Octyl Co‐grafted PrSO₃H/SBA‐15: Tunable Hydrophobic Solid Acid Catalysts for Acetic Acid Esterification

Abstract

Propylsulfonic acid (PrSO3H) derivatised solid acid catalysts have been prepared by post‐modification of mesoporous SBA‐15 silica with mercaptopropyltrimethoxysilane (MPTMS), and the impact of co‐derivatisation with octyltrimethoxysilane (OTMS) groups to impart hydrophobicity to the catalyst was investigated. Turnover frequencies (TOFs) for acetic acid esterification with methanol increase with PrSO3H surface coverage across both families, suggesting a cooperative effect between adjacent acid sites at high acid site densities. Esterification activity is further promoted upon co‐functionalisation with hydrophobic octyl chains, with inverse gas chromatography (IGC) measurements indicating that the increased activity correlates with decreased surface polarity or increased hydrophobicity.

Impact of Hydrophobic Organohybrid Silicas on the Stability of Ni2P Catalyst Phase in the Hydrodeoxygenation of Biophenols

“…To characterize the interactions of the prepared catalysts with the polar constituents of pyrolysis oils, the free energy of methanol adsorption ( and surface energies were determined by using inverse gas chromatography (IGC) for the Ni 2 P/SiO 2 ‐TEOS, Ni 2 P/SiO 2 ‐20BTSB, and Ni 2 P/SiO 2 ‐50MTES catalysts (Table ). IGC is a powerful technique to determine the surface properties associated with catalytic materials (details given in the Experimental Section) and it gives information on physical (dispersive) and chemical (specific/polar) interactions through the adsorption of alkanes and polar probe molecules, respectively . Dispersive surface energy provides insight into the surface hydrophobicity: the higher the value of dispersive surface energy, higher the hydrophobic character .…”

“…With higher dispersive surface energy, Ni 2 P/SiO 2 ‐20BTSB possesses the most hydrophobic character among the three catalysts. The literature validates dispersive surface energy as a measure of hydrophobicity of materials, with carbon samples with more hydrophobic character possessing high dispersive surface energy >150 mJ m −2 , whereas hydrophilic silica and cellulose exhibit lower values of approximately 50 mJ m −2 and 40 mJ m −2 , respectively. Hence, Ni 2 P/SiO 2 ‐20BTSB, which exhibits dispersive surface energy of 80 mJ m −2 , should be more hydrophobic than Ni 2 P/SiO 2 ‐TEOS (47 mJ m −2 ) and Ni 2 P/SiO 2 ‐50MTES (50 mJ m −2 ).…”

“…showed that HY zeolites modified with hydrophobic organosilanes showed improved stability in hot water ( T >150 °C) for cresol alkylation and alcohol dehydration and can be used for refining of biomass‐derived pyrolysis oil . Moreover, the water tolerance of propyl sulfonic acid SBA‐15 catalysts, employed in the esterification of pyrolysis bio‐oil as a pretreatment step, was improved by co‐functionalization with octyl groups …”

“…[24] Moreover,t he water tolerance of propyls ulfonica cid SBA-15c atalysts, employed in the esterification of pyrolysis bio-oil as ap retreatment step, was improved by co-functionalization with octyl groups. [25] In this contribution, we present as ystematic study of the impact of support polarity on the activity and stability of the Ni 2 Pc atalystp hase in the HDO of model compounds for pyrolysis oils. Ni 2 Ps upported on silica was chosen as am odel system,a si ti sk nown to show good HDO activity,y et owing to the hydrophilic character of silica, these catalysts show strong deactivation by oxidation processes involving water.…”

Water Tolerant and Reusable Sulfonated Hyperbranched Poly(aryleneoxindole) Acid Catalyst for Solvent‐Free Esterification

“…Hydrophobic octyl chains were introduced on PrSO3H/SBA‐15 to improve the water tolerance and evaluated in the stoichiometric acetic acid and methanol esterification. Under these conditions 40% of ester was formed after 24 h . The group of Fraile investigated the water tolerance of sulfonated hydrothermal carbon (SHTC) in the esterification of methanol and palmitic acid (methanol:palmitic acid molar ratio of 10:1, solvent free), increasing the amounts of water added up to water:palmitic acid molar ratio of 1:1.…”