Effect of Support Nature on Physicochemical Characteristics and Catalytic Properties of B-P-V-W-O x Oxide Compositions i
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EFFECT OF SUPPORT NATURE ON PHYSICOCHEMICAL CHARACTERISTICS AND CATALYTIC PROPERTIES OF B-P-V-W-Ox OXIDE COMPOSITIONS IN THE CONDENSATION REACTION BY ACETIC ACID WITH FORMALDEHYDE R. V. Nebesnyi,1 V. V. Sydorchuk,2 V. V. Ivasiv,1 S. V. Khalameida,2 O. M. Orobchuk,1 A.S. Pavliuk,1 O. V. Tsymbalista1
UDC 541.128.13
The influence of the support nature on physicochemical characteristics (surface acidity, porous structure) of complex oxide compositions B-P-V-W-Ox and their catalytic properties (activity, selectivity) in the reaction of gas-phase aldol condensation of acetic acid with formaldehyde to obtain acrylic acid was studied. It was found that the activity of catalysts varies symbolically with the size of the specific surface, and the selectivity of the formation of acrylic acid is determined by the presence of weak acid centers on the surface of the catalyst. In the presence of the catalyst B-P-V-W-Ox/TiO2 at a temperature of 375°C, acrylic acid was obtained with a yield of ~59% with a selectivity of formation of 92%.
Keywords: acrylic acid, aldol condensation, supported catalysts, porous structure, acid centers.
Acrylate monomers are valuable products of organic synthesis. Acrylic acid (AA) and its derivatives occupy an important place among them, which are widely used as raw materials for the manufacture of polymer products (plastics, coatings) and acrylic rubber as well as paints and coatings, construction adhesives, mixtures, and liquids for leather and fabric treatment [1-6]. Currently, the two-stage oxidation of propylene is the most relevant industrial method of obtaining AA, which has a number of disadvantages: use of raw materials of petroleum origin and relatively high cost of the method [7, 8]. The development of new alternative methods of obtaining AA is extremely important due to the growing demand for this product. According to numerous studies, gas-phase aldol condensation of acetic acid (AcA) with formaldehyde is one of the most promising alternative methods of obtaining AA, due to the small number of process stages and relatively low cost of raw materials, which determines its technological and economic advantages [9-11]. However, due to the low efficiency of existing catalysts for this process, the method of aldol condensation of acetic acid with formaldehyde is not introduced into industrial use. Therefore, the development of new catalysts for the above-mentioned process is an essential scientific and technical task. Basic catalysts are often used in the aldol condensation reaction, which provide acceptable selectivity, but the activity of these catalysts remains low. Acid catalysts, on the other hand, provide greater conversion of initial substances, but their use is accompanied by the formation of a large number of by-products [12-14]. It can be concluded that both the basic and acidic ________ 1 Lviv Polytechnic National University, Lviv, Ukraine 2 Institute for Sorption and Problems of Endoecology, NAS of Ukraine, Kyiv, Ukraine. E-mail: [email protected]. __________________________________
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