Synthesis And Properties Of A Zeolite Suppoted Pd Catalyst With High Stability

Due to their excellent catalytic performance,supported noble metal catalysts are widely explored by researchers.However,in practical industrial applications,the conditions for the many reactions are often very harsh,usually with high temperature or pressure,which provide a huge challenge to the stability of the catalysts.How to ensure that the noble metal nanoparticles are not deactivated by agglomeration under high temperature conditions,is a key problem in the field of catalysis.In the traditional synthesis process of the supported metal catalysts,the nano particles are randomly distributed on the support After the high temperature treatment or high temperature reaction,the active sites will inevitably migrate and agglomerate,which greatly decreases their activity.In this paper,we took use of the surface defects of mesoporous zeolite as traps to provide a polar environment to Pd precursor solution,so that they can be rationally distributed,and then the Pd nanoparticles were formed by self-reduction of the organic anion in Pd(OAc)2 in the traps of the zeolite.With Pd nanoparticles isolated by the zeolite framework,the Pd nanoparticles are sinter-resistant under high-temperature calcination and catalytic oxidation.A novel synthesis method of Pd@zeolite catalysts is introduced in this paper,and the test for high-temperature resistance and catalytic stability indicate that the catalysts prepared by this method have excellent high temperature stability,with no obvious agglomeration to the metal nanoparticles.In this paper,we first studied the self-reduction of the Pd(OAc)2 itself to forming Pd nanoparticles.The results indicated that the Pd ions in palladium acetate solution can be reduced by acetate ions and stabilized by the organic groups in the product to form Pd nanoparticles.The process is also affected by temperature and concentration conditions.Then the defected mesoporous zeolite was introduced into the system above as the support for supported catalysts.Pd precursor was enriched by the mesoporous traps on the surface of the zeolite,and after the self-reduction of the Pd(OAc)2 itself,the palladium nanoparticles were rationally positioned into traps of zeolite to obtain the Pd@zeolite catalysts with high sinter-resistant ability.Compared with the conventional supported catalyst,this catalyst can keep the nano-particles stable and non-agglomerated when calcined at 600?.Even after calcination at 800?,the CO catalytic oxidation activity of this catalyst can be well maintained.In addition,under the condition of prolonged high-temperature CO oxidation reaction,the catalyst can still keep the nanoparticles from agglomerating,with no obvious decrease of the reaction activity.