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Mass transfer intensification and kinetics of o-xylene nitration in the microreactor

  • Dong Liu , Na Fan , Shulong Li , Lu Ji , Shihao Liu , Tiehan Xing , Xiaodong Liu and Shuai Guo EMAIL logo
Published/Copyright: September 4, 2025
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International Journal of Chemical Reactor Engineering
From the journal International Journal of Chemical Reactor Engineering Volume 23 Issue 9

Abstract

Continuous-flow synthesis of nitro-o-xylene has been widely reported. However, critical scientific challenges remain unresolved, including product selectivity optimization, process economic viability, and operational safety. Herein, continuous-flow o-xylene nitration with mixed acid in a capillary microreactor is presented. A kinetic model of the pseudo-homogeneous nitration reaction was developed, and the mass transfer process was characterised by the first Damköhler number and Hatta number. Notably, the capillary microreactor exhibited limited mass transfer efficiency, restricting conversion enhancement. To address this, a heart-shaped channel plate was integrated into the micro-reaction system. Under the M-ratio of HNO3 to o-xylene was 3, residence time was 35 s, temperature was 303 K, the conversion rate of 100 % was achieved. The developed micro-reactor system significantly improved both the selectivity and conversion of o-xylene nitration, demonstrating substantial potential for industrial application.

Keywords: nitration; microreactor; kinetics; mass transfer; intensification
Corresponding author: Shuai Guo, Research Institute of Chemical Advanced Materials Shenyang Research Institute of Chemical Industry, 8 East Shen Liao Road, Shenyang, 110021, P.R. China, E-mail:

Acknowledgments

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

  1. Research ethics: Not applicable.

  2. Informed consent: Not applicable.

  3. Author contributions: D. L: Experiment design and writing; N. F: Experimentation and data; S.L L: Experimentation and data; L. J: Drawing and modelling; S.H L: Modelling; T.H X: Drawing; X.D L: Experimentation; S. G: Writing and reviewing, technical explanations.

  4. Use of Large Language Models, AI and Machine Learning Tools: None declared.

  5. Conflict of interest: The authors declared that there is no conflict of interest.

  6. Research funding: None declared.

  7. Data availability: Not applicable.

Notation

C A 0

Fluid-phase inlet reactant concentration, mol·L−1

Cp m

Average specific heat capacity, kJ·kg−1·K−1

D

Dispersion coefficient, m2·s−1

d h

Hydraulic diameter of the microchannel inlet, m

∆H r

Reaction enthalpy, kJ·mol−1

k

Observed reaction rate constant

k L

Mass transfer coefficient, m·s−1

n A

Amount of substance A, mol

q v

Volumetric feed flow rate, mL·min−1

Q total

Total heat released, kJ

Q exchanged

Heat removed, kJ

Q out

Heat carried out of the reactor, kJ

t h

Characteristic heat transfer time, s

t

Residence time, s

t r

Characteristic reaction time, s

u

Superficial velocity, m·s−1

V R

Volume of the microchannel internal, mL

X

o-xylene conversion rate, %

DaΙ

The first Damköhler number

Ha

Hatta number

Nu

Nusselt number

Re

Reynolds number

Greek letters

α

Heat transfer coefficient, W·m−2·K−1

λ f

Heat conductivity of the microreactor, W·m−1·K−1

m

Order of the reaction

ρ M

Average density of the two immiscible liquid phases, kg·m−3

φ

Volume fraction of the oil phase

μ M

Average viscosity of the two immiscible liquid phases, Pa·s

Subscripts

aq

Aqueous phase

or

Organic phase

in

Inlet of the reactor

out

Outlet of the reactor

References

[1] H. M. Brennecke and K. A. Kobe, “Mixed acid nitration of toluene,” Ind. Eng. Chem., vol. 48, no. 8, pp. 1298–1304, 1956. https://doi.org/10.1021/ie50560a029.Search in Google Scholar

[2] Z. H. Wen, F. J. Jiao, M. Yang, S. N. Zhao, F. Zhou, and G. W. Chen, “Process development and scale-up of the continuous flow nitration of trifluoromethoxybenzene,” Org. Process Res. Dev., vol. 21, no. 11, pp. 1843–1850, 2017. https://doi.org/10.1021/acs.oprd.7b00291.Search in Google Scholar

[3] S. Guo, G. K. Zhu, L. W. Zhan, and B. D. Li, “Process design of two-step mononitration of m-xylene in a microreactor,” J. Flow Chem., vol. 12, pp. 327–336, 2022, https://doi.org/10.1007/s41981-022-00228-y.Search in Google Scholar

[4] S. S. Patel, D. B. Patel, and H. D. Patel, “Synthetic protocols for aromatic nitration: a review,” ChemistrySelect, vol. 6, no. 6, pp. 1337–1356, 2021. https://doi.org/10.1002/slct.202004695.Search in Google Scholar

[5] M. Rahaman, B. Mandal, and P. Ghosh, “Nitration of nitrobenzene at high‐concentrations of sulfuric acid: mass transfer and kinetic aspects,” AIChE J., vol. 56, no. 3, pp. 737–748, 2010. https://doi.org/10.1002/aic.11989.Search in Google Scholar

[6] D. Russo, R. Marotta, M. Commodo, R. Andreozzi, and I. Di Somma, “Ternary HNO3-H2SO4-H2O mixtures: a simplified approach for the calculation of the equilibrium composition,” Ind. Eng. Chem. Res., vol. 57, no. 5, pp. 1696–1704, 2018. https://doi.org/10.1021/acs.iecr.7b04193.Search in Google Scholar

[7] G. A. Olah, R. Malhotra, and S. C. Narang, Nitration: Methods and Mechanisms, New York, VCH Publishers, 1989.Search in Google Scholar

[8] J. H. Ridd, “Mechanism of aromatic nitration,” Acc. Chem. Res.,, vol. 4, no. 7, pp. 248–253, 1971. https://doi.org/10.1021/ar50043a003.Search in Google Scholar

[9] I. Sreedhar, M. Singh, and K. V. Raghavan, “Scientific advances in sulfuric acid free toluene nitration,” Catal. Sci. Technol., vol. 3, no. 10, pp. 2499–2508, 2013. https://doi.org/10.1039/c3cy00337j.Search in Google Scholar

[10] V. Hessel, H. Löwe, and F. Schönfeld, “Micromixers-a review on passive and active mixing principles,” Chem. Eng. Sci., vol. 60, nos. 8–9, pp. 2479–2501, 2005. https://doi.org/10.1016/j.ces.2004.11.033.Search in Google Scholar

[11] C. Li, et al., “Efficient conversion rate of propane in a microchannel reactor at ambient conditions,” Nat. Commun., vol. 15, p. 884, 2024, https://doi.org/10.1038/s41467-024-45179-1.Search in Google Scholar PubMed PubMed Central

[12] D. Russo, G. Tomaiuolo, R. Andreozzi, S. Guido, A. A. Lapkin, and I. Di Somma, “Heterogeneous benzaldehyde nitration in batch and continuous flow microreactor,” Chem. Eng. J., vol. 377, p. 120346, 2019, https://doi.org/10.1016/j.cej.2018.11.044.Search in Google Scholar

[13] D. Russo, et al.., “Intensification of nitrobenzaldehydes synthesis from benzyl alcohol in a microreactor,” Org. Process Res. Dev., vol. 21, no. 3, pp. 357–364, 2017. https://doi.org/10.1021/acs.oprd.6b00426.Search in Google Scholar

[14] A. A. Kulkarni, N. T. Nivangune, V. S. Kalyani, R. A. Joshi, and R. R. Joshi, “Continuous flow nitration of salicylic acid,” Org. Process Res. Dev., vol. 12, no. 5, pp. 995–1000, 2008. https://doi.org/10.1021/op800112u.Search in Google Scholar

[15] L. Ducry and D. M. Roberge, “Controlled autocatalytic nitration of phenol in a microreactor,” Angew. Chem., Int. Ed., vol. 44, no. 48, pp. 7972–7975, 2005. https://doi.org/10.1002/anie.200502387.Search in Google Scholar PubMed

[16] Y. Cui, J. Song, C. Du, J. Deng, and G. Luo, “Determination of the kinetics of chlorobenzene nitration using a homogeneously continuous microflow,” AIChE J., vol. 68, no. 4, p. e17564, 2022. https://doi.org/10.1002/aic.17564.Search in Google Scholar

[17] J. Song, Y. Cui, G. S. Luo, J. Deng, and Y. Wang, “Kinetic study of o-nitrotoluene nitration in a homogeneously continuous microflow,” React. Chem. Eng., vol. 7, no. 1, pp. 111–122, 2022a, https://doi.org/10.1039/d1re00362c.Search in Google Scholar

[18] J. Song, et al., “Determination of nitration kinetics of p-Nitrotoluene with a homogeneously continuous microflow,” Chem. Eng. Sci., vol. 247, p. 117041, 2022b, https://doi.org/10.1016/j.ces.2021.117041.Search in Google Scholar

[19] L. Li, C. Yao, F. Jiao, M. Han, and G. Chen, “Experimental and kinetic study of the nitration of 2-ethylhexanol in capillary microreactors,” Chem. Eng. Process. Process Intensif., vol. 117, pp. 179–185, 2017, https://doi.org/10.1016/j.cep.2017.04.005.Search in Google Scholar

[20] S. Li, X. Zhang, D. Ji, Q. Wang, N. Jin, and Y. Zhao, “Continuous flow nitration of 3-[2-chloro-4-(trifluoromethyl) phenoxy] benzoic acid and its chemical kinetics within droplet-based microreactors,” Chem. Eng. Sci., vol. 255, p. 117657, 2022, https://doi.org/10.1016/j.ces.2022.117657.Search in Google Scholar

[21] L. Lan and Y. Lu, “Continuous nitration of o-dichlorobenzene in micropacked-bed reactor: process design and modelling,” J. Flow Chem., vol. 11, pp. 171–179, 2011, https://doi.org/10.1007/s41981-020-00132-3.Search in Google Scholar

[22] Y. Sharma, R. A. Joshi, and A. A. Kulkarni, “Continuous-flow nitration of o-xylene: effect of nitrating agent and feasibility of tubular reactors for scale-up,” Org. Process Res. Dev., vol. 19, no. 9, pp. 1138–1147, 2015. https://doi.org/10.1021/acs.oprd.5b00064.Search in Google Scholar

[23] S. K. Sengupta, J. A. Schultz, K. R. Walck, D. R. Corbin, and J. C. Ritter, “Synthesis of 4-Nitro o-xylene by selective nitration of o-xylene,” Top. Catal., vol. 55, pp. 601–605, 2012, https://doi.org/10.1007/s11244-012-9837-8.Search in Google Scholar

[24] J. R. Burns and C. Ramshaw, “A microreactor for the nitration of benzene and toluene,” Chem. Eng. Commun., vol. 189, no. 12, pp. 1611–1628, 2002. https://doi.org/10.1080/00986440214585.Search in Google Scholar

[25] J. M. Kohler, et al.., “Digital reaction technology by micro segmented flow-components, concepts and applications,” Chem. Eng. J., vol. 101, nos. 1–3, pp. 201–216, 2004. https://doi.org/10.1016/j.cej.2003.11.025.Search in Google Scholar

[26] J. H. Xu, J. Tan, S. W. Li, and G. Luo, “Enhancement of mass transfer performance of liquid-liquid system by slug flow in microchannels,” Chem. Eng. J., vol. 141, nos. 1–3, pp. 242–249, 2008. https://doi.org/10.1016/j.cej.2007.12.030.Search in Google Scholar

[27] G. X. Li, S. E. Liu, and Y. H. Su, “Research progress on micro-scale internal liquid-liquid mass transfer and reaction process enhancement,” CIESC J., vol. 72, no. 1, p. 452, 2021. https://doi.org/10.11949/0438-1157.20201114.Search in Google Scholar

[28] L. R. Shang, Y. Cheng, and Y. J. Zhao, “Emerging droplet microfluidics,” Chem. Rev., vol. 117, no. 12, pp. 7964–8040, 2017. https://doi.org/10.1021/acs.chemrev.6b00848.Search in Google Scholar PubMed

[29] Y. H. Su, G. W. Chen, Y. C. Zhao, and Q. Yuan, “Intensification of liquid-liquid two-phase mass transfer by gas agitation in a microchannel,” AIChE J., vol. 55, no. 8, pp. 1948–1958, 2009. https://doi.org/10.1002/aic.11787.Search in Google Scholar

[30] L. Yang, M. J. Nieves-Remacha, and K. F. Jensen, “Simulations and analysis of multiphase transport and reaction in segmented flow microreactors,” Chem. Eng. Sci., vol. 169, pp. 106–116, 2017, https://doi.org/10.1016/j.ces.2016.12.003.Search in Google Scholar

[31] K. G. Biswas, G. Das, S. Ray, and J. K. Basu, “Mass transfer characteristics of liquid-liquid flow in small diameter conduits,” Chem. Eng. Sci., vol. 122, pp. 652–661, 2015, https://doi.org/10.1016/j.ces.2014.07.029.Search in Google Scholar

[32] M. N. Kashid, A. Renken, and L. Kiwi-Minsker, “Influence of flow regime on mass transfer in different types of microchannels,” Ind. Eng. Chem. Res., vol. 50, no. 11, pp. 6906–6914, 2011. https://doi.org/10.1021/ie102200j.Search in Google Scholar

[33] R. Abiev, S. Svetlov, and S. Haase, “Hydrodynamics and mass transfer of gas-liquid and liquid-liquid taylor flow in micro channels: a review,” Chem. Eng. Technol., vol. 40, no. 11, pp. 1985–1998, 2017. https://doi.org/10.1002/ceat.201700041.Search in Google Scholar

[34] J. W. Wen, et al., “Mass transfer characteristics of vanadium species on the high-efficient solvent extraction of vanadium in microchannels/microreactors,” Sep. Purif. Technol., vol. 315, p. 123638, 2023, https://doi.org/10.1016/j.seppur.2023.123638.Search in Google Scholar

[35] A. A. Kulkarni, V. S. Kalyani, R. A. Joshi, and R. R. Joshi, “Continuous flow nitration of benzaldehyde,” Org. Process Res. Dev., vol. 13, no. 5, pp. 999–1002, 2009. https://doi.org/10.1021/op900129w.Search in Google Scholar

[36] R. J. Gillespie, E. D. Hughes, C. K. Ingold, D. J. Millen, and R. I. Reen, “Kinetics and mechanism of aromatic nitration,” Nature, vol. 163, pp. 599–600, 1994, https://doi.org/10.1038/163599b0.Search in Google Scholar PubMed

[37] S. Guo, J. Y. Cao, M. Q. Liu, L. W. Zhan, and B. D. Li, “Intensification and kinetic study of trifluoromethylbenzen nitration with mixed acid in the microreactor,” Chem. Eng. Process. Process Intensif., vol. 183, p. 109239, 2023a, https://doi.org/10.1016/j.cep.2022.109239.Search in Google Scholar

[38] S. Guo, L. W. Zhan, and B. D. Li, “Nitration of o-xylene in the microreactor: reaction kinetics and process intensification,” Chem. Eng. J., vol. 468, p. 143468, 2023b, https://doi.org/10.1016/j.cej.2023.143468.Search in Google Scholar

[39] Z. H. Wen, M. Yang, S. N. Zhao, F. Zhou, and G. W. Chen, “Kinetics study of heterogeneous continuous-flow nitration of trifluoromethoxybenzene,” React. Chem. Eng., vol. 3, no. 3, pp. 379–387, 2018. https://doi.org/10.1039/c7re00182g.Search in Google Scholar

[40] N. C. Marziano and M. Sampoli, “A simple linear description of rate profiles for the nitration of aromatic compounds in the critical range 80-98wt% sulfuric acid,” J. Chem. Soc., vol. 9, no. 9, pp. 523–524, 1983. https://doi.org/10.1039/c39830000523.Search in Google Scholar

[41] Y. Song, M. J. Shang, G. X. Li, Z. H. Luo, and Y. H. Su, “Influence of mixing performance on polymerization of acrylamide in capillary microreactors,” AIChE J., vol. 64, no. 5, pp. 1828–1840, 2018. https://doi.org/10.1002/aic.16046.Search in Google Scholar

[42] N. Kockmann, S. Karlen, C. Girard, and D. M. Roberge, “Liquid-liquid test reactions to characterize two-phase mixing in microchannels,” Heat Transfer Eng., vol. 34, nos. 2–3, pp. 169–177, 2013. https://doi.org/10.1080/01457632.2013.703508.Search in Google Scholar

[43] P. Chen, C. Shen, M. Qiu, Y. J. Bai, and Y. H. Su, “Synthesis of 5-fluoro-2-nitrobenzotrifluoride in a continuous-flow millireactor with a safe and efficient protocol,” J. Flow Chem., vol. 10, pp. 207–218, 2020, https://doi.org/10.1007/s41981-019-00068-3.Search in Google Scholar

[44] A. B. Vir and S. Pushpavanam, “Phase transfer catalysis in a microchannel: paradoxical effect of transition from kinetic control to mass transfer control,” Chem. Eng. J., vol. 317, pp. 1047–1058, 2017, https://doi.org/10.1016/j.cej.2017.02.131.Search in Google Scholar

[45] M. J. Nieves-Remacha, L. Yang, and K. F. Jensen, “OpenFOAM computational fluid dynamic simulations of two-phase flow and mass transfer in an advanced-flow reactor,” Ind. Eng. Chem. Res., vol. 54, no. 26, pp. 6649–6659, 2015a, https://doi.org/10.1021/acs.iecr.5b00480.Search in Google Scholar

[46] M. J. Nieves-Remacha, A. A. Kulkarni, and K. F. Jensen, “OpenFOAM computational fluid dynamic simulations of single-phase flows in an advanced-flow reactor,” Ind. Eng. Chem. Res., vol. 54, no. 30, pp. 7543–7553, 2015b, https://doi.org/10.1021/acs.iecr.5b00232.Search in Google Scholar

[47] Q. Song, et al., “Continuous-flow synthesis of Nitro-o-xylenes: process optimization, impurity study and extension to analogues,” Molecules, vol. 27, no. 16, p. 5139, 2022c, https://doi.org/10.3390/molecules27165139.Search in Google Scholar PubMed PubMed Central

Supplementary Material

This article contains supplementary material (https://doi.org/10.1515/ijcre-2025-0082).

Received: 2025-04-23
Accepted: 2025-07-16
Published Online: 2025-09-04

© 2025 Walter de Gruyter GmbH, Berlin/Boston

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https://doi.org/10.1515/ijcre-2025-0082
Keywords for this article
nitration; microreactor; kinetics; mass transfer; intensification

Articles in the same Issue

  1. Frontmatter
  2. Review
  3. Quantum dots for wastewater treatment for the removal of heavy metals
  4. Articles
  5. A hybrid model of prairie dog optimization and closed-form continuous-time neural networks for next generation lithium-ion and sodium-ion batteries
  6. Mass transfer intensification and kinetics of o-xylene nitration in the microreactor
  7. Transesterification process and biofuel blending actions on performance of compression ignition engine under different loading conditions
  8. Phosphate, TDS and BOD removal from industrial wastewater using combined sono-pulsed-electrochemical oxidation: optimization by response surface methodology
  9. Evaluation of degradation in lubricating oil and engine wear using Jatropha oil blended with diesel in stationary compression ignition (CI) engines
  10. Thermophysical characterization and chemical stability of Ag2O-enhanced eutectic nano-PCMs for moderate-temperature applications
  11. Experimental evaluation of a solar-assisted heat pump system as a hybrid thermal reactor for energy-efficient drying of agricultural biomass
  12. Short Communication
  13. Design of terminator-shaped chamber-based micromixers with different obstructions: a CFD approach
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