World War 2 created a driving force to improve the production of gasoline. The age of thermal refining could not produce the high octane gasoline needed for airplanes during the War. Another process that could meet the demand for the high octane aviation fuel had to be developed. Catalytic cracking was developed to meet this demand. This process required a completely different plant then that of the thermal age. After the war the improved octane gasoline that was being manufactured allowed car manufacturers to build bigger more powerful engines to burn this higher grade fuel.

World War 2 was the catalyst needed to drive companies to develop new and improved refining technologies. There were several principle processes that were developed during the catalytic refining period. Heavy fuel oil that was being used for trains was now obsolete because diesel was now the main fuel for trains. The loss of this outlet for heavy fuel oil forced refineries to further break down this product. The processes such as solvent deasphalting and visbreaking were needed to increase production. Hydrogen was now a product of production and could be use for the process known as hydrotreating. The kerosene market made a comeback and was now used to produce jet fuel after high octane aviation became obsolete. World War 2 forced companies to improve there refinery processes that lead to the catalytic refinery.

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The wastewater from refineries can not be treated in regular municipal wastewater treatment plants for a variety of reasons. Municipal wastewater treatment plants are designed to treat wastewater from residential houses. There can also be some rainwater runoff going it to these plants as well. These plants are not equipped to clean the wastewater that would be coming from a refinery. The waste water coming from a refinery is divided into four different types. The types of wastewater are Storm water, sanitary sewer water, cooling water, and the most polluted process water and steam. The process water and steam contains many forms of pollutants that include liquid hydrocarbons, suspended solids, dissolved solids, mercaptans, phenols, amines, and cyanides. These chemicals would not be able to be processed by a municipal wastewater treatment because of the toxicity of some of these compounds. These compounds have to be stripped from the sour water using steam to remove H2S, float/sink density separators, as well as settling tanks to separate heavier oils. After these processes are completed the water can be directed to a wastewater treatment plant where the water can be completely processed. There is also a secondary treatment process that uses microorganism to remove organic compounds from the waste water. This process produces a substance called biocoke.

The goal of Catalytic reforming process is to convert heavy naphtha, which contains high levels of naphthenes, into a high-octane reformate. This reformate is very low in sulfur and is an important product for blending in gasoline. This process produces hydrogen that can be used for hydro treating and hydro cracking processes. This hydrogen is used to hydrotreat the naptha feedstock. This needs to be done to protect the platinum catalyst from poisoning by sulfur or nitrogen species. Even with the hydrogen usage catalysts are still deactivated by coke deposition. The commercial catalytic processes are identified based on the type of catalyst regeneration that is used. The first type of reforming process that was used commercially is called semi-regenerative. This process was first used in 1949. These reactors need to be shut down every 3 to 24 months because the catalysts need to be regenerated because the catalysts are deactivated by coke deposition. The second type of catalytic reforming process is called cyclic. It was first introduced in 1960 and involves a swing reactor. Three of the four are in operation at one time. They use the extra reactor when one is offline for catalyst regeneration. The third type of catalytic reforming process is called continuous. This type of process was introduced in 1971. The catalyst is removed and replaced without stopping the process. This allows the catalysts to maintain a high level of activity, although this process is very expensive. There are three types of processes within catalytic reforming are Alkylation, polymerization, and isomerization. Alkylation combines light iso-paraffins with olefins to produce very high molecular weight iso-paraffins to blend with gasoline. Polymerization combines propenes and butenes to also produce higher olefins with high octane numbers to blend with gasoline. Isomerization has been used since the need for lead free gasoline has been relevant. This process isomerizes n-butane to iso-butane. Then also uses alkylation to produce high octane gasoline stocks.

Catalytic cracking and catalytic hydro cracking are two very different processes. Hydro cracking can be considered a more refined process because it is fairly new when considering refinery processes. It was first used commercially in 1958. Catalytic cracking initiates on the catalyst surface where ionic species are formed. This process produces branched chains alkanes from long straight chain alkanes. These branched chains alkanes, also called iso-alkanes, produces gasoline with very high octane #’s. This high octane gasoline is needed for modern day internal combustion engines. The high octane gasoline is produced because of the high concentrations of i- alkanes as well as the aromatics present in the catalytic cracking product. There are 3 main types of catalytic cracking Houdry, Thermafor, and Fluid catalytic cracking. Houdry catalytic cracking was the first continous commercialized catalytic cracking process. This process operates with three different reactors. This is so the process can remain continuous. This has to be done because after 10 minutes of operation there is a significant amount of coke build up in the reactor. The reactors are stripped with team and the coke burnt off before they are operational again. This process was introduced commercially in 1936. The second catalytic process is Thermafor catalytic cracking. This process was introduced in 1942. This process using one reactor and a moving bed of catalysts rather then the fixed bed in the Houdry process. This process has a much higher efficiency then the Houdry process. The Third type of catalytic cracking is Fluid catalytic cracking. This process has the highest theramal efficiency of the three and was also introduced commercially in 1942. The coke buildup is very rich in carbon which allows the production of distillates without the addition of hydrogen. All three of these processes have significant coke build up.
Catalytic hydrocracking is a much more modern process then catalytic cracking. It was first introduced commercially by chevron in 1958. The process objective of hydro cracking is similar to catalytic cracking but yet more refined. Hydrocracking aims to reduce the molecular weight and boiling point of heavy oils to produce saturated hydrocarbons. It has a wider range of feedstock then catalytic cracking. It uses highly aromatic feedstock and distillation residue, a much greater flexibility in feedstock. This process is also a hydrogen addition process unlike catalytic cracking. Catalytic cracking is a carbon rejection process. There is a advantage to hydrogen addition processes because there is no build up of low grade byproducts, such as coke. Although hydro cracking is a much more expensive process then catalytic cracking.

Thermal cracking was the first commercially used conversion process to process crude oils. It was initially implemented to produce more gasoline as well as higher octane gasoline. The higher octane gasoline was mainly used for fuels for aircrafts. The main reason thermal cracking came along was to produce light to middle distillates from heavier fractions of the crude oil. Thermal cracking became obsolete for gasoline production in modern refineries when catalytic cracking was initiated. Catalytic cracking came around in the 1930’s and could produce more gasoline at a higher octane number, then thermal cracking. Thermal cracking is still used in some modern refineries with visbreaking and coking. Visbreaking is a thermal cracking process that uses VDR as a feedstock to produce fuel oil and light products to increase distillation output of a refinery. The main goal of visbreaking is to reduce viscosity in a feedstock, but could also be used to produce lighter distillates from fuel oil. The second thermal cracking process that is used in refineries is called coking. Coking is the most severe thermal cracking process used in a refinery. It cracks the heaviest of the crude oil fractions, such as vacuum residue. Three coking processes are used to maximize the yield of distillation products. Thermal cracking is no longer the main process of a refinery but it is still plays a small role in increasing the yields of distillates.

There are currently two types of dewaxing that are being used commercially. The first dewaxing process is called solvent dewaxing. Solvent dewaxing is a physical process that separates the wax by freezing or solvent transport. The other type of dewaxing, Catalytic dewaxing, is a chemical process, which is unlike the physical process used for solvent dewaxing. Catalytic dewaxing uses a chemical process to remove the wax through a reaction of long chain n-alkenes. First the solvent dewaxing process will be discussed. The solvent is cooled until the wax compound freeze to form crystals. The solvent with the frozen wax crystals is carried into a rotary filter where the wax crystals get caught in a filter cloth. The layer of wax on this cloth is then scrapped by a blade and carried away in a solvent stream. The solution then goes through a steam stripping process to recover the solvent. The chemical process of catalytic dewaxing is much different then the process of solvent dewaxing. This process uses a selective cracking processe to “crack” n-alkanes. This cracking process takes place in pores of a catalyst that has openings about 0.6nm in diameter. This keeps out the i-paraffins because of their larger size. Hydrogen is also introduced into this process to prevent coking on the catalyst. Hydrogen prevents disproportionation which in turn prevents coking. This process has a much higher yield then the solvent dewaxing as well as producing a lube base stock with a much lower pour point. The catalytic dewaxing has many advantages over the solvent dewaxing. The chemical process of catalytic dewaxing has a much lower capital investment then that of the physical process of solvent dewaxing. The cracking of n-paraffins that takes place in catalytic dewaxing produces a by product of distillate fuels such as gasoline. Overall catalytic dewaxing is a more advantageous process then solvent dewaxing.

Solvent fractionation is a very important process with in the refinery. It is a key process in readying some products of the refinery for commercial use. Solvent fractionation is a different from distillate in a variety of ways. Distillation achieves fractionation by using differences in boiling points to separate the components of the crude oil. Solvent fractionation uses the solubility or insolubility of molecular components in a solvent to separate the key components. This process is also called deasphalting and uses vacuum distillation residue as it’s feedstock. During the first step of deasphalting the vacuum distillation residue is completely dissolved in aromatic solvents. Examples of these aromatic solids are benzene and toluene. The highest molecular weight component of VDR is called asphaltene and can be separated by precipitation using a light paraffin solvent. This light solvent is mixed with the VDR previously solubilizied in a aromatic solvent. VDR is just a abbreviation for vacuum distillation residue. Maltenes are a portion of VDR that is soluble in the light solvent. This light solvent also defines the characteristics of the separated asphaltenes. Even a lighter solvent, propane, is used to separate n-pentane solubles. This process yields soft resins and oil products. The power of non-polar solvent is measured by the Hildebrand Solubility Parameters, also know as HSP. The 1st Hildebrand parameter is dependent on two variables, surface tension and molar volume of the solvent. The 2nd Hildebrand Parameter is dependent upon energy vaporization and molar volume. Both these parameters are accurate at expressing a dissolving power of a solvent. These parameters can be calculated using the equations given within the notes. Solubility parameters increase with increasing density with surface tension, or increasing latent heat of vaporization. It is for those properties that aromatic solids have higher solvent power then aliphatic hydrocarbons. In review the strength of nonpolar solvents is described by the two hildebrand solubility parameters.

In this lesson we looked at three different types of distillation methods. They included true boiling point distillation, ASTM distillation, and Equilibrium Flash Vaporization. True boiling point distillation is done in a batch method. In this method more than 100 theoretical plates are used as well as a very high reflux ratio of 100. This method achieves the best possible separation in distillation. In this distillation the component with the lower boiling point is distilled off completely without any contamination from the other substance, Then the compound is distilled off as a pure compound. The second distillation method we reviewed was ASTM distillation. This is also a batch method but operates without any contact plates as well as a reflux ratio of zero. ASTM achieves better separation then EFV and TBP achieves better separation then ASTM. EFV uses a steady flow that is heated and then flows into a flash drum. Within this flash drum the flowing heated feed is separated into a liquid and a vapor. This method gives the lowest degree of separation of the three distillation methods. Each method is used for a specific reason. TBP is used to characterize crudes oils, ASTM is usually used for refinery products and property calculations of the components, and EFV provides data for flashing operations in refineries.

When processing crude oil vacuum distillation is needed in conjugation with Atmospheric distillation as well. If vacuum distillation was not used the outlet temperatures of the furnace would be so high that thermal cracking would occur. This thermal cracking would cause a loss of some of the product as well as equipment fouling. To lower the outlet temperature you have to lower the boiling point of the products. This is done be creating a vacuum. The pressure within the distillation column is lowered to about 10 mmHG. This is done by using a combination of vacuum pumps as well as an addition of steam to the furnace inlet and at the bottom of the vacuum tower. Under this low pressure the products will boil at a much lower temperature, which will prevent thermal cracking and equipment fouling. The Watson characterization factor can be use to estimate the upper temperature limit of crude oil to avoid coking in vacuum distillation. There is an empirical correlation between temperature and Watson characterization factor. From this correlation a line of where coking will occur can be drawn. But do to the variability of the composition of crude oil coking may occur below this limit. So a lower limit has to be drawn. The area between these lines is known as the decomposition zone. Where coking may occur depending on the composition of the crude oil. The temperature must be kept below the lower line to avoid coking.

Oil production in the United States is a very important industry. The demand for oil for power production as well as transportation is a driving factor for the amount of oil produced. Approximately 50% of all oil production goes towards transportation. In the past few decades oil production has gone through many ups and downs. The fear of a dwindling supply as well as when the oil production will peak has led to many conflicts all over the world. This has been especially true in the area labeled as the Middle East.

Oil production has been increasing greatly over the past few decades. This has been even more prevalent over the last few years. This has been especially true over the past few years in field production in the United States. The annual field production went from 6,783 thousand barrels of oil per day in 2008 to 10,000 thousand barrels of oil per day in 2013. This is very good news from an economic and political stand point but may not be good from an environmental standpoint. This increase in domestic production has led to a decrease in the imports of oil as well as increase in exports. This is a good step in the right direction of becoming a more energy independent country.

In 2008 the United States imported 12,915 thousand of barrels of oil per day. That is almost twice the amount that was produced domestically. Also in 2008 we exported roughly 1,802 thousand of barrels of oil per day. The reason we exported oil, even though we are importing more then we are producing, is because there are other markets around the world where it could be sold at higher prices. The number of imports dramatically changed from 2008 to 2013. In 2013 the United States imported 9,794 thousand barrels of oil per day. That is roughly a 32 percent decrease in total imports per day. Also in 2013 the United States exported roughly 3,594 thousand of barrels of oil per day. This is roughly a 200 percent increase over the number of exports in 2008.

This is a pretty drastic increase in just five years. These increases in field production and exports are due to an increase in oil wells discovered and utilized, although this could have a negative impact on the environment. The more oil wells that are being pump the more potential there is for accidents. This can be seen in the more recent disaster of the BP oil spill in the Gulf of Mexico. This oil spill devastated the region and the effects of it still can be felt today.

The decrease in imports also has a positive environmental impact here in the United States. Imports from the Middle East as well as Mexico are more sour crude, meaning there sulfur content can higher. There sulfur content is roughly 3% more then WTI and LLC sweet crude here in the United States. The higher the sulfur content the more refining and distillation that is required to meet the standards set forth. Less importing of these sour crudes is a good thing for the environment and oil refining here in the United States.

The refining process is crucial for production of gasoline for internal combustion engines. 50 percent of crude oil production goes towards producing gasoline. A steady supply needs to be maintained so there are no surpluses or shortages in the supply chain.

References:
1. http://www.eia.gov/todayinenergy/detail.cfm?id=7110
2. http://www.eia.gov/dnav/pet/pet_sum_snd_d_nus_mbblpd_a_cur.htm