Effect of n-butylamine modified HZSM-5 on catalytic reforming of lignite pyrolysis volatiles

The clean and efficient utilization of low-rank coal is of great significance to alleviate the shortage of petroleum resources and ensure energy security for China. Pyrolysis is an effective way of clean and efficient utilization of low-rank coal, which can obtain semi-coke, gas, and tar, providing an alternative way to produce liquid fuels and fine chemicals from non-petroleum resources. However, coal tar contains many heavy components, which seriously affects the subsequent utilization of tar. Catalytic pyrolysis can effectively control the product distribution and improve the quality of pyrolysis tar. Using the Shengli lignite as raw material, the HZSM-5(HZ5) zeolite was modified by desilication with cheap n-butylamine, and it was directly applied to the catalytic reforming of lignite pyrolysis volatiles for light aromatics without complicated NH <mathml id="65"> <mrow><msubsup><mrow /><mn>4</mn><mo>+</mo></msubsup></mrow></math>" role="presentation"> <nobr aria-hidden="true"> +4 </nobr> <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <msubsup> <mrow></mrow> <mn> 4 </mn> <mo> + </mo> </msubsup> </mrow> </math> <script type="math/mml" id="MathJax-Element-3"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msubsup><mrow></mrow><mn>4</mn><mo>+</mo></msubsup></mrow></math></script> </mathml> exchange steps. The catalysts were characterized by SEM,XRD,FT-IR,BET and NH₃-TPD to obtain the structural characteristics of the catalysts. The results show that the specific surface area, mesoporous volume, and average pore size of the catalyst are increased according to different concentrations of n-butylamine, which is beneficial to the diffusion of reactants and products, and the catalytic performance of the catalyst is improved. Low concentration of n-butylamine reduces the total acid content of catalyst, but high concentration has the opposite effect, the unsuitable acid sites easily lead to the formation of carbon deposition. The modified HZ5 shows a better catalytic performance, and the yield of light aromatics is ranked as 10-HZ5 > 30-HZ5 > 5-HZ5 >20-HZ5>HZ5. The 10-HZ5(HZ5 was treated with 10 mL n-butylamine and 20 mL deionized water) obtains the highest light aromatics yield of 25.0 mg/g. The main reason for the improvement of its catalytic performance is that it has the largest specific surface area, mesoporous specific surface area and the appropriate amount of acid. The pore structure and acid sites distribution characteristics of hierarchical HZ5 prepared by alkali treatment without NH <mathml id="66"> <mrow><msubsup><mrow /><mn>4</mn><mo>+</mo></msubsup></mrow></math>" role="presentation"> <nobr aria-hidden="true"> +4 </nobr> <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <msubsup> <mrow></mrow> <mn> 4 </mn> <mo> + </mo> </msubsup> </mrow> </math> <script type="math/mml" id="MathJax-Element-4"><math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msubsup><mrow></mrow><mn>4</mn><mo>+</mo></msubsup></mrow></math></script> </mathml> exchange can be used as reference for the development of efficient and cheap catalyst for the catalytic reforming of lignite volatiles to produce light aromatics.