Patent Publication Number: US-5292425-A

Title: Use of the reaction products of polyalkenylsuccinimides, triazoles, and aldehydes as anti foulants in hydrocarbon process media

Description:
FIELD OF THE INVENTION 
     The present invention pertains to the use of the reaction products of polyalkenylsuccinimides, triazoles and aldehydes to inhibit fouling in liquid hydrocarbon mediums during the heat treatment processing of the medium, such as in refinery processes. 
     BACKGROUND OF THE INVENTION 
     In the processing of petroleum hydrocarbons and feed stocks, such as petroleum processing intermediates, and petrochemicals and petrochemical intermediates, e.g., gas, oils and reformer stocks, chlorinated hydrocarbons and olefin plant fluids, such as deethanizer bottoms, the hydrocarbons are commonly heated to temperatures of 40° to 550° C., frequently from 200°-550° C. Similarly, such petroleum hydrocarbons are frequently employed as heating mediums on the &#34;hot side&#34; of heating and heating exchange systems. In virtually every case, these petroleum hydrocarbons contain deposit-forming compounds or constituents that are present before the processing is carried out. Examples of these preexisting deposit-forming materials are alkali and alkaline earth metal-containing compounds, e.g., sodium chloride; transition metal compounds or complexes, such as porphyrins or iron sulfide; sulfur-containing compounds, such as mercaptans; nitrogen-containing compounds, such as pyrroles; carbonyl or carboxylic acid-containing compounds; polynuclear aromatics, such as asphaltenes; and/or coke particles. These deposit-forming compounds can combine or react during elevated temperature processing to produce a separate phase known as fouling deposits, within the petroleum hydrocarbon. 
     In all cases, these deposits are undesirable by-products. In many processes, the deposits reduce the bore of conduits and vessels to impede process throughput, impair thermal transfer, and clog filter screens, valves and traps. In the case of heat exchange systems, the deposits form an insulating layer upon the available surfaces to restrict heat transfer and necessitate frequent shut-downs for cleaning. Moreover, these deposits reduce throughput, which of course results in a loss of capacity with a drastic effect in the yield of finished product. Accordingly, these deposits have caused considerable concern to the industry. 
     While the nature of the foregoing deposits defies precise analysis, they appear to contain either a combination of carbonaceous phases which are coke-like in nature, polymers or condensates formed from the petroleum hydrocarbons or impurities present therein and/or salt formations which are primarily composed of magnesium, calcium and sodium chloride salts. The catalysis of such condensates has been attributed to metal compounds such as copper or iron which are present as impurities. For example, such metals may accelerate the hydrocarbon oxidation rate by promoting degenerative chain branching, and the resultant free radicals may initiate oxidation and polymerization reactions which form gums and sediments. It further appears that the relatively inert carbonaceous deposits are entrained by the more adherent condensates or polymers to thereby contribute to the insulating or thermal opacifying effect. 
     Fouling deposits are equally encountered in the petrochemical field wherein the petrochemical is either being produced or purified. The deposits in this environment are primarily polymeric in nature and do drastically affect the economies of the petrochemical process. The petrochemical processes include processes ranging from those where ethylene or propylene, for example, are obtained to those wherein chlorinated hydrocarbons are purified. 
     Other somewhat related processes where antifoulants may be used to inhibit deposit formation are the manufacture of various types of steel or carbon black. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, the reaction products of polyalkenylsuccinimides, triazoles and aldehydes are used to inhibit fouling of heated liquid hydrocarbon mediums. Typically, such antifoulant protection is provided during heat processing of the medium, such as in refinery, purification, or production processes. 
     The reaction products of the type used herein have been disclosed in U.S. Pat. No. 4,897,086 as dispersant additives for use in lubricating oils and fuels, primarily diesel fuels. The stated purpose of the additives disclosed in the &#39;086 patent is to help reduce engine deposits, particularly with respect to fuel injectors, and to improve the stability and cleanliness of lube oil compositions. The stability of diesel fuel with an additive of the reaction product disclosed in the &#39;086 patent was shown to be improved when evaluated at 300° F. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     I have found that the reaction products of polyalkenylsuccinimides with triazoles and aldehydes-provide significant antifoulant efficacy in liquid hydrocarbonaceous mediums during the high temperature treatment of the medium. 
     It is to be understood that the phrase &#34;liquid hydrocarbonaceous medium&#34; as used herein signifies various and sundry petroleum hydrocarbons and petrochemicals. For instance, petroleum hydrocarbons such as petroleum hydrocarbon feedstocks including crude oils and fractions thereof such as naphtha, gasoline, kerosene, diesel, jet fuel, gas oil, vacuum residua, etc., are all included in the definition. 
     Similarly, petrochemicals such as olefinic or naphthenic process streams, aromatic hydrocarbons and their derivatives, ethylene dichloride, and ethylene glycol are all considered to be within the ambit of the phrase &#34;liquid hydrocarbonaceous mediums&#34;. 
     The reaction products of polyalkenylsuccinimides, triazoles and aldehydes useful in the invention are generally prepared via a two-step reaction. In the first step, a polyalkenylsuccinic anhydride is reacted with a polyamine, preferably an ethylenepolyamine, to form the desired polyalkenylsuccinimide. Then, the polyalkenylsuccinimide is reacted with a triazole, e.g., tolyltriazole and an aldehyde, e.g., salicylaldehyde in an organic solvent medium to form the desired reaction product. 
     More specifically, the starting reactant, polyalkenylsuccinic anhydride may be purchased commercially or prepared. Presently, it is preferred to buy this from Texaco. One such commercially sold polyalkenylsuccinic anhydride is sold under the trademark TLA-627. It is a polyisobutenylsuccinic anhydride (PIBSA) having the structure ##STR1## wherein, in this case, R is an isobutenyl repeat unit. The average molecular weight of the polyisobutene used to produce the PIBSA is about 1300. 
     The precursor polyalkenylsuccinic anhydride may also be prepared as reported in U.S. Pat. No. 3,235,484 (Colfer), incorporated herein by reference or by the methods reported in U.S. Pat. No. 4,883,886 (Huang), also incorporated by reference herein. As to the Colfer method, the anhydrides may be prepared by reaction of maleic anhydride with a high molecular weight olefin or a chlorinated high molecular weight olefin. In the Huang method, reaction of a polymer of a C 2  -C 8  olefin and maleic anhydride are carried out in the presence of a tar and side product suppressing agent. 
     The most commonly used sources for forming the aliphatic R substituent on the succinic anhydride compound (I) are the polyolefins, such as polyethylene, polypropylene, polyisobutene, polyamylene, polyisohexylene, etc. The most particularly preferred polyolefin (and the one used to manufacture the polyisobutenylsuccinic anhydride from Texaco) is polyisobutene. As Colfer states, particular preference is made for such a polyisobutene-containing at least about 50 carbon atoms, preferably from at least 60 carbon atoms and most desirably from about 100 to about 150 carbon atoms. Accordingly, an operable carbon atom number range for R is from about 30-200 carbon atoms. 
     Once the polyalkenylsuccinic anhydride precursor is obtained, it is reacted with a polyamine, as reported in Colfer, at temperature in excess of about 80° C. so as to form an imide. More specifically, the polyalkenylsuccinic anhydride ##STR2## wherein R is an aliphatic alkenyl or alkyl moiety having at least about 50 carbon atoms and less than about 200 carbon atoms, is reacted with a polyamine having the structure ##STR3## in which n is an integer, A is chosen from hydrocarbyl, hydroxyalkyl or hydrogen with the proviso that at least one A is hydrogen. Q signifies a divalent aliphatic radical. As Colfer indicates, the A substituents can be considered as forming a divalent alkylene radical, thus resulting in a cyclic structure. Q generally, however, is (C 1  -C 5 ) alkylene, such as ethylene, trimethylene, tetramethylene, etc. Q is most preferably ethylene. 
     Accordingly, exemplary amine components may comprise ethylenediamine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine, trimethylenediamine, bis(trimethylene)triamine, tris-(trimethylene)tetramine, tris(hexamethylene)tetramine, decamethylenediamine, N-octyltrimethylene diamine, N-(2-hydroxyethyl)ethylenediamine, 1-(2-aminopropyl)piperazine, 1,4-bis(2-aminoethyl)piperazine, bis-(hydroxypropyl)substituted tetraethylenepentamine, N-3-(hydroxypropyl)tetramethylenediamine, 2-methylimidazoline, polymerized ethyleneamine, and 1,3-bis (2-aminoethyl)imidazoline. 
     The reaction of precursor polyalkenylsuccinic anhydride with amine (II) is conducted at temperature in excess of 80° C. with use of a solvent, such as benzene, xylene, toluene, naphtha, mineral oil, n-hexane, etc. Preferably, the reaction is conducted at from 100°-250° C. with the molar amount of precursor anhydride (I): amine (II) being from about 1:5 to about 5:1 with a molar amount of 1-3:1 being preferred. 
     The polyalkenylsuccinimide so obtained will have the structure ##STR4## wherein R, Q, A and n are as previously defined in connection with structural formulae I and II. Z is either H or ##STR5## 
     After the polyalkenylsuccinimide precursor has been obtained, it is reacted with a triazole (e.g., tolyltriazole), and an aldehyde (e.g., salicylaldehyde) as reported in U.S. Pat. No. 4,897,086 to form the desired reaction product. 
     At present, preliminary studies have indicated surprisingly effective antifouling inhibition results with these reaction products. The polyisobutenyl succinimide is formed from about a 2:1 molar ratio of polyisobutenyl succinic anhydride (MW isobutenyl moiety 1300) with an ethylenepolyamine, in this case tetraethylenepentamine. 
     The triazoles have the structural formula: ##STR6## where R 1  is hydrogen or an alkyl, aryl, arylalkyl, or alkylaryl group of 1 to 12 carbon atoms. The aldehyde used in preparing the reaction product can be alkyl, aryl, alkylaryl, or arylalkyl containing 1 to 12 carbon atoms. Also included is formaldehyde, the paraformaldehyde form being more preferred, benzaldehyde, 2-ethylhexanal, salicylaldehyde, butanal, 2-methylpropanal and acetaldehyde. 
     The polyalkenyl-substituted succinimide, aldehyde, and triazole are reacted in a mole ratio of succinimide to aldehyde to triazole respectively of between about 1 to 0.1 to 0.1 and 1 to 4 to 4, preferably at a temperature of about 100° C. to 200° C. at ambient pressure. If desired, the reaction can be conducted in a carrier solvent such as xylene or toluene and in a non-reactive atmosphere. After reaction is complete, the reaction mass is treated to remove any solvent or water of reaction. The resulting product is the desired additive product. 
     The reaction products useful in the invention may be added to or dispersed within the liquid hydrocarbonaceous medium in need of antifouling protection in an amount of 0.5-10,000 ppm based upon one million parts of the liquid hydrocarbonaceous medium. Preferably, the antifoulant is added in an amount of from 1 to 2500 ppm. 
     The reaction products may be dissolved in a polar or non-polar organic solvent, such as heavy aromatic naphtha, toluene, xylene, or mineral oil and fed to the requisite hot process fluid or they can be fed neat thereto. These products are especially effective when added to the liquid hydrocarbonaceous medium during the heat processing thereof at temperatures of from 200°-550° C. 
     EXAMPLE 1 
     To a 1500-mL resin kettle equipped with overhead stirring, thermometer, an addition funnel, a condenser, and a Dean-Stark trap filled with xylene were charged 65% PIBSA (600 g, polyisobutenylsuccinic anhydride, MW 1300, 300 mmol), Mentor®28 (211 g), and xylene (180 ml). The mixture was heated to 60° C. to facilitate mixing, and tetraethylenepentamine (31.2 g, 165 mmol) was added over 15 minutes via the addition funnel. The mixture was heated at reflux for 3 hours. When water stopped collecting, the remaining xylene was removed by vacuum distillation (140° C., 71 torr), resulting in a viscous brown oil (840 g). 
     EXAMPLE 2 
     To a 500-mL resin kettle equipped with overhead stirring, thermometer, nitrogen tube, a condenser and a Dean-Stark trap filled with toluene were charged 200 g (40 mmol) of the succinimide of example 1, tolyltriazole (6.4 g, 48 mmol) and toluene (100 ml). The mixture was heated to 70° C. and salicylaldehyde added (5.9 g, 48 mmol). The mixture was heated at reflux (135° C.) for 4 hours until no more water was collected. The toluene was removed by distillation, resulting in a viscous brown oil (210 g). The material was diluted to 50% active using mineral oil and designated PBSTS. 
     Antifoulant Tests 
     The dual fouling apparatus (DFA), as described in U.S. Pat. No. 4,578,178, was used to determine the antifoulant efficacy of a polyisobutenyl succinimide reacted with (1) tolyltriazole and (2) salicylaldehyde in crude oil, as illustrated in Table 1. This compound is designated as PBSTS. The antifoulant efficacy of a polyisobutenyl succinimide antifoulant, sold commercially as a dispersant additive for automotive lubricating oils, was compared to this compound in crude oil with results detailed in Table 1. Also, the PIBSA succinimide prepared in Example 1 was compared for antifoulant efficacy. 
     The DFA used to generate the data shown in Table I contains two independent, heated rod exchangers. In the DFA tests, rod temperature was controlled while testing. As fouling on the rod occurs, less heat is transferred to the fluid so that the process fluid outlet temperature decreases. Antifoulant protection was determined by comparing the summed areas between the heat transfer curves for control and treated runs and the ideal case for each run. In this method, the temperatures of the oil inlet and outlet and rod temperatures at the oil inlet (cold end) and outlet (hot end) are used to calculate U-rig coefficients of heat transfer every 2 minutes during the tests. From these U-rig coefficients, areas under the fouling curves are calculated and subtracted from the non-fouling curve for each run. Comparing the areas of control runs (averaged) and treated runs in the following equation results in a percent protection value for antifoulants. ##EQU1## 
     
                       TABLE I                                                     
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Summary of DFA Results on PBSTS Compared to                               
Polyisobutenyl Antifoulant (PIBSA Succinimide)                            
Desalted Crude Oil, 482° C. Rod Temperature                        
Additive (ppm active)    % Protection                                     
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PIBSA Succinimide                                                         
                 (62.5)      8     (avg)                                  
               (250)         18                                           
Example 1        (62.5)      29    (avg)                                  
               (250)         27                                           
PBSTS (Example 2)                                                         
                 (62.5)      24    (avg)                                  
               (250)         28                                           
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     As shown in Table 1, the antifoulant efficacy of PBSTS was higher than that of the commercial PIBSA succinimide and equivalent to Example 1 when tested at dosages of 62.5 and 250 ppm active. 
     Another series of tests adapted to assess candidate efficacy in providing fouling inhibition during low to moderate temperature treatment of liquid hydrocarbon medium were performed. These tests are entitled the &#34;Hot Filament Fouling Tests&#34; and were run in conjunction with gas oil hydrocarbon medium. The procedure for these tests involves the following: 
     A preweighed 24-gauge Ni-chrome wire was placed between two brass electrodes in a glass reaction jar and held in place by two brass screws. 200 mLs of feedstock were measured and added into each sample jar. One sample jar was left untreated as a control with other jars being supplied with 125 ppm (active) of the candidate material. The brass electrode assembly and lids were placed on each jar and tightly secured. The treatments were mixed via swirling the feedstock. Four sample jars were connected in series with a controller provided for each series of jars. 
     The controllers were turned on and provided 8 amps of current to each jar. This amperage provided a temperature of about 125°-150° C. within each sample jar. After 24 hours of current flow, the controllers were turned off and the jars were disconnected from their series connection. The wires, which were immersed in the hot medium during the testing, were carefully removed from their jars, were washed with xylene and acetone, and were allowed to dry. 
     Each wire and the resulting deposits thereon were weighed with the weight of the deposit being calculated. 
     The deposit weight for a given wire was calculated in accordance with ##EQU2## 
     The percentage protection for each treatment sample was then calculated as follows: ##EQU3## Results are shown in Table II. 
     
                       TABLE II                                                    
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            ppm        Feedstock                                          
Additive    Actives    Type       % Protection                            
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PIBSA Succinimide                                                         
             31        CCLGO      33                                      
            125        CCLGO      89  (Avg)                               
            125        SRLGO      40  (Avg)                               
Example 1   125        CCLGO      92                                      
            125        SRLGO      66  (Avg)                               
PBSTS (Example 2)                                                         
             31        CCLGO      62                                      
            125        CCLGO      98                                      
            125        SRLGO      97                                      
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     In Table II, SRLGO means straight run light gas oil from a midwestern refinery with CCLGO indicating a catalytic cracked light gas oil from the same midwestern refinery. When tested in the CCLGO, examples 1 or 2 at 125 ppm active exhibited approximately comparable antifoulant efficacy compared to the commercial PIBSA succinimide. Example 2 was somewhat better than the PIBSA succinimide when tested at 31 ppm active in the CCLGO. When tested in the SRLGO, example 1 was somewhat better than example 2 or the PIBSA succinimide at 125 ppm active. These results confirm that the reaction products of the disclosed invention are at least comparable in antifoulant efficacy to PIBSA succinimides at low to moderate processing temperatures (about 125°-150°C.). 
     While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of the invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.