Conceptual modeling and performance evaluation of novel reactors for efficient synthesis of nylon-6,6

Cui Yan; Jiajun Wang

doi:10.1515/ijcre-2024-0036

Article

Conceptual modeling and performance evaluation of novel reactors for efficient synthesis of nylon-6,6

Cui Yan and Jiajun Wang

Published/Copyright: April 15, 2025

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From the journal International Journal of Chemical Reactor Engineering Volume 23 Issue 3

Abstract

To enhance nylon-6,6 continuous polymerization process, the comprehensive process models under four existing industrial reactor strategies and two newly proposed reactor strategies are developed and partially validated by plant data. On the basis of controlling water vapor and hexamethylenediamine (HMDA) evaporation, the comparative evaluations are conducted for these reactor strategies. The DuPont tower reactor strategy implements HMDA reflux of distillation to achieve a closer ratio of amine end groups to carboxyl end groups (1:1), and further developed multi-stage reactor strategy can improve the utilization of recovered HMDA. The proposed new process intensification strategy, i.e., employing gradient pressure reduction along with tower reactor height, increases water volatilization by 27.2 % and HMDA volatilization by 0.6 %, thereby facilitating the growth of polymer chains. Compared to other strategies, the gradient pressure reduction strategy can better control over the polymerization reaction and improve adaptability to different residence time.

Keywords: polyamide; polymerization reactor; process simulation; conceptual model

Corresponding authors: Jiajun Wang, State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, P.R. China, E-mail: jiajunwang@zju.edu.cn

Funding source: National Natural Science Foundation of China

Award Identifier / Grant number: 22078284

Research ethics: Not applicable.
Informed consent: Not applicable.
Author contributions: The authors have accepted responsibility for the entire content of this manuscript and approved its submission.
Use of Large Language Models, AI and Machine Learning Tools: None declared.
Conflict of interest: The authors state no conflict of interest.
Research funding: The National Natural Science Foundation of China (22078284).
Data availability: The raw data can be obtained on request from the corresponding author.

Nomenclature

AAPD: Average absolute deviation percentage, %
A _i: Pre-exponential factor, kg⋅mol⁻¹⋅h⁻¹
C _W ^inter: Concentration of water at the liquid-phase interface, mol·m⁻³
C _W ^L: Concentration of water in the bulk liquid phase, mol·m⁻³
c _i: Concentration of component i in the reaction phase, mol⋅kg⁻¹
c _i ^P: Input concentration of component i from previous stage, mol⋅kg⁻¹
c _i ^N: Output concentration of component i to next stage, mol⋅kg⁻¹
DPN: Number-average degree of polymerization
E _a: Activation energy, kcal⋅mol⁻¹
E _r: Extent of reaction, %
F _i ⁱⁿ ,: Feed rate of unit model i, kg⋅h⁻¹
F _i ^L: Liquid phase outlet of unit model i, kg⋅h⁻¹
F _i ^V: Vapor phase outlet of unit model i, kg⋅h⁻¹
F ^P: Input flow rate from previous stage, kg⋅h⁻¹
F ^N: Output flow rate to next stage, kg⋅h⁻¹
k _i: Rate constants of reaction equation in Table 2, kg⋅mol⁻¹⋅h⁻¹
k _i ’: Rate constants of reverse reaction equation in Table 2, kg⋅mol⁻¹⋅h⁻¹
k _L a: Liquid-phase overall mass transfer coefficient, s⁻¹
MWN: Number-average molecular weight, g⋅mol⁻¹
n: Total number of polymers with different chain lengths
n _[‐COOH]: Total number of carboxyl groups
n ‐ N H 2: Total number of amino groups
N _W ^L: Mass transfer rate of water, mol·m⁻³·s⁻¹
p: Total pressure, Pa
p _i ^V: Vapor pressure of component i, Pa
q _i: Molecular surface area of component i
Q _k: Surface-area parameter of group k
r _i: Van der Waals volume of component i
R _i: Reaction rate for reaction i, mol⋅kg⁻¹⋅ h⁻¹
R _k: Volume parameter of group k
T _s: System temperature, K
v _HMDA: Ratio of HMDA volatilization to total feed of nylon-6,6 salt
ν _ki: Number of group k in component i
w: Total mass, kg
x _exp: Experiment data of solubility of nylon-6,6 salt, %
x _sim: Simulation data of solubility of nylon-6,6 salt, %
x _i: Liquid mole fraction of component i, %
y _i: Gas mole fraction of component i, %
z: Coordination number

Greek letters

α _nm: Interaction parameter of group n and group m, K
γ _i: Activity coefficient for component i
γ _i ^c: Combinatorial molar activity coefficient for component i
γ _i ^r: Residual molar activity coefficient for component i
τ: Residence time, h
Г _k: Activity coefficient of group k
θ _i: Molecular surface area fraction of component i
φ _i: Volume fraction of component i

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Received: 2024-02-26

Accepted: 2025-03-22

Published Online: 2025-04-15

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Articles in the same Issue

https://doi.org/10.1515/ijcre-2024-0036

Keywords for this article

polyamide; polymerization reactor; process simulation; conceptual model