Hydrodesulfurization (HDS) of catalytic cracked gasoline (CCG) over Co-Mo/γ-Al2O3 catalyst was investigated to clarify the important factors for deep HDS of CCG containing 229 ppm sulfur and 30.4 vol% olefins. In the HDS reaction at 220°C, 1.6 MPa, sulfur compounds were hydrodesulfurized, whereas thiols were formed from H2S and olefins. The reactions of thiophene HDS, isoolefin and n -olefin hydrogenation (HG) were studied to clarify the active sites on the catalyst. The effects of H2S and of Co on these three reactions were examined over catalysts with different Co/(Co+Mo) ratios. Thiophene HDS was promoted by Co, isoolefin HG was little affected, and n -olefin HG was largely retarded. Three types of active sites for thiophene HDS, isoolefin HG and n -olefin HG were proposed. Oligomers of isoolefin were found in the isoolefin hydrotreated product. The possibility of improving the HDS selectivity with carbonaceous deposit by coking pretreatment was investigated for HDS reactions of CCG and model compounds. HDS selectivity (higher activity for HDS and lower activity for olefin HG) during CCG HDS was improved. A commercial scale process of CCG HDS was designed and a simulation model was studied. To calculate the sulfur content in the hydrotreated CCG accurately, the theoretical equilibrium models for thiophene HDS, thiol formation and olefin HG were considered. The results estimated using this simulator showed good correspondence with experimental results. These investigations resulted in commercial scale plant construction. Since 2004, three plants have started operation to produce 10 ppm sulfur gasoline in Japan.
The oligomerization of light olefins, such as ethylene, propylene, 1-butene and isobutene, catalyzed by methane?sulphonic acid (MSA) was evaluated to synthesize liquid hydrocarbons in a high pressure continuous flow reactor for 250 min at 20 to 40°C. The liquid hydrocarbons separated from the MSA catalyst were analyzed by combined gas chromatography with mass spectrometry. The hydrocarbons were classified by molecular weight as gasoline, kerosene and light oil. Although ethylene and propylene were slightly dissolved into the MSA, no further liquid product was obtained after the reaction period. The yield of liquid product from isobutene was larger than that from 1-butene. The selectivity for gasoline was lower than that for kerosene or light oil. The recovered MSA was replaced 10 times into the reactor to elucidate the effect of recycling on catalyst deactivation. The activity of recycled MSA was the same as the fresh catalyst. On the other hand, the reaction mixture catalyzed by sulfuric acid was not separated into the hydrocarbon layer and catalyst layer after recycling 3 times. Oligomerization of 1-butene with a small amount of water to clarify the effect of impurity showed that the catalytic activity of MSA sharply decreased with water content. Methanesulphonic acid is an effective catalyst for the selective synthesis of gas oil from butenes.
The transesterification of triolein with ethanol to make biodiesel fuel was investigated under ultrasonic irradiation to evaluate the effects of the amount of base catalyst (NaOH or KOH), molar ratio of ethanol to triolein, and temperature. Transesterification of triolein with ethanol readily proceeded under 40 kHz ultrasonic irradiation and the most suitable condition at 25°C was a molar ratio of ethanol/triolein of 6/1, base catalyst concentration of 1 wt% for both NaOH and KOH, and reaction time of less than 20 min. In addition, the effect of temperature on the ethanolysis of triolein was investigated. The apparent activation energy estimated under ultrasonic irradiation was almost the same as that reported under stirring. The present results suggest that ultrasonic cavitation provides effective emulsification of triolein and ethanol, resulting in higher rate of transesterification reaction compared with that under stirring.
LPG contains 5-10 volppm of sulfur compounds such as thiols, sulfides, and disulfides. Use of LPG as the hydrogen source for fuel cells will require the removal of sulfur content to the ppb level. Active carbon, CuO/ZnO/Al2O3, Ag-exchanged β zeolite and Ag/CeO2 were examined as sulfur adsorbents at room temperature using propane containing 2-methyl-2-propane thiol (TBM: t -butyl mercaptane), dimethylsulfide (DMS), dimethyldisulfide (DMDS), and carbonyl sulfide (COS). Sulfur compounds were not removed effectively by active carbon. CuO/ZnO/Al2O3 showed excellent removal of TBM, but removal of DMS ceased after a short time. Ag-exchanged β zeolite achieved excellent removal of TBM, DMS and DMDS, but COS was not removed. Ag/CeO2 removed all types of sulfur compounds and provided superior removal of COS compared to the other sulfur adsorbents. Ag/CeO2 and CuO/ZnO/Al2O3 tended to adsorb reactive sulfur compounds more strongly. Ag-exchanged β zeolite adsorbed sulfur compounds associatively, and the larger the negative charge of the sulfur atom of the compound, the stronger the coordination bonding between the Ag cation and the sulfur atom of the compounds. In contrast, Ag/CeO2 adsorbed sulfur compounds dissociatively, and produced sulfur atoms at room temperature.
A simple two-dimensional mathematical model capable of describing the interactions taking place in the bulk fluid and biofilm between sulfate reducing bacteria (SRB), substrates and biocide agents was used for the numerical evaluation of biocide treatment against SRB. The characteristics inherent to thick biofilms formed in large diameter oilfield pipelines were taken into account by assuming that the biocide treatment will remove little of the biofilm and not kill the SRB present in the biofilm. The evaluation model considered SRB disinfection/proliferation, and biocide deactivation within the bulk fluid, as well as many features of biofilm interactions with the bulk fluid such as mass transfer, live SRB detachment and biocide agent deactivation. These interactions are represented by simple coefficients as far as possible. Simulation results, using reported kinetic parameters for SRB, acetate and biocide agents such as chlorine and glutaraldehyde, showed that biocide treatments in oilfield water pipelines are sensitive to the disinfection rate coefficient and the biocide agent concentration as well as to the decay rate coefficient of the biocide agent in the bulk fluid, but are not sensitive to the biocide deactivation rate on the biofilm surface, nor to the SRB concentration in the biofilm. Various extreme conditions of biocide treatments were simulated using the proposed discretization method, which was adapted to take into account the biofilm interactions with the bulk fluid, to investigate the sensitivity of the numerical method and the suitability of the model developed to determine minimum effective biocide concentrations.
Solvent extraction of absorption oil by aqueous solution of methanol was evaluated using a continuous countercurrent spray column. The structure of the spray column is simple so that the mass transfer phenomenon in the column can be easily examined. The measured liquid-liquid equilibria between the absorption oil and aqueous solution of methanol phases required for calculation of mass transfer coefficients were found to agree with previous values. The operability and separability of extraction using the spray column were then studied. The density of the dispersed raffinate phase was sufficiently larger than that of the continuous extract phase to carry out countercurrent operation without entrainment of dispersed phase droplets into the continuous phase or flooding in the range investigated in this study. Mass transfers of components of interest could be detected in the bench scale spray column with effective height of about 0.5 m. The nitrogen heterocyclic compounds were extracted preferentially to other compounds, such as homocyclic compounds, from the absorption oil, and the separation of these compounds was governed by the liquid-liquid equilibrium. The highest yield and separation selectivity of nitrogen compounds with this column were about 0.4 and 30, respectively. Since the overall mass transfer coefficients increased with the flow rate of the continuous extract phase, some mass transfer resistance occurred in the continuous extract phase.
The effects of the pretreatment of various types of zeolites such as H-ZSM5, H-mordenite, H-beta, HY and gallosilicate with ethylene on their activities for the dehydration of ethanol at low temperatures ranging from 473 K to 503 K were investigated. The activities of MFI type zeolites were enhanced by their pretreatment with ethylene, whereas the activities of the other zeolites were not improved.