Bioreactors go electro – Bioreaktoren für Bioelektrotechnologie aufrüsten

The Dilemma of Supporting Electrolytes for Electroorganic Synthesis: A Case Study on Kolbe Electrolysis

“…[27,30,[39][40][41] Independent of the possible inhibition of oxygen evolution at more alkaline pH, as hift towardsn on-Kolbe products would still be expected, owing to an increased number of hydroxide, carbonate, and biocarbonate ions that increaset he spatial spacingo ft he formed alkyl-radicals at the electrode surface, rendering dimerizationl ess likely than further oxidation to carbocations. The latter are stabilized by the anions in their proximity,a ltogether shiftingt he product composition towards non-Kolbe products.H owever,t his was not found in our study; ChemSusChem 2016, 9,[50][51][52][53][54][55][56][57][58][59][60] www.chemsuschem.org the reason forw hich we can only speculate. First, the local pH at the electrode surfaced oes not have to be identical to the pH of the bulk solution.I ti sk nown from aqueous Kolbe electrolysis experiments in membrane-separatede lectrochemical cells that the pH at the anode shifts towards more acidic values, whereas the pH at the cathode becomes more alkaline (due to hydrogen evolution).…”

“…To evaluatew hich variable should be excluded, the correlation between these two variables ande ach of the three response variables was calculated using the Pearsonm ethod. [43] The k positivelyc orrelates with all three response variables (r i 3V = 0.91, r iÀE WE = 0.92, r E onset = 0.75) on ah igh significance level (p all < 310 À11 ), whereas the correlation between reactant concentration and the response variables is weaker (r i 3V = 0.10, r iÀE WE = 0.13, r E onset = 0.47) and less statistically relevant (p i 3V = 0.34, ChemSusChem 2016, 9,[50][51][52][53][54][55][56][57][58][59][60] www.chemsuschem.org p iÀE WE = 0.0003, p E onset = 0.48). Hence, only the electrolytic conductivity,t he pH, and the reactant type are taken into account for data analysis.…”

“…[30] Also, the presence of KNO 3 couldh ave decreased the adsorbate layer of organic acids at the electrode surface, thush ampering acid oxidation. Oxygen evolution was not monitored duringt his set of experiments; however,amore diversep roduct spectrum was found when KNO 3 was added.I na ddition to reactant-derived non-Kolbe products, the product spectrum observed by GCMS included, for example, NO 3 -propanetriolester,w hich proves that ChemSusChem 2016, 9,[50][51][52][53][54][55][56][57][58][59][60] www.chemsuschem.org nitrate was present in the proximity of the anode and probably helped to stabilizet he carbocation. Additionally,t he decreasing CE indicates that NO 3 À was not inert, but may have been reduced to NO 2 À at the cathode (NO 3 À + 2H + + 2e À !NO 2 À + H 2 O) [52] and re-oxidized at the anode or reactedw ith other intermediate products.…”

“…Kolbe electrolysis was performed in a2 00 mL single chamber electrochemical reactor [55] equipped with aW E( 4cm 2 geometrical area, taking into account both sides of the electrode sheet) and 5.7 cm 2 counter electrode (geometrical area, see above), asampling port for liquid samples (HPLC) and headspace samples (online GC-TCD), and an agitator (600 rpm) to assure laminar mixing. A0 .43 m valeric acid solution was prepared in deionized water.T he initial pH of the solution was adjusted to 5or1 1b yadding NaOH pellets.…”

Microbial Electrochemical Systems with Future Perspectives using Advanced Nanomaterials and Microfluidics

“…Scheme of bioelectrochemical systems (BES) as a special form of bioreactors for bioelectrosynthesis. Adapted with permission . Copyright 2015, Springer.…”