TOWARDS A NEW CLASS OF MESOPOROUS MATERIALS FOR APPLICATIONS IN PETROLEUM REFINING

摘要

This project focuses on the synthesis of mesoporous aluminophosphates, silicates and aluminosilicates as catalysts for applications in the conversion of large petroleum feedstock compounds to useful middle distillates and naphtha transportation fuels. Summarized herein is our research progress from September 1, 2003, to August 31, 2004. In previous reports it was demonstrated that mesoporous aluminophosphates with neutral framework (containing Al, P and O) could be synthesized, but their thermal stabilities were limited. In general, the materials' pore structure collapsed when calcined at 500-550 C in air or extracted in ethanol/HCl mixture to remove the surfactants, which were used as synthesis templates. New methods to improve the thermal stability of the materials needed to be explored. It was conceived that by adding divalent metals cations, such as Mg and Co, not only that the acid sites would be created by balancing the negatively charged framework (balanced by H{sup +}), but the thermal stability of the materials would be improved. In addition, methods to facilitate the interaction of hydrocarbon substrates with acid sites within the mesoporous are also needed. One concept towards improving this was to incorporate organic functional groups within or attached to the otherwise purely inorganic aluminophosphate (containing Co or Mg) or aluminosilicate pore walls of the mesopores. In the last report we detailed that mesoporous organosilicates were synthesized using block copolymer under acid conditions containing silica and phenylene (-C{sub 6}H{sub 4}-). Materials prepared with phenylene group among the silica pore walls was found to be thermally stable up to 550 C which is almost 100 C higher than the temperature used for the mild hydrocracking of petroleum. It was also highlighted that this area was the subject of recent intense research activities by other researchers. Building on precedence of the last report and on the results of other researchers, we investigated the synthesis of a wide range of mesoporous silicates containing different organic functionalities within the pore walls (using -CH{sub 2}CH{sub 2}-), simultaneously combined with additional organic functional groups extended within the mesopores and grafted through silicate linkages to the pore walls (including (SiO){sub 3}-CH{sub n}SH, (SiO){sub 3}-CH{sub n}NH (SiO){sub 3}-CH{sub n}IM and (SiO){sub 3}-CH{sub n}C{sub 6}H{sub 4}, X is imidazole) for use as potential acid catalysts in petroleum upgrading. Based on modifications to published procedures, we synthesized organic functionalized mesoporous organosilicates described above with surface area greater that 700 m{sup 2}/g, pore volume > 0.73 cm{sup 3}. The materials were stable to ethanolic extraction, but showed various degrees of thermal stability depending on the nature of the organic groups attached. We also investigated the synthesis of a wide range of mesoporous alumiophosphate containing Mg and Co in the matrix. Synthesis was also conducted on organic functionalized aluminophosphates containing similar organic functionalities described above. Syntheses of the phosphates was conducted in basic conditions with cationic surfactant, namely C{sub 16}H{sub 33}N(CH{sub 3})Cl as templates. However, the structure of all the aluminophosphates appear to collapse when the template was removed by extraction or calcination. The catalytic testing phase of the project has commenced with the assembly of a microreactor interfaced with a gas chromatograph. Further research will be focused on use the microreactor to evaluate those potential mesoporous aluminosilicate and alumiophosphate catalyst materials which has maintained some stability, as detailed in this and previous reports, and will also be focused on investigating alternative synthesis approach to strengthen the thermal stability of the aluminophosphates.