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Monolithic nickel(II)-based aerogels using an organic epoxide: the importance of the counterion

“…Depending on their preparation method, they can be made with varied stoichiometries, which can affect their chemical properties significantly [2]. Nickel(II) oxide is a semiconductor and it is also used in supported catalysts for several chemical transformations including the reformation of methane with CO 2 [5], and the oxidation of H 2 S to sulfur [6].…”

“…The primary interest in sol-gel-derived material with this structure and composition is catalytic transformations of organic molecules [12]. This type of material exhibits good activity towards oxidations of organic compounds while resisting the formation of coke on the catalyst under certain conditions [5]. There have been very limited reports on the preparation of pure nickel oxide or nickel hydroxide gels and or colloids [13].…”

Characterization of nickel–alumina aerogels with high thermal stability

“…The samples of nickel-alumina aerogels (Ni loading, 0, 5 and 10 wt%) were prepared from nickel nitrate and aluminum isopropoxide according to the procedure as previously reported [9,10]. After the supercritical drying, the aerogels were calcined in air at 500°C for 3 h followed by reducing with hydrogen (30 mL min À1 ) at 800°C for 3 h. For comparison, the nickel-alumina catalysts with 10 wt% Ni were prepared by a conventional impregnation technique using pure alumina aerogel (our own make, 287 m 2 g À1 ) and commercial alumina (GL Science, 112 m 2 g À1 ) as the catalyst supports [10]; hereafter the former is denoted as Imp(aero) whereas the latter as Imp(com).…”

“…After the supercritical drying, the aerogels were calcined in air at 500°C for 3 h followed by reducing with hydrogen (30 mL min À1 ) at 800°C for 3 h. For comparison, the nickel-alumina catalysts with 10 wt% Ni were prepared by a conventional impregnation technique using pure alumina aerogel (our own make, 287 m 2 g À1 ) and commercial alumina (GL Science, 112 m 2 g À1 ) as the catalyst supports [10]; hereafter the former is denoted as Imp(aero) whereas the latter as Imp(com). As references for characterization, NiAl 2 O 4 was prepared from Ni (NO 3 ) 2 Á6H 2 O (Wako Pure Chemical) and Al(NO 3 ) 3 Á9H 2 O (Wako Pure Chemical) according to the manner in the literature [11], whereas NiO (Wako Pure Chemical) and Ni (Wako Pure Chemical) were used as supplied.…”

“…The authors have succeeded in preparing homogeneous and monolithic NiO-Al 2 O 3 aerogels from nickel nitrate and aluminum iso-propoxide by the one-step addition of the nickel precursor to boehmite sol followed by gelation and subsequent supercritical drying [9]. The aerogel catalysts showed high CO 2 reforming activities compared to the conventional impregnation catalysts, whereas the carbon formation was successfully suppressed on the aerogels in contrast to the impregnation catalysts despite the absence of any additives such as sulfur and alkali [10]. The present paper describes the characterization of the NiO-Al 2 O 3 aerogels to reveal the factors for the stable reforming without coking.…”