DE102013009885A1 - Manufacture of synthesis gas used for chemical reactions, involves forming gas mixture of hydrogen and methane by pyrolyzing dry coal, hydrogenating gas mixture using cobalt-molybdenum sulfide catalyst and separating hydrogen sulfide - Google Patents

Abstract

A dry coal is subjected to pyrolysis to produce a gas mixture containing hydrogen, methane, nitrogen and carbon monoxide as main components, and carbon sulfide as minor component. The gas mixture is subjected to hydrogenation at 200-280[deg] C in presence of a cobalt-molybdenum sulfide catalyst which is located in an alumina support. The hydrogen sulfide formed from the hydrogenation process is separated, to obtain synthesis gas. An independent claim is included for use of cobalt-molybdenum sulfide catalyst to convert carbon sulfide into hydrogen sulfide.

Description

Field of the invention

The invention is in the field of coke oven technology and relates to a new process for the removal of carbon sulfides from coconut gas, as well as a new catalyst and its use.

State of the art

Coke oven gas (synonym: coke oven gas) is produced in coking plants in the dry distillation of hard coal. Typically, the gas contains as main constituents about 55% by weight of hydrogen, 25% by weight of methane, 10% by weight of nitrogen and 5% by weight of carbon monoxide. Thus, coke oven gas is basically suitable as a synthesis gas for chemical reactions, but the contents of carbonyl sulfide and carbon disulfide, which must be removed beforehand, are disadvantageous since they act as catalyst poisons in the case of successor reactions, for example. This means that the catalysts must be cleaned or even replaced frequently, which is directly associated with effort and costs and is also undesirable because of the stoppage of the plants.

One way to remove coke oven gas from unwanted carbon sulfides is to subject it to catalytic hydrogenation and convert the sulfur compounds to hydrogen sulfide. Although this gas is also undesirable, but can be easily washed out with aqueous solutions, such as ammonia solution.

For this purpose, methods are already known from the prior art. For example, in the German patent application DE 1545470 A1 (Pichler) proposed, in a two-stage process, to hydrogenate carbon sulfides in the presence of cobalt-molybdenum, nickel-molybdenum or nickel-cobalt-molybdenum catalysts to hydrogen sulfide and then separate it off. The reaction temperature in the examples is above 550 ° C.

The use of nickel, cobalt, molybdenum or palladium based catalysts for hydrodesulphurisation of coke oven gas is also disclosed in various earlier Japanese patent applications, for example JP 59 145288 A2 (Shinnittetsu) or JP 59 230 092 A1 (Hitachi). These methods A similar method is also known from the German patent application DE 2647690 A1 (Parsons) known. There it is proposed to hydrogenate sulfur-containing carbon compounds in the presence of catalysts based on cobalt, molybdenum, iron, chromium, vanadium, thorium, nickel, tungsten and / or uranium and to remove the hydrogen sulfide formed in an extraction column with the aid of what an alkali metal hydroxide solution. As concrete catalysts here the sulfides of the above metals are proposed. The disadvantage, however, is that here too the catalysts require a minimum temperature of 260 ° C and the hydrogenation must preferably be carried out at significantly higher temperatures, sometimes even above 400 ° C. This is not desirable for reasons of energy consumption; In addition, it comes at these temperatures to change the composition of the gas, ie it already takes place methanation.

Although the processes of the prior art are capable of converting carbon sulfides into hydrogen sulfide in high yields and thus converting coke oven gases into synthesis gases of sufficiently high quality, they all have the considerable disadvantage that these processes are carried out at very high temperatures must take place well above 280 ° C, otherwise sufficient sales are not achieved.

The object of the present invention has therefore been to improve the existing processes in such a way that the carbon sulfides and optionally also present organic sulfur compounds (eg thiophenes) are converted virtually quantitatively into hydrogen sulfide, but at significantly lower temperatures. Furthermore, the method should ensure that the ratio of carbon oxides to methane does not change, ie no methanation takes place.

Description of the invention

• (a) Steinkohle einer trockenen Pyrolyse unterwirft und dabei ein Gasgemisch erzeugt, das als Hauptbestandteile Wasserstoff, Methan, Stickstoff und Kohlenmonoxid sowie als Nebenbestandteile Kohlenstoffsulfide enthält,
• (b) das Gasgemisch bei einer Temperatur im Bereich von 200 bis 280°C in Gegenwart eines sulfidischen Kobalt-Molybdän-Katalysators, der sich auf einem Aluminiumoxid-Träger befindet, einer Hydrierung unterwirft, und
• (c) den bei der Hydrierung entstandenen Schwefelwasserstoff aus dem Gasgemisch abtrennt.

The invention relates to a process for the production of synthesis gas from coke, in which

• (a) subjecting hard coal to dry pyrolysis, thereby producing a gas mixture containing as main constituents hydrogen, methane, nitrogen and carbon monoxide and as minor constituents carbon sulfides,
• (b) subjecting the gas mixture to hydrogenation at a temperature in the range of from 200 to 280 ° C in the presence of a sulfidic cobalt-molybdenum catalyst supported on an alumina carrier, and
• (c) separating the hydrogen sulfide formed in the hydrogenation from the gas mixture.

Surprisingly, it has been found that the sulfidic cobalt-molybdenum catalysts known per se for the hydrogenation of carbon sulfides then also show a high activity and selectivity below 280 ° C. and preferably below 260 ° C. when applied to an alumina support. In fact, carbon sulfide is hydrogenated to at least 95 vol .-% to hydrogen sulfide, without the hydrogenation has an influence on the ratio carbon oxides: methane. This is an unexpected result, based on the experience quoted in the introduction DE 2647690 A1 One would have to expect that catalysts which essentially contain cobalt and molybdenum in sulphidic form also promote, to a non-negligible extent, the undesired methanation, especially when the reaction is carried out under pressure as usual.

Production of coke oven gas by pyrolysis of hard coal

In the dry distillation or pyrolysis of hard coal, which is carried out at 900 to 1400 ° C, the volatiles of the coal are released and it forms porous coke, which essentially contains only carbon. The crude gas is decomposed by fractional condensation into tar, sulfuric acid, ammonia, naphthalene, benzene and the so-called Kokereigas. The latter is composed of hydrogen, methane, nitrogen and carbon oxides and, after appropriate purification, can be used as synthesis gas for further chemical reactions.

hydrogenation

The hydrogenation of the pyrolysis gases can be carried out in a manner known per se, for which essentially fixed bed reactors have proven to be particularly suitable, which contain the catalysts in particulate form as a loose bed or solid packing. Since beds more easily lead to channeling and thus to an inhomogeneous flow profile, the embodiment in which the catalysts are arranged in packages in the reactor is preferred.

The advantage of the hydrogenation in the fixed bed reactor, however, is that high space-time yields can be achieved, which is why the process according to the invention can also be carried out at high GHSV values of about 500 to about 1,500 and preferably about 1,000 to about 1,200 l / h , Another advantage is that no special measures for the product discharge are required, because the educts - pyrolysis gas and hydrogen - are preferably fed together at the bottom of the reactor, flow through the catalyst bed where it comes to hydrogenation, and occur as products at the top of the reactor out again.

As already mentioned, a particular advantage of the process is that the hydrogenation of the sulfur compounds in the presence of the catalysts to be used according to the invention is that the reaction is possible under significantly milder conditions and leads to complete conversion of the carbon sulfides, without already monitoring methanation is. The reaction temperature is 200 to 280 and, in view of a sufficient reaction rate, preferably 240 to 260 ° C. In this case, the reactor can be heated from the outside - which means that more energy must be spent - or the reaction components are already introduced in a heated state in the reactor, the mixing, for example, in a nozzle that operates on the Venturi principle can be done.

The reaction may further be in the range of 1 to 15 bar, i. H. be carried out both pressure and under pressure. Preferred is an embodiment in which the pressure is in the range of about 5 to about 10 bar, as this prefers yield and reaction rate.

catalysts

A. Sulfidic cobalt-molybdenum catalysts

The term "sulfidic cobalt-molybdenum catalysts" are essentially catalysts to understand that contain as the actual catalyst molybdenum sulfide and cobalt as a promoter. Corresponding catalysts are prepared in a conventional manner by common sulfidation of the corresponding oxides. The MoO _{3 is} completely converted into MoS ₂ . If this is applied to the aluminum oxide support, it can lie flat on the surface ("basal bonding") or only over one edge ("edg bonding"). The cobalt is present in three forms after sulfidation: first as Co ₉ S ₈ crystals located on the support, as Co ²⁺ ions at the edges of the MoS ₂ platelets ("CoMo phase") and as Co ²⁺ ions on the tetrahedral sites in the aluminum oxide lattice. The preferred catalysts are thus predominantly, ie more than 50 mol%, preferably more than 70 mol% and more preferably more than 90 mol% of molybdenum sulfide and contain the cobalt in sulfidic form as a promoter, wherein the amount in mol -% results as a difference to 100. It follows that, in a likewise preferred embodiment, the catalysts no longer contain any other metals, especially no other transition metals.

B. alumina carrier

• • ein V_37A von mindestens 75 ml/100 g, vorzugsweise mindestens 80 ml/100 g und insbesondere mindestens 85 ml/100 g;
• • ein V_0,1μm von höchstens 31 ml/100 g, vorzugsweise höchstens 25 ml/100 g und insbesondere höchstens 15 ml/100 gM;
• • ein V_0,2μm von höchstens 20 ml/100 g, vorzugsweise höchstens 15 ml/100 g und insbesondere höchstens 10 ml/100 g; sowie
• • ein Verhältnis V_0,1μm/V_0,2μm von mindestens 1,5.

Suitable supports for the sulfidic cobalt-molybdenum catalysts are aluminas having a particularly high internal surface area, which preferably have the following characteristics:

• A V _37A of at least 75 ml / 100 g, preferably at least 80 ml / 100 g and in particular at least 85 ml / 100 g;
• • a V _{0.1 μm} of at most 31 ml / 100 g, preferably at most 25 ml / 100 g and in particular at most 15 ml / 100 gM;
• A V _{0.2 μm} of at most 20 ml / 100 g, preferably at most 15 ml / 100 g and in particular at most 10 ml / 100 g; such as
• • a ratio V _0.1μm / V _0.2μm of at least 1.5.

Alumina carriers of the type mentioned are well known from the prior art. For example, in the European patents EP 1385786 B1 and EP 1385787 B1 (Axens) describes a process for their preparation in which one grinds a hydrargillite-type alumina, hydrothermal treatment with an aqueous solution of aluminum nitrate and formic acid over 6 hours at 200 ° C and then the resulting product at 400 to 1,300 calcined. The carrier material is then extruded and is then ready for loading. As far as the nature and production of the catalyst support is concerned, reference is made to the two cited documents by way of reference.

purification

The hydrogenation products leaving the reactor, especially the fixed bed reactor, now contain the sulfur compounds in the form of hydrogen sulphide, the content being of the order of typically 50 to 300 ppm. The presence of H ₂ S is just as undesirable as that of the carbon sulfides, but unlike the latter, hydrogen sulfide is relatively easy to leach out and, above all, quantitatively. For this purpose, the hydrogenation gases are preferably passed through an absorption column and treated there, for example, in countercurrent with an aqueous base, such as sodium hydroxide or ammonia. Alternatively, however, other suitable for the purification of gases devices, such as Venturi scrubber.

After separation of the proportions of H ₂ S, the purified product is available as a high-quality synthesis gas for further chemical reactions without restriction.

Industrial Applicability

• (i) ein V_37A von mindestens 75 ml/100 g, vorzugsweise mindestens 80 ml/100 g und insbesondere mindestens 85 ml/100 g;
• (ii) ein V_0,1μm von höchstens 31 ml/100 g, vorzugsweise höchstens 25 ml/100 g und insbesondere höchstens 15 ml/100 gM;
• (iii) ein V_0,2μm von höchstens 20 ml/100 g, vorzugsweise höchstens 15 ml/100 g und insbesondere höchstens 10 ml/100 g; sowie
• (iv) ein Verhältnis V_0,1μm/V_0,2μm von mindestens 1,5.

Another object of the invention relates to the use of sulfidic cobalt-molybdenum catalysts, which are supported on alumina, for the hydrogenation of carbon sulfides to hydrogen sulfide. In this case, preferably those cobalt-molybdenum catalysts are used, which are based on the metal components predominantly of molybdenum sulfide and contain cobalt sulfide only as a promoter. Likewise preferred are such carriers for the cobalt-molybdenum catalysts, aluminas which have a high surface area and exhibit the following characteristics:

• (i) a V _37A of at least 75 ml / 100 g, preferably at least 80 ml / 100 g and especially at least 85 ml / 100 g;
• (ii) a V _{0.1 μm} of at most 31 ml / 100 g, preferably at most 25 ml / 100 g and in particular at most 15 ml / 100 gM;
• (iii) a V _0.2μm of at most 20 ml / 100 g, preferably at most 15 ml / 100 g and especially at most 10 ml / 100 g; such as
• (iv) a ratio V _0.1μm / V _0.2μm of at least 1.5.

Examples

example 1

A pilot assay for fixed bed hydrogenation was equipped with a bed of a commercially available particulate sulfidic cobalt-molybdenum catalyst on an alumina support. Subsequently, different Kokereigase were fed at the bottom of the column. These so-called feed gases differed only in terms of the amount of carbon sulfides, especially carbon disulfide. The hydrogenation was carried out at a temperature of 220 ° C and a pressure of 10 bar. The GHSV was about 1,200 l / h.

The product gas was analyzed in the sulfur GC and the proportions of hydrogen sulfide and carbon sulfide determined over the retention times. The results are summarized in Table 1. The sales refer to the hydrogenation of the share of CS ₂ . Table 1 Hydrogenation Results (by weight unless otherwise indicated as% by volume) 1 2 3 4 Feed Prod. Feed Prod. Feed Prod. Feed Prod. hydrogen 59.0 59.0 59.0 59.0 59.0 59.0 59.0 59.0 methane 27.0 27.0 27.0 27.0 27.0 27.0 27.0 27.0 nitrogen 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Carbon monoxide 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5 carbon dioxide 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 COS (ppm) 1 10 0 0 0 0 0 10 CS ₂ (ppm) 117 0 94 0 95 0 54 0 H ₂ S (ppm) 1 211 0 141 0 182 0 141 sales 95.5 100 100 93.4

The test results show that at least 95% of the carbon sulfide content is converted into hydrogen sulfide. At the same time, the ratio of the remaining constituents in coconut gas remained constant, ie. H. no methanation was observed.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 1545470 A1 [0004]
• JP 59145288 A2 [0005]
• JP 59230092 A1 [0005]
• DE 2647690 A1 [0005, 0009]
• EP 1385786 B1 [0017]
• EP 1385787 B1 [0017]

Claims (15)

Process for the production of synthesis gas from coke, characterized in that (a) hard coal is subjected to dry pyrolysis and thereby produces a gas mixture containing as main constituents hydrogen, methane, nitrogen and carbon monoxide and as minor constituents carbon sulfides, (b) the gas mixture in a Temperature in the range of 200 to 280 ° C in the presence of a sulfidic cobalt-molybdenum catalyst, which is located on an alumina support, subjected to hydrogenation, and (c) separating the hydrogen sulfide formed in the hydrogenation from the gas mixture. A method according to claim 1, characterized in that one uses synthesis gas having a proportion of 10 to 200 ppm of carbon sulfides. Process according to claims 1 and / or 2, characterized in that one carries out the hydrogenation at temperatures in the range of 240 to 260 ° C. Method according to at least one of claims 1 to 3, characterized in that one carries out the hydrogenation at a pressure of 1 to 15 bar. A method according to claim 4, characterized in that one carries out the hydrogenation at a pressure of 5 to 10 bar. A method according to any one of claims 1 to 5, characterized in that one carries out the hydrogenation at a GHSV of 500 to 1500 l / h. A method according to any one of claims 1 to 6, characterized in that one uses cobalt-molybdenum catalysts which contain no further transition metals. Method according to at least one of claims 1 to 7, characterized in that one uses cobalt-molybdenum catalysts which, based on the metal components, predominantly consist of molybdenum sulfide and contain cobalt sulfide only as a promoter. Process according to at least one of Claims 1 to 8, characterized in that high-surface-area aluminas are used as supports for the cobalt-molybdenum catalysts, which exhibit the following characteristics: (i) a V _37A of at least 75 ml / 100 g, preferably at least 80 ml / 100 g and in particular at least 85 ml / 100 g; (ii) a V _{0.1 μm} of at most 31 ml / 100 g, preferably at most 25 ml / 100 g and in particular at most 15 ml / 100 gM; (iii) a V _0.2μm of at most 20 ml / 100 g, preferably at most 15 ml / 100 g and especially at most 10 ml / 100 g; and (iv) a ratio V _0.1μm / V _0.2μm of at least 1.5. Method according to at least one of claims 1 to 9, characterized in that one carries out the hydrogenation in a fixed bed reactor. A method according to claim 10, characterized in that one uses the catalysts in the fixed bed reactor as a bed or packing. Process according to at least one of Claims 1 to 11, characterized in that, after leaving the reactor, the hydrogenation product is passed through an absorption column and the hydrogen sulphide is washed off with a basic liquid. Use of sulfide cobalt-molybdenum catalysts supported on alumina for the hydrogenation of carbon sulfides to hydrogen sulfide. Use according to Claim 13, characterized in that cobalt-molybdenum catalysts are used which, based on the metal components, predominantly consist of molybdenum sulfide and contain cobalt sulfide only as a promoter. Use according to claims 13 and / or 14, characterized in that high-surface-area aluminas are used as supports for the cobalt-molybdenum catalysts, which exhibit the following characteristics: (i) a V _37A of at least 75 ml / 100 g, preferably at least 80 ml / 100 g and in particular at least 85 ml / 100 g; (ii) a V _{0.1 μm} of at most 31 ml / 100 g, preferably at most 25 ml / 100 g and in particular at most 15 ml / 100 gM; (iii) a V _0.2μm of at most 20 ml / 100 g, preferably at most 15 ml / 100 g and especially at most 10 ml / 100 g; and (iv) a ratio V _0.1μm / V _0.2μm of at least 1.5.