Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/60—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the type L, as exemplified by patent document US3216789
  • B01J29/61—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the type L, as exemplified by patent document US3216789 containing iron group metals, noble metals or copper
  • B01J29/62—Noble metals
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G35/00—Reforming naphtha
  • C10G35/04—Catalytic reforming
  • C10G35/06—Catalytic reforming characterised by the catalyst used
  • C10G35/095—Catalytic reforming characterised by the catalyst used containing crystalline alumino-silicates, e.g. molecular sieves
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/061—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof containing metallic elements added to the zeolite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/16—Reducing
  • B01J37/18—Reducing with gases containing free hydrogen

Definitions

• the present invention concerns a pretreatment method useful for increasing the conversion and lowering the fouling rate of a reforming catalyst.
• Catalytic reforming is a well-known process that is used for raising the octane rating of a naphtha for gasoline.
• the reactions that occur during reforming include: dehydrogenation of cyclohexanes, dehydroisomerization of alkylcyclopentanes, dehydrocyclization of acyclic hydrocarbons, dealkylation of alkylbenzenes, isomerization of paraffins, and hydrocracking of paraffins.
• the hydrocracking 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 dehydrocyclization, in order to produce high yields of liquid product and low yields of light gases. These catalysts should possess good activity, so that low temperatures 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 dehydrocyclization over a long period of time.
• the temperature of the catalyst is maintained at 370°C (698°F) to 600°C (1112°F) in a reducing atmosphere.
• U.S. Patent No. 4,539,305 issued on September 3, 1985 to Wilson et al. discloses a pretreatment process for enhancing the selectivity and increasing the stability of a reforming catalyst comprising a large-pore zeolite containing at least one Group VIII metal.
• the catalyst is reduced in a reducing atmosphere at a temperature of from 250°C (482°) to 650° (1202°F).
• the reduced catalyst is subsequently exposed to an oxygen-containing gas and then treated in a reducing atmosphere at a temperature of from 120°C (248°F) to 260°C (500°F) .
• the catalyst is maintained at a temperature of from 370°C (698°F) to 600°C (1112°F) in a reducing atmosphere.
• the first reduction step is carried out in the presence of hydrogen.
• U.S. Patent No. 5,066,632 issued on November 19, 1991 to Baird et al. discloses a process for pretreating a catalyst useful for reforming a naphtha wherein the catalyst is calcined at temperatures in excess of 500°F, preferably at temperatures ranging from 500°F to about 750°F in air or in atmospheres containing low partial pressures of oxygen or in a non-reactive or inert gas such as nitrogen.
• the catalyst is then contacted with a dry hydrogen-containing gas at a temperature ranging from about 600°F to about 1000°F, preferably from about 750°F to about 950°F, at a hydrogen partial pressure ranging from about 1 atmosphere to about 40 atmospheres, preferably from 5 atmospheres to about 30 atmospheres.
• European Patent Application Publication Number 243,129 discloses a catalyst activation treatment with hydrogen at temperatures from 400°C (752°F) to 800°C (1472°F), preferably from 400°C (752°F) to 700°C (1292°F) , for a catalyst used for cracking a hydrocarbon feedstock.
• the treatment pressure may vary from 100 to 5,000 MPa but is preferably from 100 to 2,000 MPa.
• a carrier gas which contains 1-100% v/v, preferably from 30-100% v/v, of hydrogen is used.
• U.S. Patent No. 4,717,700 issued to Venkatra et al discloses a method for drying a zeolite catalyst by heating while in contact with a gas.
• the rate of catalyst temperature increase is controlled so as to limit the rate of water evolution from the catalyst and the water vapor concentration in the gas.
• the gas used to heat the catalyst is gradually increased in temperature at about 28°C per hour.
• the moisture level of the effluent gas is preferably between 500 and 1500 ppm during the drying step.
• the catalyst drying method with a subsequent reduction with hydrogen wherein the temperature is raised to a maximum temperature of 450°C is exemplified in Example 1.
• Austrian Patent Specification No. 268,210 relates to a metal-charged zeolite molecular sieve, which is suitable as a catalyst for the conversion of hydrocarbons.
• Methods for preparing the catalyst are described. It is disclosed that the catalyst prepared by such methods usually has a high water content and that it is desirable to activate the catalyst before use since the catalyst is sensitive to water.
• the recommended activation process comprises: 1) slow heating of the catalyst in air at 300 to 600°C, preferably 500°C; followed by 2) slow heating of the catalyst from room temperature to approximately 500°C in a current of hydrogen gas under atmospheric pressure.
• This reference specifically discloses the effect of a hydrogen pretreatment process on Pt-Al 2 0 3 catalysts and does not disclose the effect of hydrogen pretreatment on zeolitic catalyst. Additionally, the effects of hydrogen pretreatment of the Pt-Al 2 0 3 catalyst with respect to isomerization is disclosed. The activity for dehydrocyclization was not increased.
• the present invention is a process for increasing the conversion and lowering the fouling rate of large-pore zeolitic reforming catalysts using a pretreatment process.
• the catalyst is treated in a reducing gas at a temperature of from 1025°F to 1275°F.
• the pretreatment process in the range of 1025°F to 1275°F occurs in the presence of hydrogen at a pressure of from 0 to 300 psig for from 1 hour to 120 hours.
• the catalyst is reduced with dry hydrogen via temperature-programmed steps, with the treatment of the present invention occurring at the final temperature of from 1025°F to 1275°F.
• the procedure of the present invention which occurs in the temperature range of from 1025°F to 1275°F is considered and referred to as a "treatment" of the catalyst as opposed to a “reduction", because the catalyst has already generally been reduced at the lower temperatures prior to reaching the treatment temperature of the present invention.
• large-pore zeolitic catalysts which have been pretreated in a reducing gas in the high temperature range of from about 1025°F to 1275°F is found to have a lower fouling rate and improved activity, and have a longer run life.
• this catalyst exhibits a longer run life with heavier feedstocks than with similar catalysts using other pretreatment processes.
• run lengths with feeds containing C 9 + hydrocarbons are generally short.
• the pretreatment procedure of this invention makes it practical to process feedstocks containing as much as 5-15 wt % C 9 + hydrocarbons.
• the present inventors have discovered an advantageous high temperature catalyst treatment method.
• a high temperature treatment i.e., at 1025°F to 1275°F
• a catalyst with a reduced fouling rate and sufficient catalytic activity to yield a longer run life particularly if the temperature increase during reduction is performed in a gradual ramping or stepwise fashion, and if the water content of the effluent gas is kept as low as possible during the high temperature treatment range.
• catalysts that are on balance non-acidic still contain a few residual acidic sites.
• This high temperature treatment regimen is believed to reduce the number of acid sites on the catalyst, and thereby reduce side reactions which lead to the formation of coke.
• the improved fouling rate and conversion activity of the catalyst also allow for more beneficial use with a heavier feedstock.
• Fig. 1 of the Drawing is a graphical representation of hydrogen uptake onto catalyst as a function of temperature.
• Fig. 2 of the Drawing is a graphical representation of the fouling rates observed for different temperature treatments.
• the present invention is a process for increasing the conversion and/or lowering the fouling rate of large-pore zeolitic reforming catalysts using a pretreatment process.
• This catalyst is treated in a reducing gas at a temperature of from 1025°F to 1275°F.
• the pretreatment process occurs in the presence of hydrogen at a pressure of from 0 to 300 psig and a temperature of from 1025°F to 1275°F for from 1 hour to 120 hours, more preferably for at least 2 hours, and most preferably at least 4-48 hours. More preferably, the temperature is from 1050°F to 1250°F.
• the length of time for the pretreatment will be somewhat dependent upon the final treatment temperature, with the higher the final temperature the shorter the treatment time that is needed. For a commercial size plant, it is necessary to limit the moisture content of the environment during the high temperature treatment in order to prevent significant catalyst deactivation.
• the catalyst in order to limit exposure of the catalyst to water vapor at high temperatures, it is preferred that the catalyst be reduced initially at a temperature between 300°F and 700°F. After most of the water generated during catalyst reduction has evolved from the catalyst, the temperature is raised slowly in ramping or stepwise fashion to a maximum temperature between 1025°F and 1250°F.
• the temperature program and gas flow rates should be selected to limit water vapor levels in the reactor effluent to less than 200 ppm and, preferably, less than 100 ppm when the catalyst bed temperature exceeds 1025°F.
• the rate of temperature increase to the final activation temperature will typically average between 5 and 50°F per hour.
• the catalyst will be heated at a rate between 10 and 25°F/h.
• the gas flow through the catalyst bed (GHSV) during this process exceed 500 volumes per volume of catalyst per hour, where the gas volume is measured at standard conditions of one atmosphere and 60°F.
• GHSV's in excess of 5000 h "1 will normally exceed the compressor capacity.
• GHSV's between 600 and 2000 h "1 are most preferred.
• the pretreatment process of the present invention occurs prior to contacting the reforming catalyst with a hydrocarbon feed.
• the large-pore zeolitic catalyst is generally treated in a reducing atmosphere in the temperature range of from 1025°F to 1275°F. Although other reducing gasses can be used, dry hydrogen is preferred as a reducing gas.
• the hydrogen is generally mixed with an inert gas such as nitrogen, with the amount of hydrogen in the mixture generally ranging from l%-99% by volume. More typically, however, the amount of hydrogen in the mixture ranges from about 10%-50% by volume.
• the reducing gas entering the reactor should contain less than 100 ppm water. It is preferred that it contain less than 10 ppm water.
• the reactor effluent may be passed through a drier containing a desiccant or sorbent such as 4 A molecular sieves. The dried gas containing less than 100 ppm water or, preferably, less than 10 ppm water may then be recycled to the reactor.
• the feed to the reforming process is typically a naphtha that contains at least some acyclic hydrocarbons or alkylcyclopentanes.
• This feed should be substantially free of sulfur, nitrogen, metals and other known poisons. These poisons can be removed by first using conventional hydrofining techniques, then using sorbents to remove the remaining sulfur compounds and water.
• the catalyst of the present invention exhibits a longer run life with heavier feedstocks, e.g., containing at least 5 wt % C 9 + hydrocarbons, than similar catalysts having been subjected to a different treatment.
• feedstocks e.g., containing at least 5 wt % C 9 + hydrocarbons
• run lengths with feeds containing at least 5 wt % C 9 + hydrocarbons, and typically from 5-15 wt % C 9 + hydrocarbons are comparatively short.
• the catalyst obtained via the treatment of the present invention makes it quite practical to process such feedstocks containing the C 9 + hydrocarbons.
• the feed can be contacted with the catalyst in either a fixed bed system, a moving bed system, a fluidized system, or a batch system. Either a fixed bed system or a moving bed system is preferred.
• a fixed bed system the preheated feed is passed into at least one reactor that contains a fixed bed of the catalyst.
• the flow of the feed can be either upward, downward, or radial.
• the pressure is from about 1 atmosphere to about 500 psig, with the preferred pressure being from abut 50 psig to about
• the preferred temperature is from about 800°F to about 1025°F.
• the liquid hourly space velocity (LHSV) is from about 0.1 hr" 1 to about
• the catalyst is a large-pore zeolite charged with at least one Group VIII metal.
• the preferred Group VIII metal is platinum, which is more selective for dehydrocyclization and which is more stable under reforming reaction conditions than other Group VIII metals.
• the catalyst should contain between 0.1% and 5% platinum of the weight of the catalyst, preferably from 0.1% to 1.5%.
• the term "large-pore zeolite” is defined as a zeolite having an effective pore diameter of from 6 to 15 Angstroms. The preferred pore diameter is from 7 to 9 Angstroms.
• Type L zeolite, zeolite X, and zeolite Y, zeolite beta and synthetic zeolites with the mazzite structure are thought to be the best large-pore zeolites for this operation.
• Type L zeolite is described in U.S. Patent No. 3,216,789.
• Zeolite X is described in U.S. Patent No. 2,882,244.
• Zeolite beta is described in U.S. Patent No. 3,308,069.
• ZSM-4 described in U.S. Patent No. 4,021,447, is an example of a zeolite with the mazzite structure.
• Zeolite Y is described in U.S. Patent No. 3,130,007.
• U.S. Patent NOS. 3,216,789; 2,882,244; 3,130,007; 3,308,069; and 4,021,447 are hereby incorporated by reference to show zeolites useful in the present invention.
• the preferred zeolite is type L zeolite.
• Type L zeolites are synthesized largely in the potassium form. These potassium cations are exchangeable, so that other type L zeolites can be obtained by ion exchanging the type L zeolite in appropriate solutions. It is difficult to exchange all of the original cations, since some of these cations are in sites which are difficult to reach.
• the potassium may be ion exchanged with an alkali or alkaline earth metal, such as sodium, potassium, cesium, rubidium, barium, strontium, or calcium.
• the total amount of alkali or alkaline earth metal ions should be enough to satisfy the cation exchange sites of the zeolite or be slightly in excess.
• An inorganic oxide can be used as a carrier to bind the large-pore zeolite.
• This carrier can be natural, synthetically produced, or a combination of the two.
• Preferred loadings of inorganic oxide are from 5% to 50% of the weight of the catalyst.
• Useful carriers include silica, alumina, aluminosilicates, and clays.
• Figure 1 is a plot of hydrogen uptake onto catalyst as a function of pretreatment temperature. As can be seen from this Figure, as the pretreatment temperature is increased, the fraction of hydrogen bound to catalyst tends to decrease. If the hydrogen uptake onto catalyst is reflective of the fraction of exposed Pt atoms, then one would typically expect a decrease in activity with an increase in temperature.
• pretreating a large-pore zeolitic reforming catalyst in a reducing environment at various temperatures affects the activity of the catalyst will be demonstrated in Examples 1-8.
• the extent to which pretreating a large-pore zeolitic reforming catalyst in a reducing environment at various temperatures affects the fouling rate of the catalyst will be demonstrated in Examples 9, 10, 11 and 12.
• the benzene production is summarized in line 2 in Table 1.
• the catalyst treated at 1050°F was more active, producing more benzene, than the catalyst reduced at 900°F.
• the catalyst treated at 1050°F did not exhibit deactivation at 900°F.
• pretreating at a high temperature of 1050°F increased the activity and lowered the fouling rate of the catalyst.
• the benzene production is summarized in line 3 in Table 1.
• 1100°F was more active, producing more benzene, than the catalyst treated at 900°F.
• the catalyst reduced at 1100°F did not exhibit deactivation at 900°F.
• pretreating at a high temperature of 1100°F increased the activity and lowered the fouling rate of the catalyst.
• the benzene production is summarized in line 4 in Table 1.
• the catalyst treated at 1150°F was more active, producing more benzene, than the catalyst treated at 900°F.
• the catalyst treated at 1150°F did not exhibit deactivation at 900°F.
• pretreating at a high temperature of 1150°F increased the activity and lowered the fouling rate of the catalyst.
• the benzene production is summarized in line 5 in Table 1.
• the catalyst treated at 1200°F was more active, producing more benzene, than the catalyst reduced at 900°F.
• the catalyst treated at 1200°F did not exhibit deactivation at 900°F.
• pretreating at a high temperature of 1200°F increased the activity and lowered the fouling rate of the catalyst.
• the benzene production is summarized in line 6 in Table l.
• the catalyst treated at 1250°F was more active, producing more benzene, than the catalyst reduced at 900°F.
• the catalyst treated at 1250°F did not exhibit deactivation at 900°F.
• pretreating at a high temperature of 1250°F increased the activity and lowered the fouling rate of the catalyst.
• the benzene production is summarized in line 7 in Table 1.
• the catalyst treated at 1300°F was less active, producing less benzene, than the catalyst reduced at 900°F.
• the catalyst treated at 1350°F was less active, producing less benzene, than the catalyst reduced at 900°F.
• the feed for the catalyst performance test was a hydrotreated raffinate from an aromatics extraction unit consisting of 8.5% C 5 , 59.5% C 6 , 26.3% C 7 , and 5.8% C 8 + compounds on a weight basis. This feed was also characterized as 85.8% paraffins, 6.8% naphthenes, 6.7% aromatics, and 0.7% unknowns by weight.
• the test was carried out at a feed rate of 1.6 liquid hourly space velocity, 100 psig, and a hydrogen to feed molar ratio of 3.0.
• the catalyst bed temperature was adjusted as the run progressed to maintain 42 wt. % aromatics in the C 5 + product.
• the combined hydrogen and naphtha feedstream was treated to reduce its sulfur content to less than 5 ppb.
• the results of the test runs are shown in Figure 2.
• the catalyst fouling rates were calculated by a least squares fit of the data obtained after 200 hours on-stream.
• the catalyst reduced/treated at 500-1050°F had about one- fourth the fouling rate of the catalyst reduced at 500- 900°F (0.005 versus 0.020°F/h).
• The-start-of-run temperatures obtained by extrapolating the least squares line back to start-of-run were 852°F and 847°F, respectively.
• the yield of C 5 + product was 85 LV% of feed in both cases.
• the fouling rate is constant and the end-of-run average catalyst temperature is 935°F
• the projected run length is about two years for the catalyst treated at 1050°F compared to about six months for the catalyst treated at 900°F.
• a feed containing 2.7% C 5 and lighter, 8.5% C 6 , 49.4% C 7 , 30.8% C 8 , and 8.7% C 9 + components was reformed over the 500-1050°F reduced catalyst from Example 9.
• the feed was further characterized as containing 66.6% paraffins, 22.6% naphthenes, 10.5% aromatics, and 0.25% unknowns. Over a period of about 400 hours, the fouling rate under these conditions was 0.018°F/h which corresponds to more than six months run length.
• the catalyst comprised 0.65 wt% platinum, barium exchanged L- zeolite, and a binder.
• the reactor was heated by a three-zone electric furnace. Catalyst bed temperatures were measured by six thermocouples located in an axial thermowell.
• the reaction system comprised: the reactor, a chilled liquid-gas separator, a moisture analyzer probe, a compressor, a recycle-gas drier, and a recycle gas flowmeter.
• the moisture analyzer measured the moisture content in the recycle gas before or after the drier.
• the drier was charged with 4 A molecular sieves.
• the unit was pressurized to 70 psig with dry nitrogen containing less than 10 ppm water.
• the compressor was started. Nitrogen addition was continued in order to produce an off-gas stream and purge the system of oxygen. After two hours, the nitrogen addition rate was reduced until there was only a small off-gas stream.
• the gas circulation rate was adjusted to maintain a gas flow over the catalyst bed corresponding to a GHSV of about 1000 h " *.
• the catalyst was further dried by heating the reactor to 500°F. Water in the reactor effluent was removed by a drier, so that the recycle gas contained less than 10 ppm water. The temperature was held at 500°F until the moisture content of the reactor effluent gas dropped below 100 ppm.
• the make-up gas was then switched from nitrogen to dry hydrogen and the unit was pressurized to 100 psig. After reaching 100 psig, the hydrogen addition rate was adjusted to maintain a small gas bleed. The gas circulation rate was adjusted to obtain a GHSV of about 1000 h" 1 . Following hydrogen addition, there was an increase in the water content of the reactor effluent due to catalyst reduction. This water was removed from the recycle hydrogen stream by the recycle-gas driers. The reactor-inlet gas contained less than 10 ppm water. The reactor temperature was held at 500°F until the water in the reactor effluent again dropped below 100 ppm. The reactor temperature was then raised 10°F/h to 900°F.
• the high temperature treated catalyst was tested with several feeds at several different conditions. When tested at the conditions used in Example 9, but with a heavier feed, the fouling rate was 0.007°F/h compared to 0.025°F/h for the same catalyst reduced in the temperature range of from 500 to 900°F.
• a potassium L-zeolite catalyst also surprisingly benefits from a high temperature hydrogen treatment. Platinum was loaded onto a bound, 20-40 mesh, K-L zeolite support using the incipient wetness impregnation method and an aqueous Pt(NH 3 )C1 2 -H 2 0 solution. The impregnated material was oven-dried at 120°F overnight and calcined at 500°F for four hours.
• one-gram of the calcined material was loaded into a 3/16" I.D. tubular microreactor.
• the catalyst was dried by heating to 500°F in nitrogen flowing at a rate of 550 cc/min.
• the catalyst was reduced in 550 cc/min of hydrogen while the reactor temperature was heated from 500 to 900°F at a rate of 10°F/h.
• the activation procedure was the same except that the final temperatures were 1100 and 1150°F, respectively.
• the catalyst samples were held at their peak temperature for three hours, then cooled to 875°F for testing.
• a C 5 -C 8 raffinate stream from an aromatics extraction unit was reacted in the presence of hydrogen over each catalyst sample.
• Reactor effluent analyses were obtained by gas chromatography. Conversion and selectivity were calculated from the feed and product analyses.
• Table 2 shows that the stability of the Pt-K-L zeolite catalyst was significantly improved by high temperature reduction. Conversion after about six days on-stream was significantly higher for the catalysts treated at 1100 or 1150°F than when the reduction temperature was limited to 900°F.
• Conversion refers to the conversion of C 6 + feed components and "selectivity" is the selectivity for aromatics and hydrogen production. Both are calculated on a weight basis.

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• 1993
  • 1993-11-16 WO PCT/US1993/011052 patent/WO1994011464A1/en active IP Right Grant
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