Many types of zeolites such as beta (hereinafter, *BEA), CHA, LEV, RUT, and MFI were successfully synthesized by interzeolite conversion of FAU, *BEA, and LEV type zeolites as starting materials under various hydrothermal synthesis conditions. The crystallization rates of zeolites using such starting zeolites were notably elevated compared to rates observed in conventional hydrothermal syntheses using amorphous aluminosilicate gels. This characteristic enhancement in the crystallization rate results from the generation of locally ordered aluminosilicate species (nanoparts) through the decomposition/dissolution of the starting zeolite, resulting in assembly and evolution into another type of zeolite. The structural similarity between the starting zeolite and the final crystallized zeolite is a crucial factor for interzeolite conversion. These findings strongly indicate that the interzeolite conversion route is an attractive strategy for zeolite synthesis and zeolite design will be possible after methods to selectively assemble the nanoparts are established.
Ordered porous materials such as zeolites and ordered mesoporous silicas have important physical characteristics based on their high surface area and well-defined pore size. Control of the structure or shape of the ordered porous materials will provide new functions. This review focuses on core-shell structure; especially fabrication methods of core-shell structured zeolites with minimal defects are introduced. As an example of applications, MFI and TON-type zeolites with core-shell structure used as catalysts have high shape selectivity in the methylation of toluene with methanol and skeletal isomerization of tetradecane, respectively. As another application, synthesis of hollow porous materials from core-shell porous materials is also described. Decomposition of silica with dimethyl carbonate catalyzed by an alkali metal salt impregnated in the core was an effective method for selective removal of the core from the core-shell structure. Hollow porous materials show promise as vessels for drug delivery, catalyst vessels and microreactors.
The fact that zeolites with high external surface area allow diffusing reactants greater access to active sites, has led to interest in the preparation of nanosized zeolites. The organic template-free synthesis of nanosized zeolite has been a subject of special importance for scientific and industrial applications. Thus far, most research has focused on a bottom-up approach for the fabrication of nano-zeolites, that is, control of zeolite nucleation and crystal growth during hydrothermal synthesis. This review summarizes a new method for the top-down production of nano-zeolite powder by first milling the zeolite to produce nanoparticles. This technique destroys the outer portion of the zeolite framework thereby decreasing its ion-exchange properties and catalytic activity. To remedy this, the damaged portions were recrystallized using a dilute aluminosilicate or silicate solution after bead-milling. The combined bead-milling and post-milling recrystallization yielded nano-zeolites with high crystallinity. The nanosized powders showed higher ion-exchange properties for zeolite A and higher catalytic activity for ZSM-5, respectively.
The authors have been developing facile preparation methods of precisely structure-controlled Pt nanocrystals (NCs) by liquid reduction procedures. We have also been adopting shape and size controlled Pt NCs as model catalysts to evaluate active sites of catalysts. This review deals with our following recent research topics. We have demonstrated that control of reaction circumstances (ex., solvent polarity, additive etc.) during formation of Pt(0) nuclei and their growth led to precisely structure controlled Pt NCs, such as Pt cube and nanowire. Recently, we have succeeded to prepare very small Pt cube and site-specific deposition of Ag at corner of Pt cube. Several Pt NCs with different shapes (cube, nanowire, tetrahedron, cubooctahedron) and sizes were applied as model catalysts for olefin hydrogenation to evaluate active sites. The new strategy based on advanced nanotechnology will be expected as a novel tool to design high performance catalysts with strictly controlled active sites.
Waste oil-based drilling fluids are hazardous wastes containing oil, heavy-metal and organic pollutants. However, the common treatment methods at home and abroad these methods not only waste many useful resources (because the oil is discarded rather than recovered) but also increase the pro-environment cost of oil companies. This paper develops useful recycling and safe disposal technology of waste oil-based drilling fluids from the perspective of utility, efficiency and economy, which not only recycle useful oil but also reuse and dispose of the rest of mud and waste drilling fluids. The rate of recovery is greater than 90 %, and the quality of the recycled oil is very good and meets the requirement of −10 # diesel of cars in GB/T 19147-2003. The concentrations of oil, COD (chemical oxygen demand) and heavy metals in liquid of the processed mud are lower than the secondary standard number in GB8978-1996. The treated wastewater meets the requirements of sewage comprehensive emission.
In this study, we sought to experimentally investigate the effect of drillpipe rotation on pressure loss and cuttings transport in a horizontal annular pipe by considering both varied foam qualities of 80, 85 and 90 % and foam velocities. Additionally, the influence of foam velocity and foam quality on pressure loss and cuttings transport efficiency was investigated. The experiments were conducted in a flow loop with a 5-m long eccentric annular test section, representing the wellbore, with a 51.8-mm outer pipe and a 16-mm inner pipe that could be rotated up to 150 rpm. It has been observed that pipe rotation has a negligible effect when only foam flows in the annular pipe. Conversely, pipe rotation has a significant effect on the pressure loss and cuttings transport when the cuttings are injected into the annular pipe. Furthermore, with increasing rotational speed, the frictional pressure loss dramatically decreases and the delivered cuttings concentration increases. Moreover, experimental results show that higher foam quality and velocity increased the pressure loss and decreased the delivered cuttings concentration.
The phytoremediation potential of Dracaena reflexa to remediate diesel contaminated soil was determined in a greenhouse study. D. reflexa was planted in soil contaminated with different concentrations of diesel fuel (1, 2.5 and 5 wt%). 5 (wt%) of three different organic wastes [tea leaf (TL), soy cake (SC) and potato skin (PS)] were mixed with the soil and monitored for 270 days. The results of the biodegradation of oil and its fractions showed a reduction of 90 % and 98 % of total petroleum hydrocarbons (TPHs) in soil amended with SC, at 2.5 % and 1 % fuel, respectively. It was observed that in the non-cultivated polluted soil the TPHs, were reduced by 24-27 %. Soil amended with SC provided the greatest diesel fuel loss when compared to other organic waste supplements. D. reflexa roots did not accumulate hydrocarbons from the soil, but the number of hydrocarbon utilizing bacteria was high in the rhizosphere, thus suggesting that the mechanism of the oil degradation was via rhizodegradation. This study has shown that D. reflexa amended with organic wastes has a potential for biodegrading hydrocarbon-contaminated soil.
CODCr is a method of COD (chemical oxygen demand) measurement that is most accurate for analysis of low-salinity waters. However, CODCr is known to be affected by the chloride ion, which is present in high concentrations in saline, oilfield produced waters. In this study, three different methods of COD analyses (CODCr, CODMn, CODOH) were performed for prepared waters at 0-20 % salinity, and the effect of salinity on the results of each method was considered. Additionally, CODCr and CODMn of 11 samples of different, actual produced waters were also measured, and the validity of the results produced by each method was also considered. The results clearly indicated that values of CODCr for highly saline samples were not reliable. On the other hand, CODMn and CODOH analyses resulted in appropriate values, even in prepared water of 20 % salinity. In the case of CODMn, pre-analysis measures of chloride ion masking appear to be very important for obtaining these values. Based on this study, it is concluded that values resulting from CODMn or CODOH analysis methods were appropriate for the discussion of produced water, and the CODCr method is not recommended for the analysis of any such highly saline waters.
The catalytic activities of reduced NiMo catalysts supported on Al2O3, SiO2-Al2O3, SAPO-11 and AlSBA-15 in hydroconversion of Jatropha oil were evaluated. A high deoxygenation ratio was achieved over each reduced catalyst as well as sulfided catalysts. Catalytic performance was obviously influenced by the acidity of supports, resulting in significantly different carbon number distribution in produced hydrocarbons. High yield of 74.6 % of C11-C18 hydrocarbon products with low cloud point of ca. −16 °C was obtained in single-step hydrotreating of Jatropha oil over NiMo/SiO2-Al2O3 catalyst.