Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Silicon containing or process of making
Utility Patent
1998-12-02
2001-01-02
Padmanabhan, Sreeni (Department: 1621)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Silicon containing or process of making
C502S258000, C502S330000, C502S338000, C568S475000
Utility Patent
active
06169055
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a catalyst for the production of acrolein by the oxidation of ethane, a method for the production of the catalyst, and a method for the production of acrolein by the use of the catalyst.
2. Description of the Prior Art
Acrolein, an important raw material for the chemical industry, is generally produced by oxidation of propylene. The cost of producing acrolein is therefore high. If a method for producing acrolein directly from ethane, a cheap and abundantly available substance and oxygen is developed, it will permit a significant decrease in the cost of production. A growing need is therefore felt for the development of such a method.
Known catalysts for producing acrolein from propylene or propane include one containing copper oxide as an active component, one using a molybdenum-bismuth complex oxide as an active component, one containing molybdenum, vanadium, phosphorus, etc., and one containing molybdenum, vanadium, niobium, tellurium, etc. The production of acrolein from ethane, however, cannot be attained by using any of these catalysts.
As catalysts for producing acetaldehyde directly from ethane and oxygen, there are known one containing boron, phosphorus, etc. and one containing vanadium, silicon, etc. As catalysts for producing acetic acid from ethane and oxygen, there are known one containing vanadium, titanium, molybdenum, phosphorus, etc. and one containing molybdenum, vanadium, niobium, etc. No catalyst, however, has been available for directly producing acrolein from ethane and oxygen.
A method for producing acrolein from ethane, an inexpensive substance, and oxygen on a commercial scale has not been established.
This invention has an object of providing a technique capable of stably and inexpensively producing acrolein with high efficiency directly from ethane and oxygen.
The inventors, through a study conducted with a view to accomplishing this object, first learned that (A) a composite (or complex oxide) which has iron and silicon oxide, readily available substances with very low toxicity, as components forms an excellent catalyst for producing formaldehyde from methane and that (B) the composite mentioned above is capable of functioning as a catalyst for producing acrolein from propane. After continuing the study further based on this knowledge, they discovered that a composite (or complex oxide) resulting from the addition of an alkali metal to the composite (or complex oxide) mentioned above excels in stability and functions satisfactorily as a catalyst for efficiently producing acrolein from ethane and oxygen as raw materials.
SUMMARY OF THE INVENTION
This invention relates to a catalyst containing silicon, iron, an alkali metal, and oxygen and serving the purpose of producing acrolein from ethane as a raw material and to a method for producing acrolein by oxidizing ethane in the presence of this catalyst. This invention further relates to a method for producing a catalyst containing silicon, iron, an alkali metal, and oxygen by impregnating porous silicon oxide with a mixture of an aqueous water-soluble iron compound solution and an aqueous alkali metal solution or sequentially with said two aqueous solutions, thereby inducing adhesion of iron and an alkali component to the porous silicon oxide, and calcining the resultant porous silicon carbide having iron and alkali metal deposited thereon and to a method for producing a catalyst containing ferrosilicon, an alkali metal, and oxygen by forming a mixture of silicon and iron by the sol-gel process from a mixture of at least one member selected from the group consisting of water-soluble iron compounds and organic iron compounds with tetraethyl silicate, drying the resultant mixture, calcining the dried mixture in the presence of oxygen, and impregnating the product of this calcination with an aqueous alkali metal solution, then drying the product of impregnation, and calcining the dried product of impregnation in the presence of oxygen.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The catalyst of this invention for the production of acrolein is formed of an amorphous complex oxide using silicon, iron, an alkali metal, and oxygen as component elements.
Silicon in the form of silicon oxide is the main component of the catalyst. So long as it has a porous texture, the silicon oxide can be a product of the sol gel process or the gaseous-phase reaction process, or be a commercially available silica gel.
The iron and the alkali metal are thought to act as active components of the catalyst because they are at least partly carried in a highly dispersed state as iron ion (Fe
3+
) and an alkali metal ion (M
+
) forming the oxide on the surface (inner pore surfaces) of the porous silicon oxide.
Though not particularly limited, the process of producing the catalyst of this invention for the production of acrolein is generally as follows.
First, a catalyst precursor is obtained by incorporating iron ions in porous silicon oxide. Though the production of this catalyst precursor is not limited to a particular method, it can be attained, for example, by immersing porous silicon oxide (having a specific surface area in the approximate range of 10-1000 m
2
/g, preferably 30-600 m
2
/g) in an aqueous solution of such a water-soluble iron compound as, for example, iron nitrate, iron sulfate, iron chloride, iron phosphate, iron acetate, iron perchlorate, iron bromide, iron iodide or iron oxalate, thereby causing adhesion of an iron component to the porous silicon oxide, drying the impregnated porous silicon oxide, and then calcining the dry porous silicon oxide in the air at a temperature in the approximate range of 200-800° C., preferably in the approximate range of 300-700° C.
The catalyst precursor having an iron component contained in porous silicon oxide may otherwise be obtained by forming a silicon/iron mixture by the sol-gel process from a solution obtained by mixing at least one member selected from the group consisting of the water-soluble iron compound mentioned above and organic iron compound with tetraethyl silicate as the raw material for silicon, drying the silicon/iron mixture, and calcining the dry mixture in air at a temperature in the approximate range of 200-800° C., preferably in the approximately range of 300-700° C. Organic iron compounds usable herein include ferrocene, iron naphthenate, carbonyl iron, and iron octylate, for example.
The incorporation of the alkali metal (at least one member selected from among lithium, sodium, potassium, rubidium, and cesium) in the catalyst precursor can be achieved by any of various methods. Generally, the catalyst having silicon oxide-iron ion-alkali metal ion as a catalytically active component thereof can be obtained by immersing the catalyst precursor obtained in a powdery formed by the procedure mentioned above in an aqueous solution of such an alkali metal as alkali carbonate, alkali nitrate, or alkali hydroxide, thereby causing adhesion of the alkali metal component to the catalyst precursor powder, drying the wet catalyst precursor, and calcining the dry catalyst precursor in the air at a temperature in the approximate range of 200-800° C., preferably in the approximate range of 300-700° C.
The iron/silicon (atomic ratio) in the catalyst precursor (and the catalyst) is preferably in the approximate range of 1/100000-3/100, more preferably in the approximate range of 1/100000-5/100, and the alkali metal/silicon (atomic ratio) in the catalyst is preferably in the approximate range of 1/10000-5/100, more preferably in the approximate range of 1/1000-1/100.
When the catalyst obtained by the method described above is analyzed using laboratory instruments, it is found that the silicon is in an oxidized state, the iron is in a divalent and/or trivalent oxidized state, and the alkali metal is in a univalent oxidized state and that the iron component and the alkali metal component are uniformly dispersed on the outer surface of the porous silicon oxide (namely a silicon oxide having a
Kobayashi Tetsuhiko
Teng Yonghong
Ueda Atsushi
Agency of Industrial Science & Technology, Ministry of Internati
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Padmanabhan Sreeni
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