Mechanism on catalytic cracking tar with CaO-based catalysts for hydrogen-rich gas by DFT and experiments

As the model compound of tar, the catalytic cracking performances of toluene with CaO-based catalysts were studied by DFT simulation and fixed bed experiment. The DFT results showed the adsorption energy of toluene on (1 0 0) surfaces increased as FC < CaO < NC < NFC at 650 °C. The optimal reaction path for toluene to dissociate H was obtained in the process of toluene cracking using NC and NFC catalysts. The NC catalyst doped with Fe enhanced the catalytic activity of Ni, and the rate determining step reaction activation barrier to generate H2 was decreased from 1.50 eV to 0.58 eV. And the activation barrier for CH4 formation was higher than that for H2, which promoted the cracking reaction to produce H2. The experimental results showed that the catalytic toluene cracking effect of NFC was the best among the four catalysts at 650 °C, with 98.11% conversion rate and 93.11% H2 yield. Compared with NC, H2 yield was increased by 27.92%, CH4 yield was decreased by 50.43%. Thermogravimetric results showed that NFC was less likely to be inactivated due to carbon deposition than NC. NFC will be a kind of compound catalyst for tar cracking with high efficiency.