Continuous dinitration of toluene to dinitrotoluene in a microreactor

doi:10.11949/0438-1157.20240059

Abstract

Abstract:

In order to realize the safe and efficient production of dinitrotoluene (DNT), the behavior of toluene dinitration process was investigated by using microreaction technology with mixed acid as nitrating agent and toluene as raw material. Increasing the reaction temperature, elevating the molar ratio of nitric acid to toluene, reducing the water content of the mixed acid and decreasing N/S and integrating stirring were all conducive to the generation of DNT. Lowering the reaction temperature and increasing the water content of the mixed acid and the molar ratio of nitrate to sulfur are beneficial to reducing the 2,4-/2,6-DNT ratio. The nitrification process has been optimized for 80/20DNT products. At a reaction temperature of 75℃, a water content of mixed acid of 14%, N/S of 1/4 or 1/3, and a stirring time of 5 min, the product composition demonstrated desirable characteristics, i.e., the content of MNT in the product was less than 0.2%, 2,4-DNT and 2,6-DNT greater than 96% and other DNT less than 4%. More importantly, the ratio of 2,4-/2,6-DNT was less than 4.25. Under the conditions of adiabatic and room temperature feeding, a mixed acid water content of 14%, N/S of 1/4, and stirring time of 10 min, the product also complied with the industry standards. The study outcomes offer valuable technical insights for the continuous dinitration process of toluene and the continuous preparation of 80/20DNT products.

Key words: microreactor, microchannel, process intensification, nitration, dinitrotoluene

摘要：

为实现二硝基甲苯（DNT）的安全高效生产，采用微反应技术，以甲苯为原料、硝硫混酸为硝化剂，研究了甲苯连续二硝化反应过程基本规律。提高反应温度、增大硝酸与甲苯的摩尔比、降低混酸含水量、减小硝硫摩尔比、集成釜式搅拌操作有利于DNT的生成；降低反应温度、提高混酸含水量和硝硫摩尔比，有利于降低2，4-/2，6-DNT比值。针对80/20DNT产品进行了硝化工艺优化。在反应温度75℃、混酸含水量14%(质量分数)、硝硫摩尔比1/4或1/3、搅拌时间5 min条件下，产物中一硝基甲苯(MNT)含量小于0.2%，2，4-和2，6-DNT含量大于96%，2，4-/2，6-DNT比值小于4.25，其他DNT异构体含量均小于4%，符合行业标准。绝热条件下，室温进料，混酸含水量14%(质量分数)，硝硫摩尔比1/4，搅拌时间10 min，生产的产品质量符合行业标准。研究结果为甲苯连续二硝化工艺开发及80/20DNT产品的连续制备提供了基础。

关键词: 微反应器, 微通道, 过程强化, 硝化, 二硝基甲苯

CLC Number:

TQ 246.1

Rao CHEN, Xin ZHAO, Daixin CHEN, Shengkun JIANG, Yingjiang LIAN, Jinbo WANG, Mei YANG, Guangwen CHEN. Continuous dinitration of toluene to dinitrotoluene in a microreactor[J]. CIESC Journal, 2024, 75(3): 867-876.

陈饶, 赵鑫, 陈戴欣, 姜圣坤, 廉应江, 王金波, 杨梅, 陈光文. 微反应器内甲苯连续二硝化制备二硝基甲苯[J]. 化工学报, 2024, 75(3): 867-876.

Figures/Tables 11

References 31

1	Auer E. Supported iridium catalysts—a novel catalytic system for the synthesis of toluenediamine[J]. Catalysis Today, 2001, 65(1): 31-37.
2	Neri G, Rizzo G, Milone C, et al. Microstructural characterization of doped-Pd/C catalysts for the selective hydrogenation of 2, 4-dinitrotoluene to arylhydroxylamines[J]. Applied Catalysis A: General, 2003, 249(2): 303-311.
3	Hajdu V, Varga M, Muránszky G, et al. Development of magnetic, ferrite supported palladium catalysts for 2, 4-dinitrotoluene hydrogenation[J]. Materials Today Chemistry, 2021, 20: 100470.
4	Hajdu V, Muránszky G, Hashimoto M, et al. Combustion method combined with sonochemical step for synthesis of maghemite-supported catalysts for the hydrogenation of 2, 4-dinitrotoluene[J]. Catalysis Communications, 2021, 159: 106342.
5	Jakab-Nácsa A, Garami A, Fiser B, et al. Towards machine learning in heterogeneous catalysis—a case study of 2,4-dinitrotoluene hydrogenation[J]. International Journal of Molecular Sciences, 2023, 24(14): 11461.
6	陈利平, 陈网桦, 彭金华, 等. 二硝基甲苯硝化反应的热危险性分析[J]. 含能材料, 2010, 18(6): 706-710.
	Chen L P, Chen W H, Peng J H, et al. Thermal hazard analysis of dinitrotoluene nitration[J]. Chinese Journal of Energetic Materials, 2010, 18(6): 706-710.
7	Kulkarni A A. Continuous flow nitration in miniaturized devices[J]. Beilstein Journal of Organic Chemistry, 2014, 10: 405-424.
8	汪嘉欣, 潘勇, 熊欣怡, 等. 甲苯一步催化硝化制备二硝基甲苯反应过程及危险性[J]. 化工进展, 2023, 42(7): 3420-3430.
	Wang J X, Pan Y, Xiong X Y, et al. Reaction process and hazards of dinitrotoluene preparation by one-step catalytic nitration of toluene[J]. Chemical Industry and Engineering Progress, 2023, 42(7): 3420-3430.
9	Guggenheim T L. Chemistry, Process Design, and Safety for the Nitration Industry[M]. Washington DC: American chemical Society, 2013.
10	陈光文, 袁权. 微化工技术[J]. 化工学报, 2003, 54(4): 427-439.
	Chen G W, Yuan Q. Micro-chemical technology[J]. Journal of Chemical Industry and Engineering (China), 2003, 54(4): 427-439.
11	陈光文, 赵玉潮, 袁权. 微尺度下液-液流动与传质特性的研究进展[J]. 化工学报, 2010, 61(7): 1627-1635.
	Chen G W, Zhao Y C, Yuan Q. Advances in flow hydrodynamic and mass transfer characteristics of liquid phase in microscale[J]. CIESC Journal, 2010, 61(7): 1627-1635.
12	骆广生, 王凯, 王玉军, 等. 微化工系统的原理和应用[J]. 化工进展, 2011, 30(8): 1637-1642.
	Luo G S, Wang K, Wang Y J, et al. Principles and applications of micro-structured chemical system[J]. Chemical Industry and Engineering Progress, 2011, 30(8): 1637-1642.
13	陈光文, 赵玉潮, 乐军, 等. 微化工过程中的传递现象[J]. 化工学报, 2013, 64(1): 63-75.
	Chen G W, Zhao Y C, Yue J, et al. Transport phenomena in micro-chemical engineering[J]. CIESC Journal, 2013, 64(1): 63-75.
14	骆广生, 王凯, 吕阳成, 等. 微尺度下非均相反应的研究进展[J]. 化工学报, 2013, 64(1): 165-172.
	Luo G S, Wang K, Lü Y C, et al. Research and development of micro-scale multiphase reaction processes[J]. CIESC Journal, 2013, 64(1): 165-172.
15	Jensen K F. Flow chemistry—microreaction technology comes of age[J]. AIChE Journal, 2017, 63(3): 858-869.
16	李光晓, 刘塞尔, 苏远海. 微尺度内液-液传质及反应过程强化的研究进展[J]. 化工学报, 2021, 72(1): 452-467.
	Li G X, Liu S E, Su Y H. Research progress on micro-scale internal liquid-liquid mass transfer and reaction process enhancement[J]. CIESC Journal, 2021, 72(1): 452-467.
17	Dummann G, Quittmann U, Gröschel L, et al. The capillary-microreactor: a new reactor concept for the intensification of heat and mass transfer in liquid–liquid reactions[J]. Catalysis Today, 2003, 79/80: 433-439.
18	Su Y H, Zhao Y C, Jiao F J, et al. The intensification of rapid reactions for multiphase systems in a microchannel reactor by packing microparticles[J]. AIChE Journal, 2011, 57(6): 1409-1418.
19	Yu Z Q, Zhou P C, Liu J M, et al. Continuous-flow process for selective mononitration of 1-methyl-4-(methylsulfonyl)benzene[J]. Organic Process Research & Development, 2016, 20(2): 199-203.
20	Yan Z F, Tian J X, Du C C, et al. Reaction kinetics determination based on microfluidic technology[J]. Chinese Journal of Chemical Engineering, 2022, 41: 49-72.
21	刘卫孝, 刘洋, 高福磊, 等. 微反应器在含能材料合成与品质提升中的应用[J]. 化工进展, 2023, 42(7): 3349-3364.
	Liu W X, Liu Y, Gao F L, et al. Application of microreactor in synthesis and quality improvement of energetic materials[J]. Chemical Industry and Engineering Progress, 2023, 42(7): 3349-3364.
22	Jin N, Song Y B, Yue J, et al. Heterogeneous nitration of nitrobenzene in microreactors: process optimization and modelling[J]. Chemical Engineering Science, 2023, 281: 119198.
23	Guo S, Zhan L W, Li B D. Nitration of o-xylene in the microreactor: reaction kinetics and process intensification[J]. Chemical Engineering Journal, 2023, 468: 143468.
24	Wen Z H, Jiao F J, Yang M, et al. Process development and scale-up of the continuous flow nitration of trifluoromethoxybenzene[J]. Organic Process Research & Development, 2017, 21(11): 1843-1850.
25	Russo D, Tomaiuolo G, Andreozzi R, et al. Heterogeneous benzaldehyde nitration in batch and continuous flow microreactor[J]. Chemical Engineering Journal, 2019, 377: 120346.
26	Hussain A, Sharma M, Patil S, et al. Design and scale-up of continuous di-nitration reaction using pinched tube flow reactor[J]. Journal of Flow Chemistry, 2021, 11(3): 611-624.
27	侯跃辉, 刘璇, 廉应江, 等. 超声微反应器内三硝基间苯三酚合成工艺研究[J]. 化工学报, 2022, 73(8): 3597-3607.
	Hou Y H, Liu X, Lian Y J, et al. Synthesis process of trinitrophloroglucinol in an ultrasonic microreactor[J]. CIESC Journal, 2022, 73(8): 3597-3607.
28	Hou Z T, Chen H F, Mao J Y, et al. Novel atomization-assisted phosgenation for TDI synthesis from TDA: a theoretical study on single droplet reactivity[J]. Chemical Engineering Science, 2023, 280: 119018.
29	Zaldivar J M, Molga E, Alós M A, et al. Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime[J]. Chemical Engineering and Processing: Process Intensification, 1995, 34(6): 543-559.
30	Russo D, Marotta R, Commodo M, et al. Ternary HNO₃-H₂SO₄-H₂O mixtures: a simplified approach for the calculation of the equilibrium composition[J]. Industrial & Engineering Chemistry Research, 2018, 57(5): 1696-1704.
31	Li S F, Zhang X L, Ji D S, et al. Continuous flow nitration of 3-[2-chloro-4-(trifluoromethyl) phenoxy]benzoic acid and its chemical kinetics within droplet-based microreactors[J]. Chemical Engineering Science, 2022, 255: 117657.

Item	Quality index
Item	Premium grade	First-grade
appearance	no black impurities or suspended solids
2,4+2,6-DNT/%	≥95.0	≥95.0
2,4-/2,6-DNT	3.76~4.26	3.65~4.41
2,5+3,5-DNT/%	≤1.0	≤1.0
2,3+3,4-DNT/%	≤4.0	≤4.5
MNT/%	≤0.2	≤0.2
TNT/%	≤0.1	≤0.1
nitrocresol/%	≤0.15	≤0.15

Item	Quality index
Item	Premium grade	First-grade
appearance	no black impurities or suspended solids
2,4+2,6-DNT/%	≥95.0	≥95.0
2,4-/2,6-DNT	3.76~4.26	3.65~4.41
2,5+3,5-DNT/%	≤1.0	≤1.0
2,3+3,4-DNT/%	≤4.0	≤4.5
MNT/%	≤0.2	≤0.2
TNT/%	≤0.1	≤0.1
nitrocresol/%	≤0.15	≤0.15

φ/%	Q_org/(ml/min)	N/S	N/T	T/℃	τ/min	t_stir/min	MNT/%	DNT/%	2,4-&2,6-DNT/%	2,4-/2,6-DNT	Other DNT/%
2	2	1/1	2.10	75	6.03	0	5.73	94.17	89.30	4.48	4.87
2	2	1/1	2.10	75	6.03	5	0.77	99.23	94.15	4.52	5.08

φ/%	Q_org/(ml/min)	N/S	N/T	T/℃	τ/min	t_stir/min	MNT/%	DNT/%	2,4-&2,6-DNT/%	2,4-/2,6-DNT	Other DNT/%
2	2	1/1	2.10	75	6.03	0	5.73	94.17	89.30	4.48	4.87
2	2	1/1	2.10	75	6.03	5	0.77	99.23	94.15	4.52	5.08

φ/%	N/T	τ/min	t_stir/min	MNT/%	DNT/%	2,4-&2,6-DNT/%	2,4-/2,6-DNT	Other DNT/%
7	2.07	4.5	0	0.96	98.86	94.78	4.47	4.08
	2.18	4.4	0	0.10	99.74	95.59	4.50	4.14
	2.26	4.3	0	0.03	99.82	95.68	4.49	4.14
	2.07	4.5	5	0.10	99.73	95.57	4.49	4.16
	2.18	4.4	5	0	99.85	95.68	4.50	4.17
	2.26	4.3	5	0	99.83	95.67	4.50	4.17
10	2.05	4.3	0	9.83	90.15	86.89	4.27	3.26
	2.26	4.1	0	2.03	97.96	94.30	4.35	3.66
	2.05	4.3	5	6.71	93.26	89.89	4.26	3.38
	2.26	4.1	5	0	99.98	96.14	4.38	3.84
12	2.09	4.7	0	21.02	78.92	76.46	4.07	2.46
	2.17	4.5	0	16.68	83.31	80.60	4.12	2.71
	2.25	4.3	0	10.31	89.69	86.73	4.17	2.96
	2.09	4.7	5	7.76	92.02	89.08	4.11	2.94
	2.17	4.5	5	3.62	96.38	93.17	4.20	3.21
	2.25	4.3	5	1.31	98.69	95.31	4.26	3.38
14	2.08	4.5	0	38.66	61.33	59.52	3.95	1.81
	2.16	4.4	0	38.85	61.15	59.33	3.95	1.82
	2.26	4.3	0	34.80	65.20	63.23	3.97	1.96
	2.08	4.5	5	22.22	77.78	75.49	3.90	2.29
	2.16	4.4	5	19.14	80.86	78.45	3.92	2.40
	2.26	4.3	5	15.25	84.75	82.15	4.01	2.60