Boreskov Institute of Catalysis (Siberian Branch RAS), Novosibirsk, Russia:
M. V. Batygina, Junior Researcher, e-mail: monolasta@gmail.com
N. M. Dobrynkin, Senior Researcher
A. S. Noskov, Head of the Department of Catalytic Processes Technology

Hydrothermal synthesis of Al – O – H products was carried out by hydrolysis of aluminum chloride hexahydrate AlCl₃·6H₂O, and urea jointly. Experiments were carried out using the autoclave type reactor as a part of high pressure experimental setup (at the temperature of 423–513 K and pressure of 0.6–2.4 MPa for 3–10 hours under an argon stream). Aluminum chloride concentration in the solution was 3–20%, the argon flow rate was kept constant at 0.00125 m³/h, and the reactor pressure was corresponded to saturated water vapor pressure at the test temperature. The effect of different additives (C₂H₅OH, Na₂CO₃, NaHCO₃, Al₂O₃, (NH₂)₂CO) to a depth of aluminum chloride hydrolysis was studied. Urea is the most effective additive allowing the complete hydrolysis of the AlCl₃ at the molar ratio AlCl₃ : (NH₂)₂CO = 0.67, temperature of 433–513 K and pressure of 0.6–2.4 MPa. Results of X-ray spectroscopy and high-resolution transmission electron microscopy showed that Al – O – H product formed by hydrolysis is a highly dispersed (nano) γ-AlOOH (boehmite). Diffraction peaks (32.7^о, 44.85^о and 57.43^о) corresponding to oxychloride phase Al₄₅O₄₅(OH)₄₅Cl were found in the diffraction patterns for Al – O – H products obtained by hydrolysis of AlCl₃ at low temperatures (423 K). The considered method of hydrothermal co-hydrolysis of aluminum chloride hexahydrate and urea provides a boehmite obtaining with a yield of up to 99%. The content of chloride ion in dried to constant weight boehmite is 1.06%. The received nano-sized Al – O – H products could be useful in different applications (catalysis, nanofiltration, aluminum production, etc.).
This work was carried out with the financial support of the Ministry of Education and Science of Russian Federation. Unique identifier RFMEFI60715X0142.

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