JPH049578B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a catalyst used in a reaction for producing oxygen-containing organic compounds such as acetic acid from synthesis gas. C ₂ with particularly increased selectivity
This invention relates to a sulfur-containing rhodium catalyst capable of producing oxygen-containing compounds. BACKGROUND ART A method for producing an oxygen-containing organic compound containing mainly two carbon atoms from carbon monoxide and hydrogen, particularly an oxygen-containing compound containing acetic acid, acetaldehyde, and ethanol as components, is known. In this reaction, a heterogeneous catalyst consisting essentially of metal rhodium is used (Japanese Patent Publication No. 54-41568), and an oxygen-containing compound consisting of solid fine particles containing a combination of rhodium and manganese is used as a catalyst. Improved method for increasing the activity of the catalyst to be synthesized
43453) has been done. Furthermore, a method of suppressing the production of methane by combining lithium, potassium, cesium, rubidium, etc. is also known (Japanese Patent Application Laid-Open No. 8334-1983). As described above, there is a known method for producing a _C2 oxygen-containing compound by reacting a mixed gas of carbon monoxide and hydrogen (hereinafter referred to as mixed gas) in the presence of a catalyst containing a combination of rhodium, manganese, and an alkali metal. Specific examples thereof are summarized in the form of a table in the above-mentioned Japanese Patent Application Laid-Open No. 56-8334. This technology works to shift the distribution of C ₂ compounds produced toward the acetic acid side (lines 9 to 10 at the bottom right of p. 2 of the same publication), but in the data in the table, the distribution of C ₂ compounds is shifted toward the acetic acid side. The selectivity was about 63% in the highest of the eight cases (G), and more than 36% of hydrocarbons were produced. Based on such prior art, the present invention suppresses the production of hydrocarbons and converts C2 _- containing compounds with increased selectivity in a rhodium-containing catalyst used in the reaction for producing _C2 -oxygenated compounds from synthesis gas. The object is to provide an improved catalyst capable of obtaining oxygen compounds. In a rhodium catalyst activated by heat treatment of a rhodium compound on a support, when the heat treatment is performed in the presence of a sulfur compound, the generation of hydrocarbons is suppressed and the selectivity in the reaction of synthesis gas is significantly increased. It was found to be a catalyst that provides C ₂ oxygenated compounds. That is, the present invention relates to a rhodium-containing catalyst used in the reaction of reacting carbon monoxide and hydrogen to produce an oxygen-containing compound containing acetic acid, acetaldehyde, and ethanol as components, in which a rhodium compound supported on a carrier together with a sulfur compound is used. This is a rhodium catalyst characterized by containing active rhodium formed by heat treatment. Generally, sulfur compounds tend to form surface bonds with metals and are therefore considered to be catalyst poisons that react with active components in the catalyst and lead to deactivation of the catalyst. (for example
Elsevier Sci.Pub.Co.“Catalyst Deactivatiot”
(p. 179 (1980)) It was surprising that this sulfur compound, which is considered to be a catalyst poison, acted to improve the selectivity of the rhodium-containing catalyst to C ₂ oxygen-containing compounds. The true active species in a dynamic state under the reaction conditions of such a sulfur-containing rhodium catalyst is not necessarily clear, but as shown in the examples, when the catalyst of the present invention is used, it is possible to use a known rhodium-containing catalyst. Since a higher C ₂ oxygen-containing selectivity was obtained than in the case of the present invention, it is thought that a new active form of rhodium was formed by the reaction of rhodium on the carrier with a specific oxidizing compound. The catalyst of the present invention can be used in combination with a manganese component. For example, manganese ions or permanganate ions may be used as the manganese component and supported on the carrier together with a rhodium compound and a sulfur compound. The use of permanganate ions helps to improve the selectivity of acetic acid and provides better results when used in conjunction with the present invention. The catalyst of the present invention and its preparation method will be explained in more detail below. Examples of rhodium compounds used in catalyst preparation include inorganic acid salts such as rhodium chloride, rhodium bromide, rhodium iodide, rhodium nitrate, and rhodium sulfate; organic acid salts such as rhodium acetate, rhodium formate, and rhodium oxalate; Any compound commonly used for the preparation of noble metal catalysts, such as rhodium or ammine complex salts, clusters, rhodium carbonyl, and rhodium carbonyl acetylacetonate, can be used, but chloride is particularly recommended for ease of handling. These rhodium compounds are not in an active state (referring to the activity of synthesizing an oxygen-containing organic compound such as acetic acid from carbon monoxide and hydrogen; the same applies hereinafter) before heat treatment. The support for supporting these rhodium components together with the sulfur compound has a specific surface area of 1 to 1000.
m ² /g is preferred, and silica, alumina, silica alumina, titanium oxide, zirconium oxide, thorium oxide, magnesium oxide, activated carbon, zeolite, etc. can be used, but silica-based carriers are particularly preferred. These carriers can be used in any form such as powder or pellets. Sulfuric acid, sulfates of various metals, and sulfides can be used as sulfur compounds that are thought to act in the heat treatment step for producing an active catalyst from a rhodium compound. Manganese components that can be used in combination with the catalyst of the present invention include inorganic acid salts of manganese such as permanganates, halides, nitrates, sulfates, carbonates, acetates, formates, oxalates, etc. Mention may be made of organic acid salts of manganese. Permanganic acid can be used as such or in its metal salts, such as alkali metal salts such as lithium, sodium, etc. These components used in the preparation of the catalyst are preferably compounds that are soluble in a suitable solvent such as water, in order to facilitate loading on the carrier. Although the catalyst of the present invention is characterized in that it is prepared using a sulfur compound, as a general technique used in the catalyst preparation method, a conventional method for preparing a noble metal catalyst can be applied. For example, impregnation method,
A dipping method, an ion exchange method, a coprecipitation method, a kneading method, etc. are used. More specifically, the catalyst can be obtained by dissolving the above catalyst component in water or an organic solvent such as n-hexane or alcohol, adding a porous inorganic carrier to this solution to support the solution, and then subjecting the solution to a reductive heat treatment. The catalyst components may be supported on the carrier by simultaneously supporting all the catalyst components, by sequentially supporting each component, or by subjecting each component to reduction heat treatment as necessary. It is possible to use various methods such as a method of carrying the data sequentially or in stages while carrying out processing such as the following. To further explain the impregnation method as an example, a thermally decomposable inorganic rhodium compound (and manganese component) and a sulfur compound are made into an aqueous solution in an amount of water depending on the water absorption rate of the carrier, the carrier is added to the solution, and after stirring and mixing, heating is performed. Dry and support. Such a solid supporting rhodium (and manganese) and a sulfur compound is further heat-treated to become an active catalyst supporting finely dispersed rhodium (and manganese). The heat treatment is carried out by heating the rhodium compound supported on the carrier together with the sulfur compound to a temperature of 150°C or higher, usually under reducing conditions.
This heat treatment turns the rhodium compound into an active rhodium catalyst. For example, rhodium chloride supported together with a sulfur compound is heated in a hydrogen stream to become a metal or a low valence state close to it, and becomes active. The rhodium-based catalysts disclosed in the prior art are also described as being obtained by heating a supported rhodium compound under reducing conditions, and that the rhodium deposited is typically in the metallic form; To obtain the catalyst used in the present invention, the same heat treatment as in the prior art can be applied, except that the catalyst is in the presence of a sulfur compound. Since rhodium compounds are thought to be active mainly in the form of metals or slightly positively charged, if a rhodium salt with a high valence is supported, the heat treatment will involve reduction. However, when a low valence rhodium compound such as rhodium carbonyl is supported, heat treatment without reduction may be sufficient. The heat treatment for converting the rhodium compound into an active state may be heating to the reaction temperature under reaction conditions, that is, in the presence of hydrogen in a mixed gas of carbon monoxide and hydrogen supplied as a raw material to the reaction system. , it is desirable to activate it by carrying out a heat treatment accompanied by reduction in a hydrogen stream before using it in the reaction. The reduction treatment can be performed in the presence of hydrogen gas or a mixed gas of carbon monoxide and hydrogen. Depending on the case, it may be partially diluted with an inert gas such as nitrogen, helium, or argon. The reduction treatment temperature is 100 to 600°C, preferably 150 to 500°C. At this time, in order to maintain the activation state of each component of the catalyst in an optimal state, the reduction treatment may be performed while raising the temperature gradually or stepwise from a low temperature. Further, the reduction can also be carried out chemically using a reducing agent such as methanol, hydrazine, or formalin. There is no strict limit on the amount of each catalyst component used, but the surface area of the carrier (1 to 1000 m ² /
g). Usually the content of rhodium in the supported catalyst is 0.01-15% by weight, preferably 0.1
-10% by weight, the content of manganese is 0.001-10% by weight, preferably 0.01-5% by weight. The atomic ratio of sulfur and rhodium used in catalyst preparation is
It ranges from 0.001 to 2, preferably from 0.01 to 1. Catalysts such as those described above are used to convert synthesis gas, a mixture of carbon monoxide and hydrogen, into acetic acid-rich C ₂ oxygenates. The reaction is usually carried out in the gas phase, for example, a raw material gas containing carbon monoxide and hydrogen is passed through a fixed bed reactor packed with a catalyst. In this case, the raw material gas may contain other components other than carbon monoxide and hydrogen, such as carbon dioxide, nitrogen, argon, helium, methane, and water vapor. Further, the catalytic reactor is not limited to a fixed bed type, but may be of other types such as a moving bed type or a fluidized bed type. In some cases, a liquid phase reaction may also be carried out, in which the catalyst is suspended in a suitable solvent and a raw material gas is introduced therethrough. Although reaction conditions can be varied within a wide range,
The preferred range is the molar ratio of carbon monoxide and hydrogen.
20:1 to 1:5, preferably 10:1 to 1:
2. Reaction temperature is 200-400℃, preferably 220-350℃
°C, pressure 1 to 300 atm, preferably 20 to 200
Atmospheric pressure and space velocity are converted to standard conditions (0°C, 1 atm)
at 10 ² to 10 ⁶ Hr ^-1 , preferably 10 ³ to 5×
10 ⁴ Hr ^-1 . The catalyst of the present invention will be explained using specific examples. A catalyst obtained by supporting a sulfur compound together with rhodium and manganese components on a carrier and undergoing thermal reduction treatment produces less hydrocarbons when reacting with synthesis gas and has a high selectivity of about 75% to 80%. Gives _C2 oxygenates. The reaction results in these specific examples are summarized in Table 1. Selection rate (%)
is defined by the following formula. Number of moles of CO converted to a specific product x 100/number of moles of CO consumed Esters were calculated by dividing them into acids and alcohols, respectively.

[Table] Completely dissolve 1.9182 g of rhodium trichloride trihydrate and 0.4372 g of lithium permanganate trihydrate in 50 ml of distilled water, then add 5 ml of sulfuric acid aqueous solution (1 ml of S/
Add 30 g of silica gel (ID type silica gel manufactured by Fuji Davison Chemical Co., Ltd., the same applies hereinafter) and stir it uniformly.
Air dried overnight. After drying in a blow dryer at 110℃ for 4 hours, it was filled into a quartz glass reduction tube and heated in a hydrogen stream (20/20℃).
After heat treatment at 350°C for 2 hours, the temperature was immediately changed to a nitrogen stream and allowed to cool. Dilute 5ml of this catalyst with 5ml of silica gel.
Filled in a U-shaped reaction tube made of SUS-316, with a pressure of 100
^The raw material gas (CO:
H ₂ =2:1) was fed at a rate of 100 N/hour to carry out the reaction, and a C ₂ oxygen-containing compound was obtained with a selectivity of 77.54%. The analysis was conducted by directly introducing the reaction gas into a gas chromatograph. Example 2 A catalyst was obtained in the same manner as in Example 1, except that an aqueous solution of 0.0508 g of potassium sulfate (atomic ratio of sulfur to Rh: 1/25) was used instead of the sulfuric acid aqueous solution. The catalyst reaction test was also conducted in the same manner as in Example 1.
(The same applies to Example 3 and subsequent examples.) Example 3 Similar to Example 1, an aqueous sulfuric acid solution (atomic ratio of sulfur to Rh of 1/20) is used, and 1/10 of rhodium is used.
It is a catalyst that is heated and reduced by supporting 0.0896 g of KClO ₃ which is twice the mole amount. Examples 4 and 5 Same as Example 1, but the amount of sulfur compound supported was changed. Example 6 Potassium sulfide was used as the sulfur compound. Example 7 This is a comparative catalyst obtained by supporting and heating reducing rhodium trichloride and lithium permanganate without using a sulfur compound. The production of methane and _C2 and higher hydrocarbons is higher than in Examples 1-6.

Claims (1)

[Claims] 1 Heat treatment of a rhodium compound supported on a carrier together with a sulfur compound in a rhodium-containing catalyst used in the reaction of reacting carbon monoxide and hydrogen to produce an oxygen-containing compound containing acetic acid, acetaldehyde, and ethanol. A rhodium catalyst characterized by containing active rhodium formed by.