CS263848B1 - Process for the activation of cobalt catalyst for selective hydrogenation of aniline - Google Patents

Abstract

The proposed method solves the process of improving the gas phase cobalt catalyst properties for aniline to cyclohexylamine. The principle of the process is that the catalyst is treated with hot, preferably boiling cyclohexylamine after hydrogen reduction. The proposed process can be used in a reactor for the hydrogenation of aniline to cyclohexylamine.

Description

The invention discloses a process for converting a catalyst into a cyclohexylamine, leading to an increase in its selectivity and activity of ethoxydioxide and niline to cyclohexylamine.

The active component of the catalytic pro-selective hydrogenation of aniline to cycldhexylamine in the gas phase is metal cobalt finely dispersed on the support. In such a form, however, the manufacturer does not distribute and often does not distribute the cobalt catalyst, since this form is pyrophoric, unstable in air. The active metal dispersion must therefore be either spun; or is prepared by activating the cobalt precursors prior to the catalyst application itself.

Activation of the stabilized catalyst consists in the removal of surface-sorbed oxygen, respectively. other substances. Activation of catalyst with precursors, which are most often oxides, hydroxide, amocomplexes, event. salts of some inorganic or organic acids, is based on their conversion into metallic cobalt. This transformation occurs either through reduction, non-thermal degradation and deposition. slednouoredukeí. The reduction conditions have a considerable influence on the resulting activity and selectivity of the catalyst. For example, low temperature and insufficient reduction time lead to the preparation of a catalyst with low activity and selectivity. High temperature reduction or prolonged exposure at this temperature also results in the preparation of a small, active catalyst.

In addition to the reduction conditions, they have a considerable influence on the activity, but above all on the selectivity of the additive catalyst. While the negative influence of reduction conditions can be eliminated by their optimization, the influence of some impurities on selectivity cannot be suppressed or eliminated by selecting the reduction conditions. In a systematic study of the causes of the variable selectivity of the cobalt catalyst for the cyclohexylamine process, we have found a process that allows additionally increasing the selectivity and activity of the catalyst · prortentoiproces.

Newly proposed method of nosb activation. ČQvého. Cobalt catalyst for selective! The hydrogenation of the aniline to cyclohexylamine is based on the fact that the catalyst, after reduction with hydrogen, is treated in hot (80 to 135 ° C, preferably boiling cyclohexylamine for 2 to 24 hours). · Undesirable impurities whose surface-concentration is reduced below a certain limit value by selective extraction with cyclohexylamine.

The advantage · ¹ described a method of increasing the selectivity and activity of the cobalt catalyst for cyclohexylamine process it is that it can be realized in the process reactor, and · not only in the beginning but also during vlast- whom you catalytic process. The following examples best illustrate the present invention.

Exemplary!

The precursor of the active ingredient of the commercial cobalt catalyst for the selective hydrogenation of aniline to cyclohexylamine is a mixture of cobalt-cobalt oxide and dihydroxydicobaltate carbonate. These precursors convert to a finely dispersed, metallic cobalt upon reduction with hydrogen. In the following table, the catalytic properties of the standard reduced catalyst (1) are compared with the catalyst (2) which, after standard reduction with hydrogen, is treated at atmospheric pressure in boiling cyclohexylamine for 6 hours. The relative activity and selectivity values were measured in a laboratory integral reactor, under comparable conditions, namely, at a cooling bath temperature of 160 ° C and a molar ratio of hydrogen: aniline = 20.

Table I

Influence of activation method on properties of cobalt catalyst for selective hydrogenation of aniline to cyclohexylamine

Mark. Activation Method Relative Catalytic Cat. reduction H ₂ processing in CHA activity selectivity temperature time temperature time _PC) _ (h) (° C) (h)

260 10

260 10

1.00

1.05

CHA - cyclohexylamine

1.00

1.82

135

The selectivity value indicates the ratio of dicyclohexylamine contents in the reaction mixtures after hydrogenation of the aniline on the standard (1) and evaluated (2) catalyst at a constant conversion.

Example 2

The commercial cobalt catalyst has the same reduction as in Example 1 but differs in the provenance and quality of the cobalt-cobalt oxide. The effect of the quality of this feedstock on the properties of the commercial catalyst is evident from a comparison of catalysts (1) and (3), see Table II.

The influence of the activation method according to the invention on the properties of the catalyst is convincingly documented by a comparison of the catalytic activity and selectivity of the catalysts (3) and (4J).

Table II

Influence of activation method on properties of cobalt catalysts for selective hydrogenation of aniline to cyclohexylamine.

Mark.

cat.

reduction H ₂ temperature (° C)

Method of activation processing in CHA time temperature (h) · (° C)

1 260 10 3 260 10 4 260 10 Meaning of symbols and quantities same as in

Table I.

Example 3

The newly proposed activation method has been tested in production cyclohexylamine

Relative catalytic activity selectivity time (h)

- 0 0 1.00 0.91 1.00 0,094 135 0 1.16 0.71

reactor. The activation method of the invention was applied to one of the production batches of a commercial cobalt catalyst partially deactivated after approximately 10,000 hours of operation. The results obtained are shown in Table III.

Table III

Influence of new activation process on properties of partially deactivated cobalt catalyst for production of cyclohexylamine.

Method of activation Time activities catalysis. (h) Catalyst load (kg _A m ~ ^3. Cat ¹ ' ¹ ) Conversion (%) DCHA content (weight why) reduction of H ₂ processing in CHA temperature (° C) time (h) temperature (° C) time (hj 245 90 _ 0 0 330 94.0 9.8 245 90 120 12 10 100 330 99.5 5.0

CHA and DCHA - cyclohexylamine and dicyclohexylamine

Claims (1)

OBJECT OF THE INVENTION Process for activating a cobalt catalyst for selective aniline hydrogenation in a gas phase, characterized in that the catalyst, after reduction with hydrogen, is treated with 80 to 135 ° C with a warm, preferably boiling cyclohexylamine for 2 to 24 hours.