Long-term evaluation of palm oil mill effluent (POME) steam reforming over lanthanum-based perovskite oxides.

To replace the obsolete ponding system, palm oil mill effluent (POME) steam reforming (SR) over net-acidic LaNiO 3 and net-basic LaCoO 3 were proposed as the POME primary treatments, with promising H 2 -rich syngas production. Herein, the long-term evaluation of POME SR was scrutinized with both catalysts under the optimal conditions (600 °C, 0.09 mL POME/min, 0.3 g catalyst, & 74–105 μm catalyst particle size) to examine the catalyst microstructure changes, transient process stability, and final effluent evaluation. Extensive characterization proved the (i) adsorption of POME vapour on catalysts before SR, (ii) deposition of carbon and minerals on spent SR catalysts, and (iii) dominance of coking deactivation over sintering deactivation at 600 °C. Despite its longer run, spent LaCoO 3 (50.54 wt%) had similar carbon deposition with spent LaNiO 3 (50.44 wt%), concurring with its excellent coke resistance. Spent LaCoO 3 (6.12 wt%; large protruding crystals) suffered a harsher mineral deposition than spent LaNiO 3 (3.71 wt%; thin film coating), confirming that lower reactivity increased residence time of reactants. Transient syngas evolution of both SR catalysts was relatively steady up to 4 h but perturbed by coking deactivation thereafter. La 2 O 2 CO 3 acted as an intermediate species that hastened the coke removal via reverse Boudouard reaction upon its decarbonation. La 2 O 2 CO 3 decarbonation occurred continuously in LaCoO 3 system but intermittently in LaNiO 3 system. LaNiO 3 system only lasted for 13 h as its compact ash blocked the gas flow. LaCoO 3 system lasted longer (17 h) with its porous ash, but it eventually failed because KCl crystallites blocked its active sites. Relatively, LaCoO 3 system offered greater net H 2 production (72.78%) and POME treatment volume (30.77%) than LaNiO 3 system. SR could attain appreciable POME degradation (>97% COD, BOD 5 , TSS, & colour intensity). Withal, SR-treated POME should be polished to further reduce its incompliant COD and BOD 5. [Display omitted] • Prolonged catalytic POME steam reforming over LaNiO 3 (13 h) and LaCoO 3 (17 h). • Similar carbon deposition of spent LaCoO 3 (50.54 wt%) and spent LaNiO 3 (50.44 wt%). • Harsher mineral deposition in spent LaCoO 3 (6.12 wt%) than spent LaNiO 3 (3.71 wt%). • Overall net H 2 production of LaCoO 3 system was 72.78% larger than LaNiO 3 system. • Total POME treatment volume of LaCoO 3 system was 30.77% higher than LaNiO 3 system. [ABSTRACT FROM AUTHOR]