Vapor-phase o-alkylation of catechol with methanol over lanthanum phosphate catalyst is studied. Also, the effects of the reaction temperature and the weight hourly space velocity (WHSV) on the catalyst performance were evaluated. Expectedly, the catechol conversion and the guaiacol selectivity were inversely correlated as the secondary reactions proceeds further at higher guaiacol concentrations. Catalyst characterization indicated that the medium acidic sites played the major role in the conversion of catechol. Addition of titanium into lanthanum phosphate (La1-xTixPO4, x varies from 0.0 to 0.5) increased the surface area and acidity of the catalyst whereas a dramatic decline in the number of acidic sites, BET surface area was observed when catalyst was impregnated with up to 10% cesium. The catechol conversion first increased by addition of small quantities of titanium after which it substantially decreased. However, the catalyst selectivity to guaiacol monotonically decreased by increasing the titanium loading on the catalyst. The highest guaiacol yield was obtained using La0.9Ti0.1PO4 where a maximum in catalyst acidity per specific surface area was also observed (i.e. 0.336 mu mol g/m(2)). Moreover, a linear relation between the numbers of catalyst acid sites per surface area and the catechol conversion was observed. (C) 2013 Elsevier B.V. All rights reserved.