Method for regeneration of catalysts by removal of nitrogen poisons

A method for the regeneration of end-of-cycle catalysts is provided wherein nitrogen and other deleterious poisons are removed prior to hydrogen treatment by passing over the catalyst bed a stripping mixture consisting of an alkyl amine whose basicity is much greater than that of the indigenous nitrogen compounds found in the catalyst.

BACKGROUND OF THE INVENTION 
This invention is directed to a method for the regeneration of catalysts 
which are useful in processes wherein various oleaginous base stocks are 
upgraded, for example, catalysts which are used in lube or distillate 
dewaxing processes. 
It is well known in the art to regenerate catalyst systems by flushing them 
with steam or water, or a suitable hot gas or vapor, or even subjecting 
the catalyst to combustion to remove the impurities or poisons such as 
nitrogen compounds and various other carbonaceous matter which the 
catalysts have acquired during their utilization. 
Spent or end-of-cycle catalysts, e.g., lube dewaxing or distillate dewaxing 
catalysts, such as for example, zeolites and the binders thereof, contain 
acquired nitrogen compounds which poision the catalyst and thereby render 
it less effective with respect to activity. The nature of these nitrogen 
poisons is not precisely known, but they are thought to be aromatic in 
character and are of the basic type. Typical basicities for aromatic 
amines are in the order of K.sub.b =10.sup.-10 (Ref.: Organic Chemistry, 
2nd Ed., Morrison and Boyd, page 721). These basic nitrogen compounds are 
generally classified (Re.: The Chemistry and Technology of Petroleum, 
James G. Speight, pg, 72-5, 1980) as being homologues of pyridine and 
pyrrole. Their K.sub.b 's are about 2.times.10.sup.-9 and 
1.times.10.sup.-14, respectively. 
One well known regeneration procedure for these types of catalysts is to 
pass hydrogen over the catalyst at about 400 psig at a temperature of 
900.degree.-1000.degree. F. for about 24 hours. However, despite this 
treatment, residual nitrogen remains on the catalyst. To alleviate this 
problem of not being able to remove substantially all the nitrogen 
poisons, the novel procedure disclosed hereinbelow is offered. 
SUMMARY OF THE INVENTION 
It has now been discovered that the nitrogen poisons may be removed from 
the aforementioned catalysts if, prior to conventional prior art 
treatments, e.g., hydrogen treatment, a stripping mixture consisting of an 
alkylamine in accordance with the invention and in a suitable solvent is 
passed over the catalyst under such conditions that their critical 
temperatures are not exceeded and the amine and the solvent are maintained 
in their liquid state. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
The method disclosed herein is adaptable to a wide variety of catalytic 
systems or catalytic materials. For instance, the catalytic materials may 
be ordered porous crystalline aluminosilicates having a definite 
crystalline structure, both natural and synthetic or they may be amorphous 
and/or non-crystalline. The catalysts may also contain a hydrogenation 
component such as nickel, cobalt or molybdenum. In general, the process 
disclosed herein is suitable for use in regenerating catalyst involved in 
any hydrotreating processes. It is especially adaptable to lube dewaxing 
and distillate dewaxing processes. For example, U.S. Pat. No. Re 28,398 
(of U.S. Pat. No. 3,700,585) to Chen et al. describes as a process for 
catalytic dewaxing with a catalyst comprising ZSM-5. U.S. Pat. No. 
3,894,938 describes catalytic dewaxing process combined with catalytic 
hydrofinishing. U.S. Pat. No. 3,755,138 to Chen et al. is described as a 
process for mild solvent dewaxing to remove high quality wax from a lube 
stock which is then catalytically dewaxed to specification pour point. The 
ZSM-type catalysts disclosed therein are included among those suitable for 
use in this novel process. 
The amines useful herein as described above are alkylamines, e.g., 
n-butylamine. However, any alkylamine having from about 1 to about 36 
carbon atoms can be used herein. Dialkyl and trialkyl amines as well as 
monoalkyl amines are suitable. Suitable amines therefore include 
methylamine, butylamine and pentylamine, diethylamine, dipropylamine and 
triethylamine. 
Although the instant process is in no way limited to zeolites, they are, 
however, especially adaptable to the described process. Suitable zeolites 
include but are not limited to those of the ZSM-5 type, e.g., ZSM-5, 
ZSM-11, ZSM-12, ZSM-21, ZSM-23, ZSM-35, ZSM-38 and ZSM-48 and the like and 
their hydrogen forms. It is noted that the binders for the respective 
catalyst are part of the catalyst system subject to this novel means of 
reactivation. ZSM-5 type catalysts are more fully described in, for 
example, U.S. Pat. No. 3,702,886; U.S. Pat. No. 3,709,979; U.S. Pat. No. 
3,755,138; U.S. Pat. No. 3,832,449; U.S. Pat. No. 4,016,245 and U.S. Pat. 
No. 4,046,859, all of which are incorporated herein in their entirety by 
reference thereto. 
Suitable solvents include such organic solvents as toluene and heptane and 
the like. 
As noted hereinabove end-of-cycle catalysts such as distillate dewaxing and 
lube dewaxing catalysts are especially suitable to the novel process of 
regeneration disclosed herein. Such catalysts as mentioned hereinabove 
contain within, for example, the pores of the zeolite and the binder 
nitrogen compounds which poison the catalyst and thereby render the 
catalyst less effective with respect to activity. The standard prior art 
regeneration procedure referred to hereinabove comprising passing hydrogen 
over the end-of-cycle catalyst does not completely remove the basic 
nitrogen and other catalytic poisons. The novel process disclosed herein, 
however, substantially alleviates the problem of not being able to remove 
these poisons, particularly nitrogen. Prior to hydrogen treatment a 
stripping mixture consisting of an alkylamine, e.g., n-butylamine in a 
suitable solvent, (toluene) is passed over the catalyst which may be a 
catalyst bed or otherwise, at suitable conditions such that the amine and 
solvent are maintained in their liquid state without exceeding their 
critical temperatures. Butylamine being a stronger base than the 
aforementioned poisonous compounds replaces them in the catalyst system.

The following preferred embodiments are described herein, not as 
limitations, but as illustrations of the novel process hereof. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
A typical end-of-cycle catalyst having the residue composition as shown in 
the Table was subjected to conventional hydrogen reactivation and also to 
the amine/hydrogen reactivation described herein. The comparative data 
derived from these treatments is also shown below in the Table. 
TABLE 
______________________________________ 
Residue Remaining on Catalyst After Treatments 
End-of-Cycle 
H.sub.2 Amine/H.sub.2 
Catalyst Reactivation.sup.1 
Reactivation.sup.2 
______________________________________ 
g/100 g Cat. 
Carbon 39.53 3.90 2.55 
Hydrogen 6.18 .45 0.39 
Nitrogen 0.243 0.036 0.026 
Sulfur 0.395 0.000 0.000 
Total Wt. Residue 
46.348 4.386 2.966 
Normalized 
Composition 
Carbon, wt. % 88.92 85.97 
Hydrogen, Wt. % 10.26 13.15 
Nitrogen, wt. % 0.82 0.88 
Sulfur, wt. % 0.00 0.00 
100.00 100.00 
H/C (Atomic) 1.38 1.84 
______________________________________ 
Treatment Conditions 
.sup.1 Catalyst temperature = 950.degree. F., 14 hours, 400 psig. 
.sup.2 Strip catalyst at 150.degree. C. and 400 psig with 20% vol. % 
nbutylamine for 24 hours. Then hydrogen reactivate at 950.degree. F. for 
16 hours at 400 psig. 
These data clearly establish the utility of the present novel process, that 
is, that the invention as disclosed herein results in a 30 percent or more 
reduction in total residue after hydrogen reactivation and also disclose a 
similar reduction in the amount of nitrogen remaining on the catalytic 
material. 
Although the present invention has been described with preferred 
embodiments, it is to be understood that modifications and variations may 
be resorted to, without departing from the spirit and scope of this 
invention, as those skilled in the art will readily understand. Such 
modifications and variations are considered to be within the purview and 
scope of the appended claims.