Investigating the Acid Site Distribution of a New-Generation Methyl Chloride Synthesis Catalyst

The effect of modifying an η-alumina methyl chloride synthesis catalyst by doping with CsCl and KCl over the concentration range of 0.1–1.0 mmol g(cat)–1 is investigated by a combination of pyridine chemisorption coupled with infrared spectroscopy and mass-selective temperature-programmed desorption measurements. The loading of group 1 metal chloride is equivalent to a titrant that enables selective neutralization of Lewis acid sites present at the surface of the reference η-alumina catalyst. Specifically, a loading of 0.1 mmol g(cat)–1 is sufficient to neutralize the strong Lewis acid sites; a loading of 0.6 mmol g(cat)–1 is sufficient to neutralize the strong and medium-strong Lewis acid sites; a loading of 1.0 mmol g(cat)–1 neutralizes all of the strong and medium-strong Lewis acid sites and partially neutralizes the medium-weak Lewis acid site. These deductions connect with a catalyst design program to develop a methyl chloride synthesis catalyst that exhibits minimal formation of the byproduct dimethyl ether

The Solvation and Dissociation of 4‑Benzylaniline Hydrochloride in Chlorobenzene

A reaction scheme is proposed to account for the liberation of 4-benzylaniline from 4-benzylaniline hydrochloride, using chlorobenzene as a solvent at a temperature of 373 K. Two operational regimes are explored: “closed” reaction conditions correspond to the retention of evolved hydrogen chloride gas within the reaction medium, whereas an “open” system permits gaseous hydrogen chloride to be released from the reaction medium. The solution phase chemistry is analyzed by ¹H NMR spectroscopy. Complete liberation of solvated 4-benzylaniline from solid 4-benzylaniline hydrochloride is possible under “open” conditions, with the entropically favored conversion of solvated hydrogen chloride to the gaseous phase thought to be the thermodynamic driver that effectively controls a series of interconnecting equilibria. A kinetic model is proposed to account for the observations of the open system

The Solvation and Dissociation of 4‑Benzylaniline Hydrochloride in Chlorobenzene

A reaction scheme is proposed to account for the liberation of 4-benzylaniline from 4-benzylaniline hydrochloride, using chlorobenzene as a solvent at a temperature of 373 K. Two operational regimes are explored: “closed” reaction conditions correspond to the retention of evolved hydrogen chloride gas within the reaction medium, whereas an “open” system permits gaseous hydrogen chloride to be released from the reaction medium. The solution phase chemistry is analyzed by ¹H NMR spectroscopy. Complete liberation of solvated 4-benzylaniline from solid 4-benzylaniline hydrochloride is possible under “open” conditions, with the entropically favored conversion of solvated hydrogen chloride to the gaseous phase thought to be the thermodynamic driver that effectively controls a series of interconnecting equilibria. A kinetic model is proposed to account for the observations of the open system

Origin of Impurities Formed in a Polyurethane Production Chain. Part 2: A Route to the Formation of Colored Impurities

The quality of methylene diphenyl diisocyanate (MDI) products, which are valuable feedstocks in the industrial manufacture of polyurethanes, can be compromised by the presence of color, presumed to arise from trace impurities. One undesired branch in the synthesis chain originates with phosgenation of diaryl ureas, formed from reactions between aryl isocyanates and polyamine precursors. Subsequent key steps include, (i) breakdown of the primary compounds, substituted chloroformamidine-<i>N</i>-carbonyl chlorides (CCC), to give aryl isocyanide dichlorides, ArNCCl₂, (ii) an apparent equilibrium connecting CCC with aryl carbodiimides, and (iii) the thermolysis of ArNCCl₂ in the presence of MDI. Color formation is associated directly with the last process; it involves several events, including HCl elimination from reaction of ArNCCl₂ and MDI, formation of carbon-centered radicals, and a contribution from oxidation at the methylene bridge

Origin of Impurities Formed in the Polyurethane Production Chain. 1. Conditions for Chlorine Transfer from an Aryl Isocyanide Dichloride Byproduct

Phenyl and 4-methylphenyl isocyanide dichlorides are models for byproduct that may be formed in the later stages of certain polyurethane production chains. Photochemical electron paramagnetic resonance (EPR) studies (λ > 310 nm), using the spin trap, N-tert-butyl-α-phenylnitrone, confirm a previously made suggestion that ArNCCl2 can behave as a chlorine radical source. EPR spectra recorded during and after irradiation and supported by simulations evolve over time and indicate formation of the short-lived spin trap–Cl• adduct and a longer lived benzoyl-N-tert-butylnitroxide radical. Photolysis of C6H5NCCl2, either alone or mixed with methylene diaryl isocyanate species, in o-C6H4Cl2, a polyurethane process solvent, led to the formation of mixtures containing dichloro- and trichlorobiphenyl isomers

Origin of Impurities Formed in the Polyurethane Production Chain. 1. Conditions for Chlorine Transfer from an Aryl Isocyanide Dichloride Byproduct

Phenyl and 4-methylphenyl isocyanide dichlorides are models for byproduct that may be formed in the later stages of certain polyurethane production chains. Photochemical electron paramagnetic resonance (EPR) studies (λ > 310 nm), using the spin trap, <i>N</i>-<i>tert</i>-butyl-α-phenylnitrone, confirm a previously made suggestion that ArNCCl₂ can behave as a chlorine radical source. EPR spectra recorded during and after irradiation and supported by simulations evolve over time and indicate formation of the short-lived spin trap–Cl^• adduct and a longer lived benzoyl-<i>N</i>-<i>tert</i>-butylnitroxide radical. Photolysis of C₆H₅NCCl₂, either alone or mixed with methylene diaryl isocyanate species, in <i>o</i>-C₆H₄Cl₂, a polyurethane process solvent, led to the formation of mixtures containing dichloro- and trichlorobiphenyl isomers