Upgrading of biomass-derived butanol to light olefins on Zn-Zr mixed oxides.

LUGGREN, PABLO JORGE; FONSECA BENÍTEZ, CRISTHIAN ANDRÉS; DI COSIMO, JUANA ISABEL

Buenos Aires

Congreso; 11th WORLD CONGRESS OF CHEMICAL ENGINEERING (WCCE11); 2023

World Chemical Engineering Council (WCEC)

Different processes for light olefins production from bio-derived oxygenated compounds seek to position themselves as economically viable alternatives to the use of non-renewable and polluting resources. For example, we have recently reported the synthesis of Zn-Zr mixed oxides for the one-pot conversion of biomass-derived butyric acid to light olefins. The main olefins obtained were ethylene and isobutene, which are widely used as intermediates in the petrochemical industry. In this work, the gas-phase conversion of n-butanol (C4OL) into light olefins was studied on Zn-Zr mixed oxides and on ZnO and ZrO2 single oxides. The Zn-Zr catalysts of varied ratios of Zn/Zr (0.11–0.66) were prepared by incipient wetness impregnation of Zn on Zr(OH)4. Several techniques, such as BET surface area, XRD, and CO2 and NH3-TPD, were used to characterize the surface physical/chemical properties and to correlate the structure and performance of the catalysts. The evolution of n-butanol conversion and product yields at different contact times (32-835 h gcat./mol) and reaction temperatures (range 583 to 723 K) was studied. The reaction pathways leading to the formation of light olefins and other less abundant products were elucidated. This process involves a series of sequential steps comprising dehydrogenation, ketonization, aldol condensation, C-C bond rupture and deoxygenation reactions promoted by catalysts with acid-base properties. The products were olefins (Cn=, where n represents C atom number), ketones (CnK), aldehydes (CnAL), carboxylic acids (CnA), esters (CnE), and gases (CH4, COx and H2). A total olefin yield of 52.4% was obtained with a catalyst having 11.1 wt.% Zn at 723 K and 835 h gcat./mol. Ethylene (47.1%) and isobutene (21.2%) were the main components of the olefin fraction, the other 31.7% being pentene, isohexene, heptene, and octene. The Zn-Zr catalysts were stable and showed no sign of deactivation because the presence of water in the reactor feed and the in-situ generation of hydrogen prevented heavy product formation and active site loss.