WO2000043336A1 - Oxidative dehydrogenation process and catalyst - Google Patents

Abstract

This invention pertains to a catalyst containing a monolith impregnated with a Cr containing compound. In addition, the invention pertains to the production of olefins by the reacting hydrocarbons and an oxygen containing gas in the presence of a catalyst containing a chromium compound, a copper containing compound, a manganese containing compound and a combination thereof supported on a monolith.

Description

OXIDATIVE DEHYDROGENATION PROCESS AND CATALYST

CROSS REFERENCE TO RELATED APPLICATIONS

This application is claims benefit to provisional application 60/117,095 filed January 25, 1999, which is incorporated by reference in its entirety for all useful purposes.

FIELD OF THE INVENTION

10 This invention pertains to the production of olefins by the oxidative dθhydrogenation or cracking of saturated hydrocarbons over a catalyst containing chromium and/or chromium oxide. High yields of olefins can be obtained over structured catalysts with very short contact times and no catalyst deactivation.

BACKGROUND OF INVENTION

Currently, olefins are used as important chemical intermediates for a large number of industrial processes and consumer products. These light olefins such as ethylen^β, propylene, and butenes are usually produced by the steam pyrolysis process [Pyrolysis: Theory and Industrial Practice; Albright, L. F, et al, Eds.; Academic Press: New York, 1983]. The two major limitations of the current steam pyrolysis process are the high gas temperatures (Θ00-900°C) required and the deposition of coke on the walls of the reactor tube that require the periodic shut-down of the process for decoking. To overcome these limitations, there has been much recent interest in trying to find a catalytic alternative to the current industrial steam cracking process.

_;> Many researchers have investigated the catalytic dβhydrogenation of light alkanes as a route to obtaining alkenes for polymerization and other organic synthesis. This approach does not cofββd an oxidant. Much of this research has focused on E.. J. Catai. 1993, 142, 166-171 ; Hoang, M.; Hughes, A. E. et al, J. Catal. 1997, 171, 313-319; Hoang, M. et al, React. Kinet. Catal. Lett. 1997, 61, 21-26; Zaki, M. I. et al, Appl, Catal. 1986, 21, 359-377], Thus, the catalytic properties of supported chromium catalysts are strongly affected by the acidity/basicity of the oxide support. However, there is significant disagreement over the exact oxidation state of the active Cr surface species. Recent research has also examined the use of supported chromium oxide catalysts for the catalytic dehydrogenation of hydrocarbons [De Rossi, S. et al, Appl. Catal. A: General 1992, 81, 113-132; De Rossi, S. et al, Appl. Catai A: General 1993, 106, 125-141; De Rossi, S. et al, J. Catal, 1994, 148, 36-46; Lugo, H. J. and Lunsford, J. H., J. Catal. 1985, 91, 155-166; Udomsak, S. and Anthony, R. G., Ind. Eng. Chem Res. 1996, 35, 47-53].

SUMMARY OF THE INVENTION

This invention describes the production of olefins by catalytic partial oxidation of saturated hydrocarbons on chromium oxide supported on monoliths at very short contact times. This catalyst and process can be significantly less expensive to operate than either a standard packed bed reactor using a selective oxide catalyst at a residence time in excess of 0.1 seconds or the newer short contact time oxidative dehydrogenation process using monolith ically supported noble metals. Additionally, this catalyst produces less by-product GO which is advantageous to downstream processes. The monoliths may be composed of any oxide stable at temperature in excess of 900^OC including α-A|₂03, SiC , Mg-stabilized Zrθ2, and Y-stabilized Zrθ2 and may have a honeycomb or foam structure although the foam structure is preferred.

The support affects the activity of the chromium oxide catalyst as does the presence of various promoters, including Cu, Mn, Mg, Ni, Fe, their oxides, and combinations thereof. The preferred promoters are copper and copper oxides. The preferred metal atom ratio of promoter to chromium is between 1 :100 and 1 :2 and more preferably between 1 :15 and 1 :5.

To summarize these results, supported chromium oxide has been shown to be an effective catalyst for the oxidative dehydrogenation of ethane. As reported in the literature, the activity of the supported chromium oxide catalyst has been shown to depend upon the ceramic support material [Hoang, M. et al, J. Catal. 1997, 171,

313-319], the surface area, and the chromium oxide loading (with a lower loading showing a lower activity and shorter lifetime). The high loading chromium oxide catalyst supported on ZrO≥ monolith showed the best overall activity of all the supported chromium oxide catalysts, but could not achieve stable operation at flow rates higher than 5 SLPM. The 9 wt. % Cr2θ3/Zrθ2 catalyst outperformed the Pt-coated monolith with a higher C2H4 selectivity and C2Hg conversion, and thus higher C2H4 yield. It was also found that the addition of copper to the chromium oxide on Zrθ2 catalyst significantly increased the activity of the catalyst such that stable operation with no signs of deactivation was with GHSV (STP) up to 1 x 1 θβ hr^"1. The addition of copper to the Cr2θ3/Zrθ2 catalyst, however, did not significantly affect the product selectivity or reactant conversions.

DETAILED DESCRIPTION OF INVENTION

Any short contact time reactor can be used. The reactor used here is essentially identical to that previously described for the production of syngas [Hickman, D. A. and Schmidt, L. D., J. Catal. 1992, 136, 300-308 and references therein] and oxidative dehydrogenation of light alkanes [ Flick, D. W. and Huff, M. C, J. Catal. 1996, 178, 315-327 and references therein; Huff, M. and Schmidt, L. D., J. Phys. Chem. 1993, 97, 1 1815-11822 and references therein]. The reactor consists of a quartz tube with an inner diameter of 20 mm. The catalyst is sealed in the tube with high temperature silica-alumina felt which prevents the bypass of gases around the catalyst. To reduce the radiation heat loss in the axial and radial directions and to better approximate adiabatic operation, inert foam monoliths are placed in front and behind the catalyst as heat shields, and the reaction zone is externally insulated.

A ceramic foam monolith with 20-100 pores per linear inch (ppi) is impregnated with a Cr containing precursor such as an aqueous solution of Cr(N03)3, and then calcined in air at 600°C for at least four hours. After calcination, the chromium oxide coated monoliths were bright green in color. The chromium oxide can be supported on monoliths made from high temperature (>900°C) stable oxides including α-Al2θ3, Si0_2l Mg-stabilized Z1O2, and Y-stabiiized Zrθ2- Pt and mixtures of promoters (Cu, Mn, Mg, Ni, Fe, and combinations thereof) were deposited on the monoliths similarly using H₂PtCle or transition metal nitrate salts, respectively, in an aqueous solution. The monoliths used measured 10 mm thick and between 18-20 mm in diameter.

The gas flow for the reactor is controlled by electronic mass flow controllers. The total feed flow rate to the reactor ranged from 0.1 to 12 SLPM which corresponds to approximate contact times of 2-200 milliseconds (GHSV = 1 x 10⁵ - 2.2 x 10⁶ hr^"1 at STP) for the monolith catalyst. The reactor operates near atmospheric pressure. The reaction occurs autothermalty around 900°C.

While the reaction operates autothermalty at steady state, an external heat source is necessary to ignite the reaction. The gas mixture wfth C₂Hg:θ2:N ■

25:15:60) ignites at approximately 350°C over the chromium oxide catalyst at a flow rate of 3 SLPM which is higher than the 220°C preheat needed to ignite that reaction over a Pt coated monolith catalyst. After ignition, the external heat source is removed or reduced to the desired level of heat addition, the composition is adjusted to the desired value and steady state is established, After each change in feed conditions, the reactor is allowed to achieve steady state (<10 min.) before analysis of the reaction products by the GC. The feed gas consists of C H6 and O2 with N2 as the diluent. The level of dilution ranged from <1 to about 80%. The N2 was used as an internal GC calibration standard. Additional trials have been completed using alternative diluents: N2. He, Ar,

CO2, H2O and mixtures thereof. Some experiments were conducted with the feed composition within the flammability limits. In these instances, it is important to realize that this is a flow system with linear velocities in excess of the flame speed such that homogeneous ignition is impossible [Bolk, J. W. et al, Chem. Eng. Sci. 1996, 51].

The reaction temperature was measured by a type K (chromel/alumel) thermocouple inserted from the rear of the reactor and placed at the center of the reactor tube between the catalyst and the rear radiation heat shield. The temperature measured at the back of the catalyst, the reaction temperature, is a good measure of both the product gas phase temperature and the surface temperature of the rear face of the catalyst, since the gas phase and surface temperatures are approaching equilibrium at the catalyst exit.

In some experiments, the feed gas TO the reactor contained C2H6, O , and H with a small amount of N2 for use as an internal calibration standard. The level of H in the feed ranged from 0 to 50% which corresponds to H O2 ratios ranging from 0 to

3.0. The amount of N2 in the feed was always less than 1%. The process could recycle the H2 and not require a net import of H2 to the system.

The catalyst can contain substantially no Pt. Substantially no Pt means less than 0.1 % Pt by weight, preferably less than 0.01 % Pt by weight. Table 7 : Carbon atom and hydrogen atom selectivity, Table 8: Carbon atom and hydrogen atom selectivity, conversion, and temperature for ethane oxidation over conversion, and temperature for ethane oxidation over a 45 ppi, 4 t. % CrjOj/ ZrQj monolith as a function a 45 ppi, 6.7% Cu - 6.7% CΓIOJ/ZΓO. monolith as a of flow rate at a C₂H«tθ2 ratio of 1.5 with 20% N₂ function of flow rate at a CzIfyO. ratio of 2.4 with dilution in an autothermal reactor at a pressure of 1.2 20% Nj dilunon in an autothermal reactor at a pressure arm. of 1.2 aim.

could not be sustained for even a few minutes. Thus, for the Cr₂θ₃ AI₂θ₃ catalyst, the reaction can only be sustained inside the flammability range for the C₂H₆, 0₂, and N₂ system, and the lifetime decreases the closer the mixture is to the upper flammability boundary. However, in stark contrast to the Cr₂0;_/Al₂θ₃ catalyst, the 9 wt. % Cr₂θ3 Zrθ2 monolith sustained steady reaction up to a C₂Hβ 0₂ ratio of 1.8 with 50% N₂ dilution for over 2 hours and at a C₂H₆/O₂ ratio of 1.5 with 50% N₂ dilution at 2 SLPM, the Cu modified CraOyZrOs monolith catalyst did not show any deactivation for over 7 hours of continuous operation, while all of the previous chromium oxide containing catalyst rapidly extinguished at a C₂H60₂ ratio of 1.5 with 50% N₂ dilution.

The effects of preheat are shown in Tables 9-10 for the 9 wt. % Cr₂θ₃ α-AI₂0₃ monolith catalyst at a C₂rV0₂ ratio of 1.5 with 20% N₂ dilution at a flowrate of 2 SLPM. Results are shown as a function of time for nearly adiabatic operation (Table 9) and for autothermal operation (Table 10) where the reactants have been heated to 250°C before reaching the reaction zone. Preheat results in a catalyst lifetime of -7 hours before the reaction extinguished. The addition of preheat, however, leads to a slightly lower selectivity to C₂H₄ and a higher selectivity to CO. Preheating the feed also increased the selectivity to CH₄ and C2H2 and decreased the selectivity to C0₂. As expected, the C₂H₆ conversion increases with preheat.

The most interesting impact of preheat is shown in the temperature of the catalysis. The front and back temperature of the catalyst without preheat and the front temperature of the catalyst with preheat fall dramatically after approximately 1.5 hours of operation. However, the addition of preheat seems to provide enough energy to keep the reaction ignited with relatively stable front and back temperatures over the catalyst for several hours after the catalyst without preheat extinguished. The 250°C preheat of the feed, however, did not provide enough energy to keep the reaction from eventually extinguishing. There were also slight selectivity changes to C2H4, CH₄, and CO that correspond with the rapid drop in the temperature at the front of the catalyst.

Table 9: Carbon atom and hydrogen atom selecuviiy, conversion, and temperature for ethane oxidation over a 45 ppi, 9 wt. % CrjCty ct-Al₂0₃ monolith as a function of time at a -tyQ. ratio of 1.5 with 20% N₂ dilution m an autothermal reactor at a pressure of 1.2 ami. Data is shown for reactants entering the reactor

Table 10: Carbon atom and hydrogen atom selecϋvity. conversion, and temperature for ethane oxidation over a 45 ppi, 9 wt. % CΓ_ICH/ C.ΑI₂O₅ monolith as a function of time at a C₂-tyQ₂ ratio of 1.5 with 20% Nj dilution in an autothermal reactor at a pressure of 1.2 atm. Data is shown for reactants entering the reaαor at 250°C temperature. The reaction extinguished between hours 7 and 8.

Time on stream (hr) 0.0 0.5 1.0 1.5 2.0 4.0 6.0 7.0

Carbon atom selectivity (%)

CjH 36.3 36.6 36.5 39.1 40.5 40.4 41.1 37.0

CO 33.2 34.0 34.6 30.0 29.9 30.7 29.5 37.2

C 5.0 4,7 4.3 3.5 3.3 3.3 2.9 3.5

CH4 13.2 13.0 13.0 14.0 14.4 14.3 14.4 12.8

C:H₂ 9, 1 8.4 7.8 7.9 7.7 7.3 6.6 5.8

Other 3.2 3.3 3.8 5.5 4.2 4.0 5.5 3.7

Hydrogen atom selectivity (%)

H₂ 46.8 47.2 47.6 42.9 42.8 42,9 40.7 50.8

H,0 14.6 14.4 14.1 14.1 14.4 L4.5 15.1 10.8

Conversion (%)

C₂Hβ 98.5 98.3 98.2 98.0 97.9 97.9 97.5 97.8

O, 99.9 99.9 99.9 99.9 99.9 99.9 99.9 99.9

Temperature ( C)

Front 1180 1132 1112 670 640 595 580 565

Rear 1000 962 895 870 840 825 818 760

Example 6: The oxidative dehydrogenation of ethane was investigated with different diluents including N₂, Ar, C0₂ and H₂0. The carbon and hydrogen atom selectivitiβs, conversions and temperatures for the oxidative dehydrogenation over a 1.0 wt. % Cu - 9.0 wt. % Cr₂θ3/Zr0₂ catalyst at C₂rV0₂ ratios of 1.8 and 2.4 at a total flow rate of 2 SLPM with 20% dilution are shown in Tables 11 and 12. The product selectMties are not significantly affected by changes in the type of diluent. The ethane conversion,

Table 11. Carbon and hydrogen atom Table 12. Carbon and hydrogen atom selectivity, conversion, and selectivity, conversion, and temperature for ethane oxidative temperature for ethane oxidative dehydrogenation over a 1.0 wt. % Cu - dehydrogenation over a 1.0 wt. % Cu - 9.0 wt. % Cr₂O₃ ZrO₂ catalyst at a 9.0 wt. % Cr₂O3/ZrO₂ catalyst at a C₂H O₂ ratio of 1.8 with 20% total C₂ItyO2 ratio of 2.4 with 20% total dilution at a total flow rate of 2 SLPM dilution at a total flow rate of 2 SLPM in an autothermal reactor at a pressure in an autothermal reactor at a pressure

however, does change slightly with different diluents. Along with the decrease in ethane conversion, the reaction temperature at the back of the catalyst is also lower with the C0₂ and H₂0 diluent. Therefore, use of diluents with different heat capacities has the effect of lowering the ethane conversion and temperature at the back of the catalyst with increases in the heat capacity of the diluent used. The use of C0₂ and H₂0 which are reaction products in the oxidative dehydrogenation of ethane as the diluent does not significantly affect the product selectivity under these reaction conditions.

Example 7: Table 13 shows typical reactor performance for the oxidative dehydrogenation of propane over a variety of monolithic catalysts at nitrogen dilutions levels of 20% and 50% at total flow rate of 2 SLPM. The less expensive chromium oxide catalyst shows similar selectivity and conversion trends as the Pt catalyst with significantly less production of CO.

Table 13: Carbon atom and hydrogen atom selectivity, conversion, and temperature for propane oxidation over various catalysts at several C₃Hg/Oj ratios with 20% and 50% N₂ dilution and a total flow rate of 2 SLPM in an autothermal reactor at a pressure of 1.2 aim.

Catalyst 6 wt. % Cr₂0,/ZrO_ 6 wt. % Pt/α-Al₂0₃

Ni dilution (%) 2 0 50 20 50

CJΓ OJ 1.2 1.5 1.8 2.0 1.2 1.5 1.8 1.2 1.5 1.8 2.0 1.2 1.5 1.8 2.0

Carbon atom selectivity (%)

C₃H« 1.2 10.3 20.7 26.0 1.1 11.0 22.7 2.8 160 23.5 27.7 1.1 15.1 22.6 26.1 jH* 37.8 45.5 40.7 37.7 34.6 43. L 34.3 37.7 38.7 33.4 32.1 31.3 37.3 29.2 23.8

CO 21.0 9.1 6.3 5.3 23.3 11.0 9.2 26.6 17.0 16.5 13.9 33.6 17.8 18.5 20.7 co₂ 7.5 8.2 9.0 9.9 9.1 10.9 15.5 3.8 4.1 6.1 6.8 5.8 7.9 12.2 15.0

CH, 23.3 19.8 L6.8 15.6 21.7 17.0 13.0 22.6 18.4 15.7 15.1 20.7 16.7 13.4 1 1.2

C.K . 1.1 2.6 2.5 2.3 0.7 2.4 2.1 1.6 2.4 2.1 2.0 0.9 2.2 1.9 1.5

CjH. 5.9 1.5 0.8 0.5 74 2.0 0.5 3.1 0.8 0.1 0.1 4.5 0.5 0.2 0.1

Other 2.1 2.9 3.1 2.8 2.3 2.6 2.7 1.8 2.6 2.6 2.2 2.1 2.6 2.1 1.6

Eivdrogen atom selecti vity (%)

H₂ 20.1 9.5 7.4 6.5 19.4 10.0 7.9 16.4 8.2 6.9 5.6 19.9 8.6 8.2 6.8

H,0 13.4 15.9 16.9 17.9 18.9 19.3 26.1 17.5 19.5 24.7 24.6 21.5 23.0 29.5 36.3

Conversion (%)

C₃H, 99.9 923 74.3 60.8 100 91.5 64.0 99.3 83.3 63.8 52.5 j 99.9 83.1 57.1 39.3

O, 100 99.5 99.1 99.1 300 99.7 98.9 99.3 98.2 97.7 97.8 1 9.4 98.4 98.0 97.7

Temperature CO

Front 1066 678 584 529 1027 623 500 980 622 545 505 1 1018 941 921 849

Rear 965 875 829 808 934 852 800 969 909 876 866 1 937 831 825 815 surveying a wide variety of metal oxides for high selectivity and conversion [Carra, S. and Fomi, L, Catal. Rev. 1971 , 5, 159-198; Cimino, A. et al, J. Mol. Catal. 1989, 55, 23-33; US Patent #4535067; US Patent #4804799; US Patent #3965044; US Patent #5354935; US Patent #5254788; US Patent #5378350; US Patent #3719721; US Patent #4032589], However, these catalysts generally deactivate with time on stream due to coke build-up on the catalyst surface [Royo, G. et al, Ind. Eng. Chem. Res. 1994, 33, 2563-2570].

Catalytic oxidative dehydrogenation of hydrocarbons is an alternative to thermal pyrolysis and catalytic dehydrogenation. The oxidative dehydrogenation of C-2-C6 hydrocarbons has been examined over noble metal catalysts supported on ceramic foam monolfths [ Flick, D. W. and Huff, M. C, Appl. Catal. A 1999 187, 13-24; Flick, D.

W. and Huff, . C, Abstracts of Papers of ACS 217:018-CATL, Part 2 March 21, 1999;

Flick, D. W. and Huff, . C, Catai Lett 1997, 47, 91-97; Flick, D. W. and Huff, M. C, J.

Catal. 1998, 178, 315-327; Dietz III, A. G. et ai, J. Catal. 1998, 776, 459-473; Huff, M.

C. et ai, Catal. Today 1994, 21, 113-128; US Patent # 5905180 which are all incorporated by reference in its entirety for all useful purposes]. In general, noble metal catalysts are more expensive than oxide catalysts. The oxidative dehydrogenation of ethane over Pt-coated monolith catalysts at short contact times has been investigated concerning the maximization of C2H4 production [US Patent #5382741 ; US Patent

#5625111; Huff, M. and Schmidt, L. D., J. Phys. Chem. 1993, 97, 11815-11822; US Patent #4844837; US Patent #4940826; US Patent #5105052; US Patent #5593935; Wftt, P. M. and Schmidt, L. D., J. Catal. 1996, 163, 465-475; US Patent # 5905180]. These monolith reactors operate at very short contact times on the order of milliseconds. The yield of C2H4 with these reactors has been shown to be about 50% (C2H4 selectivity ~65% at around 80% conversion). Example 8: Table 14 shows typical reactor performance for the oxidative dehydrogenation of butane over a variety of monolithic catalysts at nitrogen dilution levels of 20% at total flow rate of 2 SLPM. Again, the less expensive chromium oxide catalyst shows similar selectivity and conversion trends with changes in the fuel to oxygen ratio as the Pt catalyst. In general, the chromium oxide catalysts have a higher conversion of the hydrocarbon and selectivity to C2H4 than the Pt catalyst. The chromium oxide catalysts produce less CO especially at the higher fuel to oxygen ratios.

Table 14: Carbon atom and hydrogen atom selectivity, conversion, and temperature for butane oxidation over various catalysts at several H_K O_? ratios with 20% dilution and a total flow rate of 2 SLPM iα an autothermal reactor at a pressure

Example 9: Table 15 shows typical reactor performance for the oxidative dehydrogenation of isobutane over a variety of monolithic catalysts at nitrogen dilution levels of 20% at total flow rate of 2 SLPM. Again, the less expensive chromium oxide catalyst shows similar selectivity and conversion trends with changes in the fuel to oxygen ratio as the R catalyst. In general, the chromium oxide catalysts have a higher conversion of the hydrocarbon and selectivity to C₂H₄ than the Pt catalyst. The chromium oxide catalysts produce less CO especially at the higher fuel to oxygen ratios.

Table 15: Carbon atom and hydrogen atom selectivity, conversion, and temperature for isobutane oxidation over various catalysts at several iC₄H_lc/0₂ ratios with 20% dilution and a total flow rate of 2 SLPM in an autothermal reactor at a pressure of 1.2 at .

In addition to Pt-coated foam monoliths, Yokoyama, et. al. [Yokoyama, C. et al,

Catal Lett 1996. 38, 81-188; US Patent # 5905180] examined the addition of various metal promoters to Pt-coated foam monoliths for the autothermal oxidative dehydrogenation of ethane at millisecond contact times. Their study found that the

5 addition of Sn and Cu to Pt-monoliths enhanced the C2H selectivity and C^Hg conversion with no deactivation or volatilization of the catalyst. For the Pt-Sn catalyst, the ethane conversion increased by up to 6% and the ethylene selectivity increased by up to 5%. For the Pt-Cu catalyst, the conversion and ethylene selectivity were higher than Pt alone, but showed less improvement than the Pt-Sn catalyst.

I D Researchers have also examined oxidative dehydrogenation over oxide catalysts

[US Patent #4658074; US Patent #5430209; US Patent #5439859; US Patent #3862255; US Patent #5759946; US Patent #4026920]. These preocessβs prodice olefins with yields less than 45%.

The activity and selectivity of chromium oxide-supported catalysts in alkane

1 dehydrogenation has been known for many decades [Frβy, F. E. and Huppke, W. F ., Ind. Eng. Chem. 1933, 25, 54; Marciily, C. and Delmon, B., J. Catal. 1972, 24, 336-347]. Due to their importance in hydrogenation, dehydrogenation, and polymerization reactions, chromium-containing heterogeneous catalysts have been studied by a variety of techniques by a large number of researchers in the past several

2 decades. For the supported chromium Phillips polymerization catalyst, much of the research has focused on the structure and oxidation state of the reactive chromium surface species [Zecchina, A. et al, J. Phys. Chem. 1975, 79, 966-972; Weckhuyβen, B. M. et al, Chem. Rev. 1996, 96, 3327-3349]. It is now generally accepted that the catalytic properties of the supported chromium oxide are due to the surface chromium

25 species formed as a result of chromium-support interactions [Kim, O. S. and Wachs, I. Example 10: The copper modified chromium oxide catalyst supported on a zirconia monolith shows excellent stability for the oxidative dehydrogenation of ethane even at high C₂Hβ/0₂ ratios and high flow rates where other catalysts tend to deactivate. Typical reactor performance is shown in Table 16.

Table 16: Carbon atom and hydrogen atom selectivity, conversion, and temperature for ethane oxidation over a 45 ppi, 6.7% Cu - 6.7% CrjOj Zτθ₂ monolith as a function of flow rate at several CJEtyOj ratios with 50% N₂ dilution in an

Example 11: The oxidative dehydrogenation of ethane was investigated where the feed gas to the reactor contained CaH_β, 0₂, and H₂ with a small amount of N₂ for use as an internal calibration standard. The level of H₂ in the feed ranged from 0 to 50% that corresponded to H2 O2 ratios ranging from 0 to 3.0. The amount of N₂ in the feed was always less than 1 %. In the range of conditions studied, no flames were observed. The addition of H₂ (Table 17) during the oxidative dehydrogenation of ethane over a 1.0% Cu - 9.0% Cr_∑O^lZrOz monolith catalyst with less than 1% N₂ dilution at a total feed flow rate of 7 SLPM results in a significant increase in the C₂H₄ selectivity. At a C₂H_β/O₂ ratio of 2.0, the selectivity to C₂H₄ increases from 56% with no H₂ addition to 76% with a Ha 0₂ ratio of 3.0 in the reactor feed. At a C₂Hβ 0₂ ratio of 2.4, the selectivity to C₂H₄ increases from 68% with no H₂ addition to 81% with a H2/O2 ratio of 3.0 in the reactor feed. The increase in the C2H4 selectivity corresponds with a decrease in the selectivity to CO and CO₂. The selectivity to CO and CO* falls proportionally with increasing H_a in the feed. The selectivity to CHU also falls slightly with increasing H₂ addition. The addition of H₂₍ however, also results in a decrease in the C₂H« conversion which falls from 94% to 81% at a C₂rVO₂ ratio of 2.0, and 60% to 66% at a

ratio of 2.4 as the H₂/O₂ feed ratio increases from 0 to 3. Along with the decrease in the C₂H_β conversion, the temperature measured at the exit of the catalyst at both C₂Hβ 0₂

ratios falls with increasing H₂ content in the feed. Thus, the overall production or yield of C₂H₄ in the reaction system is also affected by H₂ addition in the feed since the selectivity to C₂H₄ increases with H₂ addition and the C₂H_e conversion decreases with the addition of H₂. At a C₂Hβ 0₂ ratio of 2.0, the C₂H yield steadily increases with higher H2/O₂ ratios in the feed, but the marginal increase decreases at the higher H₂O₂ ratios. Thus, the selectivity to the desired product, C2H4, increases faster than the decrease in the C₂Hβ conversion with increasing t-fe concentration in the feed. At a C₂H₆/O₂ ratio of 2.4, the yield of C2H4 goes through a maximum at a H₂/O₂ of 1.0. This directly results from the fact that at a H₂/O2 below 1 , the C₂H selectivity rises faster than the corresponding decrease in C₂H₆ conversion. However, at a Hz/Oz ratio of 2 or above, the C2H4 selectivity rises slower than the decrease in the conversion of C₂H$.

Table 1 : Carbon atom and hydrogen atom selectivity, conversion, and temperature for ethane oxidation over various catalysis at several Cir Oj ratios with 20% N₃ dilution and a total flow rate of 2 SLPM in an autothermal reactor at a pressure of 1.2 arm.

EXAMPLES

Example 1 ; The oxidative dehydrogenation of ethane was examined over a variety of catalysts supported on ceramic foam monoliths at a flowrate of 2 standard liters per minute (SLPM) which corresponds to a contact time of approximately 15 ms (GHSV = 200,000 hr^"1). The ceramic foam monolith supports (alpha-alumina or magnesia stabalized zirconia were obtained from Vesuvius Hi-Tech Ceramics and contain 45 ppi (pores per linear inch). Chromium was deposited on the support surface by exposing the ceramic to a liquid solution containing chromium ions such as aqueous chromium nitrate. Platinum was deposited on the support surface by exposing the ceramic to a liquid solution containing platinum ions such as aqueous chloroplatinic acid. Copper was deposited on the support surface by exposing the ceramic to a liquid solution containing copper ions such as aqueous copper nitrate. Between depositions, the catalysts were calcined in air. Table 1 shows product carbon and hydrogen atom selectivity, conversion, and reaction temperature at several C₂H6 O₂ ratios in the feed gas with 20% N₂ dilution for 10 wt. % CraOa α-AlaOa, 9 wt. % Cr₂θ3 Zr0₂, 3 wt. % Pt/α-AfeOa, 6.7 wt. % Cu - 6.7 wt. % Cr/Zr0₂, and Pt (0.05 wt. %) modified 10 wt. % Cr₂θ3 α-AI₂θ3 catalysts. At a C₂Hβ/0₂ ratio of 1.2, the 9 wt. % Cr₂03 AI₂03 and Pt modified 0 wt. % Cr₂θ3/AI₂θ3 catalysts have a C₂H₄ selectivity around 20% compared to the 30% and 32% selectivity to C₂H4. seen for the 3 wt. % Pt/α-AfcOa and 9 wt. % Cr₂0a/ZrO₂ catalysts respectively. The CO selectivity is approximately 40% for all the catalysts except for the Cr≥Oa ZrOa catalyst which showed a slightly lower selectivity to CO of approximately 35% and the Cu modified catalyst which showed a slightly higher selectivity to CO of -50%. For the selectivity to C0₂, a significant difference can be seen between the Cr₂θ3 and Pt catalysts with more CO₂ formed over the Cr₂0₃ than over Pt. The C0₂ selectivity for the Pt-modified chromium oxide catalyst falls directly between the two single component catalysts. The CH4 selectivity, however, is essentially the same for ail the catalysts at approximately 13%. The selectivity to C-₂H₂ is slightly higher for the Cr₂θ₃ AI₂θ₃ and the Cu modified catalyst than the three other catalysts. At a C₂H₆ O_z ratio of 1.2, the highest selectivity to H₂ is about 56% for the Cr₂θ3 Al₂Oa and Pt-modified Cr₂OjyΑI₂θ3 catalysts. The H₂ selectivity for the CrgOai'ZrOa was 47% and the Pt Al₂0₃ catalyst was 39%. The corresponding selectivity to H₂O is higher for the

catalysts than the two Cr₂θ3 Al₂θ₃ catalysts.

Similar trends between the catalysts exist at higher C₂H₆0₂ ratios. The Cr₂θ3 Zrθ₂ catalyst and the Cu modified Cr₂θ3/Zrθ2 catalyst show the beet C₂H selectivity at the highest C2H6 O₂ ratios with the Cu modified Cr₂θ₃2rθ₂ catalyst showing the lowest selectivity to CO. The C₂H₆ conversion and C₂H yield is higher over the Cr₂θ3 Zrθ2 catalyst and the Cu modified OtsOs/ZrOz catalyst than over the Pt catalyst; the difference increases with increasing ratios of C₂Hβ 0₂ in the feed. At C₂H₆/O_Z ratios of 1.2 and 1.5, the C₂H₄ selectivity for the Cr₂θ3 Zr0₂ and the PVAI2O3 catalysts is essentially the same with a lower C₂H₄ selectivity for the Cu modified Cr₂θ₃/Zrθ₂ catalyst. But at the higher C₂H6O₂ ratios, the selectivity to C₂H is higher over the chromium oxide and Cu modified chromium oxide catalysts at >70% compared to <65% over the Pt catalyst. The H₂ selectivity for the Cr₂θ3 Zr0₂ catalyst and the Cu modified Cr₂Oy7r0₂ catalyst is also higher at all C₂Hβ/O₂ ratios, especially at the higher C₂H₆ O₂ ratios. The CO selectivity is tower for the chromium oxide-zirconia catalyst and at the higher C₂Hβ 0₂ ratios is approximately half of the CO selectivity for the Pt n catalyst. This reduction in CO production is even more evident at the higher C₂H₆/O₂ ratios over the Cu modified Cr₂θ₃ r0₂ catalyst. However, the selectivity towards complete combustion products. C0₂ and HgO, is higher over the Cr₂θ3/Zr0₂.

All catalysts exhibit similar C₂H₆ conversions with lower conversions at the higher C₂H₆/O₂ ratios. At C₂Hβ/0₂ ratios greater than 1.2, the chromium oxide containing

!5 catalysts all show a slightly higher C₂He conversion than the Pt monolith. In ail cases, 0₂ is essentially completely consumed.

Example 2: The oxidative dehydrogenation of ethane was examined over a large variety of catalysts supported on ceramic foam monoliths at flow rates ranging from 2 to

:o 4 standard liters per minute (SLPM) which corresponds roughly to catalyst contact times of 5-15 ms (GHSV = 80.000 - 200,000 hr¹).

Table 2 shows product carbon and hydrogen atom selectivity, conversion, and reaction temperature at a C₂Hβ 0₂ ratio of 2.0 in the feed gas with 20% N₂ dilution at a total feed flow rate of 2.0 SLPM for the oxidative dehydrogenation of ethane over single

25 component catalysts. The Cr₂θ3, CuO, and MnO_x catalysts on a Zr0₂ monolith have Table 2: Carbon atom and hydrogen atom selectivity, conversion, and temperature for ethane oxidation over various an

essentially the same reaction results under these conditions with a C₂H selectivity of -68% with over 81% conversion of the ethane feed. These catalysts, Cr₂θ3, CuO, and MnO_x, also have very low selectivity to CO of 10%, 10%, and 7%, respectively; along with a corresponding higher C0₂ selectivity than the other single component catalysts. The 3 wt. % Pt α-AI₂0₃ catalyst had a slightly lower selectivity to C₂H₄ and lower conversion of C₂Hβ than the Cr₂0₃, CuO, and MnO* catalysts. Additionally, the Pt AI₂θ₃ catalyst also had a higher selectivity to CO and lower selectivity to CO₂ than the three transition metal oxide catalysts. The 9.1 wt. % FeO„Zrθ₂ catalyst also had a lower selectivity to C₂H (51%) and lower C₂H_β conversion (74%) along with a significantly higher selectivity to CO (31%) than the Crg _δ, CuO, and MnO_x catalysts. In contrast to all the other single component catalysts, the 9.7 wt. % Ni on a Zr0₂ monolith produced primarily syngas products, CO and H₂, and not oxidative dehydrogenation products,

Example 3: Table 3 shows the results for the oxidative dehydrogenation of ethane over Crj _j/ZrOs monolith catalyst with the addition of a single promoter including Ag, Cu, FβO_Xt Ni, MnO_x, and MgO. The reaction results for a C₂Hβ O₂ ratio of 2.0 with 20% N₂ dilution at a total flow rate of 2 SLPM show that the addition of the promoters to the Cr₂θ₃ Zrθ₂ catalyst can change the product selectivities and conversion over the catalyst. The addition of Cu or Ag to the Cr₂θ3 ZrO₂ catalyst does not significantly affect the product selectivities or reactant conversions. The addition of FeO* or MgO to the Cr₂O₃ ZrO₂ catalyst results in a slight decrease in the ethane conversion from 81% to 75% and 78%, respectively, but does not significantly affect the product selectivities. In contrast, the addition of MnOx to the Cr₂Oa Zrθ2 catalyst results in a decrease in the C₂H selectivity to 61 % from 68% and a corresponding increase in the CO selectivity to 22% from 13%. The ethane conversion or the 0.8 wt. % MnO_x - 8.0 wt. % Cr₂0s/ZrO₂ catalyst, however, is the same as the 9.0 wt. % Cr_sθ3 ZrO₂.

Table 3: Carbon atom and hydrogen acorn selectivity, conversion, and temperature for ethane oxidation over various catalysts at a H«/0_ rauo of 2.0 with 20% N₃ dilution and a total flow rate of 2 S PM in an autothermal reactor at a im.

Example 4: Table 4 shows the results for multi-component catalysts for the oxidative dehydrogenation of ethane for a C₂Hβ 0₂ ratio of 2.0 with 20% dilution at a total flow rate of 2 SLPM. The addition of MgO, FeO_x, and MnO_x to a Cu/Cr₂θ3/Zrθ2 results in a lower selectivity to C₂H₄ and corresponding higher selectivity to CO along with a lower CaHβ conversion than the 1.3 wt. % Cu - 13.0 wt. % Cr2θ3 on a Zr0₂ monolith. The addition of Ni to the Cu/Cr₂θ3/Zr0₂ catalyst also resulted in a slightly lower C₂H4. selectivity, but the addition of Ni did not significantly affect the CaHβ conversion.

The addition of the Cu to the Cr₂03/Zr0₂ catalyst does not significantly affect the product selectivity or rβactant conversions as noted above. The addition of Cu. however, did significantly increase the activity of the CuO CraOs Zr k catalyst especially at higher flow rates, N₂ dilutions, and C₂I θ₂ ratios. The 1.3 wt. % Cu - 13.0 wt. %

Table 4: Carbon atom and hydrogen atom selectivity, conversion, and temperature for ethane oxidation over various catalysts at a CΑJOi ratio of 2.0 with 20% N_ dilution and a total flow rate of 2 SLPM in an autothermal reactor at a ressure of 1.2 atm.

Cr₂0₃ Zr0₂ catalyst was able to achieve stable operation at a C₂Hβ 0₂ ratio of 2.4 with 50% dilution at a total flow rate of 10 SLPM with no signs of deactivation. In contrast, the 9 wt. % Cr₂θ₃ Zr0₂ catalyst was only able to achieve stable, non-deactivating behavior at a C₂Hβ 02 ratio of 2,4 with 50% N₂ dilution at a total flow rate of less than 4 SLPM. It was also found that the addition of the Cu promoter to a MnO_x Zr0₂ catalyst did not result in the same dramatic increase in catalyst activity.

Example 5: Under some conditions, reaction is not sustained indefinitely over some of the supported chromium oxide catalysts, The onset of extinction depends on the composition of the catalyst, the CzH^lOz ratio, the support material, the weight loading of the catalyst, the flowrate, the N₂ dilution, and the preheat of the feed.

The time to extinction is shown in Table 5 as a function of C₂Hβ/0₂ ratio with 20% reactant dilution at a flowrate of 2 SLPM for the various catalysts. The sustained activity of the Cr₂θ3/AI₂θ₃ and the Pt Al₂0₃ and Cr₂θ3 Zr0₂ catalysts differ in that the Pt Al_z0_3> Cu modified Cr2θ3 Zr0₂. and the 9 wt. % Cr₂03/Zr0₂ catalyst sustain reaction for a much longer period of time than the other catalyst compositions examined. Like the Pt monolith, the 10 wt. % Cr₂θ₃/AI₂θ₃ catalyst at a C₂rV0₂ ratio of 1.2 with 20% N₂ at a flowrate of 2 SLPM has shown sustained reaction for very iong periods of time with no deactivation and product selectivity changes. However, at a C₂rV0₂ ratio of 1.5, the reaction is sustained for only 1.6 hours. Before extinction of the reaction, the product selectivity and reactant conversions are constant over the entire time period. The catalyst temperature falls slightly in the first 1.25 hours and then rapidly decreases until the reaction extinguishes. At a C₂H₆ 0₂ ratio of 1.8 with 20% N≥ dilution at 2 SLPM, the reaction over the Cr₂θ₃ Al2θ₃ monolith extinguishes after only 5-10 minutes. Table 5; The reactive lifetime of the various catalysts as a function of C₂r O. ratio in the feed with 20% N. dilution with a total feed flow rate of 2 SLPM in an autothermal reactor at a pressure of 1.2 atm.

Fuel/0₂ 1.2 1.5 1.8 2.0 2.2 2.4

Catalyst Lifetime <hrs)

3 % Pt/α -AI₂O₃ >5,0* >5.0* >5.0* >S.O* >5.0* >5.0*

9% CriOj/ZrO; >2.0* >2.0* >6,0* >2.0* >2.0* >2.0*

2* Cr₂0₃Zrθ2 >2.0* >2.0* 0.1 — — —

10% Crj α-Al >4.0* 1.6 0.1 — — —

1.5% CrjCVα -AI₂O₃ 0.1 <0,1 — — — —

6.7% Cu .6.7% C^CyZrO, > 2.0* > 1.0* >10* > 1.0* > 1.0* >2.0*

10% CrjOj/α -Al.O. Pellets > 1.0* >7.5* 0.2 0.2 — .... j 1.3 % Cu - 13.0% Crιθ₃/Zr0₂ > 1.0* >ι.o* >1.0* > 1.0* > 1.0* >5.0*

9.1%FeO Zrθ₃ >1.0* >1.0* >1.0* > 1.0* > 1.0* >1,0*

8.1 MnO-/Zτθ₂ > 1.0* >1.0* > 1.0* > 1.0* > 1.0* >1.0*

9.7 % NiZrθ₂ > 1.0* >1.0* >1.0* > 1.0* > 1.0* >1.0*

11.2%Cu0/2rO₂ >1.0* >1.0* >1.0* > 1.0* > 1.0* >1.0*

PM0% CrjO α -AlαO? >1.0* >7.0* 9.0 ... — ...

* Cataiyst did not show any signs of deacαvation

In contrast to the Cr₂03/AI₂O₃ catalyst, the reaction was sustained under these conditions for the 9 wt. % Cr2θ₃/ r0₂ catalyst and the Cu modified Cr₂θ₃Zrθ2 catalyst for longer periods, similar to the Pt/Al₂0₃ monolith catalyst. Like the Pt catalyst, a 9 wt. % Cr₂θ3Zr0₂ catalyst showed non-deactivating steady state behavior up to a C₂H₆O₂ ratio of 2.4 with 20% N₂ dilution at a total flowrate of 2 SLPM which is well outside of the flammability range for this system. At a C₂Heθ ratio of 1.8 with 20% N₂ dilution at 2 SLPM, the 9 wt. % Cr₂θ3ZrO₂ monolith catalyst did not show any deactivation after 5 hours of continuous operation, while the reaction quickly extinguished under these condition for lower chromium oxide loadings on Z1O2 and on all Cr_aθ₃AI₂0₃ catalysts. At a C₂Hβ/0₂ ratio of 1.5 with 50% N₂ dilution at 2 SLPM, the Cu modified Cr₂0₃/Zr0₂ monolith catalyst did not show any deactivation for over 7 hours of continuous operation. The chromium oxide loading of the monoliths can significantly affect the catalysts. For chromium oxide supported on Zr0₂ and Al₂0₃, the activity of the catalyst increases with the chromium oxide loading.

The other transition metal oxide catalysts (11.2 wt. % Cu/Zr0₂, 9.7 wt. % Ni/Zr0₂, 9.1 wt. % FeO*/Zr0₂, and 8.1 wt. % Mn0χ/Zr ₂) are able to sustain reaction for more than one hour under these conditions. Additionally, the addition of the promoters (Ag, Ni, Mn, Mg, Fe, Cu, their oxides, and combinations thereof) to the Cr₂θ Zrθ2 led to stable operation for several hours with no signs of deactivation at a C₂H₆/O₂ ratio of 2.4 with 20% N₂ dilution at a total flow rate of 2 SLPM.

The addition of very small amounts of Pt (> 0.001 g , -0.05 wt. %), as a co- catalyst, was examined for its influence on the ability of the supported chromium oxide catalysts to sustain reaction for extended periods. Table 5 shows the time to extinction for Pt-modified C^Os/AI≤Oa and unmodified Cr₂0*'AI₂0₃ monol^'rth catalysts at several C₂H₆ 0₂ ratios with 20% N₂ dilution at a flowrate of 2 SLPM. The activity of Pt-coated monoliths for the oxidative dehydrogenation is relatively independent of the Pt loading, even for very small amounts of Pt [Haubein, N., Effects of Support Material and Pt Loading on the Catalytic Oxidative Dehydrogenation of Ethane; University of Delaware, 1997]. The addition of Pt significantly increases the length of time that reaction can be sustained over the Cr₂θ₃/AI₂θ3 catalyst. However, the Pt-modified Cr₂θ₃ Al₂0₃ catalyst still extinguished rapidly at the higher C₂Hβ/0₂ ratios unlike the Pt Al₂0₃ catalyst.

The surface area can also influence the temporal behavior of the catalyst. The surface area of the monolith supports is approximately 200 cm² per gram, which is approximately 400 cm² of total surface area for the monoliths used here. The total surface area can be increased by replacing the monolith with a packed bed of 3 mm Al₂0₃ pellets. The surface area of blank a-AfeOa pellets is 9 m² per gram which results in a catalyst bed with approximately 27 m² of total surface area. The packed bed contained 60 Cr₂θ3 AI₂0₃ pellets, which was approximately equal in total weight to the chromium oxide monolith catalyst and resulted in an approximate bed depth of 1.5 cm. Table 6: The reactive lifetime of the various catalysi s as a function of the total feed flow rate at several C₂H«/0^ ratios m the feed with 20% N. dilution in an autothermal reactor at a pressure of 1.2 atm.

F eL/Oj 1.2 1.2 1.2 1.3 1.5 1.5 1.8 1.8 1.8

Flowrate (SLPM) 1.0 2.0 3.0 1.0 2.0 3.0 1.0 2.0 3.0

Catalyst Lifetime (hrs)

3 % Pt/α-Al₃θ₃ > 2.0* > 5.0* > 2.0* > 2.0* > 5.0* > 2.0* > 2.0* > 5.0* > 2.0*

10% α₂Oj/ α-Al2θ3 > 1.0* > 4.0* < 02 7.0 1.6 < 0.1 7 0.1 — l ,5% Cr₂0ιt α -Al₂0} > 6.5 0.1 — 0.1 < 0.1 — — —

6.7% Cu - * * * * * *

6.7% Cr₂0₃ Zr0₂

9% QI J/ZΓQ_J > 2.0* > 2.0* > 6.0* > 3.0* > 2.0* > 3.0* > 1.0* > 6.0* 2.8

4% > 2.0* > 2.0* > 5.0* > 2.0* > 9.0* 1.5 7

2% CriOj/ZrOi * > 2.0* 7 ? ? ? 0.1 —

Catalyst did not show any signs of deacuvation

Reaction was sustained over the 10 wt. % C^Oa/α-A Os pellets for more than about 7.5 hours with no sign of deactivation or changes in the product selectivity at a C₂H6 0₂ ratio of 1.5 with 20% N₂ dilution at a flowrate of 2 SLPM. Under the same conditions, the 10 wt. % Cr₂θsAI₂0₃ monolith extinguished in 1.6 hours. In addition to the difference in reactive lifetimes, the chromium oxide pellet catalyst displayed a slightly higher selectivity to C2H4 and lower selectivity to CO. The chromium oxide pellets also displayed a slightly lower C₂H₆ conversion, 94%, compared to 96% CsHβ conversion over the chromium oxide monolith. Therefore, in addition to the composition of the ceramic support, the total surface area of the catalyst can also have a significant impact upon the behavior of the supported chromium oxide catalyst.

The feed flowrate strongly affects the sustainability of reaction over the chromium oxide catalysts as shown in Table 6. For the 10 wt. % Cr₂θ₃/Al₂θ₃ catalyst at a C₂Hβ 0₂ ratio of 1.5 with 20% N₂ dilution, the reaction was sustained for 7 hours at 1 SLPM, 1.6 hours at 2 SLPM, and only a couple of minutes at a flowrate of 3 SLPM. When the chromium oxide loading is reduced, the activity of the catalyst decreases accordingly. For a 1.5 wt. % Cr₂Os/α:-Al₂θ3 monolith, reaction at 2 SLPM with 20% N₂ dilution could not be sustained even at a C₂Hβ/θ₂ ratio of 1.2. The total flowrate had to be reduced by 50% to 1 SLPM before reaction over the low chromium oxide containing catalyst was sustained for an extended period of time (>6 hrs.) In spite of the lower flowrate and hence longer contact time, the catalyst did not achieve steady state. Throughout the time survey, the catalyst showed signs of deactivation with the conversion of C₂H₆ and 0₂ falling with time on stream.

For the Cr₂θ₃ Zrθ₂ catalysts, the flowrate also strongly affects the catalyst's lifetime. At a C₂H₆ O₂ ratio of 1.5 with 20% N₂ dilution over the 4 wt. % Cr₂θ₉ Zr0₂ monolith catalyst, the reaction was only sustained for 1.5 hours at a flowrate of 3 SLPM, compared to over 9 hours at 2 SLPM. Similar decreases in the lifetime with increasing flowrate, and correspondingly shorter contact time, can be seen for the 9 wt. % Cr₂θ3 Zrθ₂ catalyst at the higher C₂H6/O2 ratios. The Cu modified Cr^/ZtOz catalyst showed no signs of deactivation for C₂Hβ/0₂ ratios up to 2.4 and total flow rates up to 4 SLPM.

In addition to the lifetime of the catalyst, the flowrate affects the product selectivity and ethane conversion shown in Tables 7 and 8. As the flowrate increases, the selectivity to C₂H₄ decreases and the selectivity to C₂H₂ increases; the H₂O selectivity decreases; and the conversion increases slightly. The most significant effect of increasing the flowrate can be observed by examining the temperatures measured at the front and back of the catalyst. At the lowest flow rates, the temperature on the front face of the catalyst exceeds the temperature at the rear face of the catalyst; while at the higher flow rates, the front temperature is much less than the rear temperature.

The lifetime of the chromium oxide catalysts is also influenced by the N₂ dilution in the feed mixture. At 50% N₂ dilution at 2 SLPM with a C₂Hβ/0₂ ratio of 1.2, the reaction over the 10 wt. %

catalyst was only sustained for 20 minutes before the reaction rapidly extinguished, and at a C₂Hβ θ₂ ratio of 1.5, the reaction

Claims

We claim: . A process to produce olefins which comprises reacting hydrocarbons and an oxygen containing gas in the presence of a catalyst comprising a chromium containing compound, a copper containing compound, a manganese

5 containing compound, or combinations thereof supported on a monolith.

2. A process as claimed in daim 1 wherein said reacting hydrocarbons comprise at least one saturated hydrocarbon containing 2 to 6 carbon atoms.

3. A process as claimed in claim 1 wherein oxygen gas comprises 5 to 40% (by volume) of the reacting feed. lo 4, A process as daimed in claim 1 , wherein the catalyst contact time is less than

0.02 seconds. 5- The process as claimed in claim 1 , wherein said chromium containing compound is a chromium oxide stable at temperature in excess of about 900°

C. i5 6. The process as claimed in claim 1 , wherein said monolith is ceramic and has a honeycomb or foam structure.

7. The process as claimed in claim 1 , wherein said monolith is composed of Al2θ₃, Siθ2, Mg-stabilized Zrθ2, Y-stabilized Zr0₂. or mixtures thereof.

8. The process as claimed in claim 1 , wherein said monolith is composed of 20 Mg-stabilized Zrθ2-

9. The process as claimed in claim 6, wherein said monolith has a foam structure and has about 20 to about 100 pores per linear inch.

10. The process as daimed in claim 6, wherein said catalyst contains substantially no platinum.

25 1 1. The process aβ claimed in claim 1 , wherein said monolith further comprises at least one promoter selected from the group consisting of Mn, Mg, Ni, Fe, Ag, Pi, and oxides thereof. 12. The process as claimed in claim 1 , wherein said catalyst is present in the substantial absence of platinum, s 13. The process as claimed in claim 1 , wherein the ratio of atoms of Cu to Cr is between about 1 :100 and about 1 :2.

14. The process as claimed in claim 1 , wherein the ratio of atoms of Cu to Cr is between 1:15 and 1:5.

15. The process as claimed in claim 4 wherein the reacting hydrocarbons and 0 oxygen containing gas contains at least one hydrocarbon at ambient temperature. 16. The process as claimed in claim 4 wherein the reacting hydrocarbons and oxygen containing gas contains at least one hydrocarbon at a temperature below about 400°C. s 1 . The process as claimed in claim 1 wherein the oxygen containing gas comprises at least one of N₂, Ar, He, C0₂, and H₂0. 18. The process as claimed in claim 1 wherein the oxygen containing gas also contains H₂. 19. A catalyst which comprises a monolith impregnated with a Cr containing o compound.

20. The catalyst as claimed in claim 19, wherein said monolith is ceramic and has a honeycomb or foam structure. 21. The catalyst as claimed in claim 19, wherein the monolith is a ceramic foam and contains about 20 to about 100 pores per linear inch. 5 22. The catalyst as claimed in claim 1 , wherein said Or containing compound is Cr oxide. 23. The catalyst as claimed in claim 22, wherein said monolith is composed of Al₂0₃, SIO2, Mg-stabilized Z1 2 or Y-stabilized ZrC>2.

24. The catalyst as claimed in claim 19, wherein said monolith is composed of Mg~stabalized Zr0₂.

25. The catalyst as claimed in claim 19, wherein copper or copper oxide is present.

26. The catalyst as claimed in claim 25, wherein the ratio of atoms of Cu to Cr is between about 1 :1 0 and about 1 :2.

27. The catalyst as claimed in claim 25, wherein the ratio of atoms of Cu to Cr is between 1:15 and 1:5.