The Study On The Catalytic Activities Of Complex Metal Oxides Derived From HTLcs In The Dehydration And Dehydrogenization Of Isopropyl Alcohol

Hydrotalcite-like-compounds (HTLcs) are the compound metal hydroxide with layered structure, whose special structure display perfect performance as new catalytic materials, so they were noticed and applied in many fields comprehensively. In this experiment, six series of CuAl,MgAl,ZnAl,NiAl,NiAlCe CuMgAl hydrotalcites had been synthesized by the method of co-precipitation with variable pH and the compositions were characterized physic-chemical nature by using XRD,FT-IR,TG-DTA and TPD. Catlytic performance were evaluated through probe reaction in the reaction of isopropanol dehydrogenation and dehydrationSurface acid-base of compound metal hydroxide was disclosured and the changed rule of preparation condition and reaction condition was discovered. The result showed that the six hydrotalcite-like-compounds had unique phase and higher crystallinity and thermal stability around 450℃. Compound metal hydroxide catalysts with big surface area and distributed uniform of active element were calcinated from the precursor Hydrotalcite. At the same time, the compound metal hydroxide catalysts presented excellent catalytic performance.CuAl,MgAl,ZnAl,NiAl dyadic Hydrotalcite precursor was calcinated into compound metal hydroxide that used to isopropanol dehydrogenation and dehydration. The change rule of catalytic effect is same with calcination temperature increasing under M²⁺/M³⁺=4 and 320℃reaction temperature: The percent conversion of isopropanol and the selectivity of acetone were parabola change increasing of calcination temperature,the selectivity of dehydrogenation product propene is reducing firstly and increasing after. The rate of conversion of isopropanol is 100% and selectivity of acetone has reached the largest 100% under 400℃calcination temperature using catalyst of CuAl compound metal hydroxide. The rate of conversion of isopropanol is 72.19% and the selectivity of acetone is 45.49%, the selectivity of propene is 54.51% under 550℃calcination temperature using catalyst of MgAl compound metal hydroxide. The rate of conversion of isopropanol is 75.46% and the selectivity of acetone is 82.41%, the selectivity of propene is 17.59% under 400℃calcination temperature using catalyst of ZnAl compound metal hydroxide. The rate of conversion of isopropanol is 73.28% and the selectivity of acetone is 72.36%, the selectivity of propene is 27.64% under 500℃calcination temperature using catalyst of NiAl compound metal hydroxide. Dyadic compound metal hydroxide has follow catalytic change rule under suitable calcination temperature: The rate of conversion of isopropanol appear parabola change and the selectivity of acetone is bigger gradually and the selectivity of propene is smaller little by little with the increasing of M²⁺/M³⁺. While M²⁺/M³⁺=1,2,4 6 and CuAl used to catalyst, the rate of conversion of isopropanol is 79.76%, 61.90%, 49.95% sequentially, the selectivity of acetone is 91.25%, 99.18%, 93.23% in turn. While MgAl used to catalyst and Mg/Al=2,4,6, the rate of conversion of isopropanol is 56.73%,72.19%,49.95% sequentially, the selectivity of acetone is 35.34%,45.49%,54.16% in turn. While ZnAl used to catalyst, the rate of conversion of isopropanol is 63.43%,75.46%,55.67% sequentially, the selectivity of acetone is 78.52%,82.41%,92.56% in turn. While NiAl used to catalyst, the rate of conversion of isopropanol is 63.43%,73.28%,71.10% sequentially, the selectivity of acetone is 58.43%,65.26%,72.14% in turn. The rate of conversion of isopropanol and the selectivity of acetone are different while M²⁺ is different, the reason is that the big electronegativity oxide appear acid, but the minor electronegativity oxide appear basic in compound metal oxide when M is different and the electronegativity of Cu,Mg,Zn,Ni is diversity, so, the acid-base of compound oxide is different which formed with Al₂O₃.NiAlCe and CuMgAl ternary Hydrotalcite precursor was calcinated into compound metal hydroxide that used to isopropanol dehydrogenation and dehydration. The percent conversion of isopropanol and the selectivity of acetone were parabola change with increasing of calcination temperature, the selectivity of dehydrogenation product propene is reducing firstly and increasing after. The rate of conversion of isopropanol appear parabola change and the selectivity of acetone is bigger gradually and the selectivity of propene is smaller little by little under suitable calcination temperature with the increasing of M²⁺/M³⁺ .The rate of conversion of isopropanol is 100% and the selectivity of acetone is 64.13%, the selectivity of propene is 35.87% under 500℃calcination temperature and 400℃reaction temperature and Ni/(A1+Ce)=2,Ce/Al=0.5 using catalyst of NiAlCe compound metal hydroxide. The rate of conversion of isopropanol is 95.22% and the selectivity of acetone reached the largest 100% under 400℃calcination temperature and 240℃reaction temperature and (Cu+Mg)/Al =3,Mg/Cul=4 using catalyst of NiAlCe compound metal hydroxideKnowing that: isopropanol dehydrogenation and dehydration is very intimate with solid catalyst surface acid-base which finished in the synergism action of L-acid and surface base. In the inversion reaction of isopropanol, compound metal oxide has better selectivity to dehydrogenation product acetone, however, selectivity to dehydrogenation product propene is low, that indicated compound metal oxide has higher base content and lower acid content.