Surface Modification of η–Al₂O₃ by SiO₂ Impregnation to Enhance Methanol Dehydration Activity

Abstract

Silica impregnated η‐Al2O3 catalysts (Si(number)Al) were prepared for methanol dehydration, with the number indicating the Si wt % added to η‐Al2O3. The Si(0.25)Al and Si(0.50)Al catalysts with the greatest number of acid sites had the highest methanol dehydration activities among the prepared catalysts. Si addition up to 0.5 wt % increased the number of the acid sites, which was slightly decreased by further Si addition. The number of weak acid sites correlated well with the catalytic activity for methanol dehydration, but was not enough to explain the higher activity of the catalysts containing silica compared with η‐Al2O3. The acid sites of the Si(1.0)Al catalyst were less than those of the η‐Al2O3 catalyst but the two had similar activity. Si addition primarily increased the Lewis acid sites, although it generated a few new Brønsted acid sites and chemical hydrogen bonded sites. Nonetheless, it was apparent that the increase of Lewis acid sites was the main reason for the enhancement of η‐Al2O3 activity by SiO2 addition. On the other hand, the new Brønsted and Lewis acid sites and the chemical hydrogen bonded sites created by Si addition should not be neglected.

SiO2-Modified Pt/Al2O3for Oxidative Dehydrogenation of Ethane: A Preparation Method for Improved Catalytic Stability, Ethylene Selectivity, and Coking Resistance

“…The new Bronsted acid sites were generated by the introduced SiO 2 layer. This is reinforced by the results reported by Jo et al 43 where new Bronsted acid site generation was identified when SiO 2 was introduced onto the pure η-Al 2 O 3 support. Meanwhile, in the wavenumber range between 3500 and 4000 cm −1 , a new inverted peak was observed at ca.…”

“…Acid sites on the surface may significantly influence the performance of the active-metal components on a catalyst. , Pyridine is often used as the probe molecule in investigating the surface acid sites on a catalyst by IR spectroscopy. Chemisorption of pyridine on Brönsted acid site leads to an IR peak at 1540 cm –1 which is assigned to the ring deformation vibration of pyridine. , Meanwhile, chemisorptions of pyridine on Lewis acid sites show a peak at 1450 cm –1 which is assigned to the deformation vibration of C–H bonds. DRIFT spectra of the Pt/Al 2 O 3 and 9c-SiO 2 /Pt/Al 2 O 3 catalysts after pyridine adsorption are shown in Figure .…”

“…Chemisorption of pyridine on Bronsted acid site leads to an IR peak at 1540 cm −1 which is assigned to the ring deformation vibration of pyridine. 42,43 Meanwhile, chemisorptions of pyridine on Lewis acid sites show a peak at 1450 cm −1 which is assigned to the deformation vibration of C−H bonds. DRIFT spectra of the Pt/Al 2 O 3 and 9c-SiO 2 /Pt/Al 2 O 3 catalysts after pyridine adsorption are shown in Figure 4.…”

Silver-Modified η-Al2O3 Catalyst for DME Production

“…Recently, copper was used to prevent the strong binding of H 2 O–Al 2 O 3 by enhancing the surface hydrophobicity with CA = 12° for 6% Cu/Al 2 O 3 catalyst that was used for the MTD reaction . Jo et al reported that the addition of Si to η-Al 2 O 3 by using TEOS (tetraethyl orthosilicate) enhanced the MTD conversion.…”

Influences of Reaction Temperature and Carrier Gas Flow‐Rate on n‐Heptane Cracking over ZSM‐5 Catalyst Without and With Activation of V2O5/Al2O3

“…Among them, catalytic cracking of naphtha represents one of the potential alternatives, due to its advantage in energy consumption, CO 2 emission, and product distribution compared to conventional steam cracking process . To maximize the propylene yield, ZSM‐5 is a common active catalyst studied for naphtha cracking or related subjects, for its high selectivity due to the particular three‐dimensional medium‐sized channel topology …”