A gas-solid fluidized bed reactor composed of Geldart Group C fine powers with the addition of nano-additives (Group C+) has recently been shown to have higher reaction conversion and better contact efficiency than the same reactor composed of Geldart Group A particles due to the increased gas holdup in the dense phase and the increased gas-solid interfacial area. Based on our earlier findings that significantly smaller bubbles were observed in such a Group C+ particle fluidized bed, the bubbling behavior is fully characterized in this work using the bubble position, diameter, rise velocity and residence time. The results indicated that bubbles were smaller in diameter, lower in rise velocity, and had a longer residence time in the Group C+ fluidized bed when compared with the same bed using Geldart Group A particles. All these factors contributed to better fluidization quality and enhanced gas-solid contact, thus improving reaction performance. (C) 2021 Elsevier B.V. All rights reserved.