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أرجو المساعده ethane to ethylene

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    muslimonline7
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    تاريخ التسجيل: Oct 2006
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    Ethylene

    Heinz Zimmermann, Linde AG, Hoellriegelskreuth, Federal Republic of Germany
    Roland Walzl, Linde AG, Hoellriegelskreuth, Federal Republic of Germany



    Ullmann's Encyclopedia of Industrial Chemistry
    Copyright © 2002 by Wiley-VCH Verlag GmbH & Co. KGaA. All rights reserved.
    DOI: 10.1002/14356007.a10_045
    Article Online Posting Date: June 15, 2000


    --------------------------------------------------------------------------------


    3. Chemical Properties

    The chemical properties of ethylene result from the carbon – carbon double bond, with a bond length of 0.134 nm and a planar structure. Ethylene is a very reactive intermediate, which can undergo all typical reactions of a short-chain olefin. Due to its reactivity ethylene gained importance as a chemical building block. The complex product mixtures that have to be separated during the production of ethylene are also due to the reactivity of ethylene.

    Ethylene can be converted to saturated hydrocarbons, oligomers, polymers, and derivatives thereof. Chemical reactions of ethylene with commercial importance are: addition, alkylation, halogenation, hydroformylation, hydration, oligomerization, oxidation, and polymerization.

    The following industrial processes are listed in order of their 1993 worldwide ethylene consumption [6]: 1. Polymerization to low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE)

    2. Polymerization to high-density polyethylene (HDPE)

    3. Addition of chlorine to form 1,2-dichloroethane

    4. Oxidation to oxirane [75-21-8] (ethylene oxide) over a silver catalyst

    5. Reaction with benzene to form ethylbenzene [100-41-4], which is dehydrogenated to styrene [100-42-5]

    6. Oxidation to acetaldehyde

    7. Hydration to ethanol

    8. Reaction with acetic acid and oxygen to form vinyl acetate

    9. Other uses, including production of linear alcohols, linear olefins, and ethyIchloride [75-00-3], and copolymerization with propene to make ethylene – propylene (EP) and ethylene – propylene – diene (EPDM) rubber








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    © 2004 by Wiley-VCH Verlag GmbH & Co. KGaA All rights reserved.

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  2. [12]
    muslimonline7
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    تاريخ التسجيل: Oct 2006
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    Ethylene

    Heinz Zimmermann, Linde AG, Hoellriegelskreuth, Federal Republic of Germany
    Roland Walzl, Linde AG, Hoellriegelskreuth, Federal Republic of Germany



    Ullmann's Encyclopedia of Industrial Chemistry
    Copyright © 2002 by Wiley-VCH Verlag GmbH & Co. KGaA. All rights reserved.
    DOI: 10.1002/14356007.a10_045
    Article Online Posting Date: June 15, 2000


    --------------------------------------------------------------------------------


    4. Raw Materials

    Table 1 lists the percentage of ethylene produced worldwide from various feedstocks for 1981 and 1992 [7]. In Western Europe and Japan, over 80 % of ethylene is produced from naphthas — the principal ethylene raw materials.



    Table 1. Raw materials for ethylene production (as a percentage of total ethylene produced)

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    Raw
    USA

    W. Europe

    Japan

    World

    materials
    1979
    1991

    1981
    1991

    1981
    1991

    1981
    1991


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    Refinery gas
    1
    3


    2





    17

    LPG, NGL
    65
    73

    4*
    14

    10*
    2*

    31*
    27

    Naphtha
    14
    18

    80
    72

    90
    98

    58
    48

    Gas oil
    20
    6

    16
    12

    0
    0

    11
    8



    --------------------------------------------------------------------------------


    *Including refinery gas




    A shift in feedstocks occurred for the period from 1980 to 1991. In the United States and Europe larger amounts of light feedstocks (LPG: propane + butane) and NGL (ethane, propane, butane) are used for ethylene production, whereas in Japan more naphtha was used in 1991 compared to 1981. The use of gas oils for ethylene production decreased slightly during the 1980s.

    Ethane [74-84-0] is obtained from wet natural gases and refinery waste gases. It may be cracked alone or as a mixture with propane. Propane [74-98-6] is obtained from wet natural gases, natural gasolines, and refinery waste gases. Butanes are obtained from natural gasolines and refinery waste gases. A mixture of light hydrocarbons such as propane, isobutane [75-28-5], and n-butane [106-97-81], commonly called liquefied petroleum gas (LPG) and obtained from natural gasolines and refinery gases, is also used as a feedstock.

    Naphthas, which are the most important feedstocks for ethylene production, are mixtures of hydrocarbons in the boiling range of 30 – 200 °C. Processing of light naphthas (boiling range 30 – 90 °C, full range naphthas (30 – 200 °C) and special cuts (C6 – C8 raffinates) as feedstocks is typical for naphtha crackers.

    A natural-cut full-range naphtha contains more than 100 individual components, which can be detected individually by gas chromatography (GC). Depending on the origin naphtha quality can vary over a wide range, which necessitates quality control of the complex feed mixtures. Characterization is typically based on boiling range; density; and ******* of paraffins (n-alkanes), isoalkanes, olefins, naphthenes, and aromatics ( PIONA analysis) by carbon number. This characterization can be carried out by GC analysis or by a newly developed infrared method [8]. Full characterization of feedstocks is even more important when production is based on varying feedstocks, e.g. feedstocks of different origins purchased on spot markets.

    The quality of a feedstock is depending on the potential to produce the target products (ethylene and propylene). Simple yield correlations for these products can be used to express the quality of a feedstock in a simple figure, the quality factor, which indicates wether yields of the target products are high or low, with aromatic feedstocks being poor and saturated feedstocks being good feedstocks.

    Quality characterization factors for naphthas have been developed, which indicate the aromatics ******* by empirical correlation. Since aromatics contribute little to ethylene yields in naphtha cracking, a rough quality estimate can be made for naphthas with a typical weight ratio of n- to isoparaffins of 1 – 1.1. The K factor is defined as [9]:



    where Tk is the molal average boiling point in K. Naphthas with a K factor of 12 or higher are considered saturated; those below 12 are considered naphthenic or aromatic. The K factor does not differentiate between iso- and n-alkanes. The U.S. Bureau of Mines Correlation Index (BMCI) [10] can also be used as a rough quality measure of naphthas:



    where T is the molal average boiling point in K and d is the relative density . A high value of BMCI indicates a highly aromatic naphtha; a low value, a highly saturated naphtha.

    Gas oils are feedstocks that are gaining importance in several areas of the world. Gas oils used for ethylene production are crude oil fractions in the boiling range of 180 – 350 °C (atmospheric gas oils, AGO) and 350 – 600 °C (vacuum gas oils, VGO). In contrast to naphtha and lighter gas feeds, these feedstocks can not be characterized by individual components.

    Gas chromatography coupled with mass spectrometry (GC – MS) or high performance liquid chromatography (HPLC) allow the analysis of structural groups, i.e., the percentage of paraffins, naphthenes, olefins, monoaromatics, and polyaromatics in the gas oil, and can be used to determine the quality of the hydrocarbon fraction. If this information is used together with data such as hydrogen *******, boiling range, refractive index, etc., the quality can be determined quite accurately. A rough estimate of feed quality can be made by using the BMCI or the calculated cetane number of a gas oil. The cetane number, normally used to calculate the performance of diesel fuels, is an excellent quality measure, since it is very sensitive to the n-paraffin *******, which is one of the key parameters for the ethylene yield. The cetane number CN is calculated as follows [11]:



    where CI = 0.9187 (T50 /10)1.26687 ()1.44227, where T50 is the volume average boiling point in°C and the refractive index at 20 °C






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  3. [13]
    اهم اهم
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    تاريخ التسجيل: Apr 2006
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    السلام عليكم..
    توجد اطروحة تتناول طرق انتاج الاثيلين واحداها التكسير الحراري للايثان عنوانها
    Economic Analysis of a New Gas to Ethylene Technology.
    وان شاء الله يفيدك
    http://txspace.tamu.edu/bitstream/ha...pdf?sequence=1

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