Organic reactions

Patented Jan. 3, 1950

2,492,984

UNITED STATES PATENT OFFICE

2,492,984

ORGANIC REACTIONS

Aristid V. Grosse, Haverford, and John C. Snyder, Darlington, Pa,, assignors to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware

No Drawing. Application May 31,1946, Serial No. 673,629

Claims.

This invention relates to the production of organic compounds, especially hydrocarbons, and particularly branched chain hydrocarbons. The invention has, as its general object, the provision of novel processes for the production of hydrocarbons from materials such as methanol or methane. Other objects will in part be obvious and in part will appear hereinafter.

We have found, in accordance with our invention, that substantial amounts of recoverable hydrocarbons having at least four carbon atoms can be obtained by subjecting methanol or its anhydride, dimethyl ether, to dehydration and condensation conditions. The process may be carried out so as to obtain as conversion products both aliphatic hydrocarbons containing a substantial proportion of branched chain hydrocarbons and aromatic hydrocarbons. The process is preferably carried out by subjecting methanol or dimethyl ether or mixtures of the two to the action of a dehydrating and condensing agent at elevated temperatures and pressures. We have found that, under the conditions of the present process, such an agent is effective to accomplish complete removal of a molecule of water from methanol and condensation, of the remainder of the molecule of methanol to produce hydrocarbons.

We prefer to treat the material to be converted by contacting it, under conversion conditions, with a dehydrating agent which is preferably of a catalytic nature. We prefer to use a dehydrating agent such that very little, if any, of the water formed in the dehydration chemically combines with the dehydrating agent under the conditions of the operation. The invention includes the use of several different types of dehydrating and condensing agents such as those of an acidic, non-oxidizing nature or metal salts of the type exemplified by metallic polyhalides having a dehydrating action and being at most incompletely hydrolyzed in the process. Dehydrating agents of the former type include phosphoric acid, and acid metallic phosphates such as acid aluminum phosphate or acid magnesium phosphate, all of which may be supported on an inert carrier such as kieselguhr. Dehydrating agents of the latter type include metallic polyhalides that are at most incompletely hydrolyzed under the conversion conditions. The hydrolysis of these halides may be suppressed, particularly when the inven(Cl. 26Q—676) tion is embodied in a continuous process, by the addition of small amounts of gaseous halides, such as hydrogen halides, to the zone in which conversion is taking place, the amount of such 5 gaseous halides being sufficient to suppress hydrolysis of the metallic halide but insufficient to react in any substantial amount with the materials being converted. Suitable halides include chlorides and higher atomic weight halides of 10 metals such as zinc, cadmium, thorium, and the like, which may be supported on a suitable inert carrier. Especially effective results have been obtained with the use of zinc chloride and therefore we prefer to employ this catalyst.

When the process is carried out at elevated temperatures, such as temperatures below 650’ G., condensation is promoted by conducting the conversion under super-atmospheric pressure conditions. By proper selection of the conversion 20 conditions as described herein, we can convert methanol and dimethyl ether to substantial amounts of recoverable hydrocarbons having at least four carbon atoms and avoid the formation of any considerable quantity of less useful 25 products, such as methane, or non-recoverable materials such as very high boiling tars or carbonaceous materials similar to coke. We prefer to operate the process so as to obtain at least 30% and preferably 50% conversion to recover³⁰ able hydrocarbons having at least four carbon atoms, based on the amount of methanol or dimethyl ether converted to such hydrocarbons. (For example, a conversion of four moles of methanol to one mole of isobutane is considered a 100% conversion of methanol to isobutane.) We have found that methanol can be converted to hydrocarbon products comprising branched chain hydrocarbons at temperatures above 250° C, and below 400° C., in the presence of a dehydrating and condensing agent such as zinc chloride with the concomitant formation of dimethyl ether, the relative amount of dimethyl ether decreasing with increase in temperature. At temperatures of about 375° G., the conversion ⁴⁵ tp hydrocarbons is by far the predominating reaction and at 425° C, there is little, if any, dimethyl ether formed. It has also been found that dimethyl ether is similarly converted to hydrocarbons at the temperatures of above 375° C, ⁵⁰ It is therefore preferred, when recoverable hydrocarbons are desired as the principal products, to

2,492,984 contact either methanol or dimethyl ether with zinc chloride at temperatures above 375° and below 650° C., such as temperatures not in excess of 500° C. In our investigations, we have found that the recoverable hydrocarbons may contain aromatic hydrocarbons. Due to the low hydrogen content of aromatic hydrocarbons, their formation is advantageous, particularly when saturated aliphatic hydrocarbons are concomitantly formed, since there is then no necessity for the formation of coke to maintain a material balance.

The conversion may be carried out as a batch process by heating methanol or dimethyl ether or both in a closed vessel in the presence of zinc chloride. Condensation of the methylene radical formed by the dehydration of the above materials to hydrocarbon products is favored by effecting the conversion at super atmospheric pressures, which pressures, however, should generally be below 5000 pounds per square inch, such as pressures in the range of 100 to 2500 pounds per square inch. The process may also be effected in a continuous manner; in which case, the vapors of dimethyl ether or methanol or a mixture of both can be contacted with zinc chloride under conversion conditions which should include superatmospheric pressure such as pressures in the above range. In any event, we operate so that the mol ratio of zinc chloride to the reactants, methanol or dimethyl ether, is not high, and thus avoid undesired side reactions such as the formation of methane or methyl chloride. We have obtained high conversion to hydrocarbons using mol ratios as low as below one and may obtain similar effects using ratios higher than one, such as ratios up to 20 to 1.

Tn accordance with one phase of the invention, methane, which may be obtained cheaply from natural or refinery gases, is reacted with sulfur trioxide to yield reaction products from which may be separated methanol and/or sulfonated products which yield additional methanol on decomposition and the methanol so obtained converted, under dehydrating and condensing conditions as described above, to conversion products from which may be recovered substantial amounts of hydrocarbons having at least four carbon atoms and containing relatively large amounts of branched chain hydrocarbons.

The reaction between methane and sulfur trioxide described above is effected at reaction conditions less severe than those under which methane is completely consumed by oxidation to the inorganic carbon oxides, carbon monoxide and dioxide, all as more fully described in our application Serial No. 673,627, filed on May 31, 1946. In general, the reaction of sulfur trioxide and methane may be aided by a catalyst, preferably a catalyst of the type known as a sulfonation catalyst. Preferred reaction conditions include the use of a catalyst comprising a metal or a sulfate of a metal of group H B of the periodic table, particularly mercury, although the reaction can be effected without the use of a catalyst; reaction temperatures above room temperature, preferably temperatures in the range of 100° to 450° C.; and a wide range of reaction pressures including atmospheric and superatmospheric pressures, the latter generally being below 5000 pounds per square inch. The relative amounts of the reactants, sulfur trioxide and methane, can be varied widely depending on other reaction conditions and the type of products desired. Methanol can be obtained from the reaction products of sulfur trioxide and methane as above or sulfonated derivatives of methane resulting from this reaction can be decomposed to methanol and sulfur dioxide, such as by pyrolysis at temperatures above 225° C., as described more fully in our application, Serial No. 673,628, filed on May 31, 1946. Methanol from either or both precesses may then be converted to hydrocarbon products comprising branched chain hydrocarbons, thus obtaining valuable hydrocarbons from methane. Sulfur dioxide from either the reaction with methane or from the decomposition of sulfonated derivatives of methane may be appropriately processed and converted to sulfur trioxide, as by oxidation using air, and the sulfur trioxide so obtained reacted with additional methane.

By such a process, methane, which is primarily useful only as a cheap fuel, is converted to hydrocarbon products useful either directly as a motor fuel or as blending agents for high octane gasoline. A fraction of hydrocarbon material consisting at least principally of isobutane may be separated, as by distillation, from the reaction products and thereafter used as a starting material for the production of other compounds as, for example, in the preparation of alkylate, a high octane blending agent for gasoline. Other branched chain paraffins can be similarly separated from the reaction products and used for gasoline blending or as chemical raw materials.

Similarly olefins, either normal or branched, may occur in the conversion products and may be used, in an impure or in a relatively pure state, in polymerization, alkylation or similar processes. It is one of the advantages of the present invention, that the ratio of branched chain hydrocarbons to normal hydrocarbons is unusually high in the reaction products and hence hydrocarbon material of high octane value may be prepared from such reaction products.

In order to illustrate processes embodying the present invention, but not to be construed as limitations thereon, the following examples are given:

Example I

Several runs were made in which methanol and zinc chloride (in amounts equal to a mol ratio of ZnCla to CH3OH of 0.6) were placed in a vessel, the vessel sealed and then heated to 425° C. for about 1.5 hours. The maximum pressure, based on the amount of methanol, the temperature and the size of the vessel, was approximately 2440 lbs./sq. in. The vessel was cooled before opening it to investigate the reaction products.

The reaction products were separated into a fraction volatile at 25° C. and atmospheric pressure, and a liquid fraction. The volatile fraction from one run was analyzed with the following results:

<td> Product</td><td colspan="2"> Mol per cent conversion of CH3OH to products · listed</td>

<td> Methane................</td><td> 1.0</td><td> 1.0</td>

<td> Ethane............</td><td></td><td></td>

<td> Ethylene........... _........</td><td> 1 3</td><td></td>

<td> Propane................</td><td> 4 0</td><td> 6.7</td>

<td> Propylene.....................</td><td> in</td><td></td>

<td> Isobutane........................</td><td colspan="2"> IQ</td>

<td> n-Butane.................</td><td> 1 5</td><td></td>

<td> Butenes.................</td><td> 0 7</td><td></td>

<td> Branched chain pentanes..............</td><td> 4.1</td><td> 31 9</td>

<td> n-Pentane...... ..................</td><td> 0.1</td><td></td>

<td> Hexanes (volatile at 25°)...................</td><td> 4.3</td><td></td>

<td> Hexenes (volatile at 25°)..............</td><td> 4.0j</td><td></td>

It is to be noted in the above results that branched

2,492,984 chain hydrocarbons constituted at least 90% of the C4 and Cs hydrocarbon material.

The liquid fraction of the reaction products from two runs contained about 20% (on the same basis as the above) of recoverable hydrocarbon material boiling between 25° C. at atmospheric pressure and 85° C. at 1.5 mm. of Hg pressure (about 246° C. at atmospheric pressure) and about 30% of higher boiling material. From the higher boiling material, hexamethylbenzene was separated and identified, in an amount corresponding to about 18% conversion of methanol. No dimethyl ether was detected in the reaction products and less than 2% of the methanol was converted to non-recoverable carbonaceous material.

Example II

A run was made, using the technique of Example I, except that dimethyl ether and zinc chloride were reacted, in amounts equal to a mol ratio of ZnCh to dimethyl ether of 1 to 16, at a temperature of 400° C. for 1 hour. The maximum pressure, on the same basis as Example I, was approximately 1050 lbs./sq. in.

Approximately 70% of the reaction mixture was volatile at 25° C. and 550 mm. of Hg pressure. The composition of this volatile material was as follows:

Per cent of conversion of

<td colspan="2"> Product</td><td colspan="2"> dimethyl ether to products listed</td>

<td colspan="2"> Methane.......................................</td><td> 13.9</td><td rowspan="2"> 13.9</td>

<td colspan="2"> Ethene.......................................</td><td> 2.8</td>

<td colspan="2"> Ethane _____ _________________</td><td> 4.9</td><td rowspan="2"> 21.4</td>

<td colspan="2"> Propene. ________ _______ .._______ _</td><td> 9.3</td>

<td colspan="2"> Propane....................................</td><td> 4.4</td><td></td>

<td colspan="2"> Isobutane..............................</td><td> 23. Οΐ</td><td></td>

<td colspan="2"> n-Butane......................................</td><td> 2.9</td><td></td>

<td colspan="2"> Butenes.. ......... .................._</td><td> 1 7</td><td></td>

<td colspan="2"> Branched chain nentanes. _ _ _ _ _</td><td> 1.0</td><td rowspan="2"> 30.9</td>

<td></td><td></td><td> 1.2</td>

<td colspan="2"> Pentanes _______ ________________________</td><td> .4</td><td></td>

<td colspan="2"> Benzene. _______ _______________________</td><td> .7</td><td></td>

<td colspan="2"> Dimethyl ether (recovered)...... ..................</td><td> 4.3</td><td> 4.3</td>

The amount of material higher boiling than the above was about 30%.

Example III

A run was made using the technique and materials of Example I except that the mol ratio of ZnCh to CH3OH was 1 to 10, the temperature 390° C., and the time 2.5 hours.

Analysis of material volatile at 24° C. and 1025 mm. of Hg pressure indicated the following compounds:

<td> Products</td><td colspan="3"> Per cent conversion of CH3OH to products listed</td>

<td> Methane __ _____________________ ____________</td><td> 0.5</td><td></td><td></td>

<td> Ethane. ___________-______- ________</td><td> 0.1</td><td></td><td></td>

<td> Ethene.. _ _____________ _____ ____________</td><td></td><td></td><td rowspan="2"> 9.5</td>

<td> Propane. ______ ______________ _____________</td><td> 5.8</td><td></td>

<td> Propene. _ ...................................</td><td> 3.6</td><td></td><td></td>

<td> n-Butane..........-..........................</td><td> 2.71</td><td></td><td></td>

<td> Isobutane ....................................</td><td> 25.0</td><td></td><td></td>

<td> Butenes. ..............................</td><td> 1.7</td><td></td><td></td>

<td> n-Pentane.. ______ ______________-_________ -</td><td> 0.6</td><td></td><td rowspan="2"> 41.1</td>

<td> Branched pentanes.. _ ______ ___________-</td><td> 7.2</td><td></td>

<td> Pentenes _____ _______ ______ _______</td><td> 0.4</td><td></td><td></td>

<td> Hexanes..........................</td><td> 2.9</td><td></td><td></td>

<td> Hexenes.. ........................ ...</td><td> 0.6</td><td></td><td></td>

<td> Dirpethyl ether . ____ _____________________</td><td> 14.5</td><td></td><td> 14.5</td>

<td></td><td></td><td></td><td></td>

By the techniques described above, it is apparent that, among other phases of the invention, we have furnished means for the con6 version of methane to useful and recoverable higher boiling hydrocarbons, such as branched chain aliphatic hydrocarbons, using, in effect, atmospheric oxygen to accomplish the transformation. Moreover the combined techniques described may be opereated integrally to· yield valuable hydrocarbon products as a final product or valuable intermediate products may be withdrawn at various points in the integrated process. Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.