Abstract
Ethylene is the primary component in most plastics, making it economically valuable. It is produced primarily by steam-cracking of hydrocarbons, but can alternatively be produced by the dehydration of ethanol, which can be produced from fermentation processes using renewable substrates such as glucose, starch and others. Due to rising oil prices, researchers now look at alternative reactions to produce green ethylene, but the process is far from being as economically competitive as using fossil fuels. Many studies have investigated catalysts and new reaction engineering technologies to increase ethylene yield and to lower reaction temperature, in an effort to make the reaction applicable in industry and most cost-efficient. This paper presents various lab synthesized catalysts, reaction conditions, and reactor technologies that achieved high ethylene yield at reasonable reaction temperatures, and evaluates their practicality in industrial application in comparison with steam-cracking plants. The most promising were found to be a nanoscale catalyst HZSM-5 with 99.7% ethylene selectivity at 240 °C and 630 h lifespan, using a microreactor technology with mechanical vapor recompression, and algae-produced ethanol to make ethylene.
Highlights
Ethylene is the most widely produced organic compound in the chemical industry
Despite much advancement being made in producing ethylene from ethanol, the process is not ready to replace fossil fuel methods in meeting the world demand for ethylene
Recent successes in increasing ethylene yield and lowering reaction temperature by modifying catalysts have revealed a number of catalysts that could be applied to industry, the most favorable one being nanoscale
Summary
Ethylene is the most widely produced organic compound in the chemical industry. The large global demand for the compound stems from its various uses as precursors to polymers such as polyethylene, found in most plastics, or surfactant chemicals such as ethylene oxide or ethylene glycol (Figure 1), according to Chemical and Engineering News (2006) [1,2]. Attention has recently shifted towards green alternatives for manufacturing ethylene, to reduce greenhouse gas emissions and dependency on limited fossil fuels Leading this green trend is the production of ethylene by catalytic bioethanol dehydration. To make ethanol dehydration more industry-friendly, many researchers have investigated different catalysts to increase ethylene yield and lower reaction temperature. This review article will discuss the catalysts recently studied that have the potential to be applied in an industrial scale ethanol to ethylene plant competitive with steam cracking plants. Because other research papers on the dehydration of ethanol to ethylene do not report findings in the context of industry, catalysts and technology in relation to production costs and feasibility are evaluated
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