JP4041513B2 - Glycerol dehydration catalyst, glycerin dehydration catalyst production method, acrolein production method, and acrolein derivative production method - Google Patents

Description

  The present invention relates to a glycerin dehydration catalyst, a method for producing the catalyst, and a method for producing acrolein and a method for producing an acrolein derivative using the catalyst.

  Biodiesel produced from vegetable oil is attracting attention not only as a substitute for fossil fuels, but also because it emits less carbon dioxide, and demand is expected to increase. When this biodiesel is produced, glycerin is produced as a by-product, so it is necessary to make effective use of it.

  As an example of utilizing glycerin, there is a method for producing acrolein using glycerin as a raw material. For example, Patent Document 1 discloses a method for producing acrolein using pumice carrying lithium phosphate as a catalyst. Patent Document 2 discloses a method for producing acrolein by using silica having lithium phosphate supported on the surface as a catalyst.

By the way, when manufacturing acrolein using a catalyst as mentioned above, manufacturing acrolein with a high yield is calculated | required. Furthermore, even when the catalyst is continuously used, a long-life catalyst in which fluctuations in acrolein yield are suppressed is desired. If a long-life catalyst can be used, acrolein derivatives such as acrylic acid, 1,3-propanediol, allyl alcohol, polyacrylic acid, polyacrylic acid salt, etc., which are conventionally known to be produced using acrolein as a raw material, can be used. It can be manufactured at low cost.
US Pat. No. 1,916,743 Japanese Patent Application No. 06-217724

  The present invention provides a catalyst for use in the production of acrolein by dehydrating glycerin, having a long life and suppressing fluctuations in the yield of acrolein, and a method for producing the catalyst. Objective.

  The present inventor has found that if a catalyst supporting P and a predetermined alkali metal is used as a catalyst for dehydrating glycerin, fluctuation in the yield of acrolein is suppressed, and in addition, acrolein can be obtained in high yield. The invention has been completed.

  That is, the present invention is a glycerol dehydration catalyst in which P and an alkali metal are supported on a carrier, wherein the alkali metal is one or more selected from Na, K, and Cs, and the alkali metal (M) The molar ratio M / P of A and P is 2.0 or less. The M / P is preferably 0.5 or less.

The present invention also includes a step of impregnating a support with an aqueous solution containing a phosphate ion and one or more alkali metal ions selected from Na ⁺ , K ⁺ , and Cs ^+; And a method for producing the glycerin dehydrating catalyst, comprising the steps of: calcination of the dried carrier. The phosphate ion used in this method may be one or more selected from PO ₄ ³⁻ , HPO ₄ ²⁻ , and H ₂ PO ₄ ⁻ .

  Furthermore, the present invention is a method for producing acrolein in which glycerin is dehydrated in the presence of the catalyst. In this method, glycerin may be dehydrated by a gas phase reaction in which vaporized glycerin is brought into contact with a catalyst.

  Moreover, this invention is a manufacturing method of the acrolein derivative which has the process of dehydrating glycerol in the presence of the said catalyst and manufacturing acrolein. Examples of the acrolein derivative include polyacrylic acid or polyacrylic acid salts such as sodium polyacrylate.

  According to the catalyst of the present invention, since P and a predetermined alkali metal are supported on the carrier, fluctuations in the yield of acrolein obtained by dehydrating glycerin can be suppressed.

  The present invention will be described based on an embodiment. The catalyst of this embodiment is a carrier supporting P and a predetermined alkali metal. The supported P is preferably an oxide. Further, the predetermined alkali metal is one selected from Na, K, and Cs, arbitrarily. In selecting the alkali metal, it is preferable to select Na and / or Cs which is excellent in acrolein yield from the beginning of the use of the catalyst. On the other hand, examples of the carrier include silica, alumina, zirconia, and titania, and silica is particularly preferable. The physical properties such as particle size and surface area of the carrier are not particularly limited.

  When the alkali metal element supported on the carrier is M, the M / P molar ratio is 2.0 or less, preferably 0.5 or less, in order to obtain acrolein in a high yield.

  The catalyst of the present embodiment can be obtained by using the evaporation to dryness method, which is a class of impregnation method. In other words, a predetermined impregnating solution is impregnated with a carrier of a powder or a molded body, water is evaporated and the carrier is dried to fix phosphorus and alkali metal on the carrier, and then the carrier is dried and fired. The catalyst of the embodiment can be obtained.

The impregnating solution used in the process for producing the catalyst of the present embodiment is an aqueous solution containing phosphate ions and one or more alkali metal ions selected from Na ⁺ , K ⁺ , and Cs ⁺ . The phosphate ion in the impregnating solution is a P source to be supported on the carrier, and is, for example, one or more selected from PO ₄ ³⁻ , HPO ₄ ²⁻ , and H ₂ PO ₄ ^−. .

The impregnating solutions are listed as Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH ₂ PO ₄ , Cs ₃ PO ₄ , Cs ₂ HPO ₄ , and CsH ₂ PO _4. Alkali metal phosphates; ammonium phosphates such as (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , (NH ₄ ) ₃ PO ₄ ; and compounds arbitrarily selected from phosphoric acid in water It is prepared by dissolving in.

In order to adjust the M / P ratio to be supported on the carrier, an impregnating solution may be prepared using a compound that can disperse constituent elements other than alkali metal by firing. Such compounds that can disperse constituent elements other than alkali metals can be dispersed as NOx gas alkali metal nitrates such as NaNO ₃ , KNO ₃ , CsNO ₃ ; carbon dioxide gas. Examples thereof include alkali metal carbonates such as Na ₂ CO ₃ , NaHCO ₃ , K ₂ CO ₃ , KHCO ₃ , Cs ₂ CO ₃ , and CsHCO ₃ . In addition, in order to adjust the M / P ratio to be supported on the carrier, an impregnating solution is prepared using alkali metal hydroxides such as NaOH, KOH, CsOH; and alkali metal chlorides such as NaCl, KCl, CsCl. You may do it.

  The temperature of the impregnating liquid when impregnating the carrier is not particularly limited, but may be 100 ° C. or lower, preferably 30 ° C. or higher, and more preferably 50 ° C. or higher.

  The carrier is fired at a firing temperature of 300 to 700 ° C., preferably 400 ° C. or higher, and more preferably 500 ° C. or higher. In addition, the atmosphere during firing is not particularly limited, but implementation in the air is simple.

  Next, a method for producing acrolein using the catalyst of the present embodiment will be described. The method for producing acrolein in the present embodiment is to produce acrolein by a gas phase dehydration reaction in which a reaction gas containing glycerin is brought into contact with a catalyst in a reactor arbitrarily selected from a fixed bed reactor, a moving bed reactor and the like. It is. The catalyst according to the present invention is not limited to an acrolein manufacturing method in which a reaction gas and a catalyst are brought into contact with each other, and can also be used in a manufacturing method in which a glycerin solution and a catalyst are brought into contact with each other. In this case, a fluidized bed reactor or the like is selected as the reactor.

  The reaction gas may be a gas composed only of glycerin, and may contain an inert gas in the glycerin dehydration reaction in order to adjust the glycerin concentration in the reaction gas. Examples of the inert gas include vaporized water and nitrogen gas. The glycerin concentration in the reaction gas is preferably 0.1 to 100 mol%, preferably 1 mol% or more, and 10 mol% or more in order to produce acrolein economically and highly efficiently. .

Since the catalyst is a highly efficient glycerol dehydration catalyst, acrolein can be obtained in a high yield even when the flow rate of the reactive gas is set to be large. The flow rate of the reactive gas is preferably 100 to 10,000 hr ⁻¹ in terms of the reactive gas flow rate (GHSV) per unit catalyst volume. Preferred is a 5000 hr ^-1 or less, in order to perform the production of acrolein economically and efficiently is 3000 hr ^-1 or less.

  The reaction temperature may be 200 to 500 ° C, preferably 250 to 450 ° C, and more preferably 300 to 400 ° C.

  The pressure of the reaction gas is not particularly limited as long as the pressure is within a range where glycerin does not condense. Usually, it is good that it is normal-pressure-1MPa, Preferably, it is 0.5 MPa or less.

  Acrolein can be produced by the above method. As already known, the produced acrolein can be used as a raw material for producing acrolein derivatives such as acrylic acid, 1,3-propanediol, allyl alcohol, polyacrylic acid, and polyacrylate. Therefore, it is naturally possible to incorporate the acrolein production method described above into the acrolein derivative production method.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.

[Preparation of catalyst]
An amount of (NH ₄ ) H ₂ PO ₄ , CsH ₂ PO ₄ , NaNO ₃ , KNO ₃ , and CsNO ₃ is added to and dissolved in 350 g of ion-exchanged water according to the target catalyst composition, and the impregnating solution is dissolved. Was prepared. In this impregnating solution, 40 g of silica powder was immersed at room temperature, and P and alkali metal were fixed on the silica surface by evaporation to dryness. Next, silica was calcined in the atmosphere at 600 ° C. for 5 hours to obtain a catalyst. Further, after roughly pulverizing the catalyst, a catalyst having a particle size of 0.7 to 2.0 mm was classified to prepare a catalyst for dehydrating glycerin in Examples. The prepared catalysts were Si ₅ P _0.2 Na _0.01 (Example 1), Si ₅ P _0.2 Na _0.02 (Example 2), Si ₅ P _0.2 Na _0.05 (Example 3), Si ₅ P _0.2 Cs _0.01 (Example). 4), Si ₅ P _0.2 Cs _0.02 (Example 5), Si ₅ P _0.2 Cs _0.05 (Example 6), Si ₅ P _0.2 Cs _0.2 (Example 7), Si ₅ P _0.2 K _0.2 (Example 8) Si ₅ P _0.2 Na _0.6 (Comparative Example 2) and Si ₅ P _0.2 Cs _0.6 (Comparative Example 3). Further, instead of the impregnating solution was prepared using NH ₄ H ₂ PO ₃ solution Si ₅ P _0.1 (Comparative Example 1).

[Manufacture of acrolein]
Acrolein was synthesized by dehydrating glycerol by the following method using a reactor in which the catalysts of Examples and Comparative Examples were fixed beds.

First, a stainless steel reaction tube (inner diameter: 10 mm, length: 500 mm) filled with 15 ml of the catalyst of Example or Comparative Example was prepared as a fixed bed reactor, and this reactor was immersed in a salt bath at 360 ° C. Thereafter, nitrogen was circulated in the reactor at a flow rate of 61.5 ml / min for 30 minutes, and then a reaction gas composed of a vaporized gas of 80 mass% glycerin aqueous solution and nitrogen (reaction gas composition: glycerin 27 mol%, water 34 mol%, Nitrogen (39 mol%) was circulated at a flow rate of 632 hr ⁻¹ .

  The effluent gas for 30 to 60 minutes and 150 to 180 minutes after flowing the reaction gas through the reactor was cooled and liquefied and collected (hereinafter referred to as “cooled liquefied product of the collected effluent gas”). Referred to as “spill”). Then, qualitative and quantitative analysis of the effluent was performed by gas chromatography (GC). As a result of qualitative analysis by GC, 1-hydroxyacetone was detected together with glycerin and acrolein. Further, the conversion rate and yield were calculated from the quantitative analysis results. Here, the conversion rate is a value calculated by (1− (number of moles of glycerin in the collected effluent) / (number of moles of glycerin introduced into the reactor in 30 minutes)) × 100. Further, the yield of acrolein is a value calculated by ((molar number of acrolein) / (molar number of glycerin introduced into the reactor in 30 minutes)) × 100.

  Table 1 below shows the results of GC analysis.

  As shown in Table 1 above, the acrolein yield when using the catalyst according to the example of the present invention supporting an alkali metal is less changed with time than the catalyst according to the comparative example not supporting an alkali metal. Can be confirmed.

Claims (7)

  A catalyst for glycerin dehydration in which P and an alkali metal are supported on a carrier, wherein the alkali metal is one or more selected from Na, K, and Cs, and the mole of the alkali metal (M) and P The glycerol dehydration catalyst, wherein the ratio M / P is 2.0 or less.   The catalyst for glycerin dehydration according to claim 1, wherein the M / P is 0.5 or less. Impregnating a carrier with an aqueous solution containing a phosphate ion and one or more alkali metal ions selected from Na ⁺ , K ⁺ , and Cs ⁺ ; drying the carrier; and The manufacturing method of the catalyst for glycerol dehydration characterized by including the process of baking the solidified support | carrier. 4. The method for producing a glycerol dehydration catalyst according to claim ³ , wherein the phosphate ion is one or more selected from PO ₄ ³⁻ , HPO ₄ ²⁻ , and H ₂ PO ₄ ⁻ . A method for producing acrolein by dehydrating glycerol in the presence of a catalyst,
A method for producing acrolein, wherein the catalyst is the glycerol dehydration catalyst according to claim 1 or 2.   The method for producing acrolein according to claim 5, wherein glycerin is dehydrated by a gas phase reaction in which vaporized glycerin is brought into contact with a catalyst.   A method for producing an acrolein derivative comprising a step of producing acrolein by dehydrating glycerol in the presence of a catalyst, wherein the catalyst is the glycerol dehydration catalyst according to claim 1 or 2. Manufacturing method.