A study of various characteristics of supported NiO/bentonite catalyst used in the polymerization of methyl methacrylate

Adsorption Science & Technology

Zahran

Yehia

2002

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.

Section: Xrd Analysissupporting

confidence: 86%

Section: Degree Of Dispersion and Specific Surface Area Of Supported mentioning

confidence: 99%

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

Adsorption Science & Technology

Zahran

Yehia

2002

“…[17] Supported transition metal complexes on silicate structures, such as bentonite, have an increased activity with a high selectivity, especially in olefin polymerization processes. [18] In the present investigation, it was attempted to correlate the catalytic activity of supported nickel(II) and copper(II) phthalocyanine complexes/bentonite in the bulk polymerization of MMA with the microstructural characteristics being investigated via scanning electron microscopy (SEM).…”

Section: Introductionmentioning

confidence: 99%

Catalytic Polymerization of Methyl Methacrylate in Different Media Using Supported Metal Phthalocyanines, 1. Bulk Polymerization in Relation to the Microcrystalline Structure of Supported Metal Phthalocyanines

Sadek¹,

Mekewi

Yehia

et al. 2001

Macromol. Chem. Phys.

Different catalyst samples of nickel(II) and copper(II) phthalocyanines supported over bentonite clay (Indian type) were prepared with complex loadings ranging between 0.2 and 2.2 wt.‐%. Catalyst activities were investigated in the bulk polymerization of methyl methacrylate (MMA) at 80°C in the absence and in the presence of sodium bisulfite as a cocatalyst. In all cases, the catalyst efficiency was evaluated in terms of conversion yield (%), polydispersity index (M̄w/M̄n) was determined via GPC analysis in toluene. The stereotacticity was determined from 1H NMR spectra. Optimum polymerization conditions were determined for both catalyst systems. Samples with metal phthalocyanines loadings of 1.8% were the most active ones. The polymers produced have controlled molecular weights, which are nearly proportional to conversion, show narrow molecular weight distributions and syndiotactic‐rich steric structures. Nickel phthalocyanine seemed to have more stereoregulating effect while copper phthalocyanine had a more enhancing effect for the living polymerization process. The microstructure of solid catalysts was investigated by means of scanning electron microscopy and were correlated with activity data.

“…For example, in our previous investigation [14], supported NiO=bentonite clay was found to catalyze the polymerization process anionically, as ions enhanced by nitrite remained in narrower pores of the catalyst system, through decomposition of nickel precursor. However, in the presence of supported Cu and Ni phthalocyanines (MPc) it was suggested that a MPc=bentonite=HSO À 3 initiating system encourages both radical and ionic mechanisms to operate together [17,19].…”

Section: Introductionmentioning

confidence: 96%

“…On the other hand, the polymerization of methyl methacrylate (MMA) has been studied in the presence of some metal oxides and complexes [e.g., [14][15][16][17][18][19][20]. For example, in our previous investigation [14], supported NiO=bentonite clay was found to catalyze the polymerization process anionically, as ions enhanced by nitrite remained in narrower pores of the catalyst system, through decomposition of nickel precursor.…”

Section: Introductionmentioning

confidence: 98%

Various Characteristics of Nanosized V₂O₅/TiO₂and MoO₃–Modified V₂O₅/TiO₂Catalytic Systems Used in Redox-Initiated Polymerization of Methyl Methacrylate

Sadek

International Journal of Polymeric Materials

et al. 2011

Various samples of nanosized V 2 O 5 (2-20 wt%)=TiO 2 catalytic systems (of particle sizes ranged between 5 and 50 nm were characterized. The effect of addition of MoO 3 (3-9 wt%), in different sequences, was followed up in view of competing interactions with titania surface. Characterization was performed through XRD, FTIR, BET, and TEM techniques. Catalytic activity of prepared samples was tested in redox-initiated polymerization of methyl methacrylate, in presence of NaHSO 3 cocatalyst. The proposed polymerization mechanism indicated participation of HSO Á 3 radicals, primarily generated on a TiO 2 surface, with V 5þ =V 4þ and=or Mo 6þ =Mo 5þ redox pairs to form active radical species with the monomer. In all cases, extremely high yields of reasonably high molecular weight polymers, of syndiotactic-structure, were functions of catalyst nanosized nature, rapid redox-initiation steps, and mode of MoO 3 addition.Keywords MoO 3 -modified V 2 O 5 =TiO 2 , redox-initiated polymerization, methyl methacrylate, V 2 O 5 =TiO 2