Application date: January 26^th, 1955

Notice of the application and the issuing of the patent: January 26^th, 1961

Process for hydrogenation of carbon oxide using suspended iron, cobalt, and nickel catalysts

Applicants

Ruhrchemie Aktiengesellchaft
Oberhausen (Rheinland) – Holten

Dr. Walter Rottig and Walter Wischermann,
Oberhausen (Rheinland) – Sterkrade,
have been named as inventors

If carbon oxide hydrogenation using iron, cobalt or nickel catalysts is performed, using iron, cobalt, or nickel catalysts that are tightly installed in a reaction oven, then the catalysts used must be extracted in certain time intervals, when working with normal pressure. This measure is necessary because the activity of the catalyst quickly abates through the deposit of high-molecular hydrocarbons on the catalyst surface. (Compare USA patent 2,238,726). Synthesis-specific products are often used for extraction. With increased pressure, it is known that the discharge of the isolated high-molecular compounds deposited on the catalyst is accomplished without additional extraction during the synthesis.

The carbon oxide hydrogenation can also be carried out with catalysts that are suspended in liquids. The different applications of this synthesis are known under the names of “wet synthesis”, “sump phase synthesis”, “sludge synthesis”, “jiggling bed synthesis” etc.

For these processes, a particular procedure has already been described (compare French patent 873,645, or Italian patent 389,201). Subsequently, a part of the suspension fluid is removed in short intervals from the suspension, washed with alkali, and is then reintroduced. Through the alkali wash, the fatty acids that accrue during the reaction are removed from the drawn-off component. This measure results in a shift of the boiling point for carbon oxide hydrogenation within the formed hydrocarbons that becomes noticeable through a strong increase of the diesel oil component and practically complete disappearance of components with a boiling point > 320°C. An increase of the total yield itself does not occur.

Additional processes have been described in which low boiling hydrocarbons, for example, with a carbon count of 5 to 7, have been introduced into the reaction solution. However, these hydrocarbons quickly vaporize and serve merely to quickly carry off the reaction heat in the strongly exothermal process of the carbon oxide hydrogenation.

It has been determined that in carbon oxide hydrogenation using iron catalysts suspended in liquids, particularly precipitation catalysts, the originally applied suspension oil, which generally possesses a boiling point of between approximately 200° and 300° C, within a relatively short time is discharged together with the forming reaction products, which thereafter changes the balance in the fluid phase between predominantly high molecular reaction products, and relatively small quantities of low molecular synthesis products. Through the predominance of high-molecular components in the suspension oil, its solvent effect on the high molecular compounds present on, and in, the catalyst is relatively small.

These high molecular compounds on, and in, the catalyst lessen its activity and thus lessen the total yield of hydrocarbons as well.

It has been found that an activity reduction of the catalysts can be avoided, if one works in such a manner with the carbon oxide hydrogenation in fluid phase, using suspended cobalt, nickel, or ideally iron catalysts in the form of precipitation catalysts, or ideally sinter or melting catalysts, that to the liquid phase of the reaction mixture, at synthesis pressures in excess of 9 ata, ideally at 11 to 60 ata, larger quantities of hydrocarbon mixtures and / or post-processed products of the carbon oxide hydrogenation, that boil to over 50%, ideally to over 75% at 180° to 320°C, particularly at 200° to 260°C, are added, proportionally in certain time intervals, without interruption of the synthesis operation, and indeed concurrently with the synthesis gas, and ideally from the bottom of the reaction vessel. By the proportional addition of larger quantities of extraction fluid, time intervals of 4 to 48 hours, ideally 4 to 24 hours, between extractions are maintained.

For a particular execution form of the process, these synthesis-based products specified for extraction, consisting of hydrocarbons mixed with oxygen containing compounds, are drawn off at a certain point in the condensation under pressure, if required via a column, and are used for extraction.

Through the introduction of the extraction oil, the concentration of high molecular compounds in the liquid phase can be significantly reduced with a concurrent increase in the concentration of lower boiling point compounds, for example, those with a boiling range of approximately 320 to 380° C, above all, however, those with a boiling range between approximately 180 and 320°C. Thereby, the high-molecular compounds present on, and in, the catalysts are dissolved by the fluid phase and this causes a sustained activity regeneration of the catalyst. As a consequence of this regeneration a significantly longer catalyst lifetime and a higher CO + H₂ conversion with lower methane formation are achieved in spite of increased gas load.

The synthesis can be executed using extractions of this kind at temperatures approximately 30 to 50°C under those required for identical synthesis conditions without extraction.

The new procedure is applicable for carbon oxide hydrogenation, ideally under recovery of hydrocarbons, as well as for synthetic processes under recovery of predominately oxygen containing compounds or primary aliphatic amines or a mixture of these three components.

All carbon oxide and hydrogen containing gases that are manufactured in accordance with known processes, can be used as synthesis gases, where the CO: H₂ ratio can vary between approximately 2:1 and 1: 10. The CO + H₂ content of the synthesis gas can be between 30 and 100 volume percent.

By using synthesis-based products that consist of hydrocarbons in a mixture of oxygen containing compounds, for extraction, these can be drawn off by a so-called intermediate separator and fed into the reactor. This air-cooled intermediate separator is located, for example, between the reactor and the thermal exchangers of the synthesis operation. The product thus removed includes, not exclusively, the usual boiling range of a diesel oil fraction; rather, it still contains components of compounds with a boiling point above 320°C. In spite of the use of liquids with a broad, and up to now not usual, boiling range for extraction, it could be determined that the effects obtained through the extraction were in many cases at least as advantageous as those obtained by the use of diesel oil with a boiling range between 180° and 320°C. Extraction oils that have an excessive portion of low-molecular hydrocarbons, such as gas fractions, are poorly suited for extraction. It is also disadvantageous when too many hydrocarbons above the 320°C boiling point are present, because blockages of the pipes and fittings can occur through flaking off of soft and hard paraffin, particularly in the case of fluctuating temperatures. Furthermore, the extraction effect is strongly reduced through these high boiling point components.

The most advantageous extraction effect is achieved with a product that is drawn off directly behind the intermediate separator.

If so much reaction water condenses in the intermediate separator that a phase separation occurs, then the lower phase, which consists essentially of water, must be separated; otherwise, the activity of the catalyst will be lessened. If no phase separation has occurred, then the quantity of condensed reaction water is so minimal that damage to the catalyst through water still contained in the extraction oil does not occur. This water content of the extraction oil should not exceed 3 % of the weight and is particularly advantageous if under 1 %.

The presence of oxygen-containing, and/or nitrogen-containing compounds, even in amounts in excess of 10% does not disturb the process.

The temperature of the added extraction oil is insignificant with regard to the extraction effect. One can work with cold extraction oil, or extraction oil, ideally warmed to 30° to 80°C, however one should ideally use oils of the respective synthesis temperature.

According to the invention, brief additions of a larger amount of extraction oil added at certain repetitive time intervals serve for the extraction of the suspension of the catalyst. An interruption of the synthesis operation during the extraction is not provisioned. One may begin with the extractions during the startup period, or in the course of the synthesis operation. They are executed at intervals of 4 to 48 hours in such a manner that the extraction time amounts to less than 60 minutes, ideally less than 15 minutes.

In the course of longer operating periods a reduction of the conversion can occur under certain conditions. As soon as this conversion reduction is recognized, it is expedient to execute one or two extractions in rapid succession with large quantities of extraction oil within a short time. Through this measure, the catalyst surface will be completely regenerated and freed from small amounts of high-molecular products that, in spite of the procedure according to the invention, have collected on the catalyst surface.

PATENT CLAIMS

1.  Process for carbon oxide hydrogenation in fluid phase using suspended cobalt, nickel, or ideally iron catalysts, in the form of precipitation catalysts, ideally sinter or melting catalysts, wherein the fluid phase of the reaction mixture at synthesis pressure above 9 ata, ideally at 11 to 16 ata, proportionally in certain time intervals, larger amounts of hydrocarbon blends, and/or not further post-processed products of the carbon oxide hydrogenation that boil to over 50 %, ideally to over 75 % , at 180° to 320°C, particularly at 200° to 260°C, are added, without interruption of the synthesis operation, concurrently with the synthesis gas, ideally starting from the floor of the reaction vessel. 

2.  Process according to Claim 1, wherein the proportional addition of larger amounts of extraction fluid can be maintained in time intervals between the extractions, of between 4 to 48 hours, ideally 4 to 24 hours.

3.  Process according to Claims 1 and 2, wherein the synthesis-based products are used.

Documents used in consideration:

French patent claim no. 873 645; Italian patent claim no. 389 201

Older patents taken into consideration: German Patent no. 1017 151.