Mixed metal oxide catalyst useful for paraffin dehydrogenation

Abstract

The invention relates to a catalyst composition suitable for the dehydrogenation of paraffins having 2-8 carbon atoms comprising zinc oxide and titanium dioxide, optionally further comprising oxides of cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), lanthanum (La), neodymium (Nd), praseodymium (Pr), samarium (Sm), terbium (Tb), ytterbium (Yb), yttrium (Y), tungsten (W) and Zirconium (Zr) or mixtures thereof, wherein said catalyst composition is substantially free of chromium and platinum. The catalysts possess unique combinations of activity, selectivity, and stability. Methods for preparing improved dehydrogenation catalysts and a process for dehydrogenating paraffins having 2-8 carbon atoms, comprising contacting the mixed metal oxide catalyst with paraffins are also described. The catalyst may also be disposed on a porous support in an attrition-resistant form and used in a fluidized bed reactor.

Claims

1. A mixed-metal oxide catalyst suitable for the dehydrogenation of paraffins having 2-8 carbon atoms comprising oxides of Transition Metals selected from the group of copper (Cu), iron (Fe), manganese (Mn), niobium (Nb) and zinc (Zn) as the active catalytic species wherein the active species makes up 0.1 to 20 wt % of the total weight of the catalyst, oxides of aluminum (Al), silicon (Si), titanium (Ti) and zirconium (Zr) or mixtures thereof as the catalyst support wherein the catalyst support makes up 10 to 90 wt % of the total weight of the catalyst, and oxides of Rare Earth metals as catalyst stabilizers selected from the group of cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), lanthanum (La), neodymium (Nd), praseodymium (Pr), samarium (Sm), terbium (Tb), ytterbium (Yb), and yttrium (Y) wherein the catalyst stabilizer makes up 0.1 to 20 wt % of the total weight of the catalyst, and characterizable by a. Activity Parameter >1500, b. Selectivity Parameter <0.2, and c. Stability parameter <0.005 measured using a test where the metal oxide catalyst is loaded in a fixed-bed reactor such that the 50>d.sub.T/d.sub.P>10 (diameter of tube to diameter of catalyst particles) and 200>L/d.sub.P>50 (length of catalyst bed to diameter of catalyst particles) and 2>d.sub.P>0.5 mm exposed to a feed stream comprising of propane at a temperature of 625° C., atmospheric pressure and a feed rate of 1 hr.sup.−1 weight hourly space velocity.

2. A mixed metal oxide catalyst suitable for the dehydrogenation of paraffins having 2-8 carbon atoms with a catalyst composition of the general formula (AC) (CS) (ST) wherein a) AC represents oxides of Transition Metals selected from the group of copper (Cu), iron (Fe), manganese (Mn), niobium (Nb) and zinc (Zn) or mixtures thereof, b) CS represents oxides of aluminum (Al), silicon (Si), and titanium (Ti) or mixtures thereof, c) ST represents oxides of Rare Earth metals selected from the group of cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), lanthanum (La), neodymium (Nd), praseodymium (Pr), samarium (Sm), terbium (Tb), ytterbium (Yb), yttrium (Y), tungsten (W), zirconium (Zr), or mixtures thereof, and characterizable by a Activity Parameter >1500, Selectivity Parameter <0.2 and a stability parameter <0.005 using a test where the mixed metal oxide catalyst is loaded in a fixed-bed reactor such that the 50>dT/dP>10 (diameter of tube to diameter of catalyst particles) and 200>L/dP>50 (length of catalyst bed to diameter of catalyst particles) and 2>dP>0.5 mm exposed to a feed stream of propane at a temperature of 625° C., atmospheric pressure and a feed rate of 1 hr.sup.−1 or 2 hr.sup.−1 weight hourly space velocity.

3. The catalyst composition according to claim 2 wherein the catalyst stabilizer makes up 1 to 15 wt % of the total weight of the catalyst.

4. The catalyst composition according to claim 2 wherein the catalyst stabilizer makes up 1 to 10 wt % of the total weight of the catalyst.

5. The catalyst composition of claim 2, wherein said catalyst composition has less than 100 ppm by weight of either platinum (Pt) or chromium (Cr).

6. The catalyst composition of claim 2 wherein the BET surface area >30 m.sup.2/g.

7. A mixed metal oxide catalyst comprising a catalyst composition of the general formula (AC) (CS) (ST) (MS) wherein a) AC (Active Catalyst) represents oxides of Transition Metals selected from the group of copper (Cu), iron (Fe), manganese (Mn), niobium (Nb) and zinc (Zn) or mixtures thereof, b) CS (Catalyst Support) represents oxides of aluminum (Al), silicon (Si), and titanium (Ti) or mixtures thereof, c) ST (Support Stabilizer) represents oxides of metals selected from the group of cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), lanthanum (La), neodymium (Nd), praseodymium (Pr), samarium (Sm), terbium (Tb), ytterbium (Yb), yttrium (Y) Tungsten (W) and zirconium (Zr) or mixtures thereof, d) MS (Mechanical Stabilizer) represents porous spheres selected from the group of alumina, silica, titania, zirconia, kaolin, meta-kaolin, bentonite, attapulgite, or mixtures thereof; and characterizable by a Activity Parameter >1500, Selectivity Parameter <0.5 and a stability parameter <0.005 using a test where the mixed metal oxide catalyst is loaded in a fixed-bed reactor such that the 50>dT/dP>10 (diameter of tube to diameter of catalyst particles) and 200>L/dP>50 (length of catalyst bed to diameter of catalyst particles) and 2>dP>0.5 mm exposed to a feed stream of propane at a temperature of 625° C., atmospheric pressure and a feed rate of 2 hr.sup.−1 weight hourly space velocity.

8. The catalyst of claim 1 wherein the active species makes up 0.1 to 7.5 wt % of the total weight of the catalyst.

9. The catalyst of claim 1 wherein the catalyst support makes up 50 to 80 wt % of the total weight of the catalyst.

10. The catalyst of claim 1 wherein the catalyst stabilizer makes up 1 to 10 wt % of the total weight of the catalyst.

11. The catalyst composition of claim 1, wherein said catalyst composition has less than 100 ppm by weight of either platinum (Pt) or chromium (Cr).

12. The catalyst composition of claim 1 wherein the BET surface area >30 m.sup.2/g.

13. The mixed metal oxide catalyst of claim 7 wherein the catalyst support comprises a mesoporous bead.

14. The mixed metal oxide catalyst of claim 1 in the form of particles wherein the number average particle size is in the range of 30-3000 micrometers.

15. The mixed metal oxide catalyst of claim 7 wherein the active catalyst species makes up 0.1 to 7.5 wt % of the total weight of the catalyst; wherein the catalyst support makes up 20 to 90 wt % of the total weight of the catalyst; and wherein the catalyst stabilizer makes up 1 to 15 wt % of the total weight of the catalyst.

16. The mixed metal oxide catalyst of claim 1 wherein the active catalyst comprises zinc and the catalyst support comprises titania.

17. The mixed metal oxide catalyst of claim 7 wherein the active catalyst comprises zinc and the catalyst support comprises titania.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates a continuous method for dehydrogenating paraffins in a fluidized bed reactor.

(2) FIG. 2 shows an x-ray diffraction spectrum (XRD) of a ZrO.sub.2 doped TiO.sub.2 support; sample AI in the Examples section.

(3) FIG. 3 shows an XRD of commercial ZnO.TiO.sub.2 sample, AK.

GLOSSARY

(4) Arrhenius Activation Energy (E): The Arrhenius equation gives the quantitative basis of the relationship between the activation energy and the rate at which a reaction proceeds. Arrhenius activation energy term from the Arrhenius equation is as an experimentally determined parameter that indicates the sensitivity of the reaction rate to temperature. From the equation, the activation energy can be found through the relation
k=k.sub.0e.sup.−E/RT

(5) Where k is the rate constant of a reaction at temperature T, k.sub.0 is pre-exponential factor, E is activation energy for the reaction, R the universal gas constant, T the reaction temperature (in Kelvin). k is calculated from conversion (x) and residence time (τ) as follows
k=−ln(1−x)/τ

(6) Activity Parameter—The catalyst activity is quantified by the activity parameter which is the pre-exponential factor in the Arrhenius equation k.sub.0 for the dehydrogenation reaction, an empirical relationship between temperature and rate coefficient using a value of 81.7 kJ/mole for E the Activation Energy for the dehydrogenation reaction using for Titania based catalyst.

(7) Selectivity Parameter—Since selectivity of propylene varies with propane conversion, a method is required to compare selectivity obtained by different catalysts under various conversions. Selectivity parameter is calculated from the ratio of the rate constant of the propylene cracking reaction (k.sub.c) measured in the absence of any diluent such as nitrogen, steam, helium or hydrogen to the rate constant of the propane dehydrogenation reaction (k.sub.d) and remains constant irrespective of the propane conversion. A catalyst producing propylene with a high selectivity will have a selectivity parameter <0.2.

(8) The selectivity parameter (=k.sub.C/k.sub.D) is calculated from propane conversion (x) and propylene yield (y) by solving the equations shown below:
k.sub.D=−ln(1−x)/τ
y=[k.sub.D/(k.sub.C−k.sub.D)][e.sup.(−kDτ)−e.sup.(kCτ)]

(9) Stability Parameter—The loss of catalyst activity with time is quantified by the stability parameter which measures the rate of change of catalyst activity with time. A catalyst with high stability will have a low stability parameter value <0.005.
Stability Parameter=|(k.sub.Dt−k.sub.D0)|/(k.sub.D0*t)

(10) Where k.sub.Dt is the rate constant of dehydrogenation of propane at time=t, k.sub.D0 is the rate constant of dehydrogenation of propane at time=0 and t is the time on stream

(11) For instance, at a reaction temperature of T=625° C. (898 K) and residence time τ=1 second, for a propane conversion of x=46% and propylene yield of y=42% Activity Parameter=35,028 Selectivity Parameter=0.23

(12) Characterization of the catalyst is conducted in the absence of a diluent gas such as nitrogen, hydrogen, steam or helium.

(13) Attrition Index: The attrition resistance of catalysts used in fluidized reactor systems are characterized by the Attrition Index determined by ASTM tests such as AJI—Air Jet Index which is the percent attrition loss at 5 hours (ASTM D5757—Standard Test Method for Determination of Attrition of FCC Catalysts by Air Jets).

(14) Calcination Temperature—The term “calcination temperature” refers to the maximum temperature utilized as an intermediate step in the catalyst synthesis procedure intended to convert the metal salts to their oxide form.

(15) Conversion—The term “conversion of a reactant” refers to the reactant mole or mass change between a material flowing into a reactor and a material flowing out of the reactor divided by the moles or mass of reactant in the material flowing into the reactor. For propane dehydrogenation, selectivity is the mass of propane reacted divided by the mass of propane fed.

(16) “Particle size” is number average particle size, and, for non-spherical particles, is based on the largest dimension.

(17) Pore size—Pore size relates to the size of a molecule or atom that can penetrate into the pores of a material. As used herein, the term “pore size” for zeolites and similar catalyst compositions refers to the Norman radii adjusted pore size well known to those skilled in the art. Determination of Norman radii adjusted pore size is described, for example, in Cook, M.; Conner, W. C., “How big are the pores of zeolites?” Proceedings of the International Zeolite Conference, 12th, Baltimore, Jul. 5-10, 1998; (1999), 1, pp 409-414.

(18) One of ordinary skill in the art will understand how to determine the pore size (e.g., minimum pore size, average of minimum pore sizes) in a catalyst. For example, x-ray diffraction (XRD) can be used to determine atomic coordinates. XRD techniques for the determination of pore size are described, for example, in Pecharsky, V. K. et at, “Fundamentals of Powder Diffraction and Structural Characterization of Materials,” Springer Science+Business Media, Inc., New York, 2005. Other techniques that may be useful in determining pore sizes (e.g., zeolite pore sizes) include, for example, helium pycnometry or low-pressure argon adsorption techniques. These and other techniques are described in Magee, J. S. et at, “Fluid Catalytic Cracking: Science and Technology,” Elsevier Publishing Company, Jul. 1, 1993, pp. 185-195. Pore sizes of mesoporous catalysts may be determined using, for example, nitrogen adsorption techniques, as described in Gregg, S. J. at al, “Adsorption, Surface Area and Porosity,” 2nd Ed., Academic Press Inc., New York, 1982 and Rouquerol, F. et al, “Adsorption by powders and porous materials. Principles, Methodology and Applications,” Academic Press Inc., New York, 1998.

(19) Regeneration Temperature—The catalyst may be regenerated under flowing air gas at elevated temperatures in order to remove heavier hydrocarbons (coke) from the active catalyst structure. The maximum temperature used in this step is referred to as the “regeneration temperature.”

(20) Residence Time (τ)—Residence time is the time a substance is in the reaction vessel. It can be defined as the volume of the catalyst bed divided by the flow rate (by volume per second) of gases into the reactor. τ=volume of Catalyst bed (m.sup.3)/volumetric flow of reactants (m.sup.3/s).

(21) Selectivity—The term “selectivity” refers to the amount of production of a particular product (or products) as a percent of all products resulting from a reaction. For example, if 100 grams of products are produced in a reaction and 80 grams of olefins are found in these products, the selectivity to olefins amongst all products is 80/100=80%. Selectivity can be calculated on a mass basis, as in the aforementioned example, or it can be calculated on a molar basis, where the selectivity is calculated by dividing the moles a particular product by the moles of all products. Unless specified otherwise, selectivity is on a mass basis. For propane dehydrogenation, selectivity is the mass of propylene produced divided by the mass of all products.

(22) Yield—The term “yield” is used herein to refer to the amount of a product flowing out of a reactor divided by the amount of reactant flowing into the reactor, usually expressed as a percentage or fraction. Mass yield is the mass of a particular product divided by the weight of feed used to prepare that product. When unspecified, “%” refers to mass % which is synonymous with weight %. Ideal gas behavior is assumed so that mole % is the same as volume % in the gas phase. For propane dehydrogenation, mass yield is the mass of propylene produced divided by the mass of propane fed. Mass yield of the inventive processes are preferably at least 50% in a single pass, preferably at least 70%.

(23) As is standard patent terminology, the term “comprising” means “including” and does not exclude additional components. Any of the inventive aspects described in conjunction with the term “comprising” also include narrower embodiments in which the term “comprising” is replaced by the narrower terms “consisting essentially of” or “consisting of.” As used in this specification, the terms “includes” or “including” should not be read as limiting the invention but, rather, listing exemplary components. As is standard terminology, “systems” include to apparatus and materials (such as reactants and products) and conditions within the apparatus.

DETAILED DESCRIPTION

(24) The catalyst can be used as powder or pellet, or can be disposed on a substrate such as a reactor wall or on beads or other support. For example, the catalyst can be deposited on a silica powder. This is sometimes termed as a catalyst material “grafted” on a support.

(25) The catalyst preferably comprises a stabilized titania support. Preferably, the titanium in the catalyst is chiefly in the form of anatase as determined by XRD. Typically, the catalyst (not including an optional support material) comprises from 10 to 95 wt % titania, preferably 50 to 95, or 70 to 95, or 80 to 93 wt % titania (calculated assuming all Ti is present as TiO2).

(26) The titania is stabilized with a stabilizing element comprising zirconium, tungsten, or a rare earth element or combinations thereof. The rare earth element, if present, preferably includes Ce and/or Y. The stabilizing element(s) are preferably present in 0.1 to 25 wt % (based on the weight of the fully oxidized, oxide form of the stabilizer element, or 0.1 to 20 wt %, or 0.5 to 20, or 1.0 to 20, or 0.5 to 15, or 0.5 to 10, or 1.0 to 15, or 2.0 to 15, or 2.0 to 10, or 4.0 to 8.0 wt % (based on the elements weight).

(27) The catalyst preferably contains zinc, preferably in the range of 0.1 to 10%, more preferably 1 to 10, or 2 to 8, or 3 to 7 wt %.

(28) Preferably, the catalyst comprises a BET surface area of at least 1, or at least 5, or at least 20, or in the range of 1 to 50, or 1 to 35 m.sup.2/g.

(29) The invention includes methods of making the catalyst, methods of dehydrogenating a paraffin having 2-8 carbon atoms (preferably propane or isobutane). The invention also includes reaction systems comprising a reactor comprising any of the catalysts described herein, a product stream comprising a paraffin having 2-8 carbon atoms (preferably propane or isobutane) passing through the reactor and in contact with the catalyst, preferably at the temperature and rate conditions described herein.

(30) In a preferred method, the catalyst is employed in the dehydrogenation of a paraffin having 2-8 carbon atoms (preferably propane or isobutane). For example, in some embodiments, the catalyst is exposed to a stream comprising at least 50 mol % propane. In some embodiments, the method is conducted with a product stream of paraffins at a space velocity of 0.1 to 10 hr.sup.−1, or 0.5 to 5, or 0.5 to 2 hr.sup.−1., and preferably at a temperature of 500 to 700 C. In some embodiments, the method is conducted for a continuous period of at least 1 second or from 1 second to 120 seconds without regeneration and with a stability such that the rate of dehydrogenation decreases by no more than 10% or no more than 5% or no more than 2% over the continuous period.

(31) Surprisingly, we have discovered that a catalyst containing titania and zinc, and stabilized by Zr, W, and/or rare earth metals exhibits a surprisingly superior combination of activity, selectivity, and stability results under conditions of propane dehydrogenation.

(32) The invention is further elucidated in the examples below. In some preferred embodiments, the invention may be further characterized by any selected descriptions from the examples, for example, within ±20% (or within ±10%) of any of the values in any of the examples, tables or figures; however, the scope of the present invention, in its broader aspects, is not intended to be limited by these examples.

Example 1

(33) The starting material was titanium (IV) oxide obtained from BASF. An appropriate amount of Zinc Nitrate Hexahydrate salt was dissolved in deionized water at room temperature to make a 10 wt % Zinc Nitrate solution. This solution was then added dropwise to the titanium (IV) oxide support. The wet catalyst was then left to dry at room temperature overnight. The catalyst was then calcined in a muffle furnace at 600° C. for 4 hours. The final catalyst had 3 wt % Zinc by weight. This catalyst is designated as Catalyst A.

Example 2

(34) The catalyst was prepared as in Example 1 using silica (SiO.sub.2) obtained from Sigma Aldrich as the catalyst support. This catalyst is designated as Catalyst B.

Example 3

(35) The catalyst was prepared as in Example 1 using ceria (CeO.sub.2) obtained from Sigma Aldrich as the catalyst support. This catalyst is designated as Catalyst C.

Example 4

(36) The catalyst was prepared as in Example 1 using gamma-alumina (.—Al.sub.2O.sub.3) obtained from Alfa Aesar as the catalyst support. This catalyst will be designated as Catalyst D.

Example 5

(37) Propane dehydrogenation experiments were performed using a fixed-bed reactor such that the d.sub.T/d.sub.P>10 (ratio of diameter of reactor tube to diameter of catalyst particles) and L/d.sub.P>50 (ratio of length of catalyst bed to diameter of catalyst particles) to ensure plug-flow behavior. The catalyst of interest was first loaded into a quartz glass lined reactor. The catalyst was activated in dry air at atmospheric pressure at a temperature of 600° C. for 4 hours. Following activation, the reactor was allowed to heat up to reaction temperature of 625° C., then purged with dry nitrogen for 0.5 hours. Propane was fed to the reactor at a WHSV equal to 1 hr.sup.−1. The flow rate was controlled by a Brooks mass flow controller. Product samples taken 5 minutes after the start of reaction were analyzed on GCs having Petrocol DH and Plot Q columns. The catalyst was regenerated at 625° C. by first purging the reactor with nitrogen and then passing air over the catalyst. The results are shown in Table 1.

(38) TABLE-US-00001 TABLE 1 Catalyst # Support Activity Parameter Selectivity Parameter A TiO.sub.2 1850 0.245 B SiO.sub.2 272 2.346 C CeO.sub.2 467 2.331 D γ-Al.sub.2O.sub.3 2694 1.244

(39) Results show that TiO.sub.2 as the best support for propane dehydrogenation. However, none of these supports showed adequate catalyst stability required for commercial application.

Example 6

(40) The starting material was titanium (IV) oxide obtained from Alfa-Aesar. An appropriate amount of Zinc Nitrate Hexahydrate salt was dissolved in deionized water at room temperature to make a 3 wt % Zinc Nitrate solution. This solution was then added dropwise to the titanium (IV) oxide support. The wet catalyst was then left to dry at room temperature overnight. The catalyst was then calcined in a muffle furnace at 600° C. for 4 hours. The final catalyst had 1 wt % Zinc by weight. This catalyst is designated as Catalyst E.

Example 7

(41) The starting material was titanium (IV) oxide obtained from Alfa-Aesar. An appropriate amount of Zinc Nitrate Hexahydrate salt was dissolved in deionized water at room temperature to make a 6 wt % Zinc Nitrate solution. This solution was then added dropwise to the titanium (IV) oxide support. The wet catalyst was then left to dry at room temperature overnight. The catalyst was then calcined in a muffle furnace at 600° C. for 4 hours. The final catalyst had 2 wt % Zinc by weight.

(42) This catalyst is designated as Catalyst F.

Example 8

(43) The starting material was titanium (IV) oxide obtained from Alfa-Aesar. An appropriate amount of Zinc Nitrate Hexahydrate salt was dissolved in deionized water at room temperature to make a 9 wt % Zinc Nitrate solution. This solution was then added dropwise to the titanium (IV) oxide support. The wet catalyst was then left to dry at room temperature overnight. The catalyst was then calcined in a muffle furnace at 600° C. for 4 hours. The final catalyst had 3 wt % Zinc by weight.

(44) This catalyst is designated as Catalyst G.

Example 9

(45) The starting material was titanium (IV) oxide obtained from Alfa-Aesar. An appropriate amount of Zinc Nitrate Hexahydrate salt was dissolved in deionized water at room temperature to make a 12 wt % Zinc Nitrate solution. This solution was then added dropwise to the titanium (IV) oxide support. The wet catalyst was then left to dry at room temperature overnight. The catalyst was then calcined in a muffle furnace at 600° C. for 4 hours. The final catalyst had 4 wt % Zinc by weight.

(46) This catalyst is designated as Catalyst H.

Example 10

(47) Catalysts E, F, G and H were tested for propane dehydrogenation activity as described in Example 5. The results are shown in Table 2.

(48) TABLE-US-00002 TABLE 2 Zinc Catalyst # Loading Activity Parameter Selectivity Parameter E 1 wt % 2615 0.912 F 2 wt % 1912 0.216 G 3 wt % 3017 0.194 H 4 wt % 5391 2.827

(49) Results shown in Table 2 clearly show that catalyst G with 3 wt % Zn loading has desired characteristics of adequate activity and selectivity.

Example 11

(50) The catalyst was prepared as in Example 6 with the only difference being the doping of the support with 10 wt % Cerium prior to addition of zinc nitrate. Titanium oxide support was doped with 10% Cerium as follows: A 10 wt % cerium nitrate hexahydrate aqueous solution was first added dropwise to the titanium oxide support. The wet catalyst was then left to dry at room temperature overnight and then calcined to 600° C. for 4 hours. The addition of Zinc to the resulting support was then followed as in example 1.

(51) This catalyst is designated as Catalyst I.

Example 12

(52) The catalyst was prepared as in Example 11 with the only difference being the titanium oxide support was doped with 10 wt % Lanthanum.

(53) This catalyst will be designated as Catalyst J.

Example 13

(54) The catalyst was prepared as in Example 11 with the only difference being the titanium oxide support was doped with 10 wt % Yttrium.

(55) This catalyst will be designated as Catalyst K.

Example 14

(56) Catalysts I, J and K were tested for propane dehydrogenation activity as described in Example 5. The results are shown in Table 3.

(57) TABLE-US-00003 TABLE 3 Catalyst # Rare Earth Activity Parameter Stability Parameter G None 2939 18.5E−03 I CeO.sub.2 2752  1.9E−03 J La.sub.2O.sub.3 2443  7.5E−03 K Y.sub.2O.sub.3 2329  3.3E−03

(58) Results shown in Table 3 show the benefit of adding a Rare Earth Oxide to TiO.sub.2 for stabilizing catalyst activity.

Example 15

(59) A composite support comprising of Titania, Zirconia and Silica with a TiO.sub.2:ZrO.sub.2:SiO.sub.2 ratio of 18:1:1 by weight was synthesized using a sol-gel hydrolysis technique. The appropriate amounts of Titanium (IV) Iso-propoxide, Zirconium (IV) propoxide and Tetra ethyl orthosilicate were mixed in 2-Propanol. The mixture was kept stirred using a magnetic bar at room temperature. Warm 0.1 M NH.sub.4NO.sub.3 aqueous solution was then added to the alkoxide mixture for hydrolysis. The resulting hydrolyzed sol-gel was allowed to stand at room temperature overnight. The sol-gel was dried and calcined at 450° C. for 4 hours. 3% Zinc was added to support as described in Example 1. This catalyst will be designated as Catalyst L.

Example 16

(60) The appropriate amount of Titanium Isopropoxide, Zirconia and Silica with a TiO.sub.2:ZrO.sub.2:SiO.sub.2 ratio of 18:1:1 by weight were mixed in 2-Propanol. Silica gel (150 Angstrom pore size) was slowly poured into the solution. The slurry mixture was stirred for 24 hours at room temperature. At the end of 24 hours, the mixture was heated at 70° C. for 1 hour. After 1 hour of heating, the excess solvent was decanted and residual solvent was driven off under the vacuum. The grafted support was hydrolyzed at 40° C. overnight. The hydrolyzed support was calcined to a temperature of 550° C. for 4 hours. The final loading of TiO.sub.2 on the silica support was 10 wt %. 3 wt % Zinc as an active metal was added to grafted support employing a wet impregnation technique as described in Example 1. This catalyst will be designated as Catalyst M.

Example 17

(61) Catalysts L and M. were tested for propane dehydrogenation activity as described in Example 5. The results are shown in Table 4.

(62) TABLE-US-00004 TABLE 4 Catalyst # Activity Parameter Selectivity Parameter L 3017 0.194 M 2926 0.204

(63) As evident from table 4, the performance of the hydrolyzed catalyst and the grafted catalyst are essentially the same despite the fact that the grafted catalyst contains >88% of inert material.

Example 18

(64) 24 gm of Titanium Tetrachloride and 1.7 gm of Zirconium Tetrachloride were dissolved in 500 ml of deionized chilled (5° C.) water. The solution was heated to 55° C. while stirring. When the desired temperature was reached, 2 molar aqueous solution of ammonium hydroxide was added to solution till it reached a pH of 7.3. The precipitate was filtered and dried overnight and then calcined to a temperature of 700° C. for 4 hours to produce the stabilized catalyst support. 0.34 gm of Zinc Nitrate Hexahydrate was dissolved in 2.5 grams of deionized water at room temperature. The solution was then added to 11 grams of the stabilized catalyst support dropwise. The wet catalyst was dried and calcined at 700° C. for 4 hours to give a Zn loading of 3 wt %.

(65) This catalyst is designated as Catalyst N.

Example 19

(66) 2.6 gm of Zinc Nitrate Hexahydrate, 24 gm of Titanium Tetrachloride and 1.7 gm of Zirconium Tetrachloride inorganic salts were dissolved in 500 ml of deionized chilled (5° C.) water. The solution was heated to 55° C. while stirring. When the desired temperature was reached, 2 M aqueous solution of ammonium hydroxide was added to the inorganic salts solution dropwise until the solution reached a pH of 7.3. The precipitate was filtered and dried overnight and then calcined to a temperature of 700° C. for 4 hours to produce the mixed-metal oxide catalyst This catalyst is designated as Catalyst O.

Example 20

(67) The catalyst was prepared as in Example 19 with the only difference being the amount of Zinc Nitrate Hexahydrate added was 1.3 gm.

(68) This catalyst is designated as Catalyst P.

Example 21

(69) The catalyst was prepared as in Example 19 with the only difference being the amount of Zinc Nitrate Hexahydrate added was 4.0 gm.

(70) This catalyst is designated as Catalyst Q.

Example 22

(71) The catalyst was prepared as in Example 19 with the only difference being the amount of Zinc Nitrate Hexahydrate added was 5.5 gm.

(72) This catalyst is designated as Catalyst R.

Example 23

(73) The catalyst was prepared as in Example 19 with the only difference being the amount of Zinc Nitrate Hexahydrate added was 8.8 gm.

(74) This catalyst is designated as Catalyst S.

(75) Catalysts J to N were tested for propane dehydrogenation following Example 5 with the only difference being the propane WHSV was 2/hr. The results are shown in the Table 5.

(76) TABLE-US-00005 TABLE 5 Zinc Loading Activity Selectivity Stability Catalyst (wt %) Parameter Parameter Parameter O   5% 28864.2  0.19 0 P 2.5% 27930.21 0.41 Not measured Q 7.5% 21791.86 0.49 Not measured R  10% 27011.41 0.44 Not measured S  15% 14768.42 1.05 Not measured

(77) The results show that excessive Zn loading can lead to inferior catalyst performance.

Example 24

(78) 2.6 gm of Zinc Nitrate Hexahydrate, 22 gm of Titanium Oxy-Sulfate and 1.7 gm of Zirconium Tetrachloride inorganic salts were dissolved in 500 ml of deionized water. The salt solution was heated to 55° C. while stirring. When the desired temperature was reached, 2 molar aqueous solution of ammonium hydroxide was added to the inorganic salts solution dropwise till the precipitate reached the pH of 7.3. The precipitate was filtered and dried overnight and then calcined to a temperature of 700° C. for 4 hours to produce the mixed-metal oxide catalyst. This catalyst is designated as Catalyst T.

Example 25

(79) The catalyst was prepared as in Example 24 with the only difference being amount of Zinc Nitrate Hexahydrate added was 1.3 gm. This catalyst is designated as Catalyst U.

Example 26

(80) The catalyst was prepared as in Example 24 with the only difference being amount of Zinc Nitrate Hexahydrate added was 4.0 gm. This catalyst is designated as Catalyst V.

Example 27

(81) The catalyst was prepared as in Example 24 with the only difference being amount of Zinc Nitrate Hexahydrate added was 5.5 gm. This catalyst is designated as Catalyst W.

Example 28

(82) The catalyst was prepared as in Example 24 with the only difference being amount of Zinc Nitrate Hexahydrate added was 8.8 gm. This catalyst is designated as Catalyst X.

Example 29

(83) The catalyst was prepared as in Example 24 with the only difference being the bulk catalyst was washed with dilute NH.sub.4OH solution followed by dilute NH.sub.4NO.sub.3 solution for 30 minutes at room temperature. This catalyst is designated as Catalyst AI. The catalyst was submitted for BET analysis.

(84) Catalysts T, U, W and AI were tested for propane dehydrogenation following Example 5 with the only difference being the propane WHSV was 2/hr. The results are shown in Table 6.

(85) TABLE-US-00006 TABLE 6 Zinc Loading Activity Selectivity Catalyst (wt %) Parameter Parameter T   5% 25217.45 0.5 U 2.5% 19352.41 0.4 W  10% 5329.02 13.71 Al 33 32762.64 0.15

(86) The results indicate that washing the precipitate with ammonium nitrate and ammonium hydroxide solutions significantly improve catalyst performance.

Example 30

(87) 2.4 gm of Zinc Nitrate Hexahydrate and 22 gm of Titanium Oxy-Sulfate inorganic salts were dissolved in 500 ml of deionized water. The salt solution was heated to 55° C. while stirring. When the desired temperature was reached, 2 molar aqueous solution of ammonium hydroxide was added to the inorganic salts solution dropwise till the precipitate reached the pH of 7.3. The precipitate was filtered, washed with 0.1 M NH4OH for 30 minutes at room temperature followed by 0.25 M NH4NO3 wash for 30 minutes at room temperature. The catalyst was dried overnight and then calcined to a temperature of 700° C. for 4 hours to produce the mixed-metal oxide catalyst. This catalyst is designated as Catalyst AJ. The catalyst was submitted for BET analysis

Example 31

(88) Commercially available Zinc Orthotitanate (ZnO.TiO.sub.2) was obtained from Alfa Aesar. The catalyst was activated in situ at 450° C. overnight. The catalyst was tested for propane dehydrogenation reaction following similar operating condition as tested for other in-home synthesized catalysts. This catalyst is designated as Catalyst AK. The catalyst was submitted for BET analysis.

Example 32

(89) The starting material was Tungsten (5 wt % WO.sub.3) stabilized titanium (IV) oxide obtained from Cristal. An appropriate amount of Zinc Nitrate Hexahydrate salt was dissolved in deionized water at room temperature to make a 10 wt % Zinc Nitrate solution. This solution was then added dropwise to the titanium (IV) oxide support. The wet catalyst was then left to dry at room temperature overnight. The catalyst was then calcined in a muffle furnace at 700° C. for 4 hours. The final catalyst had 3 wt % Zinc by weight. This catalyst is designated as Catalyst AL.

(90) Catalysts AJ to AL were tested for propane dehydrogenation following Example 5 with the only difference being the propane WHSV was 2/hr. The results are shown in the table 7. below:

(91) TABLE-US-00007 TABLE 7 BET surface Activity Selectivity Catalyst area (m.sup.2/gm) Parameter parameter AJ 8 14768.42 0.68 AK <1 1721.1 28.52 AL 87.2 35028 0.25

(92) The data shows that the surface areas of TiO.sub.2 supports drop significantly when raised to temperatures in excess of 600° C. without the presence of stabilizers such as WO.sub.3 or ZrO.sub.2.

Example 33

(93) Sample AI was submitted for XRD analysis to determine the crystalline phases present. Results are shown in FIG. 2. Based on comparison with TiO.sub.2 samples, the results show the presence of anatase phase as the major component in sample AI.

Example 34

(94) Sample AI was submitted for XRD analysis to determine the crystalline phases present. Results are shown in FIG. 3. Based on XRD comparison with Zinc-Titanate samples, the results show the presence of ZnO—TiO.sub.2 as the major component in sample AK.

(95) The XRD data show the presence of anatase phase for the ZrO2 doped TiO2 support while the commercial ZnO.TiO2 shows clearly the presence of Zinc Titanate Phase.