Research On The Catalytic Process Of Hydrogen Production From Dimethyl Ether Reforming

Hydrogen is a fuel that is regarded as having the most development potential for this century because of its clean, efficient, and renewable characteristics. The use of hydrogen gas in mobile fuel cell has led to a wide interest in the development of technology for on-board H2 production from liquid fuels, e.g., catalytic steam reforming (SR) of dimethyl ether (DME) to produce H2. Among the various hydrocarbon feeds, DME has the advantages of high energy density, non-toxicity, easy availability, safe handling/storage, and that the infrastructure in place for LPG distribution can be readily adapted for DME.In this work, the thermodynamics of hydrogen production from DME SR was analyzed to evaluate its feasibility. The type and acidic amount of a solid acid and the composition of a copper-based catalyst were studied to understand their role in the catalytic reactions. DME hydrolysis needs strong acid centers and DME hydrolysis catalysts were studied. ZSM-5(25) was selected as the most suitable solid acid catalyst because it had a strong acidity that gave a high activity in DME hydrolysis. A new methanol SR catalyst Cu-Zn-Al-Zr, codenamed CD501, was developed by optimization of the preparation method. ZSM-5(25) was used together with CD501 as a physical solid mixture to form a bifunctional catalyst for the DME SR reaction, and showed a higher catalytic activity and thermal stability than the traditional catalysts. A synergy of the coupled DME hydrolysis reaction and methanol SR reaction gave a high one-pass DME conversion and the energy consumption was also less.After the catalyst system for the process was optimized, DME SR experiments in a fixed bed reactor were carried out to study the effects of the operating conditions. The reaction kinetic parameters for the catalyzed reactions in the process were obtained by regression from experimental results and their use in the simulation of the DME reforming process achieved good results.In a membrane reactor (MR), hydrogen permeation through a palladium-silver membrane was investigated in the presence of pure hydrogen and gas mixture of hydrogen and other reaction and product components. A palladium-silver alloy membrane reactors was used to carry out DME SR by preforming both reaction and hydrogen separation in the same device. Experiment and simulation of hydrogen production process using a MR were performed. The reactor and catalyst performance data presented can provide fundamental data for a DME SR process design.