Alternative hydrocarbon solvents for cottonseed extraction

Hexane has been used for decades to extract edible oil from cottonseed. However, due to increased regulations affecting hexane because of the 1990 Clean Air Act and potential health risks, the oil-extraction industry urgently needs alternative hydrocarbon solvents to replace hexane. Five solvents,n-heptane, isohexane, neohexane, cyclohexane, and cylopentane, were compared with commercial hexane using a benchscale extractor. The extractions were done with a solvent to cottonseed flake ratio of 5.5 to 1 (w/w) and a miscella recycle flow rate of 36 mL/min/sq cm (9 gal/min/sq ft) at a temperature of 10 to 45°C below the boiling point of the solvent. After a 10-min single-stage extraction, commercial hexane removed 100% of the oil from the flakes at 55°C; heptane extracted 100% at 75°C and 95.9% at 55°C; isohexane extracted 93.1% at 45°C; while cyclopentane, cyclohexane, and neohexane removed 93.3, 89.4, and 89.6% at 35, 55, and 35°C, respectively. Each solvent removed gossypol from cottonseed flakes at a different rate, with cyclopentane being most and neohexane least effective. Based on the bench-scale extraction results and the availability of these candidate solvents, heptane and isohexane are the alternative hydrocarbon solvents most likely to replace hexane. Presented in part at the AOCS Annual Meeting & Expo, Atlanta, Georgia, May 1994.     

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.     

The Viscosity of cottonseed oil,fractionation solvents and their solutions

Cold fractionation of cottonseed oil is made difficult by the high viscosity of the oil. This study was aimed at demonstrating the effect of solvents on the viscosity of mixtures between 0°C and 25°C with a view to facilitating the fractionation of refined cottonseed oil. The solvents used were acetone, methylethylketone, methylisobutylketone, hexane and heptane. Measurements of viscosity were carried out by means of a capillary viscometer. The ratio of the viscosity of cottonseed oil to that of pure solvents is of the order of 300. The viscosities of solutions of various ratios of solvent to oil (1/3, 1/1, 3/1) are between those of cottonseed oil and the pure solvents. The effect of the solvent/oil ratio overrides that of solvent nature. The effect of solvent in reducing the viscosity of cottonseed oil is by descending order: acetone, hexane, methylethylketone, heptane, methylisobutylketone.     

Extraction of soybeans with four hydrocarbon solvents

Soybean flakes were extracted in glass extraction apparatus with four hydrocarbon solvents: hexane, isohexane, pentane, and isopentane. The amount of extracted oil was determined at 10 min intervals for 60 min. The extraction rates of the solvents increased in the following order: isopentane, pentane, isohexane, and hexane. Quality and fatty acid composition of the oils extracted by the four solvents showed no significant differences.     

Extraction of corn oil by three petroleum solvents

Summary and conclusions Rate-extractions of corn germ oil by heptane, isoheptane, and hexane at the same temperature showed the latter two to be better solvents than heptane. Extraction rate increased with the temperature. Countercurrent extraction in a continuous laboratory pilot plant showed hexane at 157°F. apparently equal to iso-heptane at 192°F. It is suggested that the boiling of the hexane at 157°F. might account for the better extraction. It can be concluded that hexane is at least as good a solvent for the extraction of corn oil from whole germ as is iso-heptane.     

Laboratory extraction of cottonseed with various petroleum hydrocarbons

Summary Solvent extraction of cottonseed with various hydrocarbons in the C₅ to C₇ range was studied to determine comparative yields and quality of oil produced with pure and commercial hydrocarbon solvents. The solvents used were Pure Grade (minimum 99 mol per cent purity) isopentane, normal pentane, cyclohexane, normal heptane, and benzene; Technical Grade (minimum 95 mol per cent purity) neohexane, diisopropyl, 2-methylpentane, 3-methylpentane, normal hexane, methylcyclopentane, and a 90 mol per cent cyclopentane; and Commercial Grade normal pentane, isohexanes, normal hexane, isoheptanes, and normal heptane. The effects of precooking the seeds and of the inclusion of hulls on yield and color of extracted oil were determined. Yields and colors of crude oils from cottonseed with both high and intermediate free fatty acid content were studied, and characteristics of the oils determined and compared. Refining losses, refined colors, and bleach colors of oils extracted with various hydrocarbons were compared. Color comparisons were made with a Gardner Color Comparator and a Fisher Electrophotometer. Other test methods used were modifications of official A.O.C.S. methods adapted to small samples. In general normal paraffins and isoparaffins were found to have some advantages over cyclic hydrocarbons. Presented at the 39th annual meeting of the American Oil Chemists' Society in New Orleans, May 4–6, 1948.     

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.     

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.     

Phase relations pertaining to the solvent winterization of cottonseed oil in hexane and in acetone-hexane mixtures

Summary Systematic phase relation data pertaining to the solvent winterization behavior of a refined cottonseed oil have been obtained for two additional solvents; namely, commercial hexane and a mixed solvent consisting of 85% by weight of acetone and 15% of hexane. Graphs have been constructed to show the effect of oil-solvent ratio, chilling temperature, holding-time, and agitation on the percentage of solid removed, the degree of winterization and the settling qualities of the solid separating. These data, with those previously reported for acetone (1), afford a basis for the selection of the optimum conditions and procedures in the application of solvent winterization to cottonseed oil and bring out the relative advantages, disadvantages, and limitations of the three solvents. The acetone-hexane mixture seems to combine the advantages and eliminate the disadvantages of either of these solvents alone. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Cottonseed extraction with a new solvent system: Isohexane and alcohol mixtures

A solvent system, consisting of isohexane and 5 to 25% alcohol, either ethanol (EtOH) or isopropyl alcohol (IPA), was tested for extracting gossypol and oil from cottonseed. The test results indicate that this new solvent system not only is effective in removing free and total gossypol but also is as efficient as n-hexane when extracting oil. The amino acid analysis of cottonseed meal, produced by the new solvent system, is similar to that produced by commercial n-hexane. Present commercial cottonseed extraction and downstream processing of cottonseed oil refining may need little change to adopt this new solvent system. This new solvent system may lead to a solution to the gossypol problem of cottonseed extraction.     

Ambient-temperature extraction of rice bran oil with hexane and isopropanol

Hexane and isopropanol were compared as solvents for use in ambient-temperature equilibrium extraction of rice bran oil (RBO). Isopropanol was as effective as hexane in extracting RBO when 20 mL of solvent was used to extract 2 g of bran. Free fatty acid levels were 2–3% in both solvents and similar to that previously reported for hexane extraction of RBO hexane extraction by this method. Larger-scale extractions with 30 g of bran and 150 mL of solvent produced oil with a similar free fatty acid content and a phosphorus level of approximately 500 ppm. The oil extracted with isopropanol was significantly more stable to heat-induced oxidation than hexane-extracted oil. Antioxidants that are more easily extracted by isopropanol than hexane may be responsible for the increased stability.     

Rice brain oil. I. Oil obtained by solvent extraction

1. Freshly milled rice bran has been extracted with commercial hexane and the recovered oil and extracted meal examined for their respective content of wax. The oils were refined and bleached by standards as well as several special methods. The crude, caustic soda refined, and several refined and bleached oils were examined spectrophotometrically.
2. When freshly milled rice bran of good quality is extracted with commercial hexane, an oil of relatively low free fatty acid content is obtained. This oil possesses good color and is as stable as other similar types of crude oils.
3. If the oils is extracted from the brain at a temperature below about 10°C. and the extraction is discontinued at the right time, the extracted oil represents 90–95% of the total lipids in the brain and contains very little wax. This wax, which is readily extracted with hot commercial hexane as well as other types of solvents, amounts to about 3–9% of the total extractable lipids.
4. When subjected to ordinary caustic soda refining methods, good rice brain oils behave much like cottonseed oils of comparable free fatty acid content. Both caustic soda refining in a hydrocarbon solvent and refining with sodium carbonate result in refining losses approximating the absolute or Wesson loss.
5. Some of the refined oils when bleached according to usual practice produce products acceptable for use in the edible trade. However, refined rice bran oil has a definitely greenish cast resulting from the presence of chlorophyll, but this color can be removed by bleaching with a small amount of activated acidic clay.

     

Properties of oil extracted from cottonseed with acetone-hexane-water solvent mixture

Slightly more neutral oil was obtained on the exhaustive extraction of raw cottonseed meats with the acetone-hexanewater (AHW) solvent mixture than was obtained under the same conditions with commerical hexane. Although most of the gossypol originally present in the seed is extracted with the oil when the AHW solvent mixture is used, the crude oils refined and bleached to yield oils of excellent colors. Methods of recovery of the solvent from the mixed solvent miscellas are reported, together with the refining and bleaching data for the recovered oils.     

Pilot plant studies on extracting cottonseed with methylene chloride

The practical feasibility of using methylene chloride to extract oil, aflatoxin and gossypol simultaneously from cottonseed flakes was demonstrated in a 56-hr experimental run using a pilot-scale, continuous extractor. Nine different trials varying in extraction time, solvent:flake ratio, flake preparation method and blending with 5% ethanol were evaluated. Residual oil contents were lower than typically achieved in extraction with hexane. Aflatoxin contents of the meals were reduced by 73–92% of the level in cottonseed meats, making possible the upgrading of a large portion of cottonseed meal that otherwise would exceed current action levels. Because gossypol also was extracted, it was possible to produce cottonseed meal that was well suited for use in poultry feeds, especially when a blend of 5% ethanol in methylene chloride was used. Meal desolventized easily, and residual levels of methylene chloride were generally less than 12 ppm. The oil was refined and bleached to acceptable quality standards, and no residual aflatoxin was detected in alkali-refined oil.     

Supercritical carbon dioxide extraction of cottonseed with co-solvents

Extraction of cottonseed lipids with supercritical carbon dioxide (SC-CO₂) was conducted with and without a cosolvent, ethanol or 2-propanol (IPA). At 7000 psi and 80°C, the reduced pressure, temperature and density of SC-CO₂ was at 6.5, 1.17 and 1.85, respectively; the specific gravity was 0.87. Under these conditions, CO₂ is denser than most liquid extraction agents such as hexane, ethanol and IPA. The extraction of cottonseed with SC-CO₂ gave a yield of more than 30% (moisture-free basis). This is comparable to yields obtained by the more commonly used solvent, hexane. The crude cottonseed oil extracted by SC-CO₂ was visually lighter than refined cottonseed oil. This was substantiated by colorimetric measurements. No gossypol was detected in the crude oil. However, crude oil extracted by SC-CO₂, to which less than 5% of ethanol or IPA as co-solvent was added, containedca. 200 ppm of gossypol, resulting in the typical dark color of cottonseed crude oil with gossypol. CO₂ extracted a small amount of cottonseed phosphatides, about one-third of that extracted by pure ethanol, IPA or hexane. A second extraction with 100% ethanol or IPA after the initial SC-CO₂ extraction produced a water-soluble lipid fraction that contained a significant amount of gossypol, ranging between 1500 and 5000 ppm. Because pure gossypol is practically insoluble in water, this fraction is believed to be made up of gossypol complexed with polysaccharides and phosphatides. Partially presented at the AOCS 1993 Annual Meeting & Expo in Anaheim, California.     

Solvent screening for non‐aqueous extraction of Alberta oil sands

Non‐aqueous extraction of bitumen from oil sands has the potential to reduce fresh water demand of the extraction process and eliminate tailings ponds. In this study, different light hydrocarbon solvents, including aromatics, cycloalkanes, biologically derived solvents and mixtures of solvents were compared for extraction of bitumen from Alberta oil sands at room temperature and ambient pressure. The solvents are compared based on bitumen recovery, the amount of residual solvent in the extracted oil sands tailings and the content of fine solids in the extracted bitumen. The extraction experiments were carried out in a multistage process with agitation in rotary mixers and vibration sieving. The oil sands tailings were dried under ambient conditions, and their residual solvent contents were measured by a purge and trap system followed by gas chromatography. The elemental compositions of the extraction tailings were measured to calculate bitumen recovery. Supernatants from the extraction tests were centrifuged to separate and measure the contents of fine solid particles. Except for limonene and isoprene, the tested solvents showed good bitumen recoveries of around 95%. The solvent drying rates and residual solvent contents in the extracted oil sands tailings correlated to solvent vapour pressure. The contents of fine solids in the extracted bitumen (supernatant) were below 2.9% for all solvents except n‐heptane‐rich ones. Based on these findings, cyclohexane is the best candidate solvent for bitumen extraction, with 94.4% bitumen recovery, 5 mg of residual solvent per kilogram of extraction tailings and 1.4 wt% fine solids in the recovered bitumen. © 2012 Canadian Society for Chemical Engineering     

炼油厂高标溶剂油类别优选研究

通过蒸馏实验对某炼油厂提供的各种石脑油的馏分范围进行测试,并用气相色谱仪对其化学组成进行详一细分析,结果表明抽余油具有制备低芳烃6号溶剂油的物质条件。实验与模拟计算表明：该抽余油经催化加氢分馏可制得芳烃〈10mg/L、d硫〈0．5mg/L的6号溶剂油;对该6号溶剂油进一步精馏则可制得纯度为99%的异己烷和纯度为98％的己烷两种高标溶剂油。与常规溶剂油及D系列溶剂油相比,正已烷价格与石脑油平均差价高达4000元/吨,且差价稳定,因此以抽余油生产正已烷/异己烷可获良好的经济效益。     

The fatty acid composition of cottonseed oil at various stages of solvent extraction

The variation in the fatty acid composition of the glyceride portion of cottonseed oil at various stages of solvent extraction has been investigated. Prime cottonseed meats were flaked and extracted in glassware rate extraction apparatus, using commercial hexane up to different degrees of extractions. The fatty acid composition of cottonseed oil obtained after extracting the flakes to different residual oil contents was determined by gas-liquid partition chromatography. No difference was found.     

Extraction of lipids from cottonseed tissue: IV. Use of hexane-acetic acid

Hexane and mixtures of hexane and 2–25% acetic acid (v/v) were used to prepare oil and protein from glanded cottonseed by solvent extraction. As the amount of acetic acid in the solvent increased, the amounts of total lipid, phospholipid, neutral oil, and gossypol in each miscella increased, but the amount of free fatty acids did not change significantly. However, the solubility of protein in 0.02N NaOH decreased as the amount of acetic acid in the solvent used to prepare each meal increased. Other aspects of using acidified hexane are described. A preliminary report was presented at the AOCS Meeting in New Orleans, April 1973. ARS, USDA.     

Acidic ethanol extraction of cottonseed

Ethanol (EtOH) is being evaluated as an alternate solvent to hexane for the extraction of glanded cottonseed. Hot EtOH, needed for efficient oil and aflatoxin extraction, binds gossypol to protein. However, this binding can be minimized by acidifying aqueous EtOH with a tribasic acid, such as phosphoric or citric. While this solvent extracts oil and gossypol, it does not affect EtOH’s ability to extract aflatoxin. The defatted cottonseed meals produced from this process contained 0.03% total gossypol (which is lower than meal prepared by most other processes) and the aflatoxin content was reduced from 69 to 2.9 ppb. These are preliminary results and additional research is needed to determine commercial feasibility. The removal of essentially all gossypol from an extracted meal has the potential to expand the use of cottonseed meal as a feed, increasing its value to both the cotton farmer and the seed processor. Presented in part at the 40th Oilseed Processing Clinic, March 4, 1991, New Orleans, LA.