EP0030020B1 - Process for the obtention of low molecular weight hydrocarbons from high molecular weight hydrocarbons or from coal - Google Patents

Description

Process for producing lower molecular hydrocarbons from higher molecular hydrocarbons or from coal.

The invention relates to a method for producing lower molecular hydrocarbons from higher molecular hydrocarbons, in particular a method for liquefying coal.

Under high molecular weight hydrocarbons solid and liquid fossil energy raw materials, such as. B. understood coal, bitumen, mineral oil, tar sand or oil shale.

The lower their molecular weight, the more valuable these hydrocarbons are for consumption. That is why efforts are being made everywhere to obtain such lower molecular weights from naturally high molecular weight hydrocarbons. Typical of this are the efforts to economically liquefy the coal, such as, for. B. from DE-A-27 11 105 and DE-A-28 03 985 are known. Various process variants are currently being investigated, which differ in terms of pressure, temperature, quality of the coal used, choice of hydrogenation gases, design of the reaction procedure (process technology in the narrower sense) and in particular with regard to the catalysts used.

It is the object of the invention to favor the conversion of high molecular weight hydrocarbon mixtures into lower molecular ones by using auxiliaries in corresponding processes and thereby to achieve a higher added value due to the more favorable C: H ratios in the end products. In particular, the invention is intended to provide an improved process for liquefying coal.

To achieve this object, the use of guanidinium compounds as auxiliaries is proposed according to the invention in a method for obtaining relatively low molecular weight hydrocarbons from higher molecular weight hydrocarbons.

“Use of guanidinium compounds” means the use of only one guanidinium compound alone or the use of a combination of different guanidinium compounds. “Auxiliaries” here mean substances which, like catalysts, are added to the starting material to be converted in relatively small amounts, but, unlike catalysts, do not work solely through their presence, but rather when the corresponding process or the physical and / or chemical processes on which it is based are carried out Reaction changed or consumed.

It was recognized that the guanidinium compounds used according to the invention as auxiliaries in the usual treatment of the hydrocarbons to be reacted under pressure and elevated temperature have the pronounced effect of stabilizing and / or breaking up the binding forces in the high molecular weight hydrocarbons and thereby the processes in the direction of enrichment to steer of lighter, lower molecular weight hydrocarbons. Here binding forces are to be understood in a broad sense; they can be physical, chemical and / or as transitional forms between the two existing binding forces. The stabilization or loosening up to the complete breakdown of the binding forces immediately facilitates the initially outlined generation of low molecular weight hydrocarbons. In addition, the solubility of the hydrocarbons treated is increased by the guanidinium compounds used according to the invention, which obviously also directly eases the recovery process. For example, in coal liquefaction, in which the coal is first suspended in an oil and a slurry is formed, the guanidinium compounds promote the release and / or dissolution of hydrocarbon mass and increase the conversion, so that fewer cycles are necessary overall. The proportion of coal released or dissolved can be up to 30% by weight of the coal supplied, in contrast to 1 or 2% in many known processes.

Within the scope of the invention, the use of the guanidinium compounds in bulk or in dissolved form is provided, e.g. dissolved in water in the case of guanidinium carbonate. The total amounts of guanidinium compounds used here are up to 10% by weight and are preferably between 0.1 and 3% by weight, based in each case on the starting material. If the guanidinium compounds are used in dissolved form, up to 10% by weight, preferably between 0.01 and 3% by weight, can be used, in each case based on the solvent. In detail, the amount used will be determined from an economic point of view.

From the point of view of economy, guanidinium carbonate is particularly suitable as an adjuvant because it is the cheapest of all guanidinium compounds. It also has other important advantages. Guanidinium carbonate is neither corrosive nor harmful to the environment, and its decay is very easy to control and can therefore be used in a targeted manner. In addition, the basic character of the carbonate part gives the guanidinium carbonate an additional reactivity which can be used advantageously in reactions with acidic groups. An interesting side effect can thus be generated by the fact that, due to the acidic nature of the phenolic and thiophenolic groups of a high molecular weight hydrocarbon mixture of fossil origin, it reacts with guanidinium carbonate to form carbon dioxide “in situ” and thus to loosening “bubbles”. Effect »is coming.

To strengthen the interaction between the treated hydrocarbon mixture and guanidinium compounds, it may be advisable to combine the guanidinium carbonate in combination with other guanidinium compounds, in particular in conjunction with carboxylic acids, preferably fatty acid guanidinium salts such as palmitates, oleates or stearates, and / or together use with guanidinium phenolates. It is not absolutely necessary to produce the corresponding guanidinium compounds in exact stoichiometric ratios and then to add them to the corresponding reaction mixture in exact weight ratios. Rather, the composition and dosage of the optimal formulation are always based on economic principles. This is an essential advantage of the invention, namely that the amounts and mixing ratios of the guanidinium compounds used in accordance with the invention can be varied within a wide range primarily according to economic considerations without sacrificing efficiency.

A further, very economical use lends itself to the fact that the guanidinium carbonate is used in excess or in excess with added acids or free acids already present in the hydrocarbon mixture, such as carboxylic acids, in particular fatty acids, sulfonic acids and / or phenols, or also with can use acidic alcohols. The weight ratio of guanidinium carbonate to free acids can be between 0.1: 1 and 10: 1. When guanidinium carbonate is used in deficit, a mixture of unreacted starting chemical and corresponding guanidinium compound is formed, which then acts as an auxiliary according to the invention. If guanidinium carbonate is used in excess, a mixture of guanidinium carbonate and corresponding guanidinium compound is formed, which acts accordingly. Maximum economy is achieved when the above-mentioned raw chemicals are waste or residue products. The waste fatty acids or the crude tar acids which are obtained in large quantities are particularly suitable as extremely economical starting products for reaction with guanidinium carbonate.

Regardless of the various configurations of the guanidinium compounds used according to the invention, the invention essentially includes the fact that guanidinium compounds have a fragmenting effect on high-molecular hydrocarbon mixtures due to the chemical structure of the guanidinium cation and thereby favor the extraction of lower molecular hydrocarbons. In addition and overlapping, there is also an effect of the guanidinium compound which promotes the solubility of the hydrocarbon mixtures.

A particularly preferred field of application of the invention is the processing of solid hydrocarbons, and here in particular the liquefaction or gasification of coal, including those gasification processes in which the coal is reacted in aqueous solution.

Here, the use of guanidinium compounds as auxiliary material makes it possible to increase the economic efficiency. The guanidinium compounds used according to the invention essentially have the effect that they facilitate the desired breaking of binding forces within the molecular lattice of the coal and accelerate the subsequent saturation of the breaking points with hydrogen in the molecular reaction process. The advantage is achieved that the use of catalysts envisaged in most of the process variants is reduced or even made completely unnecessary, and that it is also possible to use at least partially cheaper hydrogenation gases for the liquefaction or gasification of the coal instead of pure molecular hydrogen use. Both relieve the known methods directly in terms of costs.

The guanidinium compounds used according to the invention decompose at elevated temperatures to give highly reactive decomposition products which, in turn, can favor the hydrogenation reaction in a very desirable manner. This effect is particularly pronounced with guanidinium carbonate. The guanidinium carbonate from those previously used or the guanidinium carbonate is superior to the chloride, sulfate or nitrate that is also considered in this respect, for reasons of corrosion prevention, environmental protection and more controllable decay which have already been mentioned. In addition, as already stated, it is particularly inexpensive.

In principle, the guanidinium carbonate can also be used as an auxiliary in coal liquefaction alone. However, use in conjunction with fatty acid guanidinium salts is particularly advantageous here. These, in particular stearates, improve the interaction of the guanidinium carbonate with the hydrocarbon mixture in the sense of a dissolving aid, especially in the range of low temperatures, for example below 150 ° C. This advantageously contributes to the stabilization of the coal-rubbing oil suspension processed during coal liquefaction and directs the heterogeneous hydrogen / coal reaction more towards a homogeneous reaction.

The ratio of guanidinium carbonate to the guanidinium compound (s), which acts as a dissolving aid, depends on the particular liquefaction process and the properties of the starting materials. The preferred ratio of guanidinium carbonate to fatty acid guanidinium salt, in particular stearate, is between 0.3: 1 and 3: 1, with approximately 3: 1 being very particularly preferred.

In general, the guanidinium compounds used according to the invention become the starting materials at the entry of the liquefaction or gasification process, preferably in substance. For example, the addition can be carried out together with any catalysts still used. A suitable addition point in the coal liquefaction processes according to DE-A-28 03 985 and DE-A-27 11 105 is particularly suitable for the invention, which is described in DE-A with regard to its other function and its arrangement explained mixing container 2.

A suspension of the finely ground coal to be treated is provided in this mixing container. In the known processes, the suspension arrives directly in a reaction zone in which low molecular weight, liquid hydrocarbons are produced by treating the suspension under elevated pressure of typically 10 to 300 bar and at an elevated reaction temperature of typically 250 to 500 ° C.

For the purposes of the invention, it has proven to be advantageous, in deviation from this known procedure for the treatment in the reaction zone, to preheat the suspension, in which the suspension already mixed with guanidinium compound (s) and possibly already under increased pressure is placed on a suspension Intermediate temperature, which is lower than the reaction temperature, heated and held at this intermediate temperature for 1 to 30 min before the heating to the reaction temperature takes place. This preheating exploits the effect of the guanidinium compounds to the greatest extent and the conversion in the subsequent actual hydrogenation treatment is particularly high.

Overall, the invention achieves that under the most varied reaction conditions there is an increased release and / or dissolution of hydrocarbons and, accordingly, an increased conversion. This also makes it possible to carry out the hydrogenation under milder conditions than were indicated in the known processes to date. Here is the following

example

200 g of flame coal, 300 g of coal oil (boiling point above 200 ° C.) and 3 g of guanidinium stearate (= 1.5% by weight, based on the dry weight of the flame coal) were placed in a two-liter autoclave ) mixed together under 30 bar Ng pressure by intensive stirring. The mixture was then heated to an intermediate temperature of 180 ° C. and held at this temperature for 30 minutes. The mixture was then heated to a reaction temperature of 200 ° C. and again held at this temperature for 30 min. Two further tests were carried out under the same conditions with a reaction temperature of 250 ° C and 300 ° C.

In a second series of experiments from three experiments, 3 g guanidinium carbonate was used instead of 3 g guanidinium stearate. All other conditions were the same as previously described.

Finally, for comparison purposes, a third series of tests was carried out with three tests, in which work was carried out without the addition of guanidinium compounds. All other conditions were again the same as previously described.

The reaction mixtures obtained in the various experiments were worked up in 30 g portions. The portions were washed out under reflux of 100 ml of tetrahydrofuran (THF). After filtration, the degree of dissolution of the coal was determined on the basis of the analytically measured enrichment of the ash content of the residue coal. The following were found

Data

It is evident that the increased dissolution shown in the series of experiments above leads to an increased conversion when the corresponding reaction mixture is hydrogenated. Carrying out the experiment under nitrogen pressure makes it possible to demonstrate the isolated action of the guanidinium compound. If carried out in the presence of hydrogen, its additional, similar effect would partially mask the specific contribution of the guanidinium compound.

Claims (10)

1. A process for producing lower-molecular-weight hydrocarbons from higher-molecular-weight hydrocarbons, especially a process for the liquefaction of coal, characterized by the use of at least one guanidinium compound as auxiliary agent.

2. A process according to claim 1, characterized by the use of the guanidinium compounds in a total amount of up to 10 weight per cent, preferably from 0.1 to 3 weight per cent, based on the weight of the hydrocarbons used as starting material.

3. A process according to claim 1 or 2, characterized by the use of guanidinium carbonate.

4. A process according to claim 1 or 2, characterized by the use of guanidinium carbonate in combination with at least one substance selected from the group consisting of carboxylic acid guanidinium salts, guanidinium-phenolate, guanidinium-sulfonate, guanidinium-alcoholate.

5. A process according to claim 4, characterized by the use of guanidinium carbonate in combination with fatty acid guanidinium salts.

6. A process according to claim 4, characterized by the use of guanidinium carbonate in combination with guanidinium phenolates.

7. A process according to claim 4, 5 or 6, characterized by the use of the guanidinium carbonate in combination with further guanidinium compounds in a weight ratio of guanidinium carbonate to further guanidinium compounds from 0,3 : 1 to 3 : 1.

8. A process according to claim 1 or 2, characterized by the use of guanidinium carbonate in a mixture with at least one substance selected from the group consisting of carboxylic acid, phenol, sulfonic acid, alcohol.

9. A process according to any one of claims 1 to 8, where-in a suspension of solid higher-molecular-weight hydrocarbons is heated to an elevated reaction temperature under elevated pressure, characterized in that the suspension with at least one guanidinium compound being added is heated to an intermediate temperature being lower than the reaction temperature, is held at the intermediate temperature for a time in the range 1 to 30 min, and is thereafter heated to the reaction temperature.

10. A process according to claim 9 for the liquefaction of coal, characterized in that an intermediate temperature in the range 100 to 300 °C, preferably of about 200 °C, is applied.