HZSM-5/MCM-41对小球藻催化热解的影响

Effects of HZSM-5/MCM-41 Molecular Sieve Catalysts on Chlorella Pyrolysis

以HZSM-5/MCM-41为催化剂,在管式炉内对小球藻进行了催化热解研究。考察了HZSM-5/MCM-41复合催化剂中MCM-41的添加比例对小球藻热解产物影响,并采用GC-MS和元素分析对所制取生物油进行了表征。结果表明:与HZSM-5催化剂相比,90%HZSM-5与10%MCM-41混合后生物油中3,7,11,15-四甲基-2-十六烯的选择性最好。羧酸类和含氮物质分别降低12.85%、43.97%,脂肪烃和芳烃的质量分数之和达到50.34%,且不存在硬脂酰胺和油酸腈等物质。根据元素分析可知,10%的MCM-41的引入使生物油含氧量降低23.52%,O/C原子比明显降低,H/C原子比得到提高,热值达到32.995 MJ·k-1,且油品组成与生物柴油接近。热重实验表明,分子筛催化剂失活主要是由于积炭的产生,HZSM-5/MCM-41具有良好的稳定性。随着催化剂用量的增加,生物油热值增加,同时含水量也增多,HZSM-5/MCM-41与小球藻质量比例为1:5时,生物油产率最高。

Catalytic pyrolysis of chlorella was studied in a bench-top fixed bed reactor with HZSM-5/MCM-41 mixed catalysts. The effect of MCM-41 proportion in the catalyst on pyrolysis product yields was investigated, and GC-MS and elemental analysis were used to analyze the formed bio-oil composition. The results show that the selectivity of 3,7,11,15-tetramethyl-2-Hexadecene was greatly enhanced by using catalyst of mixing 10% MCM-41 with 90% HZSM-5 comparing to that of using pure HZSM-5. Carboxylic acids and nitrogen containing chemicals were reduced to 12.85% and 43.97%, respectively. The yield of total aromatic and aliphatic hydrocarbons reaches to 50.34%, while Octadecaneamide and Oleanitrile disappear in the pyrolysis oil. Elemental analysis of the bio-oil indicates that the O/C atomic ratio is decreased, and the oxygen containing level is decreased by 23.52%. The H/C atomic ratio is increased and the calorific value reaches to 32.995 MJ.kg^-1. The overall composition of the pyrolysis oil is similar to that of biological diesel. It is demonstrated that the deactivation of molecular sieve catalysts is mainly due to the coke formation, but the HZSM-5/MCM-41 catalyst exhibits good stability. An increase in catalyst/chlorella weight ratio results in increasing bio-oil calorific values and moisture contents, and the highest bio-oil yield can be achieved when the weight ratio of catalyst/chlorella is 1：5.