Derivative Hidrocarbon

-Organic compounds are divided into two main classes: hydrocarbons and hydrocarbon derivatives
-Hydrocarbon derivatives are molecular compounds of carbon and at least one other element that is not hydrogen
-Organic halides are organic compounds in which one or more hydrogen atoms have been replaced by halogen atoms
-Common organic halides include freons (chlorofluorocarbons) and Teflon (polytetrafluoroethylene)
-Naming halides uses the same format as branched-chain hydrocarbons
-The branch is named by shortening the halogen name to fluoro-, chloro-, bromo-, or iodo-
-In drawing organic halides using IUPAC names, draw the parent chain and add branches at locations specified in the name
eg.

    Cl Cl

     | |

   H-C-C-H

     | |

     H H

1,2-dichloroethane

-Organic halides react fast which is explained from the idea that no strong covalent bond is broken – the electron rearrangement does not involve separation of the carbon atoms
-Addition of halogens could be added to alkynes which results in alkenes or alkanes
-By adding halogens to alkenes, the product could undergo another addition step, by adding halogens to the parent chain, the double bond has to become a single bond in order to accommodate the halogens
eg.

 Br Br              Br Br

  | |                | |

H-C=C-H + Br-Br => H-C-C-H

                    | |

                    Br Br

-By adding hydrogen halides to unsaturated compounds will produce isomers

  H H H               H H H                    H H H

  | | |               | | |                    | | |

H-C=C-C-H + H-Cl => H-C-C-C-H       OR       H-C-C-C-H 

      |               | | |                    | | |

      H              Cl H H                    HCl H

-Substitution reaction is a reaction that involves the breaking of a carbon-hydrogen bond in an alkane or aromatic ring and the replacement of the hydrogen atom with another atom or group of atoms
-With light energy it enables the substitution reaction to move at a noticeable rate eg. C₃H₈ + BR₂ + light => C₃H₇Br + HBR
-Through substitution reaction, in order to name the reaction product, just indicate the location number of the replacement, followed by the halogen prefix (eg. Bromo-) and then state the type of parent chain. Also indicate the second product created from substitution reaction (hydrogen bromide) eg. propane + bromine => 1-bromopropane + hydrogen bromide
-Elimination is an organic reaction in which an alkyl halide reacts with hydroxide ion to produce an alkene by removing a hydrogen and halide ion from the molecule

  H H H             H H H

  | | |             | | |

H-C-C-C-H + OH => H-C=C-C-H + H-O + Br

  | | |                 |       |

  H BrH                 H       H

-Alcohols have properties that can be explained by the presence of a hydroxyl (-OH) functional group attached to a hydrocarbon chain
-Short-chain alcohols are very soluble in water because they form hydrogen bonds with water molecules
-Alcohols are used as solvents in organic reactions because they are effective for both polar and non-polar compounds
-To name alcohols, the –e is dropped from the end of the alkane name and is replaced with –ol eg. Methane => methanol
-Methanol is also called wood alcohol because it was once made by heating wood shavings in the absence of air
-These days, methanol is prepared by combining carbon monoxide and hydrogen at high temperatures and pressure with the use of a catalyst
-Methanol, however, is poisonous to humans. Consuming a small amount could cause blindness or death
-When naming alcohols with more than two carbon atoms, the position of the hydroxyl group is indicated
-Alcohols that contain more than one hydroxyl group are called polyalcohols, their names indicate the positions of the hydroxyl groups eg. 1,2-ethanediol
-Alcohols undergo elimination reactions to produce alkenes through being catalyzed by concentrated sulfuric acid, which removes or eliminates a hydrogen atom and a hydroxyl group

  H H                  H H

  | |                  | |

H-C-C-H  + acid  =>  H-C=C-H   +   H-O

  | |                                |

  H OH                               H

ethanol + acid => ethene   + water

-Ethers is a family of organic compounds that contain an oxygen atom bonded between two hydrocarbon groups, and have the general formula R₁-O-R₂
-To name ethers add oxy to the prefix for the smaller hydrocarbon group and join it to the alkane name of the larger hydrocarbon group
eg.

CH₃-O-C₂H₅ 

methoxyethane

-Ethers have low solubility in water, low boiling points, and have no evidence of hydrogen bonding
-Ethers undergo chemical change only when treated with powerful reagents under vigorous conditions
-Ethers are formed by the condensation reaction of alcohols
-Condensation reaction is the joining of two molecules and the elimination of a small molecule, usually water
-The carbonyl functional group, -CO-, consists of a carbon atom with a double covalent bond to an oxygen atom
-Aldehydes has the carbonyl group on the terminal carbon atom of a chain
-To name aldehydes, replace the final –e of the name of the corresponding alkane with the suffix –al
-Small aldehyde molecules have sharp, irritating odors whereas larger molecules have flowery odors and is used to make perfumes
-A ketone has the carbonyl group present anywhere in a carbon chain except at the end of the chain
-The difference in position of the carbonyl group affects the chemical reactivity, and enables us to distinguish aldehydes from ketones empirically
-To name ketones, replace the –e ending of the name of the corresponding alkane with –one
-The simplest ketone is acetone (propanone), CH₃COCH₃
-The family of organic compounds, carboxylic acids contain the carboxyl functional group, -COOH, which includes both the carbonyl and hydroxyl groups
-Carboxylic acids are found in citrus fruits, and other foods with properties of having a sour taste
-Carboxylic acids also have distinctive odors (like sweat from a person’s feet)
-The molecules of carboxylic acids are polar and form hydrogen bonds both with each other and with water molecules
-Carboxylic acids acid properties, so a litmus test can separate these compounds from other hydrocarbon derivatives
-To name carboxylic acids, replace the –e ending of the alkane name with –oic, followed by the word “acid”
-Methanoic acid, HCOOH, is the first member of the carboxylic acid family
-Some acids contain two or three carbonyl groups such as oxalic acid, and citric acid

    COOH               CH₂-COOH

    |                  |

    COOH             HO-C-COOH

                       |

                       CH₂-COOH

    

oxalic acid         citric acid

-When carboxylic acids undergo a condensation reaction, in which a carboxylic acid combines with another reactant, it forms two products – an organic compound and water
-Esterification is the condensation reaction in which a carboxylic acid reacts with an alcohol to produce ester and water
-carboxylic acid + alcohol => ester + water
-The ester functional group is similar to that of an acid, except that the hydrogen atom of the carboxyl group is replaced by a hydrocarbon branch
-Esters are responsible for the odors of fruits and flowers and are also added to foods for aroma and taste
-To name an ester, determine name of the alkyl group from the alcohol used in the esterification reaction
-Next change the ending of the acid name from “–oic acid” to “–oate”
-ethanoic acid + methanol => methyl ethanoate + water
-Artificial flavorings are made by mixing synthetic esters to give similar odors of the natural substance
-An amide consists of a carboxyl group bonded to a nitrogen atom
-Amides could be formed in condensation reactions
-Amides occur in proteins, the large molecules found in all living organisms
-Peptide bonds is the joining of amino acids together in proteins
-To name amides, have the name of the alkane with the same number of carbon atoms, with the final –e replaced by the suffix –amide
-Change the suffix of the carboxylic acid from “–oic acid” to –amide to have the same name results eg. ethanamide
-Amines consist of one or more hydrocarbon groups bonded to a nitrogen atom
-Through X-Ray diffraction reveals that the amine functional group is a nitrogen atom bonded by single covalent bonds to one, two, or three carbon atoms
-Amines are polar substances that re extremely soluble in water as they form strong hydrogen bonds both to each other and to water
-Amines have peculiar, horrible odors (eg. smell of rotting fish)
-The name of amines include the names of the alkyl groups attached to the nitrogen atom, followed by the suffix –amine eg. methylamine
-Amines with one, two, or three hydrocarbon groups attached to the central nitrogen atom are referred to as primary, secondary, and tertiary
-Primary amines is when a hydrogen atom attached to the nitrogen atom is replaced by a hydrocarbon group
-Secondary amines are when two hydrocarbon groups replaces the hydrogen atoms and tertiary amines replaces all of the hydrogen atoms with hydrocarbon groups
-Amines are used in the synthesis of medicines
-A group of amines found in many plants are called alkaloids
-Many alkaloids influence the function of the central nervous systems of animals
-Substitution – alkane/aromatic + halogen + light => organic halide + hydrogen halide
-Elimination – alkyl halide + OH => alkene + water |+ water + halide ion
-Elimination – alcohol + acid => alkene + water

Ethylen

Fruits, especially the old releases a gas called ethylene. Etilendisintesis by plants and cause more rapid ripening process. Selainetilen produced by plants, there is a synthetic ethylene, which etepon (2-kloroetifosfonat acid). Ethylene is a frequently used synthetic traders to accelerate ripening of fruit. Therefore the fruit that parents often put into place closed (brooded) in order to quickly cook.

         Ethylene is a unique compound found only in the form of gas. senyawaini forced ripening fruit, causing the leaves on and stimulate penuaan.Tanaman often increase ethylene production in response to stress dansebelum dead. Ethylene concentration fluctuations of the season to set kapanwaktu grow leaves and when mature buah.Selain spur ripening, ethylene also stimulate seed germination, menebalkanbatang, encourage leaf drop, and it inhibits stem elongation kecambah.Selain, ethylene delay flowering, reduce apical dominance and inisiasiakar, and inhibit seedling stem elongation.
Tomatoes are picked while still green color, and it will own after being picked riper, so farmers have enough time to sell it without worrying tomatoes will quickly rot. While other fruits such as peppers, grapes and strawberries should be picked when ripe and eaten quickly after being picked.Pitohormon Ethylene is a substance contained in tomatoes, peppers, grapes and strawberries that provides its own maturing effect on tomatoes after picking, but why only give substance Pitohormon Ethylene effects on tomatoes alone?Seeing this phenomenon the researchers from the Max PlanckInstitute of Molecular Plant Physiology Potsdam, United States, do peneltian metabolism, by comparing two tomato fruit are climacteric and non-climacteric habanero peppers. Research results, which occurs in tomatoes is, when plucked, tomatoes emit gases Ethylene Pitohormon an increase in the number of large (etilon shock) that can bersintentesis own. Synthesis of Ethylene Pitohormon contains two enzymes ACC synthase and ACC oxidase, these enzymes can lead to riper tomatoes themselves after picking, making green chloroplasts turn into colorful kloropas, forming sugar, and nutrient content changes. While on habanero peppers, Pitohormon Ethylene content did not increase after picking, so it can not be riper own.

Petroleun and the components

REFINING OF PETROLEUM

Petroleum is a complex mixture of organic liquids called crude oil and natural gas, which occurs naturally in the ground and was formed millions of years ago. Crude oil varies from oilfield to oilfield in colour and composition, from a pale yellow low viscosity liquid to heavy black 'treacle' consistencies.

Crude oil and natural gas are extracted from the ground, on land or under the oceans, by sinking an oil well and are then transported by pipeline and/or ship to refineries where their components are processed into refined products. Crude oil and natural gas are of little use in their raw state; their value lies in what is created from them: fuels, lubricating oils, waxes, asphalt, petrochemicals and pipeline quality natural gas.

An oil refinery is an organised and coordinated arrangement of manufacturing processes designed to produce physical and chemical changes in crude oil to convert it into everyday products like petrol, diesel, lubricating oil, fuel oil and bitumen.

As crude oil comes from the well it contains a mixture of hydrocarbon compounds and relatively small quantities of other materials such as oxygen, nitrogen, sulphur, salt and water. In the refinery, most of these non - hydrocarbon substances are removed and the oil is broken down into its various components, and blended into useful products.

Natural gas from the well, while principally methane, contains quantities of other hydrocarbons - ethane, propane, butane, pentane and also carbon dioxide and water. These components are separated from the methane at a gas fractionation plant.

Petroleum hydrocarbon structures

Petroleum consists of three main hydrocarbon groups:

Paraffins

These consist of straight or branched carbon rings saturated with hydrogen atoms, the simplest of which is methane (CH₄) the main ingredient of natural gas. Others in this group include ethane (C₂H₆), and propane (C₃H₈).

Hydrocarbons

With very few carbon atoms (C₁ to C₄) are light in density and are gases under normal atmospheric pressure. Chemically paraffins are very stable compounds.

Naphthenes

Naphthenes consist of carbon rings, sometimes with side chains, saturated with hydrogen atoms. Naphthenes are chemically stable, they occur naturally in crude oil and have properties similar to paraffins.

Aromatics

aromatic hydrocarbons are compounds that contain a ring of six carbon atoms with alternating double and single bonds and six attached hydrogen atoms. This type of structure is known as a benzene ring. They occur naturally in crude oil, and can also be created by the refining process.

The more carbon atoms a hydrocarbon molecule has, the "heavier" it is (the higher is its molecular weight) and the higher is its the boiling point.

Small quantities of a crude oil may be composed of compounds containing oxygen, nitrogen, sulphur and metals. Sulphur content ranges from traces to more than 5 per cent. If a crude oil contains appreciable quantities of sulphur it is called a sour crude; if it contains little or no sulphur it is called a sweet crude.

The refining process

Every refinery begins with the separation of crude oil into different fractions by distillation.

The fractions are further treated to convert them into mixtures of more useful saleable products by various methods such as cracking, reforming, alkylation, polymerisation and isomerisation. These mixtures of new compounds are then separated using methods such as fractionation and solvent extraction. Impurities are removed by various methods, e.g. dehydration, desalting, sulphur removal and hydrotreating.

Refinery processes have developed in response to changing market demands for certain products. With the advent of the internal combustion engine the main task of refineries became the production of petrol. The quantities of petrol available from distillation alone was insufficient to satisfy consumer demand. Refineries began to look for ways to produce more and better quality petrol. Two types of processes have been developed:

• breaking down large, heavy hydrocarbon molecules
• reshaping or rebuilding hydrocarbon molecules.

Distillation (Fractionation)

Because crude oil is a mixture of hydrocarbons with different boiling temperatures, it can be separated by distillation into groups of hydrocarbons that boil between two specified boiling points. Two types of distillation are performed: atmospheric and vacuum.

Atmospheric distillation takes place in a distilling column at or near atmospheric pressure. The crude oil is heated to 350 - 400^oC and the vapour and liquid are piped into the distilling column. The liquid falls to the bottom and the vapour rises, passing through a series of perforated trays (sieve trays). Heavier hydrocarbons condense more quickly and settle on lower trays and lighter hydrocarbons remain as a vapour longer and condense on higher trays.

Liquid fractions are drawn from the trays and removed. In this way the light gases, methane, ethane, propane and butane pass out the top of the column, petrol is formed in the top trays, kerosene and gas oils in the middle, and fuel oils at the bottom. Residue drawn of the bottom may be burned as fuel, processed into lubricating oils, waxes and bitumen or used as feedstock for cracking units.

To recover additional heavy distillates from this residue, it may be piped to a second distillation column where the process is repeated under vacuum, called vacuum distillation. This allows heavy hydrocarbons with boiling points of 450^oC and higher to be separated without them partly cracking into unwanted products such as coke and gas.

The heavy distillates recovered by vacuum distillation can be converted into lubricating oils by a variety of processes. The most common of these is called solvent extraction. In one version of this process the heavy distillate is washed with a liquid which does not dissolve in it but which dissolves (and so extracts) the non-lubricating oil components out of it. Another version uses a liquid which does not dissolve in it but which causes the non-lubricating oil components to precipitate (as an extract) from it. Other processes exist which remove impurities by adsorption onto a highly porous solid or which remove any waxes that may be present by causing them to crystallise and precipitate out.

Reforming

Reforming is a process which uses heat, pressure and a catalyst (usually containing platinum) to bring about chemical reactions which upgrade naphthas into high octane petrol and petrochemical feedstock. The naphthas are hydrocarbon mixtures containing many paraffins and naphthenes. In Australia, this naphtha feedstock comes from the crudes oil distillation or catalytic cracking processes, but overseas it also comes from thermal cracking and hydrocracking processes. Reforming converts a portion of these compounds to isoparaffins and aromatics, which are used to blend higher octane petrol.

• paraffins are converted to isoparaffins
• paraffins are converted to naphthenes
• naphthenes are converted to aromatics

e.g.

	catalyst
heptane	->	toluene	+	hydrogen
	C7H16	->	C7H8	+	4H2

	catalyst
cyclohexane	->	benzene	+	hydrogen
	C6H12	->	C6H6	+	3H2

Cracking

Cracking processes break down heavier hydrocarbon molecules (high boiling point oils) into lighter products such as petrol and diesel. These processes include catalytic cracking, thermal cracking and hydrocracking.

e.g.

A typical reaction:

	catalyst
	C16H34	->	C8H18	+	C8H16

Catalytic cracking is used to convert heavy hydrocarbon fractions obtained by vacuum distillation into a mixture of more useful products such as petrol and light fuel oil. In this process, the feedstock undergoes a chemical breakdown, under controlled heat (450 - 500^oC) and pressure, in the presence of a catalyst - a substance which promotes the reaction without itself being chemically changed. Small pellets of silica - alumina or silica - magnesia have proved to be the most effective catalysts.

The cracking reaction yields petrol, LPG, unsaturated olefin compounds, cracked gas oils, a liquid residue called cycle oil, light gases and a solid coke residue. Cycle oil is recycled to cause further breakdown and the coke, which forms a layer on the catalyst, is removed by burning. The other products are passed through a fractionator to be separated and separately processed.

Fluid catalytic cracking uses a catalyst in the form of a very fine powder which flows like a liquid when agitated by steam, air or vapour. Feedstock entering the process immediately meets a stream of very hot catalyst and vaporises. The resulting vapours keep the catalyst fluidised as it passes into the reactor, where the cracking takes place and where it is fluidised by the hydrocarbon vapour. The catalyst next passes to a steam stripping section where most of the volatile hydrocarbons are removed. It then passes to a regenerator vessel where it is fluidised by a mixture of air and the products of combustion which are produced as the coke on the catalyst is burnt off. The catalyst then flows back to the reactor. The catalyst thus undergoes a continuous circulation between the reactor, stripper and regenerator sections.

The catalyst is usually a mixture of aluminium oxide and silica. Most recently, the introduction of synthetic zeolite catalysts has allowed much shorter reaction times and improved yields and octane numbers of the cracked gasolines.

Thermal cracking uses heat to break down the residue from vacuum distillation. The lighter elements produced from this process can be made into distillate fuels and petrol. Cracked gases are converted to petrol blending components by alkylation or polymerisation. Naphtha is upgraded to high quality petrol by reforming. Gas oil can be used as diesel fuel or can be converted to petrol by hydrocracking. The heavy residue is converted into residual oil or coke which is used in the manufacture of electrodes, graphite and carbides.

This process is the oldest technology and is not used in Australia.

Hydrocracking can increase the yield of petrol components, as well as being used to produce light distillates. It produces no residues, only light oils. Hydrocracking is catalytic cracking in the presence of hydrogen. The extra hydrogen saturates, or hydrogenates, the chemical bonds of the cracked hydrocarbons and creates isomers with the desired characteristics. Hydrocracking is also a treating process, because the hydrogen combines with contaminants such as sulphur and nitrogen, allowing them to be removed.

Gas oil feed is mixed with hydrogen, heated, and sent to a reactor vessel with a fixed bed catalyst, where cracking and hydrogenation take place. Products are sent to a fractionator to be separated. The hydrogen is recycled. Residue from this reaction is mixed again with hydrogen, reheated, and sent to a second reactor for further cracking under higher temperatures and pressures.

In addition to cracked naphtha for making petrol, hydrocracking yields light gases useful for refinery fuel, or alkylation as well as components for high quality fuel oils, lube oils and petrochemical feedstocks.

Following the cracking processes it is necessary to build or rearrange some of the lighter hydrocarbon molecules into high quality petrol or jet fuel blending components or into petrochemicals. The former can be achieved by several chemical process such as alkylation and isomerisation.

Alkylation

Olefins such as propylene and butylene are produced by catalytic and thermal cracking. Alkylation refers to the chemical bonding of these light molecules with isobutane to form larger branched-chain molecules (isoparaffins) that make high octane petrol.

Olefins and isobutane are mixed with an acid catalyst and cooled. They react to form alkylate, plus some normal butane, isobutane and propane. The resulting liquid is neutralised and separated in a series of distillation columns. Isobutane is recycled as feed and butane and propane sold as liquid petroleum gas (LPG).

e.g.

			catalyst
isobutane	+	butylene	->	isooctane
	C4H10	+	C4H8	->	C8H18

Isomerisation

Isomerisation refers to chemical rearrangement of straight-chain hydrocarbons (paraffins), so that they contain branches attached to the main chain (isoparaffins). This is done for two reasons:

• they create extra isobutane feed for alkylation
• they improve the octane of straight run pentanes and hexanes and hence make them into better petrol blending components.

Isomerisation is achieved by mixing normal butane with a little hydrogen and chloride and allowed to react in the presence of a catalyst to form isobutane, plus a small amount of normal butane and some lighter gases. Products are separated in a fractionator. The lighter gases are used as refinery fuel and the butane recycled as feed.

Pentanes and hexanes are the lighter components of petrol. Isomerisation can be used to improve petrol quality by converting these hydrocarbons to higher octane isomers. The process is the same as for butane isomerisation.

Polymerisation

Under pressure and temperature, over an acidic catalyst, light unsaturated hydrocarbon molecules react and combine with each other to form larger hydrocarbon molecules. Such process can be used to react butenes (olefin molecules with four carbon atoms) with iso-butane (branched paraffin molecules, or isoparaffins, with four carbon atoms) to obtain a high octane olefinic petrol blending component called polymer gasoline.

Hydrotreating and sulphur plants

A number of contaminants are found in crude oil. As the fractions travel through the refinery processing units, these impurities can damage the equipment, the catalysts and the quality of the products. There are also legal limits on the contents of some impurities, like sulphur, in products.

Hydrotreating is one way of removing many of the contaminants from many of the intermediate or final products. In the hydrotreating process, the entering feedstock is mixed with hydrogen and heated to 300 - 380^oC. The oil combined with the hydrogen then enters a reactor loaded with a catalyst which promotes several reactions:

• hydrogen combines with sulphur to form hydrogen sulphide (H₂S)
• nitrogen compounds are converted to ammonia
• any metals contained in the oil are deposited on the catalyst
• some of the olefins, aromatics or naphthenes become saturated with hydrogen to become paraffins and some cracking takes place, causing the creation of some methane, ethane, propane and butanes.