HOMOGENOUS CATALYTIC COMPOSITION FOR IMPROVING LPG COMBUSTION

Abstract

The present invention discloses a homogenous cerium (Ce) catalyst composition comprising Ce(IV) complex alone, or Ce(IV) complex in a mixture with Ce(III) complex, that can significantly improve both LPG and soot combustion, resulting in higher flame temperatures, faster heating, reduced cooking time and reduced fuel consumption. The cerium(III) complex is cerium(III) 2-ethylhexanoate and the cerium(IV) complex is aqua(2-N-(2-hydroxyethylimino)-4-pentanoate) dinitrocerium(IV) [Ce(L1)(H.sub.2O)(NO.sub.3).sub.2], wherein L1 is 2-N-(2-hydroxyethylimino)-4-pentanone.

Claims

1. A homogenous catalyst composition for improving liquefied petroleum gas (LPG) combustion, the composition comprising: a cerium(IV) complex alone; or a cerium(IV) complex in a mixture with a cerium(III) complex, wherein the cerium(III) complex is cerium(III) 2-ethylhexanoate; and wherein the cerium(IV) complex is aqua(2-N-(2-hydroxyethylimino)-4-pentanoate)dinitrocerium(IV) [Ce(L1)(H.sub.2O)(NO.sub.3).sub.2], wherein L1 is 2-N-(2-hydroxyethylimino)-4-pentanone.

2. The homogenous catalyst composition as claimed in claim 1, wherein the Ce(III) complex is present in an amount ranging from 33-100 wt. % and the Ce(IV) complex is present in an amount ranging from 25-100 wt. % of the total catalyst composition.

3. The homogenous catalyst composition as claimed in claim 1, wherein the cerium(III) complex is present in a concentration range of 1.5-15 ppm of the total liquefied petroleum gas (LPG) composition.

4. The homogenous catalyst composition as claimed in claim 1, wherein the cerium(IV) complex is present in a concentration range of 0.8-10 ppm of the total liquefied petroleum gas (LPG) composition.

5. The homogenous catalyst composition as claimed in claim 1, wherein the cerium(III) and cerium(IV) complex are present in a weight ratio ranging from 1:1 to 3:1.

6. The homogenous catalyst composition as claimed in claim 5, wherein the cerium(III) and cerium(IV) complex are present in an optimum weight ratio of 2:1.

7. The homogenous catalyst composition as claimed in claim 1, wherein the catalyst composition increases flame temperature of the liquefied petroleum gas (LPG) up to 10%.

8. The homogenous catalyst composition as claimed in claim 1, wherein the catalyst composition is present in a concentration range of 2.5-20 ppm of the total liquefied petroleum gas (LPG) fuel composition.

9. A process for preparation of a homogenous catalyst composition for improving liquefied petroleum gas (LPG) combustion, the process comprising: (a) synthesis of 2-N-(2-hydroxyethylimino)-4-pentanone (L1) by reacting acetyl acetone and ethanol amine in methanol solution and stirring for 24 hours; (b) synthesis of aqua(2-N-(2-hydroxyethylimino)-4-pentanoate)dinitrocerium (IV) [Ce(L1)(H.sub.2O)(NO.sub.3).sub.2] by reacting L1 and Ce(NO.sub.3).sub.3.Math.6H.sub.2O in dimethylformamide solvent at 150? C. and keeping for 15 hours; (c) synthesis of tetraacetylacetonate cerium (IV) [Ce(acac).sub.4] by reacting acetyl acetone, triethyl amine and Ce(NO.sub.3).sub.3.Math.6H.sub.2O in methanol solution at 45? C. for 15 hours; (d) synthesis of cerium(III) 2-ethylhexanoate by reacting sodium 2-ethylhexanoate and cerium nitrate hexahydrate and stirring for 5 hours; and (e) preparation of a mixture of cerium(III) and cerium(IV) complex comprising cerium(III) 2-ethylhexanoate and aqua(2-N-(2-hydroxyethylimino)-4-pentanoate)dinitrocerium(IV) [Ce(L1)(H.sub.2O)(NO.sub.3).sub.2].

10. A process for preparation of a homogenous catalyst composition doped liquefied petroleum gas (LPG), the process comprising: (a) mixing cerium(III) 2-ethylhexanoate along with aqua(2-N-(2-hydroxyethylimino)-4-pentanoate)dinitrocerium(IV) [Ce(L1)(H.sub.2O)(NO.sub.3).sub.2] in hexane to form a solution, wherein L1 is 2-N-(2-hydroxyethylimino)-4-pentanoate; and (b) adding the solution of step (a) to liquefied petroleum gas (LPG) in a compressed gas cylinder.

Description

EXAMPLES

[0064] Having described the basic aspects of the present invention, the following non-limiting examples illustrate specific embodiments thereof. Those skilled in the art will appreciate that many modifications may be made in the invention without changing the essence of the invention.

Example 1: Synthesis of Ce(III) and Ce(IV) Complexes

(A) Synthesis of 2-N-(2-Hydroxyethylimino)-4-pentanone (L1)

[0065] A methanol solution of 2-aminoethanol (36.6 g, 0.6 mol) was added dropwise to a stirred solution of pentane-2,4-dione (60.1 g, 0.6 mol) in methanol keeping the total volume to be 600 mL. Sodium sulfate was added to remove the water generated during the condensation reaction and the mixture was stirred for 12 hours. The resulting yellow solution was diluted by addition of dichloromethane and filtered, and the solvent was removed under reduce pressure to afford 98% yield (84.3 g).

##STR00004##

(B) Synthesis of aqua(2-N-(2-hydroxyethylimino)-4-pentanoate)dinitrocerium (IV) [Ce(L1)(H.SUB.2.O)(NO.SUB.3.).SUB.2.]: CeC1

[0066] In an oven-dried single-neck round-bottom flask, L1 (143.21 mg, 1.2 mmol) was taken in a 5 mL of dimethylformamide (DMF) solvent. The temperature was kept at 100? C. and 0.5 mL aqueous solution of Ce(NO.sub.3).sub.3.Math.6H.sub.2O (130.3 mg, 0.3 mmol) was added dropwise. Upon completion of addition, the temperature was raised to 150? C. and kept for 15 hours. Afterwards, methanol was added to obtain a dark brown precipitate and washed thoroughly with methanol, ethanol, and ether several times until clear filtrate.

[0067] The CeC1 complex was characterized using IR and NMR analysis. The characterization data includes IR (neat, cm.sup.?1) 1516, 1349, 1062, 827; .sup.1H NMR (500 MHz, DMSO-d.sub.6): ? 8.31 (s, 1H), 1.90 (s, 1H), 1.23 (s, 2H), 0.85 (s, 1H), ?0.09 (m, 6H).

##STR00005##

(C) Synthesis of tetraacetylacetonatecerium (IV) [Ce(acac).SUB.4.]: CeC2

[0068] In an oven-dried single-neck round-bottom flask, acetyl acetone (300.39 mg, 3 mmol) and triethyl amine (303.57 mg, 3 mmol) were dissolved in 25 mL methanol. Ce(NO.sub.3).sub.3.Math.6H.sub.2O (217.22 mg, 0.5 mmol) was separately dissolved in 10 mL methanol. The metal solution was dropwise added to the ligand solution under magnetic stirring at room temperature. Then the resulting solution was heated for 15 hours at 45? C. Afterwards the solution was evaporated and washed with methanol, ethanol, and diethyl ether several times until clear filtrate. Finally, the resulting powdered complex was dried under vacuum system.

##STR00006##

(D) Synthesis of cerium(III) 2-ethylhexanoate: (CeC3)

[0069] In an oven-dried single-neck round-bottom flask, sodium hydroxide (240.6 g, 6.015 mol) was dissolved in 1.5 L Millipore water and stirred for about 30 minutes before cooling to room temperature. To this solution, 2-Ethylhexanoic acid (867.7 g, 6.016 mol) was added and stirred for about 2 hours to form a uniform monolayer solution of sodium 2-Ethylhexanoate. To this prepared solution of sodium 2-Ethylhexanoate, cerium nitrate hexahydrate (653 g, 1.503 mol) was added and stirred well for 5 h. The solid obtained was dissolved in 2 L of n-hexane and water has been separated by using the separating funnel, dried over Na.sub.2SO.sub.4, evaporation of n-hexane on rotary evaporator at 60? C. for 1 h resulted in cerium(III) 2-Ethylhexanoate.

[0070] The CeC3 complex was characterized using IR and NMR analysis. The characterization data includes IR (neat, cm.sup.?1) 2959, 2873, 2861, 1696, 1536, 1459, 1381, 1319, 1295, 1269, 1227. .sup.1H NMR (500 MHz, CDCl.sub.3): ? 0.70-0.92 (m, 10H), 0.94-1.24 (m, 2H), 1.30-1.53 (m, 2H), 2.43 (s, 1H).

Example 2: Preparation of Mixture of Ce(III) and Ce(IV) Complex

[0071] A mixture is prepared comprising cerium(III) and cerium(IV) complex, i.e., cerium(III) 2-ethylhexanoate (CeC3) and aqua(2-N-(2-hydroxyethylimino)-4-pentanoate)dinitrocerium (IV) [Ce(L1)(H.sub.2O)(NO.sub.3).sub.2] (CeC1).

Example 3: Preparation of Homogenous Cerium Catalyst Doped LPG

[0072] 1.266 g of cerium(III) 2-ethylhexanoate (CeC3) along with 0.633 g of aqua(2-N-(2-hydroxyethylimino)-4-pentanoate)dinitrocerium (IV) [Ce(L1)(H.sub.2O)(NO.sub.3).sub.2] (CeC1) is dissolved in 100 ml of hexane to form a solution. Therefore, the weight ratio of Ce(III) to Ce(IV) is 2:1. 10 ml of this solution is then added to 19 kg of LPG in a compressed cylinder. This refers to the composition of Cat-III and is further used in Example 4 for the combustion and optimization studies.

Example 4: Combustion Studies and Optimization of Catalyst Composition

[0073] It is known that catalytic combustion by heterogeneous catalysts is often facilitated by lattice defects in the form of variable oxidation states of the same metal or by a different metal dopant in the lattice. Cerium (Ce) is often preferred as an active metal in combustion catalysts because of its multiple stable oxidation states with relatively low potential barrier between them. In a study of the present invention, the inventors have optimized organo-cerium complexes of different oxidation states and evaluated their efficiency for LPG combustion.

(A) Increase in Flame Temperature for Catalyst Composition

[0074] For purpose of the experiment, metal additives with 10 ppm (weight/weight) concentration were added to the LPG fuel and combusted in conventional brass burners under ambient air flow. LPG flow rate was kept constant at 10 g/min through a mass flow controller. The flame temperature was measured through forward-looking infrared (FR) camera. For the study, the camera was set at a fixed distance of one meter from the flame at an elevation angle of 300. The complete flame temperature profile was captured through a high resolution camera in 1 FPS. For each test, 1000 frames were recorded. An average flame temperature, at a fixed coordinate, was calculated over a continuous 100 frames (frame no 501-600) for a quantitative comparison. The results obtained are discussed in Table 1.

TABLE-US-00001 TABLE 1 FLIR temperature measurements with varying catalyst composition Total Average flame concentration temperature of catalyst Relative ratio of metal complexes in LPG over 100 (in ppm (W/W)) Tris-2- frames at the Sr. Catalyst of the total LPG ethylhexanoate burner tip No. Composition composition iron (III) complex CeC3 CeC2 CeC1 (? C.) 1. Blank 10 0 0 0 0 1539 2. Cat-Fe 10 1 0 0 0 1555 3. CeC3 10 0 1 0 0 1641 4. CeC2 10 0 0 1 0 1561 5. CeC1 10 0 0 0 1 1594 6. Cat-I 10 0 1 0 2 1621 7. Cat-II 10 0 1 0 1 1657 8. Cat-III 10 0 2 0 1 1680 9. Cat-IV 10 0 3 0 1 1607

[0075] As can be seen from the results of Table 1, up to 10% rise in flame temperature was noticed when homogenous cerium catalysts were added to the LPG which is significantly higher as compared to comparable Iron complex, Tris-2-ethylhexanoate iron (III) complex. Optimized weight ratio of 2:1 of CeC3 (Ce(III) complex) and CeC1(Ce(IV) complex) increased the flame temperature to maximum. The synergistic effect between mixed oxidation state complexes is evident as the increase in flame temperature in the mixed catalytic system is significantly higher than when dosed individually.

[0076] Table 2 discloses the FUR temperature measurements with varying catalyst composition in terms of weight percentage.

TABLE-US-00002 TABLE 2 FLIR temperature measurements with varying catalyst composition (wt. %) Total Average flame concentration temperature of catalyst Relative wt. % of metal complexes in LPG over 100 (in ppm (W/W)) Tris-2- frames at the Sr. Catalyst of the total LPG ethylhexanoate burner tip No. Composition composition iron (III) complex CeC3 CeC2 CeC1 (? C.) 1. Blank 10 0 0 0 0 1539 2. Cat-Fe 10 100 0 0 0 1555 3. CeC3 10 0 100 0 0 1641 4. CeC2 10 0 0 100 0 1561 5. CeC1 10 0 0 0 100 1594 6. Cat-I 10 0 33.33 0 66.66 1621 7. Cat-II 10 0 50 0 50 1657 8. Cat-III 10 0 66.66 0 33.33 1680 9. Cat-IV 10 0 75 0 25 1607

[0077] As seen from Table 2, the Ce(III) complex is present in an amount ranging from 33-100 wt. % and the Ce(IV) complex is present in an amount ranging from 25-100 wt. % of the total catalyst composition.

(B) Increase in Flame Temperature for Catalyst Concentration

[0078] Further studies were carried out with the same catalyst composition (Cat-III), i.e., 2:1 ratio of CeC3 (Ce(III) complex) and CeC1(Ce(IV) complex). The effect of catalyst concentration is evaluated with FLIR camera under the same experimental conditions and is disclosed in Table 3.

TABLE-US-00003 TABLE 3 FLIR measurements at different dosage of Cat (III) Concentration of the catalyst Concentration of Concentration of Average flame mixture (in ppm) Ce(III) (in ppm) of Ce(IV) (in ppm) of temperature over 100 Sr. of the total LPG the total LPG the total LPG frames at the burner No composition composition composition tip (? C.) 1. 0 0 0 1539 2. 2.5 1.66 0.83 1579 3. 5 3.33 1.66 1614 4. 7.5 5.0 2.5 1649 5. 10 6.66 3.33 1680 6. 12.5 8.33 4.16 1697 7. 15 10 5 1707 8. 20 13.33 6.66 1712

[0079] It is observed from Table 3 that the flame temperature increases with increasing concentration of the catalyst. Flame temperature increases linearly with increasing concentration of catalyst mixture and is optimum at about 12.5 ppm concentration of catalyst mixture, beyond which the rate of increase decreases. The maximum increase in flame temperature is up to 10% due to addition of homogenous Ce catalyst mixture to LPG fuel. Additionally, the concentration of Ce(III) complex varies from 1.5-15 ppm and the concentration of Ce(IV) complex varies from 0.8-10 ppm of the total LPG composition.

(C) Effect on Cooking Time and LPG Consumption

[0080] To check the effect on cooking time and LPG consumption, the following experiment was performed. 1 kg of Millipore water (resistivity@ 25? C.: 18 M?-cm) was heated in a 1.5 Liter closed, insulated, adiabatic chamber from 25? C. to 100? C. by combusting varied concentration of catalyst doped LPG (2:1 ratio). The results are disclosed in Table 4.

TABLE-US-00004 TABLE 4 FLIR measurements at varying dosage of Cat (III) Concentration of the catalyst Concentration of Concentration of mixture (in ppm) Ce(III) (in ppm) Ce(IV) (in ppm) Time taken to LPG Sr. of the total LPG of the total LPG of the total LPG reach 100? C. consumed No composition composition composition (Sec) (g) 1. 0 0 0 347 58 2. 2.5 1.66 0.83 339 56.5 3. 5 3.33 1.66 334 55.5 4. 7.5 5.0 2.5 327 54.5 5. 10 6.66 3.33 325 54 6. 12.5 8.33 4.16 324 54 7. 15 10 5 321 53.5 8. 20 13.33 6.66 319 53.2

[0081] As can be seen from the results of Table 4, both heating time and fuel consumed decreased steadily with increased dosage. As mentioned earlier, the lower LPG fuel consumption can be correlated better to the soot combustion efficiency of the LPG rather than the flame temperature or faster kinetics alone.

(E) Effect on Soot Combustion

[0082] Direct evidence for more efficient soot combustion was obtained through x-ray photoelectron spectroscopy (XPS) spectroscopy. Soot was collected from the individual burner orifices before and after 120 mins of LPG combustion. C1s peak was monitored to analyze various oxidation states of carbon found in the soot. HR spectra was recorded for C1s peak with Al K? source at 1486.4 eV with 0.5 eV step size in binding energy mode. The obtained spectra were deconvoluted and analyzed and results are listed in the Table 5.

TABLE-US-00005 TABLE 5 XPS intensity for C1S peak Intensity (cps) Blank LPG (without catalyst) LPG with 10 ppm of Cat-III Peak Assigned % of % of % of % of position C-bonding/ total t = 120 total total t = 120 total (in eV) oxidation state t = 0 Carbon mins Carbon t = 0 Carbon mins Carbon 284.4 sp.sup.2 C (C?C) 1458 64 1911 61.8 1832 60.6 1743 61.2 285.2 sp.sup.3 C (CC) 754 33 1091 35.4 1103 36.5 821 28.8 286.7 COH 67 3 64 2.0 81 2.7 201 7 288.4 C?O 4 0 17 0.8 8 0.2 87 3

[0083] Normalized percentages of individual carbon types were considered for analysis. As can be seen from Table 5, the deconvoluted peaks arising at 286.7 and 288.4 were assigned to oxygenated carbon species. Therefore, increased percentage of these peaks would invariably indicate greater degree of combustion. Blank LPG showed no appreciable change in the total 5 percentage of the oxygenated species. It rather showed a small decrease from 3.0% for 0 mins to 2.8% upon 120 mins of combustion (addition of 286.7 and 288.4 eV peaks). LPG fuel doped with 10 ppm of Cat-III, on the other hand, showed a remarkable increase from 2.9% for 0 mins to 10% upon 120 mins of combustion of the total oxygenated species (addition of 286.7 and 288.4 eV peaks). The results clearly demonstrate more efficient soot combustion in case of additive doped LPG which in turn also improves LPG combustion efficiency.