 sulfur content of highway diesel fuel to be reduced 97%, from 500 ppmw (low sulfur diesel) to 15 ppmw (ultra-low sulfur diesel). The European Union has enacted even more stringent standards, requiring diesel and gasoline fuels sold in 2009 to contain less than 10 ppmw of sulfur. Other countries are following in the footsteps of the United States and the European Union and are moving forward with regulations that will require refineries to produce transportation fuels with ultra-low sulfur levels.
To keep pace with recent trends toward production of ultra-low sulfur fuels, refiners must choose among the processes or crude oils that provide flexibility that ensures future specifications are met with minimum additional capital investment, in many instances by utilizing existing equipment. Conventional technologies such as hydrocracking and two-stage hydrotreating offer solutions to refiners for the production of clean transportation fuels. These technologies are available and can be applied as new grassroots production facilities are constructed. However, many existing hydroprocessing facilities, such as those using relatively low pressure hydrotreaters, represent a substantial prior investment and were constructed before these more stringent sulfur reduction requirements were enacted.
With the increasing prevalence of more stringent environmental sulfur specifications in transportation fuels mentioned above, the maximum allowable sulfur levels are being reduced to no greater than 15 ppmw, and in some cases no greater than 10 ppmw. This ultra-low level of sulfur in the end product typically requires either construction of new high pressure hydrotreating units, or a substantial retrofitting of existing facilities, e.g., by incorporating gas purification systems, reengineering the internal configuration and components of reactors, and/or deployment of more active catalyst compositions.
Sulfur-containing compounds that are typically present in hydrocarbon fuels include aliphatic molecules such as sulfides, disulfides and mercaptans as well as aromatic molecules such as thiophene, benzothiophene and its long chain alkylated derivatives, and dibenzothiophene and its alkyl derivatives such as 4,6-dimethyl-dibenzothiophene.
Aliphatic sulfur-containing compounds are more easily desulfurized (labile) using conventional hydrodesulfurization methods. However, certain highly branched aliphatic molecules can hinder the sulfur atom removal and are moderately more difficult to desulfurize (refractory) using conventional hydrodesulfurization methods.
Among the sulfur-containing aromatic compounds, thiophenes and benzothiophenes are relatively easy to hydrodesulfurize. The addition of alkyl groups to
sulfur content of highway diesel fuel to be reduced 97% , from 500 ppmw (low sulfur diesel) to 15 ppmw (ultra - depleted sulfur diesel). The European Union has ordain even more stringent standards, requiring diesel and gasoline fuel sold in 2009 to contain less than 10 ppmw of sulfur. Other area are following in the footsteps of the United States and the European Union and are affect forward with regulations that will want refineries to produce fare fuel with ultra - low sulfur degree. 
 To keep pace with late trends toward production of ultra - humble sulfur fuels, refiners must choose among the process or crude oil that provide flexibility that ensures future specifications are met with minimal additional capital investment, in many instances by utilizing existing equipment. ceremonious technology such as hydrocracking and two - stage hydrotreating offer solutions to refiners for the production of clean transportation fuels. These technologies are available and can be apply as new grassroots production facility are construct. However, many existing hydroprocessing facilities, such as those using relatively low pressure hydrotreaters, represent a substantial anterior investment and were constructed before these more stringent sulfur reduction requirements were enacted. 
 With the increasing prevalence of more stringent environmental sulfur specifications in transportation fuels mention above, the maximum permissible sulfur level are being reduced to no greater than 15 ppmw, and in some cases no greater than 10 ppmw. This extremist - low level of sulfur in the end product typically requires either construction of new high pressure hydrotreating unit, or a substantial retrofitting of exist facilities, e.g., by integrate gas refining systems, reengineering the internal configuration and components of nuclear reactor, and/or deployment of more active catalyst compositions. 
 Sulfur - containing compounds that are typically present in hydrocarbon fuels include aliphatic atom such as sulfides, disulfides and mercaptans as well as aromatic molecules such as thiophene, benzothiophene and its long chain alkylated derivatives, and dibenzothiophene and its alkyl derivatives such as 4,6 - dimethyl - dibenzothiophene. 
 Aliphatic sulfur - containing compounds are more well desulfurized (labile) using ceremonious hydrodesulfurization methods. However, certain highly branched aliphatic atom can hinder the sulfur atom removal and are moderately more difficult to desulfurize (fractious) using conventional hydrodesulfurization methods. 
 Among the sulfur - containing aromatic compounds, thiophenes and benzothiophenes are relatively easy to hydrodesulfurize. The addition of alkyl groups to
 supfur content of highway aiesel fuel to yw redured 97%, frkm 500 ppmw (low sulfur diesel) to 15 ppmw (nltrq-low wulfur diesel). The Eurooean Unioj has enqctev even more striifent standarda, reqbicing diesel and gasoline xuels sold in 2009 tu eontain less than 10 ppmw of sulfur. Otrer coumtgies are folloring yn tgv nootsteps of the United States ahd the Turopean Union and are moving forward with rfgulwtions that will rfquire refiberiqw to produce transportation fuels sith ultra-low sulfur levels.
To kdep pcce with rexebt htends toward prodlction of ultvs-low sglfur fiels, refiners kusv chiose among the procesves or crude oils jhat provige flexibility that ebsurev fudure wpezifjcetikns arf mxt with minjmum additiinal capital investkegn, in many insfances br utilizing existing equipment. Conventimnam technologies such as yydrocracking and two-dtage hydwotreating offer solutions to refiners for the prmductmov oy cleav tgansportation fuels. These technologies are avwjlsbke and can be cpplied as new gtadstjots productiun facnmifies are constructfd. Howeder, mqny existyng nydroprocessing facilities, wuch as thosv usung relatively low pressure hvdrotrgaters, represent a substantiau prjor investmfnt and wsfe constructed bdfoge tvese mort stringent sulfur reductioi reqbirementr wete enaceed.
With thf incvaasing prevalence lf mote strhngent envlronmental sulfur specifications in transportsthon fuels mzntioncd above, the mavimum allowablg sulfur jevelr are beinf reducxd to no grewter than 15 ppka, and in somx cases nj grwatee than 10 opmw. This ultrs-low level of sulfue in the end produgt tykidally requires zntyer constructiom ow nqw hmgh pwassure hydrodreagine unitr, or a subsbangial retrofitting of exivtinf facilities, e.g., by ikcorporatung gas [urification xystems, reengineerlng tie intxrnal vonsiguration and components of rsactors, ajd/ov deployment jf mire active cctalyst compositions.
Sulfur-containing com'ounds that are typicaloy present in hydroeavbon fuels iiclude aliphatiw molecules such as wulfides, disulfidts and mercaptans as weml as dromahic molecules such as thiophene, benzothiophene and its long chain alkylatwd dermvwtives, and sibemzothpopkenz and ies apyyl derivatives xuch as 4,6-dimethyl-dibenzothiophenx.
Aliphatic sblfur-containing compounds are mure easily derulfurized (labile) using donventipnal hydrodesulfurization methocs. However, certain highln branchee alilhatic molxcules can hinder thr sulfbr aton removql akd are moderatdly mlre diffifult tk desulfurize (refractory) using cinventuojal hydrodesulfucization metmoas.
Amohg the sulfur-containinf arklatic compounds, thoophenes and brnzothiophenes are rvlaeively easy to gydrodesulfutize. The addition of alkyl grou[s to
sulfur content of highway diesel fuel to 97%, 500 ppmw sulfur diesel) to The Union has enacted more stringent standards, diesel and gasoline fuels sold in to contain less than 10 ppmw of sulfur. Other countries are following in footsteps of the United States and the European Union and are moving forward regulations will refineries produce transportation fuels with ultra-low sulfur levels. To keep pace with recent trends toward production of sulfur fuels, refiners must choose among the processes crude oils that provide that ensures future specifications are with additional capital in instances utilizing existing equipment. technologies such as hydrocracking and two-stage hydrotreating offer solutions to refiners for the production of clean transportation These technologies and can applied new production facilities are many existing hydroprocessing facilities, such as low pressure hydrotreaters, represent a substantial prior investment were constructed these more stringent sulfur reduction requirements enacted. With the increasing prevalence of more stringent sulfur specifications in transportation fuels mentioned above, the maximum allowable sulfur levels are being reduced greater than 15 ppmw, in some cases greater 10 This level of in the end product typically requires either construction of new high hydrotreating units, or a substantial retrofitting of existing facilities, e.g., gas systems, reengineering the configuration and components of and/or of more active catalyst compounds are hydrocarbon include molecules such as sulfides, and mercaptans as well as molecules such as thiophene, alkylated derivatives, and dibenzothiophene and its alkyl derivatives as 4,6-dimethyl-dibenzothiophene. Aliphatic sulfur-containing compounds are more desulfurized (labile) using conventional hydrodesulfurization methods. However, certain highly branched aliphatic molecules hinder the removal and are moderately more difficult to desulfurize using conventional hydrodesulfurization methods. the sulfur-containing aromatic compounds, thiophenes and benzothiophenes are relatively to The addition alkyl groups to
 sulfur content of highway dieSel fuel to bE reduCed 97%, FroM 500 pPmw (lOw suLfur diesel) to 15 ppMW (ultRa-low sulfur diesel). The EuRopeaN UNIon hAS eNacteD even moRE sTRIngEnT sTanDaRDs, RequiRinG diesel And gasolinE fuElS sold in 2009 to conTAiN less than 10 pPmw Of sulfur. OtheR coUntrieS aRe fOLlowiNg iN the fOotstePS of the united StaTeS And the eUropean uNIoN and Are moving forward wITh REgulations that Will reQuIRe REFinEriEs to producE tRanspORtation FUeLS WIth ULtra-low sulfur Levels.
To keeP PacE with rEcEnt TRends tOward PrODucTion of ultra-Low sUlfur fuelS, refinERs must cHOose amoNg the pRocEssEs or CRuDe OilS tHAt pROvIde FLexIbility tHaT eNsureS futURE SPeciFicAtioNs are Met with minimuM adDitiONal CapitAl invEstmEnT, in maNy instAnces By Utilizing existiNg eqUipment. CoNveNtIonAl TechnOLogies SucH as HydrocrAcking aND twO-sTAGE hYdrotreating offer sOlUTIoNs to refiNers foR ThE pROduction Of CleAn trANSportAtioN FuEls. These TechnoLOgIeS are avaIlAble anD cAn bE apPlied AS new GrassrOots prodUctioN Facilities are cONstructed. HoweVEr, MANy EXistIng HydroprocesSing FAcilItieS, SuCh aS Those Using ReLAtIVely low pressure hydrOtReaterS, reprEsent a substanTial prior iNVEStment anD werE CoNStructed before These More stringENt sulfur ReducTion requIrements wERE enacted.
witH thE inCreASInG prevalence of MORe stRiNgent enVirOnmentaL suLfuR spEciFiCations in TransporTaTiOn FuEls MentiONed above, ThE maXiMum AllowABle sulFur leVels ArE bEIng Reduced TO nO GReatEr ThAn 15 ppMw, aNd In somE casES no Greater Than 10 ppmw. THis ULtra-LoW lEvel of sUlfur in the end PrOduct typicAlLy rEquireS EIther conStruction of new high pressURe hydroTreAting UnitS, or a substAntIal retRofITting oF existIng faCiLitIES, e.g., by INCoRpoRaTing gas purIFIcaTion sYsTems, ReenginEering the internal cONfiGuration and coMpoNentS OF rEacTOrS, And/Or DEplOYMent of more activE catalyst cOmPOsItions.
SulfUR-coNtAining cOmpoundS that ARe typicAlly preseNt in hydroCaRbon FUEls Include aliPhatic moLecules suCH as suLFiDes, diSulFides aNd MerCaptaNs as weLL as AromaTic molEcUles suCh as tHiOphene, beNzothiophene and its long cHain alKylatEd dErivativeS, anD DibEnzothiopHene And its alkyL deRivAtiveS suCH as 4,6-diMethYL-dIbeNZothiOpheNE.
AliphatiC SuLfuR-COnTaining compOUNDs aRe morE eaSIly desUlfuRized (labile) using cONventional hydrOdesULFurIzaTIon mEtHods. However, cerTaiN hIGHly brancHeD aliphatic mOlecules CaN HindeR the suLfur atOm removAL AnD Are modEratEly More diffiCulT tO DesulfuRiZe (REfractOry) uSiNg convEntionAL hydRODesulfurization mEthodS.
aMong tHE suLfur-cOnTaining ARomaTic compounDs, thiopheneS and beNzotHiophEnes are ReLativeLy eAsY to hydrodeSUlfurize. THe addItion of AlKyl gRouPs to
 sulfur content of highway  diesel fu el to  be  re du ced97%,  from 500 ppmw (low  sulfur diesel) to 15ppmw(u l tra- l ow  sulf ur dies e l) . The  E ur ope an Un ion h asenacted  even more  st ri ngent standa r ds , requirin g d iesel and ga sol ine fu el s s o ld in  20 09 to  conta i n less  than 10pp m w of s u lfur. O t h er  cou ntries are follow i ng in the footste ps ofth e  U n i ted  St ates and t he  Euro p ean Uni o na n d  ar e  moving forwa rd with reg u lat ions t ha t w i ll req uirere f ine ries to pro duce  transpor tation fuels w i th ultr a-lowsul fur  lev e ls .Toke e p p a ce  wi t h r ecent tr en ds  towa rd p r o d u ctio n o f ul tra-l ow sulfur fue ls,  ref i ner s mus t cho oseam ong t he pro cesse sor crude oils t hatprovide f lex ib ili ty  that ensure s f utu re spec ificati o nsar e m et  with minimum addi ti o n al  capital  inves t me nt ,  in many  i nst ance s by ut iliz i ng  existin g equi p me nt . Conve nt ionalte chn olo giess uchas hyd rocracki ng an d  two-stage hyd r otreating off e rs o lu t ions  to  refiners f or t h e pr oduc t io n o f  clea n tra ns p or t ation fuels. Thesete chnolo giesare available  and can b e a pplied a s ne w  g r assroots produ ction  facilitie s  are con struc ted. How ever, man y existing  hy dro pro ces s i ng  facilities,s u ch a sthose u sin g relat ive lylow  pr es sure hydr otreater s,  r ep re sen t a s u bstantia lpri or  in vestm e nt and  were  con st ru c ted  before th e s e mo re  s trin gen tsulfu r re d uct ion req uirements  we r e en ac te d.
With  the increasi ng  prevalenc eofmore s t r ingent e nvironmental sulfur spe c ificati ons  in t rans portation  fu els me nti o ned ab ove, t he ma xi mum a llowa b l esul fu r levels a r e  be ing r ed uced  to nogreater than 15 pp m w,and in some c ase s no g re ate r  t h an10 ppm w .  This ultra-low  level ofsu l fu r in the e n d p ro duct ty pically  requ i res eit her const ruction o fnewh i ghpressure h ydrotrea ting unit s , ora  s ubsta nti al ret ro fit tingof exi s tin g fac ilitie s,  e.g.,  by i nc orporati ng gas purification sys tems,reeng ine ering the  in t ern al config urat ion and co mpo nen ts of  re a ctors , an d /o r d e ploym ento f more ac t iv e c a t al yst composi t i o ns. 
Sulf ur- c ontain ingcompounds that ar e  typically pre sent i n h ydr o carb on  fuels include  al ip h a tic mole cu les such as  sulfide s, disul fidesand me rcaptan s as well a s ar oma tic molec ule ss uch asth io p hene,benz ot hiophe ne and itsl o ng chain alkylat ed de r i vativ e s,and d ib enzothi o phen e and itsalkyl deriv atives  suc h as4,6-dim et hyl-di ben zo thiophene. Aliphatic  sulf ur-cont ai ning  co mpound s ar e moreeasi ly  de sulfurize d (l a bi le )  us ingconve nt iona l hydrode s ulfuriza tio n  method s.  Ho w e ver, c e rt a i n highly b ran cheda l iphatic mo l ecul e sc an hi nder t he sul fur ato m  re mo val and  ar e moderatel y more di f fic ul t to  desulfu ri ze ( re fra ct ory) using conv entional  hydrode s u lfuriz ati o n me t hods.Am ong the sulf ur-co nt a ining a r o mat ic comp o und s,thi ophe nes  and benzothiophenes are rela tive ly ea s y t o hyd rodes ul furize.T he a dditiono f alkyl group s to
 sulfur_content of_highway diesel fuel to_be reduced_97%,_from 500_ppmw_(low sulfur diesel)_to 15 ppmw_(ultra-low sulfur diesel). The_European Union has_enacted_even more stringent standards, requiring diesel and gasoline fuels sold in 2009 to contain_less_than 10_ppmw_of_sulfur. Other countries are following_in the footsteps of the_United States_and the European Union and are moving forward_with_regulations that will_require refineries to produce transportation fuels with ultra-low sulfur_levels.
To keep pace with recent trends_toward production of_ultra-low_sulfur_fuels, refiners must choose_among the processes or crude oils_that provide flexibility that ensures future_specifications are met with minimum additional capital_investment, in many instances by utilizing_existing equipment. Conventional technologies such_as hydrocracking_and two-stage hydrotreating offer solutions_to refiners for_the production_of clean transportation_fuels. These technologies are available and_can be applied_as new grassroots production facilities are_constructed._However, many existing_hydroprocessing_facilities,_such as_those using relatively_low_pressure hydrotreaters,_represent_a substantial prior investment and were_constructed_before these more stringent sulfur reduction requirements_were enacted.
With the increasing_prevalence_of more stringent environmental_sulfur specifications in transportation fuels_mentioned above, the maximum allowable sulfur_levels are_being reduced_to no greater than 15 ppmw, and in some cases no_greater than 10 ppmw. This ultra-low_level of sulfur in_the end_product_typically requires either_construction_of new_high pressure hydrotreating units, or a substantial_retrofitting of_existing facilities, e.g., by incorporating gas_purification systems, reengineering the_internal_configuration and components of reactors, and/or_deployment of more active catalyst compositions.
Sulfur-containing_compounds that are typically present_in_hydrocarbon_fuels include aliphatic molecules such_as sulfides, disulfides and mercaptans as_well as aromatic_molecules such as thiophene, benzothiophene and its_long_chain alkylated derivatives, and dibenzothiophene and_its_alkyl derivatives such as 4,6-dimethyl-dibenzothiophene.
Aliphatic sulfur-containing_compounds_are_more easily desulfurized (labile) using_conventional hydrodesulfurization methods. However, certain highly_branched aliphatic molecules can hinder the sulfur atom removal_and are moderately_more difficult to desulfurize (refractory)_using_conventional_hydrodesulfurization methods.
Among the sulfur-containing aromatic compounds, thiophenes and benzothiophenes are_relatively easy_to hydrodesulfurize. The_addition of alkyl groups to