(1. 武漢科技大學(xué)鋼鐵冶金及資源利用省部共建教育部重點(diǎn)實(shí)驗(yàn)室，武漢 430081；
2. 武漢科技大學(xué)鋼鐵冶金新工藝湖北省重點(diǎn)實(shí)驗(yàn)室，武漢 430081；
3. 佛山(華南)新材料研究院，佛山 528200)
摘 要: 紫鎢(WO2.72)是三氧化鎢(WO3)還原制備碳化鎢(WC)催化劑的重要中間產(chǎn)物，系統(tǒng)分析WO3至WO2.72的反應(yīng)行為對(duì)后期高效制備優(yōu)質(zhì)WC具有重要意義。本文以CO-15%CO2混合氣體為還原劑，結(jié)合模型擬合法、TG-DTA、XRD、FE-SEM和熱力學(xué)計(jì)算等方法對(duì)其還原WO3制備WO2.72的反應(yīng)機(jī)理和動(dòng)力學(xué)進(jìn)行分析。結(jié)果表明：1015~1131 K范圍內(nèi)，WO3與CO-15%CO2混合氣體的還原反應(yīng)主要由兩步過(guò)程組成，首先WO3被還原為WO2.9，而后WO2.9繼續(xù)被還原為WO2.72，即WO3→WO2.9→WO2.72，兩者相互分開(kāi)，依次進(jìn)行。動(dòng)力學(xué)分析結(jié)果表明：WO3被還原至WO2.9和WO2.9被還原至WO2.72均由界面化學(xué)反應(yīng)控速，求取的表觀活化能分別為142.182 kJ/mol和128.235 kJ/mol；該模型對(duì)變溫還原動(dòng)力學(xué)的分析同樣適用，此時(shí)表觀活化能為124.638 kJ/mol，與恒溫實(shí)驗(yàn)所得結(jié)果相符。添加一定含量(質(zhì)量分?jǐn)?shù))的Nb2O5(0~0.5%)有利于反應(yīng)速率的提高，然而Nb2O5含量過(guò)高(>0.5%)時(shí)反應(yīng)速率反而下降。結(jié)合產(chǎn)物形貌演變和物相轉(zhuǎn)變規(guī)律，本文得出了CO-15%CO2混合氣體還原WO3至WO2.72的可能反應(yīng)機(jī)理。
關(guān)鍵字: WO3；WO2.72；CO-15%CO2混合氣體；動(dòng)力學(xué)；反應(yīng)機(jī)理
（1. Key Laboratory for Ferrous Metallurgy and Resources Utilization
of Ministry ofEducation,Wuhan University of Science and Technology, Wuhan
430081, China;
2. Hubei Provincial Key Laboratory for New
Processes of Ironmaking and Steelmaking,WuhanUniversity of Science and
Technology, Wuhan 430081, China;
3. Foshan (South China) Institute for New Materials,
Foshan 528200, China）
Abstract:Purple tungsten oxide (WO2.72) is an important intermediate product during the reduction of WO3 to tungsten carbide (WC) catalysts, and the systematic analysis of the reaction behavior of WO3 to WO2.72 is an essential step for the efficient preparation of high-quality WC. In this work, the reaction mechanism and kinetics of the reduction of WO3 to WO2.72 by CO-15%CO2 mixed gases were analyzed with the adaptation of model fitting, TG-DTA, XRD, FE-SEM and thermodynamic calculations methods. The results show that the reaction of WO3 with CO-15% CO2 mixed gases is consisted of two steps in the temperature range from1015 K to 1131 K: the first step is the reduction of WO3 to WO2.9, and the second step is the reduction of WO2.9 to WO2.72, i.e., WO3→WO2.9→WO2.72, which are proceeded independently. The kinetic analysis results show that the reductions of WO3 to WO2.9 and WO2.9 to WO2.72 are both controlled by the interfacial chemical reactions with the extracted apparent activation energies of 142.182 kJ/mol and 128.235 kJ/mol, respectively. The current model is also suitable to analyze the kinetics of the non-isothermal reaction, and its apparent activation energies is extracted to be 124.638 kJ/mol, which is in good agreement with the isothermal experimental results. Adding a certain content of Nb2O5 (0~0.5%) is beneficial for the increase of the reaction rate, however, the reaction rate will be decreased when the content is beyond the limitation(>0.5%). Combining the phase transition and morphology evolution law of the reaction products during the reaction process, the possible reaction mechanism of the reduction of WO3 to WO2.72 by CO-15%CO2 mixed gases is proposed.
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