A new hierarchical macro/mesoporous titanium phosphate MTiP-1 has been synthesized through a slow evaporation method by using titanium isopropoxide and orthophosphoric acid as inorganic sources and pluronic P123 as the structure directing agent. Powder X-ray diffraction, FT-IR and electron dispersive spectroscopy (EDS) were used to analyze the framework, structure and composition of the material. The N2 adsorption/desorption isotherm of this material is of type IV, which is characteristic of a mesoporous material and it shows a Brunauer–Emmett–Teller (BET) surface area of 193 m2 g−1 together with an average pore dimension of ca. 7 nm. From scanning electron microscopic (SEM) images it is seen that there is hierarchical porosity in MTiP-1 and the mesoporosity of this material arises due to self-aggregation of tiny spherical particles of dimension ca. 15–20 nm. Transmission electron microscopic (TEM) images show the existence of randomly distributed mesopores in the material. This MTiP-1 material shows very good catalytic activity in the microwave assisted conversion of biomass and carbohydrates into 5-hydroxymethylfurfural (HMF). The catalytic reactions are carried out in different solvents like water, water–methylisobutyl ketone (MIBK), MIBK and dimethylacetamide (DMA)–LiCl. MTiP-1 also catalyzes the direct conversion of cellulose substrates and lignocellulosic biomass, sugarcane bagasse, into HMF.

https://www.rsc.org/suppdata/jm/c2/c2jm30623a/c2jm30623a.pdf

Hierarchically porous titanium phosphate nanoparticles: an efficient solid acid catalyst for microwave assisted conversion of biomass and carbohydrates into 5-hydroxymethylfurfural

Ultrafast and high-capacity adsorption of Gd(III) onto inorganic phosphorous acid modified mesoporous SBA-15

Nanoparticles of noble metals, such as silver and gold, have been investigated as one way to hinder the recombination of electrons and holes produced by irradiated semiconductors. However, the exact role silver plays in hindering electron–hole recombination is unclear. In order to assess the role of ionic silver, Ag+, and metallic silver, Ag0, on the potential photocatalytic activity of a titanosilicate ETS-10 semiconductor (i.e., a means to extend light absorption into the visible range, a means to form a Schottky barrier to hinder electron–hole recombination, as a catalyst for the production of oxygen radicals, as a means to capture electron through species reduction, etc.) the photosensitization of methylene blue (MB) was investigated under visible light irradiation. Visible light irradiation was chosen so as to decouple the effects silver nanoparticles play in this photosensitized reaction from the complexities of electron–hole pair dynamics that may be inherent to ETS-10. Ag+ and Ag0 were investigated in both their free-floating forms and utilizing ETS-10 as a substrate. All forms of silver were produced by AgNO3 dissociation. Ion exchange of as-synthesized ETS-10 from AgNO3 solutions was utilized to prepare Ag+-modified ETS-10 (Ag+–ETS-10), and H2 reduction of Ag+–ETS-10 was used to prepare Ag0 nanoparticle-modified ETS-10 (Ag0–ETS-10). In all preparations, the morphology and crystal structure of ETS-10 remained unchanged. Ag+–ETS-10 samples showed a progressive absorption edge red shift in the UV region with increasing sample Ag+ content. Unlike as-synthesized ETS-10 and Ag+–ETS-10 samples, Ag0–ETS-10 samples showed absorbance in the visible region. The absorption bands at ∼350 nm and ∼460 nm observed for Ag0–ETS-10 were attributed to the surface plasmon resonance of Ag0 nanoparticles on the surface of ETS-10 crystals. In contrast to as-synthesized ETS-10, which was essentially inactive in this illumination range, all Ag+–ETS-10 and Ag0–ETS-10 samples showed apparent enhanced activity for the degradation of MB under visible light (420–630 nm) irradiation. These results suggest that silver nanoparticles provide a “portal” for oxygen (i.e., oxygen radicals) to interact with MB radicals by providing a medium for interfacial charge transfer of an electron to oxygen adsorbed on the silver, with ETS-10 providing a reservoir for MB molecules and their radicals, and a path for injected electrons to reduce Ag+.

The role of silver nanoparticles on silver modified titanosilicate ETS-10 in visible light photocatalysis

Meldola blue immobilized on a new SiO2/TiO2/graphite composite for electrocatalytic oxidation of NADH

a b s t r a c t Covalently linked sulfonic acid ( SO3H) modified MCM-41 mesoporous catalysts was prepared, char- acterized and its catalytic activity under microwave irradiation was evaluated. The NH2-MCM-41 was first prepared by anchoring (3-aminopropyl)triethoxysilane (APTES) on Si-MCM-41 and further reacted with 1,4-butane-sultone to yield the desired acid catalyst. The mesophase and porosity of samples were determined by XRD, TEM and N2 sorption isotherm analyses. The presence of sulfonic acid moiety was confirmed by FT-IR, TG/DTA, sulfur elemental analysis and in situ IR study of pyridine and ammonia adsorptions. The catalyst showed high catalytic activity and high selectivity in tert-butylation of hydro- quinone under microwave irradiation. No leaching problem was observed after several runs, while the catalyst can be recovered and reused without loss of reactivity under the described reaction conditions. © 2012 Elsevier B.V. All rights reserved.

Sulfonic acid functionalized MCM-41 as solid acid catalyst for tert-butylation of hydroquinone enhanced by microwave heating

Mesoporous molecular sieves Si-MCM-41 (purely siliceous) and Ti-MCM-41 (partly covered with a surface layer of TiO2) were functionalized with phosphate groups by treatment with POCl3 (denoted -MCM-41(P) and Ti-MCM-41(P), respectively). With the use of TEM, X-ray diffraction, and N2 adsorption, it was shown that the initial hexagonal structure, the high specific surface area, and porosity are retained in the functionalized materials but are not as good as in the starting materials. 1H MAS NMR and 31P MAS NMR revealed that the surface of Si-MCM-41(P) consists of silicon phosphate and pyrophosphate species. That of Ti-MCM-41(P) additionally contains titanium dihydro-, hydro-, and pyrophosphate species, the latter being predominant. TPD of adsorbed ammonia for Si-MCM-41(P) and Ti-MCM-41(P) showed that functionalization leads to the creation of moderate and strong acid sites. A combination of mesoporous structure with acidic properties makes the MCM-41 functionalized with phosphate groups promising for use as ...

T. V. Kovalchuk

Papers

Synthesis, structure, and acidic properties of MCM-41 functionalized with phosphate and titanium phosphate groups.

Synthesis, Structure, and Acidic Properties of MCM-41 Functionalized with Phosphate and Titanium Phosphate Groups