Morphological effects on catalytic performance of LTL zeolites in acylation of 2-methylfuran enhanced by non-microwave instant heating

doi:10.1016/j.matchemphys.2020.122688

Materials Chemistry and Physics

Volume 244, 1 April 2020, 122688

https://doi.org/10.1016/j.matchemphys.2020.122688 Get rights and content

Highlights

•
LTL zeolites with various morphologies are prepared using bamboo leaf ash silica.
•
The morphological properties influence zeolite surface properties and acidity.
•
The catalytic behaviour of LTL zeolites is tested in acylation of 2-methylfuran.
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Nanosized LTL zeolite has the best performance among the LTL zeolites prepared.
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LTL nanozeolite shows better performance than common liquid and solid catalysts.

Abstract

Morphological characteristics of zeolites can have significant effects on the catalytic reactions. However, the roles of zeolite morphology on catalytic reactions, particularly Friedel-Crafts acylation of 2-methylfuran, are still not clear. Hence, LTL-type zeolites with different morphologies are prepared by using bamboo leaf bio-silica source where the zeolites are used to elucidate the morphological properties in this acylation reaction. The results show that LTL zeolites with short-rod, cylindrical, stick-like and nanosized shapes can be prepared by simply tuning the water content of the precursor hydrogels and the crystallization time. The morphological properties of LTL zeolites are also found to have pronounced influences on their surface properties (surface areas, pore volumes, number of micropore channels, textural properties) and acidity (amount, strength and type) where these properties affect their catalytic activity in acylation of 2-methylfuran under non-microwave instant heating condition. Furthermore, the influence of temperature and heating time on the kinetics of catalytic acylation of 2-methylfuran, and the catalytic comparative study between nanosized LTL zeolite and several homogeneous and heterogeneous catalysts are also discussed.

Graphical abstract

Introduction

The upgrading of renewable feedstock is paramount for its conversion into more valuable fuels and chemicals, and hence central to the field of petrochemical research [1]. Among these compounds, furfurals (e.g. furfural (FAL) and 5-hydroxymethylfurfural (HMF)) have been identified as very useful compounds for the production of value-added intermediates and bio-fuels [[2], [3], [4]]. Upgrading of furans to higher-value added products and fuel additives can be achieved through different approaches such as Friedel-Crafts, hydrogenation, etherification, hydrogenolysis, etc. [[5], [6], [7], [8], [9]]. Particularly, acylation of 2-methylfuran produces 2-acetyl-5-methylfuran, viz. a valuable biofuel and intermediate in pharmaceutical industry [10].

Most of the Friedel-Crafts acylation reactions is driven by catalysts with high acidity such as H₂SO₄, HF, AlCl₃ and FeCl₃ [11]. However, these homogenous catalysts are harmful, corrosive, less selective and difficult to handle. The design of cheaper, less toxic, less corrosive and reusable heterogeneous solid catalysts (zeolites [[12], [13], [14], [15], [16]], metal organic frameworks [17], clays [18], mesoporous silicas [19,20]) for the efficient catalyzing acylation reaction is a green chemistry approach. In particular, zeolites―the ordered microporous aluminosilicate minerals― have found dominating the catalyst global market [21].

The use of zeolites for catalyzing the Friedel-Crafts acylation of 2-methylfuran has been experimentally demonstrated by two research groups thus far [22,23]. Xiong et al. modified H-β zeolite using acid treatment with acetic and tartaric acids [22]. They found that the activity of zeolite in acylation of 2-methyfuran with acetic anhydride was mainly connected with the Brønsted acid sites and their acid strength. Gumidyala et al. studied the effects of pore size of H-ZSM-5 and H-β zeolites on the catalytic acylation of 2-methylfuran with acetic acid [23]. H-ZSM-5 zeolite with smaller pore size exhibited a higher turnover frequency (TOF) and improved catalyst stability than large-pore H-β zeolite where pore confinement played a crucial role in this reaction. Furthermore, their DFT calculation also showed that the acyl formation was a limiting step in the overall reaction rate.

Meanwhile, Zhang and co-workers also used DFT electronic structure calculation to study the acylation of 2-methylfuran with acetic anhydride catalyzed by H-β (Brönsted-acidic) and Sn-β (Lewis-acidic) zeolites [10]. They found that this reaction underwent different catalytic pathways whereby dissociation of the C–O–C linkage of the anhydride to acylium cation (by H-β) and acetoxy anion (by Sn-β) controlled the formation of 2-acetyl-5-methylfuran while hydrogen elimination was the rate-determining step in this coupling reaction.

Morphological properties play a crucial rule in many catalytic reactions as they provide different diffusion pathways and catalytic activity [24,25]. However, the roles of zeolite morphology on Friedel-Crafts acylation of 2-methylfuran are still not clear and hence any effort to elucidate these properties of zeolites in this reaction is urgently needed. The present work is mainly aimed on the use of new bio-silica source from bamboo leaves to synthesize LTL zeolites with different morphologies (short-rod, cylindrical, stick-like and nanosized shapes). LTL zeolite is chosen in this study for morphological effect study on catalytic acylation of 2-methylfuran because its morphology is easy to control by simply changing the water content in the precursor hydrogel and heating temperature [26]. In addition, the synthesis of LTL zeolite using bamboo leaf ash (BLA) is also interesting because bamboo leaves are renewable, easy to cultivate, abundance in Asia and have very high natural silica content (20–41%) [27].

Section snippets

Preparation of bamboo leaf ash (BLA)

Bamboo leaves (45.00 g) were first washed thoroughly with water, dried and blended into small pieces. The dried leaves were then treated with nitric acid (1.0 M, 1.0 L, Merck) under shaking (100 rpm) at room temperature for 16 h to remove unwanted inorganic impurities. The leached leaves were filtered and washed thoroughly with distilled water until the pH reached 7. The acid treated leaves were dried overnight at 60 °C before subjecting to combustion at 600 °C in air for 6 h with a heating

Characterization of LTL zeolites

LTL zeolite is a large-pore molecular sieve having an one-dimensional channel system with cylindrical shape. The unique morphology and pore opening (7.5 × 7.5 Å²) of LTL zeolite are desirable in this work since it allows 2-methylfuran (4.89 × 4.25 × 1.80 Å³) and acetic anhydride (5.89 × 3.30 × 1.81 Å³) to diffuse easily into the pores and further react on the acid sites of the zeolite (Fig. 1) [29,30]. Furthermore, the appropriate pore size of LTL zeolite also controls the formation of unwanted

Conclusion

In conclusion, LTL zeolites synthesized from bamboo leaves ash (BLA) has been reported. The results show that the zeolite with different morphologies (short-rod, cylindrical, stick-like and nanosized shapes) and aspect ratios (0.96–4.40) can be obtained by simply tuning the water content in the precursor solutions. While the framework composition (Si/Al ratio) of samples is not affected to large extent upon changing the morphology, a significant change in the surface properties (surface areas,

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The financial support from FRGS (203/PKIMIA/6711642) is acknowledged.

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Morphological effects on catalytic performance of LTL zeolites in acylation of 2-methylfuran enhanced by non-microwave instant heating

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Preparation of bamboo leaf ash (BLA)

Characterization of LTL zeolites

Conclusion

Declaration of competing interest

Acknowledgement

Catal. Today

Catal. Commun.

Appl. Catal. Gen.

Mater. Chem. Phys.

Mater. Chem. Phys.

Catal. Today

Appl. Clay Sci.

J. Mol. Catal. Chem.

Chin. J. Catal.

Appl. Catal. Gen.

Appl. Catal. Gen.

Microporous Mesoporous Mater.

J. Non-Cryst. Solid.

J. Taiwan Inst. Chem. Eng.

Mater. Lett.

Microporous Mesoporous Mater.

Appl. Catal., A

Appl. Catal. Gen.

Chin. J. Catal.

Appl. Catal. Gen.

Appl. Catal. B Environ.

Biotechnol.

ACS Sustain. Chem. Eng.

ChemSusChem

J. Am. Chem. Soc.

Chem. Rev.