Uncertainties in the determination of pyrrolizidine alkaloid levels in naturally contaminated honeys and comparison of results obtained by different analytical approaches

The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is a well-known hazard for food safety. While management strategies and controls of the honey industry aim to reduce the PA levels, uncertainties remain with regard to the safety of regionally produced and marketed honey. In addition, a previous study showed large differences of results obtained after various periods of storage and apparent differences between the analytical results of different laboratories. Therefore, this study aimed at examining these uncertainties by monitoring the impact of storage on the PA and PA N-oxide (PANO) content of two freshly harvested honeys and on possible demixing effects caused by pollen settling. Additionally, three analytical approaches – target analysis with matrix-matched calibration or standard addition and a sum parameter method – were applied for a comparative analysis of 20 honeys harvested in summer 2016. All samples originated from Schleswig-Holstein in Northern Germany where the PA plant Jacobaea vulgaris is currently observed on a massive scale. The results of the time series analyses showed that PANO levels markedly decreased within a few weeks and practically reached the LOD 16 weeks after harvest. Tertiary PAs, by contrast, remained stable and did not increase as a consequence of PANO decrease. The experiments on a putative demixing, which may result in a heterogeneous distribution of PAs/PANOs, revealed that there was no such effect during storage of up to 12 weeks. A comparison of the PA/PANO levels obtained by different analytical approaches showed that in some cases the sum parameter method yielded much higher levels than the target approaches, whereas in other cases, the target analysis with standard addition found higher levels than the other two methods. In summary, the results of this study highlight uncertainties regarding the validity and comparability of analytical results and consequently regarding health risk assessment.     

Increasing Volumetric CO2 Uptake of Hypercrosslinked Polymers through Composite Formation

To overcome the drawbacks of solid microporous materials for CO₂ capture, this proof‐of‐concept study demonstrates a low‐cost and rapid method for producing composites consisting of hypercrosslinked polymers (HCP) with a polyethyleneimine (PEI) binder. The resulting materials capture CO₂ through physical and chemical absorption simultaneously. Compared with HCP, the composites exhibit higher CO₂ uptake, higher volumetric density, and improved tolerance to water which is attributed to the PEI binder.     

锂-二氧化碳电池阴极催化剂的研究进展

锂-二氧化碳电池通过捕获、转化二氧化碳为储能物质，既可以减少二氧化碳排放量又可以作为创新的储能装置，引起了研究者们的广泛关注。本文简单介绍了锂-二氧化碳电池的工作机理、发展历程和目前研究存在的难题，通过对研究工作的总结、电池性能的对比，将不同类型的催化剂进行了系统的分类和简单的概括，综述了催化剂的设计理念和研究现状，提出了催化剂目前存在的难题与挑战，并展望了催化剂未来的发展方向。本文主要针对锂-二氧化碳电池阴极催化剂的最新研究进展进行了详细的阐述，指出高效的阴极催化剂是促进锂-二氧化碳电池电化学反应动力学、降低充电平台和过电势的关键所在。     

耦合膜分离的新型CO2低温捕集系统性能优化

CO₂捕集作为温室气体排放控制的有效手段已成为重要研究课题。作为新兴捕集技术之一，低温CO₂捕集因产品纯度高、无附加污染等优势受到关注。然而，该技术能耗和捕集率对于气体中CO₂浓度十分敏感，对于高CO₂浓度气体可获得较高的CO₂捕集率和较低能耗水平。基于此，本文提出了耦合膜分离的新型CO₂低温捕集系统，通过膜材料选择渗透性实现待捕集气体CO₂浓度主动调控，并在最优浓度下进行CO₂低温捕集。首先基于不同传统低温捕集系统特点，对比分析了不同耦合系统模式，从而确定了最优耦合系统结构。针对最优耦合系统进行了运行参数优化，并分别基于实现系统捕集能耗最低与捕集率最高的目标，获得了膜渗透侧CO₂浓度与进气CO₂浓度间的关系式，为该耦合系统中膜组件选型提供指导。研究表明，本文提出的耦合系统捕集能耗为1.92MJ/kgCO₂，相比于传统单一低温系统捕集能耗可降低16.5%。     

NNI-1型C_5/C_6烷烃异构化催化剂长周期运行分析及建议

中国石化海南炼油化工有限公司0.2 Mt/a C5/C6烷烃异构化装置以连续重整装置的拔头油为原料,使用NNI-1催化剂,采用一次通过流程,不设脱异戊烷塔和稳定塔,经设在连续重整装置内的脱丁烷塔稳定处理后作为汽油调合组分。该装置于2006年9月开工投产,截至2015年3月已连续运行3个周期。长周期运行分析结果表明:前两个周期中NNI-1催化剂具有较高的异构化活性及选择性,C5异构化率为60%左右,C6异构化率为80%左右,C6选择性为15%左右,产品辛烷值基本达到技术指标要求(RON≥78);而在第三周期运行中,催化剂积炭增加等原因导致其异构化活性及选择性降低,异构化产品辛烷值提升能力呈现逐步衰减的趋势,提高反应苛刻度已不能弥补催化剂活性下降造成的产品辛烷值降低。为保证装置长周期运行,建议择机停工对催化剂进行再生,或是直接换用与装置原料性质匹配的异构化催化剂。     

河南渑池地区铝土矿工艺矿物学及锂的赋存状态研究

通过河南省渑池地区含锂铝土矿(岩)层工艺矿物学分析,查明铝土矿的物质组成、嵌布特征、伴生锂分布特征和赋存状态,为矿产综合利用提供理论依据。结果显示:该铝土矿Al2O3含量为54.8%,铝硅比值(A/S)为2.6,铝土矿层和粘土岩层中Li2O含量均高于伴生锂边界品位,粘土岩中锂更为富集；矿物组成除一水硬铝石之外,主要是以集合体形态产出的粘土矿物。采用稀酸解析、选矿测试和电子探针分析锂的赋存状态,查明矿石中锂主要是以类质同象置换形式赋存在伊利石和高岭石等粘土矿物中；选矿富锂尾矿中Li2O可富集到0.57%左右,是锂综合回收利用的重点研究对象。