Category Archives: Week 08

Catalytic Reforming Yields, Advantages, and Disadvantages

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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 Reforming of Heavy Naphtha & EPA “Reforming”

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Similar to cracking processes, reforming processes add utility to a refinery’s end product, gasoline. Catalytic reforming converts heavy naphtha to high octane isoparaffins and aromatics for gasoline blending. Using a noble metal catalyst, the reformer dehydrogenates, cyclizes, and isomerizes the feed compounds at a high temperature, low pressure, low space velocity, and low H2 byproduct to hydrocarbon ratio. As these conditions promotes C-C breaks and formations, they also lead to slight carbon rejection, which results in coke deposits on the catalyst. Therefore, the end goal of catalytic reforming is to enhance the octane rating of the stream while limiting the amount of coke buildup.

In order to limit the production of petroleum coke, compressed hydrogen is injected into the stream at a relatively low pressure. At high H2 pressures, hydrocracking overtakes reforming processes. While high operating temperatures could inhibit hydrocracking, this parameter is limited by the material defects of the reactor. A high space velocity can also suppress the cracking reaction, however this is detrimental to reforming effectiveness. Ultimately, these parameters must be included in a cost analysis to better define the appropriate operating conditions for a specific feed.

The various process configurations also dictates the optimal working conditions of the reformer. An example from our favorite Honeywell Company, UOP, provides a simplified version of their patented continuous catalyst regeneration (CCR) PlatformingTM Process. Despite the highly favored continuity concept, the seemingly endless list of processes are all very expensive, which explains why in Fig. 1 (below) U.S. refineries will not function at full capacity in the near future. Furthermore, economics are not the only driving forces in catalytic reforming operations: regulations play an important role.

blog 8 graphFig. 1: The amount of reformer feed remains annual cyclical for the past four years. (Source: EIA)

On May 15th, the EPA’s director signed a rule proposal that could affect conversion processes in refineries throughout the country. The amended regulations would require air concentration monitors along the fenceline of refineries with an expected reduction of 5600 tons per year of toxins and 52,000 tons per year of volatile organic compounds. In order to prolong the life of the catalyst, catalytic reformers include regeneration cycles which burn off coke with air, producing air pollutants. Preceding the catalytic reformer, a hydrotreatment process removes heteroatoms from the feed but subsequently pollutes the atmosphere if not mitigated appropriately. The new rule will eliminate the previous exemption to refinery emissions limits during startup and shutdown, so the aforementioned processes may need additional scrubbing systems. This regulatory scenario illustrates the delicate balance between engineering efficiency (catalyst maintenance) and pollution mitigation.

Let me know if you would like to collaborate while commenting on the new EPA proposals!

Reference:

  1. blog 8 catalytic reforming capacity

Production Limits of Reforming

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Catalytic reforming is a conversion process present in petroleum refinery and petrochemical industries. In this reforming process, low octane naphtha is converted into a higher octane reformate products for gasoline blending and aromatic rich reformate for aromatic production.1 To accomplish this reformation, the hydrogen molecules are re-arranged and re-structured in a naphtha feedstock, while breaking some of the molecules down into smaller ones.1 The Naphtha feeds to the catalytic reforming are heavy straight run naphtha.1 it transforms low octane naphtha into high-octane motor gasoline blending stock, and aromatics rich in benzene, toluene, and xylene with hydrogen and liquefied petroleum gas as a byproduct. 1 Due to the valuable nature and demand of these products, the catalytic reforming process is one of the most important processes in petroleum and the petrochemical industry.

In United States refineries we had limits on catalytic reforming capacity. For any given refineries can and do change operations of their refineries to respond to the continual changes in crude oil and product markets, but only within physical limits defined by the performance characteristics of their refineries and the prosperities of the crude oil they process.2 Currently in the US, the refinery Catalytic Reforming Capacity as of January 1st is 2,541,250 (Barrels per stream Day).3 This production is limited due current environmental regulations set by the government for the amount of aromatics gasoline can contain.3 This is because when reformed the benzene content becomes carcinogenic, which lead to the environmental regulations limiting its use and what further processing is needed. The economics of the process all plays a key role in the capacity produced.3 Where as this process may result in a desirable product that the public wants, and producing more would lower the price in the market, the environmental impact is the limiting factor. A cheaper made product could have adverse effects on the environmental, so there needs to be limits on production and quality. This result in less production and higher costs of production and sale; however it’s a more sustainable option as a result of the added costs.

  1. Lapinski, M.L., Baird L., James, “Handbook Petroleum refining”, Ed. Meyers, R.A., The McGraw Hill Companies , R. 4.32004.

 

  1.  ICCT- AN INTRODUCTION TO PETROLEUM REFINING AND THE PRODUCTION OF ULTRA LOW SULFUR GASOLINE AND DIESEL FUEL, October 24, 2011

 

  1. http://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=8_NA_8CRL_NUS_5&f=A

Catalytic Reforming

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Write a blog post discussing the objectives of catalytic reforming and limits on catalytic reforming capacity in the U.S. refineries.

Catalytic reforming is another catalytic conversion process utilized by many petroleum refineries. This was introduced in a similar time frame as catalytic cracking – during World War II. Of course, there was a huge increase in the demand for high-octane gasoline during this time frame due to the necessity of fuel demanded from US aircraft.

There are four different reactions of catalytic reforming which all achieve the same objective of increasing the octane number. Dehydrogenation, dehydroisomerization, and dehydrocyclization are all highly endothermic reactions which produce aromatic compounds and hydrogen gas in large yields. These reactions require high temperatures and relatively low pressures, however the hydrogen pressure must be significantly high enough in order to avoid deactivating the catalyst surfaces due to coke deposition.

Hydrogen is the most valuable byproduct obtained from catalytic reforming. This is because this element can be used to essentially ‘clean up’ fuels further through processes of hydrotreating and hydrocracking. There are a couple of limits posed on catalytic reforming. Usually the feedstock must be hydrotreated before reforming can take place since the platinum catalyst used in reforming can be hindered by exposure to sulfur, nitrogen, or other heteroatom contaminants. Also, the United States and Europe hold a limit on the levels of benzene and the total aromatics for gasoline, therefore placing a limit on the amount of reformate able to be used in the blending of gasoline. The overall goal of catalytic reforming is to obtain high-octane-number gasoline while also acting as the sole internal source of the byproduct hydrogen.

Another limit pertaining to catalytic reforming is the occurrence of the undesirable side reaction of hydrocracking. This process consumes the valuable hydrogen byproduct while forming gaseous hydrocarbons which in turn decrease the yield of reformate. The principal approach to achieve high yields and high quality of reformate is increasing the selectivity of desirable reactions by means of finding the proper balance between acidic and metallic sites.