US2244018A - Method of carrying out catalytic reactions - Google Patents

Description

June 3, 1941.

J. c. MUNDAY `nm. METHOD F `CARRYING OUTYCATALYTIC REACTIONS Filed Jun 3, 1939 E/eGE G/Js Ounf Attorney lIn such l introducing the Patented June 3, 1941 METHOD or CARRYING oU'r cA'rALY'rIo REACTIONS John C. Munday and Edward W. Nicholson, Baton Rouge, La., assignors to Standard Oil Development Company, a corporation of Delaware Application June 3, 1939, Serial No. 277,156

3 Claims.

'I'his invention is directed to a method for carrying out catalytic reactions andv pertains more particularly to a method of carrying out catalytic reactions involving periodic regeneration of the catalyst.

While the' invention in some of its broader phases may have a more general application, it is peculiarly adapted to the catalytic treatment of hydrocarbon oils such as the cracking, purifying and rening of such Oils in the presence of a solid contact mass.

It has heretofore been proposed to treat hydrocarbon oils with a catalyst or other contact mass. During such treatment the mass becomes contaminated more or less rapidly with carbonaceous deposits which reduces the activity of the mass `for bringing about the desired treatment. It has also been proposed heretofore to regenerate the mass by burning said carbonaceous deposits in an oxidizing atmosphere. In most cases it is desirable to maintain the temperature during regeneration between closely controlled limits to avoid impairing the` activity of the mass.. The temperature control has been accomplished by regulating the oxygen concentration of the regenerating gases. For example it has been a practice to employ as a regeneration medium a mixture of air and products of regeneration obtained by recycling and to control the oxygen concentration by recycle gases.

According to one mode of operation the regeneration of the contact mass is carried out in the same equipment in which the reaction is carried out. When operatingA in this manner it is necessary periodically to interrupt the operating cycle in order to regenerate the catalyst.

a-mode of operation it is desirable toreduce the length of the regenerating period toa minimum. In order to reduce regenerating'time regulating the ratio of air to ,it has been a practice to supply an excess of oxygen during the final stages of regeneration.

` It also has been customary to subject the contact mass to purging treatment before and after each cracking period. The purging treatment after the cracking period and before regeneration is for the purpose of removing volatile hydrodependent purging treatments. This treatment was accomplished by passing a stripping gas such as steam or other inert gas through the reaction chamber or by evacuating the chamber. These purging treatments increase the time the equipment is out of production or in other words reduce the capacity of the cracking unit.

'I'he object of the present invention is to provide an improved method of the character above described whereby the loss of time between cracking steps may be reduced.

A further object of the present invention is to provide an improved alternating cracking and regenerating process in which the purging opera- `tion for removing regenerating gases following the regenerating period can be substantially eliminated. A further object of the invention is to provide an improved process of the character specified wherein the purging normally following the regenerating treatment is carried out concurrently with the nal regenerating treatment,

A further object of the invention is to provide an improved process of the character specified which results in a production of a higher yield of motor fuel from a given charging stock than has been possible according to the prior practices. in accordance with the 'present invention the regeneration of alcatalyst or other contact-mass is accomplished by employing a mixture of air and regeneration products as an oxidizing medium.

After the regeneration-has been substantially completed but before complete removal of the carbonaceous deposits, the air supply is discontinued and the excess oxygen content of the products of regeneration is utilized to complete,`

, mass can be returned immediately to the cracking stage without additional purging.

carbon vapors from the reaction chamber before Y oxidizing gas and the purging the cracking period and followis for the purpose of removing from the reaction chamber betreatment before ing regeneration the oxidizing gas vfore introducing the oil vapors to be cracked.

According to prior practices, each cracking portion ofthe cycle required two separate and in- With the above nature and objects in view, the invention will be better understood by reference to the accompanying drawing wherein the figure is a diagrammatic illustration of an apparatus suitable for carrying the invention into effect:

Referring to the drawing the Areference characters I0 and Il designate two reaction chambers one of which is adapted to be on the reaction step while the other ison the regeneration step. It/

will be understood that steps are changed from one reaction chamber to the other as conditions require. Fordescriptive purposes it will be assumed that the apparatus is employed for cracking oils.

The oil to be cracked is introduced into the reaction chambers I and II through a manifold line I2 having branch lines I3 and I4 leading to reaction chambers I0 and II respectively. The oil prior to passing to the manifold line I2 is vaporized and preheated to the desired reaction temperature by suitable heating and vaporizing equipment which for simplicity has been omitted from the drawing. The cracked products from the reaction chambers I0 and II are withdrawn therefrom through branch lines I5 and I6 merging with a transfer line I'I leading to a suitable recovery system (not shown) for separation and purification of the final product.

The regenerating medium comprising air diluted with recycled regenerating gases is passed through line I8 having branch lines I9 and 20 leading to reaction chambers Ill and II respectively. Gaseous products of regeneration are removed from the reaction chambers through branch lines 2I and 22 interconnected with a manifold line 23. The excess regeneration gases which are not desired to be recycled are rejected through vent ing by passing through a vheat exchange coil is passed to the suction side of a blower 26 where it is combined with the desired amount of air introduced through line 21. l

When carrying out the process in accordance with the present invention the regeneration is accomplished in the following manner. Assume that chamber I0 is on the cracking step whereas chamber I I has just completed the cracking step and is about to be regenerated. Upon completion of the cracking step in the reaction chamber II the valve in branch line I4 interconnecting reaction chamber II with the vapors to be cracked will be closed thus removing chamber II from the cracking step. Following this the catalyst contained in reaction chamber II is rst purged of cracked products either by the introduction of a suitable stripping gas such as steam, ue gas or the like through suitable pipes (not shown), or by evacuating the chamber. The products resulting from the purging operation may be subjected to fractionation to recover oil constituents therefrom. To this end the valve in line I6 may re- -main open during the purging period so that the purged products may be fractionated in the same equipment in which the oil vapors are fractionated or the valve in line I6 may be closed and the purged products separately fractionated. When the purging is accomplished regeneration is commenced by opening the valves in branch lines 20 and 22, the regenerating medium comprising air diluted with recycle regenerating gas from a previous regenerating operation is passed through the reaction chamber II, the relative amount of air and recycle gas -being controlled to maintain the temperature of the catalyst below a predetermined maximum. During the regeneration the relative proportion of air employed in the regeneration circuit is increased to hasten the regeneration. As a result the recycle gases will contain a substantial amount of excess oxygen. When the regeneration has almost reached cornpletion the air supply is discontinued and the unconsumed oxygen in the recycle gases is used to remove the nal portion of carbonaceous deposits from the catalyst mass. The particular point at line 24. The remainder after cool- Cit which the oxygen supply is discontinued will depend on the amount of excess oxygen in the recycle gases. This can be determined by simple laboratory tests and by analytical control. The amount of carbonaceous deposits retained on the catalyst when the air supply is discontinued should be suicient to reduce the oxygen content of the recycle gases to such a point that the next cracking step can be started without additional purging treatment. For example the oxygen concentration should be reduced to below about 2%. As a result upon completion of the regeneration the reaction chamber gases are 'substantially free of unconsumed oxygen .and the reaction chamber can be returned immediately to the cracking step without undergoing .any additional purging treatment. When operating in this manner the catalyst mass returned to the cracking step will contain a relatively large volume of adsorbed carbon dioxide which diffuses from the catalyst mass at a relatively slow rate. As the result during the initial portion of the cracking step the tempered due to the diiusion of residual carbon dioxide contained therein and over-cracking during the initial part of the cracking step will be avoided. According to the past procedure relatively large amounts of coke and gases are formed during the initial part of the cracking step due to the high activity of the catalyst. It has heretofore been proposed to overcome this objection `by introducing the oil to be cracked at a lower temperature during the 'initial part of the step or to increase the feed rate to compensate for increase in activity of the catalyst. The present invention makes this unnecessary since the initial high activity of the catalyst following regeneration is tempered by the presence of carbon dioxide gases adsorbed therein. Another advantage of our invention is that by 4continuing the recycling of gases after discontinuing the air supply until the excess oxygen has been largely consumed provides a supply of oxygen-free gases which may be utilized either to purge the chamber of cracked products following the cracking step or as a diluent for the air in starting a fresh regenerating step.

While we have described the invention as applied specifcally to the catalytic cracking of hydrocarbon oils it will be understood that it has a more general application to processes involving the alternate ltreatment and regeneration of the catalyst mass and particularly to the case where the freshly regenerated catalyst is over-active. For example the invention may be applied to the reforming of naphthas, either in the presence or absence of hydrogen, wherein the principal objective is to improve the octane of the feed stock rather than to convert.a higher boiling hydrocarbon into motor fuel constituents. Having described the specific embodiment of the invention it will be understood that it embraces such other modications and variations as come within the spirit and scope thereof.

We claim:

1. In a method of carrying out reactions in the presence of a solid contact mass wherein the contact mass is subjected to alternate reacting and regenerating steps the regeneration accomplished by recycling regeneration products to the mass to be regenerated in admixture with an oxygen containing gas from an extraneous source and wherein the recycle gas normally contains substantial quantities of unconsumed oxygen during the final stages of regeneration; the improvement which comprises discontinuing the supply of .extraneous oxygen containing gas before complete removal of said carbonaceous decracking activity of the catalyst will bepositso thereafter continuing the recycling of regenerating gas whereby remaining carbonaceous deposits are utilized to remove unconsunied 0Xygen in said recycle gas and thereby purge the contact mass of oxidizing gas whereby the said catalyst may be directly returned thereafter to the reaction step without additional purging treatment.

2. In the catalytic conversion of. hydrocarbon oil wherein the catalyst is subjected to alternate conversion and regeneration steps, the regeneration accomplished by passing a regenerating gas comprising recycle gas in admixture with ex traneous supply of oxygen containing gas and wherein the recycle gas normally contains a substantial amount of free oxygen during the final stages of the regenerating step; the improvement which comprises discontinuing the supply of oxygen containing gasI before@complete` removal"y of said carbonaceous deposits, thereafter continuing the recycling o1' said regenerating gas whereby further regeneration is accomplished by unconsumed oxygen in said recycle gas whereby the 'to the conversion step said catalyst may be directly returned thereafter without further purging treatment.

3. In the catalytic cracking of hydrocarbon oils wherein the catalyst is subjected to periodic regeneration treatment and wherein the regeneration is accomplished by continuously passing an oxygen containing gas from an extraneous source in adinlxture with recycle regenerating gases, through the catalyst to-be regenerated; the improvement which comprises discontinuing the lsupply of extraneous oxygen containing gas before complete removal ofsaid carbonaceous deposits, continuing -the recycling of said regenerating gas to utilize unconsumed oxygen contained therein for further regenerating said catalyst mass and to saturate said contact mass with carbon dioxide, and thereafter using said regenerating mass to 'eil'ect cracking without intermediate purging treatment and while the mass is still saturated with carbon dioxide.

JOHN Cl MUNDAY. EDWARD W. NICHOLSON.

Images