Abstract
CaO and phosphates showed synergistic effects in the regulation of pyrolysis products in the pyrolysis of when they were directly mixed with camphor wood. The alkyl phenol yield increased during the pyrolysis process of corn straw fermentation residue directly mixed with KH2PO4 supported by γ-Al2O3. Rice stalks from agricultural crops are often disposed as waste. However, the potassium phosphate impregnated raw straw pyrolysis with CaO and Al2O3 has not been reported. This paper studied the synergistic effects of CaO or Al2O3 and three potassium phosphates (i.e., KH2PO4, K2HPO4·3H2O, and K3PO4·3H2O) in the rice straw pyrolysis through pyrolysis–gas chromatography-mass spectrometer (Py-GC/MS) experiments. The results showed that CaO/Al2O3 and potassium phosphates showed synergistic effects in the regulation of the types or contents of phenols, ketones, aldehydes, etc. and increased the contents of phenols, aldehydes, acids, and levoglucosan (LG) from most samples and increased those of ketones compared with those catalyzed by potassium phosphates alone. They were suitable for the production of ketone-rich and acid-low bio-oil, which is an important precursor for the preparation of power or jet fuel. The highest contents of ketones (HCK) reached 56.65% and 56.02% in the pyrolysis of K3PO4·3H2O impregnated rice straw with CaO or Al2O3, respectively. The lowest contents of acids and acetic acid (LCA) were nearly or equal to 0, respectively. HCK and LCA were respectively significantly higher and lower than the values reported in the literatures for biomass catalytic pyrolysis using CaO/Al2O3 and potassium phosphates alone or in combination. Dehydration reactions, etc. were further promoted under the co-catalysis of the two catalysts, and some phenols could be converted to benzene products, etc. For 50% K3PO4·3H2O impregnated sample, the yields of furans reduced sharply after CaO addition. For most impregnated samples except 50% K2HPO4·3H2O and 30% and 50% K3PO4·3H2O samples, the contents of total furans and furfural increased after Al2O3 addition.
Highlights
With the fossil energy reduction, environmental degradation and other problems, more and more attention has been paid to the development and utilization of renewable energy[1,2,3,4,5,6]
Rice straw sample with 30 wt% K3PO4·3H2O impregnation was represented as 30% K3-Rs, and other samples were expressed according to this method
As illustrated above, calcined calcium oxide (CaO) was mechanically mixed with rice stalk samples impregnated with KH2PO4, K2HPO4·3H2O and K3PO4·3H2O, respectively, in the mass ratios of 0:1, 0.5:1, 1:1 and 1.5:1, in which 0:1 indicated no addition of CaO
Summary
With the fossil energy reduction, environmental degradation and other problems, more and more attention has been paid to the development and utilization of renewable energy[1,2,3,4,5,6]. Pyrolysis is an important biomass utilization technology to convert biomass directly into solid, liquid and gaseous products in the absence of oxygen under high temperatures. The primary pyrolysis bio-oil has many harmful properties, such as high oxygen content, acidity, viscosity, and low heating value [13, 15,16,17,18,19]. The use of catalysts within the pyrolysis process, known as catalytic pyrolysis, can decrease the oxygen content selectively convert biomass into high-value-added chemicals or highquality bio-oil. It has attracted the attention of many researchers[20,21,22,23]. The commonly used catalysts are metal oxide catalysts, metal salt catalysts, molecular sieve catalysts, etc
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