NHTS: A Hollow, Noble‐Metal‐Modified Titanium Silicalite

Abstract

The major drawback of direct oxidation technology (onsite hydrogen peroxide production followed by its conversion into organic oxides without refining) is the design and preparation of the bifunctional catalysts used therein. Herein we present a bifunctional catalytic material (NHTS), which is synthesized by a revised semi-in-situ method that allows a noble metal to be distributed throughout the titanosilicate framework and also results in a redistribution of active Ti species throughout the crystals, thereby enriching the sur-

Bifunctional titanosilicate with hollow structure

“…In another separate experiment with addition of HP instead of H 2 and O 2 , the formation of PO at reaction conditions is also proven directly. On the basis of aforementioned catalytic results, it can also be deduced and further testified that the formation of HP could occur over Pd species, and the direct propylene epoxidation process involving onsite HP formation followed by HP oxidizing propylene to PO, and Pd‐HTS x are exactly bi‐functional catalyst 9. Such phenomena may be due to the special preparation treatment of Pd‐HTS x , which cannot only make the introduction of Pd but also can maintain the hollow structure in Pd‐HTS x , thereby affording facilities for the molecular diffusions in Pd‐HTS x .…”

“…The presence of micropores in molecular sieves may limit the diffusion of reactant molecules into internal catalytic sites, while molecular transport in the channels or pores can be remarkably improved by creating intracrystalline mesoporosity or macroporosity (intraparticle voids) 6. In our earlier studies,7 we have presented one type of titanosilicate with hollow structure (RTS, having intraparticle voids), and quite recently, one new bifunctional titanosilicate crystals with hollow structure (NHTS) was prepared by a semi in situ procedure (including partial dissolution and recrystallization process),8, 9 their bifunctional catalytic performance was investigated and very excellent,10 while the synthetic procedure is relative complex (protector and reducer needed) and not easy to repeat completely. Here, we load noble metal on RTS via a simple but very effective route, thereby make the product become bifunctional titanosilicate with hollow structure (denoted as Pd‐HTS x , where subscript x stands for the noble metal content added in gel by weight percent).…”

Synthesis and catalytic applications of combined zeolitic/mesoporous materials

“…When this oligomerization process goes even further, small TiO 2 (crystalline anatase) particles can occur as extra-framework material, which is not built in the structure. Although crystalline TiO 2 particles are well-known for their interesting semiconductor properties and their photocatalytic activity in photodegradation processes [ 169 ], TiO 2 formation often needs to be avoided in the synthesis of Ti-containing nanoporous siliceous materials since its presence can be detrimental for the catalytic activity associated with tetrahedrally coordinated Ti [ 170 – 171 ].…”