Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Utilizing sol or gel
Reexamination Certificate
2000-10-10
2003-04-22
Fiorilla, Christopher A. (Department: 1731)
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Utilizing sol or gel
C264S232000, C264S234000
Reexamination Certificate
active
06551546
ABSTRACT:
The present invention relates to a process for producing a shaped body comprising at least one porous oxidic material and at least one metal oxide, the shaped body per se and its use as catalyst in reactions of organic compounds, in particular for the epoxidation of organic compounds having at least one C—C double bond.
Shaped bodies which comprise porous oxidic materials are used in numerous chemical processes. This necessitates a production process which allows industrially relevant quantities of shaped bodies to be produced inexpensively.
To produce shaped bodies, the porous oxidic material is generally admixed with a binder, an organic viscosity-increasing substance and a liquid for making the mixture into a paste and is densified in a kneader or pan mill. The resulting mass is subsequently shaped by means of a ram extruder or screw extruder and the shaped bodies obtained are dried and calcined.
In order to produce shaped bodies which are also suitable for producing very reactive products, it is necessary to use chemically inert binders which prevent further reaction of these products.
Suitable binders are a series of metal oxides. Examples which may be mentioned are oxides of silicon, of aluminum, of titanium or of zirconium. Silicon dioxide as binder is disclosed, for example, in U.S. Pat. Nos. 5,500,199 and 4,859,785.
In such binders, the content of alkali metal and alkaline earth metal ions should be as low as possible, which is why it is necessary to use binder sources which are low in or free of alkali metals and alkaline earth metals.
To produce the abovementioned metal oxide binders, it is possible to use corresponding metal oxide sols as starting materials. In the preparation of, for example, the abovementioned silicon dioxide binders which are low in or free of alkali metals and alkaline earth metals, silica sol which is low in or free of alkali metal and alkaline earth metals is employed as binder source.
In the preparation of silica sols, it is possible to start from alkali metal silicates, but this generally leads to undesirably high contents of alkali metal ions in the silica sol. The preparation of such silica sols is described, for example, in “Ullmann's Encyclopedia of Industrial Chemistry”, volume A 23 (1993), pp. 614-629.
JP-A-07 048 117 discloses the preparation of silica sol by hydrolysis of alkoxysilanes by means of ammonia in the presence of a large excess of alcohol; the silica sols obtained contain up to 10% by weight of silicon dioxide.
JP-A-05 085 714 describes the acid decomposition of alkoxysilanes, likewise in alcoholic medium. This gives silica sols having silicon dioxide contents of from 1 to 10% by weight.
A disadvantage of the processes for preparing silica sols disclosed in the latter two publications is the low silicon dioxide content which can be achieved in the silica sols. This makes the process uneconomical since plant capacity is wasted by excess water both in sol production and in further processing.
It is an object of the present invention to provide an industrially usable process for producing shaped bodies which have a low content of alkali metal and alkaline earth metal ions and can be used as catalysts, preferably in a fixed bed.
We have found that this object is achieved in a process for producing such shaped bodies by mixing porous oxidic material with metal oxide sol and/or metal oxide in a first step of the process, where the metal oxide sol and the metal oxide each have a low content of alkali metal and alkaline earth metal ions.
The present invention accordingly provides a process for producing a shaped body comprising at least one porous oxidic material and at least one metal oxide, which comprises the following step (i):
(i) mixing the porous oxidic material or materials with at least one metal oxide sol which has a low content of alkali metal and alkaline earth metal ions and/or at least one metal oxide which has a low content of alkali metal and alkaline earth metal ions.
The present invention likewise provides a shaped body which can be produced by the above-described process and has a content of alkali metal and alkaline earth metal ions of preferably less than 700 ppm, particularly preferably less than 600 ppm and in particular less than 500 ppm.
In a preferred embodiment of the process of the present invention, the metal oxide sol is prepared by hydrolysis of at least one metallic acid ester.
The present invention therefore also provides a process as described above in which the metal oxide sol is prepared by hydrolysis of at least one metallic acid ester.
The metallic acid esters employed for the hydrolysis can be purified prior to the hydrolysis. All suitable methods are conceivable here. Preference is given to subjecting the metallic acid esters to a distillation prior to the hydrolysis.
For the hydrolysis of the metallic acid ester, all possible methods can be used in principle. However, in the process of the present invention, the hydrolysis is preferably carried out in aqueous medium. This gives the advantage that, compared to hydrolyses known from the literature, for example from JP 07,048,117 or JP 05,085,714, in which an excess of alcohol is employed, significantly less alcohol has to be distilled off.
The hydrolysis can be catalyzed by addition of basic or acidic substances. Preference is given to basic or acidic substances which can be removed by calcination without leaving a residue. Particular preference is given to using substances selected from the group consisting of ammonia, alkylamines, alkanolamines, arylamines, carboxylic acids, nitric acid and hydrochloric acid. In particular, ammonia, alkylamines, alkanolamines and carboxylic acids are used.
The metallic acid esters used in the process of the present invention are preferably esters of orthosilicic acid.
In the process of the present invention, the hydrolysis of the metallic acid esters is carried out at from 20 to 100° C., preferably from 60 to 95° C., and at a pH of from 4 to 10, preferably from 5 to 9, particularly preferably from 7 to 9.
The molar ratio of catalytically active substance/metallic acid ester is generally from 0.0001 to 0.11, preferably from 0.0002 to 0.01 and in particular from 0.0005 to 0.008.
In the process of the present invention, the hydrolysis gives metal oxide sols, preferably silica sols, which have a content of alkali metal and alkaline earth metal ions of less than 800 ppm, preferably less than 600 ppm, more preferably less than 400 ppm, more preferably less than 200 ppm, more preferably less than 100 ppm, particularly preferably less than 50 ppm, more particularly preferably less than 10 ppm, in particular less than 5 ppm.
The present invention accordingly provides a metal oxide sol having a content of alkali metal and alkaline earth metal ions of less than 800 ppm which can be prepared by hydrolysis of at least one metallic acid ester.
The metal oxide content of the metal oxide sols prepared according to the present invention is generally up to 50% by weight, preferably from 10 to 40% by weight.
The alcohol formed in the hydrolysis is generally distilled off in the process of the present invention. However, small amounts of alcohol can remain in the metal oxide sol as long as they do not adversely affect the further steps of the process of the present invention.
An advantage for the industrial use of the metal oxide sols prepared according to the present invention is that they display no tendency to form gels. Specific precautionary measures for preventing gel formation are thus superfluous. The metal oxide sols prepared according to the present invention can be stored for a number of weeks, which makes coordination of the time at which they are prepared with further processing steps unproblematical.
In the process of the present invention, a mixture comprising at least one porous oxidic material and at least one metal oxide is prepared using a metal oxide sol prepared as described above as metal oxide source.
In principle, there are no restrictions in respect of the method of producing the mixture. Howeve
Grosch Georg Heinrich
Hesse Michael
Lockemann Christian
Möller Ulrich
Basf Aktiengesellschaft
Fiorilla Christopher A.
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