The waste gas pollution of coal chemical enterprises has the characteristics of a wide range of emissions, a large amount of emissions, and the waste gas often contains toxic and harmful substances, which form a certain obstacle to the overall development of the social economy [1–3]. At the same time, it has a great negative impact on the living environment of mankind. The crude coal gas produced by the coking furnace passes through the condenser and the raw gas produced enters the gas boiler . The main pollutants produced are sulfur dioxide (SO2), nitrogen oxides (NOx) . The discharge of these pollutants into the atmosphere has caused serious environmental problems. Therefore, the treatment of NOx is imminent [6–7].
At present, the most widely used NOx removal technology is selective catalytic reduction method in which the reducing agent selectively reacts with the NOx in the flue gas in the presence of a catalyst, and finally reduces the NOx to harmless N2 and H2O [8–9]. The reaction temperature of this method is low, generally not higher than 400°C . It is currently recognized at home and abroad with a wide range of applications and better denitration performance .
As a key factor for SCR denitration, catalyst is also an important reason for the success or failure of the entire catalytic reaction. In commercial operation, a catalyst with good performance not only has strong stability, high NO conversion rate and wide temperature window, but also has good sulfur and water resistance [12–13]. According to the different active components of the catalyst, the catalyst is divided into noble metals catalysts, molecular sieve catalysts, metal oxide catalysts. Noble metals have good stability and good low-temperature catalytic activity, and high denitration efficiency .
At present, the more mature catalysts for industrial applications are mainly the mixture of vanadium-titanium base and molybdenum trioxide or tungsten trioxide . This catalyst is mainly active in the temperature range of 380-450℃, and its pores will be formed by side reactions when the temperature is lower than 420℃ [16–18]. The blockage of ammonium sulfate causes a decrease in catalytic activity, and it is easy to leak vanadium-containing compounds into the atmosphere at high temperatures, which reduces the denitrification performance and also causes secondary pollution to the environment [19–20]. Therefore, it is imperative to develop a catalyst with good low temperature effect and high NO removal rate.
Metal-organic framework (MOFs) materials are a kind of open crystal framework materials with adjustable pore size and permanent porous structure that are assembled by metal-containing units and organic ligands under certain conditions [21–22]. Because of its ultra-high specific surface area, strong adsorption capacity, multifunctional metal center and modifiable pores, it is widely used in many fields [23–24]. Among them, in the catalytic process, on the one hand, the high specific surface of the MOFs material is conducive to the adsorption and enrichment of the substrate molecules around the active center. On the other hand, the structural properties of inorganic-organic hybrid MOFs provide the possibility to form one or more catalytic centers in a single pore. Therefore, MOFs are a new type of solid catalytic material with broad application prospects .
There are certain researches on the application of metal-organic framework to SCR denitration. At present, the prepared MOFs are compressed for denitration and have a good treatment effect, but the preparation time is too long, the preparation amount is small, and the cost is too high. Therefore, the bottleneck encountered at present is how to industrialize it.
As a kind of solid waste with relatively large output, fly ash needs to be resolved in a reasonable manner. Fly ash is a special powder mixed with regular particles and porous particles, inorganic and organic substances, hollow particles and solid particles . It is a char-like particle with a complex shape and a porous surface formed due to the volatilization and chemical reaction of the carbon particles during the combustion process. The specific surface area is about 0.8-2.4 m2 g−1. Fly ash is mainly composed of SiO2 and a small amount of CaO, Al2O3, Fe2O3, MgO, and has stable physical and chemical properties and a more complex composition structure . The application of fly ash to the preparation of catalytic materials is an important way to realize its high added value utilization. The change of its composition and structure has a great impact on the performance of the catalyst. Different active components and structures correspond to different reaction types and have a very wide range of adaptability [28–29]. Due to the relatively stable physical and chemical properties of fly ash, more and more researchers use it as a catalyst or catalyst carrier for research.
In this paper, a hydrothermal method is used to prepare Cu-BTC materials, with solid waste fly ash as the carrier. Cu-BTC is used as the active component and loaded on fly ash to prepare Cu-BTC/FA catalyst for low-temperature selective denitration. It not only improves the utilization rate of fly ash, but also reduces pollution. The purpose of improving the environment and secondary use. And most importantly, it provides a feasible basis for the industrial application of fly ash flue gas denitration loaded with Cu-BTC, which has strong practical significance.