Research progress and hot spots of hydrothermal liquefaction for bio-oil production based on bibliometric analysis.

Hydrothermal liquefaction (HTL) of biomass used HTL reaction under high temperature and pressure to produce bio-oil. This technology is considered as one of the most promising converting technology of biomass to biofuels. This paper summarized current research developments of HTL for bio-oil and analyzed its reaction mechanism and influencing factors based on bibliometric analysis. The results showed that reaction conditions and catalyst have been still global researching focuses about HTL. Compared with homogeneous catalysts, the study of HTL by using heterogeneous catalyst developed more quickly. With promotion of resource recovering, food waste, sludge, and other organic waste can also be used as raw materials for HTL for bio-oil now. The structure of this paper was shown in graphic abstract. Firstly, bibliometric analysis was conducted on hydrothermal liquefaction for bio-oil production. According to the emergency frequency of key words, catalyst, microalgae, reaction conditions, and biomass waste as raw material for hydrothermal liquefaction were determined as four parts of the paper. Finally, we speculated the development trend of hydrothermal liquefaction for bio-oil production.

Nitrogen release of hydrothermal treatment of antibiotic fermentation residue and preparation of struvite from hydrolysate.

Hydrothermal treatment (HT) is an appropriate treatment method for organic hazardous wastes such as antibiotic fermentation residue (AR). However, there is no effective way to recycle hydrolysate with high nitrogen content. In this study, penicillin fermentation residue (PR, a type of AR) was used as raw material to study the release and redistribution of N during hydrothermal process. And the influences of pH, ion ratio and reaction time on the preparation of struvite were analyzed. The results showed that the nitrogen in PR consists of Inorganic-N and Amino-N. Most of N (~70%) that entered hydrolysate was converted into org-N, NH4+-N and NO3--N. At 260 °C, the NH4+-N concentration was 2842.78 mg/L, accounting for 45.2% of total nitrogen. The remaining amino-N in the hydrochar was gradually converted to pyridine-N, pyrrole-N and quaternary-N with the increasing of temperature. At pH = 9.5, Mg2+: NH4+: PO43- = 1.3: 1: 1.15, struvite was prepared by hydrolysate. And over 95% removal rate of NH4+-N could be achieved. XRD analysis showed that the main component of the product was struvite, which was further confirmed by SEM-EDX and FT-IR. It was found that there was trace amount of MgKPO4·H2O precipitation in the product. In addition, Mg3(PO4)2 precipitation might also be formed at pH = 10.