Preparation of mononitrotoluene by continuous adiabatic nitration of excess toluene in microreactor

doi:10.16085/j.issn.1000-6613.2021-1492

Abstract

Abstract:

To reduce by-products such as polynitrophenols and organic content of spent acid in toluene kettle nitrification, the effects of flow rate, molar ratio of toluene to nitric acid and mass ratio of sulfuric acid to nitric acid on nitrification were studied under the premise of excess toluene in a micro chemical system. Results show the optimal process conditions are as follows: 73% sulfuric acid, initial temperature is 35℃, molar ratio of nitric acid to toluene is 0.6, mass ratio of sulfuric acid to nitric acid is 10, and residence time of reaction system is 240 seconds. Under above conditions, the utilization rate of nitric acid is more than 97%, DNT content is 0.84%, and polynitrophenol content is 0.12%. Compared with conventional kettle process, the continuous adiabatic nitrification can significantly shorten the reaction time and reduce polynitrophenol content by more than 50%. If toluene is excessive, toluene takes the function of extraction, and the organic content in acid phase is reduced to 0.18%, which facilitates the subsequent treatment of spent acid.

Key words: toluene, mononitrotoluene, adiabatic nitrification, microreactor

摘要：

为降低甲苯釜式硝化中多硝基酚等副产物、废酸中有机物的质量分数，本文采用微化工系统，在甲苯过量的前提下，探究流速、硝酸甲苯摩尔比及硫酸硝酸质量比等因素对硝化反应的影响。结果表明，采用73%硫酸、反应初温为35℃、硝酸甲苯摩尔比为0.6、硫酸硝酸质量比为10、反应体系停留时间为240s时工艺条件最优，此时硝酸利用率大于97%，二硝基甲苯（DNT）的质量分数为0.84%，多硝基酚的质量分数为0.12%。相较于传统釜式工艺，采用连续绝热硝化后，反应时间大幅降低，多硝基酚质量分数降低50%以上；当甲苯过量时，甲苯起到萃取的作用，酸相中有机物的质量分数降低至0.18%，有利于后续废酸处理。

关键词: 甲苯, 单硝基甲苯, 绝热硝化, 微反应器

CLC Number:

TQ246.1

JIANG Shengkun, HAN Bo, ZHAO Xin, YU Wanhe, LUO Guangsheng, DENG Jian, LIU Guangqi, WANG Jingqi, WANG Jinbo. Preparation of mononitrotoluene by continuous adiabatic nitration of excess toluene in microreactor[J]. Chemical Industry and Engineering Progress, 2022, 41(6): 2910-2914.

姜圣坤, 韩博, 赵鑫, 于万河, 骆广生, 邓建, 刘光启, 王景奇, 王金波. 微通道反应器中甲苯过量连续绝热硝化制备单硝基甲苯[J]. 化工进展, 2022, 41(6): 2910-2914.

Figures/Tables 6

样品	F_TOL/mL·min^-1	ΔT/℃	压降/MPa	TOL质量分数/%	MNT质量分数/%	DNT质量分数/%	酚质量分数/%	硝酸利用率/%
1-1	17.80	72.5	0.4	52.48	46.83	0.59	0.10	95.05
1-2	22.80	72.9	0.4	52.27	47.06	0.56	0.11	95.46
1-3	27.80	70.3	0.4	53.14	46.27	0.48	0.11	93.71
1-4	37.80	62.4	0.6	58.26	41.21	0.42	0.11	83.49
1-5	47.80	53.6	0.8	64.88	34.75	0.30	0.08	70.25
1-6	57.80	50.3	1.0	68.52	31.19	0.22	0.07	62.95

样品	$n H N O 3 / n T O L$	ΔT/℃	压降/MPa	TOL质量分数/%	MNT质量分数/%	DNT质量分数/%	酚质量分数/%	硝酸利用率/%
2-1	0.5	72.9	0.4	52.27	47.06	0.56	0.11	95.46
2-2	0.6	74.5	0.4	41.77	57.27	0.84	0.12	97.05
2-3	0.7	73.5	0.4	35.37	63.40	1.09	0.14	92.33
2-4	0.8	69.2	0.4	31.60	66.92	1.30	0.18	85.50
2-5	0.9	70.4	0.4	23.26	74.82	1.74	0.18	85.27

样品	$n H N O 3 / n T O L$	ΔT/℃	压降/MPa	TOL质量分数/%	MNT质量分数/%	DNT质量分数/%	酚质量分数/%	硝酸利用率/%
2-1	0.5	72.9	0.4	52.27	47.06	0.56	0.11	95.46
2-2	0.6	74.5	0.4	41.77	57.27	0.84	0.12	97.05
2-3	0.7	73.5	0.4	35.37	63.40	1.09	0.14	92.33
2-4	0.8	69.2	0.4	31.60	66.92	1.30	0.18	85.50
2-5	0.9	70.4	0.4	23.26	74.82	1.74	0.18	85.27

样品	$m H 2 S O 4 / m H N O 3$	ΔT/℃	压降/MPa	TOL质量分数/%	MNT质量分数/%	DNT质量分数/%	酚质量分数/%	硝酸利用率/%
3-1	9	79.9	0.4	42.84	56.15	0.91	0.10	95.28
3-2	10	74.5	0.4	41.77	57.27	0.84	0.12	97.05
3-3	11	56.5	0.4	51.58	47.75	0.56	0.11	80.73
3-4	12	44.5	0.4	59.27	40.24	0.40	0.09	67.88

样品	$m H 2 S O 4 / m H N O 3$	ΔT/℃	压降/MPa	TOL质量分数/%	MNT质量分数/%	DNT质量分数/%	酚质量分数/%	硝酸利用率/%
3-1	9	79.9	0.4	42.84	56.15	0.91	0.10	95.28
3-2	10	74.5	0.4	41.77	57.27	0.84	0.12	97.05
3-3	11	56.5	0.4	51.58	47.75	0.56	0.11	80.73
3-4	12	44.5	0.4	59.27	40.24	0.40	0.09	67.88

样品	ΔT/℃	压降/MPa	DNT质量分数/%	酚质量分数/%	硝酸利用率/%
4-1	74.5	0.4	0.84	0.12	97.05
4-2	74.4	0.4	0.83	0.11	97.01
4-3	74.5	0.4	0.84	0.12	97.08
4-4	74.5	0.4	0.84	0.12	97.07
4-5	74.6	0.4	0.85	0.12	97.12

工艺	反应时间/min	DNT质量分数/%	酚质量分数/%	酸相中有机物质量分数/%	硝酸利用率/%
传统釜式	80	0.40	0.35	0.52	>99
绝热硝化	4	0.84	0.12	0.18	>97

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