A corrosion-resistant metal elbow for petrochemical use and its preparation method

Abstract

The present invention discloses a corrosion-resistant metal elbow for petrochemical use and a preparation method thereof, which relates to the technical field of metal elbows. The present invention prepares a corrosion-resistant metal elbow applied to the petrochemical field, and impregnates the metal elbow with a dopamine solution to improve the corrosion resistance of the metal elbow. The present invention prepares a zeolitic imidazolate framework-zinc oxide composite material. The zeolitic imidazolate framework material can effectively isolate corrosive ions, has excellent corrosion resistance, and has a large specific surface area, and can graft a large amount of polyethyleneimine of glycine to form a modified zeolitic imidazolate framework material. The tortuous surface of the modified zeolitic imidazolate framework material can further prevent the erosion of corrosive media. The modified zeolitic imidazolate framework material is compounded with nano-zinc oxide to improve the dispersion of nano-zinc oxide and further improve the corrosion resistance of the metal elbow.

Description

Technical Field

[0001] The present invention relates to the technical field of metal bent pipes, and specifically to a corrosion-resistant metal bent pipe for petrochemical use and a preparation method thereof. Background Art

[0002] Metal bent pipes, as a kind of connecting parts, are widely used in fields such as hydropower, petroleum, building natural gas, and chemical industry, and play a crucial role in transporting media. In the petrochemical field, petrochemical products often work in high-temperature and high-pressure environments and are often in contact with highly corrosive chemical substances. Ordinary metal bent pipes are prone to corrosion and damage under such conditions. Although existing technologies provide certain corrosion-resistant alloys, in actual applications, there are still problems such as insufficient durability, complex manufacturing processes, and high costs.

[0003] In order to solve the above problems and improve the corrosion resistance of the corrosion-resistant metal bent pipe for petrochemical use, the present invention provides a corrosion-resistant metal bent pipe for petrochemical use and a preparation method thereof. Summary of the Invention

[0004] The purpose of the present invention is to provide a corrosion-resistant metal bent pipe for petrochemical use and a preparation method thereof to solve the problems raised in the existing technology.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A preparation method of a corrosion-resistant metal bent pipe for petrochemical use, comprising the following steps:

[0007] Step 1: Take iron, chromium, nickel, silicon, manganese, carbon, vanadium, magnesium, cerium, and phosphorus, mix them, heat them to 1550 - 1600 °C for melting, then cast, cool and form, cut and polish to obtain a metal bent pipe;

[0008] Step 2: Take pretreated nano-zinc oxide and absolute ethanol, stir evenly, dropwise add n-dodecyl mercaptan, heat to 60 - 65 °C, stir for 2 - 3 h, add a modified zeolitic imidazolate framework material, stir for 6 - 8 h, filter, wash, and dry to obtain a zeolitic imidazolate framework-zinc oxide composite material;

[0009] Step 3: Take the metal bent pipe, clean and dry it, then immerse it in a dopamine solution for 1 - 2 h, add a Tris-HCl solution containing the zeolitic imidazolate framework-zinc oxide composite material, continue to immerse for 5 - 6 h, take it out and dry to obtain a corrosion-resistant metal bent pipe for petrochemical use.

[0010] Preferably, the preparation method of the modified zeolitic imidazolate framework material comprises the following steps:

[0011] S1: Take glycine, branched polyethyleneimine, and deionized water, stir evenly, add tert-butyl hydroperoxide dropwise, and under the protection of inert gas, reflux and react at 80 - 85 °C for 3.5 - 5 h. Remove the solvent by vacuum distillation, add anhydrous methanol, stir evenly, then add hydrochloric acid aqueous solution, precipitate, centrifuge, and dry. Add deionized water, stir evenly, add sodium carbonate, adjust the pH value to 8.0, then dialyze with deionized water, freeze, and dry to obtain polyethyleneimine grafted with glycine;

[0012] S2: Take zeolitic imidazolate framework material and deionized water, stir evenly, add polyethyleneimine grafted with glycine, stir for 6 - 8 h, filter and dry to obtain the modified zeolitic imidazolate framework material.

[0013] More preferably, the preparation method of the zeolitic imidazolate framework material is as follows: Take 2-methylimidazole, zinc nitrate hexahydrate, and methanol, stir for 1 - 2 h, then let stand for 24 - 26 h, centrifuge, filter, wash, and dry to obtain the zeolitic imidazolate framework material.

[0014] More preferably, in step two, the preparation method of the pretreated nano-zinc oxide is as follows: Take dopamine solution, add nano-zinc oxide, heat up to 60 - 65 °C, stir for 7 - 9 h, filter, wash, and dry to obtain the pretreated nano-zinc oxide.

[0015] More preferably, the preparation method of the dopamine solution is as follows: Take tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain Tris-HCl buffer solution; dissolve dopamine hydrochloride in Tris-HCl buffer solution to obtain dopamine solution.

[0016] More preferably, the metal elbow pipe comprises the following components by mass percentage: 20wt% - 22wt% of chromium, 7wt% - 8wt% of nickel, 1.5wt% - 2.6wt% of silicon, 0.5wt% - 1wt% of manganese, 0.3wt% - 0.5wt% of carbon, 0.2wt% - 0.4wt% of vanadium, 0.1wt% - 0.2wt% of magnesium, 0.01wt% - 0.03wt% of cerium, 0.03wt% - 0.05wt% of phosphorus, and the balance is iron.

[0017] More preferably, in S2, the mass ratio of the zeolitic imidazolate framework material, polyethyleneimine grafted with glycine, and deionized water is: (2 - 2.5) : 1 : 300.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The present invention prepares a corrosion-resistant metal elbow pipe applied to the petrochemical field, impregnates the metal elbow pipe with dopamine solution, and improves the corrosion resistance of the metal elbow pipe.

[0020] 2. The present invention prepares a zeolitic imidazolate framework-zinc oxide composite material. The zeolitic imidazolate framework material can effectively isolate corrosive ions, has excellent corrosion resistance, and has a large specific surface area, and can graft a large amount of polyethyleneimine with glycine to form a modified zeolitic imidazolate framework material. The tortuous surface of the modified zeolitic imidazolate framework material can further prevent the erosion of corrosive media. Using the zwitterionic surfactant glycine to graft polyethyleneimine not only improves the corrosion resistance of polyethyleneimine, but also makes the surface of polyethyleneimine carry amino groups, which helps the modified zeolitic imidazolate framework material to better deposit on the surface of the metal elbow under the assistance of dopamine. The present invention controls the mass ratio of the zeolitic imidazolate framework material, polyethyleneimine grafted with glycine, and deionized water to be: (2-2.5):1:300. At this time, the metal elbow has the best corrosion resistance.

[0021] 3. The present invention uses 1-dodecanethiol to treat nano-zinc oxide, reduces the surface energy of nano-zinc oxide, improves its hydrophobicity, and thus improves the corrosion resistance of the metal elbow. The present invention combines the modified zeolitic imidazolate framework material with nano-zinc oxide, improves the dispersibility of nano-zinc oxide, and further improves the corrosion resistance of the metal elbow. Detailed implementation manners

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] There are no special restrictions on the purchasing manufacturers of all raw materials involved in the present invention. Exemplarily, they include: branched polyethyleneimine: can be purchased from Sigma-Aldrich, model: 408727; nano-zinc oxide: particle size: 10-100 nm.

[0024] Example 1: A preparation method of a corrosion-resistant metal elbow for petrochemical use, comprising the following steps:

[0025] Step 1: Preparation of the metal elbow:

[0026] Take iron, chromium, nickel, silicon, manganese, carbon, vanadium, magnesium, cerium, and phosphorus, mix them, heat them to 1570 °C for melting, then cast, cool and form, cut and polish to obtain the metal elbow;

[0027] The metal bent pipe comprises the following components by mass percentage: 21 wt% of chromium, 7.5 wt% of nickel, 2.0 wt% of silicon, 0.7 wt% of manganese, 0.4 wt% of carbon, 0.3 wt% of vanadium, 0.15 wt% of magnesium, 0.02 wt% of cerium, 0.04% of phosphorus, and the balance is iron;

[0028] Step 2: Preparation of zeolitic imidazolate framework material:

[0029] Take 0.52 g of 2-methylimidazole, 0.85 g of zinc nitrate hexahydrate, and 50 mL of methanol, stir for 1.5 h, then let stand for 25 h, centrifuge, filter, wash, and dry to obtain the zeolitic imidazolate framework material;

[0030] Step 3: Preparation of polyethyleneimine grafted with glycine:

[0031] Take 0.8 g of glycine, 1 g of branched polyethyleneimine, and 30 mL of deionized water, stir evenly, add 16 μL of tert-butyl hydroperoxide, under the protection of inert gas, reflux at 83 °C for 4 h, remove the solvent by reduced pressure distillation, add 80 mL of anhydrous methanol, stir evenly, then add 10 mL of 10% hydrochloric acid aqueous solution, precipitate, centrifuge, and dry. Add 100 mL of deionized water, stir evenly, add sodium carbonate, adjust the pH value to 8.0, then dialyze with deionized water, freeze, and dry to obtain polyethyleneimine grafted with glycine;

[0032] Step 4: Preparation of modified zeolitic imidazolate framework material:

[0033] Take 2.2 g of zeolitic imidazolate framework material and 300 mL of deionized water, stir evenly, add 1 g of polyethyleneimine grafted with glycine, stir for 7 h, filter and dry to obtain the modified zeolitic imidazolate framework material;

[0034] The mass ratio of zeolitic imidazolate framework material, polyethyleneimine grafted with glycine, and deionized water is: 2.2:1:300;

[0035] Step 5: Preparation of pretreated nano-zinc oxide:

[0036] Take a 10 mmol / L tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain a Tris-HCl buffer solution; dissolve dopamine hydrochloride in the Tris-HCl buffer solution to obtain a 2 g / L dopamine solution; take 100 mL of the dopamine solution, add 5 g of nano-zinc oxide, heat to 63 °C, stir for 8 h, filter, wash, and dry to obtain the pretreated nano-zinc oxide;

[0037] Step 6: Preparation of zeolitic imidazolate framework-zinc oxide composite material:

[0038] Take 5 g of pretreated nano-zinc oxide and 100 mL of absolute ethanol, stir evenly, add 1.2 mL of dodecyl mercaptan dropwise, heat up to 63 °C, stir for 2.5 h, add 1 g of modified zeolitic imidazolate framework material, stir for 7 h, filter, wash, and dry to obtain zeolitic imidazolate framework-zinc oxide composite material;

[0039] Step 7: Preparation of corrosion-resistant metal elbows for petrochemical use:

[0040] Take 10 mmol / L of tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain Tris-HCl buffer solution; dissolve dopamine hydrochloride in Tris-HCl buffer solution to obtain 2 g / L dopamine solution; take the metal elbow, clean and dry it, then immerse it in the dopamine solution for 1.5 h, add Tris-HCl solution containing 1.5 g / L of zeolitic imidazolate framework-zinc oxide composite material with the same volume as the dopamine solution, continue to immerse it for 5.5 h, take it out and dry it to obtain the corrosion-resistant metal elbow for petrochemical use.

[0041] Example 2: A preparation method of a corrosion-resistant metal elbow for petrochemical use, comprising the following steps:

[0042] Step 1: Preparation of the metal elbow:

[0043] Take iron, chromium, nickel, silicon, manganese, carbon, vanadium, magnesium, cerium, and phosphorus, mix them, heat up to 1550 °C for melting, then cast, cool and form, cut and polish to obtain the metal elbow;

[0044] The metal elbow comprises the following components by mass percentage: 20 wt% of chromium, 7 wt% of nickel, 1.5 wt% of silicon, 0.5 wt% of manganese, 0.3 wt% of carbon, 0.2 wt% of vanadium, 0.1 wt% of magnesium, 0.01 wt% of cerium, 0.03 wt% of phosphorus, and the balance is iron;

[0045] Step 2: Preparation of zeolitic imidazolate framework material:

[0046] Take 0.52 g of 2-methylimidazole, 0.85 g of zinc nitrate hexahydrate, and 50 mL of methanol, stir for 1 h, then let it stand for 24 h, centrifuge, filter, wash, and dry to obtain the zeolitic imidazolate framework material;

[0047] Step 3: Preparation of polyethyleneimine grafted with glycine:

[0048] Take 0.8 g of glycine, 1 g of branched polyethyleneimine, and 30 mL of deionized water, stir evenly, add 16 μL of tert-butyl hydroperoxide, under the protection of inert gas, reflux at 80 °C for 3.5 h, remove the solvent by reduced pressure distillation, add 80 mL of anhydrous methanol, stir evenly, then add 10 mL of 10% hydrochloric acid aqueous solution, precipitate, centrifuge, and dry. Add 100 mL of deionized water, stir evenly, add sodium carbonate, adjust the pH value to 8.0, then dialyze with deionized water, freeze, and dry to obtain polyethyleneimine grafted with glycine;

[0049] Step 4: Preparation of modified zeolitic imidazolate framework material:

[0050] Take 2 g of zeolitic imidazolate framework material and 300 mL of deionized water, stir evenly, add 1 g of polyethyleneimine grafted with glycine, stir for 6 h, filter and dry to obtain the modified zeolitic imidazolate framework material;

[0051] The mass ratio of zeolitic imidazolate framework material, polyethyleneimine grafted with glycine, and deionized water is: 2:1:300;

[0052] Step 5: Preparation of pretreated nano-zinc oxide:

[0053] Take 10 mmol / L of tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain Tris-HCl buffer solution; dissolve dopamine hydrochloride in Tris-HCl buffer solution to obtain 2 g / L dopamine solution; take 100 mL of dopamine solution, add 5 g of nano-zinc oxide, heat up to 60 °C, stir for 7 h, filter, wash, and dry to obtain pretreated nano-zinc oxide;

[0054] Step 6: Preparation of zeolitic imidazolate framework-zinc oxide composite material:

[0055] Take 5 g of pretreated nano-zinc oxide and 100 mL of anhydrous ethanol, stir evenly, add 1.2 mL of n-dodecyl mercaptan, heat up to 60 °C, stir for 2 h, add 1 g of modified zeolitic imidazolate framework material, stir for 6 h, filter, wash, and dry to obtain zeolitic imidazolate framework-zinc oxide composite material;

[0056] Step 7: Preparation of corrosion-resistant metal elbows for petrochemical use:

[0057] Take a 10 mmol / L tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain a Tris-HCl buffer solution; dissolve dopamine hydrochloride in the Tris-HCl buffer solution to obtain a 2 g / L dopamine solution; take a metal elbow, clean it, dry it, then immerse it in the dopamine solution for 1 h, add a Tris-HCl solution containing 1.5 g / L of zeolitic imidazolate framework-zinc oxide composite material with the same volume as the dopamine solution, continue to immerse it for 5 h, take it out, and dry it to obtain a corrosion-resistant metal elbow for petrochemical use.

[0058] Example 3: A preparation method of a corrosion-resistant metal elbow for petrochemical use, comprising the following steps:

[0059] Step 1: Preparation of the metal elbow:

[0060] Take iron, chromium, nickel, silicon, manganese, carbon, vanadium, magnesium, cerium, and phosphorus, mix them, heat them to 1600 °C for melting, then cast them, cool them to form, cut and polish them to obtain a metal elbow;

[0061] The metal elbow comprises the following components by mass percentage: 22 wt% of chromium, 7 wt% of nickel, 2.6 wt% of silicon, 1 wt% of manganese, 0.5 wt% of carbon, 0.4 wt% of vanadium, 0.2 wt% of magnesium, 0.03 wt% of cerium, 0.05 wt% of phosphorus, and the balance is iron;

[0062] Step 2: Preparation of the zeolitic imidazolate framework material:

[0063] Take 0.52 g of 2-methylimidazole, 0.85 g of zinc nitrate hexahydrate, and 50 mL of methanol, stir for 2 h, then let it stand for 26 h, centrifuge, filter, wash, and dry to obtain the zeolitic imidazolate framework material;

[0064] Step 3: Preparation of polyethyleneimine grafted with glycine:

[0065] Take 0.8 g of glycine, 1 g of branched polyethyleneimine, and 30 mL of deionized water, stir evenly, add 16 μL of tert-butyl hydroperoxide dropwise, under the protection of an inert gas, reflux and react at 85 °C for 5 h, distill off the solvent under reduced pressure, add 80 mL of anhydrous methanol, stir evenly, then add 10 mL of a 10% hydrochloric acid aqueous solution, precipitate, centrifuge, and dry, add 100 mL of deionized water, stir evenly, add sodium carbonate, adjust the pH value to 8.0, then dialyze with deionized water, freeze, and dry to obtain polyethyleneimine grafted with glycine;

[0066] Step 4: Preparation of the modified zeolitic imidazolate framework material:

[0067] Take 2.5 g of zeolitic imidazolate framework material and 300 mL of deionized water, stir evenly, add 1 g of polyethyleneimine grafted with glycine, stir for 8 h, filter and dry to obtain the modified zeolitic imidazolate framework material;

[0068] The mass ratio of zeolitic imidazolate framework material, polyethyleneimine grafted with glycine, and deionized water is: 2.5:1:300;

[0069] Step Five: Preparation of pretreated nano-zinc oxide:

[0070] Take 10 mmol / L of tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain Tris-HCl buffer solution; dissolve dopamine hydrochloride in Tris-HCl buffer solution to obtain 2 g / L dopamine solution; take 100 mL of dopamine solution, add 5 g of nano-zinc oxide, heat up to 65 °C, stir for 9 h, filter, wash and dry to obtain pretreated nano-zinc oxide;

[0071] Step Six: Preparation of zeolitic imidazolate framework-zinc oxide composite material:

[0072] Take 5 g of pretreated nano-zinc oxide and 100 mL of absolute ethanol, stir evenly, dropwise add 1.2 mL of n-dodecyl mercaptan, heat up to 65 °C, stir for 3 h, add 1 g of modified zeolitic imidazolate framework material, stir for 8 h, filter, wash and dry to obtain zeolitic imidazolate framework-zinc oxide composite material;

[0073] Step Seven: Preparation of corrosion-resistant metal elbows for petrochemical use:

[0074] Take 10 mmol / L of tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain Tris-HCl buffer solution; dissolve dopamine hydrochloride in Tris-HCl buffer solution to obtain 2 g / L dopamine solution; take a metal elbow, clean and dry it, then immerse it in the dopamine solution for 2 h, add a Tris-HCl solution containing 1.5 g / L of zeolitic imidazolate framework-zinc oxide composite material with the same volume as the dopamine solution, continue to immerse for 6 h, take out and dry to obtain the corrosion-resistant metal elbow for petrochemical use.

[0075] Comparative Example 1: Without grafting glycine, the rest is the same as in Example 1:

[0076] Step One: Preparation of metal elbows:

[0077] Take iron, chromium, nickel, silicon, manganese, carbon, vanadium, magnesium, cerium, phosphorus, mix them, heat up to 1570 °C for melting, then cast, cool and form, cut and polish to obtain metal elbows;

[0078] The metal elbow pipe comprises the following components by mass percentage: 21 wt% of chromium, 7.5 wt% of nickel, 2.0 wt% of silicon, 0.7 wt% of manganese, 0.4 wt% of carbon, 0.3 wt% of vanadium, 0.15 wt% of magnesium, 0.02 wt% of cerium, 0.04% of phosphorus, and the balance is iron;

[0079] Step 2: Preparation of zeolitic imidazolate framework material:

[0080] Take 0.52 g of 2-methylimidazole, 0.85 g of zinc nitrate hexahydrate, and 50 mL of methanol, stir for 1.5 h, then let it stand for 25 h, centrifuge, filter, wash, and dry to obtain the zeolitic imidazolate framework material;

[0081] Step 3: Preparation of modified zeolitic imidazolate framework material:

[0082] Take 2.2 g of the zeolitic imidazolate framework material and 300 mL of deionized water, stir evenly, add 1 g of branched polyethyleneimine, stir for 7 h, filter, and dry to obtain the modified zeolitic imidazolate framework material;

[0083] The mass ratio of the zeolitic imidazolate framework material, branched polyethyleneimine, and deionized water is: 2.2:1:300;

[0084] Step 4: Preparation of pretreated nano-zinc oxide:

[0085] Take a 10 mmol / L tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain a Tris-HCl buffer solution; dissolve dopamine hydrochloride in the Tris-HCl buffer solution to obtain a 2 g / L dopamine solution; take 100 mL of the dopamine solution, add 5 g of nano-zinc oxide, heat up to 63 °C, stir for 8 h, filter, wash, and dry to obtain the pretreated nano-zinc oxide;

[0086] Step 5: Preparation of zeolitic imidazolate framework-zinc oxide composite material:

[0087] Take 5 g of the pretreated nano-zinc oxide and 100 mL of absolute ethanol, stir evenly, dropwise add 1.2 mL of n-dodecyl mercaptan, heat up to 63 °C, stir for 2.5 h, add 1 g of the modified zeolitic imidazolate framework material, stir for 7 h, filter, wash, and dry to obtain the zeolitic imidazolate framework-zinc oxide composite material;

[0088] Step 6: Preparation of corrosion-resistant metal elbow pipe for petrochemical use:

[0089] Take a 10 mmol / L tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain a Tris-HCl buffer solution; dissolve dopamine hydrochloride in the Tris-HCl buffer solution to obtain a 2 g / L dopamine solution; take a metal elbow, clean and dry it, then immerse it in the dopamine solution for 1.5 h, add a Tris-HCl solution containing 1.5 g / L of zeolitic imidazolate framework-zinc oxide composite material with the same volume as the dopamine solution, continue to immerse it for 5.5 h, take it out and dry it to obtain a corrosion-resistant metal elbow for petrochemical use.

[0090] Comparative Example 2: Polyethyleneimine without glycine, the rest is the same as in Example 1:

[0091] Step 1: Preparation of the metal elbow:

[0092] Take iron, chromium, nickel, silicon, manganese, carbon, vanadium, magnesium, cerium, phosphorus, mix them, heat up to 1570 °C for melting, then cast, cool and form, cut and polish to obtain a metal elbow;

[0093] The metal elbow comprises the following components by mass percentage: 21 wt% of chromium, 7.5 wt% of nickel, 2.0 wt% of silicon, 0.7 wt% of manganese, 0.4 wt% of carbon, 0.3 wt% of vanadium, 0.15 wt% of magnesium, 0.02 wt% of cerium, 0.04% of phosphorus, and the balance is iron;

[0094] Step 2: Preparation of the zeolitic imidazolate framework material:

[0095] Take 0.52 g of 2-methylimidazole, 0.85 g of zinc nitrate hexahydrate, and 50 mL of methanol, stir for 1.5 h, then let it stand for 25 h, centrifuge, filter, wash and dry to obtain the zeolitic imidazolate framework material;

[0096] Step 3: Preparation of pretreated nano-zinc oxide:

[0097] Take a 10 mmol / L tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain a Tris-HCl buffer solution; dissolve dopamine hydrochloride in the Tris-HCl buffer solution to obtain a 2 g / L dopamine solution; take 100 mL of the dopamine solution, add 5 g of nano-zinc oxide, heat up to 63 °C, stir for 8 h, filter, wash and dry to obtain pretreated nano-zinc oxide;

[0098] Step 4: Preparation of the zeolitic imidazolate framework-zinc oxide composite material:

[0099] Take 5 g of pretreated nano-zinc oxide and 100 mL of absolute ethanol, stir evenly, add 1.2 mL of dodecanethiol dropwise, heat up to 63 °C, stir for 2.5 h, add 1 g of zeolitic imidazolate framework material, stir for 7 h, filter, wash, and dry to obtain zeolitic imidazolate framework-zinc oxide composite material;

[0100] Step Five: Preparation of corrosion-resistant metal elbows for petrochemical use:

[0101] Take 10 mmol / L of tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain Tris-HCl buffer solution; dissolve dopamine hydrochloride in Tris-HCl buffer solution to obtain 2 g / L dopamine solution; take a metal elbow, clean and dry it, then immerse it in the dopamine solution for 1.5 h, add Tris-HCl solution containing 1.5 g / L of zeolitic imidazolate framework-zinc oxide composite material with the same volume as the dopamine solution, continue to immerse for 5.5 h, take it out and dry to obtain a corrosion-resistant metal elbow for petrochemical use.

[0102] Comparative Example 3: Do not compound the modified zeolitic imidazolate framework material with nano-zinc oxide, and the rest is the same as in Example 1:

[0103] Step One: Preparation of metal elbows:

[0104] Take iron, chromium, nickel, silicon, manganese, carbon, vanadium, magnesium, cerium, phosphorus, mix them, heat up to 1570 °C for melting, then cast, cool and form, cut and polish to obtain metal elbows;

[0105] The metal elbow comprises the following components by mass percentage: 21 wt% of chromium, 7.5 wt% of nickel, 2.0 wt% of silicon, 0.7 wt% of manganese, 0.4 wt% of carbon, 0.3 wt% of vanadium, 0.15 wt% of magnesium, 0.02 wt% of cerium, 0.04% of phosphorus, and the balance is iron;

[0106] Step Two: Preparation of zeolitic imidazolate framework material:

[0107] Take 0.52 g of 2-methylimidazole, 0.85 g of zinc nitrate hexahydrate, and 50 mL of methanol, stir for 1.5 h, then let it stand for 25 h, centrifuge, filter, wash, and dry to obtain zeolitic imidazolate framework material;

[0108] Step Three: Preparation of polyethyleneimine grafted with glycine:

[0109] Take 0.8 g of glycine, 1 g of branched polyethyleneimine, and 30 mL of deionized water, stir evenly, add 16 μL of tert-butyl hydroperoxide, under the protection of inert gas, reflux at 83 °C for 4 h, remove the solvent by vacuum distillation, add 80 mL of anhydrous methanol, stir evenly, then add 10 mL of 10% hydrochloric acid aqueous solution, precipitate, centrifuge, and dry. Add 100 mL of deionized water, stir evenly, add sodium carbonate, adjust the pH value to 8.0, then dialyze with deionized water, freeze, and dry to obtain polyethyleneimine grafted with glycine;

[0110] Step 4: Preparation of modified zeolitic imidazolate framework material:

[0111] Take 2.2 g of zeolitic imidazolate framework material and 300 mL of deionized water, stir evenly, add 1 g of polyethyleneimine grafted with glycine, stir for 7 h, filter and dry to obtain the modified zeolitic imidazolate framework material;

[0112] The mass ratio of zeolitic imidazolate framework material, polyethyleneimine grafted with glycine, and deionized water is: 2.2:1:300;

[0113] Step 5: Preparation of pretreated nano-zinc oxide:

[0114] Take 10 mmol / L of tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain Tris-HCl buffer solution; dissolve dopamine hydrochloride in Tris-HCl buffer solution to obtain 2 g / L dopamine solution; take 100 mL of dopamine solution, add 5 g of nano-zinc oxide, heat up to 63 °C, stir for 8 h, filter, wash, and dry to obtain pretreated nano-zinc oxide;

[0115] Step 6: Preparation of corrosion-resistant metal elbows for petrochemical use:

[0116] Take 10 mmol / L of tris(hydroxymethyl)aminomethane solution, add hydrochloric acid to adjust the pH value to 8.5 to obtain Tris-HCl buffer solution; dissolve dopamine hydrochloride in Tris-HCl buffer solution to obtain 2 g / L dopamine solution; take the metal elbow, clean and dry it, then immerse it in the dopamine solution for 1.5 h, add Tris-HCl solution containing 1 g / L of modified zeolitic imidazolate framework material and 0.5 g / L of pretreated nano-zinc oxide with the same volume as the dopamine solution, continue to immerse for 5.5 h, take out and dry to obtain the corrosion-resistant metal elbow for petrochemical use.

[0117] Experiment:

[0118] The petrochemical corrosion-resistant metal elbows prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. The inner diameter of the metal elbow was 100 mm, the outer diameter was 105 mm, and the bend angle was 90°. Its yield strength was tested at 30°C. Referring to GB4334.7-84, a pitting corrosion test was carried out on the metal elbow using a 6% ferric chloride solution, and its corrosion rate was tested. The data obtained are shown in the following table:

[0119]

[0120] Conclusion: It can be seen from the comparison of the data in the table that in Comparative Example 1, glycine was not grafted, and the deposition effect of the modified zeolitic imidazolate framework material on the surface of the metal elbow became worse, and the corrosion resistance became worse. In Comparative Example 2, polyethyleneimine without glycine was added. At this time, the corrosion medium was easily eroded and the corrosion resistance decreased. In Comparative Example 3, the modified zeolitic imidazolate framework material was not compounded with nano-zinc oxide, and the dispersibility of the modified zeolitic imidazolate framework material and nano-zinc oxide was poor and easy to agglomerate, which affected the corrosion resistance of the metal elbow. The petrochemical corrosion-resistant metal elbow prepared by the present invention has high yield strength and good corrosion resistance.

[0121] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A method for preparing a corrosion-resistant metal elbow for petrochemical use, characterized in that: The following steps are involved: Step 1: Take iron, chromium, nickel, silicon, manganese, carbon, vanadium, magnesium, cerium and phosphorus, mix them, heat them to 1550-1600℃ to melt, then cast them, cool them to form, cut and grind them to obtain a metal elbow; Step 2: Take the pretreated nano zinc oxide and anhydrous ethanol, stir evenly, add n-dodecyl mercaptan dropwise, heat to 60-65°C, stir for 2-3h, add modified zeolite imidazole framework material, stir for 6-8h, filter, wash and dry to obtain a zeolite imidazole framework-zinc oxide composite material; Step 3: Take the metal elbow, wash it, dry it, and then immerse it in a dopamine solution for 1-2 hours, add a Tris-HCl solution containing a zeolite imidazole framework-zinc oxide composite material, continue immersing for 5-6 hours, take it out, and dry it to obtain a corrosion-resistant metal elbow for petrochemical use; The preparation method of the modified zeolite imidazole framework material comprises the following steps: S1: Take glycine, branched polyethyleneimine, and deionized water, stir evenly, add tert-butyl hydroperoxide dropwise, reflux at 80-85°C for 3.5-5h under inert gas protection, remove the solvent by reduced pressure distillation, add anhydrous methanol, stir evenly, then add aqueous hydrochloric acid solution, precipitate, centrifuge, dry, add deionized water, stir evenly, add sodium carbonate, adjust the pH value to 8.0, then dialyze with deionized water, freeze, and dry to obtain polyethyleneimine grafted with glycine; S2: Take zeolite imidazole framework material and deionized water, stir evenly, add polyethyleneimine grafted with glycine, stir for 6-8 hours, filter and dry to obtain modified zeolite imidazole framework material.

2. The method for preparing a corrosion-resistant metal elbow for petrochemical use according to claim 1, characterized in that: The preparation method of the zeolite imidazole framework material is as follows: 2-methylimidazole, zinc nitrate hexahydrate and methanol are taken, stirred for 1-2 hours, then allowed to stand for 24-26 hours, centrifuged, filtered, washed and dried to obtain the zeolite imidazole framework material.

3. The method for preparing a corrosion-resistant metal elbow for petrochemical use according to claim 1, characterized in that: In step 2, the preparation method of the pretreated nano zinc oxide is as follows: taking a dopamine solution, adding nano zinc oxide, heating to 60-65° C., stirring for 7-9 hours, filtering, washing, and drying to obtain the pretreated nano zinc oxide.

4. The method for preparing a corrosion-resistant metal elbow for petrochemical use according to claim 1 or 3, characterized in that: The preparation method of the dopamine solution comprises: taking a tris(hydroxymethyl)aminomethane) solution, adding hydrochloric acid to adjust the pH value to 8.5, and obtaining a Tris-HCl buffer; and dissolving dopamine hydrochloride in the Tris-HCl buffer, and obtaining a dopamine solution.

5. The method for preparing a corrosion-resistant metal elbow for petrochemical use according to claim 1, characterized in that: The metal elbow includes the following components, calculated by mass percentage: 20wt%-22wt% of chromium, 7wt%-8wt% of nickel, 1.5wt%-2.6wt% of silicon, 0.5wt%-1wt% of manganese, 0.3wt%-0.5wt% of carbon, 0.2wt%-0.4wt% of vanadium, 0.1wt%-0.2wt% of magnesium, 0.01wt%-0.03wt% of cerium, 0.03wt%-0.05wt% of phosphorus, and the balance is iron.

6. The method for preparing a corrosion-resistant metal elbow for petrochemical use according to claim 1, characterized in that: In S2, the mass ratio of zeolite imidazole framework material, polyethyleneimine grafted with glycine, and deionized water is: (2-2.5): 1:

300.

7. A corrosion-resistant metal elbow for petrochemical use prepared according to the method for preparing a corrosion-resistant metal elbow for petrochemical use according to any one of claims 1 to 6.

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