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rocess used in oil refining catalytic reforming is a chemical process used to convert naphthas from crude oil into 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 1 the dehydrogenation also produces significant amounts of byproduct hydrogen gas which is fed into other refinery processes such as hydrocracking and hydrodesulfurization a side reaction is hydrogenolysis which produces light hydrocarbons of lower value such as methane ethane propane and butanes continuous catalytic reforming ccr unit in addition to a gasoline blending stock reformate is the main source of aromatic bulk chemicals such as benzene toluene xylene and ethylbenzene which have diverse uses most importantly as raw materials for conversion into plastics however the benzene content of reformate makes it carcinogenic which has led to governmental regulations effectively requiring further processing to reduce its benzene content catalytic reforming is quite different from and not to be confused with the catalytic steam reforming process used industrially to produce products such as hydrogen ammonia and methanol from natural gas naphtha or other petroleum derived feedstocks nor is this process to be confused with various other catalytic reforming processes that use methanol or biomass derived feedstocks to produce hydrogen for fuel cells or other uses history edit in the 1940s vladimir haensel 2 a research chemist working for universal oil products uop developed a catalytic reforming process using a catalyst containing platinum haensel s process was subsequently commercialized by uop in 1949 for producing a high octane gasoline from low octane naphthas and the uop process become known as the platforming process 3 the first platforming unit was built in 1949 at the refinery of the old dutch refining company in muskegon michigan in the years since then many other versions of the process have been developed by some of the major oil companies and other organizations today the large majority of gasoline produced worldwide is derived from the catalytic reforming process to name a few of the other catalytic reforming versions that were developed all of which utilized a platinum and or a rhenium catalyst rheniforming developed by chevron ccr platforming a platforming version designed for continuous catalyst regeneration developed by universal oil products uop powerforming developed by esso currently known as exxonmobil magnaforming developed by engelhard and atlantic richfield oil company ultraforming developed by standard oil of indiana now a part of bp houdriforming developed by the houdry process corporation octanizing a catalytic reforming version developed by axens a subsidiary of the french institute of petroleum ifp designed for continuous catalyst regeneration typical naphtha feedstocks edit a petroleum refinery includes many unit operations and unit processes the first unit operation in a refinery is the continuous distillation of the petroleum crude oil being refined the overhead liquid distillate is called naphtha and will become a major component of the refinery s gasoline petrol product after it is further processed through a catalytic hydrodesulfurizer to remove sulfur containing hydrocarbons and a catalytic reformer to reform its hydrocarbon molecules into more complex molecules with a higher octane rating value the naphtha is a mixture of very many different hydrocarbon compounds it has an initial boiling point of about 35 c 95 f and a final boiling point of about 200 c 392 f and it contains paraffin naphthene cyclic paraffins and aromatic hydrocarbons ranging from those containing 6 carbon atoms to those containing about 10 or 11 carbon atoms the naphtha from the crude oil distillation is often further distilled to produce a light naphtha containing most but not all of the hydrocarbons with 6 or fewer carbon atoms and a heavy naphtha containing most but not all of the hydrocarbons with more than 6 carbon atoms the heavy naphtha has an initial boiling point of about 140 to 150 c 284 to 302 f and a final boiling point of about 190 to 205 c 374 to 401 f the naphthas derived from the distillation of crude oils are referred to as straight run naphthas it is the straight run heavy naphtha that is usually processed in a catalytic reformer because the light naphtha has molecules with 6 or fewer carbon atoms which when reformed tend to crack into butane and lower molecular weight hydrocarbons which are not useful as high octane gasoline blending components also the molecules with 6 carbon atoms tend to form aromatics which is undesirable because governmental environmental regulations in a number of countries limit the amount of aromatics most particularly benzene that gasoline may contain 4 5 6 there are a great many petroleum crude oil sources worldwide and each crude oil has its own unique composition or assay also not all refineries process the same crude oils and each refinery produces its own straight run naphthas with their own unique initial and final boiling points in other words naphtha is a generic term rather than a specific term the table just below lists some fairly typical straight run heavy naphtha feedstocks available for catalytic reforming derived from various crude oils it can be seen that they differ significantly in their content of paraffins naphthenes and aromatics typical heavy naphtha feedstocks crude oil name displaystyle rightarrow location displaystyle rightarrow barrow island australia 7 mutineer exeter australia 8 cpc blend kazakhstan 9 draugen north sea 10 initial boiling point c 149 140 149 150 final boiling point c 204 190 204 180 paraffins liquid volume 46 62 57 38 naphthenes liquid volume 42 32 27 45 aromatics liquid volume 12 6 16 17 some refinery naphthas include olefinic hydrocarbons such as naphthas derived from the fluid catalytic cracking and coking processes used in many refineries some refineries may also desulfurize and catalytically reform those naphthas however for the most part catalytic reforming is mainly used on the straight run heavy naphthas such as those in the above table derived from the distillation of crude oils reactions edit many chemical reactions occur in the catalytic reforming process 1 all require the presence of a catalyst almost always platinum containing and a high partial pressure of hydrogen depending upon the type or version of catalytic reforming used as well as the desired reaction severity the reaction conditions range from temperatures of about 495 to 525 c 923 to 977 f and from pressures of about 5 to 45 standard atmospheres 510 to 4 560 kpa 11 the four major catalytic reforming reactions are 12 page needed the dehydrogenation of naphthenes to convert them into aromatics as exemplified in the conversion methylcyclohexane a naphthene to toluene an aromatic noice the isomerization of normal paraffins to isoparaffins as exemplified in the conversion of normal octane to 2 5 dimethylhexane an isoparaffin the dehydrogenation and aromatization of paraffins to aromatics commonly called dehydrocyclization as exemplified in the conversion of normal heptane to toluene the hydrocracking of paraffins into smaller molecules as exemplified by the cracking of normal heptane into isopentane and ethane during the reforming reactions the carbon number of the reactants remains unchanged except for hydrocracking reactions which break down the hydrocarbons the hydrocracking of paraffins is the only one of the above four major reforming reactions that consumes hydrogen the isomerization of normal paraffins does not consume or produce hydrogen 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 13 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 the hydrogen is also necessary in order to hydrogenolyze any polymers that form on the catalyst in practice the higher the content of naphthenes in the naphtha feedstock the better will be the quality of the reformate and the higher the production of hydrogen crude oils containing the best naphtha for reforming are typically from western africa or the north sea such as bonny light oil or norwegian troll process description edit the most commonly used type of catalytic reforming unit has three reactors each with a fixed bed of catalyst and all of the catalyst is regenerated in situ during routine catalyst regeneration shutdowns which occur approximately once each 6 to 24 months such a unit is referred to as a semi regenerative catalytic reformer srr some catalytic reforming units have an extra spare or swing reactor and each reactor can be individually isolated so that any one reactor can be undergoing in situ regeneration while the other reactors are in operation when that reactor is regenerated it replaces another reactor which in turn is isolated so that it can then be regenerated such units referred to as cyclic catalytic reformers are not very common cyclic catalytic reformers serve to extend the period between required shutdowns the latest and most modern type of catalytic reformers are called continuous catalyst regeneration ccr reformers such units are defined by continuous in situ regeneration of part of the catalyst in a special regenerator and by continuous addition of the regenerated catalyst to the operating reactors as of 2006 two ccr versions available uop s ccr platformer process 14 and axens octanizing process 15 the installation and use of ccr units is rapidly increasing many of the earliest catalytic reforming units in the 1950s and 1960s were non regenerative in that they did not perform in situ catalyst regeneration instead when needed the aged catalyst was replaced by fresh catalyst and the aged catalyst was shipped to catalyst manufacturers to be either regenerated or to recover the platinum content of the aged catalyst very few if any catalytic reformers currently in operation are non regenerative citation needed the process flow diagram below depicts a typical semi regenerative catalytic reforming unit schematic diagram of a typical semi regenerative catalytic reformer unit in a petroleum refinery the liquid feed at the bottom left in the diagram is pumped up to the reaction pressure 5 45 standard atmospheres 510 4 560 kpa and is joined by a stream of hydrogen rich recycle gas the resulting liquid gas mixture is preheated by flowing through a heat exchanger the preheated feed mixture is then totally vaporized and heated to the reaction temperature 495 520 c 923 968 f before the vaporized reactants enter the first reactor as the vaporized reactants flow through the fixed bed of catalyst in the reactor the major reaction is the dehydrogenation of naphthenes to aromatics as described earlier herein which is highly endothermic and results in a large temperature decrease between the inlet and outlet of the reactor to maintain the required reaction temperature and the rate of reaction the vaporized stream is reheated in the second fired heater before it flows through the second reactor the temperature again decreases across the second reactor and the vaporized stream must again be reheated in the third fired heater before it flows through the third reactor as the vaporized stream proceeds through the three reactors the reaction rates decrease and the reactors therefore become larger at the same time the amount of reheat required between the reactors becomes smaller usually three reactors are all that is required to provide the desired performance of the catalytic reforming unit some installations use three separate fired heaters as shown in the schematic diagram and some installations use a single fired heater with three separate heating coils the hot reaction products from the third reactor are partially cooled by flowing through the heat exchanger where the feed to the first reactor is preheated and then flow through a water cooled heat exchanger before flowing through the pressure controller pc into the gas separator most of the hydrogen rich gas from the gas separator vessel returns to the suction of the recycle hydrogen gas compressor and the net production of hydrogen rich gas from the reforming reactions is exported for use in the other refinery processes that consume hydrogen such as hydrodesulfurization units and or a hydrocracker unit the liquid from the gas separator vessel is routed into a fractionating column commonly called a stabilizer the overhead offgas product from the stabilizer contains the byproduct methane ethane propane and butane gases produced by the hydrocracking reactions as explained in the above discussion of the reaction chemistry of a catalytic reformer and it may also contain some small amount of hydrogen that offgas is routed to the refinery s central gas processing plant for removal and recovery of propane and butane the residual gas after such processing becomes part of the refinery s fuel gas system the bottoms product from the stabilizer is the high octane liquid reformate that will become a component of the refinery s product gasoline reformate can be blended directly in the gasoline pool but often it is separated in two or more streams a common refining scheme consists in fractionating the reformate in two streams light and heavy reformate the light reformate has lower octane and can be used as isomerization feedstock if this unit is available the heavy reformate is high in octane and low in benzene hence it is an excellent blending component for the gasoline pool benzene is often removed with a specific operation to reduce the content of benzene in the reformate as the finished gasoline has often an upper limit of benzene content in the ue this is 1 volume the benzene extracted can be marketed as feedstock for the chemical industry catalysts and mechanisms edit most catalytic reforming catalysts contain platinum with or without some rhenium on a silica or silica alumina support base fresh catalyst is chlorided chlorinated prior to use citation needed the noble metals platinum and rhenium are catalytic sites for the dehydrogenation reactions and the chlorinated alumina provides the acid sites needed for isomerization cyclization and hydrocracking reactions 12 page needed chlorination requires finesse l...
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