CN109370638B

CN109370638B - Adsorption desulfurization method of FCC gasoline

Info

Publication number: CN109370638B
Application number: CN201811347284.6A
Authority: CN
Inventors: 陈开龙; 庄琴珠
Original assignee: Boxing Xingye Fine Chemical Industry Development Co Ltd
Current assignee: Boxing Xingye Fine Chemical Industry Development Co., Ltd
Priority date: 2018-11-13
Filing date: 2018-11-13
Publication date: 2020-12-04
Anticipated expiration: 2038-11-13
Also published as: CN109370638A

Abstract

The invention relates to an adsorption desulfurization method of FCC gasoline, the FCC gasoline is cut into light gasoline fraction and heavy gasoline fraction, the light gasoline fraction is contacted with an adsorption desulfurization catalyst, and the adsorption desulfurization catalyst comprises the following components in percentage by weight: 25.0-50.0 wt% of zinc oxide, 0.5-25.0 wt% of nickel oxide, 2.0-55.0 wt% of ZSM-5 molecular sieve, 20.0-50.0 wt% of macroporous alumina and 1.0-25.0 wt% of cerium-zirconium solid solution; the reaction process conditions are as follows: the reaction temperature is 180 ℃ and 320 ℃, the reaction pressure is 0.5-2.5MPa, and the volume space velocity is 3-8h^‑1The volume ratio of hydrogen to oil is 1-50. The catalyst has high sulfur penetration capacity, low olefin saturation rate and good regeneration and reduction stability.

Description

Adsorption desulfurization method of FCC gasoline

Technical Field

The invention relates to an adsorption desulfurization method of FCC gasoline.

Background

The gasoline adsorption desulfurization technology becomes an important means for upgrading the quality of oil products, and the technology has the characteristics of high sulfur selectivity, small octane value loss and low investment and operation cost. Most of the existing adsorbents are desulfurization adsorbents prepared by using a silicon/aluminum material as a carrier and zinc oxide/active metal (such as nickel) as an active component, and the adsorption activity is reduced due to the formation of carbon deposit, zinc sulfide, zinc silicate and zinc aluminate in the reaction process, so that the regeneration reduction is needed to recover the activity of the adsorbent. The octane number loss is large due to the occurrence of olefin saturation.

The existing gasoline adsorption desulfurization method mainly comprises the following steps: (1) and (3) desulfurization treatment: mixing and contacting sulfur-containing hydrocarbon and hydrogen donor with an adsorbent to obtain desulfurized sulfur-containing hydrocarbon and a sulfur-carrying spent catalyst; (2) regeneration treatment: mixing and contacting the sulfur-carrying spent regenerant with oxygen-containing regeneration gas to obtain a regenerant; (3) reduction treatment: mixing and contacting the regenerant with a reducing gas to obtain a reducing regenerant which is recycled as an adsorbent; and refluxing the reduction regenerant obtained in the step (3) as an adsorbent to the step (1) to form an adsorbent circulating flow path. With continuous cyclic reduction and regeneration of the adsorbent, the adsorbent often has the problems of fragmentation (strength reduction) and activity reduction, and further the desulfurization efficiency is reduced.

CN103657709A discloses a reactive adsorption desulfurization-aromatization reaction process and a catalyst thereof. The catalyst not only has the function of reaction adsorption desulfurization when the catalytic cracking gasoline raw material is hydrotreated, but also can be coupled with the reaction adsorption desulfurization reaction and the aromatization reaction, so that the octane number of the product is not obviously reduced while deep desulfurization can be achieved when the developed process and the catalyst thereof modify the catalytic cracking gasoline raw material. The FCC gasoline with the sulfur content of 300-800ppm is used as the raw material, the S content of the product gasoline is less than 10ppm, the olefin content is reduced by 10 percent, the RON loss is less than 1, and the gasoline yield is more than 95 percent. CN101905161A relates to a catalytic gasoline adsorption desulfurization catalyst and preparation and application thereof; the weight percentage composition is as follows: 10-85% of active zinc oxide, 5-80% of white carbon black, 5-30% of alumina and 4-45% of nickel oxide; (1) carrying out pyrolysis on titanium tetrachloride at 1400 ℃ under hydrogen atmosphere to obtain fumed silica; (2) mixing active zinc oxide, fumed silica, alumina and nickel salt uniformly to form slurry; (3) spraying the mixture into balls or injecting oil into balls; (4) drying the particles in the step (3), wherein the drying temperature is 110-150 ℃; (5) roasting the microspheres obtained in the step (4) at the roasting temperature of 300-550 ℃; the prepared adsorption desulfurization catalyst has the advantages of good strength, high wear resistance, good desulfurization activity, small octane number loss and low operation cost, and is very suitable for a moving bed adsorption desulfurization process.

CN108018069A discloses a sulfur-containing hydrocarbon adsorption desulfurization method and device, the method comprises: and (3) desulfurization treatment: mixing and contacting sulfur-containing hydrocarbon and hydrogen donor with an adsorbent to obtain desulfurized sulfur-containing hydrocarbon and a sulfur-carrying spent catalyst; regeneration treatment: mixing and contacting the sulfur-carrying spent regenerant with oxygen-containing regeneration gas to obtain a regenerant; reduction treatment: mixing and contacting the regenerant with a reducing gas to obtain a reducing regenerant which is recycled as an adsorbent; the adsorbent contains active metal monomers, and the reaction conditions of the reduction treatment comprise: taking a gas mixture containing non-hydrogen reducing gas as reducing gas, wherein the reducing temperature is 250-420 ℃, the reducing pressure is 0-3 MPa, and the volume space velocity of the reducing gas is 50-1000 h^-1The reduction time is 0.5-3 h. The method suppresses the formation of zinc silicate in the reduction reaction and desulfurization reaction, thereby improving the activity and strength of the regenerant. CN201310292325.7 discloses a method for adsorption desulfurization of catalytically cracked gasoline, which comprises the steps of using the catalytic gasoline subjected to selective hydrodesulfurization as a raw material (the sulfur content is less than 150 mu g/g), and performing cutting fractionation by a fractionating tower to obtain light gasoline and heavy gasoline. The light gasoline enters a fixed bed reactor to be subjected to non-hydrogenation physical adsorption desulfurization, the olefin content is not reduced by the physical adsorption desulfurization, and the octane number of the product is not lost; heavy gasoline enters a fixed bed reactor to be subjected to hydro-adsorption desulfurization and reactionThe product is blended with the light gasoline physical adsorption desulfurization product to obtain the clean gasoline product meeting the Euro V sulfur index requirement. The prior catalyst has the problems that the sulfur capacity is possibly low, zinc silicate and zinc aluminate are easily formed during regeneration and reduction, the adsorption activity is reduced, the octane number loss is large due to the occurrence of olefin saturation reaction, and the like. Therefore, it is necessary to develop a catalyst and a desulfurization process thereof, which have high breakthrough sulfur capacity, small octane number loss, good regeneration and reduction stability, and high adsorption desulfurization activity.

Disclosure of Invention

The invention provides an adsorption desulfurization method of FCC gasoline, which has high sulfur capacity of a catalyst, small octane value loss, good regeneration and reduction stability and high adsorption desulfurization activity.

An FCC gasoline adsorption desulfurization method adopts a fixed bed reactor, FCC gasoline is cut into light gasoline fraction and heavy gasoline fraction, the light gasoline fraction is contacted with an adsorption desulfurization catalyst, and the adsorption desulfurization catalyst comprises the following components in percentage by weight: 25.0-50.0 wt% of zinc oxide, 0.5-25.0 wt% of nickel oxide, 2.0-55.0 wt% of ZSM-5 molecular sieve, 20.0-50.0 wt% of macroporous alumina and 1.0-25.0 wt% of cerium-zirconium solid solution; the reaction process conditions are as follows: the reaction temperature is 180 ℃ and 320 ℃, the reaction pressure is 0.5-2.5MPa, and the volume space velocity is 3-8h^-1The volume ratio of hydrogen to oil is 1-50.

The gasoline adsorption desulfurization method provided by the invention has the advantages that the fixed bed reactor can be a fixed bed adiabatic reactor or a fixed bed isothermal reactor, and is preferably the fixed bed adiabatic reactor; further preferably, the reaction process conditions are as follows: the reaction temperature is 180 ℃ and 300 ℃, the reaction pressure is 0.5-2.0MPa, and the volume space velocity is 5-8h^-1The volume ratio of hydrogen to oil is 1-40. The cutting temperature of the light gasoline fraction and the heavy gasoline fraction is 70 ℃.

A preparation method of the adsorption desulfurization catalyst comprises the following steps: (1) dissolving nickel salt and zinc salt in nitric acid, and adding a pore-expanding agent to obtain acid liquor containing the nickel salt and the zinc salt; (2) preparing an acid solution containing a pore-expanding agent, adding a ZSM-5 molecular sieve, macroporous alumina and a cerium-zirconium solid solution into the acid solution containing the pore-expanding agent, and uniformly stirring to obtain a mixture slurry containing the ZSM-5 molecular sieve, the macroporous alumina and the cerium-zirconium solid solution, wherein the mass percentage of the pore-expanding agent in the acid solution containing nickel and zinc is more than 2 times that of the pore-expanding agent in the mixture slurry containing the ZSM-5 molecular sieve, the macroporous alumina and the cerium-zirconium solid solution calculated by oxides; adding an acid solution containing nickel salt and zinc salt into the slurry obtained in the step (2), and then adding an alkaline solution to perform a precipitation reaction; after the reaction is finished, the catalyst is obtained by filtering, washing, drying, forming and roasting.

In the preparation method of the catalyst, the addition amount of the pore-expanding agent in the step (1) accounts for 1-35% of the total mass of the nickel-zinc oxide.

The catalyst is further improved by dissolving nickel salt and zinc salt in deionized water, impregnating the surface of the catalyst, drying and roasting to obtain the catalyst, wherein the catalyst is controlled to contain 25.0-50.0 wt% of zinc oxide and 0.5-25.0 wt% of nickel oxide. The mass percentage content of nickel oxide and zinc oxide on the surface of the catalyst is 0.1-2.0 times higher than that of the nickel oxide and the zinc oxide in the catalyst. Is favorable for improving the adsorption desulfurization activity and selectivity of the catalyst, and has high adsorption desulfurization rate. The desulfurization activity and selectivity of the catalyst after 8-10 times of regeneration are higher than those of the catalyst without surface modification by nickel oxide and zinc oxide.

The mass percentage content of nickel oxide and zinc oxide on the surface of the catalyst is 0.1-2.0 times higher than that of the nickel oxide and the zinc oxide in the catalyst.

Further preferably, the adsorption desulfurization catalyst comprises the following components in percentage by weight: 25.0-45.0 wt% of zinc oxide, 0.5-20.0 wt% of nickel oxide, 10.0-55.0 wt% of ZSM-5 molecular sieve, 20.0-40.0 wt% of macroporous alumina and 1.0-20.0 wt% of cerium-zirconium solid solution.

The alkaline solution comprises: one or more of sodium bicarbonate, ammonium bicarbonate, sodium carbonate, sodium hydroxide and ammonia water. The catalyst calcination temperature is 450-650 ℃.

Preparation of cerium-zirconium solid solution: weighing cerium nitrate and zirconium nitrate according to a stoichiometric ratio, placing the weighed cerium nitrate and zirconium nitrate into a beaker to prepare a mixed solution, adding a pore-expanding agent, dropwise adding ammonia water or a sodium carbonate solution into the mixed solution under the condition of continuously stirring, carrying out coprecipitation reaction, carrying out suction filtration, drying, roasting at 800-950 ℃ for 4-8 hours, and then crushing and grinding into powder. The addition amount of the pore-expanding agent accounts for 1-30% of the mass of the cerium-zirconium solid solution.

The pore-expanding agent is methyl cellulose, active carbon, polyvinyl alcohol, urea or sodium polyacrylate; polyacrylic acid; one or more of ammonium polyacrylate, preferably sodium polyacrylate.

The pore-expanding agent is added into the catalyst step by step, the catalyst has a mesoporous and macroporous structure, and the mass percentage of the pore-expanding agent in the acid solution containing nickel and zinc is more than 2 times of that of the pore-expanding agent in the mixture slurry containing the ZSM-5 molecular sieve, the macroporous alumina and the cerium-zirconium solid solution, so that the penetration sulfur capacity of the adsorption desulfurization catalyst is improved, the olefin saturation rate of the catalyst is low, and the octane number loss is low.

The catalyst of the invention comprises: 25.0-50.0 wt% of zinc oxide, 0.5-25.0 wt% of nickel oxide, 2.0-55.0 wt% of ZSM-5 molecular sieve, 20.0-50.0 wt% of macroporous alumina and 1.0-25.0 wt% of cerium-zirconium solid solution, especially the introduction of cerium-zirconium solid solution (adding pore expanding agent in the mixing process of cerium-zirconium solid solution, ZSM-5 molecular sieve and macroporous alumina), effectively inhibits the generation of zinc aluminate/zinc silicate in the high-temperature reduction and regeneration process, and improves the reduction and regeneration stability of the catalyst. The method is suitable for removing sulfur in the catalytically cracked gasoline, the sulfur capacity of the adsorption desulfurization catalyst is reduced by 2-7% after the adsorption desulfurization catalyst is regenerated for 8 times, and the catalyst has good stability.

The present invention will be further illustrated by way of examples to illustrate the measurement method of the present invention, but the present invention is not limited to these examples.

Detailed Description

All starting materials for the present invention are commercially available.

Example 1

Preparation of cerium-zirconium solid solution: weighing 38.8g of cerium nitrate and 33.9g of zirconium nitrate according to a stoichiometric ratio, placing the cerium nitrate and the zirconium nitrate into a beaker to prepare a mixed solution, adding 4g of sodium polyacrylate, dropwise adding ammonia water or a sodium carbonate solution into the mixed solution under the condition of continuous stirring for coprecipitation reaction, then carrying out suction filtration, drying, roasting at 840 ℃ for 6 hours, crushing and grinding into powder.

Preparation of the catalyst: (1) dissolving 67.4g of nickel nitrate and 136g of zinc nitrate in nitric acid, and adding 16g of sodium polyacrylate to obtain acid liquor containing nickel and zinc; (2) preparing an acid solution containing 5.5g of sodium polyacrylate, adding 23g of ZSM-5 molecular sieve, 17g of macroporous alumina and 5.7g of cerium-zirconium solid solution into the acid solution containing sodium polyacrylate, and uniformly stirring to obtain a mixture slurry containing the ZSM-5 molecular sieve, the macroporous alumina and the cerium-zirconium solid solution; and then adding acid liquor containing nickel salt and zinc salt into the mixture slurry, adding sodium carbonate and ammonia water solution, carrying out precipitation reaction, raising the temperature of the obtained reaction product to 90 ℃, aging for 5 hours, filtering, washing, drying, molding and roasting to obtain the catalyst. The composition of the catalyst is shown in table 1.

Example 2

The preparation of cerium zirconium solid solution was the same as in example 1, the catalyst was prepared in the same manner as in example 1, the pore-expanding agent in the acid solution containing nickel and zinc was contained in an amount of 3.2 times by mass, in terms of metal oxide, as compared with the pore-expanding agent in the slurry of the mixture containing ZSM-5 molecular sieve, macroporous alumina and cerium zirconium solid solution, and the composition of the catalyst is shown in table 1.

Example 3

The preparation of the cerium zirconium solid solution is the same as that of example 1, the preparation steps of the catalyst are the same as that of example 1, and the mass percentage of the pore-expanding agent in the acid solution containing nickel and zinc is 3.8 times higher than that of the pore-expanding agent in the mixture slurry containing the ZSM-5 molecular sieve, the macroporous alumina and the cerium zirconium solid solution calculated by oxides. After obtaining the catalyst, preparing nickel salt and zinc salt to be dissolved in deionized water, impregnating the surface of the catalyst, and then drying and roasting to obtain the catalyst with modified nickel and zinc surfaces. The mass percentage content of nickel oxide and zinc oxide on the surface of the catalyst is 0.9 times higher than that of the nickel oxide and the zinc oxide in the catalyst. The composition of the catalyst is shown in table 1.

Example 4

The preparation of the cerium zirconium solid solution is the same as that of example 3, the preparation steps of the catalyst are the same as that of example 3, and the mass percentage content of nickel oxide and zinc oxide on the surface of the catalyst is 1.5 times higher than that of the nickel oxide and zinc oxide in the catalyst. The composition of the catalyst is shown in table 1.

Table 1 example/comparative catalyst composition/wt%

Examples/comparative examples	Zinc oxide	Nickel oxide	ZSM-5	Macroporous aluminium oxide	Cerium zirconium solid solution
						Example 1	37	17.3	23	17	5.7
Example 2	46	16	20	13	5.0
						Example 3	29	20	33	13.5	4.5
Example 4	31	23	19	23.5	3.5

Comparative example 1

Preparation of the catalyst: (1) dissolving 67.4g of nickel nitrate and 136g of zinc nitrate in nitric acid, and adding 16g of sodium polyacrylate to obtain acid liquor containing nickel and zinc; (2) preparing an acid solution containing 5.5g of sodium polyacrylate, adding 23g of ZSM-5 molecular sieve and 17g of macroporous alumina into the acid solution containing sodium polyacrylate, and uniformly stirring to obtain a mixture slurry containing the ZSM-5 molecular sieve and the macroporous alumina; and adding an acid solution containing nickel salt and zinc salt into the mixture slurry, adding sodium carbonate and an ammonia water solution, carrying out precipitation reaction, raising the temperature of the obtained reaction product to 90 ℃, aging for 5 hours, filtering, washing, drying, molding and roasting to obtain the comparative catalyst 1.

Comparative example 2

Preparation of the catalyst: (1) dissolving 67.4g of nickel nitrate and 136g of zinc nitrate in nitric acid, and adding 21.5g of sodium polyacrylate to obtain acid liquor containing nickel and zinc; (2) adding 23g of ZSM-5 molecular sieve, 17g of macroporous alumina and 5.7g of cerium-zirconium solid solution into acid liquor containing nickel and zinc, uniformly stirring, adding sodium carbonate and ammonia water solution, carrying out precipitation reaction, raising the temperature of an obtained reaction product to 90 ℃, aging for 5 hours, filtering, washing, drying, forming and roasting to obtain the comparative catalyst 2.

Full-fraction FCC gasoline is adopted, and the gasoline raw material has the olefin content of 31.3 v%, the sulfur content of 164ppm and the octane number of 90.6.

Cutting FCC gasoline into light gasoline fraction and heavy gasoline fraction at 70 deg.c, adsorbing and desulfurizing the light gasoline fraction, and evaluating the adsorption and desulfurization with 100ml heat insulating bed, reducing the catalyst or comparative catalyst with hydrogen at 1.8MPa for 5 hr, raising the bed temperature to 460 deg.c and maintaining for 8 hr. Catalyst evaluation process conditions: the inlet temperature of the reactor is 280 ℃, the pressure is 1.1MPa, and the space velocity is 4.5h^-1The hydrogen-oil volume ratio was 2.0, and the evaluation results are shown in Table 2. The desulfurization rate of the catalyst is more than 96.6 percent, the octane number loss is less than 0.4, the penetrating sulfur capacity is more than 28 percent, and the olefin saturation rate is less than 15 percent. The comparative catalyst 1 has large octane number loss, the comparative catalyst 2 has low desulfurization rate, large octane number loss and low penetrating sulfur capacity. After the adsorbed sulfur capacity reaches saturation, the catalyst or the comparative catalyst is regenerated, and the process conditions are as follows: heating to 260 ℃ at a heating rate of 35 ℃/h in a nitrogen atmosphere, and staying for 7 h; and then regenerating the catalyst, wherein the used regeneration gas is a mixed gas of oxygen and nitrogen, and the volume content of the oxygen accounts for 7 percent of the total gas.

TABLE 2 catalyst and comparative catalyst reaction results

After the regeneration of the catalyst 1 and 4, comparative examples 1 and 2, reactor inlet temperature 280 ℃, pressure 1.1MPa, space velocity 4.5h^-1The evaluation results are shown in Table 3, with a hydrogen-oil volume ratio of 25. Catalyst removalThe sulfur effect can be basically recovered to the level of a fresh agent, the generation of zinc silicate and zinc aluminate in the high-temperature reduction and regeneration process is effectively inhibited, and the reduction and regeneration stability of the catalyst is improved. Compared with catalysts 1 and 2, the activity is reduced after regeneration, the octane number loss is large, and the penetration sulfur capacity is reduced. After 8 times of regeneration, the desulfurization rate of the catalyst in the embodiment 1 is 92.8 percent, and the sulfur capacity is reduced by 5 percent; in example 4, the desulfurization rate of the catalyst was 94.6%, and the sulfur capacity was decreased by 3%.

TABLE 3 catalyst and comparative catalyst reaction results

	Desulfurization rate/%)	Loss of octane number	Penetration of sulfur capacity/%)
				Example 1	96.7	0.4	30
Example 4	97.8	0.2	32
				Comparative example 1	94.1	2.6	25
Comparative example 2	90.1	1.8	15

Claims

1. An FCC gasoline adsorption desulfurization method is characterized in that a fixed bed reactor is adopted, FCC gasoline is cut into light gasoline fraction and heavy gasoline fraction, and the cutting temperature of the light gasoline fraction and the heavy gasoline fraction is 70 ℃; the light gasoline fraction is contacted with an adsorption desulfurization catalyst, and the adsorption desulfurization catalyst comprises the following components in percentage by weight: 25.0-50.0 wt% of zinc oxide, 0.5-25.0 wt% of nickel oxide, 2.0-55.0 wt% of ZSM-5 molecular sieve, 20.0-50.0 wt% of macroporous alumina and 1.0-25.0 wt% of cerium-zirconium solid solution; the mass percentage content of nickel oxide and zinc oxide on the surface of the catalyst is 0.1-2.0 times higher than that of the nickel oxide and the zinc oxide in the catalyst; the reaction process conditions are as follows: the reaction temperature is 180 ℃ and 320 ℃, the reaction pressure is 0.5-2.5MPa, and the volume space velocity is 3-8h^-1Hydrogen-oil volume ratio is 1-50; the preparation method of the adsorption desulfurization catalyst comprises the following steps: (1) dissolving nickel salt and zinc salt in nitric acid, and adding a pore-expanding agent to obtain acid liquor containing the nickel salt and the zinc salt; (2) preparing an acid solution containing a pore-expanding agent, adding a ZSM-5 molecular sieve, macroporous alumina and a cerium-zirconium solid solution into the acid solution containing the pore-expanding agent, and uniformly stirring to obtain a mixture slurry containing the ZSM-5 molecular sieve, the macroporous alumina and the cerium-zirconium solid solution, wherein the mass percentage of the pore-expanding agent in the acid solution containing nickel and zinc is more than 2 times that of the pore-expanding agent in the mixture slurry containing the ZSM-5 molecular sieve, the macroporous alumina and the cerium-zirconium solid solution calculated by oxides; adding an acid solution containing nickel salt and zinc salt into the slurry obtained in the step (2), and then adding an alkaline solution to perform a precipitation reaction; after the reaction is finished, filtering, washing, drying, forming and roasting to obtain a catalyst; the catalyst was then further modified: dissolving nickel salt and zinc salt in deionized water, soaking the surface of the catalyst, drying and roasting to obtain the finished catalyst, wherein the catalyst is controlled to contain 25.0-50 wt%0 wt% zinc oxide, 0.5-25.0 wt% nickel oxide.

2. The method for adsorptive desulfurization of FCC gasoline according to claim 1, wherein the adsorptive desulfurization reaction process conditions are as follows: the reaction temperature is 180 ℃ and 300 ℃, the reaction pressure is 0.5-2.0MPa, and the volume space velocity is 5-8h^-1The volume ratio of hydrogen to oil is 1-40.

3. The method for adsorptive desulfurization of FCC gasoline according to claim 1, wherein the fixed bed reactor is a fixed bed adiabatic reactor or a fixed bed isothermal reactor.

4. The method for adsorptive desulfurization of FCC gasoline according to claim 1, wherein said cerium-zirconium solid solution is prepared as follows: weighing cerium nitrate and zirconium nitrate according to a stoichiometric ratio, placing the weighed cerium nitrate and zirconium nitrate into a beaker to prepare a mixed solution, adding a pore-expanding agent, dropwise adding ammonia water or a sodium carbonate solution into the mixed solution under the condition of continuously stirring, carrying out coprecipitation reaction, carrying out suction filtration, drying, roasting at 800-950 ℃ for 4-8 h, crushing and grinding into powder.

5. The method for adsorptive desulfurization of FCC gasoline as claimed in claim 1, wherein said alkaline solution comprises: one or more of sodium bicarbonate, ammonium bicarbonate, sodium carbonate, sodium hydroxide and ammonia water.

6. The method for adsorptive desulfurization of FCC gasoline as claimed in claim 1, wherein the pore-expanding agent is one or more of sodium polyacrylate, polyacrylic acid, ammonium polyacrylate.