Development of a catalytic coal liquefaction microreactor and testing of novel supports for coal liquefaction catalysts.

摘要

The objectives of this project were to construct a continuous Catalytic Coal Liquefaction Microreactor (CCLM) and to study coal liquefaction catalyst deactivation in this unit. The CCLM was then used to test catalysts prepared from modified alumina supports for coal liquefaction applications. The unique feature of the CCLM is its scale of operation. The reactor charges only five grams of catalyst.; A cold model study identified two successful impeller designs, one having an axial blade orientation and one with a radial orientation. The axial impeller proved to be superior for gas/liquid/solid fluidization. The internal recycle ratio was estimated to be in the order of thousands; thus the microreactor can be treated as a backmixed reactor. Correlations were developed for three key stirrer speeds that are required for successful operation of the CCLM.; Coal was introduced into the microreactor as a paste with a high pressure syringe pump. A brief coal liquefaction process variable study was conducted with Amocat 1A catalyst to identify a set of base conditions for catalyst deactivation experiments: 700 K (800{dollar}sp {lcub}circ{rcub}{dollar}F), 13.8 MPa (2000 psi), 2.0 g coal/h/g catalyst, 3:1 solvent/coal weight ratio, 0.71 liter (std)/cm{dollar}sp 3{dollar} (4000 scf/bbl) hydrogen treat rate and a stirrer speed of 1205 rpm. Catalyst deactivation was severe at these conditions. Near thermal conversions were observed after approximately 1000 weights of coal had been processed per weight of catalyst.; Pore size distributions and diffusivity measurements on the used catalysts revealed two catalyst deactivation mechanisms: (1) active site covering and pore plugging by carbonaceous material and (2) formation of a metal shell on the external surface. Either mechanism operating alone will completely deactivate the catalyst after about 20 days service.; The Amocat blank alumina support was modified in an attempt to cover the alumina surface with a monolayer of TiO{dollar}sb 2{dollar}, ZrO{dollar}sb 2{dollar}, or carbon, and CoMo catalysts were prepared from the modified supports. In this manner pore structure was eliminated as a variable when performance is referenced to Amocat 1A catalyst, which was derived from the same blank support. Modification of the alumina support did not affect catalyst performance greatly.