ColloidsandSurfacesA:Physicochem.Eng.Aspects444 (2014) 104–113

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ColloidsandSurfacesA:Physicochemicaland

EngineeringAspects

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a

MethaneadsorptioncharacteristicsoncoalsurfaceabovecriticaltemperaturethroughDubinin–AstakhovmodelandLangmuirmodel

ShixiongHaoa,b,WeiChua, ,QianJianga,XiaopengYua,b

ab

DepartmentofChemicalEngineering,SichuanUniversity,Chengdu610065,China

DepartmentofChemicalEngineering,SichuanUniversityofScience&Engineering,Zigong643000,China

highlights

graphical

abstract

Methodsforestimatingpseudo-saturationvaporpressurewereinvestigated.

Aprocedureofdeterminingtheparameter,k,inps=pc(T/Tc)kwasproposed.

Thein uenceofthecharacteristiccurveformonthepredictionwasinvestigated.

Anewformofthecharacteristiccurvewasproposed.

article

info

abstract

Articlehistory:

Received16October2013Receivedinrevisedform11December2013

Accepted24December2013Available online 3 January 2014

Keywords:Coal

Methane

D–Aequation

Pseudo-saturationvaporpressureCharacteristiccurve

Toacquiretherequiredinformationoftheadsorptionsystemundersupercriticalconditions,fourdifferentrankcoalswereselectedasstudiedsamples.ThetexturesofthecoalswerecharacterizedthroughN2adsorptionat77K.Theirsurfacemorphologieswereanalyzedbyscanningelectronmicroscopy(SEM).Thehighpressureadsorptiondataofmethaneonthecoalswereobtainedatsupercriticaltemperatures.ThedatawereanalyzedusingtheDubinin–Astakhov(D–A)andLangmuirmodels.Themethodsforestimatingpseudo-saturationvaporpressurewereinvestigated.Andthein uenceofthecharacteristiccurveformontheD–Aequationpredictionwasinvestigated.TheresultsshowthattheconstantsderivedbymatchingtheexperimentaldatatotheLangmuirmodelmightlackphysicalsigni cance,thoughtheLangmuirmodelwasofthecorrectqualitativeformtorepresenttheisothermsofmethaneoncoals.Themethodforestimatingpseudo-saturationvaporpressuresproposedbySchwarzfailedtorendertheexperimentaldatatofallontoonecharacteristiccurve.Amodi edprocedureofdeterminingthevalueofparameterkinSchwarz’sequation,i.e.ps=pc(T/Tc)kwasproposed.Itwasfoundthatthemodi edapproachgavethemostsuitabletemperature-independentcharacteristiccurveswithdeterminationcoef cientR2>0.9943.Theformofthecharacteristiccurvecouldin uencetheD–ingcubicpolynomialascharacteristiccurveformwouldresultinanabnormalpredictioni.e.theadsorptionamountwouldincreasewiththepressuredroppingwhenthepressureislessthanapproximately0.9MPaforXingq-1–5#andXujd-1#,0.8MPaforQingh-2–3#,and0.5MPaforLeiy-1#.AnewformofthecharacteristiccurvededucedfromD–Aequationwasproposed.ThepredictionuncertaintyofD–Aequationbyusingthisnewcharacteristiccurveformislessthan2.43%.

© 2013 Elsevier B.V. All rights reserved.

1.Introduction

Correspondingauthor.Tel.:+862885403836;fax:+862885461108.E-mailaddress:chuwei1965@(W.Chu).

Adsorptionphenomenaareincreasinglyutilizedtoperformdesiredbulkseparationorpuri cationpurposes[1–5].Coalisporousmaterial.Coalbedmethane(CBM)isunconventionalnatu-ralgasassociatedwithcoal.ThekeycomponentofCBMisCH4(CH4

0927-7757/$–seefrontmatter© 2013 Elsevier B.V. All rights reserved./10.1016/j.colsurfa.2013.12.047