Effect of calcination on the structure and catalytic activities of titanium incorporated SBA-15

Abstract

Well-ordered Ti-incorporated SBA-15 materials (shortly termed Ti-SBA-15) with Ti loading up to 10 mol% of Si were prepared by a one pot co-condensation method using tetraethyl orthosilicate (TEOS) as the silica source and titanium oxychloride as the Ti source in an acidic environment close to the isoelectric point of silanol groups (pH ¼ 1.27-2.37). The Ti-SBA-15 materials with Ti/Si ratios smaller than 0.05 were curved solid tubes, while those with the Ti/Si ratios between 0.05-0.1 possessed platelet morphology and short mesochannels (ca. 150-500 nm). Titanium was homogeneously distributed in the silica framework of the as-made Ti-SBA-15 materials as isolated Ti species when the Ti/Si ratios were lower than 0.03. It formed small TiO 2 nanocrystallites when the Ti loading was further increased or after the materials were calcined at temperatures higher than 500 C. It is noteworthy that tetrahedrally coordinated Ti(IV) species were generated on the superficial areas of SBA-15 silica framework upon calcination at 600-1000 C. These tetrahedrally coordinated Ti(IV) species not only stabilized the mesopore ordering up to 950-1000 C, but also acted as effective catalytic sites in cyclohexene epoxidation.

Ordered mesoporous “one-pot” synthesized Ni-Mg(Ca)-Al2O3 as effective and remarkably stable catalysts for combined steam and dry reforming of methane (CSDRM)

“…Compared to their calcined forms, the reduced materials showed slightly smaller specific surface areas and reduced pore volumes (Table 2) indicative of some thermal contraction of the alumina framework and/or pore surface condensation by dehydration and/or dehydroxylation during the high temperature reduction treatment [58]. The values remain however fully satisfying for mesoporous materials treated at such temperature, revealing a high thermal resistance.…”

Facile synthesis of one-dimensional zinc vanadate nanofibers for high lithium storage anode material

“…Among multitudinous explored materials, vanadium oxides have attracted considerable attention as potential anode materials because of the multiple valence state of vanadium and the rich structural chemistry, which enables versatile redoxdependent properties [5,10,11]. It is known that vanadium oxides can deliver prominent theoretical capacities, which are much higher than those of commercialized graphite [5].…”

“…But there is still a problem that vanadium oxides tend to become amorphous upon cycling, which cannot satisfy the practical application [12]. Therefore, a second metal cation is usually introduced to stabilize the framework of vanadium oxides [5,10]. Currently, various transition metal composite vanadium oxides and vanadate compounds have been employed as promising anode materials to build advanced LIBs.…”

Effect of Ti incorporated MWW supports on Au loading and catalytic performance for direct propylene epoxidation

“…The 100Si/Ti-MCM-36 has two peaks at 220 and 260 nm. According to Chen et al [42], the 220 nm band is assigned to charge transfer from O 2− to Ti 4+ of the tetrahedral (T d ) coordination, while the 260 nm band is attributed to charge transfer from O 2− to Ti 4+ in octahedral (O h ) coordination. Therefore, the Ti in the Ti-YNU-1 samples are all assigned to the Ti(IV) sites in T d environment, while the Ti in the Si/Ti-MCM-36 contains both the T d and O h coordination state.…”