Recovery of water from cacti for use in small farming communities

In this study, an extensive investigation was conducted to determine if declared weeds could be used as a source of water for agricultural practices in dry areas. The objective of this study was to determineif declared weeds  could successfully be used as a source of water for agricultural practices in dry areas by extracting the water by means of mechanical and chemical methods. The Cereus jamacura cactus, also known as Queen of the Night, with a moisture content of 91 wt%, was selected for this study. Both mechanical and chemical extraction methods were used to determine the maximum water yield possible. Juicing, pressing with a hydraulic cold press and pressing with rollers were used as mechanical methods to extract water from the cacti and water yields of 7.0, 4.9 and 2.9 wt% were obtained respectively. The chemical extraction processes entailed the pulping of the cacti and the filtering off of the water. The effect of pectinase, cellulase and a surfactant at a fixed dosage on the amount of water extracted (mass of water per mass of cacti used) was investigated. The quality of the water was also determined. Temperature (30 to 50°C) and pH (2.5 to 6.5) were varied to find the optimum extraction conditions. The highest water yield (55 wt% of total cacti mass) was obtained using pectinase enzymes at a temperature of 40°C and a pH of 3.5 and cellulose enzymes at a temperature of 35°C and a pH of 5.5. This relates to a yield of 550 L of water per ton of cacti, making chemical water extraction a viable option if compared to the pollution created by the annual burning of the cacti. It was concluded from this study that the water that was extracted from the C. jamacaru cacti would not be suitable for either domestic or industrial application due to the high levels of potassium (up to 2,650 ppm), phosphates (up to 2,200 ppm), sulphates (up to 3,800 ppm) and nitrates (up to 670 ppm) in the water. The high concentration of phosphates and nitrates, however, makes the extracted water an excellent fertiliser for crops requiring high nitrate and phosphate dosages. Small community farmers could thus benefit by using cacti as a source of water for small scale biofuels production plants while also obtaining an excellent additional fertiliser for crop cultivation.Keywords: Cereus jamacaru, water yield, water quality.African Journal of Biotechnology Vol. 12(40), pp. 5926-593

Influence of reactor and condensation system design on tyre pyrolysis products yields

This study investigates the effect the pyrolysis reactor and the condensing system type have on the tyre derived oil (TDO) and DL-limonene yield, as well as benzothiazole concentration in the TDO. All the experiments were performed at 475 °C and three technologies were investigated, fixed bed reactor (FBR), bubbling fluidised bed reactor (BFBR) and conical spouted bed reactor (CSBR), with the latter being the reactor that provided the highest TDO yield (58.2 wt.%). Furthermore, the CSBR enhances DL-limonene production due to its excellent features (low residence time of volatiles and high heat and mass transfer rates), which minimize secondary cracking reactions. Moreover, in order to maximize the TDO retention efficiency and selectively reduce the concentration of certain heteroaromatic species, two types of condensation systems were evaluated: tube-andshell condenser (indirect contact) and quenching condenser (direct contact). The quenching condenser not only promoted the condensation efficiency for DL-limonene, but also reduced the concentration of benzothiazole in the collected TDO. Indeed, the direct contact between water (fed into the quencher) and the hot volatile stream favours the dissolution of some polar heteroaromatic species, thus reducing the nitrogen and sulphur content in the TDO and increasing the applicability of TDO as fuel.This research was supported by the Recycling and Economic Development Initiative of South Africa (REDISA) and the National Research Foundation (NRF). It was also financed by the Ministry of Economy and Competitiveness (CTQ2016-75535-R) and the Ministry of Science, Innovation and Universities of the Spanish Government (RTI2018-101678-B-I00), the European Regional Development Fund (ERDF), the European Commission (HORIZON H2020-MSCA RISE- 2018. Contract No. 823745), the Basque Government (IT1218-19) and the University of the Basque Country (UFI 11/39). The authors acknowledge that any opinions, findings, conclusions or recommendations expressed in this material are the authors' own, and the sponsorscannot accept any liability whatsoever in this regard

Separation of Grubbs-based catalysts with nanofiltration

Thesis (Ph.D. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.This thesis describes the use of organic solvent nanofiltration (OSN) in the field of metathesis for separating homogeneous Grubbs-type catalysts from their post-reaction mixtures for the model metathesis reaction of 1-octene to 7-tetradecene and ethene. The main contributions and objectives of this study were in demonstrating: (i) the successful separation and re-use of different Grubbs-type catalysts from their post-reaction mixtures, and (ii) the successful synthesis of a newly developed catalyst, Gr2Ph, that demonstrated a longer catalytic lifetime for re-usability. The study was twofold in firstly describing the catalytic performances of different Grubbs-type catalysts for the model reaction and secondly in characterizing and describing the separation performances of the 1-octene metathesis system with OSN. In terms of catalyst performances: The catalytic performance of different Grubbs-type precatalysts (Gr1, Gr2, HGr1, HGr2 and the newly developed Gr2Ph) was studied for the model reaction by varying operating parameters, such as reaction temperature (30 to 100 °C), catalyst load (1-octene/Ru molar ratio between 1:5000 and 1:14000) and reaction environment (reaction in the presence of various organic solvents). Quantities such as product distribution, selectivity, yield, catalyst lifetime and activity were used in comparing and evaluating the efficiency of these precatalysts with each other. It was found that all three precatalysts HGM, HGr2 and Gr2Ph showed both metathesis and isomerization activity for the model reaction that was strongly temperature-dependent. Precatalysts HGr2 and Gr2Ph showed significant secondary metathesis activity while precatalyst HGM did not. It was found that the optimal reaction temperature for precatalyst HGM was 30 °C, for precatalyst HGr2 50 °C and for precatalyst Gr2Ph 80 °C. The addition of different solvents to the reaction environment had an overall negative effect towards the formation of the primary metathesis products (PMPs) of 7-tetradecene and ethylene. In this study it was postulated and demonstrated with molecular modelling, that the metathesis reaction of 1-octene with the different Grubbs-type precatalysts (HGM, HGr2 and Gr2Ph) could accurately be described by a type of release-return dissociative mechanism. It was further found that the reaction kinetics of the model reaction with the three precatalysts (HGM, HGr2 and Gr2Ph) could fairly accurately be described by a set of three inter-dependent elementary reaction rate-equations. In terms of separation performances: Five different Grubbs-type precatalysts (Gr1, Gr2, HGr1, HGr2 and Gr2Ph) and the commercially available STARMEM™ series of OSN membranes were used in this study. Parameters such as feed concentration, feed pressure, membrane pretreat-solvent and catalyst load were varied in a dead-end setup. Quantities such as the permeation rate (flux), catalyst rejection, solvent separation (selectivity), degree of swelling and contact angles were measured. It was found that the STARMEM™ 228 membrane successfully separated the different Grubbs-type catalysts from their post-reaction mixtures to below 9 ppm with catalysts rejections greater than 99%. Relative moderate fluxes were obtained that ranged from 0.2 to 15 kg.m-².h-¹. It was shown that 7-tetradecene preferentially absorbed in the STARMEM™ 228 membrane. A solvent non-separating system was observed for binary mixtures of 1-octene, 1-tetradecene and 7-tetradecene. It was found that the predominant parameters that influenced the transport of the 1-octene metathesis system through the ST-228 membrane were solvent properties (such as viscosity) » membrane-solvent interaction properties (such as sorption) > solvent-solvent structural properties (such as molar volume or effective molecular volume). The experimental permeation results for the binary mixtures of 1-octene and 7-tetradecene through the STARMEM™ 228 membrane were described by using pore-flow models, solution-diffusion models and a newly developed model that incorporates structural solvent-solvent interaction. It was found that the newly developed model best described the experimental results. A coupled reaction-separation process was applied that demonstrated the successful reusability of the in-house synthesized catalyst, Gr2Ph. The turnover number was increased from 1400 for a single pass reaction to 5500 for the overall consecutively coupled reaction-separation steps of four cycles. Catalysts Gr1, Gr2, HGM and HGr2 did not show any catalytic activity after the first separation cycle due to extremely short catalytic lifetimes of less than ten hours compared to catalyst Gr2Ph's three days. The short catalytic lifetimes of the classical precatalysts such as Gr1, Gr2, HGr1 and HGr2 in the field of alkene metathesis were solved with the synthesizing concept of modifying and binding the dissociating ligand and anionic ligand with bidentate 0,N-chelated Schiff base ligand on the second generation Grubbs-precatalyst.Doctora

Reactor technology options for distributed hydrogen generation via ammonia decomposition: a review

Hydrogen (H2) fuel obtained via thermo-catalytic ammonia (NH3) decomposition is rapidly attracting considerable interest for portable and distributed power generation systems. Consequently, a variety of reactor technologies are being developed in view of the current lack of infrastructure to generate H2 for proton exchange membrane (PEM) fuel cells. This paper provides an extensive review of the state-of-the-art reactor technology (also referred to as reactor infrastructure) for pure NH3 decomposition. The review strategy is to survey the open literature and present reactor technology developments in a chronological order. The primary objective of this paper is to provide a condensed viewpoint and basis for future advances in reactor technology for generating H2 via NH3 decomposition. Also, this review highlights the prominent issues and prevailing challenges that are yet to be overcome for possible market entry and subsequent commercialization of various reactor technologies. To our knowledge, this work presents for the first time a review of reactor infrastructure for distributed H2 generation via NH3 decomposition. Despite commendable research and development progress, substantial effort is still required if commercialization of NH3 decomposition reactor infrastructure is to be realized