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The CO adsorption and subsequent reaction with preadsorbed NO(x) on Pd and K cosupported Mg-Al mixed oxides (Pd-K/MgAlO, 1/8/100 w/w) were investigated using in situ FTIR spectroscopy. During CO adsorption, a peculiar and well-defined IR band at 2160 cm(-1) was observed. Several elaborately designed experiments such as the competitive adsorption of CO and CO(2) demonstrated that the 2160 cm(-1) band was exclusively assigned to a carbonyl species on K sites due to the CO spillover from Pd to K, which results from a strong Pd-K interaction based on temperature-programmed reduction with H(2) experiments. Importantly, the spillover of CO is found to be involved in the reduction of preadsorbed NO(x) from temperature-programmed surface reactions with CO. Thus, all adsorbed NO(x) can be reduced by CO before desorption. Like the process of "pumping" CO by Pd from the atmosphere to "irrigate the field" of the nitrates/nitrites, the adsorbed NO(x) at not only K sites adjacent to Pd but also at the remote K sites can be reduced into N(2) and N(2)O effectively.  相似文献
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The soot combustion with NO(x) and/or O(2) on potassium-supported Mg-Al hydrotalcite mixed oxides under tight contact condition was studied using temperature-programmed oxidation (TPO), isothermal reaction and in situ FTIR techniques. The presence of NO(x) in O(2) favors the soot combustion at lower temperatures (<300 °C). However, a little suppression was observed at higher temperatures (>300 °C), which was accompanied by a substantial NO(x) reduction. The ketene (C═C═O) and isocyanate (NCO(-)) species were determined as the reaction intermediates. In NO(x) + O(2), NO(2) directly interacts with the free carbon sites (C═C*) through two parallel reactions: (1) NO(2) + C═C* → C═C═O + NO; (2) NO(2) + C═C* → NCO(-) + CO(2). The two reactions can proceed easily, which accounts for the promotion effect of NO(x) on soot combustion at lower temperatures. The further oxidation of NCO(-) by NO(2) or O(2) is responsible for the simultaneous reduction of NO(x). However, the reactions between NO(2) and C═C* are limited by the amount of free carbon sites, which can be provided by the oxidation of soot by O(2) at higher temperatures. The interaction of NO(x) and catalyst results in the formation of nitrates and nitrites, which poisoned the active K sites.  相似文献
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This study investigated the effects of dietary rumen‐protected lysine (RPLys) on milk yield and composition in lactating cows fed diets containing double‐low rapeseed meal. Twenty‐four cows were divided into three groups and fed one of three dietary treatments: 10% soya bean meal (SBM) diet (control), 15% double‐low rapeseed meal (DLRSM) diet and 15% DLRSM + 32 g/d RPLys (DLRSML) diet. The results showed that no differences (P > 0.05) were observed in milk yield, 4% fat correction milk (FCM), energy correction milk (ECM), protein yield, milk fat yield, milk fat, lactose yield and lactose between control and DLRSM. Supplementation with DLRSML increased (P < 0.05) milk yield, 4% FCM, ECM, and protein yield compared with the SBM. The results indicated that DLRSM and DLRSML might be used to substitute for SBM as a protein source in lactating cows, and the latter might be more beneficial to improve the performance.  相似文献
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