Hidrodesoxigenação de ácido oleico empregando carbetos de metais de transição suportados em alumina

Abstract

Green diesel derived from microalgae is seen as na important renewable alternative with a carbono neutral balance for replacing the diesel obtained from petroleum. The catalytic reaction route of oleic acid’s hidrodeoxygenation was evaluated in a trickle bed reactor using Mo2C/γ-Al2O3 and NbMo1,75C/γ-Al2O3 as catalysts. The carbides were synthesized by temperature programmed carburation (TPC) of their precursors prepared by incipiente wetness methodology and wet impregnation for the Mo2C/γ-Al2O3 and NbMo1,75C/γ-Al2O3 respectively. It wasn’t possible to determine the crystalline phases of the carbides by X-ray diffractometry (XRD). The determination of the specific area, by N2 physisorption, indicated that no pore blocking occurred, and CO chemisorption and CO-TPD shown different active sites on the catalysts. Evaluation of the catalytic activity in the hidrodeoxygenation of oleic acid was carried out at 280 °C varying the weight hourly space velocity (WHSV) from 7 to 40 h-1 . It was observed, at first, that independently of the active phase, competitive reactions of hydrogenation of the carboxy oxygen (forming octadecenal) and of hydrogenation of the double bond (forming stearic acid) occur. Mo2C/γ-Al2O3 has proven to be more active than NbMo1,75C/γ-Al2O3, having a turnover frequency (TOF) 3 orders of magnitude higher. At higher temperatures, Mo2C/γ-Al2O3 has also shown a higher selectivity to the formation of n-C18. Therefore Mo2C/γ-Al2O3 was evaluated in HDO of Chlorella vulgaris oil and shown selective formation of n-C18.