Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 5 Articles
As the global atmospheric emissions of carbon dioxide (CO2) and other greenhouse gases continue to grow to record-setting levels,\r\nso do the demands for an efficient and inexpensive carbon sequestration system. Concurrently, the first-world dependence on\r\ncrude oil and natural gas provokes concerns for long-term availability and emphasizes the need for alternative fuel sources. At the\r\nforefront of both of these research areas are a family of enzymes known as the carbonic anhydrases (CAs), which reversibly catalyze\r\nthe hydration of CO2 into bicarbonate. CAs are among the fastest enzymes known, which have a maximum catalytic efficiency\r\napproaching the diffusion limit of 108M-1s-1. As such, CAs are being utilized in various industrial and research settings to help\r\nlower CO2 atmospheric emissions and promote biofuel production.This review will highlight some of the recent accomplishments\r\nin these areas along with a discussion on their current limitations...
Pretreatment of lignocellulose has received considerable research globally due to its influence on the technical, economic\r\nand environmental sustainability of cellulosic ethanol production. Some of the most promising pretreatment methods require\r\nthe application of chemicals such as acids, alkali, salts, oxidants, and solvents. Thus, advances in research have enabled the\r\ndevelopment and integration of chemical-based pretreatment into proprietary ethanol production technologies in several pilot and\r\ndemonstration plants globally, with potential to scale-up to commercial levels. This paper reviews known and emerging chemical\r\npretreatment methods, highlighting recent findings and process innovations developed to offset inherent challenges via a range\r\nof interventions, notably, the combination of chemical pretreatment with other methods to improve carbohydrate preservation,\r\nreduce formation of degradation products, achieve high sugar yields at mild reaction conditions, reduce solvent loads and enzyme\r\ndose, reduce waste generation, and improve recovery of biomass components in pure forms. The use of chemicals such as ionic\r\nliquids, NMMO, and sulphite are promising once challenges in solvent recovery are overcome. For developing countries, alkalibased\r\nmethods are relatively easy to deploy in decentralized, low-tech systems owing to advantages such as the requirement of\r\nsimple reactors and the ease of operation....
Perovskite structure oxygen carriers with the general formula CaMnxMg1-xO3-?? were spray-dried and examined in a batch fluidized\r\nbed reactor. The CLOU behavior, reactivity towards methane, and syngas were investigated at temperature 900�°C to 1050�°C. All\r\nparticles showed CLOU behavior at these temperatures. For experiments with methane, a bed mass corresponding to 57 kg/MW\r\nwas used in the reactor, and the average CH4 to CO2 conversion was above 97% for most materials. Full syngas conversion was\r\nachieved for all materials utilizing a bedmass corresponding to 178 kg/MW. SEM/EDX and XRD confirmed the presence of MgO in\r\nthe fresh and used samples, indicating that theMg cation is not incorporated into the perovskite structure and the active compound\r\nis likely pure CaMnO3-??.The very high reactivity with fuel gases, comparable to that of baseline oxygen carriers ofNiO, makes these\r\nperovskite particles highly interesting for commercial CLC application. Contrary to NiO, oxygen carriers based on CaMnO3-?? have\r\nno thermodynamic limitations for methane oxidation to CO2 and H2O, not to mention that the materials are environmentally\r\nfriendly and can utilize much cheaper raw materials for production. The physical properties, crystalline phases, and morphology\r\ninformation were also determined in this work....
An experiment of hydrogen preparation from steam-carbon reaction catalyzed by K2CO3 was carried out at 700�°C, which was\r\ndriven by the solar reaction system simulated with Xenon lamp. It can be found that the rate of reaction with catalyst is 10 times\r\nmore than that without catalyst. However, for the catalytic reaction, there is no obvious change for the rate of hydrogen generation\r\nwith catalyst content range from10% to 20%. Besides, the conversion efficiency of solar energy to chemical energy ismore than 13.1%\r\nover that by photovoltaic-electrolysis route. An analysis to the mechanism of catalytic steam-carbon reaction with K2CO3 is given,\r\nand an explanation to the nonbalanced [H2]/[CO 2CO2] is presented, which is a phenomenon usually observed in experiment....
An Advanced Oxidation Process (AOPs) was carried out in this study with the use of immobilized ZnO and solar/UV as an energy\r\nsource to degrade dairy wastewater. The semibatch reactor system consisted of metal plate of 800 Ã?â?? 250mm and a glass tank.The\r\nreaction time was of 3 h for 3 L of dairy wastewater. Experiments were performed based on a surface response methodology in order\r\nto optimize the photocatalytic process. Degradation was measured in percentage terms by total organic carbon (TOC). The entry\r\nvariables were ZnO coating thickness and pH, using three levels of each variable.The optimized results showed a TOC degradation\r\nof 31.7%. Optimal parameters were metal-plate coating of 100 ??m of ZnO and pH of 8.0. Since solar/UV is a constant and free\r\nenergy source in most tropical countries, this process tends to suggest an interesting contribution in dairy wastewater treatment,\r\nespecially as a pretreatment and the optimal conditions to guarantee a better efficiency of the process....
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