Before the start of America’s involvement in World War II, the demand for petroleum based products, while growing steadily, was still reasonably small especially compared to the demand during and after wartime. Thermal refineries had been the primary operational utility for generating petroleum based products like gasoline, diesel, and jet fuel from around 1910 until 1940; however they were suddenly unable to produce enough product to feed the country as well as the military vehicles, tanks, and planes at the start of WWII¹. Beyond sheer volume, there was also drastic increase in demand for high performance, high octane fuels for use in more advanced vehicle engines and as aviation fuels². To satisfy these two new problems, newly designed refineries called catalytic refineries were introduced which incorporated exceedingly more advanced cracking capabilities through the use of specialized catalysts. These catalysts worked through ionic reactions which are faster and more easily controlled than the older thermal refinery style free radical reactions³. The specialty of these new catalysts is their ability to produce much higher octane number fuels which combust more steadily and cause less damage to the internal combustion engines that use them. Non-fuel, petroleum based products such as toluene and butyl rubber made in refineries were also found to be extremely useful during WWII⁴. Toluene is a major component of trinitrotoluene (TNT) which was used heavily during World War II in explosives and butyl rubber is a man-made rubber which became a substitute for natural rubber when traditional supplies were cut off⁴.

1. Eser, Semih. “Lesson 6: Thermal Conversion Processes.” FSC 432: Petroleum Processing. N.p., n.d. Web. 27 July 2014. <https://cms.psu.edu/section/content/default.asp?WCI=pgDisplay&WCU=CRSCNT&ENTRY_ID=F20C6357261A4AE2A750C141B721E8C1>.
2. Eser, Semih. “The Thermal Refinery (1910 – 1940).” FSC 432: Petroleum Processing. N.p., n.d. Web. 27 July 2014. <https://cms.psu.edu/section/content/default.asp?WCI=pgDisplay&WCU=CRSCNT&ENTRY_ID=F20C6357261A4AE2A750C141B721E8C1>.
3. Eser, Semih. “The Catalytic Refinery (1940-1970).” FSC 432: Petroleum Processing. N.p., n.d. Web. 27 July 2014. <https://cms.psu.edu/section/content/default.asp?WCI=pgDisplay&WCU=CRSCNT&ENTRY_ID=F20C6357261A4AE2A750C141B721E8C1>.
4. “1940 – 1945 The War Years.” 90th Poster Early Years. N.p., n.d. Web. 30 July 2014. <http://www.exxonmobil.com/NA-English/Files/90thPstr3WarYears.pdf>.

While similar in nature, a municipal wastewater treatment facility and an industrial wastewater treatment facility such as one located onsite in petroleum processing plants may not be able to handle mixing input streams. This would especially be the case for adding industrial wastewater to a municipal treatment outfit because they are designed for specific types of pollutants. These pollutants include food wastes, microorganisms, viruses, bacteria, certain nutrients such as Nitrogen and Phosphorous, and household organic products such as pharmaceuticals and soaps.¹ Beyond these contaminants, municipal treatment also controls levels of suspended solids and biochemical oxygen demand (BOD) among other things which do exist in industrial wastewater, however the problems is there are more than just these pollutants coming from refineries. For example, BOD, Nitrogen, Phosphorous, and suspended solids are accompanied by contaminants like oils, hydrocarbons, mercaptans, phenols, toxic compounds such as cyanides and H₂S or even strong acids such as sulfuric acid and hydrofluoric acid. Municipal installations are simply not built to handle these types of pollutants and would therefore either slowly destroy the municipal plant or allow the toxins to flow directly into the clean water supply. A report by the EPA said that refineries may use one to two and a half gallons of water for every gallon of product they produce³ which would lead to an enormous amount of pollutants entering our water supply.

1. Velegol, Stephanie . “CE 370 – Module #7a: Wastewater Components.” Penn State College of Engineering . N.p., n.d. Web. 23 July 2014. http://www.engr.psu.edu/mediaportal/flvplayer.aspx?FileID=4b42d423-1a7d-4e05-accd-9
2. Eser, Semih. “Wastewater Treatment.” F SC 432: Petroleum Processing. N.p., n.d. Web. 23 July 2014. <https://cms.psu.edu/section/content/default.asp?WCI=pgDisplay&WCU=CRSCNT&ENTRY_ID=F20C6357261A4AE2A750C141B721E8C1>
3. “Water & Energy Efficiency by Sectors, Oil refineries.” EPA. Environmental Protection Agency, n.d. Web. 23 July 2014. <http://www.epa.gov/region9/waterinfrastructure/oilrefineries.html#water>.

Catalytic reforming is a necessary chemical process used in the petroleum refining industry which takes in straight run naphtha or partially treated light straight run naphtha, depending on the process, as a feedstock and converts it into high octane reformate and gasoline products. The earliest catalytic conversion processes date back as far as the 1930’s, however they have been continually improved upon since then with advances in techniques, catalysts, and yields to meet governmental product requirements. There are several different processes that are designated into classifications based on how their individual catalyst regeneration systems work. Those classifications are: semi-regeneration, cyclic regeneration, and continuous regeneration. Older catalytic reforming processes are typically semi-regenerative while cyclic and continuous regeneration processes are newer more advanced strategies.

Semi-regenerative methods, while useful, can be problematic because they must be turned off on a scheduled basis for the regeneration process to take place. These scheduled outages mean that the refineries cannot generate products and are therefore losing money while the units are offline. Cyclic units sought to resolve some of these issues by introducing another reactor to a two or three reactor system so that while one is turned off for regeneration the others could continue running and producing high octane fuels. The most up-to-date practices use continuous regeneration which requires no shutdown time because catalysts are momentarily removed from the reaction process, regenerated, and then introduced back in to continue the transformation of low octane feedstocks to high octane products. Continuous processes appear to be the best way to go except that they are the most expensive and most technically involved of the three methods.

Besides the regeneration methods, catalytic reforming processes, such as alkylation, dealkylation, polymerization, isomerization, and disproportionation¹, have their own advantages and disadvantages as well. Sulfur is a major issue for catalysts because it will poison the catalysts causing them to be unable to function so hydrogenation must occur prior to any of these catalytic reforming processes taking place to remove sulfur. Dehydrogenation and dehydrocylcinization as overall processes can also be problematic because they can create aromatic compounds which are regulated by the U.S. government due to their nature as carcinogens. The procedure of alkylation has an advantage over other practices in this respect because it does not produce any aromatic compounds which is why it is favored in use over other reforming types.² Alkylation is not without its drawbacks though, while it yields no aromatics alkylation does require the use of highly concentrated acids, such as hydrofluoric or sulfuric acid¹. Acids such as these can be dangerous to human health as well as the environment ^{3 4}.

1. “CIEC Promoting Science at the University of York, York, UK.” Cracking and related refinery processes. N.p., n.d. Web. 10 July 2014. <http://www.essentialchemicalindustry.org/processes/cracking-isomerisation-and-reforming.html>.
2. Eser, Semih. “Alkylation.” FSC 432: Petroleum Processing. N.p., n.d. Web. 12 July 2014. <https://cms.psu.edu/section/content/default.asp?WCI=pgDisplay&WCU=CRSCNT&ENTRY_ID=F20C6357261A4AE2A750C141B
3. “Hydrogen Fluoride (Hydrofluoric Acid).” CDC. N.p., n.d. Web. 11 July 2014. <http://www.bt.cdc.gov/agent/hydrofluoricacid/basics/facts.asp>.
4. “Sulfuric acid .” Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 18 Nov. 2010. Web. 12 July 2014. <http://www.cdc.gov/niosh/npg/npgd0577.html>.

Catalytic cracking is a petroleum refining process that dates back to as early as 1915 however it came into prominence during the Second World War. There was a need for and improved process that would provide higher quality and quantity products than the brute force tactics used in thermal cracking. By applying newer, more advanced knowledge of chemistry and chemical reactions petroleum refining could produce better yields of gasoline with higher octane ratings than thermal cracking could ever hope to accomplish.

Catalytic cracking accomplishes this goal by cracking small ionic molecules, called carbocations, off of longer straight chain alkanes. These carbocations can then reattach to an alkane molecule to create an iso-alkane which has the required higher octane ratings needed in today’s society. Catalytic cracking, as noted before, runs on relatively long straight chain alkanes and therefore the feedstocks usually consist of, light cycle oils and potentially heavy gas oils or light vacuum gas oils¹. These types of oils have the size necessary to be able to be cracked while still forming the correct length range of alkane products. The primary goal of catalytic cracking is to increase the quantity of production of higher octane gasoline than could be done from straight run products or thermal cracking, however constituents such as kerosene, LPG, heating oil, and olefins are produced as well².

Catalytic hydrocracking, also known as hydrocracking, is a refinery process that was just added in the last thirty years with a main goal of enhancing catalytic cracking. The process of hydrocracking is typically completed in two main parts: first hydrotreatment must be conducted before the actual hydrocracking can take place. Catalytic hydrocracking can bring in feedstocks such as some atmospheric residue, heavy vacuum gas oil, light cycle oil, and potentially even deasphalted oil which all contain high concentrations of aromatic and heteroatom compounds³. Because these feeds contain such high concentrations, hydrogen must be added first, during hydrotreatment, in order to convert highly stable, unsaturated aromatic compounds to saturated aliphatic compounds. Once this process has taken place the newly formed cycloalkanes are cracked in the presence of more hydrogen to prevent coking. The cracking process, called hydrocracking, forms the necessary alkane molecules needed in catalytic cracking.

Catalytic hydrocracking is beneficial to catalytic cracking not only because it can produce some of its feedstock but also because it provides a way to remove heteroatoms such as nitrogen, sulfur, oxygen, and other metals before they enter the catalytic cracker. If these contaminants were to enter the catalytic cracking system they could potentially poison the catalysts which are needed to run reactions forming the iso-alkanes.

1. “Fluid catalytic cracking.” Wikipedia. Wikimedia Foundation, n.d. Web. 4 July 2014. <http://en.wikipedia.org/wiki/Fluid_catalytic_cracking#Flow_diagram_and_process_description>.
2. “Cracking.” Encyclopedia of Earth. N.p., n.d. Web. 4 July 2014. <http://www.eoearth.org/view/article/151525/>.
3. Meister, Jill , and Roger Lawrence. “Hydrocracking, Processing Heavy Feedstocks to Maximize High Quality Distillate Fuels.” UOP. N.p., n.d. Web. 4 July 2014. <http://www.uop.com/hydrocracking-processing-heavy-feedstocks-maximize-high-quality-distillate-fuels/>.

The first thermal cracking processes were developed in 1913 with the purpose of heating atmospheric tower residues and heavy gas oils until the molecules cracked and broke apart.¹ The reason for conducting this process was to break up the less desirable petroleum products and form them into highly valuable light middle distillates such as naphtha, gasoline, and diesel fuel among others². Thermal cracking became incredibly important with the invention of the automobile which uses an internal combustion engine fired by diesel or gasoline. With more people driving, the demand for fuel skyrocketed and the cracking process made it possible to produce more gasoline and diesel than was produced from crude oil as a straight run product³. For twenty to thirty years it was the pinnacle of petroleum refining processes, however by the start of World War II thermal cracking could no longer generate the quantity or quality that was demanded. At this time automobiles and planes required higher octane fuels that simply are not capable of being produced from the simple brute force cracking process¹. Instead, a new process called catalytic cracking was introduced which was capable of yielding larger amounts of higher quality fuel. While limited in use, thermal cracking is still used today with its primary roles being the production of diesel fuel and ethylene².

1. “Petroleum Refining Process.” Petroleum Refining Process. N.p., n.d. Web. 26 June 2014. <http://www.ilo.org/oshenc/part-xii/oil-and-natural-gas/item/384-petroleum-refining-process>.
2. Semih, Eser. “Lesson 6: Thermal Conversion Processes.” FSC 432: Petroleum Processing. N.p., n.d. Web. 28 June 2014. <https://www.e-education.psu.edu/fsc432/content/lesson-6-thermal-conversion-processes>.
3. Solomon, Lee. “Visbreaking, thermal cracking, and coking.” Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 28 June 2014. <http://www.britannica.com/EBchecked/topic/454440/petroleum-refining/81801/Visbreaking-thermal-cracking-and-coking>.

Dewaxing is process carried out in oil refineries that takes in deasphalted oil as well as heavy gas oil and attempts to produce a lubricating oil base stock. Lubricating oil is desired to have low pour points, low volatility, moderate viscosity, a high viscosity index, and a high thermal stability however to produce such a substance oils must have long chain paraffinic compounds removed through one of two processes: solvent dewaxing or catalytic dewaxing.

Solvent dewaxing is a physical process where solvents such as methyl ethyl ketone or propane are added to the oil mixture and then the oil mixture is cooled in a refrigeration unit. The temperature of this refrigeration unit will be based on the amount of waxes that need to be removed to reach the desired qualities of the lubricating oil. Once the solvent is mixed in and the solution is cooled, the wax will begin to form crystals and solidify. The solid wax will build up on a cloth within the separation unit then cut off and removed via a solvent stream. As a last step this wax is run through a steam stripper where the solvent can be taken back out and recycled. The lubricating oil is run through a steam stripper to remove and recycle the solvent as well.

Catalytic dewaxing is a chemical process where the long chain paraffins are cracked through the use of a selective catalyst. This catalyst is a molecular sieve with small specifically sized pore openings which allow n-paraffins to enter and be cracked while keeping i-paraffins out of the cracking process. By having a catalyst of this nature it allows the number of n-paraffins to increase while keeping the number of i-paraffins close to the same which increases the n-paraffin to i-paraffin ratio. This is beneficial to the desired lubricating oil product because as the ratio increases the pour point decreases and thus creates a better oil. Due to the selectivity of the catalyst, catalytic dewaxing has a higher yield of more consistent products when compared to solvent dewaxing. Catalytic dewaxing often costs less to install in a refinery system than solvent dewaxing.

Solvent fractionation is a process used is the deasphalting process that separates mainly vacuum distillation residue (VDR) by dissolving it into various solvents. The initial step is to place the typically solid VDR in and aromatic solvent such as benzene or toluene which it is soluble in. After this is done an alkane solvent such as n-heptane is added to the mixture which will cause some compounds to become insoluble and precipitate out. Precipitation occurs at this step because the heptane disrupts the gradient solubility of the fractions within the benzene or toluene solvent. As the concentration of non benzene or toluene solvents increase the gradient solubility will deteriorate further. The compounds that initially drop out will be the heaviest molecular weight compounds, known as asphaltenes, of any that come out however they will be the smallest fraction that exits the mixture. There will also be fractions that will not drop out which are called maltenes. To further remove maltenes from the mixture the process can be continually repeated using lighter and lighter alkane solvents such as pentane or propane. These further steps will cause greater amounts of asphalt to precipitate out with the understanding that as more asphalt is precipitated out it will become lighter. This will balance out the heavy fractions that came out initially and lightening the weight of the asphalt overall.

The reason that aromatic solvents are even capable of dissolving the VDR is explained by the Hildebrand Solubility Parameters which measure the strength or power of solvents. The parameters are based on a combination of surface tension and molar volume or latent heat of vaporization and molar volume. As general rules go, the higher the density of a compound (which would mean a lower molar volume) and either higher surface tension or higher latent heat of vaporization will cause a solvent to be more powerful. This explains why aromatic compounds with high density, high surface tension, and latent heat of vaporization can dissolve most compounds while propane is a much poorer solvent.

Vacuum distillation is necessary in the distillation of crude oils because of the complexity of compounds that make up crude oil. Being that there are thousands of different compounds in crude that will all boil at their own boiling point, there is a very broad range of boiling temperatures. If particular compounds are heated up beyond a certain temperature they will begin to crack or break apart creating smaller hydrocarbon chains also known as coke. This coke will begin to build up on the surfaces of distillation units and closely associated units such as strippers and pump arounds. Coking can cause a myriad of different problems including heat exchangers not working correctly or plugging necessary valves, nozzles, or even pipes. In order to avoid reaching this critical coking temperature the fractions of crude with the highest boiling points are removed from the atmospheric distillation column and put into a vacuum distillation column where the pressure has been reduced which allows for the liquids to boil at lower temperatures.

As explained previously in the course, a Watson Characterization factor (K_w) can be calculated for crude oils to show their general chemical makeup when it comes to hydrocarbon type. Of the three main types of hydrocarbons, paraffinic hydrocarbons have the highest K_w values followed by naphthenic hydrocarbons and aromatic hydrocarbons. Due to the fact that paraffins are the most likely and first to initial coking a correlation between the K_w factor and vacuum distillation temperature can be seen: the higher the K_w factor, the lower the temperature must be in the vacuum distillation unit must be and vice versa. This relationship is a result of chemical bonding strengths of which aromatics have the strongest bonds and therefore require the most heat to crack. It is also known that based on the chemical makeup, below a given temperature coking will not occur so the best bet is to run below this temperature as much as possible and never run above the critical coking temperature.

There are two broad categories of distillation which are atmospheric and vacuum distillation. Within these two categories there are three distillation methods: True Boiling Point distillation (TBP), ASTM distillation, and Equilibrium Flash Vaporization distillation (EFV). As the names imply, atmospheric distillation runs at atmospheric pressure while vacuum distillation runs lower than atmospheric pressure that allows very high boiling point compounds to boil at lower temperatures.

The first of the three distillation methods, TBP, distills the crude in a batch operation. As the crude is heated each component converts to vapor at its specific boiling point. The vapor is separated from the other liquids using what are known as theoretical plates of which there are more than 100 in the column. Another aspect of this method is that the products are stringently purified using a reflux technique which involves heating and cooling vaporized distillates while in the distillation unit or just outside the unit and put back in. By combining the high number of theoretical plates with a reflux ratio, meaning the ratio of amount of reflux to amount of products, this procedure provides the greatest purity of product of the three distillation types.

ASTM works similar process to TBP however it does not use the theoretical plates or have reflux (and therefore no reflux ratio). In the end this process looks much more like a typical distillation unit which heats a liquid to a boiling point and cools and collects the condensate. This process provides slightly lower quality products.

EFV is similar to ASTM however it heats a flowing feed of crude rather than heating a batch. Once heated the feed enters a flash drum where the crude that has boiled off to vapor will separate from the other liquids. This provides the lowest quality products of the three methods.

In finding the required data to complete this assignment, the U.S. Energy Information Administration website was used. From the homepage I used the Sources and Uses dropdown menu to find the “Weekly Petroleum Status Report” (on the right hand side of the dropdown menu) which gave data up to the middle of May. This data was logged for various topics such as weekly U.S. field production, imports, exports, U.S. refiner and blender net production, and the product supplied for a small number of refinery products.

When beginning to look at the numbers, it can be seen that there is a total input of crude oil to U.S. refineries of 15,949 thousand barrels per day (KBPD), the majority of which is actually produced domestically (8,434 KBPD versus 6,469 KBPD imported)¹. This is somewhat surprising at first; however if the table is followed backward we can see that there has been a 14% increase in U.S. production and a 5.3% drop in imports since last year¹. What can be drawn from this is that America, while still being heavily reliant on oil, is currently becoming slightly less dependent on foreign oil. With this being said, the U.S. is still importing over 4,500 KBPD from Canada, Saudi Arabia, and Mexico alone². On top of the increase in domestic fuel production there has also been an increase in crude oil exported from the U.S. As of May 16^th America exported 71 KBPD which is up from 48 KBPD last year at this time¹.

Taking a step backward for a moment, it might beneficial to look in to not just the overall numbers but also the values of specific refinery products such as gasoline, kerosene, and distillate fuel oils. These three products are shown to be the largest components of refinery production currently because they are used as fuels in transportation methods³. When I was investigating these numbers I realized these were the stocks or supplies of each type of fuel in millions of barrels. So as of mid May the U.S. had a stock of 213 million barrels of gasoline, 39 million barrels of kerosene, and 116 million barrels of distillate fuel oil³. Although this seems like a large amount of each, to put things in perspective, America’s Strategic Petroleum Reserve can hold up to 727 million barrels of oil so these values are not all that large⁴. Once again looking at the fluctuations of these stocks it can be seen that gasoline and distillate fuel oil have actually decreased since this time last year while kerosene increased. There are several factors that could lead to these decreases however I believe it could be partly due to Americans driving less as gasoline prices rise⁵. With fewer miles being driven there may be less need to keep a large amounts of gasoline or distillate fuel oil stored up in case of emergency.

In the refining of crude oil there are several processes done to improve the quality of the oil products so that they meet environmental specifications set by the state and federal government. Refineries must reduce or remove the amount of nitrogen, sulfur, and organometallic compounds in the crude oil to acceptable levels. For instance, nitrogen and sulfur content can be reduced through the use of hydrotreating or hydrodesulfurization which cuts down on NO_x and SO_x emissions during combustion. Organometallics include elements like nickel, vanadium, and copper must also be taken out due to their highly corrosive and toxic natures.

References:

1. “Weekly Petroleum Status Report.” U.S. Energy Information Administration . N.p., n.d. Web. 25 May 2014. <http://www.eia.gov/petroleum/supply/weekly/pdf/table1.pdf>.
2. “Weekly Petroleum Status Report.” U.S. Energy Information Administration. N.p., n.d. Web. 25 May 2014. <http://www.eia.gov/petroleum/supply/weekly/pdf/table8.pdf>.
3. “Weekly Petroleum Status Report.” U.S. Energy Information Administration . N.p., n.d. Web. 25 May 2014. <http://www.eia.gov/petroleum/supply/weekly/pdf/table4.pdf>.
4. “Strategic Petroleum Reserve.” ENERGY.GOV. N.p., n.d. Web. 25 May 2014. <http://energy.gov/fe/services/petroleum-reserves/strategic-petroleum-reservev>.
5. “U.S. Energy Information Administration – EIA – Independent Statistics and Analysis.” Table 5.24 Retail Motor Gasoline and On-Highway Diesel Fuel Prices, 1949-2011 (Dollars per Gallon). N.p., n.d. Web. 25 May 2014. <http://www.eia.gov/totalenergy/data/annual/showtext.cfm?t=ptb0524>.