A Supported Nickel Phthalocyanine Complex as a Selective Catalyst for the Production of Styrene

Abstract

A nickel phthalocyanine complex (NiPc) supported on bentonite clay (Bihar, India) was used as a selective catalyst for the dehydrogenation of ethylbenzene to styrene. Maximum activity was observed for the catalyst sample containing 1.0 wt% NiPc/bentonite. A higher loading of complex (> 1.4 wt%) exhibited no activity and resembled polycrystalline NiPc. The texture of the studied catalyst and the mode of surface dispersion of the supported NiPc were investigated through the adsorption of N 2 and O 2 , respectively. The activity of the diluted samples could be attributed to the presence of separate highly dispersed molecules of NiPc on the bentonite surface without having a marked effect on its pore system for most active samples. The selectivity towards styrene was found to depend strongly on the NiPc surface area and the degree of dispersion. The activity was a function of the whole structure including modifications of both acid sites through different interactions and of the pore system through a penetration mechanism.

Catalytic and physical characteristics of axially modified cobalt (III) tetraphenyl porphyrin immobilized on chemically different supports

“…However, following the same lines of discussion in the previous works [23,24], a trial was made to estimate the stoichiometry of H 2 adsorption in the present cases. For this purpose, BET surface area expressed in m 2 g À1 sample ( Table 2) and net adsorption uptakes in mmol H 2 g À1 sample (Table 3) were first used to calculate the surface area available for the adsorption of one H 2 molecule in each case.…”

“…Molecular adsorption of O 2 was reported for a number of metal phthalocyanines (MPc) and tetraphenyl porphyrines (MTPP), taking place on the central metal ion [39,40], which could be accessible for O 2 either from one side or from both sides of the complex, depending on the nature of the support and the mode of complex-support interaction [23,24]. The chemisorption of H 2 at room temperature, used early by us for other cobalt catalyst systems [23,26], was tried in the present study to explore the nature of the adsorption on the investigated axially modified cobalt complex and to assess the dispersion parameters of the complex on the two different supports.…”

“…However, a limited number of works has been concerned with the effect of axial inclusion of different ligands (including H 2 O) in the metal ion of the complex on the different interactions and www.elsevier.com/locate/apcata Applied Catalysis A: General 300 (2006) [14][15][16][17][18][19][20][21][22][23] the catalyst activities [16,[18][19][20][21]. Such effects were a key factor for the development of some novel catalysts (e.g., [22][23][24][25]). …”

Catalytic Behavior of Cobalt (II) Phthalocyanine Immobilized on Bentonite Clay in Bulk Polymerization of Methyl Methacrylate

“…The results may also suggest that the interaction of CoPc molecules with a bentonite surface involves most likely the same clay acid sites that could be activated by O 2 (i.e., OH groups). This can be understood in view of the inclined stacking model of CoPc molecules on the clay surface, where the interaction may take place between nitrogen atoms of the macro-ring system and the OH's of the support, i.e., via asymmetric Brönsted interactions [8,[19][20][21].…”

“…Among the studied complexes, metal phthalocyanines (resembling the natural porphyrins structurally) have become known to catalyze many reactions both in liquid and gas phases [e.g., [5][6][7][8][9][10]. Immobilization of such complexes on a suitable solid matrix was considered as one of the promising approaches for their stabilization against dimerization and other destructive processes [1,[10][11][12].…”