预氧化HP40合金表面催化结焦的研究

A RESEARCH OF CATALYTIC COKE FORMATION ON THE PRE-OXIDATION SURFACE OF HP40 ALLOY

为研究不同的表面状态对HP40合金表面催化结焦的影响,分别以水蒸气、空气为预氧化气氛,对HP40合金试样进行了不同温度的氧化处理以及氧化后结焦实验。利用XRD,SEM,TEM对氧化层和焦炭的形貌进行了表征,采用元素分析仪和拉曼(Raman)光谱仪对焦炭的碳氢比和结构进行了分析。结果表明:合金试样经水蒸气氧化后,表面形成了针状、富铁氧化物;经空气氧化后,表面形成颗粒状、致密的富铬氧化物,随氧化温度升高部分试样的氧化层出现了剥落,剥落后的疏松、多孔表面对催化结焦有强烈的促进作用。焦炭主要为典型的催化丝状焦,焦丝的直径约80 nm,还含有少量的热裂解焦;焦炭缩合度较高,由有序状炭和无序状炭共同构成,且石墨化程度低。不同的预氧化气氛对合金表面氧化状态影响较大,但是对后续结焦过程,焦炭的形貌和结构无明显影响。

To study the effect of various HP40 alloy surface status on the catalytic coke formation,HP40 alloy samples were oxidized by steam and air respectively at different temperatures,followed by coking tests.The oxidized surfaces of the samples and the morphology of coke were characterized by SEM,EDS and XRD,furthermore,the C/H ratio and the structure of coke were analyzed by elemental analysis and Raman spectroscopy.Test results showed that when alloy sample was oxidized under steam,a layer of needle type Fe rich oxide was formed on the surface;oxidation under air,Cr rich oxide particles were well dispersed on the alloy surface,with the increase of oxidation temperature,spalling of oxide layer from the alloy surface might happen,in this case,the exposed porous surface could be an ideal area for forming catalytic coke.The coke formed was mainly catalytic filamentous coke with a diameter of about 80 nm,minor thermal cracking coke might exist too.The coke having a very condensed structure consisted of both ordered and amorphous types,and with low graphitization degree.However,the atmosphere of pre-oxidation had more influence on the oxidized surface of alloy,yet just little on the followed coking process,coke morphology and structure.