Hello and welcome to our blog about Ethylene Oxide – a unique and indispensable substance in different areas of our life. Ethylene Oxide is one of the most important organic compounds as it has many uses and chemical properties. In this blog, we explore the use of Ethylene Oxide in various industries ranging from pharmaceuticals to agriculture and textiles among others. So, lets drive into it!
Introduction
Ethylene Oxide serves as a versatile chemical primarily utilized as an intermediate in the production of various industrial chemicals, notably Ethylene Glycol. Additionally, it functions as a surface disinfectant, particularly prevalent in the healthcare and medical equipment sectors, where it substitutes steam in sterilizing heat-sensitive tools such as disposable plastic syringes. Moreover, Ethylene Oxide finds extensive application in diverse sectors, including non-contact infrared thermometers, thermal imaging systems, liquid chemical sterilization, patient lifts, surgical staplers, household and industrial cleaners, cosmetics, shampoos, polyurethanes, heat transfer liquids, plasticizers, ointments, and various fabric applications.
Manufacturing Process
This blog unveils a process for manufacturing Ethylene Oxide which has several steps. The operations fall into four main stages:
- Stage 1 involves EO reaction, EO recovery, and carbon dioxide removal
- Stage 2 focuses on removing non-condensables and purifying EO
- Stage 3 centers on glycols reaction and dewatering
- Stage 4 deals with glycols purification.
Stage 1: EO Reaction, EO Recovery, and Carbon Dioxide Removal
- Feedstock ethylene is commonly delivered via pipeline from a steam cracker. While air can supply oxygen in an air-based process, modern methods rely on pure oxygen from an air separation unit.
- The reaction between ethylene and oxygen occurs in a fixed-bed reactor with a silver catalyst in the tubes and a coolant on the shell side. Heat from the exothermic reactions is managed by the coolant, which produces steam for heating various parts of the plant.
- A substantial gas flow continuously circulates through the EO reactors. Reaction byproducts (EO, carbon dioxide, and water) are removed, while unreacted oxygen and ethylene are recycled. To mitigate fire and explosion risks, a diluent is added to the recycle gas, typically methane, enabling safe operation with higher oxygen levels.
- A small amount of organic chlorinated compound is introduced to control catalyst performance, with resulting chlorine distributed across product and effluent streams. A vent stream, known as inerts purge, reduces the accumulation of inerts and impurities in the recycle gas. This vent gas is often used as fuel.
- Additional ethylene, oxygen, and diluent are introduced into the recycle gas loop as needed.
- To manage the significant influx of inert nitrogen from the air feed, a portion of the recycle gas was redirected to a secondary EO reactor, referred to as the purge-reactor, where the majority of the ethylene was converted. EO was extracted from the purge-reactor product gas through absorption in water, while the remaining gases (such as unreacted ethylene, nitrogen, and carbon dioxide) were released into the atmosphere.
- EO mixes completely with water. At normal temperatures and without catalysts, EO's reactivity with H2O (leading to glycol formation) remains minimal across a broad pH spectrum, making water an effective medium for scrubbing EO for removal or recovery. The gas exiting the reactor is treated to recover EO by absorbing it into water. The resulting aqueous EO solution undergoes concentration in a stripper. From the top of the stripper, a concentrated EO-water mixture is directed to a stage for removing non-condensable substances and purifying EO (Stage 2). The bottom stream of the stripper consists of EO-free water, which is cooled and returned to the EO absorber.
- Typically, one or more bleed streams are extracted from the EO recovery process to prevent the buildup of glycols and/or salts. These substances undergo further processing to reclaim EO and/or glycols.
- A portion of the recycle gas exiting the EO absorber is directed through a column where carbon dioxide, produced during the oxidation process, is absorbed under pressure. It forms hydrogen carbonate in a heated potassium carbonate solution.
- The carbon dioxide is then separated from the carbonate solution in an atmospheric stripper through a reverse reaction. The carbon dioxide released from the top of the stripper can be released into the atmosphere or reclaimed for other purposes, such as in carbonated drinks, following treatment to eliminate volatile organic compounds (VOCs). The regenerated carbonate solution from the bottom of the stripper is cooled and reused in the carbon dioxide absorber. The overhead stream from the absorber, now depleted of carbon dioxide, is combined again with the recycle gas stream and directed back to the EO reactor(s).
Step 2: Non-condensables removal and EO purification
- After the initial separation process, the Ethylene Oxide (EO) and steam mixture is cleaned up. This purification step removes unwanted elements like carbon dioxide and excess ethylene. The unusable gases get sent back for recycling, while the cleaned-up EO-water mix gets separated. In most European plants, this mix gets distilled to extract high-purity EO. Leftover water might be reused or sent for further processing. The final EO product is chilled and stored. Since EO is a gas at normal temperatures, special storage methods are needed. It's typically kept under nitrogen and cooled, though pressurized storage is also an option. Any leftover EO gas from storage or other processes gets captured and recycled back into the system. Finally, for transport, EO is loaded onto pressurized railcars under a nitrogen blanket.
Step 3: Glycols reaction and dewatering
Glycols are produced by introducing a mixture of EO and water into a reactor operating at elevated temperatures, usually ranging between 150 and 250 °C. Under these conditions, reactions occur rapidly, requiring no catalyst. Sufficient residence time is provided to ensure complete conversion of EO. A reactor pressure typically between 10 and 40 barg is maintained to prevent EO vaporization. The feed to the reactor contains an excess of water to control the adiabatic temperature rise and enhance MEG selectivity. Generally, glycol products consist of 75 to 92 wt-% MEG, with the remaining portion comprising DEG and some TEG. All of the EO feed is converted into glycols, including MEG, DEG, TEG, or heavier glycols.
- The output from the glycols reactor comprises different glycol products along with surplus water. This excess water is eliminated through multiple-effect evaporation followed by vacuum distillation. After heat exchange, the purified water is returned to the glycols reactor for reuse. A portion of the recycled water is extracted to prevent impurity buildup. Low-pressure steam produced in this process serves as a heat source in various sections of the plant.
Step 4 - Glycols purification
- The glycol stream, now depleted of water, undergoes fractionation in several vacuum columns to separate and recover the different glycol products at high purity. The co-products in the MEG manufacturing process, in decreasing quantities, are diethylene glycol (DEG), triethylene glycol (TEG), and heavier glycols. These individual glycol products are then further purified through subsequent fractionation. After cooling, the glycol products are directed to storage. The residual stream from the final vacuum column contains the heavier glycols, which can either be sold for additional glycol recovery or disposed of, such as through incineration.
Step 5 - Crystallization Step
- The crystallization step follows the barium removal process to precipitate Ethylene Oxide from the solution, yielding pure Ethylene Oxide. This ensures the removal of impurities, particularly barium ions, resulting in high-purity Ethylene Oxide suitable for various applications.
- Crystallization techniques such as heat concentration or vacuum distillation are employed to precipitate Ethylene Oxide. Higher temperatures during crystallization expedite the process; however, subsequent drying at temperatures below 60°C prevents the release of water of crystallization, maintaining the product as hydrated Ethylene Oxide, which is easier to handle. Additional treatments like pulverization may be performed to adjust the physical properties of Ethylene Oxide as needed.
Applications of Ethylene Oxide
- Chemical Industry
Ethylene Oxide is used majorly for the production of Ethylene Glycol. Ethylene Glycol is a multi-functional chemical. It serves as an antifreeze which is used in automotive coolant systems to prevent freezing and protect the engines from cold. It also plays a vital role as a raw material for the synthesis of polyester fibers and resins in the textile and plastic industries. Ethylene Glycol is used as a deicing fluid for planes and runways to enable them to operate even during the winter season. It is also a humectant in cosmetics, a heat transfer medium in industrial processes, and a solvent for paints and coatings. It is used as a chemical intermediate for the manufacture of several industrial chemicals that are essential in various industries hence can be considered as the most important industrial chemical. Additional derivatives of Ethylene Oxide find application in household cleaning products and personal care items like cosmetics and shampoos. These derivatives are also utilized in industrial cleaning solutions, heat transfer fluids, polyurethanes, and plasticizers.
2. Medical
Ethylene Oxide sterilization processes can sanitize medical and pharmaceutical products that cannot support conventional, high-temperature steam sterilization procedures. Medical devices that require Ethylene Oxide sterilization include heart valves, pacemakers, surgical kits, gowns, drapes, ventilators, syringes, and catheters.
3. Agriculture
Ethylene Oxide and its derivatives play a crucial role in producing a wide array of active and inactive components utilized in insecticides, pesticides, and herbicides, tailored to meet the specific needs of the agricultural sector, thereby safeguarding crops and enhancing agricultural productivity. In agricultural crop processing, Ethylene Oxide-based demulsifiers enhance the separation of oil from water, particularly in corn oil extraction within the bioethanol production process. The extracted oil finds applications in the food industry, animal feed production, or biodiesel manufacturing. Ethylene Oxide is also instrumental in producing industrial starches from agricultural sources, known as hydroxyethyl starches, which serve as versatile inputs in various industries such as adhesives, papermaking, and laundry starch. Additionally, in veterinary and animal surgical settings, Ethylene Oxide is utilized to sterilize medical equipment, surgical instruments, and procedure kits, ensuring optimal hygiene and safety standards.
4. Oil & Gas
Ethylene Oxide derivatives play a surprising role in making oil and gas production cleaner and more efficient. These compounds help purify natural gas, prevent pipeline corrosion, and even capture carbon emissions. They also speed up oil well operations and extend equipment life, ultimately lowering the cost of petroleum products. A key family of these derivatives – ethanolamines – even contributes to cleaner burning fuels by removing impurities.
Market Outlook
The primary use of Ethylene Oxide lies in its role as a chemical intermediate for synthesizing glycol ethers, acrylonitrile, ethoxylates, ethylene glycol, and polyether polyols, all of which find extensive applications across various downstream industries. The escalating demand for these derivatives from end-user sectors is a key driver propelling the global market forward. Among these derivatives, the Ethylene Glycol segment holds dominance globally, particularly due to its widespread utilization in automotive, packaging, and pharmaceutical industries. Ethylene Glycol serves as a crucial component in the production of polyester fibers, polyethylene terephthalate (PET) resins, and automotive antifreeze. Furthermore, the increasing global population, particularly in emerging economies, is fueling demand for personal and healthcare products, further augmenting the need for Ethylene Oxide.
Ethylene Oxide Major Global Producers
Major companies in the Global Ethylene Oxide market are Sinopec, BASF, Shell, Dow Chemical, Ningbo Henyuan, Nippon Shokubai Co., Ltd., Reliance Industries Limited, SINOPEC SABIC (TIANJIN) Petrochemical Company Limited, Maruzen Petrochemical Co., Ltd., PTT Global Chemical, Sasol Limited, Saudi Kayan Petrochemical Company, Nizhnekamskneftekhim, Indorama Ventures Public Company Limited, and Others.
Conclusion:
Ethylene Oxide serves primarily as a chemical precursor for the synthesis of glycol ethers, acrylonitrile, ethoxylates, ethylene glycol, and polyether polyols, essential components utilized across diverse industries. The rising demand from the chemical sector, particularly for chemicals like Ethylene Glycol is expected to propel the global Ethylene Oxide market in the foreseeable future. Furthermore, the increasing need within the medical industry for Ethylene Oxide to sterilize medical instruments and equipment is also contributing to the growth of the Ethylene Oxide market.
