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

Abstract

Corresponding Author: a.f.lee@aston.ac.uk; +44(0)121 2044036 2 GRAPHICAL ABSTRACT Highlights  Mesoporous SBA-15 facilitates dispersion of low dimensional polyoxometallate clusters  HPW/SBA-15 is highly active for α-pinene isomerization under mild conditions  Selectivity to mono-versus polycyclic products is controlled by polyoxometallate acidity Abstract 3 A family of mesoporous SBA-15 supported H3PW12O40 (HPW) catalysts were synthesized by wetimpregnation and compared with fumed silica analogues for the solventless isomerization of α-pinene under mild conditions. Structural and acidic properties of supported HPW materials were characterized by powder XRD, HRTEM, XPS, TGA, N2 porosimetry, DRIFTS, and ammonia and propylamine chemisorption and TPD. The high area, mesoporous SBA-15 architecture facilitates the formation of highly dispersed (isolated or low dimensional) HPW clusters and concomitant high acid site densities (up to 0.54 mmol.g -1 ) relative to fumed silica wherein large HPW crystallites are formed even at low HPW loadings. α-Pinene exhibits a volcano dependence on HPW loading over the SBA-15 support due to competition between the number and accessibility of acid sites to the non-polar reactant, with the superior acid site accessibility for HPW/SBA-15 conferring a 10-fold rate enhancement with respect to HPW/fumed silica and pure HPW. Monocyclic limonene and terpinolene products are favoured over polycyclic camphene and β-pinene by weaker polyoxometallate analogues over SBA-15.

H5PW10V2O40@VOx/SBA-15-NH2 catalyst for the solventless synthesis of 3-substituted indoles

“…Textural properties of the functionalized mesoporous SBA-15 silicas were characterized by porosimetry and the resulting adsorption-desorption isotherms shown in Figure 1 and corresponding surface areas and pore volumes summarized in Table 1. All materials exhibited type IV isotherms characteristic of a conventional SBA-15 33 with type H3 hysteresis loops (indicative of slit-shaped pores), 44 with dimensions for the as-prepared VO x /SBA-15 similar to those reported for SBA-15, indicating that V incorporation into the sol-gel step had minimal impact on the mesopore structure. The small micropore contribution is often observed in the cooperative self-assembly route employed…”

“…30,31 Heteropolyacids (HPAs) are polyoxometalate inorganic cages which possess tunable (and even superacidic) Brönsted acidity. 32 HPAs can be readily incorporated into mesoporous silicas to promote acid catalyzed transformations such as terpene isomerization, wherein SBA-15 was recently shown to stabilize highly dispersed H 3 PW 12 O 40 clusters improving acid site densities and accessibility, 33 and the Biginelli condensation of substituted aldehydes with ethyl acetoacetate and urea to form 3,4-…”

Current advances in the utility of functionalized SBA mesoporous silica for developing encapsulated nanocatalysts: state of the art

“…Mesoporous silica materials [14][15][16][17][18][19][20] have not only proved their utilities as heterogeneous catalysts [21][22][23][24][25][26][27][28][29] for promoting various organic transformations, [30][31][32][33][34][35][36][37] but also nd interesting applications 38,39 in other research elds such as food chemistry, 40 production of bio-mass derived chemicals, [41][42][43][44][45] petrochemisry, 46-48 sensors, waste treatment, 49,50 optical materials and carriers. One of the most important advances in this eld is developing hybrid systems through functionalization of mesoporous silica materials.…”

Preparation and characterization of new inorganic–organic hybrid catalyst H3PMo12O40/Hyd‐SBA‐15 and its application in the domino multi‐component reaction

“…Among them, directing or post‐synthesis methods are the best strategy which lead to stable attachment and less leaching . The loading of heteropolyacids (HPAs) on the surface of SBA‐15 is known to increase the activity of catalysts . In recent years, many researchers have studied on providing the manners to prevent the leaching of active HPAs from the solid support by modification of silica supports with organic linkers .…”