High ethylene pressure favors production of acrylic acid; high carbon monoxide pressure favors βacetoxypropionic acid, and, as might be expected, undesirable carbon di oxide. Drying agents, preferably acetic anhydride, help keep the acrylic acid: β-acetoxypropionic acid ratio high, sometimes 100:1, but with increased production of carbon dioxide. Inor ganic drying agents are generally less effective than acetic anhydride. Little water. No vinyl acetate or acetaldehyde forms when zeolite is the drying agent. This indicates that very little, if any, free water is present. It also implies that the water molecule produced by conversion of cuprous chloride to cupric chloride, as part of catalyst regeneration, is held by the catalyst system as a ligand, is trans ferred to the carbon monoxide mole cule, and ends up as part of the acrylic acid. Solvents for the reaction presented a problem which was solved by use of pivalic acid. Solvents boiling above acrylic acid are most desirable, but the reaction is slow in acids boiling higher than propionic. A mixture of pivalic and acetic acids plus acetic anhydride appears to be the best for maximum acrylic acid yield. Product recovery basically is by distillation. Acetic acid comes over first, followed by acrylic acid. The still bottoms include mixed anhy drides, pivalic and β-acetoxypropionic acids, catalyst, and polymer.
The Spanish conquistadores of old dreamed of finding El Dorado, a legendary place touted for its riches. It is somehow fitting, therefore, that, if a solution to the automobile-gener ated smog problem has been dis covered, it should originate in El Dorado, Calif. For it is in this little community, nestled in the golden hills beyond Sacramento, that Azure Blue Corp. is putting the finishing touches to a novel device that hopefully will rid Otto four-stroke gasoline engines of their noxious exhaust gases. Claims that Alvin W. Evans, the corporations president, makes for the ignition amplifying system are remark able. Examples: • Carbon monoxide is all but elim inated from exhaust gases. • There's a drastic slash in nitrogen oxides and hydrocarbons emission. • Fuel economy is boosted by a factor of some 20%. The claims, if correct, might have a very important effect on the use of antiknock additives. Mr. Evans main tains that his device would rule out the root cause of engine knock and thus eliminate the need for such additives. Moreover, the need for various grades of gasoline would be eliminated because the system's main combustion ignition "doesn't discriminate among different octane ratings of fuel," as Mr. Evans puts it. Dual ratio. A dual ratio carburetion system is at the heart of the development. From one carburetor a fuel-rich mixture (air-to-fuel ratio is about 6 to 8 pounds air to 1 pound fuel) goes to a precombustion chamber that's adjacent to the spark plug. Co in cidentally, a "leaner" mixture (airto-fuel ratio, 16:1 to 18:1) is fed to the main cylinder chamber. During the compression stroke, some of the lean mixture is forced into the precom bustion chamber where it mingles with the rich mixture, thereby readjusting the air-to-fuel ratio in the chamber to about 13.7:1, a ratio that's ideal for spark ignition. When spark ignition occurs, the combustion propagation rate creates a high pressure, forcing a flame front at sonic velocity into the main com bustion chamber. This fast-traveling flame front, coupled with the consider able turbulence that it generates, causes rapid and complete combustion of all fuel within the main chamber. The result is a reduction of hydro carbon content and the presence of excess oxygen in the burned gas. And because the time interval at which the burning gases are at peak tempera ture is extremely short, oxides of ni-
trogen haven't an opportunity to develop to the extent that they now do in conventional combustion systems, Mr. Evans explains. (In practice, the oxides of nitrogen are controlled by lowering the peak temperature at which the fuel burns in the cylinder. One way to achieve this is to run the fuel mixture rich and recirculate portions of the exhaust gas.) The concept of precombustion isn't a new one, says Mr. Evans, whose entire professional career has centered on the building of auto and aircraft engines. Numerous automotive engineers have looked into it from time to time over the past 30 years or so. He attributes the failure of the idea from reaching fruition to flaws in engineering design which he contends he has overcome satisfactorily during the four years he and his associates have worked on the problem. Scavenge. The auto and oil industries are spending sizable sums annually to bring down the level of noxious gases in auto emissions. Their approach in the main is to develop systems that scavenge these gases from the exhaust before they get into the atmosphere. The advances that have been achieved in this direction have brought emissions down considerably from a few years ago, when the average car was emitting some 1000 p.p.m. of hydrocarbons, 3.5% carbon monoxide, and 1500 p.p.m. nitrogen oxides. Last month, a number of advanced-concept vehicles were shown to President Nixon's quality control panel at San Clémente, Calif. These vehicles were all designed for emission levels substantially below present and proposed regulatory requirements. Mr. Evans and physicist Karl Morghen, who played an important role in helping perfect the Azure Blue system, cite some impressive data when discussing the gaseous makeup of exhaust emanating from an auto engine that uses the device. Hydrocarbon content, expressed as hexane, rarely exceeds 10 p.p.m. Carbon monoxide content, they claim, is so small that it can't be measured precisely. Oxides of nitrogen concentration range between 35 and 37 p.p.m. The new system allegedly results in a cooler-running engine so that crankcase oil should maintain its quality over a longer period. And the exhaust gases contain enough oxygen to support combustion of the crankcase gases at an appropriate point in the hot exhaust manifold. Another factor of the Azure Blue system ("the name reflects our desire to restore the sky to its healthy blue appearance") is that it can be built into the production of new gasoline engines with a minimum of retooling. All thafs involved is the fitting of a
cylinder head—or a pair of heads in the case of V-8 engines—that includes a composite assembly made up of a dual ratio carburetor and a dual ratio induction manifold. Retrofit. But how about the 97 million registered automobiles that are on the roads today? These, too, can be adapted by installing the company's Betro-Mizer units—so called because the units can be retrofitted and they are misers on gas. These include a spark plug of novel design in which the rich fuel mixture feeds in through the body of the plug. Ignition takes place in a precombustion chamber that's part of each plug. A pair of orifices directs the resulting flame into the main chamber in a fanlike pattern, through the center of which a jet "lance" protrudes. As plans now stand, Azure Blue
will have its Retro-Mizer kits on the market early next year, retailing for $65 each. Meanwhile, Mr. Evans is drawing up a licensing arrangement that will allow other companies to make the units on a royalty basis. The exhaust emission values that Mr. Evans propounds were garnered from a seven-mode test that Aerojet General Corp. in Sacramento made with a single-cylinder dynamometer. Within the coming weeks Mr. Evans expects to arrange for more extensive evaluations to be carried out at state and federal testing laboratories. Pending their outcome, the attitude of most automotive engineers toward the Azure Blue device will remain one of open skepticism, since multicylinder engines under field operating conditions generally give quite different values, they point out.
Fertilizers can add to water pollution But banning all fertilizer use would triple food prices, USDA soil expert contends M
FERTILIZER A N D COIL,
"There are three kinds of pollution: actual, political, and hysterical." Thus did Dr. Victor J. Kilmer, TVA soils and fertilizer research chief, kick open the symposium on "Fertilizer Use and Water Quality." Little is known about the effects of fertilizer use on water quality, and the nature and extent of the problem have not been defined, he says. "This must be done through well-planned research. Otherwise, restrictive legislation based on faulty and inconclusive evidence is bound to be passed." The urgency of getting factual data
was brought home by Dr. Frank G. Viets, Jr., chief soil scientist for USDA's soil and water conservation research division at Fort Collins, Colo. He answered the question: Will controlled fertilizer use be necessary? His answer: "The question means will it be essential to limit the rate of fertilizer a farmer applies under the framework of state laws to meet the federal requirements on water quality? It is a good question because some leading scientists, often not too familiar with the needs of agriculture, have called for total bans on the use of fertilizer. Bills have been introduced into state legislatures calling for limitations on the amount of fertilizer a farmer can apply." Application. The rate of fertilizer
Land use affects nitrate content of soil and subsurface water Surface type
Virgin grassland Dryland Irrigated land (except alfalfa) Irrigated land (alfalfa) Feed lots Source:
NO3 soil content, 20-foot profile (Pounds per acre)
NO3 content in percolated water at water table (p.p.m.) Range Mean
0.1-19 5-9.5 0-36
90 261 506
11.5
79
9.5
1-44
1,436
13.4
0-41
7.4
11.1
USDA, Fort C o l l i n s , Colo.
SEPT. 22, 1969 C&EN 73
