Chapter 2 : The Composition of Petroleum and its products

Transcription

1 Petroleum Refining Chapter 2: Composition of Petroleum and its Products Chapter 2 : The Composition of Petroleum and its products Introduction Petroleum is a mixture of compounds - HC s (C & H). Range from CH4 to C85H60. Elemental Composition in crude oil 1. Table 2-1: Elemental Composition in crude oil Hydrocarbon Non-hydrocarbon Element C H N O V Ni Cu % wt Traces Traces Traces Traces Non-hydrocarbon elements (O,, and N) are present as components of complex molecules predominantly HC in character. Non-hydrocarbon elements (V, Ni, and Cu) are present from filed production operations. The boiling point of crude oil ranges from 90 to 1500 ºF. Compounds in crude oil are classified as - - Paraffins and isoparaffins - Olefins - Naphthenes - Aromatics 1 Not to mention, water, salt, sand, sediments, etc. 2-1

2 Prof. Tareq A. Albahri 2018 Kuwait University Chem. Eng. Dep. RH R--R' R---R' Thiols ulfides Disulfides (Mercaptans) Cyclic ulfides Thiophene Benzothiophene Dibenzothiophene Naphthobenzothiophene Figure 2-1: Examples of simple organic sulfur compounds in crude oil and its products. (source: peight, 'the chemistry and technology of petroleum', 1999, p.229 & 710) ROH R-COOH R-COO Alkylalcohols Carboxylic acids Carboxylic acid anhydrides R-O-R' R-COO-R' R-CO-R' Ethers Carboxylic acid esters Ketones O O O O Diphenylether Tetrahydropyran Furan Benzofuran Figure 2-2 : Examples of simple organic oxygen compounds in crude oil and its products. (source: peight, 'the chemistry and technology of petroleum', 1999, p.233) 2-2

3 Petroleum Refining Chapter 2: Composition of Petroleum and its Products R-NH 2 Amines aniline Pyrrole Pyridine Indole Indoline Quinoline Carbazole Benzoquinoline Benzo carbazole Figure 2-3: Examples of simple organic nitrogen compounds in crude oil and its products. (source: peight, 'the chemistry and technology of petroleum', 1999, p.234 & 711) Paraffins General formula (CnH2n+2) Carbon is capable of forming single, double multi-branched chains which give rise to isomers that have significantly different properties. The number for possible isomers increases in geometric progression as the number of atom increases (Table 2.2). Crude oil contains molecules with up to carbon atoms, & the number of possible paraffinic HC s is very high. 2-3

4 Prof. Tareq A. Albahri 2018 Kuwait University Chem. Eng. Dep. propane n-butane isobutane n-pentane isopentane neopentane Figure 2-4 Examples of simple paraffins in crude oil and its products Table 2-2 : Number of possible paraffinic hydrocarbon isomers. Molecule ymbol # of paraffin isomers Methane C1 1 Ethane C2 1 Propane C3 1 Butanes C4 2 Pentanes C5 3 Hexanes C6 Heptanes C7 Octanes C8 17 Nonanes C9 Decanes C10 Undecane C11 Dodecanes C Tridecanes C13 Tetradecane C14 Pentadecanes C15 Hexadecanes C16 Heptadecanes C17 Octadecanes C18 60,533 Olefins Do not naturally occur in crude oils - but are formed during processing in the thermal/catalytic cracking units like the delayed coker and the FCC. They are very similar in structure to paraffins, but at least two of the C atoms are joined by double bonds. The general formula is CnH2n. In gasoline boiling range, olefins are desirable because they have a higher RON than paraffins. However, olefins are generally undesirable in finished products, because: 2-4

5 Petroleum Refining Chapter 2: Composition of Petroleum and its Products 1. Double bonds are reactive and the compounds are more easily oxidized and polymerize to form gums and varnishes. 2. ome diolefins, formed during processing, react very rapidly with olefins to form high MW polymers and form filter plugging compounds. 3. C5 olefins have high reaction rates with compounds in the atmosphere that form pollutants. Naphthenes Are cycloparaffins in which all the bonds are single. The general formula is CnH2n. Naphthenes can have paraffin side chains. Many types of naphthenes exist in crude oil (Figure 2.4) Except for the lower MW compounds, such as cyclopentane and cyclohexane, Naphthenes are generally not handled as individual compounds. They are classified according to boiling range, and their properties are determined with the help of correlation factors such as Kw factor, or CI. 2-5

6 Prof. Tareq A. Albahri 2018 Kuwait University Chem. Eng. Dep. Cyclopentane Methylcyclopentane Dimethylcyclopentane Cyclohexane Methylcyclohexane 1,2-dimethylcyclohexane. Decalin n-decylcyclopentane (Decahydronaphthalene) Figure 2-5 Examples of simple naphthenes in crude oil and its products Aromatics These are hydrocarbons that contain one or more benzene ring. Aromatics can have paraffin side chains and can form a mixed structure with naphthenes. These mixed types have many of the chemical & physical characteristics of both of the parent compounds (the aromatic and the paraffin), but generally are classified according to the parent cyclic compound. 2-6

7 Petroleum Refining Chapter 2: Composition of Petroleum and its Products Benzene Toluene o-xylene m-xylene p-xylene cumene. Naphthalene Indan Tertahydronaphthalene Diphenyl Diphenylmethane Anthracene Phenanthrene o-terphenyl m-terphenyl p-terphenyl Pyrene Chrysene Flourene Figure 2-6: Examples of simple aromatic hydrocarbons in crude oil and its products 2-7

8 Prof. Tareq A. Albahri 2018 Kuwait University Chem. Eng. Dep. Composition of Petroleum Distillates Figure 2-7: Principal petroleum products, their boiling range temperatures and their number of carbon atoms. 2-8

9 Petroleum Refining Chapter 2: Composition of Petroleum and its Products Table 2-3 Boiling point and carbon number range for petroleum products No. Petroleum product Boling Point ( C) Carbon Number 1 LPG (-120) - 40 C3 C4 2 Gasoline (-10) C4 C13 3 Naphtha C5 C11 4 W C8 C12 5 Jet Fuel C9 C13 6 Lamp Oils C10 C17 7 Diesel Fuel & Home Heating oil C11 C23 8 Paraffins C22 C33 9 Base tocks C23 C55 10 Heavy Fuels 375+ C Waxes C36 C60 12 Asphalts C

10 Prof. Tareq A. Albahri 2018 Kuwait University Chem. Eng. Dep. Table 2-4 : Compounds Completely Identifiable in Naphtha by a Detailed Hydrocarbon GC analyzer 1. No Model Compound No Model Compound Propane Isobutane n-butane 2,2-Dimethylpropane (Neopentane) Isopentane n-pentane 2,2-Dimethylbutane (Neohexane) Cyclopentane 2,3-Dimethylbutane 2-Methylpentane 3-Methylpentane n-hexane 2,2-Dimethylpentane Methylcyclopentane 2,4-Dimethylpentane 2,2,3-Trimethylbutane Benzene 3,3-Dimethylpentane Cyclohexane 2-Methylhexane 2,3-Dimethylpentane 1,1Dimethylcyclohexane 3-Methylhexane 1-trans-3-Dimethylcyclopentane 1-cis-3-Dimethylcyclopentane 3-Ethylpentane 1-trans-2-Dimethylcyclopentane 2,2,4-Trimethylpentane (Isooctane) n-heptane Methylcyclohexane 2,2-Dimethylhexane Ethylcyclopentane 2,5-Dimethylhexane 2,4-Dimethylhexane 1-trans-2-cis-4-Trimethylcyclopentane 2,3,4-Trimethylpentane 1-trans-2-cis-3-Trimethylcyclopentane 2,3,3-Trimethylpentane Toluene 2,3-Dimethylhexane 2-methyl-3-Ethylpentane 2-Methylheptane 4-Methylheptane 3,4-Dimethylhexane 1-cis-2-cis-4-trans-Trimethylcyclopentane 3-Methylheptane 1-methyl-2-Ethylcyclopentane 1-trans-4-Dimethylcyclohexane 1,1-Dimethylcyclohexane 1-cis-3-Dimethylcyclohexane ource; Detailed Hydrocarbon Gas Chromatography Analyzer. 1-methyl-cis-2-Ethylcyclopentane 1-methyl-trans-3-Ethylcyclopentane 1-methyl-cis-3-Ethylcyclohexane 1-ethyl-1-Methylcyclopentane 1-trans-2-Dimethylcyclohexane n-octane Isopropylcyclopentane C9 Paraffin C9 Paraffin 2,2,5-Trimethylhexane 2,2,4-Trimethylhexane 2,4,4-Trimethylhexane 2,3,5-Trimethylhexane 3,4-Dimethyheptane 2,4-Dimethylheptane 1-cis-2-Dimethylcyclohexane n-propylcyclopentane Ethylcyclopentane 1-cis-2-Dimenthylcyclohexane 1,1,3-Trimethylcyclohexane 2,5-Dimethylheptane 3,3-Dimethylheptane 3,5-Dimethylheptane 2,4-Dimethylheptane 2,3,3-Trimethylhexane Ethylbenzene 1-cis-3-cis-5-Trimethylpentane 1,1,4-Trimethylcyclohexane 2,3,4-Trimethylhexane 3,3,4-Trimethylhexane m-xylene p-xylene 2,3-Dimethylheptane 1-cis-2-trans-4-Trimethylcyclohexane 1-cis-2-trans-4-cis-Trimethylcyclohexane 3,4-Dimethylheptane 3-methyl-Ethylhexane 4-Ethylheptane 4-Methyloctane 2-Methyloctane C9 Paraffin 3-Methyloctane C9 Paraffin o-xylene C9 Paraffin 1-methyl-2-Propylcyclopentane 1-methyl-trans-4-Ethylcyclohexane 1-methyl-cis-4-Ethylcyclohexane C9 Paraffin 3,3-Diethylpentane 2-10

11 Petroleum Refining Chapter 2: Composition of Petroleum and its Products Table 2-4: continued. No Model Compound No Model Compound ,2,6-Trimethylheptane 1,1,2-Trimethylcyclohexane n-nonane 1-methyl-1-Ethylcyclohexane Isopropylbenzene (Cumene) tert-butylcyclopentane tert-butylbenzene Isobutylcyclopentane 1-methyl-4-Isopropylcyclohexane ec-butylcyclopentane 1-cis-2-cis-3-cis-Trimethylcyclohexane n-butylcyclopentane 1-methyl-2-Ethylcyclohexane 3-Methylnonane n-propylbenzene n-propylcyclohexane C9-Aromatic C9Aromatic m-ethyltoluene p-ethyltoluene 1,3,5-Trimethylbenzene 2-Methylnonane 0-Ethyltoluene 2,2-Dimethyloctane 3,6-Dimethyloctane 1,2,4-Trimethylbenzene (Psuedocumene) 1-cis-methyl-3-Ethylcyclohexane 1-trans-methyl-2-Ethylcyclohexane 1-trans-2-methyl-Propylcyclohexane 1-methyl-Ethylbenzene ethyl-2,3-Dimethylcyclohexane Isobutylbenzene n-decane 1,2,3-Trimethylbenzene (Hemimellitene) 4-Methyldecane 1-methyl-2-Isopropylbenzene (o-cymene) C10 Naphthene sec-butylbenzene n-butylbenzene C10 Aromatic 1-methyl-4-Propylbenzene 1-methyl-3-Propylbenzene C10 Aromatic Isobutylcyclohexane 5-Methyldecane 1,4-Diethylbenzene C10 Aromatic C10 Aromatic 1-methyl-2-Propylbenzene trans-1-methyl-2-(4-methylpentyl)-cyclopentane 2-ethyl-1,4-Dimethylbenzene C10 Aromatic 1,4-dimethyl-2-Ethylbenzene n- Undecane 1,2,4,5-Tetramethylbenzene 1,2-dimethyl-4-Ethylbenzene C11 Aromatic 2-11

12 Prof. Tareq A. Albahri 2018 Kuwait University Chem. Eng. Dep. Composition of Vacuum Residue Vacuum residue contains thousands of complex (high molecular weight, high boiling point) hydrocarbons and organic compounds. This is divided into three main fractions. 1. Oil fraction. 2. Resin fraction 3. Asphaltene fraction. Oil + C 3 Vacuum Residue C 3 EXTRACTION Resin + C 5 /C 6 /C 7 C 5 /C 6 /C 7 EXTRACTION Figure 2-8: eparation of vacuum residue. Asphaltene (insoluble in C 3 - C 7 ) 1. Oil fraction. - Highly paraffinic. - Usually contains no metals. - Has lower and N content than the vacuum residue. 2. Resin fraction - Contains certain condensed-ring aromatics - Has substantial amount of paraffinic structure - ulfur concentrations are approximately the same as the vacuum residue (from which they are derived) - Contain %wt of the metals in the crude. - erves as a solvent for the asphaltenes MW 600 5,000 (solution techniques) MW (mass spectrometer) 3. Asphaltene fraction. - Very low H/C ratio. - Contains 80-90% of the metals in crude (Ni, V). - Consists of highly condensed aromatic ring compounds MW 5,000 10,000 (solution techniques) MW (mass spectrometer) 2-12

13 Petroleum Refining Chapter 2: Composition of Petroleum and its Products Naphthenic rings Valence bonds hetro atom (N,, O, V, Ni) Paraffinic side chain heets of highly condensed ring structure (3-5) Figure 2-9: Hypothetical asphaltene molecule structure 2-13

14 Prof. Tareq A. Albahri 2018 Kuwait University Chem. Eng. Dep. References 1. David R. Lide, CRC Handbook of Chemistry and Physics, 82 nd ed, CRC Press, (QD 65 C ) 2. James peight, The Chemistry and Technology of Petroleum, CRC Press, Klaus H. Altgelt and Boduszynski, Composition and analysis of heavy petroleum fractions, CRC Press,