A fibre-supported Rh-phosphine catalyst, Fibrecat™ was tested in hydroformylation of ethene and characterised by spectroscopic methods (NMR, DRIFT) before reaction, after pretreatments and after reaction. Fibrecat™ was an active and selective catalyst with 95% selectivity for propanal at 100° C and 0.5 MPa. Higher temperatures were required to obtain similar activity with unmodified Rh/C and Rh/SiO2 catalysts, and propanal selectivities remained less than 50%. P-31 NMR characterisations suggested that two kinds of Rh-P species were formed on Fibrecat™ during the catalyst preparation: a monophosphine species, Rh(acac)(CO)(PS-PPh2), and a diphosphine species, Rh(CO)(2)(PS-PPh2)(2). An activation period of 5-10 h at the beginning of the reaction on Fibrecat™ was required for transformation of the monophosphine and diphosphine species in contact with CO/H-2 to the active Rh-carbonyl hydrides. Evidently, Rh supported on phosphine-modified fibre forms catalytically active Rh-phosphine species with superior activity and selectivity to unmodified Rh catalysts and clearly higher activity than Rh-phosphine supported on silica. © 2005 Elsevier B.V. All rights reserved.