We have evaluated the kinetics of the catalytic oxidation of NO to NO2 using a Pt/alumina catalyst, under conditions relevant to industrial nitric acid production: NO and steam contents up to 5% and 20%, respectively, with temperatures from 250 to 350 °C, and pressures up to 4.7 bar. The objective is to replace the current homogeneous oxidation process, which requires cooling of the process gas and a long residence time, with a more intensive heterogeneous oxidation process, allowing the heat of reaction (114 kJ/mol) to be recovered. This may give a 10% improvement in overall heat recovery and, additionally, lead to reduced capital expenditure (CAPEX) and footprint of new build plants. With world production of nitric acid of 60 million tonnes per annum, the transformation from the homogeneous oxidation of NO to a heterogeneous oxidation can lead to significant environmental benefits and cost reduction.

In-situ atomic force microscopy has been used to investigate the dissolution behavior of industrially relevant silicoaluminophosphate catalysts SAPO-34 and SAPO-18. Spiral growth is prevalent on these materials and it is common for the spirals to be composites of multiple dislocation sources. The spirals dissolve via classical step retreat and the structure dissolves in a two-step process via unstable intermediates. The data support the proposition that the terminating surface of SAPO-34 is composed of double 6-rings. SAPO-34 and SAPO-18 both dissolve by removal of the same structural units with similar mechanisms.

Some of the most important nanoporous materials that are used for industrial applications are formed as intergrowths between structurally related phases. Further, the specific properties and functions are often strongly related to the nature of these intergrowths. By their nature such structures are notoriously difficult to characterize in detail and thereby formulate a structure/property relationship. We approach the problem of the industrially relevant CHA/AEI intergrowth system by getting insight into not only the structure of the materials but also the crystal-growth mechanism and show that the former is crucially dependent upon the latter. Through a detailed X-ray diffraction analysis with optimization of the CHA/AEI layer stacking sequence, it is shown that up to three distinct components are present. These consist of the two end member structures intimately cocrystallizing with an intergrowth structure. The intergrowth composition is further corroborated by nuclear magnetic resonance and unit cell ...

Adsorption equilibrium of CO2 and CH4 at three different temperatures was measured on three isoreticular Zr-MOFs: Zr(1,4-BDC) (UiO-66), Zr(4,4′-BPDC) UiO-67, and Zr(2,6-NDC) (DUT-52). Adsorption equilibrium data was measured at 298, 313, and 343 K up to 30 bar for CO2 and 80 bar for CH4. The three adsorbents have increasing surface areas, pore volumes, and pore sizes in the order UiO-66 < DUT-52 < UiO-67. The maximum CO2 and CH4 loading and selectivity follow the same trend. The relatively low isosteric heats of adsorption of CO2 for the three adsorbents indicate potential application at high partial pressures of CO2 in so-called precombustion schemes. Since equilibrium selectivity was higher for UiO-67, adsorption kinetics of pure gases was also measured in this adsorbent. Diffusion of both molecules is very fast, allowing the use of equilibrium theory for estimation of process performance of this adsorbent.

We address the metal–organic frameworks UiO-6x (x = 6, 7, 8), their band gaps, and the changes in the band gaps upon perturbations in the metal–organic framework structures. Computational studies were performed with complementary experimental band gap measurements. Band gap modulations upon hydrogen substitutions by NH2 and NO2 on the organic linker, hydroxylation and dehydroxylation of the metal center, different linker lengths (x = 6, 7, 8), and Ti and Hf substitutions for Zr were analyzed in detail. The origin of the band gap changes was thoroughly investigated, and this work confirmed a reduction in the band gap upon NH2 and NO2 substitutions. Furthermore, this work explicitly illustrated that changes in the band gap were also observed by changing the coordination around the Zr atom, whereas isovalent substitutions on the metal center did not yield significant perturbations of the band gap.

Adsorption of H2S on the Ni2(dhtp)(H2O)2·8H2O metal–organic framework (known as CPO-27-Ni or MOF-74-Ni) is characterized by in situ powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR), Raman, and UV–visible spectroscopy) and by first-principles periodic boundary conditions calculations. PXRD results show very high stability of CPO-27-Ni framework in the presence of H2S. Nevertheless, as evidenced by change in color of the sample from pale yellow to dark green, the adsorption of H2S strongly affects the coordination of Ni sites. FTIR results show the reversible molecular adsorption of H2S. Experimental and computed energies of interaction reveal good agreement. Quantitative data considering energetic aspects (calorimetric measurements) are also included. This work highlights the fundamentals of H2S adsorption onto the CPO-27-Ni framework.

The combined use of white light interferometry (WLI) and atomic force microscopy (AFM) revealed pentagonal growth spirals on the surface of SAPO-34 crystals. Detailed considerations of the crystal geometry and preferred step energies may explain the unusual shape of these growth spirals. Combining WLI and AFM is an efficient method for screening and detailed analysis of growth hillocks on crystals larger than 10 μm.

Porous crystals are strategic materials with industrial applications within petrochemistry, catalysis, gas storage, and selective separation. Their unique properties are based on the molecular-scale porous character. However, a principal limitation of zeolites and similar oxide-based materials is the relatively small size of the pores, typically in the range of medium-sized molecules, limiting their use in pharmaceutical and fine chemical applications. Metal organic frameworks (MOFs) provided a breakthrough in this respect. New MOFs appear at a high and an increasing pace, but the appearances of new, stable inorganic building bricks are rare. Here we present a new zirconium-based inorganic building brick that allows the synthesis of very high surface area MOFs with unprecedented stability. The high stability is based on the combination of strong Zr-O bonds and the ability of the inner Zr6-cluster to rearrange reversibly upon removal or addition of mu3-OH groups, without any changes in the connecting carboxylates. The weak thermal, chemical, and mechanical stability of most MOFs is probably the most important property that limits their use in large scale industrial applications. The Zr-MOFs presented in this work have the toughness needed for industrial applications; decomposition temperature above 500 degrees C and resistance to most chemicals, and they remain crystalline even after exposure to 10 tons/cm2 of external pressure.