Wastewater that comes into contact petroleum fractions cannot be treated at municipal water treatment facilities. This is because municipal water treatment does not have the equipment to clean the pollutants that are added to the water during petroleum processing. It is also not the job of the municipal water treatment to clean the many poisons that were added to the water during petroleum processing. Municipal water treatment facilities clean the water of sewage and storm run off. The kind of toxic chemicals found in the petroleum refining waste water contain poisonous compounds which under normal circumstances would never come into contact with any water stream. For instance, a multitude of hydrocarbons, aromatic compounds, such as benzene and heteroatom compounds like mercaptans, amines, phenols, cyanide’s. These polluted streams of water also contain dissolved gases like H2S and NH3, acids such as H2SO4 and HF. All of which a municipal waste water facilities is not capable of removing to a safe level for release back into the environment.

Catalytic reforming is a process which is born out the the necessity for high octane fuels which are used in transportation such as gasoline and aviation fuel.. This process takes the low octane straight run naphtha that is rich in naphthenes into high octane and low sulfur fuel which is used heavily in gasoline. Using this process a higher yield of gasoline can be achieved. In order to do this a few chemical reactions which increase the octane number of naphtha, convert the naphthenes to aromatics, and insomerize n-paraffins to i-paraffins must be completed. The catalysts used to bring these reactions to completion are generally platinum, palladium, or bimetallic formulation of platinum with Iridium or Rhenium with alumina. The process creates a large volume of hydrogen, which is a very valuable bi-product because it is in high demand for hydro-treating and hydro-cracking processes. The catalytic reformer is fed by the heavy naphtha line from the naphtha splitter. The naphtha splitter is fed by the straight run naphtha. The most desirable chemical reactions in the catalytic reforming process is dehydrogenation of naphthenes to aromatics, dehydroisomerization of alkyl-c5-naphthenes, Dehydrocyclization of n-paraffins to aromatics, and isomerization of n-alkanes to i-alkanes. These reactions increase the Research Octane Number (RON) from 75 to 110, 83 to 100, 0 to 110, and -19 to 90 respectively. 
All of these reactions except for the isomerization of n-alkanes produces hydrogen. If sufficient hydrogen is not produced coking my begin.

The catalytic reforming process is not without its limits. The United States and Europe limits the amount of benzene and other aromatics which can be found in gasoline. Because these compounds are carcinogenic and are harmful to the environment in many cases, catalytic reforming is limited. The high demand for high octane fuels and the hydrogen by product makes the process very valuable to refineries despite the production of aromatics.

Thermal cracking is the chemical process of converting larger, long straight chain alkanes found in gas oils and other crude oil fractions into shorter straight chain alkanes. These shorter alkane chains are more desired because of their use in transportation fuels like gasoline. The thermal cracking reactions are governed by free radicals. The chain reaction of free radicals starts by breaking the C-C bond in the alkanes. This forms two free radicals. This step is called the initiation reaction. The next step, the propagation reaction produces a short chain alkane and one radial, which continues the chain. The final step is the termination reaction. This process started in the 1900’s as a way to increase the yield of motor gasoline from crude oils. These high-octane fuels were used in aircraft. Catalytic cracking came into use in the 1930’s and 1940’s. Because the catalytic cracking process produced higher yields of gasoline with high octane numbers, thermal cracking is no longer a method for breaking longer chains into shorter chains for gasoline production in modern refineries. In locations where diesel fuels are in high demand thermal cracking is still used. The use of thermal cracking in modern refineries is limited to naphtha cracking of residual fractions like vacuum distillation residue.

Dewaxing is the required to remove the hydrocarbons that solidify as temperatures decrease. Removing these hydrocarbons lowers the pour point which is a desired characteristic of a fuel because it can continue to function as lower temperatures. Dewaxing can be done in one of two methods. Solvent dewaxing is a physical process of freezing and removing the waxes. Catalytic dewaxing is a chemical process which removes wax by reaction of long chain n-alkanes or wax.

Solvent dewaxing is done by refrigeration of the feedstock after it is mixed with a solvent. The temperature of the refrigeration process depends on the desired pour point of the product. If the desired pour point is very low then the refrigeration will be very low. The wax crystals are separated by a cloth filter. These wax crystals are called slack wax and can be used for making candles, cosmetics and petroleum jelly. The solvents used in this process are methyl ethyl ketone (MEK) and propane.

Catalytic dewaxing utilizes a process to crack the n-paraffins (wax). This method of selective cracking takes place in the zeiolite catalyst. The small pore size of this catalyst wont allow i-paraffins to react. Increasing the concentration of i-paraffins in the fuel lowers the pour point because there are less n-paraffins to freeze at higher temperatures. Advantages of this method over solvent dewaxing include product stability, lower capital investment, and flexibility to produce both lube oil stock and light distillates.

Deasphalting is an alternative to distillation. Just like distillation, deasphalting fractionates different components from a feed stock. Unlike distillation, the fractionation is done by using a solvent extraction process with deasphalting. This process is more often used for vacuum distillation residue.  The highest molecular weight compounds (known as asphaltene,) found in vacuum distillation residue can be separated by precipitation once a light paraffin solvent is mixed with the feed stock in an aromatic solvent like toluene. The portion of the feedstock that is soluble in a paraffin solvent is called maltenes. Maltenes can be separated using paraffin solvents like n-heptane. Using n-pentane solvents, which are lighter and weaker, we can fractionate these compounds further. These are separated into hard resin and n-pentane soluble fractions. Using propane, we can further refine the soluble fractions.  Lighter solvents can be used to further separate the feedstock. This process is important because it allows us to separate products based on demand.

In order to understand how asphaltenes can be separated out of a vacuum distillation residue utilizing the solvent extraction method, we must understand the Hildebrand Solubility Parameters (HSP) for non-polar solvents. The Hildebrand Solubility Parameters measure the strength of the solvent that is used for extraction. There are two definitions of HSP. Each are a function of molar volume, but the first definition has a variable of surface tension, where the second definition has a variable of energy of vaporization.  Using these equations we can explain how a large volume paraffin solvent can disrupt the gradient solubility of asphaltenes to allow for the solid particles precipitate and then filtered.

Vacuum distillation is a necessary process because the outlet temperatures of the atmospheric pressure distillation are so high that thermal would begin the break down the crude oil. In order to continue distilling the heaviest crude fractions of the atmospheric distillation process, the pressure must be reduced to 25 to 40mmHg. Cracking, the breaking of the chemical bonds between carbon atoms would cause coking on the metal surfaces in the column, which interferes with distillation.

Watson Characterization is used to determine an upper temperature limit for the vacuum distillation process, which avoids coking. If severe coking occurs it can plug the flow of the distillation column, which would lead to the shutting down of the entire refinery. By comparing the Watson characterization factor (Kw) to temperatures, which relate to coking propensity, a safe temperature can be determined. Bands of temperatures show where coke formation is negligible as well as uncertain. Generally the temperature that is chosen is lower than the lower temperature line of the band.

According to the EIA.gov website, the total weekly product of oil supplied was used to create seven major products. ~49% of the 18,855 thousand barrels of crude oil supplied on the 16th of May 2014 was used to make motor gasoline. This is by far the most produced product from crude oil. 8% of the supplied crude oil on this day was used to make jet fuel. 20% was used to make diesel fuel.

Crude oil inherently contains toxic compounds which must be removed in the refining process to meet safe standards when burned. Benzene, sulfur, and organometallics are some of these compounds. Because benzene is a carcinogen, only a limited amount can be found in gasoline or fuel oil.  Heavy crude oils can contain organometallic compounds like nickel and vanadium. These are toxic and corrosive in nature and are removed in the refinery. Environmental standards for sulfur requires gasoline, jet fuel, diesel, and fuel oil to be limited in the refinery.