New Microsoft Word Document (7) - BACKGROUND OF THE...

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BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns a process for removing sulfur from naphtha, a petroleum product used to make fuels like gasoline. Specifically, deactivated hydrotreating catalyst is used to selectively hydrodesulfurize naphtha while minimizing olefinloss. 2. Description of Related Information It is well known that air pollution is a serious environmental problem. A major source of air pollution worldwide is the exhaust from hundreds of millions of motor vehicles due to fuel combustion. Laws and regulations have been enactedreflecting the need to reduce harmful motor vehicle emissions through more restrictive fuel standards. Fuels containing sulfur produce sulfur dioxide and other pollutants leading to a host of environmental concerns, such as smog and related healthissues, acid rain leading to deforestation, water pollution, as well as other environmental problems. To help reduce or eliminate these environmental problems, the sulfur content of fuels has been, and will continue to be, restricted to increasinglysmaller concentrations, such as less than 100 or even 50 parts per million (ppm). The problem of sulfur in fuels is compounded in many areas where there is diminishing or no domestic source of crude oil having relatively low sulfur content. For example, in the United States the supply of domestic oil production reliesincreasingly on lower grade crude oil with higher sulfur content. The need for lower sulfur content fuel therefore increases demand for imported oil having lower sulfur content increasing trade imbalance and vulnerability due to dependence on foreignsources of oil. The sulfur content in crude oil can take the form of a wide variety of both aliphatic and aromatic sulfurous hydrocarbons. Various techniques have been developed for removing sulfur compounds. One such technique, called hydrodesulfurization(HDS), involves catalytically reacting hydrogen with the sulfur compounds. The general HDS reaction is illustrated in Equation 1. In Equation 1, the sulfur compound, RSR', may be: a thiol or mercaptan, where R is hydrocarbyl and R' is hydrogen; a sulfide or disulfide, where the sulfur is connected to another sulfur atom in R or R' hydrocarbyl groups; or may be a thiophenewhere R and R' are connected to form a heterocyclic ring. The HDS reaction consumes hydrogen (H.sub.2) and produces hydrogen sulfide (H.sub.2 S) and hydrocarbons
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wherein the sulfur atom is replaced by two hydrogen atoms. The hydrogen sulfide can thenbe separated to give a petroleum product in which the sulfur is significantly reduced or substantially eliminated. HDS is one process within a class of processes called hydrotreating, or hydroprocessing, involving the introduction and reaction of hydrogen with various hydrocarbonaceous compounds. General hydrotreating reactions with oxygen compounds,nitrogen compounds and unsaturated hydrocarbons, including olefins, are illustrated in Equations 2, 3 and 4, respectively. The hydrotreating reactions can occur simultaneously to various degrees when sulfur-, oxygen-, nitrogen-
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New Microsoft Word Document (7) - BACKGROUND OF THE...

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