Homogeneous catalyst composition for improving LPG combustion

Abstract

The present invention discloses a homogeneous cerium (Ce) catalyst composition comprising a Ce(IV) complex alone or in a mixture with a Ce(III) complex that can significantly improve both LPG and soot combustion, increasing flame temperature, heating faster, cooking time shorter, and lowering 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)(H2O)(NO3)2], where L1 is 2-N-(2-hydroxyethylimino)-4-pentanone.

Description

Technical Field

[0001] The present invention relates to a homogeneous cerium (Ce) catalyst composition containing a Ce(IV) complex alone or a Ce(IV) complex in a mixture with a Ce(III) complex, which can significantly improve the combustion of liquefied petroleum gas (LPG). When this catalyst composition is added to an LPG fuel, while reducing the LPG consumption, the flame temperature and heating rate are significantly improved. The present invention also relates to a method for producing a homogeneous catalyst composition and a method for producing an LPG fuel doped with the homogeneous catalyst composition.

Background Art

[0002] The combustion of C3 / C4 hydrocarbons, which are the main components of cooking gas LPG, is a complex phenomenon and is deterministically determined by several major parameters such as composition, calorific value of individual components, soot formation, and oxygen flow. Therefore, various possibilities are considered to improve the combustion efficiency. Also, the heat generated per unit mass of fuel directly depends on the composition of the hydrocarbon, i.e., the C3 / C4 ratio, the presence or absence of C3 / C4 olefins, etc. However, considering that the composition of LPG is optimal and depends on various external factors, using a catalyst is the only effective way to improve LPG combustion kinetics.

[0003] Several such catalysts for improving hydrocarbon combustion have been reported in the literature. U.S. Patent No. 5236467 by Excellene Ltd. discloses the use of methyl ethyl ketone and methyl tert-butyl ether for torch gas. U.S. Patent No. 3591355 by I G Corp. proposes the addition of a mixture of liquid alkanols such as methanol and alkanes such as pentane and isopentane, while U.S. Patent No. 3989479 by an individual discloses adding methanol to improve the combustion kinetics of LPG. U.S. Patent No. 8163042 by Bharat Petroleum Corp. Ltd. reports adding an organometallic compound and an aromatic amine that reduce the combustion amounts of both fuel and oxygen to the base gas.

[0004] Furthermore, it may be considered that combustion improvers also improve the combustion kinetics of LPG. However, it should be noted that none of these additives / combustion improvers can adjust the theoretical calorific value of LPG at all. In principle, the use of any combustion booster / combustion improver speeds up the kinetics, thus speeding up the cooking. However, since combustion boosters / combustion improvers cannot affect the thermodynamics of the process, nothing can improve the overall heat output from LPG combustion.

[0005] It should be noted that in order to achieve the maximum calorific value of a given LPG fuel, complete combustion must occur in the presence of stoichiometric amounts of oxygen. In such combustion, an "oxidizing flame" with abundant oxygen, blue color, and low luminosity is produced. However, under actual cooking conditions, soot and other deposits are formed in the pores and openings of the burner, so LPG fuel often obtains less oxygen than the stoichiometric requirements. As a result, LPG burns at a low flame temperature with high luminosity. Therefore, it is considered important to burn soot in order to achieve an optimal flame and maximum calorific value, which will significantly reduce the consumption of LPG fuel.

[0006] Lanthanides, especially cerium (Ce) oxides and complexes, have been widely used as combustion-improving catalysts. There are many prior literatures using homogeneous Ce-based catalysts to significantly improve propane combustion and lower the complete combustion temperature. However, there are very few corresponding literatures on homogeneous Ce complexes.

[0007] U.S. Patent No. 8,741,798 to an individual discloses a catalyst for hydrocarbon oxidation containing cerium (III) 2-ethylhexanoate which provides improvements in hydrocarbon oxidation, i.e., efficient oxidation, temperature reduction, and fuel consumption improvement. In the oxidation experiments of diesel fuel using these catalysts, the total fuel consumption was reduced by about 10% - 20%.

[0008] U.S. Patent Application No. 4264335 by Chevron USA Inc. discloses suppressing an increase in the octane requirement of gasoline by incorporating a small amount of cerium(III) or cerium(IV) 2-ethylhexanoate into gasoline. The fuel composition comprises a large amount of gasoline and about 0.05 to about 10 g of a cerium(III) or cerium(IV) salt of 2-ethylhexanoic acid per gallon of gasoline in solution.

[0009] U.S. Patent Application No. 4424165 by Corning Glass Works discloses a β-diketonate complex of Ce +3 MCe(fod)4, where M is selected from the group of Na, Li, K, Cs, and Rb. The complex Ce(fod)4 offers significant advantages over prior art cerium β-diketonate complexes in both thermal stability and volatility. This complex is stable against decomposition at a sufficiently high temperature. This complex is prepared by using a methanol solution of cerium nitrate (Ce(NO3)3·6H2O), a methanol solution of Hfod, NaOH, and hexane. The product is a crystalline mixture of NaCe(fod)4 and Ce(fod)4.

[0010] U.S. Patent Application No. 5449387 by Rhodia Ltd. discloses a novel cerium(IV) oxidation compound having the chemical formula (H2O) p [CeO(A)2·(AH) n m which is suitable as a catalyst, for example, for the clean combustion of hydrocarbon fuels. These cerium(IV) oxidation compounds may be incorporated into the filter or soot trap (reservoir) of a vehicle exhaust pipe, which are designed to capture carbon-containing particles generated by the combustion of various combustible substances or fuels.

[0011] ​Osvaldo A. Serra et al. disclose the synthesis of cerium(III) β-diketonate Ce(hdacac)3(Hhdacac)3·2H2O, which serves as a catalyst for reducing soot emissions in diesel / biodiesel applications. Due to the amphiphilic nature of the substance, this complex can dissolve in nonpolar fuels and thus generate cerium(IV) oxide particles that efficiently catalyze the oxidation of diesel / biodiesel soot. Furthermore, this complex can function as a soluble precursor for homogeneous CeO2 spherical nanoparticles.

[0012] Ziang Su et al. are associated with the design of homogeneous interfaces that can be a novel method for enhancing the catalytic combustion performance of metal oxide catalysts. When a mesocrystalline CeO2 catalyst with abundant Ce-Ce homogeneous interfaces is synthesized by the self-flaming method, this catalyst exhibits improved catalytic performance. CeO2 mesocrystals have excellent redox properties and oxygen storage capacity by forming various oxygen vacancies.

[0013] The inventors of the present invention have endeavored to develop a homogeneous catalyst composition for cooking gas LPG that can significantly reduce the cooking time and LPG fuel consumption. The homogeneous catalyst composition contains a Ce(IV) complex. To utilize the low redox potential barrier between the +3 and +4 oxidation states of cerium, which is predicted to enhance the catalytic performance, the homogeneous cerium catalyst composition also contains a mixture of Ce(IV) complex and Ce(III) complex in an optimal ratio. Furthermore, the ligand structure has been synthetically improved to enhance the catalytic performance. The resulting catalyst composition helps to simultaneously improve soot and LPG combustion, thereby ensuring that the combustion kinetics are accelerated and the oxygen availability is increased as the flame approaches the LPG fuel. This results in a higher flame temperature, faster heating, and lower fuel consumption. Summary of the Invention

[0014] The present invention discloses a homogeneous cerium (Ce) catalyst composition comprising a Ce(IV) complex alone or a Ce(IV) complex in a mixture with a Ce(III) complex, which can improve the combustion of LPG. The catalyst composition also improves the combustion of soot, increases the flame temperature, accelerates heating, and reduces fuel consumption. The Ce(III) complex is cerium(III) 2-ethylhexanoate, and the Ce(IV) complex is aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2], where L1 is 2-N-(2-hydroxyethylimino)-4-pentanone.

[0015] Technical advantages of the invention The present invention has the following advantages over the cited prior art. (i) Both Ce(III) (cerium(III) 2-ethylhexanoate) and Ce(IV) (aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2]) complexes individually increase the flame temperature, but a positive synergistic effect is observed for the mixture of Ce(III) and Ce(IV) complexes. The Ce-C1 complex, namely aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2], in particular shows a significant improvement in performance compared to a similar β-diketonate, the Ce-C2 complex, namely cerium(IV) tetraacetylacetonate. This can be attributed to the ligand L1 present in the Ce-C1 complex, which is specifically designed to improve the nucleophilicity of acetylacetone. The increase in flame temperature by adding the homogeneous Ce catalyst composition to the LPG fuel is up to 10%. Also, the highest flame temperature is achieved at an optimal weight ratio of 2:1 of the Ce(III) and Ce(IV) complexes. The flame temperature increases linearly with the increase in the concentration of the catalyst composition, and is optimal at a concentration of about 12.5 ppm of the catalyst composition, and the rate of increase decreases beyond this concentration. (ii) The catalyst composition helps to improve the combustion of soot, thereby making it easier for oxygen to approach the LPG fuel, and thus reducing the LPG fuel consumption. (iii) The catalyst composition accelerates heating, thereby reducing the cooking time. (iv) A linear decrease in heating time and fuel consumption is observed as the concentration of the catalyst composition increases.

[0016] Object of the Invention To provide a homogeneous catalyst 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 the cerium (IV) complex is aqua(2-N-(2-hydroxyethylimino)-4-pentanoato)dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2], where L1 is 2-N-(2-hydroxyethylimino)-4-pentanone, is the main object of the present invention.

[0017] Another object of the present invention is to provide a homogeneous catalyst composition for improving LPG combustion.

[0018] A method for producing a homogeneous catalyst composition, the process comprising the synthesis of 2-N-(2-hydroxyethylimino)-4-pentanone (L1), the synthesis of aqua(2-N-(2-hydroxyethylimino)-4-pentanoato)dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2]:Ce-C1, the synthesis of cerium(IV) tetraacetylacetonate [Ce(acac)4]:Ce-C2, the synthesis of cerium(III) 2-ethylhexanoate:Ce-C3, and the preparation of a mixture of cerium(III) and cerium(IV) complexes comprising cerium(III) 2-ethylhexanoate (Ce-C3) and aqua(2-N-(2-hydroxyethylimino)-4-pentanoato)dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2] (Ce-C1), is another object of the present invention.

[0019] Yet another object of the present invention is to provide a method for producing LPG doped with a homogeneous cerium catalyst composition. Abbreviations Ce: Cerium Cerium(III): Ce(III) Cerium(IV): Ce(IV) LPG: Liquefied Petroleum Gas [Ce(acac)4]: Cerium(IV) tetraacetylacetonate L1: 2-N-(2-Hydroxyethylimino)-4-pentanone Ce-C1: Aqua(2-N-(2-hydroxyethylimino)-4-pentanoato)dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2] Ce-C2: Cerium(IV) tetraacetylacetonate [Ce(acac)4] Ce-C3: Cerium(III) 2-ethylhexanoate IR: Infrared spectroscopy NMR: Nuclear magnetic resonance spectroscopy XPS: X-ray photoelectron spectroscopy FLIR: Forward-looking infrared DMF: Dimethylformamide

Best Mode for Carrying Out the Invention

[0020] Those skilled in the art will understand that the present disclosure may be subject to variations and modifications other than those clearly described herein. It should be understood that all such variations and modifications are included in the present disclosure. The present disclosure also includes, individually or collectively, all such method steps, system features, and all combinations of any one or more of such steps or features mentioned or shown herein.

[0021] Definitions Before further describing the present disclosure, for convenience, certain terms and examples used in this application are gathered here. These definitions should be read in light of the remainder of the present disclosure and understood as would be understood by those skilled in the art. The terms used herein have the meanings of terms recognized and known to those skilled in the art, but for convenience and completeness, specific terms and their meanings are set forth below.

[0022] The articles "a", "an", and "the" are used to refer to one or more (i.e., at least one) grammatical objects of the article.

[0023] The terms "comprise" and "comprising" are used in an inclusive, open sense that may include additional elements and are not intended to be construed as "consisting of only".

[0024] Throughout this application, unless the context requires otherwise, the words "comprise", "comprises", and variations such as "comprising" are understood to mean including the stated element or step or group of elements or steps but not excluding any other element or step or group of elements or steps.

[0025] The term "including" is used to mean "including but not limited to". "Including" and "including but not limited to" are used interchangeably. g but not limited to)" are used interchangeably. limited to)" are used interchangeably.

[0026] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the technical documents to which this disclosure pertains. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of this disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference.

[0027] The present disclosure should not be limited by the specific embodiments described herein, and the specific embodiments are intended for illustrative purposes only. Functionally equivalent products and processes are clearly within the scope of the present disclosure as described herein.

[0028] The present invention relates to a homogeneous Ce catalyst composition for improving the combustion of liquefied petroleum gas (LPG). This composition contains a Ce(IV) complex alone or a Ce(IV) complex in a mixture with a Ce(III) complex, which is cerium(III) 2-ethylhexanoate, and this Ce(IV) complex is aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2], where L1 is 2-N-(2-hydroxyethylimino)-4-pentanone.

[0029] In yet another embodiment, the catalyst composition is present in a concentration range of 2.5 to 20 ppm of the total LPG fuel composition.

[0030] In another embodiment of the present invention, among the total catalyst composition, the Ce(III) complex is present in an amount of 33 to 100% by weight, and the Ce(IV) complex is present in an amount of 25 to 100% by weight.

[0031] In another embodiment of the present invention, the cerium(III) and cerium(IV) complexes in the mixture are present in a weight ratio of 1:1 to 3:1, and the optimal weight ratio is 2:1.

[0032] In another embodiment, the homogeneous cerium catalyst mixture contains a Ce(III) complex, namely cerium(III) 2-ethylhexanoate, at a concentration of 1.5 to 15 ppm, and a Ce(IV) complex, namely aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2], at a concentration of 0.8 to 10 ppm.

[0033] In another embodiment of the present invention, both Ce(III)(cerium(III) 2-ethylhexanoate) and Ce(IV)(aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2]) complexes individually increase the flame temperature, but a positive synergistic effect is observed for the mixture of Ce(III) and Ce(IV) complexes. The increase in flame temperature by adding a homogeneous Ce catalyst mixture to LPG fuel is up to 10%. Also, the highest flame temperature is achieved at an optimal weight ratio of 2:1 for the Ce(III) and Ce(IV) complexes. The flame temperature increases linearly as the concentration of the catalyst mixture increases, and is optimal at a concentration of about 12.5 ppm of the catalyst mixture, and the rate of increase decreases beyond this concentration.

[0034] In another embodiment, a method for producing a homogeneous Ce catalyst composition includes the following. (a) Synthesis of 2-N-(2-hydroxyethylimino)-4-pentanone (L1 ) by reacting acetylacetone and ethanolamine in a methanol solution and stirring for 24 hours.

Chemical formula

Chemical formula

[0035] In another embodiment, the Ce-C1 complex, namely aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2], exhibits a significant improvement in performance compared to the Ce-C2 complex, namely cerium(IV) tetraacetylacetonate. This can be attributed to the ligand L1, which increases the effectiveness of the electrons of the complexed metal center (Ce(IV) complex) and modifies it from acetylacetonate to reduce the formal charge of the complexed metal center (Ce(IV) complex). Thereby, the catalytic efficiency of the redox pair (Ce(III) and Ce(IV) complexes) is significantly improved. ton.

[0036] In another embodiment, a method for producing LPG doped with a homogeneous catalyst composition is (a) Step of mixing cerium(III) 2-ethylhexanoate (Ce-C3) with aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2] (Ce-C1) in hexane to form a solution, and (b) including the step of adding the solution of step (a) to the LPG fuel in a compression cylinder.

[0037] In another embodiment, the aforementioned catalyst composition reduces the formation of soot during LPG combustion.

[0038] In another embodiment, the aforementioned catalyst composition increases the heating rate, thereby reducing the cooking time and LPG fuel consumption.

Example

[0039] Since the basic aspects of the present invention have been described, specific embodiments of the basic aspects will be described using the following non-limiting examples. Those skilled in the art will understand that many modifications can be made to the present invention without changing the essence of the present invention.

[0040] Example 1: Synthesis of Ce(III) and Ce(IV) Complexes (A) Synthesis of 2-N-(2-hydroxyethylimino)-4-pentanone (L1): A methanol solution of 2-aminoethanol (36.6 g, 0.6 mol) was added dropwise to a stirred methanol solution of pentane-2,4-dione (60.1 g, 0.6 mol), and the total volume was kept at 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 adding dichloromethane, filtered, and the solvent was removed under reduced pressure to obtain a 98% yield (84.3 g).

Chemical formula

[0041] (B) Aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2]: Synthesis of Ce-C1 In a dried one-neck round-bottom flask in the furnace, L1 (143.21 mg, 1.2 mmol) was added to 5 mL of dimethylformamide (DMF). The temperature was maintained at 100 °C, and 0.5 mL of an aqueous solution of Ce(NO3)3·6H2O (130.3 mg, 0.3 mmol) was added dropwise. After the addition was complete, the temperature was raised to 150 °C and maintained for 15 hours. Then, methanol was added to obtain a dark brown precipitate, which was washed well with methanol, ethanol, and ether multiple times until the filtrate became clear.

[0042] The characteristics of the Ce-C1 complex were clarified using IR and NMR analyses. The characterization data are as follows: IR (neat, cm -1 ) 1516, 1349, 1062, 827; 1 1H NMR (500 MHz, DMSO-d6): δ 8.31 (s, 1H), 1.90 (s, 1H), 1.23 (s, 2H), 0.85 (s, 1H), -0.09 (m, 6H).

Chemical formula

[0043] (C) Cerium(IV) tetraacetylacetonate [Ce(acac)4]: Synthesis of Ce-C2 In a dried one-neck round-bottom flask in the furnace, acetylacetone (300.39 mg, 3 mmol) and triethylamine (303.57 mg, 3 mmol) were dissolved in 25 mL of methanol. Ce(NO3)3·6H2O (217.22 mg, 0.5 mmol) was dissolved separately in 10 mL of methanol. The metal solution was added dropwise to the ligand solution at room temperature with magnetic stirring. The resulting solution was heated at 45 °C for 15 hours. Then the solution was evaporated and washed well with methanol, ethanol, and diethyl ether multiple times until the filtrate became clear. Finally, the resulting powdered complex was dried in a vacuum system.

Chemical formula

[0044] (D) Synthesis of Cerium(III) 2-ethylhexanoate: (Ce-C3) In a one-neck round-bottom flask dried in the furnace, sodium hydroxide (240.6 g, 6.015 mol) was dissolved in 1.5 L of Millipore water, stirred for about 30 minutes, and then cooled 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 homogeneous monolayer solution of sodium 2-ethylhexanoate. To the prepared solution of sodium 2-ethylhexanoate, cerium(III) nitrate hexahydrate (653 g, 1.503 mol) was added and stirred well for 5 hours. The resulting solid was dissolved in 2 L of n-hexane, water was separated using a separatory funnel, dried over Na2SO4, and n-hexane was evaporated at 60 °C for 1 hour using a rotary evaporator to yield cerium(III) 2-ethylhexanoate.

[0045] The characteristics of the Ce-C3 complex were clarified using IR and NMR analyses. The characterization data are IR (neat, cm ―1 ) 2959, 2873, 2861, 1696, 1536, 1459, 1381, 1319, 1295, 1269, 1227. 1 1H NMR (500 MHz, CDCl3): δ 0.70 - 0.92 (m, 10H), 0.94 - 1.24 (m, 2H), 1.30 - 1.53 (m, 2H), 2.43 (s, 1H) are included.

[0046] Example 2: Preparation of a mixture of Ce(III) and Ce(IV) complexes A mixture containing cerium(III) and cerium(IV) complexes, namely cerium(III) 2-ethylhexanoate (Ce-C3) and aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2] (Ce-C1), is prepared.

[0047] Example 3: Preparation of LPG doped with a homogeneous cerium catalyst 1.266 g of cerium(III) 2-ethylhexanoate (Ce-C3) is dissolved in 100 ml of hexane together with 0.633 g of aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H2O)(NO3)2] (Ce-C1) to form a solution. Thus, the weight ratio of Ce(III) and Ce(IV) is 2:1. 10 ml of this solution is added to 19 kg of LPG in a compression cylinder. This refers to the composition Cat-III and is further used in Example 4 for combustion and optimization tests.

[0048] Example 4: Combustion test and optimization of catalyst composition Catalytic combustion by homogeneous catalysts is often promoted by lattice defects of various oxidation state forms of the same metal or by different metal dopants in the lattice. Cerium (Ce) is often preferred as the active metal of combustion catalysts because of its multiple stable oxidation states with a relatively low potential barrier between oxidation states. In the tests of the present invention, the inventors optimized organic cerium complexes with different oxidation states and evaluated the efficiency of the organic cerium complexes for LPG combustion.

[0049] (A) Increase in flame temperature of catalyst composition For experimental purposes, a metal additive with a concentration of 10 ppm (weight / weight) was added to the LPG fuel and burned with a conventional brass burner under ambient air flow. The LPG flow rate was kept constant at 10 g / min by a mass flow controller. The flame temperature was measured by a forward-looking infrared (FLIR) camera. For the test, the camera was set at a fixed distance of 1 m from the flame and an elevation angle of 30°. The complete flame temperature profile was captured by a high-resolution camera at 1 FPS. In each test, 1000 frames were recorded. The average flame temperature at fixed coordinates was calculated over 100 consecutive frames (frame numbers 501 - 600) for quantitative comparison. The results obtained are discussed in Table 1. [Table 1]

[0050] As can be seen from the results in Table 1, when the homogeneous cerium catalyst was added to LPG, it was found that the flame temperature increased by up to 10%, and this temperature was significantly higher compared to the equivalent iron complex, namely tris-2-ethylhe xanthate iron(III) complex. With the optimized weight ratios of 2:1 for Ce-C3 (Ce(III) complex) and Ce-C1 (Ce(IV) complex), the flame temperature increased to its maximum value. Since the increase in the flame temperature of the mixed catalyst system is significantly higher than when added individually, the synergistic effect between the mixed oxidation state complexes is evident.

[0051] Table 2 discloses FLIR temperature measurements using various catalyst compositions in terms of weight percent.

Table 2

[0052] As can be seen from Table 2, among all the catalyst compositions, the Ce(III) complex is present in an amount of 33 - 100 weight percent, and the Ce(IV) complex is present in an amount of 25 - 100 weight percent.

[0053] (B) Increase in Flame Temperature with Respect to Catalyst Concentration Further tests were conducted using the same catalyst composition (Cat-III), namely the ratio of 2:1 of Ce-C3 (Ce(III) complex) and Ce-C1 (Ce(IV) complex). The effect of the catalyst concentration was evaluated by an FLIR camera under the same experimental conditions and is disclosed in Table 3.

Table 3

[0054] From Table 3, it is observed that the flame temperature increases as the catalyst concentration increases. The flame temperature increases linearly as the concentration of the catalyst mixture increases, and it is optimal at a concentration of about 12.5 ppm of the catalyst mixture. Beyond this concentration, the rate of increase decreases. The maximum increase in the flame temperature by adding a homogeneous Ce catalyst mixture to the LPG fuel is up to 10%. Furthermore, the concentration of the Ce(III) complex in the total LPG composition varies from 1.5 to 15 ppm, and the concentration of the Ce(IV) complex varies from 0.8 to 10 ppm.

[0055] (C) Effects on cooking time and LPG consumption To examine the effects on cooking time and LPG consumption, the following experiment was conducted. 1 kg of Millipore water (resistivity at 25 °C: 18 MΩ-cm) was heated from 25 °C to 100 °C in a 1.5 L sealed adiabatic chamber by burning LPG (2:1 ratio) doped with catalysts at various concentrations. The results are disclosed in Table 4. [Table 4]

[0056] As can be seen from the results in Table 4, both the heating time and the consumed fuel steadily decreased as the addition amount increased. As mentioned previously, the decrease in LPG fuel consumption can be better correlated with the soot combustion efficiency of LPG than with the flame temperature or the fast reaction rate alone.

[0057] (E) Efficiency for soot combustion Direct evidence for more efficient soot combustion was obtained by X-ray photoelectron spectroscopy (XPS). Soot was collected from the openings of individual burners before and 120 minutes after LPG combustion. The C1s peak was monitored to analyze the various oxidation states of carbon found in the soot. The HR spectrum of the C1s peak was recorded at a step size of 0.5 eV using an AlKα line species with a binding energy mode of 1486.4 eV. The obtained spectra were deconvolved, analyzed, and the results are shown in Table 5. [Table 5]

[0058] The normalized ratios of the individual carbon species were examined for analysis. As seen in Table 5, the deconvoluted peaks occurring at 286.7 and 288.4 were attributed to oxygenated carbon species. Thus, an increase in the ratio of these peaks always indicates a higher degree of combustion. The blank LPG did not show a perceptible change in the ratio of all oxygenated species. Instead, the blank LPG showed a slight decrease in combustion from 3.0% at 0 min to 2.8% at 120 min (sum of 286.7 and 288.4 eV peaks). On the other hand, the LPG fuel doped with 10 ppm of Cat-III showed a significant increase in combustion of all oxygenated species from 2.9% at 0 min to 10% at 120 min (sum of 286.7 and 288.4 eV peaks). From these results, it is demonstrated that more efficient combustion of soot occurs in the case of LPG doped with additives, and the LPG combustion efficiency is improved when the soot is burned more efficiently.

Claims

1. A homogeneous catalyst composition for improving the combustion of liquefied petroleum gas (LPG), wherein the catalyst composition comprises a cerium (IV) complex in a mixture with a cerium (III) complex, the cerium (III) complex is cerium (III) 2-ethylhexanoate, The cerium (IV) complex is aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium (IV) [Ce(L1)(H ２ O)(NO ３ ) ２ , and L1 is 2-N-(2-hydroxyethylimino)-4-pentanone, the cerium (III) complex and the cerium (IV) complex are present in a weight ratio of 1:1 to 2:1, the cerium (III) complex is present in a concentration range of 1.5 to 15 ppm in the entire liquefied petroleum gas (LPG) composition, the cerium (IV) complex is present in a concentration range of 0.8 to 10 ppm in the entire liquefied petroleum gas (LPG) composition, catalyst composition.

2. The catalyst composition according to claim 1, wherein the cerium (III) complex and the cerium (IV) complex are present in a weight ratio of 2:

1.

3. The catalyst composition according to claim 1, wherein the catalyst composition raises the flame temperature of the liquefied petroleum gas (LPG) by up to 10%.

4. A liquefied petroleum gas (LPG) composition comprising the catalyst composition according to claim 1 and liquefied petroleum gas (LPG), wherein the catalyst composition is present in a concentration range of 2.5 to 20 ppm in the entire liquefied petroleum gas (LPG) fuel composition, liquefied petroleum gas (LPG) composition.

5. A method for producing a homogeneous catalyst composition for improving the combustion of liquefied petroleum gas (LPG), the method comprising (a) reacting acetylacetone and ethanolamine in a methanol solution and stirring for 24 hours to synthesize 2-N-(2-hydroxyethylimino)-4-pentanone (L1), (b) React L1 and Ce(NO ３ ) ３ ·6H ２ O in a dimethylformamide solvent at 150 °C for 15 hours to synthesize aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H ２ O)(NO ３ ) ２ , (c) By reacting acetylacetone, triethylamine and Ce(NO ３ ) ３ ·6H ２ O in a methanol solution, cerium(IV) tetraacetylacetonate [Ce(acac) ４ is synthesized, (d) reacting sodium 2-ethylhexanoate and cerium nitrate hexahydrate and stirring for 5 hours (e) Preparing a mixture of cerium(III) complexes and cerium(IV) complexes containing cerium(III) 2-ethylhexanoate and aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H ２ O)(NO ３ )( ２ )], to synthesize cerium (III) 2-ethylhexanoate, and the cerium (III) complex and the cerium (IV) complex are present in a weight ratio of 1:1 to 2:1, the cerium (III) complex is present in a concentration range of 1.5 to 15 ppm in the entire liquefied petroleum gas (LPG) composition, the cerium (IV) complex is present in a concentration range of 0.8 to 10 ppm in the entire liquefied petroleum gas (LPG) composition, method for producing a catalyst composition.

6. A method for producing a liquefied petroleum gas (LPG) composition doped with a homogeneous catalyst composition, the method comprising (a) Mixing cerium(III) 2-ethylhexanoate (cerium(III) complex) with aqua(2-N-(2-hydroxyethylimino)-4-pentanoic acid) dinitrocerium(IV) [Ce(L1)(H ２ O)(NO ３ ) ２ (cerium(IV) complex) in hexane to form a solution, where L1 is 2-N-(2-hydroxyethylimino)-4-pentanoic acid, the forming step, and (b) including the step of adding the solution of step (a) to liquefied petroleum gas (LPG) in a compressed gas cylinder, the cerium (III) complex and the cerium (IV) complex are present in a weight ratio of 1:1 to 2:1, the cerium (III) complex is present in a concentration range of 1.5 to 15 ppm of the whole liquefied petroleum gas (LPG) composition, the cerium (IV) complex is present in a concentration range of 0.8 to 10 ppm of the whole liquefied petroleum gas (LPG) composition, A method for producing a liquefied petroleum gas (LPG) composition.

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