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The envisaged upgrading of lignocellulosic biomass derived feedstocks (bio-oils) in dedicated units or by coprocessing in existing units of the refinery, to partially replace crude oil in the production of transportation fuels, is a topic that has been receiving much attention from both industry and academia in recent years. Regardless of lignocellulosic biomass origin, these feedstocks are complex mixtures of many oxygenated hydrocarbons. Therefore, their upgrading toward liquid fuels must include oxygen removal. So far, two main routes have been proposed, considering many studies at laboratory scale and others from industry: catalytic hydrotreatment (HDT), mainly hydrodeoxygenation (HDO), and catalytic cracking, technologies that are already present in today's refineries configuration. HDO has been performed at high hydrogen pressure, using catalysts based on those typically applied in conventional hydrotreating, as well as a new type of supported noble metal and transition metal catalysts. Catalytic cracking occurs at atmospheric pressure, using acid catalysts, mainly the active phases of fluid catalytic cracking (FCC) catalysts (HY and HZSM-5 zeolites). The present review is then focused on the upgrading possibilities of renewable nonedible feedstocks, obtained from biomass fast pyrolysis or liquefaction, in petroleum refineries, toward the production of second generation biofuels. It includes the recent studies concerning the alternative of bio-oils coprocessing together with crude oil feedstocks. In fact, although all these feedstocks have the potential to be directly converted into transportation fuels in dedicated units, it seems more attractive to upgrade them in combination with conventional feedstocks.

Microporous silicoaluminophosphates SAPO-5, SAPO-11 and SAPO-40 have been tested as solid acid catalysts in the dehydration of xylose into furfural (FUR) under biphasic aqueous-organic conditions, at 170°C. For all materials, no decrease in catalytic activity is observed after three consecutive recycling runs. Furfural yields at 4 h using SAPO-11 (34-38%) are comparable with that for HMOR zeolite with Si/Al * 6 (34%), under similar reaction conditions, while H 2 SO 4 (0.03 M) gives 2% FUR. Complete xylose conversion is reached within 16-24 h, with furfural yields of up to 65%. Brønsted and Lewis acidity of the silicoaluminophosphates was determined through FTIR analysis of adsorbed pyridine, and tentatively correlated with the catalytic performances.

Aiming at the valorisation of furfural (Fur) via sustainable routes based on process intensification and heterogeneous catalysis, the one-pot conversion of this renewable platform chemical to useful bio-products, namely furfuryl alkyl ethers (FEs), levulinate esters (LEs), levulinic acid (LA), angelica lactones (AnLs) and -valerolactone (GVL), was investigated using a single heterogeneous catalyst, in 2-butanol, at 120 ºC. Various chemical 2 reactions are involved in this process, which requires catalysts with active sites for acid and reduction chemistry. For this purpose, it was explored for the first time the catalytic potentialities of modified versions of zeolite beta containing Al and Sn sites prepared from commercially available nanocrystaline zeolite beta via post-synthesis partial dealumination followed by solid-state ion-exchange. The post-synthesis conditions influenced considerably the catalytic performances of these types of materials. The best-performing catalyst was (Sn) SSIE -beta1 with Si/(Al+Sn)=19 (Sn/Al=27.6), which led to total yield of bio-products of 83% at 86% Fur conversion, and exhibited steady catalytic performance for six consecutive runs. A systematic catalytic study using the prepared catalysts with different bio-products as substrates, together with the molecular level and microstructural characterisation of the materials, helped understand the effects of different material properties on the specific reaction pathways in the overall system. These studies led to mechanistic insights into the reaction network of Fur to the bio-products in alcohol media, upon which a kinetic model was developed for the first time. The superior performance of (Sn) SSIE -beta1 in various steps was related to the dealumination degree, dispersion and amount of Sn-sites, and acid properties.