Catalytic composition and process for the dehydrogenation of butenes or mixtures of butanes and butenes to give 1,3-butadiene

Abstract

The present invention relates to a catalytic composition which comprises microspheroidal alumina and an active component containing a mixture comprising Gallium and/or Gallium oxides, Tin and/or Tin oxides, a quantity ranging from 1 ppm to 500 ppm with respect to the total weight of the catalytic composition of platinum and/or platinum oxides, and oxides of alkaline and/or alkaline earth metals.

Claims

1. A catalytic composition, consisting of: microspheroidal alumina modified with silica, and an active component containing a mixture comprising at least one of gallium and gallium oxide, at least one of Tin and a Tin oxide, at least one of platinum and a platinum oxide in a quantity ranging from 1 ppm to 500 ppm with respect to a total weight of the catalytic composition, and K.sub.2O, wherein the catalytic composition dehydrogenates mixtures of butenes in the co-presence of C.sub.4 paraffins in a circulating fluid-bed equipped with a reactor and regenerator with a conversion of at least about 17% and/or a selectivity of at least about 84%, wherein conversion is calculated by
{[(butanes+butenes).sub.reactor inlet(butanes+butenes).sub.outlet reactor]/(butanes+butenes).sub.reactor inlet}*100 and selectivity is calculated by
{1,3butadiene.sub.reactor outlet/[(butanes+butenes).sub.reactor inlet(butanes+butenes).sub.reactor outlet]}*100.

2. The catalytic composition according to claim 1, wherein tin oxide is present and which is at least one selected from the group consisting of SnO and SnO.sub.2.

3. The catalytic composition according to claim 1, wherein platinum oxide is present and which is at least one selected from the group consisting of PtO and PtO.sub.2.

4. The catalytic composition according to claim 1, wherein the at least one of gallium and gallium oxide is present in an amount of from 0.05% by weight to 34% by weight with respect to a total weight of the catalytic composition.

5. The catalytic composition according to claim 1, wherein the K.sub.2O is present in an amount of from 0.1% by weight to 5% by weight with respect to a total weight of the catalytic composition.

6. The catalytic composition according to claim 5, wherein the at least one of gallium and gallium oxide is present in an amount of from 0.2% by weight to 3.8% by weight with respect to the total weight of the catalytic composition.

7. The catalytic composition according to claim 5, wherein the K.sub.2O is present in an amount of from 0.1% by weight to 3% by weight with respect to the total weight of the catalytic composition.

8. The catalytic composition according to claim 1, wherein the at least one of tin and tin oxide is present in an amount of from 0.001% by weight to 1% by weight with respect to a total weight of the catalytic composition.

9. The catalytic composition according to claim 8, wherein the at least one of tin and the tin oxide is present in an amount of from 0.05% by weight to 0.4% by weight with respect to the total weight of the catalytic composition.

10. The catalytic composition according to claim 1, wherein the at least one of platinum and the platinum oxide is present in an amount of from 1 to 50 ppm by weight with respect to the total weight of the catalytic composition.

11. The catalytic composition according to claim 1, wherein the microspheroidal alumina has a surface area lower than or equal to 150 m.sup.2/g.

12. The catalytic composition according to claim 1, wherein silica is present in an amount of from 0.05% by weight to 5% by weight.

13. The catalytic composition according to claim 12, wherein the silica is present in an amount of from 0.03% by weight to 3% by weight.

14. The catalytic composition according to claim 1, wherein gallium oxide is present and which is at least one selected from the group consisting of Ga.sub.2O.sub.3 and Ga.sub.2O.

15. The catalytic composition according to claim 1, wherein the at least one of platinum and a platinum oxide in a quantity ranging from 1 ppm to 99 ppm with respect to a total weight of the catalytic composition.

16. A catalytic composition, consisting of: microspheroidal alumina modified with silica, the silica being present in an amount of 0.03 to 3% by weight, with respect to the total weight of the catalytic composition, and an active component containing a mixture comprising gallium oxide in an amount of 0.2% by weight to 3.8% by weight, with respect to the total weight of the catalytic composition, at least one of Tin and a Tin oxide in an amount of 0.001% to 1% by weight, with respect to the total weight of the catalytic composition, at least one of platinum and a platinum oxide in a quantity ranging from 1 ppm to 500 ppm with respect to a total weight of the catalytic composition, and K.sub.2O in an amount of 0.2 to 3.8% by weight, with respect to the total weight of the catalytic composition.

17. A catalytic composition, consisting of: microspheroidal alumina modified with silica, and an active component containing a mixture comprising at least one of gallium and gallium oxide, at least one of Tin and a Tin oxide, at least one of platinum and a platinum oxide in a quantity ranging from 1 ppm to 500 ppm with respect to a total weight of the catalytic composition, and K.sub.2O, wherein the catalytic composition dehydrogenates mixtures of butanes in the co-presence of C.sub.4 paraffins in a circulating fluid-bed pilot plant equipped with a reactor and regenerator with a conversion of at least about 17% and/or a selectivity of at least about 84%, wherein conversion is calculated by
{[(butanes+butenes).sub.reactor inlet(butanes+butenes).sub.outlet reactor]/(butanes+butenes).sub.reactor inlet}*100 and selectivity is calculated by
{1,3butadiene.sub.reactor outlet/[(butanes+butenes).sub.reactor inlet(butanes+butenes).sub.reactor outlet]}*100.

Description

(1) Further objectives and advantages of the present invention will appear more evident from the following description and enclosed figures, provided for purely illustrative and non-limiting purposes.

(2) FIG. 1 illustrates a process scheme relating to an embodiment according to the present invention wherein (1) is the feeding to the process, (2) is the inert product, (3) is the hot catalyst, (4) is the carrier gas of the catalyst, (5) is nitrogen for stripping, (6) is air, (7) is fuel gas, (8) are the combustion effluents, (9) is the recycling of the partially exhausted catalyst to the reaction section, (10) is the partially exhausted catalyst, (11) is the effluent of the reactor, (12) is the nitrogen for stripping, (R-1) is the Fast Riser dehydrogenation section, (R-2) is the regenerator for regenerating the catalyst, (S-1) is the separation section of the catalyst, (S-2) is the stripping section of the regenerator, (S-3) is the stripping section of the Fast Riser, V-1 and V-2 are two valves.

DETAILED DESCRIPTION

(3) An object of the present invention relates to an extremely active catalytic composition which is capable of operating with low contact times in a single dehydrogenation section having reduced dimensions.

(4) Said catalytic composition comprises a microspheroidal alumina carrier and an active component containing a mixture comprising Gallium and/or Gallium oxides, Tin and/or Tin oxides, a quantity ranging from 1 ppm to 500 ppm with respect to the total weight of the catalytic composition of platinum and/or platinum oxides, and oxides of alkaline and/or alkaline earth metals. The alumina carrier is preferably modified with silica.

(5) It is fundamental for the present invention that the platinum and/or platinum oxides be present in modest quantities in the catalytic composition, preferably from 1 ppm to 99 ppm by weight, even more preferably from 1 ppm to 50 ppm by weight. Excessively high quantities of platinum in the catalytic composition, in fact, make it necessary for the catalyst, possibly regenerated, to be subjected to further treatment with chlorine-based dispersing agents to reduce sintering problems. For this purpose, the Applicant uses extremely low quantities of Pt and/or Pt oxides so that after regeneration, the catalytic composition can be immediately re-used without further treatment neither for re-dispersion nor for reduction. The absence of the re-dispersion phase avoids acid emissions into the atmosphere.

(6) The gallium oxides are preferably selected from Ga.sub.2O.sub.3, Ga.sub.2O and mixtures thereof. The tin oxides are preferably selected from SnO, SnO.sub.2 and mixtures thereof. The platinum oxides are preferably selected from PtO, PtO.sub.2 and mixtures thereof. An oxide of alkaline metals is preferably K.sub.2O.

(7) A preferred catalytic composition comprises a mixture of gallium oxides, oxides of alkaline and/or alkaline earth metals, tin and a quantity of platinum lower than 250 ppm, supported on microspheroidal alumina modified with silica.

(8) A further preferred catalytic composition comprises a mixture of Ga.sub.2O.sub.3, K.sub.2O, SnO and Platinum supported on microspheroidal alumina modified with silica.

(9) The catalytic composition, object of the present invention, preferably contains a microspheroidal alumina carrier modified with silica, as it is particularly suitable if the reaction takes place in fluid bed reactors or in a Fast Riser reactor. The active part is deposited on the microspheres of alumina modified with silica, and can be modified with modest quantities of Platinum.

(10) The quantity of Gallium and/or Gallium oxides preferably ranges from 0.1% by weight to 34% by weight, more preferably from 0.2% by weight to 3.8% by weight, with respect to the total weight of the catalytic composition.

(11) The quantity of oxides of alkaline and/or alkaline earth metals preferably ranges from 0.05% by weight to 5% by weight, more preferably from 0.2% by weight to 3.8% by weight, with respect to the total weight of the catalytic composition.

(12) The quantity of tin and/or tin oxides preferably ranges from 0.001% by weight to 1% by weight, more preferably from 0.05% by weight to 0.4% by weight, with respect to the total weight of the catalytic composition.

(13) The concentration of platinum preferably ranges from 1 ppm to 500 ppm by weight, more preferably from 1 ppm to 99 ppm by weight, even more preferably from 1 to 50 ppm, with respect to the total weight of the catalytic composition.

(14) The quantity of silica present in the carrier ranges from 0.05% by weight to 5% by weight, more preferably from 0.03% by weight to 3% by weight, with respect to the total weight of the catalytic composition, the remaining percentage being alumina. The surface area of the microspheroidal alumina is preferably lower than or equal to 150 m.sup.2/g.

(15) The concentration of Ga.sub.2O.sub.3 more preferably ranges from 0.1% by weight to 34% by weight, more preferably from 0.2% by weight to 3.8% by weight, with respect to the total weight of the catalytic composition. The quantity of K.sub.2O preferably ranges from 0.05% by weight to 5% by weight, more preferably from 0.1% by weight to 3% by weight, with respect to the total weight of the catalytic composition. The SnO preferably ranges from 0.001% by weight to 1% by weight, more preferably from 0.05% by weight to 0.4% by weight, with respect to the total weight of the catalytic composition. The quantity of platinum preferably ranges from 1 ppm to 500 ppm by weight, more preferably from 1 ppm to 99 ppm by weight, even more preferably from 1 ppm to 50 ppm, with respect to the total weight of the catalytic composition.

(16) The catalytic composition, object of the present invention, is suitable for operating with fixed-bed and mobile-bed reactors.

(17) The catalytic composition, object of the present invention, is obtained by means of a process which essentially consists of dispersing the precursors of the active principles on the microspheres of modified alumina. This dispersion treatment can consist of impregnating said carrier with a solution containing the precursors of the active principles, followed by drying and calcination; or by means of ionic absorption, followed by separation of the liquid and activation, or by surface adsorption of volatile species of the precursors, and possible calcination of the solid. Among those listed, the preferred procedures are: impregnation of the carrier with the volume of solution equal to that given by the pores (specific porosity of the carrier [cc/g] multiplied by the gr. of carrier to be impregnated) which corresponds to the amount of carrier to be treated. This impregnation procedure is known as incipient wetness process. Or immersion of the carrier in a volume of solution, in excess with respect to that which corresponds to the pores, in which the precursors of the active ingredients are dissolved, followed by evaporation and subsequent calcination. The precursors of the active principles can be contemporaneously dispersed, in a single step, on the carrier, modified with silica, or in several steps: in the first step, the carrier, preferably modified with silica, is impregnated with the solution containing a precursor of gallium and potassium, followed by drying and calcination; or the carrier, preferably modified with silica, is impregnated with the solution containing a precursor of gallium, potassium and tin, followed by drying and calcination; in the second step, the calcined product coming from the first step is impregnated with the solution containing the precursor of platinum and tin, the impregnated product is dried and finally calcined; or the calcined product coming from the first step is impregnated with a precursor of platinum, the impregnated product is dried and finally calcined.

(18) A further object of the present invention relates to a dehydrogenation process starting from reagents selected from single butenes, or mixtures thereof, or mixtures of butenes with butanes, to give 1-3 butadiene.

(19) Said process comprises the following phases: diluting said reagents with an inert product before feeding them to a dehydrogenation section; dehydrogenating said reagents in said dehydrogenation section in the presence of the catalytic, thus producing a gaseous effluent containing 1-3 butadiene; sending at least a part of the exhausted catalytic composition to a regenerator; at least partially regenerating said catalytic composition, exhausted after the reaction, in the regenerator by feeding a stream containing an oxidant selected from air, air poor or rich in oxygen; sending the regenerated catalytic composition back to the dehydrogenation section.

(20) The part of the catalytic composition that is sent to the regenerator preferably ranges from 50% to 80% and consequently the part that is not regenerated ranges from 50% to 20%. The part of the catalytic composition that is not sent to the regenerator is recirculated directly to the dehydrogenation section.

(21) The reaction device for dehydrogenation according to the present invention can be similar to that adopted in Fluid Catalytic Cracking (F.C.C.) processes, thus obtaining a reduction in the reaction volumes. A regenerator of the catalytic composition described and claimed in the present text is associated with the dehydrogenation section. The regeneration preferably provides combustion with air of the coke deposited on the catalyst during the dehydrogenation and forms combustion products. The dehydrogenation reaction and regeneration are effected in two separate apparatuses thus avoiding the formation of mixtures of hydrocarbon in air which is potentially risky. The catalytic composition is always recirculated between the reaction section and a regenerator and vice versa, using a carrier gas. The same carrier gas can be used for diluting the feedstock at the inlet of the reaction section. The inert product for diluting the feedstock can be selected from nitrogen, methane, or another fuel gas with a maximum hydrogen content equal to 1% by weight.

(22) The inert product has the function of lowering the partial pressure of the reagents and products in order to increase the conversion and reduce the kinetics of parasite reactions so as to preserve the selectivity to the desired product. The carrier gas can be nitrogen, or methane or another fuel gas with a maximum hydrogen content equal to 1% by weight, which offer the advantage, with respect to nitrogen, of recovering the calorific value of the hydrogen without the need for cryogenic separation.

(23) In the process, object of the present invention, the use of ovens for preheating the feedstock is not envisaged, thus reducing the formation and emission of NOx. The same catalytic composition described and claimed in the present text forms the thermal vector of the dehydrogenation reaction yielding the sensitive heat accumulated during the regeneration. The combustion of the coke present on the exhausted catalytic system generates heat entirely recovered for the dehydrogenation reaction and integrated with aliquots of fuel gas added in the regeneration device to be able to completely balance the endothermic dehydrogenation reaction. Natural gas or hydrogen or fuel gas obtained from a mixture of the two, can be used as fuel gas in the regeneration section.

(24) Preferably the dehydrogenation section suitable for the present invention can be a fixed-bed reactor, a fluid-bed reactor or a mobile-bed reactor. Even more preferably, the reaction device is a Fast Riser reactor into whose base the feedstock to be dehydrogenated is charged. In the dehydrogenation section, the feedstock is mixed with the at least partially regenerated catalytic composition, described and claimed in the present text, which enters the base of the reactor. The feedstock is dehydrogenated in said reactor as the catalytic composition and feedstock advance in equicurrent, until they have passed through the whole reactor. The catalytic system is separated from the gaseous effluent at the head of the reactor, and is sent to the regeneration device. The catalytic composition, object of the present invention, can be entirely or partially sent to regeneration. The non-regenerated part is recycled directly to the reaction device. After regeneration, the catalytic composition is re-circulated to the reactor.

(25) In the dehydrogenation section, it is preferable to operate at a temperature ranging from 450 C. a 700 C. The dehydrogenation pressure preferably ranges from 0.2 atm absolute to 2 atm. The ratio inert product/feedstock (v/v) ranges from 0 to 20, preferably from 1 to 9. The inert product for diluting the feedstock can be selected from nitrogen, methane, or another fuel gas with a hydrogen content equal to 1% by weight.

(26) If the reactor is a Fast Riser, the residence time of the gas phase is less than a minute, and preferably ranges from 0.2 sec. to 5 sec.

(27) The regeneration is preferably effected in a fluid bed at a temperature higher than the operating temperature of the reaction section, preferably higher than 700 C. The pressure in the regeneration section is slightly higher than atmospheric pressure. The residence time of the catalytic system during the regeneration ranges from 5 to 60 minutes, preferably from 20 to 40 minutes. During the regeneration, the hourly space velocity of the gas phase (GHSV in Nl/h air per litre of catalyst) ranges from 1,000 to 5,000 h.sup.1, preferably from 2,000 to 3,000 h.sup.1.

(28) The regeneration of the catalytic system and combustion of the fuel can be effected with air, oxygen or any other fuel.

(29) The advantages of a reactor-regenerator system, and particularly a Fast Riser reactor-regenerator, can be summarized as follows. reduction in the reaction volumes and consequent investment; the heat required for the reaction is transferred directly by the regenerated catalyst, there are no ovens for preheating the feedstock upstream of the reaction section, with the possibility of the formation of undesired combustion by-products; no specific treatment is necessary for reducing emissions of gaseous pollutants; the reaction and regeneration take place in physically separate areas and there can be no mixing of hydrocarbon streams with streams containing oxygen; the regeneration of the catalyst effected in a fluid bed prevents the formation of high-temperature points, due to the vigorous remixing of the bed, preventing thermal stress of the catalytic formulate; the functioning of the plant does not have to be interrupted for the substitution of the catalyst as aliquots are periodically discharged and replaced with equal amounts of fresh catalyst when the unit is operating.

(30) Some non-limiting examples of the present invention are now provide hereunder.

EXAMPLE 1

(31) A microspheroidal pseudobohemite modified with silica (1.2% by weight) is prepared, having a particle diameter ranging from 5 m to 300 m, by spray drying a solution of alumina hydrate and Ludox silica. A part of the pseudobohemite is calcined at 450 C. for an hour and subsequently treated at 1140 C. for 4 hours. The calcined product has a specific surface of 70 m.sup.2/g and a specific porosity of 0.2 cc/g. A sample of 3250 g of calcined product is impregnated, by means of the incipient wetness procedure, with an aqueous solution consisting of: 573 gr of a solution of gallium nitrate (titre 9.3% by weight of Ga), 131.8 gr of a solution of potassium nitrate (titre 6.86% by weight of K) and water until the volume of the solution is brought to 1040 cc. The impregnated product was dried at 120 C. for 4 hours and finally calcined according to the thermal profile: from room temperature to 460 C. in 533 minutes and an isotherm step of 180 minutes at 460 C. 3270 gr of the calcined product consisting of 2.15% by weight of Ga.sub.2O.sub.3, 0.33% by weight of K.sub.2O, Al.sub.2O.sub.3 and SiO.sub.2 for the remaining part, were impregnated with the incipient wetness procedure with an aqueous solution containing dissolved: 230 g of anhydrous citric acid, 33.343 g of a solution of tin tetrachloride (titre 7.52% by weight of Sn) and 1.335 g of solid ammonium tetrachloro-platinite (titre 52% by weight of Pt) and water until the volume of the solution had been brought to 1046 cc. The impregnated product was dried at 120 C. for 4 hours and finally calcined according to the thermal profile: from room temperature to 120 C. in 120 minutes, followed by an isotherm step at 120 C. for 120 minutes, then from 120 C. to 250 C. in 120 minutes, from 250 C. to 730 C. in 210 minutes, followed by an isotherm step at 730 C. for 90 minutes. The weight composition of the catalytic system proves to be: 2.15% by weight of Ga.sub.2O.sub.3, 0.33% by weight of K.sub.2O, 212 ppm by weight of Pt, 766 ppm by weight of Sn, the remaining part being Al.sub.2O.sub.3 and SiO.sub.2.

EXAMPLE 2

(32) A 3250 g sample of the same calcined bohemite as Example 1 was impregnated using the same procedure described in Example 1 with an aqueous solution containing, dissolved: 573 gr of a solution of gallium nitrate (titre 9.3% by weight of Ga), 131.8 gr of a solution of potassium nitrate (titre 6.86% by weight of K) and water until the volume of the solution was brought to 1040 cc. The impregnated product was dried and calcined under the same conditions described in Example 1. 3275 gr of the calcined product consisting of 2.15% by weight of Ga.sub.2O.sub.3, 0.33% by weight of K.sub.2O, the remaining part being Al.sub.2O.sub.3 and SiO.sub.2, were impregnated with the same procedure as Example 1, with a solution containing: 230 g of anhydrous citric acid, 1.3354 g of ammonium tetrachloro-platinite (titre 52% by weight of Pt), 65.337 g of a solution of tin tetrachloride (titre 7.52% by weight of Sn). The impregnated product was dried and calcined following the same procedure adopted for preparing the catalytic system described in Example 1. The weight chemical composition of the catalytic system is: 2.15% by weight of Ga.sub.2O.sub.3, 0.33% by weight of K.sub.2O, 212 ppm by weight of Pt, 1500 ppm by weight of Sn, the remaining part being Al.sub.2O.sub.3 and SiO.sub.2.

(33) The catalytic systems prepared were tested for dehydrogenating mixtures of butenes in the co-presence of C.sub.4 paraffins, prevalently n-Butane, in a circulating fluid-bed pilot plant equipped with a reactor and regenerator. The catalytic performances are indicated in Table 2, in which conversion (A) and selectivity (B) are calculated according to the following formulae:
{[(butanes+butenes).sub.reactor inlet(butanes+butenes).sub.outlet reactor]/(butanes+butenes).sub.reactor inlet}*100 (A)
{1,3butadiene.sub.reactor outlet/[(butanes+butenes).sub.reactor inlet(butanes+butenes).sub.reactor outlet]}*100 (B)

(34) The composition of the feedstocks treated in both Examples are indicated in Table 1.

(35) TABLE-US-00001 TABLE 1 MIX 1 MIX 2 Components % by weight % by weight N2 2.288 absent CH4 absent absent 0.001 absent CO2 absent absent C2H6 absent absent C2H4 absent absent C2H2 0.083 absent C3H4 0.086 absent C3H8 0.058 absent C3H6 0.018 absent n-C4H10 12.903 27.98 iso-C4H10 3.563 absent iso-C4H8 0.690 absent 1-C4H8 52.381 13.21 2-CC4H8 12.362 21.5 2-Trans C4H8 15.450 37.31 1-3C4H6 (BTD) 0.057 absent 1-2C4H6 0.000 absent C5H12 0.030 absent C5H10 0.030 absent C6H14 0.001 absent

(36) TABLE-US-00002 TABLE 2 Catalytic Performances Riser (sec) of Molar fract. Inert type Operating. Selectiv. head reagents hydroc. feed for feed press Conv. % wt Ex. Feed T C. In Riser at react. inlet dilution (abs. atm) (%) 1,3 butadiene 1 Mix 1 528 1 0.11 Nitrogen 2 17.2 88.6 1 Mix 1 554 1 0.11 Nitrogen 2 19.9 87.7 1 Mix 1 569 1 0.11 Nitrogen 2 21.8 85.3 1 Mix 1 528 1 0.11 Methane 2 16 89.5 1 Mix 1 554 1 0.11 Methane 2 19 87.5 1 Mix 1 569 1 0.11 Methane 2 20.5 86.1 1 Mix 2 530 1 0.11 Nitrogen 2 17 87.7 1 Mix 2 550 1 0.11 Nitrogen 2 21 86 1 Mix 2 570 1 0.11 Nitrogen 2 24 82 2 Mix 2 530 1 0.11 Nitrogen 2 20 90 2 Mix 2 550 1 0.11 Nitrogen 2 23 88 2 Mix 2 570 1 0.11 Nitrogen 2 26 84