Catalytic Transformation Conditions of Ethanol on Dealuminated BEA Zeolites

Abstract

Catalysis is an important tool in obtaining a range of derivative products from renewable sources, such as ethanol. Solid-state dealumination using ammonium hexafluorosilicate on the BEA zeolite under the treatment at temperature of 190 °C, 70 mol% dealumination in the presence of humidity and washing with buffer solution at 25 °C generated larger pores. The absence of washing procedure for the same sample resulted in pore blockage. Ethanol dehydration reactions showed conversion of 72% (64% ethylene and 8% diethyl ether) for this sample at 300 °C and high weight hourly space velocity (WHSV, 3247 h-1), whereas, at the same temperature but at a low WHSV (57 h-1), the conversion was 88% (49% ethylene and 39% diethyl ether). Dealuminated BEA zeolite presented better diffusion conditions, higher hydrophobicity and generated larger pores. Impregnation with H 3 PW 12 O 40 , H 4 SiW 12 O 40 and Nb 2 O 5 explained the selectivity, showing that Lewis acid sites from Nb 2 O 5 favored the diethyl ether production.

Niobium on BEA Dealuminated Zeolite for High Selectivity Dehydration Reactions of Ethanol and Xylose into Diethyl Ether and Furfural

“…The material was dried at 120 °C (14 h), ground, and calcined at 550 °C (8 h). To obtain protonic zeolite HB, the NH 4 BEA zeolite was calcined at 550 °C (8 h) [ 9 ]. In a previous work of our group [ 9 ], Energy Dispersive X-ray fluorescence (EDXRF) results indicated that the Si/Al ratio (molSi molAl −1 ) increased from 12.5 (NH 4 BEA) to 18.7 after dealumination procedure described above.…”

“…To obtain protonic zeolite HB, the NH 4 BEA zeolite was calcined at 550 °C (8 h) [ 9 ]. In a previous work of our group [ 9 ], Energy Dispersive X-ray fluorescence (EDXRF) results indicated that the Si/Al ratio (molSi molAl −1 ) increased from 12.5 (NH 4 BEA) to 18.7 after dealumination procedure described above. The results showed that 25% of Al was removed from parent zeolite, while 13% of Si was added to the sample from the dealuminating agent (AHFS).…”

“…Then, it was kept at 80 °C, until the complete evaporation of the water. The remaining solid was ground and calcined at 550 °C (8 h) [ 9 ]. Table 1 shows the nomenclature of the catalysts.…”

“…The samples were degassed, before the analysis with heating at 300 °C (4 h) and evacuation (target pressure of 10 μm Hg). The BET equation (range of partial pressure (P/P o ) from 0 to 0.1), t-plot method, and BJH method were used to describe the experimental isotherms, and to calculate the catalyst crystallinity [ 9 ]. We considered that the *BEA zeolite, in its protonic form, was the standard sample, and had 100% crystallinity and the impregnation percentages of the supported Nb were discounted.…”

“…Typically, post-treatments, such as dealumination [ 4 ], impregnation [ 5 ], alkali treatment [ 6 ], and ion exchange [ 7 ], are carried out to increase catalytic performance. The introduction of mesoporosity through a dealumination procedure provide to be a highly efficient diffusional pathway in a confined space [ 8 ], as well as to increase the water tolerance at elevated temperatures [ 9 ].…”