Promoted skeletal iron catalysts for Fischer-Tropsch...

Details Promoted skeletal iron catalysts for Fischer-Tropsch... Promoted skeletal iron catalysts for Fischer-Tropsch...

2002-03-27

2004-08-17

Bos, Steven (Department: 1754)

Chemistry: fischer-tropsch processes; or purification or recover

Group ib metal containing catalyst utilized for the...

C518S719000, C518S721000, C502S324000, C502S327000, C502S331000

Reexamination Certificate

active

06777452

ABSTRACT:

FIELD OF THE INVENTION
This invention pertains to promoted skeletal iron catalysts for use in Fischer-Tropsch synthesis processes for converting CO and H
2
in synthesis gas feeds to produce various desired hydrocarbon products. It pertains particularly to such promoted skeletal iron catalysts having specific metal compositions and which are prepared using improved method steps for providing improved performance including elevated middle-distillate yield, increased attrition resistance and catalyst settling rates for advantageous use in slurry-phase catalytic reactors.
BACKGROUND OF THE INVENTION
The Fischer-Tropsch (F-T) catalytic synthesis process is a well-known and effective route for converting synthesis gas feeds containing CO and H
2
into chemical feedstocks and hydrocarbon liquid fuels. Precipitated iron catalysts which have been under extensive development for such processes can achieve high catalytic activities, but break down easily to sub-micron particle size during reactor operations for production of hydrocarbon liquid fuels. Such particle breakdown results in difficulties for separating the very fine catalyst particles from the hydrocarbon liquid and waxy products, and has thus hindered commercialization of such F-T synthesis process. Some skeletal iron catalysts suitable for use in F-T synthesis reaction processes have been recently disclosed by U.S. Pat. Nos. 6,265,451 and 6,277,895 to Zhou et al. However, further improvements in such skeletal iron catalysts are desired.
The promoted skeletal iron catalysts of the present invention provide good potential for use in commercial F-T synthesis processes, particularly in slurry type reactors, because the catalyst has lower cost per unit mass of active metal, and has good resistance to particle attrition during vigorous hydrodynamic conditions existing in slurry phase reactors. Also, the used catalysts are readily separable from F-T waxy products by simple gravity sedimentation or by filtration of the catalyst.
SUMMARY OF THE INVENTION
This invention provides improved promoted skeletal iron catalysts containing mainly iron and promoted with minor amount of copper, manganese, and potassium. The promoted skeletal iron catalysts contain 50-90 wt % iron, 0-5.0 wt % copper, 0.1-5.0 wt % manganese, and 0.1-3.0 wt % potassium with the remainder being aluminum. The catalyst has good particle strength and provides high catalytic activity and selectivity towards the formation of desirable hydrocarbon products from the CO and H
2
feedstreams, particularly liquid transportation fuels. The promoted skeletal iron catalyst has catalytic activity comparable to that of precipitated iron catalyst, and more favorable product selectivity towards diesel fuel than that of either precipitated or fused iron catalysts, and can be used in either fixed bed catalytic reactors or slurry bed type reactors for Fischer-Tropsch synthesis processes for producing desired hydrocarbon products. The resulting hydrocarbon liquid products are also rich in alpha-olefins which are valuable feedstocks for chemicals production.
The promoted skeletal iron catalysts of this invention are prepared utilizing improved method steps, which include mixing together iron chips or powder with the non-ferrous metal chips or powders aluminum, copper and manganese, heating and melting the metal chips mixture to form a molten metal alloy, then rapidly cooling the molten metal alloy to room temperature (15-20° C.) such as by quenching in water, and then pulverizing the resulting solid metal alloy to provide fine precursor iron alloy particles having size range of 0.1-10 mm (10-10,000 microns). A major portion of the aluminum is removed by extracting/leaching by contacting with a suitable caustic solution such as NaOH or KOH to provide base iron catalyst particles. The base catalyst particles are next impregnated or loaded with the potassium promoter to provide 0.1-3.0 wt. % potassium. The skeletal iron catalyst is activated utilizing either high-temperature fixed-bed catalyst activation or in-situ activation method steps. The resulting promoted skeletal iron catalysts have high activity for catalyzing conversion of H
2
and CO contained in syngas feedstreams to produce various desirable hydrocarbon products, and are attrition resistant and do not breakdown easily to undesired submicron particle size during extended reaction operations. Because the spent catalyst particles have higher density and are readily separable from the hydrocarbon product liquids by gravity sedimentation, this skeletal iron catalyst is especially suitable for use in slurry-phase type reactors for Fischer Tropsch synthesis processes.
The promoted skeletal iron catalysts of this invention provide various advantages compared with conventional precipitated iron or fused iron catalysts, and also provide specific improvements over the known skeletal iron catalysts. These advantages includes simplified catalyst preparation methods utilizing large size metal chips for forming a molten metal alloy which is cooled rapidly to room temperature and pulverized to desired particle size range to provide a catalyst precursor material, and an improved method for loading the potassium promotor into the catalyst precursor. The catalyst can be effectively activated in either fixed-bed or in-situ reactors. These promoted skeletal iron catalysts provide good syngas conversion (CO conversion>80%) comparable to precipitated iron catalysts under industrial conditions, and have relatively stable activity and excellent selectivity for liquid transportation fuels and alpha-olefins, particularly in slurry-phase Fischer-Tropsch synthesis processes. Also, these catalysts provide good attrition resistance and sedimentation separation of used catalyst from liquid hydrocarbon slurries withdrawn from slurry-phase Fischer-Tropsch reactors.
DESCRIPTION OF INVENTION
The present invention provides improved promoted skeletal iron catalysts having unique composition for advantageous use in Fischer-Tropsch synthesis processes for CO and H
2
feedstreams for producing desired hydrocarbon liquid products. The promoted skeletal iron catalysts contain 70-90 wt % iron with the remainder being less than 10 wt % non-ferrous metal promoters of copper and manganese, and 0.1-3 wt % potassium, with the balance being aluminum. The promoted skeletal iron catalysts have surface areas in the range of 20-80 m
2
/g, and preferably 30-65 m
2
/g, and particle size range of 10-10,000 microns.
The catalyst preparation method steps for this invention includes first mixing iron chips/powder together uniformly with selected non-ferrous metal chips/powder, particularly aluminum, copper, and manganese in the proportion of 20-80 wt. % iron and 30-70 wt. % non-ferrous metals. A typical mixture may contain by weight 35-55% iron, 40-60% aluminum, 1-15% manganese and 0-10% copper. The metals uniform mixture is heated and melted to form a molten metal alloy, which is cooled rapidly to room temperature (15-20° C.) such as by quenching in water, and then pulverized to provide catalyst precursor particles having a 10-10,000 micron size range. The catalyst precursor particles are then extracted or leached by utilizing a suitable caustic solution such as 10-50% NaOH or KOH solution at 50-90° C. temperature for sufficient time such as 20-150 minutes to remove a major portion of aluminum from the iron alloy, and thereby form the base skeletal iron catalyst precursor material.
The resulting base skeletal iron catalyst precursor is next promoted with potassium by impregnating the potassium onto the base skeletal iron catalyst utilizing a suitable organic alcohol solution containing potassium, and then dried to evaporate the alcohol solvent and provide the promoted skeletal iron catalyst containing 0.1-3 wt. % potassium. Suitable alcohol solutions containing potassium may include but are not limited to methanolic potassium hydroxide, ethanolic potassium hydroxide, or potassium carbonate.
The dried promoted skeletal iron catalyst is next reduced and/or activated such as by utiliz

Affiliated with

Also associated with

Rating

Promoted skeletal iron catalysts for Fischer-Tropsch... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Promoted skeletal iron catalysts for Fischer-Tropsch..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Promoted skeletal iron catalysts for Fischer-Tropsch... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3304925