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排序方式: 共有60条查询结果,搜索用时 15 毫秒
1.
三氟化硼-苯甲醚的分解反应是三氟化硼-苯甲醚络合物化学交换精馏法分离硼同位素不可缺少的步骤。由于三氟化硼-苯甲醚络合物分解过程中伴随苯甲醚的分解,使过程变得复杂,文中理论分析了苯甲醚分解的原因,用逆流多级串联装置研究了分解反应,并用高效液相色谱对产物进行分析;为获得反应的最佳操作条件,测定了反应时间和温度对络合物分解反应的影响,并分析了产生这种结果的原因。结果表明,当反应时间为0.5—1 h、温度为150℃时产物中苯甲醚的质量分数可达到97%以上,从而使络合物完全分解而苯甲醚最小程度的分解,确保了整个分离系统的正常连续运转。 相似文献
2.
The alkylation of phenol with methanol was investigated in vapor phase over a series of cerium-exchanged NaX zeolite with
Ce loadings ranging from 0 to 10.43 wt%. The catalyst MX-4 with 8.86 wt% cerium was found to be the best one with total cresols
selectivity of 72% at a temperature of 573 K and MeOH to phenol mole ratio of 4:1. The catalyst was also found to be quite
stable in the operating range investigated. It was established that the stronger acid sties are required for C-alkylation
compared to O-alkylation. From the study of the effects of various parameters, the optimum operating condition for highest
cresols selectivity were determined as: MeOH to phenol mole ratio, 4:1; temperature, 623 K; space-time, 10.2 kg h/kgmole under
atmospheric pressure. From the kinetic analysis of the experimental data, the apparent activation energy for the reaction
was determined as 57.2 kJ/mole. 相似文献
3.
本文建立了苯取光度法测定苯甲醚中微量苯酚的新方法。实验表明:苯酚浓度在0 ̄60微克/毫升范围内符合比耳定律;相对标准偏差为0.47;回收率为95.4 ̄104.0%。该法简便快速,重现性好,适用于工业化生产苯甲醚的质量控制。 相似文献
4.
磷钨酸铯催化合成对甲氧基苯乙酮 总被引:3,自引:2,他引:1
以磷钨酸铯(Cs2.5H0.5PW12O40)为催化剂合成了对甲氧基苯乙酮(p-MOAP),采用傅里叶变换红外光谱、X射线衍射、N2吸附和NH3程序升温脱附等方法对Cs2.5H0.5PW12O40催化剂进行了表征;考察了Cs2.5H0.5PW12O40催化剂活化温度、反应条件及反应产物等对苯甲醚乙酰化反应的影响。表征结果显示,多孔性的Cs2.5H0.5PW12O40催化剂保持了H3PW12O40的Keggin结构和酸强度,但酸量明显小于H3PW12O40。实验结果表明,适宜的p-MOAP合成条件为:300℃下活化的Cs2.5H0.5PW12O40催化剂用量为0.18g(以20mmol乙酸酐计)、n(苯甲醚):n(乙酸酐)=10、反应温度115℃、反应时间40min。在此条件下进行了4次重复实验,p-MOAP的收率达61.3%~64.8%、选择性达96.10%~96.80%。苯甲醚乙酰化反应的产物p-MOAP和醋酸对Cs2.5H0.5PW12O40催化剂的活性具有抑制作用。 相似文献
5.
硝酸盐催化碳酸二甲酯与苯酚合成苯甲醚 总被引:1,自引:1,他引:0
考察了各种硝酸盐催化剂催化碳酸二甲酯(DMC)与苯酚合成苯甲醚的反应活性及其规律,优化了反应工艺参数,并讨论了反应机理。实验结果表明,在200℃、n(DMC)∶n(苯酚)=2.0、CsNO3催化剂用量为原料质量的1.0%、10h的条件下,苯酚的转化率达98.1%,苯甲醚的选择性达99.2%。分析发现,当硝酸盐阳离子金属的电离能小于600kJ/mol时,硝酸盐具有较好的活性,且电离能与苯酚的转化率近似成线性关系,电离能越小,苯酚的转化率越高;当阳离子金属的电离能大于600kJ/mol时,硝酸盐的活性较低。苯环上引入不同取代基的苯酚的甲基化反应活性不同,供电子基团提高了苯酚的反应活性,而吸电子基团则相反;苯酚活化后生成的苯酚盐的亲核性强弱是影响甲基化反应活性的关键。 相似文献
6.
采用两步浸渍法制备了硅胶负载磷钨酸铯催化剂Cs2.5H0.5PW12O40/SiO2,将其用于催化合成对甲氧基苯乙酮(p-MOAP)。采用X射线衍射、傅里叶变换红外光谱和NH3程序升温脱附等技术对Cs2.5H0.5PW12O40/SiO2催化剂进行了表征,考察了Cs2.5H0.5PW12O40负载量、催化剂用量、反应物配比、反应温度、反应时间等对p-MOAP合成反应的影响。表征结果显示,Cs2.5H0.5PW12O40和Cs2.5H0.5PW12O40/SiO2催化剂保持了H3PW12O40的Keggin结构,且Cs2.5H0.5PW12O40/SiO2催化剂中Cs2.5H0.5PW12O40主要聚集在载体表面。实验结果表明,优化的合成p-MOAP工艺条件为:Cs2.5H0.5PW12O40负载量为30%(质量分数)的Cs2.5H0.5PW12O40/SiO2催化剂用量为4%(占总物料的质量分数)、苯甲醚与乙酸酐的摩尔比为10、反应温度100℃、反应时间120min。在此条件下,使用新鲜催化剂时,p-MOAP的收率达到83.4%,选择性达到96.1%。 相似文献
7.
A comparative study on the anisole methylation with methanol over lanthanum-promoted SnO2 catalyst and its sulfate-doped analogue is presented. A maximum 2,6-xylenol selectivity of 82% was achieved at 400°C under optimized conditions at an anisole conversion of 65% over lanthanum-promoted SnO2 catalyst. The sulfate modification resulted in the dealkylation of anisole to phenol followed by several unselective side reactions due to the creation of strong acid sites. The activity of lanthanum-modified tin oxide catalysts in the selective formation of 2,6-xylenol is ascribed to the presence of weak Lewis acid sites and comparatively stronger basic sites. 相似文献
8.
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10.
Seyedeh Homa Fasihnia Seyed Hadi Peighambardoust Seyed Jamaleddin Peighambardoust Abdulrasoul Oromiehie Maral Soltanzadeh Donatella Peressini 《Journal of food science》2020,85(8):2317-2328
Polypropylene (PP) based active composite films were prepared by adding butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylated hydroquinone (TBHQ) antioxidants using the extrusion molding process. All concentrations of BHT, 2% to 3% BHA, and 3% TBHQ significantly increased the tensile strength (TS) of the composite films compared with control films. Increasing antioxidant concentration decreased TS values for BHT films, whereas an opposite trend was observed for BHA and TBHQ films. BHA at < 2%, BHT at > 2%, and TBHQ at all added concentrations significantly reduced elongation at break (Eb) of the composite films compared to control films. Water vapor permeability (WVP) of 1% BHT film was not significantly different from control. However, other antioxidants especially at increased concentrations significantly increased WVP values. TBHQ films with 300% to 662% increase had the highest WVP and BHT films with 5% to 81% increase had the lowest WVP among composite films. All three antioxidants had a negative effect on the transparency of the films; however the effect of BHA at higher concentrations was greater. The antioxidants did not change the color attributes of the films. Films containing all antioxidants showed 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, which increased with increase in their concentration, especially for those containing 3 wt.% BHT and TBHQ. Overall, incorporating BHA and BHT into a PP matrix improved mechanical, barrier, antioxidant properties, and film appearance and consequently were proposed for the development of antioxidant active PP films. TBHQ film is not recommended for food packaging because of its weak mechanical properties (lower Eb and TS values, higher WVP, and greater migration). 相似文献