顶空-气质法测定食品包装材料中的4种有害物

目的研究食品用塑料包装材料中4种有害单体(1,3-丁二烯、丙烯腈、乙苯、苯乙烯)的顶空-气质联用检测方法。方法塑料包装材料经液氮粉碎、顶空加热后,采用质谱检测器对顶空气体进行检测,通过标准物质扫描获得目标物定性、定量离子,通过标准曲线绘制对目标物进行定性定量。结果 1,3-丁二烯、丙烯腈在0.02～2 mg/mL,乙苯、苯乙烯在0.1～10 mg/mL范围内线性良好,方法检出限分别为0.05,0.05,0.02,0.02mg/kg。对4种单体进行了加标回收试验,平均回收率在94.42%～106.07%之间,相对标准偏差为2.76%～5.91%。结论建立了食品用塑料包装材料中4种有害单体的顶空-气质联用检测方法,该方法检出限更低,节省了样品的前处理时间,为食品包装用塑料材料中有害单体的快速检测提供了方法指导。     

气相色谱内标法测定塑料制品中乙苯和苯乙烯含量的不确定度评定

目的 对气相色谱内标法测定塑料制品中乙苯和苯乙烯含量进行不确定度评定,为塑料制品中乙苯、苯乙烯含量测定的准确性提供参考。方法 依据GB 31604.16—2016采用气相色谱内标法对塑料制品中乙苯和苯乙烯含量进行测定,根据相应的测量模型,分析不确定度主要影响因素的来源,并对各影响因素引入的相对标准不确定度进行评估。结果 测量塑料制品中乙苯、苯乙烯的扩展不确定度分别为(23.83±1.50)、(23.90±1.26)mg/kg(P=95%、k=2)。结论 结果表明,混标工作液配制、试样重复测量、气相色谱仪性能是影响乙苯和苯乙烯含量测量不确定度的主要因素,应选择精度高且量程合适的量具,加强气相色谱仪的期间核查,提高实验人员操作的熟练水平,进一步减小测量不确定度,使测量结果更为准确、可靠。     

PED -01乙苯脱氢催化剂的评价试验

自主开发的PED - 01乙苯脱氢催化剂在100 mL等温评价装置上进行了重复试验和稳定性试验,在反应温度620℃、空速1.0h-1、水蒸汽与乙苯质量比2:1和常压条件下,催化剂的乙苯平均转化率为79.51％,苯乙烯平均选择性为95.91％,苯乙烯平均收率为76.25％.侧线装置上条件试验和稳定性试验结果表明,PED -01催化剂的乙苯转化率和苯乙烯平均收率均优于进口催化剂,失活速率比进口催化剂慢,具有更好的稳定性.     

On the deactivation of Fe,K/active carbon catalysts in the course of oxidative dehydrogenation of ethylbenzene with carbon dioxide

Highly active and selective Fe₂O₃–K₂O/C_act catalysts for oxidative dehydrogenation of ethylbenzene with CO₂ undergo deactivation. The course of deactivation up to a loss of 95% activity is described, and related to the formation of an inactive carbonaceous deposit. The catalysts and deposits were characterized after various times-on-stream (TOS) by textural, structural and chemical analysis, as well as by temperature-programmed decomposition and oxidation. XPS spectra of O 1s and K 2p confirmed the removal of OH and diminishing of carbonyl groups, as well as segregation of K₂CO₃ onto the surface. Prolonged TOS, at temperatures above 500°C caused removal of heteroatoms from the carbonaceous deposits and even the appearance of graphitized structure in XRD patterns. It was found that the activity depended almost linearly on the amount of and the decrease in surface area. An excess of CO in relation to styrene in the product distribution suggests that the deposit is formed owing to styrene polymerization, and further dehydrogenation, on the catalyst surface. This revised version was published online in August 2006 with corrections to the Cover Date.     

GS系列乙苯脱氢制苯乙烯催化剂

GS系列乙苯脱氢制苯乙烯催化剂是具有国际先进水平的环保型催化剂,已应用于国内大型苯乙烯生产装置,为生产企业节约了外汇并创造了较好的经济效益。与进口同类产品相比,不仅具有价格上的优势,而且产品性能相当。     

响应面法分析优化苯与乙烯的烷基化反应

对改性β-分子筛催化的苯与乙烯的烷基化反应的工艺条件进行了优化。通过单因素实验确定了反应温度、空速、乙烯与苯的摩尔比的取值范围,并用响应面法(Box-Behnken设计法)确定最佳工艺参数为:反应温度154℃,空速2h-1,乙烯与苯的摩尔比1∶3。在此条件下,苯的转化率达到56.274%、乙苯的选择性达到86.592%。     

乙烷与苯经接力催化路线制备乙苯

设计乙烷经氯氧化制备乙烯再与苯烷基化一步法制备乙苯的接力催化路线。研制铈基氧化物作为活化乙烷生成中间产物乙烯的催化剂,并耦合H-ZSM-5沸石分子筛与苯进一步烷基化生成乙苯。在Mn/CeO₂氧化物与H-ZSM-5沸石分子筛以研磨混合形成的双功能催化剂上,实现了乙烷与苯催化制备乙苯的可控接力催化。考察了氧化物的组成、氧化物与沸石分子筛的耦合方式与最适质量配比、沸石分子筛的硅铝比对接力催化反应的影响,并进行了催化剂稳定性研究。结合X射线衍射（XRD）、NH₃程序升温脱附（NH₃-TPD）、透射电子显微镜（TEM）、X射线荧光光谱分析（XRF）等表征手段分析了催化剂结构及其与催化性能的构效关系。提出后续催化剂研究的关键在于分子筛烷基化能力以及抗流失能力的提高。     

Isopropylation of ethylbenzene over MCM-22 molecular sieve

MCM-22 materials (Si/Al ratios 24, 50 and 75) were synthesized and characterized. The catalytic activity was examined in the vapour phase isopropylation of ethylbenzene with isopropyl alcohol. Based on ethylbenzene conversion, the order of activity of the catalysts is found to be MCM-22(50) > MCM-22(24) = MCM-22(75). The selective formation of p-isopropyl ethylbenzene (p-IPEB) suggests that the reaction occurs mainly inside the 10-membered ring channel. The time on stream study over MCM-22(50) showed steady conversion for 6 h with nearly the same selectivity to p-isopropyl ethylbenzene (p-IPEB) and o-isopropyl ethylbenzene (p-IPEB).     

Acidity and Catalytic Behaviors of Ordered Mesoporous Aluminosilicate Materials Containing Zeolite Building Units

The structural and acidic properties of two new highly stable meso-/microporous composite materials (MMS-H and RMM-1) developed recently were characterized by various analytical and spectroscopic techniques. Comparing to their structural analogue, Al-MCM-48, these novel aluminosilicates materials comprising zeolite secondary building units were found to have superior catalytic activities, as illustrated by ethylbenzene alkylation reaction.     

工艺杂质对稀乙烯法制乙苯烷基化反应的影响

以中国石油化工股份有限公司上海石油化工研究院开发的SEB-08稀乙烯法制乙苯烷基化催化剂为基础,研究生产过程中稀乙烯法制乙苯的原料可能携带的工艺杂质,如甲苯、非芳烃、硫化氢、水和碱性物质等对烷基化反应的影响。结果表明：（1） 循环苯中甲苯的存在使烷基化反应产物中的二甲苯含量上升,影响乙苯产品质量;（2） 丙烯对烷基化反应产物中的二甲苯含量影响不大,但丙苯含量大幅上升;（3） 正己烷、环己烷、正戊烷和1-戊烯等重质非芳烃使烷基化反应产物中的二甲苯以及重质芳烃含量有不同程度上升;（4） 催化干气携带水会对乙烯转化率有一定影响,水体积分数超过1 000×10^-6时,乙烯转化率下降明显,催化剂失活速率加快;(5) 以乙醇胺为代表的碱性物质对烷基化反应影响最明显,由于催化剂活性中心为酸性,碱性物质引起催化剂不可逆失活;(6) 硫化氢含量增加,对催化剂性能以及产品质量影响较小,但对设备及管道的腐蚀程度增加。通过研究工艺杂质对烷基化反应的影响,可为正确判断现有干气制乙苯装置生产中烷基化反应产物组成变化提供依据,为确保装置长周期稳定运行提供参考。