The Influence of Alcohols in Driving the Morphology of Magnesium Chloride Nanocrystals

Abstract

MgCl2 nanocrystals prepared in the presence of methanol and ethanol were characterized by complementing surface‐science tools with a systematic quantum‐mechanical investigation of the stability order (in terms of Gibbs free energy) of different MgCl2 surfaces in the presence of the two alcohols. Both alcohols drastically change the overall stability and the stability order of the exposed surfaces, mainly as a consequence of the entropic contribution to the Gibbs free energy, hence inhibiting or promoting crystal growth in certain directions. The environment‐dependent occurrence of the MgCl2 surfaces may influence the structure and properties of the supported TixCl4−x sites in the MgCl2/TiCl4 precatalyst, which has important implications in the design of morphologically controlled Ziegler–Natta catalysts.

Genesis of MgCl2‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

“…Moreover, very broad and weak peaks at 2q values around and 508 indicate the presence of the catalytically relevant (104) and (110) planes, respectively. [59] DR UV-Vis-NIR spectroscopy was applied to monitor the evolution of the electronic properties during the transition from the MgCl 2 -6MeOH and MgCl 2 -6EtOH precursors to the activated MgCl 2 (Figure 3). The diffraction peaks associated with the intermediate crystalline phases disappear at higher temperatures, in fair agreement with the thermogravimetric profile ( Figure 1b).…”

“…Also in this case the first spectrum is dominated by the spectroscopic manifestations of the pure alcohol, whereas the last spectrum presents only a few bands due to residual ethoxy byproducts, whose formation has already been assessed in literature. [58,59,94,95] The slightly different evolution of the two alcoholate precursors may explain the different properties of the produced MgCl 2 , in terms of specific surface area, particles size and morphology.…”

“…[77] As a part of this investigation, we studied the thermal dealcoholation of MgCl 2 -ROH adducts into high surface area MgCl 2 . While the former was recently demonstrated by Thushara et al to generate the most suitable MgCl 2 material for a surface science investigation in terms of specific surface area, nanoparticles morphology and distribution of the catalytic sites, [45,59] the results obtained starting from the ethanol adduct serve as an indispensable connection with previous literature. To the best of our knowledge this is the first attempt to monitor with an operando multi-technique approach the evolution of the MgCl 2 -nROH adducts to MgCl 2 .…”

“…[44,45] In the industrial practice, several procedures are adopted to produced MgCl 2 -based materials, including the mechanical ball-milling of MgCl 2 in the co-presence of TiCl 4 and suitable electron donors, the decomposition of previously synthesized adducts between MgCl 2 and Lewis bases (such as alcohols or ethers) in the presence of TiCl 4 , and the direct chlorination of Mg and Ti alkoxides with AlR n Cl 3-n compounds. [45,[56][57][58][59][60] In the past, Thune and coworkers monitored by FT-IR spectroscopy in ATR mode the direct transformation of the alcoholate precursor into the Ziegler-Natta pre-catalyst in the presence of TiCl 4 and an electron donor. [45,[56][57][58][59][60] In the past, Thune and coworkers monitored by FT-IR spectroscopy in ATR mode the direct transformation of the alcoholate precursor into the Ziegler-Natta pre-catalyst in the presence of TiCl 4 and an electron donor.…”

Preise der Société Chimique de France 2017

“…Bordiga wurde in dieser Rubrik vorgestellt, als sie in die Academia Europaea gewählt worden war . Sie interessiert sich für die physikochemischen Eigenschaften nanostrukturierter Materialien mit großer Oberfläche und ist Coautorin einer kürzlich in ChemCatChem erschienenen Arbeit über die Morphologie von Magnesiumchlorid‐Nanokristallen …”