【作者】 方昕；

【导师】 廖祖维； 庄壮；

【作者基本信息】 浙江大学 ， 工程硕士（专业学位）， 2021， 硕士

【摘要】 宁夏煤业公司两套MTP装置每年产生废MTP催化剂约600吨,失活的催化剂经过简单再生直接卸除,被作为“危废”回收填埋处理,每年的处理费用170万元。在日益严峻的环境保护的压力下,寻找安全、环保的废催化剂综合利用技术提高企业竞争优势和资源利用率迫在眉睫。首先对工业失活MTP催化剂进行探究,找到催化剂失活的关键因素以及规律,为MTP催化剂工业长周期运行以及合成奠定基础。以失活MTP催化剂的综合利用为出发点,寻求稳妥的处理技术路线和方案。1.采用BET、XRD、XRF、SEM、NH₃-TPD、热重、红外等表征手段对失活MTP催化剂的物化性能进行测试,利用微反评价装置对活性进行评价。以期揭示催化剂物化性质（分子筛晶粒尺寸、孔结构、酸性分布等）与反应性能之间的构-效关系,对失活催化剂进行探究。结果表明:失活MTP催化剂的骨架结构保持较完整,结晶度良好,Si O₂和Al₂O₃总含量占98%;催化剂硅铝比没有明显变化,Na、Fe和S元素含量随着床层的延伸依次降低;失活催化剂呈不规则球形,尺寸约1.5μm,表面出现明显的裂纹和斑驳,部分催化剂颗粒存在破碎。随着反应床层的纵向延伸粉化率降低,第一层粉化较严重,且强度随床层的纵向延伸先降低后增加;催化剂总酸量、弱酸、强酸量都大幅度降低,几乎并不具备强酸中心;总比表面积随着床层的纵向延伸而降低,微孔、中孔比表面积也随之降低;由于积碳量逐渐增大,催化剂孔道被堵塞。催化剂活性评价数据表明催化剂已经完全失活,不满足工业运行条件,但仍具备资源化利用分子筛的基础特性如吸附性能、Si O₂和Al₂O₃总含量高可作为合成原料重新利用。2.利用酸（盐酸/草酸）、碱等对下线MTP催化剂进行处理,并通过XRD、XRF、ICP、BET、FT-IR、SEM、NMR、Py-IR等测试方法对吸附剂物化性质进行表征,考察酸碱处理前后样品对有机物的吸附性能的影响。结果表明:废催化剂经酸碱处理后仍保持着ZSM-5分子筛结构酸处理后,H₂C₂O₄脱铝效果优于HCl。经碱处理,增大了废催化剂的比表面积及孔径,促进了介孔结构的形成;酸碱处理后进一步溶解了部分非骨架铝,有扩孔的作用。与废催化剂相比,酸碱处理后的吸附剂产品对有机物（对二甲苯和正己烷）吸附量均有明显提高。在P/P₀=0.1 MPa,H₂C₂O₄浓度为4 mol/L,Na OH浓度为0.1 mol/L时,吸附剂对二甲苯吸附量达到最大值141.032 mg/g,吸附剂对正己烷吸附量达到最大值106.886 mg/g,分别较处理前提高了20.7%和16.0%,表现出良好的吸附性能。3.利用失活MTP催化剂做为原料,水热合成制备ZSM-5分子筛,并对分子筛进行物化进行表征。结果表明,合成的ZSM-5分子筛催化剂具有典型的MFI结构,微孔孔径分布在0.6-1.0 nm,介孔区域具有较宽的孔径分布,ZSM-5分子筛催化剂颗粒与颗粒间隙较大。ZSM-5分子筛催化剂,B酸量与L酸量增大,B/L值达2.7,强酸量为0.340mmol/g,弱酸量为0.564 mmol/g,大于进口催化剂总酸量。ZSM-5分子筛催化剂甲醇转化率大于90%,寿命可达520 h。C₃⁼选择性基本保持在35-42 mol%,双烯选择性保持在40-45 mol%,P/E保持在3-7,C₂⁼-C₄⁼选择性保持在55-65 mol%,C₅⁺选择性保持在27-35mol%。考察失活MTP催化剂的两种利用方法一是制备吸附剂,吸附化工生产过程的废水,减少环境污染;二是保留催化剂其中的硅铝元素,处理后做为原料重新合成ZSM-5催化剂。这两条路线都是可以有效解决废旧催化剂并重新资源化利用的方法。更多还原

【Abstract】 Two MTP units of Ningxia coal industry company produce about 600 tons of waste MTP catalyst every year.The deactivated catalyst is directly removed after simple regeneration,and is recycled and landfill as"hazardous waste",with an annual treatment cost of 1.7 million yuan.Under the pressure of increasingly severe environmental protection,it is urgent to find safe and environmental protection waste catalyst comprehensive utilization technology to improve the competitive advantage and resource utilization rate of enterprises.Firstly,the study of MTP catalyst was carried out to find out the key factors and rules of catalyst deactivation,which laid a foundation for MTP catalyst’s industrial long-term operation and synthesis.Taking the comprehensive utilization of deactivated MTP catalyst as the starting point,we seek for a sound treatment technology route and scheme.1.The physicochemical properties of offline deactivated MTP catalyst were characterized by BET,XRD,XRF,SEM,NH3-TPD,TGA and FIR,and the activity was evaluated by micro-revaluation device.In order to reveal the structure-activity relationship between physicochemical properties（crystal size,pore structure,acid distribution,etc.）and and the reaction properties,the deactivation mechanism of the catalyst was explored.The results meaned that the skeleton structure of the deactivated MTP catalyst remained intact,the crystallinity was good,the total Si O₂and Al₂O₃content was 98%;the Si/Al ratio of the catalyst did not change significantly,and the contents of Na,Fe and S decreased with the extension of the bed;the deactivated catalyst was irregular spherical,the size was about 1.5μm,the surface appeared obvious cracks and mottles,and some catalyst particles were broken.With the reduction of the longitudinal extension of the reaction bed,the first layer is seriously powdered,and the strength decreases first and then increases with the longitudinal extension of the bed;the total acid content,weak acid and strong acid content of the catalyst decrease greatly,and there is almost no strong acid center;the total specific surface area decreases with the longitudinal extension of the bed,and the specific surface area of micropores and mesopores decreases,and the pore channel of the catalyst is blocked due to the increase of carbon deposition.The evaluation data of catalyst activity show that the catalyst has been completely deactivated and does not fit the industrial operating conditions.2.The offline MTP catalyst was processed with different solutions such as acid（hydrochloric acid/oxalic acid）and alkali,and the materialized properties of the adsorbent were characterized by XRD,XRF,ICP,BET,FT-IR,SEM,NMR,Py-IR and other test methods,investigating the influence of the samples on the adsorption properties of organic compounds before and after the acid and alkali treatment.The results indicate that the ZSM-5 molecular sieve structure is still maintained after acid-base treatment,and the H₂C₂O₄dealuminating effect is better than that of HCl after acid treatment.After alkali treatment,the surface area and pore size of the waste catalyst were increased,and the formation of mesoporous structure was promoted;after acid-base treatment,some non-bone frame aluminum was further dissolved and reamed.Compared with the waste catalyst,the adsorption capacity of organic compounds（p-xylene and n-hexane）was significantly increased by acid-base treated adsorbent products.When the P/P₀=0.1 MPa,H₂C₂O₄concentration is 4 mol/L and Na OH concentration is 0.1 mol/L,the maximum adsorption capacity of xylene and n-hexane reaches141.032 mg/g and 106.886 mg/g,respectively,which are 20.7%and 16.0%higher than those before treatment.3.ZSM-5 molecular sieve was successfully perpared through in hydrothermal synthesis method with deactivated MTP catalyst as synthetic reactant,and its physicochemical properties and activities were characterized and analyzed.The results reflect that the ZSM-5zeolite catalyst has a typical MFI framework,with pore size distribution ranging from 0.6 nm to 1.0 nm,wide pore size distribution in the mesoporous region,and large gap between particles and ZSM-5 zeolite catalyst.The ratio of B/L was 2.7,the amount of B acid was0.340 mmol/g,the weaker acid was 0.564 mmol/g,which was greater than the total acid amount of the imported catalyst.The methanol conversion of ZSM-5 molecular sieve catalyst is more than 90%,and its lifetime is up to 520h.The selectivity of C₃⁼is 35-42 mol%,diolefins 40-45 mol%,P/E 3-7,C₂⁼-C₄⁼55-65 mol%,C₅⁺27-35 mol%.Two methods for the utilization of deactivated MTP catalysts were investigated.One is to prepare adsorbent to adsorb wastewater from chemical production process to reduce environmental pollution;the other is to retain silicon and aluminum in the catalyst and use it as raw material to synthesize ZSM-5 catalyst again.These two routes can effectively solve the problem of waste catalyst and reuse.更多还原