Synthesis and Structural Characterisation of Yttrium-Doped α-Zirconium Phosphate

There has been a considerable amount of interest in the ion-exchange properties of layered zirconium phosphates. Potential applications in the remediation of nuclear waste have renewed interest in these inorganic materials, due to their high stability under the acidic conditions typically found in legacy waste pools. It has been well documented that the substitution of metals with different ionic radii into the frameworks of inorganic materials can alter the chemical properties including ion-exchange selectivity. The work presented here focusses on the synthesis and characterisation of yttrium-doped α-zirconium phosphates which are reported for the first time. Two different synthetic methods were used, reflux and hydrothermal syntheses, and the products were characterised by various methods such as powdered X-ray diffraction, MAS-NMR and scanning electron microscopy. It was found that up to 15% of zirconium could be replaced by yttrium before any noticeable impurity phases could be observed. Rietveld refinement from the doping showed that the products did not obey the Vegard’s law. However, the ion-exchange results clearly showed enhanced capacities and selectivity towards Co2+ ions for the substituted materials.

DBU-Intercalated α-Zirconium Phosphates as Latent Thermal Catalysts in the Reaction of Hexamethylene Diisocyanate and Phenol

The catalytic activity of 1,8-diazabicyclo [5,4,0]undec-7-ene-intercalated α-zirconium phosphates (α-ZrP·DBU) as thermal latent catalysts in the reaction of hexamethylene diisocyanate (HDI) and phenol was investigated. α-ZrP intercalation compounds with varying amounts of DBU (α-ZrP·xDBU, where x = 0.58, 0.44, 0.22, and 0.10) were prepared. The reaction of HDI and phenol with α-ZrP·DBU was carried out at varying temperatures for 30 min periods. The α-ZrP·DBU showed high catalytic activity in the reaction of HDI-phenol under heating conditions. The α-ZrP·DBU extended the pot lifetimes at 25 °C.

Photocatalytic Degradation of Rhodamine B Under Visible Light Irradiation by TiO2 Doped Layered Zirconium Phosphates

TiO2 doped layered zirconium phosphates were prepared by the hydrofluoric acid (HF) method and its photocatalytic performance was investigated in this study. Through the introduction of octylamine which acts as the intercalation and exfoliation reagent in the process, TiO2 could be uniformly generated and dispersed on the zirconium phosphate matrix through tetrabutyl titanate hydrolysis and calcination. The nano-scale TiO2 was obtained by applying the appropriate ratio of tetrabutyl titanate and layered zirconium phosphate in reaction. XRD, N2-sorption, FT-IR, UV-vis, SEM and TEM were used to characterize the structure and phtocatalytic properties of the samples. The photocatalytic performance of synthesized nano-scale TiO2 doped zirconium phosphates was studied by degradation of Rhodamine B (RhB). It is found that the scavenging rate of RhB could be up to 65% within 90 min under the visible light irradiation due to the relatively large active surface area and compact size of TiO2. This study highlights the potential application of TiO2 doped layered zirconium phosphate as a novel photocatalyst in photocatalytic degradation of organic pollutants.

Combination of intercalation and surface modification in layered zirconium phosphates: investigation of surface stability and reactivity

The combination of intercalation and surface modification was used to prepare heterofunctional ZrP by two synthetic pathways. The resulting materials were used to investigate the impact of the interlayer contents on the surface chemistry of ZrP.

Use of Zirconium Phosphate-Sulphate as Acid Catalyst for Synthesis of Glycerol-Based Fuel Additives

In the present work, zirconium phosphates and mixed zirconium phosphate–sulphate acid catalysts have been investigated in the acetylation of glycerol in order to obtain acetins as fuel additives. The following catalysts with chemical composition, Zr3(PO4)4, Zr(SO4)2, Zr2(PO4)2SO4, Zr3(PO4)2(SO4)3 and Zr4(PO4)2(SO4)5 have been prepared and characterized by acid capacity measurements, BET, XRD, FT-IR, XPS. The surface chemical composition in terms of P/Zr and S/Zr atomic ratios was monitored in the fresh and used catalysts. Zr3(PO4)2(SO4)3 and Zr4(PO4)2(SO4)5 showed the highest acidity associated with the synergic effect of two main crystalline phases, Zr2(PO4)2SO4 and Zr(SO4)2·4H2O. The reactions of glycerol acetylation were carried out by using a mass ratio of catalyst/glycerol equal to 5 wt% and molar ratio acetic acid/glycerol equal to 3:1. The glycerol conversion versus time was investigated over all the prepared samples in order to identify the best performing catalysts. Over Zr3(PO4)2(SO4)3 and Zr4(PO4)2(SO4)5 full glycerol conversion was achieved in 1 h only. Slightly lower conversion values were registered for Zr3(PO4)4 and Zr2(PO4)2SO4, while Zr(SO4)2 was the worst catalyst. Zr4(PO4)2(SO4)5 was the most selective catalyst and was used for recycling experiments up to five cycles. Despite a modest loss of activity, a drastic decrease of selectivity to tri- and diacetin was observed already after the first cycle. This finding was attributed to the leaching of sulphate groups as detected by XPS analysis of the spent catalyst.