[en] Graphical abstract: A series of CuO–ZnO–Al_2O_3/HZSM-5 nanocatalysts was synthesized with combustion synthesis method for direct conversion of syngas to dimethyl ether process. Various citric acid/nitrate molar ratios of 0.5, 1, 2 and 4 have been used to investigate the effect of the fuel content on physicochemical properties of synthesized catalysts. The phase evolution, morphology, functional groups, surface area and reducibility were investigated via XRD, FESEM, FTIR, BET and H_2-TPR, respectively. Increasing the fuel/nitrate ratio has enhanced the surface area and reducibility of catalysts. Furthermore, the results indicated interesting cave shaped porous morphology with a wide nanometric pore size distribution. The catalytic performance test resulted the highest catalytic activity for the sample of the fuel/nitrates molar ratio of 4 among all the samples through all the operating conditions. Furthermore, the best catalytic activity for the reaction was resulted at 300 °C and 40 bar. The time on stream test of the nanocatalyst introduced negligible activity lost over the 1060 min. - Highlights: • Combustion dispersion of CuO–ZnO–Al_2O_3 nanocatalyst over HZSM-5. • Dependency of catalytic properties on applied fuel/nitrates ratios. • Enhanced effect of fuel/nitrates ratio on syngas to DME conversion. • Reaction pathway for combustion dispersion of CuO–ZnO–Al_2O_3 over HZSM-5. • High performance in direct syngas to DME conversion over CuO–ZnO–Al_2O_3/HZSM-5. - Abstract: HZSM-5 supported CuO–ZnO–Al_2O_3 nanocatalyst was synthesized through combustion method to be used in direct syngas to dimethyl ether conversion process. The nanocatalysts were synthesized in various citric acid/nitrates molar ratios of 0.5, 1, 2 and 4 to address the optimized ratio. The effect of this ratio was investigated on the catalytic properties using further techniques; hence, the phase evolution, morphology, functional groups, surface area and reducibility were investigated via XRD, FESEM, FTIR, BET and H_2-TPR, respectively. According to the analytical results, increasing the fuel/nitrates ratio enhances the morphological properties, and reducibility. It is found that increasing the ratio results interesting cave shaped porous morphology decorated by combustion exhaust gases forming a micro-porous structure. The H_2-TPR analysis indicates reducibility enhancement after increasing the fuel content. The performance test of direct syngas to DME conversion was carried out under variable operational conditions of 10–40 bar, 225–300 °C and fixed conditions of GHSV = 600 cm"3/g h and H_2/CO = 2 M ratio. The catalytic performance tests are resulted the highest catalytic activity for the sample with the fuel/nitrates molar ratio of 4 (CZAZ4) among the prepared samples through all the operating conditions. Furthermore, the performance test demonstrates the best catalytic activity for direct syngas to dimethyl ether reaction, at 300 °C and 40 bar. The time on the stream test of the CZAZ4 nanocatalyst is studied during the process of syngas to DME conversion with a consequence of negligible activity loss over 700 min stability test.