Parallel hydrogenation for the quantification of wetting efficiency and liquid–solid mass transfer in a trickle‐bed reactor

Abstract

A novel method for the measurement of wetting efficiency in a trickle-bed reactor under reaction conditions is introduced. The method exploits reaction rate differences of two first-order liquid-limited reactions occurring in parallel, to infer wetting efficiencies without any other knowledge of the reaction kinetics or external mass transfer characteristics. Using the hydrogenation of linear-and isooctenes, wetting efficiency is measured in a 50-mm internal diameter, high-pressure trickle-bed reactor. Liquidsolid mass transfer coefficients are also estimated from the experimental conversion data. Measurements were performed for upflow operation and two literature-defined boundaries of hydrodynamic multiplicity in trickle flow. Hydrodynamic multiplicity in trickle flow gave rise to as much as 10% variation in wetting efficiency, and 10-20% variation in the specific liquid-solid mass transfer coefficient. Conversions for upflow operation were significantly higher in trickle-flow operation, because of complete wetting and better liquid-solid mass transfer characteristics.

Liquid‐to‐Particle Mass Transfer in a Structured‐Bed Minireactor

“…A feed solution of 0.34 mM K 2 Cr 2 O 7 in 1 M H 2 SO 4 was used to minimize the influence of natural convection of Cr 2 O 7 2− between the fluid and the surface of the copper particles 42. The acid‐to‐dichromate concentration ratio was about 3000, which ensures the transport of dichromate ions through the electrical double layer of the copper particle surface to occur only by forced convection, suppressing their ionic migration 38. The dissolution techniques modify the surface area of the particle and consequently their size 26.…”

“…The electrochemical method has also been employed to measure the local instantaneous liquid‐solid mass transfer coefficient at a certain position within the bed 16, 26–34. Other methods including chemical reacting systems 12, 35–39, activated carbon absorption 40, and ion exchange of Na + from aqueous solutions of NaOH 41 have also been used for the determination of liquid‐solid mass transfer coefficients. An application of the chemical method to study the gas‐liquid‐solid mass transfer effects in a small‐scale three‐phase system was published by Haase et al 12.…”

Liquid holdup and wetting efficiency in a rotating trickle‐bed reactor

“…It can be seen from Figure that the maximum internal static liquid holdup cannot be reached for both sphere sizes, which infers that pores inside the alumina packed in the RTBR were not fully filled by the liquid, and the gap was about 12%. For reactions whose rates are limited by external mass‐transfer, their catalysts are usually egg‐shell type . The nonfully filled state may benefit the reduction of internal diffusion resistance, as the liquid does not have to reach the core of catalyst sphere which is free of active sites.…”

A novel inclined rotating tubular fixed bed reactor concept for enhancement of reaction rates and adjustment of flow regimes

“…It is known that pre-wetting affects the utilization of the catalyst, the flow texture and accordingly, the trickle bed reactor performance [38]. Thus, at first the pre-wetting possibility of operating the reactor in an inclined rotating manner was determined at conditions, which promote stratified flow to periodically immerse the catalyst in the liquid.…”