The application of modified mesoporous silicas in liquid phase catalysis

This review focuses on recent developments in the preparation, properties and catalytic applications of chemically modified mesoporous silicas. Over the last few years, this group of materials has been the subject of intense activity in the materials community, and many applications have been found for these fascinating materials. This non-exhaustive review aims to highlight the key features of the materials, which are relevant and important to catalysis, and illustrates their utility with a series of recent examples.

Versatile mesoporous carbonaceous materials for acid catalysis

Starbon mesoporous materials were synthesized after pyrolysis of expanded starch and subsequently functionalised with sulfonated groups, providing highly active and reusable materials in various acid catalysed reactions.

Clean, reusable and low cost heterogeneous catalyst for amide synthesis

We have developed a heterogeneous silica catalyst that can effectively catalyse amide synthesis from acid and amine, without production of toxic by-products and with the advantage of being readily available, low cost, environmentally benign and reusable.

Microwave assisted step-by-step process for the production of fucoidan, alginate sodium, sugars and biochar from Ascophyllum nodosum through a biorefinery concept

The biorefinery is an important concept for the development of alternative routes to a range of interesting and important materials from renewable resources. It ensures that the resources are used fully and that all parts of them are valorized. This paper develops this concept, using brown macroalgae Ascophyllum nodosum as an example, by assistance of microwave technology. A step-by-step process was designed to obtain fucoidan, alginates, sugars and biochar (alga residue) consecutively. The yields of fucoidan, alginates, sugars and biochar were 14.09%, 18.24%, 10.87% and 21.44%, respectively. To make an evaluation of the biorefinery process, seaweed sample was also treated for fucoidan extraction only, alginate extraction only and hydrothermal treatment for sugars and biochar only. The chemical composition and properties of each product were also analyzed. The results indicated that A. nodosum could be potentially used as feedstock for a biorefinery process to produce valuable chemicals and fuels.

Towards a Bio-Based Industry: Benign Catalytic Esterifications of Succinic Acid in the Presence of Water

The biorefinery of the future will need to integrate bioconversion and appropriate low environmental impact chemical technologies (Green Chemistry) so as to produce a wide range of products from biomass in an economically effective and environmentally acceptable manner. The challenge for chemists is to develop chemistry that works with fermentation-derived dilute, aqueous mixtures of oxygenated chemicals (platform molecules) rather than the petroleum-derived non-aqueous, non-oxygenated feedstocks we have been working with for 50+ years and to avoid energy intensive and wasteful concentration and purification steps. Here we show that a new family of tuneable mesoporous carbonaceous catalysts derived from starch can be used to accomplish efficient chemistry in aqueous solution. Our new aqueous catalytic chemistry relies on the ability to adjust the surface properties including the hydrophobicity-hydrophilicity balance of mesoporous Starbons by carbonisation at different temperatures (250-750 degrees C). Simple treatment of these materials with sulfuric acid then provides a series of porous solid acids that can function under a range of conditions including dilute aqueous solution. The reactions of succinic acid (platform molecule) in aqueous alcohol demonstrate the outstanding activities of these new catalysts.

The combined role of catalysis and solvent effects on the Biginelli reaction: improving efficiency and sustainability

The traditional Biginelli reaction is a three-component condensation between urea, benzaldehyde and an acetoacetate ester to give a dihydropyrimidinone. An investigation into catalytic and solvent effects has returned the conclusion that the diketo-enol tautomerisation equilibrium of the dicarbonyl reactant dictates the yield of the reaction. Whereas the solvent is responsible for the tautomerisation equilibrium position, the catalyst only serves to eliminate kinetic control from the reaction. Generally, to preserve reaction efficiency and improve sustainability, bio-derivable p-cymene was found to be a useful solvent. The metal-enolate intermediate that results from the application of a Lewis acidic catalyst often cited as promoting the reaction appears to hinder the reaction. In this instance, a Brønsted acidic solvent can be used to return greater reactivity to the dicarbonyl reagent.