Tailored Ga-modified zeolites for efficient chemical recycling of polyolefins into aromatics

doi:10.1016/S1872-2067(26)65139-X

Abstract

Abstract:

Chemical recycling of plastics is emerging as a powerful strategy to tackle global plastic waste while generating high-value chemicals. In this study, we unlock the potential of Ga-promoted, structurally engineered zeolites to convert polyolefins into aromatics by tailoring acid-site properties. Commercial ZSM-5 was reimagined into shell-layer (HZ5@s1), hollow (HZ5-hol), and mesoporous (HZ5-meso) architectures, followed by Ga incorporation. Our experiments reveal how structural tuning boosts olefin production, while Ga dramatically enhances monocyclic aromatic hydrocarbons (MAH) yields—up to 63 wt% for Ga-HZ5. Catalyst performance trends highlight the synergy between architecture and Ga loading, with Ga-HZ5-hol delivering the highest combined yield (30 wt% MAH + 51 wt% light olefins) after 100 consecutive runs. Despite Ga deactivation, acid sites remain robust, shifting product selectivity toward olefins and 1,3-cyclopentadiene. Regeneration slightly reduces aromatization but improves olefin output, while less reducible GaO_x species suppress aromatic formation. Mechanistic insights reveal that butene/propylene conversion governs MAH formation, and ethylene yield correlates with acid site density—positively for Ga-free catalysts, inversely after Ga loading. These findings pave the way for the design of next-generation zeolite catalysts for efficient plastic upcycling.

Key words: Zeolite, Plastics, Aromatics, Catalytic pyrolysis, Structure-performance correlation

Qing He, Oğuzhan Akin, Parviz Yazdani, Rengui Weng, Devanshu Sajwan, Lingfeng Li, Mozhdeh Amanati, Robin J. Varghese, Kevin M. Van Geem. Tailored Ga-modified zeolites for efficient chemical recycling of polyolefins into aromatics[J]. Chinese Journal of Catalysis, 2026, 88: 408-421.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(26)65139-X

https://www.cjcatal.com/EN/Y2026/V88/I9/408

Figures/Tables 10

Fig. 1. XRD patterns (A), pyridine-FT-IR spectra (B), NH3-TPD profiles (C), and H2-TPR profiles (D) of the zeolites used in this study.

Table 1 Pore structure characteristics of the zeolites used in this work.

Sample	Specific surface area (m²/g)			Pore volume (cm³/g)
Sample	S_BET^a	S_micro^b	S_external^b	S_Total^c	V_micro^d	V_meso^e
HZ5	401.9	384.6	17.3	0.186	0.154	0.024
HZ5@s1	325.5	303.3	22.3	0.158	0.122	0.029
HZ5-hol	418.3	394.0	24.4	0.234	0.154	0.057
HZ5-meso	333.6	321.4	12.2	0.194	0.125	0.034
Ga-HZ5	361.0	350.5	10.5	0.170	0.134	0.02
Ga-HZ5@s1	277.7	254.9	22.9	0.145	0.103	0.033
Ga-HZ5-hol	377.5	372.4	5.0	0.184	0.144	0.034
Ga-HZ5-meso	331.5	329.0	2.5	0.177	0.125	0.029

Table 2 Acid site and metal site parameters of the catalysts used in this work.

Sample	Acidity^a (Pyridine-IR, mmol/g)			Acidity^b (NH₃-TPD, mmol/g)				Reducible species^c (mmol/g)
Sample	BAS	LAS	BAS/LAS	A₁	A₂	A₃	A_total	M₁	M₂	M₃	M_total
HZ5	1.029	0.224	4.59	0.413	0.141	0.418	0.972	—	—	—	—
HZ5@s1	0.592	0.176	3.36	0.239	0.082	0.099	0.420	—	—	—	—
HZ5-hol	0.438	0.381	1.15	0.242	0.085	0.053	0.380	—	—	—	—
HZ5-meso	0.963	0.428	2.25	0.313	0.086	0.225	0.623	—	—	—	—
Ga-HZ5	0.776	0.472	1.64	0.348	0.383	0.28	1.011	0.075	0.039	0.007	0.121
Ga-HZ5@s1	0.625	0.464	1.35	0.333	0.118	0.076	0.527	0.01	0.043	0.100	0.152
Ga-HZ5-hol	0.377	0.294	1.28	0.349	0.157	0.033	0.539	0.023	0.030	0.186	0.239
Ga-HZ5-meso	0.515	0.256	2.01	0.379	0.219	0.218	0.815	0.032	0.107	0.015	0.167

Fig. 2. Main product yields of LDPE catalytic pyrolysis. (A) Ga-free zeolite; (B) Ga-loaded zeolite.

Fig. 3. Evolution of product distribution during catalytic pyrolysis as a function of pulse feeding: aliphatic hydrocarbons (A) and aromatic hydrocarbons (B).

Fig. 4. Relative activity (RA1) based on MAH selectivity (A) and MAH/(LO + MAH) (B) during catalyst deactivation, and relative activity (RA2) (C) of catalysts after regeneration at 600 and 700 °C using LDPE as the feedstock.

Fig. 5. (A) GC×GC chromatogram of catalytic pyrolysis products over Ga-HZ5-meso after 100 consecutive runs using LDPE as the feedstock. (B) Variation in 1,3-cyclopentadiene yield with the number of runs.

Fig. 6. Correlation between LDPE catalytic pyrolysis product and catalyst structure. (A) Ga-free catalyst; (B) Ga-loaded catalyst.

Fig. 7. Correlation analysis of pyrolysis products.

Fig. 8. Schematic representation of the competitive dual-hydrocarbon pool mechanism governing polyolefin catalytic pyrolysis.

References

[1]	M. N. Akhtar, S. Riaz, N. Ahmad, E. A. Jaseer, Energy Fuels, 2024, 38, 11363-11390.
[2]	C. Kibuta, O. Akin, D. Withoeck, Q. He, M. Schmidt, R. J. Varghese, M. Schlummer, S. De Meester, F. D. Calik, M. Denton, A. Buettner, K. M. Van Geem, Waste Manag., 2025, 195, 167-176.
[3]	X. Zhao, M. Korey, K. Li, K. Copenhaver, H. Tekinalp, S. Celik, K. Kalaitzidou, R. Ruan, A. J. Ragauskas, S. Ozcan, Chem. Eng. J., 2022, 428, 131928.
[4]	Q. Liu, J. Shang, Z. Liu, Chin. J. Catal., 2025, 71, 54-69.
[5]	X. Wang, S. Guo, P. Song, L. Xu, X. Zhang, B. Shen, Appl. Catal. A, 2024, 677, 119704.
[6]	J. Zhang, D. Lai, Z. Chen, X. Wang, Q. Xiong, J. Li, X. Zhang, B. O. Oboirien, G. Xu, ACS Sustainable Chem. Eng., 2024, 12, 13137-13148.
[7]	K. Qian, W. Tian, S. Yan, W. Li, L. Yin, D. Guo, Z. Yang, D. Chen, Y. Feng, Fuel, 2024, 357, 129781.
[8]	H. Shim, S. Pyo, A. Kumar, Y. Khani, S. Q. Choi, K. Cho, J. Lee, Y.-K. Park, Chin. J. Catal., 2025, 73, 368-383.
[9]	J. Liu, H. Fu, G.-Z. Zhou, Z.-T. Guo, B. Hu, Y. Li, X.-Y. Jiang, Q. Lu, J. Anal. Appl. Pyrolysis, 2023, 169, 105797.
[10]	A. Eschenbacher, R. J. Varghese, E. Delikonstantis, O. Mynko, F. Goodarzi, K. Enemark-Rasmussen, J. Oenema, M. S. Abbas-Abadi, G. D. Stefanidis, K. M. Van Geem, Appl. Catal. B, 2022, 309, 121251.
[11]	B. Xu, M. Tan, X. Wu, H. Geng, F. Song, Q. Ma, C. Luan, G. Yang, Y. Tan, Fuel, 2021, 283, 118889.
[12]	X. Cui, H. Lyu, Y. Chai, B. Liu, D. Zhao, C. Liu, Sep. Purif. Technol., 2024, 349, 127881.
[13]	O. Akin, Q. He, M. Havaei, F. D. Calik, D. Withoeck, R. J. Varghese, P. Yazdani, P. Van Steenberge, K. M. Van Geem, Catal. Today, 2025, 459, 115429.
[14]	Y.-J. Du, W.-D. Hu, C.-M. Wang, J. Zhou, G. Yang, Y.-D. Wang, W.-M. Yang, Catal. Sci. Technol., 2021, 11, 2031-2046.
[15]	J. C. Groen, J. C. Jansen, J. A. Moulijn, J. Pérez-Ramírez, J. Phys. Chem. B, 2004, 108, 13062-13065.
[16]	X. Chen, Z. An, Y. Wang, Q. Ma, X. Feng, Y. Liu, C. Yang, Fuel, 2021, 290, 119798.
[17]	Y.-L. Wang, X.-C. Zhang, G.-G. Zhan, M.-M. Wang, W.-Q. Li, J.-P. Cao, Mol. Catal., 2023, 540, 113044.
[18]	K. Qiao, X. Shi, F. Zhou, H. Chen, J. Fu, H. Ma, H. Huang, Appl. Catal. A, 2017, 547, 274-282.
[19]	Y. Gu, W. Wang, C. Zhou, C. Hu, J. Anal. Appl. Pyrolysis, 2024, 181, 106573.
[20]	W. Wang, L. He, L. Wang, J. Wang, Q. Luo, H. Chen, Q. Hao, Z. Miao, D. Zhang, Q. Yao, M. Sun, Fuel, 2024, 363, 130943.
[21]	Y. H. Lim, M. Y. Gim, H. Kim, D. H. Kim, Fuel Process. Technol., 2022, 227, 107107.
[22]	J. Song, J. Wang, Y. Pan, X. Du, J. Sima, C. Zhu, F. Lou, Q. Huang, J. Environ. Manag., 2022, 322, 116096.
[23]	Y. H. Lim, H. Kim, H. Lee, K. Nam, H. W. Ryu, D. H. Kim, J. Catal., 2023, 422, 24-35.
[24]	C. Liu, E. A. Uslamin, E. Khramenkova, E. Sireci,L. T. L. J. Ouwehand, S. Ganapathy, F. Kapteijn, E. A. Pidko, ACS Catal., 2022, 12, 3189-3200.
[25]	H. Liu, J. Zhang, R. Shan, H. Yuan, Y. Chen, Energy, 2024, 295, 131068.
[26]	C. Bi, Z. Zhang, D. Han, C. Wang, J. Zhang, M. Sun, Q. Hao, H. Chen, X. Ma, Fuel, 2022, 321, 124105.
[27]	H. Xiao, J. Zhang, X. Wang, Q. Zhang, H. Xie, Y. Han, Y. Tan, Catal. Sci. Technol., 2015, 5, 4081-4090.
[28]	D. Guo, Z. Cai, Y. Ye, A. Kumar, H. Rong, B. Cui, M. Hu, J. Energy Inst., 2026, 125, 102443.
[29]	J. Zhang, M. Ma, Z. Chen, X. Zhang, H. Yang, X. Wang, H. Feng, J. Yu, S. Gao, J. Energy Inst., 2023, 108, 101235.
[30]	O. Akin, Q. He, P. Yazdani, Y. Wang, R. J. Varghese, H. Poelman, P. Van Steenberge, K. M. Van Geem, J. Anal. Appl. Pyrolysis, 2024, 181, 106592.
[31]	Y.-Q. Deng, W.-F. Zhou, H.-M. Lv, Y.-Y. Zhang, C.-T. Au, S.-F. Yin, RSC Adv., 2014, 4, 37296-37301.
[32]	O. Akin, R. J. Varghese, A. Eschenbacher, J. Oenema, M. S. Abbas-Abadi, G. D. Stefanidis, K. M. Van Geem, J. Anal. Appl. Pyrolysis, 2023, 172, 106036.
[33]	Q. He, O. Akin, Y. Ureel, P. Yazdani, L. Li, R. J. Varghese, K. M. Van Geem, Front. Chem. Eng., 2024, 6, 1439400.
[34]	L. Fu, Q. Xiong, Q. Wang, L. Cai, Z. Chen, Y. Zhou, ACS Sustainable Chem. Eng., 2022, 10, 9612-9623.
[35]	G. Li, C. Wu, P. Dong, D. Ji, Y. Zhang, Catal. Lett., 2020, 150, 1923-1931.
[36]	M. Thommes, K. Kaneko, A. V. Neimark, J. P. Olivier, F. Rodriguez-Reinoso, J. Rouquerol, K. S. W. Sing, Pure Appl. Chem., 2015, 87, 1051-1069.
[37]	C. Dai, A. Zhang, M. Liu, X. Guo, C. Song, Adv. Funct. Mater., 2015, 25, 7479-7487.
[38]	H. Lin, L. Zhu, Y. Liu, V. S. Vladimirovich, B. Oboirien, Y. Zhou, Front. Chem. Sci. Eng., 2024, 18, 125.
[39]	Y. Zheng, W. Ning, Q. Wang, X. Wei, X. Li, M. Pan, Microporous Mesoporous Mater., 2023, 355, 112578.
[40]	P. A. Kots, P. A. Doika, B. C. Vance, S. Najmi, D. G. Vlachos, ACS Sustainable Chem. Eng., 2023, 11, 9000-9009.
[41]	B. J. Lee, Y. G. Hur, D. H. Kim, S. H. Lee, K.-Y. Lee, Fuel, 2019, 253, 449-459.
[42]	A. Ausavasukhi, T. Sooknoi, D. E. Resasco, J. Catal., 2009, 268, 68-78.
[43]	I. C. Clark, H. K. Carlson, A. T. Iavarone, J. D. Coates, Energy Environ. Sci., 2012, 5, 7970-7978.
[44]	M. M. Hasan, N. Batalha, G. Fraga, M. H. M. Ahmed, L. Pinard, M. Konarova, S. Pratt, B. Laycock, Sustain. Energy Fuels, 2022, 6, 1587-1602.
[45]	Z. Yang, J.-P. Cao, C. Zhu, T.-L. Liu, X.-B. Feng, X.-Y. Zhao, H.-C. Bai, Chem. Eng. Sci., 2022, 248, 117235.
[46]	Y. Wongnongwa, P. Kidkhunthod, U. Sukkha, S. Pengpanich, K.-A. Thavornprasert, J. Phupanit, N. Kungwan, G. Feng, T. Keawin, S. Jungsuttiwong, Microporous Mesoporous Mater., 2020, 306, 110414.
[47]	Y. He, U. Sanyal, M. Guo, H. Wang, K. K. Ramasamy, Ind. Eng. Chem. Res., 2025, 64, 18553-18562.
[48]	Y. Xie, Y. Zhang, L. He, C. Q. Jia, Q. Yao, M. Sun, X. Ma, Appl. Catal. A, 2023, 657, 119159.
[49]	V. Daligaux, R. Richard, M.-H. Manero, Catalysts, 2021, 11, 770.
[50]	H. Imai, A. Oshima, R. Noguchi, Appl. Catal. A, 2026, 709, 120628.
[51]	D. S. Uysal, H. Kalıpçılar, G. Karakaş Energy Fuels, 2025, 39, 7592-7604.
[52]	J. Cabana, Z. Zhang, Z. Pan, P. Kumar, X. Wu, A. Bodi, G. A. Garcia, Y. Shen, X. Xiao, H. Ma, C. Huang, C. Liu, L. Zhao, Y. Pan, Z. Zhou, J. A. van Bokhoven, P. Hemberger, ChemSusChem, 2025, 18, e202500516.
[53]	J.-Z. Tan, M. Ortega, S. A. Miller, C. W. Hullfish, H. Kim, S. Kim, W. Hu, J.-Z. Hu, J. A. Lercher, B. E. Koel, M. L. Sarazen, ACS Catal., 2024, 14, 7536-7552.
[54]	M. Yeong Gim, Y. Hyun Lim, K.-Y. Lee, D. Heui Kim, Fuel, 2021, 304, 121497.
[55]	N. Al-Yassir, M. N. Akhtar, K. Ogunronbi, S. Al-Khattaf, J. Mol. Catal. A, 2012, 360, 1-15.
[56]	X. Sun, S. Mueller, Y. Liu, H. Shi, G. L. Haller, M. Sanchez-Sanchez, A. C. van Veen, J. A. Lercher, J. Catal., 2014, 317, 185-197.
[57]	E. A. Uslamin, H. Saito, N. Kosinov, E. Pidko, Y. Sekine, E. J. M. Hensen, Catal. Sci. Technol., 2020, 10, 2774-2785.