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Aguado, 2017. Doctoral Dissertation Chapter 1 Universidad Pablo de Olavide Biotecnología, Ingeniería y Tecnología Química 2017 Roberto Aguado Cationization of cellulose from conventional and alternative raw materials for papermaking Cationización de celulosa procedente de materias primas convencionales y alternativas para la fabricación de papel Universidad Pablo de Olavide Biotecnología, Ingeniería y Tecnología Química 2017 Roberto Juan Aguado García [email protected] Cationization of cellulose from conventional and alternative raw materials for papermaking Dissertation submitted to the Pablo de Olavide University (Seville) for the degree of Doctor of Philosophy. The thesis was developed under the supervision of Dr. Ana Moral (Pablo de Olavide University), tutor, and Dr. Antonio Tijero (Complutense University of Madrid). Cationización de celulosa procedente de materias primas convencionales y alternativas para la fabricación de papel Memoria depositada en la Universidad Pablo de Olavide (Sevilla) para la obtención del grado de doctor, realizada bajo la dirección de la Dra. Ana Moral (Universidad Pablo de Olavide), tutora, y del Dr. Antonio Tijero (Universidad Complutense de Madrid). ABSTRACT The environmental performance of the paper industry in Western countries has drastically improved over the past few decades, but manufacturers still depend on wood and on poorly biodegradable polyelectrolytes. In this dissertation, I inquire into the functionalization of cellulose from various sources to produce cationic derivatives that could partially replace those polyelectrolytes. Sources included cellulose powder, cotton linters, softwood, hardwood and different lignocellulosic residues —wheat straw, rapeseed stalks and orange tree trimmings. Commercial cellulose and linters could be cationized straightaway, while wood and waste needed chemical pulping. Specifically, residues were cooked without sulfur compounds, yielding satisfactory results both in terms of lignin removal and paper properties. The functionalization took place by treating cellulose or a chemical pulp with (3- chloro-2-hydroxypropyl)trimethylammonium chloride and sodium hydroxide in a batch reactor, aiming to produce cationic fibers or water-soluble cationic derivatives. We (the authors of the publications) took samples at different reaction stages to model reaction kinetics. Characterization of the products involved X-ray diffraction, elemental analysis, viscosity measurements, pycnometry, infrared spectroscopy, microscopy, zeta potential measurements, and potentiometric titrations. Then, cationic fibers were added to a suspension of non-modified fibers, fines and fillers to evaluate the effects on retention and optical properties. Also, soluble derivatives were tested in a suspension of mineral fillers to study flocculation kinetics. The fillers we used were precipitated calcium carbonate, ground calcium carbonate, kaolin, and titanium dioxide. Results from elemental analyses were successfully fitted —with correlation indices above 0.95— to pseudo-second order rate equations with two parameters. We found the values of these parameters to depend strongly on crystallinity. Decrystallization or amorphization of cellulose by an alkaline pretreatment increased the highest degree of substitution that could be reached, especially when working with refined pulps. Regarding the applications of cationic cellulose in papermaking, our findings contributed to understand what can be improved and what cannot. A water-soluble cationic derivative enhanced the flocculation of kaolin, whose zeta potential is clearly negative, by increasing the median equivalent spherical diameter from 4 μm to 25 μm in 2 min. It surpassed the performance of a conventional cationic polyacrylamide. The addition of cationic fibers before sheet formation improved the retention of fines, lowering the losses from 0.09 to 0.02 grams of fines per gram of pulp. As a consequence, opacity increased. However, neither soluble derivatives nor insoluble fibers improved the retention of precipitated calcium carbonate. Cationic fibers had a positive effect on the retention of titanium dioxide, which was evidenced by an increase in brightness of an unbleached pulp from 37.8% to 41.9%. Although the degree of substitution reached for softwood fibers was as high as 0.4, the lignocellulosic residues studied reached values around 0.2, good enough for cationic fibers, under much milder conditions. The procedure with lignocellulosic residues would involve mild chemical pulping with soda or ethanolamine, refining to less than 1000 PFI revolutions, mild peroxide bleaching if desired, 60 min-long alkaline pretreatment, and an even shorter cationization stage at 70 ºC. Even if papermakers keep refusing to replace wood with non-wood materials, these residues could be reused towards value- added products that may reduce the need for hardly biodegradable polyelectrolytes. KEYWORDS alkalization; cationization; cellulose; elemental analysis; functionalization; papermaking; pulp; quaternary ammonium; refining; X-ray diffraction. RESUMEN Pese a la indudable mejora ambiental que ha experimentado la industria del papel en los países desarrollados, los fabricantes aún dependen de la madera y de polielectrolitos no biodegradables. Mi proyecto de tesis doctoral explora la funcionalización de celulosa procedente de distintas materias primas para producir derivados catiónicos que puedan reemplazar parcialmente esos polielectrolitos. Las materias primas fueron: celulosa comercial en polvo, línter de algodón, madera de pino y de eucalipto, y tres residuos lignocelulósicos: paja de trigo, tallos de colza y poda de naranjo. La madera y los residuos requirieron tratamientos químicos para eliminar la mayor parte de la lignina. La cocción de los residuos, empleando métodos alternativos sin compuestos de azufre, proporcionó resultados satisfactorios, tanto en la eliminación de lignina como en las propiedades físicas del papel. La funcionalización tuvo lugar tratando celulosa o una pasta química con cloruro de (3-cloro-2-hidroxipropil)trimetilamonio e hidróxido de sodio en un reactor discontinuo, persiguiendo obtener fibras catiónicas o bien derivados solubles con carga positiva. Adquirimos muestras a diferentes tiempos de reacción para establecer un modelo cinético. Las técnicas de caracterización incluyeron difracción de rayos X, análisis elemental, medidas de la viscosidad y de la densidad, espectroscopía de infrarrojo, microscopía, medidas del potencial zeta y valoraciones potenciométricas. Además, realizamos ensayos de floculación, retención y formación de papel con las fibras modificadas. Los derivados solubles sirvieron para evaluar la cinética de la floculación de determinadas cargas minerales. Estas cargas fueron: carbonato de calcio precipitado, carbonato de calcio molido, caolín y dióxido de titanio. Los resultados de los análisis elementales se ajustaron con éxito (con índices de correlación superiores a 0,95) a ecuaciones de pseudo-segundo orden con dos parámetros. Hallamos que los valores de esos parámetros dependen de la cristalinidad. La amorfización de celulosa mediante una base fuerte, especialmente con pastas refinadas, propició un aumento en el máximo grado de sustitución alcanzado. En cuanto a las aplicaciones de la celulosa catiónica en la fabricación de papel, nuestros descubrimientos ayudaron a comprender su utilidad y sus limitaciones. Un derivado catiónico soluble mejoró la floculación de caolín, cuyo potencial zeta es negativo, aumentando su diámetro equivalente de 4 μm a 25 μm en 2 min. Este resultado fue mejor que el obtenido con una poliacrilamida catiónica convencional. Por otro lado, añadir fibras catiónicas antes de la formación del papel disminuyó las pérdidas de finos de 0,09 a 0,02 gramos de finos por gramo de pasta. Como consecuencia, la opacidad aumentó. Sin embargo, ni los derivados solubles ni las fibras modificadas aumentaron significativamente la retención de carbonato de calcio precipitado. Las fibras catiónicas tuvieron, ahora bien, un efecto positivo sobre la retención de dióxido de titanio, evidenciado por un incremento en la blancura de una pasta no blanqueada desde un 37,8% hasta un valor del 41,9%. Si bien las fibras de pino alcanzaron el mayor grado de sustitución (0,4), los residuos lignocelulósicos llegaron a valores aceptables (0,2) bajo condiciones mucho más suaves. El proceso con residuos lignocelulósicos comprendería: cocción suave con sosa o etanolamina, refino, blanqueo con baja concentración de peróxido si se desea, amorfización durante 60 minutos y cationización aún más breve a 70 ºC. Incluso si los residuos no convencen a los fabricantes de papel, pueden ser revalorizados hacia una alternativa biodegradable a los polielectrolitos convencionales. PALABRAS CLAVE alcalización; amonio cuaternario; análisis elemental; cationización; celulosa; difracción de rayos X; fabricación de papel; funcionalización; pasta; refino. This is the dedication page. If you are not skipping it, a small part of you probably expected to find your name. And why not? You may have done something quite important for me, like giving birth to me, teaching me how to read, dating me, supervising my work, lending me a book, or even reading something I have written —and still wanting to read more! Alas, your name is not here. Well, this has to end. Unless you are the kind of person who skips the dedication page, writes in passive voice all the time, or thinks that there must be different email domains for professors and students in the same university, this dissertation
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