Study On Deoxygen Catalyst Of Pt/Zeolite T Under Methane-enrichment Conditions

The presence of oxygen adversely affects the recycling of landfill gas(LFG),such as pipeline corrosion,aging,etc.To avoid this type of impact and to meet the requirements of the standard("Compressed Natural Gas for Vehicles"(GB 18047-2017)),it is necessary for LFG to deoxygen.The use of Pt-supported catalysts to catalyze the CH4 and O2 reactions has proven to be a viable deoxygenation process,and the carriers of supported catalysts have a significant impact on the performance.Therefore,to study the influence of the carrier on the Pt catalyst,a specific morphology T-type molecular sieve was prepared and its influence as the deoxidation catalyst carrier on the performance was explored.The main conclusions are as follows:(1)The rod-like zeolite T can be prepared by changing the raw material ratio.The experimental results show that rod-like zeolite T can be prepared by increasing the content of Al(sodium metasilicate)and K(KOH).The increase of sodium metaaluminate content will cause the aggregation of crystal nucleus precursors to exhibit a circular spherical morphology,while the increase of KOH content will increase the aspect ratio of the molecular sieve crystals,and rod-like zeolite Tcan be prepared due to the joint action of both.The increase of crystallization time has no obvious effect on the morphology of zeoite T,and the size has increased.After the crystallization time of rod-like zeolite T and elliptical morphology zeolite T were extended,the morphology of the crystals in the SEM image remained unchanged,and the size increased.The reason was that the crystals dissolved,recrystallized and epitaxially grown.Due to the consumption of raw materials,the size for the elliptical shape crystals does not increase after 72 hours.(2)Crystallization temperature promotes the formation of rod-like morphology by affecting the dissolution of nuclei and their precursors,and the growth rate of c-direction.Increasing the crystallization temperature has three effects:First,the aspect ratio of the zeolite T crystal increases and decreases,and the appearance of the zeolite T crystal appears close to a rod shape.Second,the size of crystals increases,and crystals become thicker and longer.Finally,the templating agent was impaired and a miscellaneous crystal was generated.In the experiment,when the temperature was higher than 180?,the crystal showed irregular morphology.(3)Rod-shaped T-type molecular sieves are more suitable as deoxygenation catalyst supports.After Pt was loaded on the surface of the elliptical morphology and the rod-shaped T-type molecular sieve,the performance was tested.The results showed that the rod-shaped T-type molecular sieve as the carrier has higher deoxidation performance.The reason is that,on the one hand,the number and specific surface area of rod-shaped T-type molecular sieves are lower than those of elliptical T-type molecular sieves,and the adsorption capacity for CO2 is lower than that of elliptical T-type molecular sieves,thereby avoiding the interference of CO2 on the catalytic reaction.On the other hand,from the SEM image and the TEM image,it could be seen that Pt practicles adheres to the surface of the T-type molecular sieve crystal.The larger size of a single rod-shaped crystal can provide more space for Pt attachment and reduce Pt aggregation between crystals.(4)The deoxidation catalytic activity of Pt/Zeoite T is higher than that of conventional Pt/y-Al2O3 and the stability is good.The performance experiments show that the Pt/Zeoite T performance tests at 10%and 100%deoxygenation temperatures are 45? and 17? lower than Pt/y-Al2O3 respectively.After several tests,the deoxygenation catalytic activity of Pt/Zeoite T has been improved and its performance remained unchanged for 20 hours.(5)T-type molecular sieve as a carrier can improve the Pt dispersion performance,obtain a stronger metal-support connection,better surface acid properties.The CO pulse chemisorption test showed that the Pt dispersion on the T-type molecular sieve surface is higher,and the Pt aggregates on the T-type molecular sieve rod surface are round and closely spaced on the T-type molecular sieve.It also proves that the T-type molecular sieve can improve the Pt dispersion.performance.In the TPR test,the Pt/T zeolite exhibited a Pt-related and higher reduction peak at 560?.In the TPD test,the Pt/T zeolite has more and more weak acids.