I HC QUC GIA H NI TRNG I HC KHOA HC T NHIN

.

L Vn Quyn

NGHIN CU CH TO AXIT RN ZrO2 BIN TNH BNG Zn V S LM XC TC CHO QU TRNH CH TO

DIESEL SINH HC T DU THC VT PHI THC PHM

Chuyn ngnh: Ha du v xc tc hu c M s: 60 44 35

LUN VN THC S KHOA HC

NGI HNG DN KHOA HC: PGS-TS TRN TH NH MAI

H Ni - 2011

MC LC

M U .................................................................. Error! Bookmark not defined.

Chng 1: TNG QUAN ...................................... Error! Bookmark not defined.

1.1. Tm kim ngun nng lng cho tng lai ... Error! Bookmark not defined.

1.2. ng dng du, m ng thc vt trong sn xut nhin liu ......................... 3

1.2.1. Sinh khi .................................................. Error! Bookmark not defined.

1.2.2. Gii thiu chung v du m ng thc vt .................................................. 4

1.2.3 Chuyn ha du , m ng thc vt thnh nhin liu .................................. 7

1.2.4. phng php este cho ha 8

1.3. Xc tc cho phn ng este ha cho tng hp Biodiesel 8

1.3.1. Mt s khi nim c bn v nhin liu sinh hc 8

1.3.2. c tnh ca Biodiesel 8

1.3.2.1. So snh tnh cht ca Biodiesel, Diesel truyn thng v du thc vt 9

1.3.2.2. u v nhc im khi s dng nhin liu Biodiesel 9

1.3.3. Cc yu t nh hng n phn ng este cho ha 13

1.3.3.1. nh hng ca hm lng axit bo t do 13

1.3.3.2. nh hng ca nhit phn ng 13

1.3.3.3. nh hng ca thi gian phn ng 14

1.3.3.4. nh hng ca t l 14

1.3.3.5. nh hng ca xc tc 15

1.4. Vt liu mao qun trung bnh cu trc trt t 17

1.4.1. Gii thiu vt liu mao qun 17

1.4.2. Vt liu mao qun trung bnh 20

1.4.3. Gii thiu v Zr v ZrO2 23

1.4.4. Cc yu t nh hng n xc tc Zirconia c sunfat ha 25

Chng 2: THC NGHIM ................................................................................. 32

2.1. Ho cht v thit b .......................................................................................... 32

2.1.1. Ha cht ......................................................................................................... 32

2.1.2. Thit b ........................................................ Error! Bookmark not defined.

2.1.3. Tng hp xc tc SO42-

/ ZrO2 - ZnO 33

2.2. Cc phng php vt l c trng xc tc ... Error! Bookmark not defined.

2.2.1 Nhiu x tia X (XRD) ................................................................................... 35

2.2.3. Hp ph v gii hp N2: BET .................................................................... 36

2.2.4. Gii hp NH3 theo chng trnh nhit : TPD-NH3 .36

2.2.5. Ph tn sc nng lng tia X: EDX ........... Error! Bookmark not defined.

2.3. Xc nh cc ch s c bn ca du Jatropha ...40

2.3.1. Xc nh ch s axit .................................................................................... 40

2.3.2. Xc nh ch s x phng ha ................................................................... 471

2.4. Phng php nh gi sn phm ................................................................... 43

2.4.1. nh gi thnh phn sn phm

2.4.2. Kim tra tnh cht ca sn phm

Chng 3: KT QU V THO LUN ............. Error! Bookmark not defined.

KT LUN ............................................................. Error! Bookmark not defined.

TI LIU THAM KHO ...................................... Error! Bookmark not defined.

PH LC HNH

Hnh 1.1. D on v s bin i nhu cu s dng ba ngun nng lng chnh

t nm 1850 n nm 2050..3

Hnh 1.2. c lng sinh khi v cha s dng trn ton th gii. .5

Hnh 1.3. Mt phn t triglyxerit trong du ht ci Canola..............................5

Hnh 1.4. Phn ng este ha cho vit di dng tng qut. ..7

Hnh 1.5. Chu trnh sn xut v s dng biodiesel ...8

Hnh 1.6. S thay i hm lng kh CO v cc ht rn bc x t ng c t-

nn s dng diesel truyn thng v hn hp diesel-biodiesel Bxx.9

Hnh 1.7. S thay i hm lng kh NOx v cc ht rn bc x t ng c t-

nn s dng diesel truyn thng v hn hp diesel-biodiesel Bxx..10

Hnh 1.8. nh hng ca nhit phn ng v thi gian phn ng n

chuyn ha ca du ht bng (cottonseed oil) 12

Hnh 1.9. Gin mt ct ca mt vt liu mao qun15

Hnh 1.10. M t cc loi mao qun c hnh thnh trong cu trc zeolit16

Hnh 1.11. Cu trc ca super axit rn ZrO2 SO42

........................................29

Hnh 2.1: Thit b phn ng trong phng th nghim . 31

Hnh 2.2. S khi tng hp SO42-

/ ZrO2 - ZnO. .. 32

Hnh2.3: S phn x tia X trn cc mt tinh th 34

Hnh2.4: Nguyn l ca php phn tch EDX. ....38

Hnh 2.5: S nguyn l ca h ghi nhn tn hiu ph EDX .39

Hnh 3.1. Kt qu nhiu x tia X gc hp ca vt liu tng hp.......................43

Hinh 3.2: ng gii hp v hp ph N2 ca vt liu.......................................45

Hnh 3.3. Gin hp ph v gii hp NH3 theo chng trnh nhit .........47

Hnh 3.4. Ph EDX ca vt liu xc tc SO42-

/ZrO2 ZnO49

Hnh3.5. Hinh nh SEM ca vt liu xc tc ZrO2/SO42-

-ZnO..49

Hnh 3.6: Gin phn tch nhit TG/DTA................................................49

Hnh 3.7: S phn lp v to nh ca mu c thi gian phn ng ngn.........57

Hnh 3.8. Sc k ca mu MJA......................................................................57

Hnh 3.9 . Ph khi lng ca Hexadecanoic acid...........................................58

Hinh 3.10. Ph khi lng ca 9-octadecanoic acid (Z)-,methyl ester............59

Hinh 3.11 Ph khi lng ca Octadecanoic acid ,methyl ester.......................60

Hnh 3.12. Sc k ca sn phm metyl este MJB..........................................61

Hnh 3.13. Ph khi lng ca 9-octadecenoic acid (z)-,methyl ester..............61

Hinh3.14. Ph khi lng ca 9,12-octadecadienoic acid (Z,Z)-methyl

ester.....................................................................................................................63

Hnh 3.15. Ph khi lng ca Pentandecanoic acid, 14-methyl -, methyl

ester.....................................................................................................................64

PH LC BNG

Bng 1.1: Mt vi thng s v tnh cht vt l ca biodiesel, diesel truyn thng v du thc vt. .10

Bng 1.2: Phn loi vt liu mao qun rn theo kch thc mao qun. ..17

Bng 1.3. nh hng ca cht nn n cht lng xc tc.............................. 26

Bng 3.1: Bng kt qu EDX hm lng ca ca vt liu ..48

Bng3.2: Ch s axit c bn ca du Jatropha.................................................50

Bng3.3: Kho st nh hng ca t l mol metanol/ du Jatropha.................52

Bng 3.4: Kho st nh hng ca thi gian phn ng...................................53

Bng 3.5: So snh hot tnh xc tc ca vt liu vi SO42-

/ZrO2 ..................56

Bng 3.6: Kt qu ca phn ng este cho ha ................................................58

M u

Biodiesel manh nha t rt sm nm 1853 nh cng trnh nghin cu ca

E.Dufy v J.Patrick v chuyn ha este ca du thc vt, nhng Biodiesel ch

c chnh thc ghi nhn vo ngy 10/08/1893, ngy m k s ngi c

Rudolf Christian Karl Diesel cho ra mt ng c Diesel chy bng du lc, sau

ngy 10/08 c chn l Ngy Biodiesl Quc t ( International BD Day).

n nm 1907 Herry Ford, ngi sng lp cng ty a quc gia Ford Motor

Company, cho ra i chic xe bng Etanol. Nhng do xng du c ngun gc t

nhin liu ha thch c gi r hn nn nhin liu Sinh hc cha c coi trng.

Nhng trong thi gian gn y, do gi xng du tng nhanh, nguy c cn kit

nhin liu ha thch e da v yu cu bc thit v chng s bin i kh hu

ton cu m nhin liu Sinh hc tr thnh mt nhu cu thit thc ca nhn loi,

nht l khi cc cng ngh bin i gen gp phn lm tng t bin sn lng

mt s sn phm nng lm nghip.

Tm li, c th hiu mt cch tng qut Diesel l loi nhin liu bt k dng cho

ng c Diesel. Da theo ngun gc, c th chia Diesel thnh 2 loi:

Petrodiesel ( thng c gi tt l Diesel) l 1 loi nhin liu lng thu

c khi chng ct du m phn on c nhit t 175 0C n 370 0C,

thnh phn ch yu l hidrocacbon t C16 C21.

Biodiesel: c ngun gc t du thc vt ( c, to, cy Jatropha, cy cao

su) hay m ng vt. Cc loi du m ng thc vt, du m thi tuy rng c

th chy iu kin thng nhng v c nht cao, mt s loi c ch s acid

ln nn chng khng th dng trc tip cho cc ng c m chng cn phi

c chuyn ho thnh Monoankyl Este ri mi em i s dng. Theo

phng din ha hc, Biodiesel l metyl este ca nhng acid bo ( trong ,

thnh phn to nng lng ch yu l gc hidrocacbon

Vo u th k XX, Rudolf Diesel dng du lc lm nhin liu cho ng

c diesel m ng pht minh ra. Tuy nhin, lc ny ngun nhin liu t du m

rt r v tr lng di do, nn khng ai quan tm n ngun nhin liu t du

thc vt. Gn mt th k tri qua, tnh hnh dn s th gii ngy cng tng

nhanh, tc pht trin kinh t - x hi cng ngy cng tng mnh, ko theo

nhu cu s dng nhin liu ngy cng nhiu, phc v cho cc lnh vc khc

nhau. iu ny dn n tnh trng ngun nhin liu ha thch vn c hn, ang

ngy cng cn kit, gi du m ngy cng t . Hn na, khi kinh t - x hi

pht trin, ngi ta bt u ch nhiu hn n mi trng, cng nh sc khe

ca con ngi, v ngy cng c nhiu quy nh kht khe hn v mc an ton

cho mi trng i vi cc loi nhin liu. Chnh nhng iu ny t ra vn

cho cc nh khoa hc, l phi n lc tm ngun nhin liu thay th, ngun

nhin liu thn thin vi mi trng, v nhin liu sinh hc tht s ln ngi.

Nhin liu sinh hc thu ht c s quan tm c bit ca nhiu nh

khoa hc trn c th gii, bi n em li nhiu li ch nh bo m an ninh

nng lng v p ng c cc yu cu v mi trng. Trong s cc nhin liu

sinh hc, th diesel sinh hc (biodiesel) c quan tm hn c, do xu hng

diesel ha ng c, v gi diesel khong ngy cng tng cao. Hn na, biodiesel

c xem l loi ph gia rt tt cho nhin liu diesel khong, lm gim ng k

lng kh thi c hi, v n l ngun nhin liu c th ti to c.

Vit Nam c nhiu ti nghin cu tng hp biodiesel t cc ngun

nguyn liu sn c trong nc nh du u nnh, du ht ci, du cao su, du

Jatropha, m c,v thu c kt qu kh tt. Tuy nhin v nn cng

nghip sn xut du m nc ta cn kh non tr, cha p ng c ngun

nguyn liu cho sn xut biodiesel quy m ln. Ngoi ra, nu sn xut

biodiesel t du n tinh ch th gi thnh kh cao, v cn nh hng n an ninh

lng thc. Do , vic tm kim ngun nguyn liu r tin, ph hp vi iu

kin ca t nc vn ang c tip tc nghin cu. Vi mc ch , vic tn

dng ngun du n ph thi, du thc vt phi thc phm v m c lm nguyn

liu cho tng hp biodiesel l c ngha thc t rt ln. Bi y l ngun

nguyn liu c tr lng tng i ln, li r tin, em li hiu qu kinh t cao.

Vic tn dng ngun nguyn liu ny cn gp phn bo v mi trng v sc

khe con ngi. Cc nghin cu v biodiesel trc y, ch yu tp trung vo

xc tc ng th. Xc tc ny cho chuyn ha rt cao, thi gian ngn, nhng

kh lc tch sn phm, v khng ti s dng c nn gi thnh sn phm cao.

V vy chng ti tin hnh nghin cu h xc tc :

- Nghin cu ch to axit rn ZrO2 bin tnh bng Zn v S

- Kho st cc yu t nh hng n hot tnh xc tc cho phn ng tng

hp biodiesel nh thi gian nung, nhit nung.

- Kho st cc yu t nh hng n hiu sut tng hp biodiesel t du

thc vt phi thc phm (C th y l t du Jatropha) vi h xc tc

ZrO2/ SO4 ZnO

- Thu hi v tinh ch glyxerin mt ph phm c gi tr ca qu trnh tng

hp biodiesel.

Chng 1: TNG QUAN

1.1. Tm kim ngun nng lng cho tng lai

Hin nay vn v nng lng ang l mt trong nhng mi quan tm

chnh ca th gii. u th k 21, nng lng ha thch cung cp hn 85 %

tng nng lng tiu th ton cu. Nng lng ha thch cung cp nng lng

cho nhng phng tin giao thng, cc nh my cng nghip, si m cc to

nh v sn sinh ra in nng phc v i sng con ngi. c rt nhiu d

on c a ra rng, vi tc tiu th nng lng ton cu hin nay th tr

lng du v kh t nhin s thng xuyn nm trn st gim mnh trong

sut th k XXI [57].

Hnh 1.1. D on v s bin i nhu cu s dng ba ngun nng lng chnh

t nm 1850 n nm 2050.

Trong tng lai s vn cn nhng ngun nng lng truyn thng nh

du m v kh t p ng nhu cu nng lng trn ton th gii. Tuy nhin

v nhng ngun nng lng l hu hn v gy ra nhng nh hng xu n

mi trng nn ngay t by gi mt vn ngy cng thc bch c t ra

l nng cao hiu sut s dng nng lng, cng nh tm kim nhng ngun

nng lng thay th, c bit l nhng ngun nng lng ti sinh c [56].

Mc d c nhiu ngun nng lng xanh v ang c con ngi sn

xut v pht trin nh: in nng c sn xut t hi nc trn mt bin, nng

lng t kh hiro, nng lng t sng bin (nhit nng bin), nng lng t

ngun nhit nng ca Tri t (a nhit), nng lng t gi, nng lng Mt

tri, nng lng ht nhn, [58] nhng vn cha c mt ngun nng lng

no kh nng thay th cho ngun nng lng ha thch truyn thng. Trn

th gii hin nay, c gn hai t ngi vn cha c tip cn vi nhng ngun

nng lng hin i ni trn. Mt trong nhng phng n c xem l kh thi

nht gii quyt bi ton tm kim ngun nhin liu thay th cho nng lng

ha thch l s dng cc loi nhin liu Sinh hc, c bit l biodiesel c

sn xut t ngun nguyn liu l cc loi du, m ng thc vt nhn c t

cc sn phm thin nhin.

1.2. ng dng du, m ng thc vt trong sn xut nhin liu

1.2.1. Sinh khi (Biomass): Sinh khi l tng trng lng ca sinh vt sng

trong sinh quyn hoc s lng sinh vt sng trn mt n v din tch, th tch

vng. Sinh khi l mt ngun nng lng c kh nng ti sinh, n c cha nng

lng ha hc, ngun nng lng t mt tri tch ly trong thc vt qua qu

trnh quang hp. Nhin liu sinh khi c th dng rn, lng, kh... khi c

t chy s gii phng nng lng [31].

Hnh 1.2. c lng sinh khi v cha s dng trn ton th gii.

1.2.2. Gii thiu chung v du, m ng thc vt

Du, m ng thc vt (Vegetable oil and animal fat): l cc lipit c

ngun gc t cc vt th sng. V bn cht Ha hc, c du v m ng thc

vt u c to thnh ch yu (~ 95 %) t cc triglyxerit ca nhng axit bo

c phn t khi ln, thng l C12 C18, v d nh axit oleic, axit linoleic, axit

palmitic, axit stearic,

Hnh 1.3. Mt phn t triglyxerit trong du ht ci Canola.

Ngoi cc triglyxerit, trong du, m ng thc vt cn c khong 5 %

axit bo t do, l loi axit n chc, mch thng v thng c s nguyn t

carbon chn. Cc axit bo khng no c th cha 1, 2 hoc 3 lin kt i, chng

d b oxi ho bi oxi khng kh lm cho du, m b hc ng (i, thiu), b

polyme ho to thnh mng, b kh v tr ni i chuyn thnh axit bo no.

Kh nng phn ng ca cc axit bo khng no tng cng vi s tng ca ni

i. Tnh cht ca du, m do thnh phn v bn cht ca cc axit bo quyt

nh. Ngoi cc axit bo t do, cn c mt lng nh photpho lipit, sp,

1.2.3. Chuyn ha du, m ng thc vt thnh nhin liu

Hin nay, du, m ng thc vt c mt vai tr quan trng trong cng

nghip ha cht v nhin liu. l ngun nguyn liu ln sn xut cc loi

dung mi, dc phm, nha, polyme, mc, sn, m phm v c bit l cc loi

nhin liu xanh nh biodiesel. Cc sn phm nhin liu c sn xut t du,

m ng thc vt v cc sn phm chuyn ha ca chng ang rt c quan

tm nghin cu bi kh nng ng dng lm nhin liu thay th cho cc loi

nguyn liu truyn thng. Mt s hng chuyn ha ch yu ca du, m ng

thc vt thnh nhin liu c tm tt nh sau:

1.2.4. Phng php este ha cho

Phn ng este ha cho hay phn ng trao i este (Transesterification)

l mt trong nhng phng php c tnh thng mi nht c th s dng sn

xut biodiesel. Cc loi ancol khc nhau nh metanol, etanol, propanol v

butanol u c th c s dng. Tuy nhin, metanol v etanol l c s dng

Biodiesel

Du, m ng thc

v t

- Diesel - Kh t (gasoline)

Nhi t phn (Cracking)

Este ha cho

rng ri nht, c bit l metanol do gi thnh r v mt vi u im khc trong

qu trnh vn chuyn v tin hnh phn ng [9]. Trong Ha hc Hu c c in,

thut ng transesterification (xem Hnh 1.4) c s dng m t mt nhm

phn ng quan trng m trong xy ra qu trnh trao i hp phn OR1 ca

este bi hp phn OR2 ca mt ancol, phn ng thng c xc tc bi axit,

baz hoc enzym [28].

Hnh 1.4. Phn ng este ha cho vit di dng tng qut.

Cc ng dng ca phn ng este ha cho khng ch dng li quy m

phng th nghim m cn m rng ra vi nhiu lnh vc thc t nhng quan

trng nht vn l trong sn xut biodiesel v glyxerin. Ngun du m thin

nhin ny c tinh ch loi b cc tp cht v tin hnh phn ng este ha

cho vi cc ancol trong s c mt ca xc tc. Ton b qu trnh l mt chui

gm ba phn ng lin tip v thun nghch vi cc sn phm trung gian l cc

mono- v diglyxerit.

Hnh 1.5. Phn ng este ha cho triglyxerit.

Cc qu trnh chuyn ha nhng phn t kch thc ln nh triglyxerit

thng phi thc hin nhng iu kin phn ng khc nghit v phi c xc

tc. Vo nhng nm 90 ca th k trc, s ra i ca vt liu mao qun trung

bnh c cu trc trt t (ordered mesoporous material) m ra nhng bc

pht trin t ph trong lnh vc xc tc, c bit l vi nhng chuyn ha ca

nhng phn t c kch thc cng knh.

1.3. Xc tc cho phn ng este ha cho tng hp biodiesel

1.3.1. Mt s khi nim c bn v nhin liu sinh hc

Nhin liu Sinh hc (biofuel): l mt trong s nhng loi nhin liu c

ngun gc t sinh khi, thut ng ny bao gm sinh khi rn, nhin liu lng v

cc loi gas Sinh hc khc. Chng l nhng cht t c bn cha carbon nm

trong chu trnh quang tng hp ngn hn. Nhin liu Sinh hc bao gm nhiu

th h, ni bt trong l th h u tin vi bioalcol, bioete, biodiesel, diesel

xanh, du thc vt, kh t tng hp, v.v[32].

Diesel Sinh hc (biodiesel): l hn hp cc alkyl este ca axit bo mch

di c sn xut t du thc vt hoc m ng vt, n c cc tnh cht tng

ng vi diesel c sn xut t du m v c th s dng trc tip trong cc

ng c diesel m khng cn phi thay i c cu ng c [6]. Biodiesel c

nhng u im chnh nh im chp chy cao, ch s xetan ln, nht thp,

tnh nhn cao, c th b phn hy Sinh hc, thn thin vi mi trng do trong

qu trnh s dng bc x t carbon monoxit, cng nh cc kh thi khc so vi

cc nhin liu ha thch thng thng [7].

1.3.2. c tnh ca biodiesel

1.3.2.1. So snh tnh cht ca biodiesel, diesel truyn thng v du thc vt

Cng ging nh diesel sn xut t du m, biodiesel c th s dng cho

cc ng c t trong. Biodiesel c th c s dng trong cc ng c t-nn

thng thng [43]. Ngoi ra, biodiesel cng c th c s dng di dng tinh

khit hoc pha trn vi diesel theo mi t l (k hiu l Bxx, v d nh B30 l 30

% biodiesel trong 70 % diesel) c th lm gim lng pht thi ht rn khi

ng c [44].

Bng 1.1 a ra mt s thng s vt l ca diesel, biodiesel v mt loi

du thc vt (Karamja). Ch s xetan ca biodiesel cao hn diesel cho thy kh

nng t chy nhin liu ca biodiesel tt hn. Cc gi tr t trng, nht v

ch s HHV (higher heating value) ca biodiesel tng i gn vi diesel, y

l nhng yu t quan trng quyt nh kh nng thay th cho diesel lm

nhin liu cho ng c t nn ca biodiesel. Ngoi ra, c th nhn ra rng

nht ca du thc vt ln hn rt nhiu so vi diesel, do vy khng th trc tip

s dng du thc vt thay th diesel c m phi chuyn v biodiesel.

Bng 1.1: Mt vi thng s v tnh cht vt l ca biodiesel, diesel truyn thng

v du thc vt.

STT Tnh cht Diesel nguyn cht

Du thc vt Karamja

Biodiesl

nguyn cht

1 T trng (gm/cc) 0,86 0,95 0,87

2 nht 4,98 8,10 6,22

3 Ch s HHV (kJ/kg) 44579 * 38500

4 Ch s xetan 47 * 50

5 im chp chy (oC) 74 * 153

Tuy nhin, c mt im khc bit ln trong s nhng tnh cht vt l ca

biodiesel v diesel truyn thng l im chp chy. Gi tr im chp chy ca

biodiesel ln hn rt nhiu so vi diesel.

1.3.2.2. u - nhc im khi s dng nhin liu biodiesel

S d vic nghin cu v pht trin cc quy trnh sn xut nhin liu Sinh

hc ni chung ang thu ht c s quan tm ca cc nh nghin cu l v trn

phng din l thuyt th vic s dng nhin liu Sinh hc khng lm cho hm

lng kh CO2 - nguyn nhn chnh gy ra Hiu ng nh knh, b tng ln trong

kh quyn. Qu trnh sn xut nhin liu sinh hc, v d nh biodiesel c m

hnh ha li trong Hnh 1.6. C th thy rng trong chu trnh sn xut v s

dng biodiesel th CO2 trong kh quyn ban u c nhng loi thc vt nh

u nnh pht trin hp th trong qu trnh quang hp.

Hnh 1.6. Chu trnh sn xut v s dng biodiesel.

Sau , du c chit xut t u nnh v c chuyn ha thnh

biodiesel. Khi biodiesel chy, CO2 v cc kh bc x khc c gii phng v

quay tr li kh quyn. Qu trnh ny khng lm tng thm hm lng CO2

trong khng kh bi sau cc loi cy trng s dng li CO2 pht trin. Tuy

nhin, khi nhin liu ha thch nh than hoc diesel b t chy th 100 %

CO2 gii phng ra s lm tng hm lng CO2 trong khng kh.

S dng biodiesel lm nhin liu s lm gim s pht thi kh CO ra

ngoi khng kh. th trn Hnh 1.7 m t s thay i hm lng kh CO bc

x t cc loi ng c s dng nhin liu diesel truyn thng v cc hn hp

nhin liu Bxx.

Hnh 1.7. S thay i hm lng kh CO v cc ht rn bc x t ng c t-

nn s dng diesel truyn thng v hn hp diesel-biodiesel Bxx.

Khi hm lng biodiesel trong hn hp Bxx tng th lng kh CO bc x

s cng gim bi trong biodiesel c nhiu oxy hn diesel nn phn ng oxi ha

gia CO v O2 din ra hon ton to thnh CO2. y l mt u im quan trng

ca biodiesel do CO l mt kh rt c, gy ra nhiu bnh v ng h hp.

Ngoi ra khng ch hm lng CO m hm lng cc ht kh thi rn bc x

cng gim i khi s dng biodiesel, nguyn nhn c th l do biodiesel c s

dng iu kin nhit cao hn nn trnh c s oxi ha khng hon ton

v tch t ca cc sn phm cha carbon to thnh cc ht thi rn.

Tuy nhin, vic s dng biodiesel lm cho hm lng kh thi NOx tng

ln do trong biodiesel th hm lng oxy nhiu hn so vi diesel truyn thng

nn trong cc qu trnh t chy th lng nhit ta ra rt ln, lng nhit ny

lm cho nhit ca cc vng khng kh tng ln rt nhanh v thc y cc

qu trnh oxi ha N2 (trong khng kh) thnh NOx.

Hnh 1.8. S thay i hm lng kh NOx v cc ht rn bc x t ng c t-

nn s dng diesel truyn thng v hn hp diesel-biodiesel Bxx.

Ngoi ra, vic s dng nhin liu biodiesel cng gy ra mt kh khn v

vn c cu ng c do n c th lm hng mt s b phn bng cao su v

khng d tng thch vi ng c, do vy khi hot ng th ng c b rung

ng mnh v nhanh hng hn.

Biodiesel hin nay c sn xut ch yu bi phn ng este ha cho

du, m ng thc vt. c mt ci nhn tng quan v nhng yu t tc ng

n phn ng v cc h xc tc v ang c s dng cho phn ng.

1.3.3. Cc yu t nh hng n phn ng este ha cho

1.3.3.1. nh hng ca hm lng axit bo t do

S c mt ca cc axit bo t do c nh hng kh nhiu ti qu trnh

este ha cho, c bit l trong trng hp s dng xc tc baz. Cc phn ng

este ha cho dng xc tc baz cn c hm lng axit bo t do < 3 %. Nu

hm lng axit bo t do > 3 % th cn s dng nhiu baz hn trung ha

FFA, ng thi sinh nhiu x phng v nc hn. X phng sinh ra lm tng

nht ca hn hp, to thnh gel v lm cho vic tch glyxerin tr nn kh khn

hn. Phn ng sinh ra nhiu nc c th lm cho metyl este b thy phn to ra

axit bo v metanol, do vy tiu tn nhiu xc tc hn v hiu sut phn ng b

gim i ng k [40].

1.3.3.2. nh hng ca nhit phn ng

Nhit c vai tr thc y tc phn ng este ha cho, v d nh i

vi phn ng metanol phn du ht bng s dng xc tc sulfuric axit th cc

gin trn Hnh 1.9 ch ra rng chuyn ha tng ln khi nhit tng.

Nguyn nhn l do khi nhit tng ln th nht ca du gim i, cc phn

t tr nn linh ng hn v kh nng tip xc xy ra phn ng tng ln. Tuy

nhin khi nhit tng ln vt qu mt ngng ti u no th nng sut to

ra biodiesel s gim v nhit phn ng cao cng thc y cc phn ng x

phng ha v thy phn metyl este. Tuy nhin, nu nhit phn ng t n

im si ca metanol, s c nhiu bong bng metanol c hnh thnh, do o s

hn ch s chuyn khi trn b mt phn cch pha. ng thi metanol b bay

hi lm gim hiu sut phn ng v gy nhim mi trng bi metanol rt

c hi. Theo mt s nghin cu th cc phn ng s dng xc tc baz tin

hnh nhit thp hn so vi cc phn ng s dng xc tc axit [15].

Hnh 1.9. nh hng ca nhit phn ng v thi gian phn ng n

chuyn ha ca du ht bng (cottonseed oil) [47].

1.3.3.3. nh hng ca thi gian phn ng

Freedman [48] nghin cu thy rng tc chuyn ha tng theo thi

gian phn ng. Ban u phn ng din ra chm do s trn ln v phn tn ca

metanol vo du, m. Sau mt thi gian th tc phn ng tng ln rt nhanh.

Tuy nhin, nu thi gian phn ng qu lu th c th xy ra phn ng ngc,

phn hy metyl este v lm gim hiu sut phn ng. ng thi, trong Cng

nghip th thi gian phn ng qu lu cng s tc ng n yu t kinh t. Vi

xc tc axit th thi gian phn ng chm hn so vi xc tc kim. Xc tc ng

th thc y phn ng nhanh hn so vi xc tc d th.

1.3.3.4. nh hng ca t l

Trong phn ng este cho ha, t s hp thc ca ancol v du 3 mol

ancol v 1 mol du. V vy, bng cch s dng lng d ancol, n s u tin to

ra alkyl este. Mc d vy, nu dng d nhiu ancol qu th s gy kh khn cho

vic tch v tinh ch sn phm. T l ph thuc vo loi xc tc. Vi

vic s dng KOH nh mt xc tc baz ng th th i hi t l

khong c 6 : 1, trong khi vi mt xc tc baz d th nh SrO hoc CaO th

t l ti u c th l 12 : 1 hoc ln hn mt cht [19, 20]. Khi cc xc tc axit

c s dng th t l ca ancol vi du i hi thng phi ln hn na.

1.3.3.5. nh hng ca hm lng xc tc

Hm lng ca xc tc cng nh hng nhiu n chuyn ha ca

glyxerit v hiu sut ca phn ng to metyl este. Thng thng th khi tng

hm lng xc tc th chuyn ha v hiu sut phn ng cng tng ln, tuy

nhin n mt gi tr ti u no th cc gi tr ny s gim.

1.3.4. Xu th s dng xc tc axit rn d th cho phn ng este ha cho

Phn ng este cho ha c th c tin hnh nh l mt qu trnh c

hoc khng xc tc. Cc xc tc axit, baz v enzym l ba loi xc tc c

nghin cu cho qu trnh sn xut biodiesel. Vic sn xut biodiesel s dng

xc tc enzym - baz thu ht c nhiu s quan tm trong nhng nm gn

y do enzym chu c cc axit bo t do v nc trong du, trnh to ra x

phng v do vic tinh ch biodiesel v glyxerin l d dng hn [36, 37], Tuy

nhin, cc enzym c s dng trong phng php sn xut biodiesel mang tnh

thng mi li c gi thnh cao. Xc tc c s dng cho phn ng este ha

cho c th l xc tc ng th [11, 12] hoc xc tc d th [1321]. u im

ca vic s dng xc tc ng th l phn ng c th tin hnh trong thi gian

ngn hn v iu kin phn ng tng i m du [7], tuy nhin cc thit b s

dng cho phn ng cn phi chu c s n mn tt. Nhc im ln nht ca

xc tc ng th l chng khng th ti s dng hoc ti sinh, thm ch xc tc

c th b tiu th trong qu trnh phn ng. Ngoi ra vic tch xc tc khi sn

phm rt kh khn, dn n nhng chi ph sn xut cao hn [23]. Hn na, cc

qu trnh s dng xc tc ng th khng thn thin vi mi trng bi c mt

lng ln nc thi c hi c to ra trong qu trnh tch loi sn phm [24].

Do vy, cn quan tm hn n vic pht trin cc xc tc axit rn nh l

mt gii php thch hp khc phc nhng vn lin quan n cc xc tc

c s dng trc nay nh xc tc ng th v xc tc c tnh base. u

im ca xc tc axit rn d th l khng b tiu th hoc ha tan trong phn ng

v do c th d dng tch loi khi sn phm. Kt qu l sn phm khng

cha cc tp cht ca xc tc v chi ph ca giai on tch loi cui cng s

c gim xung, qu trnh cng c th c thc hin lin tc. Xc tc c th

d dng ti sinh v ti s dng, ng thi cng thn thin vi mi trng hn

do khng cn x l trong giai on tch loi [26]. Nhiu loi hiroxit kim loi

[15, 25], phc kim loi [27], oxit kim loi [1320] v support [9, 21] v ang

c th nghim v kim chng v hot tnh xc tc ca chng i vi phn

ng ester ha cho triglyceride v nhn c nhiu kt qu kh thi.

Tuy nhin, mt trong nhng vn ln lin quan n xc tc d th l s

hnh thnh ca ba phase gia xc tc vi ancol v du dn ti nhng gii hn

khuch tn, do lm gim tc phn ng [38].Mt phng n khc phc

vn chuyn khi i vi xc tc d th l s dng mt lng nht nh dung

mi h tr (co-solvent) thc y kh nng trn ln ca du v metanol, qua

y nhanh tc phn ng. Tetrahydrofuran, dimetyl sulfoxit, n-hexan v

etanol c s dng thng xuyn hn vi vai tr ca mt dung mi h tr

trong phn ng ester cho ha ca du thc vt v metanol vi xc tc rn. Mt

phng n khc thc y cc qu trnh chuyn khi lin quan ti xc tc d

th l s dng cc cht hot ha cu trc (structure promoter) hoc cc xc tc

cht mang c th to ra din tch b mt ring ln hn v nhiu mao qun

hn, thc y kh nng thu ht v phn ng vi cc phn t triglyxerit c kch

thc ln.

1.4. Vt liu mao qun trung bnh cu trc trt t

1.4.1. Gii thiu v vt liu mao qun

a s cc vt liu u c mao qun v qu thc l rt kh khn nu nh

chng ta mun tm hoc tng hp mt cht rn hu nh khng c mao qun.

Ngi ta bit rng tt c nhng tnh cht vt l nh t trng, dn in v

sc bn vt liu u ph thuc vo cu trc mao qun v s khng ch trng

thi mao qun c tm nh hng quan trng n nhiu ng dng trong thc t

ca vt liu.

Hnh 1.10. Gin mt ct ca mt vt liu mao qun

Bng 1.2: Phn loi vt liu mao qun rn theo kch thc mao qun.

Phn loi vt liu c im chung V d

i mao qun

(macroporous)

dpore > 500

Loi vt liu ny hin nay c nghin

cu kh nhiu do c tnh chn lc cao

trong vai tr lm xc tc chuyn ho

cc cht c khi lng phn t cao, cu

trc phn t cng knh.

Thy tinh

Mao qun trung bnh

(mesoporous)

20 dpore 500

Loi vt liu ny l vt liu mao qun

quan trng bc nht, c rt nhiu ng

dng. Trong cng nghip ho hc, vt

liu mao qun trung bnh c ng dng

ln nht l lm cht xc tc v vt liu

hp ph.

MCM-41

SBA-15

Vi mao qun

dpore < 20

y l vt liu mao qun c ng

knh mao qun b hn 2 nm. Vt liu

Zeolite

(microporous) ny c ng dng ln trong vic lc kh

trong mi trng phng th nghim.

Nh kch thc mao qun b, n s

tng t nh 1 ci by c th gi li

cc bo t, vi khun trong khng kh.

Ngoi ra n cn c rt nhiu ng dng

khc.

c bit, cc vt liu mao qun rn c bit n vi vai tr nh cht hp

ph, cht xc tc v cht mang xc tc hiu qu do c din tch b mt ring rt

ln. Theo quy c ca IUPAC, vt liu mao qun c th c chia thnh ba loi

da vo kch thc mao qun (dpore) ca chng: vt liu i mao qun, mao

qun trung bnh v vi mao qun. Nhiu loi vt liu mao qun nh st tr

(pillared clay), nhm anodic, ng carbon v carbon mao qun c cu trc tng

t c nghin cu v trnh by trong nhiu ti liu [50].

Trong h vt liu vi mao qun, c bit n nhiu nht l cc zeolit,

chng l cc aluminosilicat tinh th hirat vi s phn b kch thc vi mao

qun hp v ng u. c bit, cc zeolit thu ht c nhiu s quan tm

mnh m bi hot tnh xc tc tt. Chng c th thc hin nhng vai tr nh l

xc tc axit hoc baz hoc xc tc cho cc phn ng oxi ha - kh trong rt

nhiu cng ngh hin i. Mt s ng dng trong cng nghip ca cc zeolit c

th k ra nh l zeolit A, X ch yu c s dng trong lnh vc trao i ion,

lm khan kh (v khng kh); zeolit Y, ZSM-5 trong cracking du m, ng

phn ha chn lc hnh hc ca cng nghip lc ha du, mordenit trong ng

phn ha parafin nh (C5 - C6) [41].

Tuy nhin, nhc im ln nht ca zeolit l chng c kch thc mao

qun nh, ch khong c 10 v cc zeolit th hin rt r hn ch ca mnh khi

trong cc qu trnh phn ng c s tham gia ca nhng tc nhn i phn t.

c bit l trong cc h thng pha lng thng c s dng tng hp cc

ha cht tinh khit th nhng gii hn v s chuyn khi l rt kht khe i vi

cc vt liu vi mao qun rn. Hin nay, nhng n lc ci thin s khuch tn

ca tc nhn phn ng ti cc tm xc tc c tp trung vo vic lm gia tng

kch thc mao qun zeolit, gim kch thc tinh th zeolit hoc b sung cc h

mao qun trung bnh vo cc tinh th vi mao qun. Mt hng nghin cu quan

trng l tp trung vo vic m rng kch thc mao qun vo phm vi mao qun

trung bnh, to iu kin cho cc phn t c kch thc ln c th xm nhp vo

h thng mao qun thc hin phn ng ti v sau sn phm d dng ri

khi h thng mao qun [41].

C mt s nghin cu cho thy rng trong qu trnh loi nhm ca zeolit

bng hi nc th cc l mao qun trung bnh vi kch thc dao ng trong

khong 100 200 c hnh thnh bn trong cu trc zeolit [41]. Tuy nhin,

vi s xut hin ca cc l mao qun c kch thc ln trong mt din tch nh

nh bn trong cu trc zeolit s dn ti s ph hy cu trc tinh th ca zeolit.

Hnh 1.11. M t cc loi mao qun c hnh thnh trong cu trc zeolit

1.4.2. Vt liu mao qun trung bnh

Hin ti, nhng nghin cu ch to vt liu mao qun trung bnh c cu

trc trt t ang c lin tc tin hnh v pht trin trn ton th gii. Nhng

u im quan trng ca loi vt liu ny l chng c h thng mao qun ng

nht, kch thc mao qun rng hn so vi cc zeolit v din tch b mt ring

rt ln (khong 500 - 1000 m2/ g), trn b mt vt liu c cha nhiu tm hot

ng, do vy tc nhn phn ng d c hot ha, thc y phn ng din ra

nhanh v hiu qu hn [50].

Trong thp nin cui ca th k 20, cc nh khoa hc hng Mobile-Oil

pht minh ra vt liu mao qun trung bnh M41-S, s ra i ca cc vt liu ny

to nn bc t ph mnh m trong lnh vc khoa hc vt liu xc tc. Vt

liu MCM-41 l i din tiu biu ca h vt liu mao qun trung bnh, c

nhiu ng dng trong nhiu quy trnh cng ngh Ho hc, Ho du [42].

c im quan trng nht ca cc vt liu mao qun trung bnh trt t l

chng c mao qun ng nht, kch thc mao qun rng, din tch b mt

ring ln, do vt liu s cha nhiu tm hot ng trn b mt nn d dng

tip cn vi tc nhn phn ng. Tuy nhin, vt liu mao qun trung bnh khng

phi l vt liu tinh th. Xt v mi quan h xa th cc mt mng, s sp xp cc

mao qun, c phn b theo quy lut tun hon nh trong mng tinh th,

nhng nhn gc gn th cc phn t (ion, nguyn t, nhm nguyn t,)

li lin kt vi nhau mt cch v nh hnh. Nh vy c th xem vt liu mao

qun trung bnh l vt liu gi tinh th.

Mt cu hi t ra l ti sao cc vt liu mao qun trung bnh c tng

hp khng dng tinh th? Cc nh khoa hc cho rng tinh th ca vt liu

lun lun c mi quan h vi mt mng (s nguyn t trong mt nm3:

Framework Density, FD). Nm 1989, Brunner v Meier nhn thy rng cc cu

trc tinh th cha nguyn t T (nguyn t trong cu trc t din - tetragonal)

u phi tun theo mt quy tc nghim ngt gia FD v kch thc vng T

(vng O) cc tiu (MINR: Minimum ring). Thc vy, cc oxit tinh th vi cu

trc MINR= 4 v ng vi khong trng cc i trong vt liu ~ 0.5. Cc vt liu

mao qun trung bnh vi phm quy lut ngha l khong trng > 0.5 v FD

nh nn vt liu mao qun trung bnh trt t khng th l vt liu tinh th. Mun

tr thnh vt liu tinh th ngi ta tm cch gia tng FD ca mng v lm gim

bt rng ngha l mng ca n phi c cu to c hn, c kh nng to ra

cc n v cu trc th cp SBU dng vng 3(T) hoc 3(O) [2].

S ra i ca vt liu mao qun trung bnh nh du mt bc pht

trin t ph trong lnh vc xc tc. Hng lot cc qu trnh lin quan n phn

ng ca nhng phn t c kch thc ln c thc hin d dng. Phn ng

c thc hin ngay bn trong mao qun, tc nhn phn ng c hot ha bi

cc tm hot ng trn thnh mao qun v tip cn d dng vi cc tc nhn

khc thc hin phn ng do khng gian phn ng hp.

Mt t im quan trng khc ca loi vt liu ny c nhiu ng dng trong cc

phn ng ha hc l kch thc ca mao qun th cp nh hn kch thc mao

qun s cp.

to ra h thng mao qun cn loi b cht to cu trc chim y

khong trng bn trong. C rt nhiu phng php loi b cht to cu trc nh:

- Nung vt liu.

- Chit bng dung mi.

- Dng l vi sng.

- Dng cht lng qu ti hn.

Trong hai phng php thng dng l nung v chit bng dung mi.

1.4.3. Gii thiu v nguyn t zirconi (Zr) v zirconi ioxit (ZrO2)

Nguyn t zirconi

Zirconi l mt kim loi rt km hot ng. Trong t nhin zirconi tn ti

dng khong vt chnh cng vi oxit silic l zicon (ZrSiO4). nc ta c

nhiu sa khong zicon, tp trung ch yu ven bin Qung Ninh v cc tnh

min Trung.

Zirconi l nguyn t thuc nhm IVB vi cu hnh in t:

1s2 2s

22p

63s

23p

63d

104s

24p

64d

25s

2

Zirconi c mu trng bc, nhit thng tinh th kim loi c mng

li lc phng (dng ) v nhit cao c mng li lp phng tm khi

(dng ).

Zirconi kh bn vi khng kh v nc nh c lp oxit ZrO2 mng bo v

v bn c vi cc tc nhn n mn.

Zirconi ch hot ng ho hc khi nhit cao: Tc dng vi O2 to ra

ZrO2 v vi halogen X2 to ra ZrX4 5. Trong cc hp cht ca zirconi, trng

thi oxi ho c trng v bn nht l + 4. l do ion Zr 4+ c cu hnh electron

bn ca kh him (Kr).

Zirconi ioxit (ZrO2)

ZrO2 l l cht rn mu trng, tn ti di mt s dng tinh th khc

nhau. Dng tinh th n nghing ca ZrO2 tn ti trong t nhin di dng

khong baledeit c cu trc tinh th khng ng u vi s phi tr bng 8.

iu kin bnh thng cu trc n nghing ca tinh th ZrO2 c th hin qua

cc thng s:

a = 5,15 b = 5,21 c = 5,3 = = 900 900

ZrO2 cng, kh nng chy v bn nhit [6]. S chuyn i hon ton cu

trc gia dng t din v dng n nghing din ra khong nhit 1193-

12000C. Qu trnh chuyn pha cu trc cng c th xy ra iu kin nhit

thp khong 20-1000C nhng p sut ca qu trnh phi l 37 KPa 15.

Theo nhiu ti liu chng minh th tinh th ZrO2 trng thi t din

c xem l mt oxit rn c tnh axit kh mnh c th s dng lm cht mang

cho cc loi cht xc tc s dng trong qu trnh ng phn ho, c bit l khi

c sunfat ho 11, 44.

Cc yu t nh hng n vic tng hp zirconi ioxit

Zirconi ioxit c iu ch bng cch nung zirconi hiroxit nhit

cao.

Zirconi hiroxit tn ti dng kt ta trng nhy, c thnh phn bin i

vi cng thc l ZrO2.nH2O. Kt ta khi mi to thnh cha nhiu nhm cu

OH dng , qua thi gian b mt nc, n tip tc b polime ho tr thnh dng

, cha nhiu cu oxi 35

Dng Dng

Hnh 1.12. Dng v dng ca zirconi hiroxit

Dng hot ng hn dng . Nhit v mi trng kim d lm dng

chuyn sang dng .

Cc tnh cht ca zirconi hiroxit ph thuc rt nhiu vo mui nguyn

liu u v gi tr pH ca dung dch trong qu trnh thc hin kt ta hiroxit

15, 18, 41. i vi cu trc, gi tr pH to kt ta c nh hng r rt nht n

s to thnh pha tinh th ca ZrO2. S iu chnh v gi tr pH cui cng c nh

hng c th nht n cht lng ca zirconi hiroxit. Ti gi tr pH < 7 trong

tinh th mui ZrOCl2.8H2O xut hin ion tetrameric Zr4(OH)8.16H2O8+ (hnh

4), phn ng polime ho din ra khi a baz vo dung dch mui.

Ngay t giai on u, lng baz a vo s thc y vic thay th bn

phn t nc ca ion tetrametric bng cc nhm OH to cu ni O...H, sau

hnh thnh lin kt. Cng thc chung ca mi phn t polime to thnh trong

qu trnh hnh thnh kt ta l ZrOx(OH)4-x .yH2On. Cng thc ny th hin

mi lin quan gia hm lng oxi, OH v hm lng kt ta thu c khi s

dng mui nguyn liu l ZrOCl2.8H2O.

Zr ZrZr

O

H

H

O

O Zr

Cu to ca dng gel sy kh qua phn tch TG thng c cng thc

chung l: ZrO2.1,23H2O-ZrO2.1,86H2O. Cng thc c th c vit li di

dng [Zr4(OH)8]8+

th hin s lin kt gia cc mt xch trong mch polime.

nh hng ca ngun mui nguyn liu n cht lng ca hiroxit l

kh r. Mui ZrOCl2.8H2O dng tinh th c cha ion tetrametic v anion Cl .

Anion Cl khng lin quan n phn ng polime ho trong qu trnh iu ch

hiroxit v nh hnh. Tuy nhin, mt lng nh anion Cl vn cn lu li

trong kt ta, lng anion ny s gim khi pH tng, do vy rt cn thit phi

to kt ta gi tr pH ln.

Vi mui ZrO(NO3).xH2O s xy ra qu trnh to phc khc vi qu trnh

polime ho ca mui ZrOCl2.8H2O. Mi nguyn t Zr c lin kt vi NO3 to

thnh mt xch [Zr(OH)2(OH)2(NO3)]+ , mi mt xch ny c lin kt vi

nhau qua lin kt hiro ca H2O vi anion NO3, hiroxit v nh hnh nhn

c trong thnh phn cu to vn c mt ca anion NO3. Nh vy, s khc

nhau trong cu trc dng gel nhn c l do vai tr ca anion NO3 v Cl c

trong mui nguyn liu u.

Gi tr pH khng n nh trong sut qu trnh hnh thnh kt ta l yu t

c nh hng phc tp n cht lng kt ta. Trc ht n s nh hng ti s

bc ca phn ng polime ho, trong mt khong pH thay i rng tng dn t

pH axit sang pH baz c rt nhiu hin tng ny sinh v lm cht lng kt

ta b nh hng.. Mt khc theo G. Ertl v cc cng s 18 th t s gia pha

t din v pha n nghing thay i theo s thay i ca pH trong qu trnh kt

ta ca zirconi hiroxit. Khi tng pH t 6-10 th pha t din trong ZrO2-SO42

tng t 73% n 100%.

1.4.4. Gii thiu v Cc yu t nh hng n xc tc ZrO2-SO42

Thc nghim chng minh rng ZrO2 khi s dng trc tip lm cht mang

xc tc th c nhiu mt hn ch bi din tch b mt ring rt b (20m2/g

nhit nung 700oC) v cu trc pha t din trong tinh th khng ng u, dn

n hot tnh xc tc khng cao. khc phc nhng nhc im trn, ngi ta

tin hnh sunfat ha mu trc khi s dng xc tc, do cc oxit c sunfat ha

c hot tnh cao i vi cc phn ng xy ra theo c ch cacbocation. S c mt

ca ion SO42-

trn b mt lm n nh pha t din chng li s chuyn pha

cu trc, do vy din tch b mt ring ca cht mang cng c tng ln so vi

mu cha c sunfat ha.

nh hng ca cht nn n cht lng xc tc

Qu trnh sunfat ho c th thc hin trn nn zirconi hiroxit v zirconi

ioxit nhng theo Jing Qi Li v cc cng s [28] th sunfat ho trn nn zirconi

hiroxit s cho din tch b mt ring ln v s mt mt lu hunh trong qu

trnh nung nh hn so vi khi thc hin trn nn zirconi ioxit (c nung t

zirconi hiroxit 5000C trong 4 gi).

nh hng ca ngun lu hunh s dng trong qu trnh sunfat ho

Theo kt qu ca J. Q. Li v cc cng s 28 th mu c hot ho bng

H2SO4 cho din tch b mt ring cao hn 2-7 ln so vi cc mu c sunfat

ho bng SO2 hoc H2S. iu ny c gii thch bi khi hot ho nn bng

SO2 hoc H2S th s tng tc khng xy ra. Cn vi H2SO4, thc t cho thy s

phn t nc mt i trn mt mol lu hunh a vo gim dn theo thi gian

sunfat ho, ngc li hm lng lu hunh trn cht mang li tng dn. iu

chng t tnh axit ca dung dch H2SO4 xc tin cho phn ng tch nc

ca zirconi hiroxit, n t phn ng vi nn tch nc v to ra cc nhm

sunfat, nh vy n s gp phn lm gim s chuyn pha cu trc ca nn, to s

n nh v lm tng din tch b mt ca cht xc tc thu c. Ngoi ra, s

dng ngun SO2 hoc H2S sunfat ho mu th sau khi ti sinh, xc tc s

khng cn l superaxit na 38.

Khi s dng (NH4)2SO4 sunfat ho mu s cho xc tc c din tch b

mt ring ln hn so vi s dng H2SO4 18. Tuy nhin qu trnh a kim loi

ln b mt cht mang, v d nh Ni2+, ion kim loi d to phc vi ion NH4+,

lm gim phn tn ca kim loi ln b mt cht mang, t lm gim hot

tnh ca xc tc.

Nh vy, ngun cha lu hunh cho qu trnh sunfat ho zirconi hiroxit

c tnh u vit nht l dung dch (NH4)2SO4 (1N hay 0.5M).

nh hng ca cc phng php sunfat ho n hot tnh xc tc

Theo mt s nh nghin cu, ng cong biu din mi quan h gia

hm lng lu hunh v hot tnh xc tc c mt im cc i, chng t mt

trong nhng yu t nh hng n hot tnh xc tc l hm lng lu hunh.

Vn chnh trong vic a ion SO42

ln b mt cht mang mt cch

hiu qu khng ch l xc nh thi gian cn thit dung dch ngm c vo

cht rn, khi lng thc ca dung dch c hp th m cn ph thuc vo

phng php sunfat ho, khi lng cht nn, xp ca cht rn, kch thc

v phn b kch thc ht rn... V vy, tm phng php ti u m bo

khi lng lu hunh trn b mt xc tc l mt vn c cc nh khoa hc

rt quan tm.

C hai phng php sunfat ho thng c s dng hin nay l phng

php thm v phng php ngm tm.

- Phng php thm: L phng php lc dung dch H2SO4 qua

lp cht nn zirconi hiroxit trc khi nung.

Phng php ny rt kh nh gi hm lng lu hunh v gy

lng ph dung dch thm H2SO4. Theo phng php ny, trong trng hp hm

lng lu hunh trn b mt vt qua % tnh ton ban u, c th iu chnh li

bng cch tng nhit nung, nhng nh vy nhng tnh cht khc ca cht

mang s b nh hng.

- Phng php ngm tm: Ngm tm cht rn trong dung dch

H2SO4 trong mt khong thi gian nht nh, sau cho bay hi t t nhit

sy thp.

u im ca phng php ny l c th iu chnh c hm

lng lu hunh tng i thng qua khi lng thc ca H2SO4 ngay trong

giai on hp ph ln b mt cht mang, ng thi c th thm vo mt lng

axit ph b tr cho s mt mt xy ra khi nung. Ngoi ra trong qu trnh

ngm xy ra phn ng ho hc gia b mt cht mang v ion SO42

lm tng

din tch b mt cht mang v n nh hm lng lu hunh trn cht mang.

Nh vy, theo cc kt qu thc nghim th s mt lu hunh trn b mt

cht mang xy ra trong c hai phng php thm v ngm tm, tuy nhin iu

ch theo phng php ngm tm th hm lng lu hunh b mt t hn v xc

tc c s n nh hn.V vy, sunfat ho zirconi hiroxit theo phng php

ngm tm s cho hiu qu kinh t cao hn cc phng php khc.

nh hng ca nhit nung

Kt ta ZrO2.nH2O sau khi c lc ra, sy kh vi tc gia nhit

thp, qua giai on nung th cu trc v nh hnh s chuyn sang cu trc t

din khi nhit t 4000C. Ngi ta nhn thy, ngay c khi cu trc tinh th

t din th trong phn t vn cn tn ti mt lng nh nc. Khi tng n nhit

650-8000C th cu trc t din bt u b ph v v chuyn sang cu trc n

nghing. Hm lng nc trong cu trc b loi ht mt cch trit khi tin

hnh nung nhit ln hn 10000C. Do , nhit nung nh hng kh ln

n hot tnh xc tc.

1.4.3. Cu trc v tnh cht axit ca superaxit ZrO2-SO42

Superaxit rn c nh ngha l mt vt liu rn c cng axit mnh

hn c axit H2SO4 100%.

Cng axit cao nht ca ZrO2-SO42

o c bng phng php s

dng cht ch th cho kt qu l H0 16.00. Nhng cng c nghin cu khc

cho rng H0 13.16 v gn y l H0 12.0 o bng phng php quang ph

k 18. Cc kt qu khc nhau c th l do khng cng phng php iu ch

cng nh phng php o. Mc d vy, ZrO2-SO42

vn c xem l mt

superaxit rn bi cng axit mnh hn H2SO4 100%.

Theo mt s tc gi th tm axit Lewis ng vai tr quan trng v lin

quan trc tip n hot tnh xc tc. Gn y, mt s nghin cu cho bit t l

tm axit Bronsted / Lewis ph thuc vo phng php iu ch, mc hidrat

ho v quan trng nht l ch nung 40, 44.

Ngi ta s dng phng php hp ph v gii hp piridin kho st

bn cht tm axit ca xc tc ZrO2-SO42 . c s kho st chnh xc hn cc

tc gi so snh vi kt qu phn tch ca H-MOR th nhn thy cng axit

ca zeolit ln hn rt nhiu so vi ZrO2-SO42 . Nh vy, kt qu nhn c

khng ph hp vi thc nghim. Do , ch c th kt lun c rng phn ln

cc trung tm axit ca ZrO2-SO42

l thuc loi tm Lewis. Ta khng th dng

phng php hp ph v gii hp piridin nh gi chnh xc cng axit

mnh ca ZrO2-SO42

.

K thut phn tch TPD hp ph v gii hp NH3 c cho l c th

nh gi c tng s tm axit mnh v cng axit rn.

T nm 1992 c cng b rng vt liu mao qun trung bnh vi cu

trc l xp trt t rt c kh nng ng dng trong cc qu trnh xc tc, hp ph

v tch cht bi chng c din tch b mt cao, th tch l xp ln v cu trc l

xp ng u nhng chng li c tnh axit yu [26, 33]. tng tnh axit ca

vt liu ny, zirconi sunfat ha c mang trn cc vt liu mao qun trung

bnh nh MCM-41 [35, 42], FSM-16 [30]... S dng phng php ny, c

nhiu vt liu c tng hp thnh cng, c axit mnh hn so vi vt liu

mao qun trung bnh thng thng. Tuy nhin, thnh cng ny vn c nhng

hn ch. Cc l xp ca vt liu mao qun trung bnh b ZrO2-SO42-

bt kn, lm

gim din tch b mt. Hn na, nhng vt liu tng hp c vn th hin tnh

axit yu hn ZrO2-SO42-

thng thng. V vy, vt liu zirconi sunfat ho c cu

trc mao qun trung bnh vi lc axit mnh v din tch b mt ln ang rt

c quan tm nghin cu.

Hnh 1.13. Cu trc ca super axit rn ZrO2 SO42

c nhiu nhm nghin cu tng hp thnh cng zirconi sunfat ho

mao qun trung bnh. Schuth v cng s 14 tng hp thnh cng zirconi

oxo photphat xp vi din tch b mt ln bng phng php s dng cht hot

ng b mt. Jentoft v cng s [45] tng hp thnh cng zirconi sunfat ha

vi cu trc mao qun trung bnh bng cch s dng cht to cu trc l

hexadexyltrimetyl amoni bromat (CATB), mt s tc gi khc th s dng cht

to cu trc l amin. Tuy nhin, d zirconi sunfat ho vi cu trc mao qun

trung bnh c tng hp thnh cng nhng hot tnh xc tc ca n vn cn

thp hn hoc l ch tng ng so vi zirconi sunfat ha thng thng trong

qu trnh ng phn ha n-parafin [23, 45]. Hn na, bn nhit ca cu

trc meso v kh nng chng li s mt hot tnh ca zirconi sunfat ho mao

qun trung bnh vn cn thp 35.

Trong khun kh lun vn ny, chng ti tng hp v nghin cu xc

tc zirconi sunfat ha c cha Zn

Chng 2: THC NGHIM

2.1. Tng hp vt liu

2.1.1. Ha cht - Cht hot ng b mt P123 - ZrOCl2.8H2O

- Amoni sunfat (NH4)2SO4

- Axit clohiric HCl 37 % - Zn(CH3COO)2 - Nc ct hai ln

2.1.2. Thit b :

- Thit b khuy t

- Autoclave.

- L nung nhit cao

- T sy

- Bnh cu hai c 250(ml)

- Nhit k

- Sinh hn hi lu

Hnh 2.1: Thit b phn ng trong phng th nghim.

2.1.3. Quy trnh tng hp

Ha tan 1,0 g Pluronic P123 vo 30 mL nc ct, thu c mt dung

dch trong sut tip thm 2,0 g ZrOCl2.8H2O v 0,06g Zn(CH3COO)2

cho vo bnh cu hai c ri tin hnh nh t dung dch NH3 vo hn hp

trn ri tin hnh khuy u hn hp trong 6h nhit 400C sau thy

nhit trong autoclave 100 oC trong 24 gi sn phm c lc sy v nung

6000C trong 5h ri thc hin trao i in vi 0,05 g (NH4)2SO4 .Sn phm

sau khi nung c tin hnh trao i ion vi (NH4)2SO4 nhiu ln tng

hm lng sunfat. Cui cng l lc tip, sy v nung 5500 C trong 5h

Hnh 2.2. S kh i tng hp SO42-/ ZrO2 - ZnO.

ZrOCl2.8H2O Khuy u trong 15

pht

Khuy u hn hp

trong 6 gi 40 oC

Zn(CH3COO)2

Dung dngNH3 long

Thy nhit trong autoclave 100 oC

trong 24 gi

Sn phm c lc, sy,

nung 650 oC trong 5 gi

Thc hin trao i ion

vi (NH4)2SO4 Lc, sy, nung tip

550 oC trong 5 gi

SO42-

/ZrO2 ZnO

Ha tan P123 vo nc ct

2.2. c trng tnh cht vt liu

Vt liu tng hp c c trng tnh cht bi cc phng php nh

Nhiu x X-ray [5], nh hin vi in t truyn qua TEM [5], hp th v gii

hp N2 [2], ph hng ngoi IR [2], gii hp NH3 theo chng trnh nhit

[4].

2.2.1. Phng php nhiu x X-ray

Chm tia Rnghen i qua tinh th b tn x bi cc nguyn t trong

tinh th. Hin tng ny xy ra trn lp v in t ca cc nguyn t. Cc

nguyn t tr thnh cc tm pht sng cu, cc sng ny s giao thoa vi

nhau. Cu trc tinh th s quyt nh v tr hnh hc cng nh cng ca

cc cc i giao thoa. V vy, mi cu trc tinh th s c mt nh nhiu x

tia X c trng.

Theo l thuyt cu to tinh th, mng tinh th cu to t nhng

nguyn t hay ion c phn b mt cch tun hon trong khng gian theo

quy lut xc nh. Khong cch gia cc nguyn t hay ion trong tinh th

khong vi Angstrom (c bc sng tia X). Khi chm tia X ti b mt tinh

th v i vo bn trong th mng tinh th ng vai tr nh mt cch t nhiu

x c bit. Cc tia tn x t nguyn t hay ion khc nhau nu tho mn mt

s iu kin nht nh s giao thoa vi nhau.

Giao thoa l hin tng tng cng bin dao ng nhng im

ny v gim yu cng dao ng nhng im khc trong khng gian do

s chng cht ca hai hay nhiu sng kt hp cng lan truyn n cc im

.

Phng trnh Vulf-Bragg

Chiu chm tia X vo tinh th to vi mt phng tinh th mt gc ,

khong cch gia cc mt phng tinh th l d nh c biu din trn hnh

18.

Hnh2.3: S phn x tia X trn cc mt tinh th

Gi s chm tia X c bc sng xc nh chiu vo mu cht th

kh nng phn x cc i ph thuc vo gc gia tia X chiu vo v mt

phng tinh th. Nu tng u n tng ng vi cc gi tr n = 1, 2, 3... th

s phn x s cc i tng ng vi cc gi tr ca nh sau:

1 = arsin 1.

d2

2 = arsin 2.

d2

3 = arsin 3.

d2

... n = arsin n.

d2

S phn x tng ng vi n = 1 c gi l s phn x bc 1, s phn

x tng ng vi n = 2 c gi l s phn x bc 2,... T cc phng trnh

trn nhn thy rng nu o c tng ng vi cc gi tr n th c th tnh

c d v chiu di bc sng ca tia X chiu vo bit. Cng ca

cc nh ph thay i theo gi tr ca hay theo bc phn x, do khi

nghin cu cng ca ph tia X c th nhn c cc thng tin v s sp

xp cc mt phng ca cc nguyn t khc nhau trong tinh th.

Tuy nhin, phng php nhiu x tia X cng c mt s hn ch nh khng

pht hin c nhng cht c hm lng thp v ty theo bn cht v mng

khng gian ca vt liu m nhy phn tch nh tnh thay i t 1% n

30%.

2.2.2. Phng php hp th v gii hp N2 Phng php ph bin xc

nh din tch b mt ring ca mt cht rn

l o s hp ph ca N2 hoc mt s kh khc

c kh nng thm nhp vo tt c cc mao

qun v tnh ton din tch b mt ring da

vo ng ng nhit hp ph.

Phng php BET (Brunauner-

Emmett-Teller) l phng php c s dng rng ri nht xc nh din

tch b mt ca vt liu thng qua phng trnh BET:

00

11

1

1

P

P

CV

C

CV

P

PV mm

Trong :

P: p sut cht b hp ph pha kh.

P0: p sut hi bo ha ca cht b hp ph trng thi lng tinh khit

cng nhit .

V: th tch cht b hp ph p sut tng i P/P0 tnh bng cm3.

Vm: th tch lp hp ph n phn t trn ton b b mt S tnh bng cm3.

C: hng s lin quan n nng lng hp ph i vi lp b hp ph

u tin hay lin quan n mc tng tc gia cht hp ph v cht b

hp ph.

Din tch b mt ring SBET ca vt liu c xc nh bi phng

php BET (Brunauer,Emmett and Teller). S phn b kch thc l c

tnh theo phng php BJH, dy thnh mao qun c trng cho tng vt

liu thuc nhm khng gian khc nhau P6mm l

W = a Dp = .d100 Dp

2.2.3. Phng php gii hp NH3 theo chng trnh nhit

Phng php gii hp NH3 theo chng trnh nhit (TPD-

Temperature Programmed Desorption) c tm ra vo nm 1960 xc

nh lc axit v lng cc tm axit tng ng trn xc tc. Ngi ta s dng

NH3 nh l mt cht d, c hp th bo ha trn cc tm axit ca b mt

xc tc. Cc mu xc tc sau khi hp th cn bng NH3 di iu kin xc

nh s c gia nhit theo chng trnh nhit . Khi nng lng nhit

cung cp ln hn nng lng hp th. Cc phn t NH3 gii hp khi b mt

cht hp th v c kh mang a qua detector xc nh lng.

Lp th biu din s ph thuc gia lng NH3 gii hp theo nhit

. Trong qu trnh gi hp NH3 theo nhit , trn nhng tm axit yu s

gii hp NH3 trc, trn nhng tm axit mnh s gii hp NH3 sau. Nh vy,

cc tm c lc axit mnh s c Tmax ln v ngc li. Tng din tch pic NH3

cho bit lng kh b hp th v t c th tnh c [H+] (S tm axit)

trn mt n v khi lng cht xc tc (mmol/g).

.Mi quan h gia nhit gii hp v nng lng (Nhit) gii hp

c biu din theo phng trnh sau:

Log(Tp2/) = - Ed /2,302. RTP + log(EdA/RC)

Trong :

: Tc gia nhit tuyn tnh .

TP : Nhit ca pic.

Ed : Nng lng gii hp.

A : Lng cht b hp ph bo ha .

C : Hng s tc gii hp.

Nh vy, th log(Tp2/) theo 1/TP s l ng thng ch quan h

tuyn tnh gia hai i lng ny trong qu trnh gii hp theo chng trnh

nhit v t c th xc nh gi tr Ed t dc ca th.

Da vo din tch peak gii hp ti cc nhit khc nhau ta c th

xc nh c lng NH3 tiu th v t nh gi c lc axit v s

lng cc tm axit tng ng. Cc tm axit yu s gii hp NH3 nhit

thp v ngc li cc tm axit mnh hn gii hp NH3 nhit cao hn.

Tm axit yu gii hp ti nhit 2000C

Tm axit trung bnh gii hp nhit t 200-4000C

Cc tm axit mnh gii hp nhit 4000C

mnh ca mt axit c nh ngha bi kh nng chuyn ha mt

baz hp th n trn b mt n thnh axit lin hp tng ng.

Nu s chuyn ha bao gm s chuyn proton sang cht b hp th th

khi cht hp th c trng cho loi axit c gi l axit Bronsted. Ngc

li, nu b mt chia s cc cp electron ca n cho cht b hp ph th n c

trng cho loi axit c gi l Lewis.

Khi baz s dng l NH3, ta c th m t hai phn ng minh ha cho

hai loi axit nu nh sau :

Axit Bronsted : A-H

+ + NH3 A

-NH4

+

Axit Lewis : A + NH3 A.NH3

A : l tm axit Bronsted hoc Lewis.

2.2.4 Ph tn sc nng lng tia X: EDX

Ph tn sc nng lng tia X, hay Ph tn sc nng lng l k thut

phn tch thnh phn ha hc ca vt rn da vo vic ghi li ph tia X pht

ra t vt rn do tng tc vi cc bc x (m ch yu l chm in t c

nng lng cao trong cc knh hin vi in t). Trong cc ti liu khoa hc,

k thut ny thng c vit tt l EDX hay EDS xut pht t tn gi ting

Anh Energy-dispersive X-ray spectroscopy.

Nguyn tc:

Hnh2.4: Nguyn l ca php phn tch EDX.

nh vi cu trc vt rn c ghi li thng qua vic s dng chm in t c

nng lng cao tng tc vi vt rn. Khi chm in t c nng lng ln

c chiu vo vt rn, n s m xuyn su vo nguyn t vt rn v tng

tc vi cc lp in t bn trong ca nguyn t. Tng tc ny dn n vic

to ra cc tia X c bc sng c trng t l vi nguyn t s (Z) ca nguyn

t theo nh lut Mosley:

C ngha l, tn s tia X pht ra l c trng vi nguyn t ca mi cht c

mt trong cht rn. Vic ghi nhn ph tia X pht ra t vt rn s cho thng

tin v cc nguyn t hc c mt trong mu ng thi cho cc thng tin v t

phn cc nguyn t ny

Hnh 2.5: S nguyn l ca h ghi nhn tn hiu ph EDX .

Tia X pht ra t vt rn (do tng tc vi chm in t) s c nng

lng bin thin trong di rng, s c a n h tn sc v ghi nhn

(nng lng) nh detector dch chuyn (thng l Si, Ge, Li..) c lm

lnh bng nit lng, l mt con chip nh to ra in t th cp do tng tc

vi tia X, ri c li vo mt ant nh. Cng tia X t l vi t phn

nguyn t c mt trong mu. phn gii ca php phn tch ph thuc vo

kch c chm in t v nhy ca detector (vng hot ng tch cc ca

detector).

chnh xc ca EDX cp mt vi phn trm (thng thng ghi nhn

c s c mt ca cc nguyn t c t phn c 3-5% tr ln). Tuy nhin,

EDX t ra khng hiu qu vi cc nguyn t nh (v d B, C...) v thng

xut hin hiu ng trng chp cc nh tia X ca cc nguyn t khc nhau

(mt nguyn t thng pht ra nhiu nh c trng K, K..., v cc nh

ca cc nguyn t khc nhau c th chng chp ln nhau gy kh khn cho

phn tch).

2.3. Xc nh cc ch s c bn ca du Jatropha

2.3.1. Xc nh ch s axit:

Ch s axit l s mg KOH cn dng trung ha ht lng axit c

trong 1g du

Cch tin hnh

Cn 3-5g mu vo bnh nn, thm vo 50ml dung mi hn hp

gm ete etylic v mt phn etanol, lc cho tan du. Trong trng hp du

khng tan ht phi va lc, va un nh trn bp cch thy ri lm ngui

n nhit 20oC. Sau cho vo bnh 5 git ch th phenolphtalein (vi

du thm mu, dng thimolphtalein) v chun b bng KOH 0,1N cho n

khi xut hin mu hng nht bn trong 30 giy.

2.3.2. Xc nh ch s x phng ha

Ch s x phng ha ca du l s mg KOH phn ng va vi 1g

du.

Cch tin hnh

Pha dung dch KOH 0,5 N trong etanol 95%, ha tan trong 30g KOH

trong 20 ml nc ct, chuyn vo bnh nh mc dung dich mt lt, thm

etanol n vch. Gi kn dung dch trong mt ngy mt m ri nhanh

chng cht lp dung dch trong vo chai mu ti, y kn bng nt cao su.

Cn 1,5-2g mu th (chnh xc 0,0002g) vo bnh nn dung tch 250

ml. Dng pipet cho thm vo 25 ml dung dch KOH 0.5 N. Lp sinh hn

hi lu v un trn bp cch thy trong 1 gi (lun lc mu trong bnh).

Tho sinh hn hi lu, thm vo hn hp va x phng ha vi git ch th

phenolphtalein 0,1% v nhanh chng chun bng dung dch HCL 0,5N.

Tin hnh chun mu trng (khng c du) vi cch lm ging nh

trn

2.4. nh gi thnh phn v kim tra tnh cht sn phm

2.4.1. nh gi thnh phn sn phm

Tin hnh cc este ha cho du thi (du n qua s dng) vi mu

xc tc tng hp. Cc phn ng c tin hnh nhng iu kin khc nhau

nghin cu nh hng ca cc yu t nh hng ti phn ng este ha

cho. Sn phm ca phn ng c thc hin trong iu kin ti u c

t trng bng phng php Sc k - Khi ph GC-MS [5]. Mu c phn

tch trn my GC-MS System - Hewlett HP 6800, Mass selective detector

Hewlett HP 5973. Ct tch HP - 5 MS crosslinked PH 5 % PE Siloxane,

30m 0,32m . Ti Trung tm Ho du, Khoa Ho hc, Trng i hc

Khoa hc T Nhin, i hc Quc Gia H Ni.

Chng 3. KT QU - THO LUN

3.1 c trng tnh cht vt liu

3.1.1. Phng php nhiu x X-ray

Nhiu x bt X-Ray c ghi vi thc o nhiu x X-Ray bt

Bruker D4 s dng bc x Cu-K .

Vi cc mng tinh th khc nhau th khng phi bt c mt no cng

thy s phn x. i vi mng lp phng tm khi th ch khi tng h + k + l

l chn th s nhiu x mi xy ra, cn dng su phng th s phn x ch

khng xut hin vi h + 2k =3N (N l s t nhin) v l l. M hnh nhiu x

tia X gc hp ca SO42-

/ZrO2-ZnO c a ra Hnh 3.1.

00-017-0075 (N) - Zinc Zirconium - Zn2Zr - Y: 36.33 % - d x by: 1.0167 - WL: 1.5406 - Cubic - a 7.39400 - b 7.39400 - c 7.39400 - alpha 90.000 - beta 90.000 - gamma 90.000 - Face-centered - Fd-3m (2

01-080-0536 (N) - Zirconium Oxide Sulfate - Zr3O5(SO4) - Y: 124.57 % - d x by: 1. - WL: 1.5406 - Hexagonal - a 6.31000 - b 6.31000 - c 10.25000 - alpha 90.000 - beta 90.000 - gamma 120.000 - Primiti

00-024-1165 (D) - Baddeleyite - ZrO2 - Y: 104.74 % - d x by: 1.0271 - WL: 1.5406 - Monoclinic - a 5.14500 - b 5.20700 - c 5.31100 - alpha 90.000 - beta 99.230 - gamma 90.000 - Primitive - P21/c (14) -

Operations: Smooth 0.150 | Import

File: ZrO2-SO4.raw - Type: 2Th/Th locked - Start: 10.000 - End: 80.019 - Step: 0.011 - Step time: 18.9 s - Temp.: 25 C (Room) - Time Started: 10 s - 2-Theta: 10.000 - Theta: 5.000 - Chi: 0.00 -

Lin

(C

ps)

0

10

20

30

2-Theta - Scale

10 20 30 40 50 60 70 80

d=

3.0

1620

d=

2.8

9675

d=

2.6

8590

d=

3.2

4865

d=

2.9

1545

d=

2.2

5347

d=

1.4

4247

d=

1.3

2456

Hnh 3.1. Kt qu nhiu x tia X gc hp ca vt liu tng hp.

Trn gin XRD ca xc tc Zirconia c bin tnh bng lu hunh v

km xut hin pha t din ca ZrO2, c trng bi cc pic ti gc 2 = 30

oC, 35

oC, 50

oC v 60oC. iu ny chng t c cu trc ca ZrO2. Ngoi ra.

Trn gin XRD cn xut hin cc pic cng hng ca ZnO ti gc 2 =

34 oC , 40

oC , 65

oC v 71 oC m s c chng minh EDX. Tm li. Qu

trnh iu ch ZrO2 bng bin tnh S v Zn gi li cu trc pha t din

ca ZrO2, ng thi s c mt ca S, Zn .

3.1.2. Phng php hp th v gii hp N2

Din tch b mt ring SBET ca vt liu c xc nh bi phng

php BET (Brunauer,Emmett and Teller). S phn b kch thc l c

tnh theo phng php BJH, dy thnh mao qun c trng cho tng vt

liu thuc nhm khng gian khc nhau P6mm l

W = a Dp = .d100 Dp

SBET (m2/g): din tch b mt ring theo BET;

Vf (cm3/g): tng th tch mao qun

Dp (nm): ng knh mao qun trung bnh theo BJH;

W (nm): dy thnh mao qun.

Da vo gin gii hp v hp ph ta thy xc tc c kch thc mao

qun trung bnh tp chung khong 50A0 l iu mong mun.

- Xc tc mu MJ sau khi c bin tnh bng Zn v S th xc tc ny c

din tch b mt ring l 93,01267 m2/g ln hn hn so vi ZrO2 , din tch

b mt ring ln s to iu kin cho s tip xc gia cht phn ng vi cht

xc tc ln. V vy lm cho lm cho tc phn ng v hiu xut tng.

Hinh 3.2: ph kch thc mao qun trong hp ph N2 ca vt liu

3.1.3. Phng php gii hp NH3 theo chng trnh nhit

T kt qu o hp ph v gii hp NH3 theo chng trnh nhit .ca

mu SO42-

/ZrO2-ZnO cho thy xc tc c ba loi tm axit tng ng vi qu

trnh gii hp ph NH3 xy ra cc nhit :

- ng vi pc c nhit gii hp 200,4 oC l tm axit yu.

- ng vi pc c nhit gii hp 380,0 oC l tm axit trung bnh.

- ng vi pc c nhit gii hp 516,4 oC v 545,7 oC l tm axit

mnh.

Cc Pic c nhit gii hp ln hn 400 oC tng ng vi tm axit

mnh. S lng tm axit mnh chim u th hn so vi cc tm axit trung

bnh v yu. Tm axit yu c c trng bi cc pc sc nhn c cng

cao nhit 545,7 oC, iu ny cho thy xc tc tng hp c c tnh axit

mnh thch hp cho phn ng este cho ha ca du Jatropha c ch s axit

cao v metanol..

Hnh 3.3. Gin hp ph v gii hp NH3 theo chng trnh nhit .

Kt qu ny cho thy vt liu tng hp c kh nng c tnh axit ph

hp vi phn ng este ha cho ca du Jtropha c ch s axit cao.

3.1.4 Ph tn sc nng lng tia X: EDX

Hnh 3.4. Ph EDX ca vt liu xc tc SO42-

/ZrO2 - ZnO

Bng 3.1: Bng kt qu EDX hm lng ca ca vt liu

O S Al Zn Zr Total(Mass%)

01 29.77 1.14 0.12 2.39 66.58 100.00

02 30.02 1.38 0.30 2.62 68.81 100.00 03 27.79 0.69 0.41 2.30 68.81 100.00

Da vo kt qu ca EDX s bin tnh thnh cng

iu ny chng t Zn v S i vo cu trc tinh th ZrO2 , ph hp vi kt qu trong c trng ca X Ray.

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

keV

002

0

400

800

1200

1600

2000

2400

2800

3200

3600

4000

Counts

OKa

AlK

a

AlK

sum

SKaSKb

ZnLlZnLa

ZnKa

ZnKb

ZrM

ZrLl

ZrLa

ZrLb

ZrLsum

Acquisition Parameter Instrument : 6490(LA) Acc. Voltage : 20.0 kV Probe Current: 1.00000 nA PHA mode : T4 Real Time : 65.17 sec Live Time : 50.00 sec Dead Time : 22 % Counting Rate: 2341 cps Energy Range : 0 - 20 keV

Hnh3.5. Hinh nh SEM ca vt liu xc tc ZrO2/SO42-

-ZnO

Qua hnh nh xem ta thy kch thc ht ng u

3.1.5 Phng php phn tch nhit TG/DTA

Hnh 3.6: Gin phn tch nhit TG/DTA

001

001

100 m100 m100 m100 m100 m

Gin phn tch nhit TG-DTA cho thy, trong khong nhit t 40

n gn 800 C, khng xy ra s mt khi lng no ng k. pic thu

nhit km theo s mt khi lng khong 60 oC - 70 oC c cho l do s

mt nc trn b mt ht xc tc. Kt qu nghin cu ny l hon ton ph

hp vi nhng kt lun trong phng php phn tch XRD. Xc tc thu

c c bn nhit cao. T kt qu ny, c th la chn nhit nung

xc tc khong 550oC nhm n nh cu trc pha t din.

3.2. Kho st hot tnh xc tc i vi phn ng este ha cho du

3.2.1 Ch s axit ca du

Cc php phn tch c tin hnh 3 ln v ly kt qu trung bnh. Ta

c bng kt qu sau:

Bng 3.2: Ch s c bn ca du Jatropha

Ch tiu Ln 1 Ln 2 Ln 3 Trung bnh

Ch s axit(mgKOH/1g

du)

5,21 5,30 5,20 5,36

Kt qu trn cho thy, ch s axit ca du Jatropha sau khi x l,

nu dng xc tc kim phn ng d to mui. V vy s dng h xc tc axit

rn l thch hp.

3.2.2. Thc hin phn ng este ha cho

Du c cho vo bnh cu hai c y trn c sn mt lng xc

tc nht nh v con khuy t. Bt my khuy v gia nhit t nhit

phng ln nhit phn ng, i trong khong 15 pht xc tc v du c

trn u vi nhau, sau cho t t metanol vo.

Khi phn ng kt thc, quay li tm loi xc tc v ru d. Hn

hp sau phn ng c a sang phu chit 500 mL, hn hp phn ng

lng khong 12 gi. Chit ly phn metyl este. Tin hnh ra metyl este

trong phu chit bng dung dch nc nng 10 % ha tan ht tp cht v

tch chng khi biodiesel. Sau khi ra bng nc nng, tin hnh ra tip

bng nc ct nng loi b ion Cl-. Khi o pH ca sn phm l khong

7 th ngng li. Sn phm sau khi ra, loi b MeOH d v cc tp cht

khc c cho vo cc thy tinh, dung tch 500 mL v tin hnh ui nc

bng cch sy 100 oC. Sau em hp th nc cn ln trong phn metyl

este bng silicagen vi thi gian hp th.

3.2.2. Kho st nh hng ca t l mol metanol/ du Jatropha Thc hin mt s phn ng gia metanol v du thi vi xc tc l vt

liu tng hp vi cc thng s sau y c gi c nh:

Th tch du : 20 mL

Hm lng xc tc: 5 % so vi khi lng du (Ddu 0,89 g/cm3)

Nhit phn ng: 60 oC

Thi gian phn ng: 10 gi

Tc khuy: 750 vng/ pht

Cc th nghim c thc hin vi cc t l mol metanol/ du Jatropha

khc nhau kho st nh hng ca yu t ny ti phn ng.

Bng 3.3: Kho st nh hng ca t l mol metanol/ du Jatropha

K hiu T l mol metanol/ du Vmetyl este (mL) to ra S to nh

MJ11 6 : 1 Ra nhiu ln vn to nh

C

MJ12 12 : 1 4,1 C

MJ13 18 : 1 13,2 Hu nh khng

MJ14 24 : 1 13,5 Khng c

Da trn nhng kt qu trn c th thy rng khi t l khng

ln th chuyn ha khng ln, nguyn nhn l do cha c c s tip

xc cn thit gia metanol vi triglyxerit. Lng metanol cn dng phi

nhiu bi du thi c nht rt cao, s tip xc gia cc cht phn ng vi

nhau kh khn. Ngi ta gi thit rng phn ng este ha cho bt u khi

cc phn t triglyxerit c hp ph ha hc trn cc tm xc tc axit hot

ng. Ti y nhm carbonyl c hot ha to ra cc carbocation,

nhng ion ny tham gia phn ng cng nucleophile (AN) vi metanol to

ra este. Khi metanol d, s tip cn ca cc phn t metanol vi carbocation

c tng cng, do vy chuyn ha tng ln.

Tuy nhin, nu nh t l qu ln th chuyn ha s gim,

iu ny c quan st thy khi tng t l t ln . Hm lng metanol

ln lm u tin phn ng chuyn triglyxerit thnh monoglyxerit.

Monoglyxerit lm tng tan ca glyxerin trong metyl este, v thc y

phn ng este ha cho glyxerin v metyl este. Metanol c s dng khng

hon ton l tinh khit nn vn cn ln nc, nu dng nhiu metanol th

hm lng nc cng tng ln v ch cn mt lng nc nh cng c th

thy phn este, ng thi to ra nh tng trong nc do to ra cc mono-

v diglyxerit, gy kh khn cho qu trnh loi b nc. Ngoi ra, nu c qu

nhiu metanol s xy ra s che ph cc tm hot ng ca xc tc, gy tr

ngi cho qu trnh hot ha nhm carbonyl ca glyxerit.

3.2.3. Kho st nh hng ca thi gian phn ng Thc hin mt s phn ng gia metanol v du thi vi xc tc l vt

liu tng hp vi cc thng s sau y c gi c nh:

Th tch du: 20 mL

Hm lng xc tc: 5 % so vi khi lng du

Nhit phn ng: 60 oC

T l : 18 : 1

Tc khuy: 750 vng/ pht

Cc th nghim c thc hin vi cc thi gian phn ng khc nhau

kho st nh hng ca yu t ny ti phn ng.

Bng 3.4: Kho st nh hng ca thi gian phn ng

K hiu Thi gian phn ng VMetyl este (mL) to ra S to nh

MJ21 4 gi Ra khng ht nh C nhiu

MJ22 8 gi Rt t C

MJ23 12 gi 13,3 Hu nh khng

MJ24 16 gi 13,5 Khng c

Cc kt qu ch ra rng thi gian phn ng c nh hng tng i

mnh n chuyn ha ca phn ng. Phn ng din ra cng lu th kh

nng phn tn ca cc tc nhn v xc tc vo nhau cng tt, chuyn ha

t c cng ln, lng glyxerin sinh ra cng nhiu. Ban u, phn ng

din ra chm do du Jatropha c nht cao, gy kh khn cho vic phn

tn metanol. n mt khong thi gian nht nh, tc phn ng tng ln

rt nhanh. Khong thi gian phn ng ti u l 12h .

3.2.4. So snh hot tnh ca cc mu xc tc SO42-

/ZrO2 - ZnO

Hot tnh vi xc tc c tnh u vit nht vi thi gian yhc hin phn

ng l 12 gi. Thc hin mt s phn ng gia metanol v du cc xc tc

th cc thng s sau y c gi c nh:

Th tch du : 20 mL

Hm lng xc tc: 5 % so vi khi lng du

Nhit phn ng: 60 oC

T l : 18 : 1

Tc khuy: 750 vng/ pht

Bng 3.5: So snh hot tnh ca hm lng xc tc so vi du

Xc tc 3% 5% 7% 9%

Vmetyl este 11,2 13,3 13,3 13,34

So vi cc xc tc SO42-

/ZrO2-ZnO th MJ23 c hot tnh xc ti u hn

c, thi gian phn ng t n chuyn ha cao nht 12 gi

3.2.5. Phn ng este ha cho du Jatropha

Kho st cc yu t nh hng ti phn ng este ha cho du

Jatropha, chng ti tin hnh la chn mt s iu kin tin hnh phn

ng este ha cho du Jatropha vi hai thi gian tin hnh phn ng khc

nhau: 12 n 18 gi.

Th tch du : 20 mL

Hm lng xc tc: 5 % so vi khi lng du

Nhit phn ng: 60 oC

T l : 18 : 1

Tc khuy: 750 vng/ pht

Bng 3.6: Kt qu ca phn ng este cho ha

K hiu Thi gian phn ng Vglyxerin (mL) tch ra S to nh

01 12 gi 13,2 Hu nh khng

02 16 gi 13,5 Khng c

Thi gian tin hnh phn ng cng ko di, hiu qu t c cng

thp. Lng nh to ra l do thi gian phn ng ko di th xy ra qu trnh

phn ng nghch, ngoi ra cn do m c basa c ch s axit t do ln, nn

qu trnh este ha to monoglyxerit d dng xy ra hn.

3.3. nh gi thnh phn v kim tra tnh cht sn phm

3.3.1. nh gi thnh phn sn phm

Mu vi thi gian 4 gi, 6 gi phn ng ester cho ha hu nh khng

xy ra m ch l s thy phn , to ra lng axit t do rt nhiu. V vy khi

ta tin hnh tch v ra to nh rt nhiu. iu c minh chng trong

hnh sau.

- Mu du chy vi thi gian ngn:

Th tch du : 20 mL

Hm lng xc tc: 5 % so vi khi lng du

Nhit phn ng: 60 oC

T l : 18 : 1

Tc khuy: 750 vng/ pht

Hnh 3.7: S phn lp v to nh ca mu c thi gian phn ng ngn

Ngoi ra iu cn c minh chng bng kt qu sc k kh sau:

Xut hin cc pic ca axit vi tin cy rt cao, trong khi chuyn ha

thnh methyl ester rt t.

Nh mu vi thi gian phn ng 4 gi hu nh khng c Methyl ester,

ton b to nh.

Hnh 3.8. Sc k ca mu sn phm

Hnh 3.9 . Ph khi lng ca Hexadecanoic acid

Hnh 3.10. Ph khi lng ca Oleic acid

Trong khi s chuyn ha v Methyl ester rt t

Hinh 3.11. Ph khi lng ca 9-octadecanoic acid (Z)-,methyl ester

Hinh 3.12.. Ph khi lng ca Octadecanoic acid ,methyl ester

- Mu du chy vi thi gian 12 16h:

Th tch du : 20 mL

Hm lng xc tc: 5 % so vi khi lng du

Nhit phn ng: 60 oC

T l : 18 : 1

Tc khuy: 750 vng/ pht

Hnh 3.13. Sc k ca sn phm

Hnh 3.14. Ph khi lng ca 9-octadecenoic acid (z)-,methyl ester

Hinh 3.15. Ph khi lng ca 9,12-octadecadienoic acid (Z,Z)-methyl

ester

Hnh 3.16. Ph khi lng ca Pentandecanoic acid, 14-methyl -, methyl

ester

Kt qu phn tch cho thy trong sn phm c cc este: Octadecanoic

acid ,methyl ester; 9,12-octadecadienoic acid (Z,Z)-methyl ester; 9-

octadecenoic acid (z)-,methyl ester; Hexadecanoic acid, methyl ester;

Tetradecanoic acid, methyl ester .

.

KT LUN

1. nghin cu tng hp vt liu mao qun trung bnh cu trc trt t

SO42-

/ZrO2-ZnO t cc tin cht ZrOCl2.8H2O, Zn(CH3COO-)2 v

(NH4)2SO4.

2. Nhiu x X-ray gc hp cho thy vt liu c cu trc ca ZrO2 , bn

cnh xut hin Pic cng hng ca ZnO iu ny c chng minh kt

qu EDX .

3. Gin TPD-NH3 cho thy xc tc c ba loi tm axit: yu (200,4

oC); trung bnh (380 oC) v mnh 516.4 0 C v (546,7 oC).

4. Tin hnh kho st cc nh hng ca thi gian phn ng este ha

cho du thi vi xc tc tng hp. Phn ng este ha cho du Jatropha

c tin hnh vi cc iu kin phn ng ti u t cc kho st vi qu

trnh este ha cho .

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MC LC PH LC HNH PH LC BNG M u Chng 1: TNG QUAN 1.1. Tm kim ngun nng lng cho tng lai 1.2. ng dng du, m ng thc vt trong sn xut nhin liu 1.2.1. Sinh khi (Biomass)1.2.2. Gii thiu chung v du, m ng thc vt 1.2.3. Chuyn ha du, m ng thc vt thnh nhin liu 1.2.4. Phng php este ha cho 1.3. Xc tc cho phn ng este ha cho tng hp biodiesel 1.3.1. Mt s khi nim c bn v nhin liu sinh hc1.3.2. c tnh ca biodiesel 1.3.3. Cc yu t nh hng n phn ng este ha cho 1.3.4. Xu th s dng xc tc axit rn d th cho phn ng este ha cho 1.4. Vt liu mao qun trung bnh cu trc trt t 1.4.1. Gii thiu v vt liu mao qun 1.4.2. Vt liu mao qun trung bnh 1.4.3. Gii thiu v nguyn t zirconi (Zr) v zirconi ioxit (ZrO2) 1.4.4. Gii thiu v Cc yu t nh hng n xc tc ZrO2-SO42 1.4.3. Cu trc v tnh cht axit ca superaxit ZrO2-SO42 Chng 2: THC NGHIM2.1. Tng hp vt liu 2.1.1. Ha cht 2.1.2. Thit b 2.1.3. Quy trnh tng hp 2.2. c trng tnh cht vt liu 2.2.1. Phng php nhiu x X-ray2.2.2. Phng php hp th v gii hp N2 2.2.3. Phng php gii hp NH3 theo chng trnh nhit 2.2.4 Ph tn sc nng lng tia X: EDX 2.3. Xc nh cc ch s c bn ca du Jatropha 2.3.1. Xc nh ch s axit2.3.2. Xc nh ch s x phng ha 2.4. nh gi thnh phn v kim tra tnh cht sn phm 2.4.1. nh gi thnh phn sn phm Chn