This study aimed to investigate the effect of MgO and titanomagnetite mixture on the high-temperature pyrolysis of radiata pine wood in a fluidised bed reactor at 850 °C. The catalytic performance of the MgO-titanomagnetite (MgO-TM) mixture was experimentally evaluated based on product distribution, gas composition, gas properties, and tar composition. The results revealed that addition of MgO-titanomagnetite resulted in a decrease in gas yield (67.2 wt.%) compared to addition of titanomagnetite (TM) alone (72.9 wt.%), but an improvement was found compared to addition of MgO alone (63.9 wt.%). The hydrogen concentration in the gas product was significantly enhanced (23.2 vol.%) compared to titanomagnetite alone (12.8 vol.%) or to non-catalytic (NC) pyrolysis (14.1 vol.%) but was similar to that with addition of MgO alone (22.6 vol.%). However, the addition of MgO and titanomagnetite mixture resulted in a reduction in CO concentration to 2.7 vol.% in the gas product whereas increased the CO2 and light olefins formation. It was also found that the addition of the MgO and titanomagnetite mixture significantly increased the total concentration of ethylene and propylene (18.3 vol.%) compared to addition of titanomagnetite (5.8 vol.%), MgO (9.0 vol.%), or non-catalytic pyrolysis (12.0 vol.%). The lower heating value of the gas product and the H2 to CO ratio (17.5 MJ/Nm3 and 8.7) were also improved with addition of the MgO-titanomagnetite mixture. These findings demonstrate that application of physically mixed MgO and titanomagnetite as catalyst is a promising method for converting biomass into a H2-rich gas product via high-temperature pyrolysis. This study offers a useful reference for the development of novel catalytic systems for biomass conversion. Graphical Abstract

In this study, high-temperature catalytic pyrolysis of radiata pine was investigated for the production of high-value gas products. Pyrolysis experiments were conducted in a fluidized bed reactor at temperatures of 600 to 850 °C. The effect of temperature and the addition of titanomagnetite as the catalyst was evaluated based on product distribution, gas composition, gas properties, and tar composition. The results show that with titanomagnetite, the maximum gas yield of 72.9% was achieved at 850 °C, which is higher than that of the non-catalytic pyrolysis at the same temperature. The main gas species in the gas product from the catalytic pyrolysis at 850 °C include hydrogen (12.8 vol%), carbon monoxide (37.6 vol%), carbon dioxide (35.8 vol%), methane (5.8 vol%), and ethylene (5.8 vol%). Also, with titanomagnetite, the maximum lower heating value of 23.0 MJ/Nm3 for the product gas was achieved at 800 °C, and the maximum value for hydrogen to carbon monoxide (0.34) was found at 850 °C. Titanomagnetite promoted the formation of oxygenated hydrocarbons such as acids, esters, and phenols in tar, but at 850 °C, the tars from both catalytic and non-catalytic pyrolysis were rich in naphthalenes (more than 40%). H2-reduced titanomagnetite performed equally as the unreduced titanomagnetite with respect to gas yield, but the hydrogen and ethylene contents in the gas from the pyrolysis at 850 °C were 21.5 and 21.8 vol%, respectively. At this temperature, the lower heating value of the gas from the catalytic pyrolysis with the H2-reduced titanomagnetite was 17.4 MJ/Nm3, and the hydrogen to carbon monoxide ratio was 2.6.