A process for the treatment of titanium-containing solid residues produced in the preparation of polyolefin catalysts

Abstract

The application discloses a treatment method of titanium-containing solid slag generated in preparation of a polyolefin catalyst, and comprises the following steps: S1, uniformly mixing titanium-containing solid slag with ammonium carbonate or ammonium bicarbonate through stirring to obtain titanium ammonium material; S2, performing stirring hydrolysis on the obtained titanium ammonium material to obtain a hydrolysis liquid; S3, performing solid-liquid separation on hydrated titanium dioxide slurry in a lower layer after layering to obtain hydrated titanium dioxide, and removing oil from ammonium chloride solution containing floating grease in an upper layer; and S4, mixing the separated liquid obtained after the solid-liquid separation in S3 with the ammonium chloride solution after oil removal to obtain a combined liquid, and sequentially performing evaporation concentration, crystallization and centrifugal dehydration on the combined liquid to obtain ammonium chloride. The application can simultaneously recover titanium dioxide and by-product ammonium chloride, has high treatment efficiency, and does not generate waste water and solid waste in the whole production process, which is beneficial to environmental protection. Meanwhile, the whole process operation is simple, the equipment requirement is low, the cost is low, and the practicability is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium-containing solid residue treatment, and particularly relates to a treatment method of titanium-containing solid residue generated in preparation of a polyolefin catalyst. BACKGROUND

[0002] Ziegler Natta catalyst is the most widely used catalyst in the polyolefin industry. The most common method for industrial preparation of Ziegler Natta catalyst is: a solution or suspension of magnesium compound reacts with excess TiCl4 to form an active MgCl2 carrier, and then is complexed with TiCl4 and an internal electron donor, and then is subjected to steps such as pressure filtration, titanium treatment and washing to obtain a solid catalyst. This process produces a large amount of TiCl4 waste liquid that does not participate in the reaction, which is usually recovered by rectification or distillation. However, in the actual rectification process of the material, the titanium tetrachloride in the waste liquid cannot be completely recovered. The pot residue is precipitated after cooling, and the titanium-containing solid residue is released when it comes into contact with wet air. The titanium-containing solid residue reacts violently with water and releases a large amount of corrosive hydrogen chloride smoke and heat. Enterprises usually self-treat or outsource the treatment of the titanium-containing solid residue as solid waste.

[0003] The commonly used treatment method is to hydrolyze the titanium-containing solid residue, and then add an alkaline neutralizing agent such as Ca(OH)2 or NaOH to neutralize the strong acid hydrolysis waste liquid. However, this treatment method generates a large amount of heat during the hydrolysis of the titanium-containing solid residue and the neutralization process with a strong base, which requires high equipment. At the same time, a large amount of waste liquid and waste residue and part of the oil and fat organic matter are generated, and the titanium element, chlorine element and oil and fat organic matter cannot be fully recovered or resourcefully utilized, which has the problems of high treatment cost, large amount of waste and the like.

[0004] To solve the above problems, Chinese patent CN115974143A discloses a method for treating solid waste of spherical polypropylene catalyst and a method for preparing titanium dioxide. The method hydrolyzes the titanium-containing solid waste of polypropylene catalyst by contacting it with water, heats the hydrolysis liquid to 80-110 DEG C at a rate of 0.5-5 DEG C / min for constant temperature treatment, and washes and calcines the solid phase obtained by solid-liquid separation to obtain titanium dioxide. This method only recovers titanium dioxide by simply hydrolyzing titanium-containing solid waste with water, but the hydrolysis releases a large amount of corrosive hydrogen chloride gas, which requires extremely high corrosion resistance of the equipment, making it difficult to achieve batch production and stable operation. Meanwhile, the hydrolysis of titanium tetrachloride is a violent exothermic reaction. To ensure the smooth progress of the hydrolysis process, sufficient cooling and heat exchange are required to remove the heat of reaction in time. Chinese patent CN103769406A provides a method for treating titanium-containing waste residue of polyolefin catalyst. The invention uses calcium hydroxide instead of the commonly used sodium hydroxide, which releases less heat and has a milder reaction. However, this method wastes a large amount of Ti and Cl elements, and actually still releases a large amount of heat, which needs to be controlled by a reactor with a water jacket and by controlling the addition rate of titanium-containing waste residue to control the reaction temperature, resulting in low processing efficiency. Therefore, the existing methods for treating titanium-containing solid residue generated during the preparation of polyolefin catalysts have corresponding deficiencies, and therefore need to be improved. SUMMARY

[0005] The purpose of the present application is to provide a method for treating titanium-containing solid residue generated during the preparation of polyolefin catalysts, which can simultaneously recover titanium dioxide and by-product ammonium chloride, has high processing efficiency, and produces no wastewater or solid waste during the entire production process, which is beneficial to environmental protection. At the same time, the entire process is simple to operate, requires low equipment, has low cost, and has strong practicality.

[0006] To achieve the above purpose, the following technical solutions are adopted:

[0007] A method for treating titanium-containing solid residue generated during the preparation of polyolefin catalysts, comprising the following steps:

[0008] S1: uniformly stirring and mixing the titanium-containing solid residue with ammonium carbonate or ammonium bicarbonate to obtain a titanium ammonium material;

[0009] S2: stirring and hydrolyzing the obtained titanium ammonium material to obtain a hydrolysis liquid;

[0010] S3: static layering, solid-liquid separation of the hydrated titanium dioxide slurry in the lower layer to obtain hydrated titanium dioxide, and oil removal of the ammonium chloride solution containing floating oil in the upper layer;

[0011] S4: mixing the separation liquid obtained after solid-liquid separation in S3 with the oil-removed ammonium chloride solution to obtain a combined liquid, and sequentially evaporating and concentrating, crystallizing, and centrifugal dewatering the combined liquid to obtain ammonium chloride.

[0012] Further, in the S1, the titanium-containing solid residue and ammonium carbonate or ammonium bicarbonate are conveyed into a mixing device in a predetermined ratio for stirring and mixing, wherein the mixing device is a horizontal stirrer or a mixing blender.

[0013] Further, the titanium-containing solid residue and ammonium carbonate or ammonium bicarbonate are mixed in a ratio of the neutralization equivalent of HCl generated by hydrolysis of the titanium-containing solid residue and ammonium carbonate or ammonium bicarbonate, or the pH of the reaction solution at the end of the hydrolysis reaction is controlled to be 3-9.

[0014] Further, in the S2, the liquid-solid ratio (v / m) is (3-10):1, the stirring time is 10-60 min, and the pH of the hydrolysis solution is 3-9.

[0015] Further, the liquid-solid ratio (v / m) is (4-5):1, and the pH of the hydrolysis solution is 3-5.

[0016] Further, in the S3, the hydrated titanium dioxide slurry in the lower layer is subjected to solid-liquid separation by pressure filtration or centrifugal dewatering.

[0017] Further, in the S3, the hydrated titanium dioxide slurry in the lower layer is first pumped into a concentration tank for further concentration, and then subjected to solid-liquid separation.

[0018] Further, in the S3, the obtained hydrated titanium dioxide is calcined to prepare a related crystal form titanium dioxide product.

[0019] Further, in the S4, the evaporation condensate obtained by evaporating and concentrating the combined liquid can be used for stirring and hydrolyzing the titanium ammonium material in the S2.

[0020] By using the above scheme, the application has the following advantages:

[0021] 1) The ammonium bicarbonate or ammonium carbonate and TiCl4 hydrolysis endothermic and exothermic processes are controlled by their characteristics, which increases the reaction temperature without the need to add cooling equipment or control the feeding speed of the reaction system, and the process operation is simple;

[0022] 2) The released HCl in the hydrolysis and the released NH3 in the decomposition of ammonium bicarbonate or ammonium carbonate contact to form NH4Cl, at the same time, the CO2 released by the decomposition of ammonium bicarbonate or ammonium carbonate and the floating oil form a bubble foam layer on the surface of the hydrolysis reaction solution, which has a "mist suppressing" effect, can inhibit the acid mist generated in the hydrolysis reaction from volatilizing and escaping, and can reduce the escape of corrosive gas, thereby avoiding the corrosion of equipment and being beneficial to environmental protection;

[0023] 3) The oil and fat organic matter entrained in the hydrated titanium dioxide can be gasified and removed in the high-temperature calcination process, thereby improving the quality of the titanium dioxide product. Attached Figure Description

[0024] Fig. 1 This is a flowchart of the present invention;

[0025] Fig. 2 This is a schematic flowchart of the present invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] Reference Figs. 1-2 As shown, the present invention provides a method for treating titanium-containing solid slag generated during the preparation of polyolefin catalysts, comprising the following steps:

[0028] S1: Mix titanium-containing solid slag with ammonium carbonate or ammonium bicarbonate until homogeneous to obtain titanium ammonium material.

[0029] In this step, titanium-containing solid slag and ammonium carbonate or ammonium bicarbonate can be transported to a mixing device in a certain proportion for stirring and mixing to obtain titanium ammonium material. The mixing device is a horizontal mixer, a mixing machine, or other conventional stirring and mixing device. The ratio of titanium-containing solid slag to ammonium carbonate or ammonium bicarbonate is the neutralization equivalent of HCl generated from the hydrolysis of titanium-containing solid slag and ammonium carbonate or ammonium bicarbonate, or in step S2, the pH of the reaction solution after the hydrolysis reaction is completed is controlled to be 3 to 9.

[0030] S2: The obtained titanium ammonium material is stirred and hydrolyzed to obtain a hydrolysate.

[0031] In this step, the obtained titanium ammonium material can be fed into a hydrolysis device and stirred for hydrolysis. The liquid-to-solid ratio is (v / m) = (3-10):1, the stirring time is 10-60 min, and a hydrolysate with pH = 3-9 is obtained. In a preferred embodiment, the liquid-to-solid ratio is (v / m) = (4-5):1, and the hydrolysate pH = 3-5.

[0032] S3: Allow to stand and separate into layers. Perform solid-liquid separation on the hydrated titanium dioxide slurry in the lower layer to obtain hydrated titanium dioxide. Remove the oil from the ammonium chloride solution containing floating grease in the upper layer.

[0033] After the hydrolysis reaction is completed, the mixture is allowed to stand and separate into layers. The lower layer is a hydrated titanium dioxide slurry, which is separated into solid and liquid by means such as pressure filtration or centrifugal dehydration. Alternatively, the lower slurry can be pumped into a concentration tank for further concentration before solid-liquid separation. Hydrated titanium dioxide can be obtained after solid-liquid separation. The hydrated titanium dioxide can be further calcined to prepare related crystalline titanium dioxide products. The upper layer is an ammonium chloride solution with floating oil on the liquid surface.

[0034] In steps S2-S3, the hydrolysis solution pH is controlled to be less than or equal to 9.0, which can effectively control the generation of magnesium hydroxide in the neutralization process and affect the quality of the titanium dioxide product; and preferably, the hydrolysis solution pH is controlled to be 3-5, which can effectively control the escape of ammonia gas generated in the evaporation process for preparing by-product ammonium chloride, and at the same time, the oil and fat entrained in the hydrated titanium dioxide will be gasified at high temperature in the calcination process, thereby not affecting the quality of the titanium dioxide product. In addition, the dissolution of ammonium bicarbonate or ammonium carbonate is endothermic, and the heat release of TiCl4 hydrolysis, and the two characteristics control the process reaction temperature to rise, without the need to increase cooling equipment or control the feeding speed of the reaction system, the reaction process system temperature is less than or equal to 40°C, and the process operation is simple.

[0035] S4: mixing the separated liquid obtained after the solid-liquid separation in S3 with the ammonium chloride solution after oil removal to obtain a combined liquid, and sequentially performing evaporation concentration, crystallization and centrifugal dewatering on the combined liquid to obtain ammonium chloride.

[0036] In steps S3-S4, the ammonium chloride solution with floating oil on the liquid surface can be deoiled by an oil separation device, and then the deoiled ammonium chloride solution is mixed with the filter press liquid or the centrifugal dewatering mother liquor of the concentrated slurry after solid-liquid separation, and then the combined liquid obtained by mixing is sequentially subjected to evaporation concentration, crystallization and centrifugal dewatering to obtain by-product ammonium chloride. At the same time, the floating oil obtained after oil removal can be sold as fuel or by-product, and the evaporation condensate water obtained by evaporation concentration can be returned to the section for preparing titanium dioxide by hydrolysis, and the entire process does not generate waste water and solid waste, which is beneficial to environmental protection.

[0037] The following is described with specific examples:

[0038] This example uses a powdered titanium-containing solid residue generated in the production of a polypropylene catalyst (which reacts violently with water and releases a large amount of heat and corrosive hydrogen chloride smoke), wherein the titanium content is 22.3wt%, and the chlorine content is greater than or equal to 50wt%. The ammonium bicarbonate used in this example has a content of greater than or equal to 99wt%, and in addition, the specific conditions not specified in the example are carried out under conventional conditions or the conditions recommended by the manufacturer. In addition, the reagents or instruments not specified by the manufacturer are all conventional products that can be purchased on the market.

[0039] The specific implementation steps are as follows:

[0040] 1) Add 1 kg of ammonium bicarbonate and 1 kg of titanium-containing solid residue into a 15L reaction kettle, stir and mix uniformly to obtain a titanium ammonium material;

[0041] 2) Pour 10L water into the stirred and mixed uniform titanium ammonium material reaction kettle, stir and react for 30min, the temperature change of the reaction process is 20-35℃ at normal temperature and pressure, and a hydrolysis liquid with pH=5 is obtained; then, the liquid is allowed to stand and separate, the upper layer of the floating oil and grease ammonium chloride solution is transferred to a separatory funnel, the lower layer is filtered and washed, and titanium dioxide hydrate is obtained; the obtained titanium dioxide hydrate is calcined in a muffle furnace at a temperature of 900℃ to obtain white titanium dioxide powder which is easy to crush, wherein the TiO2 content is ≥98wt%;

[0042] 3) The oil and water separation of the liquid surface floating oil and grease ammonium chloride solution in the separatory funnel is performed, the ammonium chloride solution is obtained, the filtered liquid is combined, evaporation crystallization is performed, and by-product ammonium chloride is obtained, wherein the ammonium chloride content is ≥93wt%.

[0043] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the treatment of titanium-containing solid residues produced in the preparation of polyolefin catalysts, characterized in that, The method comprises the following steps: S1: uniformly mixing titanium-containing solid residue with ammonium carbonate or ammonium bicarbonate to obtain titanium ammonium material; S2: stirring and hydrolyzing the obtained titanium ammonium material to obtain hydrolysis liquid; S3: standing and layering, solid-liquid separation of titanium dioxide hydrate slurry in the lower layer to obtain titanium dioxide hydrate, and oil removal of ammonium chloride solution containing floating oil and fat in the upper layer; S4: mixing the separated liquid obtained after solid-liquid separation in S3 with the oil-removed ammonium chloride solution to obtain combined liquid, and sequentially performing evaporation concentration, crystallization and centrifugal dehydration on the combined liquid to obtain ammonium chloride; In S1, the titanium-containing solid residue and ammonium carbonate or ammonium bicarbonate are conveyed to a mixing device in a predetermined proportion for stirring and mixing, wherein the mixing device is a horizontal stirrer or a mixing mixer. The titanium-containing solid residue and ammonium carbonate or ammonium bicarbonate are mixed in a proportion of the neutralization equivalent of HCl generated by hydrolysis of the titanium-containing solid residue and ammonium carbonate or ammonium bicarbonate, or the pH of the reaction liquid at the end of the hydrolysis reaction is controlled to be 3-9. In S2, the liquid-solid ratio (v / m) is (3-10):1, the stirring time is 10-60 min, and the pH of the hydrolysis liquid is 3-9. The liquid-solid ratio (v / m) is (4-5):1, and the pH of the hydrolysis liquid is 3-5.

2. The process for treating titanium-containing solid residue produced from polyolefin catalyst according to claim 1, characterized in that, In S3, the titanium dioxide hydrate slurry in the lower layer is subjected to solid-liquid separation by pressure filtration or centrifugal dehydration.

3. The process for treating titanium-containing solid residue produced from polyolefin catalyst according to claim 1, characterized in that, In S3, the titanium dioxide hydrate slurry in the lower layer is first pumped into a concentration tank for further concentration, and then subjected to solid-liquid separation.

4. The method of claim 1, wherein the titanium-containing solid residue produced from the production of the polyolefin catalyst is treated by, In S3, the obtained titanium dioxide hydrate is calcined to prepare a related crystal type titanium dioxide product.

5. The method of claim 1, wherein the titanium-containing solid residue produced from the production of the polyolefin catalyst is treated by, In S4, the evaporation condensate obtained by evaporating and concentrating the combined liquid can be used for stirring and hydrolyzing the titanium ammonium material in S2.

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