A simple solid-phase synthesis technique was applied to prepare a series of silica-based composite materials. Each material contains tungsten, manganese and an alkali oxide. To determine the influence of the alkali nature on the catalytic properties of SiO(2)-based composites, a W-Mn/SiO(2) material without any alkali was prepared. In addition, material containing tungsten, manganese and lithium without SiO(2) was synthesized. The composites were studied by XRD, TPR, BET, XPS, SDB/SEM and EDS methods. A thorough analysis of the phase parameters, which were crystallized in alkali-doped W-Mn/SiO(2) catalysts and determined by XRD, was performed for the first time. Most synthesized materials demonstrated higher catalytic activity in the oxidative coupling of methane (OCM) in comparison with the analogous materials prepared according the convenient wet impregnation method. The OCM reaction was carried out without any dilution of the methane-oxygen mixture. The results of catalytic tests were interpreted in relation to the catalyst silica-matrix phase composition. It was found that two polymorphic phases of SiO(2) coexist in each composite material. These phases are cristobalite and quartz in Li- and Na-containing material or cristobalite and tridymite in K-, Rb- and Cs-containing materials. The hypothetical T-x phase diagrams of Me(2)O-SiO(2) (where Me is an alkali metal) systems were constructed to explain the coexistence of two phases of SiO(2) in the studied catalysts. (C) 2011 Elsevier B.V. All rights reserved.