Fast pyrolysis of cashew nut shells in a bubbling fluidized bed reactor for producing high-heating value bio-oil using dolomite as a catalyst and carbon capture sorbent

A rigorous investigation of characteristic parameters (i.e., pyrolysis temperature, fluidization velocity, and sample particle size) in the fast pyrolysis of cashew nut shells using a bubbling fluidized bed reactor was conducted. The highest liquid yield of 47.87 wt% was obtained for the non-catalytic pyrolysis of cashew nut shells under the following conditions: a temperature of 475 °C, a fluidization velocity of 2.5 times the minimum velocity, and a particle size ranging from 0.45 to 0.71 mm. It was found that the main component of the oil phase was cardanol monoene, and calcined dolomite promoted dehydration, decarboxylation, cracking, and the production of aromatic hydrocarbons and syngas (H₂ and CO). In catalytic pyrolysis with the first-time use of dolomite at 550 °C, the oil phase with the highest heating value of 37.17 MJ/kg was produced, promising as a potential drop-in biofuel. In addition, the carbon capture of dolomite was investigated by analyzing its crystallographic structure, CO₂ desorption behavior, coke oxidation, and changes in elemental content. Accordingly, the catalytic pyrolysis at higher temperatures led to a stronger carbon capture in dolomite. This research has great practical significance in that dolomite is used as a catalyst to improve the quality of pyrolysis bio-oil and as a carbon capture sorbent to mitigate carbon emissions.