Axit axetic

  • View
    1.666

  • Download
    7

Embed Size (px)

Transcript

1

Trng i hc bch khoa H NiVin k thut ha hcB mn cng ngh hu c ha du

ti : Tng quan v axit axetic

GVHD: PGS-TS: Phm Thanh Huyn SVTH : 1. inh Ngc Phan hd1_k52

2. Nguyn Trng Ngha hd1_k52 3. Phm S ng hd1_k52

H ni ngy 11 thng 4 nm 20111

2

1. Tnh cht ca axit axetic1.1. Tnh cht l hc Axit axetic l cht lng khng mu hoc tinh th mu trng, c v chua, c kh nng tan v hn trong nc. T trng ca axit axetic dng lng l 1.049g/cm3 v dng tinh th l 1.266g/cm3. Tnc = 16.5oC, Ts = 118,1oC

1.2. Tnh cht ha hc Axit axetic c tnh axit, 25oC n c pKa = 4,26, th hin : Lm thay i mu qu tm Khi thm axit axetic vo dung dch Ca(OH)2 c mt phenolphtalein, dung dch mt dn mu hng Phn ng vi baz Axit axetic ha tan CuO thnh dung dch c mu xanh c trng phn ng vi oxit baz Ha tan Zn phn ng vi kim loi Tc dng vi mui ( phn ng vi CaCO3 thot kh CO2)

2

3

2. Phng php sn xut cng nghip2.1. Gii thiu chung Axit axetic trong cng nghip c sn xut theo 2 phng php: phng php sinh hc v phng php tng hp. Ngy nay, lng axit sn xut theo phng php sinh hc ch chim khong 10% sn lng th gii, nhng n vn l mt phng php quan trng dng sn xut gim (mt s iu lut v tinh khit thc phm mt s quc gia quy nh rng gim s dng trong thc phm phi c ngun gc t sinh hc). Phng php tng hp c p dng nhiu hn sn xut axit vi nng sut cao. Trong , khong 75% axit axetic c sn xut cng nghip c sn xut theo phng php cacbonyl ha metanol. Khong 15% cn li c sn xut t cc phng php thay th khc (oxy ha trc tip hydrocacbon no, oxy ha axetaldehit, oxy ha etylen) Cc phng php sn xut : Cacbonyl ha metanol Oxy ha axetaldehyt Oxy ha etylen Oxy ha RH no(n-butan,naphta) Ln men oxy ha Ln men k kh

2.2. Cng ngh cacbonyl ha metanol2.2.1. Lch s pht trin Cng ngh sn xut axit axetic t metanol v cacbonmonoxit nhit v p sut cao c hng BASF a ra t rt sm (1913) da trn phn ng: CH3OH + CO --> CH3COOH H298 = - 138,6 KJ/mol3

4

iu kin tin hnh khc nghit v nhit v p sut cng vi s c mt ca cc cht n mn mnh (cc hp cht iotua) ngn cn vic thng mi ho cng ngh ny. Nm 1914, cc nghin cu ca REPPE (BASF) cho thy rng cc kim loi nhm VIII c kh nng xc tc hiu qu cho qu trnh cacbonyl ho. iu ny dn n vic ra i v pht trin cng ngh nhit v p sut cao (250oC v 70MPa) vi xc tc CoI2. Qu trnh ny c BASF a vo p dng nm 1960 ti Luwig Shafen. Cng sut ban u l 3.600 tn/nm. Sau tng ln 12.000 tn/nm vo nm 1964 v 35.000 tn/nm vo nm 1970. Nm 1981 cng sut t 45.000 tn/nm. Nm 1966, Borden Chemical c khi ng xy dng mt nh my sn xut axit axetic trn c s cng ngh BASF ti Geimak (Bang Louisiana, M) vi nng sut ban u l 30.000 tn/nm sau tng ln 45.000 tn/nm vo nm 1968. Nm 1968, Monsanto cng b mt khm ph mi. Xc tc rhodi vi hot tnh v chn lc rt cao cho phn ng cacbonyl ho metanol thnh axit axetic. Metanol c th c cacbonyl ho ngay c p sut thng vi hiu sut chuyn ho l 99% i vi metanol v 90% i vi cacbon monoxit. Qu trnh c s dng xc tc ny c p dng nm 1970 ti bang Texas, vi cng sut ban u l 135.000 tn/nm, sau tng ln 180.000 tn/nm vo nm 1975. iu kin tin hnh qu trnh Monsanto mm hn so vi qu trnh BASF (3MPa v 180oC ).

2.2.2. Nguyn tc chung ca qu trnh Qu trnh cacbonyl ha metanol l mt phn ng ta nhit : CH3OH + CO CH3COOH H298 = - 138,6 KJ/mol

Phn ng xy ra thun li trong pha lng, nhit 220 250oC, p sut ca qu trnh phi c gi mc 30MPa. S c mt ca nc (> 30% TT) v vic s dng xc tc s gip gim bt khc nghit ca cc iu kin tin hnh qu trnh, c bit l p sut c gim xung 3 7 MPa v nhit 150 200oC

4

5

H xc tc ang c s dng gm c 3 thnh phn: pha hot ng, cht xc tin v dung mi. Pha hot ng (cc oxit, cc hp cht c kim, cc hp cht phi tr hoc mui ca kim loi qu him nh Co, Rh) c nng n 10-3M. Cht xc tin, khi mo (1M) l halogen hoc cc hp cht cha halogen.

2.2.3. Cng ngh BASF Qu trnh BASF s dng cacbonyl coban lm xc tc vi cht kch ng iotua CoI2 c dng ti sinh ti ch Co2(CO)8 v HI. Tc phn ng ph thuc vo p sut ring phn ca cacbon monoxit v nng metanol. Hiu sut thu axit axetic t 90% i vi metanol v 70% i vi cacbon monoxit.

Phn ng (1) c th chuyn ho CO bng hi nc, xc tc l Co2(CO)8 v H2 c to ra bng cch phn ly phc hydro cacbonyl. Metyl iotua lin tc tn cng bi tc nhn nucleophil l ion [Co(CO)4]- (4). Gc iotua lm cho phn ng d dng hn v n d tch hn OH-. CH3I phn ng vi phi tr bo ho d10 Co(CO)4. Qu trnh oxy ho cng hp ca CH3I vo Co(CO)4 kh khn hn vo [Rh(CO)2I2]-. Sn phm cng hp ban u l5

6

mt phc 5 phi tr d8 CH3Co(CO)4. Giai on chuyn v metyl (5) xy ra chm hn so vi qu trnh xc tc bi Rh. Khi to thnh hp cht trung gian axyl ca coban, hp cht ny khng b phn hu to coban iotua v iod khng phi tr vi coban CO2, metanol (cha 60% dimetyl ete), xc tc tun hon, xc tc mi, metyl iotua tun hon (t thp ra) c a n thit b phn ng p sut cao (b). Mt phn ca nhit phn ng c dng un nng s b nguyn liu, phn nhit cn li c tiu tn dc theo ng phn ng. Sn phm phn ng c lm lnh v a n thit b phn ly p sut cao (d). Kh thi c a vo thp ra (o) phn lng c gin n ti p sut 0,5 1 MPa trong thit b phn ly p sut trung bnh (e). Kh thot ra cng c vo thp ra (o), phn lng t thit b phn ly p sut trung bnh c a n bung gin n (f). Kh ra khi bung c a n thit b ra (p). Kh t thit b ra v thp ra l kh thi. C thit b ra v thp ra u dng metanol nguyn liu thu hi metyl iotua v cc hp cht iotua d bay hi khc. Dung dch metanol ny c a tr li thit b phn ng. Thnh phn kh thi (% th tch): CO: 65 -75%, CO2: 15-20%, CH4: 3-5% v hi metanol. Axit t bung gin n (f) chim 45% khi lng axit axetic, 35% khi lng nc, 20% khi lng este (ch yu l metyl axetat). Axit c tinh ch 5 thp chng ct. Thp th nht (h) dng ui kh t hn hp sn phm th, kh thot ra c a vo thp ra. Xc tc c tch ra bng cch chng ct cc cu t d bay hi thit b tch xc tc (i). Ti thit b sy (k) cho php nhn c axit tinh bng phng php chng ct ng ph. Sn phm nh ca thp lm kh cha axit axetic, axit formic, nc, sn phm ph, chng to hn hp ng ph vi nc. Sn phm nh ny l mt h hai pha, n c tch trong bung (g). Mt phn ca pha hu c, cha ch yu este c tr li (k), n ng vai tr l mt tc nhn ng ph Phn cn li c a n thp ph (n), y phn nng c ly ra phn y thp, phn nh nh thp c a tun hon li thit b phn ng. Phn ch yu thp lm kh c a n thp lm sch ln cui, axit axetic c ly ra nh thp, sn phm y c a n thp tch cn (m). Sn phm nh ca thp ny c a ti thp tch nc, sn phm y cha 50% khi lng axit propionic c a i thu hi.

6

7

Cng ngh BASF

2.2.4. Cng ngh MonsantoSo snh cng ngh BASF v Monsanto Thng s Thi gian Xc tc Nhit (o C) p sut ( MPa) chn lc BASF 1941 CoI2 250 68 90% ( MeOH) 70% (CO) Monsanto 1960 RhI2 200 35 99% ( MeOH) 90% (CO)

7

8

H xc tc Rhonium u vit hn Cobalt2.2.4.1. Xc tc Rhodium/iodide: Xc tc cacbonyl ha gm 2 thnh phn kim loi Rh c hot ha trn cht mang iode Xc tc to phc cht trung gian gm Rh,CO v phi t l halogen Ti sinh xc : Trc tin loi b cc ion kim loi c ln do qu trnh x l bng nha trao i ion. Sau l sau nhit phn mt phn nh un nng,ri lm lnh, kt ta thu hi cu t cha Rh. Cc hp cht ny s c b sung iot mi riha tan trong axit axetic nng di p sut CO

2.2.4.2. Thng s qu trnh cacbonyl ha metanol :

CH3OH + CO CH3COOH

H =137KJ/mol

Phn ng thu nhit : H > 0 Nhit : khong 200oC p sut : 35 MPa8

9

Xc tc : hp cht phi tr triphenylphosphin :Rh(CO)[P(C6H5)3]2Cl

rodi-clorocacbonyl-bis

2.2.4.3. C ch phn ng :

2.2.4.4. Lu trnh cng ngh Monsanto :

9

10

Cng ngh Monsanto

Phn xng c 3 phn chnh (nh s cng ngh) : Khu vc chun b xc tc : ti khu vc ny, h xc tc c chun b t rodi ioua mi v xc tc tun hon c thu hi li nh cc cng on x l sau phn ng. Dung dch thu hi ny trc ht c loi b cc ion kim loi c ln do qu trnh x l bng nha trao i ion. Sau , n c phn hy mt phn nh ung nng ri lm lnh ,kt ta thu hi cc cu t cha rodi. Cc hp cht ny s c b sung iot mi ri ha tan trong axit axetic nng di p sut CO. Khu vc cacbonyl ha : Metanol c cacbonyl ha trong pha lng, trong mt thit b phn ng c khuy. Nhit ca mi trng phn10

11

ng c gi khng i nh bay hi mt phn cc tc nhn phn ng v sn phm, do tch c nhit phn ng sinh ra. Pha kh ny cha ch yu CO, CO2, N2, metanol v metyl iot ua, c lm lnh v ra bng metanol thu hi phn ln cc nguyn liu b tch theo. Dng sn phm lng ra khi thit b phn ng c x p nhanh. Cc kh c cha axit axetic, m , metyl iotua . axit formic... c a n khu vc tinh ch. Phn lng , ch yu l phc xc tc ,metyl axetat v axit axetic c lm lnh v a tr v vng phn ng. Khu vc tch v tinh ch : thp chng u tin c thit k to ra phn on giu axit axetic nh tch b cc cu t nh v cc cu t nng ( metyl iotdua v metylaxetat ...). phn on ny sau c dehydrat ha nh chng d ng ph. Pha nc c thu hi nh thp tip tc c chuyn sang phn on loai b nc d. Dng sn phm nng c x l trong thp tinh ch tp ra axit axetic bng, cn axitaxetic to ra y thp cng c thu hi trong thp chng phn on b sung tch cc cu t sn phm nng nh axit propionic. Cc thp ny u lm bng thp hp kim cao v c cha 35 n 45 a. 2.2.4.5. nh gi cng ngh : a.u im : 100%, vi tt c cc nguyn t trong cc cht phn ng i vo sn phm S dng nng lng t hn, c bit tch v tinh ch. C nng sut cao, S dng methanol nguyn liu r hn so vi naphta trc / butan Tc phn ng nhanh. Chu k sng ca xc tc di b. Nhc im Rhodium l kim loi rt t tin - t hn vng Rhodium cng xc tc phn ng ph CO + H20 2+ H2 iu ny lm gim p sut ring phn ca kh carbon monoxide Rhodium ha tan to mun RhI3. Cn c cng on tch nc gy tn chi ph v nng lng tr li xc tc cho phn ng chnh

11

12

2.2.5. Cng ngh CATIVA ca BP 2.2.5.1. Gii thiu cng ngh : Theo quan im ca BP, CATIVA - mi ba nm sau khi thng mi ha ln u tin - vn l cng ngh hiu qu nht, quy nh v vn v chi ph vn hnh thp nht. Nm 1986 Monsanto cp php cho mt s cng ty, bao gm BP, trong BP mua bn quyn cng ngh ca Monsanto v carbonylation methanol v pht trin n hn na to ra thng hiu c quyn ca BP : CATIVA S khc bit c bn nht gia cc phin bn ca qu trnh carbonylation l cht xc tc. Cng ngh carbonylation c bn ca Monsanto l da trn xc tc rhodium, qu trnh CATIVA ca BP nh du mt bc thay i trong cng ngh bi v n chuyn hon ton ra khi rhodium thay vo l xc tc iridi da trn kt hp vi mt cht hot ha kim loi chuy