Zirconium 4 oxynitrate hydrate

Calcium nitrate tetrahydrate, ethanol, and chloroform were obtained from Merck (Darmstadt, Germany). Polycaprolactone (PCL) (ρ = 1.45 g/mL and Mn = 80,000) and zirconium (IV) oxynitrate hydrate were purchased from Sigma-Aldrich (Burlington, MA, USA), and Tetraethyl orthosilicate (TEOS) that was used as a Si source was provided by Samchun Chemical Co (Pyeongtaek-si, Republic of Korea).

Commercially available chemicals were used for syntheses as follows: cerium(III) nitrate hexahydrate 99.99%, zirconium(IV) oxynitrate hydrate 99%, lanthanum(III) nitrate hexahydrate 99.99%, praseodymium(III) nitrate hexahydrate 99.9%, europium(III) nitrate hexahydrate 99.9%, gadolinium(III) nitrate hexahydrate 99.9% from Sigma Aldrich, Germany; yttrium(III) nitrate hexahydrate 99.9% from Alfa Aesar, Germany; concentrated ammonia solution 25% from Gram-Mol, Croatia; citric acid monohydrate 99.9% from T.T.T., Croatia. To perform the catalytic reactions the analytical grade products acetaldehyde (97%), propionaldehyde (97%), butyraldehyde (97%), benzaldehyde (97%), furfural (97%), vanillin (94%), acetonitrile (99%), benzoic acid (98%), 1,2-dichloromethane (99%), 2-methylhydrofuran (99%), heptane (99%), dimethyl sulfoxide (DMSO) (99%), ethyl-acetate (EtOAc) (99%), and EtOH (96%) from Sigma-Aldrich were applied without further purification.

All the chemical, reagents and solvents are purchased from the commercially available analytical grade, and were processed without further purification. Bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O), zirconium(iv) oxynitrate hydrate (ZrO(NO₃)₂·xH₂O), are from the sigma Aldrich. Ethanol (C₂H₅OH)-china AR grade, isopropyl alcohol (CH₃CHOHCH₃) SRL-India, ethylenediaminetetraacetic acid (C₁₀H₁₆N₂O₈) SRL India, p-benzoquinone (C₆H₄O₂) SRL India, nitric acid (HNO₃ purity) lobha chemie, and sodium hydroxide (NaOH) Merck India. Cupric nitrate trihydrate (Cu(NO₃)₂·3H₂O) is from Fisher scientific chemicals. Cadmium acetate hydrate ((CH₃CO₂)₂Cd·xH₂O) and thiourea (CH₄N₂S) was collected from SRL India.

Olive stone was used as raw material to prepare the catalyst support. Olive stone, an abundant and low-cost biomass waste from the olive oil industry, was supplied by Sociedad Cooperativa Andaluza Olivarera y Frutera San Isidro, Periana (Málaga), Spain. The olive stone was initially impregnated with phosphoric acid (H₃PO₄, 85% w/w, Panreac, Castellar del Vallés, Spain) at a mass ratio 2/1 (H₃PO₄/olive stone). After that, it was dried overnight, at 60 °C, in an oven. The mixture was introduced in a tubular furnace under a 150 cm³/min N₂ (99.999%, Linde, Barcelona, Spain) flow and the temperature was raised at a heating rate of 10 °C/min to 800 °C, at which the sample remained for 2 h. Then, the sample was washed with distilled water, at 60 °C, until a constant pH was reached in the residual water, and sieved, between 100 and 300 μm. The chemically activated carbon obtained (ACP) was, subsequently, impregnated by the incipient wetness method with zirconium (IV) oxynitrate hydrate (N₂O₇Zr·xH₂O, 99%, Sigma Aldrich, St. Louis, MO, USA). The amount of salt used was calculated to obtain a zirconium mass loading of 5.25%. The impregnated sample was then dried at 120 °C overnight and heated at 250 °C for 2 h, in a muffle furnace. A more detailed description of the catalyst preparation process can be found elsewhere [30 (link)].

Hafnium(IV) chloride and zirconium(IV)
oxynitrate hydrate were purchased from Sigma-Aldrich and used as received.