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Three runs were carried out in the continuous stirred autoclave reactor with Englehard Zn-0312 T 1/8 {open_quotes}zinc chromite{close_quotes} catalyst and with decahydronaphthalene (Decalin{reg_sign}) as the slurry liquid. One short run, which was prematurely terminated by operational problems, was designed to define the effect of stirrer speed on catalyst performance. Two longer runs completed the data base required for kinetic characterization of the unpromoted {open_quotes}zinc chromite{close_quotes} catalyst. Although analysis of the data is not complete, it is evident that: (1) stirrer speed has no significant effect on the measured reaction rate, and; (2) carbon dioxide appears to inhibit catalyst activity.
Standard thermal stability tests were carried out on four liquids: decahydroquinoline (DHQ); 1, 3-Di-4 piperidylpropane (134PPDP), Naphthenic Base 37 and tetrahydronaphthalene (tetralin). Tetralin was more stable than decahydronaphthalene (Decalin{reg_sign}), and THQ was slightly less stable. Both tetralin and THQ should be evaluated further as slurry liquids in the presence of catalyst and syngas. Naphthenic Base 37 and 134PPDP do not have satisfactory thermal stability. Vapor pressure osmometry (VPO) was shown to be an unreliable technique for measuring the average molecular weight of slurry liquids. Gas chromatography/mass spectroscopy (GUMS) is a more accurate technique for pure compounds.
A set of stirrer speed experiments using the Cu/ZnO methanol synthesis catalyst showed that introducing the gas feed into the reactor through an extended dip tube eliminated the dependency of catalyst performance on stirrer speed. The methanol productivity data from the reactor gas feed configuration tests conducted in December, 1994 and January, 1995, were correlated with stirrer speed. The influence on mass transfer on catalyst performance was clearly illustrated for each gas feed location. The ''high pressure, high temperature' zinc chromite methanol synthesis catalyst showed surprising activity at temperatures as low as 300°C during the first successful stirred autoclave run with this catalyst. No C{sub 2{sup {plus}}} alcohols were detected, but significant levels of C2-C4 olefins and dimethyl ether (DME) were produced. The presence of olefins suggests that higher alcohols might have formed and subsequently dehydrated. The slurry liquid, decahydronaphthalene, showed no evidence of decomposition during 15 days of continuous operation. 2 figs., 1 tab.
This document reports work during this quarter on the project to produce higher alcohols from synthesis gas. A set of four methanol synthesis runs was conducted. Significant catalyst deactivation was experienced, and essentially all of the oil was lost from the reactor over the course of two weeks of operation. Three screening runs of potential high temperature oil were also conducted. However, essentially no oil remained in the reactor after completion of each run. A 1%Rh/1.3%Re/Al2O3 catalyst was prepared from Re and Rh carbonyls with the objective of obtaining intimate contact between Rh and Re atoms. The catalytic activity of this catalyst was explored. Mo was deposited on the catalyst from both molybdenum hexacarbonyl [Mo(CO)6] and (NH4)6Mo--O24·4H2O. The catalytic activity of the molybdenum promoted catalysts was found to be the highest achieved to date under this contract.
A detailed technical plan for research on higher-alcohol synthesis in a slurry reactor was prepared and approved internally, as part of the University's requirements for the doctoral degree. The focus of this plan is the high-pressure methanol synthesis catalyst, and modifications thereof. A major challenge of the research will be to identify a slurry medium that is stable at the typical operating temperature ofthis catalyst, i.e., about 400°C. Two shakedown runs were made in the stirred autoclave without catalyst in order to check the mechanical operation of the system and to test some of the analytical equipment. Further preparation, characterization and screening of higher-oxygenate synthesis catalysts based on rhodium were carried out. The catalyst compositions tested during the period were: Rh/Al2O3, Rh/Nb/Al2O3, Mo/Rh/Al2O3 and W/Rh/Al2O3. All catalysts contained a nominal 1 wt. % Rh. Rh/Nb/Al2O3 and Rh/Mo/Al2O3 were about twice as active for COconversion as the other catalysts. However, oxygenate yields were disappointing for all of the compositions tested. The Rh/Mo/Al2O3 catalyst had the highest carbon efficiency to oxygenates, 33%.
ASPEN computer simulation cases involving methanol, ethanol and propanol recycle have been completed. The results indicate that the yield of higher alcohols increased slightly until the quantity of recycled lower alcohol equaled the amount of that alcohol produced (i.e. when there is no net formation of the recycled alcohol). Above this point, no change in higher alcohol yield was observed. All cases were based on a 2/1 H2/CO feed ratio at 70 atm and 275°C. ASPEN PLUS simulations of the thermodynamics of higher alcohol synthesis were carried out based on non-ideal, equation-of-state models. The models used were the Peng-Robinson and the Redlich-Kwong-Aspen equations of state. The results of these simulations indicate very little difference between the results obtained with the ideal fluid model and the non-ideal models. No significant changes were found in reactant conversion, product distribution or product yield. All laboratory renovations are now complete.
A series of experiments in which the stirrer speed was varied during a methanol synthesis run with BASF S3-86 catalyst showed that mass transfer limitations were present at 750 psig reactor pressure and at space velocities of 5000 and 10000 sl/kg(cat.)-hr. There was no effect of stirrer speed on reaction rate at 2500 psig reactor pressure and 16500 sl/kg(cat.)-hr. space velocity. However, this was probably due to a close approach to equilibrium rather than to the lack of a mass transfer effect. The most plausible explanation for the presence of a mass transfer influence is the position of the gas feed dip tube relative to the agitator impeller. A second set of stirrer speed experiments using the same catalyst showed that feeding into the reactor headspace produced much lower reaction rates, compared with gas feed through a dip tube. The headspace feed also showed a strong dependence on stirrer speed, consistent with the dip tube feed results. In a ''blank' run at 375°C with decahydronaphthalene, about 110 mL of the initial charge of 150 mL remained in the reactor after 73 hours of operation at 375°C and 850 psig of hydrogen. The rate of hydrocarbon evolution was low throughout the run. Decalin is the most stable liquid identified to date. Three stirred autoclave runs with a commercial, high-pressure methanol synthesis catalyst (zinc chromite) slurried in decahydronaphthalene ended son after the initial catalyst reduction due to failures of the liquid return pump in the overhead system. However, the catalyst appeared to be reduced and the liquid appeared to be stable. 4 figs., 1 tab.