Activated alumina production process

FIELD: inorganic compounds technologies.

SUBSTANCE: invention relates to production of activated alumina appropriate as catalyst carrier for petrochemical and organic synthesis, in particular as reforming catalyst carrier. Process comprises continuous precipitation of aluminum hydroxide with pseudoboehmit structure from basic aluminum sulfate solution by neutralization with alkali reagent, filtration, autoclave treatment of resulting aluminum hydroxide precipitate in aqueous ammonia solution at pH 10.0-11.0 of reaction mixture, 135-145°C, and agitation time 1.0-2.0 h, washing of precipitate with chemically desalted water, drying, and final heat treatment.

EFFECT: improved quality of activated alumina and reduced consumption of water in washing of final product.

2 cl, 1 tbl

 

The invention relates to the chemical industry, in particular to the field of active alumina carrier of catalysts for various purposes for the petrochemical and organic synthesis, in particular reforming catalysts.

A method of obtaining the active alumina, which consists in dissolving technical aluminum hydroxide Al(OH)3in a solution of pure caustic alkali in autoclave conditions (t≥200°C), followed by neutralization obtained aluminate-alkaline solution with a solution of nitric acid (15-20% HNO3in continuous mode, filtering and washing the obtained precipitate of aluminum hydroxide pseudonimity patterns (AlOOH) chemically demineralized water (CPW), drying and calcining at 500 to 600° [1]. The method allows to obtain an active alumina content of impurity components Na2O, Fe2O3and SiO2level, respectively, of 0.03-0.035%of that of 0.025-0.03% and 0.03%, which governs the use of this active oxide (AAO) for only Hydrotreating catalysts, in particular brands TNK-2003, and excludes the possibility of applying to obtain catalysts for reforming the content in this AAO impurity components should not exceed 0,01 Na2O, 0.015 g of Fe2About3and 0.01 SiO2and, moreover, the consumption Hove for leaching extending t is 50-70 m 3/so

A method of obtaining the active aluminum oxide, consisting in the technical heat treatment of aluminum hydroxide at 460-500°in "boiling" layer to obtain aluminum hydroxide pseudonimity patterns AlOOH (flush-alumina), autoclave treatment at 120±10°With solutions of nitric acid in the course of 5.0 hours, then filtering, washing and Hove drying [2]. The method allows to reduce the consumption Hove on washing of the final product to 35.0 m3/t and the content of impurity components in the last 0.02% Na2O and 0.02 Fe2O3, 0,015 SiO2that, however, is not sufficient to produce the AOA - fundamentals of reforming catalysts.

The closest in technical essence and the achieved result is the method of obtaining the active aluminum oxide, including the production of aluminum hydroxide continuous deposition from the solution of the basic aluminum sulphate neutralization aluminate alkaline solution [3] under optimum conditions: pH value of the reaction mixture is 8.5-9.5; temperature 90-95°S, feed rate of sodium aluminate solution (alkaline module 1,3-1,6)3-9 kg/min in a solution of basic aluminum sulfate, containing 70-80 g/DM3Al2O3subsequent filtration, washing Hove, drying and heat treatment at 550° - active is aluminum oxide, which contains 0.05 to 0.08% Na 2O, and up to 0.45 to 1.0% SO42-has a specific surface 220-280 m2/year

Thus, the method does not allow to reduce the content of impurity components in the active aluminum oxide, and this is not enough to obtain catalysts for reforming, and, in addition, is characterized by high content of sulfur (sulfate ion) - impurities for this class of catalysts. Also the way the inherent drawback: increased consumption Hove, up to 120 m3/t, which complicates the issue of disposal of a significant number of the located.

The purpose of the invention is improving the quality of active aluminum oxide and reducing the consumption of washing water in the final product.

This goal is achieved as follows.

Precipitation of aluminum hydroxide pseudonimity structure is produced from a solution of the basic aluminum sulfate neutralization in a continuous mode with an aqueous solution of ammonia - NH4HE. Obtained under certain conditions: the pH of the reaction mixture, concentration and temperature, duration of erythropenia - sediment AlOOH filtered, and then subjected to autoclave treatment at slabokontsentrirovannye solutions of ammonia for the formation of patterns of pseudoboehmite and improve its physico-chemical properties, then filtered, washed what I dried and made red-hot at a temperature of 500-550°C.

In autoclave processing obtained after deposition of sediment AlOOH in slabokontsentrirovannye solution of NH4OH, the following occurs: there is a dissolution of the partially formed by neutralization of the solution of the basic aluminum sulphate sodium alunite - Na [Al6(SO4)5(OH)10]·4H2O the transformation of this double salt in pseudoboehmite AlOOH and water-soluble sodium sulfate, which allows to reduce in the final product, the content of impurity components - Na2O and SO42--ion battery. At the same time improves the morphological structure of the precipitate disappears in a residual amorphous aluminum hydroxide gel Al(OH)3formed in the initial process of neutralization of the initial solution of the basic aluminum sulfate, thereby decreasing the moisture content of the solid phase (70-75% to 40-50%) pseudoboehmite AlOOH, increases the degree of otkristallizovalas sludge pseudoboehmite: the average particle size increases with 35-45 μm (after deposition) to 45-55 μm, and the total porosity (pore volume) from 0.35-0.45 m3/g to 0.55-0.60 m3/, This allows to reduce the number captured in the intergranular residual sludge solution of aluminum sulfate, the impurity content of Na2O, Fe2About3, SO42-and SiO 2that the subsequent washing of the final sludge pseudoboehmite allows not only to reduce the content of impurities in AlOOH, but significantly reduce the consumption Hove wash.

As an initial solution to obtain an active alumina is applied to the solution of basic aluminum sulphate AlOHSO4obtained by dissolving technical aluminum hydroxide Al(OH)3in the solution of sulfuric acid (H2SO4and containing, g/DM3: 75,0 Al2O3, 0.5 Na2O 0,04 Fe2O3, 0,04 SiO2pH=3-3,5; as a precipitating reagent - 25,0%solution of NH4OH mark "h".

Example 1.

3.0 DM3solution of basic aluminum sulfate and 1.5 DM3an aqueous solution of ammonia at the same time in continuous mode are fed into the deposition reactor with mechanical stirring (Vslave=5.0 DM3with a speed of 0.2-0.3 DM3/min 0,08-0,10 DM3/min and the reaction mixture is constantly stirred while the pH values of 9.5 to 10.5 at a temperature of 85-90°C. At specified feed rate of the reactants obtaining a precipitate of aluminum hydroxide pseudonimity structure is 30-45 minutes.

Svezheosazhdennoi aluminum hydroxide, filtered, reporterette 5.0 and 7.5%solution of NH4OH in the amount of 1000 g of AlOOH (humidity 60,0%) 1.0 DM3and the resulting pulp, for example, is moved in an autoclave with mechanical stirring (V slave=1,5 DM3) processing (so-called "aging") at values of pH of 10.5, a temperature of 140°and duration of 1.5 hours.

Next, the slurry is filtered, the precipitate washed with distilled water until a negative reaction to the sulfate ion (kachestvena reaction 10%solution of BaCl2), dried at a temperature 85-92°C for 1 hour and subjected to heat treatment at a temperature of 500-550°mode weighted ("boiling") layer.

Received active aluminum oxide contains, wt%: 74,0 Al2About3, 0,006 Na2O 0,012 Fe2O3, 0,01 SiO2, 0,12 SO42-the value of Sbeats=290 m2/g, the average particle size is 45-50 μm, a total pore volume of 0.6 m3/g, x-ray phase analysis - pseudoboehmite.

Thus, the AAO may be applied as a carrier for catalysts reforming.

The table below shows the physico-chemical properties of the obtained pseudoboehmite and consumption Hove (distilled water) on his rinse under optimal process conditions of autoclave processing and output for optimal conditions.

According to the experiments shown in the table, the optimal conditions for carrying out the method of obtaining the active aluminum oxide, which increases its quality (to reduce the content of impurity comp is required) and to reduce the consumption of chemically demineralized water for the washing of the final product compared to the prototype, are: the temperature of the autoclave treatment of the slurry of precipitated aluminum hydroxide pseudonimity patterns 135-145°C, the pH value of the reaction medium (ammonia solution) 10,0-11,0, duration of erythropenia 1.0-2.0 hours (experiments 1-7).

When you exit the optimum conditions in the lower side according to the temperature value (130° - op), ceteris paribus, reduced purification from impurity components - the content of Na2O 0,016%, SO42-of 0.25, which is due to the incomplete transition of the double salt of sodium alunite in AlOOH; which entails the increase of water consumption for rinsing until the negative reaction to SO42--ion (to 35.0 DM3/kg). This explains the failure to achieve the desired product quality at lower values of pH = 9,5 (op) and duration of erythropenia τ=0.75 hours (op).

Table
no experienceProcess conditionsThe content of components, wt.%Q, DM3/kg (m3/t)The value of Sbeatsm2/gPhase composition*)
t°CpHτhNa2OFe2 3SO42-
I. Middlings obtained by prototype
1009,01,00,0150,0250,30100275Pb
II. The optimum conditions of the process of autoclaving
113510,51,50,0190,0150,1525,0280Pb
214010,51,50,0080,0120,1220,0300Pb
314510,51,50,0060,0130,1030,0275Pb
414010,01,50,010,0130,1325,0290Pb
514011,01,50,0060,0130,1030,0280Pb
614010,51,00,010,012 30,0285Pb
714010,52,00,0060,0120,1026,0290Pb
III. when you exit the optimum conditions
813010,51,50,0160,020,2535,0280Pb
915010,51,50,0070,010,0845,025585%BB+15%B
101409,51,50,0140,020,2236,0280Pb
1114011,51,50,0060,0140,0840,026590%Pb+10%B
1214010,50,750,0140,0170,2032,0275Pb
1314010,52,250,0070,010,0938,026090%Pb+10%B
(*)IB pseudoboehmite, B - boehmite)

Beyond the optimal range of process parameters in a big way in obtaining the desired quality of the final product according to the content of impurity components is further crystallization of the precipitate of aluminum hydroxide pseudonimity patterns - it appears the phase of boehmite (B): if t≥150°C to 15.0 wt.% (op) and up to 10% B, respectively, with the increase of pH≥11,5 (op) and duration of erythropenia 2.25 hours and above (op), which is unacceptable for the AOA - basis for reforming catalysts.

Thus, the proposed method is characterized by a new technique - autoclave processing of precipitated from a solution of a basic sulfate neutralization with a solution of an alkaline reagent aluminum hydroxide pseudonimity patterns with new modes and parameters, this process ensures the achievement of the technical result: improving the quality of active aluminum oxide and reducing the consumption of washing water when the implementation of the claimed invention.

Sources of information

1. Train N.P., Radchenko DU, Train J.F. ñ - Producing active alumina carrier of catalysts for hydrogenation processes. - M, Zeitangaben, 1979.

2. Technical recommendations for the use of flush-produktov the production of catalysts and adsorbents on CJSC Procatalyse" - report on x/contract No. 207/2001 JSC "Neftekhim", Krasnodar, 2002

3. SU 624883, publ. 10.08.1978.

1. The method of obtaining the active aluminum oxide, including continuous precipitation of aluminum hydroxide pseudonimity patterns from solutions of basic aluminum sulfate neutralization with a solution of an alkaline reagent, filtering, washing the precipitate chemically demineralized water, drying and heat treatment to obtain the final product, characterized in that after filtering produce autoclave processing the obtained precipitate of aluminum hydroxide in aqueous ammonia solution under the following conditions: pH of the reaction mixture 10,0-11,0, the temperature of 135-145°With time erythropenia 1,0-2,0 hours

2. The method according to claim 1, characterized in that the precipitation of aluminium hydroxide pseudonimity patterns produce a continuous deposition from a solution of a basic aluminium sulphate concentration of 75 g/DM3Al2O3neutralization 25%solution of NH4OH when the pH of the reaction mixture of 9.5 to 10.5, a temperature of 80-90°and time erythropenia 30-45 minutes



 

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