TG-MS同步脉冲外标法测定催化剂碳含量的研究及应用

设计了TG MS同步脉冲外标气体进样装置，以同步进样测定的纯CO2为外标，建立了准确测定催化剂碳含量（质量分数,下同）的TG MS定量方法。系统考察了恒温和变温条件下同步脉冲气体进样器的稳定性，得到外标气体质谱峰积分面积的相对标准偏差仅为172%和162%。以分析纯CaCO3为基准物质对脉冲气体进样器的定量环体积进行了标定，确定了准确的外标进样量为2 mL。考察了升温速率、反应气流速等热重分析条件对TG MS测定催化剂碳含量准确性的影响，并利用建立的方法定量测定了费 托合成催化剂、S Zorb催化剂、渣油加氢催化剂的碳含量，并与其它分析方法进行了比较。结果表明，同步脉冲进样可有效消除测试条件变化对分析结果的影响，所建立方法不仅可靠和准确，还可以根据CO2的释放温度推测碳的赋存形态。

Research and Application of TG-MS Synchronous Pulse External Standard Method for Determination of Carbon Content of Catalysts

The synchronously pulsed gas injector (SPI) was made for quantitative calibration of mass spectrometric analysis in a thermogravimetry mass spectrometry system (TG MS). The quantitative method of synchronous pulse TG MS (SPTG MS) was established to determine the carbon contents of catalysts by the introduction of SPI and external standard gas, a known volume of pure carbon dioxide (CO2). The stability of SPI was systematically investigated at both constant temperature and programmed temperature conditions of TG, the relative standard deviations of the MS integral area of CO2 were only 172% and 162%，respectively. The loop size of SPI was calibrated by using analytically pure CaCO3 as a standard sample, the accurate volume of injected external standard gas was sure to 2 mL. The influences of heating rate and gas flow rate of TG on the quantitative accuracy of carbon contents of catalysts determined by SPTG MS were studied. The SPTG MS was employed to determine the carbon contents of the Fischer Tropsch catalysts, the S Zorb catalysts, and the residue hydrodesulfurization catalysts, and further compared with other methods. The results demonstrated that the impacts of test conditions on quantitative results were effectively eliminated by SPI, and the SPTG MS method possessed good reliability and high accuracy, by which not only the carbon content could be accurately determined, but also the carbon speciation could be extrapolated on the basis of the release temperature of CO2.