| With the crisis of coal energy shortage and environmental pollution,the countries around the world are actively seeking to transform into green and low-carbon clean energy and renewable energy.As a carbon neutral and renewable energy source,biomass has a wide range of applications and has application prospects.Microalgae as the third-generation biomass energy is currently the research hotspot.At present,there are still some shortcomings in the reaction mechanism and synergistic effect of mixed pyrolysis between different components in microalgae.The reaction mechanism and synergistic effect of mixed pyrolysis of microalgae and carbohydrate-containing biomass have not been further studied.In order to solve the above problems,mixed pyrolysis studies were carried out with the model components of protein and carbohydrate in microalgae,and then further mixed pyrolysis studies were carried out with low-fat microalgae and sweet potato slag to explore different blending ratios and pyrolysis parameters.The formation of the lower pyrolysis products and the reaction mechanism,in order to provide a resource utilization approach for low-fat microalgae and carbohydrate-containing lignocellulosic biomass.Firstly,soybean protein and corn starch were selected as model compounds of protein and carbohydrate in microalgae.Slow pyrolysis experiments were carried out by thermogravimetric analyzer and Thermogravimetric-Fourier transform infrared spectroscopy（TG-FTIR）.The effect of gas product functional groups under different weight ratios were analyzed.The results showed that the two-componentco-pyrolysis was mainly divided into three stages of thermal weight loss.The synergistic effect was mutually promoting at235318°C,and it was mutually inhibited at 318700°C.Among the different blending ratios,the promotion and inhibition effect of 50SP was the strongest.When the protein content was30%,the synergistic effect of corn starch and soy protein was significant.The Maillard reaction produced pyrolysis intermediates containing C=C and-COOH functional groups,while releasing CO,H2O,CO2 and small molecular hydrocarbons.product.When the protein content was 70%,the synergistic effect of corn starch and soy protein was also significant.The Maillard reaction produced a large amount of nitrogen-containing heterocyclic compounds,which released gaseous products of of CO2,HCN,HCNO and small hydrocarbons,and inhibited the generation of NH3.Then,the distribution and formation of the products based on the rapid pyrolysis of model components were analyzed by gas chromatography-mass spectrometry（GC/MS）.The reaction mechanisms were analyzed during Maillard reaction of the generation of pyrolysis intermediates.The results showed that during the rapid pyrolysis of corn starch and soybean protein,the Maillard reaction happened between the carbonyl group in the side chain of the furans and the nitrogen-containing compounds,and promoted the conversion of furans with carbonyl group to the furans with hydrocarbyl group.The furans with alkyl group attained the highest output when the blend ratio was 30SP.The reducing atmosphere formed by Maillard reaction promoted C-C bond cleavage and dehydration reaction in the dehydrated sugar molecule and isomerization of furan compounds to form cyclopentanone with different side chains.At the same time,the intermolecular rearrangement reaction and the secondary reaction between the educing sugar derivatization and the Amadori compound were promoted to form a nitrogen-containing heterocyclic compounds.When the blending ratio is 70SP,the yield of nitrogen-containing heterocyclic compounds was the highest.Next,the low-lipid microalgae and sweet potato residue were selected to conduct the slow pyrolysis experiments by thermogravimetric analyzer and TG-FTIR.The effect of different blending ratios on the thermal weight loss behavior were analyzed.The results showed that the thermal weight loss process of microalgae and sweet potato residue and their mixtures under nitrogen atmosphere was also divided into three stages.Slow pyrolysis of mixtures greatly increased the reactivity of the first pyrolysis stage and promoted the pyrolysis process of proteins and carbohydrates in different biomasses.The synergistic effect indicated that there are two mutually promoting temperature ranges for theco-pyrolysis,which are 290324°C and 360380°C respectively.The optimum temperature and sample blending ratio appeared at 308°C and 373°C,and was 1CP2SPR.When the temperature was greater than 380°C,theco-pyrolysis at all blending ratios has an inhibitory effect.When the mixed sample was 1CP1SPR and 1CP2SPR,theco-pyrolysis promoted the pyrolysis of hemicellulose and lignin to form small molecular acids and phenols.At the same time,a more stable nitrogen-containing compound was formed by the Maillard reaction and the secondary reaction,and the yield of H2O and NH3 was lowered.Due to the presence of the Maillard reaction,the maximum value of the activation energy of the reaction occurred in 1CP2SPR,mainly due to the formation of more stable nitrogen-containing macromolecules.Finally,the fast pyrolysis experiment of low-lipid microalgae and sweet potato residue was carried out by gas chromatography-mass spectrometry.The product distribution and synergistic effect were analyzed.The results showed that the co-pyrolysis of microalgae and sweet potato residue promoted the pyrolysis of hemicellulose,lignin and proteins which increased the yield of acetic acid,phenols and aromatic hydrocarbons.When the pyrolysis temperature was 700°C,the carboxyl group in the hemicellulose and the amino group in the protein were promoted to form nitrogen-containing compounds,and reduced the yield of acetic acid.When the pyrolysis temperature was 500°C and 600°C,co-pyrolysis promoted the decarboxylation of long chain acids.When the pyrolysis temperature was 800°C,the high temperature promoted the removal of the methoxy group in the phenol,and increased the yield of the alkylphenol and the aromatic cyclization and condensation reaction.The co-pyrolysis formed nitrogen-containing macromolecular compounds due to the Maillard reaction,and promoted the formation of alkylfuran at the same time.Based on the Maillard reaction of proteins and carbohydrates in the pyrolysis process,the co-pyrolysis products of low-lipid microalgae and sweet potato residue can be regulated by target products,which provides evidence for resource utilization. |
