An Experimental Investigation of the Catalytic Activity of Natural Calcium-Rich Minerals and a Novel Dual-Supported CaO–Ca₁₂Al₁₄O₃₃/Al₂O₃ Catalyst for Biotar Steam Reforming

Abstract

Tar removal plays a key role in the process efficiency and viability of biomass gasification for syngas production applications. Among currently available tar treatment technologies, catalytic cracking was found to be the most attractive due to minimal energy losses by avoiding cooling of the raw product gas. Naturally available calcium-based catalysts, particularly stone dust and dolomite, have been proven to be effective for biotar cracking; however, they have poor resistance to attrition and undergo deactivation after a few carbonation/calcination cycles. As such, these characteristics play a critical role in determining the viability of their application at a large-scale. Hence to overcome the shortcomings previously stated, a novel dual supported calcium-based catalyst which includes a stable support with great mechanical strength (alumina, Al2O3, and mayenite, Ca12Al14O33) dosed with CaO nanoparticles was synthesized by wet impregnation of calcium on alumina particles with and without the assistance of ultrasonication, referred to as CA and CAU respectively. The synthesized catalysts, as well as the naturally occurring calcium rich minerals stone dust and dolomite, were physically and chemically characterized using a variety of analytical techniques. The synthesized catalysts showed superior mechanical strength up to 5 times greater than the natural minerals. Each of the natural and synthesized catalysts was then investigated in a fixed bed reactor for steam reforming of biotars. In these experiments, toluene was used as a model tar compound to assess the catalytic activity of each and determine the best option in terms of catalytic activity, cost, and mechanical strength. The synthesized CA catalyst without ultrasonic treatment exhibited better tar cracking performance in comparison to stone dust and dolomite in the temperature range of 600 to 800 °C. The synthesized CA catalyst also had the greatest performance in terms of superior surface area and mechanical strength due to the core support of Al2O3. This makes it a potential bed material for further study of tar cracking in large-scale fluidized applications.

Catalytic Cracking of Biomass-Derived Hydrocarbon Tars or Model Compounds To Form Biobased Benzene, Toluene, and Xylene Isomer Mixtures

“…25 Recently, a novel CaO-based sorbent (Ca-Fe-Al) was developed, consisting of CaO, Fe 2 O 3 , and mayenite for reforming of biomass tar by Han and co-authors. 103 Thereafter, Yin et al 104 investigated the steam reforming of toluene over natural calcium-rich minerals and a novel dual-supported CaO-Ca 12 Al 14 O 33 /Al 2 O 3 catalyst in the temperature range from 600 to 800 °C. This catalyst demonstrated better performance other studied catalysts with the highest toluene conversion of 73% at 800 °C.…”

6th Sino-Australian Symposium on Advanced Coal and Biomass Utilisation Technologies

“…Zahara et al () develop a quantitative model to describe the gasification rate catalyzed by inherent metallic species. Yin et al () investigate the catalytic activity of natural calcium-rich minerals and a novel dual-supported CaO–Ca 12 Al 14 O 33 /Al 2 O 3 catalyst for tar removal. He et al () identify the ash–bed material interaction mechanisms during the combustion and steam gasification of agricultural residues.…”