Preparation method and application of rutile titanium dioxide calcination seed crystal
阅读说明：本技术 一种金红石型钛白粉煅烧晶种的制备方法及其应用 (Preparation method and application of rutile titanium dioxide calcination seed crystal ) 是由 黄建文 何明川 陈湘涛 赵平 李缉勇 苏剑泽 于 2021-03-16 设计创作，主要内容包括：本发明提供了一种金红石型钛白粉煅烧晶种的制备方法及其应用,涉及金红石型钛白粉生产技术领域。包括以下步骤：(1)碱溶；(2)一次水洗；(3)中和；(4)二次水洗；(5)酸溶。所述的一次水洗过程中采用两次水洗的方式,即采用第一次温度高,加水量少,第二次温度低,加水量多的方法,意外地发现采用此方法进行水洗,可以更好地将碱和SO-4～(2-)洗掉,提高晶种品质；另外所述方法制备得到的晶种可以随盐处理剂一同加入钛白粉制备体系中,加入后无需进行洗涤和漂白步骤,从而减少了晶种的使用量,以TiO-2计,晶种的加入量为1.2-2.5％,即可使金红石型钛白粉粉的转化率达到99.5％以上。(The invention provides a preparation method and application of rutile titanium dioxide calcination seed crystals, and relates to the technical field of rutile titanium dioxide production. The method comprises the following steps: (1) alkali dissolution; (2) washing with water for the first time; (3) neutralizing; (4) washing with water for the second time; (5) and (4) acid dissolution. The method of twice water washing in the primary water washing process, namely the method of high temperature for the first time, less water adding amount, low temperature for the second time and more water adding amount is adopted, and the method is unexpectedly found to better wash alkali and SO 4 2‑ Washing off to improve the quality of the seed crystal; in addition, the crystal seeds prepared by the method can be added into a titanium dioxide preparation system along with a salt treating agent, and washing and bleaching steps are not needed after the crystal seeds are added, so that the use amount of the crystal seeds is reduced, and TiO is used as the crystal seeds 2 The adding amount of the seed crystal is 1.2 to 2.5 percentThe conversion rate of the rutile titanium dioxide powder can reach more than 99.5 percent.)
1. A method for preparing rutile titanium dioxide calcination seed crystal is characterized in that: the method comprises the following steps:
(1) alkali dissolution: firstly, preheating metatitanic acid and alkali liquor, and then adding the preheated metatitanic acid into the preheated alkali liquor to form orthotitanate;
(2) primary water washing: washing the orthotitanic acid salt prepared in the step (1) with water, and filtering to obtain orthotitanic acid slurry A;
(3) neutralizing: adding hydrochloric acid into the orthotitanic acid slurry A obtained in the step (2), adjusting the pH value, and heating for reaction to obtain neutralized orthotitanic acid slurry B;
(4) and (3) secondary water washing: washing and filtering the neutralized orthotitanic acid slurry B obtained in the step (3) by adding water to obtain orthotitanic acid slurry C;
(5) acid dissolution: and (4) adding hydrochloric acid into the orthotitanic acid slurry C obtained in the step (4), adjusting the pH value, heating to boil, curing, and quenching to obtain the rutile type calcined crystal seed.
2. The method of claim 1, wherein: preheating temperature of metatitanic acid in the step (1) is 95-100 ℃; the preheating temperature of the alkali liquor is 110-120 ℃; the alkali liquor is sodium hydroxide, and the concentration of the sodium hydroxide is 40-48%; the ratio of alkali to titanium is 1.68-1.75: 1; the reaction time is 1.8-2.2 h.
3. The method of claim 1, wherein: the step (1) also comprises a stirring step, wherein the stirring speed is 30-60r/min, and the stirring time is 1.8-2.2 h.
4. The production method according to claim 3, characterized in that: the step (1) also comprises a stirring step, wherein the stirring speed is 55r/min, and the stirring time is 1.8 h.
5. The method of claim 1, wherein: the washing process in the step (2) is carried out twice, the first washing temperature is 60-80 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 3-5: 1; the second washing temperature is 35-40 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 8-10: 1.
6. The method of claim 5, wherein: the washing process in the step (2) is that the first washing temperature is 60 ℃, and the volume ratio of the water addition amount to the orthotitanate is 5: 1; the temperature of the second water washing is 38 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 9: 1.
7. The method of claim 5, wherein: the washing process in the step (2) is that the first washing temperature is 80 ℃, and the volume ratio of the water addition amount to the orthotitanate is 4: 1; the temperature of the second water washing is 40 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 8: 1.
8. The method of claim 1, wherein: the temperature of the secondary water washing in the step (4) is 75-85 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 6-8: 1.
9. The method of claim 7, wherein: the temperature of the secondary water washing is 80 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 8: 1.
10. Use of the rutile titanium dioxide calcining seed crystal prepared by the preparation method of any one of claims 1 to 9 in the preparation of rutile titanium dioxide powder.
Technical Field
The invention belongs to the technical field of rutile titanium dioxide powder production, and particularly relates to a preparation method and application of rutile titanium dioxide calcination seed crystals.
Background
Titanium dioxide (TiO)2) The paint has the advantages of high refractive index, strong decoloring capacity, large covering power, strong weather resistance, good dispersibility, good color, stable physical and chemical properties and the like, and the paint prepared by using the titanium white has the advantages of bright color, less consumption, multiple varieties, long service life of paint films and the like, and is white pigment with the widest application. The performance indexes of the titanium dioxide mainly include color, covering power, tinting strength, oil absorption, particle shape, particle size distribution, dispersibility and the like. The rutile type titanium dioxide has the advantages of large covering power, high achromatism, strong pulverization resistance and the like, the photochemical stability and the glossiness of the rutile type titanium dioxide are better than those of anatase type titanium dioxide, the rutile type titanium dioxide is the best variety of white pigments, and the rutile type titanium dioxide has greater practical value.
The traditional titanium dioxide production method usually adopts a sulfuric acid method, metatitanic acid prepared by titanium liquid hydrolysis can be converted into a rutile crystal form only by calcining at high temperature for a long time, so that particle agglomeration or sintering is caused, crystal lattice defects of a product are excessive, crystal grains are overlarge and hard, the dispersibility and pigment performance of the product are further influenced, and meanwhile, certain difficulty is brought to titanium dioxide production by high-temperature operation. Therefore, in order to obtain rutile type titanium dioxide with excellent performance, the process conditions for metatitanic acid conversion must be controlled during the production process. The rutile type calcining seed crystal is added into metatitanic acid before calcining, and during calcining treatment, the seed crystal plays a role in inducing conversion in the process of converting titanium pigment from anatase type to rutile type, so that the conversion temperature is reduced, and simultaneously, the pigment particles have smooth appearance and excellent pigment performance. However, the preparation process of the rutile type calcination seed crystal is complicated, and the reports on the preparation of the rutile type calcination seed crystal are few at present, the preparation conditions disclosed in the prior art are wide in range, and the conditions for preparing the seed crystal by different methods are greatly different, so that the experimental results are generally difficult to repeat.
For example, Chinese patent application 200410045037.2 discloses a method for producing rutile titanium dioxide, and more particularly, to a method for preparing a calcination seed crystal for producing rutile titanium dioxide, wherein the technical scheme comprises the steps of alkaline cooking reaction, dilution hydrolysis, washing to remove impurities, acid neutralization, acid dissolution, cooling and the like in sequence, and the alkaline cooking reaction is carried out by heating in an alkaline-titanium ratio of 1.7:1-1.9: 1; the washing edulcoration adopt the filter-pressing mode to wash the edulcoration, this application has selected suitable alkali-titanium ratio, when reducing caustic soda consumption and washing load, make rutile crystal form content reach more than 98.5%, adopt the filter-pressing mode to wash the edulcoration, can once only accomplish the washing process, need not to wash repeatedly many times, shortened the washing time greatly, make the production cycle within 4 hours, wash the edulcoration under the pressure state, make the edulcoration effect further improve, thereby washing quality has been improved, but the seed crystal that this application prepared is added the volume ratio in the use, consequently, the cost of making the titanium pigment improve.
Chinese patent application 201611040952.1 discloses a method for preparing a calcination seed crystal for producing rutile titanium dioxide powder, which comprises the following steps: a. mixing sulfuric acid and metatitanic acid, and reacting at the temperature of 100-120 ℃ for 0.5-1h to obtain titanium sulfate clear solution; b. adding alkali liquor into the titanium sulfate clear solution for neutralization to obtain an orthotitanic acid suspension; c. filtering the titanic acid suspension, washing, and pulping a filter cake to obtain titanic acid slurry; d. adding hydrochloric acid into the orthotitanic acid slurry, adjusting the pH value to 2-2.5, then heating to 50-55 ℃, preserving heat for 10-20min, then adding hydrochloric acid, adjusting the pH value to 1.5-1.8, heating to boiling, curing for 30-45min, and then quenching to obtain the product. The method is simple and low in cost, the obtained calcined seed crystal rutile has high conversion rate and long storage time, and the seed crystal prepared by the method also has the problems of higher addition amount and higher cost for producing titanium dioxide.
However, the calcination seed crystal prepared by the calcination method disclosed in the prior art is still higher in calcination temperature in the production process of rutile titanium dioxide, and the addition amount is more, so that the improvement of the achromatism, the liquid-phase whiteness and the oil absorption of the obtained rutile titanium dioxide is not obvious.
Therefore, it is required to develop a seed crystal for calcining rutile titanium dioxide, which can reduce the calcining temperature and the addition amount in the production process of rutile titanium dioxide, and obviously improve the achromatism, the liquid phase whiteness and the oil absorption of the obtained rutile titanium dioxide.
Disclosure of Invention
The invention provides a preparation method and application of rutile titanium dioxide calcination seed crystal, which can reduce calcination temperature and addition amount of the obtained calcination seed crystal in the production process of rutile titanium dioxide by controlling various parameters in the preparation process of the rutile titanium dioxide calcination seed crystal, so that the achromatism, liquid phase whiteness and oil absorption of the obtained rutile titanium dioxide are obviously improved.
Specifically, the purpose of the invention can be realized by the following technical scheme:
a method for preparing rutile type titanium dioxide calcination seed crystal comprises the following steps:
(1) alkali dissolution: firstly, preheating metatitanic acid and alkali liquor, and then adding the preheated metatitanic acid into the preheated alkali liquor to form orthotitanate;
(2) primary water washing: washing the orthotitanic acid salt prepared in the step (1) with water, and filtering to obtain orthotitanic acid slurry A;
(3) neutralizing: adding hydrochloric acid into the orthotitanic acid slurry A obtained in the step (2), adjusting the pH value, and heating for reaction to obtain neutralized orthotitanic acid slurry B;
(4) and (3) secondary water washing: washing and filtering the neutralized orthotitanic acid slurry B obtained in the step (3) by adding water to obtain orthotitanic acid slurry C;
(5) acid dissolution: and (4) adding hydrochloric acid into the orthotitanic acid slurry C obtained in the step (4), adjusting the pH value, heating to boil, curing, and quenching to obtain the rutile type calcined crystal seed.
Preheating temperature of metatitanic acid in the step (1) is 95-100 ℃;
the preheating temperature of the alkali liquor in the step (1) is 110-120 ℃;
the alkali liquor in the step (1) is sodium hydroxide, and the concentration of the sodium hydroxide is 40-48%;
the ratio of alkali to titanium in the step (1) is 1.68-1.75: 1;
the reaction time in the step (1) is 1.8-2.2 h;
preferably, the preheating temperature of the metatitanic acid in the step (1) is 95 ℃, 96 ℃, 97 ℃, 98 ℃, 99 ℃ or 100 ℃;
the preheating temperature of the alkali liquor is 110 ℃, 111 ℃, 112 ℃, 113 ℃, 114 ℃, 115 ℃, 116 ℃, 117 ℃, 118 ℃, 119 ℃ or 120 ℃;
the concentration of the sodium hydroxide is 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47% or 48%;
the ratio of alkali to titanium is 1.68: 1. 1.69:1, 1.70:1, 1.71:1, 1.72:1, 1.73:1, 1.74:1, or 1.75: 1.
In a preferred embodiment, the preheating temperature of the metatitanic acid in the step (1) is 96 ℃; the preheating temperature of the alkali liquor is 118 ℃; the concentration of sodium hydroxide is 40%, the ratio of alkali to titanium is 1.75:1, and the reaction time is 2.2 h.
In another preferred embodiment, the preheating temperature of metatitanic acid described in the above step (1) is 98 ℃; the preheating temperature of the alkali liquor is 116 ℃; the concentration of sodium hydroxide is 42 percent, the ratio of alkali to titanium is 1.70:1, and the reaction time is 1.8 h.
In another preferred embodiment, the preheating temperature of the metatitanic acid in the above step (1) is 100 ℃; the preheating temperature of the alkali liquor is 120 ℃; the concentration of sodium hydroxide is 45%, the ratio of alkali to titanium is 1.68:1, and the reaction time is 2.0 h.
The step (1) also comprises a stirring step, wherein the stirring speed is 30-60 r/min; preferably 55r/min, and the stirring time is 1.8-2.2 h.
The washing process in the step (2) is carried out twice, the first washing temperature is 60-80 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 3-5: 1; the second washing temperature is 35-40 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 8-10: 1.
Preferably, the washing process in the step (2) is carried out in two times, the first washing temperature is 60 ℃, 70 ℃ or 80 ℃, and the volume ratio of the water addition amount to the orthotitanate is 3:1, 4:1 or 5: 1; the temperature of the second water washing is 35 ℃, 38 ℃ or 40 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 8:1, 9:1 or 10: 1.
In a preferred embodiment, the water washing process is that the temperature of the first water washing is 60 ℃, the volume ratio of the water addition amount to the ortho-titanate is 5: 1; the temperature of the second water washing is 38 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 9: 1.
In another preferred embodiment, the water washing process is that the temperature of the first water washing is 80 ℃, the volume ratio of the water addition amount to the ortho-titanate is 4: 1; the temperature of the second water washing is 40 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 8: 1.
And (3) adding hydrochloric acid for neutralization, wherein the concentration of the hydrochloric acid is 30-35%, the pH value is 2.8-3.0, and the temperature rise is 60-65 ℃.
Preferably, the hydrochloric acid is added for neutralization in the step (3), the concentration of the hydrochloric acid is 30%, 32%, 34% or 35%, the pH value is 2.8, 2.9 or 3.0, and the temperature rise temperature is 60 ℃, 61 ℃, 62 ℃, 63 ℃, 64 ℃ or 65 ℃.
In a preferred embodiment, the hydrochloric acid is added for neutralization in the step (3), the concentration of the hydrochloric acid is 32%, the pH value is 3.0, and the temperature rise temperature is 62 ℃.
In another preferred embodiment, the hydrochloric acid is added for neutralization in the step (3), the concentration of the hydrochloric acid is 35%, the pH value is 2.8, and the temperature rise temperature is 65 ℃.
The invention creatively adds a secondary washing step before the acid dissolution step, wherein the temperature of the secondary washing step is 75-85 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 6-8: 1.
Preferably, the temperature of the secondary water washing is 80 ℃, and the volume ratio of the water addition amount to the ortho-titanate is 8: 1.
In the acid dissolving step in the step (4), the concentration of hydrochloric acid is 30-35%, the pH value is 0.5-0.8, the temperature is increased to boiling at the speed of 0.7-0.9 ℃/min, curing is carried out for 30-60min, and water is added for quenching to obtain the rutile type calcining seed crystal.
Preferably, the concentration of hydrochloric acid in the acid dissolving step is 32%, the pH value is 0.6, the temperature is increased to boiling at the speed of 0.8 ℃/min, the mixture is aged for 60min, and water is added for quenching to obtain the rutile type calcining crystal seed.
Specifically, the invention provides a preparation method of rutile titanium dioxide calcination seed crystal, which comprises the following steps:
(1) alkali dissolution: firstly preheating metatitanic acid to 95-100 ℃, preheating alkali liquor to 110-120 ℃, then adding the preheated metatitanic acid into the preheated 38-48% sodium hydroxide solution, controlling the alkali-titanium ratio to be 1.68-1.75:1, and stirring and reacting at the speed of 30-60r/min for 1.8-2.2h to form orthotitanate;
(2) primary water washing: washing the orthotitanate prepared in the step (1) twice, wherein the temperature of the first washing is 60-80 ℃, and the volume ratio of the water addition amount to the orthotitanate is 3-5: 1; the second washing temperature is 35-40 ℃, the volume ratio of the water addition amount to the ortho-titanate is 8-10:1, and then the filtration is carried out to obtain ortho-titanate slurry A;
(3) neutralizing: adding 30-35% hydrochloric acid into the orthotitanic acid slurry A obtained in the step (2), adjusting the pH value to 2.8-3.0, and heating to 60-65 ℃ for reaction to obtain neutralized orthotitanic acid slurry B;
(4) and (3) secondary water washing: washing the neutralized orthotitanic acid slurry B obtained in the step (3) at 75-85 ℃ by controlling the volume ratio of water addition to orthotitanate to be 6-8:1, and then filtering to obtain orthotitanic acid slurry C;
(5) acid dissolution: adding 30-35% hydrochloric acid into the orthotitanic acid slurry C obtained in the step (4), adjusting the pH value to 0.5-0.8, heating to boiling at the speed of 0.7-0.9 ℃/min, curing for 30-60min, adding water and quenching to obtain the rutile type calcining seed crystal.
The invention also provides the application of the rutile titanium dioxide calcination seed crystal in the preparation of rutile titanium dioxide powder.
The crystal seed prepared by the method disclosed by the invention can be added into a titanium dioxide preparation system along with a salt treating agent, and washing and bleaching steps are not needed after the crystal seed is added, so that the use amount of the crystal seed is reduced, and TiO is used2The addition amount of the seed crystal is 1.2 to 2.5 percent, so that the rutile type titanium dioxide powder can be convertedThe rate reaches more than 99.5 percent.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the invention, various parameters in the rutile type titanium dioxide calcination crystal seed preparation process are reasonably controlled, namely preheating temperature of metatitanic acid and alkali liquor, alkali-titanium ratio and reaction time are controlled, so that the rutile calcination crystal seed conversion rate is obviously improved, and a large amount of researches show that the temperature has the greatest influence on the calcination crystal seed conversion rate in the crystal seed preparation process, and the alkali-titanium ratio is second, but each parameter can influence the conversion rate and the performance of a product in the material preparation process, and the rutile type titanium dioxide calcination crystal seed preparation process obviously improves the calcination crystal seed conversion rate by reasonably controlling the stirring speed in the alkali dissolving process;
(2) the invention adopts a mode of twice water washing in the first water washing process, the first time temperature is high, the water adding amount is small, the second time temperature is low, the water adding amount is large, and the invention unexpectedly discovers that the alkali and SO can be better washed by adopting the method to wash in the implementation process4 2-Washing away, and reducing the washing time;
(3) in the implementation process, the fact that the secondary water washing step is added before the acid dissolving step is unexpectedly found, so that the obtained seed crystal has high activity and improved stability;
(4) the common knowledge in the field can know that the cost of the calcined seed crystal is higher, the calcined seed crystal is added into a bleaching process in the conventional use process, but a washing step is carried out after the bleaching process, the calcined seed crystal is thinner, and is easy to penetrate and filter in the washing process, so that the waste is caused, and the addition amount of the calcined seed crystal is larger, but the rutile calcined seed crystal prepared by the technical improvement of the invention can be added into a rutile titanium dioxide powder preparation system along with a salt treating agent in a salt treatment step, so that the addition amount of the seed crystal is reduced, and the cost is saved;
(5) the calcination crystal seed prepared by the invention can ensure that the decoloring power, liquid phase whiteness and oil absorption of the obtained rutile titanium dioxide are obviously improved under the condition of less addition amount.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1 preparation method of rutile type titanium dioxide calcination seed crystal
The method comprises the following steps:
(1) alkali dissolution: firstly, preheating metatitanic acid to 96 ℃, and preheating alkali liquor to 118 ℃; then adding preheated metatitanic acid into preheated 45% sodium hydroxide solution, controlling the ratio of alkali to titanium to be 1.75:1, and stirring and reacting at the speed of 30r/min for 2.2h to form orthotitanate;
(2) primary water washing: washing the orthotitanate prepared in the step (1) twice, wherein the temperature of the first washing is 60 ℃, and the volume ratio of the water addition amount to the orthotitanate is 5: 1; the second water washing temperature is 38 ℃, the volume ratio of the water addition amount to the ortho-titanate is 9:1, and then the filtration is carried out to obtain ortho-titanate slurry A;
(3) neutralizing: adding 32% hydrochloric acid into the orthotitanic acid slurry A obtained in the step (2), adjusting the pH value to 3.0, and heating to 62 ℃ for reaction to obtain neutralized orthotitanic acid slurry B;
(4) and (3) secondary water washing: washing the neutralized orthotitanic acid slurry B obtained in the step (3) at 75 ℃ by controlling the volume ratio of water addition to orthotitanic acid salt to be 8:1, and then filtering to obtain orthotitanic acid slurry C;
(5) acid dissolution: and (4) adding 30% hydrochloric acid into the orthotitanic acid slurry C obtained in the step (4), adjusting the pH value to 0.5, heating to boiling at the speed of 0.7 ℃/min, curing for 60min, adding water, and quenching to obtain rutile type calcining seed crystals.
Example 2 preparation method of rutile type titanium dioxide calcination seed crystal
The method comprises the following steps:
(1) alkali dissolution: firstly preheating metatitanic acid to 95-100 ℃, preheating alkali liquor to 110 ℃, then adding the preheated metatitanic acid into a preheated 48% sodium hydroxide solution, controlling the ratio of alkali to titanium to be 1.68:1, and stirring and reacting at the speed of 60r/min for 1.8h to form orthotitanate;
(2) primary water washing: washing the orthotitanate prepared in the step (1) twice, wherein the temperature of the first washing is 70 ℃, and the volume ratio of the water addition amount to the orthotitanate is 3: 1; the second washing temperature is 36 ℃, the volume ratio of the water addition amount to the ortho-titanate is 9:1, and then the filtration is carried out to obtain ortho-titanate slurry A;
(3) neutralizing: adding 35% hydrochloric acid into the orthotitanic acid slurry A obtained in the step (2), adjusting the pH value to 2.8, and heating to 65 ℃ for reaction to obtain neutralized orthotitanic acid slurry B;
(4) and (3) secondary water washing: washing the neutralized orthotitanic acid slurry B obtained in the step (3) at 85 ℃, controlling the volume ratio of water addition to orthotitanic acid salt to be 8:1, and then filtering to obtain orthotitanic acid slurry C;
(5) acid dissolution: adding 30-35% hydrochloric acid into the orthotitanic acid slurry C obtained in the step (4), adjusting the pH value to 0.8, heating to boiling at the speed of 0.9 ℃/min, curing for 30min, adding water, and quenching to obtain rutile type calcining seed crystal.
Example 3 preparation method of rutile type titanium dioxide calcination seed crystal
The method comprises the following steps:
(1) alkali dissolution: firstly preheating metatitanic acid to 98 ℃, preheating alkali liquor to 116 ℃, then adding the preheated metatitanic acid into a preheated 46% sodium hydroxide solution, controlling the ratio of alkali to titanium to be 1.70:1, and stirring and reacting at the speed of 55r/min for 1.8h to form orthotitanate;
(2) primary water washing: washing the orthotitanate prepared in the step (1) twice, wherein the temperature of the first washing is 80 ℃, and the volume ratio of the water addition amount to the orthotitanate is 4: 1; the second water washing temperature is 40 ℃, the volume ratio of the water addition amount to the ortho-titanate is 8:1, and then the filtration is carried out to obtain ortho-titanate slurry A;
(3) neutralizing: adding 35% hydrochloric acid into the orthotitanic acid slurry A obtained in the step (2), adjusting the pH value to 2.8, and heating to 65 ℃ for reaction to obtain neutralized orthotitanic acid slurry B;
(4) and (3) secondary water washing: washing the neutralized orthotitanic acid slurry B obtained in the step (3) at the temperature of 80 ℃ by controlling the volume ratio of water addition to orthotitanic acid salt to be 8:1, and then filtering to obtain orthotitanic acid slurry C;
(5) acid dissolution: adding 32% hydrochloric acid into the orthotitanic acid slurry C obtained in the step (4), adjusting the pH value to 0.6, heating to boiling at the speed of 0.8 ℃/min, curing for 60min, adding water and quenching rapidly to obtain rutile type calcining seed crystal.
Example 4 preparation method of rutile type titanium dioxide calcination seed crystal
The method comprises the following steps:
(1) alkali dissolution: firstly preheating metatitanic acid to 100 ℃, preheating alkali liquor to 120 ℃, then adding the preheated metatitanic acid into a preheated 45% sodium hydroxide solution, controlling the ratio of alkali to titanium to be 1.68:1, and stirring and reacting at the speed of 50r/min for 2.0h to form orthotitanate;
(2) primary water washing: washing the orthotitanate prepared in the step (1) twice, wherein the temperature of the first washing is 75 ℃, and the volume ratio of the water addition amount to the orthotitanate is 3.5: 1; the temperature of the second water washing is 38 ℃, the volume ratio of the water addition amount to the ortho-titanate is 9.5:1, and then the filtration is carried out to obtain ortho-titanate slurry A;
(3) neutralizing: adding 30% hydrochloric acid into the orthotitanic acid slurry A obtained in the step (2), adjusting the pH value to 2.9, and heating to 65 ℃ for reaction to obtain neutralized orthotitanic acid slurry B;
(4) and (3) secondary water washing: washing the neutralized orthotitanic acid slurry B obtained in the step (3) at 82 ℃, controlling the volume ratio of water addition to orthotitanate to be 6.5:1, and then filtering to obtain orthotitanic acid slurry C;
(5) acid dissolution: adding 32% hydrochloric acid into the orthotitanic acid slurry C obtained in the step (4), adjusting the pH value to 0.7, heating to boiling at the speed of 0.75 ℃/min, curing for 50min, adding water and quenching rapidly to obtain rutile type calcining seed crystal.
Comparative example 1
The difference from example 3 is that: the primary water washing step in the step (2) is as follows: washing twice, wherein the temperature of the first washing is 55 ℃, and the volume ratio of the water addition amount to the orthotitanate is 4: 1; the second washing temperature was 55 ℃ and the volume ratio of the amount of water added to orthotitanate was 8:1, i.e., the washing temperatures were the same for the two times, and the other operations and steps were the same as in example 3.
Comparative example 2
The difference from example 3 is that: the primary water washing step in the step (2) is as follows: washing twice, wherein the temperature of the first washing is 80 ℃, and the volume ratio of the water addition amount to the orthotitanate is 4: 1; the temperature of the second water washing was 40 ℃ and the volume ratio of the amount of water added to orthotitanate was 4:1, i.e., the volume ratio of the amount of water added to orthotitanate was the same for both times, and the other operations and steps were the same as in example 3.
Comparative example 3
The difference from example 3 is that: the primary water washing step in the step (2) is as follows: washing twice, wherein the first washing temperature is 40 ℃, and the volume ratio of the water addition amount to the orthotitanate is 4: 1; the temperature of the second water washing was 80 ℃ and the volume ratio of the amount of water added to orthotitanate was 8:1, i.e., the first temperature was low and the second temperature was high, and the other operations and steps were the same as in example 3.
Comparative example 4
The difference from example 3 is that: the primary water washing step in the step (2) is as follows: washing twice, wherein the temperature of the first washing is 80 ℃, and the volume ratio of the water addition amount to the orthotitanate is 8: 1; the temperature of the second water washing was 40 ℃ and the volume ratio of the added water amount to orthotitanate was 4:1, i.e., the volume ratio of the first added water amount to orthotitanate was high, the volume ratio of the second added water amount to orthotitanate was low, and the other operations and steps were the same as in example 3.
Comparative example 5
The difference from example 3 is that: the second water washing in step (4) was omitted, and the other operations and steps were the same as in example 3.
Comparative example 6
The difference from example 3 is that: the stirring speed in step (1) was 65r/min, and the other operations and steps were the same as in example 3.
Comparative example 7
The difference from example 3 is that: the stirring speed in step (1) was 25r/min, and the other operations and steps were the same as in example 3.
Comparative example 8
Calcined seed crystals prepared in chinese patent application CN 101311120A.
Effect test:
test example rutile conversion test of seed crystals
The detection method comprises the following steps: determination of rutile content of titanium dioxide pigment ASTM D3720-99, a small amount of seed crystal is taken for acid melting, dried at 105 ℃, and then detected.
1. Principle of
Each crystal has its own specific crystal structure and lattice parameters, and different phases produce different characteristic spectral lines. Therefore, according to the relationship between the diffraction intensity and the concentration, the diffraction intensity of the specific crystal face of the phase to be measured in the diffraction sample is measured, and the rutile type and anatase type contents are calculated, so that the rutile conversion rate is obtained.
2. Instrument for measuring the position of a moving object
X-ray diffractometer and sampling machine
3. Result and data processing
The rutile content is calculated as follows:
in the formula:
k-constant related to instrument phase and phase concentration
Ia-net intensity of anatase diffraction peak
IrNet intensity of rutile diffraction peak
WaMass of anatase
WrMass of rutile
TABLE 1
Examples of the invention
Conversion rate%
Example 1
99.85
Example 2
99.55
Example 3
99.86
Example 4
99.63
Comparative example 1
99.04
Comparative example 2
99.10
Comparative example 3
98.65
Comparative example 4
98.85
Comparative example 5
99.16
Comparative example 6
98.24
Comparative example 7
98.37
Comparative example 8
99.28
According to the detection data in table 1 above, it can be seen that the conversion rates of the rutile in the calcined seed crystals prepared in examples 1-4 of the present invention can reach more than 99.5%, and especially the conversion rates of the rutile in the calcined seed crystals prepared in example 3 can reach 99.86%, which are significantly higher than those in the prior art (comparative example 8); comparative examples 1 to 4 change the specific operation steps in the first water washing process, i.e. changing the temperature or the volume ratio of the added water to the orthotitanate may affect the conversion rate of the finally obtained calcined seed crystal to a certain extent, and comparative example 5 omits the second water washing step, although the influence on the conversion rate is small, the stirring rate may significantly affect the conversion rate of the finally obtained calcined seed crystal, because the stirring process may affect the change of the crystal form in the alkali dissolving step, thereby affecting the conversion rate of the finally obtained seed crystal.
Application example 1
The seed crystal prepared in the above embodiment is used for preparing rutile type titanium dioxide powder, and the specific addition amount is 4.0% (based on TiO)2Calculated), the relevant properties of the titanium dioxide obtained by the conventional and same rutile type titanium dioxide powder preparation method (such as the method disclosed in chinese patent application 2020105464296) in the field are shown in table 2 below.
TABLE 2
Examples of the invention
Calcination temperature C
Conversion of rutile%
Whiteness degree
Oil absorption/g
Example 1
920
99.82
99.5
14.5
Example 2
925
99.67
98.5
15.2
Example 3
900
99.85
99.6
14.2
Example 4
900
99.70
99.0
15.0
Comparative example 1
900
99.42
95.1
18.2
Comparative example 2
900
99.45
95.2
18.5
Comparative example 3
900
99.38
96.0
19.6
Comparative example 4
900
99.35
96.1
19.8
Comparative example 5
900
99.58
97.2
16.4
Comparative example 6
900
99.50
94.1
18.5
Comparative example 7
900
99.52
94.1
19.0
Comparative example 8
900
99.26
91.5
18.2
According to the detection results in the table 2, the seed crystal prepared by the invention is used for preparing the titanium dioxide, and the conventional preparation method is adopted, namely, the rutile calcining seed crystal is firstly added for hydrolysis in the preparation process, then the hydrolysate is washed and bleached, and then the filtrate is subjected to salt treatment, so that the seed crystal prepared by the invention can obviously reduce the calcining temperature, the rutile conversion rate can reach 99.85% under the condition of 900 ℃, and the whiteness and the oil absorption of the prepared titanium dioxide are obviously improved. The specific operation in the first water washing process is changed in the comparative examples 1-4, the activity of the seed crystal is influenced to a certain extent, so that the conversion rate, whiteness and oil absorption of the prepared titanium dioxide are further influenced, and similarly, the whiteness and oil absorption of the titanium dioxide are influenced to a certain extent by omitting the secondary washing step in the comparative example 4; comparative examples 6-7 varying the stirring speed affected the formation in the mirror and thus the titanium dioxide performance.
Application example 2
The seed crystals obtained in the above-mentioned specific examples 1 to 4 were used to prepare rutile type titanium dioxide powder in an amount of 2.0% (based on TiO)2In the preparation method of the titanium dioxide), rutile calcination crystal seeds are added together with a salt treatment agent, and filtering is carried out after salt treatment, namely, washing and bleaching steps are not needed after the crystal seeds are added, so that waste in a mirror is reduced, and the obtained titanium dioxide has relevant properties as shown in the following table 3.
TABLE 3
Examples of the invention
Calcination temperature C
Conversion of rutile%
Whiteness degree
Oil absorption/g
Example 1
920
99.77
99.3
14.9
Example 2
925
99.65
98.2
15.8
Example 3
900
99.80
99.5
14.5
Example 4
900
99.62
98.8
15.7
Comparative example 4
900
96.24
94.2
20.5
Comparative example 8
900
95.12
90.1
20.8
According to the detection data in the table 3, the seed crystal prepared by the invention can be added into a titanium dioxide preparation system along with a salt treating agent, and the seed crystal does not need to be washed and bleached after being added, so that the addition amount of the seed crystal is reduced, the conversion rate of rutile can still reach more than 99.5% when the addition amount is 2.0%, and the whiteness and the oil absorption of the obtained titanium dioxide are not obviously influenced; the step of secondary washing is omitted in the comparative example 4, the generation of the titanium dioxide is obviously influenced without washing and bleaching in the preparation process of the titanium dioxide, so that the performance of the titanium dioxide is influenced, and the preparation of the titanium dioxide is also obviously influenced when the addition amount of the seed crystal prepared in the comparative example 8 is 2.0 percent and the washing is not carried out in the preparation process of the titanium dioxide.
The above detailed description is specific to one possible embodiment of the present invention, and the embodiment is not intended to limit the scope of the present invention, and all equivalent implementations or modifications without departing from the scope of the present invention should be included in the technical scope of the present invention.