Basic catalyst based on titanates, zirconates and hafnates

Details Basic catalyst based on titanates, zirconates and hafnates Basic catalyst based on titanates, zirconates and hafnates

1999-10-06

2001-07-17

Griffin, Walter D. (Department: 1764)

Chemistry of hydrocarbon compounds

Aromatic compound synthesis

By condensation of entire molecules or entire hydrocarbyl...

C585S446000, C585S455000, C502S344000, C502S349000, C502S525000

Reexamination Certificate

active

06262325

ABSTRACT:

The invention relates to a catalyst, to the use thereof in reactions catalyzed by strong bases, and to a process for the side-chain alkylation or alkenylation of alkylaromatic or alkylalicyclic compounds with olefins or diolefins.
The side-chain alkylation, in particular of aromatic compounds having an acidic proton in the &agr; position of the side chain, in the presence of catalysts is known.
EP-B-0 439 679 describes a process for the alkylation of alkylaromatic hydrocarbons. The reaction takes place in the presence of a catalyst composed of activated alumina doped with magnesium hydroxide and potassium metal. Also employed in place of magnesium hydroxide are calcium hydroxide, barium hydroxide or magnesium oxide. Impregnation with potassium hydride is also described.
U.S. Pat. No. 4,914,250 relates to a process for the side-chain alkylation of aromatic compounds. The catalyst employed in this case was diatomaceous earth which was present in the reaction mixture in addition to potassium or NaK and traces of water.
U.S. Pat. No. 4,922,054 likewise relates to a process for the side-chain alkylation of aromatic compounds in which diatomaceous earth was likewise employed as catalyst and was present in the reaction mixture in addition to NaK and potassium oxide. Rubidium oxide was also used in place of potassium oxide. Potassium metal was also employed in place of NaK.
JP-A-05 163 171 relates to the preparation of alkenylbenzene and its derivatives. The catalyst used comprises an alkali metal and a potassium carbonate salt and/or KOH, which are dispersed in the presence of an olefin and/or diolefin. Sodium metal is preferably used as alkali metal, and K
2
CO
3
, KHCO
3
or KNaCO
3
is preferably used as potassium carbonate salt.
The catalyst employed in EP-B-0 575 724 is prepared by impregnating zirconium oxide powder or potassium zirconate with potassium hydroxide solution, then calcining in air at 500° C. and applying metallic sodium to the support. The catalyst is employed for the side-chain alkenylation of o-xylene with butadiene.
EP-A-0 636 597 describes a process for the side-chain alkenylation of o-xylene with butadiene using as catalyst alumina, calcium oxide or zirconium oxide, each of which is impregnated with aqueous KOH and was then calcined at a temperature of from 500 to 550° C. The support is coated with metallic sodium.
These catalysts disclosed to date perform inadequately for many applications. On the one hand, the catalysts disclosed to date have low activity, which means that the space-time yield is very low. In addition there is formation of unwanted secondary products from the initially obtained primary products when the conversions are high and the service lives are prolonged. For example, in the side-chain alkylation of toluene with propene the formation of isobutylbenzene is followed by cyclizations to methylindan as well as dimerization of the olefin, for example formation of methylpentene from propene. In addition, the service life of the described catalysts is limited. As the reaction time increases, the catalysts lose activity and their byproduct spectrum shows some changes.
It is an object of the present invention to provide a catalyst for side-chain alkylation or alkenylation which avoids the disadvantages of the known catalysts and has a high activity, selectivity and service life.
We have found that this object is achieved by providing a catalyst comprising at least one alkali metal on a support which has the general formula (I)
A
n′
Ti
m′
Zr
p′
Hf
q′
O
n′+2(m′+p′+q′)
  (I)
where
A is a divalent metal,
20·(m′+p′+q′)>n′>0.05·(m′+p′+q′),
and which may be doped with at least one compound of an alkali metal and/or alkaline earth metal,
where the alkali metal/support ratio by weight is 0.01-5:1 and, when a dopant is present, the dopant/support ratio by weight is 0.01-5:1, and where the proportion of support phase corresponding to a ZrO
2
structure or an alkaline earth metal oxide structure or consisting of ZrO
2
or alkaline earth metal oxide is less than 10% by weight.
This object is further achieved by using this catalyst in reactions catalyzed by strong bases, preferably for the side-chain alkylation or side-chain alkenylation of alkylaromatic or alkylalicyclic compounds with olefins or diolefins, for the double-bond isomerization of olefins or for the dimerization of olefins.
The object is further achieved by way of example by providing a process for the side-chain alkylation or side-chain alkenylation of alkylaromatic compounds by reaction with olefins or diolefins, the reaction being carried out in the presence of a catalyst as described above.
The alkali metal/support ratio is in this connection preferably 0.01-2:1, particularly preferably 0.01-1:1. The alkali metal is moreover preferably sodium or potassium, in particular sodium. It is also possible to employ mixtures of several alkali metals.
The support consists in the undoped state of complex oxides of divalent metals A and tetravalent titanium, zirconium and/or hafnium. Examples of such oxides are titanates of the general formula ATi
m
O
1+2m
such as ATiO
3
, ATi
2
O
5
, ATi
3
O
7
, ATi
4
O
9
, ATi
5
O
11
or ATi
6
O
13
, or of the general formula A
1+m
Ti
m
O
1+3m
(i.e. n=1+m) such as A
2
TiO
4
or A
3
Ti
2
O
7
, but also compounds which belong to neither of the homologous series defined by the above general formulae, such as A
6
Ti
17
O
40
. Further oxides are also the compounds of tetravalent zirconium or hafnium corresponding to the titanates (zirconates and hafnates respectively), and the corresponding compounds of two metals, preferably of zirconium and hafnium or of titanium and zirconium, or of all three of said tetravalent metals (in which case the general formulae then correspond to those above), such as ATi
2
ZrO
7
, ATiZr
2
O
7
, AZr
2
HfO
7
or A
3
ZrHfO
7
. A is preferably selected from Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Pb, Zn, Cd, Pb and mixtures thereof, particularly preferably from Mg, Ca, Sr, Ba and mixtures thereof.
Typical representatives of the titanates are ATiO
3
with A=Mg, Ca, Sr, Ba, Fe, Cd and Zn, such as MgTiO
3
and CaTiO
3
, ATi
2
O
5
with A=Mg, Ca, Sr, Ba, Co and Fe, such as MgTi
2
O
5
, also ATi
3
O
7
, ATi
4
O
9
, ATi
5
O
11
, ATi
6
O
13
, A
2
TiO
4
and A
3
Ti
2
O
7
, with A=Mg, Ca, Sr and Ba, such as CaTi
3
O
7
, BaTi
4
O
9
, Sr
3
Ti
2
O
7
and Ba
4
Ti
13
O
30
.
Typical representatives of the zirconates are AZrO
3
with A=Mg, Ca, Sr and Ba and Pb such as CaZrO
3
and BaZrO
3
, AZr
4
O
9
and A
3
Zr
2
O
7
with A=Mg, Ca, Sr and Ba such as BaZr
4
O
9
and Sr
3
Zr
2
O
7
.
Typical representatives of hafnates are AHfO
3
with A=Mg, Ca, Sr, Ba and Pb, and AHf
4
O
9
and A
3
Hf
2
O
7
with A=Mg, Ca, Sr and Ba.
Typical representatives of compounds of titanium and zirconium or of zirconium and hafnium are, for example, CaTiZr
2
O
7
and CaTi
2
ZrO
7
or CaZrHf
2
O
7
and CaZr
2
HfO
7
.
The term “support which has the general formula (I)” means that the support consists either of one of the compounds described above alone or of a defined mixture thereof, i.e. although in the individual compound types or in the individual compound the indices n, m, p, q and, when Zr and Hf are present, p+q (where m+p+q must never be 0) are integers, when the support is viewed as a whole, the indices n′, m′, p′ and q′ in the formula (I), which characterizes the support as a whole are values averaged over all individual values for individual compound types, i.e. apart from exceptions are not integers. In the limiting case of the presence of a single compound, n, m, p and q are identical to n′, m′, p′ and q′ and are thus integers.
The catalyst preferably contains the oxides of the general formulae ATi
m
O
1+2m
, A
n
Ti
m
O
n+2m
, AZr
p
O
1+2p
, A
n
Zr
p
O
n+2p
, ATi
m
Zr
p
O
1+2(m&plu

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