Renata Patrini

Light olefins dimerization to high quality gasoline components

Abstract New attractive technologies can be designed in the field of light olefins dimerization (C3–C5) in order to obtain products useful as gasoline blending components; the technologies are characterized both by low investment costs and by high product quality. Isobutene dimerization is a powerful alternative to MTBE production whenever the use of the latter will be forbidden in gasoline. Also the dimerization of iso-amylenes and propylene, when properly designed, can give products (both the olefins and the corresponding hydrogenated derivatives) characterized by very high octane numbers. More in general all these technologies can help to debottleneck the FCC downstream when enhanced olefins production is achieved by means of new FCC catalysts and processes.

Selective synthesis of octadienyl and butenyl ethers via reaction of 1,3-butadiene with alcohols catalyzed by homogeneous palladium complexes

The selective synthesis, by telomerization of 1,3-butadiene with alcohols in the presence of palladium catalysts, both of octadienyl ethers (especially from higher linear primary alcohols) and of butenyl ethers is reported. The variation of the alcohol/diene molar ratio plays a decisive role in both the cases, excess of alcohol favouring in the former case the synthesis of octadienyl ethers with respect to octatrienes, being useful in the latter case, together with other factors such as high P/Pd and low Pd/diene molar ratios, to favour the formation of butenyl ethers. It has in fact been discovered that, for palladium catalysts, the formation of butenyl ethers is ruled by a complex mechanism involving both the reversible formation of butenyl ethers and their direct transformation into octadienyl ethers.

Homogeneous telomerization of 1,3-butadiene with alcohols in the presence of palladium catalysts modified by hybrid chelate ligands

Abstract 1,3-Butadiene telomerization with methanol and higher alcohols was investigated in the presence of different palladium(0) and palladium(II) complexes based on hybrid chelate ligands. When P ∩ O ligands were used, the resulting palladium complexes displayed poor activity and low selectivity to telomers, also in the presence of alkoxide promoters. Even worse performances were found when ionic palladium(II) or neutral palladium(0) and palladium(II) complexes based on N ∩ N chelate ligands were employed in combination with alkoxide promoters. Better results were obtained by using ionic palladium(II) complexes with P ∩ N ∩ N ligands in combination with an alkoxide promoter. Very promising results were achieved when the telomerization reaction was catalyzed by palladium(0) complexes obtained in situ from Pd(dba) 2 and P ∩ N ligands. The data are discussed and interpreted in terms of different capability of the chelate ligands, depending on their size and donor power, to give palladium complexes with metal sites at low oxidation state characterized at the same time by a sufficient stability and coordinative unsaturation to promote high catalytic activity and selectivity.

Telomerization of 1,3-butadiene with alcohols catalyzed by homogeneous palladium(0) complexes in the presence of mono- and diphosphine ligands

The homogeneous telomerization of 1,3-butadiene with alcohols for the selective synthesis of linear octadienyl ethers in the presence of catalysts prepared in situ from palladium(0) bis-dibenzylidene-acetone and different mono- and diphosphine ancillary ligands is described. With monophosphines, a correlation between basicity as well as steric hindrance of the ligand and activity and selectivity of the resulting catalyst was found. When diphosphines were used, the effect of the bite of the chelating ligand, as well as its basicity and steric hindrance on the activity and selectivity of the process was studied and discussed in terms of the relative stability of the metallacyclo moieties involved in the catalytic cycle. The above results have allowed to gain more light on the reaction mechanism.

1,3-butadiene telomerization with methanol catalyzed by heterogenized palladium complexes

Abstract The heterogenization of palladium complexes on silica as well as on functionalized styrene/divinylbenzene crosslinked resins and linear poly(styrene) is described. In particular, palladium (0) and palladium (II) derivatives were anchored to the above polymeric systems through their functionalization with bidentate ligands such as acetylacetonate and 1,3-bis(diphenylphosphino)propane moieties. The resulting heterogenized complexes were checked in the catalytic telomerization of 1,3-butadiene with methanol. Their performances were studied in terms of activity and selectivity to telomers. Whereas the heterogenization of palladium complexes either on silica or on polymer resins via the acetylacetonate ligand resulted labile during the catalytic cycle, the polymer-bound palladium complexes via the diphosphine ligand, when activated by an alkoxide, displayed activity and selectivity comparable with those of the corresponding homogeneous counterparts, without appreciable metal leaching in solution.

1,3-Butadiene telomerization with methanol catalyzed by heterogenized palladium(II) complexes anchored to polymer-bound bis(diphenylphosphino)methane moieties

The telomerization of 1,3-butadiene with methanol in the presence of heterogenized palladium(II) catalysts, obtained by anchoring the metal on both a styrene/divinylbenzene macroporous resin and a linear poly(styrene) functionalized with bis(diphenylphosphino)methane moieties, is reported. In particular, the activity and selectivity to telomers of the above catalytic systems is compared with the corresponding homogeneous counterpart and with those previously obtained with analogous heterogenized systems via polymer-bound 1,3-bis(diphenylphosphino)propane moieties. The effect of a methoxide promoter is also studied. Finally, the performances and metal leaching in solution of the above heterogenized catalysts are checked after several reaction cycles in order to verify their real heterogeneous character.

Selective propylene dimerization to 2,3-dimethylbutenes by heterogenized polymer-supported β-dithioacetylacetonate nickel(II) precursors activated by organoaluminium co-catalysts

Heterogenized nickel catalysts, prepared in situ by anchoring nickel(II) phosphino complexes to polymer-bound β-dithioacetylacetonate (sacsac) chelate ligands and activated by organoaluminium co-catalysts, have been employed for the selective propylene oligomerization to 2,3-dimethylbutenes (DMB). In particular, the effect of reaction conditions as well as of nature of phosphine ligand and organoaluminium activator was studied. The obtained data have shown that the above catalysts, at temperatures below 0°C and in the presence of chlorobenzene as reaction medium, display a very high activity and selectivity to DMB, when basic and bulky alkyl phosphine ligands and organoaluminium co-catalysts of medium Lewis acidity are used. The performances given above are very similar to those obtained with the corresponding homogeneous catalysts. Flow experiments have allowed to check that the heterogenized catalysts given above are substantially stable, maintaining their performances during the time. No significant metal leaching was detected in the course of the reaction, at least under the adopted conditions, thus suggesting that these polymer-supported nickel catalysts behave as really heterogeneous catalysts, due to the presence of the bidentate sacsac ligand able to permanently fix the metal to the resin.

Catalytic performances of homogeneous systems based on α-nitroacetophenonate-nickel(II) complexes and organoaluminium compounds in ethylene oligomerisation

Abstract The catalytic behaviour of novel α-nitroacetophenonate-nickel(II) complexes has been investigated as a function of reaction conditions, type and relative amount of the organoaluminium co-catalyst, as well as nature of the ancillary phosphine ligand, in order to orientate ethylene oligomerisation process towards specific target products. The reported data allowed to indicate that it is possible to shift the products distribution towards higher oligomers by increasing the Lewis acidity of the organoaluminium co-catalyst and by using a basic and bulky ancillary ligand such as tricyclohexylphosphine (PCy3). The catalyst productivity may be also readily modulated by choosing the proper organoaluminium co-catalyst and the suitable phosphine ancillary ligand. Under proper reaction conditions, a very high linearity (more than 80% of n-hexenes) of the C6 cut was obtained. On the other side, the mixture of the higher oligomeric components was found to have a relatively high degree of branching. This is likely due to the ability of the catalytic system to co-oligomerise ethylene with the produced dimeric and trimeric α-olefins, thus, affording more branched higher oligomers.

Novel Heterogenized Palladium(II) Complexes Anchored to Polymer Matrices Functionalized with Bis(diphenylphosphino)methane Moieties

The synthesis and structural characterization of a novel bidentate ligand such as bis(diphenylphosphino) methane bound to a cross-linked styrene/divinylbenzene resin and to linear poly(styrene) are reported. Moreover, the anchoring of palladium acetate to the above polymeric ligands is described and the structure of the heterogenized palladium(II) complexes obtained is proposed.

DME synthesis via catalytic distillation: Experiments and simulation

Abstract This paper regards the field of the chemical engineering that is commonly identified as Process Intensification (PI) . The main objective of PI is to improve processes and products to obtain technologies more safe and economic. ENI and the University of Pisa are partners in the European project INtegrating SEparation and Reactive Technologies (INSERT) that considers the integration of the two key steps common to conversion processes (reaction and separation) , to develop new configurations with advanced performances respect to the conventional ones. It has been chosen to apply Catalytic Distillation, the most promising application of the intensification principles, to the synthesis of dimethyl ether (DME) from methanol. This is one of the seven industrial case studies being investigated to test and validate the INSERT methodology.