Study On Synthesis And Properties Of Hierarchical Porous SAPO-34 By Organosilanized Multiterminal Amino Polyetheramine Template Method

Ethylene and propylene in low-carbon olefins have always been regarded as important chemical basic raw materials.At present,our country has realized the idea of a"non-petroleum route"from coal-to-syngas through methanol to low-carbon olefins（MTO）,which can solve the problem of resource constraints such as oil and natural gas,and enable our country’s energy to be used in a balanced manner.The core of MTO technology is the development and research of catalysts.SAPO-34 molecular sieve with suitable pore structure and moderate acidity has always been regarded as the most ideal and suitable catalyst and has attracted great attention.However,when catalyzing the MTO reaction,it is easy to deposit carbon and quickly deactivate,resulting in a short life.The purpose of this subject is to solve the problems faced by conventional microporous SAPO-34 molecular sieves.The soft templates KH560-D230 and KH560-T403 are fabricated through the same method of reaction by using commercial raw materials organosilane coupling agents and a variety of amino-terminated polyether amines,as the mesoporogens to successfully synthesize the hierarchical pore SAPO-34 molecular sieves,and investigated the catalytic performance of the as-synthesized samples in MTO reaction.1.In Chapter 3,organosiloxane-polyetheramine KH560-D230 fabricated by silane coupling agent KH560 and polyetheramine D230 is used as a soft template to synthesize a series of hierarchical pore SAPO-34 molecular sieves through by hydrothermal synthesis method.The best optimized conditions are obtained:the organic template precursor KH560and polyetheramine D230 react for 5 h in microwave chemical reactor at 80°C at a molar ratio of 2:1 to obtain organosiloxane-polyetheramine KH560-D230,which is introduced into the conventional SAPO-34 molecular sieves,and the mesoporous specific surface area of the hierarchical pore SAPO-34 molecular sieve is the largest;when the gel ratio n（P₂O₅）/n（Al₂O₃）=1.1,the synthesized sample is the pure phase of SAPO-34 molecular sieve,and the total specific surface area reaches the maximum(646 m²g^-1),and the mesoporation of the organic template KH560-D230 is also higher;under the premise of ensuring better molecular sieve performance,try to use less microporous structure directing agent TEAOH,and choose gel ratio n（TEAOH）/n（Al₂O₃）of 2.0;considering that the content of silicon will affect the acidity of the molecular sieve,which further affects the catalytic performance of the MTO reaction.At the same time,ensuring that that the synthesized hierarchical SAPO-34molecular sieve has the largest mesoporous specific surface area,the theoretical silica-aluminum gel ratio is selected n（Si O₂）/n（Al₂O₃）of 0.2;the influence of crystallization temperature,crystallization time and the adding amounts of organic template KH560-D230 is further explored,and finally choose the condition of crystallizing at 433K for 48h,and the organic template KH560-D230 adding amounts of 1.0m L.2.In Chapter 4,replace the two-terminal amine polyetheramine D230 with the three-terminal amine polyetheramine T403,which has a larger molecular size and more amino groups.So polyetheramine T403 can connect more epoxy group KH560 molecules.On the basis of Chapter 3,we mainly investigated the synthesis of a series of hierarchical pore SAPO-34 molecular sieves by hydrothermal crystallization method using organosiloxane-polyetheramine KH560-T403 as a soft template.The best optimized conditions are got:the organic template precursor KH560 and polyetheramine T403 react for4 h in microwave chemical reactor at 90°C at a molar ratio of 3:1 to obtain organosiloxane-polyetheramine KH560-T403,which is introduced into the traditional SAPO-34 molecular sieves,and the multi-porous SAPO-34 molecular sieve has the largest mesoporation;the effect of different silicon-aluminum ratios on the synthesis of hierarchical pore SAPO-34 molecular sieve is explored,and and the experimental results obtained are similar to those of the organic template KH560-D230.In a relatively wide range of gel n（Si O₂）/n（Al₂O₃）（0.2-0.5）,it is possible to synthesize hierarchical pore SAPO-34 molecular sieve.When the gel ratio n（Si O₂）/n（Al₂O₃）=0.2,the total specific surface area and the mesoporous specific surface area both reach the maximum,which are 668 m²g^-1and 165m²g^-1,respectively;The crystallization temperature,crystallization time and the adding amounts of organic template KH560-T403 on the synthesis of hierarchical porous SAPO-34molecular sieves are further explored.The final optimized conditions are determined as follows:choose the condition of crystallizing at 433K for 48h,and soft template KH560-T403addition amounts is 1.0 m L;Besides,the most important factor is the adding amounts of the directing agent TEAOH,which has the greatest effect on the synthesis of hierarchical pore SAPO-34 molecular sieves.The more the adding amounts of the directing agent TEAOH in the synthetic gel,the more mesoporous structure produced by the introduction of the organic template KH560-T403,the greater the specific surface area of the mesopores.However,the introduction of mesopores is bound to affect the microporous structure.On the premise of ensuring the integrity of the molecular sieve’s microporous structure,we finally choose n（TEAOH）/n（Al₂O₃）=2.2.3.This topic takes MTO reaction as the catalytic probe reaction.The catalytic performance of the self-synthesized KH560-D230 series hierarchical SAPO-34 samples,KH560-T403 series hierarchical SAPO-34 samples and conventional microporous SAPO-34samples was evaluated by methanol conversion rate,catalyst life and diene selectivity.The results show that compared with the traditional SAPO-34 molecular sieve,the synthesized hierarchical pore SAPO-34 molecular sieves have a significant improvement in the catalytic performance of the MTO reaction.On the one hand,the reason is attributed to the influence of acidity.Compared with traditional SAPO-34 molecular sieve,the acid strength and acid content of the self-synthesized hierarchical SAPO-34 molecular sieves has reduced,especially the weakened strong acid content;on the other hand,it is attributed to the existence of mesopores.At the same time,comparing the hierarchical pore SAPO-34 molecular sieve samples synthesized by the two template agents,D230 series samples showed more excellent conversion rate and product selectivity in the catalytic MTO reaction.In particular,the diene selectivity of the KD-1.0 sample is close to 85%at the highest.