CATALYST SELECTION FOR THE COUPLED METHANOL/PARAFFINS CRACKING PROCESS
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies - III: Combustion & Emission (T1-6P)
Keywords: coupled methanol paraffins cracking, catalyst selection
The study of the basic steps of a catalytic process is proposed for the simultaneous cracking of n-butane and methanol, on acid catalysts with shape selectivity, with the aim of selectively obtaining C2-C4 olefins.
The transformation of both raw materials in an integrated process has advantages such us energy compensation because this process combines the exothermic methanol conversion with the highly endothermic hydrocarbon cracking, in a thermo-neutral reaction.
Because of the high temperature needed for the process and the presence of steam in the medium, catalysts with high hydrothermal stability are required. The performance of different catalysts, with different levels of shape selectivity has been studied: HZSM-5 (with Si/Al=30 and Si/Al=280), Ni-HZSM-5 (obtained by impregnation with 1 wt% Ni) and SAPO-18. The final catalysts consist of 25 wt% of active phase agglomerated by wet extrusion with bentonite as binder (30 wt%) and with inert alumina calcined at 1000 ºC as charge (45 wt%).
The kinetic behaviour of the catalysts has been tested in an automated reaction equipment provided with an isothermal fixed bed reactor connected on-line to a gas chromatograph.
Catalyst discrimination has been carried out based on their butane cracking capacity and olefin selectivity. HZSM-5 catalyst with Si/Al=30 has been proven to have the capacity required for cracking. However, the other catalysts produce a significant increase in the concentration of light olefins compared to that obtained with the HZSM-5 zeolite. Ni incorporation into the final catalyst does not contribute to butane cracking.
Finally, coke content deposited on the catalyst has been determinated subsequent to 5 h time-on-stream runs.
Presented Monday 17, 13:30 to 15:00, in session Sustainable & Clean Technologies - III: Combustion & Emission (T1-6P).
