Waste and Biomass Valorization
·
2016
·Vol. 9
·期 1
·123-130
·
IF 0.915
Cheng Xu,Tang Yijing,Wang Biao,Jiang Jianming
The utilization of waste rice husks for biochar production has received much attention due to the energy concerns and environmental issues. But how to increase the charcoal yield and quality remains a big challenge. In this work, a two-step pyrolysis of rice husks was carried out at atmospheric pressure, consisting of a first low heating rate step followed by a high heating rate step. The effects of operation conditions at each step, including temperature, heating rate and residence time, on changes in charcoal yield and quality based on fixed-carbon yield were investigated. At the first step, switch temperature and heating rate were the predominant factors that influenced charcoal and fixed-carbon yields. The increase of charcoal and fixed-carbon yields at the first step was attributed to the rate-determined decomposition of hemicellulose. Therefore, the switch temperature should be set at those lower than the decomposition temperature of celluloses. However, at the second step, decreasing final pyrolysis temperature and shortening residence time benefited the increase of charcoal yields. Whereas, a maximum value of fixed-carbon yield was observed at the final pyrolysis temperature of 600 °C, which could result from the aromatics formed from cellulose-derived volatiles. Therefore, the switch temperature should be lower than cellulose decomposition temperature in order to reduce the cycle time for biochar production. Moreover, the charcoal and fixed-carbon yields obtained by the optimized two-step pyrolysis were higher than those by one-step pyrolysis.
研究领域:
能源与环境科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Biomass Conversion and Biorefinery
·
2021
·Vol. 13
·期 13
·11789-11802
·
IF 4.987
Zhang Liqiang,Liu Jiaojiao,Zhang Zexia,Yang Zhengda,Wang Xinwei,Li Dawei,Lin Riyi
Two-step pyrolysis (TSP) of cellulose, hemicellulose, and lignin; the three-component cross-coupling samples; and the acid-washed walnut shell (AWS) were carried out by a pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) to investigate the effects of components and their proportions on the TSP of biomass. The results showed that different components dominated the formation of different products. Cellulose generated more furans and carbohydrates in both the first (S1) and second steps (S2). Hemicellulose achieved higher selectivity of ketones, acids, and alcohols in S1, and higher selectivity of hydrocarbons in S2. Lignin mainly produced phenols in S1, and hydrocarbons and phenols in S2. The increase of holocellulose (hemicellulose and cellulose) improved the contents of aldehydes, ketones, furans, acids, and alcohols but reduced the content of phenols in S1. In S2, more holocellulose increased the contents of aldehydes, ketones, and acids, but decreased the contents of phenols, hydrocarbons, and alcohols. The generation of carbohydrates was strongly inhibited in S1 by hemicellulose and lignin. More cellulose improved the contents of aldehydes, acids, and furans in S1, and increased the content of ketones but reduced the content of acids in S2. Hemicellulose facilitated the generation of hydrocarbons, but inhabited the produce of carbohydrates in S2. The small amount of the low-content components (protein, alkali and alkaline earth metals, etc.) and the connection structure of the components resulted in the significant difference in the pyrolysis reactions and product distribution of AWS and the mixed sample with corresponding component proportion. Therefore, more influence factors, such as the low-content components, the connection structure of the components, and different pyrolysis conditions, should be considered in the near future to investigate the interactions on the two or more components in TSP.
研究领域:
能源与环境科学
·
分析化学
✓ 已验证
产品关联
DOI
高影响因子
Biomass Conversion and Biorefinery
·
2021
·Vol. 13
·期 5
·3871-3880
·
IF 4.987
Zhang Liqiang,Li Shanshan,Yang Zhengda,Wang Xinwei,Li Dawei,Lin Riyi
To explore a new way of utilizing lignin and deepen the understanding of mechanism of two-step pyrolysis (TSP) of biomass, the effects of the first step pyrolysis temperature (T1) and residence time (RT1) on TSP of lignin were studied by using pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). TSP of lignin was also compared with one-step pyrolysis (OSP) of lignin. The results indicated that higher pyrolysis temperature promoted the break of ether linkage among the structural elements of lignin and the removal of side chains. With T1 increasing, the contents of monophenols (MPs), catechols (CPs), monocyclic aromatic hydrocarbons (MAHs), and polycyclic aromatic hydrocarbons (PAHs) increased in the first step, while the contents of methoxyphenols with double bond in the side-chain (MPBSs) and methoxyphenols with no double bond in the side-chain (MPSs) increased firstly and then decreased. In the second step, with T1 increasing the contents of MPs and CPs increased firstly and then decreased, the contents of MAHs and PAHs increased significantly, and the contents of MPBSs and MPSs decreased. Higher T1 increased the yields of the most identified compounds of the first step, but decreased the yields of MPs, CPs, MPBSs, and MPSs in the second step. RT1 had great effects on the pyrolysis behaviors and product distribution of TSP of lignin, and the content of MAHs and PAHs in the second step increased significantly with RT1 increasing. Compared with OSP, the yields of MAHs and PAHs could increase in the second step. TSP of lignin could improve the selectivity of value-added chemicals remarkably, such as guaiacol, vanillin, acetovanillone in the first step, and the selectivity of benzene, toluene, m-xylene, phenol, o-cresol, and p-cresol in the second step.
研究领域:
生物质能
·
化学工程
·
分析化学
✓ 已验证
DOI
高影响因子
NEW JOURNAL OF CHEMISTRY
·
2019
·Vol. 43
·期 35
·13735-13740
·
IF 3.069
Xinyue Rao,Mengke Yuan,Huan Jiang,Ling Li,Zhongde Liu
Inspired by the knowledge that a nonchiral metal nanocrystal could be bestowed with chirality when the metal nanocrystal and the chiral molecules form complexes, in this contribution, a two-step pyrolytic route to obtain chiroptical carbon quantum dots (CQDs) was attempted through the optically active surface passivation procedure with enantiomers. Here, tartaric acid (TA) and citric acid (CA), one being a chiral molecule and the other being an achiral molecule, were used as carbon sources to produce a carbon core, respectively, and D/L-penicillamine (D/L-Pen) molecules were utilized as chiral ligands to further passivate it in the two-step pyrolytic route. The strategy is applicative no matter whether the carbon source is from chiral or achiral molecules during the first carbonization step. Also, the second pyrolytic reaction temperature, lower than the melting point of the surface passivation enantiomeric ligand, is critical to preserve the chiral information and to generate the chiral centers of the CQDs. Based on this simple approach, it is possible to envision the design and fabrication of new types of more sophisticated optically active photoluminescence carbon nanodots, which may be applied in chiral catalysis, chiral recognition and sensing.
研究领域:
材料科学
·
光学
·
化学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）