Preparation Of Carbon Support From Kraft Lignin And Its Application In Biodiesel Synthesis

The accelerating and frequently fluctuating price of conventional diesel, together with growing environmental concerns has sparked renewed attention on the search for an alternative fuel. Biodiesel (alkyl esters) from vegetable oil or animal fats via transesterification is potential substitutes for petroleum-based diesel fuel. Biodiesel is one of the most widely used biofuels in the world, due to its simplicity of production, biodegradability, non-toxicity, sulfur-free and reduction of green house gas emissions. The most widely used industrial method for the commercial production of biodiesel from vegetable oils/fats is a base catalyzed transesterification process using KOH or NaOH as the homogeneous catalysts. The major drawbacks of homogeneous catalytic reaction are as follows:the refined vegetable oils are required. These homogeneous base catalysts are corrosive and cannot be regenerated or reused, and separation of catalyst from products is difficult and requires more equipment which could result in higher production costs. In addition, the homogeneous catalysts have to be removed from the biodiesel and a large amount of waste water is generated which the process is not environmentally friendly. The heterogeneous catalysts can solve these problems encountered in homogeneous catalysts.Thinking of presenting problems, in this work, a new method has been developed to produce activated carbons (ACs) and biodiesel from kraft lignin based on the concept of green chemistry. The main research contents are as follows:First, the ACs support with various structure and physicochemical properties were prepared from low-cost, renewable kraft lignin (KL) which was obtained from paper effluent by H3PO4, KOH and K2CO3chemical activation, respectively. The BET surface area, pore volume, pore structure, morphology and the type and content of surface functional groups of ACs can be tailored by the change of the types of activating agent, activation methods and activation conditions. The prepared ACs were characterized by XRD, SEM, FTIR, cryogenic N2adsorption at77K and fractal dimensions.Then, the mesoporous ACs from KL by H3PO4activation were used to prepared carbon-based solid acid (KLC-SO3H) with SO3H, COOH and phenolic OH groups by the sulfonation of concentrated sulphuric acid. The prepared catalyst was characterized using SEM, XRD, BET, TGA and FTIR. The KLC-SO3H was found to be eco-friendly and recyclable heterogeneous catalyst for the esterification reaction of oleic acid with methanol.Due to the relative low acid strength of KLC-SO3H solid acid catalyst, we found that it is difficult to be used to catalyze transesterification reaction of rapeseed oil with methanol. So, a novel solid base catalyst K2CO3/KLC was prepared in situ by simply blending K2CO3with KL and subsequently activating at800℃for2h. The catalysts were characterized by TGA, DTA, FTIR, XRD, XPS and BET methods. The catalytic performance of prepared catalysts were evaluated by transesterification of rapeseed oil with methanol under mild reaction condition. The effect of preparation conditions of catalysts and reaction conditions on biodiesel yield of transesterification were investigated. The solid base catalyst can be reused for4times. In this work, the biodiesel from jatropha oil was also produced by a two-step process. The first-pretreatment of jatropha oil was completed by KLC-SO3H catalytic esterification, and then the second step K2CO3/KLC solid base catalytic transesterification was achieved after the KLC-SO3H was removed from the reaction mixture via centrifuge.For further development of application domain of kraft lignin activated carbons, the Ni/MAC, Pd/MAC catalysts were prepared using mesoporous activated carbons (MAC) from kraft lignin by H3PO4activation, and the catalysts were employed to catalyze the deoxygenation reaction of stearic acid, rapeseed oil, jatropha oil and correspording biodiesel. The further study is needed both for improving the activity and stabliity of catalysts and developing the difunctional or multifunctional catalyst to catalyze both deoxygenation and isomerization of biomass-derived triglycerides feeds in one step, production of green transportation fuels.