GB2290078A - Low soda, thermally reactive grade alumina - Google Patents

Low soda, thermally reactive grade alumina Download PDF

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Publication number
GB2290078A
GB2290078A GB9411191A GB9411191A GB2290078A GB 2290078 A GB2290078 A GB 2290078A GB 9411191 A GB9411191 A GB 9411191A GB 9411191 A GB9411191 A GB 9411191A GB 2290078 A GB2290078 A GB 2290078A
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GB
United Kingdom
Prior art keywords
alumina
thermally reactive
low soda
ammonium chloride
alpha
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9411191A
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GB2290078B (en
GB9411191D0 (en
Inventor
Prasanta Mukhopadhyay
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PASSARY MINERALS PVT Ltd
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PASSARY MINERALS PVT Ltd
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Priority to GB9411191A priority Critical patent/GB2290078B/en
Publication of GB9411191D0 publication Critical patent/GB9411191D0/en
Publication of GB2290078A publication Critical patent/GB2290078A/en
Application granted granted Critical
Publication of GB2290078B publication Critical patent/GB2290078B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
    • C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
    • C01F7/442—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination in presence of a calcination additive
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Compositions Of Oxide Ceramics (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Abstract

It is possible to manufacture low soda containing aluminas with higher corundum ( alpha Al2O3) content by admixing aluminum ammonium chloride, AlCl3.NH4Cl with hydrated alumina Al2O3.3H2O and subsequent calcination. Appropriate milling of calcine will make thermally reactive grades of alumina suitable for production of sintered alumina component to meet stringent product specifications.

Description

LOW SODA, THERMALLY REACTIVE GRADE ALUMINA This invention relates to manufacture of low soda containing alumina with high alpha alumina (ctA120 3) content . The processed material upon grinding to suitable degree of fineness makes thermally reactive grade of aluminas suitable for making high grade alumina ceramic shapes for electrical, electronic, and wear resistant applications Commercially calcined alumina is made from hydrated alumina Al2O3 # 3H2O . The preciptated hydrate A1203g3H2O made by "Bayer-Process" is washed and dried . Some residual soda (Na20) of around 0.35 - 0.5% remains in the hydrate which is considered undesirable as it is carried forward in the final calcined alumina.Na2O forms beta alumina ss Awl 203 , (Na2O # 11 Al2O3 ) during calcination thereby reducing the available ot A12 03 content considerably Alpha alumina trihydroxide is calcined in a rotary kiln to drive away chemically combined water. Alumina trihydrate upon calcination first forms dehydrated alumina designated as gamma alumina ( γ A12 O3). The conversion of a gamma alumina to alpha alumina ( o A1203) occurs approximately to over 1000 Celsius with an easily observable rate.
The addition of aluminum ammonium chloride A1C13 r NH4C1 in aqueous solution to alumina trihydrate Al2 03 3H2 0 will convert the soda into sodium chloride (NaCl).
Calcination of treated alumina trihydrate removes most of the soda by process of voltilization of sodium Chloride (A) The output is high purity calcined alumina having Na20 around 0.08 - 0.1% which is insignificant when compared with untreated calcined aluminas which has higher soda content 0.35 - 0.6% (B) The other advantage of the treatment of aluminum ammonium chloride is that it will also reduce the temperature of observable conversion of gamma alumina (2 A1203) to alpha alumina ( A A1203) to a significantly lower degree around 8000 Celsius . This helps higher conversion of alpha alumina of the treated hydrated alumina A1203. 3H2O compared to untreated hydrated alumina under similar calcination condition.There is a catalystic effect of addition of aluminum ammonium chloride for easy conversion of gamma to alpha variety of alumina . Halogenic atmosphere is known to have beneficial effect for gamma to alpha conversion Briquettes of treated alpha alumina trihydroxide is calcined in a rotary kiln to drive away chemically combined water. Depending on degree of calcination between 12500 14000 Celsius the calcined products contain 85 - 99% Awl203 which are suitable for preparation of thermally reactive grade aluminas The embodiment of the invention has been shown in the form of example I and II in the table shown below .The material under heading I is treated with aluminum ammonium chloride solution and II is untreated TABLE 1 EXAMPLE I EXAMPLE II Parts by Weight Parts by Weight Alumina trihydroxide 1000 gm 1000 gm Al2Q3. 3H2O Ground Aluminum ammonium 250 cc Nil chloride AlCl. NH4C1 205 aqueous solution Properties of Hydrated Alumina (A1203. 3H20 ) is given below A1203 % 64.5 Na20 % 0.38 SiO2 % 0.017 Fe2O3 % 0.018 Loss on ignition % total 110 - 1100C Celsius - 34.5 Specific gravity 2.42.
Particle size analysis % on 325 B.S.S 0.2;% less than 10 micron is over 99.37 The material can be mixed with extra water if required Homogeneous damp mixture is pressed in the form compacts. Roll type briquetting press widely used in refractory or ceramic industry is suitable for the purpose . Dried briquettes are calcined at a temperature of 1400C Celsius in a suitable kiln after drying The Properties of calcined product are given in table II TABLE 2 I (Treated ) II (Untreated % Na p 0.08% 0.58% % A1203 + 98% + 90% The treated (I) alumina is of high purity grade alumina with lower Na20 and higher alpha A12 03than II material . The high purity material has been further micronised in a fluid energy mill to make thermally reactive grade of alumina having madian micron from 0.5 to 2.5 depending on the end use, surface finish and sintering temperature . The surface area of super ground aluminium having median micron 0.5 found to over 8m2/g. The surface area of standard grade thermally reactive alumina having median micron of 2.5 micron determined to be 2.4 m 2/g.

Claims (1)

  1. CLAIM
    Addition of aluminum ammonium chloride A1C13. NH4C1 1 - 10% calculated on dry basis admixed to hydrated alumina, Al2O3. 3H20 will reduce the soda content drastically from hydrated alumina A12O3 . 3H20, during calcination . Calcining at 1400C Celsius produces a higher percentage of or A1203 containing aluminas which can be made thermally reactive alumina of desired grade upon proper milling
GB9411191A 1994-06-03 1994-06-03 Low soda,thermally reactive grade alumina Expired - Fee Related GB2290078B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9411191A GB2290078B (en) 1994-06-03 1994-06-03 Low soda,thermally reactive grade alumina

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9411191A GB2290078B (en) 1994-06-03 1994-06-03 Low soda,thermally reactive grade alumina

Publications (3)

Publication Number Publication Date
GB9411191D0 GB9411191D0 (en) 1994-07-27
GB2290078A true GB2290078A (en) 1995-12-13
GB2290078B GB2290078B (en) 1997-11-05

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Family Applications (1)

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GB9411191A Expired - Fee Related GB2290078B (en) 1994-06-03 1994-06-03 Low soda,thermally reactive grade alumina

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1332762C (en) * 2004-07-29 2007-08-22 中国石油化工股份有限公司 Method for preparing alumina supporter in structure of double peak holes
CN110342556A (en) * 2019-08-09 2019-10-18 苏州盛曼特新材料有限公司 A kind of low sodium high activity special type α-Al2O3The preparation method of micro mist

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Derwent WPI Acc. No. 71-17656S & FR2036842 A *
Derwent WPI Acc. No. 77-25343Y & DE1767511 B *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1332762C (en) * 2004-07-29 2007-08-22 中国石油化工股份有限公司 Method for preparing alumina supporter in structure of double peak holes
CN110342556A (en) * 2019-08-09 2019-10-18 苏州盛曼特新材料有限公司 A kind of low sodium high activity special type α-Al2O3The preparation method of micro mist

Also Published As

Publication number Publication date
GB2290078B (en) 1997-11-05
GB9411191D0 (en) 1994-07-27

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19990603