Designing MFI-based catalysts with improved catalyst life for C-3(=) and C-5(=) oligomerization to high-quality liquid fuels

[EN] Light olefin oligomerization is an important alternative for the production of clean liquid automotive fuels and can be performed in the presence of solid acid catalysts. Among these, medium-pore zeolites, and especially ZSM-5, have been widely described in the open literature. In this work, the relative importance of intracrystalline diffusion path lengths for the product molecules (depending on the zeolite crystal size and the presence of mesopores in the crystallites) and Bronsted acid site density are discussed for two different olefins, propene and 1-pentene. Thus, ZSM-5 samples with (a) the same crystallite size and different acid site density, (b) the same density of acid sites and different crystallite size, (c) postsynthesis generation of mesopores by different desilication seventies, and (d) samples with similar crystal size, mesoporosity, and acid site density, but with a different ratio of external to internal acid sites have been prepared and studied for oligomerization of propene and 1-pentene. The results obtained suggest that the properties required for a best-performing catalyst (maximum conversion and lowest deactivation rate) are different for these two alkenes. Whereas Bronsted acid site density is determinant for propene oligomerization when intracrystalline diffusion path lengths are below a certain critical value, the presence of a large number of Bronsted acid sites is not sufficient in the case of 1-pentene, and additional mesoporosity becomes crucial. Thus, mesoporous ZSM-5 samples prepared by postsynthesis desilication treatments present a greater improvement in initial conversion and catalyst life for 1-pentene oligomerization than for conversion of propene.The authors thank BP Products North America and Consolider-Ingenio 2010 (MULTICAT Project) for their financial support and permission to publish this work. R. Sanchis is acknowledged for technical support.Corma Canós, A.; Martínez, C.; Doskocil, E. (2013). Designing MFI-based catalysts with improved catalyst life for C-3(=) and C-5(=) oligomerization to high-quality liquid fuels. Journal of Catalysis. 300:183-196. https://doi.org/10.1016/j.jcat.2012.12.029S18319630

Coke steam reforming in FCC regenerator: A new mastery over high coking feeds

[EN] One of the crucial problems of processing residual feeds in the FCC is their high coking tendency, which limits their use in the FCC and requires them to be mixed with lighter feeds to be processed in conventional FCC units. A step-out improvement of the FCC process to use in processing heavy feeds is presented, where the heat balance in the unit is maintained by removing the high coke-on-catalyst by a combination of coke combustion and reforming, i.e., coke steam reforming (CSR) in the regenerator. This option enables using feeds with more than 10% Conradson Carbon while still maintaining the possibility to control the heat balance in the unit without using partial combustion or catalyst coolers. Although the Equilibrium catalyst has little CSR activity, we have found that hydrotalcite materials, besides having an excellent catalytic cracking selectivity for heavy feeds, also have significant CSR activity. We have demonstrated that CSR can be performed together with combustion at conditions found in the FCC regenerator so that the regenerator temperature remains within traditional limits despite higher coke-on-catalyst, and the coke on the catalyst is nearly completely removed. While the reaction rate at higher temperatures seems to obey first order, steam reforming coke removal kinetics at lower (750 degrees C) temperatures seem more complex due to the heterogeneous nature of coke.The authors thank BP Products North America and Consolider-Ingenio 2010 (MULTICAT project) for their financial support and permission to publish this work.Corma Canós, A.; Sauvanaud ., LL.; Doskocil, E.; Yaluris, G. (2011). Coke steam reforming in FCC regenerator: A new mastery over high coking feeds. Journal of Catalysis. 279(1):183-195. https://doi.org/10.1016/j.jcat.2011.01.020S183195279

Identifying challenges towards practical quantum advantage through resource estimation: the measurement roadblock in the variational quantum eigensolver

Recent advances in Noisy Intermediate-Scale Quantum (NISQ) devices have brought much attention to the potential of the Variational Quantum Eigensolver (VQE) and related techniques to provide practical quantum advantage in computational chemistry. However, it is not yet clear whether such algorithms, even in the absence of device error, could achieve quantum advantage for systems of practical interest and how large such an advantage might be. To address these questions, we have performed an exhaustive set of benchmarks to estimate number of qubits and number of measurements required to compute the combustion energies of small organic molecules to within chemical accuracy using VQE as well as state-of-the-art classical algorithms. We consider several key modifications to VQE, including the use of Frozen Natural Orbitals, various Hamiltonian decomposition techniques, and the application of fermionic marginal constraints. Our results indicate that although Frozen Natural Orbitals and low-rank factorizations of the Hamiltonian significantly reduce the qubit and measurement requirements, these techniques are not sufficient to achieve practical quantum computational advantage in the calculation of organic molecule combustion energies. This suggests that new approaches to estimation leveraging quantum coherence, such as Bayesian amplitude estimation [arxiv:2006.09350, arxiv:2006.09349], may be required in order to achieve practical quantum advantage with near-term devices. Our work also highlights the crucial role that resource and performance assessments of quantum algorithms play in identifying quantum advantage and guiding quantum algorithm design.Comment: 27 pages, 18 figure

Improved THETA-1 for light olefins oligomerization to diesel: Influence of textural and acidic properties

The increase in diesel demand, especially in Europe, and the need for high fuel quality requirements are forcing refiners to move into additional processes for production of high cetane diesel in order to meet the present market trends. Oligomerization of light olefins into middle distillate range products is a viable option. The fuel produced through this technology is environmentally friendly, free of sulfur and aromatics, and the adequate choice of the heterogeneous catalyst will direct the selectivity towards low branched oligomers, which will result in a high quality product. In this work we show the benefits of combining basic desilication treatments for generation of additional mesoporosity in mono-directional Theta-1 zeolite, with selective acid dealumination steps that restore not only the microporosity to values close to those of the parent samples, but also the total and strong Bronsted acidity. These modified Theta-1 zeolites present an outstanding catalytic behavior for oligomerization of propene, with a largely increased initial activity, a much higher resistance to deactivation with time on stream, and an improved selectivity to products in the diesel fraction, as compared to the original microporous Theta-1.The authors thank BP Products of North America for their financial support and permission to publish this work, and Consolider Ingenio 2010-Multicat, the "Severo Ochoa Program", and MAT2012-31657 for financial support. R. Sanchis is acknowledged for technical support.Martínez, C.; Doskocil, EJ.; Corma Canós, A. (2014). Improved THETA-1 for light olefins oligomerization to diesel: Influence of textural and acidic properties. Topics in Catalysis. 57(6-9):668-682. https://doi.org/10.1007/s11244-013-0224-xS668682576-9Bellussi G, Mizia F, Calemma V, Pollesel P, Millini R (2012) Microporous Mesoporous Mater 164:127–134Bellussi G, Carati A, Millini R (2010) In: Cejka J, Corma A, Zones S (eds) Zeolites and Catalysis. Wiley-VCH Verlag GmbH & Co., Weinheim, pp 449–491Martinez C, Corma A (2011) Coord Chem Rev 255:1558–1580de Klerk A (2005) Ind Eng Chem Res 44:3887–3893de Klerk A (2006) Energy Fuels 20:439–445de Klerk A (2006) Energy Fuels 20:1799–1805Egloff G (1936) Ind Eng Chem Res 28:1461–1467Degnan TF Jr, Smith CM, Venkat CR (2001) Appl Catal A Gen 221:283–294Apelian MR, Boulton JR, Fung AS (1994) US5284989, to Mobil OilQuann RJ, Green LA, Tabak SA, Krambeck FJ (1988) Ind Eng Chem Res 27:565–570Tabak SA, Krambeck FJ, Garwood WE (1986) AIChE J 32:1526–1531Corma A, Martínez C, Doskocil EJ (2013) J Catal 300:183–196Martens JA, Ravishankar R, Mishin IE, Jacobs PE (2000) Angew Chem Int Ed Engl 39:4376–4379Martens JA, Verrelst WH, Mathys GM, Brown SH, Jacobs PA (2005) Angew Chem Int Ed Engl 117(5833–583):6Pater JPG, Jacobs PA, Martens JA (1998) J Catal 179:477–482Tabak SA (1981) US4254295, to Mobil OilOccelli ML, Hsu JT, Galya LG (1985) J Mol Catal A: Chem 32:377–390Tabak SA (1984) US4504693, to Mobil Oil CorpKholer E, Schmidt F, Wernicke HJ, Pontes MD, Roberts HL (1995, Summer) Hydrocarbon Technology InternationalMartens JA, Verduijn JP (1995) WO95/19945, to Exxon Chemical Patents Inc.Verrelst WH (1995) Martens LRM, WO95/22516, to Exxon Chemical Patents Inc.Verrelst WH, Martens LRM (2000) US6143942, to Exxon Chemical Patents Inc.Verrelst WH, Martens LRM, Verduijn JP (2006) US6013851, to Exxon Chemical Patents Inc.Dakka JM, Mathys GMK, Puttemans MPH (2003) WO03/035583 to Exxon-Mobil Chemical LimitedMatias P, Sa CC, Graca I, Lopes JM, Carvalho AP, Ramoa RF, Guisnet M (2011) Appl Catal A 399:100–109Chal R, Gérardin C, Bulut M, van Donk S (2011) ChemCatChem 3:67–81Perez-Ramirez J, Christensen CH, Egeblad K, Groen JC (2008) Chem Soc Rev 37:2530–2542Verboekend D, Perez-Ramirez J (2011) Catal Sci Technol 1:879–890Serrano DP, Escola JM, Pizarro P (2013) Chem Soc Rev 42:4004–4035Verboekend D, Chabaneix AM, Thomas K, Gilson JP, Perez-Ramirez J (2011) Cryst Eng Comm 13:3408–3416Emeis CA (1993) J Catal 141:347–354Perego C, Peratello S (1999) Catal Today 52:133–145Abello S, Bonilla A, Perez-Ramirez J (2009) Appl Catal A Gen 364:191–198Corma A, Martinez C, Doskocil EJ, Yaluris G (2011) WO2011002631A2, to BP Oil International Limited. BP Corporation North America Inc., UKCorma A, Martinez C, Doskocil EJ, Yaluris G (2011) WO2011002630A2, to BP Oil International Limited. BP Corporation North America Inc, UKHan S, Heck RH, DiGuiseppi FT (1993) US5234875, to Mobil Oil CorporationPeratello S, Molinari M, Bellussi G, Perego C (1999) Catal Today 52:271–27

Effects of Void Environment and Acid Strength on Alkene Oligomerization Selectivity

The effects of channel connectivity, void environment, and acid strength on the relative rates of oligomerization, β-scission, and isomerization reactions during light alkene conversion (ethene, propene, isobutene; 2–400 kPa alkene; 473–533 K) were examined on microporous (TON, MFI, MOR, BEA, FAU) and mesoporous (amorphous silica–alumina (SiAl), MCM-41, Keggin POM) Brønsted acids with a broad range of confining voids and acid strength. Skeletal and regioisomers equilibrate under all conditions of pressure and conversion and on all catalysts, irrespective of their acid strength, void size, or framework connectivity, consistent with rapid hydride and methyl shifts of alkoxides intermediates and with their fast adsorption–desorption steps. Such equilibration is evident from detailed chemical speciation of the products and also from intramolecular isotopic scrambling in all oligomers formed from 2-¹³C-propene on TON, MFI, SiAl, and POM clusters. Previous claims of kinetic control of skeletal isomers in oligomerization catalysis through shape-selective effects conferred by void environments may have used inaccurate tabulated thermodynamics, as we show in this study. The void environment, however, influences the size distribution of the chains formed in these acid-catalyzed alkene reactions. One-dimensional microporous aluminosilicates predominantly form true oligomers, those expected from dimerization and subsequent oligomerization events for a given reactant alkene; such chains are preserved because they cannot grow to sizes that would inhibit their diffusion through essentially cylindrical channels in these frameworks. Amorphous SiAl and colloidal silica-supported POM clusters contain acid sites of very different strength; both exhibit size variations across the void space, but at length scales much larger than molecular diameters, thus preserving true oligomers by allowing them to egress the void before β-scission events. Mesoporous acids of very different strength (POM, SiAl) give similar true isomer selectivities, as also observed on MFI structures with different heteroatoms (X-MFI, where X = Al, Ga, Fe, B), which also differ in acid strength; this insensitivity reflects oligomerization and β-scission reactions that involve similar ion-pair transition states and therefore depend similarly on the stability of the conjugate anion. Three-dimensional microporous frameworks contain voids larger than their interconnecting paths, an inherent consequence of intersecting channels and cage–window structures. As a result, oligomers can reach sizes that restrict their diffusion through the interconnections, until β-scission events form smaller and faster diffusing chains. These undulations are of molecular dimensions and their magnitude, which is defined here as the ratio of the largest scale to the smallest scale along intracrystal diffusion paths, determines the extent to which oligomerization–scission cycles contribute to the size distribution of products. These contributions are evident in the extent to which chain size and the number of ¹³C atoms in each molecule formed from 2-¹³C-propene approach their binomial distributions, as they do on microporous acids with significant undulations. The general nature of these conclusions is evident from the similar effects of void shape and connectivity and of acid strength on selectivity for ethene, propene, and isobutene reactants

Characterization of selective oxidation catalysts from polyoxometalate precursors using ammonia adsorption microcalorimetry and methanol oxidation studies

Phosphomolybdic acid (H3PMo12O40) along with niobium, pyridine and niobium/pyridine exchanged phosphomolybdic acid compounds were prepared. These compounds were converted to selective oxidation catalysts by pre-treating to 693 K in an inert atmosphere. As shown previously, the active catalyst consists of partially decomposed, partially reduced Keggin units and MoOx fragments with some MoOx fragments collected around the Nb. The amount of surface Mo species reduced to the 5+ oxidation state varied among the catalysts. Ammonia adsorption microcalorimetry and methanol oxidation studies were carried out to investigate the acid sites strength and the acid/base/redox properties of each catalyst. The addition of niobium, pyridine or both increased the ammonia heat of adsorption by 30-40 kJ/mol and the total ammonia uptake. The catalyst with both niobium and pyridine demonstrated the largest number of strong sites. For the parent H 3PMo12O40 catalyst, methanol oxidation favors the redox product (∼95% selectivity). However, catalyst deactivation occurs. The presence of niobium results in similar selectivity to redox products (∼93%) but also results in no catalyst deactivation. Incorporation of pyridine to the precursor compound, in contrast, changes the selectivity to initially favor the acid product (∼62%). Again, the catalyst deactivated and selectivity changed during deactivation to favor the redox product (∼55%). Finally, the inclusion of both niobium and pyridine results in strong selectivity to the acid product (∼95%) while also showing no catalyst deactivation and stable selectivity. Specific activity for the niobium and pyridine exchanged catalyst for the methanol oxidation reaction was twice any other catalyst. Selectivity to acid products was correlated with the amount of reduced surface Mo species. Thus, the presence of pyridine appears to enhance the acid property of the active site in the catalyst while niobium appears to stabilize the active site. © 2013 Elsevier B.V

Maximizing noble metal utilization in solid catalysts by control of nanoparticle location

Maximizing the utilization of noble metals is crucial for applications such as catalysis. We found that the minimum loading of platinum for optimal performance in the hydroconversion of n-alkanes for industrially relevant bifunctional catalysts could be reduced by a factor of 10 or more through the rational arranging of functional sites at the nanoscale. Intentionally depositing traces of platinum nanoparticles on the alumina binder or the outer surface of zeolite crystals, instead of inside the zeolite crystals, enhanced isomer selectivity without compromising activity. Separation between platinum and zeolite acid sites preserved the metal and acid functions by limiting micropore blockage by metal clusters and enhancing access to metal sites. Reduced platinum nanoparticles were more active than platinum single atoms strongly bonded to the alumina binder