Synergistic coupling of tar cracking and in-situ CO2 adsorption over Ni–Ca–Al2O3 catalysts for efficient hydrogen production from biomass gasification

A Ni–Ca–Al 2 O 3 composite catalysts was developed for synergistic biomass gasification tar cracking and CO 2 fixation. • The 10Ni-Ca-Al catalyst exhibited the optimal catalytic performance, achieving a 139.2% enhancement in H 2 yield. • The catalyst showed good durability, with H 2 yield retaining 81.1% after five cycles. • Mechanistic studies further confirmed the synergistic effects among NiO, CaO, and Al 2 O 3 . Biomass gasification is a promising technology for renewable hydrogen production; however, its practical application is constrained by high tar yield and insufficient hydrogen yield. In this study, Ni-Ca-Al 2 O 3 composite catalysts were prepared and applied in a two-stage fixed-bed gasification system to enhance hydrogen production from biomass gasification through the synergistic effects of tar reforming and in-situ CO 2 adsorption. The influences of catalytic temperature, catalyst dosage, and NiO loading on gas composition, tar conversion, and catalyst stability were systematically investigated. The results show that hydrogen yield gradually increased with rising catalytic temperature. Increasing the catalyst dosage further promoted CO 2 capture and tar cracking, thereby enhancing H 2 production. The incorporation of NiO significantly improved catalytic activity, which was attributed to its acceleration of tar reforming, methane steam reforming, and the water–gas shift reaction. Among the catalysts studied, 10Ni–Ca–Al exhibited the best overall performance. Under optimal conditions (600 °C, 5 g catalyst), the gasification of pear branches resulted in increases of 108.7% in H 2 concentration and 139.2% in H 2 yield compared with the blank experiment, accompanied by a substantial reduction in tar yield to 3.6 g/kg and a tar cracking ratio of 79.7%, with a CO 2 adsorption capacity reaching 170 mg/(g cat). Characterization results confirmed that CaO effectively adsorbed CO 2 to form CaCO 3 , while NiO was reduced to metallic Ni; the synergistic interaction between the two components promoted tar cracking and enhanced H 2 yield. Cyclic stability tests demonstrated that the catalyst maintained good catalytic activity after five regeneration cycles. In summary, the Ni–Ca–Al 2 O 3 catalyst, through the dual-function coupling of tar cracking and in-situ CO 2 adsorption, provides a viable strategy for efficient hydrogen production from biomass gasification.