GB1590436A

GB1590436A - Preparation and use of alumina extrudate particles

Info

Publication number: GB1590436A
Application number: GB3532376A
Authority: GB
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 1977-11-23
Filing date: 1977-11-23
Publication date: 1981-06-03

Description

(54) PREPARATION AND USE OF ALUMINA EXTRUDATE PARTICLES (71) We, UOP INC, a corporation organized under the laws of the State of Delaware United States of America, of Ten UOP Plaza, Algonquin & Mt. Prospect Roads, Des Plaines, Illinois, United States of America, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement: The present invention relates to the manufacture and use of alumina extrudate particles.

Alumina, including aluminium oxide in the anhydrous form as well as the various hydrated forms thereof, is extensively employed in the chemical and petroleum industries. Alumina is readily manufactued as a porous, high surface area material particularly useful as a hydrocarbon conversion catalyst, or as a support or carrier material for other components catalytically active with respect thereto. Further, the adsorbent character of alumina makes it especially useful as a desiccant, or as an adsorbent for selectively removing impurities from a process stream.

Alumina is frequently employed in a fixed bed type of operation in the form of cylindrical particles generally about 0.15 to 0.3 cm in diameter. Such particles are typically manufactured by admixing a finely divided or powdered alumina with a binder and/or lubricant and compressing the mixture into pellets by means of conventional punch and die machinery. The alumina is thus formed as hard, compact pellets of relatively high average bulk density. A far less costly alternative comprises extruding the mixture through an orifice or perforated plate and cutting the resulting extrudate into particles of desired length.

The present invention seeks to provide an improved method of manufacturing alumina extrudate particles, particularly alumina extrudate particles of relatively low average bulk density, preferably a method which does not require the use of extraneous binders and/or lubricants.

According to the invention there is provided a method of preparing alumina extrudate particles which comprises forming a mixture comprising a finely divided alumina and from 2 to 10 wt.% alumina hydrosol, based on the weight of alumina plus alumina hydrosol, and adding a sufficient quantity of an aqueous liquid thereto to produce a dough extrudable at less than 11 atmospheres; extruding the resulting dough; and drying and calcining the resulting extrudate product.

The alumina hydrosol may, for example, be prepared by the hydrolysis of a suitable acid salt of aluminium, for example aluminium chloride, and reduction of the acid anion concentration of the solution, for example the chloride anion concentration thereof. Reduction of the acid anion concentration can be accomplished by subjecting the aluminium salt solution to electrolysis utilizing an electrolytic cell with a porous partition between the anode and cathode. In this manner, an acid anion deficiency is created in the cathode compartment whereby an olation reaction is promoted with the formation of inorganic polymers of colloidal dimension dispersed and suspended in the remaining liquid. In some cases, as in the case of aluminium acetate, where the acid anion is sufficiently volatile, the reduction in acid anion concentration can be effected simply by heating. A particularly suitable method is in the use of aluminium metal as a neutralizing agent in conjunction with, for example, an aqueous aluminium chloride solution. In this instance, the salt of neutralization is itself a hydrolyzable aluminium salt subject to polymerization and ultimate sol formation.

An aluminium chloride hydrosol, otherwise known as an aluminium oxychloride hydrosol or aluminium hydroxychloride hydrosol, is a preferred alumina hydrosol for use in the method of this invention. A particularly desirable aluminium chloride hydrosol is prepared by digesting aluminium metal in hydrochloric acid at about reflux temperature - usually a temperature of from 80" to 1050C. - and redcuing the chloride anion concentration of the resulting aluminium chloride solution by the device of maintaining an excess of aluminium reactant in contact with the reaction mixture as a neutralizing agent until a hydrosol containing aluminium and chloride anion in a ratio of from 0.9:1 to 1.5:1 is formed. The hydrosol is preferably prepared to contain not more than 14 wt.% aluminium, generally from 8 to 14 wt.%.

The alumina admixed with the alumina hydrosol may be any of the various aluminium oxides including aluminium oxide in the anhydrous or substantially anhydrous form, or in the form of an aluminium oxide hydrate. Thus, the alumina can be an activated alumina such as etaand/or gamma-alumina, or an alumina precursor thereof, for examPle alpha-alumina monohydrate (boehmite), alpha-alumina trihydrate (gibbsite) and/or beta-alumina trihydrate (bayerite), which, upon subsequent high temperature calcination and elimination of substantially all of the water and/or hydroxyl groups commonly associated therewith, will yield the high surface area activated form of the alumina. The alumina may be selected on the basis of its bulk density to yield a final extrudate product of predetermined bulk density, or aluminas of different bulk densities may be blended in any ratio to produce an extrudate product of desired bulk density. The present method is particularly adapted to the manufacture of extrudate particles of low bulk density, say not more than 0.5 gram/cc, and of relatively high strength. The alumina will preferably be an aluminium oxide hydrate, or blend of aluminium oxide hydrates characterized by a weight loss on ignition at 900"C. of not more than 30%, say from 20 wt.% to 30 wt.%.

Previous attempts to extrude the abovementioned aluminas were generally unsuccessful owing to the exceedingly high pressures which were necessary to achieve flow of the mix through the extrusion orifice. The high pressures invariably caused damage to the extrusion apparatus. The addition of a small amount of alumina hydrosol in accordance with the present invention provides the mix with the necessary rheological properties for extrusion at much lower pressures.

The aqueous liquid which is added to the mix to produce an extrudable dough is preferably water which is free from additives, although weak acids, for example aqueous oxalic acid, may also be used, since they may sometimes provide a desirable peptizing effect. The amount of the aqueous liquid to be used must be sufficient at less than 11 atmospheres; it may vary somewhat with changes (within the stated limits) in the proportion of hydrosol, but can be easily determined by trial and error.

After the dough has been extruded, the extrudate particles are dried and calcined.

Drying is usually effected at temperatures up to 2000C. over a period from 1 to 24 hours. Calcination is preferably in an oxidizing atmosphere, such as air, at a temperature of from 350" to 850 C., and is suitably accomplished over a 2 to 4 hour period.

The extrusion operation is suitably effected with commercial extrusion apparatus. For example, the aluminaalumina hydrosol mixture may be continuously extruded through a cylinder with an extrusion die at one end, the die comprising a multitude of cylindrical openings of an appropriate diameter to produce an extruder product of desired size. The mixture is continuously extruded through the die at a pressure of less than 11 atmospheres by means of a rotating screw, and cut into particles of desired length by means of a rotating knife.

Whilst the present invention is mainly directed to the preparation of alumina extrudate particles per se, the method may also be employed with advantage in the preparation of alumina extrudate particles containing one or more other components, for example catalytic components including in particular the platinum group metals. The catalytic component, for example platinum, or a suitable precursor thereof, for example chloroplatinic acid, can be composited with the alumina starting material by impregnation and/or ion-exchange techniques prior to admixing the alumina with the alumina hydrosol in accordance with the present invention, and the mixture extruded, dried and calcined as heretofore described. Alternatively, the catalytic component, or a suitable precursor thereof, can be composited with the extruded alumina particles by impregnation and/or ion-exchange techniques, either before or after said particles have been dried and calcined. However, in the event that the catalytic component, and particularly a precursor thereof, is added to the calcined alumina extrudate particles, the resulting composite will invariably require further calcining. Preferably, the platinum group metal is used in an amount such that the final catalyst product will contain from 0.1 to 2 wt.% platinum group metal.

An optional feature is the addition of finely divided crystalline aluminosilicate to the alumina-alumina hydrosol mixture.

According to this feature, the alumina, in a finely divided state, is dry mixed with a finely divided crystalline aluminosilicate.

Preferably, the amount of the crystalline aluminosilicate is from 0.5 to 20 wt.% of the dry mixture of alumina plus aluminosilicate.

The alumina hydrosol is then mixed and blended with the alumina-crystalline aluminosilicate mixture, and sufficient water is added to form the extrudable dough. A catalytic compound, preferably a platinum group metal, may be added with the alumina hydrosol.

Mordenite is the preferred crystalline aluminosilicate for use in the present invention. It is a zeolite, highly siliceous in nature and generally characterised by an SiO2/Al203 mole ratio of from 6:1 to 12:1.

The extruded particles produced according to this invention may be used as hydrocarbon conversion catalysts. They may be used to promote reactions including dehydrogenation, isomerisation, hydrocracking, etc. They are most suitable in the reforming of petrol to enhance the octane rating thereof.

The present invention provides a method of preparing pure alumina extrudate particles of low average bulk density. The alumina hydrosol acts as both a binder and a lubricant and avoids the need for extraneous binders and lubricants such as starch, polyvinyl alcohol or Sterotex, which must be burned from the extruded particles under controlled conditions, particularly where other catalytic components are present.

EXAMPLE I 130 grams of an alpha-alumina monohydrate having a 23% weight loss on ignition at 900"C. and an average bulk density of 0.8 grams per cubic centimetre, and 137 grams of an alpha-alumina monohydrate having a 27% weight loss on ignition at 9000C. and an average bulk density of 0.2 grams per cubic centimetre, were thoroughly drymixed and thereafter mulled and blended with 25.0 grams of an alumina hydrosol (26% Awl203) prepared by digesting aluminium in dilute hydrochloric acid at about 1 02 C., sufficient aluminium being digested to yield a hydrosol containing aluminium in about a 1.4:1 weight ratio with the chloride anion content thereof. A sufficient amount of water, in this case 300 ml, was added to form a smooth paste and the resulting mixture was extruded under about 6.8 atmospheres gauge pressure, oven-dried and calcined for two hours in air at 6500C.

The dried and calcined alumina extrudate particles had an average bulk density of 0.5 grams per cubic centimetre.

EXAMPLE II 137 grams of an alpha-aluminium monohydrate having a 27% weight loss on ignition at 9000C., 4.2 cubic centimetres of chloroplatinic acid (125 milligrams of Pt/cc), 1.10 grams of stannic chloride hexahydrate, 2.4 cc of concentrated hydrochloric acid and 23.4 grams of oxalic acid were mixed and blended with 5 grams of an alumina hydrosol. The alumina hydrosol was prepared by the method of Example I. A sufficient amount of oxalic acid (150 ml of 5.0% acid) was added to the mixture to form a smooth base and the mixture extruded under 6.8 atmospheres gauge pressure, oven-dried, and calcined for 2 hours in air at 6500C. The dried and calcined extrudate particles had an average bulk density of 0.5 grams per cubic centimetre.

EXAMPLE III In the manufacture of an extruded catalyst composition in accordance with the method of this invention, particularly useful as a reforming catalyst to produce high octane reformate product and liquid petroleum gas, 130 grams of an alpha-alumina monohydrate having a 23% weight loss on ignition at 9000C. and an average bulk density of about 0.8 grams per cubic centimetre, and 137 grams of an alpha-alumina monohydrate having a 27% weight loss on ignition at 900"C. and an average bulk density of 0.36 grams per cubic centimetre, are thoroughly mulled and dry mixed with about 17 grams of mordenite in the hydrogen form, all components of the mixture comprising finely divided particles of a size 95% of which is recoverable through a 105 micron microsieve. 8.4 cubic centimetres of chloroplatinic acid containing 125 milligrams of platinum per cubic centimetre, and 10 grams of an aluminium chloride hydrosol are then admixed and blended with the alumina-mordenite mixture, the hydrosol having been prepared by the method of Example I. A sufficient amount of deionized water (300 ml) is added to form a dough extrudable at 6.8 atmospheres gauge pressure through a perforated disc containing perforations about 0.08 cm in diameter. The extrudate particles, dried and calcined in air at approximately 650"C., have an average bulk density of from 0.4 to 0.6 grams per cubic centimetre.

WHAT WE CLAIM IS: 1. A method of preparing alumina extrudate particles which comprises: (a) forming a mixture comprising a finely divided alumina and from 2 to ]0 wt.% alumina hydrosol, based on the weight of alumina plus alumina hydrosol, and adding a sufficient quantity of an aqueous liquid thereto to produced a dough extrudable at less than 11 atmospheres; (b) extruding the resulting dough; and, (c) drying and calcining the extrudate.

2. A method as claimed in claim 1 wherein the mixture formed in step (a) further comprises a finely divided crystalline aluminosilicate.

3. A method as claimed in claim 2 wherein the crystalline aluminosilicate is present in an amount of from 0.5 to 20 wt.% of the weight of alumina plus crystalline aluminosilicate.

4. A method as claimed in any of claims 1 to 3 wherein the mixture formed in step (a) further comprises a platinum group

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

is added to form the extrudable dough. A catalytic compound, preferably a platinum group metal, may be added with the alumina hydrosol.

Mordenite is the preferred crystalline aluminosilicate for use in the present invention. It is a zeolite, highly siliceous in nature and generally characterised by an SiO2/Al203 mole ratio of from 6:1 to 12:1.

The extruded particles produced according to this invention may be used as hydrocarbon conversion catalysts. They may be used to promote reactions including dehydrogenation, isomerisation, hydrocracking, etc. They are most suitable in the reforming of petrol to enhance the octane rating thereof.

The present invention provides a method of preparing pure alumina extrudate particles of low average bulk density. The alumina hydrosol acts as both a binder and a lubricant and avoids the need for extraneous binders and lubricants such as starch, polyvinyl alcohol or Sterotex, which must be burned from the extruded particles under controlled conditions, particularly where other catalytic components are present.

EXAMPLE I

130 grams of an alpha-alumina monohydrate having a 23% weight loss on ignition at 900"C. and an average bulk density of 0.8 grams per cubic centimetre, and 137 grams of an alpha-alumina monohydrate having a 27% weight loss on ignition at 9000C. and an average bulk density of 0.2 grams per cubic centimetre, were thoroughly drymixed and thereafter mulled and blended with 25.0 grams of an alumina hydrosol (26% Awl203) prepared by digesting aluminium in dilute hydrochloric acid at about 1 02 C., sufficient aluminium being digested to yield a hydrosol containing aluminium in about a 1.4:1 weight ratio with the chloride anion content thereof. A sufficient amount of water, in this case 300 ml, was added to form a smooth paste and the resulting mixture was extruded under about 6.8 atmospheres gauge pressure, oven-dried and calcined for two hours in air at 6500C.

The dried and calcined alumina extrudate particles had an average bulk density of 0.5 grams per cubic centimetre.

EXAMPLE II

137 grams of an alpha-aluminium monohydrate having a 27% weight loss on ignition at 9000C., 4.2 cubic centimetres of chloroplatinic acid (125 milligrams of Pt/cc), 1.10 grams of stannic chloride hexahydrate, 2.4 cc of concentrated hydrochloric acid and 23.4 grams of oxalic acid were mixed and blended with 5 grams of an alumina hydrosol. The alumina hydrosol was prepared by the method of Example I. A sufficient amount of oxalic acid (150 ml of 5.0% acid) was added to the mixture to form a smooth base and the mixture extruded under 6.8 atmospheres gauge pressure, oven-dried, and calcined for 2 hours in air at 6500C. The dried and calcined extrudate particles had an average bulk density of 0.5 grams per cubic centimetre.

EXAMPLE III In the manufacture of an extruded catalyst composition in accordance with the method of this invention, particularly useful as a reforming catalyst to produce high octane reformate product and liquid petroleum gas, 130 grams of an alpha-alumina monohydrate having a 23% weight loss on ignition at 9000C. and an average bulk density of about 0.8 grams per cubic centimetre, and 137 grams of an alpha-alumina monohydrate having a 27% weight loss on ignition at 900"C. and an average bulk density of 0.36 grams per cubic centimetre, are thoroughly mulled and dry mixed with about 17 grams of mordenite in the hydrogen form, all components of the mixture comprising finely divided particles of a size 95% of which is recoverable through a 105 micron microsieve. 8.4 cubic centimetres of chloroplatinic acid containing 125 milligrams of platinum per cubic centimetre, and 10 grams of an aluminium chloride hydrosol are then admixed and blended with the alumina-mordenite mixture, the hydrosol having been prepared by the method of Example I. A sufficient amount of deionized water (300 ml) is added to form a dough extrudable at 6.8 atmospheres gauge pressure through a perforated disc containing perforations about 0.08 cm in diameter. The extrudate particles, dried and calcined in air at approximately 650"C., have an average bulk density of from 0.4 to 0.6 grams per cubic centimetre.

WHAT WE CLAIM IS: 1. A method of preparing alumina extrudate particles which comprises: (a) forming a mixture comprising a finely divided alumina and from 2 to ]0 wt.% alumina hydrosol, based on the weight of alumina plus alumina hydrosol, and adding a sufficient quantity of an aqueous liquid thereto to produced a dough extrudable at less than 11 atmospheres; (b) extruding the resulting dough; and, (c) drying and calcining the extrudate.
2. A method as claimed in claim 1 wherein the mixture formed in step (a) further comprises a finely divided crystalline aluminosilicate.
3. A method as claimed in claim 2 wherein the crystalline aluminosilicate is present in an amount of from 0.5 to 20 wt.% of the weight of alumina plus crystalline aluminosilicate.
4. A method as claimed in any of claims 1 to 3 wherein the mixture formed in step (a) further comprises a platinum group

metal compound, or such a compound is composited with the extrudate, which is then calcined.
5. A method as claimed in claim 4 wherein the platinum group metal compound is present in an amount to yield a final catalyst product containing from 0.1 to 2 wt.% platinum group metal.
6. A method as claimed in any of claims 1 to 5 wherein the alumina hydrosol is an aluminium chloride hydrosol.
7. A method as claimed in any of claims 1 to 6 wherein the alumina hydrosol is an aluminium chloride hydrosol containing from 8 to 14 wt.% aluminium in a weight ratio with the chloride anion content thereof of from 0.9 to 1.5:1.
8. A method as claimed in any of claims 1 to 7 wherein the alumina in step (a) is alpha-alumina monohydrate (boehmite) or beta-alumina trihydrate (bayerite).
9. A method as claimed in any of claims 1 to 8 wherein the alumina in step (a) has a loss on ignition at 9000C. of not more than 30 wt.%.
10. A method as claimed in any of claims 1 to 9 wherein the alumina in step (a) is an alumina, or blend of aluminas, having a bulk density of not more than 0.5 gram/cc.
11. A method as claimed in any of claims 1 to 10 wherein the aqueous liquid is water which is free of additives.
12. A method as claimed in any of claims 1 to 10 wherein the aqueous liquid is an aqueous oxalic acid solution.
13. A method as claimed in any of claims 1 to 12 wherein the extrudate is calcined at a temperature of from 350" to 850"C. in an oxidizing atmosphere.
14. A method of preparing alumina extrudate particles carried out substantially as described in any of the foregoing Examples I to III.
15. Alumina extrudate particles when prepared by a method as claimed in any of claims 1 to 14.
16. A hydrocarbon conversion process in which a hydrocarbon is subjected to hydrocarbon conversion conditions in the presence of a catalyst comprising alumina extrudate particles prepared by a method as claimed in any of claims 1 to 14.
17. A process as claimed in claim 16 wherein the hydrocarbon conversion process is the reforming of petrol to enhance the octane rating thereof.