摘要
研究以2‑甲基‑4,6‑嘧啶二酮(MPO)为原料,在微通道反应器中探索了与硝硫混酸的硝化反应规律,并进一步通过水解反应来制备1,1‑二氨基‑2,2‑二硝基乙烯(FOX‑7)。研究通过引入惰性溶剂正辛烷,使反应体系呈弹状流,反应发生于分散液滴内部,解决了硝化中间体2‑(二硝基亚甲基)‑5,5‑二硝基嘧啶‑4,6‑二酮(TNMPO)在微通道反应器中的堵塞难题,实现了过程强化和连续化;并研究了反应温度、停留时间、物料配比、水解条件等因素对产品收率的影响,提出了微反应器与搅拌釜串联的反应工艺。结果表明,在硝酸与MPO摩尔比为4.4,微反应器中停留时间3 min,反应温度30
图文摘要
1,1‑diamino‑2,2‑dinitroethylene (FOX‑7) is an important energetic material. Using 2‑methyl‑4, 6‑pyrimidinone (MPO) as raw material and n‑octane as an inert solvent, the nitration of MPO with nitrate sulfur mixed acid was studied in a microreactor, and FOX‑7 was prepared by the following hydrolysis reaction. The effects of reaction temperature, residence time, material ratio and hydrolysis conditions on the yield of FOX‑7 were studied. The reaction process of microreactor and stirred kettle in series was proposed, which could provide the basis for the industrial production of FOX‑7.
1,1‑二氨基‑2,2‑二硝基乙烯(FOX‑7)是一种新型的高能钝感炸药,具有含氮量大、爆轰性能优良、分子结构稳定、与聚合物相容性好等优点,成为国内外炸药合成领域的研究热
目前,2‑甲基‑4,6‑嘧啶二酮硝化和水解过程主要通过间歇釜式反应器进行。硝化反应放热量大(375.22 kJ·mo
微反应器作为一种新型的反应设备,在化学化工领域受到了广泛关
目前,国内外尚无在微反应器中连续合成FOX‑7的报道。基于此,本研究开展微反应器内2‑甲基‑4,6‑嘧啶二酮硝化反应,并探讨其规律。由于硝化中间体TNMPO难溶于混酸体系,引入正辛烷作为惰性溶剂与反应相形成弹状流,使反应发生于分散液滴内部并有效防止固体产物在壁面沉积和堵塞管道,实现了过程连续运行。在此基础上,研究了反应温度、停留时间、物料配比、水解反应等参数对FOX‑7产品收率的影响,为FOX‑7的安全可控和连续化生产提供技术支持。
实验试剂:2‑甲基‑4,6‑嘧啶二酮(98%,上海源叶生物科技有限公司);浓硫酸(≥95%,天津市科密欧化学试剂有限公司);正辛烷(≥95%,天津市科密欧化学试剂有限公司);发烟硝酸(≥95%,广州化学试剂厂);无水乙醇(95%,天津富宇精细化工有限公司)。
仪器:电子分析天平,ME‑204T,梅特勒‑托利多有限公司;注射泵,TYD‑01‑01,保定雷弗流体科技有限公司;不锈钢注射器,50 mL,南京润泽流体控制设备有限公司;安捷伦LC1260型高效液相色谱仪;电热恒温鼓风干燥箱,DGG‑9070A,上海森信实验仪器有限公司;恒温加热磁力搅拌器,C‑MAG HS7,艾卡(广州)仪器设备有限公司。
实验装置如

图1 微反应器连续合成FOX ‑7示意图
Fig.1 Schematic diagram of the continuous synthesis of FOX‑7in the microreactor
(1)微反应器内温度与时间对产率的影响实验
实验具体流程为:将MPO溶于浓硫酸(MPO与浓硫酸摩尔比为1∶9)配制成连续相A,A相流速QA为0.25 mL·mi
(2)微反应器与搅拌釜集成对产率的影响实验
实验具体流程为:原料配比与上述实验条件相同,改变硝酸与MPO的摩尔比,同时恒定微反应器温度为30 ℃,停留时间3 min,接样时间为15 min,在搅拌釜内于30 ℃下继续搅拌不同的反应时间,用冰水淬灭,然后搅拌2 h进行水解开环反应。抽滤,洗涤,干燥后得到最终产品进行分析检测。
(3)水解温度和水解时间对产率的影响实验
实验具体流程为:原料配比与上述实验条件相同,在硝酸与MPO的摩尔比为4.4的条件下,恒定微反应器温度为30 ℃,停留时间3 min,接样时间为15 min,在搅拌釜内于30 ℃下继续反应30 min,使用不同温度的水进行水解开环,并研究水解时间对产品收率的影响。
首先在微通道反应器中开展了2‑甲基‑4,6‑嘧啶二酮(MPO)混酸硝化过程研究,结果如

a. without n‑octane

b. with n‑octane
图2 正辛烷对反应的影响图
Fig.2 Effect of n‑octane on the reaction
研究了微反应器内反应规律,即出口处反应液直接用冰水淬灭,然后搅拌2 h进行水解开环反应。首先考察反应温度对产品收率的影响,反应结果如
进一步研究不同反应温度(15,25,35 ℃)下产品收率随停留时间的变化规律,停留时间的控制均通过改变反应器的管长来实现,结果如

a. Y‑T curve

b. Y‑t curves
图3 反应温度和停留时间对FOX‑7收率的影响曲线
Fig.3 Effects of the reaction temperature and residence time on the yield of FOX‑7. QA=0.25 mL·mi
为了进一步提高产品收率,采用微反应器与搅拌釜串联的方式增加反应时间。这一反应系统的优势是:微反应器内物料充分混合并转化大部分原料,便于移除热量使安全性提高,利用搅拌釜延长反应时间使剩余原料进一步转化。首先确定最优的硝酸用量。合成FOX‑7时,硝酸与MPO的化学计量比为4。间歇反应工艺中,硝酸与MPO的摩尔比一般控制在4.0~5.0之

图4 不同硝硫比下反应釜内搅拌时间对FOX‑7收率的影响
Fig.4 Effect of stirring time in the reaction kettle on the yield of FOX‑7 under different molar ratios of HNO3 to MPO. QA=0.25 mL·mi
水解反应是将硝化中间体TNMPO进行水解开环产生FOX‑7,并产生二硝基甲烷和二氧化碳的过程。对水解反应进行深入研究,可以保证反应过程的安全性,防止中间体发生分解,提高产品的收率和纯度。如

a. Y‑T curve

b. Y‑t curve
图5 水解温度和水解时间对FOX‑7收率的影响
Fig.5 Effects of the hydrolysis temperature and hydrolysis time on the yield of FOX‑7. QA=0.25 mL·mi
水解开环的时间也会对收率产生很大的影响。如
化工生产过程中的重复性和稳定性不可忽视。采用最佳的工艺条件,即硝酸与MPO的摩尔比为4.4、微反应器内停留时间3 min、反应温度30 ℃,串联搅拌釜保温反应30 min,冰水水解开环反应2 h,进行重复实验验证,结果如
No. | yield | purity |
---|---|---|
1 | 89.8 | 99.8 |
2 | 90.1 | 99.9 |
3 | 90.0 | 99.8 |
尝试进行实验放大,将原料流速提高至3 mL·mi
(1)在微反应器中开展了2‑甲基‑4,6‑嘧啶二酮混酸硝化过程研究,引入正辛烷作为惰性溶剂与反应相形成弹状流,使反应发生于分散液滴内部,不仅可以防止固体沉积和通道堵塞,还可以强化传质传热,实现了过程强化和连续化操作;
(2)在微反应器中系统研究了反应温度、停留时间、物料配比、水解条件等变量对FOX‑7收率的影响,在最佳工艺条件下(硝酸与MPO的摩尔比为4.4,微反应器内停留时间3 min,反应温度30 ℃,之后用冰水水解开环 2 h),产品固体收率达到73.3%;
(3)采用微反应器与搅拌釜串联的模式,利用微反应器强化硝化反应过程和移出大部分反应热,然后在搅拌釜中延长反应时间得到较高的产品收率。在前述优化条件下,搅拌时间为30 min,产品收率提高至90.1%。本研究证实了FOX‑7连续合成的潜力,为实现工业化生产奠定基础。
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