CO₂ Methanation in Microstructured Reactors – Catalyst Development and Process Design

Abstract

The sulfur tolerance of mono‐ and bimetallic ruthenium catalysts for CO2 hydrogenation was investigated in microchannel reactors. H2S was selected as a model compound. It was found that a Ru/CeO2 catalyst deactivates rapidly. Ni was a much better additive to improve the catalyst stability compared to Rh and serves as a sulfur trap. The influence of the support was evaluated showing that a SiO2‐supported catalyst has a higher stability and better selectivity compared to CeO2 and TiO2. A plant concept was developed comprising two‐step methanation with a first adiabatic reactor stage followed by a plate heat‐exchanger reactor with integrated cooling which allows more than 97 % CO2 conversion. A pilot plant will be put into operation in connection with a biogas plant and an electrolyser of 50 kW power consumption.

Direct Conversion of Carbon Dioxide to Methane over Ceria‐ and Alumina‐Supported Nickel Catalysts for Biogas Valorization

“…In spite of high exothermic reaction effects at 350°C (resulted from high CO 2 conversion), one can suspect the uniform distribution of temperature and energy dissipation in the microchannel microreactor, as well as negligible mass transport limitations with regards of high thermal conductivity of a stainless steel housing and thin catalyst layer coated on the walls of microchannel microreactor. [46,49,55] All catalysts show excellent durability in CH 4 À CO 2 À H 2 feed stream free from H 2 S. In agreement with thermodynamic considerations discussed above, conversion of CO 2 is higher than recorded in the tests performed under 2 bar, presented for packed-bed microreactor (Figure 4). Conversion of CO 2 over all catalysts is maintained for long time on very high level, ca.…”

“…Studies of the performance of microchannel microreactors with deposited catalysts (Ni20-CeO 2 , Ni20-Al 2 O 3 and Ni40-Al 2 O 3 ) were carried out under high-pressure reaction conditions, in the setup described earlier. [49] A microreactor consists of stainless steel plates each having 28 channels with 600 μm width, 400 μm depth and 50 mm length and a top plate without catalyst coating, which were sealed by laser welding along with the connection of inlet and outlet capillaries. Microchannel microreactors were fabricated by the deposition of an aqueous suspension of the catalyst powder on metallic microstructured plates.…”

“…The microchannels were completely filled with the prepared suspension and excess suspension was wiped off, similar to the procedure described elsewhere and characterised by similar methods. [49,75,76] After deposition, the microstructured plates were dried at room temperature and calcined at 400°C for 6 h. The coating thickness was in the range of 50-60 μm and the catalyst mass distribution 3.5 mg/cm 2 . The catalysts in microchannel microreactors were reduced in 20 mL min À 1 hydrogen at 500°C for 2 h prior to the experiments.…”

“…Different types of reactors have been proposed for the methanation reaction, including packed-bed, monolith, [39][40][41] fluidized bed [42,43] and heat-exchanger reactors [44][45][46] carrying microchannels. [44,[47][48][49] The aim of current studies is the determination of the effect of the presence of methane and hydrogen sulfide in the feed stream on activity, selectivity and durability of ceria and alumina supported nickel catalysts in CO 2 methanation reaction for biogas valorization. Studies were carried out by the application of packed-bed and microchannel microreactors, operated under 2 and 12.5 bar pressure, respectively.…”

“…The development of new catalysts and new reactor concepts with enhanced mass transfer and improved heat control becomes crucial point for the dynamic operation required for processes utilizing fluctuating renewable sources. Different types of reactors have been proposed for the methanation reaction, including packed‐bed, monolith, [39–41] fluidized bed [42,43] and heat‐exchanger reactors [44–46] carrying microchannels [44,47–49] …”