A new type of catalyst has been designed to adjust the basicity and level of molecular confinement of KNaX faujasites by controlled incorporation of Mg through ion exchange and precipitation of extraframework MgO clusters at varying loadings. The catalytic performance of these catalysts was compared in the conversion of C2 and C4 aldehydes to value-added products. The product distribution depends on both the level of acetaldehyde conversion and the fraction of magnesium as extraframework species. These species form rather uniform and highly dispersed nanostructures that resemble nanopetals. Specifically, the sample containing Mg only in the form of exchangeable Mg(2+) ions has much lower activity than those in which a significant fraction of Mg exists as extraframework MgO. Both the (C6+C8)/C4 and C8/C6 ratios increase with additional extraframework Mg at high acetaldehyde conversion levels. These differences in product distribution can be attributed to 1) higher basicity density on the samples with extraframework species, and 2) enhanced confinement inside the zeolite cages in the presence of these species. Additionally, the formation of linear or aromatic C8 aldehyde compounds depends on the position on the crotonaldehyde molecule from which abstraction of a proton occurs. In addition, catalysts with different confinement effects result in different C8 products.

Fast pyrolysis of biomass to produce a bio-oil followed by catalytic upgrading is a widely studied approach for the potential production of fuels from biomass. Because of the complexity of the bio-oil, most upgrading strategies focus on removing oxygen from the entire mixture to produce fuels. Here we report a novel method for the production of the specialty chemical, gluconic acid, from the pyrolysis of biomass. Through a combination of sequential condensation of pyrolysis vapors and water extraction, a solution rich in levoglucosan is obtained that accounts for over 30% of the carbon in the bio-oil produced from red oak. A simple filtration step yields a stream of high-purity levoglucosan. This stream of levoglucosan is then hydrolyzed and partially oxidized to yield gluconic acid with high purity and selectivity. This combination of cost-effective pyrolysis coupled with simple separation and upgrading could enable a variety of new product markets for chemicals from biomass.

Controlling reaction selectivity represents a fundamental challenge in heterogeneous catalysis. Here, we compare the selectivity in aqueous-phase thermal catalytic and electrocatalytic conversion of furfural and report the fundamental difference in elementary steps in the two reaction systems. Specifically, we observed that furfural alcohol and 2-methylfuran, which is the hydrogenation and hydrogenolysis product of furfural, respectively, are both primary products in electrocatalysis over a Cu electrode, with 2-methylfuran dominating the product distribution under electrode potentials between − 0.55 and − 0.75 V versus RHE. By contrast, in an aqueous-phase thermal reaction using a SiO 2 -supported Cu catalyst, furfural alcohol and its derivatives from the ring-rearrangement reaction are the major products, without production of 2-methylfuran, at the reaction temperature between 140 and 200 °C. We propose that the distinct selectivity trends for oxygenate conversion via thermal and electrocatalytic reduction result from the distinct sequence of proton attack to the aldehyde group and may be generally true for reduction reactions of other biomass-derived oxygenates.

We report a reaction platform for the synthesis of three different high-value specialty chemical building blocks starting from bio-ethanol, which might have an important impact in the implementation of biorefineries. First, oxidative dehydrogenation of ethanol to acetaldehyde generates an aldehyde-containing stream active for the production of C 4 aldehydes via base-catalyzed aldol-condensation. Then, the resulting C 4 adduct is selectively converted into crotonic acid via catalytic aerobic oxidation (62 % yield). Using a sequential epoxidation and hydrogenation of crotonic acid leads to 29 % yield of b-hydroxy acid (3-hydroxybutanoic acid). By controlling the pH of the reaction media, it is possible to hydrolyze the oxirane moiety leading to 21 % yield of a,b-dihydroxy acid (2,3-dihydroxybutanoic acid). Crotonic acid, 3-hydroxybutanoic acid, and 2,3-dihydroxybutanoic acid are archetypal specialty chemicals used in the synthesis of polyvinyl-counsaturated acids resins, pharmaceutics, and bio-degradable/ -compatible polymers, respectively.Polymers play a key role in the creation of a myriad of materials that have contributed to the development of our modern society. The current use of plastics, however, is not sustainable in the long term due to its dependence on non-renewable fossil fuels and the environmental pollution caused by plastic waste. [1] This dilemma has triggered intensive research in the development of environmentally friendly and sustainable bio-based and biodegradable polymers. [2] Polyhydroxyalkanoates (PHAs) are a class of biodegradable isotactic polymers synthesized by bacteria. [3] Until now, these family of polymer building blocks have been synthesized using genetically modified micro-organisms or enzymes. [4] However, the production cost of PHAs is nearly four times larger than its petroleum-based counterparts (circa PHAs [5] and polypropylene [6] prices are 5-6 and 1-2 $/kg, respectively). This is due to the high cost of raw materials, low conversion rates, the complex purification of the fermentation broths, and the large amounts of biomass waste generated (circa 5 kg of raw material per 1 kg of product), and low conversion rates. [7] Catalytic conversion routes of biomass-derived feedstocks to short b-hydroxy acids (e.g. lactic acid) have shown higher productivities and atom-efficiency at industrially relevant operating conditions, [8] but their application has been limited to short chain (C 3 ) molecules. Inspired by nature, we have developed a new catalytic cascade process that mimics the step-wise coupling of C 2 units that occur during the biosynthesis of PHA in bacteria. Accordingly, we have used basecatalyzed aldol-condensation followed by tandem oxidation, epoxidation and hydrogenation or hydration (Scheme 1). This catalytic cascade route has allowed us to generate mediumchain a,b-unsaturated acids (crotonic acid), a,b-dihydroxy acids (2,3-dihydroxybutanoic acid), and b-hydroxy acids (3hydroxybutyric acid), which are emerging specialty chemicals and building blocks.The process of co...

The thermal conversion of biomass resource materials into potential bio-oil by either pyrolysis or torrefaction is an attractive process with significant economic concern. However, upgrading the multistage torrefaction liquid products into valuable compounds is the greatest challenge in the biorefinery industry due to the presence of large multiple complex molecules. The product mainly contains a significant portion of acetic acid and furfural at the low-temperature fraction. In this study, we have aimed to upgrade the furfural molecule along with acetic acid by the selective oxidation reaction route. Initially, the Au/Mg­(OH)2 catalyst was employed, and the loss of catalytic activity was observed in a short period due to the instability of the materials in the acidic medium. However, using a sacrificial magnesium oxide (MgO) base with a Au/Al2O3 catalyst remarkably improved the oxidation rate and the stability of the material (both in the model compound and torrefaction stream). In every catalytic cycle, the soluble Mg2+ ion can be regenerated, and it can be successfully employed for next consecutive reactions. This understanding should help scale up the furoic acid production from the multistage torrefaction liquid.