Open flow hot isostatic pressing assisted synthesis of highly porous materials and catalysts

Mohammad Hossein Siadati, University of Texas at El Paso


Open-flow hot isostatic pressing (OFHIP) technique is applied for synthesizing molecular sieves and highly porous catalytic materials. First, the isostatic pressure is applied to the starting material/catalyst precursor, and then heat is applied. Under this condition, as the organic components gradually decompose and leave the material, the voids left behind are immediately filled/replaced by the gas (pressure medium) in flow. This substitution warrants the preservation as well as the uniformity of the voids/pores. The result is a very porous material with very uniform pore size distribution. ^ Another advantage is the production of the catalyst directly from the precursor, in the absence of solvent (neat), rendering the process simpler and less costly than previous processes. The entire process takes place under flow of the gas that is used as medium to develop the isostatic pressure. Consequently, the entire process, as well as the final product produced, is devoid of any undesirable residues. ^ This endeavor also introduces a viable technique for mass-producing porous materials/catalysts. The resulting materials are termed “amorphous sulfide sieves” to reflect their unique properties that include high surface area, narrow pore size distribution and high activity. The catalysts are potentially licensable to all petroleum and petroleum chemical companies for a wide variety of environmental and product improvement purposes. ^ The results obtained on unpromoted samples synthesized at 300°C indicate that as the synthesis pressure is increased, both surface area and catalytic activity of the materials produced increase. The increase in activity k value from 3 to 6 × 10−7 mol/g.s corresponds to increase in pressure from 100 to 800 psi, respectively. The N2 gas used as pressure medium results in highly porous materials but low activity. H 2 seems to be the ideal gas for both pressure medium and reducing agent. ^ Co-promoted catalysts synthesized at 1400 psi and 300°C show catalytic activity as high as 47 mol/g.s. Based on the activity values obtained at all pressures tested, the projected activity values if tested at 2000 psi by polynomial and exponential curve fittings would be 98 × 10−7 mol/g.s, and 142 × 10−7, respectively. ^ This manuscript contains two parts. Part One consists of eight chapters. Chapters 1 and 2 review supported/unsupported catalysts and the importance of catalysis. Chapters 3–8 provide an exhaustive overview of the existing industrial techniques for the precursor preparation and catalyst synthesis. Part Two of this manuscript covers the OFHIP technique. A separate chapter (Chapter 11) is dedicated to reviewing the Small Angle X-ray Scattering (SAXS) technique for its importance and relevance to this work. ^ Objective. The objective of this work was to synthesize catalyst(s) from the desired precursor(s) using a minimum number of processing steps. Attempts were made to transform the desired catalyst precursor to the final catalytic material in one single step. By minimizing the number of processing steps, the cost of catalyst production would be minimized, rendering a process for mass-producing catalysts desirable for industrial applications. To achieve this objective, open-flow hot isostatic pressing (OFHIP) method has been applied to transform the desired precursor(s) to the final catalyst(s). The objective set forth was achieved for catalysts with activity as high as 47 mol/g.s. has been produced by this newly developed technique. ^

Subject Area

Engineering, Materials Science

Recommended Citation

Siadati, Mohammad Hossein, "Open flow hot isostatic pressing assisted synthesis of highly porous materials and catalysts" (2004). ETD Collection for University of Texas, El Paso. AAI3125573.