Investigating the Impact of Microporosity of Aminosilica Catalysts in Aldol Condensation Reactions for Biomass Upgrading of 5-Hydroxymethylfurfural and Furfuraldehyde to Fuels

Abstract

Upgrading biomass to chemicals and fuels requires development of highly active and selective catalytic materials for important reactions such as the aldol condensation. The aldol condensation is a critical step to convert small molecules such as 5-hydroxymethylfurfural (HMF) and furfuraldehyde (FA) to larger complexes that can be used for fuels or chemicals. Whereas extensive work has examined aminosilica catalytic materials for aldol chemistry, these materials have received limited attention for HMF and FA conversion in spite of the capability of these materials to catalyze reactions in a cooperative manner. In this work, important structure–function relationships are investigated that demonstrate the impact of micropores in these materials. Materials are produced using a typical method (REG) and a method that produces limited to no micropores (NMP). The materials are grafted with aminosilanes and characterized using standard techniques. It is found that materials with limited to no micropores are more active for the aldol reaction and condensation for both FA with acetone and HMF with acetone. Additionally, the materials are tested in recycle experiments that showed the NMP catalyst retained higher activity after four catalytic cycles than the REG catalyst. Overall, the results have important implications for the design of materials for upgrading biomass into chemicals and fuels.

Interrogation of the Plasma-Catalyst Interface via In Situ/Operando Transmission Infrared Spectroscopy

“…To demonstrate this ability, plasma-induced oxidation of an organic/inorganic hybrid aminosilica material (AP-SiO 2 ) was conducted. The AP-SiO 2 (Scheme ) used here is part of a widely studied class of functionalized materials with applications in CO 2 capture and heterogeneous catalysis. ,− This class of materials was chosen for several reasons, including (1) the distinct IR features of the organic functionality and oxidation products (e.g., NO X ), (2) their straightforward synthesis onto silica supports, (3) the high achievable loading of the 3-aminopropyl groups onto the SBA-15, and (4) the existing literature characterizing the behavior and stability of primary amines in oxygen environments. For example, several previous works have reported that primary amines will oxidize at low temperatures in the presence of reactive oxygen derivatives such as ozone (O 3 ). − This process was shown to selectively form nitroalkanes in high yields without oxidizing the carbon framework.…”

Cooperative Catalysis in a Crystalline Framework with Templated Acid–Base Sites

“…Inspired by class I aldolases and other enzymes, bifunctional acid–base catalysts have been explored in multiple platforms, including small-molecule amino acid and peptide catalysts (Figure b), , functionalized organic polymers of both synthetic and biological origin (Figure c), − and amine-grafted silica (Figure d). − Clear cooperative effects have been observed in reactions relevant to biomass conversion, including the aldol condensation of biomass-derived methyl ketones into higher molecular weight biofuel precursors, and the condensation of biomass-derived aldehydes (e.g., furfural, 5-hydroxymethylfurfural) into higher value products. , …”

Synthesis of renewable C–C cyclic oxygenated compounds dedicated for high-density biofuels from biomass-derived cyclopentanone

“…14,15 Therefore, it is highly desirable to extend the carbon chain of biomassderived platform molecules to synthesize bio-fuels with similar properties to conventional gasoline and diesel. 16,17 Many strategies, such as aldol condensation, 18,19 Diels-Alder reaction, 20,21 Knoevenagel condensation 22,23 and hydroxyalkylation/alkylation 24,25 have been developed for elongating the carbon chain of bio-based platform molecules. In particular, aldol condensation is the most frequently used approach for the synthesis of high-quality fuels from bio-based molecules because aldol condensation is facilitated by acidic or basic sites under relatively mild conditions.…”