JOURNAL OF CATALYSIS 172, 281–293 (1997) ARTICLE NO. CA 971838 Oxidative Conversion of Methane to Syngas over Nickel Supported on Commercial Low Surface Area Porous Catalyst Carriers Precoated with Alkaline and Rare Earth Oxides V. R. Choudhary, 1 B. S. Uphade, and A. S. Mamman Chemical Engineering Division, National Chemical L aboratory, Pune 411 008, India Received February 18, 1997; revised July 17, 1997; accepted July 24, 1997 Partial oxidation of methane to CO and H 2 at very small contact times (4.8 ms at STP) over different supported Ni-catalysts at 700 and 800 ◦ C, CH 4 /O 2 ratio in feed of 1.8 and gas space velocity of 5.2 × 10 5 cm 3 · g −1 · h −1 (at STP) has been investigated. The catalysts were prepared by depositing NiO–MgO on different com- mercial low surface area porous catalyst carriers (obtained from M/S Norton Co., USA) consisting of refractory compounds (viz. SiO 2 , Al 2 O 3 , SiC, ZrO 2 , and HfO 2 ) at different concentrations and having different surface properties and also prepared by depositing NiO on the catalyst carriers precoated with different alkaline and rare earth oxides (viz. MgO, CaO, SrO, BaO, Sm 2 O 3 , and Yb 2 O 3 ). The catalysts have been characterized by their TPR by H 2 from 100 to 900 ◦ C, degree of NiO reduction, and H 2 chemisorption after the catalyst reduction at 900 ◦ C. The influence of support (its composition and surface properties), method of NiO and MgO deposition, support precoating agent, loadings of NiO and MgO (as support precoating agent), and calcination temperature on the conversion and selectivity has been studied. The influence of these catalyst parameters on the TPR, degree of NiO reduction, and H 2 chemisorption on the catalyst has also been studied. The catalyst characteristics are strongly influenced by the support (containing Al 2 O 3 and/or SiO 2 at higher concentrations and having higher sur- face area), precoating agent, loading of MgOprecoat on the support, particularly at lowerloadings (below 2 wt%), and also by the cata- lyst calcination temperature above 900 ◦ C. The catalyst prepared by depositing NiO on the commercial supports (except SA-5552 having much highersurface area) precoated with MgO(6 ± 1 wt%) and calcined at 900 ◦ C shows excellent performance in the catalytic process (at 800 ◦ C) with very high methane conversion (>91%), selectivity (>95%) and CO productivity (>13 mol · g −1 · h −1 , which is about two orders of magnitude higherthan that obtained in steam reforming of methane). However, the conversion and selectivity are reduced drastically when the MgOloading is decreased below 2 wt%, the MgO precoat is replaced by that of SrO or BaO or when the catalyst is calcined above 1050 ◦ C. c  1997 Academic Press 1 To whom all the correspondence should be addressed. E-mail: vrc@ ems.ncl.res.in. INTRODUCTION Catalytic oxidative conversion of methane to syngas with H 2 /CO ratio of 2.0, a versatile feedstock for the methanol and Fischer–Tropsch synthesis processes, is a process of great commercial importance. Since the last few years, ex- tensive efforts have been made for converting methane by its partial oxidation with oxygen to syngas, using different nickel, cobalt, and noble metal-containing catalysts (1–15). NiO–MgO (6), NiO–CaO (7), and NiO–Yb 2 O 3 , or other rare earth oxide (8) catalystsshowhigh activityand selectiv- ityat verylowcontact time (1–10ms) and,hence,showvery high productivity in the oxidative conversion of methane to syngas. However, because of their hygroscopic nature, the pellets of these composite mixed metal oxide catalysts have poor mechanical strength (i.e., low crushing strength and poor attrition resistance).The mechanicalstrength ofa catalyst can be improved by supporting it on a porous cata- lyst carrier having high mechanical strength. But when the above three mixed metal oxide catalysts were deposited on a sintered low surface area porous silica–alumina catalyst carrier, the activity of the catalysts was reduced very sig- nificantly (15). This was due to the formation of NiAl 2 O 4 (spinel), which is catalytically inactive and also very diffi- cult to reduce, by a solid–solid reaction between NiO (from catalyst) and Al 2 O 3 (from support). In our recent preliminary studies (14), supported nickel catalysts prepared using commercial sintered low surface- area porous catalyst carriers (containing Al 2 O 3 and/or SiO 2 ) precoated with MgO, CaO, or rare-earth oxide show very much higher activity, selectivity, and productivity in the oxidative conversion of methane to syngas than the catalysts prepared using the catalyst carriers without any precoating. The beneficial effect of the support precoating wasattributed to the elimination or drasticreduction in the formation of catalytically inactive NiAl 2 O 4 (spinel) and/or Ni 2 SiO 4 phasesresultingfrom the chemicalinteractionsbe- tween NiO and Al 2 O 3 and/or SiO 2 from support at high catalyst calcination temperature.It is,therefore,interesting to investigate in detail the effects of various parameters of 281 0021-9517/97 $25.00 Copyright c  1997 by Academic Press All rights of reproduction in any form reserved.