In the field of heterogeneous catalysis, the successful integration of enzymes and inorganic catalysts could pave the way to multifunctional materials which are able to perform advanced cascade reactions. However, such combination is not straightforward, for example in the case of zeolite catalysts for which enzyme immobilization is restricted to the external surface. Herein, this challenge is overcome by developing a new kind of hybrid catalyst based on hollow zeolite microspheres obtained by the aerosol-assisted assembly of zeolite nanocrystals. The latter spheres possess open entry-ways for enzymes, which are then loaded and cross-linked to form cross-linked enzyme aggregates (CLEAs), securing their entrapment. This controlled design allows the combination of all the decisive features of the zeolite with a high enzyme loading. A chemo-enzymatic reaction is demonstrated, where the structured zeolite material is used both as a nest for the enzyme and as an efficient inorganic catalyst. Glucose oxidase (GOx) ensures the in situ production of H2O2 subsequently utilized by the TS-1 zeolite to catalyze the epoxidation of allylic alcohol toward glycidol. The strategy can also be used to entrap other enzymes or combination of enzymes, as demonstrated here with combi-CLEAs of horseradish peroxidase (HRP) and glucose oxidase. We anticipate that this strategy will open up new perspectives, leveraging on the spray-drying (aerosol) technique to shape microparticles from various nano-building blocks and on the entrapment of biological macromolecules to obtain new multifunctional hybrid microstructures.

/pdf/hollow-zeolite-microspheres-as-a-nest-for-enzymes-a-new-3wbxugixjq.pdf

Hollow zeolite microspheres as a nest for enzymes: a new route to hybrid heterogeneous catalysts

The ammoximation of cyclohexanone using preformed hydrogen peroxide (H2O2) is currently applied commercially to produce cyclohexanone oxime, an important feedstock in nylon-6 production. We demonstrate that by using supported gold-palladium (AuPd) alloyed nanoparticles in conjunction with a titanium silicate-1 (TS-1) catalyst, H2O2 can be generated in situ as needed, producing cyclohexanone oxime with >95% selectivity, comparable to the current industrial route. The ammoximation of several additional simple ketones is also demonstrated. Our approach eliminates the need to transport and store highly concentrated, stabilized H2O2, potentially achieving substantial environmental and economic savings. This approach could form the basis of an alternative route to numerous chemical transformations that are currently dependent on a combination of preformed H2O2 and TS-1, while allowing for considerable process intensification. Description Peroxide as needed Hydrogen peroxide for commercial applications is currently mass produced through an indirect process that involves reduction and reoxidation of a quinone. The trouble with making it straight from the elements is that concentrated mixtures of hydrogen and oxygen are dangerously explosive. Lewis et al. report that direct peroxide synthesis at safe concentrations is compatible with a current industrial method for producing cyclohexanone oxime, a key precursor to nylon. The protocol could potentially offer substantial efficiency advantages for manufacturing a high-volume bulk chemical. —JSY Making hydrogen peroxide in situ could improve overall process efficiency for production of a key nylon precursor.

/pdf/highly-efficient-catalytic-production-of-oximes-from-ketones-118w6x9b.pdf

Highly efficient catalytic production of oximes from ketones using in situ–generated H2O2

The combination of inorganic heterogeneous catalysts and enzymes, in so-called hybrid chemoenzymatic heterogeneous catalysts (HCEHCs), is an attractive strategy to effectively run chemoenzymatic reactions. Yet, the preparation of such bifunctional materials remains challenging because both the inorganic and the biological moieties must be integrated in the same solid, while preserving their intrinsic activity. Combining an enzyme and a zeolite, for example, is complicated because the pores of the zeolite are too small to accommodate the enzyme and a covalent anchorage on the surface is often ineffective. Herein, we developed a new pathway to prepare a nanostructured hybrid catalyst built from glucose oxidase and TS-1 zeolite. Such hybrid material can catalyse the in situ biocatalytic formation of H2O2, which is subsequently used by the zeolite to trigger the epoxidation of allylic alcohol. Starting from an enzymatic solution and a suspension of zeolite nanocrystals, the hybrid catalyst is obtained in one step, using a continuous spray drying method. While enzymes are expectedly unable to resist the conditions used in spray drying (temperature, shear stress, etc.), we leverage on the preparation of “enzyme–polyelectrolyte complexes” (EPCs) to increase the enzyme stability. Interestingly, the use of EPCs also prevents enzyme leaching and appears to stabilize the enzyme against pH changes. We show that the one-pot preparation by spray drying gives access to hybrid chemoenzymatic heterogeneous catalysts with unprecedented performance in the targeted chemoenzymatic reaction. The bifunctional catalyst performs much better than the two catalysts operating as separate entities. We anticipate that this strategy could be used as an adaptable method to prepare other types of multifunctional materials starting from a library of functional nanobuilding blocks and biomolecules.

/pdf/hybrid-chemoenzymatic-heterogeneous-catalyst-prepared-in-one-49tvzcflka.pdf

Hybrid chemoenzymatic heterogeneous catalyst prepared in one step from zeolite nanocrystals and enzyme–polyelectrolyte complexes

The preparation of copper‐based heterogeneous catalysts dedicated to the hydrogenation of CO2 to methanol typically relies on multi‐step procedures carried out in batch. These steps are precisely tailored to introduce the active phase (Cu) and the promoters (e. g., zinc, gallium) onto a preformed support to maximize catalyst performance. However, each process step can be associated with the formation of waste and with the consumption of energy, thereby negatively impacting the environmental performance of the overall catalyst preparation procedure. Here, a direct and continuous production process is proposed for the synthesis of efficient catalysts for the CO2‐to‐methanol reaction. Gallium‐ and zinc‐promoted mesoporous Cu−SiO2 catalysts were prepared in one step by the aerosol‐assisted sol‐gel process. The catalysts consisted of spherical microparticles and featured high specific surface area and pore volume, with interconnected pores of about 6 nm. A strong promoting effect of Ga and Zn was highlighted, boosting the selectivity for methanol at the expense of CO. Upon calcination, it was shown that Cu species (initially trapped in the silica matrix) underwent a migration towards the catalyst surface and a progressive sintering. After optimization, the catalysts obtained via such direct, continuous, simple, and scalable route could compete with the best catalysts reported in the literature and obtained via multi‐step approaches.

/pdf/co2-hydrogenation-to-methanol-with-ga-and-zn-doped-xgrctlv5rr.pdf

CO2 Hydrogenation to Methanol with Ga- and Zn-Doped Mesoporous Cu/SiO2 Catalysts Prepared by the Aerosol-Assisted Sol-Gel Process*.

Cleaner and atomic economy production of hydroxylamine hydrochloride under solvent-free conditions through process intensification

The spray-forming process of the nano-titanium silicalite (TS-1) zeolite was investigated and optimized in the lab in order to obtain materials with microsphere morphology and superior catalytic activity in cyclohexanone ammoximation on the industrial scale. The effects of spray-forming parameters, such as the state of the TS-1 raw material, load ratio, solid content, binder content, and calcination temperature, on the physicochemical and catalytic properties of TS-1 microspheres were investigated in detail. It was interesting to find that the shape of the spray-forming sample formed by wet powders was more intact than the sample formed by dried powders. Furthermore, the spray-forming process was successfully scaled up to a large spray device (LGZ-1000) according to the similarity principle of load ratio, and the shape of the TS-1 microspheres was as perfect as the spray-forming samples in the lab. The similarity principle of the load ratio for the spray-forming of titanium silicate was established and verified for the first time. The spray-forming TS-1 microspheres produced in the industry were used in cyclohexanone ammoximation, and ketone conversion and oxime selectivity were as high as 99.9 and 99.4%, respectively.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.8b02561

Fabrication of Microspheres by Nano-TS-1 Crystals via a Spray-Forming Process: From Screening to Scale-up.

The synthesis of a TS-1 zeolite with high-content framework Ti and small particles has been developed by adding NH4HCO3 and suspended seeds as an assistant. With the addition of NH4HCO3, the Hofmann decomposition of the tetrapropylammonium cation (TPA+) decreased, and the framework Ti content of the zeolite increased first and then decreased while the particle became larger. With the assistance of suspended seeds, the TS-1 synthesized under a low-alkalinity system possesses small particle size and high-content framework Ti, and it shows the best catalytic activity among the prepared catalysts. Because the decomposition of TPA+ decreased, the mother liquid could be reused in the next run of preparation. Even though the recycled mother liquid was reused five times, all obtained TS-1 samples exhibited similar catalytic performances in propylene epoxidation. This work provides an efficient process for preparing TS-1 with good catalytic performance and reduces the discharge of the waste liquid.

The Clean Synthesis of Small-Particle TS-1 with High-Content Framework Ti by Using NH 4 HCO 3 and Suspended Seeds as an Assistant.

A cleaner ammoximation of cyclohexanone over Ti-MWW in dimethyl carbonate

The invention provides a safe low-energy-consumption forming method for a titanium-silicon molecular sieve spray The method comprises the steps that an additive is added into hydro-thermal synthesized titanium-silicon molecular sieve crystallization liquid at first to enable the titanium-silicon molecular sieve crystallization liquid to be preclustered to a millimeter-sized cluster; organic matter such as most water and temple agent is separated out; the preclustered cluster is dispersed into an acid aqueous solution, spraying is carried out at the low inlet temperature and the high feeding speed to enable the cluster to achieve secondary dehydration so as to be clustered into micron-sized particles, roasting is carried out, and a spherical TS-1 catalyst is obtained The problems that mixing is uneven and a spray head is blocked when raw powder spray is adopted are solved, and the potential safety hazard of organic matter carbonization or burning explosion caused when inlet and outlet temperature is too high during crystallization liquid concentration spraying is avoided

Safe low-energy-consumption forming method for titanium-silicon molecular sieve spray

The invention provides a method for preparing hydroxylamine hydrochloride, and specifically relates to a method for preparing hydroxylamine hydrochloride from hydrogen peroxide and ammonium chloride. The method comprises the following steps: catalyzing hydrogen peroxide, free ammonia and acetone or butanone to synthesize ketoxime first, and then enabling the ketoxime to react with ammonium chloride under a negative pressure to generate hydroxylamine hydrochloride, free ammonia, acetone or butanone, wherein the acetone or butanone and the free ammonia are recycled for reuse. The invention solves the problems of high raw material cost and more byproducts for preparation of hydroxylamine hydrochloride in the prior art; meanwhile, low-value ammonium chloride is used for preparing hydroxylamine hydrochloride to ensure that the cost is low, and the sustainable development of the soda industry can be promoted.

Gao Xin

Papers

Fabrication of Microspheres by Nano-TS-1 Crystals via a Spray-Forming Process: From Screening to Scale-up.

The Clean Synthesis of Small-Particle TS-1 with High-Content Framework Ti by Using NH 4 HCO 3 and Suspended Seeds as an Assistant.

A cleaner ammoximation of cyclohexanone over Ti-MWW in dimethyl carbonate

Safe low-energy-consumption forming method for titanium-silicon molecular sieve spray

Method for preparing hydroxylamine hydrochloride