Pyrolysis of Corn Straw for In Situ Dechlorination of Bio-Oil Under the Catalysis of Acidified-γ-Al2O3 Modified with Alkaline and Alkaline Earth Metal Compounds

Bio-oil’s high chlorine content severely hinders its application, because of its high corrosivity. Catalytic pyrolysis is an effective method for the dechlorination of bio-oil. Herein, the performances of the acidified-γ-Al2O3 modified with alkaline and alkaline earth metal compounds were investigated. It was found that NaOH was a better loading material than Ca(NO3)2 or Mg(NO3)2 in the support of acidified-γ-Al2O3. The optimal loading amount of NaOH was 5 wt% in the range of 1 wt%–15 wt%, and the better calcination temperature was 600 °C, compared with 800 °C. When catalyzed with Na/Al2O3 (5%, 600 °C), the organic chlorides content in bio-oil from the pyrolysis of corn straw at 500 °C was significantly reduced from 150 ppm to 29 ppm, while the inorganic chlorides content barely changed. NaAlO2 was generated in Na/Al2O3 from the solid-phase reaction between NaOH and Al2O3 by calcination. When Na/Al2O3 (5%,600 °C) and Na2CO3 were both used in two layers in a fixed-bed reactor, the organic and inorganic chlorides in bio-oil simultaneously significantly decreased, respectively, to 57 ppm and 23 ppm. The decrease in chlorides benefits the deep dechlorination of bio-oil by absorption or catalytic hydrodechlorination in a post-treatment process, which reduces the consumption of absorbent or hydrogen.