Method of producing a catalyst from clay minerals for the hydration of olefins

A method for producing a catalyst comprising phosphoric acid and a carrier, for the hydration of olefins with 2-3 carbon atoms to the corresponding alcohols, the method comprising: PA1 contacting a clay, containing essentially montmorillonite, contaminated by no more than 3% accompanying minerals and containing up to 0.5% by weight K.sub.2 O, or a mineral of the montmorillonite group, containing no potassium, but having the montmorillonite crystalline lattice, with an acid until it has an Al.sub.2 O.sub.3 content of 13-18% by weight and a surface area of 200-400 m.sup.2 /g; PA1 admixing the so-treated clay with 5-15% by weight, based on the total dry admixture, of one or more oxides of metals of Group VI of the Periodic System; PA1 adjusting the water content of the admixture to 20-35% by weight; PA1 pressing the admixture into a desired shape and calcining at 500.degree.-800.degree. C.; PA1 treating the so-formed carrier material with an acid until it has an Al.sub.2 O.sub.3 content of 1-5% by weight and a specific surface area of 150-250 m.sup.2 /g; and PA1 then impregnating the resulting carrier with phosphoric acid; and the catalysts so-produced are disclosed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method for producing a catalyst for the 
hydration of olefins from clay minerals. 
2. Description of the Prior Art 
It is known that olefins in the gaseous phase can be converted under high 
pressures with steam into alcohols. Such methods have special technical 
significance in the production of ethyl alcohol from ethylene and 
isopropyl alcohol obtained from propylene. These alcohols are synthesized 
in the presence of catalysts, usually phosphoric acid provided on 
carriers. 
Suitable carrier materials are based on pure silicic acid (e.g. 
diatomaceous earth or silica gel) or on silicic acid with greater or 
lesser clay content, such as calcined diatomaceous earth, whose structure 
is held together by clay or clay-like materials. 
Long-term solidity is a problem with carrier materials based on pure 
silicic acid. The clay-containing materials have better mechanical 
solidity, however, they have the disadvantage that when their clay-content 
is too high aluminum oxide is dissolved away during the reaction due to 
the action of the phosphoric acid. 
German Pat. No. 1 156 772 describes a method for producing a 
clay-containing carrier for phoshoric acid used as a catalyst in olefin 
hydration, in which molded contact bodies made of mineral clay silicates 
are treated with mineral acid so that the aluminum oxide content falls 
preferrably to between 1 and 5% by weight (b.w.). This material generally 
has the necessary mechanical solidity and a sufficiently low residual 
aluminum oxide content to avoid dissolving away. In contrast it has been 
observed with the use of customary contact bodies in the production of 
catalyst carriers for olefin hydration, that without preselecting the raw 
material, strongly differing catalyst activities are produced. 
Success was finally found in developing carriers for phosphoric acid on the 
basis of large pore silica gels with high hydration activity and adequate 
mechanical solidity, e.g. DE-OS No. 26 25 705 and DE-OS No. 27 19 055. 
Nonetheless, one disadvantage remained with these carriers based on 
amorphous silicic acid: upon extended exposure to the rigors of the 
hydration reaction, the amorphous silicic acid crystallised into 
cristobalite and quartz. This brought with it an irreversible, stark 
reduction of specific surface area and thus, catalytic activity, along 
with a decrease in mechanical solidity. Another disadvantage of all 
previously used hydration catalysts based on phosphoric acid on silicate 
carriers is the slow reduction of activity owing to dissipated phosphoric 
acid. Phosphoric acid must be continuously neutralized by alkali treatment 
in continuous operation in order to avoid the corrosive actions of acid 
and raw alcohol on the down stream distillation apparatus. 
The more recent development of continuous spraying of washed-away 
phosphoric acid according to DE-OS No. 26 58 946 made it possible to 
avoid, to a large extent, the continuous loss of activity and, thus, to 
considerably extend the life span of the catalyst. This, however, places 
corresponding demands on the life span of the carrier, thus eliminating 
the use of such carriers as those with which crystallization occurs under 
reaction conditions, thereby irreversibly lessening the catalytic activity 
and the mechanical solidity in the course of time. 
German patent application No. P 29 08 491.1 shows that a carrier for a 
hydration catalyst with continuing high catalytic activity can be produced 
from clay material when care is taken in the selection of the raw material 
to assure that the material consists largely of montmorillonite, which 
means that after being formed, macerated (leached) and impregnated, the 
active surface area on which the hydration of the olefins can take place 
is large. 
German patent application No. P 29 08 491.1 relates to a method for 
producing a catalyst from clay minerals for the hydration of olefins with 
2-3 C-atoms to the corresponding alcohols of phosphoric acid and carrier 
material--including the correspondingly produced catalyst--in which a clay 
containing essentially montmorillonite, contaminated by no more than 3% 
accompanying minerals such as quartz, feldspar and mica, and containing up 
to 0.5% of K.sub.2 O, is processed in a first step with acid until it has 
an Al.sub.2 O.sub.3 -content of 13-18% b.w. and, if necessary, the 
Al.sub.2 O.sub.3 --content is adjusted to 16-18% b.w. through the addition 
of precipitated clay. The result is a surface area of 200-400 m.sup.2 /g, 
preferrably 240-300 m.sup.2 /g. When the total water content is 20-35% it 
is pressed into a form, calcined at 500.degree.-800.degree. C., and the 
formed carrier material is then treated with acid in a second step until 
the Al.sub.2 O.sub.3 -content reaches 1-5% b.w., preferrably 1-3% b.w. The 
result is a surface area of 150-250 m.sup.2 /g, preferrably 180- 220 
m.sup.2 /g. Finally, the resulting carrier is impregnated in a known 
manner with phosphoric acid. 
A different mineral in the montmorillonite group, which nonetheless, 
contains the montmorillonite crystalline lattice, can be used instead of 
montmorillonite. 
It is also possible to use a fuller's earth or clay that has already been 
treated once with acid in place of a clay containing montmorillonite that 
has not yet been treated with acid. This makes the first acid treatment 
superfluous. This fuller's earth or clay should contain less than 0.1% 
K.sub.2 O; the weight ratio should be (Al.sub.2 O.sub.3 +Fe.sub.2 
O.sub.3): SiO.sub.2 =1:3.5-1:4.5. If needed, the Al.sub.2 O.sub.3 
--content in the fuller's earth or clay can be brought to the necessary 
16-18% b.w. by adding precipitated clay. 
Catalyst or catalyst carriers produced in this way from clay containing 
montmorillonite have a different origin than those formed contact bodies 
based on mineral clay silicates, increased activity, i.e. per hour and 1 
catalyst charging approximately 105-110 g of ethanol or ca. 300 g of 
isopropyl alcohol were produced. This increased activity, however, can 
only be sustained over an extended period if the phosphoric acid that is 
carried away--amounting to ca. 0.07 g per hr and 1 catalyst charging with 
ethanol--is constantly balanced by continuous replacement of an equal 
amount of acid. In addition, this dissipated acid must still be 
neutralized with an alkali treatment. 
The mechanical solidity of the catalysts lies in the range of 7-9 kg/ball, 
which is sufficient to charge a customary reactor. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Surprisingly it has now been found that additional characteristics of the 
finished catalyst can be improved by adding 5-15% b.w. of the total dry 
substance of an oxide or a mixture of several oxides of elements in group 
VI of the periodic system. Therefore, it is the object of the invention to 
provide a method for producing a catalyst from clay materials for the 
hydration of olefins with 2-3 C-atoms to the corresponding alcohols from 
phosphoric acid and carrier material, wherein clay, containing essentially 
montmorillonite and contaminated by no more than 3% accompanying minerals 
such as quartz, feldspar and mica and up to 0.5% K.sub.2 O, is treated in 
a first step with acid, and, if necesary, by adding precipitated clay, 
until it has an Al.sub.2 O.sub.3 --content of 13-18% b.w. and a surface 
area of 200-400 m.sup.2 /g, preferrably 240-300 m.sup.2 /g. Then, 5-15% 
b.w., based on the total dry substance, of one or several oxides of metal 
in group VI of the periodic system are added. Then, with a total water 
content of 20-35%, it is pressure formed, calcined at 
500.degree.-800.degree. C., and the formed carrier material is then 
treated in a second step with acid until it has an Al.sub.2 O.sub.3 
-content of 1-5% b.w., preferrably 1-3% b.w., and a surface area of 
150-250 m.sup.2 /g, preferrably 80-220 m.sup.2 /g. The carrier thus formed 
is impregnated in known manner with phosphoric acid. 
Other minerals of the montmorillonite group, containing no postassium, but 
having the montmorillonite crystalline lattice, can also be used. 
A type of fuller's earth or clay, produced from a clay with large amounts 
of montmorillonite, that has already been treated once with acid, can also 
be used in the place of a clay containing montmorillonite that has not yet 
been acid treated. This makes the first acid treatment superfluous. The 
fuller's earth or clay should contain less than 0.1% K.sub.2 O; the weight 
ratios should be (Al.sub.2 O.sub.3 +Fe.sub.2 O.sub.3): SiO.sub.2 
=1:3.5-1:4.5. If necessary, the Al.sub.2 O.sub.3 --content of the fuller's 
earth or clay can be brought to the necessary 16-18% b.w. by adding 
precipitated clay. 
The invention provides the following advantages: 
1. The mechanical solidity of the catalyst increases to about 11-13 
kg/ball. This is significant in the use of higher catalyst charges. 
2. The catalyst activity increases to ca. 130 g ethanol and ca. 350 g 
isopropyl alcohol per hr and 1 catalyst charging. 
3. The depletion of phorphoric acid is reduced to about one half, i.e. with 
ethanol to about 0.035 g per hr and 1 catalyst charging, with isopropyl 
alcohol to about 0.005 g per hr and 1 catalyst charging. 
In addition to binding the phosphoric acid more firmly to the carrier by 
way of the heteropoly acid of metal in periodic group VI, it is also 
surprising that the oxides of the metals in periodic group VI can be 
incorporated into the silicate lattice in such a manner that they are not 
dissolved away at all by the subsequent acid treatment. It is evident that 
a build up of heteropoly acid has commenced between the silicon and the 
oxides of elements in periodic group VI when calcined under the conditions 
set out above.

EXAMPLE I 
A ground, natural, raw clay, which was chosen on the basis of laboratory 
experiments in which no more than 5 g of K.sub.2 O per kg of original dry 
substance was extracted in an hour-long treatment with 20% hydrochloric 
acid at 82.degree. C., was heated at 82.degree. C. or an hour with a 20% 
hydrochloric acid solution, washed free of acid and dried. The amount of 
acid was calculated so that 8.4 moles of HCl were used for 1 kg of clay. 
The result was a material with a residual aluminum oxide (moiety) content 
of 16% b.w. and a specific surface area of 300 m.sup.2 /g: 
15 parts of tungsten oxide (WO.sub.2) were added to 100 parts of this dry 
material so that the mixture contained 13% b.w. of tungsten oxide. After 
moistening with 25% water, based on the total amount (i.e. addition of 33% 
of the dry substance as water), the material was pressed into cylindrical 
forms with a 4 mm diameter and 4 mm height and solidified by three hours 
of 600.degree. C. heat treatment. 
The contact bodies formed in this manner were treated twice with 20% 
hydrochloric acid for a total of one hour at 100.degree.-110.degree. C. 
and then rinsed acid free with water. After drying at ca. 
110.degree.-120.degree. C. the cylinders had an aluminum oxide content of 
2.7% b.w., the specific surface area was 215 m.sup.2 /g. The tungsten 
oxide content had increased to 15% b.w. 
These formed bodies were then bathed and allowed to react in 60% b.w. 
phosphoric acid for two hours and then redried at ca. 
110.degree.-120.degree. C. The H.sub.3 PO.sub.4 --content of the cylinders 
processed in this manner was 35% b.w. The intermediate compression 
resistance was 11 kg/cylinder. 
When this hydration catalyst was applied in the synthesis of ethanol from 
ethylene and water in the gaseous phase, the catalyst yield was 130 g of 
ethanol per hr and 1 catalyst charging. Phosphoric acid dissipation under 
reaction conditions was 0.035 g per hr and 1 catalyst charging. 
EXAMPLE 2 
100 parts of a highly active fuller's earth or clay with a specific surface 
area of 350 m.sup.2 /g and the following chemical analysis--72.5% 
SiO.sub.2, 14.0% Al.sub.2 O.sub.3, 4.0% Fe.sub.2 O.sub.3, 1.5% MgO, 0.8% 
CaO, 7.2 loss on ignition, K.sub.2 O 0.1%--were mixed with 8 parts of 
chromium oxide (CrO.sub.3) so that the mixture contained 7.4% chromium 
oxide. After moistening with 30% water, based on the total amount (i.e. 
addition of 43% of the dry substance as water), the material was pressed 
into balls with a 4 mm diameter and solidified in 600.degree. C. for 3 
hours. 
The contact bodies formed in this manner were treated twice with 20% 
hydrochloric acid for a total of one hour at 100.degree.-110.degree. C. 
and then rinsed acid free with water. After drying at ca. 
110.degree.-120.degree. C. the balls had an aluminum oxide content of 1.4% 
b.w., the specific surface area was 230 m.sup.2 /g. The chromium oxide 
content had increased to 9% b.w. 
These formed bodies were then bathed and allowed to react in 60% b.w. 
phosphoric acid for two hours and then redried at ca. 
110.degree.-120.degree. C. The H.sub.3 PO.sub.4 --content of the balls 
processed in this manner was 36% b.w. The intermediate compression 
resistance was 13 kg/ball. 
When this hydration catalyst was applied in the synthesis of ethanol from 
ethylene and water in the gaseous phase, the catalyst yield was 130 g of 
ethanol per hr and 1 catalyst charging. Phosphoric acid dissipation under 
reaction conditions was 0.035 g per hr and 1 catalyst charging. 
EXAMPLE 3 
100 parts of a highly active fuller's earth or clay with a specific surface 
area of 350 m.sup.2 /g and the following chemical analysis--72.5% 
SiO.sub.2, 14.0% Al.sub.2 O.sub.3, 4.0% Fe.sub.2 O.sub.3, 1.5% MgO, 0.8% 
CaO, 7.2% loss on ignition, K.sub.2 O 0.1%--were mixed with 10 parts of 
molybdenum oxide (MoO.sub.3) so that the mixture contained 7.4% of 
molybdenum oxide. After moistening with 30% water, based on the total 
amount (i.e., addition of 43% of the dry substance as water), the material 
was pressed into balls with a 4 mm diameter and solidified by 600.degree. 
C. heat for 3 hours. 
The contact bodies formed in this manner were treated twice with 20% 
hydrochloric acid for a total of one hour at 100.degree.-110.degree. C. 
and then rinsed acid free with water. After drying at ca. 
110.degree.-120.degree. C. the balls had an aluminum oxide content of 1.4% 
b.w., the specific surface area was 230 m.sup.2 /g. The molybdnm oxide 
content had increased to 11% b.w. 
These formed bodies were then bathed and allowed to react in 40% b.w. 
phosphoric acid for two hours and then redried at ca. 
110.degree.-120.degree. C. The H.sub.3 PO.sub.4 --content of the balls 
processed in this manner was 27% b.w. The intermediate compression 
resistance was 12 kg/ball. 
When this hydration catalyst was applied in the synthesis of isopropyl 
alcohol from propylene and water in the gaseous phase, the catalyst yield 
was 350 g of isopropyl alcohol per hr and 1 catalyst charging. Phosphoric 
acid dissipation under reaction conditions was .theta..005 g per hr and 1 
catalyst charging. 
EXAMPLE 4 
100 parts of a highly active fuller's earth or clay with a specific surface 
area of 350 m.sup.2 /g and the following chemical analysis--72.5% 
SiO.sub.2, 14.0% Al.sub.2 O.sub.3, 4.0% Fe.sub.2 O.sub.3, 1.5% MgO, 0.8% 
CaO, 7.2% loss on ignition, K.sub.2 O 0.1%--were mixed with 3 parts 
chromium oxide (CrO.sub.3), 3 parts molybdenum oxide (MoO.sub.3), 5 parts 
tungsten oxide (WO.sub.3), so that the mixture contained a total of 10% 
oxide of elements of periodic group VI. 
After moistening with 30% water, based on the total amount (i.e. addition 
of 43% of the dry substance as water), the material was pressed into balls 
with a 4 mm diameter and solidified in 600.degree. C. heat for 3 hours. 
The contact bodies formed in this manner were treated twice with 20% 
hydrochloric acid for a total of one hour at 100.degree.-110.degree. C. 
and then rinsed acid free with water. After drying at ca. 
110.degree.-120.degree. C. the content of oxides of elements of the VI 
periodic group had increased to 12% b.w. 
These contact bodies were then bathed and allowed to react in 60% b.w. 
phosphoric acid for two hours and then redried at ca. 
110.degree.-120.degree. C. The H.sub.3 PO.sub.4 --content of the balls 
processed in this manner was 35% b.w. The intermediate compression 
resistance was 13 kg/ball. 
When this hydration catalyst was applied in the synthesis of ethanol from 
ethylene and water in the gaseous phase, the catalyst yield was 130 g of 
ethanol per hr and 1 catalyst charging. Phosphoric acid dissipation under 
reaction conditions was 0.035 g per hr and 1 catalyst charging.