We report a study of the phase transformation of gibbsite-boehmite under hydrothermal treatment in aqueous suspension and under the ''dry steam'' conditions at T = 180-210°C and P = 1.0-1.9 MPa for 30-540 min. It is the first time that the closed mesopores formed during the splicing of large crystals in which water is encapsulated in an amount of up to 1.8% of the masses are found in boehmite. The spread of closed mesopores by the diameters depends on the conditions of hydrothermal treatment: in the aqueous suspension the mesopores are of the diameters less than 4 nm, under conditions of ''dry steam''-in the range of 4-6 nm and * 10-200 nm. With those closed mesopores, it possible to use boehmite in various fields of chemistry and technology for the encapsulation and transport of solutions containing the active components and connections. ().,-volV) (0123456789().,-volV) Boehmite (c-AlOOH) is an important mesoporous [1] material; due to the high specific surface, pore volume and presence of mesopores it is used as adsorbent [2], catalyst carrier [3], and intermediate phase in the production of alumina carriers, petrochemical and petroleum processing catalysts [4], membranes and filters [5], a component of toothpastes, enveloping and adsorbing agents in medicine. The parameters of the mesoporous system determine the adsorptive capacity of boehmite with respect to toxic organic and inorganic compounds in the wastewater treatment and in solving environmental problems [6].The dimensions of the crystals and the way they are packaged are very important for the functional materials obtained from boehmite; they affect its porous system, the temperatures of phase transitions into aluminum oxides. There are several types of boehmite: pseudoboehmite of the composition c-AlOOHÁnH 2 O (n = 0.3-1.0) with crystallite sizes of 2.5-3.5 nm (the specific surface area S p up to 450 m 2 /g and the pore volume V p up to 0.80 cm 3 /g) [7]; fine crystalline boehmite of the composition c-AlOOHÁnH 2 O (n = 0.0-0.2) with crystallite sizes of 11-13 nm (S p = 220-250 m 2 /g, V p = 0.58-0.60 cm 3 /g) [8,9]; well crystallized boehmite of the composition c-AlOOHÁnH 2 O (n = 0.0-0.2) with crystal sizes up to 80-140 nm (S p \ 150 m 2 /g, V p \ 0.15 cm 3 /g) [10]. Parameters of the boehmite porous system are varied by the method and conditions of its production.Precipitation from acidic or alkaline solutions of aluminum compounds [11,12], hydrolysis of aluminum alkoxides [13,14] produce the mesoporous pseudoboehmite with V p = 0.26-1.00 cm 3 /g, S p = 102-354 m 2 /g and pore diameters of 5.3-15.2 nm. Boehmite with V p = 0.20-0.32 cm 3 /g, S p = 100-120 m 2 /g and pore diameter 11.4-15.1 nm [15][16][17] is obtained from amorphous precipitates of aluminum hydroxides under hydrothermal conditions. A large-crystalline nonporous boehmite with S p = 3.1 m 2 /g and a pore diameter of 24.6 nm is obtained from gibbsite under the hydrothermal conditions at a temperature C 150°C [18,19].There are a few types of pores: open, deadlock and closed pores. The par...

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The paper describes the production of base monomers by dehydrogenation at PJSC «Nizhnekamskneftekhim». Special emphasis is made on the development of advanced domestic catalysts in cooperation with Kazan Federal University. Drawbacks of the existing catalytic systems and possible variants of their improvement are described.