Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
12403~t6
HALOSILANE CATALYST AND PROCESS
FOR MAKING SAME
This invention relates to particulate cupreous
catalyst and a method for making tame, end more particularly
5 to this sort of catalyst for producing an alkyd or aureole
halo5ilane (such as dimethylaichlorosilane from methyl
chloride and silicon t elevated temperature.
BACKGROUND I IRE INVENTION
A variety of cupreous catalysts have been proposed
for such Solon production. Heretofore the ones in most
general use had appreciable precipitated copper content.
Accordingly, they often were contaminated with noncupreous
material in proportions not always easy to control. The
instant invention enables the metallurgists to make a
catalyst of good activity more reproducibly using copper
oxide-rich starting materials prepared by pyrometallurgy.
BROAD STATEMENT OF TUBE INVENTION
One aspect of the instant invention is an
improvement in process for waking cupreous catalyst
composition wherein a copper oxide-preponderant grind charge
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derived from the oxidation of elemental copper and/or an
alloy thereof is subject to high energy milling with
concomitant crystal lattice distortion until the average
particle size (mass median diameter) of the resulting grind
is no larger than about 20 microns. The improvement
comprises establishing a tin concentration between about 400
and about 3000 Pam in said composition prior to or after
said high energy milling.
Another aspect of the instant invention is a
pyrometallurgically-sourced particulate catalyst composition
for organohalosilane production, said composition consisting
essentially of a major proportion of cuprous and cupric
oxides, a minor proportion of elemental copper, containing
tin in a proportion of about 400-3000 Pam, having particle
size not substantially above about 20 microns, and
exhibiting crystal lattice distortion.
DETAILED DESCRIPTION OF THE INVENTION
For efficiency and economy the cupreous
particulate providing the grind charge (i.e., the charge to
the high energy milling operation) generally are no larger
than about 80 mesh, advantageously -150 mesh, and preferably
preponderantly -325 mesh (so such charge will not unduly
restrict production in the high energy milling operation).
Average particle size of such grind charge is above 20
microns and ordinarily 90% or more of it will be at least 25
microns or coarser. Desirably these particulate should not
contain more than about 3 percent of adventitious (that is,
normally or inherently present, but not deliberately added)
material for best control of charge analysis. The grind
charge desirably is extremely low in lead and other
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impurities that are considered detrimental for Solon
catalysts.
The grind charge can contain, if desired, up to
about 10% and usually just a few percent of promoter-
providing material such as elemental zinc, iron, or the oxides or chlorides of these metals, copper chloride, even a
little antimony (below 0.05%), and silica or
aluminosilicates typically up to a few percent maximum. The
promoter can be an original part of the grind charge of
cupreous particulate, or it can be added thereto prior to
or after the high energy comminution that follows. In some
instances it can be efficient to add a promoter-providing
material such as iron and/or other metal as particles of an
alloy of such metal with at least part of the particulate
copper that is to be further processed by pyrometallurgy
(e.g., oxidation) to make such grind charge for the high
energy milling.
The tin concentration in the catalyst can be
established in one or more of a variety of ways. One can
alloy at least a part of it or simply blend at least a part
of it with the copper or copper alloy, e.g., powder, that is
to be oxidized. Another way is to add at least a part of it
as elemental metal (or a tin-bearing material such as an
oxide, or sulfide or chloride or copper/tin alloy powder) to
the grind charge for the high energy milling or even to a
preparatory milling stage such as hammer milling. Still
another way is to add at least a part of such tin-bearing
material to the grind that results from the high energy
milling.
The tin concentration in the catalyst is reckoned
as the fraction equivalent in weight to elemental tin
whether such tin is in combined form or not. It may operate
to keep the catalyst more free-flowing in use, or it may act
to form sites that are beneficially attacked by a reactant
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such as a chloride in the halosilane manufacture. Whether
the enhancement of catalyst is due to one of these or some
other reason is not known.
In a cuprous oxide-rich catalyst tin incorporation
advantageously is from about 400-1800 Pam and preferably
900-1800 Pam. Typically the copper stoichiometry of such
catalyst is 65-95% cuprous oxide, 2-28% cupric oxide, and 2-
15~ elemental copper.
In a catalyst richer in cupric oxide and elemental
copper tin incorporation advantageously is about 400-2500
Pam and preferably 900-2500 Pam. Typically the copper
stoichiometry of such catalyst is 30-65~ cuprous oxide, 28-
45% cupric oxide, and 4-25% elemental copper.
By a pyrometallurgically-sourced catalyst
composition is meant that the cupreous material going into
the grind charge is made by heating copper metal and/or a
copper compound such as a copper oxide or carbonate in an
inert and/or a chemically reactive atmosphere (usually a
reducing or an oxidizing one) or in the substantial absence
of any atmosphere. One typical source of such cupreous
material is -the mill scale that forms on the surfaces of hot
copper ingots that are exposed to air; another is from the
air-oxidized surfaces of copper machining chips and
cuttings; another is the controlled air oxidation of copper
particles; still another is from the collection of vaporized
copper and/or dusts of an oxide of copper. Such cupreous
material for making a grind charge can be from a single
pyrometallurgical source as, for example, the elf oxidation
of fine copper particles. Alternatively it can be a blend
of products from a plurality of pyrometallurgical sources.
The stoichiometry (proportions) of the catalyst
with respect to cuprous oxide, cupric oxide, and elemental
copper can be manipulated effectively by blending various
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oxidized copper materials when necessary or desirable. In
one very useful embodiment the grind charge simply is
hammer milled cuprous oxide-rich particulate (typically
about 85-90~ cuprous oxide). If greater cupric oxide is
desired, that material can be roasted in air. Another way to
make stoichiometric adjustments is to blend such cupric
oxide-enriched roasted material with the rearrested admixture
of some of the first mentioned cuprous oxide-rich
hammer milled material and some particulate copper metal.
The grind charge advantageously has been
commented previously to fairly small size in a mill with a
short retention time such as a hammer mill using swing or
fixed hammers. Other conventional pulverizing apparatus
also can be used for such operation preparatory to the high
energy milling. Thus, one can use a roller mill, an
attrition mill, or a fluid energy mill.
Especially advantageous for the instant process is
the careful selection of a grind charge of analysis as
outlined herein coupled with the fineness of grind made by
the energy comminution of such charge (to give adequate
surface area and crystal lattice distortion to the catalyst
product). Desirably such comminution is operated
continuously, that is, with continuous feed to and take-off
from the high energy milling (commenting) apparatus. Batch
milling can be used for this step if desired, however.
Illustrative of a useful batch mill is the Seiko (the
trademark of Seiko, Inc.) vibratory mill. A continuous high
energy comminution apparatus preferred is a so-called "Pall
mill, the product of Humboldt-Wedag of West Germany. A
smaller laboratory size batch vibratory mill that can be
useful is the Megapac (a trademark of Polemic Ltd.) mill.
Such mills generally are called "vibratory ball mills--
although the grinding media inside the shell(s) is often
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other than spherical in shape. Such media typically is made
of a hard ceramic (such as alumina, zircon), a steel (such
as a stainless steel, a low alloy steel, a nickel Steele
tungsten carbide, etc., all conventional grinding media.
Such mill generally oscillates with a compound motion that
is imparted to the shell(s) by an eccentric mechanism.
Another high energy mill useful for the instant
purpose is the "Szegvari mill" made by the Union Process
Company. It is basically a stirred ball mill, and it even
can be modified in accordance with the precepts of U. S.
patent 3,927,837. In summary, the high energy comminution in
the instant process is done by an apparatus that has solid
grinding media in it, is driven with substantially more
horsepower per unit weight of grinding medium than is a
conventional tumbling ball mill, and provides a prolonged
residence time (actually an average residence time in a
continuous operation) for the grind charge typically of at
least about 10 minutes to an hour or even longer if necessary
or desired.
In a matter of a half hour to an hour a large high
energy mill can community the grind charge to size much
smaller than 10 microns average size, usually 2-7 microns.
If additional size reduction is needed, the output can be
recycled for remitting.
In an advantageous processing operation for making
the catalyst the grind charge has particle size no coarser
than 150 mesh, and the particulate thereof contain about 65-
95% cuprous oxide, about 2-28% cupric oxide, and about 2-15
elemental copper.
In another useful processing operation for making
the catalyst the grind charge has at least about 95% of its
particles not substantially larger than 325 mesh and the
particulate charged contain about 30-65% cuprous oxide,
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about 28-45% cupric oxide, and about 4-25% elemental copper.
To obtain the particular stoichiometry of such charge it is
often necessary to blend two or more powders of differing
oxide and elemental copper contents.
The following examples show how the invention has
been practiced, but should not be construed as limiting the
invention. In this specification all parts are parts by
weight, all percentages are weight percentages, all
temperatures are in degrees Celsius, and all mesh sizes are
10 V. S. Standard Sieve sizes unless otherwise expressly noted;
additionally, in this specification an average particle size
means the mass median particle size as measured with the
Microtrac (a trademark of Leeds Northrup Company) or the
Hayakawa PA-720 (Hayakawa is a trademark of Pacific Scientific
15 Company) particle size analyzers, and Specific Surface Area
(SPA) is measured by the BET (Browner, Emmett, and Teller)
method. In general, the catalyst particles have a specific
surface area in the range of i/2 to 8 m2/gram/ and more
specifically in the range of 2 to 8 m2/gram.
EXAMPLE 1
Copper alloy particles containing 1200 Pam tin and
660 Pam aluminum were air-oxidized at elevated temperature
to a copper oxide-rich condition. The resulting oxidate was
pulverized to make a particulate grind charge (-150 mesh)
25 for high energy comminution. The grind charge was milled in
a Megapac TM laboratory batch mill for about 6 hours to
produce particles having average particle size of 3.9
microns (mass medium diameter as measured by the Microtrac
instrument). The Specific Surface Area was 2.4 m2/gm., and
30 crystal lattice distortion occurred. Stoichiometry was
39.2~ cuprous oxide, 44% cupric oxide, and 16.8~ elemental
copper.
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The particles had good activity and high
selectivity as a catalyst for the reaction of methyl
chloride with silicon to produce dimethyldichlorosilane.
Both the activity and selectivity were markedly higher for
this catalyst than for a related comparable one where the
tin content was about a fourth as much. The stoichiometry
of such related catalyst was 51.3% cuprous oxide, 36.6%
cupric oxide, 10.5% elemental copper, and it had Specific
Surface Area of 2.5 m2/9m.
EXAMPLE 2
Copper particles containing 1700 Pam tin were air-
oxidized at elevated temperature to a copper oxide-rich
condition. The resulting oxidate was pulverized to make a
particulate grind charge (-150 mesh) for high energy
comminution. The grind charge was milled at about 15 kg.
per hour using a Model 20U Pall mill for about a half hour
average residence time to produce particles having average
particle size of 5.4 microns (mass median diameter as
measured by the Hayakawa instrument). The Specific Surface Area
of the resulting catalyst was 2.8 m2/gm-~ and crystal
lattice distortion occurred. Stoichiometry was 70.1%
cuprous oxide, 20.0% cupric oxide, and 9.5% elemental
copper.
The particles had good activity and selectivity as
a catalyst for the reaction of methyl chloride with silicon
to produce dimethyldichlorosilane. The activity was
markedly higher for this catalyst than for a related one
commented with a larger (35U) Pall mill where the tin
content was slightly less than a fifth as much. The
stoichiometry of such related catalyst was 63.5% cuprous
oxide, 27.4% cupric oxide, 9.3% elemental copper, and it had
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Specific Surface Area of 3.2 m2/gm. The average particle
size of such catalyst (measured with the Microtrac
instrument) was 3.9 microns.
Frequently there is an exchange of oxygen in the
5 grind charge undergoing high energy comminution. In such
exchange cuprous oxide content usually increases while the
cupric oxide and elemental copper proportions decrease.
Accordingly, such comminution can be looked upon not only as
a way of subdividing the particles and inducing crystal
10 lattice distortion in the product, but also of further
adjusting stoichiometry of the product.
