Study of acid hydrolysis based synthesis of microcrystalline cellulose

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dc.contributor.advisor Morris, Michael A. en
dc.contributor.advisor Holmes, Justin D. en O'Regan, Conor 2018-09-19T11:08:16Z 2018-09-19T11:08:16Z 2018 2018
dc.identifier.citation O'Regan, C. 2018. Study of acid hydrolysis based synthesis of microcrystalline cellulose. PhD Thesis, University College Cork. en
dc.identifier.endpage 164 en
dc.description.abstract A key tenet of the industrial manufacturing process of microcrystalline cellulose (MCC) is the assumption of equivalency between approved pulps, despite the natural variation in these materials. Alkali solubility, X-ray photo-spectroscopy, X-ray Diffraction and Scanning Electron Microscopy analyses of four pulps from different wood sources and delignification processes found significant differences in cellulose composition, crystallinity and morphology. Application of thermogravimetric data to three thermal decomposition kinetic models allowed for calculation of kinetic and subsequent thermodynamic parameters. Pulps delignified via an acid-sulphite process had higher activation energies when compared with the Kraft pulps (irrespective of wood source), which was correlated to higher degree of crystallinity for these pulps. Furthermore, the frequency factor for the hardwood acid-sulphite pulp was unexpectedly significantly higher than all other pulps, linking morphological characteristics to pulp degradation kinetics not given in the current literature. Two samples of microcrystalline cellulose (Avicel® PH102 grade) produced from different starting pulps (hard and softwood) were selected for investigation. Analyses revealed that the MCC powder products showed no significant differences despite variances found in the starting pulps. For instance, the degree of polymerisation of the softwood pulp was significantly higher than the hardwood pulp. The MCC products were surprisingly found to have lower crystallinity compared to the pulps, suggesting hydrolysis of both amorphous and crystalline regions. Kinetic degradation parameters indicated lower activation energy and frequency factor for the MCC samples correlating with lower crystallinity. Importantly, there were no significant differences between the kinetic parameters of the two MCC products, indicating that differences in pulp were diminished during the MCC production hydrolysis step. A pulp sample used in the industrial MCC process was selected for an acid hydrolysis study. Degree of polymerisation reduction curves were generated for various temperature and acid concentration conditions and differences in reaction rate and equilibrium degree of polymerisation point were observed; with increasing temperature having a greater effect on both the rate and equilibrium point when compared with increasing acid concentration impact. Scanning electron microscopy and particle size distribution analyses surprisingly showed that large quantities of material remained physically intact during the early hydrolysis stages even though the degree of polymerisation reduction was at its fastest rate, an observation not given in the current literature and significant in terms of control of the reaction industrially. Furthermore, it was observed that samples continued to reduce in both particle size and degree of crystallinity throughout the degree of polymerisation equilibrium range, giving an important opportunity for identification of an optimum reaction end-point based on these parameters; such an end-point signal is not currently utilised in the industrial production of MCC and offers highly significant potential benefits to the commercial process. Hydrolysis experiments were carried out on two pulp samples produced from different wood sources and delignification processes. Degree of polymerisation reduction curves were generated and Ekenstam plots used to determine the hydrolysis reaction rates. The hardwood acid-sulphite pulp was found to have a higher reaction rate compared to the softwood Kraft pulp. Kinetic parameters revealed that the hardwood pulp had a higher activation energy but also a significantly higher frequency factor, attributed to previously identified differences in crystallinity and morphology respectively. A modified version of the industry standard equation for determining hydrolysis intensity was proposed, which for the first time quantitatively accommodated differences in pulp crystallinity and morphology by inclusion of corrected activation energy and frequency factor terms, offering significant improvement in industrial reaction control. Silicified microcrystalline cellulose (SMCC) has advantages over conventional MCC in the application of pharmaceutical tableting processes, such as improved tablet strength, retention of compressibility after wet granulation, and superior flow characteristics. Production of SMCC is achieved by addition of approximately 2% by weight of fumed silica to the MCC dispersion prior to the drying phase. Control of the silica addition in a continuous process is challenging, and in-process quality control measurement of silica content by sulphated ash method is time consuming; there is no rapid method given in the current literature. Consequently, deviations from the silica content of the SMCC dried product may not be known until hours after the material has been produced, and only then can corrective action be taken to adjust the production process. Fourier Transform - Infra Red spectroscopy studies of both SMCC and standard MCC material indicate that the silica peak at 808 cm-1 is not present in the MCC spectrum. Calibration curves were generated based on the area of this peak for samples of two grades of SMCC and compared against the sulphated ash results. No statistical difference was observed between the two methods. A new rapid method for determination of silica in SMCC products was, as a result, proposed, offering highly significant processing advantages industrially. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2018, Conor O'Regan. en
dc.rights.uri en
dc.subject Cellulose en
dc.subject Microcrystalline en
dc.subject Pulp en
dc.subject Hydrolysis en
dc.title Study of acid hydrolysis based synthesis of microcrystalline cellulose en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD en
dc.internal.availability Full text available en Not applicable en
dc.description.version Accepted Version
dc.contributor.funder DuPont en
dc.description.status Not peer reviewed en Chemistry en
dc.check.type No Embargo Required
dc.check.reason Not applicable en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false
dc.check.embargoformat Embargo not applicable (If you have not submitted an e-thesis or do not want to request an embargo) en
dc.internal.conferring Autumn 2018 en
dc.internal.ricu Environmental Research Institute (ERI) en

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© 2018, Conor O'Regan. Except where otherwise noted, this item's license is described as © 2018, Conor O'Regan.
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