Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Reexamination Certificate
2000-06-09
2002-05-07
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
C502S350000, C502S064000, C502S085000
Reexamination Certificate
active
06383966
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of producing an improved titanium-containing catalyst and its use in an epoxidation process. The catalyst is obtained by impregnating a high surface area siliceous solid with a titanium halide in a hydrocarbon solvent, or a vapor stream of titanium tetrachloride, followed by calcination. The catalyst is highly active for olefin epoxidation.
BACKGROUND OF THE INVENTION
Many different methods for the preparation of epoxides have been developed. One such method involves the liquid phase epoxidation of an olefin with an organic hydroperoxide in the presence of a solubilized transition metal catalyst. Although highly active and selective for olefin epoxidation, soluble catalysts must be recovered or recycled after use to avoid loss to a waste stream. However, it can be very expensive to recover the soluble catalysts after use. In addition, recycle decreases catalyst productivity by also recycling certain heavy substances such as acids and polymers that tend to accumulate along with catalyst in the heavy bottoms stream. The recycled heavies stream decreases epoxide selectivity or olefin conversion.
Heterogeneous (insoluble) catalysts have been developed to avoid homogeneous catalyst disadvantages. U.S. Pat. No. 4,367,342 discloses an olefin epoxidation process in the presence of an insoluble catalyst comprised of an inorganic oxygen compound of titanium. Unfortunately, the disclosed catalysts have less than optimum activity and selectivity. British Pat. No. 1,332,527 teaches a process for preparing an improved titania-silica catalyst characterized by impregnating an inorganic siliceous solid with a titanium compound in an oxygen-substituted hydrocarbon solvent, removing the solvent, and calcining the impregnated solid. Suitable solvents are limited to oxa and/or oxo-substituted hydrocarbons that are liquid at ambient conditions including alcohols, ketones, ethers, and esters. According to this patent, impregnation in an oxygen-substituted hydrocarbon solvent produced catalysts with improved properties compared to similar catalysts prepared by other methods. The alleged reason is that such catalysts have a more uniform, non-agglomerated content of titanium dioxide.
A later-filed patent application (EP 345,856) discloses the preparation of epoxidation catalysts that are alleged to be more active than the analogous catalysts obtained by previously known procedures. EP 345,856 teaches impregnation of silica with a gaseous stream of titanium tetrachloride, followed by calcination, hydrolysis, and, optionally, silylation. In a comparative example, a catalyst prepared by silica impregnated with a solution of tetra isopropyl ortho-titanate, complexed with acetyl acetone in isopropanol solvent, was found to be 4.5 times less active than the catalyst prepared by vapor phase impregnation with titanium tetrachloride. Additionally, PCT Int. Appl. WO 98/50374 discloses a catalyst prepared by a liquid phase impregnation process with a non-oxygen containing solvent. The catalyst prepared by this method has activity similar to that produced by the method of EP 345,856. Although WO 98/50374 discloses that higher surface area siliceous solids can incorporate more titanium, it does not disclose any benefits with higher surface area solids.
New methods to produce heterogeneous catalysts for olefin epoxidation have focussed on the use of high surface area, mesoporous supports such as MCM-41 and MCM-48. The methods include direct synthesis in which titanium is incorporated into the framework of the support (see Tanev, et. al.,
Nature
(1994) V. 368, 321) and a grafting technique in which titanocene dichloride is grafted onto a mesoporous silica (see Maschmeyer, et. al.,
Nature
(1995) V. 378, 159). Titanocene dichloride is taught to be superior to titanium tetrachloride or titanium isopropoxide due to lesser tendency to form unwanted oligomeric titanium-oxo species.
We have discovered an effective, convenient method of producing catalyst compositions having high epoxidation activity (and selectivity). These new catalyst compositions are significantly more active than catalysts obtained by techniques taught in EP 345,856, WO 98/50374, or by Maschmeyer, et. al.
SUMMARY OF THE INVENTION
The invention is an olefin epoxidation process comprising contacting an organic hydroperoxide with an olefin in the presence of a catalyst. The catalyst is produced by the method comprising: (a) impregnating a high surface area inorganic siliceous solid having surface area greater than 1100 m
2
/g with a titanium source; (b) calcining the impregnated solid; and (c) optionally, heating the catalyst in the presence of water. The titanium source can be either a solution of a titanium halide in a non-oxygenated hydrocarbon solvent or a vapor stream of titanium tetrachloride. Optionally, the catalyst preparation method comprises the additional step of treating the catalyst with a silylating agent.
We surprisingly found that catalysts produced by the impregnation of high surface area siliceous solids with titanium halides gave higher activity in olefin epoxidation compared to known catalyst preparation methods.
DETAILED DESCRIPTION OF THE INVENTION
The epoxidation process of the invention utilizes a titanium-containing heterogeneous catalyst that has unexpectedly been found to give superior epoxidation performance compared to materials made using other impregnation methods. In one embodiment of the invention, the catalyst preparation method is characterized by impregnating a high surface area inorganic siliceous solid, having surface area greater than 1100 m
2
/g, with a solution of titanium halide in a non-oxygenated. hydrocarbon solvent.
Suitable solvents for this purpose are those hydrocarbons that do not contain oxygen atoms, are liquid at ambient temperatures, and are capable of solubilizing the titanium halide. Generally speaking, it will be desirable to select hydrocarbon solvents wherein titanium halide concentrations of at least 0.5 percent by weight at 25° C. can be achieved. The hydrocarbon solvent should preferably be relatively volatile so that it may be readily removed from the inorganic siliceous solid following impregnation. Solvents having normal boiling points of from 25° C. to 150° C. thus may advantageously be utilized. Particularly preferred classes of hydrocarbons include C
5
-C
12
aliphatic hydrocarbons (straight chain, branched, or cyclic), C
6
-C
12
aromatic hydrocarbons (including alkyl-substituted aromatic hydrocarbons), C
1
-C
10
halogenated aliphatic hydrocarbons, and C
6
-C
10
halogenated aromatic hydrocarbons. Most preferably, the solvent does not contain elements other than carbon, hydrogen, and (optionally) halogen. If halogen is present in the solvent, it is preferably chloride.
Mixtures of non-oxygenated hydrocarbons may be used, if so desired. Preferably, the solvent used for impregnation purposes is essentially free of water (i.e., anhydrous). While oxygen-containing hydrocarbons such as alcohols, ethers, esters, ketones and the like could be present in admixture with the required non-oxygenated hydrocarbon, in one desirable embodiment of the invention only non-oxygenated hydrocarbon is present as a solvent during impregnation. Examples of suitable hydrocarbon solvents include n-hexane, n-heptane, cyclopentane, methyl pentanes, methyl cyclohexane, dimethyl hexanes, toluene, xylenes, methylene chloride, chloroform, dichloroethanes, chlorobenzene, benzyl chloride, and the like.
Unlike the procedure described in Example I of U.S. Pat. No. 4,021,454, wherein water is added to a mixture of titanium tetrachloride and silica in n-heptane, the process of this invention in preferred embodiments is characterized by the substantial exclusion of water until at least after impregnation is completed and preferably until after calcination. “Substantial exclusion” in the context of this invention means that water is not deliberately added or introduced or, if deliberately added or introduced, is removed prior to introduction of titanium halide. Th
Carroll Kevin M.
Gastinger Robert G.
Han Yuan-Zhang
Morales Edrick
Arco Chemical Technology L.P.
Carroll Kevin M.
Griffin Steven P.
Johnson Edward M.
LandOfFree
Method for making a heterogeneous epoxidation catalyst does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for making a heterogeneous epoxidation catalyst, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making a heterogeneous epoxidation catalyst will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2896290