JPH0364000B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION The present invention relates to heat exchangers, particularly those used in the processing of crude oil. In more detail,
The present invention relates to additives for reducing fouling in heat exchangers. In petroleum processing, numerous heat exchangers are utilized to heat or cool process streams.
Because refineries process very large quantities of oil, typically in the range of 25,000 to 200,000 barrels or more, heat exchangers in refineries are a very large investment. The accumulation of deposits on the heat exchanger tubes after a period of operation significantly reduces heat exchange efficiency and significantly increases energy consumption. Eventually, the heat exchanger must be removed from service and the tubes cleaned or replaced. Increasing the efficiency of heat exchangers and reducing the amount and rate of fouling results in significant energy savings in refineries and other facilities that use heat exchangers. DESCRIPTION OF THE PRIOR ART U.S. Pat.
The patent claims the use of a polyalkylene amine. U.S. Patent No. 4160648, U.S. Patent No. 4247301, U.S. Patent No.
Nos. 4,191,537, 4,233,168, 4,236,020, 4,288,612, and 4,197,409 all disclose poly(oxyalkylene) carbamates and their use in fuels and lubricants. SUMMARY OF THE INVENTION In a method for preventing fouling of a heat exchanger, a liquid hydrocarbon stream consisting of crude oil is passed at a temperature of 0 to 1500 〓 and 1 to 500 ppm of a poly(oxyalkylene) carbamate antifoulant additive (antifoulant) is added to the mixture.
additive) to said hydrocarbon stream. DETAILED DESCRIPTION OF THE INVENTION The present invention is an improvement over the invention disclosed in the aforementioned US Pat. No. 4,200,518, the entire disclosure of which is incorporated herein by reference. The poly(oxyalkylene) carbamates of the present invention have been found to be excellent in many applications as heat exchanger antifouling agents. Heat exchangers that can be utilized in the present invention are of any type that causes deposits to accumulate on the heat transfer surfaces.
The most common type of heat exchanger in use is the shell and tube heat exchanger.
exchanger). The hydrocarbon stream passing through the heat exchanger is preferably crude oil or a coker feed stream. Any hydrocarbon stream that fouls the heat exchanger can be used in the present invention, but in particular various fractions of crude oil can be used. Generally, the stream passing through the heat exchanger will be heated or cooled to a temperature in the range of 0 to 1500°. The additive of the present invention has a concentration of 600 to 1000
It is particularly effective at temperatures below . The antifouling additive of the present invention comprises a poly(oxyalkylene) carbamate. This carbamate is
It will dissolve in the hydrocarbon stream passing through the heat exchanger. Poly(oxyalkylene) carbamates useful in the present invention are well known in the art. Representative U.S. patents disclosing methods of making and using compounds in fuels and lubricants include No. 4160648, No. 4247301, and No. 4191537.
No. 4233168, No. 4236020, No. 4233168, No. 4236020, No.
No. 4288612 and No. 4197409. The disclosures of these patents, particularly those relating to the compounds and methods of preparation disclosed herein, are incorporated herein by reference. Generally, the carbamate comprises a poly(oxyalkylene) chain terminated with at least one hydroxy or hydrocarbyloxy group, the poly(oxyalkylene) chain containing 2 to 10 amine nitrogens, 2 to 40 amine nitrogens, 2 to 5 carbon atoms bonded via an oxycarbonyl group to the nitrogen atom of the polyamine with a C:N ratio of about 1:1 to 10:1.
Consisting of oxyalkylene units having 5 carbon atoms. The alkoxy group will contain 1 to 30, preferably 2 to 20 carbon atoms. This compound will have a molecular weight within the range of about 500-10,000, preferably 800-5,000. Preferred compounds can be represented by the following general formula: {wherein R represents the same or different component selected from the following: () hydrogen, () hydrocarbyl group having 1 to 10 carbon atoms () hydrocarbonyl group having 2 to 10 carbon atoms, and ( ) The group of the following formula (In the formula, g, g', g'' are integers from 1 to 2, h, h' and h'' are 0 or 1, i, i' and i'' are integers from 1 to 3, and the sum of g and h is 2, M is methyl or ethyl, j, j′ and j″ are integers and j+j′+
The sum of j'' is a value such that the molecular weight of is 500 to 5000, Z is H or a hydrocarbyl group of 1 to 30 carbon atoms. R ₁ is the same or different, a heterogeneous group of 2 to 6 carbon atoms. Alkylene or hydroxy-substituted alkylene group, R ₂ is carbonyl, alkylcarbonyl or alkylene group of 2 to 4 carbon atoms with vicinal linkage. At least one, and preferably two
and a sufficient amount of oxyalkylene units other than ethyleneoxy to cause the compound to dissolve in hydrocarbon fuels boiling in the gasoline range. a' is 0 to 1, preferably 1, b' is an integer from 0 to 4, preferably 0 to 2, c' is 0 or 1, preferably 0, and d' is 0 or 1, preferably is 0, e' is 0 or 1, preferably 1, and f' is 0 or 1, and when c' is 0, it equals 1. } Preferred, but not all polyoxyalkyleneoxycarbonyl group-substituted amines that can be used in the present invention broadly have the following general formula: {wherein U is an alkylene group having 2 to 6 carbon atoms, there are at least 2 carbon atoms between the nitrogen atoms and preferably 2 to 3 carbon atoms, a is 0 to 6 carbon atoms; an integer between 0 and 5, and preferably between 0 and 4, b is between 0 and 1, preferably 0 when a is greater than 0, a+2b is an integer between 0 and 5, and c is an integer between 1 and 4; The average composition is about 1-3. On average, there are fewer R' groups than nitrogen atoms. R is the same or different moiety selected from hydrogen or _C1 - _C10 hydrocarbyl or mono-keto, mono-nitro, monohydroxy, alkyleneoxy or alkoxy derivatives thereof, and R' has 2 to 5 carbon atoms; Preferably 2-4
More preferably poly(oxyalkylene)oxycarbonyl groups are derived from the polymerization of alkylene oxides of ethylene oxide and propylene oxide and have an average molecular weight within the range of 600 to 5000, and said groups are treated with phosgene. Chlorformylate. } Representative compounds within the above formula are: N-[poly(oxypropylene)oxycarbonyl]ethylenediamine, N[poly(oxypropylene)polyoxyethyleneoxycarbonyl]diethylenetriamine. This additive is usually formed by reacting a suitable polyether alcohol with phosgene to form a chloroformate, and reacting the chloroformate with a mono- or polyamine to form the active carbamate. Amines The amines used in the preparation of the present additives are as shown in formula A, provided that R is not of the type (the type is derived from polyether chloroformate). Polyamine Component The polyamine component represents a wide variety of amines having 2 to 10 amine nitrogens and 2 to 40 carbon atoms, with a carbon to nitrogen ratio between about 1:1 and 10:1. . In many instances, the amine component is not a pure single component, but a mixture of compounds having a predominant amount of the specified amine. More complex amines are mixtures of amines whose composition contains the indicated compound as the main product in the average composition, and with minor amounts of similar compounds relatively close to the composition of the main product. Representative R of the amine precursors include methyl, ethyl, propyl, butyl, isobutyl, pentyl,
Alkyl groups such as hexyl, octyl etc., alkenyl groups such as propenyl, isobutenyl, hexenyl, octenyl etc., 2-hydroxyethyl, 3-hydroxypropyl, hydroxy-isopropyl, 4-hydroxybutyl, 8-hydroxyoctyl etc. hydroxyalkyl groups, ketoalkyl groups such as 2-ketopropyl, 6-ketooctyl, etc., ethoxyethyl, ethoxypropyl, propoxyethyl, propoxypropyl, diethyleneoxyethyl, triethyleneoxyethyl, tetraethyleneoxyethyl, diethyleneoxyhexyl, diethylene Included are alkoxy and lower alkyleneoxyalkyl groups such as oxyoctyl and the like, acyl groups such as propionyl and the like. Preferred R groups are hydrogen, C ₁
~ _C6 alkyl groups and _C1 - _C6 hydroxyalkyl groups. Representative R ₁ groups include ethylene, 1,2-propylene, 2,2'-dimethylpropylene, trimethylene, tetramethylene, hexamethylene, 1,3,
2-hydroxypropylene and the like. Preferred alkylene groups are ethylene and trimethylene. As previously mentioned, in many instances no single compound will be used as a secondary reactant to produce the compositions of the invention. That is, mixtures will be used in which one or two compounds predominate with respect to the specified average composition and molecular weight. For example, tetraethylenepentamine, produced by the polymerization of aziridine or by the reaction of dichloroethylene with ammonia, can be used with both lower and higher amino compounds such as triethylenetetraamine, Although it may contain substituted piperazine and pentaethylenehexamine, its composition is primarily tetraethylenepentamine, and the empirical formula of the entire composition is very similar to that of tetraethylenepentamine. Polyethers The polyether or poly(oxyalkylene) materials used in the production of polyether carbamates are condensation polymers of ethylene oxide, propylene oxide and lower oxides such as butylene oxide and pentylene oxide. Preferred materials are butylene oxide polymers or poly(butylene glycol). These substances have a suitable hydrocarbyl group as a terminal group, or are capped at one end with a suitable hydrocarbyl group. For example, particularly preferred materials are capped with butyl, oleyl groups, and the like. Polyoxyalkylene chains also contain 6 to 6 carbon atoms as end groups.
Can have 20 aryloxy groups. mixture of alkyl groups, i.e. C ₁₆ , C ₁₈ and C ₂₀
Materials capped with mixtures of alkyl groups are also suitable. Compounds with two terminal hydroxyl groups can also be used, but those with only one terminal hydroxyl group are preferred, which upon chloroformylation yields the preferred monochloroformate, which is then reacted with a suitable amine. This is to produce a preferred carbamyl substance. However, some dicarbamates are also formed upon reaction with the dihydroxy material, and the presence of small amounts of these materials, although undesirable, does not adversely affect the performance of the material. This material can also be made from oxide monomers, ie, when the reactivities of the oxides are relatively equal, a random polymer can be produced. In some cases, in the case of combinations of ethylene oxide and other oxides, the reaction rate of ethylene oxide is so fast that random polymers cannot be easily produced. In such cases, block polymers are produced. The special types of polymers that can be made and those that are made commercially are those that form the initial material by polymerization of propylene oxide and then polymerize ethylene oxide onto one or both ends of the poly(oxypropylene). It is a substance manufactured by This type of substance is [Pluronics]
(Pluronics) from Wyandotte Chemicals. Preparation of Polyether Carbamates As previously mentioned, the additives of the present invention are most conveniently prepared by reacting phosgene with a poly(oxyalkylene) compound and then reacting the product with a suitable amine. . Reactions of poly(oxyalkylene) materials are carried out on an essentially equimolar basis using only a slight excess of phosgene, although excess phosgene is not harmful.
This reaction is carried out at a temperature within the range -10° to 100°C, preferably 0 to 30°C. This reaction is usually 1/
Complete within 4-5 hours. Reaction time is usually 1/2~
Probably within 3 hours. A solvent may be used in the chloroformylation reaction. Suitable solvents include benzene, toluene, and the like. Preferably, the phosgene is dissolved in a suitable solvent prior to reaction with the poly(oxyalkylene) material. The reaction between chloroformate and amine is carried out neat or in a solvent. The molar ratio of amine to chloroformate will normally be within the range of 0.5 to 5.
The temperature that can be used is -10° to 200°C. Stripping of any residual solvent by water washing and usually reduced pressure yields the desired product. The molar ratio of polyether chloroformate to amine generally ranges from about 0.2 to 20 moles amine/mol chloroformate, and more usually from 0.5 to 5 moles chloroformate.
It will be within the range of mol amine/mol chloroformate. This molar ratio will depend on the particular chloroformate and the desired ratio of polyether to amine. If polysubstitution suppression of the alkylene polyamine is desired, a large molar excess of amine is added. For example, in particular, in preparations using ethylenediamine, when the amine-chloroformate ratio was 2.5 to 1, the basic N:total N ratio in the product was 0.27, whereas the amine-chloroformate ratio The basic N:total N ratio was 0.42, indicating a very high amount of monocarbamate in the material. This reaction can be carried out in the presence or absence of a reaction solvent. Solvents are generally used when it is necessary to reduce the viscosity of the reaction product. These solvents must be inert towards the reactants and reaction products. Preferred solvents include aliphatic and aromatic hydrocarbons. Depending on the temperature of the reaction, the particular chloroformate used, the molar ratios and concentrations of the particular amine and reactants, the reaction time will vary from 1/4 to 24 hours, more usually from about 2 to 3 hours. . Time significantly exceeding 3 hours does not particularly increase the yield;
Avoid unwanted decomposition, especially at high temperatures.
Therefore, it is preferable to limit the reaction time to less than 3 hours. After the reaction has been carried out for a sufficient time, the reaction mixture is extracted with a hydrocarbon or hydrocarbon alcohol medium to remove any low molecular weight amine salts formed from the product and any unreacted alkylene polyamines. do. The product is then isolated by evaporation of the solvent. Minor amounts of halogen may be present as hydrohalide salts of polyether carbamates. Depending on the particular application of the compositions of the invention, the reaction may be carried out in the medium of the ultimate use, such as a polyether carrier, to a concentration that can be supplied as a concentrate of the cleaning composition. It can also be formed into For example, the final mixture may be in a usable form for direct mixing into fuel. A preferred polyoxyalkyleneoxycarbonyl group-substituted alkylene polyamine composition has the formula: (The above symbols are defined as follows. a is 0 to 5
an integer of 0 to 4, preferably an integer of 0 to 4, b is an integer of 0 to 1, and when a is greater than 0, preferably 0, +
2b is equal to a number from 0 to 5, c is an integer in the range from 1 to 3, on average there are fewer R groups than nitrogen atoms,
f is an integer of 2 to 3, R is hydrogen or a _C1 - _C10 hydrocarbyl group or monoketo, mononitro, monohydroxy, alkyleneoxy or an alkoxy derivative thereof, and R'' is poly(oxyalkylene)oxy with an average molecular weight of 600 to 5000. carbonyl group). The above formula is a broad, simplified and specific type of preferred poly(oxyalkylene) carbamates that can be used in the practice of this invention. Numerous poly(oxyalkylene) carbamates, not limited by the above formula, are It should be recognized that ether carbamates may also be present in small amounts.
Thus, although the above formula is of certain preferred poly(oxyalkylene) carbamates present in major amounts, these should not be construed as excluding other minor components. To substantially reduce heat exchanger fouling, generally 1 to 500 ppm, preferably 2 to 500 ppm.
99 ppm, and most preferably 5 to 29 ppm of the poly(oxyalkylene) carbamate is added to the stream passing through the heat exchanger. One of the surprising features of the present invention is the discovery that the additives described above reduce fouling of heat exchangers even in small amounts. Examples - Antifouling Tests Polybutene amines as taught in U.S. Pat. The properties were tested. In this test, the test feed material was fed into a tube at a constant rate, for a constant test time, and at a constant inlet temperature; the tube contained an electrically heated stainless steel rod; Sufficient heat was supplied to the rod to maintain the outlet temperature. As fouling deposits formed on the rod, the temperature of the rod had to be increased to maintain a constant exit temperature of the test material. The initial and final rod temperatures were measured along with the initial and final rod weights. The increase in rod temperature and the amount of deposits are indicative of the degree of fouling and rate of fouling. Comparisons were made using various feedstocks and varying concentrations of additives. The results are shown in Table 1. Feedstock A was crude oil with a sulfur content of 0.95% by weight.
Feedstock B was refinery naphtha. Feed C was crude oil with a sulfur content of 0.72% by weight.

【table】

Table: Both the poly(oxyalkylene) carbamate and polybutenamine had molecular weights in the range of 1000-2000. The above data shows that for the feedstocks tested,
Poly(oxyalkylene) carbamates have shown to be as good or surprisingly superior to the polybutenamines of US Pat. No. 4,200,518.

Claims (1)

[Claims] 1. A method for reducing fouling of a heat exchanger, comprising:
A process as described above, characterized in that 1 to 500 ppm of poly(oxyalkylene) carbamate is added to the liquid hydrocarbon stream consisting of crude oil while passing it through a heat exchanger at a temperature of 0 to 1500 〓. . 2. Transfer the hydrocarbon stream to the heat exchanger at 50~
The method according to item 1 above, wherein the passage is carried out at a temperature of 500㎓. 3. The method of claim 1, wherein said liquid hydrocarbon stream is a coke oven feed and is passed through said heat exchanger at a temperature of 600-1000°. 4. A method according to paragraphs 1, 2 or 3, wherein said hydrocarbon stream has a sulfur content of 0.1 to 5% by weight. 5. The method of item 1 above, wherein 2 to 99 ppm of said additive is added to said stream. 6. The method of paragraph 1 above, wherein 5 to 29 ppm of said poly(oxyalkylene) carbamate is added to said stream. 7. The method according to item 6, wherein the heat exchanger is a shell-and-tube heat exchanger. 8 said poly(oxyalkylene) carbamate has a poly(oxyalkylene) chain having at least one C ₁ -C ₃₀ hydroxycarbyloxy end group, and said poly(oxyalkylene) chain has an oxycarbonyl consisting of oxyalkylene units having 2 to 5 carbon atoms bonded via groups to the nitrogen atoms of the polyamine, wherein said polyamine has 2 to 10 amine nitrogens and 2
40 carbon atoms, and wherein the carbamate has a molecular weight of about 500 to 10,000. 9. The method of item 8 above, wherein the oxyalkylene unit has 3 to 4 carbon atoms. 10 The molecular weight of the carbamate is about 800~
9. The method according to claim 8, wherein the method is 5000. 11. The method according to item 8, wherein the group that terminates the poly(oxyalkylene) chain is an alkoxy group having 2 to 20 carbon atoms. 12. The method according to item 8, wherein the group that terminates the poly(oxyalkylene) chain is an aryloxy group having 6 to 20 carbon atoms. 13. The method of paragraph 11 above, wherein the alkoxy group has 16 to 20 carbon atoms. 14 The alkoxy group is C ₁₆ , C ₁₈ and C ₂₀
14. The method of claim 13, comprising a mixture of carbon groups. 15. The method according to item 9 above, wherein the amine is ethylenediamine. 16. The method according to item 9 above, wherein the amine is diethylenetriamine.