Alkylation of benzene with carbon dioxide to low-carbon aromatic hydrocarbons over bifunctional Zn-Ti/HZSM-5 catalyst

Alkylation of benzene to value-added,high octane number and low toxic toluene and xylenes provides a way to lower benzene content in gasoline pool,and is hence a method to promote fuel quality.On the other hand,CO_(2) accumulation in the atmosphere causes global warming and requires effective route for its valorization.Utilization of CO_(2) as a carbon source for benzene alkylation could achieve both goals.Herein,alkylation of benzene with CO_(2) and H2 was realized by a series of low-cost bifunctional catalysts containing zinc/titanium oxides(Zn/Ti oxides)and HZSM-5 molecular sieves in a fixed-bed reactor.By regulating and controlling oxygen vacancies of Zn/Ti oxides and the acidities of HZSM-5,benzene conversion and CO_(2) conversion reached 28.7%and 29.9%respectively,along with a total selectivity of toluene and xylene higher than 90%.In this process,more than 25%CO_(2) was effectively utilized and incorporated into the target products.Moreover,the mechanism of the reaction was analyzed and the course was simultaneously traced.CO_(2) was transformed into methanol firstly,and then methanol reacted with benzene generating toluene and xylene.The innovation provides a new method for upgrading of fuels and upcycling the emissions of CO_(2),which is of great environmental and economic benefits.