Redistribution of organohalosilanes utilizing heat treated crystalline alumina catalysts

A method of redistributing a mixture of organohalosianes, particularly methylchlorosilanes by contacting said mixture with a heat treated crystalline gamma alumina or eta alumina catalyst.

TECHNICAL FIELD 
This invention relates to a method for the redistribution of 
organohalosilanes utilizing heat treated crystalline gamma alumina or eta 
alumina catalysts. More particularly, this invention relates to the 
production of trimethylchlorosilane by the redistribution of mixtures of 
other methylchlorosilanes. 
BACKGROUND ART 
The preparation of methylchlorosilanes by direct synthesis (Rochow 
Synthesis See U.S. Pat. No. 2,380,995), results in the unavoidable 
formation of a considerable proportion of low-boiling products with a 
boiling point of less than 40.degree. C. (760 mmHg.). Said low-boiling 
products include for example, tetramethylsilane, dimethylchlorosilane, 
methyldichlorosilane, methylchlorosilane, trichlorosilane, methylchloride, 
hydrocarbons, etc. A method of converting the above-mentioned low-boiling 
product mixture into compounds (especially trimethylchlorosilane) more 
useful in the silicones industry is needed. 
Many redistribution and alkylation methods are known in the art for the 
preparation of organohalosilanes from other silanes utilizing aluminum 
catalysts and reactants, and other materials. Thus, the preparation of 
organohalosilanes from other silanes has been achieved using a wide 
variety of catalysts, co-catalysts and reactants such as silica alumina, 
zeolites, methyl chloride metallic aluminum, hydrogen chloride, aluminum 
trichloride, methylaluminum halides, etc. Generally, of the Lewis acid 
activated catalysts, aluminum trichloride was the most widely used for 
these types of reactions The utilization of aluminum trichloride and 
organoaluminum compounds as reagents and/or catalysts in these processes 
however, was fraught with numerous difficulties. 
A redistribution reaction is a rearrangement of at least two different 
substituents which are attached to a silicon atom or atoms Two or more 
silanes having differing numbers of substituents such as CH.sub.3 or Cl, 
for example, redistribute when said substituents exchange silicon sites. 
The resulting product or products still have a total of four substituents 
or atoms attached to the silicon atom, but in ratios different from that 
of the starting compounds. A typical redistribution reaction can be 
illustrated by the following: 
EQU (CH.sub.3).sub.4 Si+(CH.sub.3).sub.2 SiCl.sub.2 
.revreaction.2(CH.sub.3).sub.3 SiCl 
A disproportionation reaction is a type of redistribution reaction that 
occurs when a single silicon compound yields two or more dissimilar 
silicon compounds having substituents (i.e. CH.sub.3 and Cl) in differing 
proportions from that of the initial starting compound A 
disproportionation reaction can be illustrated by the following: 
EQU 2(CH.sub.3)2SiCl.sub.2 .revreaction.CH.sub.3 SiCl.sub.3 +(CH.sub.3).sub.3 
SiCl 
The use of organoaluminum compounds in general results in pyrophoric, 
potentially explosive, and readily hydrolyzable organoaluminum by-products 
which must be disposed of via lixiviation with water or alkali. This can 
be extremely hazardous because of the attendant hydrolysis of 
methylchlorosilanes to yield hydrogen chloride. Aluminum trichloride has 
appreciable solubility in methylchlorosilane mixtures which can produce 
separation and purification problems. Plugging problems in transport lines 
and distillation columns are usually concomitant with its use. 
Additionally, the use of aluminum trichloride involves long contact times 
ranging anywhere from two to twenty-four hours. 
U.S. Pat. Nos. 2,647,136, 2,786,861 and 3,793,357 all employ the use of an 
aluminum trichloride catalyst in the preparation of an alkylhalosilane by 
redistribution. The latter two patents also employ the use of an .tbd.SiH 
compound as the promoter or co-catalyst thus permitting the use of lower 
reaction temperatures. All of these patents, however, disclose processes 
operated under autogenous pressure and at temperatures between 
150-400.degree. C. for periods of two to twenty-four hours. Other patents 
which utilize an aluminum trichloride catalyst with or without a 
co-catalyst include U.S. Pat. Nos. 2,730,540, 3,655,710 and 3,980,686. It 
should be noted, however, that not all Lewis-acid catalysts such as "boron 
trichloride, zinc chloride, iron chloride, copper chloride, etc." exert a 
"perceptible effect" on the course of these reactions. (U.S. Pat. No. 
2,647,136, Column 3, Lines 69-75). Japanese Pat. 3026 (1964) discloses the 
preparation of phenylmethyldichlorosilane from phenyltrichlorosilane and 
tetramethylsilane utilizing an activated alumina catalyst at 240.degree. 
C. for 10 hours in an autoclave. Japanese Pat. 1822 (1957) discloses the 
preparation of methyltrichlorosilane from trimethylchlorosilane and 
silicon tetrachloride utilizing an activated alumina catalyst at 
280.degree. C. for 4 hours. Contrastingly, Japanese Pat. 23,172 (1961) 
shows that CH.sub.3 SiHCl.sub.2 is obtained by heating (CH.sub.3).sub.3 
SiCl and HSiCl.sub.3 in the presence of alumina at 200.degree.-400.degree. 
C. under autogenous conditions for up to 10 hours. Though all these 
patents disclose the use of activated alumina catalysts, the reactions 
involved require significantly longer reaction times (contact time) 
typically, of four hours or longer. 
The use of methylaluminum sesquichloride to methylate 
methyl-trichlorosilane is disclosed in U.S. Pat. No. 3,065.253. Here SiH 
compounds. e.g. methyldichlorosilane, is advantageously used to shorten 
the reaction time from 20 hours to 2 hours. 
U.S. Pat. No. 4,155,927 discloses a process for preparing 
trimethylchlorosilane by reacting methyldichlorosilane with methyl 
chloride and metallic aluminum. Methylchloride reacts with aluminum to 
form methylaluminum sesguichloride. The organoaluminum compound 
methylaluminum sesguichloride is the methylating agent which reacts with 
methyldichlorosilane to form aluminum trichloride and 
trimethylchlorosilane. This reaction is a methylation reaction not a 
redistribution reaction. This process is not catalytic. Furthermore the 
production of AlCl.sub.3 results in hazardous waste disposal problems as 
previously mentioned. 
U.S. Pat. No. 4,297,500 discloses a process for synthesizing 
trimethylchlorosilane from the low-boiling (&lt;40.degree. C.) fraction of 
the Rochow direct synthesis (U.S. Pat. No. 2,380,995) by hydrochlorination 
of this fraction in the presence of catalytic amounts of AlCl.sub.3. The 
amount of HCl employed must be at least equal to the molar amount of 
tetramethylsilane in the low-boiling fraction. AlCl.sub.3 is disclosed in 
this patent as a catalyst for the hydrochlorination reaction rather than 
redistribution. 
U.S. Pat. No. 4,158,010 discloses an improved redistribution process for 
preparing organosilanes by reacting a mixture of alkylhalosilanes with 
silanes containing an Si-H bond in the presence of organoaluminum 
compounds and hydrogen halides. The various forms or organoaluminum 
compounds utilized include: ethylaluminum dichloride, trimethylaluminum, 
methylaluminum sesquichloride, etc. This patent teaches (see Example 4) 
the synthesis of trimethylchlorosilane from the low-boiling fraction of 
the Rochow direct synthesis and added methyltrichlorosilane by heating the 
reaction mixture at reflux for 6 hours in the presence of methylaluminum 
sesquichloride and hydrogen chloride. In effect, this method combines 
hydrochlorination and methylation with redistribution at long contact 
times. 
The process of U.S. Pat. Nos. 3,065,253; 4,155 927; 4,297 500 and 4 158,010 
are all hampered by the hazardous handling and disposal problems 
associated with the use of AlCl.sub.3, organoaluminum halides and gaseous 
HCl. 
U.S. Pat. No. 3,384,652 discloses a method for the production of 
chlorosilanes and organic substituted chlorosilanes by disporportionation 
and condensation reactions of mixtures of organochlorosilanes in the 
presence of crystalline aluminosilicate catalysts (zeolites). These 
"aluminosilicate materials may also be converted to the H or acid form in 
which hydrogen ions occupy the cation ion sites" (Column 4, Lines 41-43). 
In general, "the H form is more stable in materials having SiO.sub.2 
/Al.sub.2 O.sub.3 of 3.5 or higher" (Column 4, Lines 45-47). Thus method 
utilizes zeolites having Bronsted acid sites. Moreover, as in the case of 
previous processes this reaction requires long contact times. 
U.S. Pat. No. 3,207,699 relates primarily to the preparation of catalysts 
by chemically attaching a restricted quantity of alkylsilyl groups to the 
internal surface of an acidic refractory oxide of one or more metals 
(e.g., silica-alumina) at an elevated temperature, cooling the treated 
acidic refractory oxide in an atmosphere containing no oxygen, whereby the 
catalytic properties of the acidic cracking catalyst are significantly 
modified without completely destroying the acidity of the catalyst. Prior 
to attaching the alkysilyl groups, the refractory oxide is dried at 
elevated temperatures in order to prevent the reaction of the silane with 
water because the latter reaction interferes with the desired reaction of 
the silane with the refractory oxide. This patent discloses that the 
refractory oxide contains significant cracking activity both before and 
after treatment with the silane. The treated catalysts so produced are 
disclosed as being useful as redistribution (specifically 
disproportionation) catalysts for trimethylsilane. U.S. Pat. No. 3,346,349 
relates primarily to the use of treated aluminaceous catalysts, including 
those of U.S. Pat. No. 3,207,699, as redistribution (specifically 
disproportionation) catalysts for various silanes. In U.S. Pat. No. 
3,346,349 both the class of silanes that can be used to treat the 
catalysts and the class of silanes that can be redistributed by the 
treated catalysts are expanded beyond the disclosure of U.S. Pat. No. 
3,207,699. U.S. Pat. No. 3,346,349 contains a disclosure similar to the 
disclosure of U.S. Pat. No. 3,207,699 with respect to the drying of the 
untreated catalyst and to the method of treatment of the dried catalyst 
with the silane. U.S. Pat. No. 3,346,349 makes no reference to the 
cracking activity either of the untreated catalyst or of the treated 
catalyst. However, in view of the similar treating conditions, it would 
appear that the treated catalysts of both patents should have similar 
properties. As is shown in K. Tanabe, Solid Acids and Bases, Academic 
Press. N.Y. 1970. pp. 123-133, cracking activity in silica-alumina 
catalysts is associated with the presence of Bronsted acid sites on the 
catalyst. Hence, accepting the teachings of U.S. Pat. Nos. 3,207,699 and 3 
346,349 at face value, it appears they relate to redistribution catalysts 
with Bronsted acid sites rather than Lewis acid sites. However, it is 
possible that the silanes reacted with all the Bronsted acid sites on the 
surface of the silica and alumina in the treatment process of these 
patents and so the "catalysts" actually become non-acidic during 
treatment. In view of the high redistribution temperatures actually used 
in the Examples (e.g. 510.degree. C.), the redistribution reactions 
reported in these patents may simply have been thermally-induced 
redistribution reactions as distinguished from catalytically induced 
redistribution reactions. The possible lack of catalytic activity of the 
treated oxides of these references (despite the disclosure in U.S. Pat. 
No. 3 207,699 that the treated catalysts retain significant cracking 
activity) is also consistent with the fact that the examples of the 
patents make no reference to any cracking reaction after the initial 
treatment of the silane. Japanese Pat. 23,172/1961, however, illustrates 
that methyldiohlorosilane is obtained by heating trimethylchlorosilane and 
trichlorosilane in the presence of an alumina catalyst at 200-400.degree. 
C. and under autogenous conditions for up to 10 hours. Longer residence 
times and/or higher temperatures promote the formation of silane, a known 
pyrophoric compound. 
It is an object of the present invention to provide a method for the 
redistribution and/or disproportionation of mixtures of organohalosilanes 
utilizing a heat treated crystalline alumina catalyst. 
More specifically, it is an object of the present invention to prepare 
trimethylchlorosilane from mixtures of other methylchlorosilanes, 
especially those derived from the lower-boiling fraction of the Rochow 
synthesis utilizing a heat treated crystalline alumina catalyst 
It is an object of the present invention to effect such redistribution 
and/or disproportionation reaction without the use of aluminum trichloride 
or other organoaluminum compounds. 
It is an object of the present invention to effect such redistribution 
and/or disporportionation reaction utilizing short contact times. 
It is a further objective of the present invention to effect regeneration 
and reuse of said heat treated crystalline alumina catalyst. 
SUMMARY OF THE INVENTION 
This and other objects of the invention which will be apparent to those 
skilled in the art are achieved by the present invention which relates to: 
a method for redistributing the halogen atom of a halosilane and at least 
one member selected from the group consisting of the hydrocarbyl group of 
a hydrocarbylsilane and the hydrogen atom of a hydrosilane which method 
comprises contacting a mixture of the halosilane, hydrocarbylsilane and/or 
the hydrosilane, with a heat treated crystalline gamma alumina or eta 
alumina catalyst at 200.degree. C.-450.degree. C. for a maximum contact 
time of ten minutes said heat treated catalyst having been activated at 
400.degree. C.-500.degree. C. 
In a preferred embodiment, this invention relates to: a method of 
catalytically redistributing a mixture of compounds having the formulas: 
EQU R.sub.n SiX.sub.4-n, and R.sub.m SiHX.sub.3-m 
wherein R is an alkyl group having from 1 to 55 carbon atoms, or an phenyl 
group, X is a halogen. n.ltoreq.4, and m.ltoreq.3, which method comprises 
contacting the mixture of compounds with a heat treated crystalline gamma 
alumina or eta alumina catalyst at 200.degree. C.-450.degree. C. for a 
maximum contact time of ten minutes, said heat treated catalyst having 
been activated at 400.degree. C.-500.degree. C. 
Another preferred embodiment of the present invention relates to: a method 
of catalytically redistributing the halogen, the hydrogen, the alkyl 
groups and/or phenyl groups of a single silane represented by the formula: 
EQU R.sub.n SiX.sub.4-n 
wherein R is hydrogen, an phenyl group, or an alkyl group containing from 1 
to 5 carbon atoms, X is a halogen and n has a value from 1 to 3 inclusive, 
which method comprises contacting the silane with a heat treated 
crystalline gamma alumina or eta alumina catalyst at 200.degree. 
C.-450.degree. C. for a maximum contact time of ten minutes, said heat 
treated catalysts having been activated at 400.degree. C.-500.degree. C.

DETAILED DESCRIPTION OF DRAWINGS 
The embodiments of the present invention are best understood by referring 
to FIG. 1. The silane reactants are stored in the vessel 1 and passed 
through the sintered stainless steel filter 2 to the calibrated pump 3. 
Liquid from the pump is flash evaporated at 300.degree.-400.degree. C. in 
the vaporizer 4. The inlet pressure is recorded by the pressure indicator 
5. The vaporized reactants are admitted to the reactor 6 that is made from 
Hastelloy B pipe which is equipped with reducing fittings for reactant 
introduction and product outlet and which contains a gamma alumina 
catalyst bed. Quartz wool is placed at both ends of the pipe to keep the 
.gamma.-alumina bed in place in the heated zone. The reactor is heated in 
a tube furnace 7. At the reactor outlet the gaseous silane product mixture 
is led to a condenser 8 and cooled by a suitable refrigerant, i.e., dry 
ice--isopropanol. The liquid silane product collected in the receiver 9 is 
subsequently analyzed and distilled. The practice of this invention is not 
in any way limited to the apparatus depicted herein. The valves and other 
minor fittings which would be obvious to those skilled in the art have 
been omitted. 
A better understanding of FIG. 2 will be achieved when said drawing is read 
in conjunction with the detailed description of the invention. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention is a method of redistributing the halogen of a 
halosilane and at least one member selected from the group consisting of 
the hydrocarbyl group of a hydrocarbylsilane and the hydrogen atom of a 
hydrosilane which method comprises contacting a mixture of the halosilane. 
hydrocarbylsilane and/or the hydrosilane with a heat treated crystalline 
gamma alumina or eta alumina catalyst at 200.degree. C.-450.degree. C. for 
a maximum contact time of ten minutes, said heat treated catalyst having 
been activated at 400.degree. C.-500.degree. C. 
A halosilane is defined as any silane containing a halogen atom directly 
bonded to the silicon atom. A hydrocarbylsilane is defined as any silane 
containing an alkyl group having from one to five carbon atoms or an 
phenyl group which is directly bonded to the silicon atom. A hydrosilane 
is defined as any silane containing a hydrogen atom which is directly 
bonded to the silicon atom. 
In a preferred embodiment, the present invention is a method of 
catalytically redistributing or disproportionating a mixture of compounds 
having the formulas: R.sub.n SiX.sub.4-n and R.sub.m SiHX.sub.3-m, wherein 
R is an alkyl group having from one to five carbon atoms, or an phenyl 
group, X is a halogen, n.ltoreq.4, and m.ltoreq.3, which method comprises 
contacting the mixture of compounds with a heat treated crystalline gamma 
alumina or eta alumina catalyst at 200.degree. C.-450.degree. C. for a 
maximum contact time of ten minutes, said heat treated catalyst having 
been activated at 400.degree. C.-500.degree. C. Another preferred 
embodiment of the present invention is a method of catalytically 
redistributing the halogen, the hydrogen, the alkyl groups and/or aryl 
groups of a single silane represented by the formula: 
EQU R.sub.n SiX.sub.4-n 
wherein R is hydrogen, an phenyl group or an alkyl group containing from 1 
to 5 carbon atoms, X is a halogen, and n has a Value from 1 to 3 
inclusive, which method comprises contacting the silane with a heat 
treated crystalline gamma alumina or eta alumina catalyst at 200.degree. 
C.-450.degree. C. for a maximum contact time of ten minutes said heat 
treated catalysts having been activated at 400.degree. C.-500.degree. C. 
Illustrative of the compounds represented by R are the following: 
______________________________________ 
CH.sub.3 SiCl.sub.3 (C.sub.3 H.sub.7)SiCl.sub.3 
(CH.sub.3).sub.2 SiCl.sub.2 
(C.sub.4 H.sub.9).sub.2 SiCl.sub.2 
C.sub.2 H.sub.5 SiCl.sub.3 
ArSiCl.sub.3 
(C.sub.2 H.sub.5).sub.2 SiCl.sub.2 
Ar.sub.2 SiBr.sub.2 
(C.sub.2 H.sub.5).sub.3 SiCl 
Ar.sub.3 SiCl 
(CH.sub.3).sub.4 Si (C.sub.6 H.sub.5).sub.4 Si 
(C.sub.2 H.sub.5).sub.4 Si 
(C.sub.3 H.sub.7).sub.4 Si 
______________________________________ 
Illustrative of the compounds represented by R.sub.m SiHX.sub.3-m are the 
following: 
______________________________________ 
(CH.sub.3).sub.3 SiH 
(C.sub.3 H.sub.7).sub.2 SiHCl 
(CH.sub.3).sub.2 SiHBr 
ArSiHBr.sub.2 
CH.sub.3 SiHCl.sub.2 
Ar.sub.2 SiHBr 
(C.sub.2 H.sub.5).sub.2 SiHCl 
______________________________________ 
In order to more fully understand the origin of Lewis acid sites in gamma 
alumina (.gamma.-Al.sub.2 O.sub.3) and eta alumina (.eta.-Al.sub.2 
O.sub.3), their structures must be considered. A Bronsted acid is a proton 
donor (H+). A Lewis acid is an electron pair acceptor (electron 
deficiency). 
The crystal structure of .eta.- and .gamma.-Al.sub.2 O.sub.3 is similar to 
that of spinel MgAl.sub.2 O.sub.4 (Refer to FIG. 2). In the structure of a 
spinel, all the oxygen anions are equivalent and are arranged in cubic 
close packing. The Mg.sup.2+ ions occupy the tetrahedral positions (A) in 
this cubic structure and are surrounded by four oxide anions (.omicron.). 
The Al.sup.3+ ions occupy the octahedral positions (B) wherein they are in 
turn surrounded by six oxide anions. In the spinel structure the ratio of 
metal cations to oxide anions is 3:4 and in the activated aluminas. This 
ratio is 2:3. A fraction of the cation sites, as is clear from FIG. 2 
remain vacant and the aluminas, as a result, show varying degrees of 
structural disorder. .eta.-Al.sub.2 O.sub.3 relatively more Al.sup.3+ 
ions in tetrahedral positions than does .gamma.-Al.sub.2 O.sub.3. The 
structural similarity to the spinels and the presence of hydrogen (as 
H.sup.+ at tetrahedral sites, as water of hydration or as surface 
hydroxyl groups) leads to the formulas, HO.sub.0.5 Al.sub.0.5 [Al.sub.2 
O.sub.4 ] and Al[H.sub.0.5 Al.sub.1.5 ]O.sub.4 for the .gamma.- and 
.eta.-polymorphs, respectively. The square brackets enclose the ions 
located at octahedral sites. Lewis acid activity of these aluminas 
originate in the electron deficiency of the aluminum ions at the 
tetrahedral sites. That these ions are indeed the site of Lewis acidity 
has been shown by the results of the well-known pyridine 
adsorption-infra-red spectroscopy test. (Morterra et al, Journal of 
Catalysis, Vol. 51. pp. 299-313 1978). 
Contrastingly, in alpha alumina all the Al.sup.3+ ions are located at 
octahedral sites in a hexagonal close packing arrangement of oxide anions. 
The pyridine adsorption infrared spectroscopy test shows that Lewis 
acidity does not exist in or on pure alpha alumina (Morterra et al, 
Journal of Catalysts, Vol. 54 pp. 348-364 1978). Hence pure alpha alumina 
is not useful for the instant invention. 
The nature or strength of the Lewis-acid site, the type of Lewis acid 
employed and the conditions (i.e. temperature, pressure, contact time and 
molar ratio of starting materials) of the catalysis have a determinative, 
but non-obvious effect on the redistribution reactions of silanes. For 
example, (CH.sub.3).sub.3 SiCl and SiCl.sub.4 redistribute in the presence 
of AlC1.sub.3 at 350.degree. C., 1500 Psig, 0.3 hr. according to the 
equation illustrated below (see U.S. Pat. No. 2,647,912). 
EQU (CH.sub.3).sub.3 SiCl+SiCl.sub.4 .revreaction.(CH.sub.3).sub.2 SiCl.sub.2 
+CH.sub.3 SiCl.sub.3 
The ratio of dimethyldichlorosilane to methylchlorosilane produced in the 
latter reaction depends on the contact time the temperature and the 
pressure in the autoclave. At 400.degree. C. for 10 hr. and 1250 psig. a 
different reaction pathway is evident as per the following equation see 
U.S. Pat. No. 2,590,937, Example 11): 
EQU (CH.sub.3).sub.3 SiCl+SiCl.sub.4 .revreaction.Cl.sub.3 SiCH.sub.2 
Si(CH.sub.3).sub.2 Cl+HCl 
However, in the presence of .gamma.-Al.sub.2 O.sub.3 at 280.degree. C. for 
4 hours. The same reagents yielded primarily CH.sub.3 SiCl.sub.3 (Japanese 
Pat. 1822/1957). 
Examples of suitable alumina catalysts which can be used in accordance with 
the present invention include aluminas having spinel type structures such 
as .eta.-Al.sub.2 O.sub.3 and .gamma.-Al.sub.2 O.sub.3. The hydrated 
aluminas such as gibbsite, boehmite, and bayerite, however, require 
calcination to remove water and generate to Lewis acidity. This 
calcination must be performed under carefully controlled pressure and 
temperature (heat treatment) conditions to obtain the crystalline Lewis 
acid-activated aluminas. Calcination procedures are well known to those 
skilled in the art of preparing or manufacturing activated aluminas (see 
Maczura et al. Kirk-Othmer Encylopedia of Chemical Technoloqy, 3rd Edition 
Vol. 2, pp 225-233, John Wiley and Sons, N.Y. 1978). In general, 
temperatures greater than 850.degree. C. are avoided in order to prevent 
transformation of the activated aluminas to alpha alumina. 
The activated aluminas are items of commerce. As obtained, they already 
have the spinel type structure demonstrable by its characteristic X-ray 
diffraction pattern. (See K. Weters and G. Bell, "Oxides and Hydroxides of 
Aluminum," Technical paper 19, Alcoa Research Labs. 1972). However, it is 
necessary to heat these commercial materials to remove adsorbed moisture 
and other volatile contaminants prior to their use as redistribution 
catalysts. The heat treatment or catalyst activation is done at 
400.degree. C.-800.degree. C. for periods of 0.5 to 20 hours. The 
preferred temperature range is 500.degree. C.-650.degree. C. for periods 
of 0.5-2 hrs. Activation procedures are well known to those skilled in the 
use of activated alumina catalysts (B. Linsen, "Physical and Chemical 
Aspects of Adsorbents and Catalysts." Academic Press, London 1970). 
The alumina catalysts of the instant invention must be specifically 
activated to generate Lewis acid sites. The activation and regeneration 
procedure of the instant invention differs significantly from that 
disclosed by the aforementioned U.S. Pat. Nos. 3 346,349 and 3.207,699. 
The activation and regeneration procedures of these patents actually 
destroy the acidity of the silica alumina catalyst. Neither patent 
discloses the desirability of using eta or gamma-alumina. On the contrary, 
silane-treated rehumidified eta alumina is disclosed in Example 4 of U.S. 
Pat. No. 3,207,699 as an inferior redistribution catalyst. 
Activation of the alumina (heat treatment) can be performed in a separate 
reactor or in situ in the same reactor used for the redistribution 
reaction. The latter mode is preferred because any transfer of the 
activated catalyst carries the risk of surface re-hydration. The spent 
catalyst remaining after the redistribution reaction can also be 
regenerated in situ. During activation and regeneration a dry, inert gas 
such as dried air, nitrogen, argon or helium flows through the catalyst 
bed as the temperature is raised to the desired temperature. The flow is 
maintained once this temperature has been reached as well as during the 
cooling stage. Periods as short as 0.1 hour may be used for activation. 
However, the preferred time is 0.5-2 hrs. at 500.degree. C.-650.degree. C. 
The flow rate of the dry, inert gas can cover a broad range, i.e. 0.5-50 
lit/min. At the lower limit of this range, it is only necessary to allow 
the volatile materials released from the hydrated alumina to be swept 
away. At the upper limit of this range, the maximum gas flow keeps the 
catalyst contained in the reactor. Alternatively, the regeneration and 
activation procedure may be performed in vacuo at 400.degree. 
C.-800.degree. C. or with reactive gases such as HCl or HF. When reactive 
gases are used it is essential that post-treatment with an inert gas be 
employed to destroy the Bronsted acid sites formed. 
The activated alumina catalyst may be used as a fine powder as granules or 
as pellets. The larger particle size facilitates the flow of gaseous 
reactants and products through the fixed catalyst bed. The extruded 
pellets may contain any of the common binders. e.g. clay, silica, alumina, 
graphite, etc 
To prepare an alumina catalyst containing Z5 less than 1% graphite, 
hereinafter referred to as a "graphite-1 lubricated alumina" catalyst 
graphite (less than 1%) is mixed with a powdered alumina catalyst. The 
"graphite-lubricated alumina" catalyst is then pelletized or granularized. 
The addition of graphite to an alumina catalyst increases its crush 
strength. Increasing the crush strength of the catalyst increases the 
ability of the catalyst to maintain its structural integrity and hence 
prolongs the life of the catalyst. 
The catalytic activity of the alumina depends on its crystal structure, 
pore-size distribution and surface area. These properties in turn are 
dependent on the precise activation procedure followed The preferred 
activated aluminas of this invention have median pore sizes in the range 
of 50 .ANG.-150 .ANG. and surface areas of 100-350 m.sup.2 /gm. Once the 
alumina catalyst has been Lewis-acid activated, the mixtures of 
organohalosilanes are passed through the catalyst bed at temperatures of 
200.degree. C.-450.degree. C., preferably 300.degree. C.-350.degree. C. 
for a maximum contact time (reaction time) of less ten minutes preferably 
less than five minutes, in order to achieve the same degree of 
redistribution or better than that achieved by the prior art. 
EXPERIMENTAL 
The following experimental description illustrates the present invention. 
In the experimental description the following abbreviations are used: 
______________________________________ 
Abbreviation 
Meaning 
______________________________________ 
Ar phenyl group 
Catalyst A* A gamma alumina catalyst in the form 
of 1/8 in. extrudates, with surface 
area of 224.6 m.sup.2 /gm, median pore 
diameter of 64.ANG., packing density of 
0.68 gm/cm.sup.3 and crush strength of 
15.6 FPCS, lbs. (Commercially known 
as Alumina "SA-6173"). 
Catalyst B* A gamma alumina catalyst in the form 
of 1/16 in. extrudates, with surface 
area of 211.3 m.sup.2 /gm, median pore 
diameter of 72.ANG., packing density of 
0.68 gm/cm.sup.3 and crush strength of 
11.3 FPCS, lbs. (Commercially known 
as Alumina "SA-6173"). 
Catalyst C* A gamma alumina catalyst in the form 
of 1/8 in. spheres having a surface 
area of 109 m.sup.2 /gm and crush strength 
of 13.0 FPCS, lbs. (Commercially 
known as Calsicat E-149SC). 
Catalyst D* A gamma alumina catalyst in the form 
of 1/8 in. tablets, having a surface 
area of 175 m.sup.2 /gm, median pore size 
less than 100.ANG., a density of 0.78 
gm/cc, and crush strength of 12.0 
FPCS, lbs. (Commercially known as 
Alumina AL-3438T). 
Catalyst E* A gamma alumina catalyst in the form 
of 1/8 in. spheres with a surface area 
of 312.55 m.sup.2 /gm, average pore 
diameter of 58.ANG., density of 0.68 m/cc 
and crush strength of 19.1 FPCS. 
(Commercially known as Alumina 
SA-74179). 
cc cubic centimeter 
D (CH.sub.3).sub.2 SiCl.sub.2 
DC H.sub.2 SiCl.sub.2 
DM (CH.sub.3).sub.2 SiHCl 
FPCS Flat plate crush strength, lbs. 
ft. foot 
gm gram 
hr. hour 
HVS higher boiling methylchlorosiloxanes, 
oligomeric and cyclic methylsiloxanes 
from Rochow Synthesis, generally 
having boiling points of greater than 
100.degree. C. 
Lights primarily CH.sub.3 Cl, butane and pentane, 
from Rochow Synthesis and generally 
having boiling points of less than 
37.degree. C. 
M (CH.sub.3).sub.3 SiCl 
ml. milliliters 
MD CH.sub.3 SiHCl.sub.2 
Q (CH.sub.3).sub.4 Si 
Sec. seconds 
SCFH standard cubic feet per hour 
T CH.sub.3 SiCl.sub.3 
TC HSiCl.sub.3 
Tet SiCl.sub.4 
______________________________________ 
*All catalysts were obtained commercially already having approximately 
100% Lewis activated sites thereon, but became partially inactive on 
storage. 
PROCEDURE A: Activation (Heat Treatment) of Alumina Catalysts 
In the preferred form of this process, the invention is conducted with 
activated alumina catalysts having a high proportion of Lewis-acid sites. 
It should be noted that when purchased all the catalysts utilized in these 
examples already contained approximately 100% activated Lewis acid sites. 
However, when said catalysts were handled and exposed to air, reactivation 
was necessary. 
Activation of the alumina can be performed in a separate reactor or in situ 
in the same reactor (FIG. 1) used for the redistribution reactions. The 
spent catalyst can also be regenerated in situ. During activation and 
regeneration a dry, inert gas such as air nitrogen, argon or helium is 
made to flow through the catalyst bed as the temperature is raised to the 
desired setting. Flow is maintained after this temperature has been 
attained as well as during the cooling stage. Periods as short as 0.1 hour 
may be used for activation. However, the preferred time is 0.5-2 hrs. at 
500.degree. C.-650.degree. C. It should be noted once again that 
activation time is distinguished from the reaction time which is 
substantially shorter (less than 10 minutes). The flow rate of the dry, 
inert gas can cover a broad range, 0.5-50 lit/min. At the lower end, it is 
only necessary that volatile materials released from the hydrated alumina 
be swept away. The upper limit is the maximum gas flow which still keeps 
the catalyst contained in the reactor. Alternatively, the dehydration and 
activation may be performed in vacuo at 400.degree. C.-800.degree. C. or 
with reactive gases such as HCl or HF. When reactive gases are used it is 
essential that post-treatment with an inert gas be employed to destroy the 
Bronsted acid sites formed. 
EXAMPLES 
All of the following examples utilized activated alumina catalysts and the 
apparatus outlined in FIG. 1. 
The "forecut" or "lower-boiling fraction" mentioned in the Examples, is 
that fraction of the product from the Rochow synthesis (see U.S. Pat. No. 
2,380,99) with a boiling point of less than 40.degree. C. Its principal 
components and their concentration ranges are typically as follows: 
______________________________________ 
Compound Boiling Pt. .degree.C. 
Range, Wt % 
______________________________________ 
Tetramethylsilane 
26.5 40-75 
Dimethylchlorosilane 
36.0 3-25 
Methldichlorosilane 
40.7 2-9 
Monomethylmonochlorosiline 
8.7 1-5 
Trichlorosilane 31.8 5-10 
Methyl Chloride -24.0 5-10 
Hydrocarbons 30-37 5-8 
______________________________________ 
The hydrocarbons are mostly C.sub.4 and C.sub.5 paraffins and olefins. The 
forecut contains no dimethyldichlorosilane and the desired reaction is as 
follows: 
EQU (CH.sub.3).sub.4 Si+(CH.sub.3).sub.2 SiCl.sub.2 
.revreaction.2(CH.sub.3).sub.3 SiCl 
Dimethyldichlorosilane is added to said forecut in a molar amount, which is 
at least equal to the molar amount of tetramethylsilane. In practice, a 
slight excess (up to 10%) of dimethyldichlorosilane is used in order to 
force the equilibrium reaction in favor of (CH.sub.3).sub.3 SiCl. 
The methyl lights stream, "Lights" shown in the examples, boils below 
37.degree. C. It is the product cut between methylchloride and 
methyldichlorosilane, in the methyls crude stream. After separation, the 
stream contains the following components: 
______________________________________ 
BP (.degree.C.) 
______________________________________ 
Tetramethylsilane Me.sub.4 Si 
26.5 
Dimethylchlorosilane 
Me.sub.2 SiHCl 
36.0 
Trichlorosilane HSiCl.sub.3 
40.7 
Monomethylmonochlorosilane 
MeSiH.sub.2 Cl 
8.7 
Methyl Chloride MeCl -24.0 
Hydrocarbons: 
Iso-butane Iso-C.sub.4 
-11.7 
Iso-pentane Iso-C.sub.5 
28.0 
n-pentane n-C.sub.5 36.3 
Amylene, etc. 30-37 
______________________________________ 
The stream contains hydrocarbons in addition to methylchlorosilane monomers 
and methylchloride. The hydrocarbons are the by-products of methylchloride 
cracking in the methyl reactors used in the Rochow synthesis. 
EXAMPLE 1 
Catalyst A was used in this example. The Hastelloy B cylinder reactor had 
internal dimensions of 3 ft..times.3/4 inch. 
198.5 gm of the Catalyst A was activated by heating for 0.5 hr. at 
400.degree. C. (in situ) as per procedure A in dried air. A 
methylchlorosilane mixture having the composition shown in the first row 
of Table 1 was made by blending dimethyldichlorosilane with the forecut 
from the distillation of the crude product obtained from the Rochow 
Synthesis. The mixture was vaporized at 300.degree. C. and contacted with 
the activated alumina catalyst at temperatures in the range 
200.degree.-40.degree. C. (reaction temperature). The pumping speed was 
varied to obtain a range of contact times. Samples were taken after 4-5 
time constants to ensure that the system had attained steady-state. 
Example 1 was used to determine how much conversion to 
trimethylchlorosilane (M) would be obtained in a temperature range of 
200.degree. C.-400.degree. C. an at various flow rates. The reaction began 
with zero amount (trace) of trimethylchlorosilane (M). At approximately 
300.degree. C.-400.degree. C. the maximum amounts of trimethylchlorosilane 
(M) were obtained, approximately 58.0-68.3%. As the temperature was 
increased, the conversion of tetramethylsilane (Q) and 
dimethyldichlorosilane (D) to trimethylchlorosilane (M) also increased. 
Deactivation of the catalyst bed was evident by the final entries at 
temperature range of 305.degree. C.-300.degree. C. 
TABLE 1 
__________________________________________________________________________ 
Redistribution of Methylchlorosilanes over Catalyst A 
at 200.degree. C.-400.degree. C., 0 psig 
Liquid 
Flow rate 
% % % % % % % % % 
Temp. .degree.C. 
(ml/min 
M Q D DM MD T TC Lights 
HVS 
__________________________________________________________________________ 
-- 0 trace 
35.8 
50.4 
0.9 
4.9 
trace 
2.0 
2.3 1.7 
200 0.29 30.3 
22.9 
41.5 
1.2 
0.6 
0.4 
trace 
2.1 0.8 
200 0.51 17.5 
29.4 
46.0 
1.4 
2.7 
0.4 
0.4 
2.1 0.2 
200 1.15 7.9 
33.6 
49.1 
1.2 
3.8 
0.2 
1.1 
2.4 0.7 
300 1.04 58.4 
5.1 
31.0 
1.1 
trace 
0.3 
trace 
1.8 2.2 
300 0.29 68.3 
2.7 
24.3 
0.7 
trace 
0.2 
trace 
1.7 1.8 
300 0.55 60.3 
6.9 
26.1 
1.9 
trace 
0.4 
trace 
2.1 2.1 
400 0.52 62.8 
1.3 
31.5 
0.3 
trace 
0.4 
trace 
1.5 2.1 
400 1.07 59.2 
7.0 
26.1 
2.8 
0.1 
0.5 
trace 
2.4 1.7 
400 0.27 67.1 
5.0 
21.5 
1.6 
trace 
0.4 
trace 
2.0 2.3 
399 0.54 58.2 
8.2 
25.5 
3.6 
0.2 
0.6 
trace 
2.7 1.0 
402 0.63 58.0 
8.2 
25.3 
3.8 
0.2 
0.6 
trace 
2.7 1.1 
401 0.60 58.6 
8.0 
25.1 
3.6 
0.2 
0.6 
trace 
2.6 1.1 
400 1.24 37.9 
16.6 
37.3 
3.2 
0.1 
0.9 
trace 
3.2 0.8 
305 0.55 16.6 
30.2 
45.1 
1.7 
3.2 
0.4 
0.6 
2.3 trace 
304 0.50 15.9 
30.0 
45.2 
1.8 
3.3 
0.3 
1.3 
2.1 trace 
305 0.47 15.6 
30.2 
45.4 
1.7 
3.2 
0.3 
1.2 
2.5 trace 
300 1.34 6.4 
34.6 
49.6 
1.3 
4.2 
0.2 
1.4 
2.2 trace 
__________________________________________________________________________ 
EXAMPLE 2 
Catalyst A was used in Example 2. The catalyst was activated as per Example 
1. The feed consisted of a methylchlorosilane mixture having the 
composition shown in the first row of Table 2. It was made by blending 
dimethyldichlorosilane with the forecut from the distillation of the crude 
product obtained from the Rochow synthesis Temperature pressure and liquid 
flow rates (feed rates) were further varied in order to select optimum 
operating conditions. The data is shown below in Table 2. Steady-state can 
be attained within 30 seconds at 400.degree. C., however at 300.degree. C. 
it requires 120 seconds and at 200.degree. C. about ten minutes. Since 
pyrolysis of the methylchlorosilanes is expected to be more extensive at 
400.degree. C., this experiment was done to determine the optimum 
temperature range at which the redistribution reaction could be performed. 
The optimum temperature range for the redistribution reaction ls 
300.degree.-400.degree. C. This is illustrated by the fact that the 
trimethylchlorosilane (M) concentration remained the highest (67.2%-70%) 
in this temperature range. The principal redistribution reaction is 
EQU (CH.sub.3).sub.4 Si+(CH.sub.3).sub.2 SiCl.sub.2 
.revreaction.2(CH.sub.3).sub.3 SiCl 
so pressure variations should not affect the position of equilibrium. 
Nonetheless pressure variations do affect the gas residence time. 
TABLE 2 
__________________________________________________________________________ 
Redistribution of Methylchlorosilanes over 1/8 in. Extrudate 
at 200.degree. C.-400.degree. C., 0-35 psig 
Liquid 
Press. 
Flow rate 
% % % % % % % % % 
Temp. .degree.C. 
psig. 
(ml/min 
M Q D DM MD T TC Lights 
HVS 
__________________________________________________________________________ 
-- -- -- trace 
38.7 
51.7 
1.15 
4.8 
trace 
1.3 
2.3 0.1 
400 35 0.29 67.2 
4.8 
20.8 
1.4 
trace 
0.3 
trace 
1.8 3.5 
400 35 1.17 67.4 
5.4 
20.1 
2.9 
0.1 
0.3 
trace 
2.4 1.3 
300 35 1.17 68.1 
3.6 
20.3 
3.5 
0.2 
0.4 
trace 
2.2 1.5 
300 35 0.29 70.0 
3.9 
18.1 
3.3 
0.1 
0.2 
trace 
1.8 2.4 
200 35 0.29 72.9 
3.3 
14.5 
3.9 
0.1 
0.4 
trace 
3.1 1.6 
200 0 1.17 30.2 
21.6 
39.6 
1.8 
2.4 
0.1 
1.6 
1.9 0.5 
200 0 0.29 52.1 
8.6 
31.8 
2.3 
1.3 
0.2 
1.2 
1.7 0.6 
300 0 0.29 69.2 
4.4 
18.8 
3.0 
0.2 
0.4 
trace 
2.1 1.7 
300 0 1.17 56.9 
11.8 
24.1 
2.4 
1.0 
0.3 
0.6 
2.3 0.6 
300 10 0.58 69.8 
4.8 
17.9 
3.3 
0.2 
0.4 
trace 
2.5 0.9 
400 0 1.17 65.3 
5.9 
21.0 
3.6 
0.3 
0.4 
trace 
2.9 0.6 
400 0 0.29 65.8 
5.7 
21.2 
2.2 
0.1 
0.5 
trace 
2.4 2.1 
__________________________________________________________________________ 
EXAMPLE 3 
66.6 gm of Catalyst B was activated as described in Example 1. The 
Hastelloy B cylinder reactor had internal dimensions of 1 ft..times.3/4 
in. The blend of dimethyldichlorosilane and the distillation forecut* had 
the initial composition shown in the first row of Table 3. The reaction 
was performed at 400.degree. C. This Example was done to determine the 
optimum temperature, pressure, and reaction time for the present 
invention. The optimum temperature range was 300.degree. C.-400.degree. C. 
and the optimum contact time was approximately 30 seconds. The data 
indicate that residence times of 32 seconds were sufficient for optimum 
trimethylchlorosilane (M) formation. 
FNT * As previously explained in the introduction to the examples. 
TABLE 3 
__________________________________________________________________________ 
Redistribution of Methylchlorosilanes over Catalyst B 
at 400.degree. C. 
Cumulative 
Reaction 
Contact 
Press. 
% % % % % % % % % 
Time, Hr. 
Time (sec) 
psig. 
M Q D DM MD T TC Lights 
HVS 
__________________________________________________________________________ 
0 -- -- 0 23.2 
36.5 
24.9 
1.1 
-- 
8.4 
5.9 -- 
1.25 38.7 2 44.2 
2.0 
34.4 
10.1 
1.4 
0.6 
0.6 
5.7 1.0 
2.25 44.4 2 44.4 
1.5 
31.4 
11.8 
1.8 
0.9 
0.2 
5.9 1.1 
3.5 34.5 2 44.2 
1.5 
31.0 
12.2 
1.8 
0.8 
0.2 
7.4 0.8 
4.5 38.2 2 44.2 
1.6 
30.8 
12.3 
1.9 
0.8 
0.2 
7.2 1.0 
5.5 32.0 2 43.8 
1.7 
30.9 
12.5 
1.8 
0.7 
0.3 
7.1 1.2 
6.0 7.4 0 27.9 
9.0 
35.9 
14.8 
1.0 
0.2 
3.6 
6.7 0.9 
6.3 14.7 0 34.6 
6.1 
34.5 
13.4 
1.2 
0.4 
2.1 
6.7 1.0 
6.5 2.0 0 10.7 
17.1 
38.3 
19.3 
0.9 
0.1 
6.6 
6.8 0.2 
__________________________________________________________________________ 
EXAMPLE 4 
64.2 gm of Catalyst B was charged into a Hastelloy B cylinder reactor 
having an internal dimensions of 1 ft.times.3/4 in. The catalyst was then 
activated by heating it to 400.degree. C in dried air as described in 
Example 1. The liquid methylchlorosilane blend was fed to the catalyst at 
33.5 ml/hr continuously for 54.5 hr. At that time the temperature was 
shut-off and the catalyst was purged with dried nitrogen for 48 hours. 
This Example was done to determine when degeneration of the catalyst bed 
would take place and the effect catalyst regeneration would have on 
trimethylchlorosilane production. The results (Table 4) show that 
satisfactory trimethylchlorosilane (M) production was maintained for the 
initial 54.5 hours. The amount of trimethylchlorosilane (M) production 
steadily decreased as the catalyst degenerated over a cumulative reaction 
time of over 50 hours. After catalyst regeneration was obtained with a 
nitrogen purge, the amount of trimethylchlorosilane (M) produced jumped 
from 29.8% (before catalyst regeneration) to 34.5%. 
TABLE 4 
__________________________________________________________________________ 
Continuous Redistribution of Methylchlorosilanes over Catalyst B 
at 400.degree. C., 0 psig 
Cumulative 
Reaction 
% % % % % % % % % 
Time, Hr. 
M Q D DM MD T TC Lights 
HVS 
__________________________________________________________________________ 
0 -- 39.8 
49.8 
1.1 
4.9 -- 
1.8 2.5 0.1 
1 58.5 
8.9 
25.6 
2.9 
0.3 0.5 
trace 
2.5 0.5 
2.5 55.9 
10.2 
25.4 
3.6 
0.5 0.6 
trace 
2.7 1.0 
4.0 43.2 
16.9 
32.0 
2.8 
1.2 0.6 
trace 
2.6 0.6 
6.0 48.8 
13.9 
28.8 
3.2 
0.9 0.6 
trace 
2.8 0.9 
8.0 42.3 
17.1 
31.8 
3.1 
1.4 0.6 
0.2 2.7 0.7 
10.0 39.1 
18.9 
33.6 
2.8 
1.7 0.5 
0.3 1.9 0.6 
12.0 41.7 
17.8 
31.7 
2.5 
1.2 0.9 
0.2 2.5 1.5 
14.0 36.7 
20.4 
34.7 
2.7 
1.8 0.5 
0.1 2.4 1.1 
16.0 33.9 
22.0 
36.3 
2.3 
1.8 0.5 
trace 
2.3 0.8 
19.0 36.6 
20.2 
34.7 
2.8 
1.9 0.5 
0.1 2.5 0.6 
21.0 35.2 
20.9 
35.4 
2.6 
2.0 0.5 
0.2 2.4 0.8 
23.5 43.5 
17.3 
31.3 
2.9 
1.4 0.6 
0.2 2.4 0.4 
26.5 41.2 
18.4 
32.7 
3.0 
1.4 0.6 
0.1 2.5 0.3 
29.5 35.9 
20.9 
35.1 
2.8 
1.9 0.6 
0.2 2.4 0.2 
31.5 33.4 
21.8 
36.5 
2.7 
2.2 0.5 
0.4 2.3 0.2 
34.5 31.9 
22.9 
36.6 
2.6 
2.3 0.5 
0.5 2.4 0.3 
37.5 32.4 
21.5 
39.0 
1.7 
1.9 0.5 
0.2 2.1 0.4 
40.5 31.1 
23.5 
37.6 
2.0 
2.2 0.5 
0.4 2.3 0.3 
45.5 29.8 
24.0 
38.3 
2.2 
2.3 0.5 
0.4 2.3 0.2 
48.5 35.9 
21.1 
34.9 
2.6 
1.9 0.5 
0.4 2.3 0.2 
51.5 32.8 
22.3 
36.4 
2.8 
2.1 0.6 
0.4 2.4 0.2 
54.5 29.8 
23.9 
37.8 
2.4 
2.4 0.5 
0.6 2.4 0.2 
REACTOR SHUT DOWN AND PURGED WITH DRIED N.sub.2 FOR 48 HRS. 
56.5 34.5 
19.3 
38.6 
2.2 
2.1 0.4 
0.6 1.8 0.5 
57.5 31.4 
22.6 
37.3 
2.5 
2.5 0.5 
0.8 2.2 0.2 
59.5 26.8 
24.5 
39.6 
2.4 
2.8 0.8 
0.9 2.2 0.3 
61.5 23.9 
26.4 
40.4 
2.3 
3.0 0.4 
1.1 2.3 0.2 
__________________________________________________________________________ 
EXAMPLE 5 
62.8 gm of Catalyst B was charged in a Hastelloy B cylinder reactor having 
internal dimensions of 1 ft..times.3/4 in. The feed consisted of a 
methylchlorosilane mixture having the composition shown in the first row 
of Table 5. It was made by blending dimethyldichlorosilane with the 
forecut from the distillation of the crude product obtained from the 
Rochow Synthesis. The feed flow rate of the reaction mixture was 28.3 ml 
liquid/hr and the reactor temperature was 400.degree. C. The reaction was 
performed for a total of 24 hours over a five-day period. At the end of 
each day's run the catalyst was purged overnight with dried air, dried 
nitrogen, dried HCl or dried H.sub.2 as shown in Table 5. 
This Example was done in order to determine the best regeneration 
procedure. The best regeneration results were achieved utilizing a 
nitrogen purge. This is evidenced by the fact that after regeneration with 
nitrogen after 16.75 hrs., the trimethylchlorosilane (M) concentration 
increased from approximately 15.3% to 37.4%. 
Presumably, the gases regenerate the catalyst by clearing the micropores 
which have become blocked during the reaction. When silyl residues left on 
the catalyst surface and in the pores are decomposed at the regeneration 
temperature (400.degree. C.), Bronsted acid sites result. These sites must 
be destroyed by thermal treatment to restore Lewis acidity and the desired 
catalytic activity. 
TABLE 5 
__________________________________________________________________________ 
Redistribution of Methylchlorosilanes over Catalyst B 
at 400.degree. C. with Intermittent Regeneration 
Cumulative 
Reaction 
% % % % % % % % % 
Time, Hr. 
M Q D MD DM T TC Lights 
HVS 
__________________________________________________________________________ 
0 -- 35.8 
51.6 
5.0 
0.4 trace 
2.5 4.4 trace 
0.5 55.0 
5.9 
29.3 
0.6 
2.3 0.9 
0.2 3.4 2.4 
2.75 57.4 
6.8 
25.6 
0.5 
3.6 0.9 
trace 
4.5 0.7 
5.0 57.4 
7.1 
25.2 
0.5 
3.8 0.9 
0.1 4.4 0.6 
REGENERATE WITH DRIED AIR OVERNIGHT 
6.5 42.8 
12.3 
35.2 
0.7 
3.1 0.9 
0.1 4.2 0.7 
8 37.2 
15.9 
36.8 
1.2 
3.0 0.9 
0.1 4.0 0.9 
9 26.7 
21.5 
41.0 
2.0 
2.6 1.3 
0.3 3.9 0.7 
12.0 20.4 
24.6 
43.9 
2.5 
2.1 1.3 
0.6 4.0 0.6 
REGENERATE WITH DRIED AIR OVERNIGHT 
13.0 30.0 
18.7 
42.2 
1.4 
2.2 1.0 
0.1 3.7 0.7 
14.0 19.7 
24.7 
45.1 
2.3 
2.0 1.2 
0.4 4.0 0.6 
16.75 15.3 
28.4 
45.1 
2.8 
1.7 1.4 
0.6 4.1 0.7 
HCl @ 0.5 SCFH for 0.5 hr, N.sub.2 for 0.5 hr followed by DRIED AIR 
OVERNIGHT 
17.25 37.4 
15.0 
38.5 
1.8 
1.8 0.9 
0.6 3.5 0.3 
18.75 34.0 
17.9 
38.4 
1.8 
2.1 0.9 
0.4 4.1 0.4 
19.50 20.1 
25.5 
43.8 
2.6 
1.7 1.2 
0.7 3.9 0.3 
21.50 15.2 
28.1 
45.5 
3.1 
1.5 1.4 
1.0 3.9 0.3 
23.50 13.1 
29.3 
46.5 
3.3 
1.3 1.3 
1.0 3.9 0.3 
HCl @ 0.75 SCFH for 2.5 hr, N.sub.2 for 0.5 hr followed by DRIED AIR 
OVERNIGHT 
24 17.4 
22.6 
50.7 
2.9 
1.1 0.9 
0.9 3.1 0.3 
__________________________________________________________________________ 
EXAMPLE 6 
63.2 gm of Catalyst B was used in the reactor as outlined in Example 1. The 
feed consisted of a methylchlorosilane mixture having the composition 
shown in the first row of Table 6. It was made by blending 
dimethyldichlorosilane with the forecut from the distillation of the crude 
product from the Rochow Synthesis. The liquid feed rate of the reactor was 
31.88 ml/hr. The reactor temperature was 400.degree. C. The nitrogen flow 
was sustained at this temperature for 16-18 hr. periods between successive 
runs A thru G as indicated by the straight lines between runs in Table 6. 
This Example illustrates that intermittent treatment with dried nitrogen 
restores and/or maintains catalytic activity at a desirable level of 
trimethylchlorosilane (M) production. The results achieved with the 
nitrogen purge are particularly pronounced in Runs D through G. Once 
regeneration began with nitrogen after 15.39 hrs. (end of Run C), the 
trimethylchlorosilane (M) concentration increased from 32.8% to 47.1%. 
After regeneration at 22.67 hours, the trimethylchlorosilane (M) 
concentration increased from 32.6% to 40.6%. After regeneration at 34.68 
hours. the trimethylchlorosilane (M) concentration increased from 29.7% to 
45.8%. 
TABLE 6 
__________________________________________________________________________ 
Redistribution of Methylchlorosilanes over Catalyst B at 400.degree. C. 
with Intermittent N.sub.2 Regeneration of the Catalyst 
Cumulative 
Reaction % % % % % % % % % 
Time (hr) 
M Q D MD TC DM T Lights 
HVS 
__________________________________________________________________________ 
Run 
0 -- 34.5 
53.3 
5.1 
2.6 
0.4 
-- 4.1 tr 
A 1 57.4 
6.6 
26.9 
0.4 
0.1 
3.4 
0.7 
4.0 0.5 
1.83 57.1 
6.4 
26.8 
0.5 
0.1 
3.8 
0.8 
4.0 0.5 
2.83 56.6 
6.5 
27.0 
0.6 
0.1 
3.9 
0.9 
4.0 0.4 
Run 
3.41 55.4 
7.0 
27.4 
0.6 
0.1 
4.2 
0.9 
4.0 0.4 
B 5.58 54.6 
7.4 
27.6 
0.7 
0.1 
4.2 
0.9 
3.9 0.4 
7.25 55.0 
7.3 
27.4 
0.7 
0.1 
4.1 
0.9 
4.0 0.4 
Run 
11.92 44.0 
12.5 
33.7 
1.2 
0.2 
3.4 
0.8 
3.5 0.4 
C 13.17 46.2 
11.6 
31.9 
1.1 
0.1 
3.9 
1.0 
3.7 0.4 
15.39 32.8 
17.8 
39.3 
2.3 
0.5 
2.9 
0.9 
3.6 0.2 
Run 
16.92 47.1 
10.9 
31.6 
0.8 
tr 3.7 
1.0 
3.6 1.3 
D 18.54 30.0 
18.7 
40.6 
2.1 
0.4 
2.9 
0.9 
3.5 0.8 
19.76 50.1 
9.1 
31.5 
0.9 
0.1 
3.7 
0.9 
3.3 0.4 
21.09 35.1 
17.4 
37.0 
1.8 
0.3 
3.4 
1.0 
3.5 0.3 
22.67 32.6 
18.5 
38.3 
2.0 
0.3 
3.2 
1.1 
3.7 0.3 
Run 
23.26 40.6 
13.1 
36.6 
1.6 
0.3 
3.3 
0.9 
3.2 0.2 
E 24.26 31.0 
19.5 
38.7 
2.2 
0.4 
3.2 
1.0 
3.7 0.2 
28.17 27.1 
21.1 
41.2 
2.5 
0.5 
2.8 
0.9 
3.3 0.2 
29.26 26.9 
21.6 
40.7 
2.6 
0.5 
2.8 
0.9 
3.3 0.1 
Run 
30.01 31.5 
19.1 
39.1 
2.2 
0.3 
2.9 
0.8 
3.6 0.4 
F 32.01 30.9 
20.0 
38.3 
2.2 
0.4 
3.2 
0.9 
3.8 0.2 
33.20 33.7 
17.9 
37.5 
1.9 
0.3 
3.4 
1.0 
3.7 0.6 
34.68 29.7 
19.6 
40.0 
2.3 
0.4 
3.1 
1.0 
3.6 0.3 
Run 
36.26 45.8 
12.8 
31.1 
0.9 
0.1 
4.0 
0.9 
3.9 0.5 
G 37.18 30.3 
20.0 
38.3 
2.1 
0.3 
3.4 
1.1 
3.9 0.6 
38.43 33.9 
19.1 
35.1 
1.8 
0.2 
3.8 
1.2 
4.1 0.8 
38.93 26.9 
21.7 
39.5 
2.4 
0.4 
3.1 
1.2 
4.0 0.8 
__________________________________________________________________________ 
EXAMPLE 7 
60.1 gm of Catalyst B was rinsed with a 2% HF aqueous solution (activation 
procedure) and then dried in a vacuum over at 500.degree. C. for 4 hours. 
The dried catalyst was placed in a Hastelloy B cylinder reactor having 
internal dimensions of 1 ft.times.3/4 in. The catalyst was then heated to 
400.degree. C. for reaction with the reaction mixture of 
methylchlorosilanes having the composition shown in the first row of Table 
7. Said reaction mixture was made by blending with dimethyldichlorosilane 
and the forecut from the Rochow Synthesis as illustrated in the previous 
examples. This example illustrates that HF treatment of the gamma-alumina 
catalyst is suitable as an activation procedure and also as a regeneration 
method. Hydrofluorination of alumina apparently increases the population 
of Lewis acid sites. Table 7 shows that the catalyst performance was 
comparable to that of Example 3. The amount of trimethylchlorosilane (M) 
produced, 44.2%-43.5% after 3 hrs. was certainly comparable to -hat 
produced in Example 3, which utilized a catalyst which had been activated 
utilizing a dry inert gas. 
EXAMPLE 8 
213.7 gm of Catalyst C was charged into a Hastelloy B cylinder reactor 
having the dimensions outlined in Example 1. The catalyst was activated by 
heating it to 400.degree. C. in a stream of dried air (4.89 lit/min). The 
catalyst was evaluated at 200.degree. C. and at 400.degree. C. in a manner 
analogous to that described in Example 1. The reaction mixture had the 
composition shown in the first row of Table 8 and was prepared as 
illustrated in the previous examples. 
Table 8 shows that this lower surface area catalyst also performed 
satisfactorily at 400.degree. C., but longer residence times were required 
than those shown in Examples 1 through 3. Since the gamma-alumina spheres 
(CataIyst C) utilized in this example bad smaller surface areas than the 
extrudates (Catalyst B) utilized in Example 3, longer contact times were 
needed to achieve good results. 
TABLE 7 
__________________________________________________________________________ 
Redistribution of Methylchlorosilanes over HF treated 
Catalyst B at 400.degree. C. 
Contact 
% % % % % % % % % 
Time, Hr. 
Time, (sec) 
M Q D DM MD T TC Lights 
HVS 
__________________________________________________________________________ 
0 0 trace 
19.4 
43.4 
24.4 
1.2 trace 
7.9 3.2 0.1 
1 66.5 44.2 
3.7 
31.6 
11.6 
1.3 0.8 
0.4 2.7 3.5 
2 33.9 43.5 
4.2 
29.4 
13.0 
1.6 0.8 
0.2 3.5 3.2 
3 36.8 43.5 
4.0 
29.3 
13.0 
1.8 0.9 
0.2 3.9 2.9 
__________________________________________________________________________ 
TABLE 8 
__________________________________________________________________________ 
Redistribution of Methylchlorosilanes over 
Catalyst C between 200.degree. C.-400.degree. C. 
Contact 
% % % % % % % % % 
Temp .degree.C. 
Time, (sec) 
M Q D DM MD T TC 
Lights 
HVS 
__________________________________________________________________________ 
0 0 39.5 
52.7 
0.9 
4.4 
trace 
0.2 
2.3 -- 
200 96.9 3.9 
35.6 
51.6 
0.6 
4.7 
0.4 
0.1 
3.1 -- 
200 23.6 3.7 
35.8 
51.7 
0.5 
4.4 
0.4 
0.1 
3.4 -- 
400 63.7 39.5 
19.0 
34.5 
3.0 
0.6 
0.9 
-- 
2.4 0.1 
400 71.6 38.7 
19.1 
35.0 
3.3 
0.6 
0.9 
-- 
2.4 -- 
400 72.5 37.5 
18.8 
36.4 
3.4 
0.6 
0.9 
-- 
2.4 -- 
400 90.8 37.4 
18.5 
36.7 
3.5 
0.6 
0.9 
0.1 
2.3 -- 
__________________________________________________________________________ 
EXAMPLE 9 
The addition of less than 1% graphite to a gamma-alumina catalyst increases 
the crush strength and handling ease of these catalysts. 80.3 gm of 
Catalyst D were prepared as described in Example 3. Evaluation was done at 
400.degree. C. using a methylchlorosilane blend with the composition shown 
in the first row of Table 9. The gas residence time was 22 seconds. 
This catalyst affords satisfactory production of trimethylchlorosilane (M) 
and performs as well as those catalysts evaluated in Examples 1 through 3. 
Table 9 shows the redistribution of Methylchlorosilanes over 
Graphite-Lubricated Alumina at 400.degree. C. 
EXAMPLE 10 
The disproportionation of (CH.sub.3).sub.2 SiHCl was studied at 400.degree. 
C. over Catalyst B. The catalyst was activated by heating it to 
400.degree. C in dried air (4.89 lit/min) for 0.5 hr prior to the onset of 
the reaction. 66.6 gm Catalyst B was used and the reactor was as the 
utilized in Example 1. The reaction mixture feed rates (liquid flow, 
ml/min) were varied to obtain different gas residence times. The reaction 
scheme can be illustrated as follows: 
EQU 2(CH.sub.3).sub.2 SiHCL.revreaction.(CH.sub.3).sub.2 SiCl.sub.2 
+(CH.sub.3).sub.2 SiH.sub.2 
The data indicates that dimethylchlorosilane (DM) is converted primarily 
into dimethyldichlorosilane (D) and trimethylchlorosilane (M). Both 
CH.sub.3 SiH.sub.2 Cl and (CH.sub.3).sub.2 SiH.sub.2 were found in the 
Lights (i.e. most volatile fraction) by gas chromatography and mass 
spectroscopy analysis. The results are illustrated in Table 1. This 
example illustrates that the activated alumina catalysts of this invention 
rearrange H and Cl groups as well as CH.sub.3 and Cl. 
TABLE 9 
__________________________________________________________________________ 
Redistribution of Methylchlorosilanes over Graphite-Lubricated 
Catalyst D at 400.degree. C. 
Cumulative 
Reaction 
% % % % % % % % % 
Time, hr. 
M Q D DM MD T TC Lights 
HVS 
__________________________________________________________________________ 
0 -- 34.5 
53.3 
0.4 5.1 -- 2.6 
4.1 -- 
1 44.4 
11.9 
34.5 
2.4 1.0 0.9 
0.2 
3.7 1.0 
2 48.0 
10.0 
33.7 
1.7 0.9 0.7 
0.2 
3.8 1.0 
2.67 51.5 
8.8 
30.8 
3.2 0.6 1.0 
-- 3.8 0.7 
3.50 52.3 
8.6 
29.2 
3.5 0.5 0.9 
-- 3.9 1.1 
4.25 52.8 
8.2 
29.0 
3.6 0.6 0.9 
-- 3.9 1.0 
__________________________________________________________________________ 
TABLE 10 
______________________________________ 
Redistribution of Me.sub.2 SiHCl over Catalyst B at 400.degree. C. 
Liquid Flow 
% % % % % % % % 
ml/min M Q D DM MD T Lights 
HVS 
______________________________________ 
0 0.7 -- 0.4 97.2 0.8 -- 0.1 0.8 
0.23 21.2 0.3 32.0 35.9 3.2 0.4 5.8 1.2 
0.34 13.5 0.2 29.3 45.9 2.1 0.2 7.8 1.0 
0.70 5.5 0.1 26.7 53.6 1.0 0.1 11.7 1.3 
1.40 2.2 0.1 20.6 64.7 0.9 -- 10.4 1.1 
______________________________________ 
EXAMPLE 11 
The same (unregenerated) catalyst bed (Catalyst B) used for Example 3 was 
used to redistribute a methylchlorosilane mixture containing 65.9 wt % 
SiCl.sub.4 (Tet) and 34.1 wt % (CH.sub.3).sub.4 Si (Q) at 400.degree. C. 
The liquid feed rate was 12 ml/hr. Analysis of the two samples collected 
(Table 11) showed 14.0% and 7.0% trimethylchlorosilane (M), respectively. 
The reaction scheme can be illustrated by the following equation: 
EQU (CH.sub.3).sub.4 Si+SiCl.sub.4 .revreaction.(CH.sub.3).sub.3 SiCl+CH.sub.3 
SiCl.sub.3 
Tetramethylsilane (Q) is present in the lower boiling fraction of the 
Rochow synthesis. Tetrachlorosilane (Tet) is available from the 
trichlorosilane direct process. This example was performed to determine 
what useful compounds could be produced from the waste products. Even at a 
slow feed rate, not very much conversion occurred. 
EXAMPLE 12 
A mixture containing 68.3% CH.sub.3 SiCl.sub.3 and 31.3% (CH.sub.3).sub.4 
Si was redistributed on the same catalyst bed used in Example 11 (Catalyst 
B). Reaction temperature was 400.degree. C. The samples collected 
contained about 16-17% trimethylchlorosilane. The reaction scheme can be 
illustrated by the following equation: 
EQU CH.sub.3 SiCl.sub.3 +(CH.sub.3).sub.4 Si.revreaction.(CH.sub.3).sub.3 
SiCl+(CH.sub.3).sub.2 SiCl.sub.2 
methyltrichlorsilane (T) is a byproduct and tetramethylsilane (Q) is 
present in the forecut lower boiling fraction of the Rochow synthesis. The 
results are illustrated in Table 12. Even at a residence time of 183.9 
sec. very little trimethylchlorosilane (M) is produced. 
TABLE 11 
______________________________________ 
Redistribution of Tetramethylsilane and 
Tetrachlorosilane over Catalyst B at 400.degree. C. 
Cumulative 
Reaction % % % % % % 
Time, Hr M Tet Q D T HVS 
______________________________________ 
0 -- 67.6 32.2 0.2 -- -- 
0.67 14.0 67.8 15.7 2.0 0.1 0.4 
3.5 7.0 62.5 28.7 1.1 0.3 0.4 
______________________________________ 
TABLE 12 
______________________________________ 
Redistribution of Methyltrichlorosilane and 
Tetramethylsilane over Catalyst B at 400.degree. C. 
Contact % % % % % % 
Time (sec) 
M Q D T Lights 
HVS 
______________________________________ 
-- 31.1 -- 68.3 0.1 0.4 
67.9 15.9 16.2 2.0 64.7 0.1 1.0 
183.9 16.7 21.5 2.2 59.1 -- 0.5 
______________________________________ 
EXAMPLE 13 
Another (CH.sub.3).sub.4 Si - CH.sub.3 SiCl.sub.3 mixture (composition 
shown in the first row of Table 13) was studied at 400.degree. C. This 
time the catalyst was 65.3 gm of Catalyst E activated in situ as described 
in Example 3. The contact time was 40 seconds. The content of 
trimethylchlorosilane (M) in the samples analyzed is shown in Table 13. 
This example is a repeat of the experiment performed in Example 12, 
however a new catalyst bed with a high surface area was utilized. This 
experiment was performed to determine if the contact time could be 
shortened utilizing the new catalyst bed with improved results. The 
results show improvement over the contact times shown in Example 12. 
EXAMPLE 14 
The unregenerated catalyst bed for Example 13 (Catalyst E) was used to 
redistribute a 63.4 wt % (CH.sub.3).sub.2 SiCl.sub.2 - 36.5 wt % 
(CH.sub.3).sub.4 Si mixture at 400.degree. C. and contact time of 42.4 
seconds. Trimethylchlorosilane (M) was the major reaction product as 
illustrated in Table 14. The reaction scheme of this example can be 
illustrated as follows: 
EQU (CH.sub.3).sub.2 SiCl.sub.2 +(CH.sub.3).sub.4 Si 
.revreaction.2(CH.sub.3).sub.3 SiCl 
This example was done to determine how well the catalyst bed would operate 
with pure components. There was a significant improvement in 
trimethylchlorosilane (M) production over that shown in Example 13. The 
data shows that the molar amount of (CH.sub.3).sub.3 SiCl formed is 
approximately twice the molar amount of (CH.sub.3).sub.4 Si used as 
required by the stoichiometry of the reaction. 
TABLE 13 
______________________________________ 
Redistribution of Methyltrichlorosilane and 
Tetramethylsilane over Catalyst E at 400.degree. C. 
Cumulative 
Reaction % % % % % % 
Time, hr M Q D T Lights 
HVS 
______________________________________ 
-- 47.6 -- 50.8 -- 0.5 
0.5 39.1 21.7 3.1 30.4 0.1 5.5 
1.25 30.8 32.3 2.7 32.7 0.2 1.3 
2.0 24.3 38.4 2.6 33.5 0.2 0.9 
______________________________________ 
TABLE 14 
______________________________________ 
Redistribution of Dimethyldichlorosilane and 
Tetramethylsilane over Catalyst E at 400.degree. C. 
Cumulative 
Reaction % % % % % % 
Time, hr M Q D T Lights 
HVS 
______________________________________ 
0 -- 36.5 63.4 0.1 0.1 1.0 
0.75 43.4 13.3 39.6 0.2 -- 3.6 
1.75 54.9 13.4 30.4 0.1 -- 1.2 
2.75 49.3 18.2 31.6 0.1 0.1 0.7 
______________________________________ 
EXAMPLE 15 
CH.sub.3 SiHCl.sub.2 was disproportionated at 400.degree. C. over the same 
catalyst bed previously used for Examples 13 and 14 (Catalyst E). The 
major product was CH.sub.3 SiCl.sub.3, as illustrated in Table 15. The 
reaction scheme of this example can be illustrated by the following: 
EQU 2CH.sub.3 SiHCl.sub.2 .revreaction.CH.sub.3 SiCl.sub.3 +CH.sub.3 SiH.sub.2 
Cl 
The data of Table 15 illustrate that the activated alumina catalysts of 
this invention rearranqe H and Cl groups as well as CH.sub.3 and Cl 
groups. This example further illustrates that the Lewis acid catalysts of 
this invention behave in a different and non-obvious way from the modified 
silica alumina catalysts of U.S. Pat. No. 3,346,349. 
EXAMPLE 16 
The mixture for redistribution contained 54.8 wt % CH.sub.3 SiCl.sub.3 and 
43.4 wt % H.sub.2 SiCl.sub.2. Catalyst B was heated as described in 
Example 3. No trimethylchlorosilane (M) was detected. Trichlorosilane (TC) 
was the principal reaction product. The reaction scheme of this example 
can be illustrated by the following: 
EQU H.sub.2 SiCl.sub.2 +CH.sub.3 SiCl.sub.3 .revreaction.HSiCl.sub.3 +CH.sub.3 
HSiCl.sub.2 
The data in Table 16 as well as that of Examples 10 and 15 illustrate that 
the activated alumina catalysts of this invention rearrange H and Cl 
groups as well as CH.sub.3 and Cl. 
TABLE 15 
______________________________________ 
Disproportionation of CH.sub.3 SiHCl.sub.2 over 
Catalyst E at 400.degree. C. 
Cumulative 
Reaction 
% % % % % % % % % 
Time, Hr. 
M Q D MD DM T TC Lights 
HVS 
______________________________________ 
-- -- 99.0 0.3 -- -- 0.1 0.6 
1 0.2 4.1 4.2 66.1 0.7 20.7 0.7 0.2 3.1 
1.5 0.1 6.0 4.1 61.9 0.8 23.8 -- 1.0 2.3 
2.0 0.1 7.2 4.3 57.5 1.0 26.3 0.1 0.4 2.1 
______________________________________ 
TABLE 16 
______________________________________ 
Redistribution of Methyltrichlorosilane and H.sub.2 SiCl.sub.2 over 
Catalyst B at 400.degree. C. 
Con- 
tact 
Time % % % % % % % % % 
(sec) TC DC T DM MD TET D Lights 
HVS 
______________________________________ 
1.6 43.4 54.8 -- -- 0.1 -- 0.1 -- 
62.7 40.4 7.4 37.4 0.3 6.5 6.8 0.6 -- 0.6 
84.9 42.0 9.3 32.6 0.8 6.5 7.6 0.6 -- 0.6 
92.8 42.3 8.0 31.5 0.7 6.2 10.1 0.6 -- 0.6 
21.2 35.0 13.4 40.9 0.9 5.2 4.2 -- -- 0.4 
7.8 24.4 25.0 44.1 2.1 2.8 1.2 -- -- 0.4 
______________________________________