Synthesis of Effective Kinetic Inhibitors for Natural Gas Hydrates

Abstract

Six novel polymer-based kinetic hydrate inhibitors (KHIs) were synthesized and characterized. Their performance in inhibiting both tetrahydrofuran (THF) hydrate and the synthetic gas hydrate formation was examined using two different instruments: a ball-stop apparatus and a high-pressure automatic lag time apparatus (HP-ALTA). Performance was benchmarked against two commercially available KHIs, Gaffix VC-713 and Luvicap EG, under the same working conditions. The test results from the ball-stop rig demonstrated that the new KHIs were as effective as Gaffix VC-713 and Luvicap EG in preventing the formation of THF hydrates in 3.5 wt % NaCl solutions. For the synthetic gases, most new polymers outperformed the reference KHIs at a concentration of 0.05 wt %. Polymers containing a pendant THF functional group in the side chains showed a substantial 12–16 °C decrease in the hydrate formation temperature of the gas water mixtures relative to those containing the same amount of Gaffix VC-713 or Luvicap EG. The trend of the inhibition performance of the polymers was different in THF from that measured for gas mixtures. Small amounts of ethanol added to the hydrate formation mixtures were also shown to have an effect. Investigation of the inhibition mechanism associated with these new polymers is under way.

Non-Amide Polymers as Kinetic Hydrate Inhibitors─Maleic Acid/Alkyl Acrylate Copolymers and the Effect of pH on Performance

“…This makes THFMA a useful group to incorporate into vinylic KHI polymers. Some copolymers with the THFMA monomer polymers have been investigated previously . These included VCap copolymer and a polyethoxylated methacrylate, which were shown to have good KHI performance.…”

Analysis of Influencing Factors on the Kinetics Characteristics of Carbon Dioxide Hydrates in High Pressure Flow Systems

“…Maeda et al 25 proposed that when the guest molecules used for hydrate formation are the same, the ratio of the hydrate induction time is linearly related to the ratio of the size of the test system. Therefore, although the cooling rate of the loop system used in this experiment is lower than that of other systems such as static reactors, 26 the induction time of CO 2 hydrate in the flowing system is very short.…”

Review of Kinetic Hydrate Inhibitors Based on Cyclic Amides and Effect of Various Synergists

“…Homo/copolymers of cyclic amides are generally synthesized using conventional free-radical polymerization. ,,, Although any flask can be used as the polymerization reaction vessel, a Schlenk flask is typically used. ,− It has a side arm connected to a gas line that replaces the air (having the reactive oxygen) inside the flask with an inert gas like nitrogen for air-sensitive chemical reactions . The flask is immersed in a water bath and is generally fitted with a reflux condenser.…”

“…The initial step is to mix the desired monomer to be polymerized with four to five times its weight with a solvent. , The solvents generally used are organic solvents like propanol, , ethanol, dioxane, ,,− or dimethylformamide. − Subsequently, 1–20 wt % of the radical initiator is added. The radical initiator in most cases is 2,2′-azobis (2-methylpropionitrile) (AIBN). ,,,− After that, because the presence of oxygen is detrimental to the reaction, , the system is degassed and sealed under the protection of nitrogen. , Procedures like the freeze–pump–thaw method , or a high vacuum line are used for the degassing process. The freeze–pump–thaw method is more efficient; , however, a high vacuum line is commonly used because of its simplicity. , The reaction mixture is then vigorously stirred at 800–1000 rpm, ,, preferably using a magnetic stirrer at high temperatures between 60 and 80 °C for 16–20 h − for the monomer molecules to polymerize.…”