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CATALYTIC CONVERSION OF CELLULOSE INTO

NANOCELLULOSE IN IONIC LIQUID

TAN XIAO YUN

INSTITUTE OF GRADUATE STUDIES

UNIVERSITY OF MALAYA

KUALA LUMPUR

2016

CATALYTIC CONVERSION OF CELLULOSE INTO

NANOCELLULOSE IN IONIC LIQUID

TAN XIAO YUN

DISSERTATION SUBMITTED IN FULFILMENT OF

THE REQUIREMENTS FOR THE DEGREE OF MASTER

OF PHILOSOPHY

INSTITUTE OF GRADUATE STUDIES

UNIVERSITY OF MALAYA

KUALA LUMPUR

2016

ii

UNIVERSITY OF MALAYA

ORIGINAL LITERARY WORK DECLARATION

Name of Candidate: TAN XIAO YUN (I.C/Passport No: 900608065720)

Matric No: HGA 130017

Name of Degree: Master of Philosophy

Title of Project Paper/Research Report/Dissertation/Thesis (this Work):

Catalytic Conversion of Cellulose into Nanocellulose in Ionic Liquid

Field of Study: Chemistry (Catalysis)

I do solemnly and sincerely declare that:

(1) I am the sole author/writer of this Work; (2) This Work is original; (3) Any use of any work in which copyright exists was done by way of fair dealing

and for permitted purposes and any excerpt or extract from, or reference to or

reproduction of any copyright work has been disclosed expressly and

sufficiently and the title of the Work and its authorship have been

acknowledged in this Work;

(4) I do not have any actual knowledge nor do I ought reasonably to know that the making of this work constitutes an infringement of any copyright work;

(5) I hereby assign all and every rights in the copyright to this Work to the University of Malaya (UM), who henceforth shall be owner of the copyright

in this Work and that any reproduction or use in any form or by any means

whatsoever is prohibited without the written consent of UM having been first

had and obtained;

(6) I am fully aware that if in the course of making this Work I have infringed any copyright whether intentionally or otherwise, I may be subject to legal action

or any other action as may be determined by UM.

Candidates Signature Date:

Subscribed and solemnly declared before,

Witnesss Signature Date:

Name:

Designation:

iii

ABSTRACT

Nanocellulose have emerged as a promising material and have attracted considerable

attention owing to their promising properties such as high surface area, high strength and

stiffness as well as biodegradability. In the present study, 1-butyl-3-methylimidazolium

hydrogen sulfate (BmimHSO4) and 1-butyl-3-methylimidazolium acetate (BmimOAc)

ionic liquids were utilized to function as catalyst and solvent to convert cellulose into

nanocellulose. Despite having the same cations, BmimHSO4 with higher acidity is

suggested to induce hydrolytic cleavage of glycosidic bonds. On contrary, higher

electronegativity of BmimOAc much prone to cause solvolysis of cellulose.

Comprehensive investigations on different synthesis parameters including reaction

temperature, time, concentration (mass loading of MCC) and sonication treatments were

conducted in order to control the specific architecture and properties of nanocellulose.

Improved crystallinity of nanocellulose with the preservation of crystalline cellulose I

structure has been successfully acquired with acidic BmimHSO4 through hydrolysis.

Hydrolytic reaction of BmimHSO4 performed at a temperature of 90 C for 1.5 hours has

contributed to the formation of highly crystalline nanocellulose (CrI 92.2 %) with smaller

diameter (~15 nm). Increasing the temperature and time of the hydrolytic reaction

predominantly increased the crystallinity of nanocellulose and produced smaller size of

nanocellulose. However, the crystallinity decreased gradually with further increased in

the temperature and time beyond the optimum conditions. Besides that, the cellulose

concentration (in wt%) also has significant impact on the crystallinity as well as size of

nanocellulose. Interestingly, the size of nanocellulose increased proportionally with

increasing cellulose concentration.

On the other hand, transformation of crystal structure from cellulose I into cellulose II

took place in nanocellulose obtained from solvolysis reaction with BmimOAc.

iv

Nanocellulose with a crystallinity of 78.8 % was acquired at 80 C for 1 hour of solvolysis

and cellulose was found to swell in BmimOAc. It is noteworthy that crystallinity of

nanocellulose decreased relatively with increasing temperature and time of dissolution.

Meanwhile, cellulose concentration also significantly influenced the crystallinity and size

of nanocellulose. With increasing cellulose concentration, the crystallinity dropped

gradually and size increased proportionally.

In addition, ultrasonication treatment is essentially important to improve the

crystallinity and yield smaller size nanocellulose with improved colloidal stability.

Suspension of nanocellulose prepared with BmimHSO4 and BmimOAc are considered

rather stable with their higher absolute zeta potential values of -37.5 mV and -22.3 mV,

respectively. Morphological observations demonstrated that rod-like nanocrystalline

cellulose was obtained after hydrolysis with BmimHSO4 whereas spherical cellulose

nanoparticles were acquired through solvolysis with BmimOAc. Hydrolytic reaction

imparted lower thermal stability for nanocrystalline cellulose due to the presence of

sulfate groups from BmimHSO4. While cellulose nanoparticles with enhanced thermal

stability were acquired after the solvolysis reaction.

In the present study, ionic liquids were function as both the catalyst and solvent to

prepare nanocellulose. The synthesis route with ionic liquids is an environmental friendly

approach because neither undesirable nor toxic products will be produced. Meanwhile, it

is an economical feasible process because of the high retrieval of ionic liquids (recovery

yield of about 90 %) and they are recyclable as well as reusable.

v

ABSTRAK

Nanoselulosa merupakan suatu bahan yang menjanjikan dan juga menarik perhatian

oleh kerana ciri-cirinya yang istimewa seperti memiliki permukaan yang luas, kekuatan

dan kekukuhan serta kemampuan untuk biopemerosotan. Dalam kajian ini, 1-butyl-3-

methylimidazolium hydrogen sulfate (BmimHSO4) dan 1-butyl-3-methylimidazolium

acetate (BmimOAc) cecair ionik telah digunakan sebagai pemangkin dan pelarut untuk

menghasilkan nanoselulosa daripada selulosa. Walaupun mempunyai kation yang sama,

keasidan BmimHSO4 dicadangkan menyumbang kepada hidrolisis. Sementara itu,

BmimOAc dengan keelektronegatifan yang tinggi lebih cenderung dalam proses solvolisis

untuk menghasilkan nanoselulosa. Kajian yang komprehensif dalam parameter sintesis

yang berlainan seperti suhu, masa, kepekatan (jisim tambahan MCC) dan rawatan

sonikasi telah dijalankan untuk mengawal sifat-sifat tertentu nanoselulosa.

Peningkatan hablur dengan pengekalan struktur hablur selulosa I dalam nanoselulosa

telah berjaya dihasilkan dengan menggunakan BmimHSO4. Berbanding dengan MCC,

hidrolisis pada suhu 90 C dalam masa 1.5 jam telah menyumbang kepada penghasilan

nanoselulosa dengan sifat hablur yang tinggi (CrI 92.2) serta berdiameter kecil (~15 nm).

Nanoselulosa dengan sifat hablur yang tinggi serta saiz yang lebih kecil dapat dihasilkan

dengan meningkatkan suhu dan masa reaksi hidrolitik. Walau bagaimanapun,

pemerosotan hablur nanoselulosa telah berlaku dengan meningkatkan lagi suhu dan masa

melebihi daripada keadaan optimum. Selain itu, kepekatan selulosa (dalam wt%) juga

menpunyai kesan yang agak besar dalam mempengaruhi hablur dan saiz nanoselulosa.

Dalam hal ini, saiz nanoselulosa telah bertambah berikutan dengan penambahan

kepekatan selulosa.

Manakala itu, transformasi struktur hablur dari selulosa I kepada II telah berlaku dalam

nanoselulosa diperolehi daripada reaksi solvolisis dengan BmimOAc. Nanoselulosa

vi

dengan 78.8 hablur telah berjaya diperolehkan menerui solvolisis pada suhu 80 C dalam

masa 1 jam. Selulosa didapati mengembang dalam BmimOAc. Pengurangan hablur dalam

nanoselulosa telah diperhatikan sewaktu dalam usaha meningkatkan suhu dan masa untuk

pencairan. Sementara itu, kepekatan selulosa juga didapati mempengaruhi hablur dan saiz

nanoselulosa. Hablur nanoselulosa telah merosot manakala saiz nanoselulosa mengalami

pertingkatan berikutan dengan penambahan kepekatan selulosa.

Selain itu, rawatan ultrasonikasi adalah penting untuk mengukuhkan hablur dan

menghasilkan nanoselulosa yang bersaiz kecil dengan kestabilan koloid. Larutan

nanoselulosa yang diperolehi dengan BmimHSO4 dan BmimOAc adalah dianggap agak

stabil dengan mempunyai nilai mutlak zeta potential yang tinggi, iaitu -37.5 mV dan -

22.3 mV masing-masing. Pemerhatian morfologi menunjukkan hablur nanoselulosa

dalam bentuk seperti rod telah berjaya dihasilkan menerui hidrolisis dengan BmimHSO4

manakala zarah nanoselulosa berbentuk bulat didapat

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