Renewable resources and bio-based feedstocks may present a sustainable alternative to petrochemical sources to satisfy modern society's ever-increasing demand for energy and chemicals. However, the conversion processes needed for these future bio-refineries will likely differ from those currently used in the petrochemical industry. Biotechnology and chemocatalysis offer routes for converting biomass into a variety of molecules that can serve as platform chemicals. While a host of technologies can be leveraged for biomass upgrading, condensation reactions are significant because they have the potential to upgrade these bio-derived feedstocks while minimizing the loss of carbon and the generation of by-products. This review surveys both the biological and chemical catalytic routes to producing platform chemicals from renewable sources and describes advances in condensation chemistry and strategies for the conversion of these platform chemicals into fuels and high-value chemicals.

starch or sugar-rich biomass (corn (maize), other cereals, sugar cane, etc.) into sugar, fermentation, and distillation. Advanced process: hydrolysis of ligno-cellulosic biomass, fermentation and distillation. Biodiesel production: extraction and esterification of vegetable oils, used cooking oils and animal fats using alcohols. Advanced processes: hydrogenation of oil and fat; gasification and catalytic conversion to liquid fuels (biomass to liquid, BTL). Biomethane: biogas from anaerobic digestors and landfills used as compressed gas in natural gas vehicles. ENERGY INPUT AND EMISSIONS -Because of the variety of feedstocks and processes, figures vary widely and make it difficult to identify indicative values. Sugar-cane ethanol: fossil fuel input some 10%-12% of final energy and up to 90% CO 2 reduction compared with gasoline. Corn ethanol: high energy input and much smaller CO 2 reduction (15-25%). Ligno-cellulosic ethanol: total energy input may be higher than for corn ethanol, but most such energy could be provided from biomass itself, with CO 2 reduction up to 70% (100% with power co-generation). Biodiesel: about 30% energy input and up to 60% CO 2 reduction. COSTS -High sensitivity to feedstock, process, land type and crop yield. BARRIERS -Competition with food and fibre production for use of arable land; cost; regional market structure; biomass transport; lack of well managed agricultural practices in emerging economies; water and fertiliser use; conservation of bio-diversity; logistics and distribution networks. PROCESS -Bioethanol conventional production -Bioethanol is the most common biofuel, accounting for more than 90% of total biofuel usage. Conventional production is a well known process based on enzymatic conversion of starchy biomass into sugars, and/or fermentation of 6-carbon sugars with final distillation of ethanol to fuel grade. Ethanol can be produced from many feedstocks, including cereal crops, corn (maize), sugar cane, sugar beets, potatoes, sorghum, cassava. Coproducts (e.g animal feed) help reduce production cost. If sugar cane is used, conversion into sugar is easier. Crushed stalk (bagasse) can be used to provide heat and power for the process and for other energy applications. The world's largest producers of bio-ethanol are Brazil (sugar-cane ethanol) and the United States (corn ethanol). Ethanol is used in low 5%-10% blends with gasoline (E5, E10) but also as E-85 in flex-fuel vehicles. In Brazil, gasoline must contain a minimum of 22% bioethanol.Bioethanol advanced productionWhile conventional processes use only the sugar and starch biomass components, R&D focuses on advanced processes that utilise the all available ligno-cellulosic materials. These processes hold the potential to increase variety and quantity of suitable feedstock including cellulosic wastes, maize stover, cereal straw, foodprocessing wastes, as well as dedicated fast-growing plants such as poplar trees and switch-grass. Cellulosic feedstock could be grown on non arable land or be produced from integrated crops,...

A novel hierarchically porous, hyper-cross-linked siloxane-organic hybrid (PSN-5) has been synthesized by Friedel-Crafts self-condensation of benzyl chloride-terminated double-four-ring cubic siloxane cages as a singular molecular precursor. Simultaneous polymerization of the organic functional groups and destruction of the siloxane cages during synthesis yielded PSN-5, which has an ultrahigh BET surface area (∼2500 m(2) g(-1)) and large pore volume (∼3.3 cm(3) g(-1)) that to our knowledge are the highest values reported for siloxane-based materials. PSN-5 also shows a high H(2) uptake of 1.25 wt % at 77 K and 760 Torr.

Novel pure silica sodalite with hollow sodalite-cages has been synthesized for the first time by topotactic conversion of layered silicate (RUB-15) precursor. This success has been achieved by stepwise syntheses from silicate monomers, through clusters and layers, to microporous crystals. The pretreatment of layered silicate with small carboxylic acids before conversion is a crucial step. The obtained sodalite possesses accessible micropores, as confirmed by physical adsorption of hydrogen molecules. This plate-like silica sodalite would be very promising as fillers in mixed-matrix membranes for hydrogen separation.

2-and 4-Methylbenzaldehyde, which are useful precursors for phthalic anhydride and terephthalic acid, form by sequential aldol condensations between acetaldehyde and enals and subsequent dehydrocyclization during ethanol upgrading reactions on hydroxyapatite catalysts. The selectivities for methylbenzaldehydes exceed 30%, as a result of rapid cyclization reactions and steric protection that hinders further growth. Such pathways compete with a set of alternating condensation and hydrogenation steps, known as the Guerbet reaction, which produces broad distributions of n-and iso-alcohols. The selectivities to C 8 aromatic products increase in proportion to the ratio of the acetaldehyde to ethanol concentrations. These reactions provide new pathways for the selective conversion of bioethanol to value-added chemicals.

Topotactic conversion of crystalline layered silicates into zeolite provides an opportunity to create new chemical compositions, framework types, and macroscopic morphologies that are difficult to achieve by conventional hydrothermal synthesis. We have recently reported the successful synthesis of pure silica sodalite with a unique sheet-like morphology from layered silicate RUB-15 occluding interlayer TMA+ cations. Pretreatment of RUB-15 with acetic acid was found to be crucial for topotactic dehydration–condensation between the silicate layers upon heating. In this study, a homologous series of carboxylic acids of varying concentrations is examined for their capability to generate an ordered intermediate state, and important factors for topotactic conversion are determined. Both length of the alkyl chains and concentration of the carboxylic acids strongly affected the crystallinity of the products, and well-crystallized sodalite was obtained using either acetic or propionic acid. Transmission electron microscopy showed that the sodalite with sheet-like morphology has the thickness of several hundred nanometers in which the (110) plane is oriented parallel to the surface. Two key factors elucidated for successful conversion are (i) proton-exchange of interlayer TMA+ cations to shorten the interlayer distance and to form Si–OH groups and (ii) intercalation of carboxylic acid molecules between the layers to maintain the well-ordered layered structure prior to calcination.

Condensation reactions of biomass derived C2 and C4 aldehydes form both ortho‐ and para‐tolualdehydes (2‐MB and 4‐MB, respectively). The complete reaction network and the detailed mechanisms, however, have not been fully described. Here, analysis of the products formed by sequential condensation reactions of acetaldehyde and 2‐butenal suggests that 2‐ and 4‐MB products form via aromatization of 2,4,6‐octatrienal and of highly reactive acyclic intermediate(s) formed via self‐addition of 2‐butenal, respectively. The exact positions at which C−C bonds form between C4 co‐reactants to create 4‐MB products were investigated by using reactant mixtures containing combinations of 2‐butenal, 2‐butenol, and 3‐methyl‐2‐butenal as model reactants. The last two reactants can form products that may be assigned to specific reaction pathways (not distinguishable during self‐addition of 2‐butenal) and also have decreased reactivity at specific carbon atoms. The analysis of the products suggests that 4‐MB species form via 2‐butenal self‐addition by nucleophilic attack of the α‐C to the carbonyl‐C. Additionally, Diels–Alder reactions (between C6 and C2 intermediates) do not contribute in any significant manner to the formation of 4‐MB. These findings complete the description of the reaction network that forms 2‐ and 4‐MB from acetaldehyde on hydroxyapatite.

Preparation of high-quality single-walled carbon nanotubes (SWNTs) has been advanced by controlling several parameters including the catalyst and the catalyst support material. Although zeolite has been frequently used as a catalyst support material for the synthesis of SWNTs, detailed surface properties of previously employed zeolites, and thus their role as a catalyst support material, have not been 2 sufficiently clarified yet. In this study, a clean b-plane surface of silicalite-1, which is a siliceous MFItype zeolite, was used as a model substrate for the synthesis of SWNTs. The amount of active cobalt used for SWNT generation was smaller than the initially sputtered amount, and XPS measurements revealed diffusion of cobalt into the zeolite framework. The diffused cobalt was found to interact strongly with the silica framework of zeolite. The diffusion coefficient of cobalt in silicalite-1 zeolite was estimated to be one order of magnitude larger than that in thermally oxidized SiO 2 formed on a Si substrate. This difference was ascribed to the microporous structure and lower density of zeolite. In this study, the state of the cobalt catalyst and the interaction between cobalt and the crystalline zeolite substrate is presented and discussed.