Joint research project

Catalyst development for reforming of methane with steam and carbon dioxide yielding syngas with tunable H2 and CO ratio

Project leaders
Valeria La Parola, Anita Nagyne Horvath
Agreement
UNGHERIA - HAS (MTA) - Accademia Ungherese delle Scienze
Call
CNR/HAS triennio 2019-2021 2019-2021
Department
Chemical sciences and materials technology
Thematic area
Chemical sciences and materials technology
Status of the project
New

Research proposal

Global warming and energy crisis are among the major issues threatening the health and economy of countries. The worldwide compulsory reduction of the CO2 emission and the more efficient exploitation of natural and shale gas resources initiated intense scientific research on catalytic methane conversion technologies. Three methane reforming routes can provide hydrogen and carbon monoxide mixture (syngas) with different ratio depending of the oxidant:
Dry reforming, DRM: CH4+CO2 = 2CO +2 H2 H°298 K= 247 kJ/mol
Steam reforming, SRM: CH4+H2O = CO +3 H2 H°298 K= 206 kJ/mol
Bi-reforming, BRM: 3CH4+CO2 +2H2O = 4CO +8 H2 H°298 K= 220 kJ/mol
Among the above reactions, only steam reforming is carried out industrially in large scale to produce H2 (and CO) for different purposes. H2 can be considered as a promising energy carrier because its exceptional high value of energy per mass content (142 MJ/kg vs. 46.2 Mj/Kg for gasoline), storage and transportation possibilities, safety features and reduced harmful emission. SMR is responsible of ca. 48% of the total world hydrogen production because if its low cost. The production of hydrogen may be coupled, through dry reforming (DRM), with the consumption of CO2. Moreover, the combination of steam and dry reforming results in the rarely studied bi-reforming reaction that provides syngas directly with the optimal ratio for the production of methanol, which can be further processed to olefins (MTO techniques). As it can be seen, all the above reactions are highly endothermic, that means that high temperature (above 600-700 oC) and an effective catalyst are needed for sufficient conversion.
Catalysts for these reactions need to meet stringent requirements such as high activity, reasonable life, good heat transfer, low pressure drop, high thermal stability and excellent mechanical strength. The metals active are the ones of group VIII, usually Nickel, while the supports most commonly used are ±-alumina, magnesia, calcium aluminate or magnesium aluminate.
As for the reaction mechanism, methane activation proceeds with its dissociative adsorption on the metallic active species (and usually considered as rate determining step). This step -
if surface carbon gasification is kinetically hindered - can result in the uncontrolled deposition of carbon on catalyst surface that is one of the major cause of catalyst deactivation. Moreover, the need of high reaction temperatures causes sintering of metal particles, which leads to further catalysts deactivation. For these reasons there is a strong need for stable and coke resistant catalysts. The inhibition of the build up of carbon can be generally achieved by i) the use of basic and/or reducible supports (to increase CO2 activation and/or to get active, mobile surface oxygen species; or ii) by doping with a noble metal. Metal sintering can be inhibited by tuning and optimizing metal-support interaction which has to be high enough to hinder sintering of particles, but not too strong to hinder reduction.
Under these premises, this collaboration between Italian and Hungarian team is focused on the preparation of Ni-based catalysts with long life applicable in all the above reforming reactions. Two different strategies will be pursued: i) doping the Ni catalysts with small amount of noble (Pt, Au) or post transition metals (In) or ii) modifying the support with alkaline (Na) or partially reducible oxides (CeO2, ZrO2).
The doping with noble metals, already explored by the Italian group revealed a synergetic effect of gold and platinum on Ni based catalysts which led to improved catalysts due to a modulation of the structural and reduction properties. Previous studies of the Hungarian team on sodium doped Ni/ZrO2 catalysts (0.6 w% Na- 3% Ni) showed a strong increase in stability with respect to undoped Ni/ZrO2 catalyst due to the localized Na2O incorporation which provided high basicity and resulted in a NiOxHy that is in strong interaction with the support. Moreover, bimetallic NiIn/SiO2 catalyst was active in dry reforming without coke formation due to the electronic and geometric effects of modifier indium metal atoms.
The next overall goal of the collaborative research work is to optimise the metal-support interaction in order to reduce sintering of the active phase by the application of tailored novel synthesis methods. The ability of tuning the CO/H2 product ratio by changing the reaction conditions (type of oxidants, ratio, etc) or catalyst formulation is among our aims as well.

Both research groups have wide experience in the study of dry reforming of methane. The long term cooperation between the two teams lasts since 1999 in the framework of bilateral collaborations (the last in 2010-2012, leaders: A. Horváth and A. M. Venezia) and via common participation in European projects (COST D-5, D-15 and D-36) and the joint papers testify the good complementarity of the research skills. The two partners, due to their specific competencies will carry out strictly complementary jobs. The Italian team will focus its action in the preparation of supports and catalysts, in part of the characterization (TPR, XRD, BET, XPS) and in the reaction of steam reforming. The Hungarian team will focus its activity in the complementary catalyst synthesis, characterization (HRTEM, DRIFTS, XPS experiments after different pretreatments without air-contact, isotope-labeled mechanism and coke formation studies) and in routine dry and preliminary bi-reforming experiments.
The chance to compare the results of the catalytic activity of the materials in these three important reactions will be of great importance in the optimization of the final structures developed.

Research goals

The main objective of the present project is the development of stable catalysts for dry and steam reforming. Combination of steam and dry reforming via bi-reforming on chosen catalyst samples is planned as well. The overall goal of the collaborative research work is to optimise the metal-support interaction in order to reduce sintering of the active phase by the application of tailored novel synthesis methods. Main reaction steps using isotope labeled experiments will be clarified and the source -if any- surface coke will be determined for each catalyst family.
Ni catalysts supported on ceria or ZrO2 doped alumina will be prepared. This mixed support combines the high surface area and thermal stability of alumina with the oxygen mobility of ceria and the basicity of ZrO2. Doping of Ni with small amount of noble (Pt, Au) or post transition (In) metals will be carried out and further modification of the mixed oxide support with minute amount of Na2O will be realised. The ability of tuning the CO/H2 product ratio by changing the reaction conditions (type of oxidants, ratio, etc) or catalyst formulation is among our aims as well.

Last update: 18/07/2024