Modeling of nickel-based hydrotalcite catalyst coated on heat exchanger reactors for CO₂ methanation

This study presents the kinetic modeling of CO₂ methanation reaction using 15 wt% Ni/Mg/Al hydrotalcite coated catalyst. Power law and Langmuir-Hinshelwood-Hougens-Watson (LHHW) models were used to represent the kinetics of CO₂ methanation. LHHW model displayed better representation of the kinetics and was chosen for modeling the CO₂ methanation reaction in a plate type heat exchanger reactor. Comparison between experiments, 1D model, and 2D model proved the reliability of using internally coated tubular reactor for kinetic modeling of coated catalyst. This work also performed modeling of a plate type heat exchanger reactor with catalytically coated corrugated plates for CO₂ methanation. Heat exchanger reactors with coated catalyst allow controlling the reaction temperature and thus, avoiding temperature runaway owing to the highly exothermic CO₂ methanation reaction. The corrugated pattern created by the opposing corrugated plates of the plate heat exchanger reactor proved to be excellent for distributing the flow homogeneously inside each reaction channel and the entire reactor. In this reactor, 92% CO₂ conversion was achieved at GHSV = 4400 h⁻¹, 573 K and 5 bar. The good performance of this reactor was due to the high activity displayed by Ni-hydrotalcite coated catalyst, homogeneous flow distribution and high surface area of the reactor. Thus, plate type heat exchanger reactor with catalytically coated corrugated plates proved to be suitable alternative to plate heat exchanger reactors with microchannel plates.