Palmitate coking inhibitors, methods of making and using same

Abstract

The application discloses a palmitate coking inhibitor and a preparation method and application thereof, and belongs to the technical field of coking inhibitors. The technical scheme is that palmitic acid is reacted with a potassium compound to obtain the coking inhibitor; and the potassium compound is potassium hydroxide, potassium carbonate or potassium bicarbonate. The coking inhibitor has good oil solubility, can be directly added into cracking raw oil, does not need to separately add an inhibitor nozzle and other injection equipment, reduces unnecessary plugging risks, and reduces the complexity of a process; and compared with existing oil-soluble inhibitors containing sulfur and phosphorus, the coking inhibitor has good decoking performance for gas phase coking in a middle and late stage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coking inhibitors, in particular to a palmitate coking inhibitor and a preparation method and application thereof. BACKGROUND

[0002] More than 80% of the global ethylene production adopts the tubular furnace steam cracking process, and the hydrocarbon liquid raw material often contains a large amount of aromatic components, which has a crucial effect on the operation condition of the ethylene cracking furnace.

[0003] The hydrocarbon raw material and steam are subjected to thermal cracking reaction in a high-temperature furnace tube to generate small-molecule target products such as ethylene and propylene, accompanied by a large number of side reactions, and the dehydrogenation of aromatic components generates tar and coke and other by-products, which brings many adverse effects to ethylene production, resulting in a series of adverse effects such as a decrease in target product yield, a decrease in device processing capacity, an increase in energy consumption, and a shortening of the operation cycle.

[0004] The cracking and coking mechanism of aromatic substances and its influencing factors are very complex, but the currently recognized ones include catalytic coking, gas phase coking, and free radical coking. Among them, gas phase coking is the main coking form, which refers to the coke generated in the gas flow main body. Aromatic hydrocarbons are very important intermediates for gas phase coking, some of which come from the raw material itself, and some are generated by trimerization reaction. The coking process can be represented as:

[0005]

[0006] In view of the coking of aromatic hydrocarbons, various coking inhibition technologies have been developed in recent years, including changing the cracking reaction conditions, hydrogenation thermal cracking, cracking raw material pretreatment, furnace tube surface treatment, and adding coking inhibitors. The adoption of new cracking technologies and furnace tube surface treatment processes requires a huge amount of investment to replace the cracking furnace and furnace tube, which is difficult to achieve in a short period of time, and the chemical market price changes quickly, so the investment income cannot be guaranteed.

[0007] Changing the dilution ratio of cracking and the steam measures is beneficial to reduce coking, but the effect is limited, and the increased dilution steam affects the processing capacity and yield of the device, and increases the energy consumption of the device. Therefore, adding coking inhibitors in the cracking raw material is a universally recognized and most effective method.

[0008] The reported coking inhibitors mainly include sulfur and phosphorus compounds, metal salt compounds, and organic polysiloxane compounds. For example, Chinese patent CN101294100A discloses a method for inhibiting coking of a hydrocarbon steam cracking device, which requires at least one of silica sol, alumina sol, and titania sol to be used for pretreatment of the furnace tube, and then a sulfur and phosphorus compound inhibitor is injected during the cracking process. The existing oil-soluble inhibitors containing sulfur and phosphorus are mainly used for catalytic coking at the beginning of feeding. The sulfur and phosphorus-containing inhibitors can form a layer of passivation on the surface of the furnace tube before the coking material is generated, thereby slowing down the process of catalytic coking. However, as the cracking furnace runs to the middle and later stages, catalytic coking is weakened, and gas phase coking increases. The coking layer still gradually thickens, and the oil-soluble inhibitor containing sulfur and phosphorus cannot eliminate the coking layer of gas phase coking.

[0009] Chinese patent CN1367225A discloses a method for inhibiting coking of a hydrocarbon steam cracking device. After the furnace tube is decoked, inorganic salt coking inhibitors such as potassium, lithium silicate, borate, or nitrate salts of potassium, magnesium, calcium, and barium are added to the water vapor before resuming feeding, and the duration is 1-3 hours. However, the inorganic salt is not soluble in hydrocarbon materials, and during the addition process, the inhibitor is very easy to be unevenly distributed in the pipeline, which causes the inorganic salt to deposit in the furnace tube, and even block the furnace tube, resulting in unplanned shutdown of the cracking furnace and seriously affecting the stable operation of the production. In addition, the method of using the inhibitor is very important for the effect of inhibiting coking and the smooth operation of the cracking furnace. If the injected inhibitor solution is not quickly gasified, the liquid is sprayed onto the high-temperature furnace tube, and the creep stress of the furnace tube due to continuous cold contraction and thermal expansion will cause fatigue damage. If the amount of injected inorganic salt inhibitor is too large, the inhibitor may deposit in the furnace tube or large pieces of coke may fall off and block the furnace tube.

[0010] Therefore, it is necessary to develop a new coking inhibitor to slow down the coking of light oil cracking furnaces and solve the problems existing in the existing coking inhibitors. SUMMARY

[0011] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a palmitate coking inhibitor, a preparation method and application thereof. The coking inhibitor has good oil solubility and can be directly added to the cracking raw oil, without the need for separately adding an inhibitor nozzle or other injection equipment, thereby reducing unnecessary blockage risks and the complexity of the process. Compared with the existing oil-soluble inhibitors containing sulfur and phosphorus, the coking inhibitor has good coking removal performance for gas phase coking in the middle and later stages.

[0012] The technical scheme of the present application is as follows:

[0013] In a first aspect, the present application provides a preparation method of a palmitate coking inhibitor. The palmitate coking inhibitor is obtained by reacting palmitic acid with a potassium compound. The potassium compound is an alkaline potassium salt such as potassium hydroxide, potassium carbonate, or potassium bicarbonate.

[0014] Palmitic acid can be used as a surfactant and softener due to the presence of polar head group that can connect with metal potassium ion; meanwhile, it also has non-polar chain, so that it can be dissolved in organic solvent.

[0015] Preferably, the molar ratio of palmitic acid to potassium element is 1:(1-1.1); in order to avoid super ester, preferably, the molar ratio of palmitic acid to potassium element is 1:(1.02-1.05).

[0016] In the second aspect, the application provides a coking inhibitor with lipophilicity and hydrophilicity for slowing down coking of a light oil cracking furnace, which is prepared by the above preparation method, and can be directly added into oil raw materials or water, the lipophilic group of which can capture and combine with coking precursors to inhibit further carbonization of the coking precursors. Moreover, the coking inhibitor slows down the side reaction of forming coke, and does not have negative impact on the target product yield and technical and economic indicators of the device

[0017] The mechanism of action of the coking inhibitor is that, due to the presence of long-chain hydrocarbon lipophilic group and polar head group (metal cation) in the inhibitor, the inhibitor can be dissolved in organic solvent, the long-chain hydrocarbon lipophilic group of the coking inhibitor can combine with the precursors of tar, and pull the potassium group to inhibit coking, forming a mixture of tar and coking inhibitor, which is catalytic gasification of coking matter in the presence of hot steam, that is, the coking inhibitor releases alkali metal oxide, which can catalyze the conversion of coking precursors into carbon monoxide and hydrogen, thereby eliminating and slowing down the deposition of coke on the pipe wall, and prolonging the operation cycle of the cracking furnace.

[0018] The reaction process of the coking inhibitor of the application for inhibiting coking is as follows:

[0019]

[0020] The coking inhibitor can not only inhibit early coking, but also reduce and remove the existing coke layer. The application of the coking inhibitor in a steam cracking ethylene production device solves the problems of short operation cycle, short service life of cracking furnace pipe, high energy consumption and low production efficiency in the prior art, can significantly reduce the amount of coke in the pipe, reduce the pipe wall temperature, and greatly prolong the operation cycle of the cracking furnace.

[0021] The coking inhibitor of the application does not need to use complex auxiliary facilities such as nozzles, so that deposition of the inhibitor or fatigue damage caused by the inhibitor causing cold shrinkage and thermal expansion of the furnace pipe can be avoided.

[0022] In a third aspect, the present application also provides the use of the above-mentioned palmitate coking inhibitor for retarding coking in a light oil cracking furnace. The light oil includes hydrocarbons such as ethane, propane, liquefied gas and naphtha, and the heavy oil includes hydrocarbons such as diesel and tail oil. The composition of the light oil is significantly different from that of the heavy oil, and thus the composition of the coking product in the cracking furnace tube is also different. The coking product of the light oil is relatively lighter and has a higher degree of saturation than that of the heavy oil. The carbon number of the potassium palmitate is comparable to the average carbon number distribution of the light oil, and thus the potassium palmitate has a stronger binding force with the coking product of the light oil and a better decoking effect.

[0023] In the present application, the coking inhibitor is suitable for use in cracking furnaces such as SRT-III, SRT-IV, GK-VI and CBL industrial furnaces, and simulation cracking test furnaces.

[0024] The cracking raw material suitable for use with the coking inhibitor of the present application includes light oil raw materials such as ethane, light hydrocarbon and naphtha. When the cracking furnace is used to crack liquid hydrocarbon raw materials, the inhibitor can be added to the liquid hydrocarbon raw materials or to the dilution steam. When the cracking furnace is used to crack gaseous raw materials, the inhibitor can be added to the dilution steam.

[0025] The specific use method of the coking inhibitor of the present application is as follows:

[0026] The coking inhibitor is injected into the cracking raw material by a metering pump and enters the light oil cracking furnace together with the cracking raw material. For example, the inhibitor can be injected into the cracking raw material at the inlet or outlet of the raw material pump of the heating furnace, and the inlet of the raw material pump is preferred. The mechanical stirring action of the raw material pump can be used to achieve good stirring and mixing effects. Alternatively, the inhibitor can be pre-mixed with part of the cracking raw material, and the mixture can be injected into the cracking raw material at the inlet or outlet of the raw material pump of the heating furnace through a pipeline.

[0027] Alternatively, the inhibitor can be injected into the dilution steam in advance to form a mixture of the inhibitor and the steam, and the mixture can enter the light oil cracking furnace together.

[0028] Preferably, the injection amount of the coking inhibitor is 20-60 ppm of the input amount of the cracking raw material.

[0029] In use, the injection method of the coking inhibitor of the present application can be continuous injection or intermittent injection. When the inhibitor is injected by the continuous injection method or the intermittent injection method, the injection concentration of the inhibitor, the start of the injection of the inhibitor or the stop of the injection of the inhibitor all need to be determined according to the tube wall temperature of the radiant section of the cracking furnace.

[0030] The continuous injection method refers to continuously injecting the inhibitor in small doses from the beginning of the cracking reaction of the hydrocarbon raw material in the cracking furnace, which can inhibit the rapid rise of the tube wall temperature of the cracking furnace in the initial stage of the feeding of the raw material.

[0031] The intermittent injection method refers to that in the early stage of the operation of the cracking furnace, no inhibitor is injected, and after the gradual formation of the coke layer in the radiation section pipe wall, the pipe wall thermal resistance increases, the pipe wall temperature rises to above 1000 DEG C, the system starts to inject the inhibitor; the injection is continued for 24-120h, at this time, the coke layer on the pipe wall is obviously thinned or reduced, the pipe wall thermal resistance is reduced, and when the pipe wall temperature obviously decreases by about 30-50 DEG C, the injection of the inhibitor is stopped; after a period of operation, when the pipe wall temperature obviously rises to 1000 DEG C again, the injection of the inhibitor is started again until the injection of the inhibitor cannot effectively reduce the pipe wall temperature.

[0032] Compared with the existing inorganic salt inhibitor or low molecular weight salt inhibitor, the coking inhibitor has good oil solubility, can be directly added to the raw oil, and enters the cracking furnace pipe with the raw oil, and does not need to separately add injection equipment such as inhibitor nozzle.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] 1. In the actual industrial cracking furnace operation, the existing inorganic salt inhibitor or low molecular weight organic inhibitor has poor oil solubility, and needs to be separately provided with an inhibitor nozzle to help it to be distributed into the furnace pipe. In actual operation, since the injection nozzle of the inhibitor has a small nozzle, generally 0.5-5mm in diameter, once the inhibitor storage tank and the pipeline are mixed with iron filings or other impurities, the injection nozzle of the inhibitor will be blocked, and once it is blocked, the injection of the inhibitor will fail. Moreover, the inhibitor nozzle needs to be worked in parallel by multiple groups, and in actual operation, the problem of too large or too small flow of a certain nozzle often occurs, which causes uneven injection amount of different nozzles, and the temperature of the corresponding furnace pipe with smaller injection amount is obviously higher than that of other groups, triggering the over-temperature shutdown of the cracking furnace, and the over-temperature of a single furnace pipe of the cracking furnace will affect the overall operation cycle. The coking inhibitor of the present application has good oil solubility, can be directly added to the cracking raw oil, and enters the cracking furnace pipe with the cracking raw oil, and the process is mature and stable, does not need to separately add injection equipment such as inhibitor nozzle, reduces unnecessary blockage risk, and reduces the complexity of the process; at the same time, the inhibitor has good emulsifying performance, and will not cause inhibitor deposition or fatigue damage caused by injection of the inhibitor due to the thermal shrinkage and thermal expansion of the furnace pipe, and the operation stability is increased.

[0035] 2. Compared with the existing oil-soluble inhibitor containing sulfur and phosphorus, the coking inhibitor of the present application has good decoking performance for mid-late stage gas phase coking. The existing oil-soluble inhibitor containing sulfur and phosphorus is mainly used for catalytic coking at the initial stage of feeding. The oil-soluble inhibitor containing sulfur and phosphorus can form a layer of passivation on the surface of the furnace tube before the coking material is generated, slowing down the process of catalytic coking, but as the cracking furnace runs to the mid-late stage, catalytic coking decreases and gas phase coking increases, and the oil-soluble inhibitor containing sulfur and phosphorus cannot eliminate the coking layer of gas phase coking. In the actual industrial cracking furnace operation, the coking inhibitor of the present application can be used in different stages of the cracking furnace, including the initial stage, the middle stage and the late stage, and the best application scenario is the mid-late stage of the operation of the cracking furnace, because at this time part of the coking layer has accumulated in the cracking furnace tube, and the coking inhibitor of the present application can be injected to achieve the purpose of removing the existing coking layer. Of course, the coking inhibitor of the present application can also be injected at the early stage of the operation of the cracking furnace, which can also prevent the increase of the coking layer and prolong the operation cycle of the cracking furnace.

[0036] 3. When the coking inhibitor of the present application is applied to the ethylene production device by steam cracking, the amount of coke on the furnace tube can be significantly reduced, and the operation cycle of the cracking furnace can be greatly prolonged.

[0037] 4. When the coking inhibitor of the present application is applied to the ethylene production device by steam cracking, the temperature of the cracking furnace tube wall can be reduced, the frequency of coking of the cracking furnace can be reduced, thereby prolonging the service life of the cracking furnace tube, saving the energy consumption of coking of the cracking furnace and the cost of replacing the cracking furnace tube. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic diagram of a thermal cracking device used in an embodiment of the present application.

[0039] In the figure, 1 is a cracking furnace, 101 is a thermocouple, and 2 is a quenching device. DETAILED DESCRIPTION

[0040] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application.

[0041] The coking inhibitor of the following embodiments is prepared by the following method:

[0042] Palm acid reacts with a potassium compound to obtain the coking inhibitor.

[0043] The potassium compound is potassium hydroxide or potassium carbonate.

[0044] The coking inhibitor prepared in the following embodiments is used in the following thermal cracking process:

[0045] As shown in the figure, the coking inhibitor of the present application is injected into the cracking furnace through the injection pipe, and the coking inhibitor is mixed with the oil in the cracking furnace to form a coking inhibitor solution, and the coking inhibitor solution is sprayed on the surface of the cracking furnace tube to form a coking inhibitor layer on the surface of the cracking furnace tube. Figure 1The pyrolysis apparatus shown, the pyrolysis reaction temperature is 840℃, the pyrolysis raw material is naphtha, the feeding amount is 5kg / h, the dilution ratio is 0.5, the residence time is 0.26s, the reaction material needs to be heated after passing through the feeding system and the pyrolysis furnace 1, enters the quencher 2, the liquid phase product is collected from the product separation lower port of the gas-liquid separation tank 3, the hydrocarbon composition of the pyrolysis gas after reaction and the content of carbon monoxide and carbon dioxide are sampled and analyzed from the vent port. When the pyrolysis furnace 1 furnace tube wall temperature (TMT) reaches the upper limit of 1100℃, stop feeding, record the running time as the basis for evaluating the length of the running period.

[0046] The coking inhibitor in the embodiment of the application can be injected into steam or water from injection port one or into the pyrolysis raw material from injection port two. The inorganic salt inhibitor in the comparative example can only be injected into steam or water from injection port one.

[0047] After the coking inhibitor is injected, the temperature of the pyrolysis furnace 1 is raised to above 800℃, the air is started to be mixed and maintained at 800℃, the oxygen content of the coking gas at the outlet of the quencher 2 is detected by the coking controller, the carbon monoxide and carbon dioxide content is relatively high at the beginning, reaches the upper limit of the carbon monoxide and carbon dioxide gas analyzer detection of 25%; with the continuation of the coking process, the carbon monoxide and carbon dioxide content gradually decreases, the oxygen content continuously increases, until it reaches the level of the oxygen content of the air, at this time the coking operation is completed, the total running time of the coking is recorded. In the coking operation, the temperature of the thermocouple 101 in the pyrolysis furnace 1 tube is continuously detected, which is required to be not more than 1100℃, the upper limit of the temperature resistance of 2520 material, generally set to be within 1000℃, once close to the temperature, the coking reaction is controlled by reducing the inflow amount of the coking air.

[0048] Example 1

[0049] The preparation method of the coking inhibitor of the embodiment is as follows: palmitic acid is reacted with potassium hydroxide, the theoretical molar ratio of potassium hydroxide to palmitic acid is 1:1, but considering the reversibility of the esterification reaction, in order to make the palmitic acid react completely, the amount of potassium hydroxide is a little more, therefore the molar ratio of potassium hydroxide to palmitic acid in the embodiment is 1.05:1, and finally the coking inhibitor is prepared.

[0050] The aforementioned as Figure 1The shown thermal cracking process, using continuous injection method, continuously injects the coking inhibitor in small doses into the cracking furnace 1 at the beginning of the cracking reaction of the hydrocarbon raw material, the injection amount is 50 ppm of the input amount of the cracking hydrocarbon raw material, and a feeding operation cycle is completed: the cracking reaction temperature is 840℃, the cracking raw material is naphtha, the feeding amount is 5 kg / h, the dilution ratio is 0.5, and the residence time is 0.26s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 120h; the contents of carbon monoxide and carbon dioxide are 0.05% and 0.03% respectively, and after injection, they are 0.09% and 0.07% respectively; the coking time is 0.40h.

[0051] Example 2

[0052] The difference from Example 1 is that: in this example, the intermittent injection method is used to inject the coking inhibitor in the middle period of 25h of the cracking reaction of the hydrocarbon raw material into the cracking furnace 1.

[0053] A feeding operation cycle is completed: the cracking reaction temperature is 840℃, the cracking raw material is naphtha, the feeding amount is 5 kg / h, the dilution ratio is 0.5, and the residence time is 0.26s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 110h; the contents of carbon monoxide and carbon dioxide are 0.05% and 0.03% respectively before injection, and after injection, they are 0.09% and 0.07% respectively; the coking time is 0.42h.

[0054] Comparative Example 1

[0055] The difference from Example 1 is that: in Comparative Example 1, no coking inhibitor is injected.

[0056] A feeding operation cycle is completed: the cracking reaction temperature is 840℃, the cracking raw material is naphtha, the feeding amount is 5 kg / h, the dilution ratio is 0.5, and the residence time is 0.26s; when the TMT of the cracking furnace 1 reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 50h, the contents of carbon monoxide and carbon dioxide are 0.05% and 0.03% respectively; the coking time is 1.00h.

[0057] From Examples 1-2 and Comparative Example 1, when the coking inhibitor of the present application is injected into the cracking furnace 1 using the continuous injection method, the operation cycle is prolonged by 2.4 times compared with Comparative Example 1 without injecting the coking inhibitor, and the coking time is reduced by 60%, indicating that the coking inhibitor of the present application has obvious coking inhibition effect when used by the continuous injection method. When the coking inhibitor of the present application is injected into the cracking furnace 1 using the intermittent injection method, the operation cycle is prolonged by 2.1 times compared with Comparative Example 1 without injecting the coking inhibitor, and the coking time is reduced by 55%. Therefore, from Examples 1-2 and Comparative Example 1, it can be seen that the coking inhibitor of the present application has obvious coking inhibition effect in the early and middle-late stages of operation.

[0058] Comparative Example 2

[0059] The difference from Example 1 is that Comparative Example 2 uses potassium carbonate as the inhibitor (i.e., an inorganic potassium salt inhibitor).

[0060] Using the continuous injection method, potassium carbonate was continuously injected in small doses at the beginning of the pyrolysis reaction of the hydrocarbon feedstock into the cracking furnace 1 at an injection amount of 50 ppm of the amount of the pyrolysis hydrocarbon feedstock. One feeding operation cycle was completed with a pyrolysis reaction temperature of 840°C, a pyrolysis feedstock of naphtha, a feeding amount of 5 kg / h, a dilution ratio of 0.5, and a residence time of 0.26 s. During the experiment, the carbon monoxide and carbon dioxide contents were 0.12% and 0.08%, respectively, which was significantly higher than that of Comparative Example 1, indicating that the inorganic potassium salt inhibitor also played a role in eliminating coke. However, because the inlet pressure of the cracking furnace 1 rapidly increased, it was judged that the furnace tube was blocked, and although the TMT of the cracking furnace 1 did not reach the upper limit of 1100°C, feeding was also stopped. The operation time was recorded as 60 h, and the coking time was 0.5 h. The cracking furnace 1 tube was disassembled, and white substances were found adhering to the tube wall at about 100 mm from the inhibitor injection inlet. The white substances had strong adhesion and were distributed in a ring shape, causing the tube wall to narrow. The furnace tube was dredged using pure water, and the composition of the aqueous solution was analyzed. The results showed that it was potassium carbonate, indicating that the inorganic potassium salt inhibitor lacked oil solubility and was prone to uneven distribution, leading to deposition in the furnace tube and blocking the furnace tube.

[0061] Comparative Example 3

[0062] The difference from Example 1 is that Comparative Example 3 uses dimethyl disulfide as the inhibitor (i.e., an organic sulfur phosphorus inhibitor).

[0063] Using the continuous injection method, dimethyl disulfide was continuously injected in small doses at the beginning of the pyrolysis reaction of the hydrocarbon feedstock into the cracking furnace 1 at an injection amount of 50 ppm of the amount of the pyrolysis hydrocarbon feedstock. One feeding operation cycle was completed with a pyrolysis reaction temperature of 840°C, a pyrolysis feedstock of naphtha, a feeding amount of 5 kg / h, a dilution ratio of 0.5, and a residence time of 0.26 s. When the TMT of the cracking furnace 1 reached the upper limit of 1100°C, feeding was stopped. The operation time was recorded as 70 h, which was 0.4 times longer than that of Comparative Example 1 without the injection of the coking inhibitor. The carbon monoxide and carbon dioxide contents were 0.05% and 0.03%, respectively, and the coking time was 0.7 h.

[0064] Comparative Example 4

[0065] The difference from Comparative Example 3 is that Comparative Example 4 uses the intermittent injection method, and dimethyl disulfide is injected at the middle stage of 25 h of the pyrolysis reaction of the hydrocarbon feedstock into the cracking furnace 1.

[0066] A feeding operation cycle was completed: the cracking reaction temperature was 840℃, the cracking raw material was naphtha, the feeding amount was 5kg / h, the dilution ratio was 0.5, and the residence time was 0.26s; when the cracking furnace 1TMT reached the upper limit of 1100℃, the feeding was stopped, and the running time was recorded as 55h, the carbon monoxide and carbon dioxide contents were 0.05% and 0.03% respectively, and the coking time was 0.95h. The running cycle was 0.1 times longer than that of the comparative example 1 without injecting the coking inhibitor, and the coking time was basically similar.

[0067] As can be seen from the comparative examples 1, 3-4, the organic phosphorus type inhibitor is relatively effective in inhibiting coking in the early stage of operation, and a layer of phosphorus passivation can prevent catalytic coking, but in the case of the generation of coke layer on the inner wall of the cracking furnace tube in the middle and late stages of the cracking furnace operation, the phosphorus passivation cannot be generated any more, and the coking inhibition effect is basically not available.

[0068] Comparative Example 5

[0069] The difference from the example 1 is that in the preparation of the coking inhibitor of the comparative example 5, the fatty acid is not a single palmitic acid, but a ternary mixed fatty acid composed of oleic acid, palmitic acid and stearic acid in a molar ratio of 1:1:1, and the potassium hydroxide is reacted, wherein the theoretical molar ratio of potassium hydroxide to mixed fatty acid is 1:1, but considering the reversibility of esterification reaction, in order to make the fatty acid react completely, the amount of potassium hydroxide is a little more, so in this example, the molar ratio of potassium hydroxide to mixed fatty acid is 1.05:1, and finally the ternary mixed fatty acid salt coking inhibitor is prepared.

[0070] A continuous injection method was adopted, and the ternary mixed fatty coking inhibitor was continuously injected in a small dose into the cracking furnace 1 as soon as the cracking reaction of the hydrocarbon raw material was started, and the injection amount was 50ppm of the cracking hydrocarbon raw material input amount, and a feeding operation cycle was completed: the cracking reaction temperature was 840℃, the cracking raw material was naphtha, the feeding amount was 5kg / h, the dilution ratio was 0.5, and the residence time was 0.26s; when the cracking furnace 1TMT reached the upper limit of 1100℃, the feeding was stopped, and the running time was recorded as 90h, which was 0.8 times longer than that of the comparative example 1; the carbon monoxide and carbon dioxide contents were 0.05% and 0.03% respectively before injection, and 0.07% and 0.04% respectively after injection; the coking time was 0.5h, which was 50% less than that of the comparative example 1.

[0071] As can be seen from the example 1, the comparative example 1 and the comparative example 5, the ternary mixed fatty acid salt coking inhibitor also has good coking inhibition effect, but the coking inhibition effect is relatively poor compared with the palmitate potassium coking inhibitor, because the proportion of palmitate potassium which can act on light oil coking in the ternary mixed fatty acid salt coking inhibitor is reduced, so that the coking inhibition effect is worse than that of the palmitate potassium coking inhibitor.

[0072] Experimental Example 1

[0073] Without adding any inhibitors, a thermal cracking process as shown in Figure 1 Table 1 shows the cracking product yield analyzed by chromatography. The cracking furnace was operated for 20 hours, and the cracking product was collected.

[0074] Experimental Example 2

[0075] The coking inhibitor of Example 1 was used, and a thermal cracking process as shown in Figure 1 was used. The coking inhibitor was continuously injected in small doses into the cracking furnace 1 at the beginning of the cracking reaction of the hydrocarbon feedstock, and the injection amount was 50 ppm of the amount of the cracking hydrocarbon feedstock. The cracking reaction temperature was 840°C, the cracking feedstock was naphtha, the feedstock amount was 5 kg / h, the dilution ratio was 0.5, and the residence time was 0.26 s. When the cracking furnace was operated for 20 hours, the cracking product was collected, and the yield of the cracking product was analyzed by chromatography. Table 1 shows the results.

[0076] Table 1 shows the cracking product yield of Experimental Example 1 and Experimental Example 2.

[0077]

[0078] As shown in Table 1, under the same feedstock and process conditions, the cracking yields of Experimental Example 1 and Experimental Example 2 were very close, and the main technical and economic indicators such as the ethylene, propylene, and triene yields of Experimental Example 2 were slightly higher than those of Experimental Example 1. This is because the coking inhibitor slows down the coking reaction and other side reactions, which is beneficial to the generation of target products such as ethylene. Therefore, it can be proved that the coking inhibitor of the present application does not have a negative impact on the technical and economic indicators of the device.

[0079] Example 3

[0080] The preparation method of the coking inhibitor of the present example is as follows: palmitic acid is reacted with potassium carbonate, and the theoretical molar ratio of potassium carbonate to fatty acid is 0.5:1. However, considering the reversibility of the esterification reaction, in order to make the palmitic acid react completely, the amount of potassium carbonate is slightly more, and therefore the molar ratio of potassium carbonate to palmitic acid in the present example is 0.52:1. Finally, the coking inhibitor is prepared.

[0081] The coking inhibitor of Example 3 was used, and a thermal cracking process as shown in Figure 1The pyrolysis process shown, using continuous injection method, continuously injects the coking inhibitor in small doses at the beginning of the pyrolysis reaction of the hydrocarbon raw material into the cracking furnace 1, the injection amount is 50 ppm of the input amount of the pyrolysis hydrocarbon raw material, and a feeding operation cycle is completed: the pyrolysis reaction temperature is 840℃, the pyrolysis raw material is naphtha, the feeding amount is 5kg / h, the dilution ratio is 0.5, and the residence time is 0.26s; when the cracking furnace 1 TMT reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 115h; the carbon monoxide and carbon dioxide contents are 0.09% and 0.07% respectively; and the coking time is 0.46h.

[0082] Example 4

[0083] The difference from Example 3 is that this example uses intermittent injection method, and the coking inhibitor is injected at the middle stage of 25h of the pyrolysis reaction of the hydrocarbon raw material into the cracking furnace 1.

[0084] A feeding operation cycle is completed: the pyrolysis reaction temperature is 840℃, the pyrolysis raw material is naphtha, the feeding amount is 5kg / h, the dilution ratio is 0.5, and the residence time is 0.26s; when the cracking furnace 1 TMT reaches the upper limit of 1100℃, the feeding is stopped, and the operation time is recorded as 110h; the carbon monoxide and carbon dioxide contents before injection are 0.05% and 0.03% respectively, and after injection are 0.09% and 0.07% respectively; and the coking time is 0.45h.

[0085] Although the present application has been described in detail by referring to the preferred embodiments thereof, it is to be understood that the present application is not limited to them. It is to be appreciated that those skilled in the art, on the basis of the disclosures herein, can make various modifications or substitutions of the embodiments without departing from the spirit and scope of the present application. Any modifications or substitutions made by those skilled in the art on the basis of the disclosures herein, within the technical scope of the present application, are to be embraced within the scope of the present application. Therefore, the scope of protection of the present application is to be defined by the scope of protection of the claims.

Claims

1. The application of palmitate coking inhibitor, characterized in that, A coking inhibitor is obtained by reacting palmitic acid with a potassium compound; wherein the potassium compound is potassium hydroxide, potassium carbonate, or potassium bicarbonate; the coking inhibitor is used to slow down coking in light oil cracking furnaces, and the light oils include ethane, propane, liquefied petroleum gas, and naphtha hydrocarbons.

2. The application of the palmitate coking inhibitor as described in claim 1, characterized in that, The molar ratio of palmitic acid to potassium is 1:(1-1.1).

3. The application of the palmitate coking inhibitor as described in claim 1, characterized in that, Coking inhibitors are injected into the light oil cracking feedstock tank or pipeline and enter the light oil cracking furnace together with the cracking feedstock; or coking inhibitors are injected into the dilution steam generator or pipeline and enter the light oil cracking furnace together with the dilution steam.

4. The application of the palmitate coking inhibitor as described in claim 1, characterized in that, The amount of coking inhibitor injected is 20-60 ppm of the amount of pyrolysis feedstock.

5. The application of the palmitate coking inhibitor as described in claim 1, characterized in that, Coking inhibitors can be injected using either a continuous or intermittent injection method.

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