Polyamides represent a very important class of polymers for a wide range of applications. After establishing in the 1930s with Nylon and Perlon, their impact on many branches has been continuously growing. In the context of developing sustainable polymers from renewable resources, many polyamides have meanwhile been described, which are based on natural building blocks. In addition to their sustainability, these biobased starting materials can provide special structural features to the resulting polymers and their properties, e.g., side groups, functionalities, or stereoinformation. While some biopolyamides are known for decades and well established (e.g., PA‐11, Rilsan), many other promising candidates have been described in fundamental research studies, which have high potential but whose capability—especially for large scale and/or high‐performance materials—will have to be proved in the future. Other candidates are very interesting from a scientific point of view, but with less potential for a market establishment due to price and/or feasibility reasons. This article aims at collating the recent developments in the field of biopolyamides and elucidating their properties and potential for different applications.
As petroleum prices continue to increase, it is likely that biofuels will play an ever-increasing role in our energy future. The processing of biomass-derived feedstocks (including cellulosic, starch- and sugar-derived biomass, and vegetable fats) by catalytic cracking and hydrotreating is a promising alternative for the future to produce biofuels, and the existing infrastructure of petroleum refineries is well-suited for the production of biofuels, allowing us to rapidly transition to a more sustainable economy without large capital investments for new reaction equipment. This Review discusses the chemistry, catalysts, and challenges involved in the production of biofuels. 相似文献
The direct oxidation of ethanol to acetic acid is catalyzed by multicomponent metal oxides (Mo-V-NbO(x)) prepared by precipitation in the presence of colloidal TiO(2) (Mo(0.61)V(0.31)Nb(0.08)O(x)/TiO(2)). Acetic acid synthesis rates and selectivities (~95 % even at 100 % ethanol conversion) were much higher than in previous reports. The presence of TiO(2) during synthesis led to more highly active surface areas without detectable changes in the reactivity or selectivity of exposed active oxide surfaces. Ethanol oxidation proceeds via acetaldehyde intermediates that are converted to acetic acid. Water increases acetic acid selectivity by inhibiting acetaldehyde synthesis more strongly than its oxidation to acetic acid, thus minimizing prevalent acetaldehyde concentrations and its intervening conversion to CO(x). Kinetic and isotopic effects indicate that C-H bond activation in chemisorbed ethoxide species limits acetaldehyde synthesis rates and overall rates of ethanol conversion to acetic acid. The VO(x) component in Mo-V-Nb is responsible for the high reactivity of these materials. Mo and Nb oxide components increase the accessibility and reducibility of VO(x) domains, while concurrently decreasing the number of unselective V-O-Ti linkages in VO(x) domains dispersed on TiO(2). 相似文献