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Thermolysis and analysis of TDI char by supercritical methanol using TGA, DSC, IR and SEM

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Abstract

TDI's synthetic plant generates about 5 mass % of tar by phosgenation process, which has been currently a bottleneck needed to be broken through for the worldwide TDI companies. At present, the reduction fraction of TDI tar is up to 48% relative to the mass of tar and renders the residue of solid crust known as TDI char. In this study, a suasive and effective reduction method has been found, the supercritical methanol is executed to depolymerize the TDI char, and in short, the char can be readily methanolyzed at supercritical state of methanol. With the outstanding depolymerization capability than various existing approaches, the destruction fraction can achieve 81 mass % at supercritical point. A best value as high as 95 mass % is first discovered at 270 °C, exceeding the efficiency at supercritical state. Characterizations of the intrinsic properties of raw char and char remnant after methanolysis have been implemented by TGA, DSC, FT-IR and SEM-EDS. For industrial applications, the diverse methodologies for recovering TDI or related components by alkaline hydrolysis, distillation, vacuum distillation and thermolysis are also discussed and compared with methanolysis in order to recognize the optimal abatement technique.

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Abbreviations

ATR:

Attenuated total reflectance

DNT:

Dinitrotoluene

DSC:

Differential scanning calorimeter

DTG:

Derivative thermogravimetric curve

EDS:

Energy-dispersive X-ray spectroscopy

FTIR:

Fourier transform infrared spectrometry

IPA:

Isophthalic acid

MTD:

M-toluenediamine

PCB:

Printed circuit board 

PET:

Poly(ethylene terephthalate)

SCF:

Supercritical fluid

SEM:

Scanning electron microscopy

STA:

Simultaneous thermal analysis

TDA:

Toluenediamine, o-toluenediamine

TDI:

Toluene diisocyanate

TGA:

Thermogravimetric analyzer

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Acknowledgements

We are grateful to the Fujian Dongnan Electronics Co., Ltd., for providing the samples of TDI char.

Funding

This research was funded by the Science and Technology Development Foundation of ZTRI (Grant number 332017CA0160, 332012CA0080) and the National Natural Science Foundation of China (Grant No. 51878171), Scientific Research Foundation of Fuzhou (2019-G-51), Scientific Research Foundation of the Education Department of Fujian Province (JAT190427) as well as the Scientific Research Foundation of Fujian University of Technology (Grant No. GY-Z160041 and GY-Z160042).

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Authors and Affiliations

  1. School of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou, Fujian, China

    Gen-ding Yu, Jing-ling Li, Ling-zhu Gong, Liu-fang Ni, Lei Peng, Zhu-wu Jiang, Long-bin Yang & Yih-Shing Duh

  2. Indoor Environment Engineering Research Center of Fujian Province, Fujian University of Technology, Fuzhou, Fujian, China

    Gen-ding Yu, Liu-fang Ni & Lei Peng

  3. Center of Safe and Energy-Saving Engineering Technology for Urban Water Supply and Drainage System, Fujian University of Technology, Fuzhou, Fujian, China

    Jing-ling Li, Zhu-wu Jiang & Long-bin Yang

  4. Institute of Chemical Safety, Fujian University of Technology, Fuzhou, Fujian, China

    Ling-zhu Gong & Yih-Shing Duh

  5. School of Civil Engineering, Fujian University of Technology, Fuzhou, Fujian, China

    You-gen Chen

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  1. Gen-ding Yu
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Correspondence to Jing-ling Li or Yih-Shing Duh.

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Yu, Gd., Li, Jl., Gong, Lz. et al. Thermolysis and analysis of TDI char by supercritical methanol using TGA, DSC, IR and SEM. J Therm Anal Calorim 146, 2323–2331 (2021). https://doi.org/10.1007/s10973-020-10336-3

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