EP0204750A4

EP0204750A4 - Rejuvenation of a deactivated catalyst.

Info

Publication number: EP0204750A4
Application number: EP19850905984
Authority: EP
Inventors: Dennis L Holtermann; Rodolfo V Panopio; Sue D Pandey; Leslie A Field
Original assignee: Chevron Research and Technology Co; Chevron Research Co
Current assignee: Chevron USA Inc
Priority date: 1984-11-08
Filing date: 1985-11-07
Publication date: 1987-12-02
Also published as: CA1257245A; KR870700404A; AU5201686A; NL8520394A; GB2176716A; EP0204750A1; WO1986002861A1; DE3590575T1; GB8612723D0

Description

REJU VE NATION OF A D EACTIVATED CATALYST

05

BACKGROUND OF THE INVENTION

The present invention concerns a method for rejuvenatinq a zeolitic catalyst.

Catalytic reforming is a well known process that . m is used to raise the octane rating of a naphtha for gasoline. The reactions that occur during reforming include: dehydrocyciization of acyclic hydrocarbons, dehydroqenation of cyclohexanes , dehydroiso erization of alkylcyclopentanes , isomerization of paraffins, dealky- i lation of alkylbenzenes, and hydrocrackinq of paraffins. The hydrocrackinq reaction should be suppressed because that reaction lowers the yield of hydrogen and lowers the yield of liquid products.

Reforming catalysts must be selective for 0 dehydrocyciization in order to produce high yields of liquid product and low yields of light qases. These cata¬ lysts should possess good activity, so that low tempera¬ tures can be used in the reformer. Also they should possess good stability, so that they can maintain a high activity and a high selectivity for dehydrocyciization over a long period of time. Furthermore, they should be regenerable, so that they can be reqenerated without loss of performance.

While most reforminq catalysts contain platinum 0 on an alumina support, other catalyst supports have been proposed, such as large-pore zeolites. These large-pore zeolites have pores large enough for hydrocarbons in the gasoline boil ing ranqe to pass through. Catalysts based on these zeolitic supports have been commercially unsuc- cessf l .

Recently, a new catalyst was developed that comprises: a large-pore zeolite, a Group VIII metal, and an alkaline earth metal. This catalyst has a very hiqh selectivity for dehydrocyciization, but it is hard to 0 regenerate. SϋMMARY OF THE INVENTION The present invention is based on the discovery that a catalyst can be rejuvenated by contacting the cata¬ lyst with an aqueous media selected from the group con¬ sisting of water, an aqueous solution, and a saturated water vapor. This method of reiuvenation works for large-pore zeolitic catalysts that contain at least one Group VIII metal -

In a first embodiment, at least 10 cc of aqueous media must be used per cc of catalyst, and the aqueous media must be in the liquid phase. Preferably, at least 500 cc of aqueous media is used per cc of catalyst. Prior to contacting the catalyst with an aqueous media, it should be exposed to, oxidizing conditions, preferably at a temperature of from about 200°C to about 450°C. After the catalyst is contacted with an aqueous media, it should be exposed to reducinq conditions, preferably in the presence of hydrogen at a temperature of from about 200°C to about 700°C. The steps of oxidizing the catalyst, contacting the catalyst with an aqueous media, and reducing the cata¬ lyst can be repeated as necessary, until the catalyst is rejuvenated to the desired level.

A basic solution (i.e., r>H greater than 7) can be used instead of water or a saturated water vapor. In this embodiment, the catalyst is contacted with a basic solution at a temperature of from about 70°C to about 80°C. The basic solution can be an alkali metal hydroxide solution, such as potassium hydroxide solution having a pH of at least 10.

In a second embodiment, a zeolitic catalyst can be rejuvenated, and the stability of that catalyst can be improved, by contacting the catalyst with an aqueous solu¬ tion of a metal salt or metal hydroxide, wherein the metal is either an alkali metal and an alkaline earth metal.

In a third embodiment, a zeolitic catalyst can be rejuvenated by washinq the catalyst with either a neutral" or an acidic solution, contacting the washed cata¬ lyst with an aqueous solution of a metal salt or metal hydroxide (the metal is either an alkali metal and an alkaline earth metal) , washing the contacted catalyst with a neutral solution; and dryinq the twice washed catalyst. This method is useful for both sulfur-contaminated cata¬ lysts and catalysts deactivated by other means.

Preferably, in the second and third embodiments, the concentration of the aqueous solution should be from 0.1% to 10% by weight of metal. A more preferred concen¬ tration range is from 0.1% to 3% by weight of metal. Preferably, there is from 2 to 30 cc of aqueous solution per gram of catalyst in each washing step.

Preferably, in the second and third embodiments, the metal salt or hydroxide is either a metal halide, metal nitrate, metal carbonate, metal phosphate, or metal hydroxide. The preferred metal salt is a metal hydroxide, such as potassium hydroxide.

Preferably, in the second and third embodiments, the contacting occurs at a temperature of from 25°C to 100°C (more preferably, about 80°C) , then the catalyst that has been contacted with the aqueous solution is washed with from 10 to 200 cc of water per gram of cata¬ lyst to remove excess metal, and the washed catalyst is dried. Preferably, the catalyst is contacted with an oxidizing gas at conditions which favor oxidation before the first washing step.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In its broadest aspect, the present invention involves rejuvenating a catalyst by contacting the cata¬ lyst with a large guantity of an agueous media in the liquid phase. This contacting step is an essential ele¬ ment of the present invention.

The aqueous media must be in the liquid phase. If water in the liquid phase is not present then the con¬ tacting step does not show the surprising regeneration of the present invention.

Also, a large quantity of aqueous media is required. At least 10 cc of aqueous media should be used per cc of catalyst. Preferably, at least 500 cc of aqueous media should be used per cc of catalyst.

This regeneration procedure is not only useful for sulfur-contaminated catalysts, but is also useful for catalysts deactivated by other means.

A basic solution can be used to contact the ._n sul ur-contaminated catalyst at a temperature of from about 70°C to about 80°C. Preferably, the basic solution is an alkali metal hydroxide solution, such as a potassium hydroxide solution having a pH of at least 10. This embo¬ diment has the advantaqe of minimizinq the formation of l^ acid sites on the catalyst.

A saturated water vapor in the liquid phase can be used to contact the sulfur-contamina ed catalyst, pre¬ ferably at a temperature of from about 120°C to about 180 °C. This embodiment has the advantage of allowing in situ treatment without having to remove or handle the. catalyst.

The present invention rejuvenates the catalyst without removing all the sulfur from the catalyst. While it is not fully understood how the present invention achieves its surprising rejuvenation of sulfur-contami¬ nated catalysts, one theory is that the washing might be converting the sulfur present in the catalyst to a state which is easier to be removed from the catalyst during the reduction and reforming process or a state which does not 0 interfere wi h the desired catalytic reactions.

The catalyst can be exposed to oxidizing condi¬ tions prior to contacting the catalyst with an aqueous media. While the contacting step causes a sizable rejuve¬ nation of the catalyst, the combination of the oxidizing 5 step and the contacting step causes a still more sizable rejuvenation. Preferably, the oxidation step occurs in the presence of oxygen .at a temperature of from about 200°C to about 450°C. The oxidation step alone does not rejuvenate the catalyst. 0 * It is thought that the oxidation step changes the sulfur to a water-soluble form and/or weakens the association between platinum and sulfur. This could be effected with other oxidizing agents besides oxygen, such as KMnO^, Cr0₃, etc. This could be applied to other metal-containing catalysts where sulfur is known to harm activity.

The catalyst can be exposed to reducing condi¬ tions after contacting the catalyst with an aqueous media. Preferably, the reduction step occurs in the presence of hydrogen at a temperature of from 200°C to 700 °C. Note that no rejuvenation occurs from the reduction step alone, or from reduction following oxidation without including the water step.

The ef ectiveness of this reducing step may depend on whether the solvent molecules shielding the platinum are removed faster than the sulfur is reduced. In this context, we have discovered that if the water treatment employs wet hydrogen, a more stable rejuvenated catalyst is obtained. Other reducing agents, such as water-soluble hydrazine-hydrate , NaBH^, and KBH₄, could also be used for this step.

The combination of the oxidizing step, the soak¬ ing step, and the reducing step causes a still more sizable rejuvenation than the combination of the soaking step with either only the oxidizing step or only the reducing step. These three steps can be repeated, as needed, until the catalyst is rejuvenated to the desired level .

A sul ur-contaminated catalyst can be exposed to oxidizing conditions in the presence of oxygen at a tem¬ perature of from about 200°C to about 450°C, the oxidized catalyst is contacted with at least 500 cc of a saturated water vapor in the liquid phase per cc of catalyst at .? temperature of from about 120 °C to about 180 °C, then the catalyst is exposed to reducing conditions in the presence of hydrogen at a temperature of from 200 °C to about 700 °C. These steps are repeated until the catalyst is rejuvenated to the desired level. —θ—

In a second embodiment, a large-pore zeolitic catalyst that contains at least one Group VIII metal is

05 rejuvenated by contacting the catalyst with an aqueous solution of a salt of a metal selected from the group consisting of an alkali metal and an alkaline earth metal.

An essential step of this embodiment is that the catalyst must be contacted with an aqueous solution of a

10 salt or hydroxide of a metal selected from the group con¬ sisting of an alkali metal and an alkaline earth metal. The metal salt or hydroxide may be either a metal halide, metal nitrate, metal carbonate, metal phosphate, or metal hydroxide. Preferably, the metal salt or hydroxide is

15 potassium hydroxide. Preferably, the catalyst is con¬ tacted with from 2 to 30 cc of aqueous solution per gram of catalyst at a temperature o-f from 25°C to 100°C, more preferably at a temperature of about 80°C. The aqueous solution should have a concentration of from 0.1% to 10%

20 by weight of metal, preferably from 1%. to 8% by weight of metal .

After the catalyst has^* been contacted with the aqueous solution, the catalyst is washed with from 10 to 200 cc of water per gram of catalyst to remove excess

25 metal, then the washed catalyst is dried.

The sulfur-contaminated catalyst can comprise a type L zeolite containing from 8% to 10% by weight barium and from 0.1% to 1.5% by weight platinum; and an inorganic

30 binder selected from the group consisting of silica, alumina, aluminosilicates, and clays. This sulfur-con¬ taminated catalyst is contacted at a temperature of about 30°C with from 2 to 30 cc of an aqueous potassium hydroxide solution per gram of catalyst. The agueous solu- -J tion has a concentration of from 1% to 8% by weiqht of metal. After the catalyst is contacted with a solution, it is washed with from 10 to 200 cc of water per gram of catalyst to remove excess metal, and then it is dried.

The catalyst can be washed with a neutral or •_Q acidic _^solution, then contacted with an aqueous solution of an alkali metal salt or alkaline earth metal salt, then washed with a neutral solution, and dried.

In a third embodiment, the present invention involves rejuvenating a large-pore zeolitic catalyst that contains at least one Group VIII metal by washing the catalyst with a non-basic solution, contacting the washed ._ catalyst with an aqueous solution of a salt of a metal selected from the group consisting of an alkali metal and an alkaline earth metal, washing the contacted catalyst with a neutral solution; and drying the washed catalyst. This regeneration procedure i^'s useful, not only for sul- _jc fur-contaminated catalysts, but also for catalysts deac¬ tivated by other means.

In the rejuvenation of a sulfur-contaminated catalyst, the present invention rejuvenates the catalyst without removinq all the sulfur from the catalyst. Before the catalyst has been contacted with the aqueous solution, the catalyst is washed with from 10 to 200 cc of either a neutral solution or an acidic solution per qram of catalyst-.

An essential step of this embodiment is that the catalyst must be contacted with an aqueous solution of a salt or hydroxide of a metal selected from the group con¬ sisting of an alkali metal and an alkaline earth metal. The metal salt or hydroxide may be either a metal halide, metal nitrate, metal carbonate, metal phosphate, or metal 0 hydroxide. Preferably, the catalyst is contacted with from 2 to 30 cc of aqueous solution per gram of catalyst at a temperature of from 25°C to 100°C, more preferably at a temperature of about 80 °C. The aqueous solution should have a concentration of from 0.1% to 10% by weiqht of 5 metal, preferably from 0.1% to 8% by weight of metal.

■fter the catalyst has been contacted with the agueous solution, the catalyst is washed with from 10 to 200 cc of water per gram of catalyst to remove excess metal, then the washed catalyst is dried. 0 Preferably, the catalyst is contacted with an oxidizing gas at conditions which favor oxidation before the first washing step.

In one preferred method in this embodiment, the deactivated catalyst is a sulfur-contaminated catalyst that comprises a type zeolite containing from 8% to 10% by weight barium and from 0.1% to 1.5% by weight platinum; and an inorganic binder selected from the group consisting of silica, alumina, aluminosilicates, and clays. This sulfur-contaminated catalyst is contacted with an oxidizing gas at conditions which favor oxidation, then the catalyst is washed with a neutral solution, then the catalyst is contacted at a temperature of about 80 °C with from 2 to 30 cc of an agueous potassium hydroxide solution per -gram of catalyst. The aqueous solution has a concen¬ tration of from 0.1% to 8% by weight of alkali or alkaline earth metal.' After the catalyst is contacted with a solu¬ tion, it is washed with from 10 to 200 cc of water per gram of catalyst to remove excess metal, then it is dried.

One reforming catalyst that can be regenerated by the present invention is a large-pore zeolite charged with one or more dehydrogenating constituents. The term "large-pore zeolite" is defined as a zeolite having an effective pore diameter of 6 to 15 Angstroms.

Type L zeolite, zeolite X, zeolite Y and faujasite are thought to be the best large-pore zeolites for this operation and have apparent pore sizes on the order of from 7 to 9 Angstroms. The preferred catalyst is a type L zeolite charged with one or more dehydrogenating constituents.

An alkaline earth metal can be present in the catalyst. That alkaline earth metal can be either barium, strontium or calcium. The alkaline earth metal can be incorporated into the zeolite by synthesis, impregnation or ion exchanqe. Barium is preferred to the other alkaline earths because the resulting catalyst has high activity, high selectivity and hiqh stability. The barium should preferably constitute from about 0,1% to about 35% of the weight of the zeolite, more preferably from about 1% to about 20% by weight.

The reforming catalysts according to the inven¬ tion are charged with one or more Group VIII metals, e.g., nickel, ruthenium, rhodium, palladium, iridium or platinum.

The preferred Group VIII metal is platinum, which is more selective with regard to dehydrocyciization and is also more stable under the reforming reaction con¬ ditions than other Group VIII metals. The preferred per- centaσe of platinum in the catalyst is between 0.1% and 5%, more preferably from 0.1% to 1.5%.

An inorganic oxide can be used as a.carrier to bind the large pore size zeolite. The carrier can be a natural or a synthetically produced inorganic oxide or combination_. of inorganic oxides. Preferred loadings of inorganic' oxide are from 5% to 50% by weight of the cata¬ lyst. Typical inorganic oxide supports which can be used include silica, alumina, and aluminosilicates.

EXAMPLES

The first embodiment of the present invention will be further illustrated by the following examples which set forth a particularly advantageous method and composition embodiments. While the examples are provided to illustrate the present invention, they are not intended to limit it.

Example I

A catalyst was prepared by (1) ion exchanging a potassium-type L zeolite with a sufficient volume of 0.17 molar barium nitrate solution to contain an excess of barium compared to the ion exchange capacity of the zeolite; (2) drying the resulting barium-exchanged type L zeolite catalyst; (3) calcining the catalyst at 590°C; (4) impreqnatinq the catalyst with 0.8% platinum using tetrammineplatinu (II) nitrate; (5) drying the catalyst; (6) calcining the catalvst at 260°C; and (7) reducing the catalyst in hydrogen at 480°C to 500°C. Example I I

The catalyst of Exampl e I wa s used in a pilot plan t to re form n-hexane that had been hydrof ined to remove sul f ur , oxygen and nitrogen . The re forming occurred a t 860 °F , 100 ps ig , 17 LHSV, and 5 H₂/HC . The results a fter ten and twe n ty hours are l isted in Table I.

Example III

The catalyst of Example I was used in a pilot plant to reform naphtha that had been hydrofined to remove sulfur, oxygen and nitrogen and then to which sulfur com¬ pounds were deliberately added in order to generate a sulfur-contaninated catalyst. The reforming occurred at 860°F, 100 psiq - 1.5 LHSV, and- 6 H₂/HC for 3 weeks to produce a sulfided catalyst, then the sulfided catalyst was tested by the procedures of Example II. The results of that test after ten and twenty hours are listed in Table I.

Example IV

The sulfided catalyst of Example III was oxidized at one atmosphere with 1% oxygen in nitrogen for one half hour at 400°F, one hour at 500°F, and 5 hours at 750°F ; then the catalyst was tested by the procedures of Example II. The results of that test after ten and twenty hours are listed in Table I.

Example V

The sulfided catalyst of Example Til was washed with 80°C water at 2cc/min for one hour, then the catalyst was tested by the procedures of Example II. The results of that test after ten and twenty hours are listed in Table I.

Example VI The sulfided catalyst of Example III was oxidized at one atmosphere with 1% oxygen in nitrogen for one half hour at 400°F, one hour at 500°F, and 5 hours at 750 °F; then washed with 100% steam at 212°F for 3 hours, then the catalyst was tested by the procedures of Example' II. The results of that test after ten and twenty hours are listed in Table I. ₁ Exa ple VII ^' The sulfided catalyst of Example III was oxidized at one atmosphere with 1% oxygen in nitrogen for one half hour at 400°F, one hour at 500°F, and 5 hours at 750 °F; then washed with 100% steam at 212°F for 3 hours; then reduced in H₂ for 1-1/2 hours at 900°F, then oxidized at one atmosphere with 1% oxygen in nitrogen for one half hour at 400°F, one hour at 500°F, and 5 hours at 750°F; then washed with 100% steam at 212°F for 3 hours; then the catalyst was tested by the procedures of Example II. The results of that test after ten and twenty hours are listed in Table I.

Example VIII The sulfided catalyst of Example III was oxidized at one atmosphere with 1% oxygen in nitrogen for one half hour at 400°F, one hour at 500°F, and 5 hours at 750 °F ; then washed with 100% steam at 212 °F for 3 hours; then reduced at 900°F in H₂ for 1-1/2 hours, then oxidized at one atmosphere with 1% oxygen in nitrogen for one half hour at 400°F, one hour at 500°F, and 5 hours at 750°F; then washed with 100% steam at 212°F for 3 hours; then reduced at 900°F in H₂ for 1-1/2 hours, then oxidized at one atmosphere with 1% oxygen in nitrogen for one half hour at 400°F, one hour at 5.00°F and 5 hours at 750°F; then washed with 100% steam at 212°F for 3 hours; then the catalyst was tested by the procedures of Example II. The results of that test after ten and twenty hours are listed in Table I. Table I Relative Rate Constants for

Cg saturates Benzene % Selectivity conversion formation at to Benzene at at time on time on time on

Stream Stream Stream

Example II 1 1 1 1 86 85

Example III 0.08 0.09 0.01 0.01 11 12

Example IV 0.21 0.18 0.10 0.09 40 45

Example V 0.19 0, 19 0.10 0.10 45 45

Exa le VI 0.71 0.74 0.53 0.56 75 76 Example VII 0.81 0.80 0.80 0.76 84 81

Example VIII 0.81 0.80 0.80 0.76 84 81

Examples V, VI, VII, and VIII are examples of the present invention. They show that washing, either alone or in conjunction with oxidation, rejuvenated deactivated catalysts.

Example IX

The second embodiment of the present invention will be further illustrated by the following examples which set forth particularly advantageous method and com¬ position embodiments. While the examples are provided to illustrate the present invention, they are not intended to limit it.

Fresh reforminq catalyst was prepared by (1) ion exchanging a potassium-type L with a sufficient volume of 0.17 molar barium nitrate solution to contain an excess of barium compared to the ion exchange capacity of the zeolite: (2) drying the resulting barium-exchanged type L zeolite catalyst; (3) calcining the catalyst at 590°C;

(4) impregnating the catalyst by pore fill impregnation with 0.8% platinum using tetrammineplatinum (II) nitrate;

(5) drying the catalyst; (6) calcining the catalyst at 260°C; and (7) reducing the catalyst in hydrogen at 480°C to 500°C.

A feed of n-hexane, which had been hydrofined to remove sulfur, oxygen and nitrogen, was contacted at 920°F, 100 psig, 10 LHSV, and 5 H₂/HC with a portion of the fresh reforming catalyst. The benzene selectivity and

05 hexane conversion for that run are shown in Figures 1 and 2.

A second portion of the fresh reforming catalyst was deactivated by contacting the catalyst with a sulfur- containing light straight run until about 200 ppm sulfur

10 was deposited on the catalyst. The deactivated catalyst was rejuvenated by contacting the catalyst for two hours at a temperature of about 80°##?C with an aqueous solution of potassium hydroxide having a concentration of 5% by weight of metal, wherein there was 30 cc of aqueous solu¬

15 tion per gram of catalyst; washing the catalyst that had been contacted with the agueous solution ten times with 20 cc of water per gram of catalyst (200 cc total wash) to remove excess metal; and drying the washed catalyst. A feed of n-hexane, which had been hydrofined to remove

20 sulfur, oxygen and nitrogen, was contacted at 920°F, 100 psig, 10 LHSV, and 5 H₂/HC with the rejuvenated reforming catalyst.

Examples X through XXIII

The third embodiment of the present invention

25 will be further illustrated by the following examples which set forth particularly advantageous method and com¬ position embodiments. While the examples are provided to illustrate the present invention, they are not intended to limit it.

30

A type L zeolite reforming catalyst was treated with a sulfur-containing hydrocarbon feed until the cata¬ lyst was substantially deactivated. The catalyst had been prepared by (1) extruding the catalyst with 20 wt. % of an -_j, alumina inorganic oxide binder in the shape of l/16th inch extrudate; (2) ion exchanging a potassium-type L zeolite wi h a sufficient volume of 0.3 molar barium nitrate solu¬ tion to contain an excess of barium compared to the ion exchanqe capacity of the zeolite; (3) drying the resulting 0 barium-exchanged type L zeolite; (4) calcining the cata¬ lyst at 590°C; (5) impregnating the catalyst with 0.8% platinum based on the weight of L zeolite using tetrammineplatinum (II) nitrate; (6) drying the catalyst;

(7) calcining the catalyst at 260°C in air or 50% steam;

(8) extruding the catalyst with 20 wt. % of an alumina inorganic oxide binder in the shape of l/16th inch extru¬ date; and (9) reducing the catalyst in hydrogen at 480 °C to 500 °C. The catalyst had been deactivated by the proce¬ dure of running it onstream at mild reforming conditions (100 psiq, 870°F, 2 H₂/HC, 1.5 LHSV) with a sulfur-con¬ taining naphtha feedstock (1.5 ppm dimethyl disulfide). That catalyst was then subjected to a variety of regener¬ ation procedures, and then was tested by the following test.

REGENERATION TEST

0.356 Grams of catalyst screened to 24 to 80 mesh was placed in a tubular reactor. A low surface area alpha alumina was placed above and below the catalyst. The catalyst was treated at 400 °F in hydrogen flowing at 500 cc/min. for one-half hour, then at 880 °F in hydrogen for 10 miαutes, then at 920 °F in hydrogen for on,e hour. After one hour at 920°F- the flow of hydrogen was cut back to 60 cc/min. and the pressure was built up from atmos¬ pheric pressure to 100 psiq. At this point, n-hexane was introduced at 3 cc/hr. Initial and final data was taken at approximately two hours and 18 hours after introducinq the n-hexane feed. The conversion (Conv.) , selectivity for dehydrocyciization (Sel.) , and yield of aromatics in product as mole % of the feed (Mole %) were calculated at those times.

Example X The catalyst in this example was not treated to any regeneration procedures.

Example XI The catalyst in this example was placed into a quartz reactor tube in a furnace, then 1% oxygen in nitro¬ gen was passed over the catalyst at a rate of 2 cc/gram catalyst/min. The catalyst was treated at 600 °F for one hour, then the catalyst was treated at 780 °F for five hours. The flow of oxygen was then stopped and the cata¬ lyst was cooled to room temperature. Then the catalyst was, for three times: (1) treated with a ten-fold excess of deionized water for 30 minutes at 165°F, (2) cooled, and (3) filtered. Then the catalyst was dried in air at 250 °F for two hours and treated in flowing air at 500°F for two hours.

Example XII

The catalyst in this example was placed into a guartz reactor tube in a furnace, then 1% oxygen in nitro¬ gen was passed over the catalyst at a rate of 2 cc/gram catalyst/min. The catalyst was treated at 600°F for one hour, then the catalyst was treated at 780°F for five hours_• The flow of oxygen was then stopped and the cata¬ lyst was cooled to room temperature. Then the catalyst was, for three times: (1) treated for 30 minutes at 165°F with a en-fold excess of an aqueous solution of hydrogen chloride having a pH of 3, (2) cooled, and (3) filtered.^' Then the catalyst was dried' in air at 250°F for two hours and treated in flowing air at 500 °F for two hours.

Example XIII

The catalyst of this example was placed into a guartz reactor tube in a furnace, then 1% oxygen in nitro¬ gen was passed over the catalyst at a rate of 2 cc/gram catalyst/min. The catalyst was treated at 600 °F for one hour, then the catalyst was treated at 780°F for five hours. The flow of oxygen was then stopped and the cata¬ lyst was cooled to room temperature. Then, the catalyst was heated to 176°F for two hours, and occasionally stirred, in the presence of a twenty-fold excess of an aqueous solution of 4 wt. % KOH, then cooled and filtered. Then the catalyst was for nine times: (1) mixed with a ten-fold excess of water at room temperature for one minute, (2) allowed to settle for three minutes, and (3) filtered. At this point, the pH of the effluent water was 7.5. Then the catalyst was dried in air at 250°F for 20 hours and treated in flowing air at 500 °F for two hours. Table II shows the effect of the regeneration procedures of Examples X through XIII. From this table.

05 It is apparent that regeneration with a preliminary oxida¬ tion, followed by contact with water or an aqueous solution, followed by dryinq and calcining, gives a sub¬ stantial regeneration of the deactivated catalyst. Of these four examples, Example XIII (KOH wash) gave the best

10 results.

TABLE II

The Effect of Regeneration wi th Water

15 Initial Final

Example Conv . Sel. Mole % Conv . Sel. Mole %

X 4.96 43.27 2.15 3.93 €2.29 2.45

XI 42.07 85.79 36.09 28.78 87.25 25.11

XII 14.58 68. .9. ^'85 10.58 73. 7.67

20 XIII 40.72 87.49 35.63 36.29 90.64 32.90

Example XIV The catalyst of this example was placed into a guartz reactor tube in a furnace, then 1% oxygen in nitro-

•25 gen was passed over the catalyst at a rate of 2 cc/gram catalyst/min. The catalyst was treated at 600 °F for one hour, then the catalyst was treated at 780°F for five hours. The flow of oxygen was then stopped and the cata¬ lyst was cooled to room temperature. Then, the catalyst

³⁰ was, for three times: (1) treated with a ten-fold excess of deionized water for 30 minutes at 165°F, (2) cooled, and (3) filtered. Then, the catalyst was, for three times: (1) heated to 135°F for one hour in the presence of a ten-fold excess of an aqueous solution of 0. IN KOH,

-^ (2) cooled, and (3) filtered. The catalyst was then washed with a ten-fold excess of deionized water at 140°F for one hour, then was cooled and filtered. Then the catalyst was dried in air at 250 °F for two hours and treated in flowing air at 500°F for two hours. 0 Table III shows the improvement obtainable when the catalyst is treated with a neutral solution prior to a KOH wash. From the table, it can be clearly seen that washing the catalyst with a neutral wash prior to the KOH wash gives better results than when there is no neutral wash.

TABLE III

The Effect of Neutral Wash Prior to KOH Wash

Initial Final

Example Conv. Sel. Mole % Conv . Sel. Mole %

XIII 40.72 87.49 35.63 36.29 90.64 32.90

XIV 56.73 93.13 52.83 54.15 95.10 51.49

Example XV The catalyst of this example- was heated to 176°F for two hours, and occasionally stirred, in the presence of a -twenty-fold excess of an aqueous solution of 4 wt. % KOH, then cooled and filtered. Then the catalyst was, for nine times: (1) mixed with a ten-fold excess of water at room temperature for one minute, (2) allowed to settle for three minutes, and (3) filtered. At this point, the pH of the effluent water was 7.5. Then the catalyst was dried in air at 250°F for 20 hours and treated in flowing air at 500 °F for two hours. Example XVI

The catalyst of this example was, for three times: (1) treated for 30 minute at 165°F in a ten-fold excess of an aqueous solution of hydrogen chloride havinq a pH of 3, (2) then cooled and filtered. Then the cata- lyst was, for three times: ( 1) mixed with a ten-fold excess of a solution of 0. IN KOH, (2) treated with the KOH solution for one hour at 135°F, (3) cooled, and (4) fil¬ tered. Then the catalyst was treated with a ten-fold excess of deionized water at 135°F, cooled, and filtered. Then the catalyst was dried in air at 250°F for two hours and treated in flowing air at 500 °F for two hours. Example XVII

The cata-lyst of this example was placed into a quartz reactor tube in a furnace, then 1% oxygen in nitro¬ gen was passed over the catalyst at a rate of 2 cc/gram catalyst/min. The catalyst was treated at 600°F for one hour, then the catalyst was treated at 780°F for five hours. The flow of oxygen was then stopped and the cata¬ lyst was cooled to room temperature. Then the catalyst was, for three times: (1) treated with a ten-fold excess of deionized water for 30 minutes at 165°F. (2) cooled, and (3) filtered. Then the catalyst was, for three times: (1) treated for one hour at 135°F in a ten-fold excess of a solution of 0. IN sodium carbonate, (2) cooled, and (3) filtered. Then the catalyst was, for three times: (1) treated for one hour at 135°F in a ten-fold excess of ^'deionized water, (2), and (3) filtered. Then the catalyst was -dried in. air at 250°F for two hours and treated in flowing air at 500°F for two hours.

Example XVIII

The catalyst of this example was placed into a quartz reactor tube in a furnace, then 1% oxygen in nitro¬ gen was passed over the catalyst at a rate of 2 cc/gram catalyst/min. The catalyst was treated at 600°F for one hour, then the catalyst was treated at 780°F for five hours. The flow of oxygen was then stopped and the cata¬ lyst was cooled to room temperature. Then the catalyst was, for three times: (1) treated for 30 minutes at 165°F with a ten-fold excess of an aqueous solution of hydrogen chloride having a pH of 3, (2) cooled, and (3) filtered. Then the catalyst was, for three times: (1) treated for one hour at 135°F with a seven-fold excess of a solution of 0. IN sodium carbonate, (2) cooled, and (3) filtered. Then the catalyst was, for three times: (I) treated at 135°F for one hour with a seven-fold excess of deionized at^ , (2) cooled- and (3) filtered. Then the catalyst was dried in air at 250 °F for two hours and treated in flowing, air at 500°F for two hours. Table IV shows the further improvement obtain¬ able with preliminary treatment with an acidic solution. Two pairs of data are shown, the first in each case treated with a neutral solution or no solution at all prior to treatment with the salt solution, the second in each case treated with an acidic solution first. In the differences between the first pair of data and the second, note also the advantages of using pre-oxidation prior to the agueous treatments, particularly if the acidic treat¬ ment step has been omitted.

TABLE III

The Effec t of Aci ic Wash Prior to^' Salt Wash

- Without Pre-Ox idation

Initial Final

Example Conv. Sel. Mole % Conv . Sel. Mole %

XV 27.53 82.13 22.61 8.42 65.45 5.51

XVI 56.84 93.48 53.13 58.52 96.08 56.23

With Pre-Oxidation

Initial Final

Example Conv. Sel♦ Mole % Conv. Sel. Mole %

XVII 47.96 89.29 42.82 41.77 91.84 38.36

XVIII 61.92 88.01 54.49 55.66 91.12 50.72

Example XIX The catalyst of this example was heated to 176°F for two hours, and occasionally stirred, in the presence of a twenty-fold excess of an agueous solution of 4 wt . % KOH, then cooled and filtered. Then the catalyst was, for nine times: (1) mixed with a ten-fold excess of water at room temperature for one minute, (2) allowed to settle for three minutes, and (3) filtered. <\t this point, the pH of the e f flue n t wa ter wa s 7. 5. Then the catalyst was dried in a ir at 250 °F for 20 hours .

05 Example XX

The catalyst of this example was placed into a guartz reactor tube in a furnace, then 1% oxygen in nitro¬ gen was passed over the catalyst at a rate of 2 cc/gram catalyst/min. The catalyst was treated at 600°F for one

10 hour, then the catalyst was treated at 780°F for five hours. The flow of oxygen was then stopped and the cata¬ lyst was cooled to room temperature. Then, the catalyst was heated to 176°F for two hours, and occasionally stirred, in the presence of a twenty-fold excess of an

1 aqueous solution of 4 wt. % KOH, then cooled and filtered. Then the catalyst was, for nine times: (1) mixed with a ten-fold excess of water at room temperature for one minute, (2) allowed to settle for three minutes, and (3) filtered. .At this point, the pH of the effluent water ⁰ was 7.5. Then the catalyst was dried in air at 250°F for 20 hours.

Example XXI The catalyst of this example was, for three times: (1) treated for 30 minutes at 165°F with a ten-

25 fold excess of an aqueous solution of hydrogen chloride having a pH of 3, (2) cooled, and (3) filtered. Then, the catalyst was, for three times (1) treated for one hour at 135°F with an agueous solution of 0.1N sodium carbonate, (2) cooled, and (3) filtered. Then the catalyst was, for

-*⁰ three times: (1) treated for one hour at 140°F with a ten¬ fold excess of deionized water, (2) cooled and (3) fil¬ tered. Then the catalyst was dried in air at 250°F for two hours and treated in flowing air at 500°F for two hou s.

-"^> Table V shows the importance of using a pre- oxidation step. It sets forth pairs of data obtained with and without this step.

40 TABLE V

The Effect : of Pre- -Oxidation

Initial Final

Example Conv . Sel. Mole % Conv. Sel. Mole %

XIX 24.73 83.68 20.69 18.86 82.67 15.59

XX 39.86 88.53 35.29 31.31 89.29 27.95

XXI 55.26 88.85 49.30 49.88 92.90 46.34

XVII 61.92 88.01 54.49 55.66 91.12 50.72

Example XXIIThe catalyst of this example was placed into a quartz reactor tube in a furnace, then 1% oxygen in nitrogen was passed over the catalyst at a rate of 2 cc/gram catalyst/min. The catalyst was treated at 600 °F for one hour, then the catalyst was treated at 780°F for five hours. The flow of oxygen was then stopped and the catalyst was. cooled to room temperature. Then the cata¬ lyst was, for three times: (1) treated for 30 minutes at 165°F with a ten-fold excess of an aqueous solution of hydrogen chloride having a pH of 3, (2) cooled, and (3) filtered. Then the catalyst was, for three times: (1) treated for one hour at 135 °F with a seven-fold excess of a solution of 0. IN magnesium nitrate, (2) cooled, and (3) filtered. Then the catalyst was, for three times: (1) treated at 135°F for one hour with a seven-fold excess of deionized water, (2) cooled, and (3) filtered. Then the catalyst was dried in air at 250°F for two hours and treated in flowing air at 500 °F for two hours.

Example XXIII The catalyst of this example was placed into a quartz reactor tube in a furnace, then 1% oxygen in nitro- age was passed over the catalyst at a rate of 2 cc/grams catalyst/min. The catalyst was treated at 600 °F for one hour, then the catalyst was treated at 780°F for five hours. The flow of oxygen was then stopped and the cata¬ lyst was cooled to room temperature. Then the catalyst was, for three times: (1) treated with a ten-fold excess of deionized water for 30 minutes at 165°F, (2) cooled,

-22-

and filtered. Then the catalyst was, for three times: (1) treated for one hour at 135°F with a ten-fold excess of a solution of O.IN magnesium nitrate, (2) cooled, and (3) filtered. Then the catalyst was, for three times: (1) treated for one hour at 140°F with a ten-fold excess of deionized water, (2) cooled, and (3) filtered. Then the catalyst was dried in air at 250°F for two hours and treated in flowing air at 500°F for two hours.

Finally, Table VI shows two unsuccessful treat¬ ments, one with a preliminary acidic treatment, and the other without.

TABLE VI

Initial Final

Example Con . Sel . Mole % Conv . Sel . Mole %

XXI I 6. 10 27. 41 1. 67 3. 05 30. 00 1. 19

XXIII 5. 78 21. 82 1. 26 Too 1 ow to ca lculate

While the present invention has been described with reference to specific embodiments, this application is intended to cover those changes which may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

i. A method of rejuvenating a catalyst comprising contacting said catalyst with at least 10 cc of an aqueous media in the liquid phase per cc of catalyst; wherein said aqueous media is selected from the group consisting of water, an aqueous solution, and a saturated water vapor; and wherein said catalyst comprises a large-pore zeolite containing at least one Group VIII metal.

2. A method of rejuvenating a sulfur-contaminated catalyst that comprises a large-pore zeolite containing at least one Group VIII metal comprising:

(a) exposing said catalyst to oxidizing conditions in the presence of oxygen at a temperature of from about 200°C to about 450 °C ;

(b) contacting said oxidized catalyst with at least 500 cc of an aqueous media in the liquid phase per cc of catalyst; wherein said aqueous media is selected from the group consisting of water, an aqueous solution, and a saturated water vapor; to form a wet^' catalyst;

(c) exposing said wet catalyst to reducing condi¬ tions in the presence of hydroqen at a temperature of from about 200 °C to about 700 °C ; and

(d) repeating steps (a) through (c) until the cata¬ lyst is rejuvenated to the desired level.

3. A method of rejuvenating a sulfur-contaminated catalyst according to Claim 2 wherein said large-pore zeolite is a type L zeolite.

4. A method of rejuvenating a sulfur-contaminated catalyst according to Claim 2 wherein said agueous media is a basic solution, and said catalyst is contacted with said basic solution at a temperature of from about 70 °C to about 80°C. 5. A method of rejuvenating a catalyst and improving the stability of said catalyst, wherein said method comprises contacting said catalyst with an agueous solution of a salt or hydroxide of a metal selected from the group consisting of an alkali metal and an alkaline earth metal, wherein said catalyst comprises a large-pore zeolite containing at least one Group VIII metal.

6. A method of rejuvenating a catalyst and improving the stability of said catalyst according to Claim 5 wherein said agueous solution has a concentration of from 1% to 8% by weight of metal, and wherein there is from 2 to 30 cc of aqueous solution per gram of catalyst.

7. A method of rejuvenating a catalyst and improving the stability of said catalyst according to Claim 5 wherein said metal salt or hydroxide is potassium hydroxide.

8. A method of rejuvenating a catalyst and improving the stability of said catalyst according to Claim 5 wherein said contacting occurs at a temperature of from 25°C to 100°C.

9. A method of rejuvenating a catalyst and improving the stability of said catalyst according to Claim 5 wherein said catalyst that has been contacted with said aqueous solution is then washed with from 10 to

200 cc of water per gram of catalyst to remove excess metal.

10. A method of rejuvenating a catalyst and improving the stability of said catalyst according to Claim 5 wherein said large-pore zeolite is a type L zeolite. 11. A method of rejuvenatinq a sulfur-contaminated catalyst and improving the stability of said catalyst,

05 wherein said method comprises:

(a) contacting said catalyst at a temperature of about 80 °C with an aqueous solution of potassium hydroxide, wherein said aqueous solution has a concentra¬ tion of from 1% to 8% by weight of metal, and wherein

10 there is from 2 to 30 cc of aqueous solution per gram of catalyst;

(b) washing said catalyst with from 10 to 200 cc of water per gram of catalyst to remove excess metal;

(c) drying said washed catalyst; and

15 wherein said catalyst comprises:

(A) a type L zeolite containing from 0.1% to 1.5% by weight platinum; and

(B) an inorganic binder selected from the group consisting of silica, alumina, aluminosilicates, and 0 clays.

12. A method of rejuvenating a catalyst, wherein said method comprises: 5 (a) washing said catalyst with a solution selected from the group consisting of a neutral solution and an acidic solution;

(b) contacting said washed catalyst with an agueous solution of a salt or hydroxide of a metal selected from 0 the group consisting of an alkali metal and an alkaline earth metal;

(c) washinq said contacted catalyst with a neutral solution; and

(d) dryinq said twice washed catalyst; wherein said «- catalyst comprises a large-pore zeolite containing at least one Group VIII metal.

13. A method of rejuvenatinq a catalyst according to Claim 12 wherein said metal salt or hydroxide is a _Q potassium hydroxide. 14. A method of rej uvenating a catalyst accord ing to Cla im 12 where in sa id large-pore zeolite is a type L

05 zeolite .

15. A method of rejuvenating a sulfur-contaminated catalyst, wherein said method comprises:

(a) contacting said catalyst with an oxidizing gas •1 at conditions which favor oxidation;

(b) washing said catalyst with a solution selected from the group consisting of a neutral solution and an acidic solution;

(c) contactino said washed catalyst at a temperature •15 of about 80°C with an aqueous solution of potassium hydroxide, wherein said aqueous solution of potassium hydroxide has a concentration of from 0.1% to 8% by weight of metal, and wherein there is from 2 to 30 cc of aqueous solution per gram of catalyst. - ⁰ ( - ) washing said contacted catalyst of step (c) with from 10 to 200 cc of water per gram of catalyst to remove excess metal;

(e) drying said washed catalyst of step (d); and

(f) contacting said dried catalyst with an oxidizing 2 gas at conditions which favor oxidation; wherein said catalyst comprises:

(A) a type L zeolite containing from 0.1% to 1.5% by weight platinum; and

(B) an inorganic binder selected from the group ^° consisting of silica, alumina, aluminosilicates, and clays.

5

0