SOLID STATE SYNTHESIS OF OXIDATIVE DEHYDROGENATION CATALYSTS

Abstract

Synthesize a nickel oxide-based oxidative dehydrogenation catalyst via a solvent-free process that comprises sequential steps a. mixing without added solvent a combination of a solid nickel precursor, a solid oxalate or oxalic acid and, optionally, a doping amount of a metal precursor for a period of time sufficient to convert the combination to a visually homogenous mixture; and b. calcining the visually homogeneous mixture at a temperature within a range of from greater than 250° C. to less than 800° C. for a time within a range of from 30 minutes to 360 minutes in an oxygen-containing atmosphere, preferably air, to form a calcined oxidative dehydrogenation catalyst. As a modification of the process, add an intermediate step between steps a. and b. to dry the homo geneous mixture at a temperature within a range of from 50° C. to 90° C. for a period of time within a range of from 10 minutes to 600 minutes to form a dried mixture. The resulting catalyst may be used in oxidative dehydrogenation of ethane.

Claims

1. A solvent-free process for synthesizing a nickel oxide-based oxidative dehydrogenation catalyst that comprises sequential steps as follows: a. mixing without added solvent a combination of a solid nickel precursor, a solid oxalate or oxalic acid and, optionally, a doping amount of a metal precursor for a period of time sufficient to convert the combination to a visually homogenous mixture; and b. calcining the visually homogeneous mixture at a temperature within a range of from greater than 250° C. to less than 800° C. for a time within a range of from 30 minutes to 360 minutes in an oxygen-containing atmosphere to form a calcined oxidative dehydrogenation catalyst.

2. The process of claim 1, further comprising a sequential intermediate step a′ that follows step a, precedes step b and comprises drying the homogeneous mixture at a temperature within a range of from 50° C. to 90° C. for a period of time within a range of from 10 minutes to 600 minutes to form a dried mixture, the dried mixture thereby replacing the visually homogeneous mixture in step b.

3. The process of claim 1, wherein the solid nickel precursor is selected from a group consisting of nickel nitrate, nickel hydroxide, and nickel acetate and their corresponding hydrated compounds.

4. The process of claim 1, wherein the metal precursor is selected from a group consisting of compounds of Groups IV through VI of the Periodic Table of the Elements, tin, and iron.

5. The process of claim 4, wherein the metal precursor is selected from compounds of a group consisting of tantalum, niobium, titanium, molybdenum, tungsten and zirconium.

6. The process of claim 1, wherein the solid nickel precursor, the oxalate or oxalic acid and, when used, the metal precursor, are present in amounts as follows: from 1 percent by mole (mol %) to 40 mol % solid nickel precursor, from greater than 20 mol % to 98 mol % oxalate or oxalic acid, from greater than or equal to 1 mol % to 40 mol % metal precursor, each mol % being based upon combined moles of solid nickel precursor, oxalate and metal precursor and, in each case, when added together total 100 mol %.

7. The process of claim 6, wherein the solid nickel precursor, the oxalate or oxalic acid and the metal precursor are present in amounts as follows: from 3 mol % to 30 mol %, solid nickel precursor, from 40 mol % to 94 mol %, oxalate or oxalic acid and from 3 mol % to 30 mol % metal precursor, each mol % being based upon combined moles of solid nickel precursor, oxalate or oxalic acid and metal precursor and, in each case, when added together total 100 mol %.

8. A process for effecting oxidative dehydrogenation of ethane using the nickel oxide-based oxidative dehydrogenation catalyst prepared by the process of claim 1, comprising sequential steps as follows: a. placing the calcined oxidative dehydrogenation catalyst in contact with a feedstream that comprises ethane, oxygen and, optionally, an inert diluent at a temperature of less than 350° C. at a feedstream flow rate within a range of from 50 hr.sup.−1 to 10000 hr.sup.−1 to yield a product stream that comprises ethylene, carbon dioxide and unreacted ethane. b. recovering ethylene from the product stream.

Description

EXAMPLE (Ex) 1

Synthesis of NiO.SUB.— .Catalyst

[0031] Place 4.74 grams (g) of nickel nitrate hexahydrate (Ni(NO.sub.3).sub.2.6H.sub.2O) and 1.13 g of oxalic acid (H.sub.2C.sub.2O.sub.4) in a mortar bowl. Using a pestle, mix and grind the mortar bowl contents at room temperature (nominally 25° C.) for 10 minutes to get a uniform paste. Dry the paste at 90° C. for 2 hours. Calcine the dried paste under static air at 300° C. for 4 hours to produce a black solid.

EX 2

Synthesis of Ni.SUB.0.99.Ta.SUB.0.01.O Catalyst

[0032] Replicate Ex 1 but add 0.067 grams (g) of tantalum (V) ethoxide (Ta(OCH.sub.2CH.sub.3).sub.5) to the mixture of Ex 1.

EX 3

Synthesis of Ni.SUB.0. 97.Ta.SUB.0.03.O Catalyst

[0033] Replicate Ex 1 but add 0.21 g of tantalum(V) ethoxide (Ta(OCH.sub.2CH.sub.3).sub.5) to the mixture of Ex 1.

EX 4

Synthesis of Ni.SUB.0.95.Ta.SUB.0.05.O Catalyst

[0034] Replicate Ex 1 but add 0.35 g of tantalum(V) ethoxide (Ta(OCH.sub.2CH.sub.3).sub.5) to the mixture of Ex 1.

EX 5

Synthesis of Ni.SUB.0.93.Ta.SUB.0.07.O Catalyst

[0035] Replicate Ex 1 but add 0.50 g of tantalum(V) ethoxide (Ta(OCH.sub.2CH.sub.3).sub.5) to the mixture of Ex 1.

EX 6

Synthesis of Ni.SUB.0.95.Nb.SUB.0.05.O Catalyst

[0036] Replicate Ex 1 but change the amount of Ni(NO.sub.3).sub.2.6H.sub.2O to 1.98 g and substitute 0.24 g of niobium (V) oxalate hydrate (C.sub.10H.sub.5NbO.sub.20.xH.sub.2O) for the oxalic acid H.sub.2C.sub.2O.sub.4.

EX 7

Synthesis of Ni.SUB.0.95.W.SUB.0.05.O Catalyst

[0037] Replicate Ex 1 but add 8.20 g of tungsten(VI) ethoxide (W(OCH.sub.2CH.sub.3).sub.6, 5% w/v in ethanol) into the mixture of Ni(NO.sub.3).sub.2.6H.sub.2O and H.sub.2C.sub.2O.sub.4. Evaporate the ethanol from the tungsten(VI) ethoxide before adding it to the mixture.

EX 8

Synthesis of Ni.SUB.0.95.Ti.SUB.0.05.O Catalyst

[0038] Replicate Ex 1 but add 0.20 g of titanium ethoxide (Ti(OCH.sub.2CH.sub.3).sub.4) into the mixture of Ni(NO.sub.3).sub.2.6H.sub.2O and H.sub.2C.sub.2O.sub.4.

EX 9

Synthesis of Ni.SUB.0.95.Zr.SUB.0.05.O Catalyst

[0039] Replicate Ex 1 but add 0.42 g of zirconium acetylacetonate (Zr(C.sub.5H.sub.7O.sub.2).sub.4) into the mixture of Ni(NO.sub.3).sub.2.6H.sub.2O and H.sub.2C.sub.2O.sub.4.

EX 10

Synthesis of Ni.SUB.0.85.Nb.SUB.0.15.O Catalyst

[0040] Replicate Ex 6 but change the amount of niobium (V) oxatate hydrate C.sub.10H.sub.5NbO.sub.20.xH.sub.2O to 0.80 g.

EX 11

Synthesis of Ni.SUB.0.90.Ta.SUB.0.10.O Catalyst

[0041] Replicate Ex 2 with modifications to change the amount of tantalum (V) ethoxide (Ta(OCH.sub.2CH.sub.3).sub.5) to 0.74 g.

EX 12

Synthesis of Ni.SUB.0.85.Ta.SUB.0.15.O Catalyst

[0042] Replicate Ex 2 with modifications to change the amount of tantalum(V) ethoxide (Ta(OCH.sub.2CH.sub.3).sub.5) to 1.17 g.

EX 13

Synthesis of Ni.SUB.0.80.Ta.SUB.0.20.O Catalyst Replicate Ex 2 with modifications to change the amount of tantalum(V) ethoxide (Ta(OCH.SUB.2.CH.SUB.3.).SUB.5.) to 1.66 g.

EX 14

Synthesis of Ni.SUB.0.90.Nb.SUB.0.10.O Catalyst

[0043] Replicate Ex 6 but change the amount of niobium (V) oxalate hydrate C.sub.10H.sub.5NbO.sub.20.xH.sub.2O to 0.51 g.

EX 15

Synthesis of Ni.SUB.0.80.Nb.SUB.0.20.O Catalyst

[0044] Replicate Ex 6 but change the amount of niobium (V) oxalate hydrate C.sub.10H.sub.5NbO.sub.20.xH.sub.2O to 1.14 g.

EX 16

Synthesis of Ni.SUB.0.95.Sn.SUB.0.05.O Catalyst

[0045] Replicate Ex 9 but substitute 0.30 g of tin(IV) acetate (Sn(CH.sub.3CO.sub.2).sub.4) for the zirconium acetylacetonate.

EX 17

Solid-State Synthesis of Ni.SUB.0.85.Nb.SUB.0.15.O with Nickel Hydroxide (Ni(OH) as Ni Precursor

[0046] Replicate Ex 10 but substitute 0.63 g of Ni(OH).sub.2for Ni(NO.sub.3).sub.2.6H.sub.2O.

EX 18

Solid-State Synthesis of Ni.SUB.0.85.Nb.SUB.0.15.O with Nickel Acetate (Ni(CH.SUB.3.CO.SUB.2.).SUB.2.) as Ni Precursor

[0047] Replicate Ex 10 but substitute 1.20 g of Ni(CH.sub.3CO.sub.2).sub.2 for Ni(NO.sub.3).sub.2.6H.sub.2O.

EX 19

Solid-State Synthesis of Ni.SUB.0.85.Nb.SUB.0.15.O Without Dry Process

[0048] Replicate Ex 10 but calcine the mixture after grinding directly without drying process a′.

Comparative Example (CEx) A

Synthesis of Pure NiO Without Oxalic Acid

[0049] Dry 2 g of Ni(NO.sub.3).sub.2.6H.sub.2O at 90° C. for 2 hours. Calcine the dried paste under static air at 300° C. for 4 hours to produce a black solid.

CEx B-F-sol-gel Synthesis of Ni.sub.1-xTa.sub.xO (x=0.00, 0.01, 0.03, 0.05, and 0.07) Catalysts

[0050] In a glass vessel, dissolve six (6) g of nickel nitrate hexahydrate (Ni(NO.sub.3).sub.2.6H.sub.2O) and an amount of tantalum tetraethoxyacetylacetonate (Ta(OC.sub.2H.sub.5).sub.4(C.sub.5H.sub.7O.sub.2)), 0.00 g (for Ni0 (CEx B), 0.10 g (for Ni.sub.0.99Ta.sub.0.01O) (CEx C), 0.29 g (for Ni.sub.0.97Ta.sub.0.03O) (CEx D), 0.51 g (for Ni.sub.0.95Ta.sub.0.05O) (CEx E) or 0.71 g (for Ni.sub.0.93Ta.sub.0.07O) (CEx F) in 100 mL of water to form a solution. Add two (2) g of citric acid to the solution which then turns blue. Age the blue solution at 80° C. for 24 hr. Evaporate water from the aged solution at 90° C. to form a gel. Dry the gel at 120° C. for 2 hr, 140° C. for 2 hr, and 160° C. for 12 hr to yield a black xerogel. Calcine the xerogel at 450° C. (ramp rate of 1° C./min from room temperature (nominally 25° C.) to 450° C.) for 4 hr in static air.

CEx G-sol-gel Synthesis of Ni.sub.0.95Nb.sub.0.05O

[0051] Replicate CEx C but substitute 0.35 g of niobium ethoxide (Nb(OCH.sub.2CH.sub.3).sub.4) for the tantalum tetraethoxyacetylacetonate.

[0052] CEx H-sol-gel Synthesis of Ni.sub.0.95W.sub.0.05O

[0053] Replicate CEx G but substitute 0.28 g of tungstic acid (H.sub.2WO.sub.4) for the niobium ethoxide.

CEx I-sol-gel Synthesis of Ni.sub.0.95Ti.sub.0.05O

[0054] Replicate CEx H but substitute 0.25 g of titanium ethoxide (Ti(OCH.sub.2CH.sub.3).sub.4) for the tungstic acid.

CEx J-sol-gel Synthesis of Ni.sub.0.95Zr.sub.0.05O

[0055] Replicate CEx I but substitute 0.42 g of zirconium(IV) butoxide Zr(OBu).sub.4 for the titanium ethoxide.

CEx K-solid-state Synthesis of Ni.sub.0.85Nb.sub.0.15O Without Oxalate

[0056] Replicate Ex 10 but substitute 0.38 g of niobium (V) ethoxide (Nb(OCH.sub.2CH.sub.3).sub.5)) for niobium (V) oxalate hydrate C.sub.10H.sub.5NbO.sub.20.xH.sub.2O.

CEx L—Solid-State Synthesis of Ni.sub.0.85Nb.sub.0.15O with Nickel Dichloride (NiCl.sub.2)as Ni Precursor

[0057] Replicate Ex 10 but substitute 0.88 g of NiCl.sub.2 for Ni(NO.sub.3).sub.2.6H.sub.2O. The resulting catalyst shows no activity and, as such, is not reported in Table 1.

Catalyst Activity Evaluation

[0058] Evaluate catalytic activity of the NiO catalysts of Ex 1 to 19 and CEx A to L for oxidation of ethane to ethylene using a P&ID micro-pilot apparatus equipped with a stainless steel reactor (internal diameter 4 millimeters (mm)) at atmospheric pressure (nominally 14.5 pounds per square inch (psi) (1.013250×10.sup.5 pascals (Pa)). Load 100 milligrams (mg) of the catalyst into the reactor with glass wool as a support to form a catalyst bed that has a height of approximately 5 mm. Pass a feedstream composed of 10% C.sub.2H.sub.6/5% O.sub.2 in He through the catalytic bed at a constant flow rate of 600 ml reciprocal hours (hr.sup.−1). Heat the catalytic bed up to a temperature within a range of from 250° C. to 350° C. at a heating rate of 1° C. min.sup.−1 to carry out the catalytic test at as shown in Table 1 below. Sample the reaction mixture at the outlet of the reactor at regular intervals, typically every 5 min, and analyze the reaction mixture using an on-line Varian 490 micro-GC equipped with a TCD (Thermal Conductivity Detector) and two columns, a MolSieve™ 5 Å column (Ar as carrier gas) to quantify O.sub.2, and a poraPLOT Q™ column (He as carrier gas) to quantify CO.sub.2, C.sub.2H.sub.4 and C.sub.2H.sub.6. Calculate ethane conversion and selectivity to ethylene on a carbon basis.

TABLE-US-00001 TABLE 1 300° C. 330° C. 350° C. Ex/ % % % % % % % % % CEx Catalyst Conv Sel Yld Conv Sel Yld Conv Sel Yld 1 NiO 16.2 64.5 10.4 27.7 64.4 17.8 30.7 64.3 19.7 A NiO 14.1 43.8 6.1 20.3 48.3 9.8 20.5 49.0 10.0 B NiO 7.62 66.1 5.0 16.1 65.1 10.5 22.7 64.5 14.6 2 Ni.sub.0.99Ta.sub.0.01O 19.0 73.1 13.8 32.4 72.1 23.4 36.0 71.6 25.8 C Ni.sub.0.99Ta.sub.0.01O 8.8 73.8 6.5 18.1 72.0 13.0 25.6 70.8 18.1 3 Ni.sub.0.97Ta.sub.0.03O 19.0 79.8 15.1 33.7 77.5 26.1 39.4 76.2 30.2 D Ni.sub.0.97Ta.sub.0.03O 5.9 84.7 5.0 13.2 82.0 10.8 20.2 80.0 16.2 4 Ni.sub.0.95Ta.sub.0.05O 16.2 83.5 15.0 30.0 81.2 28.5 39.1 79.4 37.3 E Ni.sub.0.95Ta.sub.0.05O 5.2 87.7 4.6 11.8 85.0 10.0 18.6 82.7 15.4 5 Ni.sub.0.93Ta.sub.0.07O 18.0 85.6 15.4 32.6 82.0 26.7 40.5 79.5 32.2 F Ni.sub.0.93Ta.sub.0.07O 2.3 88.0 2.0 5.7 88.0 5.0 9.7 86.0 8.3 6 Ni.sub.0.95Nb.sub.0.05O 9.9 62.7 6.2 20.3 64.4 13.1 28.1 66.2 18.6 G Ni.sub.0.95Nb.sub.0.05O 6.6 82.0 5.4 14.0 79.2 11.1 22.0 77.0 16.9 7 Ni.sub.0.95W.sub.0.05O 10.2 79.2 8.1 20.2 78.2 15.8 26.0 77.5 20.2 H Ni.sub.0.95W.sub.0.05O 2.4 83.5 2.0 6.0 80.3 4.8 10.1 78.5 7.9 8 Ni.sub.0.95Ti.sub.0.05O 21.0 68.2 14.3 29.4 68.2 20.1 29.2 68.0 19.9 I Ni.sub.0.95Ti.sub.0.05O 4.8 79.2 3.8 11.1 79.1 8.8 17.4 76.3 13.3 9 Ni.sub.0.95Zr.sub.0.05O 19.6 58.0 11.4 23.8 57.8 13.8 23.8 57.8 13.8 J Ni.sub.0.95Zr.sub.0.05O 6.8 66.6 4.5 14.6 66.1 9.7 21.6 65.7 14.2 10  Ni.sub.0.85Nb.sub.0.15O 16.3 82.4 13.4 30.2 80.0 24.2 38.3 78.1 29.9 K Ni.sub.0.85Nb.sub.0.15O 13.5 53.6 7.2 22.4 56.8 12.7 57.2 23.6 13.5 11  Ni.sub.0.90Ta.sub.0.10O 15.6 83.9 14.9 29.2 81.5 27.9 37.8 80.0 36.4 12  Ni.sub.0.85Ta.sub.0.15O 12.6 87.8 12.8 24.8 84.6 24.4 34.1 82.0 32.9 13  Ni.sub.0.80Ta.sub.0.20O 12.0 89.4 13.2 24.1 86.3 25.0 33.5 83.3 33.3 14  Ni.sub.0.90Nb.sub.0.10O 12.1 78.9 9.5 24.4 78.1 19.1 33.5 77.5 26.0 15  Ni.sub.0.80Nb.sub.0.20O 14.1 79.8 11.3 27.1 77.8 21.1 35.7 76.5 27.3 16  Ni.sub.0.95Sn.sub.0.05O 19.5 65.0 12.7 28.5 67.0 19.1 29.5 67.0 19.8 17  Ni.sub.0.85Nb.sub.0.15O 10.1 54.7 5.5 19.7 57.7 11.4 23.3 58.8 13.7 18  Ni.sub.0.85Nb.sub.0.15O 14.2 57.2 8.1 23.5 61.3 14.4 25.1 62.6 15.7 19  Ni.sub.0.85Nb.sub.0.15O 16.3 76.2 12.4 29.5 75.3 22.2 32.5 74.8 24.3

[0059] The data in Table 1 and the examples and comparative examples for which data is provided in Table 1 support several observations. First, with the same composition, the catalysts prepared from solid-state synthesis (Ex 1-9) have better activity than those from sol-gel method (CEx B-J). Second, the same examples and comparative examples demonstrate that solid-state synthesis of a catalyst leads to a higher ethylene yield than a catalyst having the same composition, but prepared via sol-gel synthesis. Third, solid-state synthesis is a more straightforward and efficient preparation technique than sol-gel synthesis. Fourth, oxalic acid or an oxalate salt plays an important role in preparing NiO-based catalysts via solid-state synthesis. The NiO and Ni.sub.0.85Nb.sub.0.15O synthesized without oxalate (CEx A, K) demostrate lower activity and selectivity than those prepared in the presence of oxalate (Ex 1, 10). Fifth, the catalytic performance of NiO catalysts depends upon the nickel precursor used in preparing such catalysts. By way of illustration, Ni.sub.0.85Nb.sub.0.15O prepared from Ni(NO.sub.3).sub.2.6H.sub.2O (Ex 10) exhibits much better performance than those prepared from Ni(OH).sub.2.sub._(Ex 17), Ni(CH.sub.3CO.sub.2).sub.2 (Ex 18) and NiCl.sub.2.sub._(CEx L, minimal conversion and very low selectivity). Sixth, the optional drying step can be implemented if desired, but is not essential as revealed by a comparison of Ex 19 (no drying step) with Ex 10 (drying step included) which shows similar activity.

EX 20

Stability Test on Ni—Ta—O Catalysts

[0060] Evaluate catalyst stability (Ex 4 and CEx E by passing a gas mixture of 10% C.sub.2H.sub.6/10% O.sub.2 in helium through the catalytic bed described in the catalyst activity evaluation description held at 330° C., at a total flow rate of 10 mL/min (W/F=0.6 g s/mL), and sample the reaction mixture via on-line gas chromatograph continuously for 50 hours (hr). The results (ethane conversion and ethylene selectivity) are summarized in Table 2.

TABLE-US-00002 TABLE 2 5 hr 10 hr 15 hr 20 hr 25 hr % % % % % % % % % % Catalyst Conv Sel. Conv Sel Conv Sel Conv Sel Conv Sel Ex-4 33.7 80.4 33.4 80.7 33.2 80.8 33.0 80.9 32.8 81.1 CEx E 20.1 80.9 19.2 81.5 18.8 81.8 18.4 82.1 18.20 82.0 30 hr 35 hr 40 hr 45 hr 50 hr % % % % % % % % % % Conv Sel Conv Sel Conv Sel Conv Sel Conv Sel Ex-4 32.7 81.2 32.6 81.2 32.4 81.4 32.3 81.4 32.2 81.4 CEx E 18.0 82.4 17.9 82.6 17.7 82.7 17.5 82.9 17.3 82.8

[0061] From the data presented in Table 2, the catalyst of this invention (Ex 4, solid-state synthesis) when compared to sol-gel synthesized catalysts (CEx E) exhibit not only improved productivity resulting from a combination of higher activity (conversion) and good selectivity but also higher stability with time-on-stream in low temperature (330° C.) ethane ODH.