Separation of Biomass Pyrolysis Oil by Supercritical CO2 Extraction

Supercritical CO2 extraction was employed to separate simulated and real bio-oils. Effects of extraction pressure, temperature and adsorbents on distribution coefficient (or enrichment coefficient) of five representative compounds were investigated using a simulated bio-oil, which was composed of acetic acid (AC), propanoic acid (PA), furfural (FR), acetylacetone (AA) and 2-methoxyphenol (MP). The distribution coefficients of AA, FR and MP between super-critical CO2 phase and liquid phase were bigger than 1.5, while those of AC and PA characteristic of relatively strong polarity were less than 1. Temperature and pressure also had impacts on the distribution coefficients of AA, FR and MP, especially remarkable for AA. The extraction of simulated bio-oil spiked on three adsorbents shows that adsorbents influence extraction efficiency and selectivity by changing intermolecular forces. High extraction pressure and relative low temperature are beneficial to reduce the water content in the extract. In addition, the feasibility of supercritical CO2 extraction of real bio-oil was examined. After extraction in the extraction fraction total ketones increased from 14.1% to 21.15~25.40%, phenols from 10.74% to 31.32~41.25%, and aldehydes from 1.92% to 3.95~8.46%, while the acids significantly dropped from 28.15% to 6.92~12.32%, and water from 35.90% to 6.64~4.90%. In view of extraction efficiency, the optimal extraction temperature was determined to be 55℃. Extraction efficiency of the real bio-oil increased with rising pressure. The maximal extraction efficiency of real bio-oil on water-free basis could reach to 88.6%. After scCO2 extraction, the calorific value and stability of the extract fraction evidently increased and the acidity slight decreased with nearly 100% volatility below 140℃, suggesting potentially applicable as substitute for engine fuel.

Preparation and activity evaluation of NiMoB/-Al_2O_3 catalyst by liquid-phase furfural hydrogenation

Amorphous MoNiB/γ/-Al2O3 alloy catalysts were prepared by reducing NiCI2.6H20 and （NH4）6Mo7O24.4H2O supported on γ-Al2O3 with NaBH4 as reducing agent. Using liquid-phase hydrogenation of furfural （FFR） as a probe reaction, the activity of MoNiB/γ/Al2O3 was examined. Compared to NiB and NiMoB, NiMoB/γ-Al2O3 exhibited excellent activity and selectivity towards furfuryl alcohol （FFA）. After reaction for 3.0 h at 80 ℃ and 5.0 MPa in methanol, FFR conversion reached 99% with FFA yield of 91%. The effects of doping amount of Mo and calcination temperature before NaBH4 reduction on hydrogenation activity were also investigated. The optimum Mo/Ni atom ratio and calcination temperature were found to be 1：7 and 300 ℃, respectively. XRD patterns and SEM images indicated that NiMoB over the surface of γ-Al2O3 was amorphous and highly dispersed, which was responsible for the high thermal stability of the title catalyst.