Abstract
MCM-22, MCM-36, and ITQ-2 zeolites with the intended Si/Al molar ratios of 15, 25, and 50 were synthetized and tested as catalysts for dehydration of methanol to dimethyl ether and dehydration of ethanol to diethyl ether and ethylene. The surface concentration of acid sites was regulated by the synthesis of zeolite precursors with different aluminum content in the zeolite framework, while the influence of porous structure on the overall efficiency of alcohol conversion was analyzed by application of zeolitic materials with different types of porosity—microporous MCM-22 as well as microporous-mesoporous MCM-36 and ITQ-2. The zeolitic samples were characterized with respect to their: chemical composition (ICP-OES), structure (XRD, FT-IR), texture (N2 sorption), and surface acidity (NH3-TPD). Comparison of the catalytic activity of the studied zeolitic catalysts with other reported catalytic systems, including zeolites with the similar Si/Al ratio as well as γ-Al2O3 (one of the commercial catalysts for methanol dehydration), shows a great potential of MCM-22, MCM-36, and ITQ-2 in the reactions of alcohols dehydration.
Highlights
Increasing concerns about the climate change, energy security and independence, as well as diminishing oil resources drive the search for new alternative energy sources, including fuels based on renewable raw materials
Diffractograms of the zeolitic samples of MCM-22, MCM-36, and ITQ-2 series are presented in resulted in thermal removal of interlayer templates and condensation of the zeolite layers with the formation of microporous 3D structure
The leak of (0 0 2) reflection in diffractograms of the MCM-36 samples is related to spatial modification of the zeolite layers ordering due to pillarization or delamination processes, which result in the loss of perpendicular order with the respect to c axis
Summary
Increasing concerns about the climate change, energy security and independence, as well as diminishing oil resources drive the search for new alternative energy sources, including fuels based on renewable raw materials Such new generation of fuels could be biomethanol and bioethanol and ethers obtained by their dehydration—dimethyl ether (DME) and diethyl ether (DEE), respectively. Synthesis of DME and DEE from methanol and ethanol, respectively, is reported to be via acid catalyzed, exothermic reactions In both reactions, solid acid materials were reported to be catalytically active. The studied zeolites are characterized by various porous structures—MCM-22 is microporous material, MCM-36 is silica intercalated layered zeolite with the bi-modal microporous and mesopores structure, while ITQ-2 is layered delaminated material with the microporous-mesoporous structure Another goal of the study was showing the influence of the porous structure of zeolites on their catalytic efficiency in alcohols dehydration. The reaction products—dimethyl ether and diethyl ether—significantly differ in the molecular size and differences in the overall reaction rate, related to the internal diffusion limitations, could be expected
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