Alpha-pinene isomerization on acid-treated clays

Abstract

Liquid phase isomerization of ␣-pinene was studied over a number of differently pre-treated montmorillonite clays. The effects of the acid pre-treatment parameters (acid-to-clay ratio (A/C), water-to-acid ratio (W/A), temperature and pre-treatment time) on the product distribution were investigated. It was observed that the pre-treatment with acid improved the catalytic activity of that catalyst which was activated at 200 • C for 4 h at A/C ratios between 0.2 and 0.4. Alpha-pinene consumption was very small over the catalysts prepared with an A/C ratio of 0.8. Characterization studies that were done by nitrogen and water vapor adsorption experiments and by IR measurements showed that catalysts with high differential pore volumes for pores around 2 nm and homogenous mesopore distributions and with low dealumination degrees were good catalysts for the production of camphene. Catalysts having heterogeneous mesoporosity were found to be the preferable ones for limonene production.

Liquid phase transformation of α-pinene over Beta zeolites containing aluminium or boron, titanium and vanadium as lattice ions

“…The obtained samples were washed with deionized water, dehydrated at 523 K for 2 h and then calcined up to 823 K (with a temperature ramp of 1 K min À1 ) under a dry air flow of 80 ml/min. Further on, an exchange with a 0.1 M NH 4 Cl solution (100 ml) at 363 K for 1 g sample was carried out to prepare the hydrogen forms. The synthesized Al-Beta(55) sample was first oven dried and calcined at 723 K and then subjected to the ion exchange procedure.…”

“…Many heterogeneous catalysts such as titanium dioxide, clays, halloysite, natural and synthetic zeolites, activated carbon, silica-supported rare earth oxides and sulphated zirconia are examined for a-pinene isomerization [1][2][3]. In our previous studies, liquid phase isomerization of a-pinene has been investigated over clinoptilolite based natural zeolites, which is the most abundant deposits occurred at Western Anatolia region of Turkey and over natural clays (nonswelling montmorillonite) [1,4,5]. It is established that the main reaction products are camphene and limonene.…”

Acidic sites in beta zeolites in dependence of the preparation methods

“…Nitrogen physisorption measurements (for micro-and mesopores analysis) were performed at 77 K using a static volumetric apparatus (Coulte Omnisorb 100cx) up to p/p 0 ∼ 0.95 as described in [12]. The specific total surface areas were calculated using Langmuir equation.…”

Support enhanced α-pinene isomerization over HPW/SBA-15

“…Despite the mild reaction conditions of this industrial process, its low conversion and selectivity requires significant advances to improve both atom and energy efficiency. A wide range of alternative catalysts have been explored including alloys, [14] clays, [18,19] zeolites, [20,21] sulphated zirconia, [16,22], Al-incorporated MCM-41 [23] and heteropolyacids (HPAs); [24][25][26][27][28] with strong solid acids conferring improved conversion and selectivity. [21,22,24,27,29] HPAs are polyoxometalate inorganic cages which possess high Brönsted acid strengths (approaching the superacidic region) and tunable redox activity depending on the particular constituent elements.…”