Sterically hindered hydroquinones as antifoulants for unsaturated monomers
The present invention generally relates to compounds and methods for preventing fouling caused by the radical polymerization of unsaturated compounds, particularly vinyl monomers. More particularly, it relates to the use of hindered hydroquinones to inhibit the polymerization, which result in the fouling of process equipment, and prematurely consume the vinylic monomer products.
1. A method for inhibiting polymerization during refining, transport, or storage of a hydrocarbon stream containing a hydrocarbon having an unsaturated carbon-carbon bond comprising contacting the hydrocarbon product with an effective amount of a hydroquinone compound has the structure of formula (2) or formula (3):
wherein
X 1 , X 2 , and X 3 are independently —O— or —C(H)(R 4 )— and wherein at least one of X 1 , X 2 , and X 3 is —C(H)(R 4 )—;
Z 1 , Z 2 , Z 3 , and Z 4 are independently —O— or —C(H)(R 4 )— and wherein at least two of Z 1 , Z 2 , Z 3 , and Z 4 is —C(H)(R 4 )—;
R 3 is hydrogen, alkyl, aryl, or heterocyclo;
R 4 is independently hydrogen, alkyl, aryl, or heterocyclo; and
wherein the hydroquinone compound inhibits polymerization of the hydrocarbon having an unsaturated carbon-carbon bond, and the hydrocarbon having an unsaturated carbon-carbon bond comprises ethylene, propylene, acetylene, styrene, butadiene, or a combination thereof.
2. The method of claim 1 , wherein the compound has the structure of formula (2).
3. The method of claim 1 , wherein the compound has the structure of formula (3).
4. The method of claim 1 , wherein the hydrocarbon having an unsaturated carbon-carbon bond comprises ethylene, propylene, acetylene, butadiene, or a combination thereof.
5. The method of claim 1 , wherein the method stabilizes and inhibits polymerization of the hydrocarbon having an unsaturated carbon-carbon bond during a purification or a storage process.
6. The method of claim 5 , wherein the method stabilizes and inhibits polymerization of a hydrocarbon having an unsaturated carbon-carbon bond in a primary fractionation process, process-gas compression, butadiene extraction, propane dehydrogenation, diesel and petrol fuel stabilization, olefin metathesis, styrene purification, hydroxyhydrocarbon purification, or delays the polymerization of resins and compositions comprising ethylenically unsaturated species.
7. The method of claim 6 , wherein the process is butadiene extraction or styrene purification.
8. The method of claim 1 , further comprising contacting the hydrocarbon stream with a nitroxide compound in combination with the hydroquinone of Formula 1.
9. The method of claim 8 , wherein the nitroxide compound is 2,2,6,6-tetramethylpiperidine-1-oxide, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxide, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxide, 4-ethoxy-2,2,6,6-tetramethylpiperidine-1-oxide, 4-propoxy-2,2,6,6-tetramethylpiperidine-1-oxide, 4-butoxy-2,2,6,6-tetramethylpiperidine-1-oxide, or a combination thereof.
10. The method of claim 8 , wherein the nitroxide compound is 2,2,6,6-tetramethylpiperidine-1-oxide, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxide, 4-butoxy-2,2,6,6-tetramethylpiperidine-1-oxide, or a combination thereof.
11. The method of claim 8 , wherein the nitroxide compound comprises 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxide.