工程化学“产教融合”的实践——农药氟苯唑生产工艺的改进

随着当前教育改革的不断深化,应用型高校逐渐向着产教融合模式发展。以培养学生解决问题的能力为导向,对化学相关课程进行重新建设规划。课堂教学专注于对知识的理解和诠释,而企业则以生产成本和产品利润为导向,两者之间交流的缺乏会导致学生对课堂知识难以学以致用。在工程化学教学过程中,我们将农药氟苯唑生产实践与课堂教学相结合,作为教和学的研究课题,通过优化化学反应过程来提高生产效益。这些实践不仅完善了教师的教学内容,也加深了学生对基本原理的理解。在应用的过程中也极大地提高了学生们学以致用的兴趣。

Isotopic characteristics and source analysis of atmospheric ammonia during agricultural periods in the Xichuan area of the Danjiangkou Reservoir

Nitrogen deposition is an important means of exogenous nitrogen input in reservoir water.Agricultural activities around the reservoir lead to a sharp increase in the concentration of ammonia in the atmosphere,which poses a threat to the reservoir water body.Clarifying the contribution of agricultural ammonia release to atmospheric NH_(x)(gaseous NH_(3)and particulate NH_(4)^(+)),in the reservoir area can provide a theoretical foundation for local reactive nitrogen control.We collected atmospheric NH_(3)and NH_(4)^(+)samples during the agricultural periods and analyzed the isotopic characteristics of atmospheric NH_(x)and the contribution rates of different ammonia sources in the Xichuan area of the Danjiangkou Reservoir.The results showed that the initialδ~(15)N values of NH_(3)(-30.0‰to–7.2‰)and particulate NH_(4)^(+)(–33‰to+4.9‰for finer and coarser particles,respectively)are different,and their contribution ratios from dissimilar ammonia sources are also different,among which NH_(4)^(+)is more susceptible to meteorological factors.However,since the atmospheric NH_(x)in the Xichuan area is mainly gaseous NH_(3),the final sources of atmospheric ammonia nitrogen source depend on gaseous NH_(3).Agricultural sources(59%-74%)were the main NH_(3)sources in this area.Among them,the fertilizer use emission was dominant;it had the highest contribution rate in summer during the agricultural period and a more prominent impact in areas with less human interference.Reasonable regulation of the application of high-ammonia releasing fertilizer,especially during the agricultural period in summer,is an effective way to reduce the threat of atmospheric ammonia to water health.

Effect of copper precursors on CO oxidation catalyzed by CuO-CeO_(2) prepared by solvothermal method

In this paper,the CuO-CeO_(2) catalyst was prepared by a direct solvothermal method.The effects of different copper salt precursors(copper nitrate,copper acetate,copper sulfate) on the catalytic performa nce of the prepared catalyst fo r CO oxidation were investigated.The physical and chemical properties of the prepared catalysts were characterized by X-ray diffraction(XRD),Raman spectroscopy,N_(2)physical adsorption,inductively coupled plasma-atomic emission spectrometry(ICP-AES),X-ray photoelectron spectroscopy(XPS),temperature-programmed desorption analysis of CO(CO-TPD),in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTs),and temperature-programmed reduction with H_(2)(H_(2)-TPR).The results show that the CuO-CeO_(2)catalyst prepared with copper acetate as precursor(CC-A) exhibits the best catalytic activity for CO oxidation at low temperatures,with T50and T90values of 62 and 78℃ respectively,which is mainly attributed to its large specific surface area,pore volume,CO adsorption capacity,and large amount and strong reactivity of surface oxygen.However,the CuO-CeO_(2) catalyst prepared with copper nitrate as precursor(CC-N) displays better stability and resistance to water or CO_(2) poisoning than CC-A.

Low-temperature NH_(3)-SCR of NO_(x) over MnCeO_(x)/TiO_(2) catalyst:Enhanced activity and SO_(2) tolerance by modifying TiO_(2) with Al_(2)O_(3)

A series of TiO_(2)-Al_(2)O_(3) composites with Al/Ti molar ratios of 0.1,0.2,and 0.4 were synthesized by a coprecipitation method and used as supports to prepare supported MnCeO_(x) catalysts by an impregnation method.The physico-chemical properties of the samples were extensively characterized by N_(2) physisorption,X-ray diffraction,Raman spectroscopy,scanning electron micro scopy and energy-dispersive Xray spectroscopy element mapping,X-ray photoelectron spectroscopy,H_(2)-temperature programmed reduction,ammonia temperature programmed desorption,and in-situ diffuse reflectance infrared Fourier transform spectroscopy.The catalytic activity and resistance to water vapor and SO_(2) of the asprepared catalysts for the SCR of NO_(x) with NH_(3) were evaluated at 50-250℃ and GHSV of 80000 mL/(gcat·h).The results reveal that MnCeO_(x)/TiO_(2)-Al_(2)O_(3) exhibits higher activity and better SO_(2) tolerance than MnCeO_(x)/TiO_(2).Combining with the characterization results,the enhanced activity and SO_(2) tolerance of MnCeO_(x)/TiO_(2)-Al_(2)O_(3) can be mainly attributed to higher relative concentrations of Mn4+and chemisorbed oxygen species,stronger reducibility,and larger adsorption capacity for NH_(3) and NO,which originate from the larger specific surface area and pore volume,higher dispersion of Mn and Ce species compared with MnCeO_(x)/TiO_(2).Moreover,in situ DRIFTS was used to investigate the reaction mechanism,and the results indicate that the NH_(3)-SCR reaction over MnCeO_(x)/TiO_(2) and MnCeO_(x)/TiO_(2)-Al_(2)O_(3) takes place by both the E-R and L-H mechanisms.

Research progress on bulk nanobubbles

There are still fundamental problems lying in the basic research of bulk nanobubbles.Are the bulk nanobubbles reported in the literature nano scale bubbles or contaminants in fact?At present,there is not yet sufficient experimental evidence to show that the bulk nanoparticles are only gas bubbles but not other nano scale contaminants.If they are indeed nanobubbles,what causes the bulk nanobubbles observed in the literature to be much more stable than being predicted by the Epstein-Plesset theory?This paper firstly discusses the contradiction between the traditional theory prediction and the observed lifetime of the bulk nanobubbles,and then discusses whether the so-called nanobubbles are gas aggregates.We review the existing typical models,and the influence of different conditions on the stability of bulk nanobubbles,for paving the road to a clear understanding of the stability mechanism of bulk nanobubbles.In addition,the representative production methods and characterization methods of bulk nanobubbles are discussed in order to offer some guidance to their wide range of commercial applications.