Article No : a10_045 Article with Color Figures Ethylene HEINZ ZIMMERMANN, Linde Engineering Division, Pullach, Germany ROLAND WALZL, Linde Engineering Division, Pullach, Germany 1. Introduction.......................465 5.3.2.2. Hydrocarbon Fractionation Section. .....503 2. Physical Properties .................467 5.3.3. Utilities...........................513 3. Chemical Properties ................467 5.3.4. Process Advances ...................514 4. Raw Materials .....................468 5.3.5. Plant Size . .......................515 5. Production ........................469 5.4. Ethanol based Production of Ethylene. 515 5.1. Ethylene from Pyrolysis of 5.4.1. Chemistry of Dehydration . ..........516 Hydrocarbons .....................469 5.4.2. Bioethanol as Intermediate to Ethylene. 517 5.1.1. Cracking Conditions . ..............470 5.4.2.1. First- and Second-Generation Bioethanol . 517 5.1.2. Heat Requirements for Hydrocarbon 5.4.2.2. Raw-Material Costs ..................518 Pyrolysis . .......................475 5.4.3. Production of Ethylene by Dehydration . 518 5.1.3. Commercial Cracking Yields . ..........476 5.4.4. Environmental Issues. ..............520 5.1.4. Commercial Cracking Furnaces .........482 5.4.5. Future Outlook . ...................520 5.1.5. Tube Metallurgy . ...................490 5.5. Other Processes and Feedstocks .......521 5.1.6. Thermal Efficiency of Ethylene Furnaces . 491 6. Environmental Protection ............522 5.1.7. Coking and Decoking of Furnaces and 7. Quality Specifications................522 Quench Coolers. ...................492 8. Chemical Analysis ..................523 5.2. Quenching of Hot Cracked Gas........494 9. Storage and Transportation...........523 5.3. Recovery Section ...................498 10. Uses and Economic Aspects ...........525 5.3.1. Products . .......................499 11. Toxicology and Occupational Health . 525 5.3.2. Cracked Gas Processing. ..............499 References ........................526 5.3.2.1. Front-End Section ...................499 1. Introduction In 2005 total worldwide ethylene production capacity was 112.9 Â 106 t, with an actual de- mand of ca. 105 Â 106 t/a [2], which has growth Ethylene [74-85-1], ethene, H2C¼CH2, Mr 28.52, as one of the great building blocks in projections of 3.7 to 4.3 % per year worldwide for chemistry is a large-volume petrochemical with the period of 2005–2010 [5–7]. a production of approximately 120 Â 106 t/a The production of ethylene today is based on [1–3] in 2008. It has been recovered from feedstocks derived from crude oil (! Oil Refin- coke-oven gas and other sources in Europe since ing) or from natural or associated gas (! Natural 1930 [4]. Ethylene emerged as a large-volume Gas). The leading technology applied for pro- intermediate in the 1940s when U.S. oil and duction of ethylene is steam cracking, a high chemical companies began separating it from temperature pyrolysis in the presence of steam, refinery waste gas and producing it from ethane which has been developed in the 1960s, but the obtained from refinery byproduct streams and principles have not been changed. Recent devel- from natural gas. Since then, ethylene has almost opments have been made to increase size and completely replaced acetylene for many synthe- scale of the plants and to improve overall eco- ses. Ethylene is produced mainly by thermal nomics. Today’s plants can produce up to cracking of hydrocarbons in the presence of 1.5 Â 106 t/a of ethylene in a single-train plant. steam, and by recovery from refinery cracked Alternatives have been developed such as meth- gas. anol to olefins, in which methanol derived from Ó 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/14356007.a10_045.pub3 466 Ethylene Vol. 13 Figure 1. Crude-oil price development [8–10] natural gas (! Gas Production, 5. Examples of bioethanol offers a production from renewable Complex Gas Production Plants, Chap. 1) is raw materials. converted finally into ethylene. However, none More than half of the production of ethylene of the alternative technologies has the economics is used for the production of polyethylene to be a challenge for the well-established steam- (! Polyethylene), one of the most important cracking process until today. plastic materials today. The market grows con- With the development of the prices for crude tinuously with an average rate of 4 % worldwide oil in 2007 and especially 2008, when prices and can be related to the gross national product increased from approximately 60 US$/bbl to growth in an area or a certain country. 140 US $/bbl [8–10] (Fig. 1), alternative technol- In steam crackers, per ton of ethylene signifi- ogies for production of ethylene have to been re- cant amounts of CO2 are produced, which range evaluated. A second aspect that could trigger a from 1 – 1.6 t/t, depending on the raw material significant change is the CO2 aspect, as the used for cracking. The annual growth of the production of ethylene produces significant worldwide ethylene production is typically in 6 amounts of CO2 and will be subject to the range of 5 –6 Â 10 t/a, which translates into 6 CO2 trading schemes in the future in several additional CO2 emissions of 5 – 9 Â 10 t/a. In areas. addition, due to the high temperature pyrolisis These recent changes have started several NOx emissions are produced when using the developments in the petrochemical industry, conventional technology. such as shift of huge production capacities to Besides the major industrial applications of areas with advantaged feedstocks (Middle East, ethylene, a small portion is converted into etha- South America, Central Asia, etc.) but also nol by hydration and has been a source of syn- fuelled the search for alternative production thetic ethanol for quite some time. However, with routes for commercial-scale ethylene production. the increase in oil prices and consequently the One of the most promising routes is the dehydra- increase of raw material costs for ethylene pro- tion of ethanol, a reaction known for quite some duction, the reverse reaction has become of time, but historically not used for large-scale significant interest. ethylene production, due to economics and avail- Ethylene units are centers of petrochemical ability of raw materials. However, due to the complexes in which ethylene is transferred into dramatically increasing production of bioethanol transportable intermediates or semifinished pro- worldwide, this route has to be reconsidered as an ducts with ethylene capacities of up to 1.5 Â 106 alternative to conventional ethylene production t/a and significant amounts of high-value bypro- from fossil raw materials. In addition, the depen- ducts. These sizes are required in order to utilize dence of the ethylene value chain on crude-oil the economy of scale for production of ethylene. price developments could be interrupted as In a world-scale plant of such scale, ethylene can Vol. 13 Ethylene 467 be produced at much lower specific costs than in at À50 C 1.10 MPa at 0 4.27 MPa smaller units. Explosive limits in air at Small-scale ethylene production in quantities 0.1 MPa and 20 C of 100 Â 103 – 200 Â 103 t/a is in most cases lower (LEL) 2.75 vol % or 34.6 g/cm3 not economical as many of the byproducts are upper (UEL) 28.6 vol % or 360.1 g/cm3 Ignition temperature 425–527 C produced in quantities to small for marketing. However, world-scale plants for EDC/PVC re- quire ethylene in quantities of 100 Â 103 – 200 Â 103 t/a only and ethylene supply from 3. Chemical Properties standalone crackers of this size is not feasible in most cases. The chemical properties of ethylene result from the carbon–carbon double bond, with a bond length of 0.134 nm and a planar structure. Eth- 2. Physical Properties ylene is a very reactive intermediate, which can undergo all typical reactions of a short-chain Ethylene is a colorless flammable gas with a olefin. Due to its reactivity ethylene gained sweet odor. The physical properties of ethylene importance as a chemical building block. The are as follows: complex product mixtures that have to be sepa- rated during the production of ethylene are also due to the reactivity of ethylene. Ethylene can be converted to saturated hydro- mp À169.15 C carbons, oligomers, polymers, and derivatives bp À103.71 C thereof. Chemical reactions of ethylene with Critical temperature, Tc 9.90 C Critical pressure, Pc 5.117 MPa commercial importance are: addition, alkylation, Critical density 0.21 g/cm3 halogenation, hydroformylation, hydration (see Density Section 5.4), oligomerization, oxidation, and at bp 0.57 g/cm3 at 0 C 0.34 g/cm3 polymerization. Gas density at STP 1.2603 g/L The following industrial processes are listed Density relative to air 0.9686 in order of their 2000 worldwide ethylene con- Molar volume at STP 22.258 L Surface tension sumption [11]: at bp 16.5 mN/m at 0 C 1.1 mN/m 1. Polymerization to low-density polyethylene Heat of fusion 119.5 kJ/kg (LDPE) and linear low-density polyethylene Heat of combustion 47.183 MJ/kg (LLDPE) Heat of vaporization at bp 488 kJ/kg 2. Polymerization to high-density polyethylene at 0 C 191 kJ/kg (HDPE) Specific heat 3. Addition of chlorine to form 1,2-dichloro- of liquid at bp 2.63 kJ kgÀ1 KÀ1 À1 À1 ethane of gas at Tc 1.55 kJ kg K Enthalpy of formation 52.32 kJ/mol 4. Oxidation to oxirane [75-21-8] (ethylene Entropy 0.220 kJ molÀ1 KÀ1 oxide) over a silver catalyst Thermal conductivity 5. Reaction with benzene to form ethylbenzene À4 À1 À1 at 0 C 177Â10 Wm K [ ], which is dehydrogenated to at 100 C 294Â10À4 WmÀ1 KÀ1 100-41-4 at 400 C 805Â10À4 WmÀ1 KÀ1 styrene [100-42-5] Viscosity of liquid 6.