Freeze-dried promoted and unpromoted sulfated zirconia and their catalytic potential

Abstract

A new synthesis route for sulfated zirconia and iron, manganese, and iron-manganese promoted sulfated zirconia has been investigated. Zirconium hydroxide precursors were prepared from hydrogel and hydroalcogel; freeze-drying as well as oven-drying has been employed. The pure hydroxides, sulfated, and metal promoted sulfated zirconia were calcined at 650 uC and characterised by chemical analysis, XRD, TG/DTG/ DTA, nitrogen adsorption, SEM, FTIR pyridine adsorption, and ammonia TPD. The catalytic activity of the samples was screened in the double bond isomerisation of 1-butene and the benzoylation of anisole.Significant differences in the textural and acidic properties were found for samples prepared either by freezeor oven-drying. Virtually no difference in acidity was observed between sulfated and metal promoted sulfated zirconia.Freeze-drying, especially the hydro-alcogel synthesis, was found to be a powerful preparation method for promoted and unpromoted sulfated zirconia catalysts.

Alkylation of catechol with methanol to guaiacol over sulphate-modified zirconia solid acid catalysts

“…This may be attributed to the stabilization of tetragonal crystallites of zirconia on calcination at 450 o C. However, the decrease in surface area and acidity at higher sulphate concentration is attributed to the decomposition of sulphate moieties into free elemental sulphur. This is in agreement with the reported IR results [20,21]. It is known that the variation in the calcination temperature and sulphate content on zirconia has a strong influence on the overall catalytic performance of the reaction.…”

“…Once again, the maxima observed at 5 wt.% SZ catalysts reflect the strong stabilization effect of the tetragonal form of zirconia. The subsequent decrease in the activity thereafter indicates the decomposition of SO 4 moities into free sulphur [20]. When a comparison is made between the total acidity of the SZ samples (Table 1) vs. the catechol activity (Fig 1), it is interesting to observe that both acidity and activity pass through the same maximum (i.e.…”

ZrO2/SO42−/Cu as a Multifunctional, Durable, Efficient, and Heterogeneous Recoverable Inorgano‐Nanocatalyst for the Green Preparation of Quinolines

“…The third weigh loss at temperature span 530–665 °C is related to the oxidation of copper and formation of CuO . The weight loss appeared at temperature range of 680–860 °C is due to the decomposition of sulfate as well as structural OH − groups …”

Application of infrared photoacoustic spectroscopy in catalysis

“…Kemnitz et al have applied FT-IR/PAS for pyridine adsorption [124] for the studies of surface acidity and the nature of acid sites in g-alumina [125], sulfated zirconia [126][127][128][129][130], WO 3 / ZrO 2 catalysts [131], modified zirconium and titanium dioxides [132], highly dispersed vanadium-doped metal oxides [133], chromia materials [134][135][136][137], various MgF 2 catalysts [138][139][140], and aluminium fluorides [141][142][143]. In the case of Vansant and co-workers IR/PAS is mostly a supplementary technique in the studies conducted with: silica and/or silicas surface and silica gel [144][145][146][147][148][149][150][151], MoO x layer on the surface of silica [152], adsorption of VO(acac) 2 or V(acac) 2 on silica and alumina [153][154][155], controlled deposition of iron oxide on the surface of zirconia [156], vanadium oxide deposited on thermally stable mesoporous titania [157].…”

“…The largest number of research papers which include FT-IR/ PAS catalytic investigations belongs two scientific groups chaired by Kemnitz [124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141][142][143] and Vansant [25,100,. Kemnitz et al have applied FT-IR/PAS for pyridine adsorption [124] for the studies of surface acidity and the nature of acid sites in g-alumina [125], sulfated zirconia [126][127][128][129][130], WO 3 / ZrO 2 catalysts [131], modified zirconium and titanium dioxides [132], highly dispersed vanadium-doped metal oxides [133], chromia materials [134][135][136][137], various MgF 2 catalysts [138][139][140], and aluminium fluorides [141][142][143].…”