JP2008086938A - Catalyst for producing ethylene oxide and production method of ethylene oxide using the same catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst which can produce ethylene oxide with high activity and selectivity and to provide a production method of ethylene oxide by gas-phase oxidation of ethylene by a gas containing a molecular oxygen employing the same catalyst. <P>SOLUTION: The catalyst for producing ethylene oxide is obtained by making a carrier support as a main component of α-Al<SB>2</SB>O<SB>3</SB>, wherein an intensity of the infrared adsorption spectrum in the range of wave number of 3,150 to 3,800 cm<SP>-1</SP>is substantially zero in the infrared adsorption spectrum measured by the KBr tablet method. The production method of ethylene oxide is provided which employs the same catalyst. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catalyst for producing ethylene oxide and a method for producing ethylene oxide using the catalyst, and more specifically, a catalyst for producing ethylene oxide excellent in catalytic activity and selectivity, and molecular ethylene in the presence of the catalyst. The present invention relates to a method for producing ethylene oxide by gas phase catalytic oxidation with oxygen.

  Numerous documents have been introduced in the past regarding ethylene oxide production catalysts used when ethylene oxide is produced by vapor-phase catalytic oxidation of ethylene with a molecular oxygen-containing gas.

For example, a catalyst is disclosed in which silver is supported on a support in which a coating layer of amorphous silica is provided on the outer surface of an α-alumina support and on the surface of pores (Patent Document 1). In addition, one or two or more compounds selected from the group consisting of elements in groups IIIa-VIIa and IIIb-Vb in the periodic table of the fourth, fifth and sixth periods (for example, titanium, tin, haunium, etc.) A catalyst in which silver is supported on an α-alumina support is also disclosed (Patent Document 2). Furthermore, a catalyst using a carrier containing high purity α-alumina, alkaline earth metal oxide, silicon oxide and zirconium oxide is disclosed (Patent Document 3).
Japanese Patent Laid-Open No. 2-194939 JP-A-4-363139 JP-A-6-47278

  The catalysts described in Patent Documents 1 to 3 are excellent in catalyst performance and can be sufficiently satisfied industrially. However, the production scale of ethylene oxide is very large, and even if the selectivity is slightly improved, ethylene as a raw material can be remarkably saved, so it has better catalytic performance due to its high economic effect. Development of a catalyst for producing ethylene oxide is desired.

  Accordingly, an object of the present invention is to provide a catalyst for producing ethylene oxide, which can produce ethylene oxide with high activity and high selectivity.

  Another object of the present invention is to provide a process for producing ethylene oxide in a high yield by subjecting ethylene to gas phase catalytic oxidation with molecular oxygen in the presence of a catalyst.

As a result of intensive studies on a catalyst for producing ethylene oxide and a carrier used for the catalyst, the present inventors have found that in the infrared absorption spectrum measured by the KBr tablet method, red in the region of wave numbers of 3,150 to 3,800 cm ^−1. The catalyst for ethylene oxide production prepared using a carrier mainly composed of α-alumina having an outer absorption peak of substantially zero has a substantially infrared absorption peak in the infrared absorption spectrum in the wave number region. -It has been found that it has higher activity against ethylene and higher ethylene oxide selectivity than a catalyst for producing ethylene oxide prepared using a carrier mainly composed of alumina, and the present invention is completed based on this finding. It came to.

  Therefore, the above objects are achieved by the following (1) to (4).

(1) In an infrared absorption spectrum measured by the KBr tablet method, a carrier mainly composed of α-alumina, whose infrared absorption spectrum in the region of wave numbers 3,150 to 3,800 cm ⁻¹ is substantially zero. A catalyst for producing ethylene oxide which carries silver.

(2) The catalyst according to (1), wherein the peak height of the infrared absorption spectrum in the region of wave number 3,150 to 3,800 cm ⁻¹ of the carrier is 0.1 or less.

(3) The catalyst according to (1) or (2), wherein the support has a SiO ₂ content of 0.1 to ₂ % by mass.

  (4) A method for producing ethylene oxide, characterized in that ethylene is vapor-phase oxidized with a molecular oxygen-containing gas in the presence of the catalyst according to any one of (1) to (3).

  According to the present invention, a highly active and highly selective catalyst can be obtained by using the catalyst carrier. Moreover, ethylene oxide can be manufactured with a high yield by performing a gaseous-phase catalytic oxidation reaction using the catalyst for ethylene oxide manufacture of this invention.

The catalyst for producing ethylene oxide according to the present invention comprises an α-alumina carrier having an infrared absorption peak substantially zero in the region of wave numbers of 3,150 to 3,800 cm ⁻¹ in the infrared absorption spectrum measured by the KBr tablet method. It is characterized by using. Specifically, a carrier having an infrared absorption spectrum substantially having an infrared absorption spectrum shown in FIG. 1 is used.

In the present invention, a carrier having an infrared absorption peak substantially zero in the region of wave numbers 3,150 to 3,800 cm ⁻¹ is an infrared absorption spectrum of the carrier measured by the KBr tablet method. This means that an infrared absorption peak cannot be substantially observed in the region of 3,800 cm ⁻¹ , that is, there is no clear infrared absorption peak in the spectral region. Specifically, it means that the peak area of absorbance in the spectral region is substantially zero. More specifically, in the measured infrared absorption spectrum, the straight line when the absorbance at wave number 3,150 cm ^{−1 and} the absorbance at 3,800 cm ⁻¹ are connected by a straight line, and the wave number 3,150-3,800 cm ^−1. This means that the lines of the infrared absorption spectrum in the region of are substantially overlapped.

  The infrared absorption spectrum of the carrier in the present invention is measured by a conventionally known KBr tablet method. Specifically, the catalyst carrier is ground and powdered, 1 part by mass of the carrier and 75 parts by mass of KBr are mixed uniformly, and then the infrared absorption spectrum of the pressed product is measured.

It is unclear exactly what the infrared peak in the region of wave numbers 3,150 to 3,800 cm ⁻¹ of the carrier is derived from, but it is presumed to be derived from SiOH.

  In the present invention, the phrase “substantially zero” as the infrared absorption peak means that the height of the infrared absorption peak is 0.1 or less, more preferably 0.05 or less, and still more preferably 0.03 or less.

  Here, how to obtain the peak height is as follows.

In the graph shown in FIG. 1, infrared absorption spectrum (in the figure, the thick solid line) in the absorbance at a wave number 3,150cm ^-1 X, the absorbance when the wave number 3,800Cm ^-1 and Y, X and Y Are connected by a straight line (broken line in the figure).

Of the absorption spectrum of wave numbers 3,150-3,800 cm ^−1, the portion with the highest absorbance is designated as A, and the perpendicular line from A (the thin solid line in the figure) is taken down and the point intersecting with the straight line is designated as B. .

  AB is the peak height in the present invention (that is, absorbance at point A−absorbance at point B = peak height).

  When calculating the peak height, the background of the absorption spectrum is not corrected.

About the support | carrier which has (alpha) -alumina as a main component used for the catalyst for ethylene oxide manufacture of this invention, in the infrared absorption spectrum measured by the KBr tablet method, the infrared of the area | region of a wave number of 3,150-3,800cm < ^-1 > was used. There is no particular limitation except that the absorption peak is substantially zero, but a carrier having the following composition and physical properties is particularly preferable.

  As an example of the component of the carrier mainly composed of α-alumina used in the present invention, α-alumina is 90% by mass or more, preferably 95% by mass or more, more preferably 98% by mass or more. Or alkaline earth metal (both oxide conversion) 0 to 5% by mass, preferably 0.01 to 4% by mass and transition metal oxide 0 to 5% by mass, preferably 0 to 3% by mass Can be mentioned.

The content of SiO _{2 in} the carrier is preferably 0.1 to ₂ % by mass, particularly preferably 0.3 to 1.5% by mass.

  The composition of the carrier and the content of each component described above can be determined using a fluorescent X-ray analysis method.

  There is no restriction | limiting in particular about the shape of the support | carrier used by this invention, Arbitrary shapes, such as a ring shape, spherical shape, and cylindrical shape, can be selected. Moreover, the magnitude | size (average equivalent diameter) is 3-20 mm normally, Preferably it is 5-10 mm.

The carrier used in the present invention has a BET (Brunauer-Emmet-Teller) specific surface area of 0.03 to 10 m ² / g, preferably 0.5 to ⁵ m ² / g, more preferably 1.0 to ^2.5 m ^2. Those in the range of / g are preferable. If the specific surface area is too low, it becomes difficult to carry the catalyst component in a highly dispersed state. On the other hand, if the specific surface area is too high, the number of micropores of the support increases, and in the catalyst prepared using the support, sequential oxidation of the product ethylene oxide is promoted.

  The pore volume of the carrier used in the present invention is 0.25 to 0.55 cc / g, preferably 0.3 to 0.5 cc / g, more preferably 0.35 to 0.45 cc / g. Good.

  The average pore diameter of the carrier used in the present invention is 0.1 to 5 μm, preferably 0.2 to 3 μm, more preferably 0.3 to 1.5 μm. If the average pore diameter is too large, practical carrier strength cannot be obtained. Conversely, if the average pore diameter is too small, the sequential oxidation of ethylene oxide, which is a product, may be promoted due to the residence of the product gas.

  The carrier used in the present invention has a water absorption rate of 10 to 70% by mass, preferably 20 to 60% by mass, more preferably 30 to 50% by mass. If the water absorption is lower than the above range, it is difficult to support the catalyst component. Conversely, if the water absorption is higher than the above range, a practically sufficient strength cannot be obtained.

  The ethylene oxide production catalyst of the present invention can be prepared according to a method generally employed in the preparation of an ethylene oxide production catalyst, except that the carrier showing the infrared absorption spectrum is used as the carrier.

  For example, an aqueous solution containing a silver compound alone for forming silver, a complexing agent for forming a silver compound and a silver complex, or a reaction accelerator used as necessary is prepared, and this is impregnated with a carrier. Then, it is dried and fired. This drying is preferably performed at a temperature of 80 to 120 ° C. in an inert gas atmosphere such as air, oxygen gas, or nitrogen. Baking is preferably performed at a temperature of 150 to 700 ° C., particularly 200 to 600 ° C. in an inert gas atmosphere such as air, oxygen gas, or nitrogen. In addition, you may perform this baking by 1 step | paragraph or 2 steps | paragraphs or more. Among these, preferably, the first stage is treated at 150 to 250 ° C. for 0.1 to 10 hours in an air atmosphere and the second stage is treated at 250 to 450 ° C. for 0.1 to 10 hours in an air atmosphere. is there. More preferably, the third stage is treated at 450 to 700 ° C. for 0.1 to 10 hours in an inert gas atmosphere selected from nitrogen, helium, argon and the like.

  Typical examples of the silver compound include silver nitrate, silver carbonate, silver oxalate, silver acetate, silver propionate, silver lactate, silver succinate, and silver neodecanoate. Representative examples of the chaining agent include monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and propylenediamine.

  Typical examples of the reaction accelerator include lithium, sodium, potassium, rubidium and cesium alkali metals, thallium, sulfur, chromium, molybdenum, tungsten and the like. These can be used alone or in combination of two or more. The reaction accelerator may be dissolved in the silver ammine complex aqueous solution and impregnated at the same time before the support is impregnated with the aqueous solution, or may be supported after the silver is supported.

  As the catalyst for producing ethylene oxide of the present invention, a catalyst carrying silver as a catalyst component and a reaction accelerator such as cesium is preferable. There is no restriction | limiting in particular about the load of silver and reaction accelerator, What is necessary is just to carry | support the amount effective for manufacture of ethylene oxide. For example, in the case of silver, the supported amount is 1 to 30% by mass, preferably 5 to 20% by mass, based on the mass of the catalyst. The amount of the reaction accelerator supported is usually 0.001 to 2% by mass, preferably 0.01 to 1% by mass, more preferably 0.01 to 0.7% by mass, based on the mass of the catalyst. .

  The method for producing ethylene oxide in the present invention can be carried out by a conventionally used method except that the catalyst for producing ethylene oxide of the present invention is used as a catalyst.

Specifically, for example, ethylene 0.5 to 40% by volume, preferably 5 to 30% by volume, molecular oxygen 3 to 10% by volume, preferably 4 to 9% by volume, carbon dioxide gas 1 to 30% by volume, preferably Consists of 1 to 20% by volume, the balance being an inert gas such as nitrogen, argon or water vapor, and lower hydrocarbons such as methane or ethane, and further containing 0 halides such as ethylene dichloride and diphenyl chloride as reaction inhibitors. .1～10Ppm (volume), preferably 1,000~30,000hr a raw material gas containing 0.5～5Ppm (capacity) ^-1 (STP), preferably 3,000～8,000Hr ^-1 of (STP) space velocity, 2~40kg / ^cm 2 G, the pressure of preferably ^{10~30kg / cm 2 G, 150~300 ℃} , preferably above the production of ethylene oxide at a temperature of 180 to 280 ° C. It may be contacted with the catalyst.

  The molecular oxygen-containing gas used in the present invention includes air, oxygen and enriched air.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Further, the technical scope of the present invention is not limited only to the following examples. Furthermore, in this example, various parameters were measured by the following method.

<Measurement of carrier pore distribution spectrum / pore volume / average pore diameter>
Measured by mercury intrusion method. Specifically, a carrier deaerated at 200 ° C. for at least 30 minutes is used as a sample, and Autopore III 9420W (manufactured by Shimadzu Corporation) is used as a measuring device, and a pressure range of 1.0 to 60,000 psia and 60 measurements are performed. The pore distribution spectrum, pore volume, and average pore diameter were obtained at points.

<Measurement of silica content in carrier>
Measured by fluorescent X-ray analysis.

<Measurement of specific surface area of carrier>
After pulverizing the carrier, about 0.2 g classified to a particle size of 0.85 to 1.2 mm was accurately weighed. The weighed sample was deaerated at 200 ° C. for at least 30 minutes and measured by the BET (Brunauer-Emmet-Teller) method.

<Measurement of water absorption rate of carrier>
In accordance with the method described in Japanese Industrial Standard (JIS R 2205 (1998)), the measurement was performed by the following method.

  a) The carrier before crushing was placed in a drier kept at 120 ° C., and the mass when reaching a constant weight was weighed (dry mass: W1 (g)).

  b) The carrier weighed in a) above was submerged in water and boiled for 30 minutes or more, and then cooled in room temperature water to obtain a saturated sample.

  c) The saturated sample obtained in the above b) was taken out from the water, and the surface was quickly wiped with a compress, and after removing water droplets, weighed (saturated sample mass: W2 (g)).

  d) The water absorption was calculated according to the following formula 1 using W1 and W2 obtained above.

  The conversion ratios and selectivities described in the examples and comparative examples are calculated by the following mathematical formulas 2 and 3.

  In this example, the infrared absorption spectrum of the carrier was measured under the following conditions.

<Infrared absorption spectrum measurement conditions>
(1) KBr (300 mg) and the carrier to be measured (4 mg) are mixed thoroughly while being crushed in an agate mortar.

  (2) 120 mg of the mixed powder is weighed, set in a tablet molding machine, and degassed with a vacuum pump for 3 minutes.

(3) Next, deaeration is performed for 3 minutes while applying a pressure of 600 kg / cm ² G (the finished sample is a disk having a diameter of 10 mm).

  (4) A disk-shaped sample is set in an infrared absorption spectrum measuring apparatus and heated at 110 ° C. for 1 hour.

  (5) After the sample is returned to room temperature, the infrared absorption spectrum of the sample is measured 100 times with a resolution of 4 Kaiser (infrared absorption spectrum measurement apparatus used: EXCALIBUR Series manufactured by VARIAN).

Example 1
1 liter of distilled water was added to 1 liter of carrier (a) (SiO ₂ 0.5% by mass) of α-alumina having an outer diameter of 8 mm, an inner diameter of 4 mm, and a length of 8 mm as a main component, followed by boiling and washing for 30 minutes under normal pressure. Thereafter, the washing solution was removed and washed with distilled water. Furthermore, after this boiling washing was repeated twice, it was dried at 120 ° C. for 3 hours.

  A slurry was prepared by uniformly mixing 52.0 g of silver oxalate, 0.37 g of cesium nitrate and 100 ml of distilled water, and 25 ml of ethylenediamine was added while cooling this in a water bath to prepare a silver-containing solution. 200 g of carrier (a) previously heated to 100 ° C. was put into an evaporating dish placed on a boiling water bath, and then the silver-containing solution was added and evaporated to dryness while stirring. Next, heat treatment was performed at 400 ° C. for 20 minutes in an air stream using a hot air dryer. Furthermore, this was heat-processed at 550 degreeC for 3 hours in nitrogen atmosphere, and the catalyst (A) was obtained. The silver content in the catalyst was 15% by mass.

When the infrared absorption spectrum of the carrier (a) used was measured, no infrared absorption spectrum was observed in the range of wave numbers of 3,150 to 3,800 cm ⁻¹ . The infrared absorption spectrum of the carrier (a) is shown in FIG. The physical properties of the carrier (a) are summarized in Table 1.

Examples 2-4
In Example 1, instead of the carrier (a), the carrier (b), the carrier (c) and the carrier (d) were used, respectively, and the addition amounts of cesium nitrate were 0.43 g, 0.40 g and 0.67 g, respectively. A catalyst (B), a catalyst (C) and a catalyst (D) were obtained in the same manner as in Example 1 except that. Table 1 summarizes the physical properties of the carrier (b) used for the catalyst (B), the carrier (c) used for the catalyst (C), and the carrier (d) used for the catalyst (D).

Comparative Example 1
In Example 1, catalyst (E) was obtained in the same manner as in Example 1 except that support (e) was used instead of support (a). When an infrared absorption spectrum of the carrier (e) used was measured, an infrared absorption peak was observed in the wave number range of 3,150 to 3,800 cm ⁻¹ . The infrared absorption spectrum of the carrier (e) is shown in FIG. The physical properties of the carrier (e) are summarized in Table 1.

Comparative Examples 2-4
Examples 2 to 4 were carried out except that the carrier (f) was used instead of the carrier (b), the carrier (g) was used instead of the carrier (c), and the carrier (h) was used instead of the carrier (d). Catalyst (F), catalyst (G) and catalyst (H) were obtained in the same manner as in Example 2, Example 3 and Example 4. Table 1 summarizes the physical properties of the carrier (f) used for the catalyst (F), the carrier (g) used for the catalyst (G), and the carrier (h) used for the catalyst (H).

Examples 5-6
In Example 1, instead of the carrier (a), the carrier (i) and the carrier (j) were used, respectively, and the addition amount of cesium nitrate was changed to 0.25 g and 0.20 g, respectively, as in Example 1. Thus, catalyst (I) and catalyst (J) were obtained. Table 1 summarizes the physical properties of the support (i) used for the catalyst (I) and the support (j) used for the catalyst (J).

Example 7
(A) to (J) obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were pulverized and sieved to 600 to 850 mesh, 1.2 g of which was made of stainless copper having an inner diameter of 3 mm and a tube length of 600 mm. The reaction tube was filled, and ethylene gas phase oxidation reaction was performed under the following conditions. Table 2 shows the selectivity and reaction temperature when the ethylene conversion was 10%.

<Gas oxidation reaction conditions for ethylene>
Space velocity: 6,000 hr ⁻¹ ,
Reaction pressure: 20 kg / cm ²
Raw material gas: ethylene 23% by volume, oxygen 7.8% by volume, carbon dioxide 7% by volume,
2.0 ppm ethylene dichloride and the balance (methane, nitrogen,
Argon and ethane).

It is a graph used for the method of calculating | requiring the infrared absorption peak height of the support | carrier which has (alpha) -alumina as a main component used by this invention. 2 is a graph showing an infrared absorption spectrum of a carrier (a) used for an ethylene oxide production catalyst (A) in Example 1. FIG. 2 is a graph showing an infrared absorption spectrum of a carrier (e) used for a catalyst (E) for ethylene oxide production in Comparative Example 1. FIG.

Claims (4)

In the infrared absorption spectrum measured by the KBr tablet method, silver is supported on a carrier mainly composed of α-alumina whose infrared absorption spectrum in the region of wave numbers 3,150 to 3,800 cm ⁻¹ is substantially zero. A catalyst for producing ethylene oxide. 2. The catalyst according to claim 1, wherein the peak height of the infrared absorption spectrum in the region of wave number 3,150 to 3,800 cm ⁻¹ of the carrier is 0.1 or less. The catalyst according to claim 1 or 2, wherein the support has a SiO2 content of 0.1 to ₂ mass%.   A method for producing ethylene oxide, comprising subjecting ethylene to gas phase oxidation with a molecular oxygen-containing gas in the presence of the catalyst according to any one of claims 1 to 3.

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