Production of Light Hydrocarbons from Syngas Using a Hybrid Catalyst

Abstract

A hybrid catalyst consisting of a Cu-ZnO/Al2O3 methanol synthesis catalyst and a SAPO-34 molecular sieve was shown to convert syngas into a narrow mixture of short chain paraffins centered at C2–C3 with little methane and C5+ made. This product mix is expected to be an excellent cracker feedstock for the production of olefins. The hybrid catalyst system closely couples sequential reactions on each of the two independent catalysts. The function of each of the components was unraveled by performing experiments in which the reactor was loaded with discrete layers of the individual catalysts. Methanol (MeOH) synthesis over Cu-ZnO/Al2O3 is followed by methanol conversion to dimethyl ether (DME) + steam over the acidic SAPO-34 or Cu-ZnO/Al2O3 component. Simultaneously, the so generated water feeds into the water gas shift (WGS) reaction over Cu-ZnO/Al2O3, producing H2 + CO2, and the DME/MeOH undergoes methanol to olefins (MTO) conversion over SAPO-34. The olefins are subsequently hydrogenated to paraffins over the Cu-ZnO/Al2O3 and SAPO-34 catalysts using hydrogen from the feed or hydrogen produced in the WGS reaction. Comparison of fully mixed vs layered catalyst bed systems indicated that a mixed catalyst bed is preferred to give a high CO conversion and selectivity to desired paraffin products. This scheme enables high single stage conversion by consuming methanol, thereby removing the thermodynamic constraint on that reaction step. The interactions between all the reactants and catalysts in this system create a complex relationship that is probed in this paper.

Kinetics of Direct Olefin Synthesis from Syngas over Mixed Beds of Zn–Zr Oxides and SAPO-34

“…Additionally, the regeneration demands of MTO on the molecular sieve are lowered . Initial efforts in this bifunctional bed used Cu-based methanol synthesis catalysts paired with SAPO-34, − ZSM-5, , ferrierite, USY, and BETA, which produces mainly saturated hydrocarbon products rather than olefins, indicative of the high hydrogenation activity of the Cu-based catalysts. Olefin production, as opposed to mostly paraffin production, occurs with the use of methanol synthesis catalysts with lower hydrogenation activity such as Cr–Zn–Al, Cr–Zn, or Zn–Zr based metal oxides.…”

Design of efficient bifunctional catalysts for direct conversion of syngas into lower olefinsviamethanol/dimethyl ether intermediates

“…As already mentioned, many studies by integrating a Cu- or Pd-based methanol-synthesis catalyst with a zeolite only led to the formation of saturated C 2 –C 4 paraffins or gasoline-range hydrocarbons from syngas. 23 – 26 , 35 – 37 Therefore, the development of a high-temperature methanol-synthesis catalyst with proper hydrogenation ability is the key to matching the MTO reaction for the synthesis of C 2 –C 4 olefins.…”

Reactor–Regenerator System for the Dimethyl Ether-to-Olefins Process over HZSM-5 Catalysts: Conceptual Development and Analysis of the Process Variables

“…This latter involves the production of methanol and its dehydration to DME. As a consequence, production of both oxygenates from CO 2 is favored in the DTO process. , DME has been reported as the most reactive intermediate in the direct production of hydrocarbons from syngas . The faster formation rate of olefins from DME than that from methanol using HZSM-5 zeolites , is attributed to its higher proton affinity , and its ability to react easily with the intermediate species yielding propylene .…”