低温烟气脱硝催化剂制备工艺及性能探究

Research on preparation process and denitrification performance over SCR catalyst at low temperature

为了满足低温脱硝催化剂工业化的需求,对以相同组成的氧化物粉末、工业偏钛酸、水热偏钛酸为前驱体制备的脱硝催化剂的催化性能进行了考察,并利用X射线衍射、N2吸附-脱附、热重分析、机械强度等手段对催化剂的表面结构及性质进行表征分析。结果表明,随焙烧温度升高,各催化剂的活性先升高后降低,催化剂以水热偏钛酸为原料制备的催化剂(催化剂C)更适宜于工业应用,其拥有较好的低温活性、抗压强度及成型率;经过550℃焙烧10 h后催化剂的纵向抗压强度为1.06MPa,在250℃时NO转化率为97.79%。此外,对该催化剂进行脱硝活性评价及宏观动力学分析并考察了1~3 m/s气速下催化剂活性在不同烟气温度下的脱硝性能,结果表明,随气速增加催化剂的脱硝性能逐渐降低;根据Eley-Rideal机理,建立动力学方程,推算出该催化剂的反应速率常数k,并根据Arrhenius公式求得催化剂C的SCR脱硝反应活化能为32.15 kJ/mol,指前因子A为15.37×10^(3)L/(g·min),为实际工业烟气SCR脱硝系统设计提供参考。

The NHselective catalytic reduction (NH-SCR) technique is the most popular technology for the controlled emission of NOfrom industrial flue gas. The key of this technology is to develop catalysts with high activity and low cost at low temperature. In order to meet the needs of industrialization of NH-SCR catalysts at low-temperature, the catalytic performance of denitration catalysts prepared with the same composition of oxide powder, industrial metatitanic acid and hydrothermal metatitanic acid as precursors was investigated. Whilecatalyst A and B was prepared using industrial metatitanic acid, catalyst C was made from metatitanic acid and hydrothermal metatitanic acid as Ti sources in a certain proportion. In addition, catalyst A and B were prepared by the traditional honeycomb system preparation process, while catalyst C was prepared by an improved process that can be formed in one step, and the surface structure and properties of the catalysts were analyzed by means of X-ray diffraction, Nadsorption-desorption, thermogravimetric analysis, and mechanical strength. The results showed that catalyst prepared with hydrothermal metatitanic acid was more suitable for industrial applications. It had good lowtemperature activity, compressive strength and molding rate. After calcination at 550℃ for 10 h, the longitudinal compressive strength of the catalyst was 1.06 MPa, and the NO conversion rate of the catalyst at 250℃ was 97.79%.In addition, the monolith honeycomb catalyst was evaluated for denitration activity and apparent kinetic analysis, the denitrification performance of the catalyst activity at different flue gas temperatures at a gas velocity of 1~3 m/s was investigated. The results showed that the denitration performance of the catalyst gradually decreased with the increase of gas velocity. According to the Eley-Rideal mechanism, a kinetic equation was established to calculate the reaction rate constant k of the catalyst, and according to the Arrhenius formula, the activation energy of the SCR denitrification reaction of the catalyst C was 32.15 kJ/mol, and the pre-exponential factor was 15.37×10^(3)L/(g·min),which could provide important reference for the design of SCR denitration system in the actual industrial flue gas.