CN103801300B

CN103801300B - A kind of methane and nitrogen ordinary-pressure synthesis of ammonia Catalysts and its preparation method

Info

Publication number: CN103801300B
Application number: CN201410059661.1A
Authority: CN
Inventors: 王玉琪; 王金艳; 师少飞; 张贵泉; 姚瑞清; 周立发
Original assignee: Northwest University
Current assignee: Northwest University
Priority date: 2013-09-28
Filing date: 2014-02-24
Publication date: 2016-01-13
Anticipated expiration: 2034-02-24
Also published as: CN103801300A

Abstract

The invention discloses a kind of methane and nitrogen ordinary-pressure synthesis of ammonia catalyst, described catalyst is active component with Fe, is auxiliary agent with sylvite, take active carbon as carrier, and Fe content is 1 ~ 10%, K content of quality of activated carbon is 5 ~ 12% of quality of activated carbon.Catalyst of the present invention is compared with traditional industrial synthetic ammonia catalyst (A301), catalytic effect significantly improves, maximum ammonia throughput rate improves 27 times than A301 synthetic ammonia catalyst, has the performance advantage of highly significant, has wide popularizing application prospect.

Description

A kind of methane and nitrogen ordinary-pressure synthesis of ammonia Catalysts and its preparation method

Technical field

The present invention relates to new catalyst of a kind of methane and the direct synthetic ammonia of nitrogen normal pressure and preparation method thereof.

Background technology

The unstripped gas that traditional synthetic ammonia adopts is hydrogen and nitrogen, take fused iron catalyst as major catalyst, aluminium oxide, calcium oxide etc. are co-catalyst (such as CN1091997A, CN1293593A etc.), although ferrum-based catalyst has the advantages such as cheap, good stability, but its operating pressure (10 ~ 30MPa) and operating temperature (450 ~ 550 DEG C) all higher, production process not only harsh to equipment requirement, investment is large, and energy consumption is high, complex process, less economical.Therefore seek a kind of low-temp low-pressure ammonia synthesis catalyst and become the dream of researcher.What recent domestic was succeeded in developing is active component with noble ruthenium, take active carbon as carrier, with barium, silver waits slaine to be the temperature and pressure (such as CN102950026A, CN101579627A, CN1401426A etc.) that the ammonia synthesis catalyst of auxiliary agent significantly can reduce reaction, thus has significant energy conservation and consumption reduction effects.But the hydrogen that the unstripped gas of this type of synthetic ammonia catalyst is still still traditional and nitrogen, add noble ruthenium, make cost remain high, hinder the industrial applications of catalyst.

Summary of the invention

For overcoming the deficiencies in the prior art, the object of the invention is to provide the catalyst with the main component methane of natural gas and the direct synthetic ammonia of nitrogen under a kind of normal pressure, on the basis changing traditional raw material hydrogen, simplifies production technology, reduce the requirement to equipment, save energy resource consumption;

Another object of the present invention is to provide that a kind of preparation method is simple, cheap, the preparation method of the above-mentioned catalyst that is suitable for commercial Application.

The present invention obtains above-mentioned purpose by following technical solution:

A kind of methane and nitrogen ordinary-pressure synthesis of ammonia catalyst, described catalyst is active component with Fe, is auxiliary agent with sylvite, take active carbon as carrier, and Fe content is 1 ~ 10%, K content of quality of activated carbon is 5 ~ 12% of quality of activated carbon.

Above-mentioned sylvite is selected from K ₂cO ₃, KNO ₃, KOH, KClO ₃or KI.

In above-mentioned synthetic ammonia catalyst, Fe content is 3 ~ 8%, K content of quality of activated carbon is 5 ~ 9% of quality of activated carbon.

The preparation method of above-mentioned catalyst: take active carbon as carrier, first impregnation aids potassium salt soln, after drying, then floods iron salt solutions, after drying, roasting at 300 ~ 600 DEG C in atmosphere.

The active carbon of above-mentioned use through washing, removal of impurities, roasting and dilute acid pretreatment, to wash to the coconut husk of neutrality, shell, coal mass active carbon as carrier.

Above-mentioned sylvite is selected from K ₂cO ₃, KNO ₃, KOH, KClO ₃or KI, molysite is selected from FeCl ₃, K ₃[Fe (CN) ₆] or Fe (NO ₃) ₃.The solvent dissolving sylvite or molysite is selected from water, methyl alcohol, ethanol, acetone.

Specifically, the carrier active carbon that the present invention adopts first processes in the water bath with thermostatic control of >=85 DEG C with diluted acid, is disposed, and washing is to neutral rear dry.To remove impurity, the ash content on surface and the most easily to allow the element sulphur of catalyst poisoning, the oxy radical of carrier surface can be improved simultaneously, be conducive to the load of active component, improve its decentralization at carrier surface, to obtain better catalytic activity.

Impregnation sequence of the present invention is: first impregnating metal sylvite, and rear dipping molysite will be conducive to the acquisition of highly active Fe base ammonia synthetic catalyst like this.Reason is attributed to the effect that on the one hand sylvite plays structural promoter, and first first load sylvite entered into the mesopore duct of high-area carbon, and duct in course of reaction can be avoided to cave in the minimizing of the effective active component caused; On the other hand sylvite will mainly play the effect of electronic auxiliary, and ammonia production reaction rate, to the activated disassociation of methane and nitrogen molecular, is accelerated in enhanced activity center.

Based on the needs of methane, nitrogen ordinary-pressure synthesis of ammonia, it is active component that the present invention prepares with metallic iron, alkali metal sylvite is auxiliary agent, with the novel K-Fe/PCAC catalyst that graininess cocoanut active charcoal (PCAC) etc. is carrier, compared with traditional industrial synthetic ammonia catalyst (A301), catalytic effect significantly improves, maximum ammonia throughput rate improves 27 times than A301 synthetic ammonia catalyst, has the performance advantage of highly significant, has wide popularizing application prospect.

Accompanying drawing explanation

Fig. 1 is take Fe as active component, the comparison of different carriers catalyst maximum ammonia throughput rate under normal pressure, the operating mode of 700 DEG C;

Fig. 2 is with graininess cocoanut active charcoal for carrier, and different metal is the comparison of catalyst maximum ammonia throughput rate under the operating mode of normal pressure 700 DEG C of active component;

Fig. 3 is different sintering temperature, the comparison of K-Fe/PCAC maximum ammonia throughput rate under the operating mode of normal pressure 700 DEG C;

Fig. 4 is different roasting time, the comparison of K-Fe/PCAC maximum ammonia throughput rate under the operating mode of normal pressure 700 DEG C;

Fig. 5 is the comparison of K-Fe/PCAC ammonia throughput rate under normal pressure, different reaction temperature operating modes;

Fig. 6 is the comparison of technical grade synthetic ammonia Fe series catalysts A301, graininess cocoanut active charcoal (PCAC) load A301 type catalyst A 301/PCAC and K-Fe/PCAC maximum ammonia throughput rate under the operating mode of normal pressure 700 DEG C;

Fig. 7 is the XRD of catalyst K-Fe/PCAC before and after load.

Detailed description of the invention

Below in conjunction with example, the present invention is further illustrated, but the present invention is not limited.

Embodiment 1

Select different carriers respectively: TiO ₂, ZrO ₂, HZSM-5, Al ₂o ₃, the random active carbon of ature of coal, ature of coal column charcoal and graininess cocoanut active charcoal, load Fe (NO ₃) ₃, after drying calcining, prepare CH ₄, N ₂synthetic ammonia catalyst.This catalyst and technical grade synthetic ammonia Fe series catalysts A301 are carried out synthetic ammonia contrast experiment, with the largest production speed of ammonia for evaluation index, the results are shown in Figure 1.Cocoanut active charcoal does carrier synthetic ammonia best results as seen from the figure.

Embodiment 2

Get 100g from the graininess cocoanut active charcoal (PCAC) purchased on the market, be placed in beaker distilled water washes clean, dry 3h at 110 DEG C in baking oven, be then placed in roasting 3h at Muffle furnace 350 DEG C, take out after being down to room temperature and use 30% HNO ₃solution processes 5h in the water bath with thermostatic control of>=85 DEG C, and is washed till pH=7 with distilled water, equally in an oven 110 DEG C of dry 3h, and in Muffle furnace, 350 DEG C of roasting 3h are stand-by.Get the active carbon that 6.0g handles well, with containing 1.0gKNO ₃the suitable quantity of water solution of auxiliary agent floods above-mentioned active carbon 12h at 50 DEG C, dries 12h for 110 DEG C in atmosphere, makes K/C=6/100 (weight ratio).By 2.0gFe (NO ₃) ₃9H ₂o is dissolved in appropriate water, immerses above-mentioned KNO ₃/ C catalyst, at 50 DEG C, flood 12h, dry 12h for 110 DEG C in atmosphere, roasting obtains K-Fe/PCAC ammonia synthesis catalyst, the condition that sintering temperature is 350 DEG C, this sintering temperature of time 5h(and time are K-Fe/PCAC catalyst synthetic ammonia best results, is specifically shown in Fig. 2 and Fig. 3).This catalyst 2.0g is at H ₂reaction gas is switched to, reaction gas composition N after the lower 600 DEG C of reductase 12 h of atmosphere ₂/ CH ₄=1/2(volume ratio), flow velocity is 2800ml/h, measures the catalytic activity of catalyst under normal pressure, different temperature conditions, and the largest production speed of ammonia is evaluation index, in table 1; Under equal conditions, ammonia throughput rate is shown in Fig. 4 over time, and reaction temperature is at 700 DEG C as seen from the figure, and K-Fe/PCAC catalyst ammonia throughput rate is best, but catalytic activity declines also the fastest; Fig. 5 is the XRD of catalyst K-Fe/PCAC before and after load; The diffraction maximum (2 θ are 24.78 ° of positions) of charcoal is all there is in Powder XRD pattern before and after load, after load, charcoal diffraction peak intensity weakens, but there is the characteristic peak (2 θ are 45.31 ° and 65.58 ° of positions) of obvious metallic iron, there is not the characteristic peak of potassium, reason is that interaction strong between potassium species and carrier PCAC and potassium species fully disperse at carrier surface, and this is also the main cause that sylvite can play good promoter effect.

Embodiment 3

Similar to Example 2.Unlike selecting different auxiliary agents and changing impregnation sequence, obtain CH ₄, N ₂synthetic ammonia catalyst: Fe-Zr/PCAC, Fe-Ce/PCAC, Fe-Co/PCAC, Fe-Ni/PCAC, Fe-K/PCAC and K-Fe/PCAC, under normal pressure, the operating mode of 700 DEG C, with maximum ammonia throughput rate for evaluation index is tested, the results are shown in Figure 6.As seen from the figure, be auxiliary agent with sylvite and by sylvite, molysite order load K-Fe/PCAC catalyst synthetic ammonia best results.

Embodiment 4

The process of graininess cocoanut active charcoal (PCAC) is with embodiment 1.Get the active carbon that 6.0g handles well, with containing 1.0gKNO ₃suitable quantity of water solution at 50 DEG C, flood above-mentioned active carbon 12h, in atmosphere 110 DEG C dry 12h, make K/C=6/100 (weight ratio).By the Fe (NO of different quality ₃) ₃9H ₂o is dissolved in appropriate water, immerses above-mentioned KNO ₃/ C catalyst, floods 12h at 50 DEG C, dries 12h for 110 DEG C in atmosphere, is finally placed in Muffle furnace 350 DEG C of roasting 5h, the ammonia synthesis catalyst of obtained different iron load capacity.This catalyst 2.0g is at H ₂reaction gas is switched to, reaction gas composition N after the lower 600 DEG C of reductase 12 h of atmosphere ₂/ CH ₄=1/2(volume ratio), flow velocity is 2800ml/h, in normal pressure, the catalytic activity measuring catalyst at 700 DEG C, with the largest production speed of ammonia for evaluation index, in table 2.

Embodiment 5

The preparation of K-Fe/PCAC is identical with embodiment 2.Select technical grade A301 catalyst and be active component with A301, the PCAC A301/PCAC catalyst that is carrier carried out three groups of contrast experiments of synthetic ammonia, the results are shown in Figure 7, as seen from the figure, the synthetic ammonia catalytic effect of three kinds of catalyst is: A301<A301/PCAC<K-Fe/PCAC.

Claims

1. methane and a nitrogen ordinary-pressure synthesis of ammonia catalyst, it is characterized in that: described catalyst is active component with Fe, is auxiliary agent with sylvite, take active carbon as carrier, and Fe content is 1 ~ 10%, K content of quality of activated carbon is 5 ~ 12% of quality of activated carbon,

Described catalyst take active carbon as carrier, and first impregnation aids potassium salt soln, after drying, then floods iron salt solutions, after drying, and roasting at 300 ~ 600 DEG C in atmosphere.

2. methane according to claim 1 and nitrogen ordinary-pressure synthesis of ammonia catalyst, is characterized in that: described sylvite is selected from K ₂cO ₃, KNO ₃, KOH, KClO ₃or KI.

3. methane according to claim 1 and nitrogen ordinary-pressure synthesis of ammonia catalyst, is characterized in that: Fe content is 3 ~ 8% of quality of activated carbon.

4. methane according to claim 1 and nitrogen ordinary-pressure synthesis of ammonia catalyst, is characterized in that: K content is 5 ~ 9% of quality of activated carbon.

5. the preparation method of catalyst described in claim 1, is characterized in that: take active carbon as carrier, and first impregnation aids potassium salt soln, after drying, then floods iron salt solutions, after drying, and roasting at 300 ~ 600 DEG C in atmosphere.

6. the preparation method of catalyst according to claim 5, is characterized in that: the active carbon used through washing, removal of impurities, roasting and dilute acid pretreatment, to wash to the coconut husk of neutrality, shell, coal mass active carbon as carrier.

7. the preparation method of catalyst according to claim 5, is characterized in that: described sylvite is selected from K ₂cO ₃, KNO ₃, KOH, KClO ₃or KI.

8. the preparation method of catalyst according to claim 5, is characterized in that: described molysite is selected from FeCl ₃, K ₃[Fe (CN) ₆] or Fe (NO ₃) ₃.

9. the preparation method of catalyst according to claim 5, is characterized in that: the solvent dissolving sylvite or molysite is selected from water, methyl alcohol, ethanol, acetone.

10. the application of catalyst described in claim 1 in methane and nitrogen ordinary-pressure synthesis of ammonia catalyst.