WO2022042278A1

WO2022042278A1 - A multifunctional antifoulant for coal to olefins caustic tower antifouling

Info

Publication number: WO2022042278A1
Application number: PCT/CN2021/111500
Authority: WO
Inventors: Fei XIA
Original assignee: Ecolab Usa Inc.
Priority date: 2020-08-24
Filing date: 2021-08-09
Publication date: 2022-03-03
Also published as: CN114084968A

Abstract

Methods and compositions are described to prevent or reduce fouling associated with aldol polymerization associated with caustic towers in coal to olefins or methanol to olefins processes. A method is provided that includes adding an amine or its salt to the aqueous medium; and adding an alcohol to the aqueous medium. The aqueous medium includes an aldehyde or ketone and a base.

Description

A MULTIFUNCTIONAL ANTIFOULANT FOR COAL TO OLEFINS CAUSTIC TOWER ANTIFOULING

BACKGROUND

1. Field of the Invention

The present disclosure generally relates to preventing or reducing fouling in a caustic tower. More particularly, the disclosure pertains to compositions and methods to prevent or reduce fouling associated with aldol polymerization.

2. Description of the Related Art

The coal to olefins (CTO) and the methanol to olefins (MTO) processes convert coal to other commodity products, such as olefins and gasoline. The methanol used in the CTO/MTO process can be made from coal-derived synthetic gas ( “syngas” ) or natural gas feedstock. Methanol can be produced from the catalytic conversion of hydrogen and carbon monoxide in coal-derived syngas. The CTO/MTO process includes feeding crude methanol into a reactor containing catalyst where the methanol is converted into olefins. The reaction products exit the reactor and are fed into a quench or stripping tower. The gas exiting the quench or stripping tower may then proceed to further processing and purification units, such as a cracked gas compressor, demethanizer, an acetylene saturator, or a dryer to produce pure ethylene, propylene, or other olefins.

Olefin formation from methanol proceeds through a complex network of chemical reactions potentially resulting in the formation of multiple byproducts or unwanted species. The byproducts or unwanted species and catalyst fines exit the reactor in the reaction gas. The reaction gas from the MTO reactor carries the catalyst fines and byproducts, such as poly-methylbenzene, into the quench or stripping tower. The byproducts or unwanted species become entrained in the water, and will cause fouling in the quench water loop and/or the wash water loop, especially in heat exchangers.

Caustic towers remove contaminants from the cracked gas. Cracked gas may contain acid gases such as H ₂S and CO ₂ as well as low oxygenates such as formaldehyde and acetaldehyde. Such contaminants can be removed by caustic scrubbing. Caustic scrubbing includes circulating a weak sodium hydroxide solution (about 1 wt. %) in one part of the column and a strong sodium hydroxide solution (about 5 to 10 wt. %) in the other part of the column.

Aldol polymerization is the primary mechanism of fouling in caustic towers of CTO/MTO plants. Caustic is the catalyst for aldol polymerization. There are two phases of aldol polymerization: the first phase is aldehyde catalyzed by base to form olefin aldehyde called yellow oil or red oil, which is partially soluble in caustic solution but insoluble in water; the second phase is yellow oil or red oil further polymerizing to form high molecular weight polymer in solid form. Hence, aldol polymer continues to form as long as there are aldehydes and caustic present in solution.

Usually, there are hundreds of ppm of aldehydes in caustic tower of CTO plants, much higher than that of traditional primary olefin plants, which have about tens of ppm of aldehydes.

Typically, yellow/red-oil fouling can be mitigated by washing the caustic scrubber with a hydrocarbon to dissolve away the foulants; however, the hydrocarbon wash stream can increase the risk of emulsion formation, thereby compromising the safe operation of the whole plant.

BRIEF SUMMARY

A method of reducing or preventing fouling related to aldol polymerization in an aqueous medium is provided. The method includes adding an amine or its salt to the aqueous medium; and adding an alcohol to the aqueous medium. The aqueous medium comprises an aldehyde or ketone and a base.

In some aspects, the amine or its salt is an alkyl amine, hydroxylamine, an amino acid, or any combination thereof.

In some aspects, the amine or its salt is ethylenediamine, hydroxylamine sulfate, glycine, or any combination thereof.

In some aspects, the amine or its salt is ethylenediamine.

In some aspects, the amine or its salt is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm.

In some aspects, the alcohol is a glycol.

In some aspects, the alcohol is isopropanol, 2-butanol, (2- (2-butoxyethoxy) ethanol) , or any combination thereof.

In some aspects, the alcohol is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm.

In some aspects, the method may include adding a sulfonated compound to the aqueous medium.

In some aspects, the sulfonated compound is a lignosulfonate or salt thereof.

In some aspects, the sulfonated compound is sodium lignosulfonate.

In some aspects, the sulfonated compound is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm.

In some aspects, the method includes mixing the amine or its salt and the alcohol to form a mixture and adding the mixture to the aqueous medium.

In some aspects, the aldehyde has a concentration in the aqueous medium ranging from about 10 ppm to 1000 ppm.

In some aspects, the aldehyde is acetaldehyde.

In some aspects, the aqueous medium further comprises a compound of formula (I) , (II) , or (III)

where n is an integer from 1 to 100; R is a repetitive methyl-vinyl group; and R ₁ is an aliphatic hydrocarbon.

In some aspects, the base is an alkali metal hydroxide.

In some aspects, the amine or its salt and the alcohol are added to the aqueous medium of a CTO process, a MTO process, or a natural gas to olefins process.

In some aspects, the amine or its salt and the alcohol are added to the aqueous medium in a caustic tower of a CTO process, a MTO process, or a natural gas to olefins process.

In some aspects, this disclosure describes a use of a composition comprising an amine or its salt and an alcohol for reducing or preventing fouling related to aldol polymerization in an aqueous medium.

The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter that form the subject of the claims of this application. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent embodiments do not depart from the spirit and scope of the disclosure as set forth in the appended claims.

DETAILED DESCRIPTION

Various embodiments are described below. The relationship and functioning of the various elements of the embodiments may better be understood by reference to the following detailed description. However, embodiments are not limited to those illustrated below. In certain instances, details may have been omitted that are not necessary for an understanding of embodiments disclosed herein.

The present disclosure describes methods and compositions for preventing or reducing solids formation in the caustic tower of a CTO/MTO process. Aldol polymerization is the primary mechanism of fouling in caustic towers of CTO/MTO plants. Caustic is the catalyst for aldol polymerization. There are two phases of aldol polymerization: the first phase is aldehyde or ketone catalyzed by base to form olefin aldehyde called yellow oil or red oil, which is partially soluble in caustic solution but insoluble in water; the second phase is yellow oil or red oil further polymerizing to form high molecular weight polymer in solid form. Hence, an aldol polymer continues to form as long as there are aldehydes and caustic present in solution.

Aldol polymer fouling involves the polymerization of an aldehyde or ketone in the presence of a base. For example, acetaldehyde polymerizes to form a compound of formula (I) in the presence of sodium hydroxide:

where n is an integer from 1 to 100. The compound of formula (I) may undergo further reactions such as an intramolecular diels alder or intermolecular diels alder reaction to form compounds of formulae (II) and (III) , respectively.

where R is a repetitive methyl-vinyl group; and R ₁ is an aliphatic hydrocarbon. The repetitive methyl-vinyl group refers to the group portrayed between the brackets in formula (I) . The aliphatic hydrocarbon refers to a saturated or unsaturated alkyl group ranging from 1 to 22 carbon atoms in length. In some aspects, R ₁ is a methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, or dodecyl group.

Aldol polymer formation occurs in aqueous medium containing an aldehyde or ketone in an alkaline medium. The concentration of the aldehyde or ketone in the aqueous medium ranges from about 10 ppm to 1000 ppm. In some aspects, the aldehyde is acetaldehyde or a C ₂-C ₅ aldehyde.

The aqueous medium may include a base such as an alkali metal hydroxide. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide. In some aspects, the base is sodium hydroxide. The concentration of the alkali metal hydroxide in the aqueous medium may range from about 0.1 wt. %to about 15 wt. %.

The temperature of the aqueous medium in the caustic tower may vary depending on operation needs, but is typically between about 35 ℃ to about 45 ℃.

A novel antifoulant is provided herein to address the challenges of aldol polymerization in caustic towers. The method synergistically inhibits aldol polymerization and also disperses and/or solubilizes solids formed from aldol polymerization. The antifoulant and method of adding the antifoulant can inhibit yellow oil or red oil formation and can disperse/solubilize yellow oil or red oil. Dispersed and solubilized yellow and red oil have less chance to polymerize further to form larger particles of solid polymer.

A method of reducing or preventing fouling related to aldol polymerization in an aqueous medium is provided. The method includes adding an amine or its salt to the aqueous medium; and adding an alcohol to the aqueous medium. The aqueous medium comprises an aldehyde and a base.

The amine or its salt can be an alkyl amine, hydroxylamine, an amino acid, or any combination thereof. The alkyl amine may be a di-or tri-amine. Examples of diamines include, but are not limited to, methanediamine, ethylenediamine, and 1, 3-diaminopropane. In some aspects, the amine is ethylenediamine. Other amines or their salts include hydroxylamines and amino acids. In some aspects, the amine or its salt is hydroxylamine sulfate. In some aspects, the amino acid is glycine. In some aspects, the amine or its salt is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm. In some aspects, the amine or its salt is added to the aqueous medium in an amount of about 10 ppm to about 500 ppm.

The method also includes adding an alcohol to the aqueous medium. Examples of suitable alcohols include, but are not limited to, isopropanol, 2-butanol, C ₄-C ₁₀ alcohols, and glycols such as (2- (2-butoxyethoxy) ethanol) . In some aspects, the alcohol is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm. In some aspects, the alcohol is added to the aqueous medium in an amount of about 100 ppm to about 500 ppm.

The method may optionally include adding a sulfonated compound such as a sulfonated polymer to the aqueous medium. Examples of sulfonated compounds include, but are not limited to, dodecyl benzene sulfonate and lignosulfonates or their salts. In some aspects, the sulfonated polymer is sodium lignosulfonate. In some aspects, the sulfonated compound is dodecyl benzene sulfonate. In some aspects, the sulfonated compound is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm. In some aspects, the sulfonated compound is added to the aqueous medium in an amount of about 1 ppm to about 50 ppm.

The order in which the amine or its salt and the alcohol are added to the aqueous medium is not particularly limited. In some aspects, the amine or its salt may be added before the alcohol. In some aspects, the amine or its salt may be added after the alcohol. In some aspects, the amine or its salt may be added simultaneously but separately from the alcohol.

In some aspects, the amine or its salt may be mixed with the alcohol to form a mixture and then added to the aqueous medium.

In some aspects, the amine or its salt and the alcohol are added to the aqueous medium of a CTO process, an MTO process, or a natural gas to olefins process. In some aspects, the amine or its salt and the alcohol are added to the aqueous medium in a caustic tower of a CTO process, an MTO process, or a natural gas to olefins process. In some aspects, the amine or its salt and the alcohol are added to a stream being fed into the caustic tower.

As used herein “MTO process” refers to a process that converts methanol to other commodity products, such as olefins and gasoline. The methanol used in the MTO process can be derived from coal-derived synthetic gas or natural gas feedstock. Methanol can be produced from the catalytic conversion of hydrogen and carbon monoxide in coal-derived syngas. MTO processes utilize zeolite catalysts to make the conversion of methanol to olefins economically feasible. The MTO process includes feeding crude methanol into a reactor containing catalyst where the methanol is converted into olefins. The reaction products exit the reactor and are fed into a quench or stripping tower. The gas exiting the quench or stripping tower may then proceed to further processing and purification units, such as a demethanizer, an acetylene saturator, or a dryer to produce pure ethylene, propylene, or other olefins.

In some embodiments, the method may further include dispersing or solubilizing the foulant, wherein the foulant may comprise an aldol polymer.

The compositions can optionally include one or more additives. Suitable additives include, but are not limited to, corrosion inhibitors, scale inhibitors, water clarifiers, dispersants, emulsion breakers, pH modifiers, surfactants, solvents, and combinations thereof.

Suitable corrosion inhibitors include, but are not limited to, amidoamines, quaternary amines, amides, phosphate esters, and combinations thereof.

Suitable scale inhibitors include, but are not limited to, phosphates, phosphate esters, phosphoric acids, phosphonates, phosphonic acids, polyacrylamides, salts of acrylamido-methyl propane sulfonate/acrylic acid copolymer (AMPS/AA) , phosphinated maleic copolymer (PHOS/MA) , salts of a polymaleic acid/acrylic acid/acrylamido-methyl propane sulfonate terpolymer (PMA/AMPS) , and combinations thereof.

Suitable water clarifiers include, but are not limited to, inorganic metal salts such as alum, aluminum chloride, aluminum chlorohydrate, iron sulfate, iron chloride, and polyferric sulfate or organic polymers such as acrylic acid based polymers, acrylamide based polymers, polymerized amines, alkanolamines, thiocarbamates, cationic polymers such as diallyldimethylammonium chloride (DADMAC) , and combinations thereof.

Suitable pH modifiers include, but are not limited to, alkali hydroxides, alkali carbonates, alkali bicarbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, alkaline earth metal bicarbonates and mixtures or combinations thereof. Exemplary pH modifiers include NaOH, KOH, Ca (OH) ₂, CaO, Na ₂CO ₃, KHCO ₃, K ₂CO ₃, NaHCO ₃, MgO, and Mg (OH) ₂.

Suitable surfactants include, but are not limited to, anionic surfactants, cationic surfactants, nonionic surfactants, and combinations thereof. Anionic surfactants include alkyl aryl sulfonates, olefin sulfonates, paraffin sulfonates, alcohol sulfates, alcohol ether sulfates, alkyl carboxylates and alkyl ether carboxylates, and alkyl and ethoxylated alkyl phosphate esters, and mono and dialkyl sulfosuccinates and sulfosuccinamates, and combinations thereof. Cationic surfactants include alkyl trimethyl quaternary ammonium salts, alkyl dimethyl benzyl quaternary ammonium salts, dialkyl dimethyl quaternary ammonium salts, imidazolinium salts, and combinations thereof. Nonionic surfactants include alcohol alkoxylates, alkylphenol alkoxylates, block copolymers of ethylene, propylene and butylene oxides, alkyl dimethyl amine oxides, alkyl-bis (2-hydroxyethyl) amine oxides, alkyl amidopropyl dimethyl amine oxides, alkylamidopropyl-bis (2-hydroxyethyl) amine oxides, alkyl polyglucosides, polyalkoxylated glycerides, sorbitan esters and polyalkoxylated sorbitan esters, and alkoyl polyethylene glycol esters and diesters, and combinations thereof. Also included are betaines and sultanes, amphoteric surfactants such as alkyl amphoacetates and amphodiacetates, alkyl amphopropripionates and amphodipropionates, alkyliminodiproprionate, and combinations thereof.

In the aspects where the surfactants are added separately, each surfactant may be added at the same location or at a different location in the process. The surfactants may be added simultaneously at the same or different locations, or at different times in the same or different locations.

EXAMPLES

Example 1: Aldol polymerization was simulated using acetaldehyde condensation. Different recipes of composition of inhibition, solubilization and dispersion candidates were evaluated by visual observation.

Blank is solution without any chemical treated. Different candidates with different combinations are shown in table 1. The solutions were investigated to see if the polymer was dispersed or dissolved after treatment with the different formulations (A-C) .

Table 1. Solutions Tested

The test samples were prepared using a 40 ml NaOH solution and adding acetaldehyde to the solution (about 25,000 ppm acetaldehyde) . The formulation was then added and the solution and formulation were mixed together via shaking. The solution was maintained at about 40 ℃ for several hours.

The dosage of inhibitor in solution B was three-fifth of the dosage of solution A. Visual inspection of the solutions treated with formulation B showed no obvious solid polymer formation. It is believed that 2- (2-butoxyethoxy) ethanol has solubilization effect on the aldol polymer. The combination of ethanediamine with 2- (2-butoxyethoxy) dissolved aldol polymer thereby reducing solid formation.

In addition to ethylenediamine, hydroxyl ammonium sulfate and sodium glycine were tested. A mole ratio of about 0.5: 1 of ethylenediamine to acetaldehyde achieved similar results as a ratio of about 1: 1 of hydroxyl ammonium sulfate or sodium glycine to acetaldehyde.

Visual inspection of the solutions treated with formulation A showed blocky polymer formation. But after treatment with formulation C, the solid was dispersed uniformly. Hence, the combination of ethylenediamine and sodium lignosulfonate can disperse aldol polymer after its formation.

Any composition disclosed herein may comprise, consist of, or consist essentially of any of the compounds /components disclosed herein. In accordance with the present disclosure, the phrases “consist essentially of, ” “consists essentially of, ” “consisting essentially of, ” and the like limit the scope of a claim to the specified materials or steps and those materials or steps that do not materially affect the basic and novel characteristic (s) of the claimed invention.

As used herein, the term "about" refers to the cited value being within the errors arising from the standard deviation found in their respective testing measurements, and if those errors cannot be determined, then "about" refers to within 5 %of the cited value.

All of the compositions and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While this invention may be embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. In addition, unless expressly stated to the contrary, use of the term “a” is intended to include “at least one” or “one or more. ” For example, “an amine” is intended to include “at least one amine” or “one or more amines. ”

Any ranges given either in absolute terms or in approximate terms are intended to encompass both, and any definitions used herein are intended to be clarifying and not limiting. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges (including all fractional and whole values) subsumed therein.

Furthermore, the invention encompasses any and all possible combinations of some or all of the various embodiments described herein. It should also be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.

Claims

A method of reducing or preventing fouling related to aldol polymerization in an aqueous medium, comprising:

adding an amine or its salt to the aqueous medium; and

adding an alcohol to the aqueous medium.

wherein the aqueous medium comprises an aldehyde or ketone and a base.
The method of claim 1, further comprising adding a sulfonated compound to the aqueous medium.
The method of any one of claims 1-2, wherein the amine or its salt is an alkyl amine, hydroxylamine, an amino acid, or any combination thereof.
The method of any one of claims 1-3, wherein the amine or its salt is ethylenediamine, hydroxylamine sulfate, glycine, or any combination thereof.
The method of claim 4, wherein the amine or its salt is ethylenediamine.
The method of any one of claims 1-5, wherein the alcohol is a glycol.
The method of any one of claims 1-5, wherein the alcohol is isopropanol, 2-butanol, (2- (2-butoxyethoxy) ethanol) , or any combination thereof.
The method of any one of claims 2-7, wherein the sulfonated compound is dodecyl benzene sulfonate or a lignosulfonate or salt thereof.
The method of any one of claims 2-8, wherein the sulfonated compound is sodium lignosulfonate.
The method of any one of claims 1-9, wherein the amine or its salt is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm.
The method of any one of claims 1-10, wherein the alcohol is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm.
The method of any one of claims 2-11, wherein the sulfonated compound is added to the aqueous medium in an amount of about 1 ppm to about 1000 ppm.
The method of any one of claims 1-12, further comprising mixing the amine or its salt and the alcohol to form a mixture and adding the mixture to the aqueous medium.
The method of any one of claims 1-13, wherein the aqueous medium further comprises a compound of formula (I) , (II) , or (III)

where n is an integer from 1 to 100; R is a repetitive methyl-vinyl group; and

R ₁ is an aliphatic hydrocarbon.
The method of claim 14, wherein the aldehyde has a concentration in the aqueous medium ranging from about 10 ppm to 1000 ppm.
The method of any one of claims 14-15, wherein the aldehyde is acetaldehyde.
The method of any one of claims 1-16, wherein the amine or its salt and the alcohol are added to the aqueous medium of a coal to olefins process, a methanol to olefins process, or a natural gas to olefins process.
The method of any one of claims 1-16, wherein the amine or its salt and the alcohol are added to the aqueous medium in a caustic tower of a coal to olefins process, a methanol to olefins process, or a natural gas to olefins process.
The method of claim 1, wherein the base is an alkali metal hydroxide.
Use of a composition comprising an amine or its salt and an alcohol for reducing or preventing fouling related to aldol polymerization in an aqueous medium.