After the specified time at desired conditions, the reaction was quenched by placing the autoclave in an ice water bath quickly, cooling it to room temperature, then the pressure in the reactor dropped to ambient pressure. The products in the first 40 min of the reaction could be separated into solid phase and liquid phase while only liquid phase product existed after 45 min. After filtering and washing, the solid product was dried at 80 °C for 12 h. The liquid product was diluted and then filtered with 0.45 μm filter membrane for further analysis.