Volume 30, Issue 6

The benefits of lowering the operation temperature of solid oxide fuel cells (SOFCs) have attracted great attention worldwide. There has been an enormous effort in the literature for the improvement of the electrolyte materials working at lower temperatures. The family of BiMeVOx (Bi–bismuth, Me–dopant metal, V–vanadium, Ox–oxide) materials has been found to have specific properties as oxide ion conductor (electrolyte) for low operation temperature. These materials exhibit uniquely structural features rather different from those of other solid electrolytes. It is possible to use these as the electrolyte in SOFCs. This article attempts to review the main structural and electrochemical characteristics of BiMeVOx materials in order to show a guideline for designing novel BiMeVOx-based electrolyte for low-temperature SOFCs. The prospects and challenges for the application of these materials as the electrolyte are discussed.

Flue gas desulfurization (FGD) technology has been adopted by a number of power stations for the removal of sulfur dioxide (SO 2 ) from flue gas. The wet FGD system is the most commonly used process because of high SO 2 removal efficiency and because of the availability of the sorbent used. This paper emphasizes the wet FGD process and the different types of sorbents used. Sorbent dissolution in the wet FGD process plays a significant role in the overall performance of the system. Factors such as temperature, solid-to-liquid ratio, pH, particle size, and additives can be optimized to improve the dissolution rate in the wet FGD system. Additives such as organic acids and inorganic salts can improve the dissolution rate and the desulfurization efficiency of the sorbent. Dissolution kinetics gives an understanding of the effects of reaction variables on the dissolution rate. The dissolution process is a heterogeneous reaction system consisting of fluid reactants and solid particles. This is best described using the shrinking core model that considers a reducing solid particle size as the reaction takes place.

Vinyl ester resins (VERs) are high-performance unsaturated resins derived by the addition reaction of various epoxide resins with α-β unsaturated carboxylic acids. These resins have always been classified under unsaturated polyester resins. However, VERs have remarkable corrosion resistance and superior physical properties as compared with these conventional polyester resins, which make VERs a class of their own and hallmark of today’s resin industries. Hence, there is a need to review the available literature on this important class of thermosetting resins separately. In this article, an attempt is made to review the state of the art of VERs, including synthesis, characterization, curing, thermal, chemical, oxidative properties, and applications. The main focus is on the latest developments in this area.

Formaldehyde is one of the most important intermediate chemicals and has been produced industrially since 1889. Formaldehyde is a key feedstock in several industries like resins, polymers, adhesives, and paints, making it one of the most valuable chemicals in the world. However, not many studies have been dedicated to reviewing the production of this economically important product. In this review paper, we study the leading commercial processes for formaldehyde production and compare them with recent advancements in catalysis and novel processes. This paper compares, in extensive detail, the reaction mechanisms and kinetics of water ballast process (or BASF process), methanol ballast process, and Formox process. The thermodynamics of the reactions involved in the formaldehyde production process was investigated using HSC Chemistry™ software (Outotec Oyj, Espoo, Finland). Exergy analysis was carried out for the natural gas to methanol process and the methanol ballast process for formaldehyde production. The former process was simulated using Aspen HYSYS™ and the latter using Aspen Plus™ software (Aspen technology, Burlington, MA, USA). The yield and product specifications from the simulation results closely matched with published experimental data. The exergy efficiencies of the natural gas to synthesis gas via steam reforming, methanol synthesis, and formaldehyde synthesis processes were calculated as 60.8%, 61.6%, and 66%, respectively. The overall exergy efficiency of natural gas conversion into formaldehyde was found to be only 43.2%. The main sources of exergy losses were the steam reformer and methanol loss in formaldehyde synthesis process. Despite high conversions and selectivities of these processes, the low exergy efficiency suggests that innovations in formaldehyde production processes could give a more sustainable product. Novel methods of direct conversion of natural gas or synthesis gas into formaldehyde will improve the exergy efficiency, but the conversion rate must also be increased with advancements in catalysis.

Researchers have shown that techniques such as microwave-assisted extraction, ultrasound-assisted extraction, pressurized liquid extraction, and supercritical fluid extraction developed for extraction of valuable components from plants and seed materials have been successfully used to effectively reduce the major shortcomings of the traditional method such as Soxhlet extraction. These include shorter extraction time, increase in yield of extracted components, decrease in solvent consumption, and improvement of the quality of extracts. This review presents a detailed description of the principles and mechanisms of the various extraction techniques for better understanding and summarizes the potential of these techniques in the extraction of oil from plants and seed materials. Discussions on some of the parameters affecting the extraction efficiency are also highlighted, with special emphasis on supercritical fluid extraction. A comparison of the performance of traditional Soxhlet extraction with that of other extraction techniques is also presented.