Iron catalysts experiments with

A continuous cross-flow filtration process has been utilized to investigate the effectiveness in the separation of nano sized (3-5 nm) iron-based catalyst particles from simulated Fischer-Tropsch (FT) catalyst/wax slurry in a pilot-scale slurry bubble column reactor (SBCR). A prototype stainless steel cross-flow filtration module (nominal pore opening of 0.1 pm) was used. A series of cross-flow filtration experiments were initiated to study the effect of mono-olefins and aliphatic alcohol on the filtration flux and membrane performance. 1-hexadecene and 1-dodecanol were doped into activated iron catalyst slurry (with Polywax 500 and 655 as simulated FT wax) to evaluate the effect of their presence on filtration performance. The 1-hexadecene concentrations were varied from 5 to 25 wt% and 1-dodecanol concentrations were varied from 6 to 17 wt% to simulate a range of FT reactor slurries reported in literature. The addition of 1-dodecanol was found to decrease the permeation rate, while the addition of 1-hexadecene was found to have an insignificant or no effect on the permeation rate. 

In the original derivation of (305), it was supposed (40) that the nitrogen adsorption equilibrium on the catalyst follows the logarithmic isotherms (i.e., that the surface is evenly nonuniform). In this case y — 0 and, according to (143) and (164), m — a, n — / . Experiments with iron catalyst promoted with A1203 and K20 gave m = 0.5. This was interpreted as a = 0.5 (93). 

Four iron catalysts promoted with varying amounts of potassium were reacted at 215°C in synthesis gas for 24 h and then tested using TPSR. The results of the experiments are shown in Figure 6, which tabulates the quantities of amorphous CHx carbon, carbidic, and graphitic carbon found on each catalyst. The most graphite formed on the unpromoted iron... 

Fischer s experiments with iron catalysts promoted with alkalies showed that they increased in efficiency with the strength of the base, with the exception of caesium. Working with catalysts prepared by calcining steel turnings with potassium hydroxide, Frolich and Lewis 1J7 showed that with a gas containing 40 per cent carbon monoxide passed into the reactor at a space velocity of 1250 at 200 atmospheres and 325° to 335° C. the best yields were obtained when the base comprised 2.2 per cent of the catalysts (calculated as K20). From this it appears that a strong base present in small amount with iron as the catalyst enables the best yields of liquid products to be obtained. This conclusion has been confirmed by the work of Audibert and Raineau. 

In order to investigate the catalytic activity of Ru catalysts, and compare with iron catalyst, we choose the representative iron catalyst A301 with wiistite as precursor as the reference sample. A301 has the highest activity among all of the iron-based catalysts for ammonia synthesis and now it has been widely used in ammonia synthesis industry. In order to get the reliable and comparable data of the evaluation of catalytic activity, the experiment was conducted under the same conditions and four samples were filled in four reactor contained in one shell. The results were shown in Table 6.41 and Figs. 6.56-6.58. 

As to efforts to carry out ammonia synthesis in a technical direction, studies along that line had been started in the B. A. S. F. after Wilhelm Ostwald had suggested such work in 1900. In laboratory experiments considerable yields of synthetic ammonia had been obtained by W. Ostwald (27). However, all attempts to reproduce these yields on a larger scale were futile, and finally Ostwald had to admit that in his original experiments, ammonia had probably been erroneously introduced into the synthesis reactor with a foreign source, presumably in form of an iron nitride, which had been formed by a previous treatment of the iron catalyst with ammonia. 

Metal complexes of bis(oxazoline) ligands are excellent catalysts for the enantioselective Diels-Alder reaction of cyclopentadiene and 3-acryloyl-l,3-oxa-zolidin-2-one. This reaction was most commonly utilized for initial investigation of the catalytic system. The selectivity in this reaction can be twofold. Approach of the dienophile (in this case, 3-acryloyl-l,3-oxazolidin-2-one) can be from the endo or exo face and the orientation of the oxazolidinone ring can lead to formation of either enantiomer R or S) on each face. The ideal catalyst would offer control over both of these factors leading to reaction at exclusively one face (endo or exo) and yielding exclusively one enantiomer. Corey and co-workers first experimented with the use of bis(oxazoline)-metal complexes as catalysts in the Diels-Alder reaction between cyclopentadiene 68 and 3-acryloyl-l,3-oxazolidin-2-one 69 the results are summarized in Table 9.7 (Fig. 9.20). For this reaction, 10 mol% of various iron(III)-phe-box 6 complexes were utilized at a reaction temperature of —50 °C for 2-15 h. The yields of cycloadducts were 85%. The best selectivities were observed when iron(III) chloride was used as the metal source and the reaction was stirred at —50 °C for 15 h. Under these conditions the facial selectivity was determined to be 99 1 (endo/exo) with an endo ee of 84%. 

In 1944 a fluid catalyst pilot plant was erected and operated at the Olean laboratory. A schematic flow diagram of the unit is shown in Figure 1. The unit operated well from the beginning. The conversion of jeactants exceeded that achieved by the Germans even at space velocities 10 to 20 times those used in Europe. Also, iron catalysts were developed which gave oil yields comparable with those obtained by fixed-bed operations. Typical results from these early experiments are shown in Table I. A discussion of the conditions for the different runs is given in subsequent paragraphs. 

New results of styrene formation over iron oxide single-crystal model catalysts were reported.326 In ultra-high-vacuum experiments with Fe304(lll) and a-Fe203(0001) films combined with batch reaction studies only Fe203 showed catalytic activity. The activity increased with increasing surface defect... 

For the highest concentration of catalystused [ 2.5 g per liter of toluene], pure TiO was more active than iron-doped TiO catalysts,( compare experiments 1, 3 and 5 in Table 1) however, the iron-doped TiO catalyst, containing 0.5 wt% of iron, showed higher photoactivity than pure TiO, and than iron-doped TiO, with a content of iron of 5 wt%, when a lower concentration of catalyst was used [1.25 g per liter of toluene] ( compare, chemical yields from experiments 2, 4 and 6 in Table 1) in fact, a relatively important chemical yield in benzaldehy de (-0.9%) was obtained by using Fe/TiO (0.5 wt% of iron) catalyst at the con centration of 1.25 g per liter of toluene. 

Our experiments (110) conducted at atmospheric pressure with promoted iron catalyst in the temperature range of 400-475°C have completely confirmed the theoretical deductions. It was found that for the catalyst used in the experiments m = n = 0.5, so that for the ratio of constants k (proportional to k ) the equality k/k = (K /K)0 5 should hold true. This was found to be the case e.g., at 475°C the ratio k/k from experimentation is equal to 2.53 and 2.47, while (K /K)0-5 = 2.52. 

The state of iron ammonia catalysts is dealt with in the following chapters, and x-ray, magnetic, and electric data will be discussed together with adsorption measurements. Information about the catalysts combined with kinetic experiments has led to a fairly good qualitative understanding of ammonia synthesis on iron catalysts, but owing to the extremely complicated nature of the catalyst surface during reaction, a quantitative treatment based on data of catalyst and reactants will not be attained in the near future. 

The hypothesis of formation of oxygenated compounds as intermediate products was rejected by Eidus on the basis of experiments on the conversion over cobalt of methyl and ethyl alcohols and formic acid which were found to form carbon monoxide and hydrogen in an intermediate step of the hydrocarbon synthesis (76). Methylene radicals are thought to be formed on nickel and cobalt catalysts (76) by hydrogenation of the unstable group CHOH formed by interaction of adsorbed carbon monoxide and hydrogen, while on iron catalysts methylene radicals are probably formed by hydrogenation of the carbide (78,81). Carbon dioxide was found to interact with the alkaline promoters on the surface of iron catalysts as little as 1 % potassium carbonate was found to occupy 30 to 40% of the active surface area. The alkali also promotes carbide formation and the synthesis reaction on iron (78). 

A heterogeneity was demonstrated for the surfaces of iron, tungsten, and also for oxide catalysts consisting of various phases, in accordance with poisoning experiments on these catalysts. One of the important functions of promoters is to develop active sites on the surface of certain catalysts, as, e.g., on the promoted iron catalysts used in the ammonia synthesis. 

The iron catalysts used in the temperature programmed adsorption experiments were synthesized using iron nitrate precipitated with a base. In the case of the copper/iron catalysts the base used was Na2C03 and for the iron/potassium catalysts, NaOH was used to precipitate... 

---