A New Class of Mesoporous Catalysts for Applications in Petroleum Refining
This project was funded under the Historical Black Colleges and Universities program.
The goal is synthesize and test a new class of mesoporous molecular sieve catalysts.
Clark Atlanta University
The project explored liquid crystals (cylindrical micellar rods) forming micelles to serve as the template around which mesoporous metal-aluminophosphate oxides (MeAPOs) form. The formation of the mesoporous MeAPO structures was induced by the electrostatic interactions between positively charged surfactants and negatively charged MeAPO precursor species by the liquid-crystal templating mechanism. Using this approach, Mg, Mn, Co, Fe, and V were introduced in the precursor gel to synthesize the corresponding MgAPO, MnAPO, CoAPO, FeAPO, and VAPO. Various mesoporous catalysts with tunable acid, redox properties, and pored size ranges thus could be prepared. Successful incorporation of these ions into the molecular sieve framework leads to large concentrations of accessible, well-spaced (and dispersed), and structurally well-defined catalytically active sites.
The synthesis of mesoporous MeAPOs using neutral surfactants also will be explored in this research. The underlying concept is that the MeAPO precursor gel can be ordered around self-assembled non-ionic or neutral surfactant liquid crystal by hydrogen bonding.
The research provides an improved understanding of this new class of mesoporous catalysts to address the growing demand for improved catalysts for the upgrading of heavy feedstocks such as heavy crudes and petroleum residuum.
The microporous counterparts to the aluminophosphate mesopores were first synthesized by Union Carbide researchers. In the 1980s, the company prepared a new class of zeolite-like, micorporous aluminophosphate oxide molecular sieves (ALPOs) with maximum pore size of approximately 1 nanometer. They later introduced a range of divalent and transition metals (Me) into the ALPO neutral framework, thereby created novel acidic and redox MeAPO catalysts. Through ongoing research, the use of MeAPOs for the conversion of heavy petroleum feedstock under mild hydrocracking conditions has been investigated.
Several researchers have investigated the vast catalytic activities of micorporous MeAPOs in commercially important catalytic reactions, including the cracking of alkanes, xylene and olefin isomerization, and a wide range of aromatic reactions.
A systematic study of the influence of synthesis variables (gel composition, time, and temperature) was carried out.
In general, syntheses were conducted by combining aluminum and phosphorus precursors, cetyltrimethylammonium chloride as surfactant, tetramethylammonium hydroxide, and water with a typical molar composition of the synthesis mixture as:
xAl2O3: P2O5:0.5CTACl:2.6TMAOH:351H2O, where x = 0.29-2.34.
A variety of hexagonal and lamellar AlPO4 with pore size distribution in the 20-40¿ range was prepared in the presence of long-chain CTACl surfactant. The products depended on the molar composition of the synthesis mixture. The aluminum source had significant influence on the products obtained. Products formed using pseudoboehmite alumina (catapal B), were more stable than those formed with aluminum isopropoxide. Aluminum hydroxide gave thermally unstable products. The influence of these and other synthesis variables was described. Mesoporous aluminophosphates, with well-defined pores of sizes that depend on the aluminum-to-phosphorus ratio, were obtained using Catapal B as aluminum source.
Training of graduate and undergraduate students in this field of research continues.
Current Status (October 2005)
The project is complete.
Project Start: September 1, 2000
Project End: February 28, 2005
Anticipated DOE Contribution: $191,996
Performer Contribution: $14,000 (7% of total)
NETL - Kathy Stirling (firstname.lastname@example.org or 918-699-2008)
Clark Atlanta U. - Conrad Ingram (email@example.com or 404-880-6898)