US2647042A - Production of hydrogen-rich gases - Google Patents

Description

Patented July 28, 1953 PRODUCTION OF HYDROGEN-RICH GASES George Alexander Mills, Ridley Park, Pa., assignor to Houdry Process Corporation, Wilmington, DeL, a corporation of Delaware No Drawing. Application July 23, 1946,

Serial No. 685,765

8 Claims.

This invention relates to the treatment of solid contact masses which have hydrocarbonaceous materials deposited thereon as a result of previous processing, and is particularly concerned with the production of hydrogen-rich gases from such material.

Many hydrocarbon conversion processes involve the contact of hydrocarbons at elevated temperatures, such as temperatures above 200 F. and below 1100 F., with a contact mass comprising a refractory, inorganic solid having catalytic or other desired properties such solids often being porous or adsorbent. As a result of such contact, at least a part of the original hydrocarbons is converted into hydrocarbons of different molecular weight or structure or both. During the contacting process, the contact mass accumulates a hydrocarbonaceous deposit which contains carbon and hydrogen combined in compounds of undetermined composition and is essentially non-volatile. Such hydrocarbonaceous deposits, commonly referred to as coke, are formed in processes such as the polymerization of unsaturated hydrocarbons; the vapor phase cracking of naphthas, gas oils, or higher boiling hydrocarbon fractions; the liquid phase cracking or viscosity breaking of gas oils or higher boiling hydrocarbon fractions, such as reduced crudes; in the mixed phase cracking of high boiling hydrocarbon fractions; or the vapor phase treatment or reforming of virgin or cracked gasolines; in the dehydrogenation and hydrogenation of petroleum fractions, and the like. In a similar fashion, other contacting processes, which are effected at lower temperatures, such as temperatures below 200 F. and which do not result in a change of molecular structure of the bulk of the material treated and which may be non-catalytic, such as the decolorization of lubricating oil by the use of adsorbent clays, result in somewhat similar deposits on the contact mass used in the process. Frequently, contact masses used in noncatalytic operations at low temperatures do manifest some catalytic activity for the conversion of hydrocarbons when the temperature is increased to temperature levels within the range previously stated. At any event, at least a portion of the hydrocarbonaceous deposit on the contact mass accumulated as a result of processes such as those described above is relatively non-volatile in the sense that when the contact mass comprising such a deposit is contacted with a stripping gas, such as steam, at elevated temperatures below 1000 F., a considerable deposit of hydrocarbonaceous material, which generally contains 2 about 5 to 10 weight per cent of hydrogen, remains on the contact mass.

In commercial processes of the classes referred to above, the hydrocarbonaceous deposits affect the activity of the contact masses deleteriously and it is the usual practice to burn off the deposits by the use of air or other oxygen-containing gas and thus prepare the contact mass for further use. The products of such combustion are carbon dioxide, carbon monoxide, and water which are vented to the atmosphere. Accordingly, the deposits are regarded as waste materials, their only value residing in the heat recoverable in some instances from the combustion process.

It has been discovered in accordance with the invention, that useful materials, in particular hydrogen, may be efficiently obtained from contact masses having such hydrocarbonaceous material deposited thereon by subjecting such a contact mass under non-oxidizing conditions to temperatures at which pyrolysis of the hydrocarbonaceous material is effected. It has been found that such a heat treatment, which is particularly effective at temperatures above 1200 F., especially temperatures in the range of 1200 to 1800 F., produces hydrogen-rich gases from which substantially pure hydrogen may be recovered by simple and effective methods. Although the thermal treatment reduces the amount of the carbonaceous deposit by the amount of the evolved gases, some of the deposit remains, but is so changed in nature that the contact mass in many instances can be employed again without removal of the residual coke in the process in which the mass was originally used. In some cases, it is desirable, particularly in processes where high catalytic or absorbent activity is important, to remove most of the remainder of the deposit by the usual regeneration method.

In a typical embodiment of the present invention, hydrogen-rich gases are obtained by thermally treating a contact mass having catalytic activity in a non-oxidizing atmosphere at a temperature in the preferred range of 1300 F. to a temperature below that at which thermal deactivation of the catalytic properties of the contact mass occurs. Thus a siliceous contact mass of the type described below, which contact mass has been used for the catalytic conversion of a hydrocarbon fraction such as a gasoline or a heavy gas oilunder cracking conditions including temperatures in the range of about 800 to 1050 F. and which has thereby accumulated a deposit of hydrocarbonaceous material, is ther- 3 mally treated, and thereafter the contact mass and the hydrogen-rich gases evolved by decomposition of the hydrocarbonaceous deposit are separated. The thermally treated contact mass may then, as described herein, be used again in a hydrocarbon conversion process.

The hydrogen-rich gases consist principally of hydrogen with same methane and very minor amounts (generally less than 5 volume per cent) of higher boiling hydrocarbons. The hydrogenrich gases as produced can be used in other processes utilizing hydrogen where the presence of either methane in amounts less than 50 volume per cent or of a flushing gas if used, would not be harmful. When high concentrations of hydrogen are desired, the hydrogen may be concentrated by preferential adsorption of the methane and other hydrocarbon gases present using, as is known to the art, a selective solid adsorbent or an absorbing oil, or by compression, liquefaction, and fractionation or by preferential diffusion; or by similar methods for the physical separation of gases, any of which may be combined with appropriate chemical treatments. The concentration of hydrogen may also be increased by another type of process in which steam is admixed with the separated hydrogen-rich gases in an amount equivalent to the methane present and such a mixture passed over a catalyst, such as a reducible oxide on a refractory support, for example nickel oxide on magnesia, at temperatures of 1400 to 1800 F., thereby converting the methane and steam to hydrogen and carbon monoxide, the latter being converted to carbon dioxide by addition of more steam and a second catalytic treatment at about 700 F. and the carbon dioxide removed by absorption in an ethanolamine.

The contact mass may be heated to the temperature of the thermal treatment by indirect or direct heat exchange. In the latter event, a hot inert gas, such as nitrogen, helium, or other non-oxidizing gases, may be used, the inert gas also serving to flush out the hydrogen-rich gases, whose complete removal is particularly desirable if the contact mass is to be subsequently contacted with an oxidizing gas such as air. The complete removal of the hydrogen-rich gases can also be effectively accomplished by evacuation using a pump. One particularly desirable mode of direct heat exchange is by recirculation of the hydrogen-rich gases, which can be separated from the contact mass, heated to a temperature above that of the thermal treatment and returned to the thermal treatment zone.

When the thermal treatment of a contact mass as described above is operated in conjunction with a commercial cracking operation, a considerable amount of hydrogen is produced. A commercial catalytic cracking unit with a throughput of 10,000 barrel of oil per day, may produce 60 tons of coke or hydrocarbonaceous deposit per day, under normal operating conditions. This coke contains about 4 tons of hydrogen, over 75% of which can be recovered by the thermal treatment herein described.

In another typical embodiment of the invention, contact masses which have accumulated a hydrocarbonaceous deposit as a result of a relatively low temperature (under 800 F.) catalytic conversion of hydrocarbons, such as catalytic polymerization, are subjected to elevated temperatures above 1200 F. and generally below 1800 F. whereby hydrogen-rich gases are obthe conversion of hydrocarbons, a relative inexpensive contact mass of low catalytic activity is frequently used and is discarded after a single operation. The present invention furnishes means whereby the hydrocarbonaceous deposit on such material is utilized to yield useful products. For example, a raw clay or a spent crackin catalyst may be used to lower the boiling range or to remove the coke forming compounds such as tars from a high boiling petroleum fraction such as a reduced crude. A typical operation involves contacting a crude distillate residuum with spent cracking catalyst at temperatures of the order of 600 F. under pressures sufficient to maintain the hydrocarbon fraction in the liquid phase for a length of time insufficient to form considerable amounts of gasoline. Another such operation involves contacting the hydrocarbon fraction with contact mass having at least a moderate cracking activity at temperatures in the range of 220 to 600 F. at atmospheric pressure in the presence of steam. In such processes, the hydrocarbonaceous deposit may amount to 5 to 10 weight percent or more of the contact mass. When contact masses comprising hydrocarbonaceous deposits accumulated as a result of relatively low temperature processes are used in the production of hydrogen-rich gases in accordance with the present invention, it is preferred to purge such contact masses with an inert stripping gas such as steam, for example, at an intermediate temperature, such as temperatures in the range of 600 to 1000 F. to remove volatile hydrocarbons before subjecting such contact masses to temperatures of over 1200 F. for the production of hydrogen-rich gases. When the contact mass is to be discarded after the thermal treatment, temperatures above the temperature of thermal deactivation may be used, such as temperatures up to 1800 F. With the proper equipment, temperatures higher than 1800 F. may be used.

Contact masses adapted to be processed in accordance with the present invention should be solids and are preferably inorganic in nature and sufficiently refractory to withstand the temperature of thermal treatment or higher without a change in state and without reacting chemically with the hydrocarbonaceous deposit so as to preclude the liberation of hydrogen. Suitable contact masses include raw or activated siliceous clays, such as bento-nite, or bauxi'tes or artifically produced colloidal siliceous contact masses comprising silica in admixture with one or more refractory oxides such as alumina, zirconia, urania, thoria, magnesia, beryllia and the like, or phosphates of zirconium, beryllium, thorium and the like. When activated clays are used in accordance with the invention and such clays are to be reused for the conversion of hydrocarbons, it is preferred tosubject them to temperatures below 1500 F. unless they have been specially processed to withstand higher temperatures, whereas artificially produced siliceous contact masses, for example, silica-alumina, may, in most cases, be subjected. to temperatures as high as 1700 F. without substantial loss in catalytic activity. Where such contact masses are to be discarded after being used once, somewhat higher temperatures, such as 1800 F., may be used in the production of the hydrogen-rich gas. Contact masses other than the inorganic compounds described above, such as activated carbon, may be thermally treated with similar results when such contact masses have a hydrocarbonaceous deposit Example I A siliceous contact mass was artificially produced by precipitating a silica-alumina hydrogel in a basic menstruum, drying the hydrogel, re-

moving from the gel thus prepared the zeolitically held alkali metal by base exchange and then calcining molded pellets of ground gel. This contact mass was used for the catalytic cracking of a light East Texas gas oil at 880 F. for 15 minutes whereby a hydrocarbonaceous deposit accumulated on the catalyst. This deposit contained, in addition to combined hydrogen, about 16 grams of carbon per liter of contact mass (about 2 weight percent based on the contact mass). A portion of the contact mass on which the hydrocarbonaceous deposit had accumulated, was subjected to a temperature of about 1350 F. for about 4 hours, in the presence of helium as a flushing gas. About 2290 cc. of hydrogen per liter contact mass were evolved, with about 1150 cc. of methane and only about 192 cc. of higher boiling hydrocarbons per liter of contact mass being also evolved; the major portion of these gases being evolved in the first half hour of treatment.

The gas evolved from the thermal treatment was separated from contact mass and collected in a gas holder. This gas is eifective in the hydrogenation of aromatic hydrocarbons using a nickel catalyst.

Example II methane and higher boiling hydrocarbons on" activated charcoal.

It is to be understood that when hydrocarbonaceous material is stated herein to be deposited on a contact mass as a result of contact with hydrocarbons that such material may be deposited on all surfaces available to gaseous contact by the hydrocarbons and thus material within a piece of a porous contact mass is included by such a statement.

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.

I claim as my invention:

1. The process which comprises the steps of effecting catalytic conversion of hydrocarbons at an elevated temperature in the presence of a refractory inorganic contact mass with the concomitant deposition of a non-volatile hydrocarbonaceous material on said contact mass, after the termination of the step involving the catalytic conversion of hydrocarbons, subjecting contact mass comprising said non-volatile hydrocarbonaceous material to thermaltreatment in the presence of inert gas and in a non-oxidizing atmosphere at a temperature above 1200 F. and not in excessof 1800 F., thereby decomposing said,hydrocarbonaceousmaterial with the evolution of gas consisting predominantly of hydrogen.

2. The process which comprises the steps of efiecting catalytic conversion of hydrocarbons at an elevated temperature above 200 F. and below 1100 F. in the presence of a hydrocarbon conversion catalyst consisting essentially of silica and at least one refractory metal oxide, thereby causing the concomitant deposition of a nonvolatile hydrocarbonaceous material on said catalyst, after the termination of the step in-- volving the catalytic conversion of hydrocarbons, subjecting catalyst comprising said non-volatile hydrocarbonaceous material to thermal treatment in the presence of inert gas and in a nonoxidizing atmosphere at a temperature above 1200 F. and not in excess of 1800 F., thereby decomposing said hydrocarbonaceous material with the evolution of gas consisting predominantly of hydrogen.

3. The process of claim 2 in which the previous step is a catalytic conversion of hydrocarbons under cracking conditions and in which the catalyst is silica-alumina.

4. The process which comprises the steps of efiecting catalytic conversion of hydrocarbons at an elevated temperature in the presence of a refractory inorganic hydrocarbon conversion catalyst with the concomitant deposition of a hydrocarbonaceous material on said catalyst, after the termination of the step involving the catalytic conversion of hydrocarbons, stripping catalyst comprising said hydrocarbonaceous material of volatile hydrocarbons with steam at temperatures between 600 F. and 1000 F., subjecting catalyst so stripped to thermal treatment in the presence of inert gas and in a non-oxidizing atmosphere at a temperature above 1200 F. and not in excess of 1800 F., thereby decomposing said hydrocarbonaceous material with the evolution of gas consisting predominantly of hydrogen, and separating said catalyst and said gas consisting predominantly of hydrogen.

5. The process which comprises the steps of efiecting catalytic conversion of hydrocarbons at an elevated temperature in the range of about 200 F. and below 1100 F. in the presence of a refractory inorganic hydrocarbon conversion catalyst with the concomitant deposition of a nonvolatile hydrocarbonaceous material on said catalyst, after the termination of the step involving the catalytic conversion of hydrocarbons, subjecting catalyst comprising said non-volatile hydrocarbonaceous material tothermal treatment in the presence of inert gas and in a non-oxidizing atmosphere at a temperature above 1200 F. and not in excess of 1800 F., thereby decomposing said hydrocarbonaceous material with the evolution of gas consisting predominantly of hydrogen, separating said catalyst and said gas and recovering a gaseous fraction consisting essentially of hydrogen from said gas.

6. The process which comprises the steps of effecting catalytic conversion of hydrocarbons at an elevated temperature above 200 F. and below 1100 F. in the presence of a refractory inorganic hydrocarbon conversion catalyst with the concomitant deposition of a non-volatile hydrocarbonaceous material on said catalyst, after the termination of the step involving the catalytic conversion of hydrocarbons, subjecting catalyst 7 comprising said non-volatile hydrocanbonaceous material to thermal treatment in the: presence of inert gas and in a non-oxidizing. atmosphere at a temperature in the range of 1300" to 1700 F., thereby decomposing: said hydrocarbonaceous 5 material with the evolutionof gas consisting predominantly of hydrogen,. and separating said catalyst and said gas: consisting predominantly of hydrogen.

'Z. The process of claim 6 in which the catalyst is siliceous and has catalytic cracking activity;

8. The process of claim 6 in which the cat-' alyst is derived from clay and has catalytic crack'- ing activity and in which the temperature or thermal treatment is less than. 1500 F.

GEORGE: ALEXANDER References Glted in the file of this patent UNITED STATES PATENTS Number- Name Date 306,810 Chesebrough Oct. 21, 1884 2,300,15L Hemminger. Oct. 2'7, 1942 2,391,336 Ogarzaly Dec. 18, 1945 OTHER REFERENCES Gas Engineers Handbook," McGraw-Hill,

New York (1934') page 347.

The Chemistry of Petroleum Derivatives by Ellis, Chemical Catalogue Co., New York (1934) vol.- 1, pages 38', 39 and 40..

Claims (1)

1. THE PROCESS WHICH COMPRISES THE STEPS OF EFFECTING CATALYTIC CONVERSION OF HYDROCARBONS AT AN ELEVATED TEMPERATURE IN THE PRESENCE OF A REFRACTORY INORGANIC CONTACT MASS WITH THE CONCOMITANT DEPOSITION OF A NON-VOLATILE HYDROCARBONACEOUS MATERIAL ON SAID CONTACT MASS, AFTER THE TERMINATION OF THE STEP INVOLVING THE CATALYTIC CONVERSION OF HYDROCARBONS, SUBJECTING CONTACT MASS COMPRISING SAID NON-VOLATILE HYDROCARBONACEOUS MATERIAL TO THERMAL TREATMENT IN THE PRESENCE OF INERT GAS AND IN A NON-OXIDIZING ATMOSPHERE AT A TEMPERATURE ABOVE 1200* F. AND NOT IN EXCESS OF 1800* F., THEREBY DECOMPOSING SAID HYDROCARBONACEOUS MATERIAL WITH THE EVOLUTION OF GAS CONSISTING PREDOMINANTLY OF HYDROGEN.