(321c) Numerical Design and Experimental Evaluation of a Direct Solar Reactor for the Catalytic Dry Reforming of Methane

Methane dry reforming is a process to produce “syngas” (H2 and CO) which is a major precursor for many chemicals and ultra-clean fuels. It is also a CO2 assisted process that leads to the conversion of CO2 to higher value products and an overall reduction of CO2 emissions from the chemical industry. For this reason, there is a good number of studies and reviews towards improving the process efficiency, designing new catalysts, and utilizing solar energy. This study is part of a bigger effort that explores novel catalysts and processes for CO2 conversion, with the goal of achieving processes in which CO2 input is greater than CO2 output at any stage, with the ultimate objective of significantly lowering Qatar’s CO2 footprint. This study focuses on the utilization of solar energy to activate the Atomic Layer Deposition (ALD) based catalyst and drive the dry reforming reaction directly. First, we present the numerical design of a lab scale solar tubular reactor and second, the experimental evaluation of the reactor and dry-reforming reaction conversion efficiencies.

The thermal and optical performance of a solar tubular reactor/receiver depends upon the geometry of the receiver, optical and thermophysical properties of a receiver’s material and reaction conditions. Initially, out 7kW high flux solar simulator (HFSS) is modeled using a commercial software, TracePro®, to obtain the intensity and distribution of the incident radiation flux. The tubular receiver has an internal diameter of 20 mm and an “active” length of 20 mm. To achieve the maximum possible optical efficiency and homogenous heating of the receiver a novel cavity is designed which reflects and focuses the incident flux on the tubular receiver. Multiple scenarios were investigated and optimum results are presented here.

Following the solar reactor manufacturing, an experimental setup was fabricated to study the performance of the proposed catalysts under simulated on-sun conditions. Two different catalysts have been used in a fixed bed configuration (0.2 g catalyst premixed with 2 g of inert quartz), a commercial and an ALD-based Ni/Al₂O₃. The gas mixture (CH₄, CO₂, Ar, He with 5%: 5%: 1%: balance) was fed into the reactor at weight hourly space velocities (WHSV) in the range of flow 2,000 ml/min/g to 10,000 ml/min/g. The catalytic bed was directly irradiated with a high flux solar simulator using 1-5 Xe arc lamp (6 kW each) producing three different temperature levels (550 ᵒC, 650 ᵒC and 850 ᵒC). Herein we report the methane reforming conversion efficiencies and catalysts’ activities. Also, the morphological, chemical, and stability changes of the catalytic particles have been studied and reported here.