CA1100477A - Catalyst comprising phosphoric acid on silica gel, its preparation and use - Google Patents
Catalyst comprising phosphoric acid on silica gel, its preparation and useInfo
- Publication number
- CA1100477A CA1100477A CA276,092A CA276092A CA1100477A CA 1100477 A CA1100477 A CA 1100477A CA 276092 A CA276092 A CA 276092A CA 1100477 A CA1100477 A CA 1100477A
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- Prior art keywords
- particles
- catalyst
- water
- hydrogel particles
- hydrogel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/0072—Preparation of particles, e.g. dispersion of droplets in an oil bath
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/14—Phosphorus; Compounds thereof
- B01J27/16—Phosphorus; Compounds thereof containing oxygen, i.e. acids, anhydrides and their derivates with N, S, B or halogens without carriers or on carriers based on C, Si, Al or Zr; also salts of Si, Al and Zr
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/03—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by addition of hydroxy groups to unsaturated carbon-to-carbon bonds, e.g. with the aid of H2O2
- C07C29/04—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by addition of hydroxy groups to unsaturated carbon-to-carbon bonds, e.g. with the aid of H2O2 by hydration of carbon-to-carbon double bonds
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Dispersion Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Catalysts (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
ABSTRACT
A catalyst comprising phosphoric acid supported on porous silica gel particles having both R high water resistance and a high bulk crushing strength and a pore volume of at least 0.6 ml/g, said particles having been obtained by the following successive steps:
(a) preparing a silica hydrosol by mixing an aqueous solution of an alkali metal silicate with an aqueous solution of an acid, (b) converting the hydrosol into droplet form, and (c) allowing the droplets to gel in a liquid which is immiscible with water, whereupon the hydrogel particles emerging from said liquid have been separated off and freed from water and alkali metal compounds by the following sequence of consecutive steps:
(I) removing by evaporation at least 25% of the amount of water present in the hydrogel particles, (II) decreasing the alkali metal content of the hydrogel particles in an aqueous medium to less than 1%w, calculated on dry material, and (III) drying and calcining the silica particles.
These catalysts exhibit improved water resistance and a higher hulk crushing strength than the known phosphonic acid/porous silica gel catalysts used for olefin hydration to produce alkanols.
A catalyst comprising phosphoric acid supported on porous silica gel particles having both R high water resistance and a high bulk crushing strength and a pore volume of at least 0.6 ml/g, said particles having been obtained by the following successive steps:
(a) preparing a silica hydrosol by mixing an aqueous solution of an alkali metal silicate with an aqueous solution of an acid, (b) converting the hydrosol into droplet form, and (c) allowing the droplets to gel in a liquid which is immiscible with water, whereupon the hydrogel particles emerging from said liquid have been separated off and freed from water and alkali metal compounds by the following sequence of consecutive steps:
(I) removing by evaporation at least 25% of the amount of water present in the hydrogel particles, (II) decreasing the alkali metal content of the hydrogel particles in an aqueous medium to less than 1%w, calculated on dry material, and (III) drying and calcining the silica particles.
These catalysts exhibit improved water resistance and a higher hulk crushing strength than the known phosphonic acid/porous silica gel catalysts used for olefin hydration to produce alkanols.
Description
Th.is invention relates to a novel catalyst compri.sing phosphoric acid impregnated on a porous silica gel support, and to a process for the preparation thereot. It relates, moreover, to the use of said catalysts, in particular to the production of alkanols, such as ethyl or isopropyl alcohol, by hydration of the corresponding olefins in the presence of such a catalyst.
From the ~nited Kingdom Patent Specifications 1,371,905 and 1J306~14 it is known to use a silica gel, such as "Davison Grade 57"*, impregnated with phosphoric acid as a catalyst for the preparation of alcohols by olefin hydration.
It has now been found that important properties of the catalysts in question, particularly the water resistance and the bulk crushing strength of the catalyst particles, can be much improved if the porous silica gel used as the carrier material for the phosphoric acid is prepared by a special procedure.
The present invention provides a catalyst comprising phos-phoric acid supported on porous silica gel particles, which may optionally contain small amounts of a filler, the silica gel particles having both a high water resistance and high bulk crushing strength, and a pore volume of at least 0.6 ml/g, said particles having been obtained by the following successive steps:
*Trademark _ z _ '`'~`'~') .
A catalyst comprising phosphoric acid supported on porous silica gel particles having both a high water resistance and high bulk crushing strength and a pore volume of at least 0.6 ml/g, said particles having been obtained ~y the following successive steps:
(a) preparing a silica hydrosol by mixing an aqueous solution of an alkali metal silicate wi~h an aqueous solution of an acid, (b) converting the hydrosol into droplet form, ancl ~c) allowing the droplets to gel in a liquid which is immiscihle with water, whereupon the hydrogel particles emerging from said liquid have been separated off and freed from water and alkali metal compounds by the following sequence of consecutive steps:
(I) removin~ by evaporation at least 25% of the amount of water present in the hydrogel particles, (II) decreasing the alkali metal content o~ the hydro~el particles m an aqueous medium to less ~han l~w, calculated on dry material, and ~III) drying and calcining the silica particles.
The novel catalyst, i~ accordance with the invention, has proved to possess superior properties as compared with those o~ the catalysts described in the prior art. This applies in particular to the bulk crushing `` ,~,1 ' s-trength, both before and after use in the hydra-tion of olefins, such as ethylene, -to -the corresponding alcohol.
Globular silica gel particles preferably used as -the support for-the phosphoric acid may be obtained as follows: ~irst of all a silica hydrosol is prepared by mixing an aqueous solu-tion of an alkali metal silicate with an aqueous solution of an acid. This may very sui-tably be performed by leading the starting solutions separately into a mixing chamber where mixing of the solutions -takes place by stirring. As the alkali metal silicate and the acid, sodium silicate and sulphuric acid, respectively, are very suitable. After the silica hydrosol has been formed, it is converted in-to droplet form and allowed to gel in a liquid which is immiscible, or substantially immiscible, with water. This may very suitably be performed by introducing the hydrosol via a small aperture in the bottom of the mixing chamber into the upper end of a vertically disposed tube filled with oil. Gelation occurs whilethe~hydrosol drople-ts move downwards through the oil. At -the bottom of the tube -the globular hydrogel particles may be caught in an aqueous phase, such as water or, preferably, an aqueous solution of a salt such as Na2S04, particularly a salt solution having substantially the same salt concentration as that presen-t in the hydrogel par-ticles.
' ~. : '',' ' - ~ ' ' ' The hydrogel particles are -then separated from -the aqueous phase, e.g. by filtra-tion, whereupon they are subjected -to the water removal step. It is also possible to carry out the water removal s-tep in the oil af-ter gelation has taken place.
In the water removal step, according to a preferred embodiment of the invention, at least 25%, and preferably at least 50%, of the water present in the hydrogel particles is removed therefrom by evaporation, removal of ~rom 60 to 90% of the water being most preferred.
This water removal step may be carried out in various ways. Water may advantageously be removed from the hydrogel particles by contacting -them with a gas stream, e.g. a stream o~ air, either or not at elevated temperature.
~ater may also be removed fromthe hydrogel par-ticles by heating them at atmospheric pressure or at reduced or elevated pressure. Other ways o~ removing water ~ -~rom the hydrogel par-ticles are by contacting them with an inert liquid at a temperature above 100C, or by contacting them at an eleva-ted temperature wi~h steam or a steam-containing gas stream. Examples of treatments which may very suitably be applied for removing at least 25% of -the water present in thehydrogel particles are the following:
a) heating the hydrogel particles at a temperature of about 100C at reduced pressure, :' ' :
,': ' L7~
b) heatingthe.hydrogel particles at a temperature above 100 C in a stream of air, c) heating the hydrogel particles at a temperature of about 100 C at reduced pressure followed by heating the particles at a temperature of about 500C in a stream of air, d) contacting the hydrogel particles with a hydrocarbon oil at a temperature above 100C, e) heating the hydrogel particles at a temperature above 100C in an autoclave at autogenous pressure, and f) heating the hydrogel particles in a stream of air and steam.
I-t is particularly recommended to remove the water by contacting the hydrogel particles wi-th a gas stream in such a way, that the particles are heated to a temperature in the range 55 to 180C, and more preferably in the range 100 to 170C. Excellent results are obtained by using a stream of air having a temperature of ~rom 100 to 300C, especially from 180 to 2205.
The temperature to whlch the hydrogel particl.es are hea-ted has a significant in~luence on the te*ture, i.e. pore volwne and pore diameter, of the catalyst support to be prepared. For example, larger or smaller pore volwmes (corresponding with smaller or larger pore diameters) may be obtained, according as .said .:
temperature is on the l~wer or higher side, resp~ctively, : ' . .
.. : . ,: , .. . . : ... ,... .~ . .
of the ranges indicated above Thus, when it is desired to prepare a catalyst having a relatively large pore volume, heating e.g. to about 135C has proved to be very suitable.
After the treating step, in which at least 25% of the water present in the hydrogel particles is removed therefrom by evapora-tion, the alkali metal content of the hydrogel particles is decreased in an aqueous medium to less than 1 %w calculated on dry material.
This alkali metal removal may very suitably be performed by trcating the hydrogel particles with an aqueous solution of an ammonium salt, e.g. the nitrate or the sulphate, ammonium hydroxide, or an inorganic or organic acid, for example~ hydrochloric, sulphuric, nitric or acetic acid. Subsequently, a water wash may be applied, if necessary. Treat-ment with an aqueous solution of NH4N03 has given excellen~ results.
Suitably, the treatment is carried out by percolation of the aqueous solution in question through the hydrogel particles.
~lthough the operations for removing at least part of the water and for reducing the alkali metal content are most preferably carried ou~ in the consecutive order described above, a reverse sequence of operations is not excluded.
Finally the hydrogel particles are dried and calcined.
Drying and calcining of the hydrogel particles may e.g. be carried out by heating the particles for 7~
from 1 to 5 hours at a temperature of 100-200C and ~50-550C, respectively. If desired~ the calcination may be followed by a hydro-thermal treatment, e.g. a treatment with steam.
If desired, a small amount of a filler may be incorporated into the silica particles according to the invention. Incorporation of a filler may be attractive for various reasons. In the first place the porosity of the ultimate silica particles may be influenced by this measure, with the result, for example, of a larger pore volume Further, for certain applications of the silica particles, the presence of e.g. an alumina filler therein may be attractive. It is also possible to decrease the cost of preparation of the silica particles by incorporating therein a cheap filler. The incorporation of the f:iller into the silica par-ticles may very suitably be performed by adding the filler to the aqueous solution of the alkali metal silicate and/or to the aqueous solution of the acid from which the hydrosol is prepared by mixing. F.xamples of suitable fillers are kaolin, montmorillonite, bentonite, precipitated silica fillers, aluminas, zeolites and amorphous precipitated silica-aluminas.
With respect to the amount of filler which may be incor-~0 porated into the silica particles according 6?47~
to -the invention, it has been found that the presence of a filler in the silica particles reduces the bulk crushing streng-th of the particles, which effect is more pronounced according asthe filler content of the particles is higher. Since, however, the so]-gel method as a rule provides globular silica particles with a very high bulk crushing strength, a small decrease is of no importance, and filler containing globular silica particles which possess the high bulk crushing strength aimed at (see below) can easily be prepared, provided that the quantity of filler incorporated therein amounts to no-t more than ~5 /w of the quantity of silica present in the hydrosol from which the silica particles are prepared. Incorporation of larger amounts of filler in the silica particles en-tails -the risk that silica particles with an inferior bulk crushing strength are obtained.
The silica gel particles prepared according -to the procedure aescribed above are usually obtained in a globular form or in the form of pelle-ts of more or less spheroidal shape, and they have a very high water resistance and bulk crushing strength. This applies also to the catalyst of the invention, which comprises phosphoric acid supported on said silica particles.
~he p-re volume of the silica which s~ou1d be at least .
_ g _ 7~
0.6 ml/g, does not exceed, as a rule, 2.2 ml/g and usually is in the range 0.8 to 1.5 ml/g, a pore volume ranging from 1.0 to 1.~ being preferred.
The expression "particles with a high water resistance"
used in this patent application refers to particles having a water re-sistance of at least 80%, preferably of at least 90%. The water re-sistance of the silica particlesJ for example, globular silica particles, is determined in a standard test in which 100 of the globular silica particles are contacted for 5 minutes at room temperature with a volume of water which amounts to 5 times the volume of the 100 globular silica ~ -particles. Thereafter the particles are inspected to determine the amount of particles which show cracks or have disintegrated. The water resistance of the globular silica particles is expressed as the percent-age of particles which have not been damaged by the contact with water.
The expression "particles with a high bulk crushing strength" used in this patent application refers to particles having a bulk crushing strength (BCS) of, at least 10 kg/cm , preferably of at least 11 kg/cm . The BCS, which is a measure of the mechanical strength, of the particles, is defined as the pressure exerted by a circular plun-ger with a surface area of 6 cm2 on a 25 ml sample of a number of particles in a cyll.nder.
- 1 0 - .
at which the quanti-ty of fines passing through a 1~25 ~m sieve amounts to 0.5% (w/w) of the sample.
It is to be lmders-tood in this connection that a relation exists between the bulk crushing s-trength and the pore volume, in the sense that, as a rule, an increase in pore vo]ume results in a decrease of the BCS and vice-versa. Since, in accordance with the present invention, the silica gel particles are to be impregnà-ted with phosphoric acid, it is desirable that they have a relatively high pore volume, say larger than about 1.0 ml/g, in order to produce highly active catalysts which are suitable for the hydration of alkenes to alkanols. Silica gel par-ticles having the mos-t favourable pore volumes can be prepared, however, only a-t -the expense of the BCS which is lower than the attainable maximum. The figures for the BCS and the pore volume mentioned above, therefore, represent a compromise in respect of the desired properties.
The novel catalyst of the invention may be prepared by means of any of the conventional techniques. According -to a preferred method, silica gel particles, prepared as hereinbefore described are impregnated with phosphoric acid. Suitably, an aqueous phosphoric acid is used having a concentration of, for example, from 20 to 85%, preferably from 55 to 75%. Good results are obtained by lrnmersion of the globular silica gel support in the aqueous phosphoric acid, e .e. for 0.5 to 5 hours, .
.
- 11 - ' . .
.
.
followed by draining off the excess acid and drying the impregnated support inthe usual way, for example by heating at about 150C.
The catalyst of the present invention may be applied in various chemical reactions, e.g. in the polymerization or oligomerization of lower olefins, but especially in -the hydration of olefins to the corresponding alcohols.
Although it is recommended to apply the catalyst of the invention in the globular or spheroidal form in which it is usually obtained by the procedure described above, it may also - at least in part - be present in another form, e.g. in the form of smaller particles which may be produced by fragmentation, ei-ther before or after the impregnation with phosphoric acid, of the globular par-ticles initially obtained. Altera-tions in the shape may, moreover, be brought about in the course of the production of the hydrogel particles, if desired.
According to a par-ticular impor-tant aspect of the invention, there is provided a process for the prepara-tion of an alkanol, in which process an olefin and water are contacted at eleva-ted tempera-ture and pressure, in the presence of a ca-talyst as hereinbefore described.
Suitable olefins are those containing from 2 to 10 carbon atoms, especial1y ~hose baving from 2 .
~ :`
i7~
to 5 carbon a-toms, Most preferred are ethylene and propylene.
The reactants are generally applied in the gaseous s-tate. The feed ratio and the reaction condi-t;ons may vary widely, depending inter alia on the starting material used. Thus, ethanol may suitably be prepared using a molar ratio water/ethylene in the range 0.2:1 to 1.0:1, preferably 0.3:1 to 0.6:1, a temperature in the range 200 to 300C, preferably 220 to 270C, and a pressure of from 50 to 90 atg. Isopropyl alcohol may be prepared for example, using a mole ratio water/
propylene ranging from 0.1:1 to 0.5:1, a temperature of ~rom 140 -to 250C, and a pressure of from 15 -to 50 a-tg. The gas space velocity of the feed mixture may range from e.g. 5 -to 100 min , preferably f`rom 8 to 35 min , and in particular from 15 to 35 min A process for the preparation of ethanol by hydration of ethylene, using as the catalyst a dia-tomaceous earth, has been described, for example, by C.R. Nelson and M.L. Courter in Chem. Engng. Progr. 50 (195~) pp.
526 to 531.
EXhMPLE I
(a) Preparation of silica gel support An aqueous sodium waterglass solution comprising 12 ~Ow SiO2 and having a Na20/SiO2 molar ratio of 0~3 was mixed continuously in a mixing chamber with an aqueous 1.2 N sulphuric acld solution in a volume . . .
-7~
ratio acid solution/waterglass solution of 0.75. A~ter a residence time of a few seconds in the mixing chamber, the hydrosol was continu-ously ejected from the m:ixing chamber through an aperture in the bottom thereof into a vertically disposed tube with a length of 1,8 m filled with a paraffinic oil at 25C ~"ONDINA 33"* J marketed by SIIEL.L). I'he hydrosol jet was thus converted into droplet form~ and the hydrosol droplets - which had an average diameter of 6 mm - were allowed to pass through the oil by gravity. During the fall through the tube gelation occurred. The globular hydrogel particles were caught at the bottom of the tube in an aqueous 0.25 M Na2SO4 solution of 25C and separated by filtration. The water content of these globular hydrogel particles was determined in a standard test in which a sample was heated in three hours from room temperature to 600C and thereafter kept at 600C for one hour. The water content of the hydrogel particles appeared to be 9~) %w.
The silica hydrogel particles were dried for 0.5 hours in a stream of air having a velocity of 2240 Nl/h and a temperature of 200C, the temperature of the hydrogel particles being allowed to rise to 135C. After this treatment the water content of the hydrogel par-ticles amounted to 14 %w. ~ubsequently, an aqueous *Trademark -- 1~ -0.1 M solution of ammonium nitra-te was percolated through the hydrogel particlesl which were then washed with water, dried for 2 hours at 100C and calcined for 3 hours at 500C. A reduction of the sodium content to about 0.02 %w was thus achieved. The globula:r silica par-ticles obtained showed a water resistance of 9~%. They had an average particle size of 3.5 mm, a pore volume of 1.19 ml/g, and a bulk crush-ing strength of 11.2 kg/cm2 The "pore volume" is defined herein as the specific pore volumeJ determined by means of a water titration method in which the amount of water taken up by a dried sample under specified conditions has been measured, ~b) Impregnation with pho~horic acid The resulting support, as well as a commercially available silica gel support of comparable size and texture, was impregnated with 60% aqueous phosphoric acid by immersion therein, followed by draining off the excess acid and drying at 150C. The commercial sup-port, used for comparison only, was "Davison Grade 57*" ex W, R. Grace Ltd.
In Table I below, the bulk crushing strength ~BCS) - both before and after impregnation with phosphoric acid - is shown, as well as the average particle size, pore volume and average pore diameter of the silica *Trademark ..
support.
The results obtained show, inter alia, the superior BCS of -the impregnated support of -the invention (sample A) as compared with that of the commercial suppor-t (sample B).
- 16 - :
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o ~ W) ~ Lr~
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~ ~ _ P~ ~J ~
¢ ~4 ~
0~7 EXAMPLE II
.
Pre~aration of Ethanol ~ilica gel particles impregnated with phosphoric acid, which had been prepared as described in Fxample I, were applied as catalysts in the preparation of ethanol by hydration of ethylene as follows:
The catalyst (25 ml or 20 g) was charged to a vertically disposed reactor tube of stainless steel (AISI 316) having a diameter of 25 mm and a length lQ of 300 mm, the catalyst bed being enclosed by stainless steel balls of 2 ~m diameter which occupied a volume of 75 ml both above and below the catalyst hed. Temperature measurements were made by means of a pyrometer tube havin~ an outer diameter of 6 mm and which was fitted in the centre of the catalyst bed.
A mixture of gaseous ethylene and water in a molar ratio water/ethylene of o.56 : 1 was passed continuously through the reactor tube in an upward direction at ;
an average temperature of 270C. The space velocity
From the ~nited Kingdom Patent Specifications 1,371,905 and 1J306~14 it is known to use a silica gel, such as "Davison Grade 57"*, impregnated with phosphoric acid as a catalyst for the preparation of alcohols by olefin hydration.
It has now been found that important properties of the catalysts in question, particularly the water resistance and the bulk crushing strength of the catalyst particles, can be much improved if the porous silica gel used as the carrier material for the phosphoric acid is prepared by a special procedure.
The present invention provides a catalyst comprising phos-phoric acid supported on porous silica gel particles, which may optionally contain small amounts of a filler, the silica gel particles having both a high water resistance and high bulk crushing strength, and a pore volume of at least 0.6 ml/g, said particles having been obtained by the following successive steps:
*Trademark _ z _ '`'~`'~') .
A catalyst comprising phosphoric acid supported on porous silica gel particles having both a high water resistance and high bulk crushing strength and a pore volume of at least 0.6 ml/g, said particles having been obtained ~y the following successive steps:
(a) preparing a silica hydrosol by mixing an aqueous solution of an alkali metal silicate wi~h an aqueous solution of an acid, (b) converting the hydrosol into droplet form, ancl ~c) allowing the droplets to gel in a liquid which is immiscihle with water, whereupon the hydrogel particles emerging from said liquid have been separated off and freed from water and alkali metal compounds by the following sequence of consecutive steps:
(I) removin~ by evaporation at least 25% of the amount of water present in the hydrogel particles, (II) decreasing the alkali metal content o~ the hydro~el particles m an aqueous medium to less ~han l~w, calculated on dry material, and ~III) drying and calcining the silica particles.
The novel catalyst, i~ accordance with the invention, has proved to possess superior properties as compared with those o~ the catalysts described in the prior art. This applies in particular to the bulk crushing `` ,~,1 ' s-trength, both before and after use in the hydra-tion of olefins, such as ethylene, -to -the corresponding alcohol.
Globular silica gel particles preferably used as -the support for-the phosphoric acid may be obtained as follows: ~irst of all a silica hydrosol is prepared by mixing an aqueous solu-tion of an alkali metal silicate with an aqueous solution of an acid. This may very sui-tably be performed by leading the starting solutions separately into a mixing chamber where mixing of the solutions -takes place by stirring. As the alkali metal silicate and the acid, sodium silicate and sulphuric acid, respectively, are very suitable. After the silica hydrosol has been formed, it is converted in-to droplet form and allowed to gel in a liquid which is immiscible, or substantially immiscible, with water. This may very suitably be performed by introducing the hydrosol via a small aperture in the bottom of the mixing chamber into the upper end of a vertically disposed tube filled with oil. Gelation occurs whilethe~hydrosol drople-ts move downwards through the oil. At -the bottom of the tube -the globular hydrogel particles may be caught in an aqueous phase, such as water or, preferably, an aqueous solution of a salt such as Na2S04, particularly a salt solution having substantially the same salt concentration as that presen-t in the hydrogel par-ticles.
' ~. : '',' ' - ~ ' ' ' The hydrogel particles are -then separated from -the aqueous phase, e.g. by filtra-tion, whereupon they are subjected -to the water removal step. It is also possible to carry out the water removal s-tep in the oil af-ter gelation has taken place.
In the water removal step, according to a preferred embodiment of the invention, at least 25%, and preferably at least 50%, of the water present in the hydrogel particles is removed therefrom by evaporation, removal of ~rom 60 to 90% of the water being most preferred.
This water removal step may be carried out in various ways. Water may advantageously be removed from the hydrogel particles by contacting -them with a gas stream, e.g. a stream o~ air, either or not at elevated temperature.
~ater may also be removed fromthe hydrogel par-ticles by heating them at atmospheric pressure or at reduced or elevated pressure. Other ways o~ removing water ~ -~rom the hydrogel par-ticles are by contacting them with an inert liquid at a temperature above 100C, or by contacting them at an eleva-ted temperature wi~h steam or a steam-containing gas stream. Examples of treatments which may very suitably be applied for removing at least 25% of -the water present in thehydrogel particles are the following:
a) heating the hydrogel particles at a temperature of about 100C at reduced pressure, :' ' :
,': ' L7~
b) heatingthe.hydrogel particles at a temperature above 100 C in a stream of air, c) heating the hydrogel particles at a temperature of about 100 C at reduced pressure followed by heating the particles at a temperature of about 500C in a stream of air, d) contacting the hydrogel particles with a hydrocarbon oil at a temperature above 100C, e) heating the hydrogel particles at a temperature above 100C in an autoclave at autogenous pressure, and f) heating the hydrogel particles in a stream of air and steam.
I-t is particularly recommended to remove the water by contacting the hydrogel particles wi-th a gas stream in such a way, that the particles are heated to a temperature in the range 55 to 180C, and more preferably in the range 100 to 170C. Excellent results are obtained by using a stream of air having a temperature of ~rom 100 to 300C, especially from 180 to 2205.
The temperature to whlch the hydrogel particl.es are hea-ted has a significant in~luence on the te*ture, i.e. pore volwne and pore diameter, of the catalyst support to be prepared. For example, larger or smaller pore volwmes (corresponding with smaller or larger pore diameters) may be obtained, according as .said .:
temperature is on the l~wer or higher side, resp~ctively, : ' . .
.. : . ,: , .. . . : ... ,... .~ . .
of the ranges indicated above Thus, when it is desired to prepare a catalyst having a relatively large pore volume, heating e.g. to about 135C has proved to be very suitable.
After the treating step, in which at least 25% of the water present in the hydrogel particles is removed therefrom by evapora-tion, the alkali metal content of the hydrogel particles is decreased in an aqueous medium to less than 1 %w calculated on dry material.
This alkali metal removal may very suitably be performed by trcating the hydrogel particles with an aqueous solution of an ammonium salt, e.g. the nitrate or the sulphate, ammonium hydroxide, or an inorganic or organic acid, for example~ hydrochloric, sulphuric, nitric or acetic acid. Subsequently, a water wash may be applied, if necessary. Treat-ment with an aqueous solution of NH4N03 has given excellen~ results.
Suitably, the treatment is carried out by percolation of the aqueous solution in question through the hydrogel particles.
~lthough the operations for removing at least part of the water and for reducing the alkali metal content are most preferably carried ou~ in the consecutive order described above, a reverse sequence of operations is not excluded.
Finally the hydrogel particles are dried and calcined.
Drying and calcining of the hydrogel particles may e.g. be carried out by heating the particles for 7~
from 1 to 5 hours at a temperature of 100-200C and ~50-550C, respectively. If desired~ the calcination may be followed by a hydro-thermal treatment, e.g. a treatment with steam.
If desired, a small amount of a filler may be incorporated into the silica particles according to the invention. Incorporation of a filler may be attractive for various reasons. In the first place the porosity of the ultimate silica particles may be influenced by this measure, with the result, for example, of a larger pore volume Further, for certain applications of the silica particles, the presence of e.g. an alumina filler therein may be attractive. It is also possible to decrease the cost of preparation of the silica particles by incorporating therein a cheap filler. The incorporation of the f:iller into the silica par-ticles may very suitably be performed by adding the filler to the aqueous solution of the alkali metal silicate and/or to the aqueous solution of the acid from which the hydrosol is prepared by mixing. F.xamples of suitable fillers are kaolin, montmorillonite, bentonite, precipitated silica fillers, aluminas, zeolites and amorphous precipitated silica-aluminas.
With respect to the amount of filler which may be incor-~0 porated into the silica particles according 6?47~
to -the invention, it has been found that the presence of a filler in the silica particles reduces the bulk crushing streng-th of the particles, which effect is more pronounced according asthe filler content of the particles is higher. Since, however, the so]-gel method as a rule provides globular silica particles with a very high bulk crushing strength, a small decrease is of no importance, and filler containing globular silica particles which possess the high bulk crushing strength aimed at (see below) can easily be prepared, provided that the quantity of filler incorporated therein amounts to no-t more than ~5 /w of the quantity of silica present in the hydrosol from which the silica particles are prepared. Incorporation of larger amounts of filler in the silica particles en-tails -the risk that silica particles with an inferior bulk crushing strength are obtained.
The silica gel particles prepared according -to the procedure aescribed above are usually obtained in a globular form or in the form of pelle-ts of more or less spheroidal shape, and they have a very high water resistance and bulk crushing strength. This applies also to the catalyst of the invention, which comprises phosphoric acid supported on said silica particles.
~he p-re volume of the silica which s~ou1d be at least .
_ g _ 7~
0.6 ml/g, does not exceed, as a rule, 2.2 ml/g and usually is in the range 0.8 to 1.5 ml/g, a pore volume ranging from 1.0 to 1.~ being preferred.
The expression "particles with a high water resistance"
used in this patent application refers to particles having a water re-sistance of at least 80%, preferably of at least 90%. The water re-sistance of the silica particlesJ for example, globular silica particles, is determined in a standard test in which 100 of the globular silica particles are contacted for 5 minutes at room temperature with a volume of water which amounts to 5 times the volume of the 100 globular silica ~ -particles. Thereafter the particles are inspected to determine the amount of particles which show cracks or have disintegrated. The water resistance of the globular silica particles is expressed as the percent-age of particles which have not been damaged by the contact with water.
The expression "particles with a high bulk crushing strength" used in this patent application refers to particles having a bulk crushing strength (BCS) of, at least 10 kg/cm , preferably of at least 11 kg/cm . The BCS, which is a measure of the mechanical strength, of the particles, is defined as the pressure exerted by a circular plun-ger with a surface area of 6 cm2 on a 25 ml sample of a number of particles in a cyll.nder.
- 1 0 - .
at which the quanti-ty of fines passing through a 1~25 ~m sieve amounts to 0.5% (w/w) of the sample.
It is to be lmders-tood in this connection that a relation exists between the bulk crushing s-trength and the pore volume, in the sense that, as a rule, an increase in pore vo]ume results in a decrease of the BCS and vice-versa. Since, in accordance with the present invention, the silica gel particles are to be impregnà-ted with phosphoric acid, it is desirable that they have a relatively high pore volume, say larger than about 1.0 ml/g, in order to produce highly active catalysts which are suitable for the hydration of alkenes to alkanols. Silica gel par-ticles having the mos-t favourable pore volumes can be prepared, however, only a-t -the expense of the BCS which is lower than the attainable maximum. The figures for the BCS and the pore volume mentioned above, therefore, represent a compromise in respect of the desired properties.
The novel catalyst of the invention may be prepared by means of any of the conventional techniques. According -to a preferred method, silica gel particles, prepared as hereinbefore described are impregnated with phosphoric acid. Suitably, an aqueous phosphoric acid is used having a concentration of, for example, from 20 to 85%, preferably from 55 to 75%. Good results are obtained by lrnmersion of the globular silica gel support in the aqueous phosphoric acid, e .e. for 0.5 to 5 hours, .
.
- 11 - ' . .
.
.
followed by draining off the excess acid and drying the impregnated support inthe usual way, for example by heating at about 150C.
The catalyst of the present invention may be applied in various chemical reactions, e.g. in the polymerization or oligomerization of lower olefins, but especially in -the hydration of olefins to the corresponding alcohols.
Although it is recommended to apply the catalyst of the invention in the globular or spheroidal form in which it is usually obtained by the procedure described above, it may also - at least in part - be present in another form, e.g. in the form of smaller particles which may be produced by fragmentation, ei-ther before or after the impregnation with phosphoric acid, of the globular par-ticles initially obtained. Altera-tions in the shape may, moreover, be brought about in the course of the production of the hydrogel particles, if desired.
According to a par-ticular impor-tant aspect of the invention, there is provided a process for the prepara-tion of an alkanol, in which process an olefin and water are contacted at eleva-ted tempera-ture and pressure, in the presence of a ca-talyst as hereinbefore described.
Suitable olefins are those containing from 2 to 10 carbon atoms, especial1y ~hose baving from 2 .
~ :`
i7~
to 5 carbon a-toms, Most preferred are ethylene and propylene.
The reactants are generally applied in the gaseous s-tate. The feed ratio and the reaction condi-t;ons may vary widely, depending inter alia on the starting material used. Thus, ethanol may suitably be prepared using a molar ratio water/ethylene in the range 0.2:1 to 1.0:1, preferably 0.3:1 to 0.6:1, a temperature in the range 200 to 300C, preferably 220 to 270C, and a pressure of from 50 to 90 atg. Isopropyl alcohol may be prepared for example, using a mole ratio water/
propylene ranging from 0.1:1 to 0.5:1, a temperature of ~rom 140 -to 250C, and a pressure of from 15 -to 50 a-tg. The gas space velocity of the feed mixture may range from e.g. 5 -to 100 min , preferably f`rom 8 to 35 min , and in particular from 15 to 35 min A process for the preparation of ethanol by hydration of ethylene, using as the catalyst a dia-tomaceous earth, has been described, for example, by C.R. Nelson and M.L. Courter in Chem. Engng. Progr. 50 (195~) pp.
526 to 531.
EXhMPLE I
(a) Preparation of silica gel support An aqueous sodium waterglass solution comprising 12 ~Ow SiO2 and having a Na20/SiO2 molar ratio of 0~3 was mixed continuously in a mixing chamber with an aqueous 1.2 N sulphuric acld solution in a volume . . .
-7~
ratio acid solution/waterglass solution of 0.75. A~ter a residence time of a few seconds in the mixing chamber, the hydrosol was continu-ously ejected from the m:ixing chamber through an aperture in the bottom thereof into a vertically disposed tube with a length of 1,8 m filled with a paraffinic oil at 25C ~"ONDINA 33"* J marketed by SIIEL.L). I'he hydrosol jet was thus converted into droplet form~ and the hydrosol droplets - which had an average diameter of 6 mm - were allowed to pass through the oil by gravity. During the fall through the tube gelation occurred. The globular hydrogel particles were caught at the bottom of the tube in an aqueous 0.25 M Na2SO4 solution of 25C and separated by filtration. The water content of these globular hydrogel particles was determined in a standard test in which a sample was heated in three hours from room temperature to 600C and thereafter kept at 600C for one hour. The water content of the hydrogel particles appeared to be 9~) %w.
The silica hydrogel particles were dried for 0.5 hours in a stream of air having a velocity of 2240 Nl/h and a temperature of 200C, the temperature of the hydrogel particles being allowed to rise to 135C. After this treatment the water content of the hydrogel par-ticles amounted to 14 %w. ~ubsequently, an aqueous *Trademark -- 1~ -0.1 M solution of ammonium nitra-te was percolated through the hydrogel particlesl which were then washed with water, dried for 2 hours at 100C and calcined for 3 hours at 500C. A reduction of the sodium content to about 0.02 %w was thus achieved. The globula:r silica par-ticles obtained showed a water resistance of 9~%. They had an average particle size of 3.5 mm, a pore volume of 1.19 ml/g, and a bulk crush-ing strength of 11.2 kg/cm2 The "pore volume" is defined herein as the specific pore volumeJ determined by means of a water titration method in which the amount of water taken up by a dried sample under specified conditions has been measured, ~b) Impregnation with pho~horic acid The resulting support, as well as a commercially available silica gel support of comparable size and texture, was impregnated with 60% aqueous phosphoric acid by immersion therein, followed by draining off the excess acid and drying at 150C. The commercial sup-port, used for comparison only, was "Davison Grade 57*" ex W, R. Grace Ltd.
In Table I below, the bulk crushing strength ~BCS) - both before and after impregnation with phosphoric acid - is shown, as well as the average particle size, pore volume and average pore diameter of the silica *Trademark ..
support.
The results obtained show, inter alia, the superior BCS of -the impregnated support of -the invention (sample A) as compared with that of the commercial suppor-t (sample B).
- 16 - :
X' o h rl ~t~ c~
U~
~. ~
U~
a~ ~ g ,_ ..
o ~ W) ~ Lr~
4~ a~
.D ~:4 o o o~
a~ ~d ¢~ ~ , ;, ~ ~ a~ ~
O
~1 P~ a> ,~ Lr~ u, . .
~ t-~
h O
,_ .~ .
~ I~ ~ .
H ~1 ~ g ~ ~
~ u~ ~ h h &~ ~ L
~ ~ _ P~ ~J ~
¢ ~4 ~
0~7 EXAMPLE II
.
Pre~aration of Ethanol ~ilica gel particles impregnated with phosphoric acid, which had been prepared as described in Fxample I, were applied as catalysts in the preparation of ethanol by hydration of ethylene as follows:
The catalyst (25 ml or 20 g) was charged to a vertically disposed reactor tube of stainless steel (AISI 316) having a diameter of 25 mm and a length lQ of 300 mm, the catalyst bed being enclosed by stainless steel balls of 2 ~m diameter which occupied a volume of 75 ml both above and below the catalyst hed. Temperature measurements were made by means of a pyrometer tube havin~ an outer diameter of 6 mm and which was fitted in the centre of the catalyst bed.
A mixture of gaseous ethylene and water in a molar ratio water/ethylene of o.56 : 1 was passed continuously through the reactor tube in an upward direction at ;
an average temperature of 270C. The space velocity
2~ was 40 min 1 which corresponds with 18.5 ml of liquid water per hour and to Llo Nl of ethylene per hour at a total pressure o~ 60 bar.
As appear~ from a GLC analysis a~ter a reaction period of 31 hours, ethanol is formed with very high selectivity. No by-products have been detected and~
notably, no ether formation has taken pla~ce.
Further results of the experiment are given in table 2 below.
. . .
U~N
E:
Ln 4~
U~
t~
h c;~ t') O b~ Ll~ ~t 4~ ~ ~
~ ,' O ~,_ ., O ~ ~o: 11~ 0 ,~ ~ , . .
O O a~ ~
~ h ~ N
O O
a)l ~ ~ ' .
~ . .
E~ ~
O
h O Lt~ ..
0~ h -1 00 ~ : :
~4 bO
~od 3 ~ o ,_~
Il~ In ~_ ~ -r~ ~e t~ r~
~ g ~4 u~ h O
LU ~ ~
td ~ ~ h n ~ ai .
,..
7~7 From table 2 it is seen that the B~S after use of the catalyst for the production of ethanol is much higher when applying the catalyst of the invention, as compared with a catalyst prepared from a com~ercial carrier.
As appear~ from a GLC analysis a~ter a reaction period of 31 hours, ethanol is formed with very high selectivity. No by-products have been detected and~
notably, no ether formation has taken pla~ce.
Further results of the experiment are given in table 2 below.
. . .
U~N
E:
Ln 4~
U~
t~
h c;~ t') O b~ Ll~ ~t 4~ ~ ~
~ ,' O ~,_ ., O ~ ~o: 11~ 0 ,~ ~ , . .
O O a~ ~
~ h ~ N
O O
a)l ~ ~ ' .
~ . .
E~ ~
O
h O Lt~ ..
0~ h -1 00 ~ : :
~4 bO
~od 3 ~ o ,_~
Il~ In ~_ ~ -r~ ~e t~ r~
~ g ~4 u~ h O
LU ~ ~
td ~ ~ h n ~ ai .
,..
7~7 From table 2 it is seen that the B~S after use of the catalyst for the production of ethanol is much higher when applying the catalyst of the invention, as compared with a catalyst prepared from a com~ercial carrier.
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A catalyst comprising phosphoric acid supported on porous silica gel particles having both a high water resistance and high bulk crush-ing strength and a pore volume of at least 0.6 ml/g, said particles having been obtained by the following successive steps:
(a) preparing a silica hydrosol by mixing an aqueous solution of an alkali metal silicate with an aqueous solution of an acid, (b) converting the hydrosol into droplet form, and (c) allowing the droplets to gel in a liquid which is immiscible with water, whereupon the hydrogel particles emerging from said liquid have been sepa-rated off and freed from water and alkali metal compounds by the following sequence of consecutive steps:
(I) removing by evaporation at least 25% of the amount of water present in the hydrogel particles, (II) decreasing the alkali metal content of the hydrogel particles in an aqueous medium to less than 1%w, calculated on dry material, and (III) drying and calcining the silica particles.
(a) preparing a silica hydrosol by mixing an aqueous solution of an alkali metal silicate with an aqueous solution of an acid, (b) converting the hydrosol into droplet form, and (c) allowing the droplets to gel in a liquid which is immiscible with water, whereupon the hydrogel particles emerging from said liquid have been sepa-rated off and freed from water and alkali metal compounds by the following sequence of consecutive steps:
(I) removing by evaporation at least 25% of the amount of water present in the hydrogel particles, (II) decreasing the alkali metal content of the hydrogel particles in an aqueous medium to less than 1%w, calculated on dry material, and (III) drying and calcining the silica particles.
2. A catalyst as claimed in claim 1, characterized in that at least 50% of the amount of water present in the hydrogel particles has been removed by evaporation.
3. A catalyst as claimed in claim 2, characterized in that 60 to 90% of the amount of water present in the hydrogel has been removed by eva-poration.
4. A catalyst as claimed in claim 1 characterized in that the eva-poration of water from the hydrogel particles has been effected by contact-ing them with a gas stream.
5. A catalyst as claimed in claim 1 characterized in that during the water removal by evaporation the temperature of the hydrogel particles was allowed to rise to 55 to 180°C.
6. A catalyst as claimed in claim 5 characterized in that the tem-perature of the hydrogel particles was allowed to rise to 100 to 170°C.
7. A catalyst as claimed in claim 4 characterized in that the gas stream was a stream of air of from 100° to 300°C.
8 A catalyst as claimed in claim 7, characterized in that the stream of air had a temperature of from 180° to 220°C.
9. A catalyst as claimed in claim 1 characterized in that the alkali metal compounds have been removed by treatment of the hydrogel particles with an aqueous solution of ammonium nitrate
10. A process for the preparation of a catalyst as claimed in claim 1, characterized in that silica gel particles obtained according to the pro-cedure defined therein, are impregnated with phosphoric acid
11. A process as claimed in claim 10, characterized in that the im-pregnation is carried out by immersion of said particles in aqueous phosphoric acid of 20 to 85 %w concentration, followed by draining off the excess acid and drying the impregnated support.
12, A process as claimed in claim 11, characterized in that the con-centration of the aqueous phosphoric acid is in the range 55 to 75 %w.
13. A process for the production of an alkanol, characterized in that an olefin and water are contacted at elevated temperature and pressure in the presence of a catalyst as claimed in claim 1.
14. A process as claimed in claim 13, characterized in that an ole-fin having from 2 to 5 carbon atoms is used.
A process as claimed in claim 14, characterized in that the ole-fin is ethylene or propylene
16. A process as claimed in claim 15, characterized in that the re-action is carried out at a temperature in the range 200 to 300°C, at a pres-sure of from 50 to 90 atg, and using a water/ethylene molar ratio in the range of 0.2:1 to 1.0:1.
17. A process as claimed in claim 16, characterized in that the temperature is in the range 220 to 270°C, and the water/ethylene molar ratio is in the range 0.3:1 to 0.6:1.
18. A process as claimed in claim 16, characterized in that the gas space velocity of the feed mixture ranges from 8 to 35 min-1.
19. A process as claimed in claim 18 characterized in that the gas space velocity of the feed mixture ranges from 15 to 35 min-1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB17723/76 | 1976-04-30 | ||
| GB1772376A GB1564223A (en) | 1976-04-30 | 1976-04-30 | Catalyst comprising phosphoric acid on silica gel its preparation and use |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1100477A true CA1100477A (en) | 1981-05-05 |
Family
ID=10100100
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA276,092A Expired CA1100477A (en) | 1976-04-30 | 1977-04-13 | Catalyst comprising phosphoric acid on silica gel, its preparation and use |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS52133095A (en) |
| AU (1) | AU509571B2 (en) |
| BE (1) | BE853785A (en) |
| BR (1) | BR7702712A (en) |
| CA (1) | CA1100477A (en) |
| DE (1) | DE2719055A1 (en) |
| ES (1) | ES458266A1 (en) |
| FR (1) | FR2349359A1 (en) |
| GB (1) | GB1564223A (en) |
| IT (1) | IT1075516B (en) |
| NL (1) | NL7704657A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1177811A (en) * | 1981-04-13 | 1984-11-13 | Theo G. Spek | Process for the preparation of silica particles; silica particles with a narrow pore diameter distribution, catalysts made therefrom and use of these catalysts |
| GB9214688D0 (en) * | 1992-07-10 | 1992-08-19 | Bp Chem Int Ltd | Olfin hydration catalysts |
| TW321634B (en) | 1994-07-05 | 1997-12-01 | Mitsui Toatsu Chemicals | |
| GB9805107D0 (en) * | 1998-03-10 | 1998-05-06 | Bp Chem Int Ltd | Catalyst and use therof |
| KR101110800B1 (en) | 2003-05-28 | 2012-07-06 | 도꾸리쯔교세이호진 상교기쥬쯔 소고겡뀨죠 | Process for producing hydroxyl group-containing compound |
| US8558036B2 (en) | 2010-11-15 | 2013-10-15 | Saudi Arabian Oil Company | Dual phase catalysts system for mixed olefin hydrations |
-
1976
- 1976-04-30 GB GB1772376A patent/GB1564223A/en not_active Expired
-
1977
- 1977-04-13 CA CA276,092A patent/CA1100477A/en not_active Expired
- 1977-04-21 BE BE1008090A patent/BE853785A/en unknown
- 1977-04-28 IT IT2294477A patent/IT1075516B/en active
- 1977-04-28 JP JP4859077A patent/JPS52133095A/en active Pending
- 1977-04-28 DE DE19772719055 patent/DE2719055A1/en not_active Withdrawn
- 1977-04-28 ES ES458266A patent/ES458266A1/en not_active Expired
- 1977-04-28 NL NL7704657A patent/NL7704657A/en not_active Application Discontinuation
- 1977-04-28 AU AU24668/77A patent/AU509571B2/en not_active Expired
- 1977-04-28 BR BR7702712A patent/BR7702712A/en unknown
- 1977-04-29 FR FR7713012A patent/FR2349359A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| ES458266A1 (en) | 1978-07-01 |
| DE2719055A1 (en) | 1977-11-10 |
| GB1564223A (en) | 1980-04-02 |
| BE853785A (en) | 1977-10-21 |
| JPS52133095A (en) | 1977-11-08 |
| AU2466877A (en) | 1978-11-02 |
| BR7702712A (en) | 1978-03-21 |
| IT1075516B (en) | 1985-04-22 |
| AU509571B2 (en) | 1980-05-15 |
| FR2349359A1 (en) | 1977-11-25 |
| NL7704657A (en) | 1977-11-01 |
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