Preparation method and use of Cu-SSZ-13 molecular sieve based catalyst

Abstract

The invention provides a preparation method of a Cu-SSZ-13 molecular sieve based catalyst. The preparation method comprises the following steps of adding sodium aluminate, sodium hydroxide, a silica solution, copper sulfate, tetraethylenepentamine and an organic template agent to deionized water, and performing stirring so as to obtain gel; and performing a reaction in a reaction kettle, then performing cooling, performing centrifugal filtration, performing washing, performing drying, and performing calcining so as to obtain the Cu-SSZ-13 molecular sieve based catalyst. The method disclosed by the invention is simple in technology, low in cost, energy-saving, and environmentally-friendly. Use of a copper salt solution ion exchange and calcining technology many times is avoided, and the defect that a conventional technology needs performing later-period ion exchange so as to reduce content of active components is overcome. The silica alumina ratio of the Cu-SSZ-13 molecular sieve based catalyst prepared by the method disclosed by the invention is adjustable within the range of 7.9- 26.7, and the percentage by mass of copper is in the range of 0.47 -8.6wt%, excellent NH3-SCR catalytic activity, water thermal stability, alkali metal poisoning resistance and noble metal poisoning resistance can be kept in a wide-temperature window.

Description

technical field [0001] The present invention relates to a method for preparing Cu-SSZ-13 catalyst in situ with a double-template one-step method, and the catalyst prepared by the method and the catalyst application thereof. The Cu-SSZ-13 catalyst is used for post-treatment of diesel vehicles ( Purification process of nitrogen oxides in the catalytic converter of Urea-SCR) system. Background technique [0002] Chabazite (CHA) structure molecular sieve, also known as chabazite, belongs to the rhombohedral crystal system and has a three-dimensional eight-membered ring channel system. The structure contains cage columns composed of six-membered rings and CHA cages alternately. It is 0.38nm×0.38nm, which belongs to the small-pore molecular sieve. The Cu-SSZ-13 catalyst prepared with SSZ-13 as the carrier has high activity and high hydrothermal stability in the process of purifying nitrogen oxides in diesel vehicle exhaust Urea-SCR system Resistance, anti-alkali metal poisoning, ...

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Problems solved by technology

In this route, expensive templating agents are generally used, such as N,N,N-trimethyl-1-adamantylamine cation (US NO.4,544,538), benzyl quaternary ammonium ion (US NO.60 / 826 , 882) and benzyl trimethyl quaternary ammonium ions (US NO.60 / 882, 882), resulting in high cost of synthetic SSZ-13 carrier, while the introduction of copper ions in the synthesis route of Cu-SSZ-13 molecular sieve requires ion exchange method, that is, the SSZ-13 carrier and a certain concentration of copper salt precursor solution are exchanged at a certain temperature, filtered, washed, dried and calcined at a high temperature, and due to the limitation of the SSZ-13 carrier pore size and exchange capacity, in order to ensure the active component The loading capacity and high dispersion of copper require multiple ion exchange processes, which not only affect the stability of the molecular sieve carrier skeleton, but also have a low utilization rate of the copper salt precursor solution during the exchange process, and consume a large amount of pure water during the washing process , the high-temperature calcination process needs to consume energy; another method is to use in-situ synthesis, and use ion exchange to reduce the content of active components to obtain Cu-SSZ-13. Cu-SSZ-13 molecular sieve catalyst (Ren L.M.et al.Designed copper-amine complex as efficient template for one-pot synthesis of Cu-SSZ-13zeolite with excellent activity for selective catalytic reduction of NO x by NH 3 , Chem.Commun.2011,47:9783; Ren Limin et al. Design and synthesize Cu-SSZ-13 molecular sieve with excellent activity by a new copper amine complex template agent, Acta Catalytica Sinica, 2012, 3:92; CN 101973652A), this technology The route reduces the synthesis cost and promotes the possibility of commercial application of Cu-SSZ-13 molecular sieve catalyst, but the introduction of a large number of copper amine complexes in the synthesis process causes the content of active component copper in the catalyst to be too high. After ion exchange, the copper content of Cu-SSZ-13 synthesized with different initial sol ratios remains in the range of 9.5-10.1wt.%. Excessive copper content not only causes side reactions (ammonia oxidation reaction), but also intensifies The formation of copper aluminate, which causes the collapse of the molecular sieve framework

He Hong et al. discussed the post-treatment method of in-situ synthesis of Cu-SSZ-13 molecular sieves. First, they tried to control the content of active components of the catalyst from the number of ammonium nitrate solution exchanges. However, after two ion exchanges, the Cu in the Cu-SSZ-13 catalyst The content is only reduced from 3.8wt.% to 3.6% (Xie L.J.et al.Excellent performance of one-pot synthesized Cu-SSZ-13catalyst for the selective catalytic reduction of NO x with NH 3 , Environ.Sci.Technol, 2014,48:566.); secondly, using acid solution to replace ammonium nitrate exchange solution, this method still cannot effectively control the content of active components (CN103157505A)

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