Activation of Clayzic and its effect on the relative rates of benzylation of aromatic substrates

Abstract

The effects of the activation of K 1 0 montmorillonite supported zinc chloride ('Clayzic') by different methods o n the reactivity of the catalyst in the Friedel-Crafts benzylation of benzene and halobenzenes have been investigated. There is an optimum temperature for thermal activation in air at which point a rate enhancement, compared t o unactivated Clayzic, in the benzylation of benzene of greater than 30 has been achieved. The rate limiting factor for these reactions is believed to be the ability of the aromatic substrate to enter the polar mesopores containing the active zinc ions in Clayzic, causing unexpected and activation-dependent rate trends to be observed. Activation of Clayzic is believed to reduce the polar nature of the pores, so aiding partitioning of the substrate into the catalyst.

From Conventional Lewis Acids to Heterogeneous Montmorillonite K10: Eco‐Friendly Plant‐Based Catalysts Used as Green Lewis Acids

“…In general, clayzic presents a slight residual lamellar structure, contains more or less equal amounts of both Brønsted and Lewis acid sites, and has a pore distribution centered around 5–6 nm pore radius; these features contribute to its higher catalytic activity and activation temperature . Moreover, many authors supported these unexpected results through the preferential adsorption of certain molecules onto the catalytic surface of the heterogeneous catalyst, which occupied the active catalytic sites.…”

Kinetic studies for processes of liquid-phase alkylation of aromatics over solid acid catalysts

“…In 2 O 3 /Hb 7 > FeCl 3 /K10, InCl 3 /K10 32 > GaCl 3 /K10 32 > TlO x / ZrO 2 30 > H 0.5 Cs 2.5 PW 12 O 40 1 > Ga 2 O 3 /HZSM-5 31 > Clayzic 24 with k 1 -values differing by one order of magnitude from the first to the last member of the series. Note that, apart from one case, the mentioned catalysts are supported metal chlorides or oxides.…”

“…Table 2 offers, for the same catalyst (Clayzic), the opportunity to compare an unactivated sample with a thermally activated one, under the same conditions: 23,24 activation increased the rate by more than one order of magnitude. The kinetic effect of alkyl substituents on benzene is less clear: with Clayzic as the catalyst, toluene and ethylbenzene reacted faster than benzene, 24,25 while with InCl 3 /K10 as catalyst, toluene and mesitylene were found to be slightly less reactive than benzene. 32 One group of studies (Table 1) employed the kinetic model corresponding to eqn.…”

Hydration of α‐Pinene over SO42−/Zr‐MCM‐41 in Supercritical Carbon Dioxide

“…Method of introducing SO 4 2− and calcination temperature greatly affected the catalytic activity of SO 4 2− /Zr‐MCM‐41. Calcination not only increases the stability and mechanical intensity of catalyst, but also enhances SO 4 2− correlation with Zr‐MCM‐41 . Figure – shows the dependence of catalytic activity on calcination temperature.…”