Affected mechanisms of oxygen-deficient pretreatment on reduction of NO by biochar

doi:10.11949/0438-1157.20250619

Abstract

Abstract:

As the core technology for biomass reburning denitrification, improving its efficiency is crucial for achieving rapid NO reduction. Aiming at the lack of theoretical support for the targeted design of existing denitrification biochar, this study constructed models of pristine and oxygen-deficient pretreated biochars (BCraw and BCoxy), respectively. It analyzed the influence mechanism of oxygen-deficient pretreatment on biochar reduction of NO from a microscopic perspective. The research found that the reduction of NO by BCraw is primarily composed of four processes: NO adsorption and dissociation, hydrogen atom migration, cleavage and recombination of aromatic rings, and N₂ desorption. Compared to BCraw, the conjugation effect of phenolic hydroxyl groups in BCoxy optimized the NO reduction pathway, reducing the energy barrier (Gap value) for N₂ desorption from 546.65 kJ/mol to 409.40 kJ/mol. Temperature-programmed reduction (TPR) experiments on biochar showed that the NO reduction capability of BCoxy is 1.04 times that of BCraw, further validating the reliability of the simulation results. These findings elucidate the mechanism by which oxygen-deficient pretreatment influences biochar reduction of NO, providing a theoretical foundation for the design of highly efficient biochar-based denitrification materials.

Key words: biofuel, oxidation, pretreatment, computational chemistry, NO

摘要：

生物炭还原NO作为生物质再燃脱硝技术的核心，其效率的提升对实现NO的快速减排至关重要。针对现有脱硝生物炭定向设计缺乏理论支撑这一问题，分别构建原始与贫氧预处理生物炭模型（BCraw和BCoxy），从微观角度解析贫氧预处理对生物炭还原NO的影响机制。研究发现，BCraw对NO的还原主要由NO吸附及裂解、氢原子迁移、芳香环裂解重组以及氮气脱附四个过程组成。与BCraw相比，BCoxy中酚羟基的共轭效应优化了NO的还原路径，氮气脱附能量Gap值由546.65 kJ/mol降为409.40 kJ/mol。生物炭的程序升温还原实验（TPR）结果表明，BCoxy对NO的还原能力是BCraw的1.04倍，进一步验证了模拟结果的可靠性。上述结果阐明了贫氧预处理对生物炭还原NO的影响机理，为生物炭基高效脱硝材料设计提供了理论基础。

关键词: 生物燃料, 氧化, 预处理, 计算化学, NO

CLC Number:

TQ 35

Lei ZHANG, Jiawei KANG, Haoran LI, Wenpeng HONG. Affected mechanisms of oxygen-deficient pretreatment on reduction of NO by biochar[J]. CIESC Journal, 2025, 76(12): 6696-6707.

张雷, 康嘉伟, 李浩然, 洪文鹏. 贫氧预处理对生物炭还原NO的影响机制研究[J]. 化工学报, 2025, 76(12): 6696-6707.

Figures/Tables 15

Fig.1 The optimized models of BCraw and BCoxy

Table 1 Ultimate and proximate analyses of rice husk

元素分析/%（质量分数，daf）					工业分析/%（质量分数，ar）
C	H	N	S	O^①	水分	挥发分	固定碳	灰分
66.70	3.34	1.16	0.38	28.42	7.35	60.41	19.10	13.14

Fig.2 Schematic diagram of the experimental system of the multi-stage precise temperature control horizontal tube furnace

Fig.3 The orbit information of BCraw, BCoxy and NO

Table 2 The LUMO-HOMO gaps during the reduction of NO by BCraw and BCoxy

反应	LUMO-HOMO能量差值/eV
BCraw-NO
反应Ⅰ	Gap Ⅰ = BCraw (LUMO) - NO (HOMO) = 0.83
反应Ⅱ	Gap Ⅱ = NO (LUMO) - BCraw (HOMO) = 3.51
BCoxy-NO
反应Ⅲ	Gap Ⅲ= BCoxy (LUMO) - NO (HOMO) = 0.87
反应Ⅳ	Gap Ⅳ= NO (LUMO) - BCoxy (HOMO) = 3.28

Table 3 The CLEI values of primary atoms in BCraw and BCoxy structures

模型	CLEI/(e·eV)
模型	C₁	N₂	C₃	C₄	C₅
BCraw	0.05620	0.06942	0.01546	0.06249	0.03673
BCoxy	0.06183	0.06233	0.01628	0.05067	0.02498

Fig.4 The distrubition of ADCH charges of BCraw and BCoxy

Fig.5 The diagrams of geometric optimization of intermediates and transition states in the reaction of BCraw-NO

Fig.6 The energy barrier diagram of BCraw-NO reaction

Fig.7 The diagrams of geometric optimization of reactants, intermediates, transition states and products in the reaction of BCoxy-NO

Fig.8 The energy barrier diagram of BCoxy-NO reaction

Fig.9 SEM images of BCraw and BCoxy

Fig.10 The oxygen-containing functional groups on the surface of BCraw and BCoxy

Fig.11 The reduction characteristics of NO by biochar

Table 4 The reduction characteristic parameters during the reaction between biochar and NO

模型	(dc_NO/dt)_max/(μmol/(mol·℃))	t₀/s	t_max/s	T_i/℃	T_max/℃
BCraw	-3.70	4206	4419	701	736.5
BCoxy	-3.33	4512	4626	752	771

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