The preparation of oil-soluble metal carbonate colloids is of interest in the area of lubricant additives. This study presents a novel mass-transfer intensified approach for efficient preparation of monodisperse CaCO3 nanopartides as overbased nanodetergents based on W/O microemulsion using a high-gravity rotating packed bed (RPB) reactor. The effects of high gravity level, gas-liquid ratio, gas and liquid flow rates were systematically investigated. The as-prepared products had good transparency, an average particle size of about 6 nm, a high storage stability of over 18 months, a solid content of 38.5 wt% and a highest total base number (TBN) of 417 mgKOH/g. As compared to conventional stirring tank reactor (STR), the product prepared in the RPB reactor had better monodispersity and stability, smaller average particle size, narrower size distribution and higher TBN. Furthermore, the RPB reactor had a greatly shortened carbonation reaction time from 120 min of SIR to 53 min, increasing the production efficiency by about 56%. (C) 2017 Elsevier B.V. All rights reserved.