当前位置：文档库 › 简单_快速_清洁合成高纯度二烷基咪唑四氟硼酸离子液体_英文_

简单_快速_清洁合成高纯度二烷基咪唑四氟硼酸离子液体_英文_

Arti cle I D :100123555(2009)0120001206

Rece i ved da te:2008207216;Revised date:2008208204B i ography:Zhu Lai 2ying,fe male,in 1981,master candidate

3Corres ponding audor:

Si m ple,Rapi d and Clean Synthesis of D i a lkyli m i dazoli u m

Tetrafluoroborate i on i c L i qui ds with hi gh Purity

WANG Rui 2feng

a,b,c ,Z HANG Q ing 2hua a ,L I U Shi 2m in a ,L I Zuo 2peng a

L I J ian a

,CHE N Zheng 2jian a

,DENG You 2quan

3,a

Centre for Green Che m istry and Catalysis,L anzhou Institute of Che m ical Physics,Chinese A cade m y of Sciences,

L anzhou,730000;

The N ational L abora tory of A pplied O rgan ic Che m istry,L anzhou U niversity,L anzhou,730000;

Gradua te School of the Ch inese A cade m y of Sciences,B eijing 100039,P .R.China .)

Key words:i onic liquids;one 2step;high purity;synthesis;green che m istry CLC nu m ber:O643.3

D ocu m en t code:A

I onic liquids (I L s )are more and more app lied in

acade m ic research and industry as electr olyte and s ol 2vent substitutes .Recently,these liquids have als o

been used as lubricants [1],heat transfer agents,

[2],[3]

perfor mance additives in paints,[4]

p r ocess fluids f or

separati on p r ocesses [5],[6],catalyzts [7]

and in analyti 2

cal devices .[8]

W ith the in 2dep th devel opment of I L re 2search,a salient point e merging fr om several recent

studies concerns the purity of I L s .[9]

The p revi ous

literatures [10],[11]

showed that possible i m purities in conventi onal I L s such as dialkyli m idaz olium BF 4and PF 6salts were unreacted alkyli m idaz oles,alkyl hal 2ides,B r 2

,Cl 2

,and water etc .,in which B r 2

and Cl

were dom inating i m purities .No w,it has been recog 2nized that the purity of I L s has great effect on their physicoche m ical p r operties and perf or mance .

For ex 2

a mp le,the p resence of Cl 2

or B r 2

can result in obvi ous increase of the viscosity of an I L .

[10]

I n s ome transi 2

ti on 2metal catalyzed reacti ons,even ppm quantities of halides in I L s can pois on ex pensive catalysts,render 2ing the m useless .

I n additi on,the i m purities in I L s

may result in the physicoche m ical data of I L s reported in the p revi ous literatures are omnifari ous .On this ac 2count,t o devel op ne w r outes t o I L s with high purity,in particular hal ogen 2free I L s,has been one of the

challenges in current I L researches .

Currently,the most used app r oach for p reparati on of I L s still e mp l oys a t w o 2step method,i .e .,a quater 2nizati on reacti on with the ai m of f or m ing an I L p recur 2s or containing a target cati on,and f oll owed by a me 2tathesis p r ocess leading t o the desired p r oduct .Howev 2er,there are many shortcom ings of this method,such as poor purity,l ong reacti on ti m e,large a mounts of in 2organic wastes,and tr oubles o me purificati on p r oce 2dures .T o achieve the goal of highly pure I L s thr ough a clean and rap id r oute,great endeavor has been made and several halide 2free synthetic app r oaches including one 2step alkylati on of N 2alkyli m idaz ole by using alkyl sulfates,

[11]

carbonates,

[12]

or phos phates

[13]

etc .as

alkylating agent have been devel oped .

Recently,Egashira et al .

[14]

devel oped an effi 2

cient method f or the one 2step synthesis of tetrafluor obo 2rate I L s by alkylati on of N 2alkyli m idaz ole with trialky 2l oxonium salts .

I n comparis on with traditi onal ani on

metathesis method,this app r oach not only avoids the use of alkyl halides efficiently,reduces the reacti on ti m e greatly,but als o si m p lifies the purificati on p r ocess re markably .However,in their work,only three I L s (i .e .[MM I m ]BF 4,[E M I m ]BF 4,[MMM I m ]BF 4)were p repared,and the contents of main i m purities in

　第23卷第1期分子催化

Vol .23,No .1 2009年2月

JOURNAL OF MOLECULAR C AT ALYSI S (CH I N A )

Feb .　2009　

these I L s were measured .I n this work,we syste mati 2

cally synthesized a series of highly pure dialkyli m idaz o 2liu m tetrafluor oborate salts via alkylati on of N 2alkyli m i 2daz ole with Et 3O +BF 4-or Me 3O +BF 4-(Sche me 1).The possible i m purities in I L s such as hal ogen i ons,inorganic metal i ons,and unreacted alkyli m idaz oles have been deter m ined,and the differences bet w een one 2step method and t w o 2step method in purity are par 2ticularly e mphasized

Sche me 1One 2step r oute for synthesizes dialkyli m idazoliu m

tetrafluor oborates I L s .

Results and D iscussi on

Firstly,as a rep resentative exa mp le,the synthesis of [E M I m ]BF 4is conducted .W e m ixed the anhydr ous diethyl ether s oluti on of 12methyli m idaz ole with an equivalent molar a mount of Et 3O +

BF 4

in an ice bath

i m mediately accompanied with a str ong exother m ic phenomenon,and after stirring f or about 5m inutes,the resulting m ixture s pontaneously f or m t w o i m m iscible layers .The t op layer is identified as by 2p r oduct Et 2O,whereas the bott om layer is identified as the target p r oduct [E M I m ]BF 4with high purity .

Si m ilarly,independently treating 12ethyl 2,12bu 2

tyl 2,12hexyl 2,12octyl 2,and 12decyli m idaz ole etc .with Et 3O +

BF 4

or Me 3O +BF 4

could p r oduce the corre 2

s ponding BF 4salts in a >99.0%yield .For the I L s with different alkyl chain length,the reacti on ti m e is al 2s o different .Generally,reacti ons f or I L s with the alkyl chain of

I n comparis on with traditi onal t w o 2step

method which usually needs several days,the ne w ap 2p r oach reduces the reacti on ti m e greatly,and si m p lifies the purificati on p r ocess re markably .

I n our op ini ons,a mong the widely used I L s,[E M I m ]BF 4has comparatively great potential app lica 2ti ons due t o its better physicoche m ical p r operties,i .e .l ower viscosity,higher i onic conductivity,higher ther 2mal stability etc .To find out a relatively better synthe 2sis r oute for [E M I m ]BF 4,Me 3O +

BF 4-

and Et 3O

BF 4

-are used res pectively .W e can see that there are

no obvi ous differences bet w een the m on purity,yield (Table 2,entry1a,1b )and reacti on conditi ons,but in vie w of the synthetic cost the reacti on bet w een Et 3O +

BF 4

and 12methyli m idaz ole as materials will be

p reponderant .

Table 1Ha li de 2free route to h i ghly pure I L s by usi n g oxon i u m s a lts a s an a lkyl a ti n g agen t Reactant Oxoniu m salts Pr oducts T (o

C )Ti m e (m in )

12methyli m idazole Et 3O +

BF 42[E M I m ]BF 4025512butyli m idazole Et 3O +BF 42[BE I m ]BF 4rt 1012hexyli m idazole Et 3O +BF 42[HE I m ]BF 4rt 6012octyli m idazole Et 3O +BF 42[OE I m ]BF 4rt 12012decyli m idazole Et 3O +BF 42[DE I m ]BF 4rt 12012ethyli m idazole Me 3O +BF 42[E M I m ]BF 4025512butyli m idazole Me 3O +BF 42[BM I m ]BF 4rt 1012hexyli m idazole Me 3O +BF 42[HM I m ]BF 4rt 6012octyli m idazole Me 3O +BF 42[OM I m ]BF 4rt 12012decyli m idazole

Me 3O +BF 42

[DM I m ]BF 4

120

A lkyli m idazole was obtained according t o the method of ref .18.

2 分子催化第23卷　

H igh yield is another main feature of ne w one2step method.A s can be seen fr om the data in Table2,the yields of I L s for med upon one2step method are>99.0 %,whereas only a84.0%yield f or[DE I m]BF4and a94.1%yield f or[E M I m]BF4can be obtained by t w o2step method.One point is needed t o be clarified that,the l ow yield of traditi onal method may be partly caused by those tr oubles ome purificati on p r ocedures such as liquid2liquid extracti on.I n contrast,the purifi2 cati on p r ocess in ne w one2step method is very si m p le, and thus greatly avoids the l oss of I L s.

I n appearance,1,32dialkyli m idaz olium[BF4] I L s should be col orless,but actually they are frequent2ly not,in particular those I L s with l ong alkyl chains.[15]Some researchers thought that the chr omo2 i m purities were the p r oducts of side reacti ons occurring at high te mperature when halide salts are synthe2 sized.[16],[17]It is worth noting that,the I L s obtained by the ne w app r oach are all col orless,which may be exp lained by the result that all reacti ons can p r oceed s moothly at relatively l ower te mperatures(0～25 o C).[18]The vivid p ictures of[OM I m]BF

,[DM I m] BF4,[OE I m]BF4,[DE I m]BF4(left,by one2step method)and their counter parts(right,by t w o2step method),res pectively,are given in Figure2

Fig.2Picture of f our I L s fr om one2step method(left)and t w o2step method(right).

T o compare the differences of t w o synthetic meth2

ods,we measured the main i m purity contents such as

hal ogen i ons,s odiu m i on and N2alkyli m idaz ole in nine

I L s obtained by t w o methods res pectively,and the re2

sults fr om i on selective electr ode and Gas Chr omat ogra2

phy are listed in Table2.For all I L s made by t w o2step

method,the residual B r2,Cl2and Na+can be found,

even being purified carefully(described in Experi m en2

tal)before measure ment.Among these hal ogen i m puri2

ties,the Cl2contents are given as0.17～1.02%and

the maxi m u m value bel ongs t o[H M I m]BF4.The B r2

contents are given as0.71～2.95%and the maxi m u m

value bel ongs t o[OM I m]BF4.The range of Na+con2

tents are0.06～0.83%,in which the m ini m um and

maxi m u m values bel ong t o[OE I m]BF4and[E M I m]

BF4,res pectively.For all I L s obtained by one2step

method,the i on selective electr ode measure ments

showed that hal ogen i ons(Cl2or B r2)and Na+could

not be detected in the range of detecti on li m it,which

means that hal ogen and Na+content should be less than

ppb grade.

Since B r2or Cl2i m purities as electr oche m ical ac2

tive s pecies can be easily oxidized at l ower oxidative

potentials,the purity can als o be reflected fr o m the cy2

clic volta mmogra m of an I L t o a certain extent.Thus,

here take[E M I m]BF4as a typ ical exa mp le,the elec2

tr oche m ical behavi or of[E M I m]BF4p repared by ne w

method and traditi onal ani on metathesis was als o stud2

ied,and a si m p le comparis on bet w een the m was

dra wn,as shown in Fig.2.Fr om the cyclic volta mme2

try of[E M I m]BF4,no unexpected reducti on or oxida2

ti on peaks are observed,and the expected reducti on

peak is observed clearly at22.2V,which als o p r oves

that the[E M I m]BF4p repared by one2step method was

highly pure.

3第1期王瑞峰等:简单、快速、清洁合成高纯度二烷基咪唑四氟硼酸离子液体

Table 2Y i elds and Pur ity of I L s prepared by two d i fferen t m ethods

Entry I L s method Yield a

(%)

Cl 2/B r 2

(%)

Na +

(%)Unreacted alkyli m idazoles (%)

[E M I m ]BF 4

a )One 2step >99.022222

b 22222b 22222b

(E I m )b )One 2step >99.022222

b 22222

b 22222b

(M I m )T wo 2step

94.11.13(B r 2

)

0.83

22222b

(M I m )2

[BM I m ]BF 4

One 2step >99.022222

22222

b 22222b

(B I m )

T wo 2step

90.40.17(Cl 2

)

0.75

0.02(M I m )3

[HM I m ]BF 4

One 2step >99.022222

b 22222

b 0.05(H I m )T wo 2step

90.01.02(Cl 2

)

0.11

0.02(M I m )4

[OM I m ]BF 4

One 2step >99.022222

22222

b 0.12(O I m )T wo 2step

87.22.95(B r 2

)

0.14

0.12(M I m )5

[DM I m ]BF 4

One 2step >99.022222

b 22222

b 0.05(D I m )T wo 2step

86.52.33(B r 2

)

0.23

0.02(M I m )

[BE I m ]BF 4

One 2step >99.022222

b 22222

b 22222b

(B I m )

T wo 2step

91.10.93(Cl 2

)

0.16

0.09(E I m )7

[HE I m ]BF 4

One 2step >99.022222

b 22222

b 0.53(H I m )T wo 2step

88.30.27(Cl 2

)

0.310.22(E I m )

[OE I m ]BF 4

One 2step >99.022222b

22222

0.25(O I m )

T wo 2step

85.30.96(B r 2

)

0.06

0.09(E I m )9

[DE I m ]BF 4

One 2step >99.022222

22222

b 0.20(D I m )T wo 2step

84.0

0.71(B r 2

)

0.10

0.13(E I m )

a is olated yields

b under detected li m it .M I m ,E I m ,B I m ,H I m ,O I m and D I m stand for 12methyli m idazole,12ethyli m idazole 12butyli m idazole,12hexyli m idazole,12octyli m idazole and12decyli m idazole,res pectively

Fig .3Cyclic voltammogra m of [E M I m ]BF 4(A:T wo 2step method )and (B:Ne w method )at

a glass carbon working electr ode .

A s t o unreacted alkyli m idaz ole i m purity,the con 2

tent of 0.02～0.22%in I L s (excep t for [E M I m ]BF 4)by t w o 2step method was obtained,whilst the con 2tent of 0.05～0.53%was detected for I L s with the al 2kyl chain of C 62C 10by one 2step method .Considering

the fact that the molar weight of s ome alkyli m idaz oles

(e .g .octyl 2or decyli m idaz ole )is much higher than that of methyli m idaz ole or ethyli m idaz ole,the result of slightly higher alkyli m idaz ole content in ne w app r oach is als o reas onable .I n additi on,the alkyli m idaz ole con 2tent is als o different f or I L s obtained by different oxoni 2u m salts .For exa mp le,the 12decyli m idaz ole content in [DE I m ]BF 4(0.20%)is higher than that in [DM I m ]

BF 4(0.05%),which indicated that Me 3O +BF 4-is

more active than Et 3O +BF 4

in alkylati on reacti ons .

Based on the above studies,the main i m purities in all I L s by ne w method are the unreacted alkyli m id 2az oles,the content of which are <0.53%,indica 2ting that the purities of these I L s should be >99.0%.Further,if higher purity is needed,these alkyli m i 2daz oles can als o be efficiently re moved by diethyl e 2ther 2washed t o obtain higher purity I L s .Take [HE I m ]

4 分子催化第23卷　

BF4as a exa mp le,after washed ten ti m es by diethyl e2 ther,12hexyli m idaz ole was not detected by Gas Chr o2 mat ography in[HE I m]BF4any more.Additi onally, the alkyli m idaz ole content in[E M I m]BF4,[BM I m] BF4and[BE I m]BF4are under the detected li m it, which showed that these I L s possess ultra2high purity.

Conclusi on

I n summary,nine dialkyli m idaz olium tetrafluor ob2 orate I L s with high purity,in particularly those[BF4]2 I L s with the alkyl chain of C62C10,have been p repared by alkylati ons of N2alkyli m idaz ole with trialkyl oxoniu m salts.The possible i m purity contents in I L s such as hal ogen i ons,inorganic metal i ons,and unreacted al2 kyli m idaz oliu m,have als o been measured in detail. The results show that this is an efficient p r ot ocol f or p reparing[BF4]2I L s with high purity(>99%).I n comparis on with currently the most common synthetic method,the ne w app r oach not only avoids hal ogen conta m inati on comp letely,but als o reduces reacti on ti m e greatly and si m p lifies purificati on p r ocess re mark2 ably.To this end,it is worthy t o be noted that many kinds of highly pure I L s based on pyridiniu m,quater2 nary phos phoniu m,and quaternary a mmonium etc. cati ons,can als o be p repared thr ough this p r ot ocol,i.

e.,via the reacti ons of N2or P2containing compounds with trialkyl ox oniu m salts,and further investigati on on this as pect is ongoing.

Acknowledg m en t

W e are grateful t o the Nati onal Natural Science Foundati on of China for the financial support(No. 20225309and20533080)

References and Notes

[1]　Lu,Q,W ang H,Ye C,et al.Tribol.Int.[J],2004,

37:547

[2]　O lbert G,M attke T,Fiene M,et al.Ger m any,Ger.

Pat.A ppl.,DE[P]200321031641810316418,2004 [3]　Van ValkenburgM E,Vaughn R L,W illia m s M,et al.

Proc.Electroche m.Soc.[J],2002,19:112

[4]　W eyershausen B,Leh mann K.Green Che m.[J],2005,

7:15

[5]　Beste Y A,Schoen makers H,A rlt W.et al.BASF AG,

Ger m any,Ger.Pat.A ppl.,DE[P],2003210336555

10336555,2005

[6]　Jork C,SeilerM,Beste Y A,et al.J.Che m.Eng.D a2

ta.[J],2004,49:852

[7]　a.Shao L i2li(邵丽丽),W ang W en2juan(王雯娟),

Peng Hui2qi(彭惠琦),et al.J.M ol.Catal.(China)

(分子催化)[J],2007,21(6):520～524

b.Deng Chang2xi(邓昌 ),Yang Yong(杨　勇),

Yuan You2zhu(袁友珠)..J.M ol.Catal.(China)(分

子催化)[J],2007,21(1):13～18

[8]　B s mann A,Schubert T J S,Ger many.B r.Pat.A ppl.

G B[P],20052107722414553,2005.

[9]　Gall o V,Mastr orilli P,Nobile C F,Romanazzi G,et al.

J.Che m.Soc.D alton T rans.[J],2002,4339

[10]Seddon K R,Stark A,T orres M J.Pure A ppl.Che m.

[J],2000,72:2275

[11]Holbrey J D,ReichertW M,S watl oski R P,et al.Green

Che m.[J],2002,4:407

[12]Holbrey J D,Reichert W M,Tkatchenko I,et al.

Che m.Co mm un.[J],2003,28

[13]Kuhl m ann E,H i m m ler S,Giebelhaus H,et al.Green

Che m.[J],2007,9:233

[14]Egashira M,Ya ma mot o Y,Fukutake T,et al.J.Fluo2

rine Che m.[J],2006,127:1261

[15]Earle M J,Gordon C M,Plechkova N V,et al.A nal.

Che m.[J],2007,79:758

[16]Far mer V,W elt on T.Green Che m.[J],2002,4:97

[17]Bonh te P,D ias A P,Papageorgi ou N,et al.Inorg.

Che m.[J],1996,35:1168

[18]Analysis and M easure ment.Bef ore analysis and measure2

ment,each I L must be transferred in clean and dry rea2

gent bottles and kep t in a vacuu m(p ressure102221023

mbar)at952100℃f or4hours f or the re moval of any

volatile i m purities,in particularly water.1H NMR s pec2

tra were recorded on a B ruker AMX FT4002MHz NMR

s pectr ometer.Che m ical shifts are reported in delta(δ)

units,exp ressed in parts per m illi on(ppm).I nfrared

s pectra were recorded as a thin fil m on s odiu m br om ide

and abs or p ti ons were reported in wavenu mbers(c m21).

The hal ogen and Na+contents were measured using

M ETTER T OLE DO Seven M ulti meter with Cl2,B r2and

Na+i on selective electr odes at25℃.The alkyl i m idaz2

ole content was measured by f oll owing method.Seven

standard diethyl ether s oluti ons(100mL)of methyl i m2

idazole were p repared and concentrati ons were0.10%,

0.20%,0.50%,1.0%,1.5%,2.0%,2.5%,

res pectively.0.10μL of these s oluti ons were injected and

第1期王瑞峰等:简单、快速、清洁合成高纯度二烷基咪唑四氟硼酸离子液体

analyzed by Agilent6820Gas Chr omat ography,res pec2

tively.After which,calibrati on curve of peak areas vs

concentrati ons was obtained for analyzing methyl i m idaz2

ole contents.[BM I m]BF4(11.9325g)p repared by old

method was washed by10mL diethyl ether ten ti m es t o

extract the methyl i m idazole in this salt,then the diethyl

ether was concentrated t o1.0mL and0.10μL was injec2

ted.The concentrati on of methyl i m idazole was obtained

as0.20%using above calibrati on curve.Hence,the

content of methyl i m idazole in this salt was0.02%

(0.20%1.0mL/11.9325).This is a typ ical exa mp le

and others are si m ilar.

[19]Preparati on of alkyli m idazole.Excep t that N2methyli m id2

azole and N2ethyli m idazole are commercially available

and used without further purificati on,all other N2alkyli m2

idazoles such as N2butyli m idazoles,N2hexyli m idazoles,N2octyli m idazoles and N2decyli m idazoles were p repared according t o the reported method.16Here take N2octyli m i2 dazole as a typ ical exa mp le,the p reparati on p r ocedure was as f oll ows.Sodiu m(25.3g1.10mol)was added t o 300mL ethanol taken in a beaker and stirred,ice bath was needed.1H2i m idazole(68.1g1.00mol)was added t o this syste m after s odiu m disappearing and stirred for1. 5h.After which,12br omooctane(183g0.95mol)was added t o this syste m and stirred at40o C for10h.On comp leti on of the reacti on,generated s odiu m br om ide was re moved by filter and ethanolwas re moved by distillati on. Octyl i m idazole was collected at163～164o C by distil2 lati on under125～130mmHg.O ther N2alkyli m idazoles such as12butyl2,12hexyl2,and12decyli m idazole could als o be synthesized by a si m ilar method.

简单、快速、清洁合成高纯度二烷基咪唑四氟硼酸离子液体

王瑞峰a,b,c,张庆华a,刘士民a,李作鹏a,李　健a,陈正件a,邓友全a,3

(a中国科学院兰州化学物理研究所绿色化学研究发展中心,甘肃兰州730000;

b兰州大学应用有机国家重点实验室,甘肃兰州730000;

c中国科学院研究生院北京100039)

摘　要:通过三烷基钖四氟硼酸盐与烷基咪唑作用一步合成了一系列二烷基咪唑四氟硼酸离子液体,所有反应在室温下5～120分钟内完成,产率均>99%.对以上离子液体中可能含有的主要杂质进行了测定,结果表明,通过一步法合成的离子液体中卤素离子、Na+和卤代烷的含量均低于检出限,烷基咪唑的含量在0～0.53wt%范围内.此方法具有简单、快速、清洁等优点,是一种制备高纯度离子液体可行方法.

关键词:离子液体;一步法;高纯度;合成;绿色化学

6 分子催化第23卷　