SU889610A1 - Method of modifying zeolites - Google Patents

Description

I

The invention relates to methods for ion-exchange modification of zeolites and can be used in technological processes when zeolites are exposed to water vapor at high temperatures.

Methods are known for modifying zeolites by ion exchange, including contacting the starting sodium forms of zeolites with aqueous solutions of potassium or rubidium salts, which results in the replacement of ions with sodium ions of potassium or rubidium and, accordingly, the thermal stability of zeolites 1.

The disadvantage of these methods is the relatively small increase in the thermal stability of the modified zeolite.

The closest to the invention in its technical nature is a method of modifying zeolites by ion exchange, including contacting the starting zeolite with aqueous cerium-containing solutions at pH 4.5-5.5, followed by washing, drying and calcining 2.

A very small increase in thermal stability is also characteristic of the cerium ion exchange form obtained by this method.

The purpose of the invention is to increase the thermal stability of zeolites.

The goal is achieved by the fact that in the method of modifying zeolites, the initial zeolite is contacted with a solution of a thorium salt at a pH of 2.5-3.0.

Example. For ion exchange modification. Take low-silica zeolites (NaA and NaX), which have the lowest thermal stability of all general purpose zeolites of the composition:

NaA 0.98 Na O-Agg Oj 2, OSiOj NaX 0.95,. Hj-G 50 g each of the zeolite samples are treated with 350 ml (NciA) and 280 ml (NaX) 0.1. an aqueous solution of thorium nitrate TC (OH) 4 4H2, On qualifications. h The pH of the prepared solutions was adjusted to 2.75 with ammonia. Ion exchange is carried out with constant stirring on a magnetic stirrer at 25 s. Zeolite treatment is carried out repeatedly using a new solution each time. The duration of one treatment is 30 minutes. Exchange rate

sodium, thorium is determined by chemical analysis of equilibrium solutions. The processing of the original zeolites lead to the degree of exchange

t

.

After that, the zeolites are filtered off and washed with distilled water until a negative reaction to the N0 ion (reaction with diphelamino). Cooked zeolites are dried at and calcined at 400 C.

Example 2. Zeolites NaA and NaX are calcined at 40Qc for 3 hours and in an amount of 50 g are treated with 350 ml (NaA) and 280 ml (NaX) 0/1 n. a solution of thorium nitrate Th (NO3) i - 4Н2.O qualifications h in methyl alcohol. Nitric acid, which is precipitated by dissolving thorium nitrate in methanol, is neutralized with ammonia solution to a pH of 2.75. Washing of the modified zeolites is carried out with methyl alcohol. The remaining conditions are similar to example 1. The integrity of the zeolite crystal structure of the modified zeolites is analyzed by X-ray. It is established that zeolites retain their crystalline structure. The determination of the stability of zeolites with respect to the action of the water of the vapor is carried out under conditions simulating industrial ones. The zeolite calcined at 3 hours is treated in a quartz reactor with 100% water vapor. Water vapor is fed into the reactor in an amount of 100 volumes per volume of zeolite per hour at 550 s and atmospheric pressure for 12 hours. 5 Preservation of zeolite crystallinity is determined by X-ray, adsorption capacity by adsorption of water vapor by exsiccator at 20 ° C and, 3.

Comparative data on thermal stability of the original zeolites and zeolites, modified by the proposed and known methods are presented in table. /

Famous

0.5 KNaA

0.5 KNaX

0.5 RbNaA

0.5 RbNaX

0.3 CeNaA

0.5 CeNaX

The proposed (exchange in aqueous solutions) 0,5 ThNaA

0.5 ThNaX

(exchange in alcohol solutions) 0.5 ThNaA

0.5 ThNaX

Claims (1)

1. D. Brek. Zeolite molecules of p-refining and petrochemistry. M., sieves. M., Mir, p. 50, 1976. Himi, p. 49, 1974 (prototype).