U.S. patent application number 09/764147 was filed with the patent office on 2002-07-25 for regeneration method of heterogeneous catalysts and adsorbents.
This patent application is currently assigned to Europeenne De Retraitement De Catalyseurs-Eurecat. Invention is credited to Brahma, Nilanjan, Dufresnce, Pierre, Locatelli, Francois, Mendakis, Georges, Robinson, James.
Application Number | 20020098971 09/764147 |
Document ID | / |
Family ID | 25069817 |
Filed Date | 2002-07-25 |
United States Patent
Application |
20020098971 |
Kind Code |
A1 |
Robinson, James ; et
al. |
July 25, 2002 |
Regeneration method of heterogeneous catalysts and adsorbents
Abstract
Process for the regeneration of a solid catalyst or of a solid
adsorbent wherein the catalyst or the adsorbent is used in the form
of a bed in a regeneration zone, in which bed the catalyst is in
motion, said process comprising at least one heating step under a
reductive atmosphere.
Inventors: |
Robinson, James;
(Friendswood, TX) ; Brahma, Nilanjan; (League
City, TX) ; Mendakis, Georges; (League City, TX)
; Locatelli, Francois; (Valence, FR) ; Dufresnce,
Pierre; (Valence, FR) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
Arlington Courthouse Plaza I
Suite 1400
2200 Clarendon Boulevard
Arlington
VA
22201
US
|
Assignee: |
Europeenne De Retraitement De
Catalyseurs-Eurecat
|
Family ID: |
25069817 |
Appl. No.: |
09/764147 |
Filed: |
January 19, 2001 |
Current U.S.
Class: |
502/34 ;
502/53 |
Current CPC
Class: |
B01J 38/10 20130101;
B01J 20/3408 20130101; B01J 38/22 20130101; B01J 2220/56 20130101;
B01J 20/18 20130101; B01J 20/3483 20130101; B01J 37/18 20130101;
B01J 20/3458 20130101; B01J 23/94 20130101; B01J 23/96 20130101;
B01J 20/0225 20130101 |
Class at
Publication: |
502/34 ;
502/53 |
International
Class: |
B01J 038/10 |
Claims
1. Process for the regeneration of a solid catalyst or of a solid
adsorbent wherein the catalyst or the adsorbent is used in the form
of a bed in a regeneration zone, in which bed the catalyst is in
motion, said process comprising at least one heating step under a
reductive atmosphere.
2. Process according to claim 1 wherein the said heating step is
carried out under a non-oxydative atmosphere.
3. Process according to claims 1 or 2 carried out between 250 and
650.degree. C.
4. Process according to claim 3 carried out between 300 to
550.degree. C.
5. Process according to one of claims 1 to 4 wherein the reductive
atmosphere is a hydrogen-containing atmosphere.
6. Process according to one of claims 1 to 5 wherein after the
reductive treatment, a subsequent oxidative treatment is carried
out.
7. Process according to any of claims 1 to 6 wherein the said bed
in motion is selected in the group consisting of mobile or moving
beds, circulating or slurry beds, fluidized beds, expanded beds,
ebullated beds, and beds such as belt beds or rotary beds.
8. A process according to any of claims 1 to 7 wherein the catalyst
or the adsorbent contains an amorphous or zeolitic support.
9. A process according to claim 1 to 7 wherein the said material
contains at least one metal belonging to Group VIII.
10. A process according to claim 9 wherein the said material
contains palladium.
11. A process according to claim 9 wherein the said material
contains nickel.
12. A process according to claim 9 for the regeneration of a
hydrogenation catalyst.
13. A process according to claim 10 for the regeneration of a
nickel-containing adsorbent.
Description
DESCRIPTION OF THE INVENTION
[0001] Process for the regeneration of a solid catalyst or of a
solid adsorbent wherein the catalyst or the adsorbent is used in
the form of a bed in a regeneration zone, in which bed the catalyst
is in motion, said process comprising at least one heating step
under a reductive atmosphere.
PRIOR ART
[0002] Heterogeneous catalysts and adsorbents are used in a number
of applications in refining, petrochemicals and chemicals
industries. They show their full performance at start of run, but
after some time on stream usually deactivate more or less slowly
depending on the application and the conditions of use. One reason
of this activity loss is the formation of carbon deposits,
typically called coke, restricting either the access or the nature
of the active sites. A well-known countermeasure is the removal of
these deposits by a controlled combustion, usually called
regeneration. This operation can be performed either inside the
reactor (in-situ method), either outside in a dedicated unit. For
fixed bed units, this last method is more and more practiced for a
number of reasons, as better temperature control leading to a
higher activity recovery, time savings, environmental
constraints.
[0003] Another reason of deactivation of catalysts and adsorbents,
especially those containing transition metals, is the poisoning of
the metallic phase by various compounds brought during the run by
the feedstock, one common poison being sulfur-containing molecules.
Group VIII metals, either precious, as Platinum or Palladium, or
not, as Nickel, are known to be deactivated by the adsorption of
Sulfur.
[0004] The typical off-site regeneration techniques are based on a
controlled combustion under diluted oxygen in various moving bed
systems, either rotary furnaces such as Rotolouvres (U.S. Pat. Nos.
4,551,437 or 4,605,371), or belt furnaces and fluidized bed systems
(EP-A-1002 581). One of the key elements of the process is to
control oxygen partial pressure, which in turn governs the kinetics
of carbon elimination and thus the heat release from the oxidation
reactions. This operation of regeneration has often to be preceded
of stripping step consisting of heating step, either under air or
inert atmosphere (nitrogen or lean gas) in order to eliminate some
free hydrocarbons contained in the catalyst porosity, just by
promoting a phenomenon of evaporation.
INVENTION
[0005] It has now been discovered that this conventional technique
could be significantly improved in a number of cases by adding a
heating step under a hydrogen-containing atmosphere before an
optional oxidative step. In some cases the hydrogen treatment alone
can be sufficient to restore the catalyst or adsorbent activity.
This process can be applied on any type of heterogeneous catalysts
or adsorbents either made of an amorphous or crystalline material
as for instance a zeolite. This thermal treatment with an hydrogen
containing gas can be associated with other treatment steps, such
as oxygen containing gas treatment, or inert gas treatment, or
solvent extraction for removal of leachable impurities or an
association of these steps.
[0006] This step in the presence of hydrogen containing gas seems
specifically useful for some metal containing catalysts,
specifically when metals belong to Group VIII type, such as for
instance Platinum, Palladium or Nickel. The process applies also
for some adsorbents, for instance Nickel containing adsorbents that
are used for example as sulfur traps for purification of
hydrocarbon feedstocks. After some time on stream they are more or
less deactivated, meaning that their Sulfur adsorption capacity is
greatly diminished. The new procedure according to this invention
involving a treatment under hydrogen containing gas would be more
efficient for restoring the adsorption capacity than a conventional
regeneration with an oxidizing atmosphere.
[0007] In order to implement the process according to the present
improvement, it is rather essential that during said process, the
particles of the catalyst or of the adsorbent, i.e. the catalyst
bed or the adsorbent bed, is in motion, said beds being selected
for instance from the group consisting of mobile or moving beds,
circulating beds, slurry beds, fluidized beds, expanded beds,
ebullated beds or beds such as belt beds or rotary beds.
[0008] This treatment in a reductive atmosphere has proved to be
superior to the conventional oxidative one step treatment. It is
also better than a two step treatment consisting of Nitrogen
followed by an Oxygen containing atmosphere. It appears that in
some cases Hydrogen is more efficient than air for the removal of
some types of carbon containing compounds, and also more efficient
than Nitrogen. When the reductive treatment is not sufficient for
removing all the carbonaceous species, then a subsequent oxidative
treatment (conventional for instance) may be needed. In this case
the residence time needed for completing carbon elimination is very
much shortened compared to a direct oxidative treatment alone.
[0009] In the prior art, the oxidative treatment takes place at
temperature between 300.degree. C. and 700.degree. C., and more
typically between 400.degree. C. and 600.degree. C. The stripping
step under air or nitrogen may be performed in a wider range of
temperatures, depending on the boiling points of hydrocarbons to be
stripped, typically between 20.degree. C. and 500.degree. C. This
hydrogen treatment step according to the invention can also been
practiced in the low range of temperatures, i.e. around
20-200.degree. C. In this case the main phenomenon involved is
mainly a stripping under a non oxidative atmosphere and the
benefits of using Hydrogen instead of Nitrogen would be rather
narrow. On the other hand, it has been found according to an
improvement of the present invention that the use of higher
temperatures such as 250 to 650.degree. C. and more specifically
300 to 550.degree. C. brings a specific advantage.
[0010] Applications
[0011] The benefits of the invention are probably most visible when
the coke deposit has some aliphatic character, which is the case
for instance if catalyst has been used in an application at rather
low temperature under hydrogen pressure. One example where such
conditions are used is the process of selective hydrogenation of
olefinic cuts downstream a steam cracker. Catalysts used for these
applications contain Palladium, alone or associated with a second
metal (e.g. Silver or Gold), finely dispersed on a support, often
alumina based. Typical catalysts for the C2 or C3 cut treatment
contain a low Palladium amount (less than 0.1% weight). One side
reaction is the so-called formation of green oil, these long chain
oligomers being still often found in the porosity of these
deactivated catalysts. The operation of regeneration will have to
take place at moderate temperature, due to the intrinsic
sensitivity of these materials. A conventional regeneration in
oxidative conditions, either with or without nitrogen stripping,
may produce in these low temperature conditions a product with some
gray to black zones, so still containing some traces of carbon. On
the other hand, a pretreatment with hydrogen will remove a large
part of carbon and the subsequent oxidative step can thus be much
easier.
[0012] Another case of application of this new regeneration method
can be for the catalysts used in aromatics hydrogenation, for
example benzene transformation to cyclohexane, or hydrogenation of
various other heavier aromatics containing feedstocks. These
catalysts are often containing a rather high amount of Nickel,
typically 30 to 60 wt %. Another case where the carbon deposit can
have a somehow aliphatic character is encountered with shape
selective zeolites used for various hydrocarbon transformations.
Their internal porosity of channels and cavities of these
crystallized aluminosilicates is small enough to limit the
formation of polyaromatic rings by steric hindrance. One well-known
case is the zeolite ZSM5 (or the approaching structure Silicalite)
with a channel dimension around 5.5 Angstroms. So this method can
also be used with profit for regeneration of aluminosilicates.
Another application of this invention is for the reactivation of
the adsorbents called in the industry as Sulfur traps. In the
refining or petrochemical industry, some catalysts extremely
sensitive to sulfur need to be protected by a Sulfur guard bed. For
instance, between a naphtha hydrotreater and the reformer or the
isomerizer downstream, a "Sulfur Guard Bed" protects the Platinum
containing catalysts loaded in these units. Its role is to remove
sulfur compounds present in hydrotreated naphtha feedstock, as
mercaptans, thiophene or hydrogen sulfide. These compounds are
found at concentrations typically below 1 part per million in
normal operation, and potentially higher during some upsets of the
naphtha hydrotreating unit. Some sulfur guard beds are also
installed in the chemical industry in order to protect
hydrogenation catalysts containing either precious metals (Pt, Pd),
nickel or copper chromites. In most cases, hydrogenation units
consist of several reactors in series in which the first one
usually plays the role of adsorbing sulfur compounds of the
feedstock. Some nickel hydrogenation catalysts can be fully
deactivated after adsorption of 1 wt % sulfur. The most common
sulfur traps available on the market are nickel-based materials,
with typically a Nickel content of 20 to 60 wt %. They exhibit a
high sulfur adsorption capacity for H.sub.2S and mercaptans as well
as a lower affinity for thiophenes. The nickel containing traps,
once contaminated with Sulfur has to be discarded. To the best of
our knowledge, there is no technique allowing restoring the
properties of a spent sulfur material. The conventional techniques
of high temperature treatment either under nitrogen or under oxygen
containing atmosphere are not able to restore the adsorption
properties of these spent materials, even if a partial sulfur
elimination can be observed. It has now been discovered that a
heating step under a hydrogen-containing atmosphere could somehow
restore the adsorption properties for Sulfur contaminated Nickel
traps more efficiently than conventional techniques.
EXAMPLE 1
Comparative
[0013] A spent Nickel based material, used as a sulfur absorbent
for light hydrocarbon feeds, was used to evaluate various
regeneration routes. It contained about 52 wt % Nickel, the rest
being silicon and aluminum oxide. Sulfur content is 17.2 wt %,
measured by a LECO analyzer, and hydrocarbons content, measured by
weight loss under Nitrogen up to 500.degree. C. in a Setaram
thermobalance is 5.7 wt %. Stripping of mentioned spent catalyst is
performed under nitrogen at 500.degree. C. in a laboratory rotating
furnace setup. Catalyst feedrate is 50 grams/hour with a residence
time of 2 hours in the furnace hot zone and a flow rate of 500
liters /hour of nitrogen. After the treatment, the hydrocarbon
analysis is below 0.5 wt % and Sulfur content is 17.6 wt %. This
procedure does not reduce the sulfur but removes light hydrocarbon
species. The product is then submitted to an adsorption test using
butyl mercaptan. This sulfur molecule is chosen as light naphtha
feedstock typically contains mercaptans and thiophenes. The
procedure is the following: 5 grams of catalyst are heated up to
180.degree. C. and kept there for 4 hours, with a gas (10
liters/hour) containing 10 mol % of butyl mercaptan in nitrogen.
After the test, the system is purged with nitrogen at 180.degree.
C. for 1 hour (2 liters/hour flow rate) and the sulfur content of
the catalyst is analyzed. The sulfur uptake of this nitrogen
stripped product in the mercaptan adsorption test is 6.1 wt %. This
is about 1/3 of the capacity of a fresh material in these same
conditions, and thus means that the material is not very attractive
for reuse.
EXAMPLE 2
Comparative
[0014] The material of example 1 is further treated at 450.degree.
C. under air. The same laboratory rotating furnace setup as
mentioned in example 1 is used. Catalyst feed-rate is 50 grams/hour
with a residence time of 2 hours at a flow rate of 500 liters/hour
of air. The sulfur content is reduced to 5.6 wt %. The sulfur
uptake of this air regenerated product in the mercaptan adsorption
test as mentioned is 0.2 wt %, which means that the material is
virtually inactive.
EXAMPLE 3
[0015] The air-regenerated product as obtained in example 2 is
subsequently activated under hydrogen at 450.degree. C.The same
laboratory rotating furnace setup as mentioned in example 1 is
used. Catalyst feed-rate was about 50 grams/hour with a residence
time of 2 hours at a flow rate of 500 liters/hour of hydrogen.
Sulfur content remains virtually unchanged at 5.3 wt %. The Sulfur
uptake of this activated material in the mercaptan adsorption test
is 13.8 wt %, which means that the material may be qualified for a
potential re-use in an industrial unit.
EXAMPLE 4
[0016] The air-regenerated product as obtained in example 2 is
subsequently activated under hydrogen at 600.degree. C., all
conditions being the same as described in example 3 except
temperature. Sulfur content decreases to 3.3 wt %. The Sulfur
uptake in the mercaptan adsorption test is 15.6 wt %. Product is
still better than in example 3 and is thus improved by the high
temperature treatment.
EXAMPLE 5
[0017] The raw material as mentioned in example 1 is treated
directly under hydrogen at 600.degree. C. The same laboratory
rotating furnace setup as mentioned in example 1 is used. Catalyst
feed-rate is about 50 grams/hour with a residence time of 2 hours
at a flow rate of 2 liters /hour of hydrogen. Sulfur content is
reduced to 2.9 wt %. The Sulfur uptake of this material in the
mercaptan adsorption test is 16.3 wt %, meaning that it may be
qualified for a potential re-use in an industrial unit.
EXAMPLE 6
Comparative
[0018] Around 1 kg of spent catalyst applied for selective
hydrogenation of ethylene cut from steam cracking is used. It
contains a low amount of Palladium, less than 0.1 wt % supported on
alumina. Carbon content from the LECO analyzer is 4.7 wt %. It is
treated according to a two-step process. Stripping of mentioned
spent catalyst is performed under Nitrogen at 450.degree. C. in a
laboratory rotating furnace setup. Catalyst feed-rate is 50
grams/hour with a residence time of 2 hours in the furnace hot zone
and a flow rate of 500 liters/hour of nitrogen. At this point,
Carbon content is 1.2 wt %. Then the oxidative regeneration step is
performed in the same conditions replacing nitrogen by dry air at a
temperature of 450.degree. C. At the end of the treatment, carbon
content is 0.1 wt % but the product still shows some black and gray
shadows.
EXAMPLE 7
[0019] The raw material as used for example 6 is treated first by
Hydrogen at 450.degree. C. in the laboratory rotating furnace
setup. Catalyst feed-rate is 50 grams/hour with a residence time of
2 hours and a flow rate of 500 liters/hour of hydrogen. Carbon
content is 0.5 wt %. Then the oxidative regeneration step is
performed in the same conditions replacing Hydrogen by dry air at a
temperature of 450.degree. C. At the end of the treatment, carbon
content is 0.1 wt % and the product is homogeneously light
gray.
EXAMPLE 8
[0020] The raw material used for example 6 is leached first by a
solvent in order to remove some light hydrocarbons. Around 300 g of
this spent catalyst are placed in a beaker, covered with 600 ml of
white spirit and left 1 hour at 80.degree. C. and filtered. The wet
catalyst is then treated by Hydrogen at 450.degree. C. in the
laboratory rotating furnace setup. (50 grams/hour in weight of dry
product, residence time 2 hours, 500 liters/hour of hydrogen.
Carbon content is 0.3 wt % after the leaching and the Hydrogen
steps. Then the oxidative regeneration step is performed in the
same conditions replacing hydrogen by dry air at a temperature of
450.degree. C. At the end of the treatment, carbon content is 0.1
wt % and the product is homogeneously light gray.
EXAMPLE 9
[0021] An activity test is performed to qualify the performance of
both products of examples 6 and 7 in selective acetylene removal of
a mixed ethylene cut. The feedstock has the following composition
(expressed in % volume): Hydrogen 26.6; Ethylene 42.3; Methane
30.8%, Acetylene 0.26; Carbon monoxide 0.032. The test starts at
38.degree. C. and temperature increases at 2.5.degree. C./min. The
so-called cleanup temperature T.sub.cu is determined when the
acetylene composition goes down to 20 ppm. Then at increasing
temperature ethylene gets more and more hydrogenated and runaway
can be reached. T.sub.ra is noted for a 3% volume ethylene
conversion. Then, temperature is decreased back to 38.degree. C.
and then procedure is repeated. A new couple of temperatures
T'.sub.cu and T'.sub.ra is determined. The difference
T'.sub.ra-T'.sub.cu is defined as the operating window. The best
catalyst has the lowest cleanup temperature and the largest
operating window. The product of example 6 regenerated according to
a prior art procedure has a cleanup temperature of 50.0.degree. C.
and an operating window of 22.2.degree. C. The product of the
example 7 regenerated according to the invention has a cleanup
temperature of 48.5.degree. C. and an operating window of
24.9.degree. C.
EXAMPLE 10
Comparative
[0022] A spent massive nickel containing catalyst, used in an
application of aromatic hydrogenation, is also used to compare the
conventional regeneration with the new method. It contained about
52 wt % Nickel, the rest being alumino silicate support. It is
contaminated with 0.9 wt % sulfur and 6.7 wt % carbon. Regeneration
of mentioned spent catalyst is performed under air at 300.degree.
C. in a laboratory rotating furnace setup. Catalyst feed-rate is
set at 50 grams/hour with a residence time of 2 hours in the hot
part of the furnace and airflow is 500 liters/hour. The product is
then fed again under air at 450.degree. C. to the same rotating
furnace set up in the same condition. The residual sulfur content
of the regenerated product is 0.6 wt % while the carbon content is
reduced to 0.6 wt %. A representative sample of the product is
collected, grinded and sieved between 16 and 25 ASTM sieve. A 0.5 g
sample is submitted to a benzene hydrogenation test. Sample is
mixed with inert alumina of same granulometry and loaded in the
basket of an autoclave from Autoclaves Engineer. Reactor is closed,
purged with nitrogen for 0.5 hour. A hydrogen flow of 1 liter/h is
applied and reactor is heated up to 400.degree. C. for 4 hours with
the objective of achieving a reduced state. Reactor is then allowed
to cool down under Nitrogen flow to ambient temperature. At this
point 50 ml of a mixture 80/20 of cyclohexane/benzene is added
through a calibrated pump, and catalyst temperature adjusted to
100.degree. C. Reactor pressure is adjusted and regulated to 1 Mpa.
A gas dosage system operating at 3 Mpa of Hydrogen is connected to
the reactor and the pressure of this gas burette is monitored
through a pressure transducer and recorded with time. The activity
result is expressed by the rate constant of hydrogen consumption
kinetics.
[0023] Result is found for this regenerated catalyst at 12.1
10.sup.-3 s.sup.-1.
EXAMPLE 11
Comparative
[0024] The spent catalyst as used in example 10 is regenerated
under air in two steps in the laboratory rotating furnace in the
same conditions as in example 10, except temperature: first step
still at 300.degree. C., and then second step at 550.degree. C. The
residual sulfur and carbon contents of the regenerated product are
respectively 0.4 and 0.1 wt %. A representative sample of the
product is collected and submitted to a benzene hydrogenation test
as described in Example 10. The same procedure is used including
the in-situ reduction step at 400.degree. C. Activity is measured
at 10.9 10.sup.-3 s.sup.-1. No improvement is noted with the higher
temperature despite the reduction in C and S levels.
EXAMPLE 12
[0025] The spent catalyst as used in example 11 is regenerated
under hydrogen in one step in the laboratory rotating furnace at a
temperature of 450.degree. C. Catalyst feed-rate is set at 50
grams/hour with a residence time of 2 hours and hydrogen flow is
500 liters/hour. The residual sulfur content of the regenerated
product is lowered at 0.7 wt % while the carbon content is reduced
to 1.8 wt %. A representative sample of the product is collected
and submitted to a benzene hydrogenation test as described in
Example 10. The same procedure is used including the in-situ
reduction at 400.degree. C. Activity is measured at 14.7 10.sup.-3
s.sup.-1.
EXAMPLE 13
[0026] The spent catalyst as used in example 11 is regenerated
under hydrogen in one step in the laboratory rotating furnace at a
temperature of 550.degree. C. All other conditions are the same
than example 12. The residual sulfur content of the regenerated
product is lowered at 0.3 wt % while the carbon content is reduced
to 1.2 wt %. A representative sample of the product is collected
and submitted to a benzene hydrogenation test as described in
Example 10. The same procedure is used including the in-situ step
reduction at 400.degree. C. Activity is measured at 16.3 10.sup.-3
s.sup.-1.
[0027] The preceding examples can be repeated with similar success
by substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples. Also, the preceding specific embodiments are to
be construed as merely illustrative, and not limitative of the
remainder of the disclosure in any way whatsoever.
[0028] The entire disclosure of all applications, patents and
publications, cited above and below, are hereby incorporated by
reference.
[0029] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention,
and without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *