Title of Invention	A PROCESS FOR THE PRODUCTION OF ALUMINA
Abstract	A process for the production of alumina comprising: (a) dissolution of Gibbsite (A12O3, 3H20) in nitric acid providing an acid solution of aluminum nitrate products; (b) decomposition at 300-700oC with free air supply of the acid solution to alumina and Nox; (c) regeneration of the formed NOx to concentrated nitric acid and recycling of produced nitric acid to step (a); and (d) recovery of the alumina product formed in step (b) by means selected from spraying onto the inner surface of one or more rotary kilns, drying in a fluid bed, and drying in a steel band conveyor furnace.

Title of Invention

A PROCESS FOR THE PRODUCTION OF ALUMINA

Abstract

A process for the production of alumina comprising: (a) dissolution of Gibbsite (A12O3, 3H20) in nitric acid providing an acid solution of aluminum nitrate products; (b) decomposition at 300-700oC with free air supply of the acid solution to alumina and Nox; (c) regeneration of the formed NOx to concentrated nitric acid and recycling of produced nitric acid to step (a); and (d) recovery of the alumina product formed in step (b) by means selected from spraying onto the inner surface of one or more rotary kilns, drying in a fluid bed, and drying in a steel band conveyor furnace.

Full Text	The present invention relates to a process for the production of alumina containing material in particular for use in the preparation of catalyst carriers. The state of the art methods for preparing alumina include use of raw materials produced by precipitation as exempli¬fied by mixing bases such as alkaline aluminate and alka¬line hydroxide bases with an acid such as HNO3, HaS04 and H3PO4, in addition to Al (NO3) and Al2[S04)3, Useful carriers for refinery processing catalysts are produced from alumina and intermediate products like pseudo boehmite owing their large surface area and high porosity. The known methods for preparing alumina catalyst carriers are costly in terms of purchase of the acid and basic raw materials being employed in the preparation process and, furthermore, expense to pH adjustments, washing steps and wastewater treatment. The general object of this invention is, thus, to provide an improved process for the production of alumina such as aluminum oxide and pseudo boehmite for use in the prepara¬tion of catalyst carriers, wherein production of alumina is carried out by simplified and inexpensive steps. Compared to the known methods, the advantages of the invention in¬cludes, furthermore, high product yield through reduced loss of material during the processing. SUMMARY OF THE INVENTION The process of this invention comprises the following steps: a) dissolution of Gibbsite {AI2O3, 3H2O) in nitric acid providing an acid solution of Al(N03)3 by reaction (i): Al2O2 3H2O+6HNO3 2 Al(N03}3 + 6 H2O b) thermal decomposition of the acid solution into alumi¬ num hydroxides and NOx gases by reaction (ii): 2 Al (N02)3+6H20 -> Al2O3; Z H2O+6 N02t(6-Z) H2O+3/2 O2 ; and c) regeneration of NOx gasses in one or a series of ab¬ sorption towers to concentrated nitric acid according to reaction (iii): 6 NOs+a H2O+3/2 O2 -* 6HNO3 The overall reaction, i.e. (i)+(ii)+(iii) is then: Al2O3, 3H20+3 H2O -> AI2O3, Z H20+(6-Z) H2O, wherein Z = 0.5-3 In a specific embodiment of the invention, NO2 being formed in the above reaction (i) is partly regenerated in absorp¬tion towers. Reaction {ii) results in formation of nitric acid that is recycled and utilised for dissolution of Gibbsite, which is the sole raw material in the process. Though, due to minor loss of the nitric acid to be recy¬cled, occasionally small amounts of nitric acid in addition to what is being currently regenerated have to be added, to maintain or enhance dissolution of the Gibbsite raw mate¬rial . Decomposition in the above step (b) may be performed by spraying the acidic solution from step (a) onto the inner surface of one or more rotary kilns with free supply of air at 300-700°C. However, by using this method, measures may be taken in order to prevent sticking of the product to the inner surface of the rotary kiln, e.g. by means of one or more sliding chains. In order to be efficient, the chains must be relatively heavy and are to be present inside each kiln in such a way that they slide down on surface, while the kiln rotates, and thereby prevent the solid material from adhering to the surface. Adhesion of the prepared material from the decomposed acid solution to the inner side of said kiln may also be pre¬vented by other physical or chemical means known in the art. The alumina product can be further improved by addition of an organic compound capable of reducing nitrates. Those components can be glucose or similar compounds. The reac¬tion between the organic compound and the nitrate will then generate a faster decomposition of the nitrates through mi- nor local explosions, and, thus, reduce the size of the formed particles. Example Preparation of alumina from aluminium nitrate (A1(N03)3 * 9H2O). 225 g A1(N03)3 9H2O) are dissolved in 100 g water and 1 g 65% by weight HNO3. The solution is clear without any re¬maining crystallites. The solution is then pumped into a preheated rotating fur¬nace (length 1.5 m inclination 1°), rotating at 30 rpm. The temperature in the furnace is 350°C. The pumping speed is around 5-20 ml/min. Alumina in its boehmite form starts to form when the solution comes into contact with the walls of the furnace by decomposition of the nitrates. The formed product is in shape of very porous foam that can easily be grinded to a powder suitable for further process¬ing. WE CLAIM: 1. A process for the production of alumina comprising: Ca) dissolution of Gibbsite (Al203, 3H2O) in nitric acid providing an acid solution of aluminum nitrate prod¬ucts; (b) decomposition at 300-700°C with free air supply of the acid solution to alumina and Nox; (c) regeneration of the formed NOx to concentrated nitric acid and recycling of produced nitric acid to step (a); and (d) recovery of the alumina product formed in step (b) by means selected from spraying onto the inner surface of one or more rotary kilns, drying in a fluid bed, and drying in a steel band conveyor furnace. 2. The process according to claim 1, wherein decomposition of the acid solution in step (b) is enhanced by addition of an organic compound being active in reduction of nitrates. 3. The process according to claim 1, wherein the rotary kiln is equipped with one or more chains of a heavy mate¬ rial, which slide on the inner surface of the kiln, while rotating the kiln.

Full Text

The present invention relates to a process for the production of alumina containing material in particular for use in the preparation of catalyst carriers.
The state of the art methods for preparing alumina include use of raw materials produced by precipitation as exempli¬fied by mixing bases such as alkaline aluminate and alka¬line hydroxide bases with an acid such as HNO3, HaS04 and H3PO4, in addition to Al (NO3) and Al2[S04)3, Useful carriers for refinery processing catalysts are produced from alumina and intermediate products like pseudo boehmite owing their large surface area and high porosity.
The known methods for preparing alumina catalyst carriers are costly in terms of purchase of the acid and basic raw materials being employed in the preparation process and, furthermore, expense to pH adjustments, washing steps and wastewater treatment.
The general object of this invention is, thus, to provide an improved process for the production of alumina such as aluminum oxide and pseudo boehmite for use in the prepara¬tion of catalyst carriers, wherein production of alumina is carried out by simplified and inexpensive steps. Compared to the known methods, the advantages of the invention in¬cludes, furthermore, high product yield through reduced loss of material during the processing.

SUMMARY OF THE INVENTION
The process of this invention comprises the following steps:
a) dissolution of Gibbsite {AI2O3, 3H2O) in nitric acid
providing an acid solution of Al(N03)3 by reaction (i):
Al2O2 3H2O+6HNO3 2 Al(N03}3 + 6 H2O
b) thermal decomposition of the acid solution into alumi¬
num hydroxides and NOx gases by reaction (ii):
2 Al (N02)3+6H20 -> Al2O3; Z H2O+6 N02t(6-Z) H2O+3/2 O2 ; and
c) regeneration of NOx gasses in one or a series of ab¬
sorption towers to concentrated nitric acid according to
reaction (iii):
6 NOs+a H2O+3/2 O2 -* 6HNO3
The overall reaction, i.e. (i)+(ii)+(iii) is then:
Al2O3, 3H20+3 H2O -> AI2O3, Z H20+(6-Z) H2O,
wherein
Z = 0.5-3
In a specific embodiment of the invention, NO2 being formed in the above reaction (i) is partly regenerated in absorp¬tion towers. Reaction {ii) results in formation of nitric

acid that is recycled and utilised for dissolution of Gibbsite, which is the sole raw material in the process.
Though, due to minor loss of the nitric acid to be recy¬cled, occasionally small amounts of nitric acid in addition to what is being currently regenerated have to be added, to maintain or enhance dissolution of the Gibbsite raw mate¬rial .
Decomposition in the above step (b) may be performed by spraying the acidic solution from step (a) onto the inner surface of one or more rotary kilns with free supply of air at 300-700°C. However, by using this method, measures may be taken in order to prevent sticking of the product to the inner surface of the rotary kiln, e.g. by means of one or more sliding chains. In order to be efficient, the chains must be relatively heavy and are to be present inside each kiln in such a way that they slide down on surface, while the kiln rotates, and thereby prevent the solid material from adhering to the surface.
Adhesion of the prepared material from the decomposed acid solution to the inner side of said kiln may also be pre¬vented by other physical or chemical means known in the art.
The alumina product can be further improved by addition of an organic compound capable of reducing nitrates. Those components can be glucose or similar compounds. The reac¬tion between the organic compound and the nitrate will then generate a faster decomposition of the nitrates through mi-

nor local explosions, and, thus, reduce the size of the
formed particles.
Example
Preparation of alumina from aluminium nitrate (A1(N03)3 *
9H2O).
225 g A1(N03)3 9H2O) are dissolved in 100 g water and 1 g 65% by weight HNO3. The solution is clear without any re¬maining crystallites.
The solution is then pumped into a preheated rotating fur¬nace (length 1.5 m inclination 1°), rotating at 30 rpm. The temperature in the furnace is 350°C.
The pumping speed is around 5-20 ml/min. Alumina in its boehmite form starts to form when the solution comes into contact with the walls of the furnace by decomposition of the nitrates.
The formed product is in shape of very porous foam that can easily be grinded to a powder suitable for further process¬ing.

WE CLAIM:
1. A process for the production of alumina comprising:
Ca) dissolution of Gibbsite (Al203, 3H2O) in nitric acid providing an acid solution of aluminum nitrate prod¬ucts;
(b) decomposition at 300-700°C with free air supply of the acid solution to alumina and Nox;
(c) regeneration of the formed NOx to concentrated nitric acid and recycling of produced nitric acid to step (a); and
(d) recovery of the alumina product formed in step (b) by means selected from spraying onto the inner surface of one or more rotary kilns, drying in a fluid bed, and drying in a steel band conveyor furnace.
2. The process according to claim 1, wherein decomposition
of the acid solution in step (b) is enhanced by addition of
an organic compound being active in reduction of nitrates.
3. The process according to claim 1, wherein the rotary
kiln is equipped with one or more chains of a heavy mate¬
rial, which slide on the inner surface of the kiln, while
rotating the kiln.

Documents:

0080-mas-2001 abstract-duplicate.pdf

0080-mas-2001 abstract.pdf

0080-mas-2001 claiims-duplicate.pdf

0080-mas-2001 claiims.pdf

0080-mas-2001 correspondence-others.pdf

0080-mas-2001 correspondence-po.pdf

0080-mas-2001 description (complete)-duplicate.pdf

0080-mas-2001 description (complete).pdf

0080-mas-2001 form-1.pdf

0080-mas-2001 form-19.pdf

0080-mas-2001 form-26.pdf

0080-mas-2001 form-3.pdf

0080-mas-2001 form-5.pdf

0080-mas-2001 others.pdf

0080-mas-2001 petition.pdf

« Previous Patent

Next Patent »

Patent Number

217083

Indian Patent Application Number

80/MAS/2001

PG Journal Number

21/2008

Publication Date

23-May-2008

Grant Date

24-Mar-2008

Date of Filing

30-Jan-2001

Name of Patentee

HALDOR TOPSOE A/S

Applicant Address

NYMOLLEVEJ 55, DK-2800 KGS, LYNGBY,

Inventors:

#	Inventor's Name	Inventor's Address
1	KELD JOHANSEN	HASPEHOLM ALLE 4, DK-3600 FREDERIKSSUND,

PCT International Classification Number

C01F 7/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/180,164	2000-02-04	U.S.A.