US3502564A - Hydroprocessing of coal - Google Patents

Description

United States Patent 3,502,564 HYDROPROCESSING 0F COAL Russell L. Hodgson, Walnut Creek, Calif., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Nov. 28, 1967, Ser. No. 686,345 Int. Cl. Cl0g [/06 US. Cl. 208--9 6 Claims ABSTRACT OF THE DISCLOSURE The in situ preparation of a hydrogenation-liquefication catalyst impregnated on the coal results in significant improvement in catalytic activity. Metal naphthenates and sulfides are particularly appropriate catalysts for in situ preparation.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for the hydrogenation-liquefication of coal to liquid hydrocarbon oils. More particularly it relates to an improved process wherein a hydrogenation catalyst is prepared on the coal itself, i.e. in situ.

Description of the prior art A practical process for converting coal to liquid fuels as a means of utilizing the extensive energy reserves in the worlds coal deposits has been a much sought after goal since it was first demonstrated nearly 60 years ago that coal could be hydrogenated to liquid products. Particularly large research efforts were carried out in Germany prior to and during World War H and in the United States by the Bureau of Mines following the war. The number of publications and patents in this area is astronomical, as witnessed by a Bureau of Mines bibliography compiled at the outset of their efforts in the late 1940s containing over 6,000 entries. [1. L. Wiley and H. C. Anderson, Bureau Mines Bull. 485: Part I (1950); Part II (1951); Part III (1952)]. Work on coal hydrogenation has not waned in recent years; in fact, it is approaching fruition in the form of economical processes for converting coal into refinable liquid products.

Several unique problems associated with the conversion of coal to refinable liquid products result from its chemical and physical nature. Not only is the starting raw material a solid, but even if complete conversion of the organic matter were possible, an appreciable amount of inorganic ash remains. The amounts of nitrogen, sulfur, and especially oxygen which must be removed are far in excess of those normally encountered in processing even the most refractory heavy petroleum oils. Finally, the condensed nature of the coal molecule results in a low hydrogen/carbon ratio, necessitating the addition of large amounts of hydrogen.

In general, processes developed for conversion of coals into liquid products require that the coal is first broken down to a liquid state which can be processed further by more or less conventional petroleum refining techniques such as hydrocracking, reforming, etc. While the first step may be merely a thermal treatment, there are significant advantages for catalytic hydrogenative decomposition or liquefication. However, the most effective means known require very high pressures in the range of 2000 to 6000 psi. and temperatures in the range of 500 C. Thus, the conversion of coal is generally conducted in a multistage process in which the first stage often involves hydrogenation-liquefication followed by extraction of the resulting middle oils. A similar process is Gorin, US. 3,143,489

ice" Numerous catalysts for the hydrogenation reactionv have been proposed. These are added to the coal in various ways. One method is to hydrogenate coal extract in an ebulating bed of the catalyst. Another method is to tumble powdered coal with the catalyst. impregnation of coal with a catalyst has also been proposed and is an effective method. In impregnation, the coal is slurried with a catalyst which is dissolved or dispersed in aliquid medium and the liquid removed by evaporation, etc. Thus efficient dispersion of the catalysts, necessarily used in small amounts, with the coal is effected. Despite the multitude of suggestions there is still great incentiveto improve activity for the hydrogenation so as to obtain conversion at lower temperatures and pressures.

Catalysts which have been found effective are metal compounds, particularly metal halides and metal sulfides.

. Another class of catalysts are metal naphthenates, some of which are highly active. Naphthenates also have the advantage of being hydrocarbon soluble, allowing the use of a hydrocarbon impregnation medium and thus better contact and dispersion.

SUMMARY OF THE INVENTION It has now been discovered that preparation of the catalytic compounds, in situ, results in far more effective catalytic action than mere impregnation with the final {catalytic compound. By in situ preparation it is meant the formation, from ionic species and components of the desired catalytic chemical compound in admixture with the coal, i.e. after impregnation of the coal with one component.

In broad aspect, the invention is a process for the hydrogenation of coal wherein a hydrogenation catalyst is formed on coal in situ by impregnation of the coal with a component of the desired catalytic compound followed by subsequent conversion to a desired catalytic form of the metal. For example powdered coal is impregnated with a metal salt which is converted to the metal sulfide.

In a preferred embodiment of the invention, the process is effected with a catalyst selected from metal sulfides and metal naphthenates which are prepared in situ on the coal.

Surprisingly, it has been discovered that the effectiveness of a metal sulfide or naphthenate catalyst is greatly increased if the coal is first impregnated with a metal salt which is subsequently converted, in its dispersed state, to the corresponding sulfide or naphthenate. Particularly impressive are some of the in situ prepared sulfided metal naphthenate catalysts. The effectiveness significantly surpasses that of a single step impregnation of the catalytic compound itself.

In an embodiment of the invention powdered coal is impregnated with a siutable solution of a metallic salt of the hydrogenative metal, e.g. molybdenum chloride, the solvent removed and the salt then sulfided by an appropriate sulfur compound which either reacts with, or decomposes to a form which can react with the metal salt dispersed on the catalyst. Hydrogen sulfide is a convenient and especially suitable sulfiding medium. This embodiment has the additional advantage of allowing impregnation of catalytic compound such as metal sulfides which because of their insolubility cannot be impregnated directly on the catalyst. Heretofore insoluble compounds could only be incorporated by suspension.

Hydrogenation after impregnation may be accomplished by various means known in the art. In a continuous hydrogenation process, the powdered catalystimpregnated coal is generally formed into a paste with a heavy hydrocarbon oil, e.g. a cycle oil and passed into a hydrogenation zone. Any other method of continuous or batch hydrogenation may be used for the coal impregnated according to the inventioneither batch or continuous with or without a solvent. The hydrogenation may be carried out over a wide range of conditions depending upon the catalyst used, the type of coal being processed and desired degree of conversion. With coal impregnated with catalysts prepared in situ by the method of the invention; in general, lower temperatures and hydrogen pressures are required.

Temperatures in the range of ZOO-600 C. and hydrogen pressures from 500-3000 p.s.i.g. may be used. With conventional impregnations, i.e. the coal being impregnated with the catalytic compound itself, temperatures in excess of 500 C. are usually employed to eflFect substantial coal conversion at hydrogen pressure in the range of 2500 to 3000 p.s.i.g. With coal impregnated with catalysts formed in situ, hydrogenation can generally be effected at lower temperatures, in the range of 350-450" C. and at hydrogen pressures in the range of 1000-2000 p.s.i.g.

It has also been found that successive hydrogenations are advantageous to increase conversion, preferably without intermediate impregnation of additional catalyst. With coal impregnated with catalyst prepared in situ, a series of hydrogenations of successive extractive residues leads to a significant increase in conversion.

Any hydrogenation metal salt which can be converted to metal sulfides and/ or naphthenates are suitable for the practice of the invention. Nickel, tin, molybdenum, cobalt, iron and vanadium salts are especially preferred, particularly the halogen salts of these metals.

The process of the invention may be effectively carried out for the hydrogenation of any type of coal as for example, bituminous, subbituminous or lignite coal. The coal is preferably ground or pulverized into a powder to increase the efiiciency of impregnation.

Any suitable solvent may be used as a carrier for the impregnate, water being of course a logical choice in many instances. However, a lower boiling solvent which can be easily recovered is desirable in many applications. The requirements are solubility of the impregnate in the solvent and non reactivity of the solvent with the coal. For example, ether has proved a particularly suitable solvent for impregnation of such salts as molybdenum chloride. The concentration of the impregnate in the solvent is not critical. It should be as high as possible on the one hand to minimize solvent requirements and recovery and on the other hand not too high to impair the dispersion or to render the physical properties of the solution unmanageable. Use of appropriate concentrations within these broad limits is within the skill of those in the art.

When the catalyst is converted, in situ, to the sulfide, any sulfur compound which gives the sulfide compound, i.e. which reacts with the impregnated metal salt is suitable. Hydrogen sulfide is preferred. Again concentration is not critical and any available hydrogen sulfide containing gas may be used, as, for example, hydrogen sulfide oif-gas from refinery streams are appropriate. Relatively pure hydrogen sulfide may, of course, be used. Elevated temperatures are desirable for sulfiding, for example, temperatures in the range of 200-500" C. are suitable. In general, sufficient sulfur should be added to convert substantially all the metal to the sulfide form.

Sulfiding may be conducted in the same reactor vessel as the hydrogenation reaction or in a separate sulfiding reactor. In one aspect of the invention the catalyst can be impregnated with a metal salt, as for example, molybdenum chlorides, the solvent removed and the impregnated coal passed to a suitable reactor capable of high pressure operation where it is sulfided and subsequently hydrogenated. Sulfiding and hydrogenation can be carried out in separate zones of the same continuous reactor, sulfiding preceding hydrogenation.

Metal naphthenates are known to be very effective hydrogenation catalysts. These are conventionally incorporated with the coal, by impregnation of the preformed metal naphthenate, e.g. cobalt naphthenate. In the process according to the invention significant catalytic enhancement results if the metal naphthenate is formed on the coal by impregnation of the coal either with the metal ion or the naphthenate ion followed by conversion of the impregnated species to the metal naphthenate. For example cobalt naphthenate can be prepared by impregnation of powdered coal with naphthenic acid and then contacted with a cobalt halide salt to form cobalt naphthenate. It is especially preferred to further react the metal naphthenate with a sulfur compound such as H S. The exact nature of the resulting catalytic compound is not known but the results are striking as will be illustrated in the examples.

The following examples serve to illustrate but are not to be considered limiting the invention.

EXAMPLE I A series of experiments were made on the hydrogenation-liquification of Illinois No. 6 coal. Representative analysis of this coal is shown in Table I.

Table I Elemental analysis (percent w.): 1 Illinois No. 6 coal Carbon 78.9 Hydrogen 5.4 Nitrogen l.5 Sulfur 4.3 Oxygen 9.9 H/C (atomic ratio) 0.8 Moisture (percent w.) l0.9 Ash (percent w.) 13.3

1 Analysis on a moistnre-and-ush-free (MAF) basis.

To illustrate the effectiveness of the in situ preparation of metal sulfide catalysts according to the process of the invention, samples of powdered coal were impregnated with MoCl which was converted to the sulfide form. The powdered coal was impregnated from an ether solution of the MoCl the ether being subsequently removed by evaporation.

One sample was simply mixed with MoS for comparison. MoS could not be impregnated in the conventional means because of its insolubility. The coal with incorporated catalyst was placed in an autoclave reactor at 400 C. for one hour under hydrogen pressure maintained at 1400-1500 p.s.i.g.

After hydrogenation the products were first collected by venting the reactor at 200 C. to obtain gases, liquids boiling up to 200 C., and water. Next the residue was extracted for /2 hour with each of three portions of refiuxing benzene and water followed by a 24 hour Soxhlet extraction with methyl ethyl ketone. The extent of reaction was determined both from the recovered products and from the loss in weight of the coal and is reported on a moisture-and-ash-free (MAF) basis in terms of solubilization and conversion, defined as follows:

Extractable products Conversion (percent w. MAF) Coal fed Recovered residue Coal fed The results are shown in Table II.

TABLE II Solubilization, Conversion, percent w. percent w. Run N 0. Catalyst MAF MAF 3-1 1 2% MOS 32 34 59 -64 79 as 1% M0015 60 b5 A-5 1% M0015 sulfided 76 82 A-6 0.1% M0015 30 47 A-7 0.1% M0015 sulfided 52 L54 1 MoS mixed with powdered coal. 2 MoCl was impregnated from an other solution.

These results clearly show the eifett of in situ preparation of sulfide catalysts. In every case the solubilization and conversion was markedly increased by in situ sulfiding.

It should be noted that the conditions are very mild by conventional standards. While a number of catalysts give greater solubilization conversion at 500 C. and 3000 psi. H pressure than the present results, the severe conditions are serious detriments to the commercial feasibility of the process and the increased conversion at the mild conditions used is a significant achievement.

It is also demonstrated in this example that catalyst in very low concentration, e.g. 0.1% w. are eifective when incorporated into the coal in situ.

EXAMPLE II Additional experiments were made by impregnating powdered Illinois No. 6 coal with various salts which were converted to the sulfide in the same way as described in Example I. Conditions for hydrogenation were also the same as described in Example I.

The results are shown in Table III.

The enhancement in catalytic effectiveness is clearly evident resulting in the case of sulfided (NH Mo O in nearly triple the solubilization and conversion over thermal hydrogenation without catalyst but otherwise under the same conditions.

EXAMPLE III "Elfective impregnated catalysts are the metal naphthenates. These are of commercial interest because of the availability of naphthenic acids in crude oil. These acids are currently removed from the oil and frequently disposed of as fuel. Several experiments with both nickel and cobalt naphthenates were carried out with results being shown in Table IV. The conditions were the same as in Example I. Impregnation with naphthenic acid itself gave only a slight increase in reaction over thermal treatment without catalyst. The in situ preparation of nickel naphthenate at a controlled pH was more eifective with both the solubilization and conversion approaching 40%. Cobalt naphthenate, previously prepared, as a 6% metal-containing mixture was impregnatedto the extent of 2% w. (0.1% w. Co) to give solubilization and conversion of 35-40%. Sulfiding of this previously prepared n-aphthenate material after impregnation did not affect the results. The preparation of cobalt naphthenate in situ from naphthenic acid and cobalt sulfate gave improved results, the solubilization and conversion being about 45%. When this naphthenate 6 was sulfided, the coal solubilization and conversion increased to again illustrating the advantage of sulfiding even the naphthenate catalyst prepared in situ.

I claim as my invention:

1. A process for hydrogenation of coal comprising sequentially impregnating coal with a solution containing ions of a metal, the sulfide or naphthenate of which have activity as a hydrogenation catalyst, and with a compound that reacts with the ions to form the metal sulfide or naphthenate in situ, contacting the resultant mixture with hydrogen at elevated temperature and pressure and recovering a liquid product therefrom.

2. The process of claim 1 wherein said compound that reacts with the ions is hydrogen sulfide.

3. The process of claim -1 wherein said compound that reacts with the ions is hydrogen naphenate.

4. The process of claim 1 wherein the metal is cobalt.

5. The process of claim 1 wherein the metal naphthenate is sulfided after sequential in situ impregnation by contacting with a sulfur compound at elevated temperature.

6. The process of claim 4 wherein the cobalt naphthenate is sulfided after sequential in situ impregnation with a sulfur compound at elevated temperature.

References Cited UNITED STATES PATENTS 1,894,926 1/1933 Varga 20810 1,923,576 8/1933 Krauch et al 20810 1,946,341 2/1934 Von Szeszich 2Q;810 1,950,333 3/1934 Von Szeszich 20810 2,025,882 12/1935 Michot-Dupont 20'8-9 2,058,789 10/ 1936 Herold et al. 208--10 1,723,431 8/ 1929 Melamid 20'8---9 2,170,976 8/ 1939 Pier 208-9 2,221,952 11/1940 Pier 2089 3,143,489 8/1964 Gorin 208-8 DELBERT E. GANTZ, Primary Examiner VERONICA OKEEFE, Assistant Examiner U.S. Cl. X.R. 20810