Robert L. Spicer

Activity and selectivity of precipitated iron Fischer-Tropsch catalysts

Abstract Low-temperature (230°C), slurry phase Fischer-Tropsch synthesis (FTS) was conducted with precipitated iron-silicon catalysts under industrially relevant conditions (flow=3.1 Nl h −1 g-Fe −1 , H 2 :CO=0.7, P=1.31 MPa). The effects of activation gas (hydrogen, carbon monoxide, or syngas) and promoters (potassium and copper) on activity and selectivity were explored. Optimum potassium promotion was 4–5 at%, relative to iron. Promotion with copper lowered the reduction temperature and increased FTS activity, regardless of the activation gas used. Carbon monoxide activation gave the highest activity for a 100Fe/ 4.4Si/5.2K catalyst (atomic percent, relative to iron) while syngas activation was superior for a 100Fe/4.4Si/2.6Cu/5.2K catalyst. Selectivity of the FTS product was not affected by the activation gas employed or copper promotion; however, potassium promotion increased wax and alkene selectivity. A syngas activated 100Fe/4.4Si/2.6Cu/5.2K catalyst gave the best overall performance at 230°C. Alkene selectivity was >75% for the C 2 -C 11 fraction, methane selectivity was 12 + selectivity was >70 wt%.

Structural features in the formation of the green rust intermediate and γ-FeOOH

Abstract Electron microscopy data reveal a pattern of changes in the particle shape/morphology during the preparation of γ-FeOOH. The initial shapeless material develops to form large thin hexagonal crystals which are shown to be Green Rust-II (GR-II). With the initial, sudden pH decrease from about 8 to 6.5 at about 33% conversion of the total amount of Fe 2+ that is oxidized, small, dense, hexagonal Fe 3 O 4 particles are formed in addition to, or instead of, the GR-II hexagonal crystals. The large thin hexagonal crystals of GR-II contain holes. The disappearance of Fe 3 O 4 and GR-II particles with further oxidation is accompanied by the development of needle-like γ-FeOOH particles. The formation of γ-FeOOH by a pathway involving only GR-II is therefore an oversimplification of the actual process.

A study of the oxidation of ferrous hydroxide in slightly basic solution to produce γ-FeOOH

Abstract During the reaction of Fe(II) with oxygen, three regions of nearly constant pH are observed, each separated by two regions where there is an abrupt pH change. Data for the oxidation of a suspension with [Fe(II)] [OH −1 ] = 7 2 and 0.22 M Fe(II) indicate that the oxidation to Fe(III) and the associated hydrolysis to produce a proton are rapid compared to the reaction that consumes the proton generated during the first step. It is suggested that the oxidation occurs in the aqueous solution, and that the slow step is due to the proton reacting with a solid Fe(II) species to produce soluble Fe(II). Fe3O4 is formed at, or near, the first step in the oxidation-pH curve, and then redissolves as oxidation continues. The amount of Fe(II) and Fe(III) in the solid and solution have been determined at several stages of the oxidation, and these are consistent with the amount of oxygen consumed during the reaction.

FISCHER-TROPSCH CATALYSTS. ATTRITION OF CARBIDED IRON CATALYST IN THE SLURRY PHASE

ABSTRACT Unsupported iron Fischer-Tropsch synthesis catalyst, formed to a spherical shape and calcined in air, were carbided at 270°C with CO for 24 hours. Following carbiding, the material retained the shape and size of the calcined metal oxide. During agitation by rolling of a slurry, the average particle diameter decreased by about 50% during 450 hours; the attrited material retained a spherical shape so that size reduction was not due primarily to particle fracture. The average particle size (1/d3) was approximately linearly related to the rolling time, and the particle size distribution was fitted by the Weibull Probability Function.

A Comparison of Fischer-Tropsch Synthesis in a Slurry Bubble Column Reactor and a Continuous Stirred Tank Reactor

A Slurry Bubble Column Reactor (SBCR) is a gas-liquid-solid reactor in which the finely divided solid catalyst is suspended in the liquid by the rising gas bubbles. SBCR offers many advantages over fixed-bed type reactors such as: 1) improved heat transfer and mass transfer; 2) isothermal temperature profile is maintained; and 3) relatively low capital and operating cost. Fischer-Tropsch Synthesis (FTS) takes place in a SBCR where the synthesis gas is converted on catalysts suspended as fine particles in a liquid. The synthesis gas flows in a bubble phase through the catalyst/wax suspension. The volatile products are removed with unconverted gases, and the liquid products are separated from the suspension. A gas distributor located in the bottom of the reactor produces the bubbles in the reactor. A considerable interest has been expressed in using the SBCR to carry out FTS particularly for the conversion of stranded natural gas into liquids. Currently, the Center for Applied Energy Research (CAER) is utilizing a Prototype Integrated Process Unit (PIPU) system for scale-up research of the FTS. The purpose of this study was to compare the performance and activity decline of a precipitated Fe/K Fischer Tropsch Synthesis (FTS) catalyst in a revamped slurry bubble column reactor (SBCR) to that of previous CSTR and SBCR runs using the same catalyst and operating conditions. The activity decline measured in the revamped SBCR system was shown to be similar to that of the CSTR experiments. The apparent activity decline in a previous SBCR run was due a transient startup effect from the slurry filtration system.

Catalytic hydrotreatment of coal-derived naphtha

ABSTRACT ABSTRACT A naphtha derived from the liquefaction of a subbituminous (Black Thunder) or a bituminous coal (III. #6) was hydrotreated on a pilot plant scale, to provide a feedstock sufficiently low in heteroatoms for further studies in reforming. Two commercial catalysts, a Ni/Mo and a Co/Mo on alumina, were employed in the processing of the naphtha samples. The Black Thunder naphtha was processed for over 120 hours, twice using the Co/Mo catalyst and once using the Ni/Mo catalyst. For this naphtha, the removal of nitrogen was extremely difficult using the catalysts and conditions employed in this study. An average of 51.6% of the nitrogen was removed during each of the three passes. The oxygen compounds in this naphtha were relatively easily removed. During the first pass over the Co/Mo catalyst, 94.0% of the oxygen was removed.

A comparison of reactors in coal liquefaction

Abstract The data presented in this study illustrate the similarities and differences in the yield and selectivities obtained from different types of coal liquefaction reactors. The results suggest that the comparison of data in the literature obtained from different reactors should be done with careful consideration. The differences and similarities in the yields obtained depend not only on the reactor type but also on the feedstock employed and the residence time in the reactors. Data generated using microreactors are adequate for the selection of operating conditions for conversion in larger scale reactors.

SCANNING ELECTRON MICROSCOPY STUDY OF CO-PRECIPITATED IRON OXIDE CATALYSTS

ABSTRACT Iron oxide Fischer-Tropsch catalysts were prepared using a sol-gel method to incorporate varying amounts of silica (SiO2) and a constant amount of potassium oxide (K2O) promoters. The sol-gel slurries containing different Fe/Si ratios were dried using a spray dryer. The spray-dried materials were calcined at 300°C prior to the use as catalysts for the Fischer-Tropsch reaction. Scanning electron microscopy (SEM), combined with energy dispersive X-ray spectroscopy (EDS) and elemental dot mapping (EDM) techniques, was utilized to characterize the structural morphology for these promoted iron oxide catalysts. The results indicate that the promoters (SiO2, k2O) are evenly distributed throughout the catalysts, and no agglomerated regions of iron, silica or potassium could be observed. Thus, the sol-gel preparation, followed by spray drying produces industrial catalysts of fine particle morphology and a uniform distribution of the promoters.

Hydroprocessing a western Kentucky tar sand bitumen alone and coprocessing with a western Kentucky #9 coal. Catalytic studies in a 1/8 tpd pilot plant

A western Kentucky tar sand bitumen and western Kentucky # 9 coal were coprocessed in a 1/8 ton per day pilot plant using a Co-Mo-Al2O3 catalyst in an ebullated catalyst bed reactor. Steady state conversion data has been obtained for operation with bitumen alone and with the coal/bitumen combination. Process stream products were blended according to mass balance data representing both operational periods and analyzed. The product slates indicate that the addition of the coal did not impact the overall product slate in either yield or quality to a significant extent. The data also show that these two western Kentucky resources, located within a few miles of each other, can be successfully processed on a pilot plant scale.