Ex-situ catalytic fast pyrolysis of wheat straw over acid-base catalysts for the production of high-added value bio-based chemicals

Abstract

When the objective of thermal pyrolysis is to maximise bio-oil production, the optimal operating conditions are: biomass with particle size of 2 – 3 mm to favour heat transfer, temperatures in the range of 500 – 600 °C, high heating rates (fast pyrolysis) and short residence times (2 – 3 s). Fluidised bed reactors are therefore one of the most commonly used systems in this research area. Under these conditions, bio-oil yields in the order of 70 – 75 wt.% can be achieved. In recent years, a great research effort has been put into the development of catalytic processes to improve bio-oil properties, by removing most of the water and oxygen present and increasing the molecular weight of its components in order to produce mainly hydrocarbons. However, this route has shown to have many limitations, due to the very complex nature of bio-oil and the relatively low economic value of the products finally obtained. In this context, the general objective of the present Doctoral Thesis is to study new routes for the valorisation of lignocellulosic biomass from agroforestry residues by means of a combination of cascade thermo-catalytic treatments, in order to maximise the production not only of aromatic hydrocarbons but also of oxygenated compounds of commercial interest. The aim is to maximise bio-oil production by means of a catalytic pyrolysis process that includes basic and multifunctional catalysts, and their selectivity towards oxygenated products of different nature with application as raw materials...