The enormous quantity of food wastes discarded annually forces a look into alternatives for this interesting feedstock.

Sixty R3SiX/solvent (S) and R2HSiX/S systems with R = methyl, ethyl, butyl and S = methylene chloride, DMPU, DMSO, sulfolane, HMPA, acetonitrile, pyridine, N-methylimidazole, and triethylamine were investigated with the help of NMR spectroscopy for different concentration ratios of R3SiX/S and R2HSiX/S as well as different temperatures. With the help of measured δ29Si and δ13C chemical shifts as well as 1 J Si - C and 2 J Si - P coupling constants, typical NMR parameters for R3SiX and R2HSiX, R3Si(S)+, R2HSi(S)+, and R2HSi(S)2 + were established and discussed to distinguish between possible silylium cation−solvent complexes and equilibria between them. In addition, the NMR/ab initio/IGLO method (based on the continuum solvent model PISA and IGLO-PISA chemical shift calculations) was used to determine geometry, stability, and other properties of Me3Si(S) n + and Me2HSi(S) n + complexes in different solutions. NMR measurements and ab initio calculations clearly show that R3Si(S)+ and R2HSi(S)+ complexes with tetracoordinated Si are formed with solvents (S) more nucleophilic than methylene chloride while complexes with two S molecules and a pentacoordinated Si atom can only be found for R3 - n H n Si+ cations with n ≥ 1. This is a result of internal (hyperconjugative) stabilization of R3Si+ by alkyl groups and external stabilization by S coordination, as well as of steric factors involving R and S. Complex binding energies are in the range of 40−60 kcal/mol, which is significantly different from complex binding energies in the gas phase. In all cases investigated, (weakly) covalent bonds between Si and S are formed that exclude any silylium cation character for the solvated R3Si+ and R2HSi+ ions.

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Biofuel pellets derived from wood raw material are an important carbon neutral source of energy.