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The hydrochlorination of 4-benzylaniline in chlorobenzene to produce 4-benzylaniline hydrochloride has been examined. This has required spectroscopic and computational analysis of the solvation of gaseous HCl in the process solvent. The characterisation of the reagent and product of the hydrochlorination reaction by various techniques, including FTIR and (1)H NMR spectroscopy and X-ray diffraction, is described. The infrared spectrum of the hydrochloride salt contains a strong Fermi resonance interaction, readily distinguishing it from that of the starting material. Using the structural results as a basis, the lattice energies of reagent and product have been evaluated by the recently developed PIXEL method. This method allows the contributions of specific intermolecular interactions to the total lattice energy to be assessed and, in this case, tentatively correlated with solubility measurements.

In connection with an initiative to enhance heat recovery from the large-scale operation of a heterogeneously catalyzed nitrobenzene hydrogenation process to produce aniline, it is necessary to operate the process at elevated temperatures (>100 °C), a condition that can compromise aniline selectivity. Alumina-supported palladium catalysts are selected as candidate materials that can provide sustained aniline yields at elevated temperatures. Two Pd/Al 2 O 3 catalysts are examined that possess comparable mean Pd particle sizes (∼5 nm) for different Pd loading: 5 wt % Pd/Al 2 O 3 and 0.3 wt % Pd/Al 2 O 3 . The higher Pd loading sample represents a reference catalyst for which the Pd crystallite morphology has previously been established. The lower Pd loading technical catalyst more closely corresponds to industrial specifications. The morphology of the Pd crystallites of the 0.3 wt % Pd/Al 2 O 3 sample is explored by means of temperature-programmed infrared spectroscopy of chemisorbed CO. Reaction testing over the range of 60–180 °C shows effectively complete nitrobenzene conversion for both catalysts but with distinction in their selectivity profiles. The low loading catalyst is favored as it maximizes aniline selectivity and avoids the formation of overhydrogenated products. A plot of aniline yield as a function of WHSV for the 0.3 wt % Pd/Al 2 O 3 catalyst at 100 °C yields a “volcano” like curve, indicating aniline selectivity to be sensitive to residence time. These observations are brought together to provide an indication of an aniline synthesis catalyst specification suited to a unit operation equipped for enhanced heat transfer.