Synthesis of nano-sized porous γ-alumina powder via a precipitation/digestion route

• Published in: Applied catalysis. A, General Vol. 321; no. 2; pp. 109 - 116
• Main Authors: Potdar, H.S., Jun, Ki-Won, Bae, Jong Wook, Kim, Seung-Moon, Lee, Yun-Jo
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 11.04.2007; Elsevier
• Subjects: Boehmite; Catalysis; Chemistry; Colloidal state and disperse state; Digestion; Exact sciences and technology; General and physical chemistry; Nanocrystals; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Porous materials; Precipitation; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; γ-Al 2O 3; Precipitation; Boehmite; Nanocrystals; Digestion; γ-Al 2O 3; Aluminium oxide; Nanoparticle; γ-Al2O3; Porous material; Powder; Heterogeneous catalysis; Synthesis; Alumina; Nanocrystal
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2007.01.055

Synthesis of spherical nano-sized porous γ-alumina powder via a boehmite precursor possessing controlled physical and chemical characteristics obtained through controlled precipitation/digestion reaction at 70 °C in aqueous medium which give comparable catalytic activity in dehydration reaction of methanol to DME as that of γ-alumina powder derived from Catapal-B boehmite. ▪ As a part of a study for the preparation of nano-sized γ-Al 2O 3 powder with controlled porosity and pore size distribution, a precipitation/digestion route was exploited to generate a boehmite precursor having a narrow size distribution of spherical nano-sized particles: size 3.5 nm with surface area ∼261 m 2/g, average pore diameter of 4.86 nm, and pore volume ∼0.377 cm 3/g. In this route, aqueous solution of aluminum nitrate and sodium carbonate were added simultaneously drop by drop to a well-stirred 200 ml volume of deionized water (taken in a round-bottom flask) at 70 °C to precipitate boehmite precursor in the pH range of 7.5–8.5 after digestion at the same temperature for 3 h. The boehmite precursor thus obtained is further washed with deionized water first to avoid ‘Na’ contamination and then by ethanol/acetone. The digested precipitate was finally air dried at room temperature. The calcinations of as-dried boehmite precursor at 550 °C/5 h in air produced porous nano-sized γ-Al 2O 3 powder particles having spherical shape with size of 4.5 nm. These powder particles showed BET surface surface area ∼220 m 2/g with average pore diameter of 7.0 nm and pore volume ∼0.487 cm 3/g. However, room temperature precipitation/digestion produces non-crystalline boehmite that gave poorly crystallized γ-Al 2O 3 powder particles with lower surface area ∼133.90 m 2/g; these had higher average pore diameter of 26.67 nm with pore volume of 1.02 cm 3/g. In methanol conversion to DME reaction, γ-Al 2O 3 catalyst made from precipitation/digestion at 70 °C gave a similar yield of DME when compared with the yield for γ-Al 2O 3 prepared from commercial Catapal-B boehmite sample.