A protective layer containing lead compounds before a layer of a copper-containing catalyst to prevent its contamination with chlorine and sulfur

 

(57) Abstract:

This invention relates to catalysts and in particular to the copper catalysts. Described composite material containing a layer of powdered copper-containing catalyst before the catalyst layer protective layer powder composition containing absorbent chloride - (a) at least one compound of lead other than lead oxide, which interacts with hydrogen chloride, and (b) its bearer. The connection lead is preferably a nitrate of lead. The combined material is especially suitable for low-temperature reactions of conversion, where the carbon monoxide is reacted with steam to produce hydrogen and carbon dioxide. The technical effect of improving the performance of the catalyst by reducing the degree of decontamination. 2 C. and 12 C.p. f-crystals, 6 PL.

This invention relates to catalysts, particularly copper catalysts.

Copper catalysts are often used for reactions involving hydrogen, for example for the reaction of simple hydrogenation and methanol synthesis (where carbon oxides interact with hydrogen), for decomposition of methanol (where methanol, often in a mixture with steam, razvrat with steam to produce hydrogen and carbon dioxide) and the reverse reaction conversion. Often with the aim of obtaining optimal activity and stability of catalyst the catalyst was prepared with copper in finely dispersed form, for example, by precipitation of copper compounds in the presence of (or together with) one or more materials of the media, especially compounds of zinc, magnesium, chromium and/or aluminum. After such deposition, the composition is heated to convert copper compounds and, if necessary, also the materials of the carrier into the corresponding oxides. Before use in the desired reaction, the copper oxide reduced to metallic copper. Particularly suitable catalysts for the above reactions are compositions of copper/zinc oxide/aluminum oxide and copper/zinc oxide/chromium oxide. In some cases, part of the zinc may be replaced by magnesium and/or part of the aluminum oxide or chromium oxide may be replaced with cerium oxide or rare earth metal such as lanthanum oxide.

Copper catalysts are easily deactivated by chlorine compounds, such as hydrogen chloride present in the process gas involved in the reaction. Trace amounts of such compounds of chlorine may result from pollutants that are in the materials, such as hydrocarbon source with whom are active copper, forming chloride of copper. As the chloride of copper is a relatively low melting temperatures, which are commonly used catalysts, for example, when 150-300, copper is mobilized with the formation of aggregates, which leads to loss of dispersion of the copper and to the subsequent loss of catalyst activity. Also, when the components of the catalyst are zinc oxide and/or magnesium, likewise can be formed corresponding chlorides, and they are similarly subject to mobilization, leading to the loss of the stabilizing effect of the oxides of zinc or magnesium, which again leads to subsequent loss of the dispersion and activity of copper.

To overcome this problem in GB 1357335 it is proposed to provide a protective layer prior to copper catalyst for the conversion, and the protective layer contains solid particles or contains material, which is more basic than zinc oxide. Examples of the proposed protective layers are oxides of alkali metals, alkaline earth metals, manganese, yttrium or lanthanum deposited on the aluminium oxide particles. Also known application of part of the copper-containing catalyst as a sacrifice of the protective layer.

However, when process gas saderia conditions, for example, when the violation of technological process, water will condense on the protective layer and/or the catalyst. In such circumstances, the chlorides formed during the interaction of the basic substance in a protective layer with a chlorine pollutants from the process gas can be flushed out of the protective layer in the catalyst, again leading to loss of the dispersion and activity of the catalyst.

Was discovered alternative material for the protective layer, which reduces the risk of deactivation of the catalyst.

Accordingly, serves a blend containing a layer of powdered copper-containing catalyst before the catalyst layer protective layer powder composition containing a) at least one compound of lead other than lead oxide, which interacts with hydrogen chloride, and (b) its bearer.

The invention also provides a method in which the process gas is subjected to a catalytic reaction using a layer of a copper-containing catalyst, comprising passing a process gas through the protective layer, as mentioned above, before passing through a layer of a copper-containing catalyst.

In the present invention in a protective see It is preferable to use a connection lead, which undergoes decomposition to the oxide of lead or restoring flow of hydrogen containing gas to elemental lead only slowly at temperatures below 300 C, especially below 350C. and most preferably below 400 C. the Preferred lead compounds include lead nitrate, lead carbonate, basic lead carbonate and aluminate" lead.

Thus, it was found that the carrier impregnated with lead nitrate, dried and calcined at 300 C for 2 hours, gives better performance than similar material obtained from the use of lead acetate. They believe that obtaining superior results due to the fact that the nitrate of lead is not exposed to significant decomposition when heated at 300 C for 2 hours and heated material is not exposed to significant recovery when treated with a mixture of hydrogen/carbon monoxide at about 225 C. In contrast, similar to the material obtained with the use of lead acetate instead of lead nitrate and heated for 2 hours at 300 C, shows obvious presence of metallic lead after processing gas mixture of hydrogen/carbon monoxide at 225 C. Sow decomposition when heated for 2 hours at 300 or restoring to elemental lead when processing a mixture of hydrogen/carbon monoxide at 255 C.

Also particularly effective is the product obtained by joint precipitation of compounds of lead and aluminum from an aqueous solution of soluble salts of lead and aluminum. Analysis of x-ray diffraction of this product revealed that at least some amount of lead may be present in the form of "aluminate" lead, having a structure similar to magnesium aluminate MD4Al2(OH)143H2Oh and oxide/hydroxide of lead 3b 2b(OH)2.

The media can consist of particles of inert material, such as aluminum oxide, chromium oxide, zirconium dioxide, titanium dioxide or, less preferably, silicon dioxide. The carrier preferably has a relatively high surface area, for example about 50 m2/, To ensure adequate protective effect without the need for excessive volume of particles of the protective layer of the particles of the protective layer preferably have a lead content of at least 2% by weight, more preferably at least 5% by weight, especially at least 10% by weight, most preferably at least 15% by weight. Particles of the protective layer can be obtained by impregnation prior formovies to remove water and/or by treatment with a suitable reagent, including heating, as necessary, for the conversion of salt lead to the desired compound of lead. Examples of suitable reagents include urea and ammonium or alkali metals, particularly sodium, carbonates. Alternative particles of the protective layer can be obtained by deposition of lead compounds in the presence of particles of the carrier or joint deposition of lead and compounds of the media or a predecessor of the media followed by heating as necessary, and the formation of precipitated compounds in the molded particles before or after a similar stage of heating.

The preferred material for the protective layer is a powder composition comprising a nitrate of lead and its media, especially the oxide carrier such as alumina.

Particles of the protective layer preferably have a maximum and minimum size in the range from 1.5 to 20 mm, especially 3-6 mm

The protective layer and the catalytic layer are used as the fixed layer and may be in the same vessel or in multiple vessels, and the protective layer is located before the catalytic layer. Preferably the process gas flows down through the catalytic layer: thus, cultic protective layer on top of the particles of the catalytic layer. If desired, between the protective layer and the catalyst layer can be a layer of inert material to facilitate the depositing of the protective layer without destroying the catalytic layer.

The invention finds particular application in respect of the conversion reactions. In this process, the process gas stream containing carbon monoxide and steam and often other components such as hydrogen, carbon dioxide, methane and/or nitrogen, is passed through a layer of a copper-containing catalyst, particularly a catalyst copper / zinc oxide / aluminum oxide or copper / zinc oxide / chromium oxide, in which a certain amount of zinc oxide may be replaced by magnesium oxide, and/or some amount of aluminum oxide and/or chromium oxide may be replaced by oxides of rare earth metals at a temperature in the range from 150 to 300, especially when the inlet temperature in the range from 150 to 250 C. the Process gas preferably contains 1-4% by volume of carbon monoxide and at least one mole of steam per mole of carbon monoxide. Preferably the process gas contains 20-50% by volume of steam. Usually the process is conducted at a flow rate of wet gas in the range from 2000 to 5000 h-1and at a pressure in the range to absorbitivity sulfur compounds, and, therefore, the layer will also act as a sulfur - protective layer,

The invention is illustrated by the following examples in which tests various protective layers, by downloading 0,393 ml (0.50 g) particles predecessor standard low-temperature catalyst conversion in the form of a copper oxide / zinc oxide / alumina containing about 50% by weight of copper oxide and having a particle size in the range of 0.6-1.0 mm, in the microreactor, with a layer of particles of fused aluminum oxide (0.25 g) with a particle size 0.6-1.0 mm above the catalyst precursor conversion and 0,197 ml particles of protective material with a particle size 0.6-1.0 mm over the particles of fused alumina, that gives a full layer of catalyst volume 0,70 ml.

The copper oxide in the catalyst precursor is recovered to metallic copper by passing a stream of nitrogen containing 2% by volume of hydrogen, down through the microreactor at a pressure of approximately 28 abs. bar (28000 kPa) at a flow rate of 15 liters/hour (under standard conditions) at the same time as the micro-reactor is heated from ambient temperature to 220 C and maintain at this temperature for 95 minutes, getting the total recovery time is 3.5 hours.

Activity catalysis of the gas mixture, containing 1 part by volume of steam into 2 parts by volume of gas composition, %: H255, CO215, WITH 5 and N225, through the microreactor at a temperature of 220C and a pressure of approximately 28 abs. bar (28000 kPa).

To simulate contamination of chlorine after the gas mixture passed through the catalyst bed for about 6 hours, to the gas mixture model HC1, receiving the concentration of Hcl in the wet gas 5,2 o'clock N. M. (ppm) by volume (test method 1) and 1 h N. M. (ppm) by volume (test method 2). When such fixed test different variations of CO conversion with time is measured using the built-in infrared detector. The decrease in conversion WITH time is indicative for loss of catalyst activity.

Example 1

30 g of particles of gamma-alumina size 0.6-1.0 mm and having a BET surface area of 350 m2/g immersed in 200 ml of an aqueous solution of nitrate of lead (II) at 60-70 C and the approximate concentration of 6.8 g of lead nitrate (II) per 100 ml of solution. The material removed from the solution after 20 minutes, allow to drain (drain) and dried at 110 C for two hours and then calcined in a furnace at 300 C for two hours. Analysis of the resulting material (sample A) shows the content of the Pb(NO3)2100 ml of solution. Chemical analysis of the resulting product (sample B) shows the lead content of 10.7% by weight.

Example 3

Repeat example 1 but using an aqueous solution with an approximate concentration of 37 g Pb(NO3)2100 ml of solution. After annealing the material at 300 With the sample re-immersed in the second aqueous solution containing about 37 g Pb(NO3)2100 ml solution, and then drain, dried at 110 C for two hours and then calcined in a furnace at 300 C for two hours. Chemical analysis of this material (sample C) gives the lead to 19.9% by weight, and infrared analysis shows that a small amount of lead nitrate decomposes to lead oxide. Part of the sample is heated in air to 900 C for 2 hours to ensure complete decomposition of lead compounds to lead oxide. The lead content after heating up to 900 is 23.7% by weight.

Example 4

1.5 M solution PA2CO3and 5 liters of a solution containing 1843 Al(NO3)3N2O and 15,05 g Pb(NO3)2, heated to 80 C and add to 1 liter of demineralized water at a temperature of 70 with the speed and eno, raybaut and filtered and then dried at 110 for 16 hours. The dried samples are then calcined in a furnace at 300 C for 6 hours, add 2% by weight of graphite and the resulting product into pellets of size of 0.6 to 1.0 mm lead Content in the product is 3.5% by weight. Despite the stage of leaching, the concentration of residual sodium in the product (sample D) is about 1.1% by weight. Analysis of x-ray diffraction shows that the part of the lead had a phase structure that is similar to the Mg4Al2(OH)143H2Oh, and, therefore, presumably a "aluminate" lead. Also present phase structure 3b 2b(OH)2.

Examples of materials of the protective layer testing, as described above. To the first comparison (comparative sample X) the protective layer is a 0,197 ml raw particles of gamma-alumina as used for obtaining protective materials in examples 1-3, and as a second comparative sample (comparative sample Y) protective layer is a 0,197 ml of catalyst particles. For test method 1% CO conversion was determined over a period of 5 days, and the measurements were carried out at intervals of about 2-3 hours (primer is 6 hours for 11 days. To facilitate comparison of the measured CO conversion was done on a graph against time and through points built a smooth curve for each sample. (Individual points show small deviations from a smooth curve). These graphs were determined conversion at regular intervals (every 6 hours for test method 1 and every 24 hours for test method 2), which are presented in the following tables 1 and 2, where the numbers define the % CO conversion, rounded to the nearest whole number.

From table 1 it is evident that the materials of the protective layer according to the invention have similar efficacies for about 30 hours, and the protective layer of the sample And sometimes lower, perhaps due to the relatively low lead content. With this attitude it is estimated that the number of hydrogen chloride, served on the protective layer 30 hours was approximately the amount required for the conversion of total lead in the protective layer of the sample In the chloride lead (II). Sample D effective sample despite the fact that it has a much lower lead content. A protective layer of aluminum oxide, a comparative sample X, initially as effective as protective layers according to the invention, it is possible, in re the activity is rapidly deteriorating, showing that he has only a limited capacity for chloride. Use sacrifice catalyst layer as a protective layer, that is, as in the comparative sample Y, initially gives better performance compared to the protective layers according to the invention as a result of the presence of additional catalyst, available for catalysis of the reaction conversion (which here acts with such high bulk velocity that the reaction is more active than limit equilibrium at the operating conditions, the conversion of carbon monoxide required to achieve equilibrium, would be more than 99%). However, the comparative sample Y shows that the performance of the catalyst decreases rapidly, although not as fast as when using raw aluminum oxide as a protective layer.

Calculations show that for sample b and sample C in test method 2 significant decontamination begins when the total number of submitted HCl equivalent to a conversion of about 75 and 95%, respectively, lead chloride lead. Again lead protective layers are more effective in protection against deactivation than using a sacrifice layer of the catalyst.

Example 5

Example 6

Repeat example 5 and then dried granules are re-immersed in water, drain and dried as described in example 5 two more times. Analysis of the resulting material (sample F) shows the lead content of 10.9% by weight.

Example 7

For comparison (comparative sample Z sample pellets chromium oxide as used in example 5 is dipped in water and dried as described in example 5.

The samples are tested as described above: before testing the pellets are ground to a particle size of 0.6 to 1.0 mm the Results are shown in table 3.

From table 3 and from the comparison with the data for samples a and b in table 1 shows that the chromium oxide is a suitable vehicle, but less effective than gamma-alumina of examples a and B.

Example 8

The sample With additional testing as follows. To simulate the violation of technological process, including pollution by chlorides and subsequent condensation of the steam, catalysis is E. To simulate pollution by chlorides to the gas mixture for 6 hours add 5,2 o'clock N. M. (ppm) HCl. Then adding HCl to the gas mixture is stopped and the reaction is continued using free HC1 gas is approximately 30 hours. Then the reaction temperature is reduced to 180C for 3 hours. Although the temperature is not sufficiently low to cause condensation of vapor in the bulk phase, it is low enough to cause some condensation of steam inside the pores of the catalyst and the protective layer. Then the temperature was raised to 220C and maintain at this level for a further 15 hours.

Conversion WITH reduced from the original 95 to about 88% for 6 hours, in which Hcl was added to the gas mixture. In the next 30 hours, the conversion was slowly dropped to about 85%. By reducing the temperature to 180 conversion quickly fell to around 27%, but quickly rose back up to approximately 85% when the temperature was again raised to 220 C, which shows that condensation of the steam did not cause apparent long-term damage.

In order to compare the above procedure is repeated, using instead impregnated with lead pellets of aluminum oxide commercial chloride-protective layer (comparative example W), the content is with a bulk density of about 0.75 g/ml and BET surface area of about 113 m2/g, which after ignition at 900 To have the content of sodium oxide, Na2O, and about 14% by weight. They are tested in the same way. The conversion of carbon monoxide decreases with the initial values of 95 to 88% within 6 hours, in which Hcl is present in the gas mixture, and then gradually drops to about 84% in the next 30 hours. At lower temperatures the conversion of carbon monoxide quickly drops to below 20%, but in contrast to material impregnated with lead, the sample can not be restored when the temperature back up to 220, but remains below 20%.

Example 9

259 g of particles of gamma-alumina size 0.6-1.0 mm and having a BET surface area of 350 m2/g immersed in 800 ml of an aqueous solution of nitrate of lead (II) at 60-70C and at an approximate concentration of 55 g of lead nitrate (II) per 100 ml of solution. The material removed from the solution after 30 minutes, drain, dried at 110C for two hours. Part of the dried product is calcined in an oven at 150C for two hours, getting a sample of the G, while Prokaeva remaining in the oven at 200 C for 2 hours, obtaining a sample N.

Analysis of x-ray diffraction pattern G before and after its contact at 220 With gas sessie changes that indicates that when the test conditions, the nitrate of lead is not restored. Analysis of recovery when the programmable temperature also showed that the recovery did not occur at temperatures below 220 .

Example 10

303 g of particles of gamma-alumina size 0.6-1.0 mm and having a BET surface area of 350 m2/g immersed in 800 ml of an aqueous solution of nitrate of lead (II) at 60-70C and at an approximate concentration of 55 g of lead nitrate (II) per 100 ml of solution. The material removed from the solution after 30 minutes, drain, dried at 110 C for two hours, then calcined in a furnace at 300 C for two hours. The above process is repeated using calcined nitrate of lead impregnated with aluminum oxide obtained as described above, and a fresh quantity of a solution of lead nitrate. After annealing at 300 With the resulting material is subjected to repeated immersion in a third time, again using a fresh quantity of a solution of lead nitrate. The lead content in the calcined material amounts to 25.5% by weight (sample J). After annealing at 300 C for two hours, the portion of the sample J, annealed at 400 C for two hours, getting a sample, and the second portion of the sample J calcinate is 0C for two hours, to ensure the decomposition of lead nitrate to oxide of lead. In each case, the observed weight loss, indicating that prior to such heating at 900 With a significant portion of the nitrate of lead is not decomposed to the oxide of lead. The lead content in the samples before and after heating up to 900 shown in table 4.

Samples G, H, J, K and M, as well as commercially available catalyst (sample N), containing the lead oxide supported on alumina and containing 20,4% by weight of lead, was tested as described above using 1 h N. M. (ppm) HCl (test method 2). The results are shown in table 5.

When compared with the data of table 2 shows that, despite the high lead content of the sample N, the lead oxide to aluminum oxide is only slightly more efficient than the sample X - granules of aluminum oxide used to produce a protective material according to the invention. Performance comparison of samples K and M, which was hot at 400 and 550 C, respectively, showed that the sample M is much less effective compared To and only slightly more efficient than the sample N, which illustrates that during annealing at 550 C is very strong decomposition of lead nitrate.

Example 11

3H2O in 100 ml instead of solutions of lead nitrate.

The samples, after annealing at 300 C, 300 C-400 C and 300-550 With identified samples P, Q and R respectively, and the lead content in them amounted to 34.3, 34,6, and 34,9% by weight, respectively. Infrared analysis showed that all samples P, Q and R acetate of lead has undergone partial decomposition, it is possible to lead oxide. Analysis of x-ray diffraction pattern P after his contact at 220 C With a gas mixture of steam / hydrogen / carbon dioxide / carbon monoxide / nitrogen, as used in the test method, showed that under the test conditions lead compounds in the sample P was restored to elemental lead.

The samples were tested as shown above (test method 2), and the results are shown in table 6.

When compared with the data of table 2 shows that the lead acetate offers a slight advantage over the particles of gamma-alumina (comparative example X).

1. Composite material containing a layer of powdered copper-containing catalyst and, before catalyst layer, a protective layer powder composition containing absorbent chloride and a carrier, characterized in that the absorbent chloride soem hydrogen.

2. Combined material under item 1, where the connection lead is a compound that does not undergo significant decomposition when heated for 2 h at 300C or restoring to elemental lead when processing a mixture of hydrogen/carbon monoxide when S.

3. Combined material under item 2, where the connection lead is a nitrate of lead.

4. Composite material according to any one of paragraphs.1-3, where the copper-containing catalyst is a catalyst of copper/zinc oxide/aluminum oxide or copper/zinc oxide/chromium oxide.

5. Combined material under item 4, where the catalyst also contains magnesium oxide and/or oxide of rare-earth metals.

6. Composite material according to any one of paragraphs.1-5, where the particles of the protective layer have a maximum and minimum size in the range of 1.5-20 mm

7. Composite material according to any one of paragraphs.1-6, where the carrier is selected from aluminum oxide, chromium oxide, zirconium dioxide and titanium dioxide.

8. Composite material according to any one of paragraphs.1-7, where the particles of the protective layer contain at least 2% by weight of lead.

9. Composite material according to any one of paragraphs.1-8, where the particles of the protective layer are impregnated prior the removal of water.

10. Composite material according to any one of paragraphs.1-8, where the particles of the protective layer is produced by deposition of lead compounds in the presence of particles of the carrier or joint deposition of lead compounds and the carrier, or the precursor of the medium, followed by heating as necessary, and the formation of precipitated compounds molded particles before or after this stage of heating.

11. The method of carrying out catalytic reactions with the use of a layer of a copper-containing catalyst, comprising passing a process gas through the protective layer of the powder composition containing absorbent chloride and the media, before passing the specified process gas through a layer of a copper-containing catalyst, characterized in that the absorbent chloride contains at least one compound of lead other than lead oxide, which interacts with hydrogen chloride.

12. The method according to p. 11, where the process gas contains carbon monoxide and steam, and optional hydrogen, carbon dioxide, methane and/or nitrogen.

13. The method according to p. 12, where the process gas passes through the copper-containing layer when the inlet temperature in the range 150-S.

14. The method according to p. 12 or 13, where the technology is

 

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