Massimo Lami

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.

Mechanistic studies on the homogeneous nickel-catalyzed low temperature methanol synthesis

Abstract In situ IR monitoring of the Ni(CO)4/MeONa catalytic system for low temperature methanol synthesis has revealed the involvement of the [HNi(CO)3]− species in the catalysis. Two new methods for the synthesis of the anion were discovered and the model reactivity of [HNi(CO)3]− was also investigated. The overall results led us to suggest a catalytic cycle in which methanol is carbonylated to methyl formate with MeONa as the catalyst, while [HNi(CO)3]− catalyzes the hydrogenolysis of methyl formate to methanol.

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.

Hydroformylation of Z-2-butene with the PtCl2(cod)/SnCl2/L catalytic system: Part 3. The effect of the phosphorus ligand L☆

Abstract In a study on the hydroformylation of the internal olefln, 2-butene, with the catalytic system PtCl2(cod)/SnCl2 in the presence of a phosphorus ligand L, the ligand has been varied in an attempt to achieve high selectivities with respect to the linear aldehyde, n-pentanal. Forty ligands were examined and the catalytic results are discussed in terms of steric and electronic parameters. When the ligand is not too bulky, the reactivity is determined solely by the electronic parameter. Very promising results were obtained with aryl phosphites as the phosphorus ligands; selectivities in n-pentanal of 65–75% have been achieved, along with a high activity of the catalytic system. The proportion of hydrogenation is relatively low (5–10%). A considerable disadvantage with this catalytic system is the instability of phosphite ligands under the reaction conditions; however, use of cyclic phosphites has been found to enhance the stability of the system.

Methanol carbonylation to methyl formate catalyzed by strongly basic resins

The liquid phase methanol carbonylation to methyl formate has been investigated both with homogeneous sodium methoxide, the industrial catalyst for this process, and with heterogeneous strongly basic resins. The strongly basic resins Amberlyst A26 and Amberlite IRA 400 displayed a higher activity than sodium methoxide. The activation procedure and the dependence of the reaction rate on CO pressure have also been investigated.

Catalyst system and process for the liquid-phase production of methanol from synthesis gas

A catalyst system for the liquid-phase production of methanol from synthesis gas is described, consisting of: one or more copper compounds; one or more alkoxides of the lanthanum group of formula (R1 O)x Ln and/or one or more inorganic oxides of the lanthanum and/or aluminium group; one or more alkaline and/or alkaline-earth alkoxides of formula (Ra O)x M, if at least one alkoxide of the lanthanum group is present, then one or more alkoxides of the titanium group of formula (Rt O)x T is present, where R1, Ra and Rt, which can be the same or different, are C1 -C10 alkyl groups, M is the alkaline or alkaline-earth metal, Ln is an element or the lanthanum group, T is an element of the titanium group, x is equal to the valency of the metal or element.

Hydroformylation of linear butenes with the platinum/tin/triphenylphosphine catalytic system part 2. The effect of promoters

Abstract This study concerns the hydroformylation of n-butenes to n-pentanal and 2-methylbutanal using PtCl2(cod)/PPh3/SnCl2 as a catalyst precursor in the presence of various promoters. The addition of pyridine gives rise to a system with slight isomerizing and hydrogenating abilities but its activity is disappointingly low. The addition of iminium chlorides such as (PPN)Cl results in a very active system with increased stability and decreased isomerizing and hydrogenating behaviours as compared to the unpromoted system. The presence of higher concentrations of SnCl3− may be responsible for the different characteristics of this promoted system. Finally, a new system without phosphorus ligands, viz. PtCl2(cod)/(PPN)Cl/SnCl2, was found. This system will hydroformylate both terminal and internal olefins, but shows a marked hydrogenating behaviour.

Hydroformylation of linear butenes with the platinum/tin/triphenylphosphine catalytic system part 1

Abstract The hydroformylation of n-butenes to n-pentanal and 2-methylbutanal using PtCl2(cod)/PPh3/SnCl2 as a catalyst precursor was investigated. It was found that three competing processes take place: substrate hydroformylation, isomerization and hydrogenation. The isomerizing behaviour is closely related to the operating temperature: at low temperatures the system does not isomerize, while at higher temperatures it does. The PPh3/Pt molar ratio also plays an important role in determining the isomerizing behaviour and selectivity to linear aldehyde. Selectivity in n-pentanal from 2-butenes in isomerizing conditions reaches 40–70%. 2-Chlorobutane is a typical byproduct of this system; it is obtained by the reaction of n-butenes with HCl produced in the activation phase of the catalyst precursor. Acidity probably plays a key role in catalytic systems operating at T > 100 °C.

Hydrotreating of petroleum residues with dispersed catalysts derived from thiomolybdates and molybdenyl acetylacetonate

Abstract The effect of the catalyst precursor formulation on the hydrotreatment of Belayim atmospheric residue was investigated and different Q 2 [Mo x S y ] complexes were tested. The effect of the counterion Q and of the y / x ratio were examined; the most interesting results were obtained for S/Mo ⩽ 4 with [Mo 3 S 9 ] 2− as the best precursor and with phosphonium salts as the best counterions. Phosphorus promotion might be related to vanadium demetallation. These results were compared with those obtained by using MoO 2 (acac) 2 (acac = acetylacetonate) as the catalyst precursor. In order to discriminate between thermic and catalytic aspects, the effect of catalyst concentration was carefully examined; the higher the concentration, the higher the removal of heteroatoms from the residue without producing too many light products.

Hydroformylation of linear butenes with the PtCl2(cod)/ SnCl2 catalytic system promoted by P(OPh)3 Part 4.☆

Abstract The hydroformylation of Z -2-butene to n-pentanal and 2-methylbutanal using PtCl 2 (cod)/ SnCl 2 /P(OPh) 3 as a catalyst precursor has been investigated. Selectivities in n-pentanal of 70–75% have been obtained with high activity of the catalytic system. The hydrogenation percentages are not very high (⩽ 10%). Equimolar mixtures of 1- and 2-butenes have been hydroformylated by this catalytic system with a selectivity in n-pentanal of 80%. A marked disadvantage of this system is represented by the instability of P(OPh) 3 under reaction conditions due to acid-catalyzed hydrolysis reactions. The addition of pyridine and iminium chlorides such as (PPN)Cl slows down the P(OPh) 3 decomposition. The addition of (PPN)Cl results in a very active system, with higher stability and lower isomerizing and hydrogenating power compared with the unpromoted system. As a result, a new catalytic system, viz . PtCl 2 (cod)/SnCl 2 /P(OPh) 3 /(PPN)Cl, has been obtained for the selective hydroformylation of Z -2-butene to 2-methylbutanal and of 1-butene to n-pentanal.