Nghin cu xc tc d th

- 1 -

BI 1 XC NH ACID CA CC XC TC RN BNG PHNG PHP HP PH V GII HP PH NH3 THEO CHNG TRNH NHIT (TEMPERATURE PROGRAM DESORPTION) HAY NH3-TPD. I. C S L THUYT: Ngui ta s dng NH3 nh l mt cht d, c hp ph bo ha trn cc tm acid ca b mt, khong nhit hp ph ha hc ca vt liu rn xp. Khi tng nhit tuyn tnh xy ra s gii hp ph NH3. Ap dng nh lut Lambert Beer o hp thu A theo nng C v dng ng chun A=f(C). Da vo ng chun ny xc nh nng NH3 hp ph ln tm acid ca xc tc. Theo dng ng cong gii hp ph theo nhit cho ta bit nng lng hot ha gii hp ph khc nhau. Cc tm c lc acid mnh s c nhit gii hp ln, Ehh ln v ngc li. Tng lng NH3 gii hp cho ta tng s tm acid (nng H+) trn mt n v khi lng cht xc tc. Ngoi phng php ny cn s dng mt vi phng php khc chng hn:

Chun bng Amin Quang ph hp thu hng ngoi Nhit lng k Phn tch nhit khi lng Hp ph v gii hp ph cc baz kh

Trong cc phng php trn ch c phng php quang ph hp thu hng ngoi l cho php phn bit c tm acd Brontesd hay Lewis. Phng php phn tch nhit khi lng v TPD cho php nh gi mt tm acid cng nh lc acid ca tng tm. II. THC NGHIM:

Qu trnh tin hnh theo cc bc : 1. Lp ng chun A = f(C) :

Ly chnh xc 1.481 g NH4Cl ha tan trong 1 lt H2O , t dung dch trn ly ra 1 ml ri nh mc thnh 50 ml . Dng burt ly ln lt 0.2 ; 0.4 ; 0.6 ; 0.8 ; 1.0 ; 1.2 ; 1.4 ; 1.6 ; 1.8 ; 2.0 ml dung dch nh mc thnh 25 ml bng dung dch HCl 10-4 M .

Trc khi cho vo my quang ph cn phi thm vo 2 ml dung dch phenol-cn, 2 ml dung dch nitrorusside , 5 ml dung dch oxy ha .

Mu chun c nng NH4Cl khc nhau nn trn my quang ph ta thu c hp thu khc nhau. phng th nghim dng my quang ph PC Spectronic Genesys 2 PC v hp thu ly bc sng 625 m .

2. Qu trnh xc nh acid : Ong hp ph l ng ch U, c ng knh 35mm, cao 180mm. Bn trong c

gn ming xp bng thy tinh lp xc tc. Cn 0,2g xc tc cho vo ng ch

Nghin cu xc tc d th

- 2 -

U, tin hnh hat ha xc tc 3500C, trong 5h loi hi nc v cc kh b hp ph ln xc tc. y kn ng xc tc trnh ht m tr li v lm ngui n nhit

phng, sau cho hp ph no NH3 ln cc tm acid trn xc tc trong thi gian khang 1h. Sau lp ng ch U ny vo h thng kh NH3 bng chng trnh nhit v c h thng gii hp nh hnh v:

K hiu cc thit b : 1- Bnh cao p cha N2 . 2- Van iu chnh kh N2 3- Ong lc kh 4- B phn kim tra tc dng kh 5- My iu khin nhit theo chng trnh . 6- Cp nhit in 7- L gia nhit 8- Detector TCD 9- Cp ni 10- Interface: chuyn i tn hiu thnh in 11- B phn ghi ra ph

III. KT QU TNH TON V X L KT QU:

Xc tc dng: Ga 7SM 11 : 268 mg H7SM 5 : 200 mg Dy chun: Nng dung dch chun :

1

3 4

2

5

7

6

8

910

11

Nghin cu xc tc d th

- 3 -

)/(7.27)/(0277.05.53

481.1 LmmolLmolMmN

Dung dch chun pha long 50 ln c nng l :

)/(554.050

7.2750

LmmolNn

Kt qu phn tch dy chun : Ly cc th tch Vi ca dung dch chun C0 = 0,554 (mmol/lt) pha thnh cc

dung dch o c cc Ci

Th tch dd chun Vi (ml)

0.4 0.6 0.8 1.0 1.2 1.4 1.6

Nng dd o Ci x103 (mmol/lt)

8,864 13,296 17,728 22,16 26,592 31,024 35,456

ABS 0,075 0,125 0,175 0,196 0,233 0,351

Phng trnh hi quy tuyn tnh:

BxAy A = -0,0315 B = 9,4765 r = 0,952 Vy ta c phng trnh hi quy : Y = - 0,0315 + 9,4765.X

Nghin cu xc tc d th

- 4 -

O TH O HAP THU CHUAN

y = 9.4765x - 0.0315

00.05

0.10.15

0.20.25

0.30.35

0.4

0 0.01 0.02 0.03 0.04Nong o NH3 (mmol/l)

o

hap

thu

A

Kt qu o mu : - hp thu khi o mu l: ABS = 0,181 Cm o = 0,02242 (mmol/lt) - Mu pha long 25 ln : Cm b = 0,5605 (mmol/lt) - Th tch mu ban u: Vm b = 100ml - S mol NH3 ban u: nm b = Cm b . Vm b = 0,5605.0,1 = 0,05605 (mmol) - acid:

)/(12.0468,0

05605,03 gmmolm

nXxt

NH

Nghin cu xc tc d th

- 5 -

BI 2 NGHIN CU HOT TNH XC TC TRONG PHN NG OXY HA HON TON TOLUEN

I- MC CH TH NGHIM : Nghin cu phn ng oxy ha hon ton toluen vi xc tc LaCrO3 c

thc hin trn h phn ng vi dng . Phng php ny c u im l gn vi iu kin thc t v khng i hi lng xc tc v nguyn liu ln .

II- C S L THUYT : Cc xc tc kim loi chuyn tip nh kim loi phn nhm 8, nhm 1, cc

kim loi qu nh Pt thng l cc xc tc oxiha. Nhng kh c th chn c mt xc tc c hot tnh cao ng thi c kh nng chn lc cao. Thng xc tc c hot tnh cao th chn lc li km.

Trong kh thi t cc nh my v ng c ni chung thng c cc hp cht hydrocacbon nh : Hp cht mch vng , andehyt , acid , olefin , diolefin , parafin nn trong qu trnh nghin cu ta chn mt cht c trng nht , d kho st nh gi cho phn ng chuyn ha su hydrocacbon v cng l cht tng i kh b oxy ha hn cc hp cht hydrocacbon khc trong kh thi , trong bi ny ta chn Toluen .

Trong qu trnh oxy ha bi xc tc c hng lat hp cht trung gian c hnh thnh (cn gi l sn phm th cp ) . Xc tc tt l xc tc u tin cho cc qu trnh oxy ha su hydrocacbon thnh CO2 v H2O , khng hnh thnh cc hydrocacbon trung gian c hi hn nh benzalancol , acid benzoic , benzaldehyt , acetol , alkan , alken hay hnh thnh di dng sn phm th cp rt nhanh ri sau b oxy ha su tip to thnh CO2 v H2O .

III- HA CHT V THIT B:

1. B phn cung cp kh mang , nh lng np nguyn liu: Bao gm h thng np kh mang ( cc bnh kh nn oxy , nit ) , van tit lu ,

lu ling k v bnh cha nguyn liu . 2. B phn ng:

Gm c ng phn ng c gn cp nhit in t trong l phn ng . L phn ng c h thng iu khin nhit t ng thng qua cp nhit in t bn trong l , cp nhit in Ni/Ni-Cr chnh xc 10C .

ng phn ng lm bng thy tinh gm hai nhnh : ng thng ng c bc bi ng xon . ng knh ng l 7 mm . Lng xc tc s dng l 200-300 mg cho mi phn ng . Lp xc tc dy khong 1 cm c t gia hai lp bng thy tinh mng , m bo cho ch dng l tng , gim bt nh hng khuch tn ni v cc gradien nng , nhit . 3. B phn tch sn phm phn ng:

S dng thit b my sc k kh Sau mi thi im phn ng nht nh , hn hp nguyn liu v sn phm

c ly bng xylanh thy tinh bm vo my sc k phn tch .

Nghin cu xc tc d th

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Da vo thi gian v din tch cc pic ca cc cu t hydrocacbon nguyn liu v sn phm , ta c th nh lng mu v phn tch , tnh c chuyn ha v chn la ca cc phn ng oxy ha hydrocacbon .

Ty vo bn cht ca mi cu t v cc iu kin khi o mu , mi cu t s c lu trong ct vi nhng khong thi gian nht nh . Do , trn sc k , mi mi sc k s xut hin ng vi v tr v ln nht nh .

cng iu kin ca my sc k , ta phn tch mu chun v mu sn phm . 4. Nguyn liu s dng:

Nguyn liu s dng nghin cu phn ng oxy ha hydrocacbon trn xc tc LaCrO3 l Toluen vi tinh khit 100% .

IV- TIN HNH TH NGHIM :

1. Khi qut qu trnh th nghim: ui hi nc v dung mi hp ph trong xc tc bng dng nit , vi

lu lng dng 8 lt /h , nhit 1500C trong khong 1 gi ri nng nhit ln 5000C .

Hot ha xc tc trong dng oxy nhit 5000C trong 2 gi , lu lng dng oxy 2 lit/h .

H nhit trong bnh phn ng xung n nhit phn ng . Trn nguyn liu v kh mang theo t l thch hp , ch n nh ri dn

qua lp xc tc phn ng . Ly mt lot mu nguyn liu v em phn tch . Nng dn nhit ch phn ng n nh th bm mt lot mu o cc

nhit tng ng ( t 1200C cho n khi chuyn ha vt 95% th kt thc ) v em phn tch sn phm my sc k kh .

S th nghim nh sau :

Nghin cu xc tc d th

- 7 -

bnh nit

1 2

bnh oxy

1 2

4

5

8

3

6

7

Ch thch: 1- B lm kh . 2- Lu lng k 3- ng nguyn liu 4- Van ba chiu . 5- Thit b phn ng . 6- L trch mu u vo. 7- L trch mu u ra. 8- B iu khin nhit . Sau khi th nghim xong , tt l phn ng , kha cc van kh , tt my sc k

v cc dng kh ca my . ch mu ngui , ly mu ra v sinh ton h thng. 2. Trnh t tin hnh th nghim: Chun b: - Cn 500mg xc tc cho vo ng thng ng ca bnh phn ng ( sau khi bnh phn ng c ra sch v sy kh) theo trnh t : 1 lp bng thu tinh, 1 lp xc tc, 1 lp bng thu tinh. - Nguyn liu Toluen cho vo ng nguyn liu n ngp bu phun kh, lun c gi nhit phng trong sut qu trnh th nghim. - Lp bnh phn ng v ng nguyn liu vo h thng ri m cc van kh oxy, nit v m my sc k kh. o tc dng kh: - Dng van tinh chnh tc cc dng kh - Dng ng o tc kh oxi v nit theo t l VN2 : VO2 = 4:1 lt/gi. - Cn kim tra li lu lng dng kh trc mi phn ng v lu lng dng tng. Qu trnh lm sch xc tc: Cc mu xc tc sau khi iu ch c x l v hot ho trong thit b phn ng trc khi tin hnh phn ng nh sau:

Nghin cu xc tc d th

- 8 -

- M van Nit, chnh van 3 chiu theo hng dng nit vo bnh phn ng. Sau m van chnh lu lng nit, cho dng lu lng nit l 3,2 lt/gi lm sch xc tc, li cun hi nc ra khi xc tc. - M cng tc gia nhit, iu chnh nhit 1500C v tng dn 5000C. Qu trnh hot ho: - Khi t n nhit cn thit th hot ho xc tc thm 2 gi na, vi lng dng oxi 0,8 lt/gi. Trn dng: - Sau khi hot ho xc tc, tin hnh trn dng bng cch iu chnh van 2 chiu cho dng nit vo bnh nguyn liu, nhp chung vi dng oxi, kh nit s li cun hi bo ho nguyn liu. T l trn dng VN2 : VO2 = 4:1 ging vi t l khng kh. - Phn ng v phn tch nguyn liu v sn phm: sau khi trn dng, cho dng hn hp kh i vo bnh phn ng cha xc tc. Sau 20 pht h thng n nh, ly mu nguyn liu v sn phm em phn tch trn my sc k kh. 2. Kt qu o v th: Kt qu o c:

Nhit 220 230 239 250 259 269 280 290

Sv 230869 229945 199157 122561 159003 137849 110198 192059 Sr1 229931 219578 179962 98630 115630 4253 644 0*

Sr2 225321 219486 166644 97901 121124 4204 630 0*

x% 1.40 4.53 12.98 19.82 25.55 96.93 99.42 100.00 Sv: din tch cc peak trn sc k ca dng nguyn liu vo. Sr: din tch cc peak trn sc k ca dng sn phm ra. X%: chuyn ho.

X% = 100* 1 SvSrSr

*2)21(

th: X = f(T)

Nghin cu xc tc d th

- 9 -

o th bieu dien o chuyen hoa theo thi gian

0.0

20.0

40.0

60.0

80.0

100.0

120.0

200 220 240 260 280 300

Nhiet o 0C

o

chuy

en h

oa %

chuyn ho: chuyn ho hon ton trong khong nhit 280 - 2900C, lc ny trn sc k khng thy Peak ca sn phm u ra.

BI 3 NGHIN CU NG HC CA PHN NG DEHYDRATE HO ISOPROPANOL TRN XC TC ACID RN I. MC CH CA TH NGHIM: Lm quen vi phng php dng thy ng trong nghin cu phn ng xc tc d th. Nghin cu hot xc tc zeolit trong phn ng dehydrat ho isopropanol. II. L THUYT: Rt lu ngi ta bit rng mt vi oxyt lm xc tc cho phn ng dehydrat ha ru. Mc du phn ng hin nay c nghin cu nhiu nhng c ch tng

Nghin cu xc tc d th

- 10 -

giai on xy ra trn b mc cht xc tc cha c s thng nht. C mt vi kin cho rng tnh cht acid ca oxy nhm khng c ngha i vi phn ng dehydrat ru thnh olefin. Mt vi tc gi li cho rng trung tm Lewis c tc dng xc tc. Khi u c Na hot tnh xc tc gim xung. Khi nghin cu quang ph hng ngoi nhng mu Al2O3 b u c, nhng trung tm Lewis qua kim cng lm gim hat tnh xc tc. Khi nghin cu hn hp oxyt nhm Alumosilikat v nh hnh v tinh th (Zeolit) ta nhn thy cc cht ny c hot tnh rt cao, cho phn ng dehydrat ha ru. V nhng tc gi tm thy s ph thuc tuyn tnh gia hat xc tc v acid. V vy ngi ta dng phn ng dehydrat ha isopropanol nh phn ng m hnh ha nghin cu phn ng ca cc cht acid rn. Trong bi th nghim ny ta nghin cu hot xc tc ca cht xc tc Zeolit trong phn ng dehydrat ha isopropanol. III. THC HNH: 1. S th nghim nh sau :

Cn 500mg - Al2O3 ( mu mi 22/4/06 ) cho vo ng phn ng v nung nhit 3830C trong 1 gi kh nc. Mu xc tc sau khi kh nc, h nhit xung 3830C v gi cho n nh nhit ny chun b cho giai on phn ng.

1. Ga 8. L phn ng 2. Van 9. Cp nhit in 3. Van ly kh sn phm 10. Lp ct gi nhit 4. Buret o lu lng kh 11. Lp xc tc 5. Dung dch mui bo ha 12. ng cha xng sn phm 6. iu khin nhit 13. Bnh nc ngng t 7. Bm vi lng

Nghin cu xc tc d th

- 11 -

Isopropanol lng c bm vo bnh phn ng qua bm siu vi lng, tc dng ca isopropanol c chnh 0,3ml/pht vi thi gian bm l 10 pht. Sn phm gm 2 phn: phn lng v phn hi. Phn lng c gi bnh cu, phn hi c a ra h thng o tc dng. Vic o tc dng c thc hin song song vi qu trnh phn ng. Kh sinh ra c dn vo phn di ca ng. IV. KT QU O V TNH TON: 1. Kt qu o: - Vn tc dng isopropanol: v0=0,3ml/pht - Khi lng ring: 20 = 0,785g/ml - Chu vi ca ng thy tinh: L = 103 mm - Chiu cao ct kh (trong 5 pht): h = 412 mm - Chiu cao ct kh theo thi gian (t pht th 1 n pht th 5): hi

Thi gian(pht) 1 1 1 1 1

hi (mm) 93 87 78 77 77

2. Kt qu tnh ton: - ng knh ng: d = L/= 32.786mm = 0,032786 m - Din tch y: Sd= d2 / 4. = 0,0008554 m2 - Th tch ct kh theo thi gian (lt): Vi = Sd.hi - Vn tc dng isopropanol: v0= 0,3ml/pht - S mol isopropanol theo thi gian (mol/pht): n0= v0. /60 = 3,925.10-3 mol/pht - Vn tc dng Propylen theo thi gian (lt/pht): vi =Vi /ti (ti =1 pht) - S mol kh theo thi gian (mol/pht): ni = vi /R.T R=22,4/273 ( lt/mol.K) T= 273 + t0C = 298 K ( cho t0C =250C ) - chuyn ha theo thi gian: xi = 100% * ni /n0

ti (pht) hi (mm) v2i (lt/pht) ni (mol/pht) n0(mol/pht) xi(%)

1 93 0.07955 0.003254 0.003925 82.89

Nghin cu xc tc d th

- 12 -

1 87 0.07442 0.003044 0.003925 77.54

1 78 0.06672 0.002729 0.003925 69.52

1 77 0.06587 0.002694 0.003925 68.63

1 77 0.06587 0.002694 0.003925 68.63 3. th biu din s bin i hiu sut phn ng theo thi gian:

o th bieu dien o chuyen hoa theo thi gian

60.00

65.00

70.00

75.00

80.00

85.00

0 1 2 3 4 5 6Phut th i

o

chuy

en h

oa (%

)

Nghin cu xc tc d th

- 13 -

Bi 4 NGHIN CU NG HC CA PHN NG CRACKING n-HEXAN BNG PHNG PHP DNG VI LNG

I- MC CH TH NGHIM: Lm quen vi phng php dng vi lng trong nghin cu cc phn ng

xc tc d th. Nghin cu hot ca cc xc tc axit rn cho phn ng cracking pha kh.

II- C S L THUYT: 1. S lc v phn ng cracking:

Cracking l qu trnh ha hc phc tp thng uc ng dng nhm bin i nhng phn on nng ca du m thnh nhng sn phm nh hn, c gi tr kinh t cao hn.

Trong cng nghip c 3 phng php thc hin phn ng cracking bao gm: cracking nhit; cracking xc tc v hydrocracking, trong cracking xc tc c hiu sut kh cao v c ng dng nhiu nht.

Xc tc c dng trong phn ng cracking thng l xc tc axid, trong qu trnh phn ng cht phn ng dng hi chuyn ng cng chiu vi bt xc tc v nhit phn ng khong 5000C. 2. Phn ng cracking n- hecxan.

Thc hin th nghim phn ng ccacking n-hexan, s dng xc tc zeolit ZSM-5 (Si/Al= 10-75). Cng thc ho hc: NanAlnSi96-nO192~16H2O (n 27). S c mt ca xc tc c tc dng tng ch s octan v tng hiu sut to olefin nh. Nguyn nhn l do kh nng cracking chn lc hnh dng tt, tc dng ng phn ha cc hydroccbon mch thng to mch nhnh trong xng.

Phng php thc nghim dng n-hecxan gi l php th . Tc phn ng cracking ph thuc vo kh nng to cacbocation ca hydrocabon. Phn ng cracking n- hecxan l phn ng bc hai theo s bin i hm lng nhm trong zeolit.

V c ch p cracking n- hecxan trn ZSM- 5 tn ti 2 c ch cnh tranh: c ch cacbeni v cabocation:

Theo c ch cacbocation: nC6H14 + HZ nC6H15+Z-

Nghin cu xc tc d th

- 14 -

Theo c ch cacbenion:

u tin, phn t n-hecxan b tch H+ trn tm Bronsted (hoc tm Lewis) ca zeolit, to cacbeni bc 2 C6H13+ hp ph trn b mt zeolit. Ion C6H13+ b phn ct lin kt C- C theo quy tc , to 1 olefin v mt ion cacbeni th cp hp ph trn zeolit theo cc p sau:

CH3C+H CH2CH2CH2CH3 C3H6 + C3H7+ a C4H8 + C2H5+

CH3CH2 C+HCH2CH2CH3 b a b C5H10 + CH3+

Cc ion cacbeni bc 2 th cp sinh ra li tip tc tham gia vo cc qu trnh ng phn ha to ion bc cao hn, chuyn dch hydrua to sn phm l cc parafin.

V d:

n C4H9+ ng phn ha i C4H9+

i-C4H9+ + i C6H14 Dch chuyn hydrua i C4H10 + i C6H13 Tm li: ngh s th t trong c ch cracking n- hecxan dng

xc tc ZSM-5.

Nghin cu xc tc d th

- 15 -

3. L thuyt ca phng php dng vi lng:

Hot v chn la ca cc phn ng izooctan c xc nh bng phng php dng vi lng. Phng php ny c u im l gn vi iu kin thc t v khng i hi lng xc tc v nguyn liu ln.

S th nghim c m t trn hnh sau:

7

4

6

5

3

21

bnh nit

Ch thch: 1- ng lm kh. 2- Lu lng k . 3- Bnh n - hexan. 4- Van ba chiu. 5- Bnh phn ng . 6- L trch mu. 7- B iu khin nhit .

Nghin cu xc tc d th

- 16 -

III- THC HNH : 1. Cc bc tin hnh th nghim: - Hot ho 100mg xc tc ZSM-5 bng dng kh N2 lu lng 1 l/h 5000C trong vng 2h. - Dng hn hp kh N2 (1 l/h) + H2 (1 l/h) li cun hi n-hexan vo bnh phn ng cha xc tc hot ho, nhit phn ng c gi 5000C. - C sau mi 15 pht, ly 2 mi mu l sn phm phn ng a vo my sc k kh phn tch thnh phn cc cht.

2. Kt qu phn tch sn phm: Sn phm phn ng c phn tch trn my sc k CHROMATROGAS-

CHROMOTOGRAPH-GCHF 18-3 vi ct phn tch SE-30.3 m (ct nhi). Detector FID.

Cc s liu c my tnh tnh ton theo t l din tch ca peak nguyn liu trn tng din tch cc peak v cho ta kt qu di dng phn trm sn phm cn li.

IV- KT QU TH NGHIM: Cc s liu phn tch trn my sc k nh sau:

CC S LIU THU C THI GIAN MU % C1,C2 %C3 % iso - C4 % n - C4 % n - C6

15 1a 14.382 19.054 3.162 8.999 43.942 1b 13.431 17.077 2.728 7.724 48.021

30 2a 12.825 16.15 2.9 8.173 44.388 2b 15.564 18.732 2.414 8.125 43.421

45 3a 10.329 17.224 1.789 6.157 36.556 3b

60 4a 7.748 12.95 1.894 6.787 62.935 4b 6.382 12 1.285 5.286 67.059

75 5a 4.736 11.532 1.39 5.137 74.61 5b

90 6a 4.954 10.739 2.332 6.118 70.168 6b

105 7a 7b 5.211 10.848 2.414 6.621 69.804

120 8a 5.517 11.91 2.479 6.846 67.729

Nghin cu xc tc d th

- 17 -

8b 4.798 11.417 2.076 6.183 70.444

TNH TRUNG BNH CC MU THI GIAN MU % C1,C2 %C3 % iso - C4 % n - C4 % n - C6

15 1 13.9065 18.0655 2.945 8.3615 45.9815 30 2 14.1945 17.441 2.657 8.149 43.9045 45 3 10.329 17.224 1.789 6.157 36.556 60 4 7.065 12.475 1.5895 6.0365 64.997 75 5 4.736 11.532 1.39 5.137 74.61 90 6 4.954 10.739 2.332 6.118 70.168

105 7 5.211 10.848 2.414 6.621 69.804 120 8 5.1575 11.6635 2.2775 6.5145 69.0865

CHUYN HA THEO THI GIAN

THI GIAN (pht) CHUYN HA (%) 15 54.0185 30 56.0955 45 63.444 60 35.003 75 25.39 90 29.832 105 30.196 120 30.9135

th chuyn ha theo thi gian:

Nghin cu xc tc d th

- 18 -

O TH O CHUYEN HOA THEO THI GIAN

010203040506070

0 50 100 150Thi gian (phut)

o

chuy

en h

oa (%

)

V. TR LI CU HI: 1. Cc c im xc tc Cracking: - Tnh cht nhiu giai on: chuyn cht n b mt, hp th hat ha trn b mt, phn ng trn b mt gia cc cht b hp ph vi nhau hay gia cht b hp ph v cht trong th tch, gii hp ph sn phm, chuyn sn phm vo pha th tch. - Hydrocacbon mch cng di cng d Cracking - Cracking olefin d hn parafin, do olefin d to cc ion cacbony v d ct hn - Hydrocacbon c mch cacbon cng di phn ng cng d (nh phn t Toluen c mch ankyl ngn nht nn khng b cracking) - to mch di: mao qun ln, xc tc acid mnh, xc tc phi bn. S cc ha: L s kt hp hai ion cacbony to thnh phn t ln nm trong mao qun xc tc nn phn t ny khng ra ngoi c.

Nghin cu xc tc d th

- 19 -

Ngn nga cc ha: Siu bn xc tc, dng dng ra xc tc.

2.Nu cc loi ct, u d ca sc k kh:

* Cc loi ct sc k kh: c 2 loi chnh

- Ct nhi (phn loi t khng phn cc n phn cc)

- Ct mao qun (phn loi t khng phn cc n phn cc)

* Cc loi u d sc k kh:

- u d dn nhit

- u d ion ho ngn la FID

- u d cng kt in t ECD

- u d ion ho nhit NPD ( c trng cho hp cht N,P)

- u d ngn la FPD ( c trng hp cht P,S ) nh pht ra bc x xanh lc hay xanh l v o c t bo quang nhn (photomultiplier)

3. Nu cc phng php kim tra hot tnh xc tc:

c hai phng php chnh : phng php tnh(tin hnh trong h thng kn v phng php dng ( tin hnh trong h thng m):

Hot tnh ca xc tc tu thuc vo acid ca xc tc (da vo t l cc thnh phn tng hp).

Loi xc tc c acid cao: dng trong phn ng cracking.

Loi xc tc c acid va: dng trong phn ng reforming.

Loi xc tc c acid thp: dng trong phn ng isomer ho.

Cc phng php kim tra hot tnh xc tc: Ngi ta dng NH3 nh mt cht d, c hp ph bo ho trn cc tm acid ca b mt xc tc, sau gii hp ph xc nh acid bng:

o Phng php hp ph v gii hp ph NH3 theo chng trnh nhit TPD.

o Phng php chun bng amine. o Phng php quang ph hp thu hng ngoi. o Phng php nhit lng k. o Phng php phn tch nhit khi lng TGA. o Phng php hp ph v gii hp ph cc baz kh.

Nghin cu xc tc d th

- 20 -

Trong cc phng php trn, ch c phng php quang ph hp thu hng ngoi l cho php phn bit c tm acid Bronsted hay acid Lewis. Phng php phn tch nhit khi lng TGA v TPD cho php nh gi mt tm acid cng nh lc acid ca tng tm.

4. Nu c im Zeolite ZSM-5:

- Cng thc ho hc: NanAlnSi96-nO192.16H2O (n 27). - T l: Si/Al= 10 75 - L xc tc zeolite acid. - Din tch b mt xc tc: 400 425 m2/g. - Khi lng ring: 15mg/m3. - Dng bt, mu trng, khng mi. ZSM 5 l loi xc tc dng zeolite khng ng nht, c hot tnh cao tm c. ZSM 5 c d dng chnh trong cc phn ng chuyn i hydrocarbon, chng hn nh meta-xylene sang dng para-xylene. ZSM 5 l loi xc tc dng zeolite vi t l Silica/ Nhm cao. S thay th 1 ion Al3+ bng 1 ion Si4+ i hi phi c b sung thm 1 proton. Tnh cht thm 1 proton ny lm cho ZSM 5 c tnh acid cao, c tnh ny l cho ZSM 5 c hot tnh cao. ZSM 5 l loi vt liu c cu trc l xp cao, v trong cu trc ca n c cu trc l 2 chiu c tnh giao nhau. ZSM 5 c 2 dng l, c 2 dng ny c hnh thnh bi 10 nguyn t oxy to vng (10-membered oxygen rings). Nhng l u tin thng v c mt ct dng hnh ellipse. Nhng l th 2 giao vi nhng l thng th nht 1 gc, to thnh hnh zig zag, v to thnh hnh trn trn lt ct. Cu trc l ca ZSM 5 nh hnh bn di:

Tnh cht cu trc l 2 chiu c nht ny cho php mt phn t c th di

chuyn t 1 v tr ny trong xc tc n bt c v tr no trong mu xc tc. Qu trnh m rng cc khe h (l hng) trong ZSM 5 l cc l dng thng, hnh ellipse.

Nghin cu xc tc d th

- 21 -

Hin nay, ZSM 5 c s dng hiu qu trong qu trnh chuyn i methanol thnh gasoline vi dng zeolite c cu trc l xp c hnh thnh t nhng vng 10-oxygene to thnh cc l ct giao nhau hnh zig-zag. Loi xc tc ny rt quan trng cn thit trong qu trnh hnh thnh sn phm gasoline mong mun. Dng zeolite vng 8-oxygene s khng chuyn i c phn t hydrocarbon 6C tr ln, loi hydrocarbon ny c kch thc phn t khng ph hp vi cu trc l xp nh ca loi zeolite ny. Loi zeolite vng 12-oxygene vi l xp ln hn c s dng trong sn xut cc thnh phn hydrocarbon C11 v C12, tuy nhin thnh phn ny khng c mong mun c trong cc sn phm gasoline.

5. Khng th s dng 1 dng kh.