DE2743031A1 - Metal phthalocyanine catalysts prodn. - by sublimation and conversion to adduct with nitric oxide or oxygen, used for nitric oxide removal - Google Patents

Abstract

Prodn. of metal phthalocyanines (MPc) with high catalytic activity is effected by converting technical MPc into very pure form by double sublimation (typically 10-5 torr inert gas, 400 degrees C) and then into MPc adducts or MPc oxyadducts, with much higher activity than the purified MPc, by treatment with NO or O2 at over 250 degrees C; or by conversion to MPc oxyadducts by sublimation in the presence of O2 at partial pressures up to 10-2 at 400 degrees C. These catalysts are specified for use in the redn. esp. hydrogenation or decompsn. of NO, (mainly) to N2 (and some NH3). They are selective, retain their activity well and contain much less metal than highly pure metal oxides.

Description

Procedure for eliminating nitric oxide (NO

and for the production of suitable catalyst substances description The rfindng mainly relates to a method for eliminating nitrogen oxide (NO) in high concentrations as well as new catalyst substances that are particularly suitable for the Hydrogenation or decomposition of the NO are useful.

The purpose of the invention is to create inexpensive catalysts, preferentially convert the NO into non-toxic products such as N2, 02 and 1120.

NO is formed in every combustion process and is different Contains concentrations in smoke gases. The maximum determined NO content in Exhaust gases is around 3% o in nitric acid plants.

In the air, NO is oxidized to nitrogen oxides (NOx), mainly to IJ02. NO and nitrogen oxides are highly toxic and their disposal is therefore necessary. Up to now are in the environmental protection regulations of the FRG for the emission of NOx no limit values are set, but it is intended to do so in the next few years perform. In the long term, the aim is to completely eliminate NO in exhaust gases.

Three principal methods of eliminating NO have been described so far.

At temperatures above 7000C the reduction of NO is carried out Reducing agents such as hydrocarbons, CO and H2 carried out, but mainly by NH3.

Catalytic reactions take place at much lower temperatures carried out. As reducing agents, similar to the ones, do not come catalyzed Hydrocarbons, CO, H2 and NH3 reactions are possible. Used as catalysts The following metals or their oxides are used: A transition metals, in particular the of the 8th and 1st subgroups, are the inner transition metals of the 6th period (lanthanides), A] #s wet processes have hitherto been aqueous solutions of alkalis and sulfites used for the absorption of NO, some with special oxidizing agents such as H2O2, ozone, KMnO4 or the like. Transition metal complexes that are known as Oxygen carriers act are used. Also organic metal complex compounds are used for disintegration in non-aqueous solutions.

The disadvantages of the methods mentioned arise as follows.

Reduction of NO in the absence of catalysts can only be achieved at high levels Temperatures are carried out. If coke is used as a reducing agent, must generated CO can subsequently be oxidized to C02.

Removal of NO by catalytic processes are also available Associated disadvantages. The activity of the catalysts can reach a final value decrease by a few percent, based on the initial value. Arise as a by-product sometimes considerable amounts of N20.

Catalytic reduction by NH3 is only possible in a limited temperature range feasible, since at higher temperatures catalytic oxidation of the NH3 is present 02 to NO occurs. In the case of catalytic hydrogenation, NH3 has always been formed in addition to N2 found that with some catalysts, NH3 is the only product.

Complete hydrogenation to N2 is desirable.

If NO is absorbed in solvents in oxidized form, it is true NO removed from the flue gases, but the resulting nitric oxide solutions must processed in a separate procedure.

During decomposition reactions in solutions of organic metal complexes predominantly N20 produced.

The objects resulting therefrom are thereby achieved according to the invention solved that highly purified and chemically treated as catalysts iY! etallphthalocyanine (MPc, M = metal) can be used. Depending on the MPc used, different Reactions optional, e.g. B. decomposition or hydrogenation are catalyzed.

So far, MPc have been used as catalysts in the liquid phase, in isolated cases too been used in gas-solid reactions.

The basic idea is that the MPc in the gas-esters catalysis a high degree of purity can be used in their metal-specific activities and these activities can be enhanced by chemical treatment. The so MPc adducts obtained can then selectively one of several possible reactions catalyze and, depending on the composition of NO-containing gas mixtures, for elimination used by NO.

The advantages achieved with the invention result as follows.

1. By using technically manufactured MPc, the Material costs within limits, the metal content is around 10 to 20 percent by weight the total catalyst mass compared to metal oxides in the highest oxidation state, in which the metal content is over 60%, as shown in the table below.

Substance MnPc / MnO2 CoPc / Co203 NiPc / NiO CuPc / CuO metal% 10 63 10 71 10 79 11 80 2. I> already by subliming twice in a high vacuum (typically Torr gates inert gas at 4000C) are cleaned MPc and are already as specific Catalysts can be used.

3. I) by treating with 02, the activities during NO decay increase.

4. By treating with NO, the activities in NO hydrogenation can be reduced improve significantly.

5. The activity of the adducts obtained according to 3. decreases by a maximum of NO decay only by 50% of the initial value up to constancy.

In order to achieve the above advantages, the following have been made in general Conditions that are listed individually in the examples are met.

Work was carried out with undiluted NO pulses (degree of purity: 99.8%) in a carrier gas (He, H2) from 0.17 cm3 to 0.84 cm3 (based on room temperature) in a temperature range from room temperature to a maximum of 4250C. The contact times lie between 0.17 sec and 1.7 sec, the apparent volume of the catalyst bed is depending on the density of the bed, between 0.75 cm3 and 3 cm3. The BET surfaces are lying between 1 and 14 m2 / g.

Examples Example 1 (MnPc) Chemically pure MnPc is hardly active.

If MnPc is sublimed in the presence of O 2 (up to 10 2 Torr), it becomes partially obtained a MnPc-oxy adduct which is catalytically active. The structure of the received Oxy product is not yet exactly hardened, like old Ti? -Spectroscopic investigations show, installation of 0p in the interior of the grid must be assumed.

Over 125 mg of Oxy-MnPc obtained by sublimation in the presence of 02, 0.75 cm3 of NO are conducted in the H2 stream. Only decay occurs. At 395 0C, constancy is achieved after 6 pulses, the conversion decreases from 5.7% at the beginning. to a final value of 4%.

Example 2 (MnPc) After O2 activation by passing over an inert gas / O2 mixture (O2 content: 5) at temperatures above 2000C the conversion rises to a final value of 54%; the Mn-Oxy-Pc content and thus the activity are thus more than tenfold.

Example 3 (MnPc) Over 125 mg of oxy-MnPc, obtained by sublimation in the presence of O2, 0.41 cm3 of NO are passed in the He stream. Sales decrease from initially 3.3% to 2.5% until constant at 3800C. Will be 0.61 cm3 of NO over this Passing the sample, the conversion drops at approximately the same temperature of 2.4% to 2%.

The examples make it clear that MnPc with appropriate treatment with 02 gets a high activity and -even at a very high level f # 2 excess only the decay is catalyzed. N20 is obtained as a by-product, its proportion does not exceed 5% of total sales.

Example 4 (CoPc) Are over 250 mg by sublimation at 10 4 Torr CoPc obtained from inert gas is passed 0.68 cm3 of NO in the H2 stream, the conversion is then 6% o at 416 0C. By applying 100 pulses of the same volume above 5 (JC ° C a CoPc adduct is partially produced that contains NO in bound form. In order to a conversion of 11% is achieved at 4070C for 0.22 cm3 NO.

The conversion decreases with increasing NO volume, for 0.62 cm3 NO becomes one Conversion of 8.7% determined, of which 3.5% is due to NH3 formation, Example 5 (CoPc) Over 500 mg of CoPc treated with NO, 0.84 cm3 of NO are passed in the He stream Temperature is 425 0C. NO decay occurs only in traces.

A comparison of Examples 4 and 5 thus shows that NO in The presence of H2 is well hydrogenated, while decomposition hardly occurs.

Example 6 (NiPc) Pure NiPc, obtained by sublimation at 10 -4 Torr inert gas, is almost inactive, both during decomposition and hydrogenation. Will NiPc treated with NO at temperatures above 2500 C, increases in the H2 flow Activity considerable. The adduct obtained in this way can be described as NiPc-N02, as shown by IR spectroscopic investigations. By treatment with 100 pulses NO At 0.74 cm3, a conversion of 19.3% at 3800C of NiPc-N02 is determined, the only one Product is N2.

Example 7 (NiPc) On 250 mg NiPc-NO2 (see example 6) 0.35 cm3 NO When brought into a stream of H2, NO is mainly hydrogenated to NH3.

The FJms; ftz is 52i 'at 3670C.

Example 8 (NiPc) 0.68 cm3 of NO become over 500 in the He flow at 3970C mg NiPc-N02. The conversion for the NO decay is below 3Xoo.

It thus shows that NiPc-N02 is a very active catalyst, in which the NO decomposition is negligible, the hydrogenation, however, considerable conversions results. With increasing NO concentration it is mainly hydrogenated to N2 and H20, with decreasing NO concentration to NH3.

Example 9 (CuPc) Chemical treatment with NO at temperatures above of 300 ° C. increases the conversion slightly, i.e. not much more than 10 '', related on the conversion of the untreated CuPc.

At 425 0C, a conversion of 2.7% for 0.2 cm3 of NO and 0.3 cm3 NO 2.6% conversion and for 0.43 cm3 NO 2% conversion. NH3 couldn't be detected.

Example 10 (CuPc) With an initial weight of 500 mg CuPc, the Conversion 5% if 0.72 cm3 NO are used.

It turns out that CuPc is not a very active catalyst, that Within the investigated NO concentrations, hydriet exclusively to N2 and H2o will. The decay is from subordinate #linK.

@ Higher efficiency and thus complete elimination of NO in high Concentrations with simultaneous lowering of the reaction temperature can be achieved achieve the following measures.

1. Increase in the initial weight of the catalyst This results in a weight of 3 g CoPc, which was treated with NO, see example 4, had a conversion of 3 for at 35 ° C the NO decomposition in He, while 500 mg with the same BET surface area up to 4250C almost are ina @ tive.

2. Increase in the exposure times of NO or 02 for maximum retention of the MPc adducts (see Examples 2, 4 and 6) Enlargement of the BET surface area Wie sich the measures according to points 1 - 3 have an effect, is shown in example 11.

Example 11 (CoPc) 4 g of CoPc obtained by sublimation are mixed with 200 NO pulses ao, 72 cm³ pretreated at 350 ° C. The BET surface area was before NO treatment Enlarged by grinding to 5 times the value according to example 4 been. The conversion at 412 0C is 98.5%, of which 59% and 39% are accounted for by N2 formed on NH3.

is the results obtained according to Examples 1 to 12 scientific criteria had to meet is the consistency of the used Catalyst substances secured at the specified temperatures. For the practical Use to remove NO can work up to temperatures of 550 0C which also results in higher sales.

Claims (9)

# tent claims 1. Process for the production of catalytically highly active MPc, characterized in that technically produced MPc by @@ single sublimation (typically 10-5 Torr inert gas, 400 ° C) in very small pores and by acting of NO are converted into MPc adducts at temperatures above 2500C, dio essentially have a higher activity than the purified MPc. 2. Process for the preparation of catalytically highly active MPc, thereby characterized that by the action of 02 at temperatures above 250 0C MPc-Oxy adducts are obtained, which are catalytically much more active than that purified MPc. 3. Process for the preparation of MPc-Oxy adducts by sublimation, characterized in that the sublimation in the presence of 02 to partial prints of 10 2 is carried out at 4000C. 4. Process for the reduction, in particular hydrogenation, of NO in high levels Concentrations, characterized in that according to claim 1 preferably IIiPc adducts and CoPc adducts are used, the NO predominantly to N2 and less hydrogenate to NH3. 3 5. The method according to claim 4, characterized in that CuPc is used according to claim 1 and thus NO is hydrogenated exclusively to N2 will. * Process for the elimination of NO by decomposition, characterized in that according to claim 2 and / or claim 3 preferably MnPc-oxy adduct is used which catalyzes only the decomposition even in the 112 excess. 7. The method according to claim 4, characterized in that for hydrogenation according to claim 1 all MPc of the 3d group, like. The MPc of 8. Subgroup and mixtures are used. 8. The method according to claim 6, characterized in that for the NO decay all MPc of the 3d group, like. the MPc of the 8th subgroup as well as Mixtures are used. 9. The method according to claim 4, 5 and 7, characterized in that that hydrocarbons, NH3, CO and mixtures thereof are used as reducing agents will.