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STATEMENT OF WORK

Project Title:

Iron-Based Mixed Metal Carbide Fischer-Tropsch Catalysts

Contractor:

Clemson University
Department of Chemical Engineering
Clemson, SC 29634-0909
Grand Forks, ND 58202
(864) 656-6614

Program Area:

Fuels & Chemical Sciences

Partners:

Louisiana State University
RTI
Rentech

Süd-Chemie, Inc.

South Carolina Energy Office
Louisiana Energy Office

Project Description:

The objectives of Clemson University's project is to

develop more active, selective, attrition resistant and stable Fe FTS catalysts based on formulations containing a second metal (besides Cu) capable of forming mixed metal carbides with Fe.

Management Plan

The unique nature of STAC requires that projects be supported by multiple State entities, and to the extent necessary any other entity. As indicated in the STAC Agreement, it is the Contractor’s responsibility to coordinate the execution of work under the Contract, incorporated by reference hereto. Contractor, in conjunction with the other State entities, and to the extent necessary any other entity, shall conduct the project in accordance with the Management Plan –  described below.

Administration

Clemson University will be the prime contractor and will carryout initial catalyst preparation, catalyst characterization and fundamental reaction studies.  LSU will carry out the XAFS studies of selected catalysts, selected gas-phase FT reactions, and will assist RTI and Rentech in the economic analysis.  RTI will prepare the spray-dried catalysts and carry out CSTR studies of FTS on selected catalysts.  Rentech will provide an industrial perspective and will make several long-term runs in a pilot-scale SBCR.  Dr. Goodwin will serve as P.I. and overall project director.  Drs. Gangwal and Spivey will serve as co-PIs, while Dr. Bohn and Dr. Hu will coordinate the efforts at Rentech and Süd-Chemie, respectively.  This organization is based on the optimized utilization of all the participants' strengths and expertise.  The project brings together an interdisciplinary team at university, research institute, industrial, and state governmental locations.

There will be an annual meeting of the project team members from RTI, LSU, Clemson, the SCEO, and LSEO in Clemson each year in order to coordinate the investigations.  Additional meetings may take place at national technical meetings.  These meetings will be in addition to a monthly conference call among the research collaborators.

The project brings together a team of researchers uniquely qualified to carry out the proposed research on the synthesis of Fe-based mixed carbide FTS catalysts.  Collaboration already exists among the team members.

Task 1.0: Catalyst Preparation [Clemson, RTI, Süd-Chemie]

The proposed research will consider a wide range of bulk Fe catalyst formulations based on (100-x)Fe/xMe/5Cu/4.2K/17SiO₂, where Me indicates the second metal known to form carbides, and x is 10 or smaller.  The second metals (Me) to be studied will include Co, Mn, Mo, and Cr, known to form carbides and to result in interesting catalysts when added to Fe.  In addition, other transition metals known to form carbides will also be investigated.  These will be selected from Re, W, Zr, V, and Ta.  A few 3-metal systems will be studied as well.  Approximately 30 catalysts will be prepared in small quantities of 30-50 g, primarily by coprecipitation.  Prior to characterization/reaction, the catalysts will be activated (preferentially in-situ) using CO- and syngas-pretreatments, typical in the temperature range of 250-300°C.  The conditions of carburization will be investigated since this may be affected by the addition of the second metal Me.  In addition, H₂-pretreatment will also be used for comparison.  Based on initial reaction studies, medium and large batches of the more promising formulations (for slurry phase testing) will be prepared by spray drying at RTI and Süd-Chemie, Inc., respectively.

Task 2.0: Catalyst Characterization [Clemson, LSU, RTI]

The catalysts prepared will be characterized by BET (total surface area), CO chemisorption (surface metal atoms), XRD (Fe and Me crystalline phases formed), TPR (reducibility of the metal phases), and XAFS (metal atom coordination, neighboring atoms, atomic distances).  In-situ XAFS studies will be carried out at LSU's Synchrotron beam line to study the formation of mixed metal carbide phases at a function of catalyst composition, reaction phase composition, time, and temperature.  Catalysts that show interesting reaction properties will be characterized to a greater degree.  Catalyst candidates for further study in continuous stirred-tank reactor (CSTR) and slurry bubble column reactor (SBCR) runs will be evaluated using a jet cup attrition test apparatus to verify acceptable attrition resistance.

Task 3.0: Gas Phase FTS and Surface Reaction Studies [Clemson University, LSU]

Reaction characterization of all catalysts prepared will be done using CO hydrogenation at various pressures, low H₂/CO ratios (ca. 0.7), and temperatures of 230-300°C.  The activity, selectivity, and deactivation characteristics of the catalysts will be determined as a function of reaction conditions and gas phase concentration.  At LSU, gas phase FTS reactions will be carried out using small samples of the catalysts to measure overall CO conversion and selectivity to desired products.  The objective of these studies will be to measure the overall effects of metal alloying before more detailed SSITKA FTS studies at Clemson.

SSITKA of CO hydrogenation will be carried out at Clemson to determine definitively if the reaction sites on the mixed metal catalysts are similar to those on a more typical bulk Fe catalyst and to ascertain the necessary properties of a catalyst for higher activity and selectivity.  In brief, a quartz micro-reactor with ID of 8 mm will be used and a switch in isotopic labeling of the reactant species (¹²CO vs. ¹³CO) will be made at various times-on-stream.  The effluent gas will be analyzed by online gas chromatography and mass spectrometry.

Task 4.0: Slurry Phase FTS [RTI, Rentech]

Several 10-day slurry-phase CSTR FTS runs at RTI) and 10-day SBCR FTS runs (at Rentech) will be conducted to evaluate the most promising catalysts under reaction conditions more typical of commercial practice with regards to activity, selectivity, attrition resistance, and stability.  The catalysts developed will be benchmarked to the commercial Fe catalyst of Ruhrchemie and an attrition-resistant catalyst, HPR-43, developed by the PIs and currently under evaluation for commercial application.

The RTI CSTR reactor system allows volatile liquid products of reaction to be collected in a hot 130°C wax trap followed by a cold 10°C oil + water trap.  Also, heavy wax samples are periodically collected through a sintered stainless steel filter into a wax receiver.  Products are analyzed using 3 gas chromatographs.  CO and hydrogen conversion are calculated.  Selectivity values are also calculated and reported as CO₂, C₁, C₂, C₃, C₄, C₅ to C₉, C₁₀ to C₂₀, and C20+.  The alpha value for the catalyst will be calculated using the slope of the Schultz-Flory-Anderson plot for C₃₅ to C₅₀ hydrocarbons to avoid the bias due to the starting wax.

The SBCR to be used at Rentech has a 1.61" inside diameter and is 26' tall.  It is designed to operate at temperatures up to 300°C and pressures up to 500 psig.  The reactor is externally heated with 14 zones of electrical heat allowing reactor heat losses to be minimized or a reactor temperature profile to be established. An internal cooling tube is used to transfer the exothermic heat of reaction to a cooling oil stream.  Reactor slurry level is maintained with a patented wax/catalyst separation system that separates produced wax from reactor catalyst and returns the catalyst back to the reactor.   Feed gas and tail gas analyses are determined with a Hewlett-Packard G2891A gas chromatograph.  Liquid hydrocarbon analyses are determined with a Hewlett-Packard 5890 gas chromatograph.  Reactor performance reports are generated every 3 hours and a detailed mass balance report run is generated every 24 hours.  A total of three 10-day SBCR runs will be made at 375 psig, H₂/CO = 0.7, and 260°C.

Task 5.0: Evaluation of Commercial Potential [RTI, Rentech, Clemson]

An economic evaluation will be carried out at RTI, with support from Rentech, Clemson, and LSU, of the use of the candidate catalysts (i.e. catalysts showing attributes superior to the benchmark catalyst) to determine their impact on a process involving syngas generation (from coal to biomass), syngas cleanup, and conversion by FTS to liquid fuels.

Project Tasks, Status, and Deliverables

Last Updated: 10/24/06