Biodiesel has emerged as a promising renewable and clean energy alternative to petrodiesel. While biodiesel has traditionally been prepared through homogeneous basic catalysis, heterogeneous acid catalysis has been investigated recently due to its ability to convert cheaper but high free fatty acid content oils such as waste vegetable oil while decreasing production cost. In this work, the esterification of free fatty acid over sulfated zirconia and activated acidic alumina in a batch reactor was considered. The models of the reaction over the catalysts were developed in two parts. First, a kinetic study was performed using a deterministic model to develop a suitable kinetic expression; the related parameters were subsequently estimated by numerical techniques. Second, a stochastic model was developed to further confirm the nature of the reaction at the molecular level. The esterification of palmitic acid obeyed the Eley-Rideal mechanism in which palmitic acid and methanol are adsorbed on the surface for SO?/ZrO?-550°C and AcAl?O? respectively. The coefficients of determination of the deterministic model were 0.98, 0.99 and 0.99 for SO?/ZrO?-550°C at 40, 60 and 80°C respectively and 0.99, 0.98 and 0.96 for AcAl?O? at the same temperature. The deterministic and stochastic models were in good agreement. / Master of Science

Lignin, en av huvudkomponenterna i lignocellulosabiomassa, utgör en stor mängd av sidoströmen från massaindustrin. Lignin är aromatiska makromolekyler som förekommer i rikliga mängder i naturen och uppvisar unika antioxidant-, uv-skyddande, anti-ultravioletta, antikorrosiva och antimikrobiella egenskaper, etc. Ligninbaserade produkter är ännu inte kommersialiserade eftersom de är begränsade av den kemiska heterogeniteten hos lignin som separerats från olika råvaror och producerats i olika industriella processer. Istället förbränns lignin vanligtvis för värme- och elproduktion efter extraktion. Tillvägagångssätt för att bevara värdefulla egenskaper hos lignin och samtidigt övervinna begränsningar har blivit heta ämnen. I detta projekt genomfördes kemiska modifieringar av kraftlignin från olika naturliga råvaror, gran och eukalyptus, där fenolgrupperna ersattes av alkylgrupper med olika kedjelängder (kolnummer 1, 6 och 12). De kemiska strukturerna och de termiska egenskaperna hos kraftlignin studerades med en kombination av analytiska metoder. Egenskaperna hos två typer av tekniska kraftligniner och dess derivat undersöktes även för jämförelse. Resultaten visade att kemiskt modifierat lignin kan vara ett lovande råmaterial för förädlade produkter som till exempel ligninbaserade nanopartiklar. / Lignin, one of the major components in lignocellulose biomass, makes up a large amount of sidestream from the pulp industry. As an abundant feedstock of bio- originated aromatic macromolecules, lignin shows unique antioxidant, UV-protective, anticorrosive, and antimicrobial properties, etc. However, limited by the chemical heterogeneity of lignin separated from different bioresources and industrial procedures as well as its recalcitrance as macromolecules, lignin-based products are not yet commercialized, while lignin is commonly burnt for heat or power generation after extraction. Approaches of preserving valuable properties of lignin meanwhile overcoming limitations have become heated topics. In this project, chemical modifications of kraft lignin from different natural bio-origins, spruce and eucalyptus, were conducted, with alkyl groups of various chain lengths (carbon numbers 1, 6 and 12) substituting the phenolic groups. A combination of analytical methods for characterizing the chemical structures and thermal properties of kraft lignin and chemically modified kraft lignin were studied. Meanwhile, the characteristics of two kinds of technical kraft lignin and their derivatives were investigated for comparison. Results highlighted that chemically modified lignin could be a promising material to serve as a feedstock for value-added products such as lignin-based nanoparticles.