R. O. Butterfield

Transesterification kinetics of soybean oil 1

Transesterification of soybean oil (SBO) and other triglycerides with alcohols, in the presence of a catalyst, yields fatty esters and glycerol. Di- and monoglycerides are intermediates. Reactions are consecutive and reversible. Rate constants have been determined for each reaction with a computerized kinetic program. The effects of the type of alcohol, 1-butanol or methanol (MeOH); molar ratio of alcohol to SBO; type and amount of catalyst; and reaction temperature on rate constants and kinetic order were examined. Forward reactions appear to be pseudo-first order or second order depending upon conditions used. Reverse reactions appear to be second order. At a molar ratio of MeOH/SBO of 6:1, a shunt reaction was observed. Energy of activation was determined for all forward and reverse reactions under a variety of experimental conditions from plots of log k vs 1/T. Values ranged from 8–20 kcal/mol.

High-performance liquid chromatographic method for quantitation of free acids, mono-, di- and triglycerides using an infrared detector

Abstract Methyl ester, mono-, di- and triglyceride classes were separated and quantitated by high-performance liquid chromatography. Baseline separations were achieved on an amino-, cyano-bonded Partisil column with a gradient from hexane-chloroform (60:65) to hexane-chloroform-acetonitrile (25:65:35). The eluate was monitored by an infrared detector set at 5.72 μm, and peak areas were determined by computer integration. Methyl 9,10-dihydroxystearate was used as an internal standard. The total run time and recycling time was 35 min. A precision of 10% or better was obtained for all components, even at the 1% (w/w) level.

Preparation of 9,15-octadecadienoate isomers1

Linolenic acid was reduced with hydrazine to produce a mixture containing a max of dienoic acids. After methylation this mixture was separated into trienoic, dienoic, monoenoic, and saturated esters by countercurrent distribution (CCD) with acetonitrile and hexane. The dienoic ester was further fractionated by CCD with methanolic silver nitrate and hexane to separate purecis,cis-9,15-octadecadienoate and the equimixture ofcis,cis-9,12- and 12,15-octadecadienoates.Following isomerization of thecis,cis-9,15-octadecadienoate with selenium, the geometric isomers were fractionated by CCD with methanolic silver nitrate and hexane. Puretrans,trans and purecis,cis isomers were isolated, as well as an unresolved mixture ofcis,trans andtrans,cis isomers. The characteristics of these isomers and related compounds are compared as determined by CCD, IR absorption, and capillary gas-liquid chromatography (GLC).

Double bond analysis of dienoic fatty acids in mixtures

Mixtures of dienoic fatty acids such as occur in edible hydrogenated fat products cannot be analyzed by current methodology. A method of ozonization, reduction to alcohol fragments by sodium borohydride, gas chromatographic analysis for alcohol, alcohol ester, and internal dialcohol fragments, and computer resolution of a matrix of linear simultaneous equations, is described that gives the analysis of the diene isomers.

Analog computers and kinetics of hydrogenation

Investigations of the kinetics of consecutive reactions frequently require complicated calculations to determine specific reaction rate constants from experimental data. Analog computers permit a convenient empirical adjustment of rate constants in kinetic equations to match experimental results. Once an electronic network analogous to the chemical reaction system is set up, specific reaction rates can be determined by adjusting potentiometers, which are the analogs of the rate constants, until an acceptable fit of calculated and experimental data is reached. Applicability of a small analog computer to the kinetics of hydrogenation is presented.

Relative reduction rates of fatty acid isomers by hydrazine

Mixtures of fatty acids and of hydrocarbons have been reduced by hydrazine in ethyl alcohol solution at 50 C. Samples were removed during reduction for analysis and the relative reduction rates calculated by digital computer.cis-15-Octadecenoic acid is reduced 1.3 times as fast as itscis-9-isomer. No differences were found amongcis-6,9- and -12-octadecenoic acids.cis-3-Octadecene was also reduced 1.3 times as fast as thecis-9-isomer andcis-1-octadecene 8.6 times as fast. Elaidic acid was reduced 1.27 times as fast as oleic.

Calculation of catalyst selectivity in vegetable oil hydrogenation

The description of catalysts in terms of the rates of reactions they promote is now feasible. Several procedures have been published in the literature for determining selectivity of hydrogenation catalysts, particularly as ratios of reaction rates. The present contribution reviews these procedures, tests their performance with sample data, and compares their merits.

Competitive hydrogenation rates of isomeric methyl octadecadienoates

Determination of the relative reaction rates of isomeric methyl octadecadienoates is possible by competitive reduction of a mixture containing an inactive diene and a radioactively labeled isomer. The hydrogenation rate of methylcis-9,cis-12-octadecadienoate with platinum and nickel catalysts is compared to the hydrogenation rate of each of several isomers of methyl octadecadienoate, and the relative rate of the competitive hydrogenations is calculated by a digital computer. Methylcis-9,cis-12 linoleate is reduced the most rapidly of all the dienes studied. The relative rates of the positional isomers tend to decrease with the increasing number of methylene groups between the double bonds, except when one of the double bonds is in the more reactive 15 position. Comparison of the geometric isomers shows thattrans,trans diene is hydrogenated at a slower rate thancis,cis linoleate.

Micro vapor-phase hydrogenation monitored with tanden chromatography-radioactivity: III. Isomeric monoenes

Micro vapor-phase hydrogenation and radiotracer techniques have been utilized to investigate the effect of geometric configuration and double bond position on the rate of hydrogenation of octadecenoates. These techniques provide for simultaneously monitoring the time course of vapor-phase hydrogenation both for an essentially pure monoene isomer by thermal conductivity and for methyl oleate by radioactivity. The two hydrogenations proceed independently but have identical parameters of temperature, flow rate and catalyst activity. The experimental data are plotted, relative reaction rates are calculated and theoretical curves are drawn by a digital computer system with plotter accessory. Experiments with nickel catalysts indicate that rates of reduction are affected by both the position and configuration of the double bond.cis-15-Octadecenoate is reduced 1.4 times faster than itscis-9 isomer. Bothcis-9- and -12-octadecenoate are reduced at approximately equal rates.cis-9-Octadecenoate was reduced 1.4 times as fast as thecis-6 isomer. Oleate was reduced 1.27 times as fast as elaidate.

Diene-to-saturate shunt in fat hydrogenation

In matching experimental data to kinetic models for hydrogenation of methylcis-9,cis-15-linoleate, ethylene glycol diundecylenate and 1,7-octadiene with platinum or palladium catalysts, only if a diene-to-saturate shunt of 15- to 25% is included can a good fit be secured between the model and experimental composition. With nickel the shunt is much smaller or absent. Although the shunt might be attributed most readily to a liquid diffusion effect, its independence of temperature, viscosity and presence or absence of solvents and catalyst support suggests that some other factor is responsible. Evidence for similar shunts is found for other materials, including soybean triglycerides.