ITSTUDIES ON THE EFFECT OF UREA ON THE COMPATIBILITY OF PMMA/PVC MIXTURES IN DMF BY A DILUTE- SOLUTION VISCOMETRY METHOD

The interaction between poly(methymethacrylate) (PMMA) and poly(vinyl chloride) (PVC) has been studied indilute urea solutions of dimethylformamide (DMF) at 28℃ using a dilute solution viscometry method. The results show thatthe polymer mixtures are compatible in DMF solution in the absence of urea. The influence of urea addition on the degree ofcompatibility of the polymer mixtures has been studied in terms of the compatibility parameters (△b_m and △[η]_m). It wasfound that the compatibility of the polymer mixtures is decreased with increasing urea addition, passing through a minimumat 0.5 M urea.

Homogeneous Synthesis and Characterization of Quaternized Cellulose Derivatives in NaOH-urea Aqueous Solutions

Quaternized cellulose( QC) derivatives were synthesized by reacting cellulose with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride( CHPTAC) in an aqueous solution of Na OH-urea. The chemical structures and physical properties of the obtained QC derivatives were characterized using nitrogen content analysis,Fourier transform infrared spectroscopy( FT-IR),~1H-nuclear magnetic resonance(1H-NMR),X-ray diffraction( XRD),and thermal gravity analysis( TGA). The FT-IR and ~1H-NMR results confirmed the successful introduction of cationic quaternary ammonium groups into the main chain of cellulose. A series of QC derivatives with the degree of substitution( DS) values ranging from 0. 33 to 0. 80 were derived by adjusting the molar ratio of CHPTAC to anhydroglucose unit( AGU) of cellulose,concentration of cellulose in the Na OH-urea solution,as well as reaction temperature and time. According to the DS values of the QC derivatives,the optimized synthetic conditions were as follows: 25℃ reaction temperature,3% cellulose in Na OH-urea solution,the molar ratio of etherification agent to glycosidic cellulose of 15∶ 1,and 12 h reaction time. The TGA and XRD results revealed that the crystalline structure was destroyed during etherification,and the thermal stability of the QC derivatives was lower than that of cellulose.

Structure Elucidation of Hydroxypropyl Cellulose Homogenously Prepared from NaOH/Urea Aqueous Solution

Hydroxypropyl celluloses(HPC) were homogenously synthesized by the reaction of cellulose with propylene oxide in NaOH/urea aqueous solution.Water-soluble HPC with molar degree of substitution(MSNMR) in the range of 0.52~0.78 was prepared from microcrystalline cellulose,cotton linters,and spruce sulfite pulp.The structure of the HPC samples was characterized by means of FT-IR,NMR,gas chromatography(GC),and size exclusion chromatography(SEC) analyses.Three types of cellulose samples with different molecular weights were found to dissolve well in the NaOH/urea solvent with no obvious differences in reactivity and regioselectivity.The relative reactivity of hydroxyl groups in the glycosyl unit was in the following order:O-6>O-2>O-3.In addition,the results of the study indicated that the tandem reaction during hydroxypropylation could be ignored.

Effect of seed soaked with urea solution on the cold tolerance of rice seedlings

In the Yangtze river aera,the first crop of indi-ca rice is sown in late Mar to early Apr andtransplanted in early May.Usually,seedlingsperish when abnormal low temperature of 6-10℃ lasted for 3 d or longer.The effect ofsocking seed with urea solution on increasingthe cold tolerance at the seedling stage was

尿素水溶液(AUS32)生产中的质量控制

柴油发动机氮氧化物还原剂尿素水溶液(AUS32)通常用于柴油车SCR系统中的还原剂,是控制柴油发动机污染物排放的重要产品,其质量好坏直接关系到柴油车尾气排放及SCR系统的使用寿命。针对车用尿素溶液生产过程中的质量控制,从原材料(尿素颗粒、水、包装)、生产过程、产品质量检验等方面进行总结,为车用尿素生产企业的产品质量控制提出建议及参考,促进车用尿素水溶液产品质量不断提高。

尿素水解制氨系统尿素储存优化与应用

为解决尿素颗粒储存系统劳动强度大、工作环境差及尿素料仓板结的问题,以某电厂为例,对尿素输送、储存工艺进行了优化设计。当尿素耗量大时,采用气力输送方式将尿素颗粒直接输送到尿素溶解罐内配制成尿素溶液,以尿素溶液储存代替尿素颗粒储存,解决了尿素储存的问题,并提高自动化水平和劳动生产率,同时避免在空气湿度大的环境中,尿素颗粒会在料仓内板结而影响后续系统的运行问题。

车用尿素水溶液产品质量分析

车用尿素水溶液作为柴油车尾气处理液,是柴油车尾气达标的必备环保产品,能减少交通运输对环境的污染,应用前景广阔。从近几年诸多监督抽查情况看,产品质量仍需提高。因此,文章通过对该产品的全部指标进行分析,结合行业现状,提出相应的改进建议。

含腐殖酸液体肥(UAN型)在叶菜上的应用

为考察含腐殖酸液体肥(UAN型)在叶菜上的应用效果,以竞品液体肥为对照,以香叶饺子菜、上海青、生菜、菠菜为试验对象,开展了田间小区试验。结果表明:与对照处理相比,冲施含腐殖酸液体肥(UAN型)处理的4种叶菜的株高、地上部和地下部鲜质量均高于对照处理的;上海青和菠菜的叶片叶绿素相对含量(SPAD值)低于对照处理的,香叶饺子菜和生菜的叶片SPAD值高于对照处理的;4种叶菜的维生素C含量低于对照处理的,而硝酸盐含量高于对照处理的。

柴油车尿素溶液品质在线检测方法研究

选择性催化还原(SCR)是目前满足柴油机排放法规的主流后处理技术。在SCR系统中,尿素水溶液被用作将NOX转化为N2的还原剂,以确保发动机排放达到法规标准。为了实现发动机排放的实时监测,保证尿素品质满足要求,提出了一种基于车载诊断(OBD)系统数据的柴油车尿素溶液品质检测方法。通过对国六柴油车SCR系统工作原理和尿素喷射量计算方法的深入分析,提出了基于NH3影响偏差因子的尿素品质检测方法。通过对一辆柴油车添加三种不同浓度尿素溶液进行实际道路行驶测试,验证了该方法的可行性。结果表明,所提方法能够有效检测尿素品质,并为发动机排放的实时控制提供了可靠的数据支持。

基于NaOH-Urea预处理的微纤化纤维素制备研究

为开发高效制备微纤化纤维素的方法,探讨了基于氢氧化钠-尿素(NaOH-Urea)混合溶液对玉米芯微晶纤维素进行预处理后采用机械法处理的微纤化纤维素制备工艺。采用傅里叶变换红外光谱仪(FT-IR)、X射线衍射仪(XRD)、热重分析仪(TG)、场发射扫描电镜(FESEM)对制备的微纤化纤维素化学结构、结晶度、热稳定性及微观形貌进行表征。结果表明,制备的微纤化纤维素为纤维素Ⅰ型;微纤化纤维素的结晶度为60. 4%,得率高达78%;微纤化纤维素结晶度较玉米芯微晶纤维素有所提高;制备的微纤化纤维素表现出优良的热稳定性,热降解温度达238℃;微纤化纤维素呈棒状,直径为5～20 nm,长度大于200 nm。

Numerical Simulation of Urea Based SNCR Process in a Trinal-Sprayed Precalciner

In order to study the combustion characteristics,NOx emission and NH3 slip in a new trinal-sprayed precalciner,the simulations of combustion and aqueous urea solution based selective non-catalytic reduction(SNCR)process were conducted by computational fluid dynamics in this precalciner,the effects of different injection heights,different injection flow rates and stratified injection under different flow rates on SNCR process were studied.The results showed that the flow field was symmetrically distributed in the precalciner,and the flue gas from the rotary kiln formed the recirculation region on both sides of the cone body,which increased the residence time of the solid particles.The temperature was mainly between 1100 K and 1250 K in the middle and upper column of the precalciner,which met the demand of the pulverized coal combustion and raw material decomposition.The concentration of NO at the outlet of the precalciner was 559 ppm,moreover,different injection heights and different injection flow rates had a strong influence on NOX removal efficiency and NH3 slip.The aqueous urea solution should be injected at SNCR-1 to prolong the residence time of NH3,and injection flow rate had an optimal flow rate but not the higher the better.When the injection flow rate under stratified injection was 0.019 kg/s,which could play a better optimization role on NO removal efficiency on the basic of the injection flow rate.In consideration of cost effective,a stratified injection with an injection flow rate of 0.019 kg/s and an injection height of 20 m,25 m and 30 m was suggested as a compromise of a satisfactory NOx reduction rates and reasonable NH3 slip.Under this condition,numerical simulation result showed that NOx concentration at the outlet of precalciner was 297.27 mg/Nm3 and NH3 slip was 4.67 mg/Nm3,meeting emission standard.

Electrochemical Performance of Solid Polymer Electrolyte PEO_(20)-LiTf-Urea_(1.5)

A new solid polymer electrolyte PEO20-LiTf-Urea1.5 was prepared by solution casting technique. The energy of frontier orbitals for the components of the electrolyte was predicted by quantum chemistry calculations, and TG stability and electrochemical features were measured. Urea exhibited a lower HOMO energy than PEO, implying its enhanced stability against electrochemical oxidation. Experimentally addition of urea increases the ionic conductivity, which guarantees conductivity requirement for lithium ion batteries. It also results in significant improved electrochemical stability with good thermal stability. Favorable lithium stripping/plating performance is yielded, and it confirms the good stability of the solid electrolyte interphase for the PEO20-LiTf-Urea1.5 system.

尿素硝酸铵溶液对玉米产量、养分吸收及潮土氮素积累的影响

采用大田试验,设置对照(CK,不施氮肥)、尿素处理(U,纯N 240 kg/hm^(2))、尿素硝酸铵溶液处理(UAN,纯N 240 kg/hm^(2))、80%UAN处理(80%UAN,纯N 192 kg/hm^(2))和80%UAN配施双氰胺处理(80%UAN+DCD,DCD用量为12 kg/hm^(2))共5个处理,研究不同用量UAN对玉米产量、养分吸收及潮土氮素积累的影响。结果表明:U处理和UAN各处理间玉米穗长、行粒数、千粒重和产量无显著差异,但UAN各处理株高均显著高于U处理。U及UAN各处理间玉米总吸氮量无显著差异,但U、UAN处理氮素农学效率、氮素利用率和氮素偏生产力显著低于80%UAN和80%UAN+DCD处理。各处理土壤硝态氮含量表现为U>UAN>80%UAN+DCD>80%UAN。UAN处理土壤铵态氮含量明显高于其他施氮处理,80%UAN+DCD处理土壤铵态氮含量高于80%UAN处理。各施氮处理土壤铵态氮积累量为0.10~0.73 kg/hm^(2),UAN处理积累量最高,80%UAN+DCD处理最低;各施氮处理土壤硝态氮积累量为5.70~9.19 kg/hm^(2),U处理积累量最高,80%UAN处理最低。等氮量投入条件下,氮肥形态对玉米产量及构成因素、氮素农学效率、氮素利用率和氮素偏生产力无显著影响;80%UAN及添加DCD可显著提高氮素农学效率、氮素利用率和氮素偏生产力。UAN减量及配施DCD可降低土壤中硝态氮和铵态氮的迁移积累。综合农学和环境效应来看,在本试验条件下,UAN减量20%配施DCD是一种较为科学合理的施肥管理方式。

In-situ assembly of 2D/3D porous nickel cobalt sulfide solid solution as superior pre-catalysts to boost multi-functional electrocatalytic oxidation

In this work,we fabricated an efficient pre-catalyst based on(Ni,Co)S2solid solution with hierarchical architecture and high porosity to boost urea oxidation reaction and electrocatalytic oxidation of organic small molecules.The interaction between Ni and Co can optimize the electronic structure,resulting in the improved conductivity and accelerated charge transfer rate.The 2D/3D architecture can enrich more active species and endow the mass and electron transport to facilitate the surface oxidation and the following catalytic process.Post-structure and catalytic characterizations confirm the surface oxidation of(Ni,Co)S_(2)during the stability test,and the in-situ formed Co(Ni)based(oxy)hydroxides exhibit superior catalytic activity and facilitated charge transfer ability.As a result,the optimal(Ni,Co)S_(2)solid solution pre-catalyst displays facilitated catalytic behavior and good stability for multifunctional electrocatalytic oxidation,in which a high conversion of benzyl alcohol(97.50%),a good selectivity to benzoic acid(93.78%)and a satisfied faraday efficiency(91.86%)can be achieved.

基于计算流体力学的柴油机选择性催化还原系统尿素水溶液喷雾特性分析

为探究影响柴油机排气管尿素水溶液(urea water solution,UWS)雾化效果的因素,搭建了UWS喷射试验台架,通过激光粒度仪测得尿素液滴粒径分布,并运用Rosin-Rammler函数对试验获得的累积粒径分布进行非线性拟合,利用计算流体力学(computational fluid dynamics,CFD)软件对柴油机负荷工况、UWS喷射温度和排气管壁温3种不同因素对UWS喷雾雾化特征、NH3浓度分布及液膜形成的影响进行仿真计算。结果表明:低负荷工况下的排气流量和温度低,UWS喷入量少,尿素液滴分解NH3的速率较低,80 ms时刻NH3主要分布在排气管中游;中高负荷工况,排气温度高、UWS喷入量多,有利于尿素蒸发热解生成NH3,该时刻NH3浓度区域偏离轴线,贴近排气管上表面;喷雾液滴粒径随UWS喷射温度的升高而减小,范围在1~12μm,空间内NH3浓度小幅增加,液膜沉积率随喷射温度升高显著降低;排气管壁温对UWS喷雾液滴粒径和蒸发热解速率影响较大,壁温升高加快了液滴粒径减小的速度,当壁面温度为473K时,150ms时刻下液滴粒径主要集中在30μm以下,附着壁面的液膜厚度明显减小直至消失,尿素结晶问题得以改善。

HNCO hydrolysis performance in urea-water solution thermohydrolysis process with and without catalysts

The thermolysis of urea-water solution and its product, HNCO hydrolysis is investigated in a dual-reactor system. For the thermal decomposition below about 1073 K, the main products are ammonia (NH3) and isocyanic acid (HNCO) whereas at higher temperatures the oxidation processes take effect and the products include a low concentration of nitric oxide (NO) and nitrous oxide (N2O). The gas HNCO is quite stable and a high yield of HNCO is observed. The ratio of NH3 to HNCO increases from approximately 1.2 to 1.7 with the temperature. The chemical analysis shows that H radical is in favor of HNCO hydrolysis by instigating the reaction HNCO+H·→·NH2+CO and high temperature has positive effect on H radical. The hydrolysis of HNCO over an alumina catalyst made using a sol-gel process (designated as γ-Al2O3) is investigated. The conversion of HNCO is high even at the high space velocities (6×105 h-1) and low temperatures (393–673 K) in the tests with catalysts, which enhances HNCO hydrolysis and raises the ratio of NH3 to HNCO to approximately 100. The pure γ-Al2O3 shows a better catalytic performance than CuO/γ-Al2O3. The addition of CuO not only reduces the surface area but also decreases the Lewis acid sites which are recognized to have a positive effect on the catalytic activity. The apparent activation energy of the hydrolysis reaction amounts to about 25 kJ/mol in 393–473 K while 13 kJ/mol over 473 K. The overall hydrolysis reaction rate on catalysts is mainly determined by external and internal mass-transfer limitations.

Light weight, mechanically strong and biocompatible α-chitin aerogels from different aqueous alkali hydroxide/urea solutions

Light weight and mechanically strong α-chitin aerogels were fabricated using the sol-gel/self-assembly method from α-chitin in different aqueous alkali hydroxide(KOH, Na OH and Li OH)/urea solutions. All of the α-chitin solutions exhibited temperature-induced rapid gelation behavior. 13 C nuclear magnetic resonance(NMR) spectra revealed that the aqueous alkali hydroxide/urea solutions are non-derivatizing solvents for α-chitin. Fourier transform infrared(FT-IR), X-ray diffraction(XRD) and cross-polarization magic angle spinning(CP/MAS) 13 C NMR confirmed that α-chitin has a stable aggregate structure after undergoing dissolution and regeneration. Subsequently, nanostructured α-chitin aerogels were fabricated by regeneration from the chitin solutions in ethanol and then freeze-drying from t-Bu OH. These α-chitin aerogels exhibited high porosity(87% to 94%), low density(0.09 to 0.19 g/cm^3), high specific surface area(419 to 535 m^2/g) and large pore volume(2.7 to 3.8 cm^3/g). Moreover, the α-chitin aerogels exhibited good mechanical properties under compression and tension models. In vitro studies showed that m BMSCs cultured on chitin hydrogels have good biocompatibility. These nanostructured α-chitin aerogels may be useful for various applications, such as catalyst supports, carbon aerogel precursors and biomedical materials.

SCR系统在船舶上的应用

结合SCR系统在船舶上的应用及船舶排放法规TIER III和SCR化学反应基本原理,介绍SCR系统设备组成及船舶高/低SCR系统的选型、系统设计、工厂联合试验、船级社证书获取、船舶安装、船舶试验等,以期推动船舶SCR系统的设计及实船安装应用,通过技术进一步推广,最终实现经济和商业利益的最大化。

脲醛预缩液(UFC)生产脲醛胶的优势

介绍了生产脲醛预缩液(UFC)并以此为原料生产脲醛胶的工艺过程。生产脲醛预缩液的工艺过程是以甲醇为原料,用铁钼催化剂催化氧化原料气,制得高浓度甲醛气体,在甲醛吸收塔中用尿素溶液一次吸收制成。利用UFC生产脲醛胶,具有生产工艺简单、原料易得、产品抗老化能力强等优点。

大麻落麻纤维素膜制备及性能

将大麻长麻纺过程中产生的落麻溶解在氢氧化钠/硫脲/尿素水溶液中得到再生纤维素纺丝原液,通过相转化法制备出大麻落麻再生纤维素膜,并对大麻落麻纤维素的提取、溶解性能、成膜效果及再生纤维素膜的结构和性能进行研究。根据各项研究结果得出:4%浓度碱液处理后的大麻落麻纤维的纤维纯度较高,一定条件下能很好的溶解于氢氧化钠/硫脲/尿素溶剂中;当纤维素浓度达到6%时,可得到形貌较好的纤维素薄膜;纤维素经溶解制膜后,纤维素膜在较大程度上仍保留着纤维素的特征,纤维素晶型从纤维素Ⅰ转变为纤维素Ⅱ,纤维素薄膜的表面呈波纹状,并具有不均匀的多层结构。