Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Phosphorus or compound containing same
Reexamination Certificate
2001-02-28
2002-07-02
Dentz, Bernard (Department: 1625)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Phosphorus or compound containing same
C502S234000, C502S247000, C502S350000, C502S353000, C549S258000, C549S259000, C549S260000, C549S505000
Reexamination Certificate
active
06413903
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to catalysts useful in the oxidation of hydrocarbons. for example butadiene. The catalysts comprise vanadium oxides incorporated in a matrix comprising oxides and oxyhydroxides of silicon, titanium, tantalum and/or niobium derived using sol gel chemistry.
TECHNICAL BACKGROUND
This invention relates to a catalyst comprising vanadium oxides incorporated in a matrix comprising oxides and oxyhydroxides of silicon, titanium. tantalum and/or niobium derived using sol gel chemistry, optionally in the presence of an organic directing agent. This invention also relates to a process for the preparion of furan and maleic anhydride, more specifically, to a method for preparing furan and maleic anhydride by a vapor-phase catalytic oxidation reaction from 1,3 butadiene.
Furan is used as a chemical building block for the production of other industrial chemicals such as tetrahydrofuran, pyrrole and thiophene. Maleic anhydride can be used to manufacture tetrahydrofuran, polyester resins, fumaric and tartaric acids, pesticides, preservatives and other industrial products.
E. I. Ko, in the Handbook of Heterogeneous Catalysis, ed. by G. Ertl et al, Vol. 1. 2.1.4 (1997) reviews generally the use of sol-gel processes for the preparation of catalytic materials. There is no disclosure of or suggestion of vanadium oxides, vanadium phosphorus oxides, or vanadium antimony oxides dispersed in and distributed throughout high surface area oxides of silicon and/or titanium as being useful catalysts for the oxidation of butadiene.
Japanese Patent Application SHO 46-22009 discloses the preparation of catalysts comprising oxides of molybdenum, bismuth and vanadium in a silica matrix and their utility in the oxidation of butadiene.
U.S. Pat. No. 4,622,310 discloses inorganic phosphate aerogels. The utility disclosed is as porous inert carrier materials (supports) in polymerization and copolymerization processes. Use of the inorganic phosphates as supports in hydrocarbon oxidation processes wherein the catalyst species is V
2
O
5
, MoO
3
, Ag. Cu, PCI
3
and BiO
23
(sic. Bi
2
O
3
is meant) are described. There is no disclosure nor suggestion of incorporating the catalytic material within the inorganic phosphate gel matrix.
U.S. Pat. No. 5,264,203 describes the preparation of large pore crystalline materials, for example silicoaluminophosphates, optionally comprising a metal, by use of an organic directing agent.
SUMMARY OF THE INVENTION
This invention provides compositions comprising catalytic species selected from the group consisting of vanadium oxides, vanadium phosphorous oxides and vanadium antimony oxides incorporated in a matrix material selected from the group of oxides and oxyhydroxides of silicon, titanium, tantalum and niobium, which compositions are prepared by sol gel chemistry, optionally in the presence of an organic directing agent.
This invention further provides an improved process for the oxidation of butadiene to furan and maleic anhydride, the improvement comprising the use of a composition comprising catalytic species selected from the group consisting of vanadium oxides, vanadium phosphorous oxides and vanadium antimony oxides incorporated in a matrix material selected from the group of oxides and oxyhydroxides of silicon, titanium, tantalum and niobium, which compositions are prepared by sol gel chemistry, optionally in the presence of an organic directing agent.
DETAILED DESCRIPTION OF THE INVENTION
Catalysts that are highly reactive for the oxidation of butadiene were synthesized by incorporating catalyst species into matrices containing silicon, titanium, tantalum and niobium oxides and oxyhydroxides to generate high surface area catalysts. Specific catalytic species employed include vanadium oxides, vanadium phosphorus oxides, and vanadium antimony oxides. Bar matrix is meant a skeletal framework of oxides and oxyhydroxides which can be derived from the hydrolysis of alkoxides and other reagents.
The catalysts of the present invention may be prepared by various methods. A non-aqueous solution containing the catalyst species and matrix precursors (generally, but not necessarily, alkoxides) is added to solution containing water, acid or base, alcohol and, optionally, an organic directing agent to form a catalyst precursor gel or gelatinous material and subsequently drying the gel. Alternatively, a solution containing water, acid or base and alcohol is added to a nonaqueous solution containing catalyst species, matrix precursors, and, optionally, an organic directing agent. In general, the optional organic directing agent can be in the aqueous or non-aqueous solutions. The catalytically active species can be in the aqueous or non-aqueous solutions. The order can be (i) aqueous solutions added to non-aqueous solutions, or (ii) non-aqueous solutions added to aqueous solutions.
The inorganic metal alkoxides used in this invention, i.e. the alkoxides of silicon, titanium, tantalum and niobium may include any alkoxide which contains from 1 to 20 carbon atoms and preferably 1 to 5 carbon atoms in the alkoxide group, which are preferably soluble in the liquid reaction medium. In this invention, preferably, C1-C4 systems, ethoxides, isopropoxides or n-butoxides are used.
One of the criteria for the starting material are inorganic alkoxides or metal salts which will dissolve in the specified medium or solvent. Commercially available alkoxides can be used. However, inorganic alkoxides can be prepared by other routes. Some examples include direct reaction of zero valent metals with alcohols in the presence of a catalyst. Many alkoxides can be formed by reaction of metal halides with alcohols. Alkoxy derivatives can be synthesized by the reaction of the alkoxide with alcohol in a liqand interchange reaction. Direct reactions of dialkylamideg with acohol also form alkoxide derivatives.
The catalytic species, i.e., the vanadium oxides, vanadium phosphorous oxides and vanadium antimony oxides are derived from soluble alkoxides or salts. Preferred species include NH
4
VO
3
, vanadium trisisopropoxide, and antimony (III) n-butoxide (Sb (OC
4
H
9
)
3
.
The organic direct agent, if present, is selected from the group consisting aliphatic amines, aromatic amines, cyclic aliphatic amines, polycyclic aliphatic amines and an amonium or phosphonium ion. A preferred organic directing agent is dodecylamine.
After combining the solutions employed, the alkoxides will react and polymerize to form a gel. As polymerization and crosslinking proceeds viscosity increases and the material can eventually set to a rigid “gel”. The “gel” consists of a crosslinked network of the desired material which incorporates the original solvent within its open porous structure. The “gel” may then be dried, typically by either simple heating in a flow of dry air to produce an aerogel or the entrapped solvent may be removed by displacement with a supercritical fluid such as liquid CO
2
to produce an aerogel, as described below. Final calcination of these dried materials to elevated temperatures (>200° C.) results in products which typically have very porous structures and concomitantly high surface areas.
Depending on the alkoxide system and the water/alkoxide ratios used, a discernible gel point can be reached immediately or hours later. The molar ratio of the total water added (including water present in aqueous solutions), can vary according to the specific inorganic alkoxide being reacted. Generally, a molar ratio of water to alkoxide within the broad range of 3 to 150 is within the scope of this invention. It is understood that the order of addition of the various solutions can be reversed.
The addition of acidic or basic reagents to the gellation reaction can have an effect on the kinetics of the hydrolysis and condensation reactions, and the microstructure of the oxide/hydroxide matrices derived from the alkoxide precursor which entraps or incorporates the soluble metal reagents. Generally, a pH range of 1-12 can be used, with a pH range of 1-6 preferred for these experiments.
A
Dentz Bernard
E. I. du Pont de Nemours and Company
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