Technology and the formation of ethyl acetate. The iodide promoters do not appear to carry over into the products. According to Knifton, acetic acid homologization appears to be sensitive to at least four operating parameters: ruthenium and methyl iodide promoter concentrations, syngas composition, and operating pressure. In general, under the experimental conditions the reactions are first order with respect to the initial ruthenium concentration. Yields of higher acids are increased with higher promoter (methyl iodide) concentrations, but there are complications introduced by a tendency for the corresponding esters to form, particularly at low promoter/catalyst ratios. In the case of acetic acid homologization, ethyl acetate and ethyl propionate become the principal products at low iodide concentrations. Despite stoiohiometry to the contrary, the maximum yield of propionic acid from acetic acid is achieved with a carbon monoxide/ hydrogen ratio of 1:1. No acetic acid homologization is observed without hydrogen; homologization generally increases with increased hydrogen concentration. There is also a parallel increase in the generation of carbon dioxide, ethane, and propane in the off-gases. The maximum yield and selectivity of propionic acid from acetic acid occur at an operating pressure of about 100 atm. Within the pressure limitations of the equipment, yields of butyric and valeric acids continue to rise at higher pressures. The development work at Texaco has concentrated on acetic acid reactants. But, Knifton says, the process is generally applicable to the higher acid reactants. For straight-chain acids, the homologs generated are the corresponding acids containing one more carbon atom in the chain. There are traces of branched-chain isomers in the product mixture but the straight-chain isomers dominate. Increasing the chain length does not drastically affect conversion or yield with a given catalyst/promoter combination. Homologization with branchedchain acids often is accompanied by structural rearrangements. In particular, there is a tendency to generate tertiary acids in which the alphacarbon atom is bonded to three alkyl groups. In all cases, straight and branched chains, the by-products are carbon dioxide, water, and the corresponding hydrocarbons. Knifton explains t h a t labeling studies with carbon-13 and deuteri28
C&EN April 27, 1981
um were used to understand the mechanism better and to confirm the carbon source for the higher-molecular-weight products. The results appear to be consistent with the notion that carbon monoxide addition to the carbonyl carbon of the acid substrate is the dominant step in the reaction sequence. The mechanism for the homologization of carboxylic acids with ruthenium catalysts and iodide promoters has not been established definitely. However, Knifton offered a leading candidate that has been supported by independent research outside Texaco. The ruthenium-catalyzed homologization suggested by Knifton is probably in competition with at least four other alternative reaction pathways leading to the formation of hydrocarbons, aliphatic alcohols, higher-molecular-weight acids, and other rearranged products. As had been noted in previous research dealing with syngas generation of longer-chain products, the effectiveness of ruthenium catalysts is somewhat dimmed by their great ability to promote hydrogénation. From the viewpoint of producing hydrocarbons this is a desirable characteristic. However, if the higher acids are desired it is a handicap. Alternative mechanisms for the reaction system are being considered by Knifton's group using other substituted acids. An area of synthesis closely related to the homologization of higher carboxylic acids is the generation of vicinal glycol esters from syngas. Knifton also described work on this synthesis, particularly with respect to ethylene glycol acetate esters prepared with ruthenium catalysts. The aliphatic carboxylic acids, such as acetic acid, are simultaneously the reactant and reaction medium for reactions with carbon monoxide and hydrogen. The general synthesis is believed to be represented by the equation 2CO + 3H2 + 2RCOOH—• H2OOCR + 2H 2 0 H2OOCR Acetic acid solutions of ruthenium(III) salts combined with large cationic species such as quaternary phosphonium and ammonium salts are the preferred catalytic precursors. The major by-products of the synthesis are methyl and ethyl acetate. Thermodynamic considerations
favor the formation of the acetate esters from synthesis gas in acetic acid media over direct synthesis of ethylene glycol by rhodium catalysis. The formation of glycol acetate esters is believed to be the result of catalysis by a solubilized anionic ruthenium carbonyl species. The reaction is influenced considerably by cocatalyst species, pressure, and other factors. In particular, the ruthenium hydrocarbonyl cluster [HRu3(CO)n]"~ has been detected by NMR spectra. Knifton says that the presence of such large cationic species as RiuP"1" should help stabilize the ruthenium cluster, but substitution of such solvents as acetic anhydride, which has a high dielectric constant, does not noticeably increase selectivity to glycol diacetate. D
Hypochlorite process eliminates discharges Separating inorganic compounds by the process of fractional crystallization is a slow, time-consuming experiment when practiced in the laboratory. But when an inorganic chemicals producer uses it in a manufacturing process to avoid discharge of effluents, it is an advance in chemical technology. That's just what Potasse et Produits Chimiques, a subsidiary of Rhône-Poulenc located in Thann, France, is doing. The company has developed a novel "clean technology" process that produces neutral calcium hypochlorite with a 75 to 80% active chlorine content and with total recycling of the reaction medium. It is a nonpolluting process in which there is no systematic discharge of wastes. The reaction medium and mother liquors are totally recycled. The process thus eliminates discharge of hypochlorite into landfills, and leaching into groundwater is avoided. Before the process was put into use, more than 50% of the byproduct materials—sodium and calcium chlorides, chlorates, and hypochlorites—were placed in landfills or discharged as effluents. Neutral calcium hypochlorite is a solid, stable product with a high concentration of active chlorine that is widely used as a germicide for eliminating undesirable microbial activity in swimming pools. Discharges from the production of calcium hypochlorite can result, for example, from accidental or periodic formation of suspensions of calcium
hypochlorite and sodium chloride crystals, which are hard to separate. The French process makes use of fractional crystallization to separate sodium chloride from the calcium hypochlorite product found in the reaction medium. Sodium chloride crystals thus produced are about y40 the size of calcium hypochlorite crystals. The two thus are separated easily by décantation with simple, small-volume equipment. In the process, three raw materials—slaked lime, caustic soda, and chlorine—are converted to neutral calcium hypochlorite, the desired product, and a by-product sodium chloride. Slaked lime containing at least 97% calcium hydroxide is suspended in recycled mother liquor, called dibasic mother liquor, that contains a low concentration of hypochlorite ion and is almost saturated with respect to chloride ion. The milk of lime (calcium hydroxide suspension) formed is added simultaneously to the mother liquors resulting from separation of the two products. The recycled hypochlorite ion makes possible the precipitation of dibasic calcium hypochlorite with the lime. The grain size of this hypochlorite—Ca(C10)2 · 2Ca(OH)2—is controlled by the presence of a bed of preformed crystals during precipitation. This dibasic suspension is concentrated to collect the dibasic
mother liquor for subsequent preparation of the milk of lime and washing of the sodium chloride by-product. The thickened dibasic suspension and caustic soda are chlorinated simultaneously: Ca(C10)2. 2Ca(OH)2 + 4NaOH + 4C12 — 3Ca(C10)2 + 4NaCl + 4H 2 0 This reaction is conducted in the presence of preformed neutral calcium hypochlorite and sodium chloride crystals at a temperature not exceeding 20° C. The two types of crystals formed are separated with a slow-agitation decanter. The suspension, enriched with sodium chloride, is treated with part of the dibasic mother liquor collected during concentration of the dibasic suspension to dissolve most of the calcium hypochlorite produced. After drying or filtration, the salt can be reused in electrolysis (to make chlorine and caustic soda). The resulting mother liquor, called clarifying mother liquor, is recycled to precipitation of the dibasic compound. The hypochlorite suspension is dried or filtered, and the resulting mother liquor, called neutral mother liquor, also is recycled to precipitation of the dibasic compound as well as to chlorination. The hypochlorite cake is granulated and dried. D
New catalysts cut polyolefins costs Cost cutting by polyolefin makers is receiving a boost from new high-yield, high-efficiency catalysts developed jointly in Italy and Japan. In addition to saving production costs, the jcatalysts have permitted process simplification and provided better products in the bargain. These improvements are expected to keep polyolefins competitive with other construction and fabrication materials for some time to come. At the recent national meeting of the American Chemical Society in Atlanta, Cipriano Cipriani, director of product development for El Paso Polyolefins Co., illustrated the improvements in catalysts and processes for polypropylene production. Most existing process variations, such as liquid and slurry, will benefit. In El Paso's case, the process in question was a bulk monomer process, which has been extensively upgraded with the introduction of a new catalyst system developed by Italy's Montedison and Japan's Mitsui in 1979. The exact composition of
Protein Functionality in Foods
the catalyst system hasn't been disclosed. Commercial trials with the improved catalyst system reveal that the deashing step in the older process can be eliminated completely along with the auxiliary solvent recovery and recycle systems. Nearly 65% of the total energy required by the older process was consumed in the solvent recovery system's distillation units. This energy requirement is eliminated. Consequently, makeup solvents and treatment chemicals are no longer needed. High polymer yields provided by the new catalysts eliminate the need for catalyst residue removal and cleanup. The improved yield is attributed to direct synthesis of at least 95% crystalline polymer, a considerable improvement over the older process. Total steam requirements were reduced 85%, with most of it being saved through elimination of the solvent recovery systems. Electrical energy consumption was simultaneously reduced 12%. D
ACS S y m p o s i u m Series N o . 147 John P. C h e r r y , Editor Southern Regional Research USDA
Center,
Based on a symposium sponsored by the Division of Agricultural and Food Chemistry of the American Chemical Society. Since functionality is such a high priority research area, this book will be useful to food processors, engineers, chemists, and physicists. This fourteen-chapter volume updates and presents new information on the physicochemistry of functionality, the roles of protein for improving the functional properties of foods, and the application of data from model test systems to actual food ingredients. CONTENTS Protein Functionality · Color · Flavor Volatiles as Measured by Rapid Instrumental Techniques · Texturization · Solubility and Viscosity · Adhesion and Cohesion · Gelation and Coagulation · Whippability and Aeration · Water and Fat Absorption · Emulsifiers: Milk Protein · Emulsification: Vegetable Proteins · Nutrient Bioavailability · Enzyme Modification of Proteins · Multiple Regression Modelling of Functionality
332 pages (1981) Clothbound $36.75 LC 81-97 ISBN 0-8412-0605Order from: SIS Dept. Box 49 American Chemical Society 1155 Sixteenth St., N.W. Washington, D.C. 20036 or CALL TOLL FREE 800-424-6747 and use your credit card.
April 27, 1981 C&EN
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