Abstract
Plastic waste management has become a pressing global issue. A viable and sustainable alternative to incineration is the conversion of polyethylene into chemicals or fuels by through hydrocracking. To improve the catalytic performance during hydrocracking, bifunctional catalysts are required, in which the zeolite imparts the acid function, and the metallic function is provided by a noble or transition metal, such as nickel. In this study, acid supports were synthesized using two strategies, namely zeolitisation and desilication, for comparison. The synthesized materials exhibited Si/Al molar ratios of approximately 10, hierarchical micro-/mesoporosities, and a bifunctional character after incorporation of nickel up to 5 wt%. The materials were extensively characterized by various techniques, including powder X-Ray diffraction, N2 sorption, acidity measurement, and scanning electron microscopy. The characterization results showed that the desilicated HZSM5 zeolite was the most effective support for nickel impregnation, leading to a quantitative conversion of High-Density Polyethylene (HDPE) by hydrocracking and the formation of predominantly hydrocarbons with 5 carbon atoms. A clear disparity in composition, with a prevalence of a gasoline-type fraction, was observable in the liquid phase from HZSM5 to Ni particles supported on hierarchical HZSM-5 (Ni@m-HZSM-5w). The hierarchy factor (HF), the molar ratio between Lewis and Brønsted acid sites, and the accessibility factor (ACI) were combined to form the interplay factor (IF). The investigation resulted in materials with IF values between 0.35 and 7, and a positive correlation between HDPE conversion and IF values is observed. In conclusion, this study suggests that the desilication of HZSM5 zeolite is a promising route for the development of efficient catalysts for the hydrocracking of plastic waste.
| Original language | English |
|---|---|
| Article number | 112605 |
| Number of pages | 15 |
| Journal | Microporous and Mesoporous Materials |
| Volume | 356 |
| DOIs | |
| Publication status | Published - Jun 2023 |
Bibliographical note
Funding Information:Dr. Sabino Armenise and Dr. Wong Syie Luing, have received support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant Agreement No. 754382, GOT ENERGY TALENT . Dr. Armenise want to dedicate special thanks to Sorbonne University and to all research department of Cepsa who help to characterize the catalysts and to C. Prieto, J. Frontela, B. Aramburu and R. Larraz to support this postdoctoral research. This research has been carried out during the postdoctoral position at URJC-CEPSA. Funding from Fundação para a Ciência e Tecnologia, Project UIDB/00100/2020, Project UIDP/00100/2020 and Project LA/P/0056/2020 is also gratefully acknowledge. The publication is part of the TED2021-129688B project, funded by MCIN/AEI / 10.13039/501100011033 and by the European Union "NextGenerationEU"/PRTR. The content of this publication does not reflect the official opinion of the European Union. Responsibility for the information and views expressed in this paper lies entirely with the authors.
Funding Information:
The aim of this synthesis approach was to produce a microporous/mesoporous hierarchical support starting from a mesoporous material, here a mesocellular alumino-silica foam (Al-MCF). The hierarchical mesoporous material was prepared using controlled microwave heating of Al-MCF in the presence of fluorides and tetrapropylammonium bromide in order to partially convert amorphous alumina-silica at the surface into a HZSM5 deposit.The impacts of the desilication and “zeolitisation” treatments over the morphological properties of HZSM5 and Al-MCF, respectively have been investigated by SEM and TEM analysis of the Ni-free solids. In the series of HZSM5-based materials (Fig. 3a–b), the main 2D morphology was maintained. The only difference was a homogeneous modification in the surface roughness of the zeolite after the desilication process. In the series of Al-MCF materials (Fig. 3c–d), the parent support showed a typical morphology for classical foams structure with, apparently, 3D interconnected channels with a regular, qualitatively, bi-modal distribution of “pore-mouth”. After the most aggressive “zeolitisation” conditions (“Z2”), an apparent increase in the roughness of the external surface was also observed. The formation of additional small particles (indicated by red arrows in Fig. 3d) probably indicates the nucleation of solid parts at the expense of the mesocellular framework, following an increase in the hardness of the “zeolitisation” conditions.In heterogeneous acid catalysis, the reaction kinetics can be limited by the diffusion to and from active sites. In order to understand catalysis results, especially for hierarchical supports, the definition of an accessibility index (ACI) was shown to be useful. Pérez-Ramírez et al. [61] defined such an index as the number of acid sites detected by the probe molecule divided by the total amount of Al in the material.Al-MCF and the materials derived from “zeolitisation” were also characterized by a very intense band at 3743 cm−1. According to the literature [70], this band corresponds to Si–OH groups in a weak interaction with an aluminum atom, giving rise to a lower acid character than that in HZSM5. The “zeolitisation” process seems to have a non-negligible effect on the amount of these OH groups (divided by 2 for Al-MCFZ2), in agreement with the acidity measurements done by pyridine adsorption. However, regardless of the “zeolitisation” treatment, a band at ca. 3610 cm−1, which is characteristic of Si(OH)Al (BAS of HZSM5), was not detected. “Zeolitisation” under microwave radiation only modified the Al–Si framework without significant formation of zeolite. Ni incorporation decreased the number of OH groups by 5%, compared to the “zeolitized” Al-MCF support. However, this variation is relatively weak and should be considered with caution as it is close to the measurement accuracy.Dr. Sabino Armenise and Dr. Wong Syie Luing, have received support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant Agreement No. 754382, GOT ENERGY TALENT. Dr. Armenise want to dedicate special thanks to Sorbonne University and to all research department of Cepsa who help to characterize the catalysts and to C. Prieto, J. Frontela, B. Aramburu and R. Larraz to support this postdoctoral research. This research has been carried out during the postdoctoral position at URJC-CEPSA. Funding from Fundação para a Ciência e Tecnologia, Project UIDB/00100/2020, Project UIDP/00100/2020 and Project LA/P/0056/2020 is also gratefully acknowledge. The publication is part of the TED2021-129688B project, funded by MCIN/AEI/10.13039/501100011033 and by the European Union "NextGenerationEU"/PRTR. The content of this publication does not reflect the official opinion of the European Union. Responsibility for the information and views expressed in this paper lies entirely with the authors.
Funding
Dr. Sabino Armenise and Dr. Wong Syie Luing, have received support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant Agreement No. 754382, GOT ENERGY TALENT . Dr. Armenise want to dedicate special thanks to Sorbonne University and to all research department of Cepsa who help to characterize the catalysts and to C. Prieto, J. Frontela, B. Aramburu and R. Larraz to support this postdoctoral research. This research has been carried out during the postdoctoral position at URJC-CEPSA. Funding from Fundação para a Ciência e Tecnologia, Project UIDB/00100/2020, Project UIDP/00100/2020 and Project LA/P/0056/2020 is also gratefully acknowledge. The publication is part of the TED2021-129688B project, funded by MCIN/AEI / 10.13039/501100011033 and by the European Union "NextGenerationEU"/PRTR. The content of this publication does not reflect the official opinion of the European Union. Responsibility for the information and views expressed in this paper lies entirely with the authors. The aim of this synthesis approach was to produce a microporous/mesoporous hierarchical support starting from a mesoporous material, here a mesocellular alumino-silica foam (Al-MCF). The hierarchical mesoporous material was prepared using controlled microwave heating of Al-MCF in the presence of fluorides and tetrapropylammonium bromide in order to partially convert amorphous alumina-silica at the surface into a HZSM5 deposit.The impacts of the desilication and “zeolitisation” treatments over the morphological properties of HZSM5 and Al-MCF, respectively have been investigated by SEM and TEM analysis of the Ni-free solids. In the series of HZSM5-based materials (Fig. 3a–b), the main 2D morphology was maintained. The only difference was a homogeneous modification in the surface roughness of the zeolite after the desilication process. In the series of Al-MCF materials (Fig. 3c–d), the parent support showed a typical morphology for classical foams structure with, apparently, 3D interconnected channels with a regular, qualitatively, bi-modal distribution of “pore-mouth”. After the most aggressive “zeolitisation” conditions (“Z2”), an apparent increase in the roughness of the external surface was also observed. The formation of additional small particles (indicated by red arrows in Fig. 3d) probably indicates the nucleation of solid parts at the expense of the mesocellular framework, following an increase in the hardness of the “zeolitisation” conditions.In heterogeneous acid catalysis, the reaction kinetics can be limited by the diffusion to and from active sites. In order to understand catalysis results, especially for hierarchical supports, the definition of an accessibility index (ACI) was shown to be useful. Pérez-Ramírez et al. [61] defined such an index as the number of acid sites detected by the probe molecule divided by the total amount of Al in the material.Al-MCF and the materials derived from “zeolitisation” were also characterized by a very intense band at 3743 cm−1. According to the literature [70], this band corresponds to Si–OH groups in a weak interaction with an aluminum atom, giving rise to a lower acid character than that in HZSM5. The “zeolitisation” process seems to have a non-negligible effect on the amount of these OH groups (divided by 2 for Al-MCFZ2), in agreement with the acidity measurements done by pyridine adsorption. However, regardless of the “zeolitisation” treatment, a band at ca. 3610 cm−1, which is characteristic of Si(OH)Al (BAS of HZSM5), was not detected. “Zeolitisation” under microwave radiation only modified the Al–Si framework without significant formation of zeolite. Ni incorporation decreased the number of OH groups by 5%, compared to the “zeolitized” Al-MCF support. However, this variation is relatively weak and should be considered with caution as it is close to the measurement accuracy.Dr. Sabino Armenise and Dr. Wong Syie Luing, have received support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant Agreement No. 754382, GOT ENERGY TALENT. Dr. Armenise want to dedicate special thanks to Sorbonne University and to all research department of Cepsa who help to characterize the catalysts and to C. Prieto, J. Frontela, B. Aramburu and R. Larraz to support this postdoctoral research. This research has been carried out during the postdoctoral position at URJC-CEPSA. Funding from Fundação para a Ciência e Tecnologia, Project UIDB/00100/2020, Project UIDP/00100/2020 and Project LA/P/0056/2020 is also gratefully acknowledge. The publication is part of the TED2021-129688B project, funded by MCIN/AEI/10.13039/501100011033 and by the European Union "NextGenerationEU"/PRTR. The content of this publication does not reflect the official opinion of the European Union. Responsibility for the information and views expressed in this paper lies entirely with the authors.
Keywords
- Accessibility factor
- HDPE hydrocracking
- Hierarchy factor
- Interplay factor
- Mesocellular foam
- Nickel
- Zeolite
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