CN110823800A - Analysis method of methanol fuel metal corrosion inhibitor - Google Patents
Analysis method of methanol fuel metal corrosion inhibitor Download PDFInfo
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention discloses an analysis method of a methanol fuel metal corrosion inhibitor, which comprises the following steps: by taking the currently commercialized methanol gasoline corrosion inhibitor as a reference, detecting and contrasting a gas-mass spectrum on an instrument through a gas chromatography-mass spectrometry instrument, and analyzing to obtain related similar components so as to narrow the research range of effective additives; step 2: further tests are carried out by utilizing an electrochemical workstation, a series of related concentration groups and related metal electrodes are configured, polarization curve mapping is respectively carried out on an electrochemical instrument, the corrosion inhibition effect of the corrosion inhibitor, the optimal preparation proportion of the corrosion inhibitor and the corresponding corrosion mechanism are analyzed, and the optimal selection of the corrosion inhibitor is achieved. The benzotriazole and cyclohexane of the invention have good corrosion inhibition effect on metal copper and steel, which not only improves the corrosion inhibition of methanol fuel on metal, but also prevents the surface of the metal from rusting.
Description
Technical Field
The invention relates to the technical field of methanol fuels, in particular to an analysis method of a methanol fuel metal corrosion inhibitor.
Background
The vehicle methanol gasoline is a novel vehicle fuel developed in recent years, and is developed to adapt to the increasingly prominent current resource and environmental problems in China, the energy resource condition of rich coal, poor oil and little gas and the influence of the world political and economic pattern on the energy supply and demand situation. The method is an important component for maintaining the petroleum safety in China and a strategic choice for supporting the sustainable development of energy in China in the future. The methanol fuel is used as a novel alternative energy for adjusting the traditional energy structure and promoting the development of circular economy, and is a typical low-carbon energy characterized by energy consumption reduction, pollution reduction, low-carbon utilization and mixed development. The methanol fuel is a preferred product for replacing petroleum by virtue of excellent properties of good environmental protection, high cost performance, mature technology, resource guarantee and the like. The active promotion of the industrialization of the methanol fuel is one of the most important measures for developing low-carbon energy and circular economy.
Methanol is the main component of methanol automobile, especially methanol gasoline for high proportion automobile. Methanol gasoline has the advantages of abundant raw material sources, high octane number, and less carcinogens (e.g., acetaldehyde, benzene, and 1, 3-butadiene) emitted by combustion, compared to conventional gasoline. However, methanol fuel also has the following problems in use:
(1) has high corrosion to metal
The most fatal disadvantage of the methanol fuel in the use process is that the methanol fuel has high corrosivity to metal, and causes corrosion and abrasion to an engine fuel system. This becomes a key issue that limits the development of methanol fuels. Methanol is corrosive to metals because methanol generally contains acidic materials during production and its inherent water absorption causes it to contain a small amount of water during storage, and the presence of water in methanol fuel activates the problems of acid corrosion and electrochemical corrosion of metals. When no water is contained in the gasoline, the acid corrosion is very weak, and is mainly copper sheet corrosion caused by active sulfide; when water exists in the methanol fuel, acid ionization is caused, so that acid corrosion of the active metal is intensified. Compared with hydrocarbons, alcohols have a greater chemical oxidation effect and higher electrical conductivity on some metals, which exacerbates the electrochemical corrosion effect between different metals.
(2) Swelling effect on rubber parts
Methanol is one of the solvents commonly used in chemical and chemical processes. Because of its small molecular size and hydroxyl groups which are susceptible to interaction with other molecules, methanol fuel, particularly methanol in high proportions, produces a large swelling effect on rubber parts of automotive fuel supply systems, and also swells, hardens, softens or cracks synthetic rubbers for seals and other parts of oil pumps.
(3) Emission of engine
The result of a low-proportion methanol gasoline emission test shows that after M15 methanol gasoline is used on the existing vehicle, the emission situation is slightly improved compared with that of a gasoline engine, the CO is reduced by about 30%, the H, C is reduced by more than 25%, and the N, O, S is reduced by about 8%. The methanol and formaldehyde content in the M15 cab and around the oil depot were tested to be below the maximum concentrations allowed in the residential area. Meanwhile, the combined toxicity research of the M15 methanol-gasoline mixed fuel shows that the methanol and the gasoline in the M15 have no toxicity increasing effect. As long as the operating procedures are followed, there are substantially no safety issues.
It should be noted that the methanol fuel additive is also an important factor influencing the emission of methanol gasoline, and if metal ions and elements such as nitrogen, sulfur, phosphorus and the like which influence the subsequent emission of an engine are doped in the additive, the emission result of the whole vehicle is seriously influenced.
Idea for solving use problem of methanol gasoline
(1) Corrosiveness of
There are two basic approaches to prevent methanol fuel corrosion of engine metals: firstly, the metal material of the engine is changed, and the engine is manufactured by using corrosion-resistant metal, for example, the iron alloy is changed into nickel alloy, hard particles are added into a sintering material of a valve seat, and lead infiltration treatment, chrome plating of a piston ring and the like are carried out; secondly, adding an anti-corrosion additive into the fuel. In contrast, the former is expensive and only suitable for the manufacture of new engines, while the latter is simpler, less expensive and more effective.
(2) Swelling action
In order to fundamentally solve the swelling effect of methanol on rubber parts, the best method is to research and replace non-metallic materials which are suitable for methanol fuel, so that the rubber parts are resistant to both gasoline and methanol fuel. However, since the current state of the art and material cost issues do not make it possible to replace all the materials of the vehicle, the solution of the combustion performance of methanol fuel from the fuel perspective by adding a corrosion swelling inhibitor is an effective way to solve the problem of corrosion swelling.
Therefore, the key point of solving the problems of corrosivity and swelling in the use process of the methanol gasoline is to develop a proper additive.
Much research has been done to slow down corrosion. The corrosion inhibitor is a corrosion resistant material developed from the aspect of engine materials, and a novel corrosion inhibitor, a cosolvent, a detergent dispersant and a vapor pressure inhibitor are developed from the aspect of chemical additives. Compared with the two methods, the former method has high cost and is only suitable for manufacturing the new engine, while the latter method is simpler, has low cost and better effect. The research method has the advantages of being visual, obvious in effect, long in time consumption, poor in variable control, not beneficial to optimization selection of a series of variables, and rapid and convenient in screening of the optimal concentration and the optimal composite proportion of the corrosion inhibitor.
Disclosure of Invention
The invention aims to provide an analysis method of a methanol fuel metal corrosion inhibitor, which improves the corrosion inhibition effect of methanol fuel metal and solves the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for analyzing a methanol fuel metal corrosion inhibitor comprises the following steps:
step 1: by taking the currently commercialized methanol gasoline corrosion inhibitor as a reference, detecting and contrasting a gas-mass spectrum on an instrument through a gas chromatography-mass spectrometry instrument, and analyzing to obtain related similar components so as to narrow the research range of effective additives;
step 2: carrying out further tests by using an electrochemical workstation, configuring a series of related concentration groups and related metal electrodes, respectively carrying out polarization curve mapping on an electrochemical instrument, and analyzing the corrosion inhibition effect of the corrosion inhibitor, the optimal preparation proportion of the corrosion inhibitor and the corresponding corrosion mechanism to achieve the optimal selection of the corrosion inhibitor;
and step 3: the results of the above studies are detected by using a metal corrosion meter under the condition of approaching to actual use, the actual effect is observed, and the improvement is continuously carried out.
Further, the method for electrochemically researching metal corrosion comprises the following steps: polarization curve epitaxy, linear polarization, three-point, four-point.
Further, the analysis process comprises analysis of a commercialized corrosion inhibitor, analysis of corrosion inhibition effect and optimal proportion of cyclohexylamine, analysis of corrosion inhibition effect and optimal proportion of benzotriazole, and research of corrosion inhibition effect after mixing benzotriazole and cyclohexylamine.
Further, in the commercial corrosion inhibitor analysis, the optimal addition ratio of the selected commercial corrosion inhibitor is firstly measured, and a series of concentrations are configured for polarization curve determination.
Further, the research content of the corrosion inhibition effect of the mixed benzotriazole and cyclohexylamine comprises electrochemical analysis and corrosion instrument effect detection.
Compared with the prior art, the invention has the beneficial effects that: the invention analyzes and researches the corrosion inhibitor of the methanol gasoline through a series of experiments, and finally obtains the optimal mixing proportion of the two components:
(1) for metallic copper: when the content of benzotriazole in methanol is 0.0008mol/L, the corrosion inhibition effect is good, and when the volume proportion of cyclohexylamine in methanol is 0.05%, the corrosion inhibition effect is best.
(2) For metallic steels: when the content of benzotriazole in methanol is 0.0004mol/L, the corrosion inhibition effect is good, and when the volume proportion of cyclohexylamine in methanol is 0.09%, the corrosion inhibition effect is obvious.
(3) When benzotriazole is compounded with cyclohexylamine: the corrosion inhibition effect is best when the materials are compounded in a volume ratio of 3:7, and the best proportioning is that 0.03192g of benzotriazole and 0.35ml of cyclohexylamine are added into each liter of methanol for mixing. The corrosion inhibition effect on copper after the composition is carried out is better.
Drawings
FIG. 1 is a linear graph of corrosion current density obtained by the polarization curve epitaxy method of the present invention;
FIG. 2 is a linear plot of corrosion current density measured from cathodic polarization curves in accordance with the present invention;
FIG. 3 is a 15 minute GC-MS spectrum of a product of the invention;
FIG. 4 is a comparative mass spectrum of a product of the invention with benzotriazole;
FIG. 5 is a diagram of an electrochemical testing system according to the present invention;
FIG. 6 is a Tafel plot of the present invention;
FIG. 7 is a plot of the polarization of copper versus concentration for a series of corrosion inhibitors in accordance with the present invention;
FIG. 8 is a cathodic polarization graph of cyclohexylamine versus steel according to the present invention;
FIG. 9 is a plot of the polarization of cyclohexylamine versus copper according to the present invention;
FIG. 10 is a cathodic polarization graph of the corrosion of benzotriazole to steel of the present invention;
FIG. 11 is a polarization curve diagram of benzotriazole and cyclohexylamine as composite corrosion inhibitors of the present invention for copper;
FIG. 12 is a diagram of a standard color panel according to the present invention;
FIG. 13 is a graph showing the corrosion of metals according to the present invention;
FIG. 14 is an image of methanol solution after immersion in the copper sheet corrosion meter of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a method for analyzing a methanol fuel metal corrosion inhibitor includes the following steps:
step 1: by taking the currently commercialized methanol gasoline corrosion inhibitor as a reference, detecting and contrasting a gas-mass spectrum on an instrument through a gas chromatography-mass spectrometry instrument, and analyzing to obtain related similar components so as to narrow the research range of effective additives;
step 2: carrying out further tests by using an electrochemical workstation, configuring a series of related concentration groups and related metal electrodes, respectively carrying out polarization curve mapping on an electrochemical instrument, and analyzing the corrosion inhibition effect of the corrosion inhibitor, the optimal preparation proportion of the corrosion inhibitor and the corresponding corrosion mechanism to achieve the optimal selection of the corrosion inhibitor;
and step 3: the results of the above studies are detected by using a metal corrosion meter under the condition of approaching to actual use, the actual effect is observed, and the improvement is continuously carried out.
There are several methods for electrochemically investigating metal corrosion: polarization curve epitaxy, linear polarization, three-point, four-point, etc. Polarization curve epitaxy is commonly used.
The polarization curve epitaxy method is to use a cathodic polarization curve and an anodic polarization curve to intersect the straight line part epitaxy of the E-lgi curve at an etching potential, so as to obtain an etching current, as shown in FIG. 1. The straight line part of the curve is a strong polarization area and is a Tafel straight line area.
The theory of the method is as follows: when a metal is corroded, O + ne (1) reduced by a depolarizer and M ═ Mn + + ne (2) dissolved by oxidation of the metal are carried out in parallel, and the same number of electrons participate in the reaction.
If both reactions are controlled electrochemically, andEcorrequilibrium potential E far from the above two reactionse,1And Ee,2I.e. the polarization is stronger, the current density of the reduction reaction:
i1＝i1 0exp[a1nF(Ee,1-Ecorr)/RT](1)
current density of oxidation reaction:
i2＝i2 0exp[b2nF(Ecorr-Ee,2)/RT](2)
at the corrosion potential, the corrosion is in a steady state, i1＝i2＝i0corr
When the metal is anodically polarized, the potential of the metal is from EcorrThe anode polarization current density starts to move △ E in the positive direction when:
iA＝i1＝i2＝△i
＝i2 0exp[b2nF(Ecorr+△E–E2)/RT]-i1 0exp[a1nF(Ee,1-Ecorr-△E)/RT]
＝icorr{exp[b2nF△E/RT]-exp[a1nF△E/RT]} (3)
when the anodic polarization is large enough, i.e., △ E is large enough, the second term of the above equation is negligible, resulting in:
iA＝icorrexp[b2nF△E/RT](4)
or
△E＝-bAlgicorr+bAlgiA(5)
In the formula bA＝2.3RT/b2nF
When the cathodic polarization is relatively strong, the current density of metal dissolution is negligible, from E at the metal potentialcorrAfter moving △ E in the negative direction, the following relationship can be derived using the method described above:
△E＝-bKlgicorr+bKlgiK(6)
in the formula bK＝2.3RT/a1nF
Both equations are similar to the Tafel equation, and △ E plots the logarithm of the polarization current as a straight line1＝b2The two lines are symmetrical.
As can be seen from FIG. 1, in the strongly polarized region, the anodic polarization current density iACurrent density i of dissolution by oxidation of metal2Coincide and the cathodic polarization current density ik is equal to the current density i reduced by the depolarizer1And (4) overlapping. Intersection point of two Tafel straight line extension lines or Tafel straight line extension line and EcorrThe current density corresponding to the intersection of the horizontal lines is the corrosion current density icorr. B is determined from the slope of the straight line segmentAAnd bk。
The polarization curve epitaxy method has the advantages that: the advantage of polarization curve epitaxy is that b need not be knownAAnd bk. The method is simple and rapid. Especially, the method is widely applied to judging the action mechanism of various additives or screening corrosion inhibitors and the like. According to i of the polarization curvecorrThe relative size of (A) can be used to judge whether the additive is an accelerator or a corrosion inhibitor; the influence of the additive on the anodic process or the cathodic process or on both the cathodic and the anodic process can be determined from the polarization curve.
Limitations of polarization curve epitaxy: polarization curve epitaxy has limitations that apply when the process of etching the cathode or anode, or both, is controlled by an electrochemical step. It is often used to determine the corrosion rate of metals in acidic solutions because in this case the Tafel straight-line segment of the polarization curve is easily measured. The method has the main defects that the polarization is strong, so that passivation can occur when the anode polarization curve is measured; the cathodic polarization curve was determined to possibly reduce the oxide film on the metal surface. In addition, since the corrosion potential changes with time, it does not stabilize until a certain time. Therefore, when the current density is high, the polarization of the cathode and the anode may be measured to cause a difference in polarization and a significant change in the surface state of the electrode, and the relationship may deviate from the linear relationship. Again from curve EcorrSlightly different, i obtained as a resultcorrThe values will differ slightly. Generally, only in rottingUnder the condition of low etching speed, the straight line of the anode polarization Tafel can be easily measured. In the case that the anode polarization Tafel straight line is not easy to obtain, the cathode polarization Tafel straight line and E ═ E can be independently usedcorrThe horizontal lines of (a) intersect and the intersection point is the corrosion current density, i.e. the self-corrosion rate, as shown in fig. 2.
Experimental results and discussion of the invention
(1) Gas chromatography mass spectrometer test and data analysis
A gas chromatography-mass spectrometer is used for testing a certain commercial methanol gasoline additive to obtain a corresponding map (figures 3 and 4), the map is contrasted and analyzed with the map of benzotriazole and benzotriazole which shows good corrosion inhibition effect on metal in the referred data, the matching degree of the two components in the product is very high and both exceed 95 percent, the product can be determined to contain the substance, and the product can also be found to contain various additives from the gas chromatography-mass spectrometer, wherein the components are not single, but are mostly organic benzene rings and some oil ester substances.
(2) Measurement of corrosion by electrification using float device of oil meter
On the basis of the analysis, the benzotriazole is used for carrying out a comparative experiment on the corrosion inhibition effect of the oil pump. The experimental instrument is two sets of oil meter floater electrifying devices which are respectively provided with 0.0008mol/L benzotriazole, 0.0008mol/L dimer linoleic acid and methanol, and 0.0008mol/L product and methanol, the oil meter floater is used for electrifying detection, the sensitivity of the floater (which is equivalent to a slide rheostat under the actual action) is detected by using the resistance gear of a universal meter, the sensitivity is detected every 2h, the sensitivity of the universal meter for detecting the resistance change of the oil meter floater (whether the numerical value has a gradual change trend along with the slow pulling of a hand pull rod) is recorded in the electrifying time of less than 4h, the sensitivity of the floater in the first two hours is good in the electrifying time of 4h, and the floater in the last 2h is insensitive, so that the floaters are corroded along with the prolonging of the electrifying.
(3) Electrochemical measurements
The RST3000 electrochemical workstation and related software are used for carrying out measurement on a polarization curve, a three-electrode system is adopted, a working electrode is a metal sample, a reference electrode is a Saturated Calomel Electrode (SCE), an auxiliary electrode is a platinum electrode, the scanning potential is basically from 1500mV to 400mV, the scanning speed is 50mV/s, and a metal sheet is soaked for one hour under various concentrations before an experiment. The test system is shown in figure 5.
The anode curve obtained in the experiment deviates significantly from the linear relationship as shown in fig. 6. The anodic polarization curve may be passivated due to the strong anodic polarization, or the corrosion potential may change with time and may not be stabilized until a certain time due to the high current density. Therefore, when the current density is high, concentration polarization and the electrode surface state change significantly due to the measurement of cathode and anode polarization, and the measurement may deviate from the linear relationship. And again due to E on the curvecorrSlightly different, and the resulting value icorr will be slightly different. Generally, the anodic polarization Tafel straight line is easier to measure only when the corrosion rate is not high. In the case that the anode polarization Tafel straight line is not easy to obtain, the cathode polarization Tafel straight line and E ═ E can be independently usedcorrThe horizontal lines of (a) intersect, and the intersection point is the corrosion current density, i.e., the self-corrosion rate.
The experimental process data were recorded and analyzed as follows:
(1) commercial corrosion inhibitor analysis
Firstly, the optimal addition proportion of the selected commercial corrosion inhibitor is measured, a series of concentrations are configured for polarization curve determination, a gas chromatograph-mass spectrometer is used for testing the methanol gasoline additive to obtain a corresponding map, and the result is shown in the following figure 7, and tables 1 and 2:
TABLE 1 polarization curve data for corrosion inhibitor series concentrations versus copper
And (3) data analysis: from the image and the linear relation data, it can be seen that the current data change rule from the blank group (pure methanol) to the condition that the volume ratio of the corrosive agent to the methanol is 0.10% can be intuitively seen that when the volume ratio accounts for 0.08%, the current density is minimum, and the current data change rule has an inhibiting effect on the electrochemical processes of the cathode and the anode of the copper electrode, in comparison, the inhibiting effect on the cathode process of the electrode is larger, the slope of the cathode polarization curve when the self-corrosion potential of the copper electrode respectively moves from the blank 744 negative to 536 is smaller, which indicates that the reduction reaction of the cathode oxygen can be inhibited by the addition of the corrosion inhibitor, an obvious active dissolution area appears on the anode polarization curve, and the larger the membrane resistance is, the smaller the membrane capacitance is, and the better the corrosion inhibition effect is.
And (4) conclusion: the current density of the commercial corrosion inhibitor is the minimum when the volume ratio is 0.08%, and the corrosion inhibitor has the best corrosion inhibition effect on copper at the concentration.
TABLE 2 Corrosion inhibitor series concentration versus polarization curve fitting data for steel
And (4) conclusion: from the table, it can be seen that the current density of the commercial corrosion inhibitor is the minimum when the volume ratio is 0.07%, and the self-corrosion speed of the reaction steel with good data under the condition of basically no potential deviation is the minimum, which shows that the corrosion inhibitor has the best corrosion inhibition effect on the steel at the concentration.
(2) Corrosion inhibition effect and optimal proportion analysis on cyclohexylamine
TABLE 3 polarization curve fitting data of cyclohexylamine corrosion inhibitor to steel
Data analysis and conclusion: from the polarization curve of FIG. 8 and Table 3, it can be seen that the current density becomes gradually smaller as the amount of the corrosion inhibitor is increased, the slope of the cathode tafel curve is smaller than that of the blank, and when the volume ratio is 0.10%, the current density continues to decrease to 1.064X 10-7Considering that the dosage of the added corrosion inhibitor is very micro and is generally in the order of ten-thousandth, the selection ratio is 0.09 percent, and the corrosion inhibition effect of the cyclohexylamine on the steel is relatively ideal。
TABLE 4 polarization curve fitting data of corrosion inhibitors to copper in cyclohexylamine series concentration
As can be seen from fig. 9 and the data in table 4: the cyclohexylamine has the lowest current density at a volume ratio of 0.05%, and the self-corrosion rate of the reaction steel with good data is the lowest under the condition that the potential basically has no deviation, and the corrosion inhibition concentration is the best at the concentration.
(3) Corrosion inhibition effect and optimal proportion analysis of benzotriazole
TABLE 5 polarization curve fitting data of benzotriazole series concentration corrosion inhibitor to steel
And (3) data analysis: from fig. 10, table 5 and the linear relationship data made, it can be seen visually that: when the concentration is 0.0004mol/L, the current density is the minimum, the self-corrosion potential of the steel electrode is basically unchanged, and the slope is smaller than that of the blank, which shows that the addition of the corrosion inhibitor can inhibit the reduction reaction of cathode oxygen, the self-corrosion speed is the minimum and the corrosion inhibition effect is the best at this time, and for steel, the corrosion inhibition effect of the benzotriazole at the methanol concentration of 0.0004mol/L is the best.
TABLE 6 polarization curve fitting data of benzotriazole series concentration corrosion inhibitor to copper
(4) Corrosion inhibition effect research of mixed benzotriazole and cyclohexylamine
① electrochemical analysis
The optimal proportion of the corrosion inhibitor under the independent action is obtained from the experiments, and the corrosion inhibition effect of copper is researched after the benzotriazole and the cyclohexylamine are mixed on the basis. Firstly, referring to the previous research and matching proportion, the optimal proportion of the single components of the benzotriazole and the cyclohexylamine is compounded as follows:
TABLE 7 polarization curve data of corrosion inhibitor formed by compounding benzotriazole and cyclohexylamine at different optimal concentrations and volume ratios to copper
Combining the data in FIG. 11 and Table 7, it can be seen that the current density is 1.47X 10 when the ratio of benzotriazole to cyclohexylamine is 3:7-8And a corrosion inhibition current density of 2.54 x 10 less than the optimum concentration of cyclohexylamine for copper-7And the current density is also less than 7.84 multiplied by 10 when the benzotriazole exists alone at the best mixture ratio-8. Therefore, the two have certain synergistic effect after being compounded.
② Corrosion Meter Effect detection
And detecting the composite concentration by using a copper sheet corrosion meter, and comparing the composite concentration with a standard colorimetric plate to obtain a corrosion degree value. The experimental temperature is controlled at 50 ℃, the experimental time is 9h, and the effect is shown in figure 13.
From the left of FIG. 13, there are no immersion of pure copper, commercial reagent immersion, 1:9 of benzotriazole and cyclohexylamine, 3:7 of benzotriazole and cyclohexylamine, 5:5 of benzotriazole and cyclohexylamine, 7:3 of benzotriazole and cyclohexylamine, 9:1 of benzotriazole and cyclohexylamine, and no corrosion inhibitor added to the blank group (methanol immersion).
In the drawing, 1:9 soaking solution of benzotriazole and cyclohexylamine, 3:7 soaking solution of benzotriazole and cyclohexylamine, 5:5 soaking solution of benzotriazole and cyclohexylamine, 7:3 soaking solution of benzotriazole and cyclohexylamine, 9:1 soaking solution of benzotriazole and cyclohexylamine, and commercial corrosion inhibitor soaking solution are shown in fig. 14.
Table 8 corrosion grade of composite corrosion inhibitor on copper: complexing agent (benzotriazole cyclohexylamine)
And (4) conclusion: the current density data, the measurement result of the corrosion meter and the color of the corrosion inhibition soaking solution are considered comprehensively, and the synergistic effect of the current density data, the measurement result and the color of the corrosion inhibition soaking solution is the best when the ratio is 3: 7.
(5) Benzotriazole and cyclohexylamine corrosion inhibition mechanism
① benzotriazole
Benzotriazole adsorbs on the surface of metal to form a thin film to protect the metal from corrosion of harmful media, and is widely used as an antirust agent and a corrosion inhibitor for metals (such as silver, copper, lead, nickel, zinc and the like).
There is one N-H and two nitrogen atoms in the molecule with unshared electron pairs. Benzotriazole was originally thought to adsorb to metal surfaces via unshared electron pairs on nitrogen atoms, as with typical corrosion inhibitors. However, the film formed on the surface of the copper plate treated with benzotriazole has a high decomposition temperature and cannot be easily removed by a general chemical reagent unless a reagent such as ammonia or cyanogen which forms a complex having a large stability coefficient with copper is used, and it is found that benzotriazole is not easily adsorbed on copper. The corrosion inhibition of benzotriazole is generally considered to be an adsorption film type mechanism, i.e. benzotriazole is firstly gasified and dissolved in a condensed water layer on the copper surface, and then reacts with the copper surface to form a complex film, and the reaction is as follows:
the complex film is thin and compact and is insoluble in water. Therefore, on one hand, the effect of corrosive substances with the outside is isolated, on the other hand, the charge state and the interface property of the metal surface are changed, and the energy state of the metal surface tends to be stabilized, so that the corrosion inhibition effect is achieved. Due to the permeation and volatilization, the benzotriazole can also reach the rust layer deeply, so that the original rust layer is stable, and further rust can be prevented, and the benzotriazole is also suitable for rust protection of copper cultural relics. Benzotriazole is an excellent corrosion inhibitor for a plurality of metals, and a plurality of researchers believe that the corrosion inhibition effect of benzotriazole comes from the complex of benzotriazole and metal surface. Recent studies show that benzotriazole and Cu form a complex film on the surface of metal, thereby effectively inhibiting the dissolution of the metal.
② Cyclohexylamine
The cyclohexylamine is a solvent and can be applied to resins, coatings, fats and paraffin oil. It can also be used for preparing desulfurizer, rubber antioxidant, vulcanization accelerator, plastic and textile chemical auxiliary agent, boiler feed water treatment agent, metal corrosion inhibitor, emulsifier, antiseptic, antistatic agent, latex coagulant, petroleum additive, bactericide, pesticide and dye intermediate. Can be adsorbed by the metal surface to form a layer of film which covers the metal surface and plays a role in inhibiting corrosion.
The electrochemical and infrared measurement results are combined, so that the corrosion inhibition effect is greatly different for different acid groups of the cyclohexylamine vapor phase corrosion inhibitor. According to the infrared test result, the corrosion inhibition effect is supposed to be inhibited mainly by covering the surface of Fe by forming a covalent bond between O in an N acid group functional group in a cyclohexane functional group and Fe. In the corrosion inhibitors studied, the basic functional groups were all cyclohexylamine, whereas the acidic functional groups were very different. For example acidic functional groups H2CrO4、H3PO4、HNO2And H2CO3The first order ionization constants of the acids are 0.16 and 7.52X 10-3、5.1×10-4And 4.3X 10-7The acidity of the acid functional group is changed from large to small, the electron cloud density of N atoms in amino functional groups in cyclohexylamine is directly influenced by the acidity of the acid functional group, the stronger the acidity, the smaller the electron cloud density of the N atoms, the greater the electronegativity, the easier the covalent bond is formed with Fe atoms, the better the corrosion inhibition effect is, and the further corrosion inhibition mechanism needs to be further researched.
Other additives of the invention
① antioxidant
In the process of storage and use, the fuel is inevitably contacted with oxidizing substances such as oxygen in the air, so that the fuel is oxidized and deteriorated, the acidity and the viscosity of the fuel are changed, even colloid is generated, and the normal use of the fuel is influenced, and in order to avoid the phenomenon, a proper amount of antioxidant 2, 6-di-tert-butyl-p-cresol is added into the additive.
2, 6-di-tert-butyl-p-cresol is a free radical chain reaction terminator, can react with the active free radical of an oxidant, consumes the generated oxidizing free radical, prevents the active free radical from acting with fuel, and protects the active free radical.
② detergent dispersant
The main function of the detergent dispersant is to keep the interior of the engine clean, so that the generated insoluble substances are in a colloid suspension state and carbon deposit, paint film or oil sludge is not further formed. The invention selects alkyl calcium salicylate (T109) with better detergency and succinimide with better dispersibility.
③ coloring agent
If desired, the addition may be made according to national standards.
According to the invention, the corrosion inhibitor of the methanol gasoline is researched through series experiments, so that benzotriazole and cyclohexane have good corrosion inhibition effects on metal copper and steel, the composite effect of the metal copper and the steel is researched, the optimal mixing proportion of the metal copper and the steel is obtained, the theoretical data obtained by using a copper sheet corrosion instrument has obvious detection effect and good discrimination, and the optimal mixing proportion of the metal copper and the steel is finally obtained, and the conclusion is as follows:
(1) for metallic copper: when the content of benzotriazole in methanol is 0.0008mol/L, the corrosion inhibition effect is good, and when the volume proportion of cyclohexylamine in methanol is 0.05%, the corrosion inhibition effect is best.
(2) For metallic steels: when the content of benzotriazole in methanol is 0.0004mol/L, the corrosion inhibition effect is good, and when the volume proportion of cyclohexylamine in methanol is 0.09%, the corrosion inhibition effect is obvious.
(3) When benzotriazole is compounded with cyclohexylamine: the corrosion inhibition effect is best when the materials are compounded in a volume ratio of 3:7, and the best proportioning is that 0.03192g of benzotriazole and 0.35ml of cyclohexylamine are added into each liter of methanol for mixing. The corrosion inhibition effect on copper after the composition is carried out is better.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.
Claims (5)
1. A method for analyzing a methanol fuel metal corrosion inhibitor is characterized by comprising the following steps:
step 1: by taking the currently commercialized methanol gasoline corrosion inhibitor as a reference, detecting and contrasting a gas-mass spectrum on an instrument through a gas chromatography-mass spectrometry instrument, and analyzing to obtain related similar components so as to narrow the research range of effective additives;
step 2: carrying out further tests by using an electrochemical workstation, configuring a series of related concentration groups and related metal electrodes, respectively carrying out polarization curve mapping on an electrochemical instrument, and analyzing the corrosion inhibition effect of the corrosion inhibitor, the optimal preparation proportion of the corrosion inhibitor and the corresponding corrosion mechanism to achieve the optimal selection of the corrosion inhibitor;
and step 3: the results of the above studies are detected by using a metal corrosion meter under the condition of approaching to actual use, the actual effect is observed, and the improvement is continuously carried out.
2. The method of analyzing a methanol fuel metal corrosion inhibitor according to claim 1, wherein the method of electrochemically investigating metal corrosion comprises: polarization curve epitaxy, linear polarization, three-point, four-point.
3. The analysis method of the methanol fuel metal corrosion inhibitor according to claim 1, wherein the analysis process comprises analysis of a commercial corrosion inhibitor, analysis of corrosion inhibition effect and optimal proportion of cyclohexylamine, analysis of corrosion inhibition effect and optimal proportion of benzotriazole, and research of corrosion inhibition effect after mixing of benzotriazole and cyclohexylamine.
4. The method of claim 3, wherein the commercial corrosion inhibitor analysis is performed by first measuring the optimal addition ratio of the selected commercial corrosion inhibitor, and configuring a series of concentrations for polarization curve determination.
5. The analysis method of the methanol fuel metal corrosion inhibitor according to claim 3, wherein the research content of the corrosion inhibition effect of the mixed benzotriazole and cyclohexylamine comprises electrochemical analysis and corrosion meter effect detection.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109839348A (en) * | 2017-11-24 | 2019-06-04 | 北京蓝星清洗有限公司 | A kind of method of quick screening engine cooling liquid formulation |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101914396A (en) * | 2010-08-18 | 2010-12-15 | 上海化工研究院 | Automobile methanol gasoline microemulsion and preparation method thereof |
| CN103952195A (en) * | 2014-05-10 | 2014-07-30 | 山西丰喜新能源开发有限公司 | Automotive methanol gasoline composite additive and preparation method for same |
| US20140260708A1 (en) * | 2013-03-13 | 2014-09-18 | Baker Hughes Incorporated | Use of detection techniques for contaminant and corrosion control in industrial processes |
| CN105542877A (en) * | 2015-07-20 | 2016-05-04 | 张邦武 | Methanol fuel, improved gasoline and preparation method of methanol fuel |
| CN108707489A (en) * | 2018-05-02 | 2018-10-26 | 璧靛嘲 | A kind of environment-friendlygasoline gasoline additive and preparation method thereof |
-
2019
- 2019-11-20 CN CN201911138665.8A patent/CN110823800A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101914396A (en) * | 2010-08-18 | 2010-12-15 | 上海化工研究院 | Automobile methanol gasoline microemulsion and preparation method thereof |
| US20140260708A1 (en) * | 2013-03-13 | 2014-09-18 | Baker Hughes Incorporated | Use of detection techniques for contaminant and corrosion control in industrial processes |
| CN103952195A (en) * | 2014-05-10 | 2014-07-30 | 山西丰喜新能源开发有限公司 | Automotive methanol gasoline composite additive and preparation method for same |
| CN105542877A (en) * | 2015-07-20 | 2016-05-04 | 张邦武 | Methanol fuel, improved gasoline and preparation method of methanol fuel |
| CN108707489A (en) * | 2018-05-02 | 2018-10-26 | 璧靛嘲 | A kind of environment-friendlygasoline gasoline additive and preparation method thereof |
Non-Patent Citations (3)
| Title |
|---|
| 刘东: "原子力显微镜研究苯并三氮唑对铜的缓蚀作用", 《应用化工》 * |
| 李威威等: "车用甲醇燃料金属腐蚀抑制剂的研究", 《云南化工》 * |
| 蔡铎昌: "《电化学研究方法》", 30 September 2005, 电子科技大学出版社 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109839348A (en) * | 2017-11-24 | 2019-06-04 | 北京蓝星清洗有限公司 | A kind of method of quick screening engine cooling liquid formulation |
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