CS258691A3 - Catalyst for lower hydrocarbons oxidation coupling - Google Patents

Description

1

Catalyst for the oxidative coupling of lower hydrocarbons

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a catalyst for the oxidative coupling of hydrocarbons, in particular methane, and in particular to the oxidative coupling of steam for the selective conversion of methane to hydrocarbons having two or more carbon atoms with a selectivity close to 100 algae and a yield of at least about 8 and such events. Oxidation coupling using the catalyst of the invention.

The invention has been developed in connection with the DE-AC03-76SF00098 contract between the United States Department of Energy and the Lawrence Berkeleylaboratory University of California, and therefore has certain rights of the United States Department of Energy.

BACKGROUND OF THE INVENTION It has long been known in the chemical industry that hydrocarbons 3 can be made of a longer chain length from a so-called raw material, especially methane, and this is particularly advantageous, especially since conversion in excess of available natural gas methane gas to higher levels is possible. gaseous or liquid hydrocarbons, which may be used for the production of synthetic liquid fuels and other general chemicals for the chemical industry.

Many researchers pay close attention to this field, the literature in this field is voluminous and offers a large number of methods including catalytic conversions using different catalysts. Indeed, it is possible to convert methane to longer-chain hydrocarbons at present, however, the methods described so far have numerous drawbacks, such as adverse economics, excess impurities and undesirable process parameters. 2 In the oxidative coupling of methane, selectivity, conversion, and yield are observed as the fastest process parameters. 3 by forming hydrocarbons, with two or more carbon atoms, the formation of carbon monoxide and carbon dioxide mainly compete. By selectivity, the desired formed hydrocarbons having two, three or four / C2 / carbons are understood as the percentage of total converted carbon atom material. Hence, the higher selectivity means that a higher amount of CO oxides has been produced during the process. At the same time, 00χ means the loss of raw material and oxygen, which is, however, important, is the formation of larger amounts of CO as an impurity that has to be removed from the recycled methane by washing in an alkaline solution. The term conversion refers to the percentage of C ^ ^ raw material which reacts in a single pass through the reactor, i.e., the conversion indicates the difference between the amount of unreacted C ^ feed in the product and in the initial charge. The reaction coefficients in the oxidation co-ordinate are hydrocarbons having two or more carbon atoms, water and carbon oxides C0 '. As a rule, the amount of conversion is dependent on the catalyst used and the characteristics of the reactor, as well as the characteristics of the process itself, thus varying the rates depending on the flow rate, the amount of catalyst, the temperature, and the like. methods known in the art and, in the case of known reactors, are generally less than about 50. Therefore, the circulation of the product by the reactor in the known plants is absolutely necessary. Since the increase in the oxide content of the CO 2 reaction cancels, it is necessary to remove these oxides in the case of all low selectivity coupling processes that all prior art oxidative coupling processes contain. The yield is defined as the product of selectivity and conversion. This parameter is expressed as a percentage of the desired hydrocarbon with two or more carbon atoms formed from a certain amount of feedstock in a given reactor and under given operating conditions. An important parameter for evaluating conventional methods is - 5 - relative yield of a hydrocarbon with two and / or more carbon atoms.As important to note that the process of achieving 100 selectivity can be better in terms of overall cost than a process with lower selectivity, although higher yields and conversion rates are achieved in such a process

The subject-matter of the invention is a catalyst for the oxidative coupling of hydrogen to higher hydrocarbons according to the invention, in which the alkaline earth metal oxide, the transition metal oxide, is present. metal and small amounts of alkali oxide.

The invention also relates to a process for the oxidative coupling of methane in which a higher selectivity with respect to hydrocarbons having two and more carbon atoms is achieved. The invention also relates to a method of oxidative coupling in which the formation of carbon C oxides is eliminated to the highest possible extent (L < + >

And the necessity of these oxides.

The present invention relates to catalysts which promote oxidation copulation while achieving high selectivity and which are easy to produce.

The invention also relates to a process with an improved economy for the need for reagents, minimizing the need for oxygen and using steam, so that the process can be safely performed below the flammability temperature. details of the method are apparent from the following description; the advantage is the ability to work at a lower temperature than the prior art adaptations, as is apparent to those skilled in the art. In the process, the oxidative coupling of shorter chain length hydrocarbons, particularly methane, is carried out such that methane, along with a catalyst consisting of alkali metal and alkaline earth metal oxides and transition metal, together with steam and a small amount of oxygen at relatively low temperatures in the range of 500 to 100 ° G. The optimal molar ratio of the gaseous mixture introduced is - 4 - methane: oxygen: water about 3: 1: 6y, 5. The pressure can be of value to the environment or is carried out under overpressure of 3450 - and in the process is a significant catalyst and process for its preparation. the catalyst's deletion is generally greater than the prior art catalysts, i.e., 80% or more, and substantially 100, of the preferred catalysts of the present invention. The optimum setting depends on this field. efficiency considerably on the chemical composition and on the method of preparation of the catalyst. A preferred catalyst is a mixture of calcium, nickel, and the oxide in the form of oxides in an atomic ratio of about 2: 1: 0.01.

The catalyst is prepared by drying, decomposing and oxidizing the mixed aqueous solutions of calcium nitrate and nickel carbonate at elevated temperatures and adding a small amount of potassium nitrate during the process. Optimal catalysts can also be prepared by similar methods from the corresponding hydroxides.

The catalyst compositions of the present invention are generally more preferred than those known in the art, particularly for their selectivity. SUMMARY OF THE INVENTION The present invention provides a catalyst and a process for the preparation thereof, wherein the catalyst of the present invention achieves a selectivity equal to or greater than 99 since the catalyst permits the oxidation of methane without the evolution of carbon oxides of the formula. its recirculation and insulation. A further description of the catalysts is particularly preferred for catalysts. In view of the characterization of the catalysts of the invention and the coupling reaction mechanism, it is recalled that a perfect explanation is lacking in this sense; however, the coupling reaction appears to occur on the surface of the catalyst and thus does not involve gas phase reactions, unlike most methods known in the art and described. Carbon balance studies, comparing reactor input and output, indicate that carbon loss occurs when the reactor is started. Carbon is probably deposited on the catalyst and this seems to be an important process factor. - 5 -

The catalyst composition, which achieves 100% selectivity in the methane vapor coupling, is the activated calcium, nickel, and potassium oxides at a 2: 1 atomic ratio; 0.1. Small amounts of carbon oxides 00 are not acceptable. however, it is even a few percent, since the recirculating amount of carbon oxides 00 increases and the reactor product then needs to be purified. Acceptable variations in the catalyst composition of the following is 0 and / or 1 may vary from 2: 1 to about 4: 1, with an Itfi / K ratio of from about 1: 0.05 to about 1: 0.2.

As noted above, precipitation of the catalyst can play a significant role in the preparation of the catalyst of desirable characteristics. It has been found that the following process, the preparation of catalysts to achieve a catalyst selectivity greater than or equal to 99%, can be prepared from aqueous calcium nitrate solutions, nickel nitrate and potassium nitrate. The catalyst may be prepared from hydroxides or carbonates. It is important that the anions in the solution be the same. It is preferable to produce the catalyst using aqueous nitrate solutions as starting material. From the hydroxides or carbonates, the catalyst is produced in the same manner. Aqueous solutions of nitrates are prepared with a concentration as high as possible with respect to their solubility. Suitable amounts of the solutions are mixed to achieve the desired O / W ratio. The appropriate solution is then dried and decomposed in air at about 700 ° C to form the corresponding oxides. Or, the potassium nitrate solution can be added to the dried and decomposed mixture of calcium and nickel oxides, followed by pro-injection. drying and decomposition in air at a temperature of 700 ° C after the formation of the powder mixture, the catalyst is then used in this form or it can be pelleted by compression or extrusion. In order to be introduced into the reactor, the catalyst of the carrier is satisfactory and the catalyst can therefore be used without the carrier. However, it may be desirable to use an inert carrier such as a porous alumina or silica support to increase the surface area and to allow the catalyst to pass through the catalyst at higher spatial speeds and higher conversions. To produce a supported catalyst, the carrier material is added to the solution of the mixture prior to drying, followed by the procedure described above. The catalyst must be activated before use. Activation may be carried out prior to introduction of the catalyst into the reactor, or preferably in a reactor after loading but before loading. Activation, the catalyst is exposed to oxygen, "Sp, for example, about 2 ml of oxygen per gram of catalyst, at a temperature of about 680 ° C, the time for which the catalyst is activated is important in that the activation for a longer time increases the conversion and also increases the specific selectivity for hydrocarbons with a greater chain length and also affects the olefin / paraffin ratio as shown in the following Table I. The catalysts of the present invention are rendered capable of converting methane to hydrocarbons having 3-4 carbon atoms and activating stage is a means to optimize the production of the desired hydrocarbon species.

Table I,

Effect of activation in situ on the catalystActivation by oxygen before reaction ·

1-8 mechanistic studies and experiments have shown that the above-described specific catalysts result in almost 100% selectivity, selectivity significantly improves, wherein the oxides of the alkaline earth metal, the transition metal with a small amount of alkali oxide are formed. By this small amount is meant less than 1/20, or about 1/20 to about 1/10Q, by weight with respect to the total weight of the catalyst. In particular, the preferred alkaline earth metal oxide for the catalysts of the invention is magnesium, calcium and barium; the preferred transition metal is iron, cobalt, and nickel; and the preferred alkali metal is lithium, sodium and potassium. The preferred metal alkaline / transition metal molar ratio may vary from about 2: 1 to about 4: 1, with the preferred molar transition metal / alkali metal ratio being 1: 0.05 to about 1: 0.2. The preparation of the catalysts and their activation are carried out in the same manner as described for the preferred catalyst, that is, the initial mixture of soluble metal salts and the same anions, preferably nitrates in the presence or absence of a carrier, is airborne at a temperature of 650 to 750 ° C to convert the nitrate oxides, followed by oxygen activation for about 1 to about 48 hours at about 700 ° C. In addition to the method of preparing the catalyst as described above, the following factors seem to have an important effect on the efficiency of the catalyst: measurement of material balance, shows that a deficiency appears in the course of the oxidative coupling reaction. carbon, which is probably due to carbon deposition on the catalyst surface. As shown in Table II, material. the balance does not reach 100% until approximately three hours of operation.

Table II Time / Minutes. Balance, Carbon /// 25 70 50 95 100 98 200 100 400 100 - 9 - Furthermore, water has an important effect in the oxidation coupling reaction, whereby the process selectivity is greatly influenced when the water-replaces process. inert gas. In Table III. values are given for the procedures whereby the steam is replaced by helium, demonstrating the dramatic effect of the conversion, whereby the conversion is restored to the original values when the helium is again replaced by steam.

.Table III .'Po steam Temperature Thinner min ° C 85 600 Steam 200 '600 Helium 300' 600 Helium 400 600 Steam.

Selectivity Conversion Yield of carbon monoxide carbonate% 100% 9.5 9.5 75 5.0. 5.8 15 2.1 0.5 90 11.0 9.9. Photoemission studies of X-rays of active and inactive catalysts show signals associated with hydroxide, coagulation, and higher "oxidation" levels. active, catalysed, compared to nickel oxide for a less active catalyst.

The method of use of the catalysts according to the invention is explained in more detail by the following description with reference to the accompanying drawings; Fig. 1 is a process diagram; Fig. 2 shows both material and balance. for carbon, the performance of the catalyst as a function of the carbon for the most selective catalysts in the case of methane coupling in the presence of steam under standard conditions, with the graph showing the deviation, -a KOaHiO and +++ proportions; Fig. 3 shows the effect of temperature on Oa / Ni / X - 2: 1: 0.1 on the example of oxidative copulaemethane in the presence of steam.

The main aspect of the use of the catalyst is the conversion of methane to ethane and ethylene, as above, even higher hydrocarbons can be prepared depending on the pretreatment of the catalyst, and a higher degree of conversion can also be used. coupling hydrocarbons including methane and olefinic or paraffinic hydrocarbon hydrocarbons to form longer hydrocarbon hydrocarbons having, for example, 3 to 10 carbon atoms. The reaction is carried out in a reactor 10, the feed stream passing through the catalyst in the chamber 11, which is opened by the heating means 12, thereby controlling the temperature in the reactor and maintaining it at the desired level. Typically, the reactor 10 is equipped with a measurement and control device for pressure, temperature and flow using temperature control elements 15, temperature sensors 14, flowmeter 14a, and flowmeter 16a.

Inlet 17 into the reactor 10 is charged with methane, oxygen and steam, which is then passed through the catalyst in chamber 11. In the embodiment shown, methane is supplied from methane bomb 18, oxygen from oxygen tank 19 by the screw pump 20. The water is transferred to steam in line 21. In the process unit, methane, oxygen and steam can be supplied from conventional industrial sources. Since only the fraction of introduced hydrocarbon feed is converted to higher hydrocarbons, recirculation of the corresponding fraction from the reactor outlet is required, as shown in Fig. 2 by a dotted line 32 extending from outlet 23 to inlet A1 of reactor 10. . '<· /

The product discharged through the outlet 2g is introduced into the expander 24. The water is separated in the water tank 25. In the production unit 1, where it is necessary to separate the carbon oxides C0, due to the use of a catalyst having a selectivity of less than 100, a recirculating loop is included with a conventional washing machine for this purpose. The product is analyzed and monitored by analytical control devices, as shown in the illustrated embodiment, as a chromatographic unit 26 having a container 27 and a valve 28 for supplying a known calibration mixture 29. In operation, the catalyst is introduced into the reactor and activated as described above. In the operation of the reactor, two catalyst chambers 11 may be used to allow continuous operation in alternating chambers, meaning that the batch is processed in one chamber while the catalyst is filled into the second chamber and activated in the second chamber.

As mentioned above, the catalyst can also be activated prior to introduction into the chamber when the catalyst is activated, the temperature in the reactor is raised to 550 to 650 ° C, steam is generated by heating the tube 21 to a temperature of about 140 ° d and into the reactor at -

Methane, oxygen and steam are added. The composition of the charge, expressed in saline ratios of OH 2 / O 2 / QQ, may be 2/1/4 to b / 1/8, with 3 / / l / n, 5 being the optimal molar ratio. It reminds us that the process is below the methane and oxygen explosion limits.

The use of steam reduces the consumption of either oxygen and the ability to work at relatively low temperatures (known in the literature) using temperatures of 705 to 900 ° C, it is considered to be of great advantage to use the catalyst of the invention, but also to allow safe operation. The preferred feed rate is about 40 moles of methane per 1 g of catalyst per hour. the reaction shows the carbon material balance that carbon is absorbed for about three hours, on the catalyst, and FIG. 2 is the material balance graph versus time. the catalyst is long, the hydrocarbon yield is constant over a period of two days of operation, and small but permissible amounts of carbon oxides can form during preheating. develops as a pit gas phase reactions in the preheating zone and cannot be attributed to the " lower catalyst selectivity. A comparison of blank tests on inert ceramic granules and on the catalyst shows that the conversion of the methane gas to carbon dioxide is actually reduced. catalyst.

Figure 3 is a variation of the selectivity, conversion, and yield of proCa / h 1 / K - 2: 1: 0.1 catalyst since the temperature rises from 600 ° to 750 ° and then decreases again to 600 ° C. As can be seen, the selectivity is dramatically reduced from 100% to less than 10% and then slightly better than 30% when the temperature returns to 600 ° C.

The invention is illustrated by the following non-limiting examples. EXAMPLES Example 1 A catalyst comprising calcium and nickel oxides - 12 - was prepared in an atomic ratio of 2: 1 with a solution of nitrates by air drying, nitrate oxidation with oxides in air at 700 ° C and activation of the catalyst in oxygen at 680 ° C. 0 for 20 hours, the catalyst is fed into the reactor and allowed to pass through the methane, oxygen and water in a mole ratio of 5 to about 10 hours. 1! b, 5 at 600 ° C and ambient pressure, at a rate of 40 moles of methane per gram of catalyst per hour. The higher hydrocarbon selectivity in the product is about 80 at about 10? Methane conversion to yield 8 hydrocarbons of 2 and 3 carbon atoms. Example 2 A catalyst containing calcium oxides, nickel and potassium in an atomic ratio of 2: 1: 0.1 from a nitrate solution of 4 ** is prepared by drying the calcium and nickel nitrates in air, dissolving them into oxides in air at a temperature of 700 ° C, by adding potassium nitrate solution, re-drying and decomposing at room temperature. 700 ° C and activation of the catalyst in an oxygen stream at 600 ° C for 20 hours when the methane / oxygen / water mixture is passed in a molar ratio of 3: 1: 6.5 over this catalyst at 600 ° C and beyond at ambient pressure at 40 mol methane, 1 g of catalyst per hour, the selectivity for hydrocarbons having 2 and more carbon atoms in the product is 100% at a methane conversion of about 11 $ and yields hydrocarbons of two or more carbon atoms of 11%. V- •; g &amp; EXAMPLE 3 A catalyst containing calcium oxides, nickel and potassium in an atomic ratio of 4: 1: 0.1 is prepared as described in Example 2. This catalyst exhibits the same conversion of selectivity as that of Example 2. 15 - Example 4 A catalyst containing, calcium oxides, potassium nickel in an atomic immersion of 2: 1: 0.1, as described in Example 2, and activated in a 1-hour &lt; RTI ID = 0.0 &gt; 7GQ-C &lt; / RTI &gt; . While testing this catalyst for the oxidation coupling of methane under the conditions described in Example 1, selectivity of 100% to hydrocarbons with two and more carbon atoms is achieved and the methane conversion is only. 2 7 ’· The selectivity for hydrocarbons with 2 carbon atoms is ^ 2 ^ 2 and 2% for the hydrogen-3-a-carbon. The olefin / paraffin meter in hydrocarbons having 2 and more carbon atoms is 0.2. Example 5 The catalyst of Example 2 was prepared and activated in an oxygen stream at 660 ° C for 40 hours. Uses of use. of this catalyst for the oxidative coupling of methane as described in Example 1, selectivity of ICO-to-hydrocarbons having 2 or more carbon atoms is achieved, with methane conversion of 9.5 µg. carbon atoms are 66./ and C uhlíku uhlíkuod hydrocarbons of 4/3 carbon atoms / olefin / paraffin is 0.6.

It will be apparent to those skilled in the art that various variations are possible within the scope of the present invention.

Industrial. usability

Metal oxide composite catalyst allowing methane to ethane, ethylene and higher hydrocarbons at 600 ° C, in the presence of oxygen and steam of 60 to 100% over methane conversion

Claims (8)

- 14 - 3 h T 0 H E L H L L L I L I C I C I C - 'CD <. Π <r <J · Γ Γ Γ J c c c c S S ^ é J J J J J J J J J J J J J J J J J J J J J J J J J J J J J J J J J J Γ The catalyst according to claim 1, wherein the metal of the alkaline earth metal is selected from the group consisting of magnesium, calcium, strontium and barium. 3. Catalyst according to claim 1, characterized in that the transition metal is selected from the group consisting of iron, cobalt and nickel. 3. The catalyst according to claim 1, wherein the atomic ratio of the alkaline earth metal to the transition metal is about 2: 1 to about 4: 1 and the atomic ratio of the transition metal. metal to alkali metal is about 1: 0.0 5 to 10: 0.2. 6. The catalyst of claim 1 wherein the catalyst is activated by exposure to oxygen at elevated temperatures for 1 to 48 hours. 7. The catalyst of claim 6, wherein said catalyst is activated at a temperature of 700 ° C. 8. The catalyst of claim 1 wherein the catalyst is obtainable by mixing aqueous solutions of salts containing alkaline earth metal cations, transition metal, and alkali metal and the same anions, by heating the solutions in the presence of oxygen to the solvent, and to a solution thereof. by oxidizing said products of alkaline earth metal, transition metal and alkali metal. - 15 - '-9. "Catalyst according to claim 1, wherein the catalyst is nitrate or hydroxide. 10. Catalyst according to claim 1, wherein the catalyst is 3-e-t-1-m-, -a-t-ly-z-t-t It is applied to the granular and inert substrates. ,; Ί1. Catalyst according to claim. 1, characterized by o.i.r. It is pelletized. __ -! ' «· <· V '' · '' 1 't t i * J. p 12. Catalyst as claimed? characterized in that it consists of a mixture of calcium, nickel and potassium oxides . Catalyst according to Claim 12, characterized in that the molar ratio of calcium to nickel is about 2 to about 4 and the molar ratio of nickel to potassium is about 1: 0.05 to 1: 0.2. 14. A process for converting methane to paraffins, and olefins having 2 to 3 carbon atoms and to. 4 carbon atoms having a selectivity of approximately 80%, wherein the oxygen and vapor admixture of methane at 500 to 600 ° C under ambient pressure or up to 3450 kPa pressure is passed through the catalyst based on alkaline earth metal, transition metal and alkali metal oxide according to claims 1 to 13. 15. The method of claim 14, wherein the catalyst is a calcium oxide, nickel oxide and a potassium catalyst. 16. The process of claim 14 wherein the calcium oxide nickel oxide catalyst is an atomic ratio of about 2: 1: 0.1, oxidized in an oxygen stream at 700 DEG C. for 1 to 48 hours prior to use. for a conversion reaction. A process according to claim 14, characterized in that a catalyst is used for the base of magnesium oxide, iron oxide and sodium. Iš. A method according to claim 14, characterized in that the molar ratio of methane, oxygen and vapor is 2: 1: 4 to 5, 1, 8. the molar ratio of methane, oxygen and steam is about 3: 1 and 6.3 and the temperature is about 600 ° C.