reforming xuc tac che bien dau

7/30/2019 Reforming Xuc Tac Che Bien Dau

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A . Phn m u.

Cng vi s pht trin ca cc ngnh cng nghip hng u th

ngnh cng nghip ho du cng pht trin mnh v c nhng vaitr quan trng trong cuc sng.

Trong cng nghip ha du mi qu trnh u c nhng nggp khng nh cho s pht trin ca ngnh xc tc hc khngngng tng ln khi ngy cng c nhng i hi cao v cht lngca sn phm, khi tin hnh phn ng. Xc tc rt cn thit cho

phn ng, xc tc lm cho cc phn ng c tin hnh mt cchnhanh chng, chnh xc nht, ng thi em li hiu qu cao chosn phm thu c do c tnh chn lc. c c nh vy nn xctc khng ngng ci tin em li hiu qu cao hn trong cngnghip lc ho du.

c bit trong cng nghip lc ho du xut hin qu trnhRefocrming xc tc, qu trnh ny cng em li nhng kt qucao thc y s pht trin cho ngnh cng nghip ch bindu. Trong cc loi nhin liu, xng l nhin liu quan trng nht,xng c tr s octan cao cho php ng c hot ng tt hnnhiu, do cc nh khoa hc tm kim nhng phng phptt nht sn xut xng c tr s octan cao ngay t nhng nm

u th k ny. Nm 1911 Zekisky v cc cng s ph t hin raphn ng chuyn ho cycloancan su cnh thnh aren trn xc tcplatin v paladi phn ng ny t c s khoa hc cho qutrnh Reforming xc tc. Trc i chin th gii do nhu cu v cc

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Do c vai tr quan trng trong cng nghip ch bin du nnqu trnh Reforming xc tc ngy cng c nghin cu v pdng rng ri trn th gii. Hin nay lng xng thu c t qa

trnh Reforming xc tc chim 25% ton b lng xng thu ctiu th trn th gii. Trong cng nghip ch bin ho duhin i, qu trnh ny cng c ngha ln lao khi to ra snphm c tr s octan cao m khng cn pha thm ch, trnh nhim mi trng.

Cho nn qu trnh Reforming xc tc trong ch bin du c

quy m rt ln, to nn nhng bc tin quan trng cho s phttrin cu ngnh cng nghip lc ho du ngy cng phc vnhiu hn cho i sng. Chnh v vy m n nhm giithiu v ton b qu trnh Reforming xc tc. C s ho hc,xc tc nguyn liu, sn phm, c ch, ng hc ca qatrnh, cc quy trnh cng ngh in hnh s dng trong

cng nghip. ng thi n ny nh gi ton b qu trnv vai tr ca n.

B. Tng quan l thuyt.

I. Mc ch ca qu trnh.

Theo lch s pht trin ca qu trnh Reforming xc tc thngay t nm u xut hin qu trnh em li hiu qurt cao trong lc ho du m c bit l hiu sut xng tngln ng thi cht lng ca xng c ci thin mt cch r rt.

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Mc ch chnh ca qu trnh Reforming xc tc l nngcao tr s octan ca xng do dn n nng cao hiusut s dng du m t trong cng nghip lc ho du, em

li vai tr quan trng trong i sng, v d: Khi tng tr soctan ca xng t 66 ln 88 th chi ph xng cho mt nmgim i 22%. ng thi qu trng Reforming xc tc l snxut hydro cacbon thm trong gm c Bezen, Toluen,Xylen ... lm nguyn liu cho cng nghip ho du v tnghp hu c.

Ngoi ra, qu trnh Reforming xc tc cn thu c kh hydrok thut vi gi r nht so vi cc qu trnh iu ch hydrokhc. Mt khc y chnh l ngun thu H 2 cn c ng dngtrong nhiu qu trnh lm sch sn phm du m v chbin du.

Qua ta thy rng, cc mc ch ca qu trnh Reforming

xc tc c vai tr rt quan trng trong cc nh my ch bindu m.

II. C s ho hc.

Reforming xc tc l mt qu trnh chuyn ho ho hc phctp s dng nguyn liu l xng chng ct trc tip v gny nh s pht trin ca cc qu trnh lm sch bng hydro

m ta c th s dng xng ca cc qu trnh lc du khc( xng ca qu trnh cc ho, xng caracking nhit ... ). Qutrng ny c tin hnh trn xc tc hai chc nng, thngcha Pt c mang trn oxyt nhm. Trong qu trnh Reforming

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cc parafin mch thng v cc cyclo parafin b chuyn hothnh cc hp cht thm v isoparafin lm tng tr s octanca xng.

Mc ch ca qu trnh sn xut xng c tr s octan cao( RON trong khong t 95 102 ) m khng phi pha thm ch.ng thi, do sn phm ch yu trong qu trng l hydrocacbon thm nn qu trnh cn c ng dng thu BTX( kh nguyn liu l phn on naphta nh c nhit si

t 310 340 0F ) l nhng nguyn liu qu cho tng hp hu

ho du.

Do cc phn ng xy ra trong qu trnh Reforming xc tcl nhng phn ng isome ho, hydro ho, dehydro ho ngvng, dehydro ho v cc phn ng ph khc.

1. Phn ng dehydro ho .

y l phn ng nhm to ra hydro cacbon thm, ng thiphn ng dehydro ha cn thu nhit mnh v phn ng xy ra

vi Naphten chim t 18 50% trong nguyn liu. Phn ngdehydro ho cyclohexan v dn xut ca n c tc kh lnkhi ta dng xc tc c cha Pt Hp cht ch yu ca Naphtenl cyclopetan v cyclohexan ( trong cyclopetan nhiu hncyclohexan ) Cyclohexan b dehydro ho trc tip to thnhhp cht thm.

CH3CH3

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+ 3H 2 (1).

Sau phn ng RON tng v tr s octan ca cyclohexan l 75

cn tr s octan ca Toluen

l >100. Cn cyclopetan khi b tc phn ng dehydro hoxy ra nhanh m cn bng ca phn ng isome ho c iukin chuyn ho thnh cyclopetan l 95% cn cyclohexanch l 5%. Do phn ng dehydro ho naphten c tc ln m trong qu trnh Reforming s nhn c nhiu RH thm

v hydro.

2. Phn ng dehydro ho ng vng .

Phn ng ny xy ra vi cc parafin, xy ra kh hn so vi phnng ca naphten. Ch c nhit cao mi c th nhn chiu xut RH thm ng k Dehydro ho parafin to rahydrocacbon thm. Khi tng chiu di ca cc mch cacbontrong parafin, hng s cn bng to RH thm cng c tngln.

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CH3

n C8H18

+4H 2 (2). CH3

Sau phn ng tr s octan nghin cu tng t 0 ( tr s octanca n-octan ) ln >100 ( tr s octan ca xylen ).

Phn ng to vng nm cnh cng xy ra, nhng sau snphm li tip tc bin i thnh vng thm.

C2H5

n C7H16

+ H 2 (3).

Nhng phn ng xy ra chm, c xc tc bi c thnh phnkim loi v thnh phn c tnh axit ca xc tc. Phn ng thunhit ny thng xy ra t thit b gia cho n thit b cuicng ca qu trnh. ng thi dehydro ho ng vng parafin to RH thm l mt trong nhng phn ng quan trngnht ca Reforming xc tc, nh phn ng ny m cho php

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bin i mt lng ln cc hp cht c tr s octan thp canguyn li thnh cc RH thm l cu t cao octan.

3. Phn ng isome ho.

y l phn ng nhm bin i isome ho n-parafin isoparafin. Trong c t 15 75% parafin mch thng c trs octan nghin cu < 50. Parafin mch thng c th b isomeho to thnh mch nhnh.

CH3

n C5H12CH2CH2CHCH3 (4).

Vi cc n-parafin nh, s isome ho lm ci thin tr s octanphn ng chuyn ho n-pentan thnh iso-pentan, lm tng tr

s octan t 62 ln 92. Phn ng isome ho parafin xy ra khnhanh v c xc tc ch yu bng chc nng axit ca xc tc.

Ngoi ra trong phn ng olefin cng c th b isome ho nhngthng l hydro isome ho do s c mt ca hydro trong mitrng phn ng.

Hepten-1 + H 2CH3CH2CH2CH2CHCH3 (5).

CH3

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Phn ng isome ho naphten cng c tin hnh nhanh chngbi c thnh phn axit v kim loi ( mc nh hn ) ca xctc.

Phn ng ny sp xp li phn t m khng kt hp hoctch hydro do n khng b nh hng bi p sut.

4. Phn ng Hydro ho .

Phn ng hydro ho xy ra vi olefin trong nguyn liu tothnh parafin. Phn ng c thc hin d dng trong iukin ca qu trnh Reforming, thnh phn olefin cng c thchuyn ho trc tip thnh Aromatic.

Phn ng ny nhm chuyn ho cc hydro cacbon cha nothnh no, lm gim s to cc gy nn s kh hot tnh caxc tc.

5. Phn ng Hydro cracking .

y l phn ng cracking vi s c mt ca hydro. Phn ngny b mch parafin to thnh mt parafin khc v mt olefin.Di s c mt ca hydro phn ng b bo ho ngay lp tc.

n - C9H20 + H 2 n C5H12 + n C4H10 (6).

n-parafin b chia nh thnh n-parafin khc c mch ngn hn

do phn ng khng lm tng c tr s octan. Khngnhng th, phn ng cn lm mt mt xng do s b gy ccparafin c s cacbon di 8 thnh cc sn phm kh. Do vy,

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hiu sut xng s gim, phn ng xy ra kh chm v ch yuc xc tc bi chc nng axit ca xc tc.

Naphten cng c th tham gia phn ng hydro cracking. Giai

on u tin ca phn ng ny l t vng vi s c mtca hyro to thnh parafin.

C2H5

+ H 2CH3(CH2)5CH3 (7).

6. Nhng phn ng ph trong qu trnh Reforming xctc.

Phn ng ca cc hydro cacbon thm c thay th xy ra nhsau:

CH3CH3

+ 2

(8).CH3

Hydricacbon thm cng c th b hydroalkyl ho.

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CH3 CH3

C2H5

+ H 2+ C 2H6 (9).

Cc phn ng ph ca hp cht thm khng mong mun l

phn ng to cc, to ra nhng hp cht a vng ngng t trntm hot tnh ca xc tc.

Cc hp cht d vng cha N v S b hydrosulfua ho vhydronit ho to ra H 2S hoc NH3.

+ 4H 2 C5H12 + H2S(10).

S CH3

y l nhng phn ng lm gim hm lnglu hunh trongxng, do n l phn ng ph c li.

*. Phn ng to cc.

S to cc trong qu trnh l khng mong mun, nhng do stng tc ca olefin v diolefin, cc hp cht thm a vng mto thnh cc. Cc s kh to ra nu ta thao tc iu kin

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nhit thp, p sut cao v t l H 2/RH cao. y l mtphn ng phc tp.

S to thnh cc ph thuc vo nhiu yu t:

- Nhit phn ng.

- p sut hydro.

- nng ca nguyn liu v chnh l cc hp cht phi hydrocacbon, olefin v cc cht thm a vng l cc hp cht gp phn thc y nhanh qu trnh to cc. hn ch s to

cc, ngi ta phi s dng p sut hydro va sao cho ccch to ra khong 3 4% so vi lng xc tc trong khong thigian 6 thng n 1nm. Nhng nu tng p sut hydro s lmcn tr qu trnh to thnh RH thm, cn tr phn ng.

*. Trong iu kin tin hnh qu trnh Reforming cn xy racc phn ng ph, tuy khng lm nh hng nhiu n cn

bng ca cc phn ng chnh nhng li c nh hng ln n hot ng, bn ca xc tc.

+ Phn ng phn hu v kh cc hp cht cha oxy, nit, luhunh to thnh H 2S, NH3, H2O.

+ Phn ng ngng t ca cc hp cht trung gian khng bn nholefin, diolefin vi RH thm dn n to thnh cc cht nha

v cc bm trn b mt xc tc.

III. Xc tc cho qu trnh.

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Xc tc cho qu trnh c s dng l loi xc tc a chc,chc nng oxy hokh v chc axit baz. Chc nng oxy hokh c tc dng xc tin cho cc phn ng hydro hokh

hydro. Cn chc nng axit c tc dng thc y cc phn ngxy ra theo c ch ioncacboni nh ng phn ho v hydrocracking.

Bng 1: Nhng thnh phn ca xc tc

Cht mang xctc.

Thnh phndehydro ho.

% Thnh phnkhc.

%

oxit nhm. Molipden. 10 15oxit nhm. Platin. 0,3 0,

6oxit nhm. Crm. 10 15 Halogen. 0 1oxit nhm. Molipdat

coban.oxitslic-oxitnhm.

Platin. < 10.

u tin vo nm 1940 ngi ta p dng qu trnh Reformingu tin vi cht xc tc l

axit molipden c mang trn oxit nhm. Xc tc tt phi c

chuyn ho chn lc tt c hydro cacbon thnh hp cht thmmt cch nhanh chng ch vi mt lng nh xc tc. Xc tcPlatin c chn lc cao nht v hot tnh ln nht nhng githnh t. Thnh phn akylcyclohexan chuyn ho nuiu kin phn ng thch hp v ng hc thnh phn

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akylcyclopen tan chuyn ho thnh hp cht thm phi quagiai on isome ho nn chuyn ho ca thnh phn nyph thuc vo hot tnh ca xc tc cho phn ng isome ho

cao nht cn xc tc crm thp nht, xc tc ny c chnlc tt v n nh cao. Xc tc cho phn ng Reformingc 2 chc nng: Chc nng hydro ho - dehydro ho cho phnng chuyn ho parafin thnh olefin, cc hp cht vng nothnh cc hp cht thm c xc tc bi kim loi v chc nngisome ho, c xc tc nh tnh axit ca cht mang theo c

ch ion cacboni. Nhng xc tc nh tnh axit ca cht mangtheo c ch ion cacboni. Nhng xc tc nh oxit crm v oxitmolipden trn cht mang l oxit nhm th hin c 2 chc nngny trn b mt kim loi cn xc tc Pt trn cht mang axitth th hin hai chc nng nhng hn hp kim loi. C hottnh vi phn ng hydro ho v dehydro ha cn oxit nhm c hot ho c tnh axit ( bng mui flo hoc clo ) chot tnh vi phn ng isome ho v hydro cracking. Nhngxc tc a kim loi lm gim p sut ca qu trnh.

S kh hot tnh xc tc do to thnh cc lin quan n ccht mang v kim loi. Cc to ra do nhng phn ng ph cahydrocacbon c bit l olefin. S kh hot tnh xc tcnhanh nu p sut ring phn ca hydro thp v nhit cao. Xc tc b kh hot tnh d ti snh bng cch tchy t cc.

Trc y ngi ta s dng cc cht xc tc oxit trong qu trnhReforming nh MnO/Al 2O3. Loi xc tc ny r tin, bn vi lu

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hunh, song n c nhc im l c hot tnh thp, nn trongqu trnh Reforming phi c th hin ch cng ( vntc th tch thp ~0,5h -1, nhit cao ~340 0C ), iu

kin ny cc phn ng hydro cracking xy ra mnh. tng chon lc ca qu trnh cn phi thc hin p sut

14 20 atm. Nhng s gim p sut li thc y qu trnh tocc, do vy khng ko di c thi gian lm vic ca xc tc,lm gim cht lng xng thu c. Do c tt c nhng l do trndn n khng s dng loi xc tc ny.

Bng 2: Kt lun v hot tnh vi phn ng dehydro ho camt vi xc tc kim loi v oxit kim loi.

Xc tc, % khi lng. Hot tnh cho phn ng

dehydro ha mol, C 6H6 xctc.

34% Cr 2O3 ng to gen vi

Al2O30,5

10% MoO3 ng kt ta viAl2O3

3

5% Ni trn Al 2O3 hoc SiO2 -Al2O3

13

1%Co trn Al 2O3 135% Ni trn SiO 2 2001% Ph trn Al 2O3 3200,5 Pht trin trn Al 2O3 hocSiO2 - Al2O3

1400-4000.

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Xc tc Pt/ Al 2O3

Vo nm 1949, hng UOP (Universal Oil Co, M ) s dngxc tc Pht trin v Al 2O3 lm thnh phn chnh to

thnh mt dng xc tc c hot tnh v chn lc cao(90 95% ).

Xc tc ny c s dng, cho n nm 1970. Hm lng Pht

trin trong xc tc l 0,3 0,8% trng lng, nhit phn ng

l 500 0C v p sut l 30 35 at. Trong Pht trin xc tincho qu trnh oxi ho kh cn Al 2O3 l axit rn, ng thiPht trin mang chc nng xc tc cho phn ng hydro ho vkh hydro. in hnh l trong Reforming chng lm tng tc phn ng kh H 2 ca naphten, kh hydro ng vng ccparrrafin, c ngha l ng vai tr thc y qu trnh hydrocacbon thm. Ngoi ra n cn thc y qu trnh hydro halin tc cc sn phm trung gian ( hydro ho cc hp chtkhng no to ra trong qu trnh ) cho nn hn ch c qutrnh to cc, ko di tui th v tng cht lng sn phm.

Kim loi Platin ( Pt ).

Pt c a vo xc tc dng khc nhau, ph bin l dngdung dch ca axit platin cydodric H 2 ( PtCl6 ). Pt l cu ttuyt vi cho xc tc Reforming, ng thi n c kh nnghot tnh rt tt cho phn ng dehydro-hydro ho. Trong qatrnh Reforming, Pt lm tc ca ph ng kh hydro, cchydro cacbon naphten, kh hydro vng ho cc hydro cacbonparafin to thnh RH thm. Ngoi ra n cn thc y qu

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trnh no ha cc hp cht trung gian l olephin, diolephin, lmgim tc to thnh cc bm trn xc tc m l nguynnhn chnh lm gim hot tnh ca xc tc. Hm lng Pt trn

xc tc chim khong 0.3 0,7% khi lng. Cht lng tt camt cht xc tc Reforming c cc tnh cht : hot tnh, chn lc cao v n nh cao. Nu hm lng Pt ln hn0,6% th xc tc d b thiu kt.

Pt thng c phn tn trn cht mang di dng nhng tinh th

nh c ng knh t 8 100 0A. Khi nguyn liu cha hm lng

parafin cao v dng xc tc cha 0,35% Pt th xng thu c ctr s octan cao ln ti 102 ( RON ) m khng cn pha nc ch.Khi c pha thm 0,8ml nc ch nhng vn mun t tr sRON=102 th xc tc phi c 0,8%Pt.

Khi a thm cc nguyn t t him vo s c tc dng kmhm s thiu kt ca cc vi tinh th Pt v xc tc c n

nh, bn nhit cao hn hn xc tc ch c Pt nguyncht.

Cht mang oxit nhm.

Al2O3 trong xc tc l cu t mang chc nng axit ca cht xctc. Tnh axit ca oxit nhm l do trn b mt c cha nhmOH. Al2O3 xc tc cho phn ng isome ho d xy ra nh phnng thay i v tr ni i trong Buten. N kh xc tc chonhng phn ng isome ho xy ra, kh v axit ca nyu.Do phi tng axit ca oxit nhm trong xc tcbng cch hot ho n.

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tng axit, ngi ta thm vo halogen hu c ( cchp cht cha Clo hu c ) ( C 2H4Cl2 ) v do ngoi tcdng tng axit n cn tc dng lm n nh phn tn Pt

nh n to ra cc phc hp Pt Al 2O3, ngoi ra cc cht xc tc tthc y cc phn ng cracking trong iu kin phn ng:

Hm lng cho thm vo 0.5 1% trng lng.

axit ca n c vai tr c bit quan trng khi ch binnguyn liu vi hm lng Pt ln: Cc tm axit kch ng phnng hydro cracking ca cc parafin v phn ng ng phn

ho hydro cacbon napten 5 cnh thnh 6 cnh v tip theo l cc napten 6 cnh b kh hydro to thnh hydro cacbonthm. Cht mang Al 2O3 cn phi c tinh khit trong hm lng Fe v Na khng qa 0,02% trnglng.

Al2O3 c s dng lm cht mang ch yu 2 dng tinh theta v gama. Dng eta c tnh axit v din tch b mt ban

u cao hn gama nhng sau khi ti sinh hoc s dng mtthi gian th b mt gim i v ch dng c vi ln tisinh. Cn dng gama bn nhit hn m vn duy tr c dintch b mt ban u sau khi ti sinh v s dng, n c ths dng sau vi trm ln ti sinh v ti sinh yu ca n ckhc phc bng cch a hologen vo, theo phng php phn

tch o c th din tch b mt cu xc tc l175 300m 2/g. Th tch l xp l 0,45 0.50 cm 3/g ht xc tc

c dng phi hoc cu c ng knh t 1/12 1/16in.

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Do vy cht lng tt ca mt cht xc tc Refoming phi cnhng tnh cht: chn lc, hot tnh v n nh cao.

Bng 3: Mt s c trng v tnh cht ca xc tc Reforming.

Cc chs.

Xt ( LinX c )ATT-0,65.

8815 TOR

RY- 302France.

RD-150M- c.

R-16 M.

% Pt ( %trng l-

ng).

0,6 o,65

o,35 0,58 0,37 0,55

ngknh ht(m/in).

1,8 - 2,2 1,5 1,5 3,0

V mtring

(m2

/g).

180 - 240 280

- 160 200

Ch s bn(kg/mm)

0,97 - 1,2 - -

ngknh l(A0)

- - 40 120 40 120 80 100

Thtch l(ml/g)

- - - - 0,75 0,88

Cht Cl F Cl Cl Cl

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kchng.

Trong thc t, cc ch tiu c bn c dng nh gi chtlng ca xc tc. Hiu sut xng n nh, tr s octan caxng, hiu sut RH thm, hiu sut v thnh phn ca snphm kh v thi gian lm vic ca xc tc.

Bt u t nhng nm 1960, ngi ta thit k cc dychuyn Reforming vi p sut H 2 thp nht c th xy ra

nhiu RH thm hn, nng cao tr s octan m cn tng hiusut xng, iu ny rt ngn thi gian ti sinh xc tc.ng thi vi nghin cu thay i ch cng ngh ngi tacn thc y vic nghin cu tm kim xc tc mi, honthin hn, c bn cao hn. l xc tc a kim loi.

Ngoi Pt, hin nay cn s dng cc xc tc khc nh nguyn t

I2, Re, Mioxen ( xc tc nhiu kim loi) v mt s cht kchhot nh Mo, Sn, Co, kim loi kim v kim th hoc nhiukim loi lm tng hot tnh xc tc v lm cho Pt phn bu khng b thiu kt Sn (thic) khng lm tng hot tnhxc tc nhng cng khng lm gim m li gim gi thnh xctc. Trong xc tc cn c b sung thm cc nguyn t thuc

phn nhm Na v Ca nhm hn ch tm hydro genoliseparafin v ngng t cc hp cht khng no to nha, cc nguynt khc lm cht kch ng nh C, Xi, Ge nhm khng ch axit ca cht mang. Nng Pt v cc cht kch ng thng

c khong 1 3%.

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Trong nhng nm 90 ca th k ny, hng UOP xy dngdy chuyn vi lp xc tc chuyn ng UOP lm vic vi psut thp, ch khon 3,5at (50psi). Khi p sut thp th

chn lc ca xc tc tng cao, nht l khi ch bin nguynliu c hm lng RH parafin ln. Khi lm tng vai tr ca

phn ng dehydro vng ho parafin: 50 60%RH thm nhn c t chuyn ho parafin. Do tr s octan ca snphm c th t c RON >100.

Ngoi ra, hng Philips nghin cu phn ng dehydro ho trn

xc tc Pt vi s c mt ca Sn trn Zn Al 2O3 hoc Ca Al2O4 vihm lng cc hnh thnh trn b mt xc tc rt t. Thnh

xc tc bao gm 0,05 5%Pt, 0,1 0,5%Sn, 80 98% Zn Al2O4,

hoc l Ca Al2O4. Nhit tin hnh l 500 570 0C.

Bng 4: Cc giai on ci tin ti Lin Bang Nga.

Cc giai on ci tin -thay i v thnhphn xc tc.

1 2 3

Cht mang. Al 2O3 Al2O3 Al2O3Kim loi chnh. Pt Pt PtCht kch ng.axit F Cl Cl

Kim loi khc. Re,Ge,Pb,Sn.

Tn xc tc. ATT. 56 ATT. 64 KP. 102-104.

Ch cng ngh.

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p sut trong h thngMpa.

3,5 4 3 3,5 1,2 2

Cc xc tc KP. 102,104 c bn c cao hn so vi xc tcATT 64 ti ba ln trong khi hm lng ca Pt li nh hn 1 1,5ln. Ngoi ra cng c nhng cng trnh nghin cu s dng

phc ( PtCl 2 C[nCl3]2) mang trn cht mang Al 2O3 trong phn

ng dehydro ho parafin. Hm lng Pt chim khong 0,3 0,8%

trng lng, nhit phn ng l 500 0C, p sut 30 35at.

ng thi hin nay c nhiu s ci tin xc tc nh bin tnhchng cho thm mt kim loi na hoc thay i cht mang( axit rn ) cht mang ( axit rn ) xc tin cho phn ngng phn ho, cracking nh: Pht trin/ FO 2, Pt/ Al2O3, Pt/FO2-Al2O3Pt-O2. axit rn. Pt-Re, cn cc axit rn l cc axit , Al 2O3,FO2, alumino silicat, zeolit. Vic cho thm kim loi ny nhmmc ch tng hot tnh ca xc tc v gim gi thnh.

1. Chun b xc tc.

Xc tc kim loi c th c ch to bng phng php ngmtm hoc trao i ion trn cht mang c b mt ring lnnh oxit nhm hoc oxit silic.

Trong phng php ngm tm, cht mang c tm dung dchmui kim loi. Sau ht xc tc c lm kh v c nungnng khng kh chuyn mui kim loi thnh oxit kim loi,oxit ny b kh bng nc kh ion ra mui v ion kim loicn li trn b mt, ri xc tc c mang v kh .

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cht tiophen v H 2S hay S nguyn t. Do m bo thigian lm vic lu di cho xc tc th hp cht S cn c loib khi nguyn liu trc khi a vo l phn ng.

T thc t Reforming, nu hm lng lu hunh qu ln s lmgim hiu sut v cht lng ca xng, ng thi nng luhunh cao cng lm tng tc phn ng kh hot tnh caxc tc, c bit l p sut hydro thp khi i hi phitng H 2/RH. Nu c mt H 2S trong kh tun hon s lm tngkh nng n mn thit b b phn ng xon ca l t

nng. Khi xc tc tip xc vi nguyn liu cha lu hunh,khng ch kim loi trn xc tc b ng c m ngay c Al 2O3cng b bin i n c tc dng vi hp cht lu hunh tothnh sunfat nhm Al 2(SO4)3. Do vy lm cho qu trnh ti sinhxc tc phc tp hn v i hi mc ti sinh su hn.Ngay c khi ti sinh chuyn Al 2(SO4)3 v Al2O3 nhng hot

tnh ca xc tc vn gim xung ng k so vi khi nguynliu khng cha lu hunh.

b. S ng c ca hp cht nit.

Cc hp cht nit c trong nguyn liu cng nh hng xun hot tnh ca xc tc khi tip xc vi cc cht cha nitnh NH3, hot tnh ca xc tc gim nhanh, c bit l

chnh chc axit. V NH 3 mang tnh baz v lm trung hocc tm axit ca xc tc, do n s lm gim tc ccphn ng ng phn ho, vng ho v hydro cracking. Hm l-

ng cho php ca Nit trong nguyn liu ch l 1ppm, nn a

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s cc qu trnh Reforming u p dng qu trnh hyroho lm sch nguyn liu.

c. nh hng ca nc.

Hm lng ca nc nh hng ti xc tc rt r rng. N khngch lm gim nhanh hot tnh ca chc axit ca xc tc mcn lm tng qu trnh n mn thit b, trong hm lng n-

c c khng ch trong gii hn 10 15ppm. Bin php tchnc l phi s l trc bng qu trnh lm kh khi dng hoc lphun kh clorua vo khi nguyn liu cha nc.

Chng hn nh qu trnh UHa forming, vi nguyn liu cha15ppm nc, ngi ta phun clorua vo xc tc ti sinh trongmt thi gian cn thit khi phc li hot tnh ban uca xc tc. Trong mt s trng hp khc, ngi ta s dng1,5ppm hp cht ciclo propylen phun vo khi hm lng nctrong nguyn liu ti 50ppm. Ngi ta thy rng xc tc trncht mang SiO 2 - Al2O3 ( v d catforming ) l loi rt nhy vinc, th bin php trn rt hu hiu.

d. nh hng ca kim loi.

Cc kim loi nh asen, ch ... c mt trong nguyn liu l cccht lm ng c xc tc. S c mt ca ch trong nguynliu c th do nhiu nguyn nhn khc nhau, nhng thng donguyn liu, do vn chuyn hoc lu kho. Cc hp cht chtch ng dn trn xc tc gy nn s kh hot tnh xc tcbng cch lm mt chc nng hydro ho v dehydro ho caxc tc. Biu hin ca ng c ch c th quan st d dng

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v c s gim nhit thit b phn ng u tin. Mc d c th loi b s kh hot tnh thm na nhng hot tnh mt khng khi phc li c na. Do s thay th xc tc

nhng lp u tin thng l do ng c ch nn hm lng chophp thng nh hn 0,02ppm v ca asen thm ch cn nhhn 0,001ppm m trong asen cn gy c hn c ch.

e. nh hng ca hm lng olephin v cc.

Cc hp cht olephin thc y nhanh qu trnh to cc, hm l- ng ca n trong nguyn liu cn phi nh hn 2%. Cc lng

li trn xc tc v lm gim kh nng to sn phm mongmun ca xc tc, nguyn nhn ca s gim hot tnh ny ldo s khc nhau v cu trc ca sn phm cc, thay i vphn b khi lng ca cc trn kim loi v cht mang khi thayi iu kin to cc ph thuc vo cht lng nguyn liu,iu kin hot ng ca qu trnh nh p sut, vn tc, th

tch.Phn ng to cc l nhng phn ng vng ho v polime hoc xc tc bi axit ca olephin to thnh hp cht a phn ckhi lng phn t cao hn. Nhng hp cht ny li tip tcphn ng dehydro ho v polime ho su hn, cc phn ngny xy ra nhanh chng nu p sut ring phn hydro thp.

gim lng cc to thnh trn b mt kim loi ngi ta tmcch loi b cc tm axit mnh trnh phn ng ngng t( bng cch thm Sn, Re ) hoc loi b cc sn phm giu

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cacbon bng cch hydro ho. S kh hot tnh xc tc cng cth do Pt b thiu kt nhit cao lm gim phn tn.

Thay i cc tnh cht cc xc tc khi lm vic.

Trong qu trnh lm vic xc tc cn b thay i cc tnhcht vt l khi tip xc vi nhit cao v thng xuyn phitip xc vi cc c t trn. S thay i ny ca xc tcReforming c phn thnh cc loi nh sau:

- Nhng thay i c tnh cht tm thi, ngha l khi phcli cc tnh cht ban u ca n bng qu trnh ti sinhxc tc. l cc thay i do s to cc hay ng c thunnghch bi cc hp cht ca oxy, nit. lu hunh.

- Nhng thay i vnh vin, l nhng thay i khngc kh nng ti sinh. V d do s thiu kt nhit caom b mt ring ca xc tc v cu trc Al 2O3 cng nh phn tn ca kim loi Pt gim i. S thay i ny cn dxy ra hn nu xc tc l n kim loi hay khi ti sinh xctc nhit khng c khng ch cht ch. Do nhngthay i ny s lm gi ho nhanh xc tc, v n mtthi gian no th phn xc tc gi ho ny phi cthay th bng xc tc mi c hot tnh cao hn nhmgi cho hot tnh chung ca xc tc khng thay ingha l hiu sut v cht lng ca xng c n nhtrong qu trnh.

3. Ti sinh xc tc.

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Ti sinh xc tc l qu trnh phc hi hot tnh ban u caxc tc bng cch loi b cc lng ng trn xc tc. Trongqu trnh ti sinh xc tc cc phng php c th la chn c

thc hin khc phc nhng nh hng ca s ng cxctc tm thi nu thit b ngng lm vic trc khi nh hngca s kh hot tnh c loi b. chnh l mc ch ti sinhxc tc. hot tnh v hot ng ca xc tc sau thigian lm vic thng b gim ng k so vi xc tc mi.

Hm lng Pt trong xc tc mi v xc tc lm vic ging

nhau nhng phn tn khc nhau v nht l hm lng Clothay i ng k. xc tc lm vic hm lng Clo gimrt nhiu.

Hnh 5: nh hng ca thi gian lm vic ti hiu sut v chtlng sn phm ca qu trnh Reforming xc tc.

Bng thc nghim vi cc phn ng mu chun cho thy hot

tnh dehydro ca xc tc lm vic gim 1,5 ln so vi xctc mi, cn kh nng ng phn ho gim rt nhiu. S gimhot tnh dehydro c gii thch bng s bin i trng thica Pt trong xc tc ( do tnh ng, ng t cc tinh th Pt t

10 15A0 tng ln 200A 0 v ln hn na v gim s tm hotng. Mc d hm lng Pt trn xc tc mi v xc tc lm

vic nh nhau.Do khi phc tnh cht ca xc tc, xc tc lm vicphi c ti sinh, m mi mt qu trnh Reforming yu cumt iu kin ti sinh ring.

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Trong cng nghip ngi ta p dng nhng bin php ti sinhsau:

a. Dng phng php oxy ho.

Phng php ny nhm t chy cc bm trn xc tc bng oxy

ca khng kh nhit 300 500 0C. Qu trnh ny nhiugiai on, cc giai on c th hin nh sau: Sau khingng cp liu, mt lung kh tun hon c thi vo xc tc loi b nhng hydro cacbon nng cn li trong thit b,thit b gia nhit, thit b phn ng, h thng tun hon khc tch ra khi nhng thit b khc. Cc qu trnh u aoxy vo thit b u tin v ln lt n thit b phn ngcui cng, nhng mt s qu trnh a oxy vo thit b u vcui cng mt lc tit kim thi gian v mt lng ln cctrong thit b cui cng phi mt nhiu thi gian loi b.

Tuy nhin lng oxy a vo thit b cui cng cn c kim tra.

Trong qu trnh bn ti sinh oxy ly t khng kh hoc oxyho lng: Nh ti sinh p sut 100psi vi khng kh l phngphp ph bin nht. Bng cch s dng oxy nguyn chttrong mi trng nit, thit b ti sinh c th ti sinh xc tc p sut cao hn.

b. B sung hp cht Clo.

Trong qu trnh lm vic hm lng Clo trn cht mang gimdn. khc phc ngi ta b sung cc hp cht hu c chaClo vo sau khi ti sinh oxy ho - kh ( sau khi t cc). Qutrnh ti sinh bng Clo khng nhng tc dng lm hot

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tnh axit tng ln m cn tc dng tch cho cc hp cht kimloi lng ng trn xc tc. Hm lng st, ch v bitmut gimr rng. Phng php ny thch hp cho xc tc b gim

axit, ng thi hm lng Clo trn xc tc c khng ch saocho mc 1% khi lng, l nng ti u cho chc axit caxc tc. Pt/` Al 2O3.

c. Dng phng php kh.

Phng php ny thch hp vi nhng xc tc b lu hunh vnit lm ng c. Sau khi t cc, xc tc c kh bng H 2 hon nguyn cc tm kim loi v gii phng cc hp cht l-u hunh tch ng trn xc tc. Qu trnh ny thng c tin

hnh p sut cao ( p 200 atm v nng H 2 > 10% ).

Ngoi ra cn c phng php ti sinh ngoi thit b lnhng xc tc b lng ng cc c a ra khi thit b vc a n mt thit b ti sinh xc tc ring, thit b nycacbon b loi b nh qu trnh oxy ho. Xc tc c ti sinhsau c a li thit b. Phng php ny c u im l ckh nng iu khin nhit tt hn so vi trng hp ti sinhngay ti thit b.

4. Tui th xc tc.

chn lc ca hu ht ca cc xc tc gim theo thi gian sdng. Xc tc mt hot tnh dehydro ho to thnh cc hocdo nhng thay i vt l trong cc thnh phn v cu trcca xc tc. S gim hot tnh hydro ho mnh hn s gimhot tnh hydro cracking do khi nhit c thay i b

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EA = 20kal/mol.

n C7 C1 C6 EA = 45kcal/mol.

n C7 iso C7 EA= 25kcal/mol.

Cc EA = 30kcal/mol.

S c ch phn ng N Hecxan ( C 6H14 ).

......................................

Trong nguyn liu cha nhiu H 2-C vng no th xng thu cc tr s octan cng cao.

Cc hydro cacbon c phn t lng ln d b hydro crackinghn cc hydro cacbon c phn t lng nh. Cc phn ng nycng c tc dng tch cc lm tng hiu sut xng v tr soctan ca xng ( do isoparafin ) cn khi iu kin cng, cchydro cacbon c phn t lng nh cng b hydro cracking, lcny cho hiu sut kh v cc tng ln v vy nhng phn ng

li c tc dng tiu cc. ng thi axit ca xc tc c nh h-ng ln n phn ng hydro cracking. axit cng ln thphn ng hydro cracking cng xy ra mnh ( chnh l ti

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sao ngi ta khng dng aluminosilicat ) l cht mang m dngAl2O3. V Al2O3 c axit nh hn.

Ngoi ra trong qu trnh cn c cc phn ng ph, cc phn

ng ny va mang li hiu qu, va lm c hi. C li l ccphn ng hydro ho cc hp cht cha O, N, S, d dng xy ra

trn cc xc tc c hot tnh hydro ho nhit 300 500 0C

v 14 17atm to thnh cc hp cht H 2S, NH3, H2O v tch cchng ra khi sn phm.

RSH + H2 RH + H2S

Nu hm lng S cha trong nguyn liu t 0,1 0,5% bng cchdng phn ng trn. Cn li l cc phn ng ngng t, trng hpcc hydro khng no v thm, hydro cracking to nhiu kh vcc.

Parafin Olephin Piliolephin.

- H2 T/H. Trong nhit cng cao lng olephin to ra cng nhiudn n phn ng trng hp cng tng, cn nu tng p sutth c th hn ch phn ng ngng t v to cc, tuy nhinnu p sut H 2 qu ln, phn ng hydro cracking li xy ra

mnh v cn bng phn ng xiclohecxan bezen s chuyn

dch v bn tri, tc l gim bt hm lng hydro cacbon thm.V nhng l do trn, phi la chn iu kin, ch Reforming cho thch hp hn ch sn phm thu c hi.

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Ngoi ra trong c ch ca qu trnh Reforming xc tc thc ch phn ng c a ra vi xc tc ph bin nht caqu trnh. Xc tc Pt/ Al 2O3. Lng Pt c s dng sao cho hot

tnh dehydro ho ln hn isome ho olephin l hp cht trunggian ca phn ng, nhng trong iu kin Reforming c mt dng vt. C naphten v parafin u b dehydro ho thnholephin trn tm dehydro ho cu xc tc. Cyclohecxen tiptc b hydro ho nhanh chng thnh cromatic, ankylcyclopenten b isome ho thnh cyclohexen trn tm cc hot

tnh axit. Cyclohexen li tip tc phn ng ca n trn tmdehydro ho to thnh nhng cu trc alkyl hoc b vngho thnh naphten.

Khi p sut thp n-heptan d chuyn thnh aromatic hn dng iso ca n, t l ca nhng phn ng cao ( n- heptanchim u th ) ln hn chuyn ho thp. Parafin c s

nguyn t cacbon ln hn 7 b chuyn ho thnh hp chtthm d dng hn heptan. iu ny cho thy hp cht trunggian naphten khng c to thnh t parafin trn xc tc Ptbng cch ni hai u nguyn t cacbon li. Xc tc Pt to ranhng dn xut ca cyclopentan bng cch ni nguyn tcacbon th hai hoc th su li, alkyl cyclopentan c tothnh nh vy b isome ho thnh alkyl cyclohexan.

i vi phn ng hydro ho v dehydro ha, c ch n ginnht l c ch ca Bonhoeffer-farkas da trn c s s hpth ho hc ca cc cht phn ng. Theo c ch ny, mtphn t hydro b hp th trn 2 tm hot tnh kim loi lm

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phn ly lin kt H-H. Trong phn ng hydro ho nguyn thydro trn b mt nh vo olephin b hp th theo 2 giaion, giai on to thnh hp cht trung gian b hp th, th-

ng l cc gc alkyl. Phn ng hydro ho thng l bc 1 vi psut ring phn ca hydro, l bc 0 hoc m vi p sut ringphn ca olephin. Cc phn ng to hp cht thm to ra chyu trn thnh phn kim loi ca xc tc hai chc nng. Phnng dehydro ho metyl cyclohexan l bc 0 i vi metylcyclohexan v hydro nhit nh hn 372 0C. Trong nhng

iu kin giai on gii hn vn tc l giai on gii hptoluen trn b mt. C ch phn ng dehydro ho cyclohexanqua giai on hp th cyclohexan ng thi phn ly hocsau khi hp th phn ly nhanh chng 6 nguyn t hydro.Phn ng to thnh lin kt ca hp cht thm thng qua tng

tc vi orbital ca kim loi. Cc bc phn ng nh sau:

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Mt lng nh ca dien pha kh v cyclohexan c mt trongsn phm chng t phn ng dehydro ho xy ra theo tng bcv mt lng nh sn phm trung gian b gii hp. Cyclopentankhng b dehydro ho to ra cc dien tr khi tin hnh nhit cao nhng n b hydro cracking d dng to ra pentan. iu

ny ch rng cc dien kh c to thnh do vn hnh hctrn b mt xc tc, cc alkyl cyclopentan v alkyl cyclohexanc nhng v tr b chn ( gem-dialkyl, spiran ) khng bdehydro ho, nhit m cyclohexan c th phn ng d

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S gii hp vng 5 hoc 6 cnh c th xy ra- vng c thhp ph li trn b mt hoc thay i nhng nguyn t Cthc t lin kt vi b mt m khng cn gii hp lin kt C-C

gia 2 nguyn t b hp ph c th b v.- Nguyn t H c nh tr li phn t b hp th sau

gii hp th ta c 1 isoparafin.

Ti cn bng. Phn ng isome ho trn cht mang oxit nhmc thc hin theo c ch ion cacboni. S isome ho alkankh hn nhiu alken, xc tc axit mnh v nhit cao c

nh hng n phn ng ny. Alkan kh kt hp vi proton canhm oxit xc tc nhng nhng vt ca alken th c th kthp vi proton d dng to ra ion cacboni lm tng tc qutrnh isome ho parafin. S vn chuyn hydro ni b phn tnh cc ion cacboni nh sau:

..............

Do vy, cc parafin mch thng u tin b hydro ho tothnh olephin, olephin ny b isome ho trn tm axit ca xctc to thnh iso-olephin li b hydro ho to thnh isoparafin.C ch ny cho php ng dng nhng xc tc c axitkm mnh hn v c th iu khin c, khng xc tin chonhng phn ng khng mong mun ( phn ng

hydrocracking ) v phn ng to cc, so vi nhng tm axitmnh ca xc tc cracking. S isome ho olephin xy ra nhanhchng trn tm axit ca xc tc.

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Olephin c th b vng ho trn nhng tm axit. C ch nyvn cha c nghin cu nhng s vng ho ca olephin khngxy ra theo c ch ion cacboni trn axit nhm hot ho v

s to ra cacboni vng khng thy xut hin trong iu kinReforming. Do c th phn ng ny lin quan n s kthp proton v lin kt li nh tm axit.

Vy phn ng c th xy ra trn 2 nhm axit baz cnh nhautrn b mt xc tc.

..........................................

Phn ng m vng trn xc tc axit ca metyl cyclopentan xyra bng cch kt hp trc tip proton vo mch vng to ioncacboni khng vng.

,,,,,,,,,,,,,,,,,,,,,,,

C ch tng t c th gii thch cho phn ng vi dien to

thnh metyl cyclopentan: V d 1,5 hexadien to ra metylcyclopentan, metyl cyclopentan v bezen trong metylcyclopenten chim u th. Phn ng xy ra do s alkyl ho niphn t khi trung tm cation ang pht trin xa lin kti to thnh vng 5 hoc 6 cnh.

Phn ng hydrocracking xy ra trn tm axit ca xc tc tun

theo c ch ion cacboni nh phn ng hydro cracking tngnhanh ca cht phn ng tng do d dng b gy mch ccparafin. Hydrocarcking b gy mnh c parafin mch thng vmch nhnh.

S phn ng Reforming ca nhng hydro cacbon 6C.

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,,,,,,,,,,,,,,,,,,,,,,,,,,,

Qua s , nhng phn ng song song vi honh xy ratrn tm axit ca xc tc v nhng phn ng song song vi

tung xy ra trn nhng tm kim loi cht phn ng, n-hexan c dehydro ho u tin trn kim loi to ra hexanmch thng. Hexen ny ti tm axit bn cnh, n v nhhp isohexen v i ti trung tm kim loi, y n c th bhp th v b hydro to thnh isohexen. ng thi ion cacbonith cp cng c th phn ng to thnh metyl

cyclopentan. Cht ny tip tc phn ng to thnhcyclohexen v sau thnh bezen.

V. Nguyn liu v sn phm.

1. Nguyn liu.

Ngi ta thng dng phn on xng cht lng thp c khong

si t 62 1800

C lm nguyn liu cho qu trnh Reforming. Trong thc t cng nghip ch bin du, nhn cc cu t

cao octan cho xng, ngi ta dng phn on si t 85 180 0C

hay 105 180 0C. Phn on xng c im si nh hn 60 0Cl khng thch hp v n khng cha cyclo ankan v ankan ckh nng chuyn ho thnh aren, m ch cha cc hydrocacbon c s cacbon nh hn 6, ch c kh nng chuyn hothnh cc hydro cacbon kh. Nhng nu im si cao hn180 0C, nhiu cc lng ng trn xc tc lm gim thi giansng ca xc tc trong iu kin phn ng.

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0 0Xng Reforming.

Trng lng ring, d 204

thnh phnhydro cacbon %

0,78

5

0,78

9

0,79

6

0,79

8

0,7

95

0,8

04

Cha no. 1,2 0,9 0,8 0,9 0,7 0,5Aren 6,45 64,7 65,5 65,4 67,

568,5

No 34,5 34,4 33,7 33,7 31,

8

31,

0Hiu sut %Xng n nh 75,0 76,5 77,7 76,0 81,

088,3

Hydro 1,2 1,2 1,3 1,3 1,6 2,2

Hm lng tp cht c trong nguyn liu cng phi c khngch trc khi thc hin qu trnh trnh ng c xc tc. nh gi cht lng nguyn liu Reforming xc tc thng quathnh phn ho hc ca nguyn liu, hng UOP a ra mt schun tng quan K UOP c xc nh theo biu thc sau:

K UOP = 12,6 ( N + 2Ar )/100.

Trong :

N: l hm lng % ca naphten.

Ar: l hm lng % ca RH thm.

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Trong nguyn liu Reforming xc tc, K UOP v c bit ltng s N + 2Ar thay i trong khong rng ( tng N + 2Ar

c th t 30 80). Nu K UOP = 10 th nguyn liu cha nhiu

RH thm hn, nu K UOP = 11 th nguyn liu cha nhiunaphten v RH thm mt vng. Cn nu K UOP = 12 l nguynliu cha mt hn hp bng nhau gia RH vng v RH parafinv nu K UOP = 13 th nguyn liu ch yu l RH parafinic. Dovy, nu K UOP thp hay tng N+2Ar c trong nguyn liucng cao th nguyn liu cng cha nhiu naphten v nguyn

liu cng thun li nhn xng Reforming c tr soctan cao. Ngoi ra, thnh phn phn on cng nh hng lnn cc ch tiu ca qu trnh Reforming xc tc.

Cc hp cht phihydro cacbon, c bit l cc hp cht ca luhunh v nit trong nguyn liu phi gim ti cc tiu v nhhn gii hn cho php. V cc hp cht ny ch lm tng tc

cc phn ng ngng t to cc, to nha, u c xc tcv lm gim nhanh hot tnh ca xc tc. Do nguyn liutrc khi a vo Reforming xc tc u c qu cng on xl bng hydro ha lm sch loi b cc hp cht phihydrocacbon, cc hp cht olephin, diolephin v c kim loi do nhimbn vo nguyn liu Reforming trong qu trnh ch bin. Cchp cht phihydro cacbon s c loi ra dng hi nh: NH 3 , H2Sv H2O nh qu trnh hydro ho lm sch. Tu thuc vo ch cng ngh v nht l xc tc m qu trnh hydro ho lmsch s t c cc ch tiu v cht lng cho nguyn liuReforming xc tc.

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Bng 7: Cht lng xng Platforming.

Cc thng s Hm lng parafin trong nguynliu %65% < 40%

Trng lng ring 20 0C(g/cm 2)

0,785 0,738 0,796 0,722

Thnh phn ct phnon ( 0C )Nhit si u 49 42 58 58

Nhit si 10% 82 76 96 110Nhit si 50% 135 138 140 140Nhit si 90% 172 171 170 168Nhit si cui 202 215 198 205

Thnh phn ho hc ( %, TL )Hydro cacbon khng no 2,2 0,9 1,0 0,5

Hydro cacbon thm 59,0 65,4 62,0 685Paraphin + Naphten 38,8 33,7 37,0 31,0

Tr s octan, MON 80 85 80 85 Tr s octan, RON 89 95 89 95

Xylen: Thu c sau qu trnh l hn hp cc ng phn ca

Xylen. Hiu sut Xylen hn hp sau khi tch Bezen v Aren nhtrch ly trong dung mi chn lc cao ( 799% ). Xylen cng cs dng pha trn vi xng ( c th dng ngay hn hp BTX )hoc dung mi. Ngoi ra cn thu c sn phm kh hydro

Trong kh ny cha 70 90% th tch hydro.

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VI Cc yu t nh hng n qu trnh.

C nhiu loi Reforming khc nhau nhng vn c nhng yu tchung nh hng n qu trnh l:

1. Loi c tnh xc tc:

Xc tc phi c la chn sao cho ph hp vi tng qu trnh hiu sut, hot tnh v bn ca n i vi qu trnhphi l ti u. Do vy, ta c th thay i thnh phn ca xctc nh hm lng Clo, hm lng Platin ...Cn i vi xc tc haikim loi th loi v lng kim loi th hai l nhn t chnh trongvic la chn xc tc. Hot tnh xc tc c th thay i bngcch thay i loi xc tc hoc cn bng Clo - nc trong xctc. chn lc ca xc tc l kh nng xc tc to ra snphm mong mun ti iu kin cho. chn lc cng thayi theo loi xc tc v cn bng Clo nc trong xc tc.

bn ca xc tc c xc nh bi nhit v p sut qutrnh, s tin s l nguyn liu loi b lu hunh, nit voxy. Xc tc Pt trong oxit nhm hot ho c bn tt nhngxc tc Pt trong oxit nhm oxit silic li kh hot tnh rtnhanh v n c hot tnh axt mnh v xc tc cho phn nghydro cracking rt nhanh.

Trong nhng nm gn y, t ng bn ca xc tc ng-i ta s dng xc tc Pt- Re hoc xc tc nhiu kim loi.

Xc tc Pt-Re. Al 2O3 c u im l c bn cao vi s khhot tnh xc tc bi cc, cho php lm vic kh lu p suthot ng kh thp. Do s bin i axt ca cht mang di

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tnh

th trungbnh

A0

% dehydroho vng

vng %

isome ho%

hydrocracking

10

12

33

73

158

44452

Pt trncht mangt do

3,0

3,5

4,6

7,0

9,8

23,4

74

37,4

32,8

26,8

21,6

17,7

12,4

0,4

9,0

10,6

14,2

21,7

24,3

28,9

0,1

50,6

53,1

54,4

49,7

48,2

35,3

25,5

Vn tc phn ng dehydro ho ph thuc vo din tch bmt ca Pt. Hm lng Pt trnh by hnh sau:

............................................................................................

2. nh hng ca p sut.

Cc qu trnh Reforming u km theo qu trnh tng th

tch nh kh H 2 ca naphten, vng ho. p sut ca qu trnhl nhn t chnh nh hng n hiu sut v s quay vngxc tc, p sut t 400 n 500psi thch hp thi gianquay vng xc tc di.

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Do s gim p sut, cn bng phn ng dehydro ho chuynv pha lm tng hiu sut sn phm thm v hydro, sgim p sut lm gim kh nng hydro cracking. Vic tng

phn ng dehydro ho v gim phn ng hydro cracking lmtng hiu sut C 5 v sn phm Reforming do s gim psut lm tng t l cc. p sut thp th s kh hot tnh xyra nhanh n mc thi gian sng ca xc tc l 1 nm. Ccthit b bn ti sinh khng thun li cho hot ng p sutthp cho n khi a vo xc tc hai v nhiu kim loi lm

gim mc to cc. Trong nhng h thng nhiu thit bhoc thm tr trong cng mt thit b gim p sut cth thay i theo s thay i t l cp liu v t l khtun hon.

p sut cn c quyt nh bi hot tnh v chn lc xctc.

V d: Trc y s dng xc tc Mo/ Al 2O3 , P=15 20 at. Cnby gi dng xc tc pht trin / Al 2O3 duy tr P =20 40 attrong h thng m hot tnh to cht thm vn m bo. psut trong h thng nh hng n hiu sut to hydro cngnh hng ng k n qu trnh. Khi khng c hydro thkhng xy ra phn ng v b mt kim loi b che ph bi

cc, khi tng p sut hydro, b mt kim loi c lm sch mtphn v c phn ng dehdyro v dehydro ng vng uxy ra.

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p sut ring phn hydro cng nh hng n phn ng isomeho v dehydro isome ho. Nu trong iu kin lm vickhc ca qu trnh l khng i, khi tng p sut th vn tc

cc phn ng hydro cracking v kh ankyl s tng ln, trong tr-ng hp ny cn bng s dch chuyn v pha to parafin.Khi gim P trong h thng, dn n gim P ring phn ca H 2

lm tng mc thm ho cc parafin v naphten.

3. Vn tc th tch.

Vn tc th tch l i lng o lng naphta phn ng trn mtlng xc tc cho trc trong thi gian cho trc. Khi vn tc cpliu ca naphta c tnh theo th tch trn gi v lng xctc c tnh theo th tch th gi l vn tc th tch( CHSV ) khi lng cht phn ng v xc tc tnh theo khi lngth gi vn tc th tnh theo khi lng ( WHSV ). Vn tc thtch nh hng n cht lng sn phm ( tr s octan ). Vn

tc th tch cng ln, tr s octan cng cao, nh hng canhit thit b c th thay th vn tc th tch v cngxc nh cht lng sm phm. Vn tc th tch c nh hngnh n hiu sut sn phm v bn xc tc.

Gi tr ca CHSV trong khong t 1 3h. Tr nhng gi trthp ca vn tc th tch (


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Tu theo mc ch ca qu trnh Reforming m chn nguynliu cho thch hp. nhn xng c tr s octan cao th phi

chn nguyn liu c nhit si 85 180 0C. Nu nhit si

thp hn 85 0C ( Nguyn liu nh ) th khi b hydro crackings to thnh nhiu kh, l sn phm khng mong munca qu trnh. Cn nu chn xng c nhit si t

180 220 0C th s tng cng phn ng trng hp to cc bmtrn xc tc, lm gim hiu qu ca xc tc.

Ngoi ra thnh phn hydro trong nguyn liu cng nh hng

rt ln, nu tng hm lng naphten v thm cng nhiu thhiu sut xng cng cao.

................................................

Hnh 5: nh hng thnh phn hydro cacbon ca nguyn liun hiu sut xng.

nhn hydro cacbon thm BTX lm nguyn liu cho tnghp ho du th ta chn xng nguyn liu c t 0 si hp:

sn xut Bezen: Nguyn liu c t 0 si 62 85 0C

sn xut Toluen: Nguyn liu c t 0 si 85 120 0C

sn xut Xylen: Nguyn liu c t 0 si 120 140 0C

Nhng thnh phn khc c mt trong nguyn liu nh hm l- ng Clo... cng nh hng n qu trnh, c bit l nhot tnh v bn xc tc. nh hng ca hm lng nc trongdng hydro tun hon n hot tnh v bn xc tc ctrnh by trong hnh.

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...............................

7. Hiu ng nhit ca qu trnh.

Cc phn ng ch yu ca qu trnh Reforming xc tc lphn ng kh hydro cc hydrocacbon Naphten 6 cnh thnhhydrocacbon thm v kh hydro vng ho cc hydrocacbonParafin thnh hydrocacbon thm. Cc phn ng ny u kmtheo s thu nhit. Ngoi ra cn c phn ng hydrocracking,phn ng ny km theo s to nhit v cn c mt s phnng ph xy ra yu v hiu ng nhit c th b qua. V vy

hiu ng nhit ca qu trnh c xc nh bi su cacc phn ng kh hydro, kh hydro vng ho v hydrocracking.

Qu trnh chuyn ho nguyn liu giai on u ch yuxy ra cc phn ng kh hydro, kh hydro vng ho nn hiung nhit ca giai on ny quyt nh ch yu su

ca 2 dng phn ng trn.

Nhng do cc phn ng kh hydro cc Naphten xy ra nhanhhn nhiu so vi phn ng hydro vng ho cc hydrocacbonParafin v vy gi tr hiu ng nhit y ph thuc chyu vo hm lng cc hydrocacbon Naphten trong nguyn liu.

Qu trnh chuyn ho nguyn liu giai on cui, khi ccphn ng thm ho hu nh cn bng th vai tr ca phnng hydrocracking quyt nh hiu ng nhit ca giai onny. Ngi ta thy rng tt nhit gim i r rt ccthit b phn ng trong cc h thng Reforming xc tc.

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Trong tnh ton k thut, hiu ng nhit ca qu trnh thngc tnh cho 1kg nguyn liu. Ni chung hiu ng nhit caqu trnh Reforming xc tc trong mi trng hp u c gi

tr m ln. Ngi ta thy rng gi tr hiu ng nhit s dngnguyn liu khc nhau th khc nhau. V d khi s dngnguyn liu c hm lng Naphten cao hn s khc khi s dngnguyn liu xng Parafin cao. Gi tr trung bnh ca hiu ngnhit i vi nguyn liu xng Parafin th nm trong gii hn

t - 50 - 70 kcal/kg. Cn i vi nguyn liu xng nhiu

Naphten th nm trong gii hn -100 -140kcal/kg. Ta thyrng khi ch bin xng nguyn liu cc phn on hp vimc ch nhn hydrocacbon thm BTX th gi tr hiu ngnhit cn cao hn, c bit l nguyn liu cha nhiuNaphten.

8. nh hng ca lu lng nguyn liu.

Khi tng lu lng nguyn liu hay gim lng cht xc tc trongcc thit b phn ng n s lm gim thi gian tip xc cacc cht tham gia phn ng cht trung gian vi cht xc tc vlm tng hiu sut xng n nh, tng hm lng hydro trongkh tun hon, gim hiu sut hydro cacbon thm v tr soctan gim.

ng thi khi tng tc th tch ( hay tng lu lng ) ca phnng hydro ca naphten. hydro cracking cc parafin nng,ng phn ho butan v pentan s chim u th v xy ranhanh hn cn cc phn ng i hi thi gian ln nh kh

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hydro vng ho parafin kh ankyl, v hydro cracking cc hydrocacbon nh xy ra yu hn. T thy rng vi mc chca qu trnh Reforming xc tc s nhn BTX, qu trnh phi

c tin hnh trong iu kin thi gian lu lng nguyn liutrong vng phn ng t, ng thi c ngha l tc thtch khi s dng nguyn liu v naphten ln, nhit si s

dng trung bnh v p sut thp t 10 20 at.

9. c tnh ca thit b.

Cc thit b phn ng c phn loi thnh 2 loi chy xungv chy xuyn tm. Trong thit b xuyn tm i vo nhv chy xung qua lp xc tc, sn phm i ra t y .

...........................................................................

Trong thit b xuyn tm, nguyn liu i vo t nh v snphm i ra t y nhng nguyn liu chy ngang qua 1 lp xctc vng n dng nguyn liu r nhnh i vo xc tc.

Thit b bn t i sinh thng l mt dy gm 3 n 4 thit b.Kch thc ca thit b u tin thng nh hn so vi thit bcui cng. Nhng phn ng thu nhit rt nhanh, xy ra thitb u tin c th lm gim nhit thit b n mc mnhng phn ng tip theo b ngng li, lp xc tc nm diim c nhit ny hot ng khng c hiu qu. Do vynn s dng thit b c kch thc nh, ng thi nhng phnng xy ra thit b cui cng tng i chm, do kch th-c thit b phi ln. S phn chia kch thc thit b c a ratrong bng 10.

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tc to cc t cng ngh c s ln ti sinh xc tc tngln. V d hng ESSO p dng qu trnh Reforming xc tcvi p sut bng 6 Kg/cm 2 trong Reator vi lp xctc c nh

nhng c b sung thm 1 l phn ng ph. Thay i mi nhtl t nm 1971 hng UOP a ra cng ngh xc tc chuynng vi qu trnh ti sinh xc tc lin tc ( CCR ) cng ngh

ny cho php gim p sut t 20 Kg/cm 2 xung cn 10 12Kg/cm2 v khi c xc tc th h mi cng ngh ny cho php

gim p sut xung cn 3 3,5 Kg/cm 2 ( Hng UOP v FIN ).

ng nhin xc tc th h mi c gi thnh cao hn ( ngaycht mang cng t hn: 35F/kg so vi 2F/kg ca xc tc FCC). Nhng n c p dng v ch tiu kinh t: Tng tr s octan,tng hiu sut xng v lng kh H 2.

S ci tin theo hai hng: Ci tin xc tc v ci tin cngngh.

Bng 11: Trnh t ci tin xc tc v cng ngh

1940

Reforming xc tc u tin s dng xc tc Molipden.

1940

Pht trin xc tc Pt.

Thp nin 1950 rt nhiu qu trnh Reforming xc tcc pht trin t xc tc Pt.

1960

Pht trin xc tc a kim loi ( ngoi Pt cn c cc kimloi khc )

197 Qu trnh Reforming t i sinh xc tc lin tc ra i.

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kh nng ti sinh lin tc xc tc b cc ho, qa trnh CCRcho php dng p sut thp v thao t c lin tc, hng nm chaphi thay xc tc mi. Cng nh gim p sut m hiu sut RH

thm v H 2 tng ln ng k.Ngy nay, qu trnh CCR vi p sut siu thp v c th lmvic p sut 3,5 at. Hu nh tt c cc qu trnh Reformingxc tc mi c xy dng u l qu trnh CCR.

Bng 12: Cc hng i u trong qu trnh ci tin Reformingxc tc.

Tn qutrnh

Hngthitk

Loi reator Loi xc tc Loi l tisinh

Policyastormer

UOP Xc tc cnh

R.11-R12

Pt =

0,375 0,75

Ti sinh ginon

Powerformerr

Xc tc cnh

KX, RO, Bo

( Pht trin,Re )

Ti sinh ginon

TFPReforming

TFP Xc tc cnh

RG400

Pt=0,2 0,6

Ti sinh ginon

MAONAformer

England

Xc tc cnh

RD 150,

(Pt=0,6)E500

Ti sinh ginon

Reniormer CRC Xc tc c F(Pt,Re) Ti sinh gin

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2. Nhm th hai bao gm cc qu trnh vi thi gian lm vicca xc tc ngn v ti sinh xc tc tin hnh tng thitb phn ng m khng ngng h thng. Vic thit k nh

vy i hi cn phi c thit b phn ng d tr trong hthng. Tuy phc tp v c cu ng dn v b phn iukhin nhng li c th duy tr h thng lm vic p sutv nhit cao.

3. Nhm th ba l cc qu trnh vi lp xc t c chuyn ng.Vic ti sinh xc tc c tin hnh cc thit b ti sinh

ring.1. S cng ngh ca qa trnh Plat Reforming vi

xc tc c nh.

Trong cng nghip ch bin du, qu trnh Reforming vi lpxc tc c nh vn cn kh ph bin, y iu kintin hnh qu trnh c chn m bo thi gian gia cc

ln ti sinh ln ( thng 6 thng n 1nm ).

Qu trnh ti sinh xc tc c tin hnh ng thi trong ttc cc Reator. Thi gian tng cng ti sinh v bo dng

thit b l 20 40 ngy/nm.

Hot ng ca s .

Nguyn liu sau khi c lm sch s b phn xng lm schbng hydro ho c cho sang trn vi kh cha hydro tunhon ri cho qua thit b trao i nhit (1) ri vo bung thnht ca l t (2) ti l t hn hp c t nng n520 0C ri a sang thit b phn ng ri a sang thit b th

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qua bm hi lu tr li nh thp n nh. Phn cn li a rakhi h thng a vo phn xng phn chia theo phn onkh. mi trng hydro v iu kin nhit 525 0C d gy

n mn kim loi. V vy, phn trong v kim loi ca thit bphn ng cn c mt lp lt bng b tng, ngoi ra phn trongthit b phn ng t mt ci cc bng thp t l giahai thnh cc v thit b phn ng l mt lp kh ngn nhit b mt kim loi khng cao qu 150 0C. Nhit nyphi kim tra cht ch bng pin nhit in. Nu nhit

lp ny cao qa d gy n mn lm hng thit b phn ng.S Reforming xc tc c nh c th hin hnh:

Loi s c bn ca Reforming xc tc s dng linbang Nga c dn ra bng 16.

Bng 13: S c bn Reforming xc tc ti Lin bang Nga.

Loi Cng sut

nghntn/nm

Thnh phnphn onca nguynliu ( 0C )

Sn phm cbn

A35-5 300 85 180 XngA35-11/300 300 85 180

105 140

Xng

Nilon-xng

A35-11/600 600 85 180 XngA35-11/300-95

300 85 180 Xng

A35-11/600 85 180 Xng

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c im ring bit ca s l cc Reator trng ln nhauthnh mt khi. Xc tc chuyn ng t chy t Reator trnxung Reator cui cng, sau xc tc lm vic c chuyn

sang thit b ti sinh khi phc li hot tnh ri np tr liReator th nht to thnh mt chu k kn.

a. B phn Reator.

Nguyn liu c trn vi kh H 2 tun hon c t nng n

nhit phn ng ( 526 530 0C ), trong cc thit b trao inhit v b phn th nht ca l ng ri c np vo reatorth nht ( trn cng ). Sau khi tip xc vi xc tc n b bini ( s ph thuc vo kht khe, cc iu kin cngngh ca qu trnh ) to ln sn phm c tr s octan caohn hay RH thm nhiu hn.

Khi reator gm 4 thit b trng ln nhau theo trc thngng. Kch thc tng dn t trn xung di v u l loixuyn tm. S cu to ca reator trong mi reator c thitk v ng dn xc tc b phn phn phi, b phn cch ly vcc thit b khc sao cho ph hp vi qu trnh chuyn ngca xc tc v cc phn ng ho hc xy ra.

Lng xc tc cha trong reator rt khc nhau, khi m reator

th nht ch cha 10 20% lng xc tc th reator cui cha50% tng lng xc tc. T l phn b xc tc trong cc reatorthng theo t s 11/1,5/2,5/5 ( vi s 4 reator ) xc tc lm vic c chuyn sang l ti sinh xc tc, hn hp khi phnng i ra khi reator th nht c qua l t nung li n

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nhit phn ng ri c np ngay vo reator th hai. C nhvy cho n reator th t. Sau reator th t hi kh sn phmc lm lnh do trao i nhit vi nguyn liu sau c ng-

ng t v lm lnh tip bc chuyn sang b phn tch snphm. thit b tch sn phm c chia thnh RH lng ngngt v hi kh giu H 2. Phn ln kh ny c quay li reator nhmy nn kh tun hon, phn kh cn li c trn vi b phnti sinh ri i vo ct n nh sn phm.

b. B phn l ti sinh xc tc.

Xc tc lm vic chy t yl ca reator cui cng xungb phn khu xc tc bonke cha, sau n chy xung ngnng NO/. Ngi ta dng kh cha hydro tun hon t my nntun hon y xc tc v vn chuyn n ln nh v bphn tch bi pha trn l ti sinh. b phn tch ny ngita b xung mt lng kh hydro tun hon tch cc ht bi

mn ca xc tc ri xung y b phn tch bi ri chyxung l ti sinh.

- Ti sinh xc tc gm 4 bc.

Ba bc u l:

+ t chy cc.

+ Clo ho.+ Lm kh ( sy kh ).

Ba bc ny xy ra vng ti sinh, cn bc th t l kh xc tcxy ra trong b phn kh ring.

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gy nhim xc tc rt thp ( Vanadi v Niken


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Ch s cc %TL 5,2 0.77 0,53 0,52Hm lng nha %TL 14,0 1,14 6,50 2,02

Hm lng asphalten %TL 2,7 0,17 0,64 0,15Nguyn t %TLCacbon 85,96 83,24 83,89 83,44Hydro 13,40 14,29 14,00 13,86Nit 0,22 0,04 0,035 0,037Lu hunh 0,14 0,04 0,04 0,08

Thnh phn chng ct

%TLn 200 0C 14,10 18,89 18,54 20,78n 350 0C 37,80 46,56 48,64 55,51n 500 0C 67,60 77,50 79,88 89,53Vanadium (ppm) 2,50


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reforming xuc tac che bien dau

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