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The effect of Cu loading on the selective catalytic reduction of NO x by NH 3 was examined over a series of Cu ion-exchanged (20-80%) SSZ-13 zeolite catalysts. High NO reduction efficiencies (80-95%) were obtained over all catalyst samples between 250 and 500°C, and at the gas hourly space velocity of 200,000 h -1 . Both NO reduction and NH 3 oxidation activities under these conditions were found to increase slightly with increasing Cu loading at low temperatures. However, NO reduction activity was suppressed with increasing Cu loadings at high temperatures ([500°C) due to excess NH 3 oxidation. The optimum Cu ion exchange level appears to be *40-60% since higher than 80% NO reduction efficiency was obtained over 50% Cu ion-exchanged SSZ-13 up to 600°C. The NO oxidation activity of Cu-SSZ-13 was found to be low regardless of Cu loading, although it was somewhat improved with increasing Cu ion exchange level at high temperatures. During the ''fast'' SCR (i.e., NO/ NO 2 = 1), only a slight improvement in NO x reduction activity was obtained for Cu-SSZ-13. Regardless of Cu loading, near 100% selectivity to N 2 was observed; only a very small amount of N 2 O was produced even in the presence of NO 2 . The apparent activation energies for NO oxidation and NO SCR were estimated to be *58 and *41 kJ/mol, respectively.

Side on! Combined FTIR and NMR studies revealed the presence of a side-on nitrosyl species in the zeolite Cu-SSZ-13. This intermediate is very similar to those found in nitrite reductase enzyme systems. The identification of this intermediate led to the proposal of a reaction mechanism that is fully consistent with the results of both kinetic and spectroscopic studies.

Graphical Abstract Keywords Copper loading · Cu/SSZ-13 · NH 3 adsorption · Chabazite · Six-membered rings · Large cages · Si/Al ratio

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Cellulose is a major component of plant cell walls and is the most abundant macromolecule on earth. The two major allomorphs ofthis biopolymer are cellulose I and cellulose II. Cellulose I, the dominant form in nature (1), consists of a microfibrillar crystalline array of linear P-1,4-glucan chains, all ofwhich are oriented parallel to one another with the same polarity (2). The extended chain conformation of cellulose I allows the formation of microfibrils having extraordinary mechanical strength. Normally, cellulose II is formed from cellulose I through chemical treatments that alter the crystal structure (e.g., mercerization) (3, 4). The cellulose II allomorph also is produced by a few organisms in nature (3,5,6).