Did You Know About Polymerization.

Examples of alkene polymerisation, in which each double bond Styrene monomer units reformed as a single bond with another styrene monomer and forms polystyrene.
Polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains. Polymerization is classified into several systems: addition-condensation system and chain growth system gradually. Other forms of ring-opening polymerization chain polymerization similar to natural. Polymerization polymers include proteins such as silk, enzymes and muscle fibers. polymers are also called macromolecules. For example, the addition of polymers: polyethylene, Teflon, PVC, PVA, and PMMA. Condensation polymers for example: nylon, kevlar, silicon rubber, and polyester.
Polymerization Reactions, Polymer Formation, Addition, Free Radicals, Ion, Condensation, Chemistry.
Polymerization Reactions, Polymer Formation, Addition, Free Radicals, Ion, Condensation, Chemical - Carothers, USA chemists classify polymerization mechanism into two groups, namely the addition polymerization and condensation polymerization. Addition polymerization involves a chain reaction. The cause may be a chain reaction of free radicals or ions. Addition polymerization occurs at a compound having a double bond, such as ethene.
Condensation polymerization reaction of two molecules of more than one function air-force generating large molecules with functional groups are also more than one followed by the elimination of a small molecule.

a. Addition polymerization. 

Addition polymerization occurs in three stages, namely triggering, propagation, and termination. Therefore, the chain carrier can be either ionic or free radical addition polymerization then classified into free radical polymerization and ionic polymerization.

1) Free Radicals. 

Free radicals are usually formed through the decomposition of less stable substance with a certain energy. Free radicals triggers the polymerization. Triggering substances such as peroxide compounds, such as dibenzoyl peroxide and azodiisobutironitril.
Dibenzoyl peroxide
Figure 1. Dibenzoyl peroxide into free radicals easily.
If free radicals represented by R • and monomer molecules expressed by CH2 = CHX triggers the phase can be described as follows.

R • + H2C = CHX → R - CH2 - CHX •

Phase propagation is an extension (elongation) of free radicals formed in stage triggers with other monomers:

R - CH2 - CH2 = CHX CHX • + → R - CH2 - CHX - CH 2 - CHX •

Termination phase may occur in the following way.
Termination phase free radicals or through disproportionation reaction:

Disproportionation reaction of free radicals

The rate of polymerization can be controlled by using inhibitors (inhibitors) and to slow down (retarder). Inhibitor reacts with free radicals when free radicals are formed. Polymerization will not continue until all inhibitors exhausted.
Quinones can act as an inhibitor to the polymerization system causes many quinones react with free radical generating steady radicals due to resonance. This stable free radical polymerization can not lead further.
The substance is commonly used to slow the oxygen gas. This gas is less reactive than the inhibitor. How it works is slowing substances through competition with monomer to react with free radicals so the polymerization rate decreases. The equation is:
decrease in the rate of free radical polymerization

2) Ionic Polymerization. 

Addition polymerization may occur through a mechanism that does not involve free radicals. In this case, the carrier can be either chain carbonium ions (cationic polymerization) or karbanion ion (anion polymerization).
In the cation polymerization, monomer is a chain carrier carbocations. The catalyst for this reaction is a Lewis acid, such as AlCl3, BF3, TiCl4, SnCl4, H2SO4, and other strong acids.
Free radical polymerization requires energy or high temperature, cationic polymerization vice versa is best done at low temperatures.
For example, the polymerization of 2-metilpropena lasted optimum at -100 ° C in the presence of BF3 or AlCl3 catalyst.
Cationic polymerization of monomers that have occurred in the group easily release electrons. In polymerization catalyzed by acid, triggering phase can be described as follows.
Cation ionic polymerization
HA is the acid molecule, such as HCl, H2SO4, and HClO4. In the triggering phase, the proton transferred from the acid to the monomer to produce carbonium ions (C +).
Propagation addition of monomers to form carbonium ions, the process is almost the same as the propagation of free radicals.
monomer addition to carbocations,
Chain termination can occur through a variety of processes. The simplest process is the incorporation of carbonium ions and anions partner (called a counter ion).
carbonium ions and anions merger partner
In anionic polymerization, the monomer is a chain carrier karbanion (C-). In this case, the monomer is a chain carrier that has a cluster with high electronegativity, such propenitril (acrylonitrile), 2-metilpropenoat (methyl methacrylate), and feniletena (styrene).
Cations such as polymerization, anionic polymerization reactions at low temperature optimum. Catalysts that can be used is an alkali metal, alkyl, aryl, and alkali metal amides.
anionic polymerization reaction optimum
Examples are potassium amide (KNH2) that the liquid ammonia solvent can accelerate the polymerization of monomers CH2 = CHX in ammonia. Ionized potassium amide going strong so that triggers can take place as follows.
Propagation is the monomer addition karbanion produced, namely:
monomer addition at karbanion
Termination of the polymerization process of the anion is not so clear as in the cationic polymerization because the incorporation of anion chain with counter ion (K +) does not occur. However, if there is little water, carbon dioxide, or alcohol will terminate chain growth.

b. Condensation Polymerization. 

Condensation polymerization involves the incorporation of small molecules to form larger molecules by condensation reactions. If ethanol and acetic acid is heated with a little concentrated sulfuric acid, ethyl acetate ester will be formed with the removal of water molecules. Esterification reaction will stop, because there is no longer functional group that can form a polymer.
However, if every reactant molecule containing two or more functional groups then the next reaction should be formed. For example, the reaction between two monomers heksanadioat acid (adipic acid) and ethane-1 ,2-diol (ethylene glycol).
Condensation Polymerization
It can be seen that the reaction product still contains two functional groups. Therefore, subsequent reaction with a monomer can occur, both at the tip of the hydroxyl and carboxyl end.
Formed polymer containing repeating units (-OCH2-CH2-OOHCH-(CH2) 4-CO-). Molecular mass gradually increased and the reaction time is very long if the expected molecular mass of the polymer formed very large. Thus, different condensation polymerization with addition polymerization.
At the termination of condensation polymerization does not occur. Polymerization continues until there are no more functional groups that can form a polymer. However, the polymerization reaction can be controlled by changing the temperature. For example, the reaction can be stopped by means refrigerated, but the polymerization can be started again if the temperature is raised.
How to stop a more lasting reaction is to use a tip termination. For example, the addition of a little acetic acid on the growth of polymer reaction. Therefore, a single functional bergugus acetic acid, the acid once it reacts with the growing chain end it will not happen again further reaction. Thus, the ongoing polymerization can be controlled.

Petroleum processing. 

Crude oil contains a variety of hydrocarbon compounds with different physical properties. To obtain material of good quality and in accordance with the requirements necessary to crude oil processing stage that includes the distillation, cracking, reforming, polymerization, treating, and blending.

Distillation. 

Distillation or distillation is a separation method based on a mixture of compounds boiling point differences in the components making up the mixture. Crude oil contains a mixture of hydrocarbons having a boiling point varies from methane (CH4) which has the lowest boiling point to residues that have the highest boiling point so as not vaporised on heating. With this distillation, crude oil is heated at a temperature of 370 ° C, then the resulting vapor is condensed and flows (condensed) at the appropriate temperature. How distillation using some level of cooling or condensing temperature rise is called distillation.
The distillation process takes place as follows. At first, crude oil is heated at a temperature of 370 ° C to boil and evaporate. Fraction of crude oil that does not evaporate into the residue. Petroleum residues include paraffin, wax, and asphalt. These residues have a carbon chain with the number of atoms of more than 20 C atoms. Crude oil is vaporized in the process of this stylized rose to the top of the column and subsequently condensed at different temperatures. Petroleum fractions are not condensed continue to rise to the top of the column so it came out as natural gas.

Cracking. 

Cracking is the decomposition (breakdown) hydrocarbon molecules are large molecules into smaller compounds. An example of this is the conversion of cracking diesel oil or kerosene (kerosene) into gasoline.

There are two ways of cracking process. 

How to heat (thermal cracking): 

Cracking is the process of using high temperature and low pressure.
Way catalyst (catalytic cracking):
Is the cracking process using powdered platinum or molybdenum oxide catalysts.
This breakdown process produces gas in large quantities and better quality. For example, solving the n-decane compounds into ethene and n-octane.

Reforming. 

Reforming of gasoline is changing the form of the molecule is less good quality (straight carbon chain) into a better quality petrol (branched carbon chain). Both types of gas have the same molecular formula but different structural forms that this process is also called isomerization. Reforming is done by using a catalyst and heating.

Polymerization. 

Polymerization is the process of incorporation of small molecules into large molecules. For example, the incorporation of compounds isobutene with isobutane compounds that produce high-quality gasoline, ie isooctane

Treating. 

Treating petroleum refining is the process by removing impurities-impurities. Ways of treating the process as follows.
a) Copper sweetening and treating doctor is the process of eliminating the impurities that cause odor.
b) Acid treatment is the process of sludge removal and color repair.
c) desulfurizing (desulfurization) is the element sulfur removal process.

Blending. 

To obtain a good quality gasoline blending done (mixing), there are approximately 22 mixing ingredients (additives) that can be added to the treatment process. The mixing ingredients, among others tetraethyllead (TEL), MTBE, ethanol, and methanol. These additives can increase the octane.

PETROLEUM PROCESSING. 

Petroleum is usually located 3-4 km below sea level. Petroleum is obtained by making the wellbore. Crude oil obtained is collected in tankers or piped to the station or to a refinery tank.
Crude oil (oil cude) black viscous liquid and smelled dreadful. Crude oil can not be used as fuel or for other purposes, but must be processed first. Crude oil contains about 500 types of hydrocarbons with an atomic number of C-1 through 50. Boiling point of hydrocarbons increased with increasing number of C atoms inside the molecule. Therefore, the processing is done through distillation of petroleum-rise, where crude oil is separated into groups (factions) with similar boiling points.

1. DISTILLATION.

Let me repeat that distillation is the separation of petroleum fractions based on differences in their boiling points. In this case is a distillation fractionation. At first, crude oil is heated in a pipe flow in the furnace (furnace) until the temperature of ± 370 ° C. Crude oil that has been heated is then entered into the fractionation column in the flash chamber (usually located in the lower third fractionation column). To keep the temperature and pressure in the column with steam assisted heating (steam hot water and high pressure).
Crude oil is vaporized in the distillation process of rising to the top of the column and subsequently condensed at different temperatures. Components of the higher boiling point will remain in liquid form and fall to the bottom, while the lower boiling point will evaporate and rise to the top through the lid-lid-called bubble lid. Getting to the top, the temperature of which is contained in the lower fractionating column, so each time the component with higher boiling points will separate, while the component lower boiling point rise to the upper part again. So then that component is a component that reaches peak at room temperature is a gas. Gaseous component is called petroleum gas, then thawed and called LPG (Liquefied Petroleum Gas).
Fraction of crude oil that does not evaporate into the residue. Petroleum residues include paraffin, wax, and asphalt. These residues have a carbon chain of more than 20.

Petroleum fractions produced by boiling ranges are as follows: 

1. Gas 

Range of carbon chain: C1 to C5
Boiling Route: 0 to 50 ° C

2. Gasoline (Petrol) 

Range of carbon chain: C6 to C11
Boiling Route: 50 to 85 ° C

3. Kerosene (Kerosene) 

Range of carbon chain: C12 to C20
Boiling Route: 85 to 105 ° C

4. Diesel fuel 

Range of carbon chain: C21 to C30
Boiling Route: 105 to 135 ° C

5. Heavy Oil 

Carbon Ranai Range: C31 to C40
Boiling Route: 135 to 300 ° C

6. Residue 

Carbon chain range: above C40
Boiling Route: above 300 ° C
Fractions of petroleum distillation process storied yet have the quality that fits the needs of society, so it needs further processing which includes the process of cracking, reforming, polymerization, first treating, and blending.

2. CRACKING. 

After going through the distillation stage, each of the resulting purified fraction (refinery), as shown below:
Cracking is the decomposition of hydrocarbon molecules into large hydrocarbon molecules are small. An example of this is the treatment cracking diesel oil or kerosene to gasoline.
This process is primarily intended to improve the quality and acquisition gasoline fractions (gasoline). The quality of gasoline is determined by the nature of the anti-knock (knock) are expressed in octane number. Numbers given in isooktan 100 octane (2,2,4-trimethyl pentane) which has a special anti-knocking and octane number 0 is given in n-heptane, which have anti-knock properties are poor. Gasoline that will be tested in comparison with a mixture of isooctane and n-heptane. Octane number is influenced by multiple molecular structure of hydrocarbons.

There are 3 ways cracking process, namely: 

a. How to heat (thermal cracking), 

namely the use of high temperature and low pressure.
Examples of reactions in the cracking process is as follows:

b. Way catalyst (catalytic cracking), 

namely the use of a catalyst. The catalysts used are usually SiO2 or Al2O3 bauxite. The reaction of catalytic cracking via carbonium ion cracking mechanism. At first the catalyst due to acidic protons appends olevin molecules or ions attract hydride from alkanes resulting in the formation of carbonium ions:

c. Hydrocracking 

Hydrocracking is a combination of cracking and hydrogenation to produce unsaturated compounds. The reaction is carried out at high pressure. Another advantage of this is that the hydrocracking of sulfur contained in the oil is converted to hydrogen sulfide which is then separated.

3. Reforming. 

Reforming is a change of molecular shape gasoline quality is not good (straight carbon chain) into a better quality petrol (branched carbon chain). Both types of gasoline has the same molecular formula different structure forms. Therefore, this process is also called isomerization. Reforming is done by using a catalyst and heating.
Reforming examples are as follows:
Reform could also be a change in the molecular structure of paraffinic hydrocarbons into aromatic compounds with high octane number. In this process the molybdenum oxide catalyst used in the reaction Al2O3 clay. Sample or platinum in:

4. Alkylation. 

Alkylation is an increase in the number of atoms in the molecule becomes longer molecules and branched. In the process of using strong acid catalysts such as H2SO4, HCl, AlCl3 (a strong Lewis acid). General reaction is as follows:
RH + CH2 = CR'R'' R-CH2-CHR'R "
Polymerization is the process of incorporation of small molecules into large molecules. General reaction is as follows:
M CnH2n Cm + NH2 (m + n)
An example is the incorporation of compounds polymerization of isobutene with isobutane compounds produce high quality gasoline, ie isooctane.

5. TREATING 

Is treating petroleum refining by removing impurities-impurities. Ways of treating process is as follows:
Copper sweetening and treating physicians, the process removes impurities that can cause bad odor.
Acid treatment, sludge removal process and improve color.
Namely the removal process dewaxing wax (paraffin n) of high molecular weight fraction produces lubricating oil for lubricating oils with low pour point.
Deasphalting namely the elimination of lubricating oil fraction of bitumen used for
Desulfurizing (desulfurization), namely the elimination of elemental sulfur.
Sulfur is a compound that is naturally contained in the oil or gas, but its existence is not cool because it can cause a variety of problems, including corrosion of process equipment, poison the catalyst in the process of processing, less savory smell, or gaseous byproducts of combustion exhaust toxic (sulfur dioxide, SO2) and lead to air pollution and acid rain. Various attempts were made to remove sulfur compounds from petroleum, among others, using the process of oxidation, selective adsorption, extraction, hydrotreating, and others. Sulfur is removed from oil is then taken back as elemental sulfur.
Desulfurization is a process used to remove sulfur compounds from petroleum. Basically there are 2 ways desulfurization, namely by:
1. Using solvent extraction, and
2. Decomposition of sulfur compounds (generally contained in petroleum compounds in the form of mercaptans, sulfide and disulfide) is catalytically selective hydrogenation process to hydrogen sulfide (H2S) and hydrocarbon origin of the sulfur compounds. Hydrogen sulfide is produced from the decomposition of sulfur compounds are then separated by fractionation or washing / stripping.
However, in addition to the above two ways, today there are also other desulfurization techniques, namely bio-desulfurization. Bio-desulfurization is the removal of sulfur from petroleum selective metabolism by utilizing microorganisms, ie by converting hydrogen sulfide into elemental sulfur catalyzed by enzymes of sulfur metabolism of certain types of microorganisms, without changing the flow of hydrocarbons in the process. The reaction is aerobic reactions, and performed in aerated environment. The advantages of this process is that it can be difficult to get rid of the sulfur compounds are removed, for example, alkylated dibenzothiophenes. Type of microorganism used for bio-desulfurization process is generally derived from Rhodococcus sp, but more research is also developed for the use of other types of microorganisms.
This process was developed with the need to get rid of the sulfur content in the medium on the amount of gas flow, which is too little if removed using amine plant, and too much to be removed using a scavenger. In addition to natural gas and hydrocarbons, bio-desulfurization is also used to remove sulfur from coal.
Shell-Paques process for desulfurization of Bio-Gas Flow
One of the licensing process for the desulfurization of bio-gas flow is Shell Paques from Shell Global Solutions International and Paques Bio-Systems. This process has been applied commercially since 1993, and currently there are approximately about 35 units of bio-desulfurization with Shell-Paques license to operate in the entire world.
This process can remove sulfur from the gas stream and produce hydrogen sulfide with capacities ranging from 100 kg / day up to 50 tons / day, using a microorganism Thiobacillus which also acts as a catalyst for bio-desulfurization process. In this process, the gas stream containing hydrogen sulfide is passed to the absorber and is contacted on soda solution containing microorganisms. Mengabsorbi soda compound hydrogen sulfide, and then flowed into a tank of bioreactor THIOPAQ atmospheric aerated where microorganisms convert hydrogen sulfide into elemental sulfur in a state biological pH 8.2 to 9. Sulfur reaction then proceeds through a process of decantation to separate the liquid soda. Soda liquid is returned to the absorber, while sulfur is obtained as a cake or as a pure liquid sulfur. Because it is hydrophilic so easily absorbed by the soil, the sulfur produced from this process can also be used as a fertilizer feedstock.
The advantages of the Shell-Paques process is:
Can get rid of large amounts of sulfur (the removal efficiency of hydrogen sulfide can achieve 99.8%) to leave the content of hydrogen sulfide in the gas flow is very low (less than 4 ppm-volume)
gas purification and retrieval (recovery) integrated sulfur in 1-process flue gas (flash gas / vent gas) from this process contains no harmful gases, so before being released into the environment does not need to be burned in a flare. This makes the process ideal for locations where processes require combustion (eg flare or incinerator) is not possible.
eliminating the potential hazards of handling solvent used to dissolve the hydrogen sulfide in the extraction process
hydrophilic nature of the biological sulfur eliminates the risk of blockage (plugging or blocking) on ​​the pipe
Bio-catalyst used is self-sustaining and able to adapt to the various conditions of the process
Configuration process is simple, reliable and safe (among other operates at low temperature and pressure) so it is easy to operate
Shell-Paques process can be applied to natural gas, amine regenerator flue gas, fuel gas, synthesis gas, and the flow of oxygen-containing waste gases can not be processed with solvents.

6. BLENDING. 

Blending process is the addition of additive materials into petroleum fractions in order to improve the quality of the product. Gasoline which has a range of quality requirements is an example of petroleum products in the most widely used across various countries with different weather variations. To meet the gas quality is good, there are about 22 mixing ingredients that can be added to the treatment process. 
Among the ingredients are well-known mixing tetra ethyl lead (TEL). TEL serves to raise the octane number of gasoline. Similarly, the lubricant, in order to obtain good quality then the processing required the addition of additives. The addition of TEL can increase the octane number, but it can cause air pollution.
Thank you for reading this article. Written and posted by Bambang Sunarno. sunarnobambang86@gmail.com
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http://primadonablog.blogspot.com/2014/03/did-you-know-about-polymerization.html
DatePublished: March 3, 2014 at 20:09
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Tag : Polymerization.