US2392588A - Catalytic treatment of carbonaceous materials - Google Patents

Description

I Patented Jan. 8,1946

CATALYTIC TREATMENT OF CABBONACEOUS MATERIALS Bernard S. Greensfelder and William A. Bailey,

Jr., Oakland, Calii'., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application May 9, 1944, Serial No. 584,808

' This invention relates to the treatment of carbonaceous materials at elevated temperatures under substantial hydrogen pressure in the presence of catalysts to prqduce lower boiling products having an enhanced ratio of hydrogen to carbon. Treatments of this kind have been referred to in the past as destructive hydrogenations. This designation may have been approprlate for previous methods of operation in which the reaction was to a very large extent an u'ncontrolled decomposition of the starting material with a more or less concurrent addition of hydrogen to the resulting mixture of products. It

does not adequately characterize the present of the periodic table have been stressed because they retain their hydrogenation activity in the presence of impurities, such as sulfur compounds, usually present in the feed stocks. The products obtained in the past, however, have-not been of the most advantageous quality, particularly in respect to the engine performance characteristics of the motor fuels produced. I

It is an object of the present invention to eliminate, or at least reduce, the foregoing and other disadvantages of previous methods of treating carbonaceous materials with hydrogen to produce lower boiling hydrocarbons of higher hydrogen content. Another object is to provide more advantageous catalysts for reactions of this type.- A further object is to produce gasolines of improved octane number and engine performance characteristics from higher boiling carbonaceous materials. Still other objects and advantages of the invention will be apparent from the following description of a preferred method of carrying out the invention. v

The conversion of solid carbonaceous materials such as coal, etc., into marketable liquid hydrocarbons by hydrogenation is usually performed in a plurality of stages. First, the coal is made into a paste with heavy oil, the catalyst is added and the mixture treated with hydrogen at pressures of 200 to 1000 atmospheres and about 4&0 to 500 0., for example. The wide boiling range oil thus produced contains a substantial amount (50% to 55%) of heavy oil which is separated and used to prepare coal paste for further treatment. The middle boiling range 011 (lower boiling products of about 300 to 400 C. end point) is subjected to a second destructive hydrogenation stage to increase the yield of gasoline. For clarity, the invention will be described with particular reference to the treatment of intermediate boiling range hydrocarbons which comprise the feed to the second stage of destructive hydrogenation. This description will serve to illustrate the principles of the invention since the same methods of operation may be used for the treatment of petroleum products, coal tars, shale oils and the like. However, the invention is not limited thereby with respectto the source or nature of the feed stocks, or as to the particular manner of treatment of any carbonaceous material capable of destructive hydrogenation. According to the invention, hydrocarbons of improved properties are produced by treating higher boiling carbonaceous materials with hydrogen at pressures above about 200 atmospheres in the presence of a new catalyst comprising essentially alumina and boric oxide. Mixtures of alumina with silica and other diflicultly reducihie oxides have been proposed as carriers for a wide variety of hydrogenation catalysts and it has also been suggested in some cases that small amounts of boric acid may ormay not be incorconstituent which co-actswitfi'the boria to infiuence the reactions of the invention in an advantageous manner which is not achieved by the use of either constituent alone or by either constituent in other combinations. Thus, neither the alumina alone nor the mixture of alumina. and boria is to be regarded as merely a support for a hydrogenation catalyst, even if such should be present. Rather, the. specific mixtures of alumina and boria used constitute the active catalysts in the process. It was not to be expected that catalysts of this type would be advantageous for these reactions because they are not hydro- "genation catalysts in theaccepted sense of the term. since, for example, they are not capable of effecting substantial addition of hydrogen to lower olefins under the usual hydrogenation conditions for'suchyreactions. Nevertheless, in the process of the invention these catalysts not only serve to. promote-a desirable mode of hydrogenation but also have an. advantageous isomerizing 1. action. y ldi p oducts of excellent engine performance characteristics, accompanied by, only a low amoimt of degradation to gaseous hydrocarbons. v

The desired properties of the new catalysts can be obtained only by the use of alumina in, the proper form. Either crystalline or gel'aluminas may be employed. Thus the alumina maybe a porous alpha or beta alumina trihydrate.

going'types of alumina or a synthetic alumina gel maybe used. In any case, for production of a highly active catalyst it is essential that the alumina have a specific surface of at least 100 square meters per gram as determined by the method of Emmett and Brunauer and a bulk density of between about 0.4 and 1.0 gm./cc. at the time of preparation of the catalyst. These prop erties are fixed by the methods used for preparation and treatment of the alumina. The spexerogel or crystalline A1203 WitinHaBQni E perature preferably greater than 75C. Shah be employed to yield a high B20: content. The

boron compounds which may be decomposed to mixture is then calcined, at about 200 to 600 C.

to convert the boric acid to boric oxide. Other the. oxide by heating in this range or at lower temperatures may be used-instead of boric acid.

For both gel and crystalline aluminas the boric oxide may be applied in solution in an alcoholic solvent. Alternatively, the alumina may be im-' f alpha alumina monohydrate or gamma alumina. Furthermore, the alumina may be in the form of a porous natural or calcined bauxite consisting predominantly of one or more of the forecific surface of the final catalyst is also preferably v at least 100 square meters per gram but may become lower during use while still remaining usable although less active.

Siutablecrystalline aluminas may be obtained, for example, by the slow crystallization of .alpha alumina. trihydrate or beta alumina trihydrate pregnated by exposure. to water vapor carrying hydrated boric oxide, or to vapors of an alkyl borate which will leave a residue of B20: when decomposed by heating. It is sometimes advantageous when using gel forms of alumina to incorporate the chosen compound in the alumina during the precipitation step. In such cases it is of course not feasible to wash theprecipitated gel or to subject it to any other subsequent treat-" ment which would remove the added boron compound. Consequently, more careful control of'th precipitation is necessary in order to avoid inclusion of undesirable constituents in the finished catalyst.

It is essential that the catalyst contain between 6% and 30% B20: based upon the total weight of A120: and B20: present and most preferably between about 8% and 25% is used. Lower concentrations of boric'oxidegive inferioreatalysts and excessive amounts are also detrimental. In some cases two or more impregnations and calcinations may be necessary in order to incorporate the desired amountof boria.

Regardless of the method of catalyst prepare tion used it is important that a suitable heat treatment to activate the catalyst and insure the desired surface characteristics be provided. As

from alkali .aluminate solutions followed by par- Suitable alumina gels may be prepared by sevv eral different methods. One convenient way is to precipitate an alumina gel from a solution of a soluble aluminum salt such as the nitrate, sulfate or chloride with abuse such as ammonium hydroxide or sodium hydroxide. Instead of aluminum salts, ametal aluminate or aluminum amalgam may be used in preparing the alumina gel.

-Whatever the method of precipitation used, it

may be desirable to remove the precipitant from oxide. Excessive amounts of alkali metal salts reduce the activity of the catalyst and may be removed by water washing the gel. The properties of the final catalyst may be improved by pepthe alumina prior to incorporation of the-Doric v previously indicated, this treatment may advantageously be applied to the alumina prior to incorporation of the boron. However, it is also feasible to activate the catalyst by heating after incorporation of the boric oxide by any of the previously described methods. Heating at a temperature above about 250 C., for example between about 300 and 600 C., until the alumina is substantially converted to the alpha monohydrate or gamma form is a suitable method of activation. Small amounts of silicon or titanium dioxide may also be incorporated in the catalyst to increase its surface further, but such oxides should constitute-not more than 20% by weight of the finishedcatalyst.

The amounts of other constituents should also be carefully controlled in order to lnsurethe desired activity and selectivity of the catalyst.

Thus, for example, the iron content should be below 3% and preferably is less than 1%.

The conditions used in carrying out the process of the invention with the new catalyst vdepend upon the particular material being treated and the type of product desired, and may vary considerably. In all cases, however, it is essentization of A120: in. the hyrogel, xerogel, or crysexample.

' talline state by treatment with acetic acid, for

The boric oxide maybe incorporated into the alumina in'a number of diflerent ways. when alumina in gel form is used, the desired amount of boria may be incorporated'by homogenizing the wet hydrous gel with boric acid or by imp egnating the hydrous or dried gel with a boric tial that the pressure he maintained above 200 atmospheres. A hydrogen feed ratio above one mole per mole of hydrocarbon treated is also desirable. Temperatures between about 250 and about 600 C. are genera-lly suitable and the hydrocarbon feed rate may vary from about 0.1 to about 10 volumes per volume of catalyst per hour. These conditions are interdependent and the optimum for any one factor, while ordinarily fall- 7 ing within the foregoing limits, will depend upon the other conditions used.

acid solution. In the .case of impregnation of The process of the invention may be carried g alysts of th invention.

lyst case; the hydrocarbon to be treated may be in liquid, in mixed liquid-vapor, or in the vapor phase, and is passed together with hydrogen over the catalyst under the appropriate reaction conditions. For such operations it may be desirable to have the catalyst deposited on a support of suitable inactive material, such as kieselguhr among many others. Such supports are not at all essential; thus, when operations are carried outwith the catalyst in finely divided form and suspended in the fluid hydrocarbon to be treated, catalyst supports are preferably not used.

As previously pointed out, the process and catalysts of the invention should give gasoline boiling products which equal or excel (particularly in regard to engine performance characteristics) those obtained by other procedures' Thus, for example, one of th best-known prior art methods of "destructive hydrogenation uses as catalyst tungsten sulfide deposited on a montmorillonite type support such as hydrogen fluoride treated Terrana or Super-Filtrol." When this catalyst is used for the destructive hydrogenation of Elwerath gas oil employing the following reaction conditions:

Temperature C 400-420 Pressure atmospheres 250 Total hydrocarbon feed rate kg./l./hr 1 Hydrogen rate m. /hr./l 2

Alumina (substantially gamma form) "per cent-.. 75

Boris clo.. Y Ines on ignition do 9 Surface area "so. meters/gram 300 Bulk density 0.85 Iron per cent max 0.2

Using a catalyst of this type a similar yield of gasoline hydrocarbons boiling below 180? C. and having an octane number of 75/76 should be obtained while operating under the above-named conditions except for the necessary elevation of the pressure to 600 atmospheres.

The catalysts of the invention have along effective lite in the process. Stability to high temperature is a salient characteristic of the cat- Theymay be readily regenerated in case of loss of activity resulting from the deposition of carbonaceous material on their surface. Regeneration with air or oxygencontaining gases is readily secured with these catalysts, whereas those incorporating a heavy metal sulfide may be permanently injured and at best must be subjected to careful re-sulflding treatment after exposure to air or oxygencontaining gases. A'ny tendency for the catalyst to lose boria during regeneration or in normal steam containing boric acid into the reactor. The added boric acid may be converted to boric oxide operations may be compensated for by adding v boric acid to the catalyst in place, by passing either before or during subsequent use of the catalyst for conversion of the carbonaceous material being treated. Still other variations in the process may be made. and it will be understood that the invention is not limited to the details disclosed by way of illustration nor by any theory advanced in explanation of the more advantageous results obtained.

We c as our invention:

1., A process of producing lower boiling hydrocarbons in the gasoline range which comprises treating a higher boiling carbonaceous material with hydrogen under a pressure 0! at least 200 atmospheres, at between about 200 and 600 C. in the presence of a catalyst containing less than 20% silica comprising alumina and boric oxidein which the boric oxide content is between and 30% of the total weight of alumina and boric oxide, said catalyst having a specific surtace of at least square meters .per gram,. a bulk density between about 0.4 and 1.0 and containing less than 3% iron and not more than 2% sodium.

2. A process or producing lowerboiiing hydrocarbons in the gasoline range which comprises treating a higher boiling carbonaceous material with hydrogen under a pressure of at least 200 atmospheres, at between about 200 and 600 C. in the presence oi as catalyst containing less than 20%5 silica. comprising a porous gamma alumina having a specific surface of at least 100 square meters per gram, having thereon between 6.4% and 43% of boricoxide, said catalyst having a bulk density between about 0.4 and 1.0 and containing less than 3% iron andnot more than 2% sodium.

3. A process of producing lower boiling hydrocarbons in the gasoline range which comprises treating a higher boiling carbonaceous material with at least an equal molecular amount of hydrogen under a pressure of at least 200 atmos-.

pheres at a temperature between 200 and 600 C. in the presence of an alumina gel having a specific surface of at least 100 square meters per gram admixed with between 6.4% and d3% or boric oxide based on the weight otalumina present, said catalyst containing less than 20% silica and having a bulk density between about (PA and 1.0 and containing less than 3% iron'and not more than 2% sodium.

' 4. A process of producing lower boiling hydrocarbons from higher boiling carbonaceous material which comprises contacting said higher boiling material and a substantial molecular excess of hydrogen under a pressure of at least 200 atmospheres at between 200 and 600 C. with a catalyst containing less than 20% silica prepared by impregnatinga porous alumina with boric acid and" subjecting the resulting mixture to a heat treatment to convert said acid to boric oxide and form a silica-free catalyst containing 6% to 30% boric oxide based on the total weight of boric oxide and alumina present and having a 20% 7 momprlsWnTniTnTboHeoxide in ch the boric oxide content is between 8% and 30% of the total weight of alumina and catalyst consisting of aluminaand boric oxide containing between 6% and 30% oi boric oxide by weight.

6. A process of producing lower boiling hydrocarbons Irom higher boiling carbonaceous ma-.

'terial'which comprises contacting said higher boiling material and a substantial molecular excess of hydrogen under a, pressure of at least 200 atmospheres at between 200 C. and 600 C. in

the presence of a catalyst containing less than "i boric oxide, said catalyst having a, specific surface of at least 109 square meters per gram, a bulk density between about 0.4 and 1.0 and containingless than 3% .iron and not more than 2% sodium. t

BERNARD S. GREEN WILLIAM A. BAILEY, J2.