Tuning the structural -OH on hydroxyapatite with fluorine significantly promoting the catalytic performance of CH4-CO2 reforming

Dry reforming of methane (DRM) represents a highly promising process for syngas production, as it simultaneously utilizes two predominant greenhouse gases (CH 4 and CO 2 ). However, the deactivation caused by carbon deposition, which originates from rate gap between carbon accumulation and removal, has been one of the most difficult problems solved, severely restricting its application. Herein, a series of hydroxyapatite (CaHAP) supports with structural hydroxyl (-OH) replaced by F − (CaHAP-xF) were employed to prepare Ni/CaHAP-xF catalysts for DRM. Effects of F − introduction on the surface property of CaHAP supports and DRM reaction behavior were explored. Ca 2p XPS and CO 2 -TPD indicate that F − weakens the electron density of adjacent Ca 2+ (which is the main CO 2 adsorption site), thereby enhancing the CO 2 adsorption. FT-IR, H 2 -TPR, TEM, and CO 2 -DRIFTS, in combination with reaction test results, manifest that F − incorporation modulates -OH quantity on the surface and activates the neighboring structural -OH, which strongly affects the distribution of the adsorbed CO 2 , as well as the existing state of the introduced Ni. Appropriate F introduction promotes Ni dispersion, resulting in high CH 4 cracking rate. Further, it is testified that the structural -OH species participate in the decarbonization reaction, especially those activated by F significantly accelerate the carbon removal. Thus, the catalyst with high dispersion of Ni (2Ni/CaHAP-0.98F) exhibits the best performance of DRM under the harsh conditions. CH 4 and CO 2 conversions of 59.2% and 72.8% were achieved at low temperature (700 °C) and high WHSV (48,000 mL·h −1 ·g −1 ).