Corrosion inhibition of mild steel by imidazolines and their precursors in a carbon dioxide (CO 2 )-containing environment was studied using rotating cylinder electrode (RCE) and linear polarization resistance (LPR) techniques. Corrosion rate-time/concentration profiles and minimum effective concentrations obtained for a series of imidazolines and amides were evaluated in terms of the respective contributions of their constituent parts (imidazoline ring, amide/amine group, and hydrocarbon chain) to overall corrosion inhibition. Formation of the inhibitor film was studied in terms of the bilayer/multilayer film model. FIGURE 9. Corrosion rate/potential-inhibitor concentration dependence for stearic amide/imidazoline constant concentration treatments.FIGURE 10. Corrosion rate/potential-time response for lauric imidazoline constant concentration treatment at 0 rpm and 6,000 rpm.

Gas hydrate interparticle cohesive forces are important to determine the hydrate crystal particle agglomeration behavior and subsequent hydrate slurry transport that is critical to preventing potentially catastrophic consequences of subsea oil/gas pipeline blockages. A unique high-pressure micromechanical force apparatus has been employed to investigate the effect of the molecular structure of industrially relevant hydrate antiagglomerant (AA) inhibitors on gas hydrate crystal interparticle interactions. Four AA molecules with known detailed structures [quaternary ammonium salts with two long tails (R1) and one short tail (R2)] in which the R1 has 12 carbon (C12) and 8 carbon (C8) and saturated (C–C) versus unsaturated (CC) bonding are used in this work to investigate their interfacial activity to suppress hydrate crystal interparticle interactions in the presence of two liquid hydrocarbons (n-dodecane and n-heptane). All AAs were able to reduce the interparticle cohesive force from the baseline (23.5 ± 2.5 mN m–1), but AA-C12 shows superior performance in both liquid hydrocarbons compared to the other AAs. The interfacial measurements indicate that the AA with an R1 longer alkyl chain length can provide a denser barrier, and the AA molecules may have higher packing density when the AA R1 alkyl tail length is comparable to that of the liquid hydrocarbon chain on the gas hydrate crystal surface. Increasing the salinity can promote the effectiveness of an AA molecule and can also eliminate the effect of longer particle contact times, which typically increases the interparticle cohesive force. This work reports the first experimental investigation of high-performance known molecular structure AAs under industrially relevant conditions, showing that these molecules can reduce the interfacial tension and increase the gas hydrate–water contact angle, thereby minimizing the gas hydrate interparticle interactions. The structure–performance relation reported in this work can be used to help in the design of improved AA inhibitor molecules that will be critical to industrial hydrate crystal slurry transport.

Amorphous dithiazine is produced from a solution of tris-(2-hyroxyethyl)-hexahydro-s-triazine (I) that is heavily consumed by hydrogen sulfide (H2S). Previously, it has been reported that the chemical structure of amorphous dithiazine is a polymeric structure which involves opening of the dithiazine ring. Evidence is presented here that the first step in this polymerization reaction is conversion of the terminal hydroxyl functionality into a terminal thiol. Thereafter, the thiol initiates the ring opening of the dithiazine to yield a polymeric, highly insoluble material. It has been observed that the critical chemical species in the initiation of this chain reaction is the bisulfide anion. This bisulfide anion is produced from the reaction of H2S with ethanolamine liberated in the sulfur insertion reaction undergone by tris-(2-hyroxyethyl)-hexahydro-s-triazine (I). This process has been artificially induced by the reaction of monomeric or crystalline 5-hydroxyethyldithiazine (II) and ethanolammonium hydrosulfide.

PRINCE, WATKINS, FRONCZEK, GANDOUR, WHITE AND GOKEL 895included as fixed contributions with C--H 0.95 A and B = l'3Beq of the bonded C atom. The N--H hydrogen atoms were refined isotropically.The function minimized was Y w(lFol-IFcl) 2, and weights were assigned as w = 4FoZLp[S2(C+ RZB) + (0.02Fo2)2]-1, where S = scan rate, C = total integrated peak count, R = scan time/background counting time, B = total background count, Lp = Lorentz-polarization factor, using the Enraf-Nonius

No abstract