catalytic performance of modified kaolin clay with big pore for the hydrodesulfurization of diesel

Preparation and catalytic performance of modified kaolin clay with big pore for the hydrodesulfurization of diesel

Guofu Wan ÆAijun Duan ÆZhen Zhao ÆWeiqiang Huang ÆTao Dou

Published online:30May 2007

ÓSpringer Science+Business Media,LLC 2007

Abstract A kind of metakaolin materials with big pores was prepared from natural kaolin clays.The prepared metakaolin was introduced into alumina as composite support for hydrotreating application.A series of nickel–tungsten catalysts (NiO 2.9wt%,WO 327.2wt%)sup-ported on alumina-metakaolin,alumina-titania and bare alumina also were prepared.Electron microprobe analysis including SEM and TEM,BET and temperature pro-grammed desorption of NH 3were used for the samples characterization.Their hydrodesulfurization (HDS)activity for diesel were evaluated and compared.The results showed that NiW/alumina-metakaolin had excellent HDS activity and alumina-metakaolin support could be a good candidate support for hydrotreating catalysts.Keywords Kaolin clays ÁSupport material ÁHydrodesufurization ÁNickel–tungsten ÁDiesel

1Introduction

Environmental concern has led to increasingly stringent regulations on sulfur,nitrogen and aromatics content in fuels [1].Specifically,the removal of alkylated dibenzo-thiophenes,the most refractory sulfur compounds in gas oil [2,3]needs to be addressed to arrive at low-sulfur trans-portation fuels.The demand for a better environment has triggered studies on the synthesis of more efficient catalysts for removing sulfur from petroleum fuels.And most

researches are concerning the development of new supports for hydrotreatment catalysts.Traditional hydrotreating (HDT)catalysts are composed of a molybdenum sulfide (or tungsten sulfide)phase promoted by cobalt or nickel and usually supported on alumina [4,5].The origin of the al-most exclusive use of alumina as support has to be ascribed to its outstanding textual and mechanical properties and its relatively low cost.However,in many cases,the catalytic activities of alumina-supported catalysts are lower than those of catalysts supported on other supports such as TiO 2-anatase and zirconia [6,7].Nevertheless,the specific surface area of such supports remained 100m 2/g (after calcinations at 773K)restricting the use of such supports.Numerous efforts have been devoted to the preparation of such supports with high specific surface area and meso-porous or large macroporous structures for HDT applica-tions.In order to overcome the small specific surface of TiO 2,the combination of composite oxides are developed.For instance,TiO 2is combined with alumina,zirconia or SiO 2,TiO 2–Al 2O 3composite being the most studied [8,9].These combination oxides often imply the genesis of new acid-base properties which are appropriate for hydrotreat-ing applications.These composite supports are found to be very efficient catalysts for the conversion of dibenzothi-ophene (DBT)and its alkyl-derivatives [8–10].

Natural clays have also attracted attention since these supports provide thermal and mechanical resistance,and relatively acidic properties.Kaolin [11],Co-smectite cat-alysts [12],montmorillonite [13,14],and modified raw materials were applied to the treatment of residual oils [15].Using the same approach,P.Salerno et al.[16]demonstrated the interest of Al-pillared montmorillonite-based NiMo catalysts for HDS of gas oil.In our present work,kaolin clays were also introduced into alumina as composite supports for NiW catalyst of hydrodesufuriza-

G.Wan ÁA.Duan ÁZ.Zhao (&)ÁW.Huang ÁT.Dou

State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing 102249,P.R.China e-mail:zhenzhao@

J Porous Mater (2008)15:231–236DOI 10.1007/s10934-007-9127-1