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PETROLEUM Defination of Petroleum Crude oil : Petroleum is a naturally occurring flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, containing mostly hydrocarbons, but con...

PETROLEUM Defination of Petroleum Crude oil : Petroleum is a naturally occurring flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, containing mostly hydrocarbons, but containing also some compounds of oxygen, nitrogen and sulfur. Theories about the origin of petroleum: Inorganic Theories: 1-Berthelot Hypothesis Berthelot in 1866, considered acetylene the basic material, and large quantities of acetylene were assumed to have been produced by the reaction of water with carbides", which in turn were formed by the action of alkali metals on carbonates; the conversion of acetylene to petroleum was accounted for by elevated temperatures and pressures, for example, alkali metal H2O CaCO3 CaC2 HC CH Calcium Calcium Acetylene carbonate carbide petroleum 2- Mendelejeff Hypothesis Another theory in which acetylene is also considered the basic material was described by Mendelejeff, who proposed that the action of dilute acids or hot water on mixed iron and manganese carbides produces a mixture of hydrocarbons from which petroleum evolved: H+H2O Petroleum Fe3C + Mn3C Hydrocarbone Iron Manganese carbide carbide  The main facts which go against it are: Natural petroleum contains sulphur and )a( nitrogen compounds, chlorophyll, haemen, ect. The carbide theory fails to explain their presence of all above in petroleum as they are all essentially of organic origin. Organic or Biosynthesis Theories Engler Hypothesis : Engler in 1911, was the first author to postulate that an organic substance other than coal was the source material of petroleum; he invoked the concept of three separate development stages. In the first stage, animal and vegetable deposits accumulate on the bottom of inland seas (lagoon conditions) and are then decomposed by bacteria; the carbohydrates and the bulk of the protein are converted into water- soluble material or gases and thus removed from the site. The fats, waxes, and other fat-soluble and stable materials (rosins, cholesterol, and others) remain, and indeed it has been demonstrated that organic matter subjected to decomposition undergoes an increase in fat content to form Kerogen. In the second stage, high temperatures and pressures cause carbon dioxide to evolve from compounds containing a carboxyl group, and water is produced from the hydroxy acids and alcohols to leave a bituminous residue. Continued application of the heat and pressure causes light cracking, producing a liquid product with high olefin content (protopetroleum). Engler also produced experimental evidence that showed that distillation of fats under pressure brought about the formation of a petroleum type of material, and he assumed that time and high pressure offset the fact that the temperature in oil source rocks is lower than that used experimentally. In the third stage, the unsaturated components of the protopetroleum are polymerized under the influence of contact catalysts ، ‫أﻳﻀﺎ دﻟﻴ ً ﺗﺠﺮﻳﺒﻴًﺎ أﻇﻬﺮ أن ﺗﻘﻄﻴﺮ اﻟﺪﻫﻮن ﺗﺤﺖ اﻟﻀﻐﻂ أدى إﻟﻰ ﺗﻜﻮﻳﻦ ﻧﻮع ﻣﻦ اﻟﻤﻮاد اﻟﺒﺘﺮوﻟﻴﺔ‬ ً ‫أﻧﺘﺞ إﻧﺠﻠﺮ‬ ‫واﻓﺘﺮض أن اﻟﻮﻗﺖ واﻟﻀﻐﻂ اﻟﻌﺎﻟﻲ ﻳﻘﺎﺑ ن ﺣﻘﻴﻘﺔ أن درﺟﺔ اﻟﺤﺮارة ﻓﻲ ﺻﺨﻮر ﻣﺼﺪر اﻟﺰﻳﺖ أﻗﻞ ﻣﻦ ﺗﻠﻚ‬ ‫ ﺗﺘﻢ ﺑﻠﻤﺮة اﻟﻤﻜﻮﻧﺎت ﻏﻴﺮ اﻟﻤﺸﺒﻌﺔ ﻟﻠﺒﺘﺮول ا وﻟﻲ ﺗﺤﺖ ﺗﺄﺛﻴﺮ‬، ‫ ﻓﻲ اﻟﻤﺮﺣﻠﺔ اﻟﺜﺎﻟﺜﺔ‬.‫اﻟﻤﺴﺘﺨﺪﻣﺔ ﻓﻲ اﻟﺘﺠﺮﺑﺔ‬ ‫ﻣﺤﻔﺰات اﻟﺘ ﻣﺲ‬ and thus the polyolefins are converted into naphthenic and/or paraffinic hydrocarbons. Aromatics were presumed to be formed either directly during cracking, by cyclization through condensation reactions. The following points are in support with this theory: 1- Petroleum wells are usually near sea-shores. 2- Marine fossils are found in crude oil. 3- Nitrogen and sulphur compounds are present in petroleum. 4- Fatty substances, on distillation under pressure, give a liquid similar to petroleum. 5- Marine animals contain some metals as iron, vanadium, magnesium... etc., and these are found in the ashes left after burning petroleum. Chemical Composition of Petroleum: Petroleum is a mixture of hundreds of hydrocarbons of all type with water, salts, sulfur and nitrogen containing compounds and some metal complexes. The elementary composition of crude oil usually falls within the following ranges. C% = 85-90 H %= 11-14 S% = 0 - 3 N%= 0- 0.63 Petroleum is primarily a mixture of paraffinic, naphthenic and aromatic hydrocarbons (90-95%) and represents therefore its main natural source. It contains also sulfur, oxygen and nitrogen compounds in small 1- Hydrocarbon compounds: paraffins and isoparafins: Gasses and lighter fractions They are mainly present in the gasses and lighter fractions of petroleum (crude). (C1-C4) associated gas methane, ethane, propane and butane, methane is the lightest of the hydrocarbon gasses, its density with respect to air is 0.55; propane and butane are much heavier. The lightest of these hydrocarbons is pentane C5H12 followed by hexane C6H14, heptane C7H16 octane C8H18. There are three isomeric modifications of pentane:  n-pentane isopentane H H H H H H H H H H C C C C C H H C C C C H H H H H H H H H H C H H H H C H H H H C C C H H H neopentane H C H H Hexane has 4, heptane has 8 and octane has 17 isomeric modifications. The number of possible isomers increases rapidly as the number of carbon atoms increase in the molecule. From C16 (hexa decan) solid constituents. 2-Naphthenic hydrocarbons (Cycloparafins) : It may be found in the higher petroleum fractions. Cycloparafins of other type e.g. cycloheptanes may be found only in insignificant quantities. Paraffins and cycloparafines are the most important ‫ﻳﻤﻜﻦ اﻟﻌﺜﻮر ﻋﻠﻴﻬﺎ‬ ‫ﻓﻲ اﻟﻜﺴﻮر‬ constituents of petroleum..‫اﻟﺒﺘﺮوﻟﻴﺔ ا ﻋﻠﻰ‬ ‫ﺳﻴﻜﻠﻮﺑﺎراﻓﻴﻦ‬ Low boiling point fractions of petroleum contain naphthenes of 5 ‫ﻣﻦ ﻧﻮع آﺧﺮ ﻋﻠﻰ‬ ‫ﺳﺒﻴﻞ اﻟﻤﺜﺎل ﻳﻤﻜﻦ‬ to 6 rings, cyclopentane and cyclohexane and its derivatives. ‫اﻟﻌﺜﻮر ﻋﻠﻰ ﺳﻴﻜﻠﻮ‬ ‫ﻫﻴﺒﺘﺎﻧﺎت ﺑﺸﻜﻞ‬ ‫ﺿﺌﻴﻞ ﻓﻘﻂ‬ H2 ‫ اﻟﺒﺎراﻓﻴﻨﺎت‬.‫ﻛﻤﻴﺎت‬ C ‫واﻟﺴﻴﻜﻠﻮﺑﺎراﻓﻴﻨﺎت‬ H2C CH2 ‫ﻫﻲ ا ﻛﺜﺮ أﻫﻤﻴﺔ‬ H2C CH2 ‫ﻣﻜﻮﻧﺎت اﻟﺒﺘﺮول‬. ‫ﺗﺤﺘﻮي أﺟﺰاء‬ H2C CH2 H2C CH2 ‫اﻟﺒﺘﺮول ذات ﻧﻘﻄﺔ‬ C C ‫اﻟﻐﻠﻴﺎن اﻟﻤﻨﺨﻔﻀﺔ‬ H2 H2 ٥ ‫ﻋﻠﻰ ﻧﺎﻓﺜﻴﻦ ﻣﻦ‬ Cyclohexane ، ‫ ﺣﻠﻘﺎت‬٦ ‫إﻟﻰ‬ Cyclopentane ‫ﺳﻴﻜﻠﻮﺑﻨﺘﺎن‬ ‫وﺳﻴﻜﻠﻮﻫﻜﺴﺎن‬ Naphthene hydrocarbons increased in petroleum fractions above ‫وﻣﺸﺘﻘﺎﺗﻪ‬. ‫زادت‬ ‫ﻫﻴﺪروﻛﺮﺑﻮﻧﺎت‬ ‫اﻟﻨﻔﺜﻴﻦ ﻓﻲ ا ﺟﺰاء‬ 400‫اﻟﺒﺘﺮوﻟﻴﺔ أﻋﻠﻰ‬ 400°C. 3-Aromatic hydrocarbons: Petroleum contains considerable quantities of aromatic hydrocarbons which are of a cyclic structure. The simplest of these hydrocarbons is benzene C6H6 and Toluene. The benzene hydrocarbons are distinguished by their ability to combine in groups of two, three and more rings. These hydrocarbons include: C10H8 C14H10 Naphthalene Anthracene ‫وﺗﺟدر اﻹﺷﺎرة‬ ‫إﻟﻰ أن ﻧﺳﺑﺔ‬ ‫اﻟﮭﯾدروﻛرﺑوﻧﺎت‬ Also, they combine with naphthene rings giving: ‫اﻟﺟزﯾﺋﯾﺔ‬ ‫ﻋﺎﻟﯾﺔﺗﺗﻛون ﻣن‬ ‫ ﻓﻲ‬50 ‫ إﻟﻰ‬20 ‫اﻟﻣﺎﺋﺔ ﻣن ﺟﻣﯾﻊ‬ any may others ‫ﻣﻛوﻧﺎت‬ ‫اﻟﺑﺗروﻟﺑﺷﻛل‬ ‫رﺋﯾﺳﻲ‬ C9H10 C10H12 ‫اﻟﮭﯾدروﻛرﺑوﻧﺎت‬ Indan Tetraline ‫ذات اﻟﺑﻧﯾﺔ‬ ‫ واﻟﺗﻲ‬، ‫اﻟﻣﺧﺗﻠطﺔ‬ It should be noted that the high molecular hydrocarbons of ‫ھﻲ ﻣزﯾﺞ‬ ‫ﻣﻧﺣﻠﻘﺎت ﻋطرﯾﺔ‬ petroleum comprising from 20 to 50 per cent of all its components are ‫وﻧﻔﺛﯾن وﺳﻼﺳل‬ mainly hydrocarbons of mixed structure, which are a combination of ‫ﺑﺎراﻓﯾن‬. aromatic and naphthene rings and paraffin chains. 4-Olefins Olefins do not naturally occur in crude oils. However, they are formed during its processing. They are very similar to paraffins, but they exhibit double bonds. CH3-(CH=CH)n-CH2 ---- B. Non-hydrocarbon Compounds 1. Sulfur Compounds Table 1: Nomenclature and types of Organic sulfur compounds Acidic RSH Thiols (Mercaptans) Non 0acidic RSR' Sulfides S Cyclic sulfides RSSR' Disulfides thiophene Thalphene S Benzothiophene S Dibenzothiophene S S Naphthobenzothiophene S The presence of sulfur compounds in finished petroleum products often produces harmful effects. CH2CH2SCH2CH3 Diethyl sulphide S (3-Thiapentane Thiacyclohexane S S Thiahydrindane 1-Thiaindan  S S Benzothiophene Dibenzothiophene Why is sulfur removed from crude oil? There are several reasons why it is good to remove sulfur from crude oil. 2- ‫إذا ﺑﻘﻲ‬ 1- Sulfur present in the crude oil can harm the catalysts that are used in ‫اﻟﻛﺑرﯾت ﻓﻲ وﻗود‬ the refining of crude oil into the many useful products obtained from ‫ أو‬/ ‫اﻟدﯾزل و‬ crude oil. Catalysts are generally very expensive materials and anything 3-‫ﻓﻲ ﺣﺎﻟﺔ وﺟود‬ ‫اﻟﺑﻧزﯾن ﻟﮫ ﺗﺄﺛﯾر‬ ‫ﺗﺂﻛل ﻓﯾﺎرﺗﻔﺎع‬ that inhibits their activity or shortens their life increases the cost of the ‫اﻟﻛﺑرﯾت ﻓﻲ اﻟوﻗود ﯾﺗم‬ ‫درﺟﺔ اﻟﺣرارة‬ refining process. ‫ﺗﺣوﯾل اﻟوﻗود ﻋﻧد‬ ‫ﻋﻠﻰ ﻣﺣرك‬ ‫ اﺣﺗراﻗﮭﺈﻟﻰ‬SO2 ‫اﻟﻣﺣرك‬ ‫وھو ﻧذﯾر ﻣﻌروف‬ 2- If sulfur remains in diesel fuel and/or gasoline has corrosive effect at ‫ﻟﻠﻣطر اﻟﺣﻣﺿﻲ‬ high temperature on motor engine. 3-If sulfur is present in fuel, when the fuel is burned it will be converted to SO2 which is a known precursor to acid rain. 4- Sulfur compounds are generally lower octane ratings of gasoline 2. Oxygen Compounds Oxygen in organic compounds can occur in a variety of forms (Table 2), and it is not surprising that the more common oxygen- containing compounds occur in petroleum. The total oxygen content of petroleum is usually less than 2%, although larger amounts have been reported Table 2: Nomenclature and types of the common organic oxygen compounds Acidic Alcohols Methyl alcohole CH3-O-H Phenyl alcohole (Phenol) C6H5-O-H Non- acidic Ether Dimethyl ether CH3-O-CH3 Diphenyl ether C6H5-O-C6H5 Cyclic ether H2 C H 2C CH2 Tetrahydropyran (pentamethylene oxide) H 2C CH2 O Carboxylic acids O Acetic acid H3C C H O O Benzoic acid C 6H 5 C H O Carboxylic acid anhydrides O Acetic anhydride H3 C C O H3C C O Carboxylic acid esters O H3C C Ethyl acetate O C2H5 Ketones O Dimethyl ketone (Acetone) H3C C CH3 Furans HC CH HC CH O Benzofuran O Nitrogen compounds 1-Nonbasic Pyrrole C4H5N N H Indole C8H7N N H Carbazole C12H9N N H Benzocarbazole C16H11N N N H H 2-Basic Pyridine C5H5N N Quinoline C9H7N N Indoline C8H9N N H Benzoquinoline C13H9N N  4. ‫اﻟﺑورﻓﯾرﯾﻧﺎﺗﺎﻟﺑورﻓﯾرﯾﻧﺎت ھﻲ ﻧوع ﻣن اﻷﻧواع اﻟﻛﯾﻣﯾﺎﺋﯾﺔ اﻟﺗﻲ ﺗﺣدث ﺑﺷﻛل طﺑﯾﻌﻲ واﻟﺗﻲ ﻣن اﻟﻣﻌروف أﻧﮭﺎ‬ ‫اﻋﺗﺑﺎرا ﻣﻧﻔﺻﻼً ﻓﻲ ھذا اﻟﻘﺳم ﺑﺳﺑب ﺗﻔردھم ﻛﻛﯾﺎﻧﺎت‬ ً ‫ ﯾﺗم إﻋطﺎؤھم‬.‫ ﻋﺎ ًﻣﺎ‬50 ‫ﻣوﺟودة ﻓﻲ اﻟﺑﺗرول ﻷﻛﺛر ﻣن‬ ‫ وال‬، ‫ ال ﯾﺗم اﻋﺗﺑﺎرھﺎ ﻋﺎدة ﻣن ﺑﯾن ﻣﻛوﻧﺎت اﻟﺑﺗرول اﻟﻣﻌﺗﺎدة اﻟﻣﺣﺗوﯾﺔ ﻋﻠﻰ اﻟﻧﯾﺗروﺟﯾن‬.‫ﻛﯾﻣﯾﺎﺋﯾﺔ ﻣﻧﻔﺻﻠﺔ وﻣﺗﻣﯾزة‬ ً ‫ﺗﻌﺗﺑر ﻣﻌدﻧًﺎ ﯾﺣﺗوي ﻋﻠﻰ ﻣﺎدة ﻋﺿوﯾﺔ ﺗﺣدث أﯾ‬ ‫ ﻧﺗﯾﺟﺔ ﻟﮭذه اﻟﺗﺣﻘﯾﻘﺎت اﻟﻣﺑﻛرة ﻧﺷﺄ‬.‫ﺿﺎ ﻓﻲ ﺑﻌض اﻟزﯾوت اﻟﺧﺎم‬ ً ‫ﻣﻔﮭوم اﻟﺑورﻓﯾرﯾﻧﺎت ﻛواﺳﻣﺎت ﺣﯾوﯾﺔ ﯾﻣﻛن أن ﺗﻧﺷﺊ راﺑطﺎ ﺑﯾن اﻟﻣرﻛﺑﺎت اﻟﻣوﺟودة ﻓﻲ اﻟﻐﻼف اﻷرﺿﻲ وﺳﻼﺋﻔﮭﺎ‬ ‫اﻟﺑﯾوﻟوﺟﯾﺔ اﻟﻣﻘﺎﺑﻠﺔ‬. 4. Porphyrins Porphyrins are a naturally occurring chemical species that have been known to exist in petroleum for more than 50 years. They are, given separate consideration in this section because of their uniqueness as separate and distinct chemical entities. They are not usually considered among the usual nitrogen-containing constituents of petroleum, nor are they considered a metallo containing organic material that also occurs in some crude oils. As a result of these early investigations there arose the concept of porphyrins as biomarkers that could establish a link between compounds found in the geosphere and their corresponding biological precursors. CRUDE OIL CLASSIFICATION: Crude oils can be arbitrarily classified into three or four groups depending on the relative ratio of the hydrocarbon classes that predominates in the mixture. The following describes three types of crudes: According to types of hydrocarbons 1. Paraffinic—the ratio of paraffinic hydrocarbons is high compared to aromatics and naphthenes. 2. Naphthenic—the ratios of naphthenic and aromatic hydrocarbons are relatively higher than in paraffinic crudes. 3. Aromatic ( asphaltic) —contain relatively a large amount of polynuclear aromatics,a high asphaltene content, and relatively less paraffins than paraffinic crudes. The different types of crude oil are also classified based on the American Petroleum Gravity (API) gravity and viscosity. 1-Light crude oil is defined as having an API gravity higher than 31.1 °API 2- Medium oil is defined as having an API gravity between 22.3 °API and 31.1 °API 3- Heavy oil is defined as having an API gravity below 22.3 °API. Classifications are made based on the sulfur content as well. 1- Low sulfur content of sulfur means 'sweet' and the presence of high content sulfur is known as 'sour'. From 0.2-1.0 % 2- Medium sulfur content oil 1-2.5% 3- Heavy sulfur content oil more than 3%