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Gleaming into Glycerine: Manufacturing Processes and Applications

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ChemAnalyst

Glycerin might seem like a basic ingredient, a clear, odorless liquid found on countless product labels. But behind its simple appearance lies a world of surprising benefits. From keeping your skin healthy to aiding medical treatments, Glycerin's uses extend far beyond the cosmetic aisle.


In this blog post, we'll delve into the fascinating world of Glycerin. We'll explore its surprising origins, from everyday sources like vegetable oils to its role in industrial applications. We'll also uncover the science behind Glycerin's effectiveness in skincare and its potential health benefits. So, whether you're a curious consumer or a skincare enthusiast, get ready to discover the hidden potential of this versatile molecule!


Introduction


Glycerin, a dense and transparent liquid devoid of scent, offers a multitude of advantages spanning from medicinal applications to cosmetics. Its versatility manifests in skincare routines, either in its pure form or as an ingredient integrated into various beauty products. Derived from sources like soybean, palm oil, coconut oil, as well as animal origins and petroleum, Glycerin finds extensive industrial utility. Its diverse applications encompass the manufacturing processes of explosives, paints, varnishes, inks, textiles, and adhesives.


Commonly recognized under the names glycerol and Glycerine, this compound falls under the category of sugar alcohols due to its chemical structure, although it lacks any intoxicating properties. It exhibits complete solubility in water, ether, and alcohol, alongside its hygroscopic nature, facilitating the absorption of moisture from the environment. Endorsed by the Food and Drug Administration (FDA) as a safe food additive, Glycerin holds the generally recognized as safe (GRAS) status and earns approval for incorporation into skincare formulations and other cosmetic products. Remarkably, it ranks as the third most prevalent ingredient in cosmetics.


Manufacturing Process


Glycerin can be derived from various industrial processes, including methylesters production, fats saponification, and fat splitting, each involving different by-products. Depending on the initial by-product, the production process varies. For by-products like sweet water from fat splitting and spent lyes from saponification, the process entails chemical treatment, concentration, Glycerin distillation, and refining.


  • In the treatment phase, hydrochloric acid is utilized to reduce the solubility of fatty acids, which are then separated. Sweet water undergoes a single filtration before distillation, while spent lyes are filtered twice, both before and after neutralization.


  • The crude Glycerin undergoes further processing in a distillation, deodorizing, and bleaching facility. The distillation process involves washing, rectification, and condensation steps.


  • In the final purification stage, activated carbon is used in the bleaching section to eliminate color and odor, resulting in pure Glycerin.

Transesterification


Transesterification process involves the conversion of methyl esters from triglycerides (oils) and methanol (alcohol) into glycerol and fatty esters (or biodiesel). Both homogeneous and heterogeneous catalysis methods are employed in the production of biodiesel and consequently, glycerol.


  • Initially, vegetable oils react with methanol in the presence of the catalyst. Subsequently, glycerol separation from the product mixture occurs via a settler unit. The residual flow undergoes treatment in a unit designed to remove the catalytic component using mineral acids, resulting in the generation of two streams: one for glycerol recovery and another for an evaporator, which separates biodiesel from other by-products. The glycerol purification unit yields three output streams: the first containing 80%–95% glycerol, the second comprising water, dissolved salts, and unreacted methanol (recycled back to the reactor), and the third stream containing fatty esters.


  • To enhance the conversion of vegetable oil, the process involves two reaction steps. In the first reactor, vegetable oil and methanol are introduced. The resulting product stream undergoes heat exchange to vaporize some unreacted methanol, with the remainder directed to a decanter for the separation of polar (predominantly glycerol) and non-polar (mostly vegetable oil and biodiesel) components. Subsequently, the non-polar stream undergoes a second reaction in the second reactor to further increase biodiesel production and recover methanol. Here, the product stream undergoes heat exchange to remove all unreacted methanol, while the decanter separates biodiesel from polar components. The polar streams from both decanters are directed to another heat exchanger to recover any remaining methanol, with the residual portion directed to a final decanter for the separation of vegetable oil and unreacted glycerol.

 

SIEBTECHNIK GMBH, one of the leading producers of Glycerin also uses this method. Bio-diesel production involves the transesterification of fats or oils with methanol, typically catalyzed by a basic catalyst. This reaction converts one mole of triglyceride into three moles of biodiesel (ester) and one mole of glycerol. Consequently, each batch of biodiesel generates approximately 10% by weight of glycerol. This glycerol, known as crude glycerol, is a by-product of the transesterification process. The transesterification reaction is pivotal in transforming renewable fats and oils into biodiesel, replacing glycerol molecules in triglycerides with methanol to yield biodiesel and glycerol. It's worth noting that the glycerol obtained in this process is impure, containing various contaminants, hence its classification as crude glycerol. Proper management of this by-product is crucial for bio-diesel production, ensuring efficient resource utilization and environmental sustainability.

Propylene Chlorination


In the propylene chlorination process, allyl chloride is generated at a temperature of 510°C in the presence of hypochlorous acid at 38°C. Subsequently, allyl chloride undergoes a reaction to form Glycerine dichlorohydrine. Following this, glycerol dichlorohydrine is hydrolyzed either by caustic soda in a 6% Na2CO3 solution at 96°C or directly into Glycerine, with epichlorohydrin removed as overhead in a stripping column. Finally, epichlorohydrin is hydrated to Glycerine using caustic soda. This process enables a final glycerol yield of approximately 90%.


Saponification


The traditional method of splitting natural fats and oils through saponification with alkali, such as caustic soda or sodium hydroxide, has been practiced for centuries. Commonly employed in this process are caustic alkali or alkali carbonates. Alternatively, calcium hydroxide in the form of milk of lime can also serve as a reagent. In this saponification procedure, fats and oils are heated with a caustic soda solution and salt. The triglycerides within the fats and oils react with the caustic soda, resulting in the formation of soap and glycerol. The addition of salt induces the separation of the mixture into two distinct layers – the upper layer consisting of soap and the lower layer, known as spent lye, containing glycerol, water, excess caustic soda, and salt. Continuous saponification processes, known as consap, are also utilized for soap production.


REFINING


Refining crude natural glycerol typically involves distillation, often followed by activated carbon treatment. In some instances, ion exchange is utilized.


Distillation


The process utilizes vacuum distillation to separate Glycerine from organic components and salts, operating at temperatures of up to 175°C. The remaining substance is then directed to a thin film evaporator to enhance Glycerine yield. Furthermore, a decanter is employed to separate salt from the residue, reducing waste and increasing Glycerine recovery. Pharmaceutical-grade Glycerine, the main product, undergoes purification through adsorption on activated carbon beds to bleach it, diverting light impurities to technical-grade Glycerine. These methods not only ensure efficient Glycerine separation but also minimize waste and improve overall recovery of this valuable substance.

Major Applications of Glycerine


  1. Cosmetics & Personal Care:


Glycerin offers significant benefits for skin health due to its properties as a humectant, solvent, and lubricant, making it a valuable ingredient in skincare formulations. Its capacity to reduce moisture loss helps in keeping the skin hydrated for extended periods compared to other moisturizers. Studies affirm Glycerin's potent moisturizing effects, establishing it as a robust and efficient humectant, particularly beneficial for dry skin. Glycerin holds significant utility in personal care products, serving as a versatile ingredient due to its properties as a humectant, solvent, lubricant, and alternative to sorbitol, another sugar alcohol used as a sweetener. It finds widespread application in various products including toothpaste, mouthwash, skin care formulations, deodorants, soaps, and baby care products. In these formulations, Glycerin contributes to moisturization, texture enhancement, and overall product efficacy, making it a staple in the personal care sector.


  1. Food & Beverages:


Glycerin plays a multifaceted role in the food industry, commonly found in processed, packaged, and frozen foods where it serves various purposes. Acting as an emulsifier, it stabilizes ingredients and prevents separation, while also serving as a sugar substitute, adding sweetness to food products. Its humectant properties help preserve foods by preventing moisture loss, while also acting as a solvent for food coloring and flavors, aiding their dispersion. Additionally, Glycerin acts as a softening agent in candies, cakes, and meat/cheese casings, contributing to their texture and quality.


  1. Pharmaceuticals:


Glycerin serves as a vital component in the production of several pharmaceutical items, including suppositories, where it forms the base for medications enclosed in solid Glycerin pieces. Additionally, Glycerin is utilized in the manufacturing processes of cough medicines, gel capsules, certain medications, and specific types of anesthetics, playing essential roles in formulation consistency, delivery methods, and therapeutic efficacy within the pharmaceutical industry.


Market Outlook


The primary driver of market growth is the widespread adoption of Glycerin in personal care and cosmetics. It is extensively utilized in various products like toothpaste, soaps, shaving creams, and skin and hair care items to enhance smoothness and lubrication. Glycerin's ability to prevent moisture loss from these products makes it a valuable component, employed as denaturants, fragrance ingredients, oral care agents, hair conditioning agents, and skin protectants.


Glycerine Main Players


Significant companies in the Global Glycerine market are The Procter & Gamble Company, Dow Chemical, Renova S.A., Emery Oleochemicals, Vantage Specialty Chemicals, Louis Dreyfus Company, General Lagos, BOJAGRO S.A., Vance Group Ltd., Owensboro Grain Company, The Vegetables Vitamins Foods Company Pvt. Ltd., PMC Biogenix, Inc., Thai Glycerine Co., Ltd., and Others.


Conclusion:


Glycerine finds extensive utilization across diverse industries, notably in food and beverages as a sweetener, and in medicinal and cosmetic formulations as an emollient. Its water-absorbing properties, attributed to hydroxyl groups, make it invaluable in these applications. With recognized antibacterial and antiviral qualities, Glycerine is a common ingredient in skincare products, aiding in skin healing and smoothness. In the pharmaceutical industry, it features prominently in various medications, including cough syrups, expectorants, and allergen immunotherapies. Additionally, nitroGlycerin stands out as a prevalent treatment for chronic angina. Glycerin’s versatility extends to topical treatments for conditions like psoriasis and wounds. Market drivers for Glycerine include the healthcare, cosmetic, and medical industries, where its moisturizing properties are leveraged to treat skin ailments and promote hygiene awareness. This increasing demand is expected to fuel the global Glycerine market in the coming years, driven by its antimicrobial properties and diverse applications across multiple sectors.


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