DE1060854B - Process for the production of hydrocarbons from carbon oxide and water vapor on cobalt catalysts - Google Patents

Description

Process for the production of hydrocarbons from carbon monoxide and water vapor on cobalt catalysts Addition to Patent 1034164 The invention relates to a further development of the method according to patent 1 034 164 for the production of longer-chain, of aliphatic compounds, especially of hydrocarbons, through the conversion of gas mixtures consisting entirely or partially of carbon oxide and water vapor in the presence of cobalt catalysts.

According to the process of the main patent, the cobalt catalyst, the may contain activators and / or carriers in addition to cobalt, without pretreatment with carbon monoxide or carbon monoxide-hydrogen mixtures at temperatures between 150 and 2500 C and pressures between 1 and 200 at with a synthesis gas from carbon oxide and water vapor is applied, 0.3 to 2.8 parts of carbon oxide per part of water vapor contains.

There is no information about an optimal range in the main patent the flow rate of the synthesis gas or the optimal gas loading of the Contain catalyst; according to the current state of knowledge about heterogeneous catalytic Gas reactions, in particular the related carbon dioxide hydrogenation according to Fischer and Tropsch had to expect that the space velocity (volume of synthetic gas [NTP] per volume of catalyst and hour) also in the case of the carbon oxide-water vapor reaction can be changed in wide areas. In principle, this is also the case. Space velocity and conversion are roughly inversely proportional, when the gas load is doubled sales fell by about half. The so-called space-time yield (yield of condensed hydrocarbons and / or oxygen-containing products per catalyst space and time unit) is therefore independent of the gas load in a first approximation and constant. For the yield per catalyst space and unit of time, it is in this Case no matter whether the synthesis with high gas loading and small conversion per single gas throughput through the catalyst layer or with correspondingly lower Gas load and therefor high turnover per gas passage is operated. In the first case is the arrangement of several reaction stages connected in series or the application a gas cycle is required. Such methods are state of the art known.

In the case of some catalysts, the space-time yield increases with increasing Gas pollution even on. In this case, the reaction is carried out with a high gas load and therefore preferable to low sales with a single gas passage.

As far as the conditions correspond to the expectations, how they are based on experience with older, well-known processes of hydrocarbon synthesis could be derived. For such catalysts where the space-time yield of condensed hydrocarbons remains constant with increasing gas load or increases, the process is sufficiently described in the main patent.

Information about the gas load is not necessary, as this depends on the procedural implementation of the synthesis according to known points of view and can be chosen arbitrarily without inventive effort.

Surprisingly, however, it has now been shown that this freedom with regard to the gas pollution is by no means given in all cases. At a Range of catalysts, in particular supported cobalt catalysts containing promoters, it is for the achievement of optimal yields of usable, condensed products indispensable to regulate the space velocity in such a way that already at one time Gas passage between about 50 and 95 to 980/0 of the synthesis gas are implemented. The space-time yield goes both below and above the optimum range of condensed products.

It is well known that carbon monoxide and water vapor can act in different ways react with each other. The main competing reactions are: (1) Synthesis reaction 3 C O + H2 H, O = (- CH, -) f2CO, (2) water gas reaction .... CO t H2 O = C O2 + H2 (3) Methane formation 4 C O + 2 H2 O = CH4 + 3 C O2 [The synthesis reaction describes the formation of higher hydrocarbons or corresponding oxygen-containing ones Derivatives, (- C H2 -) means a link in the hydrocarbon chain.] The through the Technique of the main patent achieved technical progress lies in the first place therein, the carbon oxide with previously unattained selectivity after reaction (1) to convert to higher hydrocarbons; on the other hand, any favoring of the Reactions (2) or (3) result in a reduction in this yield.

When using the catalysts mentioned leads to an increase in Space velocity above that defined by a conversion of about 50 to 98 ovo Range to favor the water gas reaction if the value falls below the In the area, methane formation is gaining increasing influence. According to the invention therefore a space velocity is maintained at which the carbon oxide is already at one time Passing through the catalyst layer reacts to about 50 to 980/0; Then it will be almost no hydrogen or methane formed and the carbon oxide practically exclusively converted to higher hydrocarbons after the synthesis reaction (1).

Naturally, it is not possible to find the optimum range of space velocity differently than to be defined by the turnover with a single gas passage. The absolute values the space velocities corresponding to a certain conversion are extreme to a large extent on the other operating conditions such as pressure, temperature, gas composition as well as the type and current operating condition of the catalytic converter. This is not unlike almost all known heterogeneous catalytic gas reactions. Depending on Combination of these conditions can produce the space velocity required for the same conversion (Gas load) differ by orders of magnitude. Since the invention is not related to any The combination of these conditions is also a direct, numerical one Limiting the optimum range of space velocity is pointless.

Rather, it becomes clear and sharp through the given sales range limited from 50 to 980/0.

For any particular combination of the reaction conditions mentioned is a coal only at a certain, small range of space velocity oxide turnover from 50 to 980/0 possible. This range can be set once for RG = 10 and once for RG = 100, sometimes even RG = 1000, but it usually won't be any more than about + 200/0 sweep over this absolute value.

The essential content of the invention is not to be numerical to adhere to the defined space velocity, but the space velocity depending on to regulate the other operating conditions so that a numerically defined area the carbon oxide conversion (50 to 980/0) is not fallen below or exceeded. That is possible in any case, which is necessary for given other operating conditions Space velocity range can basically be determined by a few measurements and conveniently adhered to during the synthesis.

The synthesis conditions delimited in the main patent with regard to Temperature (150 to 2500 C, preferably 180 to 2500 C), pressure (1 to 200 ata) and synthesis gas composition (ratio of carbon oxide to water vapor between 0.3: 1 and 2.8: 1) as well as the information about the preferred use if possible Synthesis gases rich in steam and reactivation by steam naturally apply also for the process modification described here.

Example a) Synthesis with a total carbon dioxide conversion in the range of the invention (85.80 / 0) Via a hydrogen-reduced Co-Th O2 Mg O-kieselguhr catalyst At a pressure of 10 ata and a temperature of 2280 C, a carbon oxide-water vapor mixture was created with a volume ratio of 1.5 CO: 1 H2O and a nitrogen content of 5.90 / 0 directed.

After about 200 hours of operation, the total carbon dioxide conversion was at a space velocity of about 30 (RG = volume of synthesis gas [NTP] per volume Catalyst and hour) 85.80 / 0, the degree of liquefaction 98.90 / 0. The proportions of the Competing reactions in the total carbon monoxide turnover were as follows: (1) Synthesis reaction to Cs + KW ...... 97.60 / o (203 g / Nm8 CO) (2) water gas reaction ...... .... 1.40 / 0 (0.9 g / Nm3 C O) (3) Methane formation. ..... .......... 1.0% (1.8 g / Nm3CO) 100.00 / o The carbon oxide was thus worked up almost completely to form higher hydrocarbons. b) Synthesis when the total carbon dioxide conversion is too high (1000 / X) A reduction in the Space velocity with otherwise unchanged operating conditions from 30 to about 10 led to an increase in the total conversion of carbon monoxide to 1000 / o, i.e. in an area above half of the range to be maintained according to the invention from 50 to 980/0. This exceeding of the upper limit of the total turnover permissible according to the invention led to an increase in the proportion of methane formation in total sales of 1.0 24.30 / 0, i.e. about 24 times as much; the proportion of the water gas reaction went slightly return. The higher hydrocarbon yield decreased to about 153 g / Nm3 C O.

(1) Synthesis reaction ... ... 74.6% (approx. 153 g / Nm3 C O) (2) water gas reaction .. ..... 1.1% (approx. 0.7 g / Nm3C O) (3) methane formation. . . 24.3% (about 44 g / Nm3C O) The synthesis with sales over 980/0 is technically considerably less favorable than an inven- Proper process management, for example in accordance with section aj c) Synthesis when the total conversion of carbon dioxide is too low (240/0) When the Space velocity from 30 to 150, the total CO conversion fell to 240/0, the shares the secondary reactions in the total turnover, especially the water gas reaction, increased a multiple.

(1) Synthesis reaction ..... . . . . . . . 76.60 / 0 (about 159 g / Nm3 CO) (2) water gas reaction. ..... 14.70 / 0 (approx. 9 g / Nm3 CO) (3) Methane formation. . ....... 8.70 / 0 (about 16g / Nm3CO) Such a mode of operation is also the one according to the invention Process management according to section a) clearly inferior.

Under different operating conditions (normal pressure, different gas composition etc.) the absolute values are different, the dependence of the side reactions is fundamental but the same in terms of space velocity. The best space-time yields will be achieved with sales between 50 and 980/0.

It should again be expressly pointed out that this after the Invention achievable advantages not generally when applied to the method of the main patent. With a number of cobalt catalysts, the reaction can just like in older hydrocarbon syntheses with conversions outside of the above defined area, so especially with a small conversion per gas passage carried out without affecting the space-time yield by increasing the side reactions going back. For the time being it cannot be predicted on the basis of theoretical considerations, in what way a certain catalyst must be operated. Practically can however, this can be determined by simple preliminary tests. The procedure according to this Invention Particularly in the case of promoter-containing carrier contacts, the Fischer-Tropsch catalyst type is used significant.

Claims (1)

PATENT CLAIM: Process for the production of hydrocarbons from carbon oxide and water vapor to preferably activators and / or carriers containing cobalt catalysts of a known type at temperatures between 150 and 2500 C, pressures between 1 and 200 ata using synthesis gas mixtures with 0.3 to 2.8 parts of carbon oxide per part of water vapor according to patent 1034164, thereby characterized in that the synthesis gas with one of the other operating conditions in such a way adjusted space velocity is passed over the catalyst that the total carbon dioxide conversion even with a single gas passage is between 50 and 980/0. ~~~~~~~~ In References considered: U.S. Patent No. 2,579,663.