Elucidating the effect of barium halide promoters on La_(2)O_(3)/CaO catalyst for oxidative coupling of methane

The industrialization of oxidative coupling of methane(OCM)is restricted by the low once through yield of C_(2)hydrocarbons.Recently,the halogen-assisted OCM process has been attempted to overcome this issue,but the reaction stability was poor due to the rapid loss of gas-phase halides or molten alkali halides.In this work,the barium salts,particularly barium halides(BaCl_(2)and BaF_(2)),were demonstrated to be efficient promoters to improve the OCM reactivity of La_(2)O_(3)/CaO catalyst by increasing both C_(2)selectivity and C_(2)H_(4)/C_(2)H_(6)ratio,and simultaneously achieving outstanding reaction stability.The promoting mechanism can be understood in two aspects.On the one hand,the introduction of barium salts increased the amount of surface electrophilic oxygen species,serving as the alkaline active sites for selective methane activation.On the other hand,the barium halide additives induced the in-situ formation of methyl halide intermediates facilitating C_(2)H_(6)dehydrogenation,and their intimate contact with catalyst substrate restricted the rapid halogen loss and thereby improved the catalytic stability.This work not only provides a class of efficient OCM catalyst,but also offers a highly stable halogen-assisted reaction strategy.

Effects of the transverse electric field on nanosecond pulsed dielectric barrier discharge in atmospheric airflow

In this paper,an asymmetric electrode geometry(the misalignment between the ends of highvoltage and grounded electrodes)is proposed in order to investigate the effects of the transverse electric field on nanosecond pulsed dielectric barrier discharge(DBD).The results show that diffuse discharge manifests in the misaligned region and the micro-discharge channel in the aligned region moves directionally.Moreover,the diffuse discharge area increases with the decrease of the discharge gap and pulse repetition frequency,which is consistent with the variation of the moving velocity of the micro-discharge channel.When airflow is introduced into the discharge gap in the same direction as the transverse electric field,the dense filamentary discharge region at the airflow inlet of asymmetric electrode geometry is larger than that of symmetric electrode geometry.However,when the direction of the airflow is opposite to that of the transverse electric field,the dense filamentary discharge region of asymmetric electrode geometry is reduced.The above phenomena are mainly attributed to the redistribution of the space charges induced by the transverse electric field.

Neighborhood Modularization‑based Artificial Bee Colony Algorithm for Disassembly Planning with Operation Attributes

The recycling and remanufacturing of end-of-life products are significant for environmental protection and resource conservation.Disassembly is an essential process of remanufacturing end-of-life products.Effective disassembly plans help improve disassembly efficiency and reduce disassembly costs.This paper studies a disassembly planning problem with operation attributes,in which an integrated decision of the disassembly sequence,disassembly directions,and disassembly tools are made.Besides,a mathematical model is formulated with the objective of minimizing the penalty cost caused by the changing of operation attributes.Then,a neighborhood modularization-based artificial bee colony algorithm is developed,which contains a modular optimized design.Finally,two case studies with different scales and complexities are used to verify the performance of the proposed approach,and experimental results show that the proposed algorithm outperforms the two existing methods within an acceptable computational time.

NaOH-NaCl亚熔盐法活化含钾岩石制备SOD沸石

为了实现含钾岩石的高效利用,以NaOH-NaCl混合碱为助剂进行亚熔盐法活化含钾岩石的研究。采用X射线衍射(XRD)、扫描电镜(SEM)及滴定法对反应前后的产物组成进行分析。结果表明,含钾岩石活化的适宜条件为:m(NaOH)/m(potassic rocks)=0.7、m(NaCl)/m(potassic rocks)=0.7、m(H2O)/m(potassic rocks)=1.0、反应温度160℃,反应时间120 min。在该条件下,K+浸出率可达92%,碱浓度下降至41wt%,低于常规亚熔盐体系的介质浓度,活化后产物为SOD沸石。通过分析合成后母液组成,设计母液的循环工艺,实现NaCl的循环利用。该法显著减少了亚熔盐活化含钾岩石过程中的碱用量,并实现矿石的高效活化,为含钾岩石的综合利用提供新途径。

苦卤合成碱式硫酸镁晶须及后序分离工艺

用苦卤与工业液碱NaOH水热反应合成碱式硫酸镁(MOS)晶须,考察了原料配比、反应温度、液碱浓度及反应时间对液相组成和产品形貌的影响,用XRD和SEM等手段对产品进行表征,并对反应后母液进行钾盐和钠盐分离。结果表明,适宜的MOS合成条件为Mg^2+与OH^-摩尔比1:1.5及NaOH浓度4 mol/L、反应温度200℃、反应时间7 h。合成晶须后的母液按Mg2+与OH-理论摩尔比1:2反应,使母液中Mg2+完全转化为Mg(OH)2晶体。除镁后母液根据0和25℃时Na^+, K+//Cl^-, SO42--H2O四元体系相图、25和100℃时NaCl-KCl-H2O三元体系相图,通过蒸发浓缩结晶和低温结晶分离出NaCl, Na2SO4·10H2O和KCl。

聚丙烯酸复合铝改性膨润土制备及其对Cr(Ⅵ)的吸附

为改善膨润土对Cr(Ⅵ)的吸附性能,用铝、丙烯酸聚合及十六烷基三甲基溴化铵改性合成聚丙烯酸复合铝改性膨润土。采用X射线衍射、红外光谱和扫描电子显微镜对天然膨润土和改性膨润土进行表征。结果表明,在25℃、溶液pH=5~6时,0.5g吸附剂对200 mL浓度为20 mg/L Cr(Ⅵ)的平衡吸附量为1.996 mg/g,平衡吸附时间为130 min,且固液分离容易。吸附过程较好地符合Lagergren二级吸附动力学方程和Freundlich等温吸附方程,颗粒状吸附剂对Cr(Ⅵ)的吸附以络合吸附为主。

273 K及323 K条件下NaCl–NaBr–CH_(3)OH三元体系相平衡研究及其应用

为了对苦卤结晶析出的Na(Cl,Br)固溶体中氯化钠组分和溴化钠组分进行分离,测定了NaCl–NaBr–CH_(3)OH三元体系在273及323K温度时的溶解度数据,根据测得的液相点和湿渣相点确定了对应的固相点,由此绘制出了两个温度下的相图。结果显示,273及323 K温度下该三元体系的相图特征相似,均只有一个共饱点、两条饱和溶解度曲线,对应的固相结晶区有三个:NaCl纯盐结晶区、NaCl和Na(Cl,Br)固溶体共结晶区、Na(Cl,Br)固溶体结晶区。NaBr在无水甲醇中溶解度的增大导致NaCl溶解度大幅减小,说明NaBr对NaCl产生了较强的盐析效应,273 K时两种溶质在甲醇中的溶解度均比323 K时的溶解度大。依据273和323 K的NaCl–Na Br–CH_(3)OH体系相图及298 K的NaCl–NaBr–H_(2)O体系相图设计了分离Na(Cl,Br)固溶体中氯化钠和溴化钠的工艺。

磷化渣废液除锌制备高纯度磷酸三钠

为了实现磷化渣碱溶后所得废液的综合利用,采用中和沉淀法和硫化钠沉淀法去除磷化渣废液中的杂质锌,对中和沉淀法和硫化钠沉淀法的工艺条件进行优化,并由此设计磷化渣废液除锌制备高纯度磷酸三钠的生产工艺。对于中和沉淀法,在反应体系pH=8.85,反应时间为10 min时,Zn^(2+)去除率可达97.96%;对于硫化钠沉淀法,在反应体系pH=6.85,硫化钠投加量与Zn^(2+)的摩尔比为1:1,反应时间为10 min时,Zn^(2+)去除率可达99.80%。相比于中和沉淀法除锌制备磷酸三钠工艺,硫化钠沉淀法除锌制备磷酸三钠工艺具有更高的磷酸三钠纯度,为98.85%,固相产品中Zn^(2+)含量更低,仅为0.0004%,符合化工行业分析纯标准。该工艺大幅度地回收了磷化渣废液中的PO_(4)^(3-)离子和Na^(+)离子,为实现磷化渣综合利用的工业化提供新思路。