JPH0424107B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydro-conversion
conversion) relating to the removal of metal contaminants from the catalyst. In particular, it relates to the selective removal of metal contaminants from a catalyst on a refractory oxide support without dissolving the support by treatment with a buffered oxalic acid solution. Hydroconversion catalysts used in the treatment of petroleum feedstocks are
deactivation due to factors such as contamination with metals typically found in oil and crude oil. The use of acids in the regeneration process of hydroconversion catalysts is known. U.S. Pat. No. 2,380,731 discloses that by contacting a spent catalyst with an organic acid and a dilute mineral acid,
Removal of iron and other metals from catalytic cracking catalysts. An aqueous oxalic acid solution is preferred.
US Pat. No. 3,020,239 describes the removal of panadium from molybdenum-containing catalysts using an aqueous glycolic acid solution. Other hydroxy acids and compounds similar to glycolic acid are unsatisfactory because they simultaneously remove molybdenum. Concentration adjustment is preferred to avoid leaching of aluminum from the carrier material. US Pat. No. 3,791,989 describes the removal of panadium from group or group metal-containing hydroprocessing catalysts by contacting the catalyst with an aqueous oxalic acid solution prior to combustion removal of coke deposits. In Example 1, contaminated catalyst particles are boiled with a concentrated oxalic acid solution to remove vanadium preferentially over nickel or molybdenum. British Patent No. 1245358
The reverse order is described in the issue, in which the deactivated carrier-supported group or group catalyst is first subjected to a coke burn-off step, and then 0.5 M~
Wash with an aqueous oxalic acid solution having a saturated concentration.
If the contact time with oxalic acid is limited, the catalytic metal will not be removed. In U.S. Patent Nos. 4,089,806 and 4,122,000,
A group B and/or group metal-containing hydrodesulfurization catalyst on a refractory support is regenerated using a combination of oxalic acid and nitric acid and/or nitrate. Dissolution of the alumina support is stated to occur when oxalic acid alone is used in environments harsh enough to remove substantial amounts of panadium. moreover,
According to US Pat. No. 3,536,637, ion exchange resin contaminated with iron is regenerated by contacting the contaminated resin with oxalic acid. Oxalic acid is known to be useful for removing certain metal contaminants from hydroconversion catalysts supported on inorganic oxide supports such as alumina; and also have the disadvantage of dissolving or removing the carrier material. The present inventors found that when buffering an oxalic acid aqueous solution,
It has been discovered that the above drawbacks can be overcome without adversely affecting the ability of oxalic acid to remove metal contaminants.
The method of the present invention for removing metal contaminants from a hydroconversion catalyst comprising Group B or at least one metal from Group B or Groups supported on a refractory inorganic oxide therefore provides It consists of contacting with a buffered aqueous oxalic acid solution. In another embodiment of the invention, a contaminated catalytic cracking catalyst comprising at least one of alumina or silica or silica-alumina or zeolite or clay is treated with a buffered aqueous oxalic acid solution. Contaminant metals are removed by a method comprising contacting. The method of the present invention using buffering allows oxalic acid to be used at various concentrations without dissolving the metal oxide supports typically used in hydroconversion catalysts. Moreover, even at high extraction temperatures, the oxalic acid solution can be kept in contact with the contaminated catalyst for a long time without removing the catalytically active metal from the support. Buffering oxalic acid also allows it to be used to regenerate catalytic cracking catalysts without dissolving the catalyst. The hydroconversion catalysts in question are those in which either the active catalyst component or the support material is susceptible to attack by mineral acids and/or organic acids. During normal commercial use, these catalysts become contaminated by metal contaminants and coke formation and become deactivated. Acid regeneration of the deactivated catalyst is used to remove metal contaminants. However, if the support or catalyst is susceptible to acid attack,
Substantial problems arise because loss of support leads to loss of active catalyst components. Such losses are often unacceptable or the contact time of the acid with the contaminated catalyst is limited to such an extent that substantial amounts of metal contaminants cannot be removed. Particularly concerning hydroconversion catalysts,
Includes catalytic cracking catalysts, reforming catalysts, and resid conversion catalysts. Catalysts for catalytic cracking are acidic metal oxides such as alumina, silica, silica-alumina, zeolites, clays, especially acid-treated clays, silica-zirconia, silica-magnesia, alumina-boria, silica-titania. The above catalyst for catalytic cracking as a carrier and hydrogenation-dehydrogenation metal (e.g.
Co, Ni, W, V, Mo, Pt, Pd or a combination thereof) becomes a hydrogen cracking catalyst. In general, B metals or B metals or group metals or combinations thereof supported on acidic supports as described above are subjected to various catalytic hydroconversions such as resid conversion, reforming, etc. hydroconversion). Condensed Chemical Dictionary
Defined in the periodic table on page 662 of the 9th edition. Preferred catalytic materials are alumina or silica-alumina or zeolites as supports for Co or Mo or Re or platinum group metals, alone or in combination. Metal contaminants may arise from metal components of the feedstock or reactor columns and transfer lines used during production. Examples of metal contaminants that can be removed with oxalic acid include iron, panadium, nickel, sodium, magnesium, chromium, copper, strontium, lithium, and lead. Such metals are generally undesirable because they can lead to catalyst deactivation through catalyst poisoning and/or blockage. As previously mentioned, oxalic acid extraction to remove metal contaminants can also result in acid attack of the acid sensitive support and/or the active catalyst metal. Additionally, some oxalic acid treatments include
Some require high temperatures and/or high concentrations of acid, thus exacerbating the above problems. The inventors have discovered that buffering oxalic acid can solve these problems without adversely affecting the ability of oxalic acid to extract metal contaminants. The buffer of the present invention contains an aqueous oxalic acid solution of 2 to
10, preferably a buffering agent capable of buffering within the PH range of 4.5 to 8.5. Preferred buffers are those that do not contain sufficient Group A cations or Group A cations to cause catalyst poisoning. An example of a preferred buffer is ammonium acetate. Another group of buffers for the removal of metal contaminants from hydroconversion catalysts includes water/
Included are buffers useful in non-aqueous solvent systems. For example, in a 90% MeOH/10% H ₂ O solution, 0.01 molar oxalic acid, 0.01 molar ammonium oxalate will change the pH.
Buffer to 4.23. In a 60% MeOH/40% _H2O solution, this same buffer gives a pH of 2.58
Controls (Buffers for PH and Metallon
Control)” DD Perrin and B. Dempsey (D.
D.Perrin and B.Dempsey), John Wiley and Sons,
New York, 1974, p. 84-88]. Aqueous/non-aqueous systems are useful for removing metal contaminants from hydroconversion catalysts because dissolution of alumina is greatly inhibited compared to aqueous systems. In some cases, the buffer can include low concentrations of Group A components. In this case, such buffer systems may be useful for removing metal contaminants from hydroconversion catalysts. The amount of buffer required depends on the concentration of oxalic acid used. The oxalic acid concentration can range from 0.0001M to 5.0M, with a concentration range of 0.01 to 2.0M being preferred. The required concentration of buffer is the PH of oxalic acid.
is sufficient to keep it within the desired range. As the concentration of oxalic acid increases, depending on the buffering capacity,
Generally, a larger amount of a given buffer will be required. The temperature range is from about 0°C to about 100°C, preferably from 20 to 75°C. Higher temperatures have no particular benefit with respect to metal contaminant removal and may cause excessive acid attack of the support and/or catalyst metal. Unlike regular oxalic acid, buffered oxalic acid can be contacted with deactivated catalyst for extended periods of time without dissolving the support material. The method of contacting the catalyst with the buffered oxalic acid solution is not critical. The deactivated catalyst can be soaked in a buffered oxalic acid solution. Then, at predetermined time intervals, samples of the catalyst or buffered oxalic acid solution are removed and tested for the extent of metal contamination. Alternatively, continuous extraction can be performed, for example by recycling the buffered oxalic acid in a countercurrent extractor. Preferred embodiments for the removal of metal contaminants from hydroconversion catalysts typically include one metal or another metal (preferably Re) supported on an acidic support such as alumina or silica-alumina. or noble metals) on the regeneration of homing catalysts containing Pt.
Reforming catalysts include Fe, Pb, Cu, Ca, Na
It gradually becomes contaminated with metals such as
Fe is particularly troublesome. 0.5M oxalic acid supported on contaminated γ-Al ₂ O ₃
When slurried with Pt or Pt/lr or Pt/Re catalysts and heated, along with the desired Fe contaminants,
Significant amounts of support and precious metals are removed. In contrast, ammonium acetate-buffered oxalic acid extraction with the same catalyst system selectively removes Fe and γ
- Very little catalyst loss occurs, which is attributable to mechanical losses rather than chemical attack on the alumina support. For Fe removal using buffered oxalic acid solution,
Low temperatures of 20-75°C are preferred. After extraction, the Pt/Re catalyst was extracted in the presence of _O2 .
It was baked at 500°C for 4 hours. _H2 and of regenerated catalyst
The chemisorption value of Co was almost the same as that of the fresh catalyst, and no toxic effect or surface modification was shown by treatment with buffered oxalic acid solution. Fe-extracted Pt/lr catalyst was compared for naphthalene homing activity against unextracted catalyst containing 0.35 wt% Fe and fresh Pt/lr catalyst. After 400 hours, the extracted catalyst had only a 25% reduction in reforming activity compared to the fresh catalyst, compared to the reduced reforming activity of the catalyst that was not extracted with an acid solution of buffered oxalic acid. was 70%. The method of the present invention will be further explained below with reference to Examples. Catalyst The catalyst has a BET surface area of 150 to 190 m ² /g.
It was supported on an Al ₂ O ₃ support. Pt/Re/Al ₂ O ₃ This platinum-rhenium bimetallic catalyst is a commercially available sample with an initial composition of 0.3% Pt, 0.3%
Re, 0.9% Cl (all percentages are by weight unless otherwise noted). Pt/lr/Al ₂ O ₃ This platinum-iridium bimetallic catalyst was a commercially available sample. Fresh catalyst is 0.3% Pt,
Contains 0.3% LR, 0.7% Cl. Many used Pt/
lr/Al ₂ O ₃ samples were also obtained from the refinery. Pt/Al ₂ O ₃ This monometallic platinum catalyst was a commercially available sample and had a composition of 0.3% Pt and 0.7% Cl. Iron-doped catalyst/Fresh Pt/Re/Al ₂ O ₃
and Pt/lr/Al ₂ O ₃ catalyst using the incipient wetness method using a standardized aqueous iron nitrate solution.
A known amount of Fe was added according to the procedure), and 120
After drying under air for 16 hours at 0.degree. C., the impregnation was calcined at 270.degree. C. for 4 hours under 20% O ₂ /He (500 c.c./min) to ensure nitrate decomposition. Among the following Examples, Examples 5, 6, and 7 are examples of the present invention. Example 1 This example is a reference example showing the harmful effect of Fe on chemisorption of noble metal bimetallic catalysts. Sinfelt and Yates (J.
Hydrogen and carbon monoxide chemisorption studies were performed using the conventional glass vacuum apparatus described in Catal, 8, 82 (1967). Hydrogen and carbon monoxide adsorption values were measured at 25±2° C. on reduced and evacuated samples. Typically, each adsorption point was left for 30 minutes. Assuming that the hydrogen adsorption value at zero pressure corresponds to the saturation coverage of the metal,
The H/M ratio was calculated. The hydrogen adsorption value at zero pressure is determined by Benson, Bondart, Wilson and Hall [J.Cata., 4 , 704 (1965) and
17, 190 (1970)], it was determined by extrapolation of the high-pressure linear portion of the isotherm. CO/M
The ratio was calculated by measuring the carbon monoxide _adsorption value on the reduced, exhaust sample and assuming that this value represents the total carbon monoxide weakly bound to the _Al2O3 support and strongly bound to the metal surface. The sample was then evacuated (10 ^-5 Torr) for 10 minutes at room temperature and a second carbon monoxide isotherm was measured. Since the second isotherm measures only carbon monoxide weakly adsorbed on the support, the difference between the two isotherms gives the amount of carbon monoxide strongly bound to the metal component. The amount of strongly bound carbon monoxide at 100 Torr is determined by the saturation coverage of the metal.
coverage). The hydrogen chemisorption properties of fresh Pt/Re and Pt/lr catalysts and iron-impregnated Pt/Re and Pt/lr catalysts are shown in Table 1. TABLE The last column in Table 1 normalizes the hydrogen adsorption values for iron contaminated catalysts with respect to the adsorption values for fresh Pt/Re and Pt/lr catalysts. It was found that the hydrogen chemisorption capacity of both bimetallic catalysts decreased systematically as the iron concentration increased. At 0.36% iron concentration, the hydrogen adsorption values of both bimetallic catalysts are 40-50% lower than that of fresh catalyst. The Fe/noble metal molar ratio of catalysts containing 0.1-0.8% Fe ranges from 0.5-4. Thus, an iron concentration of 0.2% is high enough to interact with all noble metal components present in the Pt/Re and Pt/lr reforming catalysts. The significant decrease in the H/M value that occurs at low iron concentrations points to the fact that iron alloys or physically adheres to a significant fraction of the noble metals. A reduction in chemisorption capacity may necessarily reduce reforming activity. This is because H-H and C-H bond activation processes are very important in catalytic reforming. Example 2 This example is a reference example showing the influence of iron on the reforming activity of a bimetallic catalyst. The naphthalene homing reaction was carried out in a 25 c.c. stainless steel fixed bed isothermal hydrotreater operated in one pass mode. The reforming experiment was carried out at 487-489℃, 14.06
It was carried out under a total pressure of Kg/cm ² gauge pressure (200 psig).
The weight space velocity is 2.1WHW, and hydrogen is
It was fed at a rate of 6000SCFH ₂ /BBL. A commercially available naphtha feedstock was used and the sulfur concentration was adjusted to 0.5 ppm by addition of thiophene. After hydrogen reduction at 500 °C, using a dilute _H2S / _H2 mixture,
The catalyst was sulphurized. We conducted a research method octane rating (RON) analysis of Reformate.
Octane number was used to define relative catalytic activity (RCA). The naphthalene homing activities of fresh Pt/Re and Pt/lr catalysts and iron-contaminated Pt/Re and Pt/lr catalysts are shown in comparison in Table 2. Table: The relative catalytic activities clearly show that 0.36% iron has a significant detrimental effect on both bimetallic catalysts. Similar coke formation was observed for all catalysts. The 55-65% lower activity exhibited by iron-containing catalysts indicates that the noble metal is deactivated by interaction with iron. In these catalysts, Fe/
Since the noble metal molar ratio is around 2, Pt, lr, Re
There will be enough iron available to denature all of the The reduced reforming activity is consistent with the reduced hydrogen chemisorption capacity seen with iron-contaminated catalysts. Example 3 This example is a comparative example showing the solubility of γ-Al ₂ O ₃ in water, oxalic acid solution, and ammonium acetate buffered oxalic acid solution, and these solubility are shown in Table 3 for comparison. . [Table] γ-Al ₂ O ₃ slurry after refluxing in H ₂ O for 30 min.
The PH reaches a self-buffering level of approximately 5.0. The acidity _{of Al2O3} - _H2O slurries is known in the art. Slurry _{of Al2O3} in oxalic acid is 100
It exhibits a pH of about 2 at °C. Thus, the acidity of the _Al2O3 -oxalic acid slurry is about three orders _of magnitude greater than the acidity of _{the Al2O3} - _H2O slurry. _Al2O3 -ammonium acetate buffered oxalate slurry was found to maintain _a relatively constant PH value of about 4.4 times in contrast to oxalate slurry. Thus, the PH of the buffered slurry is similar to the PH of the aqueous slurry of Al ₂ O ₃ . PH value can be recovered unchanged from the slurry
reflected in the amount of Al ₂ O ₃ . Essentially complete _Al2O3 recovery was obtained from the _H2O and buffered oxalic _acid slurry. However, oxalic acid slurry readily dissolves significant amounts _{of Al2O3} . After refluxing for 30 minutes,
Approximately half of the starting amount of Al ₂ O ₃ was converted to soluble aluminum species. Example 4 This example is a comparative example showing non-selective extraction of iron from a noble metal catalyst. Pt catalyst, Pt/lr catalyst,
The results of a representative study using oxalic acid solution for extraction of iron from Pt/Re catalysts are shown in Table 4. [Table] After 60 minutes at 50℃ with 0.5M oxalic acid solution, approx.
10% _Al2O3 support is dissolved _. When the extraction is carried out at 100 °C, 30-40% of _{the Al2O3} carrier is dissolved in 60 minutes. These significant losses of support are too high to seriously consider oxalic acid as an extractant for metal contaminants. High temperature (100℃)
During the extraction carried out in , a significant proportion of the precious metal components are extracted along with the iron. The loss of Re is particularly noticeable,
It cannot be suppressed by lowering the extraction temperature or reducing the concentration of the oxalic acid solution. Example 5 This example, in contrast to Example 4, demonstrates the invention providing selective extraction of iron from noble metal catalysts using buffered oxalic acid. Pt catalyst, Pt/lr catalyst, Pt/
The results of studies using ammonium acetate buffered oxalic acid solutions for the extraction of iron from Re catalysts are shown in Table 5. The iron-contaminated catalyst was typically reduced under _H2 before extraction with buffered oxalic acid solution. [Table] [Table] Compared to the oxalic acid slurry, the buffered oxalic acid solution does not dissolve the Al ₂ O ₃ support. The apparent catalyst loss of 2-4% is primarily due to mechanical loss over time of the slurry rather than dissolution of the Al ₂ O ₃ into the buffer solution. Although iron is selectively extracted, no obvious removal of precious metals occurs even at an extraction temperature of 100 °C. The extraction data further indicates that iron removal is advantageous at lower processing temperatures. This behavior is consistent with the fact that iron oxalate complexes are more stable at lower temperatures. In the case of a 2% iron contaminated Pt/lr catalyst, the influence of catalyst particle size on extraction efficiency is shown. The smaller the catalyst particle size, the more surface is expected to be exposed to the extraction medium. Thus, under given extraction conditions, removal of iron and other extractable contaminants should be more advantageous with smaller particle sizes.
This is consistent with the fact that more iron was removed from the powdered catalyst. The extraction data shown in Table 5 was obtained from crude slurry experiments and was not optimized. However, by recycling the catalyst into fresh extraction medium or by devising the extraction method so that the catalyst is continuously contacted with a buffered oxalic acid solution, the It is reasonable to think that all the iron can be removed. Buffered oxalic acid solutions can also be used for the removal of iron and other extractable metals such as Na, V, Ni, Cu, etc. from a wide variety of hydrocarbon conversion catalysts. Although oxalic acid is preferred for metal contaminant removal, oxalic acid can also be substituted for other organic acids in the method of the invention. Example 6 It is known that iron can act as a poison for noble metal catalysts. This example demonstrates the beneficial effects of the present invention of iron removal on the chemisorption behavior of Pt/Re catalysts. The results are shown in Table 6. An increased chemisorption of the catalyst was observed, close to that of fresh catalyst. 【table】
Extracted with um-buffered oxalic acid solution
[Table] When 0.37% iron is added to fresh Pt/Re catalyst,
_H2 and Co adsorption values decreased by about 50%. When this iron-contaminated catalyst is extracted with ammonium acetate buffered oxalic acid solution at 50°C, the iron concentration starts from 0.37%.
It decreased to 0.08%. The extracted catalyst was calcined at 500° C. under 20% O ₂ /He for 4 hours to ensure that the last traces of extractant were removed from the catalyst surface. After the extraction and calcination steps, the chemisorption value increased to a value close to that exhibited by fresh catalyst. by iron removal
The recovery of chemisorption values for the Pt/Re catalyst indicates that the buffered oxalic acid extractant does not poison or modify the metal surface. The redispersed Pt/lr catalyst showed lower hydrogen and carbon monoxide adsorption values than the fresh catalyst.
X-ray diffraction measurements of the redispersed catalyst showed neither a Pt nor an LR diffraction pattern, thus it is reasonable to assume that the catalyst is well dispersed. Therefore, the presence of 0.35% iron on the redispersed catalyst may be responsible for the unusually low hydrogen and carbon monoxide adsorption values. By extracting iron from the catalyst with ammonium acetate buffered oxalic acid solution, the iron concentration was reduced from 0.35% to 0.1%.
It declined to . After the standard extraction procedure, the catalyst was calcined at 270° C. under 2% O ₂ /He for 4 hours. The iron-extracted and calcined pt/lr catalyst exhibited hydrogen and carbon monoxide adsorption values that were somewhat lower than those exhibited by the redispersed catalyst. Since the iron extraction catalyst was only subjected to a 270 °C calcination step, the low chemisorption values may be due to residual amounts of adsorbent adhering to the metal surface.
The low chemisorption values exhibited by this extraction catalyst did not adversely affect the reforming activity of this catalyst, as described below. This finding suggests that residual extractant
This suggests that it can be removed from the catalyst at high reforming temperatures. Example 7 In this example, the naphthalene homing activity of a redispersed Pt/lr catalyst (containing 0.35% Fe) was compared to a fresh Pt/lr catalyst.
The catalyst and Fe are compared with the catalyst extracted according to the invention. The results are shown in Table 7. The reforming reaction conditions are as described in Example 2. Table: After 400 hours of feeding, the redispersed catalyst exhibited a reforming activity that was only 30% of that of the fresh catalyst. The reduced reforming activity exhibited by the redispersed catalyst suggests that iron contamination is one important factor for deactivation. After iron extraction, the reforming activity of the extraction catalyst after 400 hours of feeding is about 80% of the activity of fresh Pt/lr catalyst. Thus,
Removal of iron from the redispersed sample will provide a significantly more active catalyst. 0.37 effect on reforming activity of Pt/Re catalyst
The adverse effects of % Fe are shown in Table 8. Table: The reforming activity of the iron-contaminated catalyst after 350 hours of feeding is only 50% of the fresh activity. The same iron-contaminated catalyst showed 50% lower hydrogen and carbon monoxide adsorption values than the fresh catalyst (see Table 6). Thus, for iron-contaminated Pt/Re catalysts, there is excellent agreement between catalytic activity and chemisorption measurements. Extraction of 80% iron from this iron-contaminated Pt/Re catalyst yields a catalyst with hydrogen and carbon monoxide adsorption values and reforming activity close to those of fresh catalyst. This agreement between chemisorption values and catalytic reforming activity indicates that iron poisons bimetallic catalysts by interacting with metal components. The proportion of noble metals inactivated by iron increases with increasing iron concentration. Example 8 This example is a comparative example showing that mineral acids are not equivalent to oxalic acid in removing iron from the catalyst. 0.28%Pt, 0.27%lr, 2.0% on _{Al2O3 support}
The Fe-containing catalyst was treated with hydrochloric acid and hydrochloric acid buffered with ammonium acetate with the results shown in Table 9. [Table] Dried.
These results indicate that buffered hydrochloric acid results in large carrier losses with little iron removal.

Claims (1)

Claims: 1. A hydroconversion catalyst comprising group B or at least one metal from group B or group supported on a refractory inorganic oxide, or alumina or silica or silica alumina or zeolite or clay. A method for removing metal contaminants from a catalytic cracking catalyst comprising at least one catalyst, the method comprising contacting the contaminated catalyst with an ammonium acetate buffered oxalic acid solution. 2 Ammonium acetate buffered oxalic acid solution lowers the pH to 2
2. The method of claim 1, wherein the method is buffered with sufficient ammonium acetate to maintain a concentration of .about.10. 3 The concentration of oxalic acid is 0.0001M to 5.0M,
A method according to claim 1. 4. The method of claim 1, wherein the temperature is about 0<0>C to 100<0>C. 5 Claim 1, wherein the carrier is acid-soluble
The method described in section. 6. The method of claim 1, wherein the catalyst also comprises at least one of Co or Mo or Re or platinum metal supported on alumina or silica alumina or zeolite. 7. The method of claim 1, wherein the contaminated catalyst is contacted with the ammonium acetate buffered oxalic acid solution for a sufficient time to extract the metal contaminants without dissolving the inorganic oxides. 8. The method of claim 1, wherein the ammonium acetate buffered oxalic acid solution is a mixture of oxalic acid in an aqueous/non-aqueous solvent system.