Isopropanol Dehydrogenation To Acetone Over Geopolymer Supported Multi-metallic Catalysts

Chemical heat pumps have been proposed as strong candidate for energy savings;as it utilizes the endothermic and exothermic reactions to upgrade the temperature level of thermal energy stored in chemical substances.In Isopropanol/Acetone/Hydrogen chemical heat pump system,the catalytic dehydrogenation of isopropanol to acetone was considered as an important process.Several heterogeneous catalysts have been investigated for isopropanol dehydrogenation.However,most of the catalysts were not very effective and their selectivity toward acetone was quite low at low temperatures.Geopolymers was increasingly studied as an environment-friendly material.In addition,its network closely similar to zeolite framework structure,which opens opportunities for geopolymer to be used as amorphous materials in numerous areas.Hence,in this thesis we have focused on the development of such catalytic systems where the performance of geopolymer supported metal catalyst can be realized along with the stabilizing effect of different metals on geopolymer support called bimetallic and trimetallic catalysts and its applications for isopropanol dehydrogenation the results are as follows:In the first part,several geopolymer supported bimetallic catalysts for isopropanol dehydrogenation was satisfactorily prepared by modified wet impregnation and reduction method.All the catalysts show an excellent activity in term of isopropanol conversion and acetone selectivity.In addition,XRD,SEM,EDX and TEM analysis confirmed the formation of amorphous geopolymer from the polymerization of metakaolin.It was also revealed that copper and nickel metal were supported over geopolymer.A bimetallic catalyst containing 5wt.%Cu and lOwt.%Ni loading in geopolymer has a high conversion of 23.18%and selectivity of 88.24%at the optimum conditions(90?,3 hours,and catalyst amount of 0.15 g).In addition,from kinetic results the reaction rate constant(k),activation energy(Ea)and Frequency factor(k0)were found to be 0.00071 s-1,15.22 MJ/Kmol and 2.44×105 m3/m3 catalyst · s,respectively.Nevertheless,the catalyst remains stable and maintains its catalytic activity up to three cycles.Furthermore,trimetallic catalysts such as(Ru5/Geo,Ru5-Cu1-Ni1/Geo,Ru5-Cu5-Ni5/Geo,and Ru5-Aui-Ni1/Geo)were developed.XRD,SEM,and TEM analysis confirmed that the ruthenium metal was supported over geopolymer and particles are spherical in shape and uniform in size.It was demonstrated that the addition of a third metal to bimetallic catalyst improved catalytic activity for isopropanol dehydrogenation due to synergetic effects.It was found that activity of the catalyst depend on the ratio of metal and it shows a good synergetic effect when the ratio of Ru:Cu:Ni was 1:1:1.Rus-Cus-Nis/Geo catalyst was the best as it shows a conversion of 23.32%with a selectivity of and 92.63%towards acetone after 2 hours at a reaction temperature of 90 ?.Furthermore,from kinetic results the reaction rate constant(k),activation energy(Ea)and Frequency factor(k0)were found to be 0.0008 s-1,15.49 MJ/Kmol and 1.94x105 m3/m3 catalyst's,respectively.In addition,the catalyst was stable than bimetallic catalyst and can be reused without any significant loss in catalytic activity up to 4 cycles.This finding demonstrates that the new geopolymer supported metallic catalysts could be promising for dehydrogenation of isopropanol and would be of interest for chemical heat pump system due to its excellent catalytic activity and recyclability under mild condition and making it cost-effective due low price of geopolymer raw material.Finally,rigorous material and energy balances for isopropanol dehydrogenation process of were performed using Aspen Plus.Nevertheless,sensitivity and energy analysis for isopropanol dehydrogenation process on major equipment such as flash separator and distillation column was performed to optimize the process to achieve high purity of the products.It was concluded that the enthalpy and exergy efficiency increases as the endothermic reaction heat and reboiler duty increases when exothermic reaction heat assumed constant.