The reformer converts low-octane naphthas into octane-boosting components blended into gasoline.
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Some refinery naphthas also contain some olefinic hydrocarbons, such as naphthas derived from the fluid catalytic cracking, visbreakers and coking processes used in many refineries. Those olefin-containing naphthas are often referred to as cracked naphthas. In some (but not all) petroleum refineries, the cracked naphthas are desulfurized and catalytically reformed (as are the virgin naphthas) to produce additional high-octane gasoline components.
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Some petroleum refineries also produce small amounts of specialty naphthas for use as solvents, cleaning fluids and dry- cleaning agents, paint and varnish diluents, asphalt diluents, rubber industry solvents, recycling products, and cigarette-lighter, portable-camping-stove and lantern fuels. Those specialty naphthas are subjected to various purification processes. Sometimes the specialty naphthas are called petroleum ether, petroleum spirits, mineral spirits, paraffin, benzine, hexane, ligroin, white oil or white gas, painters naphtha, refined solvent naphtha and Varnish makers' & painters' naphtha (VM&P;). The best way to determine the boiling range and other compositional characteristics of any of the specialty naphthas is to read the Safety Data Sheet (SDS) for the specific naphtha of interest.
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Before describing the reaction chemistry of the catalytic reforming process as used in petroleum refineries, the typical naphthas used as catalytic reforming feedstocks will be discussed.
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Rhenium in the form of rhenium-platinum alloy is used as catalyst for catalytic reforming, which is a chemical process to convert petroleum refinery naphthas with low octane ratings into high-octane liquid products. Worldwide, 30% of catalysts used for this process contain rhenium. The olefin metathesis is the other reaction for which rhenium is used as catalyst. Normally Re2O7 on alumina is used for this process.
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The city's surrounding fields are rich in crude petroleum and are dotted by a series of oil wells established during the communist dictatorship. Only a fraction of these wells are operating today, but the city includes a working refinery, and outputs of naphthas are significant. The refinery was owned by Taçi Oil through ARMO (Anika Mercuria Refinery Associated Oil, owned by Anika Enterprises). In 2013 ARMO was sold to Heaney Assets Corporation, an Azerbaijan corporation.
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Merox is an acronym for mercaptan oxidation. It is a proprietary catalytic chemical process developed by UOP used in oil refineries and natural gas processing plants to remove mercaptans from LPG, propane, butanes, light naphthas, kerosene and jet fuel by converting them to liquid hydrocarbon disulfides. The Merox process requires an alkaline environment which, in some process versions, is provided by an aqueous solution of sodium hydroxide (NaOH), a strong base, commonly referred to as caustic. In other versions of the process, the alkalinity is provided by ammonia, which is a weak base.
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Catalytic reforming is a chemical process used to convert petroleum refinery naphthas distilled from crude oil (typically having low octane ratings) into high-octane liquid products called reformates, which are premium blending stocks for high-octane gasoline. The process converts low-octane linear hydrocarbons (paraffins) into branched alkanes (isoparaffins) and cyclic naphthenes, which are then partially dehydrogenated to produce high-octane aromatic hydrocarbons. The dehydrogenation also produces significant amounts of byproduct hydrogen gas, which is fed into other refinery processes such as hydrocracking. A side reaction is hydrogenolysis, which produces light hydrocarbons of lower value, such as methane, ethane, propane and butanes.
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Light hydrocarbon feeds such as ethane, LPGs or light naphtha give product streams rich in the lighter alkenes, including ethylene, propylene, and butadiene. Heavier hydrocarbon (full range and heavy naphthas as well as other refinery products) feeds give some of these, but also give products rich in aromatic hydrocarbons and hydrocarbons suitable for inclusion in gasoline or fuel oil. Typical product streams include pyrolysis gasoline (pygas) and BTX. A higher cracking temperature (also referred to as severity) favors the production of ethylene and benzene, whereas lower severity produces higher amounts of propylene, C4-hydrocarbons and liquid products.
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Fire breathing is typically performed with a high flash point fuel, such as lamp oil (liquid paraffin), while fire eating is performed with low flash point fuels, such as white gas or naphtha. Highly purified fuels are preferred by fire performers due to their minimized toxicity, but other, more dangerous fuels may sometimes be used, such as ethanol, isopropanol, kerosene, gasoline, or charcoal lighter fluid. All fuels run the risk of causing pneumonitis if inhaled, however longer chain oils are more persistent than smaller molecules. Alcohols and volatile naphthas are likely to be absorbed or expelled from the body by evaporation and respiration.
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The most common use of platinum is as a catalyst in chemical reactions, often as platinum black. It has been employed as a catalyst since the early 19th century, when platinum powder was used to catalyze the ignition of hydrogen. Its most important application is in automobiles as a catalytic converter, which allows the complete combustion of low concentrations of unburned hydrocarbons from the exhaust into carbon dioxide and water vapor. Platinum is also used in the petroleum industry as a catalyst in a number of separate processes, but especially in catalytic reforming of straight-run naphthas into higher-octane gasoline that becomes rich in aromatic compounds.
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The conventional Merox process for extraction and removal of mercaptans from liquefied petroleum gases (LPG), such as propane, butanes and mixtures of propane and butanes, can also be used to extract and remove mercaptans from light naphthas. It is a two-step process. In the first step, the feedstock LPG or light naphtha is contacted in the trayed extractor vessel with an aqueous caustic solution containing UOP's proprietary liquid catalyst. The caustic solution reacts with mercaptans and extracts them. The reaction that takes place in the extractor is: :2RSH + 2 NaOH → 2NaSR + 2 H2O In the above reaction, RSH is a mercaptan and R signifies an organic group such as a methyl, ethyl, propyl or other group.
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After the cracking temperature has been reached, the gas is quickly quenched to stop the reaction in a transfer line heat exchanger or inside a quenching header using quench oil. The products produced in the reaction depend on the composition of the feed, the hydrocarbon-to-steam ratio, and on the cracking temperature and furnace residence time. Light hydrocarbon feeds such as ethane, LPGs, or light naphtha give mainly lighter alkenes, including ethylene, propylene, and butadiene. Heavier hydrocarbon (full range and heavy naphthas as well as other refinery products) feeds give some of these same products, but also those rich in aromatic hydrocarbons and hydrocarbons suitable for inclusion in gasoline or fuel oil.
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However, both the dehydrogenation of naphthenes and the dehydrocyclization of paraffins produce hydrogen. The overall net production of hydrogen in the catalytic reforming of petroleum naphthas ranges from about 50 to 200 cubic meters of hydrogen gas (at 0 °C and 1 atm) per cubic meter of liquid naphtha feedstock. In the United States customary units, that is equivalent to 300 to 1200 cubic feet of hydrogen gas (at 60 °F and 1 atm) per barrel of liquid naphtha feedstock.US Patent 5011805, Dehydrogenation, dehydrocyclization and reforming catalyst (Inventor: Ralph Dessau, Assignee: Mobil Oil Corporation) In many petroleum refineries, the net hydrogen produced in catalytic reforming supplies a significant part of the hydrogen used elsewhere in the refinery (for example, in hydrodesulfurization processes).
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These by-product gases may also contain hydrogen cyanide, hydrocarbons, sulfur dioxide or ammonia. Gases with an H2S content of over 25% are suitable for the recovery of sulfur in straight-through Claus plants while alternate configurations such as a split-flow set up or feed and air preheating can be used to process leaner feeds.Gas Processors Association Data Book, 10th Edition, Volume II, Section 22 Hydrogen sulfide produced, for example, in the hydro-desulfurization of refinery naphthas and other petroleum oils, is converted to sulfur in Claus plants. The reaction proceeds in two steps: :2 H2S +3 O2 → 2 SO2 \+ 2 H2O :4 H2S +2 SO2 → 3 S2 \+ 4 H2O The vast majority of the 64,000,000 tonnes of sulfur produced worldwide in 2005 was byproduct sulfur from refineries and other hydrocarbon processing plants.
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The refinery HDS feedstocks (naphtha, kerosene, diesel oil, and heavier oils) contain a wide range of organic sulfur compounds, including thiols, thiophenes, organic sulfides and disulfides, and many others. These organic sulfur compounds are products of the degradation of sulfur containing biological components, present during the natural formation of the fossil fuel, petroleum crude oil. When the HDS process is used to desulfurize a refinery naphtha, it is necessary to remove the total sulfur down to the parts per million range or lower in order to prevent poisoning the noble metal catalysts in the subsequent catalytic reforming of the naphthas. When the process is used for desulfurizing diesel oils, the latest environmental regulations in the United States and Europe, requiring what is referred to as ultra-low-sulfur diesel (ULSD), in turn requires that very deep hydrodesulfurization is needed.
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