| The catalyst evaluation unit of CO2/CH4reforming to syngas have been completed. Then the relevant research of the catalysts NiO/γ-Al2O3for CO2/CH4reforming were carried out. The precipitating agents and the carriers were investigated for NiO/γ-Al2O3catalysts activity, stability and yields of H2. The results are as follows:(1) The CO2/CH4reforming to syngas catalyst evaluation unit was set up and debugged. Then determined that could be used for CO2/CH4Syngas Catalytic performance.(2) The precipitant effect on catalyst performance. Taking Na2CO3, NH3-Ⅱ2O, NH2(CH2)2OH,(NH2)2CO, NH4HCO3and NaOH as precipitating agents, respectively, to prepare catalysts which were NiO/γ-Al2O3. Then EDS, XRD and H2-TPR were characterized and analyzed. Evaluation experiment conditions:10h, GHSV=18000mL·h-1·gcat.-1, T=800℃and CO2/CH4=1.5. The experimental results showed that not only the catalyst Ni-NH2(CH2)2OH had high activity, good stability and H2yield, but also had a certain resistance to carbon deposition. The CH4conversion rate was remained above80%, CO2conversion rate was remained above60%. H2yield fell from66%to64%with an average decline rate of0.16%·h-1; the coke was only0.51g. EDS characterization results showed that the precipitant NH2(CH2)2OH made80%of the nickel deposited on the carrier; XRD characterization results showed that not only the precipitant NH2(CH2)2OH conducive to the NiO dispersion but after reduction can obtain small size of the Ni grain, which was only5.3nm; H2-TPR characterization results showed that the catalysts reduction temperature were determined as800℃, and there were three kinds of nickel which were free state NiO, Crystalline state NiO and spinel crystalline species NiAl10O16. The proportion of the total reduction peak area of NiO on the total reduction peak area was84% of Ni-NH2(CH2)2OH, indicating that reproduction is good. Therefore, compared with the other five sets of catalyst, precipitant NH2(CH2)2OH catalyst had the best evaluation results.(3) Preparation and Characterization carriers. Using templates with the sol-gel method to prepare four group carriers1#,2#,33and4#, and compared with commercial γ-Al2O3. N2adsorption test results showed that the pore volumes was about0.39nm in which mCTAB:mMC=0.02%:1, but its surface area up to477m2·g-1and average pore diameter was only3.3nm. NH3-TPD results showed that when mCTAB:mMC=0.02%:1,2#obtained the weakest surface relatively acidic.(4) The carriers effect on the catalyst performance. The purchase of γ-Al2O3was prepared as catalyst0#-C and homemade carriers were prepared as catalysts1#-C,2#-C,3#-C and4#-C. And then they were characterized and analyzed by XRD and H2-TPR. Evaluation conditions were as the same as the former, the evaluations were found that not only2#-C had the highest activity, H2yield and stability. CH4conversion fell from94%to93%with an average decline rate of0.1%·h-1; CO2fell from82%to63%with an average decline rate of1.9%·h-1; H2yield fell from75%to71%, the average decline rate of0.41%·h-1. XRD characterization results showed that the NiO dispersed on catalyst2#-C was the best, after reduction Ni grain size was only5.8nm. H2-TPR characterization results indicated that the proportion of total NiO reduction peak area in the total reduction peak area was86%of2#-C, which had good reduction.(5)2#-C catalyst for626h life test results:the stable conversion of methane and carbon dioxide were90%and65%, respectively. After the experiment, the amount of coke up to30.0g, the average carbon deposition rate was about0.096g·h-1, suggesting that it exists the long-term poor resistance to carbon deposition, resulting in its activity and poor stability. |
PDF Full Text Request