CS227136B1 - Method of thermally treating and initiating catalysts of mo12,bia,cob,nic,fed,sie,mf and ox types for oxidation of olefins to unsaturated aldehyds and acids - Google Patents

Description

In the gas phase oxidation of olefins to the corresponding unsaturated aldehydes and acids, the removal of heat from the reaction tube may be a limiting factor for the productivity of the catalytic charge. Reaction heat also has a positive effect on the reaction rate, and this positive feedback disadvantageously increases the parametric sensitivity of the reactor. To reduce p; For example, the catalyst bed's sensitivity is typically an inert material such that at the locations of the expected highest reaction rate (mostly at the beginning of the tube) the inert dilution is greatest. However, this method of adjusting the activity of the catalytic bed cannot detect a continuous change in the reaction rate along the tube and also does not affect the lateral differences in reaction rate caused by the lateral temperature distribution in the tube. These disadvantages are avoided by the process of the present invention.

The present invention is based on the fact that transition metal molybdate catalysts are composed of:

^{! io} 12 ^Bi b ^Ni and ^Co to the ^Fe d ^Si e ^M f ⁰ X wherein M is an alkali metal or alkaline earth metal and wherein a = 0.5 to 7, b = 1-4, c = 0-4, d = 0.1 to 3, e-0 to 30, f = 0.1 to 1, continuously lose activity with increasing annealing temperature. At the same time, the selectivity of these catalysts is not reduced up to 500 DEG C., a catalyst prepared by a conventional process, i.e. by mixing solutions of the starting compounds, concentrating and drying the suspension, is therefore annealed to a temperature of not more than 460 DEG C. The catalyst thus prepared is charged into the catalytic reactor, diluted with an inert material in such a proportion that when the reaction mixture is introduced into the catalytic bed, the temperature in the bed rises above the annealing temperature but does not exceed 500 G. at a temperature of 30 to 60 K lower than

227 138, the operating temperature and the olefin and oxygen concentration are 5 to 50 " relative to the operating values. Deactivation of the catalyst after initiation of the reaction will cause a continuous increase in activity along the bed as well as an optimal distribution of activity across the bed in such a way that catalyst deactivation occurs most where normally the bed would be most warmed up. This results in a uniform distribution of the reaction rate along and across the bed and thus a uniform temperature field without steep increases at the beginning and in the bed axis. As a result, the parametric sensitivity of the reactor is decreased and the selectivity of the reaction is usually increased.

The catalyst composition Κω Βΐ ^ ^ ^ Οο Νί Ρθ ^ ^ 0 ^ _χ Κφ was after annealing to 4Q0 ° C, packed in a stainless steel tube, 27 mm diameter, immersed in a salt bath. The catalyst bed was diluted with 75% by volume of inert material. When the temperature reached 270 ° C, dosing of the reaction mixture containing propene, water vapor and air at a ratio of 1: 4.5 to 8.3 was started at a room speed of 1350 h. The temperature of the salt bath was increased at 5 K / h up to 320 Deň: 32 ° C. After stabilizing the temperature profile along the pipe, the proportion of water vapor in the feed was gradually reduced to 1: 3.2: 8.3. The catalyst was partially deactivated during the process and the following results were obtained:

- initial reaction rate was 20.0 _and piers ^ ^ .h

- propene conversion: 65.5 mol.

- selectivity to useful products (acrolein + acrylic acid): 86,2 mol% ·

Example 2 - Comparative

The catalyst of Example 1 was diluted with 83% by volume of inert material to prevent deactivation of the catalyst. Under the conditions of Example 1, results were obtained:

- initial reaction rate was 26.7 _and piers ^ ^ .h

- Propene conversion: 51.0 mol%.

selectivity for useful products: 78.4% mpl ₀

Claims (1)

XP method of heat treatment and the initiation of operation of catalysis - tors of type ^M O] _2 ^Bi and ^Co b ^Ni c ⁱ ®d ^Si e ^M f ⁰ x ^{PR0 oxidation} of olefins to unsaturated aldehydes and acids oxygen in the gas phase, wherein M I or an alkali metal an alkaline earth metal a wherein a = 0.5 to 7, b = 1 to 4 c = 0 to 4, d = 0.1 to 3, e = 0 to 30, f = 0.1 to 1, characterized in that during the heat treatment, the catalyst is annealed to a temperature of not more than 460 ° C, and in the catalytic reactor, the catalyst is diluted with an inert material only to such an extent that during catalyst operation the temperature in the catalyst bed rises to 400-500 ° C; by reducing the end of the olefin trace and the feed air by 5 to 50% relative to the operating values and by starting at 30 to 60 K below the operating temperature ·