PTQ Q4 2022 Issue

High throughput experimentation meets chlorine chemistry A novel high throughput unit designed for the accelerated testing of HCl oxidation catalysts under industrially relevant conditions

Enrico Lorenz, Moritz Dahlinger, Tobias Zimmermann and Jean-Claude Adelbrecht hte GmbH Markus Frietsch Gasmet Technologies GmbH

C hlorine is one of the most abundant commodity chem- icals in the world. About 85% of all pharmaceuticals and more than 50% of chemicals are derivatives from the chlorine value chain.¹ Two of the largest chlorine con- sumers are vinyl chloride synthesis (PVC monomer) and the production of isocyanates (methylenediphenyl/toluene diiso- cyanate [TDI/MDI]). However, the chlorination of organic compounds is always adversely affected by hydrochloric acid (HCl), which is formed as a byproduct. While HCl is essentially recycled within the PVC value chain to a major extent, isocyanate production is flooding the market with byproduct HCl, at strong growth rates. If excess HCl cannot be recycled or valorised directly via muriatic acid, it needs to be disposed of by neutralisation or deep welling, which is expensive and detrimental to the environment. Chlorine recovery is the more desirable option from an economic point of view since it enhances the overall process efficiency and reduces the dependency on fluctuations in the chlorine market price and availability. The catalytic oxidation of HCl via the Deacon process is an attractive way to restore chlorine since it is much more energy-saving than the state-of-the-art electrochemical processes.² Since the current solutions for the Deacon processes

involve active but expensive Ru catalysts, the search for cheaper alternatives based on Cu or Cr is of commercial interest.³ - ⁵ However, even if promising catalyst candi - dates are developed, suitable laboratory test protocols are strongly limited in the parameter space, scale, or runtime due to the corrosiveness of the chemistry. We have devel- oped a high throughput lab-scale technology that is able to test 16 catalysts in parallel under industrially relevant conditions to address the challenges of chlorine chemistry. Experimental Unit design and operation Standard laboratory equipment is usually assembled with stainless steel components. Therefore, it suffers from severe corrosion by contact with strong acidic components like HCl or chlorine, especially in a wet gas environment. Although advanced alloys with a high Ni content significantly reduce corrosion, they do not avoid it completely. A few polymer- based materials like PTFE or glass are chemically resistant but prone to breakage when operating under high tempera- ture or pressure. The contrast of chemical versus mechanical resistance is one of the core issues that must be overcome for the high throughput testing of chlorine chemistry, especially when approaching industrially relevant testing protocols.

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Vent

HCl

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Water

STD

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Figure 1 Simplified flow sheet of the 16-fold high throughput unit including feed section, parallel reactors, online analytics, and off-gas treatment

PTQ Q4 2022