Shravanthi Galiveti Department of Chemistry The Green Path to Ethylene 3 Production Sucrose, starchy and ligno-cellulosic biomass, can be used to produce bioethanol. Sucrose biomass such as sugarcane, sugar beets and sweet sorghum, can be converted to ethanol via fermentation by yeast. Starchy biomass, such as corn and wheat must first be hydrolyzed before fermentation. Ligno-cellulosic biomass, e.g. wood, straw and grass, follow a more complicated process of hydrolysis and fermentation.3 1 Introduction Ethylene is one of the most important feedstocks for the chemical industry – 75% of petrochemical products are derived from ethylene, as well as the largest produced by volume – 142 million tons of ethylene was produced in 2011, and this figure is growing.1,2 However it’s derived from finite fossil fuels and produces the most greenhouse gas (GHG) emissions, so a greener alternative is needed.2 Currently around 99% of ethylene is produced through hydrocarbon cracking. Ethylene used to be made from ethanol until 1940, when the steam cracking of petrochemical feed stocks offered a cheaper alternative. Bio-ethylene can be produced through catalytic, gas - solid phase, dehydration of ethanol.4 The process can achieve a high selectivity with yields between 94-99% and uses activated phosphoric acid, oxides, molecular sieves, or other miscellaneous acids as catalysts. Alumina based catalysts are most common in today’s industrial reactors.1 The global market for biopolymer production is expanding, with ethylene used in the production of around half of all plastics, many new bio-ethylene plants have been commissioned.3 The recent boom in shale gas production will lower the price and availability of ethane; this is likely to have negative effects on the bio-ethylene industry.5 Dehydration 6 Conclusion Catalyst 4 What is it? Benefits Bio-ethylene is a chemically identical version of ethylene that is derived from bioethanol, which in turn comes from biomass sources. Bioethanol is a widely used fuel in the transport industry, with about 100 billion liters produced yearly.3 No new technology needed for conversion of bio-ethylene to derivates. Average life cycle GHG emissions can be up to 40% lower and 60% more fossil fuel energy is saved. Sucrose derived ethanol process byproducts generate electricity that can be exported. Renewable energy source – less dependence on finite fossil fuels. Economic benefit - lowers import of fossil fuels and stimulates local employment. Large biomass reserves, with global production expected to produce between 1.5 – 4.5 x1011 GJ by 2050. Bio-polymers can be sold for a premium price of approximately 15-30%.3 Ethylene Derivatives Others 8% Ethylene Benzene 7% EDC 13% Ethylene Oxide 13% References 1. 2. Y. Yu, and M. Zhang, Ind. Eng. Chem. Res, 2013, 52, 9505-14 C. Eckert, W. Xu, W. Xiong, S. Lynch, J. Ungerer, L. Tao, R. Gill, P. Maness, J. Yu, Biotechnol Biofuels, 2014, doi: 10.1186/1754-6834-7-33. Industry The USA is the world’s largest producer of bio-ethylene, contributing 63% of global production and Brazil is second, with 24%. The largest bio-ethylene plants are capable of producing around 200kt of bio-ethylene per year. Pre-treated ethanol is fed into the reactor. • Temperatures are in the region of 300− 500 °C • Pressure of 0.1− 0.2 MPa • Main byproduct - diethyl ether - generated at <573K The crude ethylene is then purified in a series of towers.1 2 Polyethene 59% 5 Barriers ⤫ Future biomass availability is uncertain. Depends upon food requirements, and industry demand from the chemical, energy and transportation sectors. ⤫ Biomass from food feedstocks such as corn and sugarcane, reduces food supply, thus adversely affecting prices. Especially damaging in developing countries. ⤫ EU import duty on ethanol - upto $310 per ton, unfavourable to import for use as a feedstock. ⤫ Bio-ethylene production is more expensive than the global average petrochemical production costs by 10-130%. ⤫ Conversion of pristine land to biomass products can release a significant amount of GHG emissions.3 3. 4. 5. Mean Ethylene Production Cost3 2570 2060 1650 Climate change is a serious threat to our world. Bio-ethylene is a step in the right direction to lowering the environmental impact of the ethylene and wider chemical industries. Furthermore, the gap between finite fossil fuels and bio-based fuels is likely to narrow in the long run as oil reserves are depleted and technology advances. Ligno-cellulosic biomass shows the greatest potential, as it requires less land, 100% of the material can be converted, and has little effect on food supply.3 In the future bio-ethylene will be an increasingly important part of the chemical industry. . 1190 1220 1100 EU-sugar beets China-sweet sorghum India-sugarcane USA-corn Brazil-sugarcane Global-petrochemical IEA-ETSAP and IRENA, Production of Bio-Ethylene: Technology Brief, IRENA Report, 2013 G. Chen, M. K. Patel, Chem Rev, 2012, 112, 2082-99 Market outlook: Shale gas impacts bio-based chemicals, http://www.icis.com/Articles/2013/06/07/9676331/marketoutlook-shale-gas-impacts-bio-based-chemicals.html, (accessed April 2013).
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