Deng Zhao,Yu Wang,Guanwei Wang,Wenming Han,Hua Liu,Huashan Wang,Hui Liu,Shuai Guo
Although alkali metal potassium (K)-catalyzed char gasification has been widely studied, the detailed mechanism of this process is still not fully understood. To study this catalytic mechanism in more detail, high-temperature in-situ DRIFTS experiments were carried out for the gasification of cellulose char with K and cellulose char without K under H 2 O and O 2 atmospheres, transient gasification experiment of char with K under H 2 O atmosphere, and char with K gasification under isotope water atmospheres. Peaks at 1945 cm −1 and 2020 cm −1 were observed. Combined with the theoretical spectra obtained by quantum chemical simulations and the prediction of catalytic gasification intermediates by molecular dynamics simulations, these two peaks were confirmed to represent char-polyynes species. Based on this result, a new mechanism is proposed: K interacts with carboxyl groups and aromatic ketones to promote desorption, thereby exposing active sites. Then, K reacts with the edge of the activated char to form numerous highly active char-polyynes species. The polyynes edge of this char-polyynes phase provides ideal adsorption–desorption sites, enabling further reaction with the gasifier. Thus, gas desorption is promoted. The adsorption and desorption peaks of catalytic gasification under the H 2 O atmosphere were located at 1400 cm −1 and 1300 cm −1 , and these peaks represented stable adsorption states and unstable desorption precursors, respectively. Based on this, adsorption–desorption theory was analyzed more comprehensively, and the adsorption–desorption process was divided into three stages: initial adsorption, intermediate conversion, and desorption. The comprehensive new mechanism proposed in this paper provides a better understanding of the nature of char catalytic gasification at a deeper level.
Tiankai Zhang,Yongfa Zhang,Qi Wang,Xuemei Lv,Yunhuan Luo
In this paper, the changes in solid-phase carbon structure and the formation of carbon nanotubes in the process of K-catalyzed pyrolysis of bituminous coal were investigated. The results showed that the content of carbon nanotubes in K-catalyzed coal pyrolysis products increased with the extension of residence time. When the residence times were 0, 30 and 90 min, the yields of carbon nanotubes in the coal pyrolysis products were 1.98 wt%, 6.85 wt% and 10.16 wt%, respectively. It was found that the aromatic carbon C C, C H and ether carbon C-O-C structures in coal were the main carbon sources for the growth of carbon nanotubes. The probable growth mechanism of carbon nanotubes in the process of K-catalyzed coal pyrolysis was proposed to be as follows: aromatic C C and C H structures in coal convert K components such as K 2 CO 3 and K 2 O into metal K, and then metal K converts carbon atoms in the ether bond C-O-C structure into carbon atoms or clusters, which generate carbon nanotubes under the action of Fe catalyst particles in coal. This method provides a new strategy for the simultaneous high-value utilization of coal resources and macroscopic, low-cost preparation of carbon nanotubes.
Wang Lu,Mingwei Xia,Ziyue Tang,Yingquan Chen,Xianhua Wang,Haiping Yang,Hanping Chen
Poly-generation of porous char and H 2 -rich syngas is a key technology for the full and high-value use of carbon and hydrogen elements in biomass. In this study, the synergistic evolution and regulation mechanisms of H 2 and porous carbon during K-assisted bamboo gasification were investigated using fixed-bed pyrolysis-gasification system. The results show that, due to steam activation, both the H 2 production rate and the physicochemical properties of char initially increase and then decline with prolonged gasification time, reaching their peak in the middle stage of the process. The hydrogen conversion rate further indicates that partial gasification achieves higher production efficiency, which is favorable for the poly-generation. K accelerates the evolution of both char and H 2 , enhancing their quality and ultimately enabling the poly-generation of 31.5 mmol/g H 2 and porous carbon with a S BET of 1917 m 2 /g. Moreover, K promotes oxygen enrichment in char, particularly the incorporation of O=C-OR and C=O groups on the char surface, thereby improving the functional applicability of the carbon.
危险品化学品经营许可证（带存储）