Shape-selective catalysts for Fischer-Tropsch chemistry : atomic layer deposition of active catalytic metals. Activity report : January 1, 2005 - September 30, 2005.

Cronauer, D. C. (Chemical Sciences and Engineering Division)

关键词: ADVANCED PHOTON SOURCE;    CARBON MONOXIDE;    CATALYSTS;    COATINGS;    COBALT;    COBALT OXIDES;    DEPOSITION;    HYDROCARBONS;    HYDROGEN;    IRON;    MEMBRANES;    MOLECULAR WEIGHT;    OXIDES;    PARTICULATES;    PROGRESS REPORT;    RUTHENIUM;    SILICA;    SURFACE AREA;    SURFACE COATING;    WAXES;   

DOI  :  10.2172/1011836
RP-ID  :  ANL-09/21
PID  :  OSTI ID: 1011836
Others  :  TRN: US1102308

美国|英语

来源: SciTech Connect

【 摘 要 】

Argonne National Laboratory is carrying out a research program to create, prepare, and evaluate catalysts to promote Fischer-Tropsch (FT) chemistry - specifically, the reaction of hydrogen with carbon monoxide to form long-chain hydrocarbons. In addition to needing high activity, it is desirable that the catalysts have high selectivity and stability with respect to both mechanical strength and aging properties. The broad goal is to produce diesel fraction components and avoiding excess yields of both light hydrocarbons and heavy waxes. Originally the goal was to prepare shape-selective catalysts that would limit the formation of long-chain products and yet retain the active metal sites in a protected 'cage.' Such catalysts were prepared with silica-containing fractal cages. The activity was essentially the same as that of catalysts without the cages. We are currently awaiting follow-up experiments to determine the attrition strength of these catalysts. A second experimental stage was undertaken to prepare and evaluate active FT catalysts formed by atomic-layer deposition [ALD] of active components on supported membranes and particulate supports. The concept was that of depositing active metals (i.e. ruthenium, iron or cobalt) upon membranes with well defined flow channels of small diameter and length such that the catalytic activity and product molecular weight distribution could be controlled. In order to rapidly evaluate the catalytic membranes, the ALD coating processes were performed in an 'exploratory mode' in which ALD procedures from the literature appropriate for coating flat surfaces were applied to the high surface area membranes. Consequently, the Fe and Ru loadings in the membranes were likely to be smaller than those expected for complete monolayer coverage. In addition, there was likely to be significant variation in the Fe and Ru loading among the membranes due to difficulties in nucleating these materials on the aluminum oxide surfaces. The first series of experiments using coated membranes demonstrated that the technology needed further improvement. Specifically, observed catalytic FT activity was low. This low activity appeared to be due to: (1) low available surface area, (2) atomic deposition techniques that needed improvements, and (3) insufficient preconditioning of the catalyst surface prior to FT testing. Therefore, experimentation was expanded to the use of particulate silica supports having defined channels and reasonably high surface area. This later experimentation will be discussed in the next progress report. Subsequently, we plan to evaluate membranes after the ALD techniques are improved with a careful study to control and quantify the Fe and Ru loadings. The preconditioning of these surfaces will also be further developed. (A number of improvements have been made with particulate supports; they will be discussed in the subsequent report.) In support of the above, there was an opportunity to undertake a short study of cobalt/promoter/support interaction using the Advanced Photon Source (APS) of Argonne. Five catalysts and a reference cobalt oxide were characterized during a temperature programmed EXAFS/XANES experimental study with the combined effort of Argonne and the Center for Applied Energy Research (CAER) of the University of Kentucky. This project was completed, and it resulted in an extensive understanding of the preconditioning step of reducing Co-containing FT catalysts. A copy of the resulting manuscript has been submitted and accepted for publication. A similar project was undertaken with iron-containing FT catalysts; the data is currently being studied.