Phase equilibrium data pertaining to the extraction of cottonseed oil with ethanol and 2-propanol

Summary Basic phase relation data have been obtained relative to the extraction of cottonseed oil with ethanol and 2-propanol, especially as affected by water in the solvent. Mutual solubility diagrams have been constructed for cottonseed oil with ethanol and 2-propanol of various aqueous concentrations. Tie-line data at 30° C. have been obtained for the ternary ethanol-cotton-seed oil-water and 2-propanol-cottonseed oil-water systems. These combined data will be of assistance in the selection of the most desirable temperatures and moisture concentrations in the solvent extraction of cottonseed with these alcohols. Comparison with results previously published for soybean oil suggests that the mutual solubility data for cottonseed oil and aqueous ethanols are applicable to other vegetable oils over a wide range of iodine values. In general, the results indicate that 2-propanol is the more desirable solvent since complete miscibility with the oil can be attained at temperatures below its normal boiling point even at moisture contents as high as 10% by weight whereas ethanol can tolerate only about 1.5% of water. High moisture contents result in more effective separation of the oil from the solvent when the miscella is cooled after extraction. Constant boiling aqueous ethanol and 2-propanol present the disadvantage of requiring greater than atmospheric pressure during extraction in order to attain complete miscibility with the oil. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Process engineering economic evaluation of the ethanol extraction of cottonseed: Preliminary analysis

This preliminary analysis was undertaken to determine if the operations being developed for the aqueous ethanol extraction of cottonseed oil are economical and whether further research of this process should be pursued. Results of the conversion of hypothetical hexane extraction plants to ethanol extraction, in the plant capacity range of 300-600 tons of cottonseed flakes/day and operating 150-350 days annually, show that two unconventional operations, namely, chill-separation of miscella exiting the extractor and reduction of oil in recycled ethanol by reverse osmosis, require less energy and are less expensive than conventional alternatives. However, additional work is needed to determine the overall efficiency of an alcohol process as compared to a conventional hexane process.     

Miscella refining test method for the determination of cottonseed oil color

Most of the cottonseed oil mills in the United States have already converted to expander solvent extraction and miscella refining. This practice permits mills to produce and market a consistently light-colored, prime bleachable summer yellow cottonseed oil at reduced cost and refining loss. A laboratory-scale miscella refining test was developed to asses the oil quality in terms of its color. The test involves the addition of 3 parts oleic acid per 100 parts of crude oil in the miscella followed by refining with 2.5 parts NaOH when crude oil contains less than 4.5% free fatty acid (FFA). When crude oil contains FFA between 4.5 and 7.5%, no oleic acid is added prior to refining with 2.5 parts NaOH. When crude oil contains FFA higher than 7.5%, no oleic acid is added and the caustic addition table in American Oil Chemists' Society Method Ca 9a-52 is followed. The test was conducted at room temperature and gave reproducible colors comparable to commercially refined oils.     

Deacidification of sulfur olive oil. I. Single-stage liquid-liquid extraction of miscella with ethyl alcohol

In this study, a systematic and detailed investigation on liquid-liquid extraction of sulfur olive oil miscella in hexane with aqueous ethanol solutions was performed. Optimal extraction conditions for recovery of free fatty acids (FFA) with a minor loss of neutral oil were determined in bench-scale single-stage extractions. It was concluded that, to ensure deacidification with a low triglycerides loss, it is appropriate to extract the miscella with 30% or more dilute ethanol solutions. It was also noted that under these circumstances the free fatty acid percentage extracted is not affected by increases in contents of FFA and partial glycerides of sulfur olive oil, and the solvent must be saturated with hexane before extraction. Changing the oil:hexane ratio in miscella from 1:2 to 2:1 by weight did not have any significant effect on extraction results.     

Biodiesel Feedstock from Emulsions Produced by Aqueous Processing of Yellow Mustard

The multi-stage treatment of stable oil-in-water emulsions produced during non-enzymatic aqueous processing of dehulled yellow mustard flour with cyclic ethers [tetrahydrofuran (THF) and 1,4-dioxane] was investigated to produce a single-phase oil-solvent-water miscella suitable for biodiesel production. While the single-stage treatment of yellow mustard emulsion recovered 97 % and 95 % of the oil by using 4:1 THF:oil and 9:1 dioxane:oil weight ratios, respectively, miscella phases containing more than 7 % water formed, which made them unsuitable as biodiesel feedstock. Multi-stage treatments of the emulsion using lower THF:oil and dioxane:oil weight ratios were further developed to produce oil-solvent-water miscella phases with low water content. While three-stage extraction of emulsions using 0.5:1, 1:1, 1.5:1, and 2:1 dioxane:oil weight ratios did not destabilize the emulsion, three-stage extraction using 0.5:1 and 0.75:1 THF:oil weight ratios effectively recovered over 97 % of the oil, resulting in the production of oil-rich miscella phases containing only 1 % and 1.5 % water, respectively. These miscella phases were analyzed for free fatty acid and phosphorus contents and proved to be excellent feedstocks for the preparation of high-purity methyl esters through single-phase base-catalyzed transmethylation.     

Solvent extraction of oil from soybean flour II— pilot plant and two-solvent extractions

The process of grinding soybeans to a fine flour and extracting the flour with hexane was studied on a pilot plant scale. The crude oil from the pilot plant study had 15 ppm phosphorus and was suitable for physical refining after a light acid pretreatment and bleaching. The refined oil showed a Lovibond color of 1.4 yellow and 0.3 red. The pilot plant study also showed that grinding of the soybeans and the separation of solid from miscella were the most difficult steps in solvent extraction with fine flour. A laboratory study on separation of miscella from meal by aqueous ethanol reduced the hold-up volume, but it did not remove all the miscella. A test with betacarotene showed that only the miscella outside the flour particles was displaced. Aqueous ethanol solutions used as a second solvent extracted additional nontriglyceride materials (primarily phospholipids) from the meal. Also, the free fatty acid content of the oil was increased with aqueous ethanol solution wash. The quality of the extracted crude oil was lowered by using a second solvent, but it had the advantage of needing only one centrifugation to separate miscella from meal.     

Alcoholic extraction of vegetable oils. V. Pilot plant extraction of cottonseed by aqueous ethanol

Summary Cottonseed flakes were extracted by aqueous ethanol in a countercurrent pilot plant unit to determine the effect of operating variables and the optimum operating conditions. This investigation has shown that direct extraction of cottonseed, using aqueous ethanol as a solvent, is a feasible process in the type of equipment developed previously in this laboratory. The optimum operating conditions for the ethanol extraction of cottonseed have been established. The pilot plant extractions have shown that in this process a prime quality of crude oil and lightcolored meal of good quality, with negligible free gossypol content, are obtained. Presented at the spring meeting, American Oil Chemists' Society, April 29-May 1, 1957, New Orleans, La.     

Solvent extraction of cottonseeds with hexane and water as co-solvents

Summary By stirring violently for four hours at 4,100 r.p.m. a mixture of dehulled and flaked cottonseed meal, hexane, and water, with respective hexane/meal and water/meal weight ratios of 6:1 and 1:5, all the pigment glands of the seed are broken, the oil content of the meal is reduced to about 1%, and a miscella phase only, free of water, is produced as all the water added remains with the meal. Extracted meal thus obtained is easily filtered from the miscella and air-dries to an easily handled, non-sticky cake. If the water is increased in the mixture to a water/meal ratio of 2:5, other results remain about the same, but the meal is excessively sticky and is difficult to filter from the miscella. Pre-soaking the meal in solvent before extraction has little or no effect, under our conditions of extraction, on the amount of oil left in the meal. It is proposed that solvent extraction of cottonseed oil proceeds according to the normal laws of diffusion. Rapid solvent action is believed to be hindered not by presence of a difficulty dissolving “resistance” proposed in other work but rather by presence in the meal of lyophobic molecules, such as absorbed water, which offer strong intra-molecular repulsion to solvent penetration. In consequence it is necessary to provide strong shearing action and turbulence to promote frequent contacts between the oil cell and the miscella. Commercial applications of results are discussed. This paper is based upon a thesis submitted by Donald McNeil in partial fulfillment of the requirements for the degree of Master of Science in Chemical Engineering, Columbia University, June, 1950. Contribution Number 10 from the Chemical Engineering Laboratories, Engineering Center, Columbia University, New York, N. Y.     

Isopropanol as a solvent for extraction of cottonseed oil

Phase equilibrium data for the system; cottonseed oil-isopropanol-water were determined at 30°C. and compared with data for the system; cottonseed oilethanol-water. The relative phase distribution of fatty acids and cottonseed oil in mixtures with isopropanol and water was studied under varying conditions of water and fatty acid concentrations. These tests showed the fatty acids to be highly concentrated in the alcohol-water phase. Flaked cottonseed meats were extracted in continuous extraction apparatus with 91% isopropanol, 99% isopropanol, and mixtures of commercial hexane and isopropanol. Analytical data on the extractions show that 91% isopropanol is an efficient solvent for extracting active gossypol along with the oil. Rat and swine feeding tests of the isopropanol extracted meal showed it to be highly superior to hydraulic meal as a source of protein. A method was developed for treatment of the cottonseed-isopropanol miscella by liquid-liquid extraction to separate purified oil and fatty acid fractions from other materials in the extract.     

Cottonseed extraction with mixtures of acetone and hexane

Cottonseed flakes were extracted with mixtures of n-hexane and acetone, with the concentration of acetone varying between 10 and 75%. Adding small amounts of acetone (≤25%) to n-hexane significantly increased the extraction of free and total gossypol from cottonseed flakes. Sensory testing detected no difference in the odor of cottonseed meals produced either by extraction with 100% n-hexane or by extraction with a 10∶90 (vol/vol) mixture of acetone/hexane. More than 80% of the free gossypol was removed by the 10∶90 mixture of acetone/hexane, whereas pure n-hexane extracted about 47% of the free gossypol from cottonseed flakes. A solvent mixture containing 25% acetone removed nearly 90% of the free gossypol that was removable by extraction with pure acetone; the residual meal had only a minimal increase in odor. In contrast, cottonseed meals produced by extraction with pure acetone had a much higher odor intensity. The composition of the cottonseed crude oil was insignificantly affected by the acetone concentration of the extraction solvent. The results indicate that mixtures of acetone and n-hexane can be used as extraction solvents to produce cottonseed crude oil without the concomitant development of odorous meals.     

Continuous refining of crude cottonseed miscella

A simple, easily controlled process for continuous caustic refining of crude cottonseed miscella in a two-stage system is described. The effect of crude oil quality, oil: hexane ratios, temp, mixing conditions and chemical treatment are noted. The chemical reactions in the process are followed microscopically. The process yields a refined oil of less than: 1.0 bleach oil color, 0.03% free fatty acid and 15 ppm soap, and with 30~40% oil savings over Official Cup Loss. The by-product soap may be used advantageously in the meal from the extractor unit. Presented at the AOCS Meeting in Minneapolis, 1963.     

A Highly Stable Soybean Oil-Rich Miscella Obtained by Ethanolic Extraction as a Promising Biodiesel Feedstock

Soybean oil is industrially obtained upon hexane extraction. In biodiesel production, soybean oil is submitted to phospholipid removal in order to improve its quality before transesterification. An extraction process was employed to produce ethanolic oil-rich miscella, which can be directly transesterified to produce biodiesel without prior refining. We assessed the oxidative stability of the miscella and three other soybean oils, namely degummed, alkali-refined, and refined–bleached–deodorized (RBD) oil. In vitro antioxidant assays as well as the identification and quantification of tocopherols and isoflavones were also performed. Although hexane-extracted oils showed higher tocopherol contents than miscella, this latter sample and its direct biodiesel demonstrated superior stability in accelerated tests. Miscella also outperformed hexane-extracted oils in all in vitro assays. This behavior can be explained by the presence of phenolic compounds with higher affinity to ethanol than hexane, which was confirmed by the identification of isoflavones glycitein, genistein, and acetyldaidzin, found only in miscella. This study showed that the ethanolic extraction of soybean oil generated a highly stable lipid feedstock for biodiesel manufacture.     

The Isolation of Yellow Mustard Oil Using Water and Cyclic Ethers

An aqueous extraction process (AEP) was developed for dehulled yellow mustard flour with the aim of producing yellow mustard oil for industrial applications, as a by-product of food protein production. During AEP, most of the oil extracted was bound in a stable oil-in-water emulsion that must be destabilized to recover free oil. The oil distribution after aqueous extraction and the composition of the emulsion produced were determined. The emulsion was solubilized in organic solvents including tetrahydrofuran (THF) and 1,4-dioxane to fully recover the oil in a single-phase oil–solvent-water miscella. Over 97 and 95% of the oil in the emulsion was successfully recovered using 4:1 THF:oil and 9:1 dioxane:oil weight ratios, respectively. The oil recovery from the emulsion was optimized, based on experimentally prepared ternary phase diagrams of THF/oil/water and dioxane/oil/water. The results suggest that this technically viable approach can successfully recover essentially all of the oil from the emulsion, equivalent to an overall free oil recovery of ~63% from dehulled yellow mustard flour.     

Deacidification of sulfur olive oil. II. Multi-stage liquid-liquid extraction of miscella with ethyl alcohol

In this study, laboratory-scale multi-stage cross- and counter-current extractions of sulfur olive oil miscella with 70 and 80% ethanol saturated with hexane were investigated. For cross-current extraction, the extraction factor for free fatty acids was constant in each extraction stage. Therefore, the extraction factors determined in single-stage extractions were used to calculate the extracted free fatty acid percentages for cross-current and counter-current multi-stage extractions and results were in close agreement with the experimental data. It was possible to determine the amount of solvent and the number of stages required for counter-current extraction to remove the desired amount of free fatty acids from a given sulfur olive oil with 70 or 80% ethanol. Comparison of the results for these two solvents showed that 80% ethanol was more suitable.     

Color stability of glandless cottonseed oil

The color stability of oil extracted from glandless cottonseed contaminated with various levels of glanded cottonseed was studied. The rate of darkening in bleached color of cottonseed oil during storage was proportional to the original glanded cottonseed or gossypol content in the oil and to time and temperature of storage. Glandless cottonseed with 0–10% glanded seed contamination, as might be expected in commercial production of glandless cotton, yielded oil with equivalent or better color when conventionally refined and bleached after 30 days storage at 25 to 40 C than miscella refined oil from glanded cottonseed. This indicates that new oil mills for extracting glandless cottonseed need not invest in miscella-refining units in order to produce high quality oil.     

Plant scale comparisons of various refining methods for cottonseed oil

Three different refining processes were commercially compared by processing 15,148 metric tons of cottonseed with free fatty acid content varying between 7.1% and 8.9%. All of the seed was prepressed and solvent extracted in the Sanbra plant at Bauru, Brazil. The Ranchers Miscella refining process operating on seed averaging 8.8% F.F.A. yielded more oil of lighter color per ton of seed processed than either of the other processes compared, even though the average F.F.A. of the seed processed during the Ranchers Miscella Refining test averaged 1.7% higher than the seed used in the Sanbra process and 1.1% higher than the average F.F.A. for the seed used in the Low Loss Refining test. In another comparison, screw pressed oil, Modified Soda Ash refined was compared to Ranchers Miscella refining with seed containing about 0.5% F.F.A. The results showed 42% lower refining loss and a color of 3.5 Red Lovibond units less for Ranchers Miscella refined oil than for Modified Soda Ash refined oil. The average cost of converting crude cottonseed oil to prime bleachable summer yellow oil by the miscella refining process described is 20.8￠ per hundred weight of oil (not including refining loss). These costs include the prorated cost of control laboratory, plant labor and supervision, fuel, power, chemicals, depreciation, taxes and insurance.     

Biodiesel Production from Mustard Emulsion by a Combined Destabilization/Adsorption Process

Tetrahydrofuran, added to the oil‐in‐water emulsions formed by the aqueous processing of yellow mustard flour, produced oil/water/THF miscellas containing 1–2 % water. The high water content prevented the direct conversion of the system to fatty acid methyl esters (FAME) through a single‐phase base‐catalyzed transmethylation process. Dehydration of these miscellas by adsorption on 4A molecular sieves at room temperature using either batch or continuous fixed‐bed systems successfully reduced the water content to the quality standards needed for biodiesel feedstock (0.3 %). Equilibrium adsorption studies for the uptake of water from oil/THF/water miscella phases at room temperature allowed quantitative comparison of the water adsorption capacity based on the oil and THF concentrations of the miscellas. Batch contact was used to investigate the dominant parameters affecting the uptake of water including miscella composition, adsorbent dose and contact time. The adsorption of the water was strongly dependent on adsorbent dose and miscella oil concentrations. The regeneration of molecular sieves by heating under nitrogen at reduced pressure for 6 h at 275 °C resulted in incomplete desorption of miscella components. The adsorption breakthrough curves in terms of flow rates, initial water and oil miscella concentrations were determined. The dehydrated miscella phases were reacted with methanol in a single‐phase base‐catalyzed transmethylation process with high yields (99.3 wt%) to FAME. The resulting FAME met the ASTM international standard in terms of total glycerol content and acid number.     

Hexane and heptane as extraction solvents for cottonseed: A laboratory-scale study

For many years, commercial-grade hexane has been the preferred solvent for extracting oil from cottonseed. Recent environmental and health concerns about hexane may limit the use of this solvent; therefore, the need for a replacement solvent has become an important issue. Heptane is similar to hexane, but does not have the environmental and health concerns associated with the latter. On a laboratory scale, delinted, dehulled, ground cottonseed was extracted with hexane and heptane. The solvent-to-meal ratio was 10:1 (vol/wt). The yield and quality of the oil and meal extracted by heptane were similar to that extracted by hexane. Extraction temperature was higher for heptane than for hexane. A higher temperature and a longer time were required to desolventize miscella from the heptane extraction than from the hexane extraction. Based on these studies, heptane offers a potential alternative to hexane for extracting oil from cottonseed.     

Alternative hydrocarbon solvents for cottonseed extraction: Plant trials

Hexane has been used for decades to extract oil from cottonseed and is still the solvent of choice for the edible-oil industry. Due to increased regulations as a result of the 1990 Clean Air Act and potential health risks, the edible-oil extraction industry urgently needs an alternate hydrocarbon solvent to replace hexane. Based on laboratory-scale extraction tests, two hydrocarbon solvents, heptane and isohexane, were recommended as potential replacements for hexane. A cottonseed processing mill with a 270 MT/day (300 tons/day) capacity agreed to test both solvents with their expander-solvent process. Extraction efficiencies of isohexane and heptane, judged by extraction time and residual oil in meal, refined and bleached color of miscella refined oil, and solvent loss, were comparable to that of hexane. However, fewer problems were encountered with the lower-boiling isohexane than with the higher-boiling heptane. With isohexane, the daily throughput increased more than 20%, and natural gas consumption decreased more than 40% as compared to hexane.     

Solvent extraction of cottonseed meats

In the experimental countercurrent extraction of flaked cottonseed meats by trichloroethylene the residual oil content of the extracted flakes decreased with: first, a decrease in the final oil content of the final miscella; second, decrease in the flake moisture down to 8.64%; third, decrease in flake thickness; fourth, increase in temperature; and fifth, increase in extraction time. For the batch of cottonseed meats used the following equation was developed: whereR is percent residual extractables,b is flake thickness in feet,D is meat diameter in feet,ϑ is extraction time in hours,μ in viscosity, lb. per ft. hr.,ρ is density, lb. per cu. ft., andt is extraction temperature in degrees F. Not enough data were secured by extraction with hexane to check the equation developed for trichloroethylene extraction. Hexane is a poorer solvent for cottonseed oil than trichloroethylene. The amount of oil remaining in the meal is affected to a greater extent by the miscella concentration in hexane extraction than in trichloroethylene extraction.