From micro- to nano-size catalytic membrane hydrogenation reactors with accumulated hydrogen

Preconditions and prospects of development of the new generation nano-sized membrane reactors are studied in this work. In such reactors hydrogenation reactions will be performed for the first time in the pores of ceramic membranes actively employing hydrogen which is preliminarily adsorbed in mono- and multilayered oriented carbon nanotubes with graphene walls (OCNTG) formed on the inner surface of pores. It is shown with the use of microfiltration membranes “TRUMEM” (Daverage ˜ 130 nm) that reactions of CO oxidation (over a Cu0,03Ti0,97O2 ± δ catalyst) and oxidative conversion of methane to synthesis gas and light hydrocarbons (over La + Ce/MgO) are significantly intensified when membranes are used. Almost the same value of methane conversion as in a flow reactor is reached in a membrane catalytic module at temperatures which are lower by 100–170 °C. Investigation of hydrogen adsorption, storage and desorption regularities in nano-sized membrane reactors was performed via forming of OCNTG in the pores of ultrafiltration membranes “TRUMEM” (Daverage = 50 nm and 90 nm) and their saturation with hydrogen under 10–13 MPa. It is found that the amount of adsorbed hydrogen reached 14.0% of OCNTG weight. Adsorption of hydrogen in OCNTG is characterized for the first time by thermogravimetric analysis (TGA) coupled with mass-spectrometric analysis. Hydrogen desorption under atmospheric pressure occurs at ˜175 °C. Adsorptivity to hydrogen of three carbon structures, nanocrystallites of pyrocarbon (NCP), their superposition, and OCNTG, is studied. It is found that this property is characteristic only for the latter structure. A new effect of hydrogen variation of performance (HVP) is found: hydrogen adsorbed in OCNTG affects the transport properties of membranes decreasing their performance on liquids 4–26-fold which confirms high activity of hydrogen indirectly, the dissociative mechanism of hydrogen adsorption being probably the basis.