PRODUCTION OF STEARIC ACID

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PRODUCTION OF STEARIC ACID

A project report submitted to the Department of Chemical Engineering / University of Technology

In partial fulfillment of the requirements for the degree of B.Sc. in Chemical Engineering.

By

Supervised by

Academic Year 2023-2024

University of Technology

Chemical Engineering Department

Branch of Oil and Gas Refining Engineering

Dina Kareem Tabark Hashim

Dr. Teeba Mohammed University of Technology

Chemical Engineering Department

Branch of Oil and Gas Refining Engineering

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List of Contents

List of Tables

Table 1 Physicochemical properties of stearic acid at 20 °C [7]...5

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List of Figures

Figure 1 structure of stearic acid...3

IV

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Chapter One

Introduction

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1. 1 Overview

Stearic acid is a saturated fatty acid with an 18-carbon chain. The IUPAC name is octadecanoic acid. It is a soft waxy solid with the formula CH3(CH2)16CO2H.The triglyceride derived from three molecules of stearic acid is called stearin. Stearic acid is a prevalent fatty-acid in nature, found in many animal and vegetable fats, but is usually higher in animal fat than vegetable fat. It has a melting point of 69.4

°C and a pKa of 4.50. [1]

Its name comes from the Greek word στέαρ "stéar", which means tallow. The salts and esters of stearic acid are called stearates. As its ester, stearic acid is one of the most common saturated fatty acids found in nature and in the food supply, following palmitic acid. Dietary sources of stearic acid include meat, poultry, fish, eggs, dairy products, and foods prepared with fats; beef tallow, lard, butterfat, cocoa butter, and shea butter are rich fat sources of stearic acid.[2]

Figure 1 stearic acid shape

Of the saturated fatty acids consumed in the United States, stearic acid consumption is second (26% of total saturated fatty acid intake) to palmitic acid

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(56% of total saturated fatty acid intake). [2] Stearic acid is more abundant in animal fat (up to 33% in beef liver[: 739 ) than in vegetable fat (typically less than 5%). The important exceptions are the foods cocoa butter (34%) and shea butter, where the stearic acid content (as a triglyceride) is 28–45%. Examples of the use of stearic acid in food manufacturing include baked goods, frozen dairy products, gelatins, puddings, hard candy, and nonalcoholic beverages. [2]

In biosynthesis, stearic acid is produced from carbohydrates via the fatty acid synthesis machinery wherein acetyl-CoA contributes two-carbon building blocks.

Stearic acid is obtained from fats and oils by the saponification of the triglycerides using hot water (about 100 °C). The resulting mixture is then distilled.[3]

Commercial stearic acid is often a mixture of stearic and palmitic acids, although purified stearic acid is available. Commercially, oleic acid, as found in palm and soy, can be hydrogenated to give stearic acid.

3 Figure 2 structure of stearic acid

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Fatty Acids are divided into sections :

1.Saturated fatty acids 2.Unsaturated fatty acids Saturated fatty acids :

Saturated fatty acids are acids that do not contain double bonds between carbons atoms are saturated with two hydrogen atoms. An example of this :

•Saturated fatty acids with short chains such as ( butyric acid )

•Saturated fatty acids with long chains such as ( stearic acid , palm acid ) Unsaturated fatty acids :

Unsaturated fatty acids are fatty acids that contain at least a double or triple bond between two carbon atoms .It is similar in chemical composition to saturated fatty except that at least one carbon atom in the middle of the carbon chain binds to one hydrogen atom rather than two atoms ( Not saturated with hydrogen ), An example of this :

•Fatty acids with a single double bond such as (oleic acid)

•Fatty acids contain two double bonds such as ( linoleic acid )

•Fatty acid contain three double bonds such as ( linolenic acid ) • Fatty acid contain four double bonds such as ( arachidonic acid ) [2]

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1.2 Chemical Properties

Chemically . Stearic Acid is present as a white solid.and is odorless in nature.

Stearic acid is tallow in taste. but which can be reacted to form many derivatives.

Physically. high-boiling point 721°F at normal pressure[4]. miscible with water and alcohol [5]

The Melting point of Stearic acid is 156.7°F at normal pressure. The melting point of Stearic acid is high because it is saturated fat and it takes more heat to dissociate the structure. stearic Acid is a waxy, colorless or white solid that exudes a mild odor. It is soluble in oil but only slightly dissolves in water[5], thus it floats.

Stearic Acid is a long-chain fatty acid that, due to its 18-carbon chain, is also referred to as Octadecanoic Acid. This valuable saturated fatty acid is the main constituent of both Cocoa and Shea butter.The density o Stearic acid is 0.86°F at normal temperature and pressure.It is stable at normal room temperature and pressure.When it is heated above the boiling point it decomposes to emit acrid smoke and irritating fumes.The pH of Stearic acid is around 5.5. It is a weak acid much like all organic acids.The molecular mass of Stearic acid is 284.48 g/mol.[6]

1.3 Physical Properties of Glycerol

Table 1 Physicochemical properties of stearic acid at 20 °C [7]

Chemical formula ^C3H₅(OH)₃ Units Appearance white solid.and

Odor Pungent, oily

Molecular mass 284.484 g/mol

Density 0.9408 g/cm³

Viscosity 7.79 mPa.s

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Melting point 69.3 ^°C

Boiling point 361 ^°C

Heat capasity 501.5 J/mol·K

Specific Heat J/g 2.30 J/g

Thermal conductivity 0.173 W/m

Flash Point 230 ^{° F}

Surface tension 64.00 mN/m

Solubility in water 0.597 mg/L Miscible

Vapor pressure 0.01 kPa (150°C)

1.4 Chemical reaction of stearic acid

1.4.1 Stearic Acid-Modified CuO Coating Metal Surface with Super hydrophobicity and Anti-Corrosion Properties

Recently, studies to find a non-toxic surface modifier are gaining more interest.

Stearic acid is one of the alternative materials due to its non-toxicity property and relatively lower cost in comparison to other modifiers. Therefore, it has a high potential to be used as a chemical modifier. Stearic Acid has been used in preparing, e.g., a super hydrophobic ZnO coating on a glass [8], [9]and a super hydrophobic zinc nano-coating in X65 steel [10]In this work, the possibility of implementing stearic acid on a CuO-coated steel substrate as a surface modifier in order to fabricate a super hydrophobic coating using a series of facile methods was explored. A super hydrophobic CuO coating on steel substrate was prepared through a series of treatments, which include electrodeposition, solutionimmersion, and stearic acid modification. Surface characterization by Scanning Electron 6

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Microscope (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS), corrosion test, and wettability test were carried out. As a result, the fabricated super hydrophobic CuO coating surface exhibited excellent water-repellency as well as anti-corrosion properties

1.4.2 Solvent-free esterification of stearic acid and ethylene glycol with heterogeneous catalysis in a stirred batch microwave reactor

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Figure 3 . Schematic diagram of the fabrication of superhydrophobic CuO coating.

Figure 4 Illustration of the reaction between stearic acid and hydroxyl group of CuO layer.

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Ethylene glycol distearate (EGDS) is extensively used in the pharmaceutical and cosmetics industries. Even in textile industries as a softener, EGDS is in demand.

In this paper, synthesis of EGDS by esterification of ethylene glycol and stearic acid has been described using a solid acid catalyst under microwave (MW) irradiation in a solvent-free system. Conventional heating takes more than 4–6 h to give a mixture of EGDS and ethylene glycol monostearate (EGMS). Under MW irradiation, the highest conversion of 97% of the acid was obtained in 10 min. The reaction mixture was analyzed by acid value, FT-IR, ¹H-NMR and mass spectroscopy. The EGDS synthesis was optimized concerning various parameters such as reaction time, different catalysts, catalyst loading (wt/wt%), temperature, and MW power. Heterogeneous catalysis, intensified with MW irradiation, makes the esterification process more promising route for possible application at industrial scale.

Ethylene glycol distearate (EGDS) is used in cosmetic materials like shampoo, conditioners, body washes and soaps, hair colouring, acne treatment, and anti- ageing products It is also incorporated in the heating, ventilation and air conditioning systems of electronic cars. EGDS has important property as a phase- changing material Current studies in its synthesis aim to replace homogenous acid catalysts by heterogeneous catalysts. There are many heterogeneous catalysts reported to synthesize industrially important esters In addition to polymer-based catalysts, such as Amberlyst, sulfated zirconia has been studied by many researchers for catalyzing esterification reactions Biocatalysts are also incorporated in the synthesis of ethylene glycol di-stearate .[11]

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Figure 5 esterification of ethylene glycol and stearic acid

1.4.3 Synthesis of a new hydrophobic coating film from stearic acid of buffalo fat (waxy stearyl stearate)

This experiment involved the chemical conversion of pure stearic acid from buffalo adipose tissue to a waxy stearyl stearate, which was subsequently applied as a coating film to extend the shelf life of recently harvested fruits. Fat was extracted from minced adipose tissue using the dry rendering procedure, and it was then characterized. The extracted fat was hydrolyzed into a mixture of free fatty acids and glycerol. The supercritical CO2 extractor was used for stearic acid individual extraction in pure form from the free fatty acid mixture, and it was confirmed according to its melting point (69.2–70.0 °C), elemental analysis, GC–

MS for esterified fatty acids. The isolated stearic acid was used for the synthesis of a new hydrophobic wax named stearyl stearate. The chemical structure of the prepared compound was established according to its elemental analysis and spectral data. The new hydrophobic wax was used as a coating film to enhance the 9

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shelf life of freshly harvested tomato fruits. Therefore, stearyl stearate solution (2.00% w/v diethyl ether) was used for tomato coating and compared to chitosan- coated tomatoes, where weight loss, pH, fruit firmness, ascorbic acid concentration, and total soluble solids were studied for a period of 15 days at 23 ± 1.0 °C and 65 ± 2.0% relative humidity. The results revealed that coating with stearyl stearate solution (2.00% w/v diethyl ether) could delay tomatoes’ ripening during the experiment condition. A sensory evaluation of the coated tomatoes was carried out and showed acceptable taste for the tomatoes that were coated with stearyl stearate. On the other hand, the acute oral toxicity of stearyl stearate using albino mice showed complete safety up to 25 g/kg mice weight. [12]

The purpose of this study was to prepare a new hydrophobic coating film with a waxy texture, in order to be able for fruit coating, and to control the water permeability through the fruit epidermis, thus enhancing the shelf life of the freshly harvested fruits. And it was achieved via preparation of stearyl stearate, due to absence of any unsaturation center with in the very long hydrocarbon chain. In addition, buffalo fat can be considered as a byproduct, and it well known by its high concentration of stearic acid. Thus, buffalo fat was used as a cheap source for our synthesis. So, freshly harvested tomatoes were chosen as a typical example for enhancing its shelf life using the prepared film.[13]

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1.5 Uses and application of stearic acid

1.5.1 As food additive

The direct use of stearic acid in food is not common. It can be used for its lubricity, emulsification and soft properties in gum and candy. Also, it can be used as a coating agent, and to produce stearates and emulsifiers. Stearic acid is a common saturated fatty acid. Saturated means, when it comes to the structure of the carbon chain there is not a lot of double bonds, hence the carbon is saturated and has more room for hydrogen. Being saturated also means that it is solid at room temperature.

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The following food list may contain it: Bakery ,Dairy ,Sauces, seasonings, snacks ,Desserts & ice cream .Cocoa products, Chewing gum ,Vitamins & dietary supplements [13]

1.5.2 Soaps and cosmetics

Stearic acid is mainly used in the production of detergents, soaps, and cosmetics such as shampoos and shaving cream products.[13] Stearate soap, such as sodium stearate, could be made from stearic acid but instead are usually produced by saponification of stearic acid-containing triglycerides. Esters of stearic acid with ethylene glycol (glycol stearate and glycol distearate) are used to produce a pearly effect in shampoos, soaps, and other cosmetic products.[13]

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Figure 6 stearic acid As Soaps and cosmetics

1.5.3 Lubricants, softening and release agents

In view of the soft texture of the sodium salt, which is the main component of soap, other salts are also useful for their lubricating properties. Lithium stearate is an important component of grease. The stearate salts of zinc, calcium, cadmium, and lead are used as heat stabilisers PVC. Stearic acid is used along with castor oil for preparing softeners in textile sizing. They are heated and mixed with caustic potash or caustic soda. Related salts are also commonly used as release agents, e.g.

in the production of automobile tires. As an example, it can be used to make castings from a plaster piece mold or waste mold, and to make a mold from a shellacked clay original. In this use, powdered stearic acid is mixed in water and the suspension is brushed onto the surface to be parted after casting. This reacts with the calcium in the plaster to form a thin layer of calcium stearate, which functions as a release agent.[15]

Steric acid can be converted to zinc stearate, which is used as a lubricant for playing cards (fanning powder) to ensure a smooth motion when fanning. Stearic

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acid is a common lubricant during injection molding and pressing of ceramic powders.[16]

1.5.4 Niche uses

Being inexpensive, nontoxic, and fairly inert, stearic acid finds many niche applications . [13]Varied examples of stearic acid use in manufacturing include soaps and greases, household soap products, synthetic rubber, cosmetic and pharmaceutical creams and lotions, candles, phonograph records, lubricants, shoe and metal polishes, food packaging, and rubber compounds.[13]

Stearic acid is used as a negative plate additive in the manufacture of lead-acid batteries.[citation needed] It is added at the rate of 0.6 g per kg of the oxide while preparing the paste. It is believed to enhance the hydrophobicity of the negative plate, particularly during dry-charging process. It also reduces the extension of oxidation of the freshly formed lead (negative active material) when the plates are kept for drying in the open atmosphere after the process of tank formation. As a consequence, the charging time of a dry uncharged battery during initial filling and charging (IFC) is comparatively lower, as compared to a battery assembled with plates which do not contain stearic acid additive. Fatty acids are classic components of candle-making. Stearic acid is used along with simple sugar or corn syrup as a hardener in candies.[13]

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1.5.5 APPLICATIONS

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 Chem into for metallic soaps & greases, household soap products, synthetic rubber vulcanization activators, alkyd & epoxy resins for surface coatings, synthetic rubber polymerization emulsifier; component of cosmetic formulations, pharmaceutical creams, of candles; lubricant in pharmaceutical tablet formulations; release agent in baked goods & confectioneries

 For suppositories, coating enteric pills, ointments and for coating bitter remedies. Manufacturing stearates of aluminum, zinc, and other metals, stearin soap for opodeldoc, candles, phonograph records, insulators, modeling compounds; impregnating plaster of Paris; in vanishing creams and other cosmetics.

 In preparation of sodium stearate, which is the solidifying agent for the official glycerin suppositories; in enteric tablet coating; ointments; and for many other commercial products, such as toilet creams, vanishing creams, solidified alcohol, etc., (when labeled solely for external use, it is exempt from the requirement that it be prepared from edible fats and oils)

 Stearic acid is widely used in cosmetics, plastics plasticizers, mold release agents, stabilizers, surfactants, rubber vulcanization accelerator, waterproof agent, polishing agent, metal soap, metal mineral flotation agents, softeners and pharmaceuticals as well as other organic chemicals. Stearic acid can also be used as the solvents of oil-soluble paint, crayons lubrication agent, stencil lighting agent and the emulsifier of stearic acid glyceride.

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 Stearic acid can also be widely used in the manufacturing of PVC pipe, sheet material, profiles and film and is the PVC heat stabilizers with good lubricity and excellent stability against light and heat. In the application of polyvinyl chloride pipe, stearic acid helps prevent the "coke" during the processing and is effective heat stabilizer during PVC film processing while also preventing the discoloration of the finished film discoloration caused by exposure.

 The mono-or multi-alcohol ester of stearic acid can be used as cosmetics, nonionic surfactants and plasticizers. Its alkali metal salt can be dissolved in water and is a major component of soap. Other kinds of salts can be used as waterproofing agents, lubricants, bactericides, coating additives and PVC stabilizers.

 Generally applications of stearic acid exploit its bifunctional character, with a polar head group that can be attached to metal cations and a nonpolar chain that confers solubility in organic solvents. The combination leads to uses as a surfactant and softening agent. Stearic acid undergoes the typical reactions of saturated carboxylic acids, notably reduction to stearyl alcohol, and esterification with a range of alcohols

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Reference

[1] J. R. Loften, J. G. Linn, J. K. Drackley, T. C. Jenkins, C. G. Soderholm, and A. F. Kertz, “Invited review: Palmitic and stearic acid metabolism in lactating dairy cows,” J. Dairy Sci., vol. 97, no. 8, pp. 4661–4674, 2014.

[2] J. E. Hunter, J. Zhang, and P. M. Kris-Etherton, “Cardiovascular disease risk of dietary stearic acid compared with trans, other saturated, and unsaturated fatty acids: a systematic review,” Am. J. Clin. Nutr., vol. 91, no. 1, pp. 46–63, 2010.

[3] D. J. Anneken, S. Both, R. Christoph, G. Fieg, U. Steinberner, and A.

Westfechtel, “Fatty acids,” Ullmann’s Encycl. Ind. Chem., 2000.

[4] M. P. Sawant and L. V Gavali, “CONVERSION OF COPPER SULPHATE TO COPPER CHLORIDE USING CHLORINE GAS,” 2016.

[5] A. W. Ralston and C. W. Hoerr, “The solubilities of the normal saturated fatty acids,” J. Org. Chem., vol. 7, no. 6, pp. 546–555, 1942.

[6] P. Prasad, “Development of dolomite bricks with positive plc.” 2014.

[7] D. R. Lide, CRC handbook of chemistry and physics, vol. 85. CRC press, 2004.

[8] A. B. Gurav et al., “Superhydrophobic surface decorated with vertical ZnO nanorods modified by stearic acid,” Ceram. Int., vol. 40, no. 5, pp. 7151–

7160, 2014.

[9] J. Zhang, Z. Liu, J. Liu, E. Lei, and Z. Liu, “Effects of seed layers on controlling of the morphology of ZnO nanostructures and 16

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superhydrophobicity of ZnO nanostructure/stearic acid composite films,”

Mater. Chem. Phys., vol. 183, pp. 306–314, 2016.

[10] Y. Feng, S. Chen, and Y. F. Cheng, “Stearic acid modified zinc nano- coatings with superhydrophobicity and enhanced antifouling performance,”

Surf. Coatings Technol., vol. 340, pp. 55–65, 2018.

[11] B. Vijayakumar, P. Iyengar, G. Nagendrappa, and B. S. Prakash, “Direct esterification of carboxylic acids with p-cresol catalysed by acid activated Indian bentonite,” 2005.

[12] M. H. Suárez, E. M. R. Rodríguez, and C. D. Romero, “Chemical composition of tomato (Lycopersicon esculentum) from Tenerife, the Canary Islands,” Food Chem., vol. 106, no. 3, pp. 1046–1056, 2008.

[13] K.-K. Oh et al., “The orchestration of Cornus kousa fruit and gut microbiota for anti-obesity via integrated pharmacological analysis based on metabolomics,” 2023.

[14] E. P. on F. A. and N. S. added to F. (ANS) et al., “Re evaluation of fatty‐ acids (E 570) as a food additive,” EFSA J., vol. 15, no. 5, p. e04785, 2017.

[15] A. Nora, A. Szczepanek, and G. Koenen, “Metallic Soaps. Ullmann’s Encyclopedia of Industrial Chemistry 2005.” Wiley-VCH, Weinheim.

[16] W. J. Tseng, D.-M. Liu, and C.-K. Hsu, “Influence of stearic acid on suspension structure and green microstructure of injection-molded zirconia ceramics,” Ceram. Int., vol. 25, no. 2, pp. 191–195, 1999.

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