J.M. Escola

Nanocrystalline ZSM-5: a highly active catalyst for polyolefin feedstock recycling

Nanocrystalline HZSM-5 (crystal size around 25–60 nm) shows remarkable activity in the catalytic cracking of LDPE, HDPE and PP despite the low temperatures (340–380 °C) and catalyst loadings used (plastic/catalyst mass ratio=100). Gaseous hydrocarbons are the main products with a maximum centered at C 4 , which are formed through a carbocationic end-chain cracking mechanism. The selectivity towards C 3 −C 5 hydrocarbons is enhanced on decreasing the cracking temperature, reaching a 95–100 % at 340 °C. PIONA analyses of the liquid hydrocarbons obtained at higher temperatures (380 °C) indicate that the highest amount of olefins (47%) is obtained in the cracking of the linear HDPE. In contrast, the branched PP leads mainly towards aromatic compounds (38%).

Catalytic conversion of polyethylene into fuels over mesoporous MCM-41

Tetrahedral Al-containing MCM-41, prepared under ambient conditions, exhibits suitable catalytic properties for the conversion of low-density polyethylene into hydrocarbon feedstocks.

Hierarchical mesoporous Pd/ZSM-5 for the selective catalytic hydrodeoxygenation of m-cresol to methylcyclohexane

Mesopore incorporation into ZSM-5 enhances the dispersion of Pd nanoparticles throughout the hierarchical framework, significantly accelerating m-cresol conversion relative to a conventional microporous ZSM-5, and dramatically increasing selectivity towards the desired methylcyclohexane deoxygenated product. Increasing the acid site density further promotes m-cresol conversion and methylcyclohexane selectivity through efficient dehydration of the intermediate methylcyclohexanol.

24-P-13-Catalytic properties of micelle templated microporous and mesoporous materials for the conversion of low-density polyethylene

Publisher Summary This chapter presents the catalytic properties of micelle templated microporous and mesoporous materials for the conversion of low-density polyethylene. Both microporous and mesoporous micelle-templated aluminosilicates exhibit high catalytic activity for the low-density polyethylene (LDPE) cracking. Aluminium (Al)-SBA-15 materials are used for the first time as higly effective catalyts for the conversion of polyolefins. The most active catalyts, according to their turnover frequency (TOF) values, are those with the highest silicon (Si)/A1 atomic ratios, which has been assigned mainly to a lower deactivation kinetic. For all the samples investigated, the main products are liquid hydrocarbons within the range C5–C14.

(nBuCp)2ZrCl2 supported over mesoporous propyl sulfonic silica–alumina: a highly active heterogeneous catalyst for ethylene polymerization

Mesoporous silica–alumina functionalized with propyl sulfonic acid groups was synthesized and used as a support for MAO–(nBuCp2)ZrCl2 for the ethylene polymerization. Mesoporous silica–alumina (Si/Al = 25) functionalized with 10 wt% propyl sulfonic exhibited remarkable activity with negligible leaching, due to the presence of tetrahedral aluminum, incorporated into the framework.

Liquid phase oligomerization of 1-hexene over mesoporous aluminosilicates and nanocrystalline HZSM-5

Liquid phase oligomerization of 1-hexene towards C 9 –C 30 hydrocarbons at 200°C and 50 bar was studied over different mesoporous aluminosilicates (Al-MCM-41 and Al-SBA-15), nanocrystalline and micrometer HZSM-5 (60 nm and 7 μm respectively). The oligomerization yield of 1-hexene was around 80–90% for all the tested catalysts except for micrometer HZSM-5, for which only 10% of oligomerization was attained. Nanocrystalline HZSM-5 led to 93% selectivity towards oligomerization, mostly trimers (32%) and heavy oligomers (24%) due to high contribution of the external surface area of the nanocrystals. Both mesoporous Al-MCM-41 and Al-SBA-15 led towards close oligomerization values (>85%) due to its large surface area. However, Al-SBA-15 showed the highest amount of dimers (42%), likely due to its lower BET surface area, the microporosity presence and the slightly different acid nature.

Synthesis of microporous surfactant-templated aluminosilicates

Microporous aluminosilicates have been synthesized in the presence of organic surfactants according to a procedure based on a two-step sol–gel process at room temperature; varying the surfactant chain length and/or the Si/Al ratio, materials with pore diameters adjustable in the range 1.0–2.5 nm have been obtained; the Al atoms in the as-synthesized samples present tetrahedral coordination, even for materials with high Al content (Si/Al = 6).