Scale-Up of Agrochemical Urea-Gypsum Cocrystal Synthesis Using Thermally Controlled Mechanochemistry

Abstract

Atom-and energy-efficient synthesis of a crystalline calcium urea sulfate ([Ca(urea) 4 ]SO 4 ) cocrystal was explored using thermally controlled mechanochemical methods with calcium sulfate compounds containing various amounts of crystalline water (CaSO 4 •xH 2 O, x = 0, 0.5, 2). Small-scale (200 mg) experiments in a shaker mill were first performed, and the progress was monitored by in situ Raman spectroscopy and in situ synchrotron powder X-ray diffraction. Time-resolved spectroscopy data revealed that the presence of water in the reagents' crystalline structure was essential to the reaction and largely determined the observed reactivity of different calcium sulfate forms. Reactions at elevated temperatures were shown to proceed significantly faster on all synthetic scales, while changes in rheology caused by adding external water hindered the reaction progress. The average yield of a 21 mm horizontal twin-screw extruder experiment was ∼5.5 g/ min of extrusion (∼330 g/h). Energy consumption during the milling reactions required to achieve complete conversion ranged from 7.6 W h/g at 70 °C for a mixer mill to 3.0 W h/g at a 50 g scale and 4.0 W h/g at a 100 g scale for a planetary mill or 4.0 W h/g at both 70 °C and RT for a twin-screw extruder, showing a significant improvement in energy efficiency at large-scale production. The obtained crystalline cocrystal exhibited a significantly lower solubility in aqueous solutions, nearly 20 times lower per molar basis compared to that of urea. Furthermore, reactive nitrogen emissions in air at 90% relative humidity, measured as NH 3 , showed slow and nearly linear nitrogen loss for the cocrystal over 90 days, while the same level of emissions was achieved with urea after 1−2 weeks, showing the potential of this cocrystal material as a large-scale nitrogen-efficient fertilizer.

The synchrotron radiation source PETRA III and its future ultra-low-emittance upgrade PETRA IV

“…PETRA III serves a broad user community, covering a very broad range of scientific fields, from physics [1][2][3][4], chemistry [5,6], and biology, to medicine [7,8], materials [9][10][11], geo- [12][13][14][15] and environmental [16,17] science, archaeometry [18], and nanotechnology [19,20]. With this, it makes an important contribution to solving the grand societal challenges, e.g.…”

Sustainable Synthesis of Diamondoid Ethers by High-Temperature Ball Milling

“…This setup was used to synthesize different derivatives containing urea and amido groups, 63 nucleophilic aromatic substitutions (S N Ar) products, 63 and prebiotic oligomerization of amino acids. 64 Moreover, high-temperature ball milling on a laboratory scale was exploited in the scale-up of the syntheses of S N Ar and Knoevenagel reactions, 65 as well as agrochemicals based on urea and gypsum cocrystals, 66 using the continuous mechanochemical manufacturing by twin-screw extrusion. The mentioned examples demonstrate the versatility of mechanochemical synthesis and showcase a wide range of substrates.…”

Induction-heated ball-milling: a promising asset for mechanochemical reactions

“…Noticeable exceptions include the work by Užarević and co-workers, who designed a specific reactor with an included sapphire window to monitor ball-milling reactions under heat-treatment using Raman spectroscopy, 17 and the recent investigations by Michalchuck and co-workers. 28 In this general context, because of the very attractive prospect of being able to combine heating and milling (Table S5), [29][30][31] it appeared to us as an important goal to be able to propose alternative heating approaches, which would (i) be directly adaptable to standard commercially available ball-milling machines, without requiring a re-design of the milling jars (especially because synthesis outcomes can be modified when varying the geometry or composition of the milling jar and beads), 32,33 (ii) offer the possibility to perform efficient heating when using reactors transparent to Xray or Raman-laser beams (e.g. made of PMMA or polycarbonate) in order to perform in situ and/or operando analyses of the media during the heating, and thereby follow the course of the reactions.…”