Co-Processing Fat-rich Material into Diesel Fuel

Sammanfattning: The thesis concerns aspects of method for increased use of alternative fat-rich material in diesel fuel and improve the cold properties of down-stream co-processed diesel fuel. The PhD thesis is a part of ‘Towards sustainable bio-refinery’ group which is funded by Preem AB and Swedish Energy Agency. Co-processing of fat-rich material into renewable fuel to scale-up refinery infrastructure with number of benefits like enrich the renewable carbon content, remove environmentally concerned heteroatom, improve the quality of fuel and reduce the dependency of conventional fossil fuels. The research focused to minimize the H2 dependent for upgrading process. In relation to minimize H2 consumption, it is experimented with Fatty Acid Methyl Ester (FAME) and/or rapeseed oil to hydroprocess carboxyl group in thermal treatment, followed with catalytic hydroprocessing. From our result, it shows that FAME and/or rapeseed oil on medium temperature ( 300 to 370oC) without any catalyst gives lighter cracking and cyclic group formation with longer contact time on inert material. From the result, α- and β-carbon breakage is evidence during thermal decomposition without any effect by H2 partial pressure. Here, Decarbonylation involved during thermal cracking without effect of H2 partial pressure and catalyst. Increase in CO in a gas outlet confirms the breakage in the α-carbonyl group during high temperature. To conclude, Pre-heating technique on fat-rich material influences a significant part of the upgrading process with or without limited H2 use. Catalytic hydroprocessing of FAME and/or rapeseed oil at operating temperature of 350oC between 4.0 and 10.0 Mpa total pressures with a sulfide NiMo/γ-Al2O3 catalyst results to retain a selective product in the form of C15, C16, C17 and C18 with traces of lighter hydrocarbons. This catalyst has stronger activity on carboxyl group compare on C-C group. Tall oil FAME is already an established diesel fuel additive but apart from the highly functional FAME, the processing of tall oil also gives a heavier fraction of resin acids. In a project studied the hydroprocessing of a mixture of 10-30 % of FAME and/or tall oil with Light gas oil (LGO) in a catalytic reactor using NiMO/γ-Al2O3 like catalyst. This experiment was run for different temperatures (300 °C to 405 °C) and different flow rates. Different aspects have been studied from the results: weight percentage of hydrocarbons C17 and C18 in the product, sulphur and aromatics contents, the cloud point and volume percentage for gas products like methane, CO2 and CO. The resin acids, modeled by abietic acid, can be catalytically hydrogenated. The resin acid fraction relatively end-up with mono- and di-aromatics but restricted to Poly-aromatics formation. Isomerization of higher alkanes leads into branched compounds to narrow diesel fraction and reduce cloud point. Bi-functional catalyst prepared with zeolite show immersive isomeric catalytic properties in last decades. The special feature of the zeolite, which has weak acidic sites, enhance Bronsted acidity leads low coking on active sites. The selectivity of product has been studied with structure and pore dimension depends on high Silica content. The test over 10 wt% n-hexadecane in LGO was studied by adjusting temperature, space velocity and pressure parameter. The result concludes that moderate temperature (230oC to 270oC) and pressure between 4.0 and 7.0 MPa have yielded better reaction condition. The isomeric group selectivity peak at 250oC considered as optimum for high yield of isomeric group in relation to cracking as undesired mechanism. Isomeric naphtha like ethylene, i-pentane, i-butane were observed in fuel gas outlet.