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Hierarchical Macroporous Mesoporous Materials for Biodiesel Synthesis. Karen Wilson,1* Adam F. Lee1 and Jean-Philippe Dacquin.1,2 1 Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT, UK. 2 Present address: UCCS, University of Lille, Lille, France. ABSTRACT The combination of dwindling oil reserves and growing concerns over carbon dioxide emissions and associated climate change is driving the urgent development of routes to utilize renewable feedstocks as sustainable sources of fuels. Catalysis has a rich history of facilitating energy efficient selective molecular transformations and contributes to 90% of chemical manufacturing processes and to more than 20% of all industrial products. In a post-petroleum era catalysis will be central to overcoming the engineering and scientific barriers to economically feasible routes to bio-fuels. This article will highlight some of the recent developments in the development of solid acid and base catalysts for the transesterification of oils to biodiesel. Particular attention will be paid to the challenges faced when developing new catalysts and importance of considering the design of pore architectures to improve in-pore diffusion of bulky substrates. INTRODUCTION Concerns over dwindling oil reserves, CO2 emissions from fossil fuel sources and associated climate change is driving the urgent need for clean, renewable energy supplies. The most easily implemented and low cost solutions for transportation needs are those based upon liquid fuels derived from biomass [1]. To be sustainable so called 'second generation' bio-fuels should be sourced from non edible components of crops (stems, leaves and husks), forestry waste or alternative non-food crops such as switch grass or Jatropha curcas which require minimal cultivation. In addition, there is growing potential for using oil triglycerides (TAG) from algae which can annually yield 80-180 times the amount of oil per hectare compared to plants [2]. The conversion of TAGs to biodiesel via catalytic transesterification has the potential to be an energetically efficient and attractive means to generate fuel [1]. Free fatty acids (FFA) in plant oils and animal fats are however problematic for conventional biodiesel manufacturing routes as the base catalysts employed are unable to remove the organic acid [3]. Thus, traditional biodiesel synthesis involving soluble bases such as KOMe, NaOMe, also employ an acid catalysed pre-esterification step to remove any FFAs, before the oil is contacted with the soluble base catalyst (Scheme 1). While acids (e.g. H2SO4) are less active in the transesterification step, if the oil has a high FFA content, as common for waste oil, a single step acid catalysed process may prove more cost effective. Unfortunately, these homogeneous acid and base catalysts can corrode reactors (and engine manifolds if carried through to the fuel), and their removal from the resulting bio-fuel is energy intensive, requiring aqueous quench and neutralisation steps, which themselves result