A three-dimensional view of structural changes caused by deactivation of fluid catalytic cracking catalysts

Since its commercial introduction three-quarters of a century ago, fluid catalytic cracking has been one of the most important conversion processes in the petroleum industry. In this process, porous composites composed of zeolite and clay crack the heavy fractions in crude oil into transportation fuel and petrochemical feedstocks. Yet, over time the catalytic activity of these composite particles decreases. Here, we report on ptychographic tomography, diffraction, and fluorescence tomography, as well as electron microscopy measurements, which elucidate the structural changes that lead to catalyst deactivation. In combination, these measurements reveal zeolite amorphization and distinct structural changes on the particle exterior as the driving forces behind catalyst deactivation. Amorphization of zeolites, in particular, close to the particle exterior, results in a reduction of catalytic capacity. A concretion of the outermost particle layer into a dense amorphous silica–alumina shell further reduces the mass transport to the active sites within the composite

Toxicovigilance Activities: Evaluation of the Contribution of Poison centres - Results from the DeNaMic Project

Poison centres may be involved in toxicovigilance activities, but the extent of their contribution is not well known at the European level. A studywas conducted to quantify and qualify toxicovigilance activities of poisons centres, as a subcomponent of the DeNaMiC project. Method: A bibliometric study ofpublished literature for the quantification of scientific activities and a survey by questionnaire for the qualification of toxicovigilance activities within European poisonscentres. Results: Out of 284 papers found in the literature search 25% concerned toxicovigilance activities for household products and of these poisons centrescontributed one third. There were limited data on toxicovigilance in the medical literature. When compared to pharmacovigilance, toxicovigilance represented onefourth of the number of pharmacovigilance publications.There was also limited information on the nature of toxicovigilance activities carried out, however, the number of publications had increased in the last decade.Frequent topics of concern included identifying groups of household products, populations or circumstances at risk, and general statistics on exposures. The questionnairesurvey was sent to 89 possible poisons centres in 33 nations. A total of 25 poisons centres from 18 nations replied. From these, 20 (80%) stated they wereinvolved in some form of toxicovigilance activity. In more than half of the centres this was a voluntary rather than officially requested activity. Of the 20 poisons centres,15 (75%) participated in a toxicovigilance network.The majority of poison centres (23/25) did not receive any specific budget to support toxicovigilance activities.The range of activities described as toxicovigilance was varied. Conclusions: There is limited scientific literature on toxicovigilance, however awareness hasincreased in the last decade and poisons centres are the main contributors. Toxicovigilance activities are not homogenous throughout European poisons centres:there is a variable degree of official recognition and a variable understanding of what constitutes toxicovigilance by the poisons centres themselves. There is limitedfinancial support for toxicovigilance and no specific budget is allocated to this task. European poisons centres should come to a common understandingof what constitutes toxicovigilance in order to put together a persuasive argument for this to be better funded