Isomerization and Dimerization of Pinene using Al‐Incorporated MCM‐41 Mesoporous Materials

Abstract

A series of Al‐incorporated mobile crystalline materials (Al‐MCM‐41) were prepared by hydrothermal synthesis and characterized by XRD, N2 adsorption (isotherms), inductively coupled plasma (ICP) analysis, 27Al magic angle spinning (MAS) NMR spectroscopy, and in situ pyridine adsorption (IR analysis). All samples exhibit an ordered structure with the majority of Al species in framework positions, except those with an SiO2/Al2O3 ratio ≤10. The concentration of acid sites is closely related to the Al content in the unit cell. In the presence of Al‐MCM‐41, both α‐ and β‐pinenes are quickly transformed into isomerized products, which then couple to form homo‐ and heterodimers. Lewis acid sites are active in triggering both the isomerization and dimerization reactions, but weak Brønsted acid sites seem inactive for the dimerization. Al‐MCM‐41 has a greater activity than many other microporous and layered materials, and can be easily regenerated. The activity correlates well with the concentration of acid sites, and the sample with an SiO2/Al2O3 ratio of 20 shows the highest activity.

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.…”

Biosynthesis of hydrocarbons and volatile organic compounds by fungi: bioengineering potential

“…For example, for the production of the monoterpene dimer jet fuel described above, three enzymes were tested from among the 11 that were known to produce β-pinene, all of which came from plants (Degenhardt et al 2009; Sarria et al 2014). Several other dimerization strategies have been reported that have utilized both α and β pinene (Chen and Forbus Jr 1990; Booth and Phillips Jr 1998; Chapaton et al 2004; Zou et al 2012). Filamentous fungi have been observed to produce both α and β pinene, though α is considerably more common (Table 1).…”

Highly-selective solvent-free catalytic isomerization of α-pinene to camphene over reusable titanate nanotubes

“…In recent years, the use of heterogeneous catalyst is a shi toward green and environmental-friendly technologies. Various solid acid catalysts, such as zeolites, 3,4 iron-modied zeolites, 5 sulfated zirconia, 6 modied layered aluminosilicates, 7 Al-incorporated MCM-41, 8 MSU-S mesoporous materials, 9 W 2 O 3 /Al 2 O 3 , 10 phosphotungstic heteropoly acids, 11 Ti-SBA-15 (ref. 12 and 13), and ionic liquids 12 have been employed for the isomerization of a-pinene.…”