In light of the depletion of fossil fuels and the increased daily requirements for liquid fuels and chemicals, CO 2 should indeed be regarded as a valuable C 1 additional feedstock for sustainable manufacturing of liquid fuels and chemicals. Development and deployment of CO 2 capture and chemical conversion processes are among the grand challenges faced by today's scientists and engineers. Very few of the reported CO 2 capture and conversion technologies have been employed for industrial installations on a large scale, where high-efficiency, cost/energy-effectiveness, and environmental friendliness are three keys factors. The CO 2 capture technologies from stationary sources and ambient air based on solvents, solid sorbents, and membranes are discussed first. Transforming CO 2 to liquid fuels and chemicals, which are presently produced from petroleum, through thermochemical, electrochemical, photochemical, and biochemical routes are discussed next. The relevant state-of-theart computational methods and tools as a complement to experiments are also briefly discussed. Finally, after pointing out the advantages and disadvantages of the currently available technologies for CO 2 capture and conversion, ideas and perspectives for the development of new techniques, opportunities, and challenges are highlighted.

No abstract

No abstract

A shift to utilize more renewable energy sources has been motivated by issues of energy security, environmental protection, and sustainable development. Biofuels are among the promising forms of renewable energy as they can be produced from a wide variety of feedstocks (e.g., traditional agriculture crops, energy crops, forestry products, municipal solid waste, etc.). Biorefineries are processing facilities that convert biomass into value-added products such as biofuels, specialty chemicals, and pharmaceuticals. To enhance material and energy recovery within processing facilities, an integrated biorefinery is proposed. Since the potential pathways and products in an integrated biorefinery are extensive, product allocation is a complex task. The main challenge in designing an integrated biorefinery is to synthesize a sustainable biorefinery with maximum economic performance while causing minimum environmental impact. Since such objectives are often conflicting in nature, fuzzy mathematical programming is adapted in this work to synthesize a sustainable integrated biorefinery that fulfills both considerations simultaneously.

INTRODUCTIONThe precipitation and size-selective fractionation of nanoparticles is a crucial and, sometimes, necessary stage of postsynthesis nanomaterial processing to fine-tune the size-dependent properties of nanoparticles for their intended application. Unfortunately, these processes (specifically size-selective fractionation) are somewhat trial-and-error in their application, and predicting the size and size distribution of the recovered nanoparticle fractions is quite difficult. The ability to predict the size and size distributions of the nanoparticles that would disperse and precipitate at different solvent conditions would greatly reduce the need for experimentation and would provide new, physical insights into the underpinning thermophysical phenomena.Traditionally, the size-selective fractionation of nanoparticles has been accomplished through the controlled reduction of solvent strength of a thermodynamically stable nanoparticle dispersion by the addition of an antisolvent 1 (e.g., aliphatic-thiol stabilized nanoparticles dispersed in hexane can be precipitated and fractionated through the addition of ethanol). This liquid-liquid solvent/antisolvent precipitation and fractionation process produces large amounts of organic waste, is very time-intensive, and is capable of producing only monodisperse fractions through repetition. Another method of size-selectively precipitating nanoparticles was developed 2-4 to alievate some of the drawbacks of the liquid-liquid precipitation and fractionation process which makes use of the tunable physicochemical properties of gas-expanded liquids (GXLs): mixtures of an organic solvent and a pressurized gas. An organic solvent (e.g., hexane) dispersion of aliphatic-ligand (e.g., dodecanethiol) stabilized metallic (e.g., gold) nanoparticles can be precipitated when pressured to subvapor pressure levels with CO 2 . The CO 2 partitions (dissolves) into the organic solvent, and as CO 2 is a nonsolvent for the aliphatic ligand tails, the solvent strength of the overall solvent mixture is reduced, thus inducing precipitation of the nanoparticles. The degree to which CO 2 is added to the solvent is simply a function of the applied CO 2 pressure; i.e., CO 2 has a greater solubility at higher applied pressures. Several apparatuses have been developed to make use of this phenomenon to size-selectively fractionate polydisperse nanoparticles. Details on these methods are available elsewhere, 2,4 but in short, if an organic dispersion of nanoparticles is pressurized with CO 2 to a point where only a portion of the nanoparticles precipitate (the largest nanoparticles will precipitate first upon worsening solvent conditions), the nanoparticles which remain dispersed (the smallest nanoparticles) in the solvent mixture can be removed from the precipitated nanoparticles, thereby achieving an effective fractionation.Modeling of these postsynthesis processes involving aqueous nanoparticle dispersions has been successfully accomplished through the use of Derjaguin, Landau, Verwey, and Over...