ALBERT

Description: Abstract The evolution of planetary boundary‐layer (PBL) was investigated using observations from laser ceilometer, eddy covariance system and automatic meteorological station in the north of Nanjing city during an air pollution episode in 2016‐2017 winter. Based on 7‐day observation under clean to polluted day, we recorded the temporal variations of backscatter signals observed by the ceilometer, and then inter‐compare planetary boundary‐layer height (PBLH) retrieved from individual methods. The results show that backscatter signal gradient, standard deviation, and wavelet transform analysis methods generated similar PBLH values and PBL diurnal variation patterns. Moreover, the PBL structure varied diurnally, with distinct patterns corresponding to clean and polluted days. Based on these measurements, the relationships between PBLH, weather conditions, and contaminants were analyzed. Results show that: on clean days, strong surface turbulence exchange makes the PBL fully developed and makes the PBLH increased sharply after sunrise, with a maximum of 1483 m; on polluted days, stable synoptic conditions and the weaker wind speeds facilitated the accumulation of air pollutants, leading to smaller net surface radiation and weaker turbulence. Consequently, these conditions during polluted days led to lower PBLH values, which were typically less than 900 m.

Description: An integrated continuous process, which combines catalytic distillation and extractive distillation in one column, is investigated for the synthesis of high-purity methylal from methanol and formalin in the presence of a cation-exchange resin catalyst. A feed with methanol:formaldehyde 2:1 molar ratio is chosen to evaluate the effects of operating parameters, such as extractant feeding position, ratio of extractant to feed, reflux ratio, and reboiler temperature, on the continuous synthesis of methylal. Under the optimum operating conditions and with water as extractant, the extractive catalytic distillation process operated continuously, producing a methylal purity of 98.7 % (H 2 O: 〈 1.30 %) with 98.0 % formaldehyde conversion. An integrated continuous process combining catalytic distillation and extractive distillation in one column is applied for high-purity methylal synthesis from methanol and formalin in the presence of a cation-exchange resin catalyst. Under optimum conditions, using water as extractant, the extractive catalytic distillation process provided a methylal purity of 98.7 % with 98.0 % formaldehyde conversion.

Description: An integrated continuous process, which combines catalytic distillation and extractive distillation in one column, is investigated for the synthesis of high-purity methylal from methanol and formalin in the presence of a cation-exchange resin catalyst. A feed with methanol:formaldehyde 2:1 molar ratio is chosen to evaluate the effects of operating parameters, such as extractant feeding position, ratio of extractant to feed, reflux ratio, and reboiler temperature, on the continuous synthesis of methylal. Under the optimum operating conditions and with water as extractant, the extractive catalytic distillation process operated continuously, producing a methylal purity of 98.7 % (H 2 O: 〈 1.30 %) with 98.0 % formaldehyde conversion. An integrated continuous process combining catalytic distillation and extractive distillation in one column is applied for high-purity methylal synthesis from methanol and formalin in the presence of a cation-exchange resin catalyst. Under optimum conditions, using water as extractant, the extractive catalytic distillation process provided a methylal purity of 98.7 % with 98.0 % formaldehyde conversion.

Description: A design approach based on diverse pinch point and mathematical programming for optimal integration of heat exchanger networks (HENs) is described. The effect of the dissimilar film heat transfer coefficients on the area target is considered by different pinch and composite curves. The approach combines insightful pinch analysis and rigorous mathematical programming, which enable systematic and automatic designs. A software platform is developed for the design of HENs. An example illustrates the application of the proposed approach. The article focuses on the integration of heat exchanger networks (HENs) with process streams of different heat transfer coefficients. A design approach based on a diverse pinch point and mathematical programming for optimal integration of HENs is described. A case study demonstrates the effectiveness of the proposed method. The developed software platform allows for the rapid solution of the HEN design problem.

Description: Soot oxidation with NO (in the absence of gas phase O 2 ) on potassium-supported Mg-Al hydrotalcite mixed oxides (K/MgAlO) was studied using a temperature-programmed reaction and in situ FTIR techniques. Nitrite and the ketene group were identified as the reaction intermediates and thus a nitrite-ketene mechanism was proposed in which surface active oxygen on K sites of K/MgAlO is transferred to soot by NO through nitrites. In the absence of gas phase O 2 , soot oxidation with NO at lower temperatures (below 450 °C) is limited by the amount of active oxygen on the K sites. This kind of active oxygen is not reusable but can be replenished in the presence of gas phase O 2 . Soot oxidation with NO on K/MgAIO was studied by temperature-programmed reaction and in situ FTIR. The nitrite and the ketene group were identified as the reaction intermediates and thus a nitrite–ketene mechanism was proposed, in which surface active oxygen on K sites is transferred to soot by NO through nitrites, forming the ketene group.

Description: Niobium and Ta concentrations in ultrahigh-pressure (UHP) eclogites and rutile from these eclogites and associated high pressure (HP) veins were used to study the behaviour of Nb–Ta during dehydration and fluid-rock interaction. Samples were collected through a ∼2 km profile at the Bixiling complex in the Dabie orogenic belt, Central-Eastern China. All but one eclogite away from veins (EAVs) display nearly constant Nb/Ta ratios ranging from 16.1 to 19.2, with an average of 16.9 ± 0.8 (2 SE), similar to that of their gabbroic protolith from the Yangtze Block. Nb/Ta ratios of rutile from the EAVs range from 12.7 to 25.3 among different individual grains, with the average values close to those of the corresponding bulk rocks. These observations show that Nb and Ta were not significantly fractionated by prograde metamorphism up to eclogite facies when no significant fluid-rock interaction occurs. In contrast, Nb/Ta ratios of rutile from eclogites close to veins (ECVs) are highly variable from 17.8 to 49.8, which are systematically higher (by up to 17) than those of rutile from the veins. These observations demonstrate that Nb and Ta were mobilized and fractionated during localized fluid flow and intensive fluid-rock interaction. This is strongly supported by Nb/Ta zoning patterns in single rutile grains revealed by in situ LA-ICP-MS analysis. Ratios of Nb/Ta in the ECV-hosted rutile decrease gradually from cores towards rims, whereas those in the EAV-hosted rutile are nearly invariable. Furthermore, the vein rutile shows Nb/Ta zoning patterns that are complementary to those in rutile from their immediate hosts (ECVs), suggesting an internal origin for the vein-forming fluids. The Nb/Ta ratios of such fluids evolved from low values at the early stage of subduction to higher values at later supercritical conditions with increased temperature and pressure. Quantitative modelling was conducted to constrain the compositional evolution of metamorphic fluids during dehydration and fluid-rock interaction focusing on Nb–Ta distribution. The modelling results based on our proposed multistage fluid phase evolution path can essentially reproduce the natural observations reported in the present study.

Description: Migmatites are predominant in the North Qinling orogen. However, the formation ages of the migmatites are poorly constrained. This paper presents a combined study of CL image, U-Pb age, trace element, and Hf isotope of zircon in migmatites from the North Qinling unit. In the migmatites, most zircon grains occur as new, homogeneous crystals, while some are present as overgrowth rims around inherited cores. Morphological and trace element features suggest that the zircon crystals are metamorphic and formed during partial melting. The inherited cores have oscillatory zoning and yield U-Pb ages of c . 900 Ma, representing their protolith ages. The early Neoproterozoic protoliths probably formed in an active continental margin, being a response to the assembly of the supercontinent Rodinia. The migmatite zircon yields Hf model ages of 1911 ± 20 to 990 ± 22 Ma, indicating the protoliths were derived from reworking of Paleoproterozoic to Neoproterozoic crustal materials. The anatexis zircon yields formation ages ranging from 455 ± 5 to 420 ± 4 Ma, with a peak at c . 435 Ma. Combined with previous results, we suggest that the migmatization of the NQ terrane occurred at c . 455 to 400 Ma. The migmatization was about 50 Ma later than the c . 490 Ma ultra-high pressure metamorphism, indicating that they occurred in two independent tectonic events. By contrast, the migmatization was coeval with the granulite-facies metamorphism and the granitic magmatism in the North Qinling unit, which collectively argue for their formation due to the northward subduction of the Shangdan Ocean. Ultra-high pressure rocks were distributed mainly along the northern margin and occasionally in the inner part of the North Qinling unit, indicating that they were exhumed along the northern edge and detached from the basement by the subsequent migmatization process. This article is protected by copyright. All rights reserved.