Study On Preparation Of Core-Shell Nanoclusters SAPO-34@UIO-66 Loaded（Pt,Pd） And Their Hydrogenation For CO₂

SAPO-34 molecular sieve has attracted much attention because of its excellent catalytic performance in methanol to olefins(MTO)reaction,but it has the defects of easy coking and deactivation.Recent studies have shown that reducing grain size can effectively prolong the catalytic lifetime.In addition,MOFs composites with enhanced functions or new properties formed by the assembly of MOFs materials and functional materials have been favored by researchers in recent years.In this study,nano-sized SAPO-34 molecular sieve with clusters shape was synthesized firstly,subsequently assembled with UIO-66 and then anchoring metal nanoparticles(MNPs)to obtain new multifunctional MOFs composites.Finally,its catalytic performance for CO2 hydrogenation was studied.Nanoscale SAPO-34 molecular sieve was prepared by adopting dry gel conversion(DGC)method,and the effect of the solvent,aluminum sources,silicon sources,the ratio of water and dry gel on the morphology and size of crystal was explored.It turns out that there was a relatively regular cluster morphology and better crystallinity under ethanol as solvent,aluminum isopropanol was used as aluminum source,tetraethyl orthosilicate as silicon source and the ratio of water and dry gel being 2:20.Then it was characterized by various tests.In this paper,nano-sized SAPO-34 molecular sieve and UIO-66 were assembled to obtain core-shell composites SAPO-34@UIO-66 with uniform UIO-66 membrane,and then it was loaded with Pt NPs,obtaining Pt dispersed-uniformly multifunctional Pt/SAPO-34@UIO-66 catalyst.The catalytic performances for CO2 hydrogenation were tested under different conditions.It was found that the catalyst Pt12/SAPO-34@UIO-66 at the condition of 400℃,3 MPa,CO2:H2=1:3 showed the best effect,the selectivity and yield of CO being 89.2%and 24.26%,respectively.