Zn_(x)Zr/HZSM-5 as efficient catalysts for alkylation of benzene with carbon dioxide

Alkylation of benzene with carbon dioxide and hydrogen to produce toluene and xylene could increase the added-value of surplus benzene as well as relieve environmental problems like green-house effect.In this work,the alkylation benzene with carbon dioxide and hydrogen reaction was proceeded by using the mixture of zinc-zirconium oxide and HZSM-5 as bifunctional catalyst.The equivalent of Zn/Zr=1 displays the best catalytic performance at 425℃ and 3.0 MPa,and benzene conversion reaches 42.9%with a selectivity of 90%towards toluene and xylene.Moreover,the carbon dioxide conversion achieves 23.3%and the carbon monoxide selectivity is lower than 35%,indicating that more than 50%carbon dioxide has been effectively incorporated into the target product,which is the best result as far as we know.Combined with characterizations,it indicated that the Zn and Zr formed a solid solution under specific conditions(Zn/Zr=1).The as-formed solid solution not only possesses a high surface area but also provides a large amount of oxygen vacancies.Additionally,the bifunctional catalyst has excellent stabilities that could keep operating without deactivation for at least 80 h.This work provides promising industrial applications for the upgrading of aromatics.

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.