聚丙烯中空纤维支撑液膜提溴研究

以聚丙烯为膜材料、煤油为有机溶剂构成支撑液膜体系,研究了工艺条件对提溴传质过程的影响。结果表明,吸收液甲酸钠的浓度为0.1 mol/L时吸收效果较好;脱溴效率和传质系数均随原料液pH的增大而明显下降;原料液流量和吸收液流量越大,传质系数增大,脱溴率升高,在原料液体积流量达到80 L/h时,传质系数稳定在3.0×10-6m/s;原料液温度升高,溴在煤油和水中的分配系数升高,传质速度加快,脱溴率增加。     

木聚糖酶酶活的具体测定方法

介绍和比较了测定木聚糖酶酶活的 3种方法 ,详述了工作曲线法测定木聚糖酶酶活的具体操作方法及注意事项 ,并提供了实际应用     

农地乐52．25％乳油防治甜菜夜蛾田间药效试验与示范

试验结果表明,农地乐 ５２．２５ＥＣ防治甜菜夜蛾速效性好于对照药剂抑太保和除尽,药后 １ｄ的防效,１０００、６６７倍液达 ８０％以上,５００倍液达 ９０％以上。药后 ７ｄ的防效,１０００、６６７倍液为 ９１．４％～９３．３％,与抑太保 １０％乳油 １０００倍液相当;５００倍液为 ９６．７％,与除尽相当。农地乐 ５２．２５ ＥＣ防治甜菜夜蛾的持效期为 ７～８天。农地乐对作物安全。示范面积２．１× １０３ｈｍ２,平均防 效达 ８５％以上。农地乐 ５２．２５ ＥＣ已成为冀东防治甜菜夜蛾的首选药剂。     

高密度聚乙烯阻燃性能的研究

研究了含卤阻燃剂、无机阻燃剂、稳定剂、氯化聚乙烯和不同分子量的基础树脂对高密度聚乙烯的阻燃性和力学性能的影响。     

响应面分析法优化铝酸锶长余辉发光材料制备工艺研究

采用高温固相法制备出初始发光亮度高、余辉时间长的SrAl₂O₄：Eu ²⁺,Dy ³⁺长余辉发光材料,对其发光性能进行了研究。以初始发光亮度为响应指标,采用响应面分析法确定了制备初始发光亮度高的铝酸锶长余辉发光材料最优工艺条件：烧结温度为1 306.74 ℃、激活剂物质的量分数为0.03%,辅助激活剂物质的量分数为0.03%,助熔剂物质的量分数为0.28%,在此条件下得到的初始亮度实际测量值为2 991 mcd/m ²,与理论预测值2 998.71 mcd/m ²基本吻合。该研究可为制备初始发光亮度高、余辉时间长的铝酸锶长余辉发光材料提供参考。     

异烟肼衍生物对聚L-乳酸性能的影响

以异烟肼和均苯三酸为原料合成了新型均苯三酸三异烟肼,考察了其对聚L-乳酸(PLLA)结晶性能和热稳定性的影响。结果表明:均苯三酸三异烟肼起到了异相成核的作用,能有效提升PLLA的结晶速率,其中添加质量分数2.0%的均苯三酸三异烟肼可使PLLA有最大非等温结晶焓,但过量的均苯三酸三异烟肼却不利于PLLA的结晶。均苯三酸三异烟肼的加入不会改变PLLA的热分解行为,但随着均苯三酸三异烟肼含量的增加,其起始分解温度下降。     

基于钠基吸附剂的烟气脱碳系统余热利用研究

针对基于钠基固体吸附剂的燃烧后脱碳技术应用于燃煤电厂后综合能耗偏高的问题,本文提出与供热机组结合的碳捕集/供热双机组系统,利用低温热网回水回收系统低品位余热。依据双机组的抽汽混合与否构建了两种系统流程,分析了两种不同方案下的系统性能。研究结果表明,在有效回收脱碳系统碳酸化反应余热后,独立抽汽方案中碳捕集综合能耗从4.05GJ/t CO₂降低至1.26GJ/t CO₂,而混合抽汽方案中碳捕集综合能耗降低至1.13GJ/t CO₂,同时双机组系统的热网供热量较单供热机组分别增加了67.5%和72.8%,经济效益显著。分析了混合抽汽方案的系统中碳捕集综合能耗随相关运行参数变化的规律,发现碳酸化反应温度和热网回水温度因为能够直接影响系统余热利用程度因而更易对碳捕集综合能耗产生影响。     

Effect of shielding rates on upward flame spread over extruded polystyrene foam in vertical channel and heat transfer mechanism

Fire hazard of extruded polystyrene (XPS) thermal insulation materials has aroused public concern. In order to develop flame spread theory and the guideline for fire risk assessment of XPS, an experimental study on upward flame spread behavior and heat transfer mechanism of XPS in a vertical channel with different frontal shielding rates was conducted. Maximum temperature at the place 2 cm from XPS surface and at the center of channel first increase and then decrease as the shielding rate rises. The former is higher than the latter. Experimental value of average flame height rises as the shielding rate increases. A model for predicting the flame height is built, and the predicted results are consistent with the experimental results. Moreover, the relation between flame height and pyrolysis height under different shielding rates is obtained. The flame spread rate rises as the shielding rate increases. A prediction model of flame spread rate is established, and its prediction results are more accurate compared with those from previous models. The model also predicts that radiative heat transfer is the dominant heat transfer mode, accounting for 93% of the total heat transfer. This work is beneficial for fire risk assessment and fire safety design of building façade.     

Malic acid production from renewables: a review

Malic acid derived from fossil resources is currently applied in the food and beverage industries with a medium global production capacity. However, in the transition from a fossil-based to a bio-based economy, biotechnologically produced l -malic acid may become an important platform chemical with many new applications, especially in the field of biopolymers. In this review, currently used petrochemical production routes to dl -malic acid are outlined and insights into possible bio-based alternatives for microbial l -malic acid production are provided. Besides ecological reasons, the possibility to produce enantiopure l -malic acid by microbial fermentation is the biggest advantage over chemical synthesis. State-of-the-art and open challenges concerning production host engineering, substrate choice and downstream processing are addressed. With regard to production hosts, a literature overview is given covering the leading natural production strains of Aspergillus, Ustilago and Aureobasidium, as well as Escherichia coli as the most important engineered recombinant host. The utilization of renewable substrates as an alternative to glucose is emphasized in particular as a key aspect for a competitive bio-based production. Out of the alternative substrates discussed in this review, the industrial side-streams crude glycerol and molasses seem to be most promising for large-scale l -malic acid production. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Fabrication of high-purity HfSi2 powder via molten salt-assisted magnesium thermal reduction

In this work, high-purity HfSi₂ powders were successfully fabricated via a molten salt-assisted magnesium thermal reduction method using HfO₂ and Si as raw materials. The effects of reaction temperature and time on the formation of HfSi₂ were systemically investigated. The morphological and phase composition of as-prepared HfSi₂ powders were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen/oxygen determinator. The results indicated that as-obtained HfSi₂ powders possess the orthorhombic structure with approximately 6.4 μm in size and the oxygen content as low as 0.20%. This work can provide a novel route to fabricate the high-purity transition metal silicides powders.