ALKYL HOA BENZEN B A N G PROPEN TREN ZEOLIT H-ZSM-5

Tran Thi N h i i Mai, N g u y e n Thi Ha, Le Thai Stfn, N g u y i n Thi IVIinh Thif, N g u y i n Thi V i e t N g a Khoa hod hoc, DHKHTN, DHQGHN

ALKYLATION OF BENZENE BY PROPENE OVER H-ZSM-5 ZEOLITE

SUMMARY

The reaction of synthesis ofiso-propyl benzene has been an impor­

tant signification in chemical industry. It had been carried on different

catalysts but the obtained results hadn't been satisfactory until the zeo­

lite ZSM-5 was invented. Experiments has shown that it can be good

catalyst for the alkylation of benzene by propen.

MODAU

Phan ling ankyl boa benzen thanh iso-propyl benzen (IPB) - mot san pham trung gian trong qua trinh san xuat phenol va axeton - c6 vai tro quan trong trong c6ng nghiep. Miic do tieu thu cumen (hay IPB) nam 1990 la 6,3 trieu tan va khdng ngifng tang len [1]. TrUdc day, phan iing tong hdp cumen dUa tren he xiic tac Friden-Kraft hoac axit photphoric r^n (SPA) [1]. Tuy nhien, cac xiic tac nay deu ton tai nhieu ban che nen viec tim kiem mot he xiic tac t6't hdn cho phan utng la can thie't. Su ra ddi cua zeolit ZSM-5, mot loai zeolit c6 tinh chon loc hinh hoc cao va rat ben nhiet da md ra hudng ting dung mdi nhieu trien vong cho phan ling ankyl boa trong do c6 qua trinh tong hdp cumen. Nhieu loai xuc tac da dUdc nghien ciiu ling dung cho phan ling nay [1,2,3] va da dUdc thudng mai boa nhu zeolit Mordenit, zeolit Y... nhUng ngay nay cac to hdp loc hoa dau da dan dUdc thay the hoan

190

toan, sxi dung xiic tac zeolit ZSM-5, nhd dac tinh chon loc hinh hoc cua xiic tac nay. Mat khac, do tinh ch^'t phUc tap cua phan ling nen cong nghe san xuat cumen vkn lu6n dUdc cai tien, chang ban nam 1999, qua trinh tong hdp cumen tii benzen va propen svL dung zeolit ZSM-5, vdi ky thuat chUng cat xiic tac, da dUdc hang Mobil dUa vao san xuat d Thai Lan. Viec sii dung zeolit ZSM-5 d^ kh^c phuc dUdc nhieu nhudc diem cua cac xiic tac trUdc do nhU: thdi gian lam viec cua xiic tac dai hdn, qua trinh phu va tbii cap it hdn, khong gay an mon thie't hi va 6 nhilm moi trUdng...

Cling vdi sU hinh thanh va phat trien cua nganh c6ng nghiep loc boa dau d Viet Nam thi viec nghien ciiu kha nang iing dung ciia olephin C3= (san pham ciia qua trinh loc dau) dong thdi nghien ciiu kha nang dng dung ciia xiic tac zeolit ZSM-5 la can thie't. Tren cd sd do chung t6i da khao sat phan ting propyl hoa benzen hkng propen tren zeolit H-ZSM-5.

THUC NGHlfiM

Miu xuc tac sii dung la Na-ZSM-5 cd ty sd Si/Al = 43. Chuyen dang Na-ZSM-5 ve dang H-ZSM-5 b^ng each trao ddi vdi dung dich NH4C1 va nung d 550OC de loai NH3. Miic do trao ddi dUdc danh gia theo phUdng phap phd hap thu nguyen tii, xac dinh ham lUdng Na trUdc va sau khi trao ddi. Xiic tac sii dung la cac hat cd kich thudc tii 0,5 den 1,0 mm. San pham phan ling dUdc ngUng tu va phan tich tren may s^c ki khi Shimadzu-14B va may s^c ki khi khd'i phd GCMS-HP6890.

K £ T QUA v A THAO LUAN

Trong thUc te, phan ling tong hdp cumen tiif benzen va propen da dUdc nghien ciiu va di vao san xu^'t d quy mo c6ng nghiep, sii dung xiic tac SPA tii nam 1945 [1]. Ciing vdi sU phat trien cua khoa hoc vat lieu, nhieu xiic tac khac nhau da dUdc thxi nghiem cho phan ling nay. Tuy nhien, viec thUc hien phan iing cho do chon loc cao theo cumen con gap nhieu khd khan.

191

Khi thUc hien phan iing tong hdp cumen tut benzen va propen tren Mordenit bien tinh, Meima va cong sU [1] cho thay trong san pham phan ling luon sinh ra di iso-propyl benzen (DIPB) va mot s6 san pham nang khac. Becker va cong sU [2] cung cho ket qua tUdng tU. Ching ban, tren xiic tac Mordenit, d ty le mol C3 : Ce = 1 : 5,6; td'c do dong 30 ml/phiit va nhiet do 150°C, ham lUdng DIPB trong san pham phan Ung la 45,1 % va naphtalen thu dUdc d dang vet, con khi nang nhiet do len 400°C thi lUdng DIPB giam xud'ng con 0,6% nhUng cac san pham nang khac lai len den 37,3% [1] (cac san pham nay vdi cac thie't hi phan tich trUdc day khdng xac dinh dUdc cau tao). Dieu nay c6 the giai thich tii dac diem cua phan ting ankyl boa. Phan tii mono ankyl benzen sinh ra (d day la IPB) c6 mat do electron d nhan thdm Idn hdn benzen nen dl tham gia phan iing ankyl hoa hdn benzen de tao ra cac san ph^m the nhieu l^n. Ngoai ra sU phiic tap cua san pham con do sU ankyl boa benzen b^ng cac anken sinh ra trong cac phan iing tbii cap. Do do, nhiing xiic tac c6 dUdng kinh 16 mao quan Idn nhU zeolit Y, Mordenit... thi deu thuan Idi cho sU hinh thanh cua cac san ph^m cong kenh. NgUdc lai, doi vdi zeolit ZSM-5, do he mao quan c6 kich thudc trung binh (5,3x5,6 A va 5,1x5,7 A) va kha dong deu [3,4] nen san pham phu cong kenh bi ban che.

Bang 1 trinh bay ket qua phan tich san ph^m phan ting d dieu kien nhiet do 300*^C, toe do dong (tinh theo benzen) 3 gid'^ va ty le mol nguyen lieu C3 : Cg = 1 : 4.

Bang 1. Phan tich san pham tren GCMS-HP6890

STT 1 2 3 4 5 6 7 8 *>

10 11

Hop chat

Benzen loluen

htyl benzen p-xylen Cumen

n-propyl benzen 1 -metyl propyl benzen

n-buiyl benzen 1-metyl butyl benzen

n-pentyl benzen San pham nhe

Ham luong % theo khoi lircmg

34,3

U 1,6 hi 17,5 5,8 7,0 3,̂ 2,1 ,̂3

b,«

192

Nhu vay, ben canh san pham chlnh la cumen, phan iing con sinh ra mot so'san pham khac nhU n-pentyl benzen, toluen, etyl benzen, p-xylen... sU xuat hien cua cac san pham nay cho thay qua trinh oligome hoa cac phan tii propen va qua trinh crackinh cac san pham oligome boa da xay ra. Bang 1 ciing cho thay cac san pham cong kenh nhU naphtalen, antraxen, cac poli ankyl benzen... hau nhU khdng xuat hien. Dieu do the hien Uu diem chon loc hinh hoc ciia ZSM-5 so vdi cac xiic tac khac [3,5,6,7].

Mot khd khan ma cac xiic tac ciia qua trinh tong hdp cumen trUdc do thUdng gap phai la sU giam nhanh chong boat tinh xiic tac theo thdi gian. Xiic tac SPA mat boat tinh nhanh chong d nhiet do cao, xiic tac Mordenit va Y giam boat tinh do sU tao c6'c lam che phu tam boat dong tren be mat mao quan [1]. Ddi vdi ZSM-5, do cau triic he mao quan dong deu vdi kich thudc 16 trung binh nen da ban che dUdc ra t nhieu qua trinh tao co'c. Khao sat phan Ung d cac thdi diem khac nhau cho thay san pham phan iing kha dn dinh (bang 2).

•> Bang 2: Anh hUofng cua thdi gian tien hanh phan iing

den san pham phan iing

Thoi gian (phut)

Do chuyen hoa theo benzen (%)

Cumen (%)

Do chon loc theo cumen (%)

15

41,1

16,9

41,1

60

41,9

17,5

41,7

120

40,5

17,2

42,4

Dieu kien phan iing: Nhiet do: 300^C

Tdc do the tich: 3 gid "̂

Ty le mol nguyen lieu: C3 : C6 = 1 : 3

Trong nghien ciiu va trong cong nghe, ben canh viec lUa chon loai xiic tac thi dieu kien tien hanh phan iing ciing anh hUdng rat manh den xu hUdng hinh thanh san pham cuo'i ciing. Khao sat anh hudng cua nhiet do va ty le mol nguyen lieu den ke't qua phan iing cho thay phan ling tdng hdp cumen kh6ng n^m ngoai quy luat chung: do chuyen

193

hoa nguyen lieu cang cao thi do chon loc theo san pham chinh cumen cang tha'p.

Bang 3. Anh hudng cua ty le mol nguyen lieu

^̂ 6 : ^3

2,5

3,0

4,0

6,0

Do chuyen hoa theo benzen (%)

42,0

39,0

31,6

13,5

Do chon loc theo cumen (%)

28,0

43,3

56,5

70,1

San ph^m phu (%)

30,0

22,3

13,8

4,1

Do H-ZSM-5 c6 tinh axit cao nen qua trinh oligome boa cac phan tii propen rat de xay ra.Viec nang cao ty le mol Ce : C3 c6 vai tro ban che qua trinh oligome hoa nay nen mac dii do chuyen hoa nguyen lieu giam nhUng do chon loc theo cumen lai tang nhanh, tiic la ham lUdng san pham phu giam di nhieu (bang 3). Day la bai toan dat ra cho cac nha cong nghe trong san xu^'t c6ng nghiep vi viec tach cumen ra khdi h6n hdp phan ting d do chuyen hoa tha'p (tiic la d do chon loc cao) de hdn nhieu so vdi viec tach cumen ra khdi hdn hdp san pham phiic tap d do chuyen boa cao. Day ciing la cC sd cua sU ddi mdi c6ng nghe san xuat cumen cua hang Mobil. Trong cong nghe ma hang Mobil l^p dat tai Thai Lan nam 1999, propen sau .khi tiep xiic vdi benzen trong Id phan ling chiia xiic tac dUdc tach ngay ra khdi he phan iing de tranh sU oligome hoa [8].

-> Bang 4. Anh hUdng cua nhiet do den san pham phan iing

Nhiet do («C)

Do chuyen hoa theo benzen (%)

Ham luong cumen(%)

Do chon loc theo cumen(%)

Phan nhe(%)

Phan ndng(%)

250

32,2

10,8

33,6

12,5

8,9

300

39,6

17,2

43,4

11,0

11,4

350

38,9

9,9

25,4

8.1

20,9

194

Dieu kien phan iing: Ty le mol nguyen lieu: Cg : C3 = 3 : 1

T6'c do dong: 3 gid'-"-.

Bang 4 trinh bay ket qua phan iing d cac nhiet do tieu bieu khac nhau. Mac du do chuyen boa nguyen lieu thay ddi khdng nhieu nhUng cac san pham cuo'i cung lai khac nhau kha Idn. Do chon loc theo cumen dat cao nhat d khoang 300°C, tha'p hdn so vdi nhiet do cua qua trinh alkyl hoa benzen bang etylen tren Mordenit (khoang 350^C) [2]. Dieu nay la hdp ly vi so vdi etylen thi propen la tac nhan alkyl hoa boat dong hdn.

Nhiing nghien ciiu ban dau nay cho thay H-ZSM-5 la mot xiic tac tot cho phan ling tdng hdp cumen, dong thdi cho thay mo'i lien he chat che giiia cau tnic va boat tinh xiic tac cua ZSM-5. .Ben canh nhiing thuan Idi da dat dUdc, tinh axit cao con la mot ban che' cua ZSM-5 trong phan iing nay. Viec nghien ciiu tim ra nhiing he xiic tac mdi dd'i vdi qua trinh cumen hien van luon la hudng nghien ciiu ciia cac nha khoa hoc va cac nha c6ng nghe tren the' gidi ciing nhU trong nhiing nam dSu the ky XXI xiic tac MCM-22 dang htia hen sU thUdng mai hoa doi vdi qua trinh nay [9].

Ktr LUAN

Zeolit ZSM-5 c6 kha nang kh^c phuc nhieu nhUdc diem cua cac xiic tac trUdc do trong phan iing tdng hdp cumen tii benzen va propen.

Dac trUng cau triic la thu^in Idi ciia ZSM-5 trong phan iing nghien ciiu. San pham cumen cd do chon loc cao, sU tao thanh cac san pham nang bi ban che.

TAI LifiU THAM KHAO

[1]. G.R. Meima, M.J.M. Van Der Aalst, M.S.U. Samson, J.M. Garces, J.L. Lee, Cumen Production Based on Modified Mordenit Catalysts, Proceedings of the 9̂ 1̂ International Zeolits Confernce, Montreal, p.327-334 (1992).

[2]. K.A. Becker, H.G. Karge, W.D. Streubel, Benzen Alkylation

195

with Ethylene and Propylene over H-Mordenite as Catalysts, J. Catal, Vol.28, p.403-413 (1973).

[3]. Nguyen Hiiu Phii, Nguyin Hong Lien, Tap chi hod hoc, T.37, s6'4, Tr.3-6(1999).

[4]. Sankarasubier Narayaman. Calorymetric measuments of aci­dity oftemplated and non-templated H-ZSM-5 zeolites and their correlation with catalytic activity, J.App.Cat, Vol. 143,p.337-342 (1996)

[5]. S. Siffert, L. Gaillard and B.-L. Su, In situ FIR studies of the alkylation of benzene by propene on a series of H-Beta zeolites, 12̂ *̂ International zeolite conference, Materiels Rechearch Society, p.121-123 (1999).

[6]. S. Siffert, L. Gaillard and B.-L. Su. Alkylation of benzene by propene on a series of Beta zeolites, J. Mol. Catal.,153 (1-2), p.267-279 (2000).

[7]. A.V. Smirnov. Benzene alkylation with propene over Ga, B and Al pentasils, 10*̂ ^ International zeolit conference, Berlin, p.1797-1804 (1994).

[8]. Ngo Thi Thuan, Tran NhU Mai, Nguyen Tien Thao, Nguyen Thanh Bao, Vu Ngoc Toan. Xuc tdc H-ZSM-5 trong mot so'phan i2ng hod dau, Hoi nghi xiic tac - hap phu toan quo'c lan thii 2, Ha Noi (2001).

[9] A. Corma and H. Garcia. Lewis Acids: From Conventional Homogeneous to Green Homogeneous and Heterogeneous Catalysis, Chem. Rev. 2003, 103, 4307-4365.

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