Methods for the preparation of alumina beads formed by dewatering a highly dispersible gel

Patent metadata

Field	Value
Publication number	US-2018021754-A1
Application number	US-201515537794-A
Country	US
Kind code	A1
Filing date	Dec 16, 2015
Priority date	Dec 18, 2014
Publication date	Jan 25, 2018
Grant date	—

Abstract

A process for the preparation of an alumina in the form of beads with a sulphur content in the range 0.001% to 1% by weight and a sodium content in the range 0.001% to 1% by weight with respect to the total mass of said beads is described, said beads being prepared by shaping an alumina gel having a high dispersibility by drop coagulation. The alumina gel is itself prepared using a specific precipitation preparation process in order to obtain at least 40% by weight of alumina with respect to the total quantity of alumina formed at the end of the gel preparation process right from the first precipitation step, the quantity of alumina formed at the end of the first precipitation step possibly even reaching 100%. The invention also concerns the use of alumina beads as a catalyst support in a catalytic reforming process.

First claim

1 . A process for the preparation of an alumina in the form of beads with a sulphur content in the range 0.001% to 1% by weight and a sodium content in the range 0.001% to 1% by weight with respect to the total mass of said beads, said process comprising at least the following steps:
a) at least one first step for the precipitation of alumina, in an aqueous reaction medium, using at least one basic precursor selected from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide and at least one acidic precursor selected from aluminium sulphate, aluminium chloride, aluminium nitrate, sulphuric acid, hydrochloric acid and nitric acid, in which at least one of the basic or acidic precursors comprises aluminium, the relative flow rate of the acidic and basic precursors being selected in a manner such as to obtain a pH of the reaction medium in the range 8.5 to 10.5 and the flow rate of the acidic and basic precursor or precursors containing aluminium being regulated in a manner such as to obtain a percentage completion of said first step in the range 40% to 100%, the percentage completion being defined as being the proportion of alumina formed in equivalents of Al 2 O 3 during said first precipitation step with respect to the total quantity of alumina formed at the end of the precipitation step or steps, said first precipitation step being operated at a temperature in the range 10° C. to 50° C., and for a period in the range 2 minutes to 30 minutes; b) a step for heat treatment of the suspension obtained at the end of step a) at a temperature in the range 50° C. to 200° C. for a period in the range 30 minutes to 5 hours in order to obtain an alumina gel; c) a step for filtration of the suspension obtained at the end of the heat treatment step b) followed by at least one step for washing the gel obtained; d) a step for drying the alumina gel obtained at the end of step c) in order to obtain a powder; e) a step for shaping the powder obtained at the end of step d) by drop coagulation in order to obtain the green material; f) a step for heat treatment of the green material obtained at the end of step e) at a temperature in the range 500° C. to 1000° C., in the presence or absence of a stream of air containing up to 60% by volume of water.

2 . The process according to claim 1 , in which the basic precursor is sodium aluminate.

3 . The process according to claim 1 , in which the acidic precursor is aluminium sulphate.

4 . The process according to claim 1 , in which the percentage completion of said precipitation step a) is in the range 45% to 90%.

5 . The process according to claim 1 , in which in the case in which the percentage completion obtained at the end of the first precipitation step a) is less than 100%, said preparation process comprises a second precipitation step a′) after the first precipitation step.

6 . The process according to claim 5 , in which a step for heating the suspension obtained at the end of the precipitation step a) is carried out between the two precipitation steps a) and a′), said heating step being operated at a temperature in the range 20° C. to 90° C. for a period in the range 7 to 45 minutes.

7 . The process according to claim 5 , in which said second step a′) for precipitation of the suspension obtained at the end of the heating step is operated by adding to said suspension at least one basic precursor selected from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide and of at least one acidic precursor selected from aluminium sulphate, aluminium chloride, aluminium nitrate, sulphuric acid, hydrochloric acid and nitric acid, in which at least one of the basic or acidic precursors comprises aluminium, the relative flow rate of the acidic and basic precursors being selected in a manner such as to obtain a pH of the reaction medium in the range 8.5 to 10.5 and the flow rate of the acidic and basic precursor or precursors containing aluminium being regulated in a manner such as to obtain a percentage completion of the second step in the range 0 to 60%, the percentage completion being defined as being the proportion of alumina formed in equivalents of Al 2 O 3 equivalents during said second precipitation step a′) with respect to the total quantity of alumina formed at the end of step a′) of the preparation process, said step being operated at a temperature in the range 40° C. to 90° C., and for a period in the range 2 minutes to 50 minutes.

8 . The process according to claim 1 , in which said step e) for shaping by drop coagulation comprises preparing a suspension comprising the dried powder, a pore-forming agent selected from greases, oils and mineral waxes, fats, hydrocarbons and oil cuts, a surfactant selected from non-ionic surfactants or ionic surfactants and water, with stirring.

9 . The process according to claim 8 , in which the quantity of pore-forming agent, expressed as the ratio of the mass of pore-forming agent to the total mass of alumina expressed as the percentage of Al 2 O 3 engaged in the suspension, is in the range 0.2% to 60%.

10 . The process according to claim 8 , in which the proportion of surfactant present in the emulsion, defined as being equal to the ratio of the mass of surfactant to the mass of pore-forming agent, is in the range 1% to 25% by weight.

11 . The process according to claim 8 in which, during the preparation of the suspension comprising the dried powder, a charge of alumina or of alumina precursor is added to a quantity of charge, expressed as the % by weight of Al 2 O 3 , of less than or equal to 30% by weight with respect to the total weight of the suspension in equivalents of Al 2 O 3 .

12 . Alumina beads with a sulphur content in the range 0.001% to 1% by weight, and a sodium content in the range 0.001% to 1% by weight with respect to the total mass of said beads which are capable of being obtained by a process according to claim 1 .

13 . Alumina beads according to claim 12 , having a BET specific surface area of more than 220 m 2 /g.

14 . A process for the catalytic reforming of a hydrocarbon feed comprising n-paraffinic, naphthenic and aromatic hydrocarbons, using a catalyst comprising at least one or more metals selected from group VIII of the periodic classification and a support comprising amorphous mesoporous alumina beads prepared in accordance with the preparation process according to claim 1 , said process being operated at a temperature in the range 400° C. to 700° C., a pressure in the range 0.1 to 4 MPa and a mass flow rate of feed treated per unit mass of catalyst per hour in the range 0.1 to 10h −1 .

Assignees

• Ifp Energies Now

Inventors

• Boualleg Malika
• Dandeu Aurelie

Classifications

• C01F7/441

  by calcination · CPC title

• C10G35/06

  characterised by the catalyst used · CPC title

• B01J21/04 Primary

  Alumina · CPC title

• B01J20/28069

  Pore volume, e.g. total pore volume, mesopore volume, micropore volume · CPC title

• C01F7/141

  from aqueous aluminate solutions by neutralisation with an acidic agent · CPC title