Pd-based catalysts prepared from ultra-pure SiO2 and doped with 5000 ppm Li, Ca and La were subjected to CO hydrogenation (H-2/CO = 2, p = 9 bar, T = 553 K) in a flow reactor directly attached to an ultra-high vacuum chamber with facilities for X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The catalysts exhibited high selectivity (usually above 99%) for methanol synthesis and their activities were found to increase in the order Li < Ca < La. Subsequent analysis by SIMS revealed the presence of surface formate and methoxy on the silica support. No such species were found to be bound to the Pd particle surface. These conclusions are based on the detection of COO(H) and SiOCH3 ions while respective Pd-based species were absent from the mass spectra. This indicates a mechanism to be in operation in which hydrogen is activated on Pd metal and subsequently spilled over to the support in order to react with formate to methanol. XPS studies of SiO2 samples containing 10 wt% of Ca, in the absence of Pd metal, demonstrated Si 2p and O Is line shifts to lower binding energies as compared to pure SiO2. The spectra bear strong similarities with those of wollastonite, "CaSiO3". A comparable behavior was found for Mg-doped SiO2 but not for K- or Cs-doped SiO2, which show low activity in methanol formation.