季铵盐/酰胺类低共熔溶剂的制备及其对纤维素的溶解性能
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摘要
以季铵盐类和酰胺类化合物为原料,合成了包括四甲基氯化铵/己内酰胺(TMACl/CPL)、四乙基氯化铵/己内酰胺(TEACl/CPL)、四丁基氯化铵/己内酰胺(TBACl/CPL)、四丁基醋酸铵/己内酰胺(TBAAc/CPL)、四丁基硫酸氢铵/己内酰胺(TBAHSO4/CPL)、四丁基溴化铵/己内酰胺(TBABr/CPL)等系列季铵盐/酰胺类低共熔溶剂(DES)。通过红外和核磁表征了季铵盐和酰胺之间C=O—H—C和C—N—H—C多重氢键的形成过程。应用DES溶解纤维素时,探讨了季铵盐/酰胺类DES中烷基链长、阴离子结构、溶解时间、温度和黏度等对纤维素溶解性能的影响,结果表明:丁基比乙基和甲基具有更高的溶解能力;不同的阴离子Br~-、Cl~-、Ac~-和HSO_4~-中,Ac~-与己内酰胺的作用可为纤维素溶解过程中提供更多的活性位点; TBAAc/CPL为较优的DES,在100℃、70 min,纤维素的溶解度为7.8%。季铵盐/酰胺类组分间的氢键结构对纤维素的溶解作用机制研究发现:纤维素原有的致密有序结构转化为毛糙无序状态,纤维素典型—OH、—CH伸缩振动吸收峰、以及C—O—C不对称伸缩振动峰均未发生改变,纤维素在TBAAc/CPL中溶解时未发生衍生反应,XRD分析发现纤维素再生后的2θ由15.36°、16.68°和22.10°转变为21.99°,晶型由纤维素Ⅰ型变为Ⅱ型。
A series of ammonium-based ammonium salts and amides were used as raw materials to prepare deep eutectic solvents( DES), namely, tetramethylammonium chloride/caprolactam( TMACl/CPL), tetraethylammonium chloride/caprolactam( TEACl/CPL),tetrabutylammonium chloride/caprolactam( TBACl/CPL),tetrabutylammonium acetate/caprolactam( TBAAc/CPL),tetrabutylammonium hydrogen sulfate/caprolactam( TBAHSO_4/CPL), and tetrabutylammonium bromide/caprolactam( TBABr/CPL). The formation process of hydrogen bonds of C=O—H—C and C—N—H—C between ammonium salt and caprolactam were studied by FI-IR,~1 H NMR,~(13) C NMR and MS. Then,DES was used to dissolve cellulose. The effects of alkyl chain length,anion,time,temperature,viscosity and the hydrogen-bond network structure of DES on the dissolution of cellulose were explored,respectively. It was found that butyl had higher ability to dissolve cellulose than that of ethyl and methyl. Accould afford more reactive sites than Br~-,Cl~-,Ac~- and HSO_4~-. TBAAc/CPL was a preferable solvent and the dissolubility of cellulose was 7. 8% under 100 ℃ and 75 min. Moreover,the dissolution mechanism of hydrogen bond on cellulose wasinvestigated. The results showed that the raw dense and ordered structure of cellulose were changed to coarse and disordered state,and the structure of —OH,—CH and C—O—C didn' t change. The cellulose was directly dissolved in ammonium-based DES,and no other derivatives were generated. XRD analysis showed that the 2θ of cellulose before and after regeneration changed from 15.36°,16.68°,and 22.10° to 21.99°,and the cellulose crystal form was changed from cellulose Ⅰ to type Ⅱ.
A series of ammonium-based ammonium salts and amides were used as raw materials to prepare deep eutectic solvents( DES), namely, tetramethylammonium chloride/caprolactam( TMACl/CPL), tetraethylammonium chloride/caprolactam( TEACl/CPL),tetrabutylammonium chloride/caprolactam( TBACl/CPL),tetrabutylammonium acetate/caprolactam( TBAAc/CPL),tetrabutylammonium hydrogen sulfate/caprolactam( TBAHSO_4/CPL), and tetrabutylammonium bromide/caprolactam( TBABr/CPL). The formation process of hydrogen bonds of C=O—H—C and C—N—H—C between ammonium salt and caprolactam were studied by FI-IR,~1 H NMR,~(13) C NMR and MS. Then,DES was used to dissolve cellulose. The effects of alkyl chain length,anion,time,temperature,viscosity and the hydrogen-bond network structure of DES on the dissolution of cellulose were explored,respectively. It was found that butyl had higher ability to dissolve cellulose than that of ethyl and methyl. Accould afford more reactive sites than Br~-,Cl~-,Ac~- and HSO_4~-. TBAAc/CPL was a preferable solvent and the dissolubility of cellulose was 7. 8% under 100 ℃ and 75 min. Moreover,the dissolution mechanism of hydrogen bond on cellulose wasinvestigated. The results showed that the raw dense and ordered structure of cellulose were changed to coarse and disordered state,and the structure of —OH,—CH and C—O—C didn' t change. The cellulose was directly dissolved in ammonium-based DES,and no other derivatives were generated. XRD analysis showed that the 2θ of cellulose before and after regeneration changed from 15.36°,16.68°,and 22.10° to 21.99°,and the cellulose crystal form was changed from cellulose Ⅰ to type Ⅱ.
引文
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[2]WANG S,LU A,ZHANG L N. Recent advances in regenerated cellulose materials[J]. Progress in Polymer Science,2016,53:169-206.
[3]ISIK M,SARDON H,MECERREYES D. Ionic liquid and cellulose technologies:Dissolution,modification and composite prepara-tion[M]∥MECERREYES D. Applications of Ionic Liquids in Polymer Science and Technology. Berlin/Heidelberg:Springer-Verlag Berlin Heidelberg,2015:135-152.
[4]张盈盈,陆小华,冯新,等.胆碱类低共熔溶剂的物性及应用[J].化学进展,2013,25(6):881-892.ZHANG Y Y,LU X H,FENG X,et al. Properties and applications of choline-based deep eutectic solvents[J]. Progress in Chemistry,2013,25(6):881-892.
[5]GARCIA H,FERREIRA R,PETKOVIC M,et al. Dissolution of cork biopolymers in biocompatible ionic liquids[J]. Green Chemistry,2010,12:367-369.
[6]FRANCISCO M,van den BRUINHORST A,KROON M C. New natural and renewable low transition temperature mixtures(LTTMs):Screening as solvents for lignocellulosic biomass processing[J]. Green Chemistry,2012,14:2153-2157.
[7]ZDANOWICZ M,SPYCHAJ T,MAKA H. Imidazole-based deep eutectic solvents for starch dissolution and plasticization[J]. Carbohydrate Polymers,2016,140:416-423.
[8]VIGIER K D O,CHATEL G,JERME F. Contribution of deep eutectic solvents for biomass processing:Opportunities,challenges,and limitations[J]. ChemCatChem,2015,7(8):1250-1260.
[9]陈洪章.纤维素生物技术[M].北京:化学工业出版社,2005:134-149.CHEN H Z. Cellulose Biotechnology[M]. Beijing:Chemical Industry Press,2005:134-149.
[10]SEGAL L,CREELY J J,MARTIN A E,et al. An empirical method for estimating the degree of crystallinity of native cellulose using the X-ray diffractometer[J]. Textile Research Journal,1959,29:786-794.
[11]RINALDI R. Instantaneous dissolution of cellulose in organic electrolyte solutions[J]. Chemical Communications,2011,47:511-513.