Generating Superbasic Sites on Mesoporous Silica SBA-15

Abstract

Superbasic sites have been generated on the mesoporous silica materials for the first time, through a new strategy to prepare the MgO-modified SBA-15 in one-pot synthesis and then to disperse KNO3, possessing the good textural structure of the host and the high basic strength (H -) of 27.0. The in situ coated Mg species passivated the silanol groups on the surface of siliceous SBA-15 so that the mesostructure of SBA-15 could be reserved after the composite was loaded with KNO3 and activated at high temperature. Existence of the special protection layer of MgO on the surface of SBA-15 was also beneficial for decomposition of KNO3 to form superbasic sites on the mesoporous silica. The influence of coating amount of MgO on the protection of the textural properties of SBA-15 is examined and discussed in terms of consuming surface silanol groups. Dispersion and decomposition of KNO3 on the MgO layer is also explored. Other metal oxides such as CaO, ZnO, and Al2O3 are in situ coated on the surface of SBA-15 through one-pot synthesis and their function of protecting SBA-15 is evaluated for comparison with MgO.

Generating Basic Sites on Zeolite Y by Potassium Species Modification: Effect of Base Precursor

“…Unfortunately, this type of basic materials possesses relatively small surface areas and disordered pore arrangement, since they are derived from oxide hosts. Ordered mesoporous silicas such as MCM-41 and SBA-15 were also employed as the hosts for solid bases [11][12][13]. However, their stability was relatively poor due to the amorphous walls; also, the silica hosts may react with strongly basic guest and sometimes lead to the destruction of mesoporous structure [5,13].…”

One‐Pot Synthesis of Potassium‐Functionalized Mesoporous γ‐Alumina: A Solid Superbase

“…[5,6] Owing to the reaction of these strongly basic species with silica, however, most of the solid bases reported to date are relatively weak, which suggests that it is difficult to generate superbasicity on mesoporous silica. [7,8] In contrast to silica, alumina, especially that of the g-type, is a well-known support for a variety of solid strong bases, [9][10][11] which means that the occurrence of mesoporous aluminas affords a good opportunity to prepare mesoporous superbasic materials. [12][13][14] Unfortunately, the stability of mesoporous aluminas is relatively poor and structural damage occurs to a greater or lesser extent even if postsynthesis modification is performed carefully.…”

“…KNO 3 -coated mesoporous boehmite (AlOOH) with a K/Al atomic ratio (n) of between 0 and 0.27 (Table 1) is obtained initially (denoted as MA-B (n = 0) or KMA(n)-B (n > 0)). The formation of both KNO 3 and boehmite is crucial for subsequent generation of the superbase as they are precursors of K 2 O [8,11] and g-Al 2 O 3 , [15,16] respectively. The conversion of KNO 3 and boehmite occurs in the subsequent calcination step, where KNO 3 is decomposed to the strongly basic species K 2 O on the g-Al 2 O 3 formed in situ.…”

Low-cost and effective phenol and basic dyes trapper derived from the porous silica coated with hydrotalcite gel

“…In a typical NH 3 -TPD or CO 2 -TPD experiment, the sample was activated at 873 K for 2 h prior to adsorption of NH 3 or CO 2 at 298 K. After the physical adsorbed CO 2 was purged by carrier gas flow at 298 K for 1-2 h, the sample was heated to 773 K at a rate of 8 K min À1 , meanwhile the liberated NH 3 or CO 2 was detected by an on-line Varian 3380 gas chromatograph [24].…”