Synthesis of Si-Modified Pseudo-Boehmite@kaolin Composite and Its Application as a Novel Matrix Material for FCC Catalyst

Fluid catalytic cracking (FCC) has been the primary processing technology for heavy oil. Due to the inferior properties of heavy oil, an excellent performance is demanded of FCC catalysts. In this work, based on the acid extracting method, Si-modified pseudo-boehmite units (Si-PB) are constructed in situ and introduced into the structure of kaolin to synthesize a Si-PB@kaolin composite. The synthesized Si-PB@kaolin is further characterized and used as a matrix material for the FCC catalyst. The results indicate that, compared with a conventional kaolin matrix, a Si-PB@kaolin composite could significantly improve the heavy oil catalytic cracking performance of the prepared FCC catalyst because of its excellent properties, such as a larger surface area, a higher pore volume, and a good surface acidity. For the fresh FCC catalysts, compared with the FCC catalysts using conventional kaolin (Cat-1), the gasoline yield and total liquid yield of the catalyst containing Si-PB@kaolin (Cat-2) could obviously increase by 2.06% and 1.55%, respectively, with the bottom yield decreasing by 2.64%. After vanadium and nickel contamination, compared with Cat-1, the gasoline yield and total liquid yield of Cat-2 could increase by 1.97% and 1.24%, respectively, with the bottom yield decreasing by 1.80 percentage points.

Continuous Carbonation for Synthesis of Pseudo-Boehmite by using Cross-Flow Rotating Packed Bed through the Reaction of NaAlO2 Solution with CO2 Gas

This research established a novel method for the preparation of pseudo-boehmite (PB) via a continuous carbonation of CO₂ gas and a NaAlO₂ solution in a cross-flow rotating packed bed (CF-RPB). In the CF-RPB, the NaAlO₂ solution can be sheared into fine liquid filaments and droplets, and react in full contact with the CO₂ gas. Effects of synthesis parameters, including the concentration of the NaAlO₂ solution, the gas-liquid ratio, the rotating speed of the CF-RPB, and the final pH of the solution on the crystal structure of PB, were fully investigated. A series of characterizations, including X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis, were carried out to explain the evaluation results and to find the relationship between PB properties and the synthetic conditions. The results showed that PB with a high specific surface area (495 m²/g) and large pore volume (2.125 cc/g) can be obtained when the concentration of the NaAlO₂ solution was 0.1 mol/L, the gas-liquid ratio was 3:1, the rotating speed of RPB was 600 rpm, and the final pH was around 10.5. PB obtained by this method had a higher quality compared with that using a stirred tank reactor. Moreover, the continuous carbonation can be efficiently batch-produced, which provided a new idea for an industrial application.