کمپلکس ها ی فتالوسیانین بعنوان کاتالیزور

HETEROGENEOUS PHTHALOCYANINE CATALYST FOR LIQUID-PHASE OXIDATION

OF SODIUM SULFIDE AND MERCAPT!DES

A~ G. Akhmaduilina, I. K. Khrushcheva,

A. M. P~zgarov, and N. Mo Abramova

UDC 541.128.13

Oxidative detoxification of sour caustic wastes and demercaptization of light hydrocarbon

feedstocks are based on the reaction of catalytic oxidation of sodium sulfide and

mercaptides by molecular oxygen. The most active and stable catalysts for the oxidation

of sodium sulfide and mercaptides are phtha!ocyanine compounds of cobalt [i, 2]. The use

of homogeneous catalysts in these processes is economically infeasible, since such catalysts

are consumed continuously.

Heterogeneous catalysts prepared by adsorptive impregnation of porous supports (activated

carbon, alumina, bauxites, silica gel, aluminum and magnesium oxides, etc.) with solutions

of phthalocyanines [3-5] are unstable in aqueous caustic media under conditions of

vigorous sparging of the solution by oxygen-containing gas. Under these conditions, catalysts

prepared by grafting metal phthalocyanines to a polymeric Base are more stable [6-9];

however, they are not yet being used commercially, because of difficulties in preparation.

Using the principle of coloring polymers by pigments in the bulk [i0], we have developed

heterogeneous phthalocyanine catalysts that are distinguished by high mechanical

strength and chemical resistance in aqueous caustic media. These catalysts can be prepared

in the form of granules, in the same equipment used to obtain carbon black concentrates or

dye concentrates in polyethylene or polypropylene production. Packing elements can be prepared

from the catalyst granules in casting machines orlextruders that are installed in

lines for the mass production of finished articles in the same manufacturing operations.

As the finely dispersed particles of the metallophthalocyanine are fused into the polymer,

they are strongly bound to the polymeric support. Partial mechanical wear (abrasion)

of the catalyst does not lower its activity in service, since the catalystts surface is renewed,

and particles of the phthalocyanine that were formally located in the bulk polymer

are now brought into service.

Laboratory samples of the heterogeneous catalysts were prepared by roll-mixing the

catalytically active component with the molten polymer until a uniform mass was obtained,

after which shavings with a thickness of 0.25 mmwere formed. The specific surface of the

catalyst was 150 cm2/g.

The heterogeneous catalysts were tested for activity and stability in liquid-phase

oxidation of sodium sulfide and a sodium mercaptide by molecular oxygen in a sparged allglass

batch reactor (diameter 30 mm, height 330 mm) at atmospheric pressure, temperature

40~ and oxygen feed space velocity 30 min -I. As model solutions we used a 5% aqueous

solution of NaOH with 0.i M sodium sulfide and a 15% aqueous solution of NaOH with 0.65 M

sodium n-butyl mercaptide. The solution/catalyst ratio was 5:1, the total catalyst surface

area was 1500 cm 2, and the oxidation time was 30 min. The content of sodium sulfide or

mercaptide in the solution to be oxidized was determined potentiometrically (GOST [All-

Union State Standard] 22985-78).

It was established that in the preparation of the heterogeneous catalysts, it is best

to use only water-insoluble metallophthalocyanines and plastic polymers.

When electron-acceptor substituents such as --CI or--CH~CI, or electron-donor substituents

such as -C(CH~)3, are introduced into the benzene ring of cobalt phthalocyanine,

the level of catalytic activity of the heterogeneous catalysts is raised. However, in view

of the availability of the unsubstituted cobalt phthalocyanine (it is produced at the M.

V. Frunze Zavol'zhe Chemical Plant), it can be recommended for use as the catalytic component

of the commercial sulfur removal catalyst KS-I.