Search

A nanosheet zeolite ITQ-2 formed by delamination of MCM-22 zeolite precursor was used and tested as a catalyst for the aromatization of acetylene. Along with MCM-22 (calcined form of MCM-22 zeolite precursor) zeolites, the resulting materials were successfully prepared and characterized in terms of pore structure and surface property. The performance of aromatization of ITQ-2 zeolites was comparable to that of MCM-22 zeolites. Due to the isolated and thin-layer structure, ITQ-2 zeolites had a significant fraction of external active sites. This feature seemed to result in relatively higher amount of C3–C8 aliphatic compounds rather than the C6–C8 aromatic compounds because of the shortened residence and, thus, reaction time. We first found that the cumulative C3–C8 aliphatic products in the case of ITQ-2 zeolites increased with the amounts of external surface area, while no clear relation was observed for the case of MCM-22 zeolites. Second, the initial selectivity towards aromatics was found to clearly show a linear relation with the concentration of Bronsted acid sites regardless of the used catalyst. In addition, the nanosheet ITQ-2 zeolites showed a much slower deactivation unlike the traditional microporous MCM-22 zeolites. Finally, to investigate the difference in the catalytic performance, we rebuilt the reaction pathways from acetylene to the aromatics and aliphatics.

A dielectric barrier discharge (DBD) plasma regeneration reaction was conducted at atmospheric pressure and temperature. This method was found to be very effective in removing carbon deposits after a non-oxidative aromatization from acetylene. When a fresh H-ZSM-5 catalyst was used for the aromatization, coke was by-produced and it could be ascribed to the primary reason for deactivation. By applying the DBD plasma to the deactivated catalyst bed at ambient temperature and pressure, the removal of carbon deposition with microdischarge and aeration was very effective; therefore, it is believed that additional thermal activation might not be necessary. More amount of coke was removed by supplying higher power to the catalyst bed. According to the results of XRD, physisorption, 27Al MAS NMR, and NH3-TPD analyses, it was confirmed that the structure and the acid site distribution of H-ZSM-5 were successfully retained even after the plasma treatment. Aromatization over the plasma-regenerated catalyst led to mild deactivation at the early stage and afforded comparable BTX selectivity to fresh H-ZSM-5 catalyst. Compared with the results obtained using the thermally regenerated catalyst, the structural stability was found to be higher and the BTX selectivity was kept higher during most of the reaction time for the plasma-regenerated catalyst.

This life cycle assessment evaluates the environmental impacts of two emergent masonry blocks designed to serve as sustainable replacements for conventional masonry blocks. The emergent blocks offer the same strength, durability, and form as conventional structural concrete blocks, and include hollow cores to enable placement of reinforcement in accordance with standard construction practices. The first emergent block consists of stabilized engineered soil that is compacted to reduce the use of ordinary Portland cement and eliminate curing. The second block, which is also compacted, contains alkali activators that promote a geopolymerization reaction among naturally occurring aluminosilicate clays, eliminating the need for ordinary Portland cement. QuantisSuite 2.0 software is used to perform a cradle to gate life cycle assessment comparing the environmental impacts of the two blocks to conventional concrete blocks across a range of indicators. The compacted stabilized soil block offers 46% less embodied carbon than conventional concrete block, which it outperforms in all categories except water consumption. The compacted alkali-activated block reduces embodied carbon by 42% when compared to concrete block, but has a higher impact on ecosystem, water withdrawal and resources. In terms of ecosystem and health indicators, the compacted stabilized soil block is the preferred building block, while conventional concrete block architectural blocks are the most water efficient. As understanding of alkali activation improves and manufacturing of compacted block is optimized, further environmental benefits are possible in both stabilized soil block and the alkali-activated block.

A dielectric barrier discharge (DBD) plasma reactor was employed for non-oxidative coupling of methane. The coupling reaction in the DBD plasma bed was conducted near atmospheric pressure and room temperature. In the bed, dielectric materials such as ordered mesoporous silica (KIT-6), sea sand silica, and α-Al2O3 were employed. This non-catalytic reaction system could successfully activate C H bond to produce methyl radicals and light hydrocarbons without additional thermal energy and oxidant molecules. The gap distance between dielectric particles was determined by their sizes, which was experimentally shown. The effects of gap distance were found significant on the conversion and the selectivity. The existence of maximum conversion at a specific gap distance was experimentally observed and could be described successfully by using a newly developed concept of micro-electrodes. Based on the concept, the minimum threshold electric potential difference between the dielectric particles could be successfully estimated, where the conversion was shown to be maximized. Furthermore, it seemed quite possible to control the compositions of ethane, ethylene, and acetylene by properly adjusting the size or the gap distance of particles.

The e-commerce market has been more diversified via B2B or P2P, and the size of this market has gradually been expanded as well. A noteworthy phenomenon is the P2P market, which has shown a rapid, approximately 200-fold or more increase in size since 2005. Specifically, the online secondhand-goods market that makes transaction easier and more convenient has attained a fast growth as well, but either sellers or buyers of secondhand goods are properly protected due to a lack of legal regulations on secondhand-goods transaction. The purpose of this study was to examine problems with online secondhand-goods transaction and to suggest some reform measures. There is something wrong with the legal status of brokers for secondhand-goods sales. According to the current law, individual brokers are neither mail-order sellers nor mail-order brokers. So they don`t have lots of liabilities, and it means that the burden of risk is all imposed on buyers. Therefore it`s suggested that individual brokers should be defined as `involved operator of electronic commerce` so that proper liability might be imposed on them.

This study analyzes the patterns and determinants of interlocal cooperation by examining the interlocal expenditures made in 2,684 American cities with a population over 10,000 and all 3,034 counties for the fiscal year 2002. This study found that metropolitan cities that have access to numerous municipal service providers in a county are more actively involved in interlocal cooperation than those that do not have such access. In the case of counties, citydominated counties that have professional county administrators (or council-elected executives) are more likely to be involved in interlocal cooperative arrangements than countydominated rural counties with no professional county administrators (or elected county executives). This is because professional county administrators (or council-elected executives) in city-dominated counties could easily find municipal service providers in their county. Thus, the availability of qualified municipal service providers appears to be one of the most important factors in facilitating interlocal cooperation in American cities and counties. This study also found that the pattern and the level of interlocal cooperation diverge somewhat between cities and counties, in part due to differences in the functional responsibility between counties and cities.

Critical speeds and aerodynamic flutter instability of various optical disks are experimentally studied in this paper. The two nodal diameter modes of ASMO and CD/DVD disks have the lowest critical speeds at 3800 and 6900 rpm, respectively, where the backward natural frequency vanishes. As the rotational speed increases, aeroelastic disk flutter is observed. Experiments using ASMO disks show that the three nodal diameter mode causes flutter instability at 8750 rpm. At the flutter speed, the vibration amplitude of the flutter mode grows dramatically. The natural frequencies of multiple vibration modes remain almost constant in the post-flutter region, which is called frequency lock-on. CD/DVD disks do not experience flutter up to 14,000 rpm.