Abstract
Zn/MCM-41 mesoporous materials have been prepared via classic wet impregnation, employing zinc nitrate as precursor and tested for activity and stability in the Friedel-Crafts alkylation of toluene with benzyl chloride under microwave irradiation and continuous flow. The modified materials were characterized by means of a number of analytical techniques, and surface and textural properties were thoroughly checked. Materials containing the highest Zn loading (15 wt %) provided full conversion after 5 minutes reaction under microwave irradiation (300 W, 120 °C). Materials were proved to be stable and reusable for several cycles with an optimum performance under continuous flow conditions.
Highlights
The design of cost-competitive, highly active, and stable catalytic systems constitutes a significant challenge in the field of materials engineering for the 21st century [1]
An intensity decrease accompanied by diffraction line widening could be observed at increased Zn content, pointing out a deterioration in long-range ordering
FWHM corresponding to the main (100) peak of the X-ray powder diffraction (XRD) patterns provided hints of the widening of the peaks, which increased with the Zn loading in the support
Summary
The design of cost-competitive, highly active, and stable catalytic systems constitutes a significant challenge in the field of materials engineering for the 21st century [1]. Much effort has been made in recent years to investigate the use of solid acid systems, including porous aluminosilicates as alternative catalysts to homogeneous systems for acid catalyzed processes [2,3,4]. Lewis acids, including AlCl3 , FeCl3 , HF, BF3 , and ZnCl2 , have been typically used in Friedel-Crafts alkylation [5,6]. Recovery, separation, and disposal of homogeneous Lewis acids and their originated waste has several environmental, health, and safety issues. The utilization of solid acids, such as nanostructured materials, can provide alternative recycling and separation possibilities, minimizing pollution and waste. Alkylation reactions have been extensively catalyzed by a large variety of solid acids, such as: β-zeolites [7]; ZSM-5 modified with Ga, Zn, In, and Fe [8,9,10,11]; Fe, Ga, and Al-SBA-15
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