WO2009022780A1

WO2009022780A1 - Method of preparing improved catalyst for production of acrylic acid

Info

Publication number: WO2009022780A1
Application number: PCT/KR2008/001126
Authority: WO
Inventors: Eun-Kyoung Song; Kyong-Yong Cha; Jin-Do Kim; Hyun-Ju Cho
Original assignee: Lg Chem, Ltd.
Priority date: 2007-08-13
Filing date: 2008-02-27
Publication date: 2009-02-19
Also published as: KR100954045B1; CN101778669B; JP5180303B2; CN101778669A; JP2010535628A; KR20090016919A

Abstract

The present invention provides a method of preparing an oxide catalyst for the production of acrylic acid by preparing a catalyst precursor from the solution mixture of molybdenum salt, vanadium salt, tellurium salt and niobium salt and drying and firing thereof. The present invention is characterized by the addition of acid complex mixture comprising carboxylic acid, peroxide and sulfuric acid compounds as an additive to obtain the catalyst precursor. According to the method of the invention, the oxide catalyst for the production of acrylic acid having excellent catalytic activity can be prepared.

Description

METHOD OF PREPARING IMPROVED CATALYST FOR PRODUCTION OF ACRYLIC ACID

Technical Field

[1] The present invention relates to a method of preparing an oxide catalyst for the production of acrylic acid, more precisely a method of preparing an oxide catalyst for the production of acrylic acid which facilitates the production of acrylic acid having enhanced activity, compared with the conventional catalyst for the production of acrylic acid, by preparing the catalyst precursor by adding acid complex mixture comprising carboxylic acid, peroxide and sulfuric acid compounds. Background Art

[2] To produce acrylic acid by direct oxidation of propane, studies have been focused on

4-components complicated oxide catalyst such as MoVTeNbO catalyst. Without changes of components of the catalyst, the improvement of reaction activity of the catalyst is still limited, resulting in unsatisfactory improvement of the catalytic activity. Therefore, it is required to develop a highly active catalyst having increased propane conversion rate and acrylic acid selectivity.

[3] As an effort to increase catalytic activity, the addition of additives has been tried. For example, according to Applied catalysis A: General VoI 257, Issue 1, 67(2004), the addition of nitric acid in the production of complicated oxide catalyst resulted in the increase of catalytic activity, which was the highest at around pH 2.0 - 2.5. However, the catalytic activity of the catalyst prepared by the above method was not good enough for commercialization and had the problem of narrow range of the activity. Korean Patent Publication No. 2001-006725 and US Paten No. 6,642,174B2 describe the production of complicated oxide catalyst of MoVTeNbO comprising the same composition as the one of the present invention. But at that time, no additives were used during the production of the catalyst and the activity of the produced catalyst was far behind that of the present invention.

[4] Therefore, it has been an urgent request to develop a novel method of preparing a catalyst for the production of acrylic acid which has improved activity in wider range. Disclosure of Invention Technical Problem

[5] It is an object of the present invention to provide a method of preparing a catalyst for the production of acrylic acid that has excellent propane conversion rate and acrylic acid selectivity during the production of acrylic acid by gas phase oxidation of propane and improved catalytic activity. Technical Solution

[6] The above object and other objects of the present invention can be achieved by the following embodiments of the present invention.

[7] The present invention is described in detail hereinafter.

[8] To achieve the above objects, the present invention provides a method of preparing an oxide catalyst for the production of acrylic acid comprising the steps of preparing a catalyst precursor from the solution mixture of molybdenum salt, vanadium salt, tellurium salt and niobium salt and drying and firing thereof. The method of the present invention characteristically includes the additional step of adding an additive to the solution mixture of those metal salts and at this time the additive is characteristically acid complex mixture comprising carboxylic acid, peroxide and sulfuric acid compounds.

[9] The oxide catalyst for the production of acrylic acid of the present invention prepared by the above method is represented by formula 1.

[10] Chemistry Figure 1

[Chem.l]

Moi.₀V_aTe_bNb_cO_n

[11] In the formula 1,

[12] Mo is molybdenum, V is vanadium, Te is tellurium and Nb is niobium;

[13] a, b, c and n indicate molar rate of vanadium, tellurium, niobium and oxygen atoms, respectively, which are 0.01<a<l;0.01<b<l;0.01<c≤l; and

[14] n is the number determined by atomic value and weight of another element.

[15] The present invention provides a method of preparing an oxide catalyst for the production of acrylic acid comprising the steps of preparing a catalyst precursor from the solution mixture of molybdenum salt, vanadium salt, tellurium salt and niobium salt and drying and firing thereof. The method of the present invention additionally includes the step of adding an additive to the solution mixture of those metal salts and at this time the additive is characteristically acid complex mixture comprising carboxylic acid, peroxide and sulfuric acid compounds.

[16] The method of the invention includes the step of preparing a solution mixture by nixing the compound mixture of molybdenum (Mo) salt, vanadium (V) salt, tellurium (Te) salt and niobium (Nb) salt with a solvent. The solvent herein is preferably selected from the group consisting of distilled water, alcohol, ether and carboxylate. In each metal salt compound, counter ion of a metal can be same or different. Particularly, molybdenum (Mo) salt, vanadium (V) salt and tellurium (Te) salt are dissolved in distilled water to prepare a solution mixture, to which niobium (Nb) salt dissolved in distilled water is added, followed by full mixing. The molybdenum (Mo) salt compound is exemplified by ammonium paramolybdate, molybdic acid, sodium molybdate and molybdenum trioxide. The vanadium (V) salt compound is exemplified by ammonium metavanadate, vanadium halide such as VCl ₄ and vanadium alkoxide such as VO(OC ₂H₅)₃. The tellurium (Te) salt compound is exemplified by telluric acid and tellurium dioxide, and the niobium (Nb) salt compound is exemplified by ammonium niobium oxalate, niobic acid, and niobium oxalate. When the niobium salt dissolved in distilled water is added separately, a precipitate is generated over the time, and even if the solution mixture is continuously stirred, the precipitate is still formed simply as being dispersed in the solution.

[17] The method of the invention includes the step of adding an additive into the above solution mixture. The additive used in this invention is acid complex compound comprising carboxylic acid, peroxide and sulfuric acid compounds. The sulfuric acid compound is preferably one or more compounds selected from the group consisting of sulfuric acid, particularly concentrated sulfuric acid at the concentration of at least 95%, ammonium sulfate and sulfur dioxide. The carboxylic acid is not limited to specific one, and any carboxylic acid having one or more functional groups can be accepted, but the carboxylic acid herein is preferably dicarboxylic acid such as oxalic acid, succinic acid, tartaric acid and glutamic acid. The peroxide is not limited and any organic or inorganic peroxide, for example, dialkyl peroxide or acyl peroxide can be used. In particular, hydrogen peroxide is more preferred considering easy handling and price.

[18] The content of each component included in the acid complex mixture is preferably

0.05 - 1.5 mol for 1 mol of molybdenum (Mo) atom added thereto as a form of molybdenum salt. If the content of each compound, particularly the content of the sulfuric acid compound is less than 0.05 mol for 1 mol of molybdenum atom, the catalyst will exhibit very low propane conversion rate and acrylic acid selectivity in the whole reaction temperature range. On the contrary, if the content is more than 1.5 mol, the catalyst will have rather high acrylic acid selectivity at low temperature but have very low propane conversion rate of up to 10%, and the selectivity will be rapidly decreased as temperature goes up.

[19] The additive included in the catalyst of the invention plays a role in improving the catalytic activity but at the same time it accelerates the precipitation of the catalyst precursor in the solution mixture of metal salts. Such precipitate of the catalyst precursor can be collected by evaporating distilled water, precisely by evaporating distilled water using a rotary vacuum dryer. The drying temperature is not limited but has to be the temperature causing effective evaporation of water, which is preferably around 100⁰C or up. The dried catalyst precursor is pulverized, ccmpression^rDlded by using an oil press, and then pulverized again. The obtained catalyst precursor particles are sieved to prepare even powder, followed by firing. The preferable particle size of the catalyst precursor particle is 100 - 300 μm. It is possible to perform firing right after the drying and pulverization of the catalyst precursor but it is preferred to firing thereof after compression molding and pulverizing. The reason to perform compression molding first is that the compression molding increases density of the catalyst so as to increase propane conversion rate during the propane-catalyst reaction.

[20] The method of the invention includes the step of firing the catalyst precursor to obtain the final catalyst. Firing is generally composed of two stages. The first stage is firing at 150 - 25O⁰C for 1 - 4 hours in the flow of air, and the second stage is firing at 500 - 65O⁰C for 1 - 4 hours in the flow of nitrogen or an inert gas.

[21] The oxide catalyst for the production of acrylic acid of the present invention prepared by the above method is represented by formula 1.

[22] [Chemistry Figure 1]

[23]

Moi_.0V_aTe_bNb_cO_n

[24] In the formula 1,

[25] Mo is molybdenum, V is vanadium, Te is tellurium and Nb is niobium;

[26] a, b, c and n indicate molar rate of vanadium, tellurium, niobium and oxygen atoms, respectively, which are 0.01<a≤l;0.01<b<l;0.01<c<l; and

[27] n is the number determined by atomic value and weight of another element.

[28] The catalyst of the invention is used for the production of acrylic acid by gas phase oxidation of propane with providing high propane conversion rate and acrylic acid selectivity. Brief Description of the Drawings [29] The application of the preferred embodiments of the present invention is best understood with reference to the accompanying drawings, wherein:

[30]

[31] Fig. 1 is a graph illustrating the propane conversion rate and acrylic acid selectivity during the production of acrylic acid by gas phase oxidation of propane according to the catalysts of examples and comparative examples. Best Mode for Carrying Out the Invention

[32] Practical and presently preferred embodiments of the present invention are illustrative as shown in the following Examples.

[33] However, it will be appreciated that those skilled in the art, on consideration of this disclosure, may make modifications and improvements within the spirit and scope of the present invention.

[34]

[35] Example 1

[36] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

0.352 g of telluric acid were dissolved in 50 m# of distilled water at room temperature, resulting in a clear solution. 4 m# of distilled water in which 0.3626 g of ammonium niobium oxalate was dissolved was added thereto, followed by stirring for 180 minutes to prepare a solution mixture.

[37] To the solution mixture were added 0.403 g of oxalic acid aqueous solution (oxalic acid was dissolved in distilled water at the concentration of 1 mol/kg of hydrogen ion), 0.918 g of sulfuric acid aqueous solution and 6.011 g of hydrogen peroxide aqueous solution (hydrogen peroxide was dissolved in distilled water at the concentration of 1 mol/kg), followed by stirring for 60 minutes.

[38] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 /M in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen. As a result, the final catalyst was prepared. The predicted composition of the catalyst was supposed to be Mo_{1 0}V₀₃Te₀₂₃Nb_{0 12}O_n based on the molar ratio of the metal salts. However, since the melting point of Te was comparatively low, which was 449.5⁰C, lots of Te was evaporated during the firing. Sb, the actual content of Te was lower than expected. This phenomenon was commonly observed in the following examples. [39] Example 2

[40] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

0.352 g of telluric acid were dissolved in 50 mi of distilled water at room temperature, resulting in a clear solution. 4 mi of distilled water in which 0.3626 g of ammonium niobium oxalate was dissolved was added thereto, followed by stirring for 180 minutes to prepare a solution mixture.

[41] To the solution mixture were added 0.75 g of oxalic acid aqueous solution (oxalic acid was dissolved in distilled water at the concentration of 1 mol/kg of hydrogen ion), 0.75 g of sulfuric acid aqueous solution and 7.5 g of hydrogen peroxide aqueous solution (hydrogen peroxide was dissolved in distilled water at the concentration of 1 mol/kg), followed by stirring for 60 minutes.

[42] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[43] Example 3

[44] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

0.352 g of telluric acid were dissolved in 50 mi of distilled water at room temperature, resulting in a clear solution. 4 m# of distilled water in which 0.3626 g of ammonium niobium oxalate was dissolved was added thereto, followed by stirring for 180 minutes to prepare a solution mixture.

[45] To the solution mixture were added 0.5 g of oxalic acid aqueous solution (oxalic acid was dissolved in distilled water at the concentration of 1 mol/kg of hydrogen ion), 1.0 g of sulfuric acid aqueous solution and 5.0 g of hydrogen peroxide aqueous solution (hydrogen peroxide was dissolved in distilled water at the concentration of 1 mol/kg), followed by stirring for 60 minutes.

[46] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[47] Example 4 [48] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

0.352 g of telluric acid were dissolved in 50 m# of distilled water at room temperature, resulting in a clear solution. 4 mi of distilled water in which 0.3626 g of ammonium niobium oxalate was dissolved was added thereto, followed by stirring for 180 minutes to prepare a solution mixture.

[49] To the solution mixture were added 1.0 g of oxalic acid aqueous solution (oxalic acid was dissolved in distilled water at the concentration of 1 mol/kg of hydrogen ion), 1.0 g of sulfuric acid aqueous solution and 0.5 g of hydrogen peroxide aqueous solution (hydrogen peroxide was dissolved in distilled water at the concentration of 1 mol/kg), followed by stirring for 60 minutes.

[50] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[51] Comparative Example 1

[52] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

0.352 g of telluric acid were dissolved in 50 mi of distilled water at room temperature, resulting in a clear solution. 4 mi of distilled water in which 0.3626 g of ammonium niobium oxalate was dissolved was added thereto, followed by stirring for 240 minutes to prepare a solution mixture.

[53] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[54] Comparative Example 2

[55] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

[56] To the solution mixture was added 0.918 g of sulfuric acid aqueous solution (sulfuric acid was diluted in distilled water at the concentration of 1 rnol/kg of hydrogen ion), followed by stirring for 60 minutes.

[57] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[58] Comparative Example 3

[59] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

[60] To the solution mixture was added 0.403 g of oxalic acid aqueous solution (oxalic acid was diluted in distilled water at the concentration of 1 mol/kg of hydrogen ion), followed by stirring for 60 minutes.

[61] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[62] Comparative Example 4

[63] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

[64] To the solution mixture was added 6.011 g of hydrogen peroxide aqueous solution

(hydrogen peroxide was diluted in distilled water at the concentration of 1 mol/kg), followed by stirring for 60 minutes.

[65] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[66] Comparative Example 5

[67] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

[68] To the solution mixture were added 0.403 g of oxalic acid aqueous solution (oxalic acid was dissolved in distilled water at the concentration of 1 mol/kg of hydrogen ion) and 6.011 g of hydrogen peroxide aqueous solution (hydrogen peroxide was dissolved in distilled water at the concentration of 1 mol/kg), followed by stirring for 60 minutes.

[69] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[70] Comparative Example 6

[71] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

[72] To the solution mixture were added 0.403 g of oxalic acid aqueous solution (oxalic acid was dissolved in distilled water at the concentration of 1 mol/kg of hydrogen ion) and 0.918 g of sulfuric acid aqueous solution, followed by stirring for 60 minutes.

[73] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[74] Comparative Example 7 [75] 1.178 g of ammonium paramolybdate, 0.234 g of ammonium metavanadate and

[76] To the solution mixture were added 1.0 g of oxalic acid aqueous solution (oxalic acid was dissolved in distilled water at the concentration of 1 mol/kg of hydrogen ion), 0.5 g of sulfuric acid aqueous solution and 1O g of hydrogen peroxide aqueous solution (hydrogen peroxide was dissolved in distilled water at the concentration of 1 mol/kg), followed by stirring for 60 minutes.

[77] Distilled water was evaporated by using a rotary vacuum dryer, which was further dried at 12O⁰C for complete drying and then pulverized to give a compact. The compact was pulverized again to give catalyst particles of 180 - 250 μm in particle size. The selected catalyst particles proceeded to the first firing at 200⁰C for 2 hours in the presence of air, followed by the second firing at 600⁰C for 2 hours in the presence of nitrogen.

[78] [Experimental Example]

[79] Selective oxidation of propane was induced by using the catalysts prepared in examples 1 - 4 and comparative examples 1 - 7.

[80] A fixed-bed type reactor was filled with 0.1 g of the catalyst, to which the supply gas

(propane:oxygen:nitrogen:water = 5.85:11.69:58.02:24.44) was inserted at 340 -400⁰C at the hourly space velocity of 1,3291Ir¹. The results are shown in Figure 1. The comparison of selectivity to the same conversion rate (25%) is shown in Table 1.

[81] As shown in Figure 1, when the catalysts prepared in examples of the invention were used for the production of acrylic acid, propane conversion rate and acrylic acid selectivity were increased, and therefore acrylic acid yield was increased.

[82] Table 1

[Table 1]

[83] As shown in Table 1, the acid complex mixture comprising 3 different compounds was used in examples 1 - 4 as a precipitant. In those cases, acrylic acid yield was excellent, compared with the cases using single compound or the acid complex mixture comprising two different compounds as a precipitant (comparative examples 1 - 6). The catalysts prepared by using the acid complex mixture comprising 3 different compounds in examples 1 - 4 also gave higher acrylic acid yield than the catalyst of comparative example 7 which was prepared by using the acid complex mixture comprising 3 different compounds but in which the content of the additive exceeded 1.5 fold for 1 mol of molybdenum.

Industrial Applicability

[84] As explained hereinbefore, an oxide catalyst for the production of acrylic acid having high catalytic activity can be prepared by the method of the present invention.

[85] [86] Those skilled in the art will appreciate that the conceptions and specific em bodiments disclosed in the foregoing description may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims.

Claims

[1] A method of preparing an oxide catalyst for the production of acrylic acid comprising the steps of preparing a catalyst precursor from a solution mixture of molybdenum salt, vanadium salt, tellurium salt and niobium salt; and drying and firing the catalyst precursor, in which the step of adding an additive to the solution mixture of the metal salts is additionally included and the additive herein is acid complex mixture comprising carboxylic acid, peroxide and sulfuric acid compounds.

[2] The method of preparing an oxide catalyst for the production of acrylic acid according to claim 1, wherein the sulfuric acid compound is selected from the group consisting of sulfuric acid, ammonium sulfate and sulfur dioxide.

[3] The method of preparing an oxide catalyst for the production of acrylic acid according to claim 1, wherein the contents of carboxylic acid, peroxide and sulfuric acid compounds are respectively 0.05 - 1.5 mols for 1 mol of molybdenum atom added as a form of molybdenum salt.

[4] The method of preparing an oxide catalyst for the production of acrylic acid according to claim 3, wherein the carboxylic acid is oxalic acid, the peroxide is hydrogen peroxide and the sulfuric acid compound is sulfuric acid.

[5] The method of preparing an oxide catalyst for the production of acrylic acid according to claim 1, wherein the catalyst is represented by the following formula 1. [Chemistry Figure 1]

Moi.oV_aTe_bNbcO_n

wherein, Mo is molybdenum, V is vanadium, Te is tellurium and Nb is niobium; a, b, c and n indicate molar rate of vanadium, tellurium, niobium and oxygen atoms, respectively, which are 0.01<a<l;0.01<b<l;0.01<c≤l; and n is the number determined by atomic value and weight of another element.

[6] The method of preparing an oxide catalyst for the production of acrylic acid according to claim 1, wherein the catalyst precursor is directly obtained from the solution mixture of metal salts by evaporating a solvent without using any other separators and the solvent is water.

[7] The method of preparing an oxide catalyst for the production of acrylic acid according to claim 1, wherein the firing was performed firstly at 150 - 25O⁰C for 1 - 4 hours in the flow of air and then at 500 - 65O⁰C for 1 - 4 hours in the flow of nitrogen or an inert gas.