Preparation Of High-performance Combustion Catalyst And Research Of Its Sensing Propetry To Methane

Methane is a natural gas widely used in industrial and domestic applications.Its leakage results in explosions and fires, with that in coal being particularlydisastrous and fatal. Therefore, highly sensitive and stable CH4sensors areurgently needed. To date, the catalytic combustion methane sensor has beenwidely applied for detecting methane in homes and coal mines because of itssimple structure, low cost, good stability and anti-poisoning properties. Pd/Al₂O₃is recognized as the most active catalyst for the combustion of CH₄. However,this catalyst suffers from deactivation problems mainly due to large Pdaggregations on Al₂O₃that occur during combustion, further affect the sensor’ssensing performance.In this work, γ-Al₂O₃and Pd were used as carrier and catalyst, varioussensing samples were gained with different parepared conditions, inludingloading method and loading amounts of Pd, loading time and the acidity of theimpregnated solution. The characterization of catalyst samples were measured byX-ray diffraction （XRD）, BET-specific surface areas, and transmission electronmicroscopy （TEM）. The catalytic combustion methane sensor was fabricated bycoating the above samples. The influence of prepared condition on catalyst andthe performance of meathen sensor was futher studied.From the research, we found that the prepared conditions have great effect on the morphology, dispersion state of noble metal Pd on γ-Al₂O₃，thereby affectingthe sensing performance of sensor.（1） Different Pd loading methods result indistinct Pd morphologies. Among the three loading methods （decompressiondistillation, ultrasonic impregnation, and isometric impregnation） described inthis study, isometric impregnation gave the uniform nanorod structure, thecorresponding meathen sensor gave the highest sensitivity as well as the mostrapid response and recovery rates.（2） Pd loading amount could influence the Pddispersion, and then affect the sensing property and stability of catalystcombustion meathen sensor. The15wt%Pd/Al₂O₃-based sensor had the highestsensing properties and stability among the three Pd loading amounts. In anotherword, the sensitivity and ability to resist organic silicon of Pd/Al₂O₃-based sensorwere improved with the increasing of Pd loading amount.（3） the loading timeand the acidity of the impregnated solution are closely related to Pd dispersionand the sensor’s sensing performance. At2and6h of loading, the Pdnanostructure was the uniform nanorods and the Pd/γ-Al₂O₃catalyst had thelargest specific surface area, the highest sensitivity and the most rapid responseand recovery rates to methane. Pd dispersion on γ-Al₂O₃was improved when thehydrolysis rate of Pd（NO₃）₂was restricted to10vol%HNO₃in a Pd（NO₃）₂impregnation solution, and the sensitivity and stability of methane sensors basedon Pd/γ-Al₂O₃were enhanced.