The process of producing synthetic gas from waste plastics by steam reforming was investigated. To evaluate this process,
the steam reforming of the oils derived from low-density polyethylene and polystyrene were carried out using a laboratory-scale
fluidized bed of Ni-Al2O3 catalysts. The performance of gasification in terms of carbon conversion, gas yield, and gas compositions was examined. Although
oils derived from plastics contain many kinds of heavy hydrocarbons and aromatics, they were well gasified at temperatures
above 1023 K with a steam/carbon ratio of 3.5 and a weight hourly space velocity of 1 h−1. The hydrogen content of the product gas was very high at approximately 72 vol% for polyethylene-derived oil and 68 vol%
for polystyrene-derived oil. These compositions agreed well with the values calculated from chemical equilibrium. 相似文献
A mathematical model describing the rate of carbon disulfide (CS2) removal due to coupled reactions has been developed. Kinetic studies were carried out in a fixed bed reactor under atmospheric pressure and a range of temperatures (85–125 °C). The effects of flow rate, CS2 inlet concentration, temperature and relative humidity were analyzed. A kinetic model based on axial dispersion, external and internal mass-transfer resistances, as well as effects of S deposition on the inner-face of the catalyst was in agreement with the CS2 experimental breakthrough curves. The mathematical model can be used for process design and scale up of similar systems. 相似文献
In this study, economically favorable CoCl2 catalysts at four different amounts were supported on activated carbon (AC) for NaBH4 dehydrogenation. Supported catalyst could achieve hydrogen release for 2,060 cycles, which is equivalent to 103 days of uninterrupted operation. Slow and continuous hydrogen release was observed in all experiments. Even 1 g of NaBH4 can carry 1.2 L of hydrogen, and in hydrolysis process, it liberates 2.5 L of hydrogen that indicates the decomposition of water. EDX analysis and reverse burette measurements show that CoCl2 could be homogeneously distributed on and permanently joined to the support surface. Kinetic investigation of the dehydrogenation reaction fits zero order kinetics, and activation energy was calculated to be 48 kJ/mol. 相似文献
Technologies such as thermal, oxidative, reductive, and microbial methods for the remediation of polychlorinated biphenyls (PCBs) have previously been reviewed. Based on energy consumption, formation of PCDD/F, and remediation efficiency, reductive methods have emerged as being advantageous for remediation of PCBs. However, many new developments in this field have not been systematically reviewed. Therefore, reductive technologies published in the last decade related to remediation of PCBs will be reviewed here. Three categories, including catalytic hydrodechlorination with H2, Fe-based reductive dechlorination, and other reductive dechlorination methods (e.g., hydrogen-transfer dechlorination, base-catalyzed dechlorination, and sodium dispersion) are specifically reviewed. In addition, the advantages of each remediation technology are discussed. In this review, 108 articles are referenced. 相似文献
● Advances, challenges, and opportunities for catalytic water pollutant reduction.● Cases of Pd-based catalysts for nitrate, chlorate, and perchlorate reduction.● New functionalities developed by screening and design of catalytic metal sites.● Facile catalyst preparation approaches for convenient catalyst optimization.● Rational design and non-decorative effort are essential for future work. In this paper, we discuss the previous advances, current challenges, and future opportunities for the research of catalytic reduction of water pollutants. We present five case studies on the development of palladium-based catalysts for nitrate, chlorate, and perchlorate reduction with hydrogen gas under ambient conditions. We emphasize the realization of new functionalities through the screening and design of catalytic metal sites, including (i) platinum group metal (PGM) nanoparticles, (ii) the secondary metals for improving the reaction rate and product selectivity of nitrate reduction, (iii) oxygen-atom-transfer metal oxides for chlorate and perchlorate reduction, and (iv) ligand-enhanced coordination complexes for substantial activity enhancement. We also highlight the facile catalyst preparation approach that brought significant convenience to catalyst optimization. Based on our own studies, we then discuss directions of the catalyst research effort that are not immediately necessary or desirable, including (1) systematic study on the downstream aspects of under-developed catalysts, (2) random integration with hot concepts without a clear rationale, and (3) excessive and decorative experiments. We further address some general concerns regarding using H2 and PGMs in the catalytic system. Finally, we recommend future catalyst development in both “fundamental” and “applied” aspects. The purpose of this perspective is to remove major misconceptions about reductive catalysis research and bring back significant innovations for both scientific advancements and engineering applications to benefit environmental protection. 相似文献
In this paper, highly stable, powerful, and recyclable magnetic nanoparticles tethered N-heterocyclic carbene-palladium(II) ((CH3)3[email protected]3O4) as magnetic nanocatalyst was successfully synthesized from a simplistic multistep synthesis under aerobic conditions through easily available low-cost chemicals. Newly synthesized (CH3)3[email protected]3O4 magnetic nanocatalyst was characterized from various analytical tools and catalytic potential of the (CH3)3[email protected]3O4 magnetic nanocatalyst was studied for the catalytic reduction of toxic 4-nitrophenol (4-NP), hexavalent chromium (Cr(VI)), Methylene Blue (MB) and Methyl Orange (MO) at room temperature in aqueous media. UV-Visible spectroscopy was employed to monitor the reduction reactions. New (CH3)3[email protected]3O4 magnetic nanocatalyst exhibited excellent catalytic activity for the reduction of toxic environmental pollutants. Moreover, (CH3)3[email protected]3O4 magnetic nanocatalyst could be easily and rapidly separated from the reaction mixture with the help of an external magnet and recycled minimum five times in reduction of 4-NP, MB, MO and four times in Cr(VI) without significant loss of catalytic potential and remains stable even after reuse. 相似文献
Pt/CeO2–ZrO2–SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2–ZrO2–SnO2 were successfully dispersed on the γ-Al2O3 support. Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt(6.4 wt.%)/Ce0.68Zr0.17Sn0.15O2.0(16 wt.%)/γ-Al2O3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8 hr, and the selectivity to acetic acid reached to 95% and higher after the reaction for 4 hr and longer. 相似文献
In this study, post plasma-catalysis degradation of mixed volatile organic compounds (benzene, toluene, and xylene) has been performed in a hybrid surface/packed-bed discharge plasma reactor with Ag-Ce/g-Al2O3 catalyst at room temperature. The effect of relative air humidity on mixed VOCs degradation has also been investigated in both plasma-only and PPC systems. In comparison to the plasma-only system, a significant improvement can be observed in the degradation performance of mixed VOCs in PPC system with Ag-Ce/γ-Al2O3 catalyst. In PPC system, 68% benzene, 89% toluene, and 94% xylene were degraded at 800 J·L–1, respectively, which were 25%, 11%, and 9% higher than those in plasma-only system. This result can be attributed to the high catalytic activity of Ag-Ce/γ-Al2O3 catalyst to effectively decompose O3 and lead to generating more reactive species which are capable of destructing the VOCs molecules completely. Moreover, the presence of Ag-Ce/γ-Al2O3 catalyst in plasma significantly decreased the emission of discharge byproducts (NOx and O3) and promoted the mineralization of mixed VOCs towards CO2. Adding a small amount of water vapor into PPC system enhanced the degradation efficiencies of mixed VOCs, however, further increasing water vapor had a negative impact on the degradation efficiencies, which was primarily attributed to the quenching of energetic electrons by water vapor in plasma and the competitive adsorption of water vapor on the catalyst surface. Meanwhile, the catalysts before and after discharge were characterized by the Brunauer-Emment-Teller and X-ray photoelectron spectroscopy.